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1

Anisotropic Cartesian Grid Adaptation  

Microsoft Academic Search

A three-dimensional grid adaptation method using the concept of anisotropic Cartesian grid has been developed to improve the efficiency of an existing Cartesian grid adaptation method by reducing the total number of cells needed to compute a flow field. The present grid adaptation is carried out by performing both grid coarsening and refinement in such a way that the cell

Paulus R. Lahur; Yoshiaki Nakamura

2005-01-01

2

Flow simulation around an airfoil using a body-fitted grid modified from Cartesian coordinates  

NASA Astrophysics Data System (ADS)

Flow past a NACA0012 airfoil is simulated using a body-fitted coordinates derived from Cartesian coordinates instead of using C or O-type grids, or unstructured grids. The simulations solve the incompressible Navier-Stokes equations using a multi-directional finite difference methodology. No explicit turbulent model is incorporated in the numerical model. A third-order upwind scheme is employed to assure stability of the solution. Results of high Reynolds and small angles of attack are presented to show the applicability of the present method.

Bethancourt, Angel; Kuwahara, Kunio; Komurasaki, Satoko

2004-11-01

3

Cartesian Coordinate System  

NSDL National Science Digital Library

This lesson is designed to develop students' understanding of the Cartesian coordinate plane. Topics include plotting coordinates and slope. This lesson provides links to discussions and activities related to the Cartesian coordinate system as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

4

Anisotropic Cartesian Grid Adaptation  

NASA Astrophysics Data System (ADS)

A three-dimensional grid adaptation method using the concept of anisotropic Cartesian grid has been developed to improve the efficiency of an existing Cartesian grid adaptation method by reducing the total number of cells needed to compute a flow field. The present grid adaptation is carried out by performing both grid coarsening and refinement in such a way that the cell aspect ratio can take an arbitrary value, keeping the grid smoothness. This flexibility necessitates the concept of unstructured approach. Two test cases: a cylinder in supersonic flow and an ONERA M6 wing in transonic flow show that the present method can well capture 2D and 3D flow features. In the cylinder case, the number of cells after the final adaptation cycle is one or two orders of magnitude less than that of the corresponding isotropic grid; in the ONERA M6 case it becomes about half as many. This remarkable saving in the 2D case is achieved because the spanwise domain is covered by only one cell in the present method, unlike conventional isotropic approaches. As a result of the decrease in the number of cells, the anisotropic grid requires less time to solve the flow and less amount of total memory, though the amount of memory per cell actually increases because of its unstructured property.

Lahur, Paulus R.; Nakamura, Yoshiaki

5

Grid refinement in Cartesian coordinates for groundwater flow models using the divergence theorem and Taylor's series.  

PubMed

Grid refinement is introduced in a numerical groundwater model to increase the accuracy of the solution over local areas without compromising the run time of the model. Numerical methods developed for grid refinement suffered certain drawbacks, for example, deficiencies in the implemented interpolation technique; the non-reciprocity in head calculations or flow calculations; lack of accuracy resulting from high truncation errors, and numerical problems resulting from the construction of elongated meshes. A refinement scheme based on the divergence theorem and Taylor's expansions is presented in this article. This scheme is based on the work of De Marsily (1986) but includes more terms of the Taylor's series to improve the numerical solution. In this scheme, flow reciprocity is maintained and high order of refinement was achievable. The new numerical method is applied to simulate groundwater flows in homogeneous and heterogeneous confined aquifers. It produced results with acceptable degrees of accuracy. This method shows the potential for its application to solving groundwater heads over nested meshes with irregular shapes. PMID:22409243

Mansour, M M; Spink, A E F

2012-03-12

6

Implementing the fast marching eikonal solver: Spherical versus Cartesian coordinates  

Microsoft Academic Search

Spherical coordinates are a natural orthogonal system to describe wavefronts emanating from a point source. While a regular grid distribution in the Cartesian coordinate system tends to undersample the wavefront description near the source (the highest wavefront cur- vature) and oversample it away from the source, spherical coordinates, in general, provide a more balanced grid distribution to characterize such wavefronts.

Tariq Alkhalifah; Sergey Fomel

1997-01-01

7

Coordinates and the Cartesian Plane  

NSDL National Science Digital Library

The lesson begins with a short refresher lecture on how points are written in (x,y) format and orientation with the Cartesian plane axes. The lecture also covers which directions are positive and which are negative on an x-y plane. Students learn about what it means for a relation to be a function and how to determine domain and range of a set of data points. Prerequisite knowledge: Familiarity with the coordinate plane, coordinates, and equations are helpful, but not required.

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

2007-01-01

8

Explicitly computing geodetic coordinates from Cartesian coordinates  

NASA Astrophysics Data System (ADS)

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

Zeng, H.

2013-04-01

9

3D Euler Solutions Using Automated Cartesian Grid Generation.  

National Technical Information Service (NTIS)

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 sp...

J. E. Melton F. Y. Enomoto M. J. Berger

1993-01-01

10

Coordinates and the Cartesian Plane  

NSDL National Science Digital Library

A brief refresher on the Cartesian plane includes how points are written in (x,y) format and oriented to the axes, and which directions are positive and negative. Then students learn about what it means for a relation to be a function and how to determine domain and range of a set of data points.

VU Bioengineering RET Program, School of Engineering,

11

Beamtracking in cylindrical and cartesian coordinates  

SciTech Connect

For the design of devices with circular optical axes, e.g. bending magnets or spectrometers, the use of cylindrical coordinates for field calculations could be favourable. Additionally, in case of applications like bending systems with nonorthogonal entry and exit faces, the coupling of cylindrical and cartesian coordinates improves the simulation of fringe fields. In this context we have implemented a consistent coupling between the two coordinate systems and have extended the tracking code of the electromagnetic simulator MAFIA to cylindrical coordinates. This extensions could be of interest for the calculation of transfer maps of ionoptical devices using the tracked particle orbit as reference trajectory and including fringe field effects in a more general manner. We will give a short introduction to the extensions and show some examples for bending systems with nonorthogonal entries. {copyright} {ital 1997 American Institute of Physics.}

Schillinger, B.; Weiland, T. [Technische Hochschule Darmstadt, Fachbereich 18, FG TEMF, Schlossgartenstr. 8, 64289 Darmstadt (Germany)

1997-02-01

12

Beamtracking in cylindrical and cartesian coordinates  

SciTech Connect

For the design of devices with circular optical axes, e.g. bending magnets or spectrometers, the use of cylindrical coordinates for field calculations could be favourable. Additionally, in case of applications like bending systems with nonorthogonal entry and exit faces, the coupling of cylindrical and cartesian coordinates improves the simulation of fringe fields. In this context we have implemented a consistent coupling between the two coordinate systems and have extended the tracking code of the electromagnetic simulator MAFIA to cylindrical coordinates. This extensions could be of interest for the calculation of transfer maps of ionoptical devices using the tracked particle orbit as reference trajectory and including fringe field effects in a more general manner. We will give a short introduction to the extensions and show some examples for bending systems with nonorthogonal entries.

Schillinger, B.; Weiland, T. [Technische Hochschule Darmstadt, Fachbereich 18, FG TEMF, Schlossgartenstr. 8, 64289 Darmstadt (Germany)

1997-02-01

13

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

NASA Astrophysics Data System (ADS)

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

Civicioglu, Pinar

2012-09-01

14

Cartesian to geodetic coordinates conversion on a triaxial ellipsoid  

NASA Astrophysics Data System (ADS)

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

Ligas, Marcin

2012-04-01

15

Cartesian based grid generation/adaptive mesh refinement  

NASA Astrophysics Data System (ADS)

Grid adaptation has recently received attention in the computational fluid dynamics (CFD) community as a means to capture the salient features of a flowfield by either moving grid points of a structured or by adding cells in an unstructured manner. An approach based on a background cartesian mesh is investigated from which the geometry is 'cut' out of the mesh. Once the mesh is obtained, a solution on this coarse grid is found, that indicates which cells need to be refined. This process of refining/solving continues until the flow is grid refined in terms of a user specified global parameter (such as drag coefficient etc.). The advantages of this approach are twofold: the generation of the base grid is independent of the topology of the bodies or surfaces around/through which the flow is to be computed, and the resulting grid (in uncut regions) is highly isotropic, so that the truncation error is low. The flow solver (which, along with the grid generation is still under development) uses a completely unstructured data base, and is a finite volume, upwinding scheme. Current and future work will address generating Navier-Stokes suitable grids by using locally aligned and normal face/cell refining. The attached plot shows a simple grid about two turbine blades.

Coirier, William J.

1992-04-01

16

A normal ray refinement technique for Cartesian-grid based Navier–Stokes solvers  

Microsoft Academic Search

In this work, a novel technique called normal ray refinement (NRR) is developed, implemented and investigated. Normal ray refinement is designed to allow for the viscous fluid flow simulations using an unstructured Cartesian grid framework in a computationally efficient manner. A key benefit of using a Cartesian grid method is that the grid can be automatically generated, thereby saving a

Stephen M. Ruffin; Mina Zaki; Susheel Sekhar

2012-01-01

17

A cartesian grid embedded boundary method for hyperbolic conservation laws  

SciTech Connect

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

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

2004-10-03

18

Parallel Simulation of Moving Boundary Flow Using Overset Adaptive Cartesian/Prism Grids and DES.  

National Technical Information Service (NTIS)

Two major tasks have been undertaken in this year: the development of OverCart- the overset Cartesian/prism grid generator and adaptor, and the enhancement of the flow solver to handle moving overset Cartesian/prism grids. Satisfactory progresses have bee...

Z. J. Wang

2004-01-01

19

Various parameterizations of "latitude" equation - Cartesian to geodetic coordinates transformation  

NASA Astrophysics Data System (ADS)

The paper presents a solution to one of the basic problems of computational geodesy - conversion between Cartesian and geodetic coordinates on a biaxial ellipsoid. The solution is based on what is known in the literature as "latitude equation". The equation is presented in three different parameterizations commonly used in geodesy - geodetic, parametric (reduced) and geocentric latitudes. Although the resulting equations may be derived in many ways, here, we present a very elegant one based on vectors orthogonality. As the "original latitude equations" are trigonometric ones, their representation has been changed into an irrational form after Fukushima (1999, 2006). Furthermore, in order to avoid division operations we have followed Fukushima's strategy again and rewritten the equations in a fractional form (a pair of iterative formulas). The resulting formulas involving parametric latitude are essentially the same as those introduced by Fukushima (2006) (considered the most efficient today). All the resulting variants are solved with Newton's second-order and Halley's third-order formulas. It turns out that all parameterizations of the "latitude equation" show a comparable level of performance.

Ligas, M.

2013-09-01

20

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

SciTech Connect

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

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

2000-06-27

21

Rapid and precise method to convert a two dimensional image from Cartesian to polar coordinate system  

Microsoft Academic Search

A method is described to convert a two-dimensional image, which is the pattern of the scattered electrons from on target gas measured by a torodial type analyzer with a detector consists of a pair of multichannel plates and a position sensitive detector from detector’s recording system, a Cartesian coordinate system, to a polar coordinate system in which physical quantities (the

Weimin Wu; Yoshihiro Kato; K. Yamazaki; M. Yoshino; A. Danjo; N. Kobayashi

1997-01-01

22

Interactive visualization of fluid dynamics simulations in locally refined cartesian grids  

Microsoft Academic Search

The work presents interactive flow visualization techniques specifically adapted for PowerFLOW TM, a lattice based CFD code from the EXA corporation. Their Digital Physics TM fluid simulation technique is performed on a hierarchy of locally refined cartesian grids with a fine voxel resolution in areas of interesting flow features. Among other applications, the PowerFLOW solver is used for aerodynamic simulations

Martin Schulz; Frank Reck; W. Bertelheimer; Thomas Ertl

1999-01-01

23

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

Microsoft Academic Search

The present paper deals with the implementation of non-penetration boundary conditions at solid walls for three-dimensional inviscid flow computations on Cartesian grids. The crux of the method is the curvature-corrected symmetry technique (CCST) developed by the present authors for body-fitted grids. The method introduces ghost cells near the boundaries whose values are developed from an assumed flow-field model in vicinity

Andrea Dadone; Bernard Grossman

2007-01-01

24

Fully Isotropic Fast Marching Methods on Cartesian Grids  

Microsoft Academic Search

\\u000a The existing Fast Marching methods which are used to solve the Eikonal equation use a locally continuous model to estimate\\u000a the accumulated cost, but a discontinuous (discretized) model for the traveling cost around each grid point. Because the accumulated\\u000a cost and the traveling (local) cost are treated differently, the estimate of the accumulated cost at any point will vary based

Vikram V. Appia; Anthony J. Yezzi

2010-01-01

25

Boundary data immersion method for Cartesian-grid simulations of fluid-body interaction problems  

NASA Astrophysics Data System (ADS)

A new robust and accurate Cartesian-grid treatment for the immersion of solid bodies within a fluid with general boundary conditions is described. The new approach, the Boundary Data Immersion Method (BDIM), is derived based on a general integration kernel formulation which allows the field equations of each domain and the interfacial conditions to be combined analytically. The resulting governing equation for the complete domain preserves the behavior of the original system in an efficient Cartesian-grid method, including stable and accurate pressure values on the solid boundary. The kernel formulation allows a detailed analysis of the method, and it is demonstrated that BDIM is consistent, obtains second-order convergence relative to the kernel width, and is robust with respect to the grid and boundary alignment. Formulation for no-slip and free slip boundary conditions are derived and numerical results are obtained for the flow past a cylinder and the impact of blunt bodies through a free surface. The BDIM predictions are compared to analytic, experimental and previous numerical results confirming the properties, efficiency and efficacy of this new boundary treatment for Cartesian grid methods.

Weymouth, G. D.; Yue, Dick K. P.

2011-07-01

26

The Cartesian grid method for solving partial differential equations in spherical geometry  

Microsoft Academic Search

ABSTRACT Cartesian coordinates are used to solve the nonlinear shallow-water equations on the sphere. The two-dimensional equations, in spherical coordinates, are first embedded in a three-dimensional system ina manner that preserves solutions of the two-dimensional system. Solutions of the three-dimension al system, with appropriate initial conditions, also solve the two-dimensional system on,the surface of the sphere. The higher dimen- sional

P. N. Swarztrauber; D. L. Williamson; J. B. Drake

1998-01-01

27

A Cartesian grid method for efficiently solving 2D incompressible flow around multiple moving objects.  

NASA Astrophysics Data System (ADS)

Multiple objects interacting in unsteady flows are complex but ubiquitous. Examples include sedimentation of particles in unsteady fluids and interactions of dragonfly wings for maneuver. Modeling these phenomena poses challenges in devising efficient and accurate computational methods. Here we present a 2D Cartesian grid method using streamfunction-vorticity formulation that treats the multiple objects as embedded discontinuities in the flow, and is second-order accurate in space and time. The method only uses O(N*ln(N)+M) per operation step, where N is the number of nodes in the regular Cartesian grid and M is the number of nodes in the immersed object surface discretization. A typical computing time for presented results is about 1.5 hours on a 930 MHz desktop PC. We tested the method against the canonical example of flow past a cylinder, and obtained new results on the flow and forces of two cylinders moving relative to each other.

Russell, David; Wang, Jane

2002-11-01

28

An Accurate Cartesian Grid Method for Viscous Incompressible Flows with Complex Immersed Boundaries  

Microsoft Academic Search

A Cartesian grid method has been developed for simulating two-dimensional unsteady, viscous, incompressible flows with complex immersed boundaries. A finite-volume method based on a second-order accurate central-difference scheme is used in conjunction with a two-step fractional-step procedure. The key aspects that need to be considered in developing such a solver are imposition of boundary conditions on the immersed boundaries and

T. Ye; R. Mittal; H. S. Udaykumar; W. Shyy

1999-01-01

29

Superconvergence Of The Local Discontinuous Galerkin Method For Elliptic Problems On Cartesian Grids  

Microsoft Academic Search

. In this paper, we present a super-convergence result for the Local DiscontinuousGalerkin method for a model elliptic problem on Cartesian grids. We identify a special numericalflux for which the L2-norm of the gradient and the L2-norm of the potential are of order k + 1=2and k + 1, respectively, when tensor product polynomials of degree at most k are

Bernardo Cockburn; Guido Kanschat; Ilaria Perugia; Dominik Schötzau

2000-01-01

30

An Efficient Euler Method on Non-Moving Cartesian Grids with Boundary-Layer Correction for Wing Flutter Simulations  

Microsoft Academic Search

This paper presents an e-cient Euler method on Cartesian grids coupled with an integral Boundary-Layer method. The unsteady Euler equations are solved using cell-centered flnite volume method by the implicit-explicit dual-time stepping scheme. The wall boundary con- ditions on the wing are implemented on the wing chord plane by flrst order approximation so that non-moving Cartesian grids can be used.

Zhichao Zhang; Feng Liu; David M. Schuster

31

Computing reaching dynamics in motor cortex with Cartesian spatial coordinates.  

PubMed

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

Tanaka, Hirokazu; Sejnowski, Terrence J

2012-10-31

32

Numerical method for calculation of the incompressible flow in general curvilinear co-ordinates with double staggered grid  

Microsoft Academic Search

A solution methodology has been developed for incompressible flow in general curvilinear co-ordinates. Two staggered grids are used to discretize the physical domain. The first grid is a MAC quadrilateral mesh with pressure arranged at the centre and the Cartesian velocity components located at the middle of the sides of the mesh. The second grid is so displaced that its

A. Shklyar; A. Arbel

2003-01-01

33

Pipelined Cartesian-to-Polar Coordinate Conversion Based on SRT Division  

Microsoft Academic Search

This brief proposes a new Cartesian-to-polar coordinate conversion technique based on the radix-4 SRT division. The coarse quotient is used to derive the magnitude and the coarse phase by referring to tables, while the fine quotient is applied to linearly interpolate the fine phase to be added to the coarse phase. Compared to the CORDIC-based techniques, the proposed conversion requires

Sung-Won Lee; Ki-Seok Kwon; In-Cheol Park

2007-01-01

34

Forward and Inverse Transformations between Cartesian and Channel-fitted Coordinate Systems for Meandering Rivers  

Microsoft Academic Search

The spatial referencing of river channels is complicated by their meandering planform, which dictates that Euclidean distance\\u000a in a Cartesian reference frame is not an appropriate metric. Channel-fitted coordinate systems are thus widely used in application-oriented\\u000a geostatistics as well as theoretical fluid mechanics, where flow patterns are described in terms of a streamwise axis s along the channel centerline and

Carl J. Legleiter; Phaedon C. Kyriakidis

2006-01-01

35

Calculation of three-dimensional boundary layers. II - Three-dimensional flows in Cartesian coordinates  

Microsoft Academic Search

This paper presents a general method for solving the laminar and turbulent boundary-layer equations for three-dimensional flows in Cartesian coordinates. In the equations the Reynolds shear-stress terms appearing in the momentum equations for turbulent flows are modeled by an eddy-viscosity formulation developed by the author. The governing equations are solved by a very efficient two-point finite-difference method. The accuracy of

T. Cebeci

1975-01-01

36

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

SciTech Connect

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

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

1997-01-31

37

General solution technique for transient thermoelasticity of transversely isotropic solids in Cartesian coordinates  

NASA Astrophysics Data System (ADS)

In the present paper we propose a new general solution technique for transient thermoelastic problems of transversely isotropic solids in Cartesian coordinates. The solution technique consists of five fundamental solutions. By considering the relations among the material constants of transverse isotropy, the solution technique is classified into five groups. One among those corresponds to Goodier's thermoelastic potential function as well as the generalized Boussinesq solutions and the Michell function. For an application of the solution technique, an inverse problem of transient thermoelasticity in a transversely isotropic semi-infinite solid is analyzed.

Noda, N.; Ashida, F.; Okumura, I. A.

1992-07-01

38

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

NASA Astrophysics Data System (ADS)

Aims:We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to demonstrate that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations while offering advantages, such as the absence of a grid singularity, for certain applications, e.g., circumbinary disks and disk-jet simulations. Methods: We employ the Pencil Code, a 3D high-order finite-difference MHD code using Cartesian coordinates. We solve the equations of ideal MHD with a local isothermal equation of state. Planets and stars are treated as particles evolved with an N-body scheme. Solid boulders are treated as individual superparticles that couple to the gas through a drag force that is linear in the local relative velocity between gas and particle. Results: We find that Cartesian grids are well-suited for accretion disk problems. The disk-in-a-box models based on Cartesian grids presented here develop and sustain MHD turbulence, in good agreement with published results achieved with cylindrical codes. Models without an inner boundary do not show the spurious build-up of magnetic pressure and Reynolds stress seen in the models with boundaries, but the global stresses and alpha viscosities are similar in the two cases. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24 ± 0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of Maxwell to Reynolds stresses decreases with increasing temperature, dropping from 5 to 1 when the sound speed was raised by a factor 4, maintaing the same field strength. We also study the dynamics of solid boulders in the hydromagnetic turbulence, by making use of 106 Lagrangian particles embedded in the Eulerian grid. The effective diffusion provided by the turbulence prevents settling of the solids in a infinitesimally thin layer, forming instead a layer of solids of finite vertical thickness. The measured scale height of this diffusion-supported layer of solids implies turbulent vertical diffusion coefficients with globally averaged Schmidt numbers of 1.0 ± 0.2 for a model with ??10-3 and 0.78 ± 0.06 for a model with ??10-1. That is, the vertical turbulent diffusion acting on the solids phase is comparable to the turbulent viscosity acting on the gas phase. The average bulk density of solids in the turbulent flow is quite low (?p = 6.0×10-11 kg m-3), but in the high pressure regions, significant overdensities are observed, where the solid-to-gas ratio reached values as great as 85, corresponding to 4 orders of magnitude higher than the initial interstellar value of 0.01.

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

2008-03-01

39

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

SciTech Connect

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

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

2011-01-01

40

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

41

Modeling complex boundaries using an external force field on fixed Cartesian grids in large-eddy simulations  

Microsoft Academic Search

In the present study a methodology to perform large-eddy simulations around complex boundaries on fixed Cartesian grids is presented. A novel interpolation scheme which is applicable to boundaries of arbitrary shape, does not involve special treatments, and allows the accurate imposition of the desired boundary conditions is introduced. A method to overcome the problems associated with the computation of the

Elias Balaras

2004-01-01

42

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

PubMed

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

Boschitsch, Alexander H; Fenley, Marcia O

2011-05-10

43

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

NASA Astrophysics Data System (ADS)

A Cartesian grid method for computing flows with complex immersed, moving boundaries is presented. The flow is computed on a fixed Cartesian mesh and the solid boundaries are allowed to move freely through the mesh. A mixed Eulerian-Lagrangian framework is employed, which allows us to treat the immersed moving boundary as a sharp interface. The incompressible Navier-Stokes equations are discretized using a second-order-accurate finite-volume technique, and a second-order- accurate fractional-step scheme is employed for time advancement. The fractional-step method and associated boundary conditions are formulated in a manner that properly accounts for the boundary motion. A unique problem with sharp interface methods is the temporal discretization of what are termed ``freshly cleared'' cells, i.e., cells that are inside the solid at one time step and emerge into the fluid at the next time step. A simple and consistent remedy for this problem is also presented. The solution of the pressure Poisson equation is usually the most time-consuming step in a fractional step scheme and this is even more so for moving boundary problems where the flow domain changes constantly. A multigrid method is presented and is shown to accelerate the convergence significantly even in the presence of complex immersed boundaries. The methodology is validated by comparing it with experimental data on two cases: (1) the flow in a channel with a moving indentation on one wall and (2) vortex shedding from a cylinder oscillating in a uniform free-stream. Finally, the application of the current method to a more complicated moving boundary situation is also demonstrated by computing the flow inside a diaphragm-driven micropump with moving valves.

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

2001-11-01

44

A fully conservative finite-volume method for incompressible Navier-Stokes equations on locally refined nested Cartesian grids  

NASA Astrophysics Data System (ADS)

A second-order-accurate finite-volume method is developed for the solution of incompressible Navier-Stokes equations on locally refined nested Cartesian grids. Numerical accuracy and stability on locally refined nested Cartesian grids are achieved using a finite-volume discretization of the incompressible Navier-Stokes equations based on higher- order conservation principles - i.e., in addition to mass and momentum conservation, kinetic energy conservation in the inviscid limit is used to guide the selection of the discrete operators and solution algorithm. Hanging nodes at the interface are implicitly slanted to improve the pressure-velocity projection, while the other parts of the grid maintain an orthogonal Cartesian grid topology. The present method is found to significantly improve the computational efficiency while it is straightforward to implement. The present method shows superior conservation of mass, momentum, and kinetic energy compared to the conventional methods employing interpolation at the interface between coarse and fine grids in simulations of Taylor vortex, lid-driven cavity flow, and flow over a square cylinder.

Sifounakis, Adamandios; You, Donghyun; Singh, Satbir

2011-11-01

45

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

SciTech Connect

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

Warnock, R.L. [Stanford Univ., CA (US). Stanford Linear Accelerator Center; Ellison, J.A. [Deutsches Elektronen-Synchrotron, Hamburg (Germany)]|[Univ. of New Mexico, Albuquerque, NM (US). Dept. of Mathematics and Statistics

1997-08-01

46

Thermodynamic integration of the free energy along a reaction coordinate in Cartesian coordinates  

NASA Astrophysics Data System (ADS)

A generalized formulation of the thermodynamic integration (TI) method for calculating the free energy along a reaction coordinate is derived. Molecular dynamics simulations with a constrained reaction coordinate are used to sample conformations. These are then projected onto conformations with a higher value of the reaction coordinate by means of a vector field. The accompanying change in potential energy plus the divergence of the vector field constitute the derivative of the free energy. Any vector field meeting some simple requirements can be used as the basis of this TI expression. Two classes of vector fields are of particular interest here. The first recovers the conventional TI expression, with its cumbersome dependence on a full set of generalized coordinates. As the free energy is a function of the reaction coordinate only, it should in principle be possible to derive an expression depending exclusively on the definition of the reaction coordinate. This objective is met by the second class of vector fields to be discussed. The potential of mean constraint force (PMCF) method, after averaging over the unconstrained momenta, falls in this second class. The new method is illustrated by calculations on the isomerization of n-butane, and is compared with existing methods.

den Otter, W. K.

2000-05-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

48

Conversion between Cartesian and geodetic coordinates on a rotational ellipsoid by solving a system of nonlinear equations  

NASA Astrophysics Data System (ADS)

A new method to transform from Cartesian to geodetic coordinates is presented. It is based on the solution of a system of nonlinear equations with respect to the coordinates of the point projected onto the ellipsoid along the normal. Newton's method and a modification of Newton's method were applied to give third-order convergence. The method developed was compared to some well known iterative techniques. All methods were tested on three ellipsoidal height ranges: namely, (-10 - 10 km) (terrestrial), (20 - 1000 km), and (1000 - 36000 km) (satellite). One iteration of the presented method, implemented with the third-order convergence modified Newton's method, is necessary to obtain a satisfactory level of accuracy for the geodetic latitude (?? < 0.0004") and height (?h < 10-6 km, i.e. less than a millimetre) for all the heights tested. The method is slightly slower than the method of Fukushima (2006) and Fukushima's (1999) fast implementation of Bowring's (1976) method.

Ligas, Marcin; Banasik, Piotr

2011-01-01

49

Development of high-performance cooling structure for PDP TV sets using computational fluid dynamics simulation with heat transfer based on Cartesian grid system  

Microsoft Academic Search

A simple and high-performance ldquomulti-flowrdquo cooling structure for plasma display panel television sets was developed using computational fluid dynamics with heat transfer based on Cartesian grid system. Upward flow induced by natural convection and fans in the conventional cooling structure has mainly contributed to cooling the plasma panel and boards. However, simulation results indicated that shortcut flows between the bottom

Nobuyuki Isoshima; Masatoshi Watanabe; Ken Tsukamoto; Mikio Shiraishi

2008-01-01

50

A Supra-Convergent Finite Difference Scheme for the Poisson and Heat Equations on Irregular Domains and NonGraded Adaptive Cartesian Grids  

Microsoft Academic Search

We present finite difference schemes for solving the variable coefficient Poisson and heat equations on irregular domains\\u000a with Dirichlet boundary conditions. The computational domain is discretized with non-graded Cartesian grids, i.e., grids for\\u000a which the difference in size between two adjacent cells is not constrained. Refinement criteria is based on proximity to the\\u000a irregular interface such that cells with the

Han Chen; Chohong Min; Frédéric Gibou

2007-01-01

51

Comparison of Cartesian Grid Configurations for Application of the Finite-Difference Time-Domain Method to Electromagnetic Scattering by Dielectric Particles  

Microsoft Academic Search

Two grid configurations can be employed to implement the finite-difference time-domain FDTD tech- nique in a Cartesian system. One configuration defines the electric and magnetic field components at the cell edges and cell-face centers, respectively, whereas the other reverses these definitions. These two grid configurations differ in terms of implication on the electromagnetic boundary conditions if the scatterer in the

Ping Yang; George W. Kattawar; Kuo-Nan Liou; Jun Q. Lu

2004-01-01

52

Interacitve Visualization of Fluid Dynamics Simulations in Locally Refined Cartesian Grids  

Microsoft Academic Search

This work presents interactive flow visualization techniques specificallyadapted for PowerFLOWTM, a lattice-based CFD code fromthe EXA corporation. Their Digital PhysicsTMfluid simulationtechnique is performed on a hierarchy of locally refined cartesiangrids with a fine voxel resolution in areas of interesting flow features.Among other applications the PowerFLOW solver is usedfor aerodynamic simulations in car body development where the advantagesof automatic grid generation

Martin Schulz; Frank Reck; Wolf Bartelheimer; Thomas Ertl

1999-01-01

53

On coordinate transformation and grid stretching for sparse grid pricing of basket options  

Microsoft Academic Search

We evaluate two coordinate transformation techniques in combination with a coordinate stretching for pricing basket options in a sparse grid setting. The sparse grid technique is a basic technique for solving a high-dimensional partial differential equation. By creating a small hypercube sub-grid in the 'composite' sparse grid we can also determine hedge parameters accurately. We evaluate these techniques for multi-asset

C. C. W. Leentvaar; C. W. Oosterlee

2006-01-01

54

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

Microsoft Academic Search

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

S. Ahmad; S. Luo

1989-01-01

55

On coordinate transformation and grid stretching for sparse grid pricing of basket options  

NASA Astrophysics Data System (ADS)

We evaluate two coordinate transformation techniques in combination with grid stretching for pricing basket options in a sparse grid setting. The sparse grid technique is a basic technique for solving a high-dimensional partial differential equation. By creating a small hypercube sub-grid in the [`]composite' sparse grid we can also determine hedge parameters accurately. We evaluate these techniques for multi-asset examples with up to five underlying assets in the basket.

Leentvaar, C. C. W.; Oosterlee, C. W.

2008-12-01

56

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

Microsoft Academic Search

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

Shaheen Ahmad; Shengwu Luo

1988-01-01

57

Comparison of Cartesian grid configurations for application of the finite-difference time-domain method to electromagnetic scattering by dielectric particles.  

PubMed

Two grid configurations can be employed to implement the finite-difference time-domain (FDTD) technique in a Cartesian system. One configuration defines the electric and magnetic field components at the cell edges and cell-face centers, respectively, whereas the other reverses these definitions. These two grid configurations differ in terms of implication on the electromagnetic boundary conditions if the scatterer in the FDTD computation is a dielectric particle. The permittivity has an abrupt transition at the cell interface if the dielectric properties of two adjacent cells are not identical. Similarly, the discontinuity of permittivity is also observed at the edges of neighboring cells that are different in terms of their dielectric constants. We present two FDTD schemes for light scattering by dielectric particles to overcome the above-mentioned discontinuity on the basis of the electromagnetic boundary conditions for the two Cartesian grid configurations. We also present an empirical approach to accelerate the convergence of the discrete Fourier transform to obtain the field values in the frequency domain. As a new application of the FDTD method, we investigate the scattering properties of multibranched bullet-rosette ice crystals at both visible and thermal infrared wavelengths. PMID:15376440

Yang, Ping; Kattawar, George W; Liou, Kuo-Nan; Lu, Jun Q

2004-08-10

58

Cartesian Diver  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2006-01-01

59

Complex Frequency Shifted PML Auxiliary Differential Equation Implementation for Seismic Wave Modeling in Cartesian, Spherical and General Curvilinear Coordinates  

NASA Astrophysics Data System (ADS)

The perfectly matched layer (PML) has been widely used in seismic wave modeling to absorb waves at nonphysical boundaries surrounding the computational domain. The traditional PML performs poorly in absorbing low-frequency waves, evanescent waves or waves at grazing incidence. By using a complex frequency-shifted (CFS) stretching function, the Convolutional-PML (C-PML) has proven to be more efficient under these circumstances. However, updating the auxiliary memory variables in the CFS C-PML involves convolution operators and needs an algorithm different from the numerical scheme used in the interior domain. We propose an alternative unsplit-field CFS PML implementation using auxiliary differential equations (ADE) to update the auxiliary memory variables. Equations of the CFS ADE-PML are all first-order differential equations and do not involve convolution or integral terms. The same numerical scheme used in the interior domain can be used to solve the CFS ADE-PML equations, and is thus straightforward to use with a higher-order time matching scheme. The memory requirement is the same as the CFS C-PML, one memory variable for each derivative. The CFS ADE-PML can be implemented as a perturbation to the original wave equations on each face of the computational domain and does not require tracking the indexes of the edges or corners. At the free surface, the CFS ADE-PML equations are derived taking the free surface boundary condition into account, which is crucial to effectively absorb surface waves when the free surface coincides with the normal stress components in the staggered-grid finite-difference method. The parameters of the CFS stretching function contribute to an effective wave speed decrease in the normal direction of the PML layer and a frequency dependent damping in the PML layer. Our numerical tests indicate the optimal parameters lead to the effective shortest wavelength in the PML layer to twice or triple the cell size. In spherical and general curvilinear coordinates, the ADE CFS-PML can be implemented by mapping to a local orthogonal coordinate and correct the original equations along normal direction. Numerical tests indicate the efficacy of the ADE CFS-PML and stable solution can be obtained in spherical and general curvilinear coordinates.

Zhang, W.; Shen, Y.

2009-12-01

60

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

61

Enhancing the Capture of Two-dimensional, Shock-Induced Detonation Fronts using Harten's Artificial Compression Method on Underresolved Cartesian Grids  

NASA Astrophysics Data System (ADS)

In the problems of detonation we are going to present here, the capture of shocks is crucial, since from its accuracy depends the very physical relevance of the whole solution. We already obtained some improvements in the capture of detonation fronts on underresolved grids in the one-dimensional case thanks to Harten's artificial compression [1], [2], and we now turn to two-dimensional cartesian grids. In two space dimensions, the complexity of the discontinuity implies not only the location and speed of the front, but also its shape. These three aspects will be explored here, for the ZND detonation model, based on Euler's system. We will use two-dimensional central schemes for main computations, namely the classical ``Lax-Friedrichs'' first order scheme and the second order ``Jiang-Tadmor'' scheme [3]. To each of these methods, we will add two different versions of ACM (Artificial Compression Method), one that uses space splitting, and the other based on directional differencing [4]. Finally, as ACM require a good knowledge of the regions of the solution potentially carrying discontinuities, it will be assisted by a DoD (Detector of Discontinuities) based on the entropy production rate.

Rouch, Olivier

2009-09-01

62

Concurrent negotiation and coordination for grid resource coallocation.  

PubMed

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 is that it is one of the earliest works that consider a concurrent negotiation mechanism for Grid resource coallocation. The concurrent negotiation mechanism is designed for 1) managing (de)commitment of contracts through one-to-many negotiations and 2) coordination of multiple concurrent one-to-many negotiations between a consumer and multiple resource providers. The novel contributions of this paper are devising 1) a utility-oriented coordination (UOC) strategy, 2) three classes of commitment management strategies (CMSs) for concurrent negotiation, and 3) the negotiation protocols of consumers and providers. Implementing these ideas in a testbed, three series of experiments were carried out in a variety of settings to compare the following: 1) the CMSs in this paper with the work of others in a single one-to-many negotiation environment for one resource where decommitment is allowed for both provider and consumer agents; 2) the performance of the three classes of CMSs in different resource market types; and 3) the UOC strategy with the work of others [e.g., the patient coordination strategy (PCS )] for coordinating multiple concurrent negotiations. Empirical results show the following: 1) the UOC strategy achieved higher utility, faster negotiation speed, and higher success rates than PCS for different resource market types; and 2) the CMS in this paper achieved higher final utility than the CMS in other works. Additionally, the properties of the three classes of CMSs in different kinds of resource markets are also verified. PMID:19884094

Sim, Kwang Mong; Shi, Benyun

2009-10-30

63

High-Order Methods for the Numerical Simulation of Vortical and Turbulent Flows A symmetry-preserving Cartesian grid method for computing a viscous flow past a circular cylinder  

Microsoft Academic Search

This article deals with a numerical method for solving the unsteady, incompressible Navier-Stokes equations in domains with arbitrarily-shaped boundaries, where the boundary is represented using the Cartesian grid approach. We introduce a novel cut-cell discretization which preserves the spectral properties of convection and diffusion. Here, convection is discretized by a skew-symmetric operator and diffusion is approximated by a symmetric, positive-definite

Roel Verstappen; Marc Dröge

64

What is the Grid ? Tentative Definitions Beyond Resource Coordination  

Microsoft Academic Search

Abstract— Ian Foster’s What is The Grid ? paper gives the generally accepted definition of Grid and Grid computing. While sound, it does not precisely define the involved concepts, which may,lead to misunderstandings. We propose a tentative set of definitions for Grid, Grid computing and related concepts such as Virtual Organization, Grid resource sharing architectures and

Cyril Briquet; Pierre-Arnoul de Marneffe

65

A non-staggered grid, fractional step method for time-dependent incompressible Navier-Stokes equations in curvilinear coordinates  

SciTech Connect

A numerical method for solving three-dimensional, time-dependent incompressible Navier-Stokes equations in curvilinear coordinates is presented. The non-staggered-grid method originally developed by C. M. Rhie and W. L. Chow for steady state problems is extended to compute unsteady flows. In the computational space, the Cartesian velocity components and the pressure are defined at the center of a control volume, while the volume fluxes are defined at the mid-point on their corresponding cell faces. The momentum equations are integrated semi-implicitly by the approximate factorization technique. The intermediate velocities are interpolated onto the faces of the control volume to form the source terms of the pressure Poisson equation, which is solved iteratively with a multigrid method. The compatibility condition of the pressure Poisson equation is satisfied in the same manner as in a staggered-grid method; mass conservation can be satisfied to machine accuracy. The pressure boundary condition is derived from the momentum equations. Solutions of both steady and unsteady problems including the large eddy simulation of a rotating and stratified upwelling flow in an irregular container established the favorable accuracy and efficiency of the present method.

Zang, Yan; Street, R.L.; Koseff, J.R. (Stanford Univ., CA (United States))

1994-09-01

66

A Global Ocean Model Based on Icosahedral-Hexagonal Grids With a Hybrid Vertical Coordinate  

Microsoft Academic Search

This talk will present results from a new ocean general circulation model (OGCM). The ocean model uses an icosahedral-hexagonal grid to tile the surface of the sphere and hybrid (floating) coordinates to discretize the vertical depth of the ocean. The use of icosahedral-hexagonal grids leads to a highly uniform and isotropic discretization of the sphere and eliminates problematic grid singularities

T. D. Ringler; J. Baumgardner; D. A. Randall

2003-01-01

67

SuMMIT - A framework for coordinating applications execution in mobile grid environments  

Microsoft Academic Search

The infrastructure of mobile grid presents some challenges to allow the interaction between mobile devices and grid environments, such as (a) applications submission and monitoring facilities in an automated and coordinated manner, (b) disconnections during execution of applications, and (c) selection of suitable grid resources for their execution. This article presents a framework, coined as SuMMIT, that employs the workflow

Anubis G. M. Rossetto; Vinicius C. M. Borges; Alexandre P. C. Silva; M. A. R. Dantas

2007-01-01

68

Cartesian Bicategories II  

Microsoft Academic Search

The notion of cartesian bicategory, introduced by Carboni and Walters for\\u000alocally ordered bicategories, is extended to general bicategories. It is shown\\u000athat a cartesian bicategory is a symmetric monoidal bicategory.

A. Carboni; G. M. Kelly; R. F. C Walters; R. J. Wood

2007-01-01

69

High-order finite-volume adaptive methods on locally rectangular grids  

Microsoft Academic Search

We are developing a new class of finite-volume methods on locally-refined and mapped grids, which are at least fourth-order accurate in regions where the solution is smooth. This paper discusses the implementation of such methods for time-dependent problems on both Cartesian and mapped grids with adaptive mesh refinement. We show 2D results with the Berger-Colella shock-ramp problem in Cartesian coordinates,

P. Colella; M. Dorr; J. Hittinger; D. F. Martin; P. McCorquodale

2009-01-01

70

Coordination of Cloud Computing and Smart Power Grids  

Microsoft Academic Search

The emergence of cloud computing has established a trend towards building massive, energy-hungry, and geographically distributed data centers. Due to their enormous energy consumption, data centers are expected to have major impact on the electric grid by significantly increasing the load at locations where they are built. However, data centers and cloud computing also provide opportunities to help the grid

Amir-Hamed Mohsenian-Rad; Alberto Leon-Garcia

2010-01-01

71

Interconversion Between Truncated Cartesian and Polar Expansions of Images  

Microsoft Academic Search

In this paper, we propose an algorithm for lossless conversion of data between Cartesian and polar coordinates, when the data is sampled from a 2-D real-valued function (a mapping: ) expressed as a particular kind of truncated expansion. We use Laguerre functions and the Fourier basis for the polar co- ordinate expression. Hermite functions are used for the Cartesian coordinate

Gregory S. Chirikjian

2007-01-01

72

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

Federal Register 2010, 2011, 2012, 2013

...sharing among Federal agencies and non-Federal participants with interests and responsibility for middleware, Grid, and cloud projects. The MAGIC Team reports to the Large Scale Networking (LSN) Coordinating Group (CG). Public Comments: The...

2013-02-01

73

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

Federal Register 2010, 2011, 2012, 2013

...sharing among Federal agencies and non-Federal participants with interests and responsibility for middleware, Grid, and cloud projects. The MAGIC Team reports to the Large Scale Networking (LSN) Coordinating Group (CG). Public Comments: The...

2012-09-20

74

Agent Concept for Intelligent Distributed Coordination in the Electric Power Grid  

Microsoft Academic Search

Intelligent agents and multi-agent systems promise to take information management for real-time control of the power grid to a new level. This report presents our concept for intelligent agents to mediate and coordinate communications between Control Areas and Security Coordinators for real-time control of the power grid. An appendix describes the organizations and publications that deal with agent technologies.

DOUGLAS C. SMATHERS; STEVEN Y. GOLDSMITH

2001-01-01

75

Multi-agent coordination for DER in MicroGrid  

Microsoft Academic Search

Multi-agent system (MAS) is one of the most exciting and the fastest growing domains in agent oriented technology which deals with modeling of autonomous decision making entities. This paper presents an application of MAS for distributed energy resource (DER) management in a MicroGrid. MicroGrid can be defined as low voltage distributed power networks comprising various distributed generators (DG), storage and

T. Logenthiran; Dipti Srinivasan; David Wong

2008-01-01

76

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

2013-06-12

77

Convective-difference scheme using a general curvilinear coordinate grid for incompressible viscous flow problems  

Microsoft Academic Search

A numerical scheme analyzing unsteady two-dimensional incompressible viscous flow using a general curvilinear coordinate grid is proposed. In this scheme, the unsteady Navier-Stokes equations are solved by a convective-difference scheme using a staggered square grid in transformed space and an interpolation formula considering TVD concept, and an elliptic equation of pressure is solved by the iteration scheme. The continuity condition

Yoshihisa Matsumoto; Hisaaki Daiguji

1992-01-01

78

FIELD-TEST UPSCALING OF MULTI-AGENT COORDINATION IN THE ELECTRICITY GRID  

Microsoft Academic Search

With the share of distributed energy resources and renewable energy source (DER\\/RES) rapidly increasin g in the electricity grid, a new way of coordination is required to look after the interests of all the stakeholders. The PowerMatcher multi-agent coordination concept has b een demonstrated in two relatively small field tests, i n which a single optimisation goal was achieved. Currently,

Bart ROOSSIEN

2009-01-01

79

SuMMIT An Architecture for Mobile Devices to Coordinate the Execution of Applications in Grid Environments  

Microsoft Academic Search

Several researches related to mobile grid, usually, do not have features such as tasks submission and monitoring facilities in a automated and coordinated manner, which these tasks work together to solve a single problem. This article presents an architecture that employs the workflow concept for providing automated and coordinated features for executing applications in grid configurations. The architecture, coined as

V. C. M. Borges; J. S. Dias; A. G. M. Rossetto; M. A. R. Dantas

2007-01-01

80

Tensor product B-spline method for numerical grid generation.  

National Technical Information Service (NTIS)

We present a tensor product B-spline method for fast elliptic grid generation. The Cartesian coordinate functions for a block are represented as a sum of tensor product B-spline basis functions defined on the computational domain for the block. The tensor...

J. Manke

1989-01-01

81

Cartesian Genetic Programming  

Microsoft Academic Search

This paper presents a new form of Genetic Programming called Cartesian Genetic Programming in which a program is represented as an in- dexed graph. The graph is encoded in the form of a linear string of integers. The inputs or terminal set and nod e outputs are numbered sequentially. The node functions are a lso separately nu mbered. The genotype

Julian F. Miller; Peter Thomson

2000-01-01

82

An efficient method for flutter prediction by solving the Euler and boundary-layer equations on non-moving Cartesian grids  

Microsoft Academic Search

This dissertation presents an efficient inviscid-viscous coupling method for airplane wing flutter prediction. For the inviscid part, the Euler method is employed for accurate resolution of shock-waves and vorticity. For viscous effects, an integral boundary-layer method is developed and coupled with the Euler solver in a semi-inverse manner. In order to avoid the burden of generating body-fitted grids as well

Zhichao Zhang

2005-01-01

83

A second-order discretization of the nonlinear Poisson–Boltzmann equation over irregular geometries using non-graded adaptive Cartesian grids  

Microsoft Academic Search

In this paper we present a finite difference scheme for the discretization of the nonlinear Poisson–Boltzmann (PB) equation over irregular domains that is second-order accurate. The interface is represented by a zero level set of a signed distance function using Octree data structure, allowing a natural and systematic approach to generate non-graded adaptive grids. Such a method guaranties computational efficiency

Mohammad Mirzadeh; Maxime Theillard; Frédéric Gibou

2011-01-01

84

Universal Transverse Mercator Grid Tables for Latitudes 0-80 degrees Australian National Spheroid (Meters). Volume I. Transformation of Coordinates from Grid to Geographic.  

National Technical Information Service (NTIS)

This manual presents tabulated data as: Tables for Transformation of Coordinates from Geographic to Grid; Tables for the Computation of Convergence; Tables for the Computation of Scale Factor; and Powers of p.

1967-01-01

85

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

NASA Astrophysics Data System (ADS)

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

Powell, Kenneth G.

1995-10-01

86

A Cartesian Diver Experiment  

Microsoft Academic Search

MOST of us are familiar with the lecture-table experiment known as the Cartesian Diver. A variation of this is shown in Fig. 1a. In this apparatus the diver is replaced by a test-tube T floating upside down in the water, being buoyed up by just the right quantity of air, A. The tall jar is nearly filled with water, and

John Satterly

1928-01-01

87

Universal Transverse Mercator Grid Table for Latitudes 0-80 degrees Australian National Spheroid (Meters) Coordinates for 5-Minute Intersections.  

National Technical Information Service (NTIS)

This manual presents tables containing the Universal Transverse Mercator Grid coordinates of every 5-minute intersection of latitude and longitude for latitudes 0 degrees to 80 degrees on the Australian National Spheroid. Maps, published by the Army Map S...

1967-01-01

88

Hall MHD on Block-Adaptive Grids  

NASA Astrophysics Data System (ADS)

This proceedings paper is based on a much longer research paper that was published during the conference (Toth et al. 2008). We present a conservative second order accurate finite volume discretization of the magnetohydrodynamics equations including the Hall term on three dimensional block adaptive grids with Cartesian or generalized coordinates. Both explicit and implicit time integration schemes are developed. The parallel scaling and robustness are demonstrated by three dimensional simulations of planetary magnetospheres.

Tóth, G.; Ma, Y.-J.; Gombosi, T. I.

2009-04-01

89

Singularities as Features of Deformation Grids  

Microsoft Academic Search

Biological shape differences often are represented as diffeomorphisms of a Cartesian coordinate grid. This paper suggests\\u000a that their spatially discrete, localized features, for instance the details that suggest underlying developmental or pathological\\u000a processes, can often be identified with variants of the singularity (x,y) ? (x,x\\u000a 2\\u000a y + y\\u000a 3). This is an unfamiliar singularity, generic of codimension 1, at

Fred L. Bookstein

1998-01-01

90

Domination of generalized Cartesian products  

Microsoft Academic Search

The generalized prism ?G of G is the graph consisting of two copies of G, with edges between the copies determined by a permutation ? acting on the vertices of G. We define a generalized Cartesian product GH that corresponds to the Cartesian product G?H when ? is the identity, and the generalized prism when H is the graph K2.

S. Benecke; Christina M. Mynhardt

2010-01-01

91

Numerical modeling of conjugate heat transfer on complex geometries with diagonal Cartesian method. Part 1: Methods  

SciTech Connect

In this study, a diagonal Cartesian method for thermal analysis is developed for simulation of conjugate heat transfer over complex boundaries. This method uses diagonal line segments in addition to Cartesian coordinates. The velocity fields are also modeled using the diagonal Cartesian method. The transport equations are discretized with the finite analytic (FA) method. The current work is validated by simulating a rotated lid-driven cavity flow with conjugate heat transfer, and accurate results are obtained.

Lin, W.L.; Carlson, K.D.; Chen, C.J. [Florida A and M Univ., Tallahassee, FL (United States)]|[Florida State Univ., Tallahassee, FL (United States)

1999-05-01

92

Direct Numerical Simulation on a Cartesian Mesh of the Flow through a Tube Bundle  

NASA Astrophysics Data System (ADS)

In this paper, we present a three-dimensional direct numerical simulation (DNS) of a turbulent flow through a staggered tube bundle. The Navier-Stokes equations are discretized on a staggered Cartesian grid with the help of the finite-volume approach. The complex geometry of the tube bundle is implemented by the diagonal cartesian method (DCM). The advantage of this method, in comparison with body-fitted coordinate approaches, is that it leads to less complicated algorithms and, therefore, to more efficient computations. The principle of this method is described in this paper. Simulations of the flow through a tube bundle are carried out at Re=6000 on four different meshes with various grid spacings. Results of the simulations on the finest mesh are compared with the experimental data of Simonin and Barcouda [Measurements of fully developed turbulent flow across tube bundle. In 3ème Conférence Internationale sur les Applications de l'Anéemometrie Laser à la Mécanique des Fluides, 1986] and with the large-eddy simulations (LES) of Rollet-Miet et al. ["LES and RANS of turbulent flow in tube bundles", Int. J. Heat Fluid Flow, 20 (1999) pp. 241-254]. Based on this comparison we conclude that an accurate simulation of a flow through a tube bundle can be performed with the DCM.

Moulinec, C.; Pourquié, M. J. B. M.; Boersma, B. J.; Buchal, T.; Nieuwstadt, F. T. M.

2004-01-01

93

A convective-difference scheme using a general curvilinear coordinate grid for steady incompressible viscous flow problems  

Microsoft Academic Search

A numerical scheme for analyzing the steady two-dimensional incompressible viscous flow using a general curvilinear coordinate grid is proposed. In this scheme, the unsteady Navier-Stokes equations are solved by a convective-difference scheme using a staggered square grid in transformed space. An elliptic equation of pressure is solved by the Tchebyscheff SLOR method. The substantial derivative term in the convective-difference scheme

Yoshihisa Matsumoto; Hisaaki Daiguji

1992-01-01

94

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.

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

2010-01-01

95

Collision-Free Cartesian Trajectory Generation Using Raster Scanning and Genetic Algorithms  

Microsoft Academic Search

An algorithm for Cartesian trajectory generation by redundant robots in environments with obstacles is presented. The algorithm combines a raster scanning technique, genetic algorithms and functions for interpolation in the joint coordinates space in order to approximate a desired Cartesian curve by the robot's hand tip under maximum allowed position deviation. A raster scanning technique determines a minimal set of

Andreas C. Nearchou; Nikos A. Aspragathos

1998-01-01

96

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

97

Protective Relay Coordination for Micro-grid Operation Using Particle Swarm Optimization  

Microsoft Academic Search

With the increasing penetration of distribution generation (DG), micro-grid operation becomes an attractive and valuable option. In order for micro-grids to become a viable option, issues such as micro-grid control and protection must be addressed and well established. The paper focuses on micro-grid protection and proposes the use of directional overcurrent relays for protecting a micro-grid consisting of synchronous based

H. H. Zeineldin; E. F. El-Saadany; M. M. A. Salama

2006-01-01

98

Interconversion between truncated Cartesian and polar expansions of images.  

PubMed

In this paper, we propose an algorithm for lossless conversion of data between Cartesian and polar coordinates, when the data is sampled from a 2-D real-valued function (a mapping: R2 --> R) expressed as a particular kind of truncated expansion. We use Laguerre functions and the Fourier basis for the polar coordinate expression. Hermite functions are used for the Cartesian coordinate expression. A finite number of coefficients for the truncated expansion specifies the function in each coordinate system. We derive the relationship between the coefficients for the two coordinate systems. Based on this relationship, we propose an algorithm for lossless conversion between the two coordinate systems. Resampling can be used to evaluate a truncated expansion on the complementary coordinate system without computing a new set of coefficients. The resampled data is used to compute the new set of coefficients to avoid the numerical instability associated with direct conversion of the coefficients. In order to apply our algorithm to discrete image data, we propose a method to optimally fit a truncated expression to a given image. We also quantify the error that this filtering process can produce. Finally the algorithm is applied to solve the polar-Cartesian interpolation problem. PMID:17688200

Park, Wooram; Chirikjian, Gregory S

2007-08-01

99

Two-Liquid Cartesian Diver  

ERIC Educational Resources Information Center

It is quite easy to make a version of the well known Cartesian diver experiment that uses two immiscible liquids. This allows students to test their knowledge of density and pressure in explaining the diver's behaviour. Construction details are presented here together with a mathematical model to explain the observations.

Planinsic, G.; Kos, M.; Jerman, R.

2004-01-01

100

G-lambda: Coordination of a Grid scheduler and lambda path service over GMPLS  

Microsoft Academic Search

Abstract At iGrid2005, we conducted a live demonstration where our Grid scheduling system co-allocated computing and network ,resources with advance reservation through Web services interfaces using the Grid Resource Scheduler (GRS), the Network Resource Management System (NRM), which is capable of GMPLS network resource management, and a GMPLS-based network test-bed, for the first time. The goal of the G-lambda project

Atsuko Takefusa; Michiaki Hayashi; Naohide Nagatsu; Hidemoto Nakada; Tomohiro Kudoh; Takahiro Miyamoto; Tomohiro Otani; Hideaki Tanaka; Masatoshi Suzuki; Yasunori Sameshima; Wataru Imajuku; Masahiko Jinno; Yoshihiro Takigawa; Shuichi Okamoto; Yoshio Tanaka; Satoshi Sekiguchi

2006-01-01

101

A multigrid solver for the steady incompressible Navier-Stokes equations on curvilinear coordinate systems  

SciTech Connect

A multigrid solver for the steady incompressible Navier-Stokes equations on a curvilinear grid is constructed. The Cartesian velocity components are used in the discretization of the momentum equations. A staggered, geometrically symmetric distribution of velocity components is adopted which eliminates spurious pressure oscillations and facilitates the transformation between Cartesian and co-or contra-variant velocity components. The SCGS (symmetrical collective Gauss-Seidel) relaxation scheme proposed by Vanka on a Cartesian grid is extended to this case to serve as the smoothing procedure of the multigrid solver, in both [open quotes]box[close quotes] and [open quotes]box-line[close quotes] versions. Due to the symmetric distribution of velocity components of this scheme, the convergence rate and numerical accuracy are not affected by grid orientation, in contrast to a scheme proposed in the literature in which difficulties arise when the grid lines turn 90 from the Cartesian coordinates. Some preliminary numerical experiences with this scheme are presented. 13 refs., 15 figs., 1 tab.

Lin-Bo Zhang (State Key Lab. of Scientific and Engineering Computing, Beijing (China))

1994-07-01

102

A tensor product B-spline method for numerical grid generation  

SciTech Connect

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

Manke, J.

1989-10-01

103

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

104

Using the pseudospectral method on curved grids for 2D elastic forward modeling  

SciTech Connect

When applying the conventional Fourier pseudospectral method (FSM) on a Cartesian grid that has a sufficient size to propagate a pulse, spurious diffractions from the staircase representation of the curved interfaces appear in the wavefield. It is demonstrated that these non-physical diffractions can be eliminated by using curved grids that conform to all the interfaces of the subsurface. Methods for solving the 2D acoustic wave equation using such curved grids have been published previously by the authors. Here the extensions to the full 2D elastic wave equations are presented. The curved grids are generated by using the so-called multiblock strategy which is a well-known concept in computational fluid dynamics. In principle the subsurface is divided into a number of contiguous subdomains. A separate grid is generated for each subdomain patching the grid lines across domain boundaries to obtain a globally continuous grid. Using this approach, even configurations with pinch outs can be handled. The curved grid is taken to constitute a generalized curvilinear coordinate system. Thus, the elastic equations have to be written in a curvilinear frame before applying the numerical scheme. The method implies that twice the number of spatial derivatives have to be evaluated compared to the conventional FSM on a Cartesian grid. However, it is demonstrated that the extra terms are more than compensated for by the fewer grid points needed in the curved approach.

Nielsen, P. [Haldor Topsoe A/S, Lyngby (Denmark); If, F. [COWIconsult, Lyngby (Denmark); Berg, P. [Danish Hydraulic Inst., Horsholm (Denmark); Skovgaard, O. [Technical Univ. of Denmark, Lyngby (Denmark). Mathematical Inst.

1995-04-01

105

Internal-to-Cartesian back transformation of molecular geometry steps using high-order geometric derivatives.  

PubMed

In geometry optimizations and molecular dynamics calculations, it is often necessary to transform a geometry step that has been determined in internal coordinates to Cartesian coordinates. A new method for performing such transformations, the high-order path-expansion (HOPE) method, is here presented. The new method treats the nonlinear relation between internal and Cartesian coordinates by means of automatic differentiation. The method is reliable, applicable to any system of internal coordinates, and computationally more efficient than the traditional method of iterative back transformations. As a bonus, the HOPE method determines not just the Cartesian step vector but also a continuous step path expressed in the form of a polynomial, which is useful for determining reaction coordinates, for integrating trajectories, and for visualization. PMID:23703109

Rybkin, Vladimir V; Ekström, Ulf; Helgaker, Trygve

2013-05-23

106

Coordination  

NSDL National Science Digital Library

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

Olivia Worland (Purdue University;Biological Sciences)

2008-06-06

107

The structure of integral dimensions: contrasting topological and Cartesian representations.  

PubMed

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 coordinate system, just as with spaces defined by separable dimensions. This approach entails a rich geometrical structure that has never been questioned but may not be psychologically meaningful for integral dimensions. In particular, Cartesian models carry a notion of orthogonality of component dimensions, such that if 1 dimension is diagnostic for a classification or discrimination task, another can be selected as uniquely irrelevant. This article advances an alternative model in which integral dimensions are characterized as topological spaces. The Cartesian and topological models are tested in a series of experiments using the perceptual-learning phenomenon of dimension differentiation, whereby discrimination training with integral-dimension stimuli can induce an analytic representation of those stimuli. Under the present task design, the 2 models make contrasting predictions regarding the analytic representation that will be learned. Results consistently support the Cartesian model. These findings indicate that perceptual representations of integral dimensions are surprisingly structured, despite their holistic, unanalyzed nature. PMID:22799263

Jones, Matt; Goldstone, Robert L

2012-07-16

108

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

SciTech Connect

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

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

2008-11-25

109

Sink or Swim: The Cartesian Diver.  

ERIC Educational Resources Information Center

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

Pinkerton, K. David

2001-01-01

110

Fuzzy logic based coordinated controller for wind\\/battery\\/IDSMS hybrid micro-grid power system  

Microsoft Academic Search

This paper presents the simulation analysis of wind power, battery energy storage system (BESS), and intelligent demand side management system (IDSMS) hybrid micro-grid power system to improve the power quality of the hybrid generation system. A fuzzy logic based control strategy is proposed to regulate the frequency fluctuation and the battery stage of charge (SOC) at expected conditions. As a

Xiangjun Li; Dong Hui; Xiaokang Lai; Minggao Ouyang; Yong Min

2010-01-01

111

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

PubMed

This paper sets out to explore the effects of voxel resolution, from 2 mm down to 0.1 mm for Cartesian co-ordinates and the differences between Cartesian and spherical polar co-ordinates for a standardized test-bed model of the eye. This model was taken from the work of Yoriyaz et al (2005 Radiat. Prot. Dosim. 115 316-9) who have developed a detailed geometric description of the eye including choroid, retina, sclera, lens, cornea, anterior chamber, vitreous humour and optic nerve for ophthalmic brachytherapy. The spherical co-ordinate model has radial and angular steplengths of 0.1 mm and 0.25°, respectively. The current density averaged over 1 cm(2) and the 99th percentile value of the induced electric field have been calculated in the retina and central nervous system for uniform magnetic fields. The Cartesian co-ordinate calculations proceed in a sequence of grids at 2, 1, 0.5, 0.2 and 0.1 mm resolution with the potentials from the previous calculation at a coarser grid providing the boundary conditions on the finer grid. The 0.2 mm grid provides the boundary conditions for the spherical polar calculations. Comparisons are made with the International Commission on Non-Ionizing Radiation Protection reference levels. PMID:21725142

Dimbylow, Peter

2011-07-01

112

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

NASA Astrophysics Data System (ADS)

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

Dimbylow, Peter

2011-07-01

113

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

114

Coordination of active and reactive distributed resources in a smart grid  

Microsoft Academic Search

The authors present a methodology for assessing centralized control of active and reactive distributed resources in a smart distribution grid. The methodology is based on three- phase optimal power flow and is able to deal properly with unbalanced conditions and both single-phase and three-phase control resources. Single-phase resources that can be exploited by means of this approach are domestic loads,

Marco Bronzini; Sergio Bruno; Massimo La Scala; Roberto Sbrizzai

2011-01-01

115

Dynamic modeling for LES of turbulent jet mixing in spherical coordinates without explicit test filtering  

NASA Astrophysics Data System (ADS)

The dynamic model for LES requires explicit test filtering of grid-resolved quantities to compute model coefficients. On a regular, Cartesian grid, the test filter at any location in the computational domain is usually implemented by taking a local average of quantities at neighboring grid points. In complex flows involving irregular or unstructured grids, or simulations performed in non-Cartesian coordinate systems, the test filtering operation is less intuitively interpreted. Another approach (Chester, Charlette, Meneveau (2001)) approximates test filtering by expanding grid-resolved quantities locally in a truncated Taylor series. In this work, we implement this test filter approximation in LES of scalar mixing in a round turbulent jet. This approach provides a more robust and consistent definition of the test filter on the spherical coordinate grid used in the simulation, and allows more accurate determination of the dynamic coefficient for the subgrid scale (SGS) models. Previous studies have shown the resolved-scale scalar field to be particularly sensitive to the numerics of the simulation, including the spatial discretization scheme, filter width, as well as the amount of `backscattering' allowed by the subgrid scalar flux model. We aim to determine how the evolution of the dynamic coefficients for the SGS stress and SGS scalar flux models influences the mixing properties of the simulated turbulent jet, at both the resolved and subgrid scales, and how closely the resulting velocity and scalar fields correlate with experimental measurements.

Sun, O. S.; Su, L. K.; Burton, T. M.

2006-11-01

116

Development of accurate standardized algorithms for conversion between SRP grid coordinates and latitude/longitude  

SciTech Connect

The Savannah Rive Plant (SRP) is a nuclear production facility operated by E.I. du Pont de Nemours and Co. for the United States Department of Energy. SRP is located along the Savannah River in South Carolina. Construction of SRP began in the early 1950`s. At the time the plant was built, a local coordinate system was developed to assist in defining the locations of plant facilities. Over the years, large quantities of data have been developed using ``SRP Coordinates.`` These data include: building locations, plant boundaries, environmental sampling locations, waste disposal area locations, and a wide range of other geographical information. Currently, staff persons at SRP are organizing these data into automated information systems to allow more rapid, more robust and higher quality interpretation, interchange and presentation of spatial data. A key element in this process is the ability to incorporate outside data bases into the systems, as well as to share SRP data with interested organizations outside as SRP. Most geographical information outside of SRP is organized using latitude and longitude. Thus, straightforward, accurate and consistent algorithms to convert SRP Coordinates to/from latitude and longitude are needed. Appropriate algorithms are presented in this document.

Looney, B.B.; Marsh, J.T. Jr.; Hayes, D.W.

1987-10-12

117

Irreducible Cartesian tensor expansions of scalar fields  

Microsoft Academic Search

It is shown how a scalar function V (‖R + ?ni=1 ai‖) of a sum of n + 1 vectors can be expanded as a multiple Cartesian tensor series in the vectors ai. This expansion is a rearrangement of the multiple Taylor series expansion of such a function. In order to prove the fundamental theorem, Eq. (3.1) below, generalized Cartesian

H. Moraal

1975-01-01

118

Metric Coordinate Systems  

Microsoft Academic Search

Coordinate systems are defined on general metric spaces with the purpose of generalizing vector fields on a manifold. Conversion formulae are available between metric and Cartesian coordinates on a Hilbert space. Nagumo's Invariance Theorem is invoked to prove the analogue of the classical Cauchy-Lipschitz Theorem for vector fields on a locally compact coordinatized space. A metric space version of Nagumo's

Craig Calcaterra; Axel Boldt; Michael Green; David Bleecker

2002-01-01

119

The Moviegoer's Cartesian Theater: Moviegoing as Walker Percy's Metaphor for the Cartesian Mind  

Microsoft Academic Search

Binx Bolling is the moviegoing protagonist of The Moviegoer (1961), Walker Percy's first novel. In an interview, Percy once referred to Binx as a “victim” of Descartes. Did Percy intend some connection between Binx's moviegoing and his unfortunate, Cartesian heritage? In this essay, I argue that Percy used Binx's moviegoing as a metaphor for his having a Cartesian mind. As

Woods Nash

2011-01-01

120

Lagrange-Galerkin Methods on Spherical Geodesic Grids: The Shallow Water Equations  

NASA Astrophysics Data System (ADS)

The weak Lagrange-Galerkin finite element method for the 2D shallow water equations on the sphere is presented. This method offers stable and accurate solutions because the equations are integrated along the characteristics. The equations are written in 3D Cartesian conservation form and the domains are discretized using linear triangular elements. The use of linear triangular elements permits the construction of accurate (by virtue of the second-order spatial and temporal accuracies of the scheme) and efficient (by virtue of the less stringent CFL condition of Lagrangian methods) schemes on unstructured domains. Using linear triangles in 3D Cartesian space allows for the explicit construction of area coordinate basis functions thereby simplifying the calculation of the finite element integrals. The triangular grids are constructed by a generalization of the icosahedral grids that have been typically used in recent papers. An efficient searching strategy for the departure points is also presented for these generalized icosahedral grids which involves very few floating point operations. In addition a high-order scheme for computing the characteristic curves in 3D Cartesian space is presented: a general family of Runge-Kutta schemes. Results for six test cases are reported in order to confirm the accuracy of the scheme.

Giraldo, Francis X.

2000-05-01

121

The Cartesian method for solving partial differential equations in spherical geometry  

Microsoft Academic Search

Cartesian coordinates are used to solve the nonlinear shallow-water equations on the sphere. The two-dimensional equations, in spherical coordinates, are first embedded in a three-dimensional system in a manner that preserves solutions of the two-dimensional system. That is, solutions of the three-dimensional system, with appropriate initial conditions, also solve the two-dimensional system on the surface of the sphere. The higher

Paul N. Swarztrauber; David L. Williamson; John B. Drake

1998-01-01

122

Multi-stencils fast marching methods: a highly accurate solution to the eikonal equation on cartesian domains.  

PubMed

A wide range of computer vision applications require an accurate solution of a particular Hamilton- Jacobi (HJ) equation, known as the Eikonal equation. 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 multi-stencils fast marching (MSFM), which computes the solution at each grid point by solving the Eikonal equation along several stencils and then picks the solution that satisfies the upwind condition. The stencils are centered at each grid point and cover its entire nearest neighbors. In 2D space, 2 stencils cover the 8-neighbors of the point, while in 3D space, 6 stencils cover its 26-neighbors. For those stencils that are not aligned with the natural coordinate system, the Eikonal equation is derived using directional derivatives and then solved using higher order finite difference schemes. The accuracy of the proposed method over the state-of-the-art FMM-based techniques has been demonstrated through comprehensive numerical experiments. PMID:17627044

Hassouna, M Sabry; Farag, A A

2007-09-01

123

A high-resolution mapped grid algorithm for compressible multiphase flow problems  

NASA Astrophysics Data System (ADS)

We describe a simple mapped-grid approach for the efficient numerical simulation of compressible multiphase flow in general multi-dimensional geometries. The algorithm uses a curvilinear coordinate formulation of the equations that is derived for the Euler equations with the stiffened gas equation of state to ensure the correct fluid mixing when approximating the equations numerically with material interfaces. A ?-based and a ?-based model have been described that is an easy extension of the Cartesian coordinates counterpart devised previously by the author [30]. A standard high-resolution mapped grid method in wave-propagation form is employed to solve the proposed multiphase models, giving the natural generalization of the previous one from single-phase to multiphase flow problems. We validate our algorithm by performing numerical tests in two and three dimensions that show second order accurate results for smooth flow problems and also free of spurious oscillations in the pressure for problems with interfaces. This includes also some tests where our quadrilateral-grid results in two dimensions are in direct comparisons with those obtained using a wave-propagation based Cartesian grid embedded boundary method.

Shyue, K.-M.

2010-11-01

124

A Supra-Convergent Finite Dierence Scheme for the Variable Coecient Poisson Equation on Fully Adaptive Grids  

Microsoft Academic Search

We introduce a method for solving the variable coecient Poisson equation on fully adaptive Cartesian grids that yields second order accuracy for the solutions and their gradients. We employ quadtree (in 2D) and octree (in 3D) data structures as an ecient means to represent the Cartesian grid, allowing for constraint-free grid generation. The schemes take advantage of sampling the solution

Chohong Min; Frédéric Gibou; Hector D. Ceniceros

125

A generalized coordinate ocean model and a comparison of the bottom boundary layer dynamics in terrain-following and in z-level grids  

Microsoft Academic Search

Sensitivity studies with a new generalized coordinate ocean model are performed in order to compare the behavior of bottom boundary layers (BBLs) when terrain-following (sigma or combined sigma and z-level) or z-level vertical grids are used, but most other numerical aspects remain unchanged. The model uses a second-order turbulence closure scheme that provides surface and BBL mixing and results in

Tal Ezer; George L. Mellor

2004-01-01

126

Maintain rigid structures in Verlet based Cartesian molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

An algorithm is presented to maintain rigid structures in Verlet based Cartesian molecular dynamics (MD) simulations. After each unconstrained MD step, the coordinates of selected particles are corrected to maintain rigid structures through an iterative procedure of rotation matrix computation. This algorithm, named as SHAPE and implemented in CHARMM program suite, avoids the calculations of Lagrange multipliers, so that the complexity of computation does not increase with the number of particles in a rigid structure. The implementation of this algorithm does not require significant modification of propagation integrator, and can be plugged into any Cartesian based MD integration scheme. A unique feature of the SHAPE method is that it is interchangeable with SHAKE for any object that can be constrained as a rigid structure using multiple SHAKE constraints. Unlike SHAKE, the SHAPE method can be applied to large linear (with three or more centers) and planar (with four or more centers) rigid bodies. Numerical tests with four model systems including two proteins demonstrate that the accuracy and reliability of the SHAPE method are comparable to the SHAKE method, but with much more applicability and efficiency.

Tao, Peng; Wu, Xiongwu; Brooks, Bernard R.

2012-10-01

127

Material translations in the Cartesian brain  

Microsoft Academic Search

This article reexamines the controversial doctrine of the pineal gland in Cartesian psychophysiology. It argues initially that Descartes’ combined metaphysics and natural philosophy yield a distinctly human subject who is rational, willful, but also a living and embodied being in the world, formed in the union and through the dynamics of the interaction between the soul and the body. However,

Nima Bassiri

128

Strong perfectness of the generalized Cartesian product of graphs  

Microsoft Academic Search

In this paper we give a necessary and sufficient condition for the generalized Cartesian product to be strongly perfect. The special case of the result is the known theorem concerning the Cartesian product of two graphs.

Maria Kwasnik; Alina Szelecka

1997-01-01

129

Newtonian molecular dynamics in general curvilinear internal coordinates  

Microsoft Academic Search

A simple formulation of Newtonian molecular dynamics in general internal coordinates is given. Our equation for the internal acceleration does not require the transformation matrix from internal to Cartesian coordinates, only the much simpler first and second-order transformation from Cartesians to internals. The formulation has a simple, common general expression for the centrifugal\\/Coriolis contribution to the internal acceleration. The method

P. Pulay; B. Paizs

2002-01-01

130

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

131

Graphing and the Coordinate Plane  

NSDL National Science Digital Library

This lesson is designed to introduce students to graphing coordinates and lines in the Cartesian coordinate plane. This lesson provides links to discussions and activities related to graphing as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

132

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

133

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

134

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

PubMed

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

Pilly, Praveen K; Grossberg, Stephen

2012-01-30

135

How Do Spatial Learning and Memory Occur in the Brain? Coordinated Learning of Entorhinal Grid Cells and Hippocampal Place Cells  

Microsoft Academic Search

Spatial learning and memory are important for navigation and formation of episodic memories. The hippocampus and medial entorhinal cortex (MEC) are key brain areas for spatial learning and memory. Place cells in hippocampus fire whenever an animal is located in a specific region in the environment. Grid cells in the superficial layers of MEC provide inputs to place cells and

Praveen K. Pilly; Stephen Grossberg

136

How Do Spatial Learning and Memory Occur in the Brain? Coordinated Learning of Entorhinal Grid Cells and Hippocampal Place Cells  

Microsoft Academic Search

Spatial learning and memory are important for navigation and formation of episodic memories. The hippocampus and medial entorhinal cortex (MEC) are key brain areas for spatial learning and memory. Place cells in hippocampus fire whenever an animal is located in a specific region in the environment. Grid cells in the superficial layers of MEC provide inputs to place cells and

Praveen K. Pilly; Stephen Grossberg

2012-01-01

137

a Tensor Product B-Spline Method for Numerical Grid Generation  

NASA Astrophysics Data System (ADS)

We present a tensor product B-spline method for fast elliptic grid generation. The Cartesian coordinate functions for a block are represented as a sum of tensor product B-spline basis functions defined on the computational domain for the block. The tensor product B-spline basis functions are constructed so that the basis functions and their first partials are continuous on the computational domain for the block. The coordinate functions inherit this smoothness: a grid computed by evaluating the coordinate 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 elliptic grid generation equations using collocation. This assures that the computed grid has the smoothness and resolution expected for an elliptic grid with appropriate control. The collocation equations are solved with an ADI solution algorithm analogous to the ADI solution algorithm for the finite difference method. The speed of the method derives from the smoothness of the B-spline basis functions; in effect, a fine grid in the physical domain is obtained by constructing a smooth expansion of the coordinate functions on a coarse grid of knots in the computational domain. Thus the tensor product B-spline method will be faster than the finite difference method, if a sufficiently smooth fine grid in the physical domain can be obtained for an appropriately coarse grid of knots in the computational domain. We implemented the tensor product B-spline method in a multi-block grid code for testing and comparison to the finite difference method. For the grid generation problems studied the tensor product B-spline method was 2 to 13 times faster than the finite difference method. We also introduced and tested in a multi-block grid code two new techniques for automatic analysis and processing of block interfaces in arbitrary multi-block grids: a graphical method to analyze block interfaces and an interface block method with overlap conditions to process block interfaces.^1 ftn ^1This research was supported in part by Boeing Computer Services Co., Seattle, WA, by AFSOR -86-0154 and by DOE-627815.

Manke, Joseph Walter

138

General Noncommuting Curvilinear Coordinates and Fluid Mechanics  

Microsoft Academic Search

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

S. A. Alavi

2006-01-01

139

General noncommuting curvilinear coordinates and fluid Mechanics  

Microsoft Academic Search

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

S. A. Alavi

2006-01-01

140

A breakthrough in neuroscience needs a “Nebulous Cartesian System”  

Microsoft Academic Search

The Cartesian System is a fundamental conceptual and analytical framework related and interwoven with the concept and applications of Newtonian Dynamics. In order to analyze quantum processes physicist moved to a Probabilistic Cartesian System in which the causality principle became a probabilistic one. This means the trajectories of particles (obeying quantum rules) can be described only with the concept of

Erol Ba?ar; Bahar Güntekin

2007-01-01

141

A High-Resolution Rotated Grid Method for Conservation Laws with Embedded Geometries  

Microsoft Academic Search

We develop a second-order rotated grid method for the approximation of time de- pendent solutions of conservation laws in complex geometry using an underlying Cartesian grid. Stability for time steps adequate for the regular part of the grid is obtained by increasing the domain of dependence of the numerical method near the embedded boundary by constructing h-boxes at grid cell

Christiane Helzel; Marsha J. Berger; Randall J. LeVeque

2005-01-01

142

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

Tao, Liang; Rescigno, T. N. [Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720 (United States); McCurdy, C. W. [Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720 (United States); Departments of Applied Science and Chemistry, University of California, Davis, California 95616 (United States)

2010-08-15

143

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

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

Guest inclusion and interpenetration tuning of Cd(II)/Mn(II) coordination grid networks assembled from a rigid linear diimidazole Schiff base ligand.  

PubMed

Cd(II)/Mn(II) coordination grid networks containing large meshes have been assembled from a long rigid ligand, 2,5-bis(4'-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and M(CF(3)SO(3))(2) (M = Cd and Mn) salts, and their interpenetration change upon guest inclusion has been investigated with a series of aromatic molecules. Without guest molecules, the grid networks are triply interpenetrated to form closely packed layer structures [M(ImBNN)(2)(CF(3)SO(3))(2)](n) (M = Cd (1) and Mn (2)), but when guest molecules are introduced, the triply interpenetrated frameworks are changed to doubly interpenetrated ones with the inclusion of various aromatic molecules, namely, {[M(ImBNN)(2)(CF(3)SO(3))(2)] superset guest}(n) (M = Cd, guest = o-xylene (3), naphthalene (4), phenanthrene (5), and pyrene (6); M = Mn, guest = benzene (7), p-xylene (8), naphthalene (9), phenanthrene (10), and pyrene (11)). These complexes have been characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, and IR spectra. The guest-inclusion/desorption behaviors of representative complexes have been studied by thermogravimetric analyses and (1)H NMR measurements. The grid networks display strong preference for aromatic guest inclusion, but less selectivity toward shape and size difference. Tuning of network interpenetration from 3-fold to 2-fold has been successfully achieved through the introduction of guest molecules, when the network displays flexibility to change cavity size to match the guest molecules. PMID:19035763

Wang, Qing; Zhang, Jianyong; Zhuang, Chun-Feng; Tang, Yu; Su, Cheng-Yong

2009-01-01

146

Generalized Curvilinear Coordinates in Hybrid and Electromagnetic Codes  

Microsoft Academic Search

This paper describes the elements for writing hybrid and electromagnetic plasma simulation codes in generalized curvilinear coordinates. The coordinate system is described by a table giving the three-dimensional Cartesian coordinate positions of a structured curvilinear coordinate mesh. The paper shows how to calculate the ge- ometric coefficients of the differential operators describing the electromagnetic field and how to calculate the

Daniel W. Swift

147

Relativistic trajectory equations for charged particles in general orthogonal curvilinear coordinates  

Microsoft Academic Search

The relativistic trajectory equations are given in orthogonal curvilinear coordinates for charged particles moving in arbitrary electrostatic and magnetic fields without restrictions. The trajectory equations for Cartesian and cylindrical coordinates are presented as special cases.

M. Szilagyi

1986-01-01

148

A Coupled Model For The North Sea and The Baltic Sea With General Vertical Coordinates  

NASA Astrophysics Data System (ADS)

A new three-dimensional baroclinic circulation model, originally developed for sim- ulating tidal flow in wadden sea areas, is applied for reproducing the annual cycle in the North Sea and the Baltic Sea with realistic forcing. This so-called General Estuarine Transport Model (GETM), which is based on the primitive equations, pro- vides a choice between several high-order turbulence closure models since the General Ocean Turbulence Model (GOTM) is linked to GETM. The main numerical features of GETM are the mode splitting technique allowing for different time steps for the barotropic and the baroclinic mode, the terrain-following general vertical coordinate providing horizontally homogeneous layer thicknesses near the surface and the bed, and positive-definite high-order advection schemes based on the Total Variation Di- minishing (TVD) principle. In the horizontal, curvilinear grids may be used, which includes Cartesian and spherical coordinates as special cases. Several annual simulations on Cartesian grids with horizontal resolutions of 3 nm and 6 nm will be presented. At the open boundaries, tidal elevations from the TOPEX- POSEIDON data set, and temperature and salinity profiles from the monthly mean climatology (Janssen et al. 1999) are used. As surface forcing meteorological parame- ters from the ECMWF re-analysis are used. River run-off data are provided by SMHI. The monthly mean climatology is also used for initial conditions for temperature and salinity. The advantages and drawbacks of this approach will be discussed. Here, the focus will be on the use of the general vertical coordinate as contrasted to the more common geopotential coordinate and the coordinate.

Burchard, H.; Bolding, K.; Hansen, C.; Mattsson, J.

149

Visualizing flow over curvilinear grid surfaces using line integral convolution  

Microsoft Academic Search

Line Integral Convolution (LIC), introduced by Cabral and Leedom in Siggraph '93, is a powerful technique for imaging and animating vector fields. We extend the LIC paradigm in three ways:1. The existing technique is limited to vector fields over a regular Cartesian grid. We extend it to vector fields over parametric surfaces, specifically those found in curvilinear grids, used in

Lisa K. Forssell

1994-01-01

150

Simulation of three-wave interactions for focused beams with an assistant curvilinear coordinate system  

NASA Astrophysics Data System (ADS)

We present a numerical model to deal with optical nonlinear processes at a strong focusing situation where general methods possibly fail to work. We find a special curvilinear coordinate system through which a new paraxial wave equation set is developed and its eigenmode transmission solutions are derived. On the basis of the wave equations, a detailed algorithm for second-harmonic generation is proposed with the Fourier-space method. Numerical results in non-walk-off and walk-off cases show that the new model can handle wave interactions on the strong focusing L/b>>1 condition within a relative small sampling grid, with which traditional methods will lose efficiency, and can provide unique features in comparison with the model in a Cartesian coordinate system. Concrete assessment of the new model is rendered by error analysis.

Huang, Jin Jer; Hu, Xiao Yong; Ren, De Ming; Qu, Yan Chen

2006-07-01

151

Orientation domains: A mobile grid clustering algorithm with spherical corrections  

NASA Astrophysics Data System (ADS)

An algorithm has been designed and tested which was devised as a tool assisting the analysis of geological structures solely from orientation data. More specifically, the algorithm was intended for the analysis of geological structures that can be approached as planar and piecewise features, like many folded strata. Input orientation data is expressed as pairs of angles (azimuth and dip). The algorithm starts by considering the data in Cartesian coordinates. This is followed by a search for an initial clustering solution, which is achieved by comparing the results output from the systematic shift of a regular rigid grid over the data. This initial solution is optimal (achieves minimum square error) once the grid size and the shift increment are fixed. Finally, the algorithm corrects for the variable spread that is generally expected from the data type using a reshaped non-rigid grid. The algorithm is size-oriented, which implies the application of conditions over cluster size through all the process in contrast to density-oriented algorithms, also widely used when dealing with spatial data. Results are derived in few seconds and, when tested over synthetic examples, they were found to be consistent and reliable. This makes the algorithm a valuable alternative to the time-consuming traditional approaches available to geologists.

Mencos, Joana; Gratacós, Oscar; Farré, Mercè; Escalante, Joan; Arbués, Pau; Muñoz, Josep Anton

2012-12-01

152

A fully nonlinear Boussinesq model in generalized curvilinear coordinates  

Microsoft Academic Search

Based on the fully nonlinear Boussinesq equations in Cartesian coordinates, the equations in generalized coordinates are derived to adapt computations to irregularly shaped shorelines, such as harbors, bays and tidal inlets, and to make computations more efficient in large near-shore regions. Contravariant components of velocity vectors are employed in the derivation instead of the normal components in curvilinear coordinates or

Fengyan Shi; Robert A. Dalrymple; James T. Kirby; Qin Chen; Andrew Kennedy

2001-01-01

153

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

154

Coordinate Conversion and Tracking for Very Long Range Radars  

Microsoft Academic Search

The problem of tracking with very long range radars is studied in this paper. First, the measurement conversion from a radar's r-u-v coordinate system to the Cartesian coordinate system is discussed. Although the nonlinearity of this coordinate transformation appears insignificant based on the evaluation of the bias of the converted measurements, it is shown that this nonlinearity can cause significant

X. Tian; Y. Bar-Shalom

2009-01-01

155

A new (cartesian) reaction path model for dynamics in polyatomic systems, with application to H-atom transfer in malonaldehyde  

SciTech Connect

A new kind of reaction path model for describing reactions in polyatomic molecular systems is presented, one which is based on the cartesian coordinates of the atoms. Not only does this lead to a simpler treatment of the interaction between the )openreverse arrowquotes)system)closereverse arrowquotes) (i.e., the reaction coordinate) and the )openreverse arrowquotes)bath)closereverse arrowquotes) (the other degrees of freedom) than earlier reaction path models based on the (curvilinear) steepest reaction path, but in many cases it also provides a more natural description of the dynamics. The resulting Hamiltonian has the standard form of a cartesian )openreverse arrowquotes)system)closereverse arrowquotes) linearly coupled to a harmonic )openreverse arrowquotes)bath)closereverse arrowquotes), the dynamics of which is treated in this paper by the basis set method of Makri and Miller. Application to a model of H-atom transfer in malonaldehyde shows that the overall approach - both the cartesian reaction path model and the basis set method treatment of the dynsmics - is quite successful. 20 refs., 1 tab.

Ruf, B.A.; Miller, W.H.

1987-08-01

156

``Yin-Yang grid'': An overset grid in spherical geometry  

NASA Astrophysics Data System (ADS)

A new kind of overset grid, named Yin-Yang grid, for spherical geometry is proposed. The Yin-Yang grid is composed of two identical component grids that are combined in a complemental way to cover a spherical surface with partial overlap on their boundaries. Each component grid is a low-latitude part of the latitude-longitude grid. Therefore the grid spacing is quasi-uniform, and the metric tensors are simple and analytically known. One can directly apply mathematical and numerical resources that have been written in the spherical polar coordinates or latitude-longitude grid. The complemental combination of the two identical component grids enables us to make efficient and concise programs. Simulation codes for geodynamo and mantle convection simulations using finite difference scheme based on the Yin-Yang grid are developed and tested. The Yin-Yang grid is suitable for massively parallel computers.

Kageyama, Akira; Sato, Tetsuya

2004-09-01

157

Trajectory modelling and teaching of robots under Cartesian path control  

Microsoft Academic Search

This paper gives an approach to the description and modelling of the most widely spread trajectories in modern technology by means of minimum number of stored base positions and orientations. The teaching process of robots under Cartesian path control is discussed and input data for the succession of action, for position, orientation and velocity of the end link (tool or

M. D. MARKOV; V. B. ZAMANOV; D. N. NENCHEV

1983-01-01

158

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

159

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

160

Vertex and edge PI indices of Cartesian product graphs  

Microsoft Academic Search

The Padmakar–Ivan (PI) index of a graph G is the sum over all edges uv of G of the number of edges which are not equidistant from u and v. In this paper, the notion of vertex PI index of a graph is introduced. We apply this notion to compute an exact expression for the PI index of Cartesian product

M. H. Khalifeh; H. Yousefi-azari; A. R. Ashrafi

2008-01-01

161

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

162

The Cartesian cogito , epistemic logic and neuroscience: Some surprising interrelations  

Microsoft Academic Search

One cannot discuss contemporary philosophy of mind without the ghost of Descartes skulking around in the shadows. And one cannot understand Descartes without understanding his famous cogito insight, put forward for the first time publicly 350 years ago? Twenty-five years ago I showed what the nerve of the Cartesian insight is. 2 Descartes is not inferring sum from cogito, but

Jaakko Hintikka

1990-01-01

163

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

164

Rupture Dynamics Simulation for Non-Planar fault by a Curved Grid Finite Difference Method  

NASA Astrophysics Data System (ADS)

We first implement the non-staggered finite difference method to solve the dynamic rupture problem, with split-node, for non-planar fault. Split-node method for dynamic simulation has been used widely, because of that it's more precise to represent the fault plane than other methods, for example, thick fault, stress glut and so on. The finite difference method is also a popular numeric method to solve kinematic and dynamic problem in seismology. However, previous works focus most of theirs eyes on the staggered-grid method, because of its simplicity and computational efficiency. However this method has its own disadvantage comparing to non-staggered finite difference method at some fact for example describing the boundary condition, especially the irregular boundary, or non-planar fault. Zhang and Chen (2006) proposed the MacCormack high order non-staggered finite difference method based on curved grids to precisely solve irregular boundary problem. Based upon on this non-staggered grid method, we make success of simulating the spontaneous rupture problem. The fault plane is a kind of boundary condition, which could be irregular of course. So it's convinced that we could simulate rupture process in the case of any kind of bending fault plane. We will prove this method is valid in the case of Cartesian coordinate first. In the case of bending fault, the curvilinear grids will be used.

Zhang, Z.; Zhu, G.; Chen, X.

2011-12-01

165

Topological coordinates for deformed nanotubes  

NASA Astrophysics Data System (ADS)

Starting from the topological arrangement of carbon atoms an algorithm is given for the construction of nanotube Cartesian coordinates. The final relaxed structures were obtained by a molecular mechanics calculation where the carbon-carbon interactions were supposed only between neighboring atoms of the initial tiling. In a given tiling we obtained toroidal or helical structures depending on the special position of the super cell parallelogram.

László, István; Rassat, André

2003-10-01

166

COLORMAPS_COORDS: Octave functions for colormaps and coordinate system conversion  

Microsoft Academic Search

A variety of M-files for use in Octave providing colormaps and coordinate system converters (RGB-HSV, Cartesian-polar-spherical). Revised to include new functions delaunay, imhist, imadjust, mat2gray, pink.

Kai Habel

2000-01-01

167

Grid Kids  

NSDL National Science Digital Library

In this geography activity, learners use grid lines to find exact locations on a map. Learners also reflect on how creating a map helps them think about their special place in the world in new ways. They will explore key terms including coordinates, latitude, and longitude and play a fun game using their handmade maps. This activity is featured on pp.13-16 (part of a lesson that begins on page 8) of the "National Geographic MAPS: Tools for Adventure" unit of study for grades 3-5. Note: learners should complete the preceding activity "Picture Your World" on pp.10-12 before starting this activity.

Indianapolis, The C.; Society, National G.

2006-01-01

168

Polar versus Cartesian velocity models for maneuvering target tracking with IMM  

NASA Astrophysics Data System (ADS)

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

Laneuville, Dann

169

Equipartition Principle for Internal Coordinate Molecular Dynamics.  

PubMed

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

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

2012-07-01

170

Equipartition Principle for Internal Coordinate Molecular Dynamics  

PubMed Central

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

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

2012-01-01

171

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

172

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

173

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

NASA Astrophysics Data System (ADS)

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

Kirshman, David

174

A Comparison of Cartesian Genetic Programming and Linear Genetic Programming  

Microsoft Academic Search

Two prominent genetic programming approaches are the graph-based Cartesian Genetic Programming (CGP) and Linear Genetic Programming\\u000a (LGP). Recently, a formal algorithm for constructing a directed acyclic graph (DAG) from a classical LGP instruction sequence\\u000a has been established. Given graph-based LGP and traditional CGP, this paper investigates the similarities and differences\\u000a between the two implementations, and establishes that the significant difference

Garnett Carl Wilson; Wolfgang Banzhaf

2008-01-01

175

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

176

Smoothing of Time-Optimal Feedrates for Cartesian CNC Machines  

Microsoft Academic Search

\\u000a Minimum-time traversal of curved paths by Cartesian CNC machines, subject to prescribed bounds on the magnitude of acceleration\\u000a along each axis, usually involves a “bang-bang” control strategy in which the acceleration bound is realized by one or another\\u000a of the machine axes at each instant during the motion. For a path specified by a polynomial parametric curve and prescribed\\u000a acceleration

Casey L. Boyadjieff; Rida T. Farouki; Sebastian D. Timar

2005-01-01

177

Kalman filter techniques for accelerated Cartesian dynamic cardiac imaging.  

PubMed

In dynamic MRI, spatial and temporal parallel imaging can be exploited to reduce scan time. Real-time reconstruction enables immediate visualization during the scan. Commonly used view-sharing techniques suffer from limited temporal resolution, and many of the more advanced reconstruction methods are either retrospective, time-consuming, or both. A Kalman filter model capable of real-time reconstruction can be used to increase the spatial and temporal resolution in dynamic MRI reconstruction. The original study describing the use of the Kalman filter in dynamic MRI was limited to non-Cartesian trajectories because of a limitation intrinsic to the dynamic model used in that study. Here the limitation is overcome, and the model is applied to the more commonly used Cartesian trajectory with fast reconstruction. Furthermore, a combination of the Kalman filter model with Cartesian parallel imaging is presented to further increase the spatial and temporal resolution and signal-to-noise ratio. Simulations and experiments were conducted to demonstrate that the Kalman filter model can increase the temporal resolution of the image series compared with view-sharing techniques and decrease the spatial aliasing compared with TGRAPPA. The method requires relatively little computation, and thus is suitable for real-time reconstruction. PMID:22926804

Feng, Xue; Salerno, Michael; Kramer, Christopher M; Meyer, Craig H

2012-08-27

178

Cartesian positioning system for localization of blast and ballistic fragments: a phantom-based pilot study.  

PubMed

Our purpose was to demonstrate the consistency of radiologists' three-dimensional measurements of simulated blast fragment locations in vitro in an effort to objectively localize retained fragments and wound paths. We designed a phantom consisting of 10 nail heads (simulating blast fragments) glued to wooden pegs that were randomly situated at distances from a reference point within a plastic tub. The x, y, and z coordinates of simulated fragments were recorded in Cartesian 3-space relative to the reference point. Computed tomography images of the phantom were acquired. Differences in x, y, and z positions as determined by three observers were summed for each fragment. Agreement between recordings of coordinates across readers was assessed using the intraclass correlation coefficient. Summed differences in coordinate positions as determined by readers ranged between 0.00 and 1.204 cm (mean: 0.732 cm). Across readers, the intraclass correlation coefficient for each dimension was >0.99. We found excellent agreement among readers with minimal discrepancy of measured locations of simulated fragments. Our results provide a foundation for trajectory analysis necessary to lead to automated organ damage reporting for immediate assessment in the emergency department and for forensic investigation and long-term epidemiological analysis. PMID:22165660

Folio, Les; Fischer, Tatjana; Shogan, Paul J; Frew, Michael; Bunger, Rolf; Provenzale, James M

2011-11-01

179

Simulations of Low-temperature Plasmas with Adaptive Cartesian Mesh  

NASA Astrophysics Data System (ADS)

Many problems of gas discharge physics are characterized by the presence of large gradients of plasma parameters in localized domains (streamers, filaments, ionization fronts, etc). For such problems, the ability to dynamically adapt the mesh resolution to local plasma properties can substantially increase the accuracy and efficiency of simulations. This paper describes a new tool for plasma simulation with Adaptive Mesh Refinement (AMR) using octree Cartesian mesh. We demonstrate the benefits of AMR for simulation of streamer development in high-pressure corona discharges, classical low-pressure DC discharges, and micro-plasma devices.

Kolobov, V. I.; Arslanbekov, R. R.

2012-07-01

180

Benchmark Solutions of 2-D Steady Incompressible NS Equations in General Curvilinear Coordinates with NonOrthogonal Grid Mesh; Driven Skewed Cavity Flow  

Microsoft Academic Search

The numerical method presented by Erturk et al. (2005, IJNMF, in Press) is reformulated in its most general form, in general curvilinear coordinates, and tested on non-orthogonal flow problems. The governing 2-D steady incompressible Navier-Stokes equations is solved for the solution of the benchmark problem \\

E. Erturk; B. Dursun

2005-01-01

181

Compact-range coordinate system established using a laser tracker.  

SciTech Connect

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

Gallegos, Floyd H.; Bryce, Edwin Anthony

2006-12-01

182

Grid Computing and Applications  

ScienceCinema

'Grid' computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high-performance orientation. In this talk, Dr. Foster defines this new field. First, he reviews the 'Grid problem,' which he defines as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources - what he refers to as virtual organizations. In such settings, we encounter unique authentication, resource access, resource discovery, and other challenges. It is this class of problem that is addressed by Grid technologies. He presents an extensible and open Grid architecture, in which protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. He also reviews major Grid projects worldwide and describes how they are contributing to the realization of this architecture.

183

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

184

Feature-driven Cartesian adaptive mesh refinement for vortex-dominated flows  

NASA Astrophysics Data System (ADS)

We develop locally normalized feature-detection methods to guide the adaptive mesh refinement (AMR) process for Cartesian grid systems to improve the resolution of vortical features in aerodynamic wakes. The methods include: the Q-criterion [1], the ?2 method [2], the ?ci method [3], and the ?+ method [4]. Specific attention is given to automate the feature identification process by applying a local normalization based upon the shear-strain rate so that they can be applied to a wide range of flow-fields without the need for user intervention. To validate the methods, we assess tagging efficiency and accuracy using a series of static vortex-dominated flow-fields, and use the methods to drive the AMR process for several theoretical and practical simulations. We demonstrate that the adaptive solutions provide comparable accuracy to solutions obtained on uniformly refined meshes at a fraction of the computational cost. Overall, the normalized feature detection methods are shown to be effective in driving the AMR process in an automated and efficient manner.

Kamkar, S. J.; Wissink, A. M.; Sankaran, V.; Jameson, A.

2011-07-01

185

General Noncommuting Curvilinear Coordinates and Fluid Mechanics  

NASA Astrophysics Data System (ADS)

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.

Alavi A., S.

2006-10-01

186

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

187

Simulation of Moving Boundary Flow Using Overset Adaptive Cartesian/ Prism Grids and DES.  

National Technical Information Service (NTIS)

Development of improved weapon systems requires better understanding of the complex aerodynamics created by moving boundaries. Carriage and release of conventional weapons from aircraft and aerial refueling fall in this category. The flow problem involvin...

Z. J. Wang L. Zhang

2003-01-01

188

Stability of a Cartesian grid projection method for zero Froude number shallow water flows  

Microsoft Academic Search

In this paper a Godunov-type projection method for computing approximate solutions of the zero Froude number (incompressible)\\u000a shallow water equations is presented. It is second-order accurate and locally conserves height (mass) and momentum. To enforce\\u000a the underlying divergence constraint on the velocity field, the predicted numerical fluxes, computed with a standard second\\u000a order method for hyperbolic conservation laws and applied

Stefan Vater; Rupert Klein

2009-01-01

189

Marker-Based, 3-D Adaptive Cartesian Grid Method for Multiphase Flow around Irregular Geometries  

Microsoft Academic Search

Computational simulations of multiphase flow are challenging because many practical applications require adequate resolution of not only interfacial physics associated with moving boundaries with possible topological changes, but also around three-dimensional, irregular solid geometries. In this paper, we focus on the simulations of fluid\\/fluid dynamics around complex geometries, based on an Eulerian-Lagrangian framework. The approach uses two independent but related

Eray Uzgoren; Jaeheon Sim; Wei Shyy

190

Parallel Unsteady Overset Mesh Methodology for a Multi-Solver Paradigm with Adaptive Cartesian Grids.  

National Technical Information Service (NTIS)

This paper describes a new domain-connectivity module developed to support Chimera-based interfacing of different CFD solvers for performing time- dependent adaptive moving-body calculations of external aerodynamic flows. The domain-connectivity module co...

A. M. Wissink J. Sitaraman M. Floros M. Potsdam

2008-01-01

191

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

192

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

2012-12-01

193

Constructing the ASCI Computational Grid  

Microsoft Academic Search

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

Judy I. Beiriger; Wilbur R. Johnson; Hugh P. Bivens; Steven L. Humphreys; RONALD E. RHEA

2000-01-01

194

Cartesian Impedance Control Techniques for Torque Controlled LightWeight Robots  

Microsoft Academic Search

The paper compares various approaches to imple- menting a compliant Cartesian behavior for robotic manipulators: impedance, admittance and stifiness control. A new controller structure is proposed, which consists of an impedance controller enhanced by lo- cal stifiness control. This structure consistently takes into account the two time scale property of the joint and Cartesian control loops. The DLR light-weight robot,

Alin Albu-schäffer; Gerd Hirzinger

2002-01-01

195

Invoking a Cartesian Product Structure on Social States: New Resolutions of Sen's and Gibbard's Impossibility Theorems  

Microsoft Academic Search

The purpose of this article is to introduce a Cartesian product structure into the social choice theoretical framework and to examine if new possibility results to Gibbard's and Sen's paradoxes can be developed thanks to it. We believe that a Cartesian product structure is a pertinent way to describe individual rights in the social choice theory since it discriminates the

Herrade Igersheim

2006-01-01

196

A robust distributed controller of a single-link SCARA?Cartesian smart materials robot  

Microsoft Academic Search

In this paper, dynamic modelling and controller design are presented for a SCARA?Cartesian smart materials robot, a flexible SCARA?Cartesian robot bonded with piezoelectric actuators and sensors for better control performance. Conventionally, controller design is usually carried out for a truncated model of partial differential equations (PDEs). In this paper, a novel distributed controller is developed directly based on PDEs, which

S. S. Ge; T. H. Lee; J. Q. Gong

1999-01-01

197

Extensions of the Zwart-Powell Box Spline for Volumetric Data Reconstruction on the Cartesian Lattice  

Microsoft Academic Search

In this article we propose a box spline and its variants for reconstructing volumetric data sampled on the Cartesian lattice. In particular we present a tri-variate box spline reconstruction kernel that is superior to tensor product reconstruction schemes in terms of recovering the proper Cartesian spectrum of the underlying function. This box spline produces a C2 reconstruction that can be

Alireza Entezari; Torsten Möller

2006-01-01

198

Automatic fuzzy Cartesian granule feature discovery using genetic programming in image understanding  

Microsoft Academic Search

Variables defined over Cartesian granule feature universes can be viewed as multidimensional linguistic variables. These variable universes are formed over the cross product of words drawn from the fuzzy partitions of the constituent base features. Here we present a constructive induction algorithm, which identifies not only the Cartesian granule feature model but also the concepts\\/variables in which the model is

James F. BALDWIN; Trevor P. MARTIN; J. G. Shanahan

1998-01-01

199

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

Microsoft Academic Search

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

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

200

Orbital Stability for Rotating Planar Vortex Filaments in the Cartesian and Arclength Forms of the Local Induction Approximation  

NASA Astrophysics Data System (ADS)

The local induction approximation (LIA) is commonly used to study the motion of a vortex filament in a fluid. The fully nonlinear form of the LIA is equivalent to a type of derivative nonlinear Schrödinger (NLS) equation, and stationary solutions of this equation correspond to rotating planar vortex filaments. Such solutions were first discussed in the plane by Hasimoto [J. Phys. Soc. Jpn. 31 (1971) 293], and have been described both in Cartesian three-space and in the arclength formulation in subsequent works. Despite their interest, fully analytical stability results have been elusive. In the present paper, we present elegant and simple proofs of the orbital stability for the stationary solutions to the derivative nonlinear Schrödinger equations governing the self-induced motion of a vortex filament under the LIA, in both the extrinsic (Cartesian) and intrinsic (arclength) coordinate representations. Such results constitute an exact criterion for the orbital stability of rotating planar vortex filament solutions for the vortex filament problem under the LIA.

Van Gorder, Robert A.

2013-09-01

201

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

PubMed

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

Campolo, Domenico

2012-01-06

202

A Method of Adaptive Mesh Refinement on Cartesian Unstructured Meshes  

NASA Astrophysics Data System (ADS)

A general method for a dynamic meshing library with built-in localized adaptive mesh refinement (AMR) routines for hexahedral meshes is presented. Current block-based AMR methods apply stacked nested finer grids to regions of the computational domain, solve the governing equations of the flow within the fine grid, and then interpolate the fine grid values to the coarse grid. Unlike existing libraries, the proposed method is designed to generate fully unstructured grids that may be refined and coarsened on-the-fly up to an arbitrary level. This approach allows for h-refinement without the memory and computational expense of calculating masked coarse grid cells, as is done in block-based AMR. The hexahedral nature of the meshes simplifies the finite-volume algorithms, reducing the computational expense of refinement when compared with arbitrary tetrahedral-mesh solvers. Complex surfaces can be quickly modeled by successive refinement of control volumes while retaining numerical stability and minimizing the size of the grid.

Ballesteros, Carlos; Herrmann, Marcus

2011-11-01

203

Practical conversion from torsion space to Cartesian space for in silico protein synthesis.  

PubMed

Many applications require a method for translating a large list of bond angles and bond lengths to precise atomic Cartesian coordinates. This simple but computationally consuming task occurs ubiquitously in modeling proteins, DNA, and other polymers as well as in many other fields such as robotics. To find an optimal method, algorithms can be compared by a number of operations, speed, intrinsic numerical stability, and parallelization. We discuss five established methods for growing a protein backbone by serial chain extension from bond angles and bond lengths. We introduce the Natural Extension Reference Frame (NeRF) method developed for Rosetta's chain extension subroutine, as well as an improved implementation. In comparison to traditional two-step rotations, vector algebra, or Quaternion product algorithms, the NeRF algorithm is superior for this application: it requires 47% fewer floating point operations, demonstrates the best intrinsic numerical stability, and offers prospects for parallel processor acceleration. The NeRF formalism factors the mathematical operations of chain extension into two independent terms with orthogonal subsets of the dependent variables; the apparent irreducibility of these factors hint that the minimal operation set may have been identified. Benchmarks are made on Intel Pentium and Motorola PowerPC CPUs. PMID:15898109

Parsons, Jerod; Holmes, J Bradley; Rojas, J Maurice; Tsai, Jerry; Strauss, Charlie E M

2005-07-30

204

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

2012-01-01

205

Two-dimensional flows in general curvilinear coordinates  

Microsoft Academic Search

\\u000a In the present chapter a numerical method to simulate 2D flows about complex geometries is described. These simulations are\\u000a necessary in real applications; in fact, often in nature, the bodies have complex shapes and seldom their boundaries lie on\\u000a a coordinate line of a system of Cartesian or cylindrical coordinates. An example is the flow past an airfoil or the

Paolo Orlandi

206

Using Line Integral Convolution for Flow Visualization: Curvilinear Grids, Variable-Speed Animation, and Unsteady Flows  

Microsoft Academic Search

Line integral convolution (LIC), introduced by Cabral and Leedom (1993) is a powerful technique for imaging and animating vector fields. We extend the LIC technique in three ways. Firstly the existing algorithm is limited to vector fields over a regular Cartesian grid. We extend the algorithm and the animation techniques possible with it to vector fields over curvilinear surfaces, such

Lisa K. Forssell; Scott D. Cohen

1995-01-01

207

MAGNETIC GRID  

DOEpatents

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

Post, R.F.

1960-08-01

208

Beyond grid security  

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

209

The Largest Topologically Cartesian Closed Categories of Domains as Topological Spaces  

Microsoft Academic Search

\\u000a A subcategory of the category CONT of continuous dcpos is called topologically cartesian closed(tcc for short) if it is closed with respect to finite topological products and function spaces equipped with the Isbell topology.\\u000a We prove that a full subcategory of CONT is tcc if and only if it is cartesian closed (by means of category) and the Isbell topology

Hui Kou; Maokang Luo

210

An immersed boundary method for compressible flows using local grid refinement  

Microsoft Academic Search

This paper combines a state-of-the-art method for solving the three-dimensional preconditioned Navier–Stokes equations for compressible flows with an immersed boundary approach, to provide a Cartesian-grid method for computing complex flows over a wide range of the Mach number. Moreover, a flexible local grid refinement technique is employed to achieve high resolution near the immersed body and in other high-flow-gradient regions

M. D. de Tullio; P. De Palma; G. Iaccarino; G. Pascazio; M. Napolitano

2007-01-01

211

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

212

Algebraic Grid Generation  

NASA Astrophysics Data System (ADS)

Chapter 5 describes formulas for general unidirectional transfinite interpolations. Multidirectional interpolation is defined by Boolean summation of unidirectional interpolations. Examples of various types of blending function are reviewed, in particular, the functions defined through the basic stretching coordinate transformations for singular layers described in Chap. 4. The chapter ends with a description of a procedure for generating triangular, tetrahedral, or prismatic grids through the method of transfinite interpolation.

Liseikin, Vladimir D.

213

The Grid  

ScienceCinema

By now almost everyone has heard of 'The Grid', or 'Grid Computing' as it should more properly be described. There are frequent articles in both the popular and scientific press talking about 'The Grid' or about some specific Grid project. Run II Experiments, US-CMS, BTeV, the Sloane Digital Sky Survey and the Lattice QCD folks are all incorporating aspects of Grid Computing in their plans, and the Fermilab Computing Division is supporting and encouraging these efforts. Why are we doing this and what does it have to do with running a physics experiment or getting scientific results? I will explore some of these questions and try to give an overview, not so much of the technical aspects of Grid Computing, rather of what the phenomenon means for our field.

214

Computational Grids  

Microsoft Academic Search

In this introductory chapter, we lay the groundwork for the rest of the book by providing a more detailed picture of the expected\\u000a purpose, shape, and architecture of future grid systems. We structure the chapter in terms of six questions that we believe\\u000a are central to this discussion: Why do we need computational grids? What types of applications will grids

Ian T. Foster; Carl Kesselman

2000-01-01

215

Overture: The grid classes  

SciTech Connect

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

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

1997-01-01

216

Taxonomy of Grid Business Models  

Microsoft Academic Search

Grid Computing, initially intended to provide access to computational resources for high-performance computing applications, broadened its focus by addressing computational needs of enterprises. It became concerned with coordinating the on-demand, usage-based allocation of resources in dynamic, multi-institutional virtual organizations, and eventually creating new business models based on this technology. This trend in Grid computing holds a lot of potential in

Jörn Altmann; Mihaela Ion; Ashraf Adel Bany Mohammed

2007-01-01

217

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

218

Deforming composite grids for solving fluid structure problems  

NASA Astrophysics Data System (ADS)

We describe a mixed Eulerian-Lagrangian approach for solving fluid-structure interaction (FSI) problems. The technique, which uses deforming composite grids (DCG), is applied to FSI problems that couple high speed compressible flow with elastic solids. The fluid and solid domains are discretized with composite overlapping grids. Curvilinear grids are aligned with each interface and these grids deform as the interface evolves. The majority of grid points in the fluid domain generally belong to background Cartesian grids which do not move during a simulation. The FSI-DCG approach allows large displacements of the interfaces while retaining high quality grids. Efficiency is obtained through the use of structured grids and Cartesian grids. The governing equations in the fluid and solid domains are evolved in a partitioned approach. We solve the compressible Euler equations in the fluid domains using a high-order Godunov finite-volume scheme. We solve the linear elastodynamic equations in the solid domains using a second-order upwind scheme. We develop interface approximations based on the solution of a fluid-solid Riemann problem that results in a stable scheme even for the difficult case of light solids coupled to heavy fluids. The FSI-DCG approach is verified for three problems with known solutions, an elastic-piston problem, the superseismic shock problem and a deforming diffuser. In addition, a self convergence study is performed for an elastic shock hitting a fluid filled cavity. The overall FSI-DCG scheme is shown to be second-order accurate in the max-norm for smooth solutions, and robust and stable for problems with discontinuous solutions for a wide range of constitutive parameters.

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

2012-05-01

219

Transformed shoreline-following horizontal coordinates in a mesoscale model: A sea-land-breeze case study  

Microsoft Academic Search

A hydrostatic and incompressible mesoscale model with transformed horizontal coordinates is presented. The model is applied to study the sea-land-breeze circulation over Rio de La Plata. One of the new coordinates is shoreline-following and the other one is locally quasi-perpendicular to the first one. The original set of equations in the Cartesian coordinates is rewritten in the curvilinear coordinates. This

Guillermo J. Berri; M. N. Nunez

1993-01-01

220

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

SciTech Connect

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

Sebastian Schunert; Yousry Y. Azmy; Damien Fournier

2011-05-01

221

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

PubMed

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

Gillot, Pascale

2010-01-01

222

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

223

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

SciTech Connect

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

Reister, D.B.

1997-04-01

224

High Dimensional Clustering Using Parallel Coordinates and the Grand Tour  

Microsoft Academic Search

In this paper, we present some graphical techniquesfor cluster analysis of high-dimensional data. Parallel coordinateplots and parallel coordinate density plots aregraphical techniques which map multivariate data into atwo-dimensional display. The method has some elegantduality properties with ordinary Cartesian plots so thathigher-dimensional mathematical structures can be analyzed.Our high interaction software allows for rapidediting of data to remove outliers and isolate clusters

Edward J. Wegman; Qiang Luo

1996-01-01

225

Approximations to wire grid inductance.  

SciTech Connect

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

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

2004-06-01

226

coordinate plane  

NSDL National Science Digital Library

Become familiar with the coordinate plane. Learn the quadrants and how to graph points and read points on a coordinate plane. You are required to do the assignment and take the quiz. The other resources are to help prepare you for the quiz and book assignment. This is a quick review of the lesson.The Coordinate Plane This is a game to practice plotting and reading points.coordinates game *Assignment: Watch Powerpoint 3.3 and fill in your ...

Olsen

2010-10-07

227

Note on transformation to general curvilinear coordinates for Maxwell's curl equations  

Microsoft Academic Search

Maxwell's curl equations are formulated in curvilinear non-orthogonal coordinates in three dimensions in a manner that enables to preserve conventional Cartesian mesh for the finite-difference schemes by means of mere redefinition of the permittivity and permeability coefficients. It is highlighted that in the previous works on this subject [Ward and Pendry 1996 J. Modern Opt. 43 773; 1998 Phys. Rev.

Dzmitry M. Shyroki

2003-01-01

228

Systematic derivation of anisotropic PML absorbing media in cylindrical and spherical coordinates  

Microsoft Academic Search

A simple and systematic derivation of anisotropic perfectly matched layers (PMLs) in cylindrical and spherical coordinates is presented. The derivation is based on the analytic continuation of Maxwell's equations to complex space. Through field transformations, results for Cartesian anisotropic PML media are recovered and, more importantly, a generalization of the anisotropic PML to cylindrical and spherical systems is obtained, providing

F. L. Teixeira; W. C. Chew

1997-01-01

229

Academic Coordination.  

ERIC Educational Resources Information Center

|Coordination of higher education within national sets is discussed in this working paper. The structural bases of national coordination, the tasks of higher education and the prevailing structure of embedded power, are described. The national general patterns of coordinative organization that appear frequently among national systems of higher…

Clark, Burton R.

230

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

231

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

ERIC Educational Resources Information Center

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

Lelwica, Michelle Mary

2009-01-01

232

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

233

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

Microsoft Academic Search

This paper presents the development of a mesh adaptation module for a multilevel Cartesian solver. While the module allows mesh refinement to be driven by a variety of different refinement parameters, a central feature in its design is the incorporation of a multilevel error estimator based upon direct estimates of the local truncation error using ? ? ? ? -extrapolation.

M. J. Aftosmis; M. J. Berger

2002-01-01

234

Enumeration of perfect matchings of a type of Cartesian products of graphs  

Microsoft Academic Search

Abstract Let G be a graph and let Pm(G) denote the number,of perfect matchings of G. We denote the path with m vertices by Pm and the Cartesian product of graphs G and H by G × H . In this paper, as the continuance of our paper [W. Yan, F. Zhang, Enumeration of perfect matchings of graphs with reflective

Weigen Yan; Fuji Zhang

2006-01-01

235

The Rift in the Modern Mind: Tocqueville and Percy on the Rise of the Cartesian Self  

Microsoft Academic Search

Alexis de Tocqueville and Walker Percy are two of the most insightful commentators on the conditions of modernity. Placed in dialogue with one another, their work betrays startlingly parallel modes of thought and a complementary diagnosis of modernity's ills. In essence, they claim that the rise of Cartesian doubt robs men of their ability to cope with the world. They

Matthew Sitman; Brian Smith

2007-01-01

236

The Cartesian frame of reference: A structure unifying the description of dyslexia  

Microsoft Academic Search

It is shown that six phenomena often associated with dyslexia may be attributed to the lack of a visual, Cartesian frame of reference. These phenomena are (1) reading errors due to letter reversal, inversion, or rotation, (2) form recognition of all classes of mono-oriented objects which is independent of the figure's egocentric orientation, (3) defective visual sequential scanning, resulting in

Graham Richardson

1974-01-01

237

Onset of buoyancy-driven convection in Cartesian and cylindrical geometries  

NASA Astrophysics Data System (ADS)

We perform a linear stability analysis to examine the onset of buoyancy-driven convection relevant to subsurface carbon dioxide sequestration in confined, porous Cartesian and cylindrical domains. Our work amends the analysis in an earlier study on cylindrical geometries. We consider Cartesian geometries where the aspect ratio between the two horizontal dimensions is not necessarily equal to one. Two key elements of the stability analysis are: (1) the critical time and (2) the critical wavenumber. Lateral boundaries have a much greater influence on the critical wavenumber than on the critical time. The confinement due to these boundaries impedes the onset of convection to the extent that convection cannot even occur in domains that are smaller than a certain size. Large aspect ratios can significantly reduce boundary effects. Patterns of the earliest-growing perturbation mode in the horizontal plane reveal many interesting dynamics which have not been examined in previous stability analyses. We illustrate several differences between patterns in Cartesian geometries and patterns in cylindrical geometries. Based on observations from earlier papers, we hypothesize that the contrasts between the Cartesian and cylindrical patterns may lead to significantly different behavior in the two geometries after the onset of convection. Our results may guide future numerical studies that can investigate this hypothesis and may help with understanding the onset of buoyancy-driven convection in real systems where lateral boundary effects are significant.

Myint, Philip C.; Firoozabadi, Abbas

2013-04-01

238

Implicit Context Representation Cartesian Genetic Programming for the assessment of visuo-spatial ability  

Microsoft Academic Search

In this paper, a revised form of Implicit Context Representation Cartesian Genetic Programming is used in the development of a diagnostic tool for the assessment of patients with neurological dysfunction such as Alzheimer's disease. Specifically, visuo-spatial ability is assessed by analysing subjects' digitised responses to a simple figure copying task using a conventional test environment. The algorithm was trained to

Stephen L. Smith; Michael A. Lones

2009-01-01

239

Comonoids in chu: a large cartesian closed sibling of topological spaces  

Microsoft Academic Search

ComK may be defined as the (cartesian closed) category of comonoids in chuK, or equivalently as dic- tionaries D for which any crossword over D has its main diagonal in D. Com2 resembles Top, ordinary topological spaces. Common to both are the Alexandro posets and the Scott DCPOs, while the topological space R and the dual DCPO {1 < ...

Vaughan R. Pratt

2003-01-01

240

Human Consciousness and its Transcendental Conditions: Kant's Anti-Cartesian Revolt  

Microsoft Academic Search

Kant’s philosophy is deeply systematic. Understanding his account of human consciousness requires considering some of his\\u000a broader systematic analyses, to the extent required here to understand his account of consciousness, which is of great philosophical\\u000a and historical interest. “Anti-Cartesianism” and “externalism” are key issues in recent philosophy of mind.

KENNETH R. WESTPHAL

241

Simulation of Conservative Congruence Transformation: Conservative Properties in the Joint and Cartesian Spaces  

Microsoft Academic Search

The stiffness characteristics of robot systems via the conservative congruence transformation (CCT) and the conventional congruence transformation (CT) between the joint and Cartesian spaces are investigated. A stiffness matrix is conservative if: 1) the force resulting from the stiffness matrix is conservative, and 2) the work done by such force along a closed path is zero. The criteria result in

Shih-feng Chen; Imin Kao

2000-01-01

242

Unifying via conformal mapping coarse-mesh neutron diffusion calculations in Cartesian and hexagonal geometries  

Microsoft Academic Search

Modern design methodology for nuclear reactor core designs performs routinely three-dimensional core modeling. The modeling is done with a class of highly accurate nodal method of solving the neutron diffusion equation, which is orders of magnitude faster than the finite difference method. However, these modern nodal methods are powerful only for Cartesian geometry problem applications. For hexagonal geometry problems, there

Y. A. Chao

1995-01-01

243

C[squared] = Creative Coordinates  

ERIC Educational Resources Information Center

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

McHugh, Shelley R.

2007-01-01

244

Thin Wire Modeling for FDTD Electromagnetic Calculations in the Two-Dimensional Cylindrical Coordinate System  

NASA Astrophysics Data System (ADS)

In this paper, the equivalent radius of a thin wire represented using the FDTD method in the two-dimensional (2D) cylindrical coordinate system is identified as 0.135?r, where ?r is the lateral side length of the rectangular cells, while that of a thin wire represented in the 3D Cartesian coordinate system is known to be 0.230?r. Furthermore, it is shown that the technique proposed by Noda and Yokoyama to represent a thin wire having an arbitrary radius in the 3D Cartesian coordinate system can be applied successfully to representing such a thin wire in the 2D cylindrical coordinate system if 0.135?r is used for the equivalent radius instead of 0.230?r.

Taniguchi, Yohei; Baba, Yoshihiro; Nagaoka, Naoto; Ametani, Akihiro

245

Rototranslational sum rules for electromagnetic hypershielding at the nuclei and related atomic Cartesian derivatives of the optical rotatory power.  

PubMed

Two molecular properties, the nuclear electromagnetic hypershielding (psi(gamma,alphabeta) ('I)) and the gradient of the electric dipole-magnetic dipole polarizability (nabla(Igamma)G(alphabeta) (')), have been calculated using the time-dependent Hartree-Fock method. Provided the Hellmann-Feynman theorem is satisfied, these quantities are equivalent and are related through the nabla(Igamma)G(alphabeta) (')=eZ(I)psi(gamma,alphabeta) ('I) relation, where Z(I) is the atomic number of atom I and e the magnitude of the electron charge. In such a case, the determination of the nuclear electromagnetic hypershielding presents the computational advantage over the evaluation of the gradient of G(alphabeta) (') of requiring only the knowledge of nine mixed second-order derivatives of the density matrix with respect to both electric and magnetic fields (D(alpha,beta)(-omega,omega)) instead of the 3N (N is the number of atoms) derivatives of the density matrix with respect to the Cartesian coordinates (D(Igamma)). It is shown here for the H(2)O(2) molecule that very large basis sets such as the aug-cc-pVQZ or the R12 basis are required to satisfy the Hellmann-Feynman theorem. These basis set requirements have been substantiated by considering the corresponding rototranslational sum rules. The origin dependence of the rototranslational sum rules for the gradient of G(alphabeta) (') has then been theoretically described and verified for the H(2)O(2) molecule. PMID:18601317

Liégeois, Vincent; Champagne, Benoît; Lazzeretti, Paolo

2008-06-28

246

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

247

Polar coordinate based nonlinear function for frequency-domain blind source separation  

Microsoft Academic Search

This paper presents a new type of nonlinear function for independent component analysis to process complex-valued signals, which is used in frequency-domain blind source separation. The new function is based on the polar coordinates of a complex number, whereas the conventional one is based on the Cartesian coordinates. The new function is derived from the probability density function of frequency-domain

Hiroshi Sawada; Ryo Mukai; Shoko Araki; Shoji Makino

2002-01-01

248

Trajectory Coordinate Constraints in Multibody Railroad Vehicle Systems  

NASA Astrophysics Data System (ADS)

In this investigation, the formulation of trajectory coordinate constraints in terms of the absolute coordinates is developed for the use in the computer simulations of railroad vehicle system applications. Examples of trajectory coordinate constraints are the specified forward velocity of a vehicle or a wheelset along a curved track or specified yaw angle of a vehicle or a wheelset with respect to a body trajectory coordinate system. The relationship between the trajectory coordinates and the absolute coordinates is defined and then used to write the trajectory constraints in terms of the absolute coordinates at the position, velocity, and acceleration levels. The motion of the trajectory coordinate system can be uniquely defined in the track body coordinate system using the arc-length coordinate defined along the space curve. It is demonstrated that the use of the trajectory coordinates leads to simple linear constraint equations, while the trajectory constraint equations become highly nonlinear functions of the absolute coordinates. This is mainly due to the nature of the nonlinear relationship between the absolute Cartesian and trajectory coordinates. A numerical example is presented in order to demonstrate the use of the proposed formulations in the analysis of multibody railroad vehicle systems.

Sugiyama, Hiroyuki; Shabana, Ahmed A.

249

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

250

MammoGrid: A Service Oriented Architecture Based Medical Grid Application  

Microsoft Academic Search

The MammoGrid project has recently delivered its first proof-of-concept prototype using a Service-Oriented Architecture (SOA)-based Grid application to enable distributed com- puting spanning national borders. The underlying AliEn Grid infrastructure has been se- lected because of its practicality and because of its emergence as a potential open source standards-based solution for managing and coordinating distributed resources. The resul- tant prototype

Salvator Roberto Amendolia; Mohammad Waseem Hassan; Tamas Hauer; David Manset; Richard Mcclatchey; Dmitri Rogulin; Tony Solomonides

2004-01-01

251

The MammoGrid Virtual Organisation - Federating Distributed Mammograms  

Microsoft Academic Search

The MammoGrid project aims to deliver a prototype which enables the effective collaboration between radiologists using grid, service-orientation and database solutions. The grid technologies and service-based database management solution provide the platform for integrating diverse and distributed resources, creating what is called a 'virtual organisation'. The MammoGrid Virtual Organisation facilitates the sharing and coordinated access to mammography data, medical imaging

Richard McClatchey; Dmitry Rogulin

2005-01-01

252

Systemanalys av solkraft vid samkoerning med det svenska kraftnaetet med lagring av solenergi i vattenmagasin. (Systems analysis of solar power at co-ordination with the Swedish electric power grid, with storage of solar energy in water magazines).  

National Technical Information Service (NTIS)

This report deals with introduction of solar power on a large scale basis into the Swedish grid, and storage of solar energy in water magazines. The electric power production from the sun fluctuates between zero at night and up to 4.2 - 25.4 GW at noon in...

C. Olsson N. Edin

1995-01-01

253

Grid-Optimized Dispersion-Relation-Preserving Schemes on General Geometries for Computational Aeroacoustics  

Microsoft Academic Search

In this paper, we investigate the dispersion-relation-preserving property of a finite difference scheme on general geometries for computational aeroacoustics, where nondispersive and nondissipative properties are of critical importance. The analysis pertains to the application of the optimization algorithm of the dispersion-relation-preserving (DRP) scheme in wave number space to the general geometries—nonuniform Cartesian and curvilinear grids. In many computational aeroacoustics applications,

Cheolung Cheong; Soogab Lee

2001-01-01

254

Sun's grid model  

Microsoft Academic Search

The grid creates a universal source of computing power. Grid opportunity drivers are commodity servers with improving performance, high speed networking enabling distributed computing, Linux OS\\/ Solaris X86, grid resource management software maturing. Grid are accessed and managed through grid software like N1 grid engine.

S. See

2004-01-01

255

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

256

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

NASA Astrophysics Data System (ADS)

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

Qiu, Zhi-cheng

2012-07-01

257

Concatenate Coordination and Mutual Coordination  

Microsoft Academic Search

We tell of the evolving meaning of the term coordination as used by economists. The paper is based on systematic electronic searches (on “coord,” etc.) of major works and leading journals. The term coordination first emerged in professional economics around 1880, to describe the directed productive concatenation of factors or activities within a firm. Also, transportation economists used the term

Daniel B. Klein; Aaron Orsborn

2008-01-01

258

Hybrid Simulation of EMIC Waves in Curvilinear Coordinates  

NASA Astrophysics Data System (ADS)

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

Hu, Y.; Denton, R.

2008-12-01

259

Plasticity of intermediate mechanics studentsâ coordinate system choice  

NSDL National Science Digital Library

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

Sayre, Eleanor C.; Wittmann, Michael C.

2010-03-11

260

Continuous motion planning in unknown environment for a 3D cartesian robot arm  

Microsoft Academic Search

The approach (called Continuous Path Planning, or CPP) developed in [1,10] for non-heuristic path planning for a point automaton or various planar robot arms moving in an environment with unknown obstacles, is extended here on a three-dimensional (3D) cartesian arm. The task is to move the arm endpoint from the starting to a target position. The arm body is assumed

Vladimir J. Lumelsky

1986-01-01

261

A parallel performance study of the Cartesian method for partial differential equations on a sphere  

SciTech Connect

A 3-D Cartesian method for integration of partial differential equations on a spherical surface is developed for parallel computation. The target computer architectures are distributed memory, message passing computers such as the Intel Paragon. The parallel algorithms are described along with mesh partitioning strategies. Performance of the algorithms is considered for a standard test case of the shallow water equations on the sphere. The authors find the computation time scale well with increasing numbers of processors.

Drake, J.B. [Oak Ridge National Lab., TN (United States); Coddington, M.P. [Swarthmore College, PA (United States)

1997-04-01

262

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

Microsoft Academic Search

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

C. B. Carrico; G. Palmiotti; E. E. Lewis; M. Mills

1992-01-01

263

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

Microsoft Academic Search

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

Carrie Paechter

2004-01-01

264

Astronomical Coordinates  

NSDL National Science Digital Library

The celestial coordinate system is a projection of earth's coordinate system into the celestial sphere. Being just like Earth's system it contains an "equator", lines of "latitude" and "longitude", and even poles. (Though we don't use the same words for it.) One suggestion one might have would be to just extend the Earth's latitude, longitude, and equator out into the night sky, but the Earth is constantly spinning. For the Celestial coordinates, we have to pick some fixed reference to go by.

Joiner, David; The Shodor Education Foundation, Inc.

265

Extensions of the Zwart-Powell box spline for volumetric data reconstruction on the cartesian lattice.  

PubMed

In this article we propose a box spline and its variants for reconstructing volumetric data sampled on the Cartesian lattice. In particular we present a tri-variate box spline reconstruction kernel that is superior to tensor product reconstruction schemes in terms of recovering the proper Cartesian spectrum of the underlying function. This box spline produces a C2 reconstruction that can be considered as a three dimensional extension of the well known Zwart-Powell element in 2D. While its smoothness and approximation power are equivalent to those of the tri-cubic B-spline, we illustrate the superiority of this reconstruction on functions sampled on the Cartesian lattice and contrast it to tensor product B-splines. Our construction is validated through a Fourier domain analysis of the reconstruction behavior of this box spline. Moreover, we present a stable method for evaluation of this box spline by means of a decomposition. Through a convolution, this decomposition reduces the problem to evaluation of a four directional box spline that we previously published in its explicit closed form. PMID:17080870

Entezari, Alireza; Möller, Torsten

266

Progress in the Simulation of Steady and Time-Dependent Flows with 3D Parallel Unstructured Cartesian Methods.  

National Technical Information Service (NTIS)

The proposed paper will present recent extensions in the development of an efficient Euler solver for adaptively-refined Cartesian meshes with embedded boundaries. The paper will focus on extensions of the basic method to include solution adaptation, time...

M. J. Aftosmis M. J. Berger S. M. Murman

2002-01-01

267

Programming Grid Applications with GRID Superscalar  

Microsoft Academic Search

The aim of GRID superscalar is to reduce the development complexity of Grid applications to the minimum, in such a way that writing an application for a computational Grid may be as easy as writing a sequential application. Our assumption is that Grid applica- tions would be in a lot of cases composed of tasks, most of them repetitive. The

Rosa M. Badia; Jesús Labarta; Raúl Sirvent; Josep M. Pérez; José M. Cela; Rogeli Grima

2003-01-01

268

Structured Grid Generation Based on Unstructured Grid.  

National Technical Information Service (NTIS)

An idea of structured grid generation is presented. To save the user work, an unstructured grid is generated, then a partial differential equation is solved by finite element method on the grid. Finally, a structured grid is obtained by searching contour ...

M. Suzuki

1989-01-01

269

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

270

The NCRC Grid Scheduling Environment  

SciTech Connect

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

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

2011-01-01

271

Solving for MHD Equilibrium on Unstructured Grids  

NASA Astrophysics Data System (ADS)

The present work describes a method for determining the MHD equilibrium in an axi-symmetric torus using two-dimensional finite elements on an unstructured triangular grid. This work is motivated by the proposed development of an adaptive mesh stability code that will solve the ideal linearized stability problem with a resistive wall. In order to create an automatically adapting grid, an unstructured triangular grid is initially generated for the equilibrium evaluation. The Grad-Shafronov equation is modified to accommodate a static toroidal flow velocity. The resulting equation is then solved on the generated grid in the natural cylindrical (R, ?, Z) coordinate system. By working in the natural coordinate system, there are no singular points to be dealt with in the system. However, there are several numerical problems associated with solving the system of equations that are presented. Benchmark results against the Solov’ev equilibrium as well as the PEST and HELENA codes are also presented.

Thomas, Michael; Freidberg, Jeffrey

1999-11-01

272

A finite difference thermal model of a cylindrical microwave heating applicator using locally conformal overlapping grids: part II--numerical results and experimental evaluation.  

PubMed

In this paper, we present numerical results obtained from a robust, locally conformal 3-D Orthogonal Grid Finite Difference (OGFD) thermal algorithm introduced in Part I of our current investigation [Al-Rizzo et al., 2006] integrated with an Orthogonal Grid Finite-Difference Time Domain (OGFDTD) scheme [Al-Rizzo et al., 2000], which accurately models the volumetric electromagnetic (EM) power deposition pattern. A unified meshing scheme, which utilizes identical overlapping grids in Cartesian and cylindrical coordinates, is employed within the load zone in the OGFDTD and OGFD models. Local temperature profiles excited by the absorbed microwave energy were measured at seven locations within the sample as a function of heating time. In order to benchmark, or validate our model, an alternative analysis of the coupled EM and thermal simulations was performed using state-of-the-art, Finite Element Method-based Ansoft's High Frequency Structure Simulator (HFSS) and the coupled thermal/stress analysis tool ePHYSICS (http://www.ansoft.com). Additionally, we compare our numerical simulations against measured dynamic temperature profiles induced within a mineral ore sample maintained for exposure period of 28.5 minutes inside a cylindrical multimode heating furnace energized at 915 MHz with a microwave source power of 12.5 kW and accompanied with significant temperature elevation. A combination of convective and radiation thermal boundary conditions are considered at the interfaces between the cavity walls, air, and sample. There is a general agreement between simulated and measured spatial and temporal temperature profiles, which validates the proposed model. Results indicate that inevitable fluctuations in the frequency spectrum and output power of the magnetron, non-uniformity of sample packing, and heat released by uncontrolled exothermic chemical reactions have a significant effect on the comparisons between measured and computed temperature patterns. PMID:17278792

Al-Rizzo, Hussain M; Adada, Rami; Tranquilla, Jim M; Ma, Feng; Ionescu, Bogdan C

2006-01-01

273

Parsing Coordinations  

Microsoft Academic Search

The present paper is concerned with sta- tistical parsing of constituent structures in German. The paper presents four ex- periments that aim at improving parsing performance of coordinate structure: 1) reranking the n-best parses of a PCFG parser, 2) enriching the input to a PCFG parser by gold scopes for any conjunct, 3) reranking the parser output for all possi-

Sandra Kübler; Erhard W. Hinrichs; Wolfgang Maier; Eva Klett

2009-01-01

274

Magnetosheath Coordinates  

Microsoft Academic Search

The eventual goal of this work is to develop an approximate analytical representation of solar-wind streamlines in the magnetosheath surrounding a magnetosphere of rather general shape. Previous analytical representations of magnetosheath streamlines and magnetic fields have invoked magnetopause shapes that conform to standard coordinate systems (e.g., spherical, cylindrical, paraboloidal, ellipsoidal), but it seems now that such a restriction on magnetopause

M. Schulz; M. W. Chen

2010-01-01

275

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

276

COORDINATORS: Coordination Managers for First Responders  

Microsoft Academic Search

COORDINATORs are coordination managers for fielded first responders. Each first response team is paired with a COORDINATOR coordination manager which is running on a mobile computing device. COORDINATORs provide decision support to first response teams by reasoning about who should be doing what, when, with what resource, in support of which other team, and so forth. COORDINATORs respond to the

Thomas Wagner; John Phelps; Valerie Guralnik; Ryan VanRiper

2004-01-01

277

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

PubMed

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

Schmidt, P P

2005-12-22

278

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

2011-01-01

279

Coordinate Plane  

NSDL National Science Digital Library

5th Grade Math State core Standard 3, Objective 2a: Locate points defined by ordered pairs of integers. Congratulations for earning a game day in the computer lab! Remember that even though it is game day I expect you to stay on task and follow directions. We have been talking in math about graphing integers on the coordinate plane. The games for today require that ...

Zilles, Miss

2007-10-31

280

Extending Diffusion Monte Carlo to Internal Coordinates  

NASA Astrophysics Data System (ADS)

Diffusion Monte Carlo (DMC) is a powerful technique for studying the properties of molecules and clusters that undergo large-amplitude, zero-point vibrational motions. However, the overall applicability of the method is limited by the need to work in Cartesian coordinates and therefore have available a full-dimensional potential energy surface (PES). As a result, the development of a reduced-dimensional DMC methodology has the potential to significantly extend the range of problems that DMC can address by allowing the calculations to be performed in the subset of coordinates that is physically relevant to the questions being asked, thereby eliminating the need for a full-dimensional PES. As a first step towards this goal, we describe here an internal coordinate extension of DMC that places no constraints on the choice of internal coordinates other than requiring them all to be independent. Using H_3^+ and its isotopologues as model systems, we demonstrate that the methodology is capable of successfully describing the ground state properties of highly fluxional molecules as well as, in conjunction with the fixed-node approximation, the ?=1 vibrationally excited states. The calculations of the fundamentals of H_3^+ and its isotopologues provided general insights into the properties of the nodal surfaces of vibrationally excited states. Specifically, we will demonstrate that analysis of ground state probability distributions can point to the set of coordinates that are less strongly coupled and therefore more suitable for use as nodal coordinates in the fixed-node approximation. In particular, we show that nodal surfaces defined in terms of the curvilinear normal mode coordinates are reasonable for the fundamentals of H_2D^+ and D_2H^+ despite both molecules being highly fluxional.

Petit, Andrew S.; McCoy, Anne B.

2013-06-01

281

The MammoGrid Project Grids Architecture  

Microsoft Academic Search

The aim of the recently EU-funded MammoGrid project is, in the light of\\u000aemerging Grid technology, to develop a European-wide database of mammograms\\u000athat will be used to develop a set of important healthcare applications and\\u000ainvestigate the potential of this Grid to support effective co-working between\\u000ahealthcare professionals throughout the EU. The MammoGrid consortium intends to\\u000ause a Grid

Richard McClatchey; Predrag Buncic; David Manset; Tamas Hauer; Pablo Saiz; Dmitri Rogulin

2003-01-01

282

A Workflow-Based Grid Portal for Problem Solving Environment  

Microsoft Academic Search

\\u000a In this paper, we present a Workflow-based grId portal for problem Solving Environment(WISE) which has been developed by integrating\\u000a workflow, Grid and web technology to provide an enhanced powerful approach for problem solving environment. Workflow technology\\u000a supports coordinated execution of multiple application tasks on Grid resources by enabling users to describe a workflow by\\u000a composing many existing applications and new

Yong-won Kwon; So-hyun Ryu; Jin-sung Park; Chang-sung Jeong

2004-01-01

283

Representation of Relative Variability on a Semilogarithmic Grid  

Microsoft Academic Search

THERE are two types of semi-logarithmic grids : one, called arith-log grid (a system of rectangular co-ordinates, in which the axis of abscissæ is divided arithmetically and that of ordinates logarithmically), is frequently used for graphical representations because, on such a grid, the relative increase or decrease of the intensity of a phenomenon is shown immediately by the slope of

H. V. Muhsam

1946-01-01

284

Reliability Modeling for the Advanced Electric Power Grid  

Microsoft Academic Search

The advanced electric power grid promises a self-healing infrastructure using distributed, coordinated, power electronics\\u000a control. One promising power electronics device, the Flexible AC Transmission System (FACTS), can modify power flow locally\\u000a within a grid. Embedded computers within the FACTS devices, along with the links connecting them, form a communication and\\u000a control network that can dynamically change the power grid to

Ayman Z. Faza; Sahra Sedigh; Bruce M. Mcmillin

2007-01-01

285

Darwin's evolution theory, brain oscillations, and complex brain function in a new "Cartesian view".  

PubMed

Comparatively analyses of electrophysiological correlates across species during evolution, alpha activity during brain maturation, and alpha activity in complex cognitive processes are presented to illustrate a new multidimensional "Cartesian System" brain function. The main features are: (1) The growth of the alpha activity during evolution, increase of alpha during cognitive processes, and decrease of the alpha entropy during evolution provide an indicator for evolution of brain cognitive performance. (2) Human children younger than 3 years are unable to produce higher cognitive processes and do not show alpha activity till the age of 3 years. The mature brain can perform higher cognitive processes and demonstrates regular alpha activity. (3) Alpha activity also is significantly associated with highly complex cognitive processes, such as the recognition of facial expressions. The neural activity reflected by these brain oscillations can be considered as constituent "building blocks" for a great number of functions. An overarching statement on the alpha function is presented by extended analyzes with multiple dimensions that constitute a "Cartesian Hyperspace" as the basis for oscillatory function. Theoretical implications are considered. PMID:18805445

Ba?ar, Erol; Güntekin, Bahar

2008-07-31

286

GRID-MAS integration and the principle of immanence  

Microsoft Academic Search

This position paper proposes to bring together the integra- tion of Grid and MAS with the notion of immanence. On one hand, Grid is known to be an extraordinary infrastructure for coordinating distributed computing resources and Virtual Organisations (VOs). On one other hand MAS interest focusses on complex behaviour of systems of agents. Immanence is a principle that emerges from

Pascal Dugenie

2008-01-01

287

Improving nuclear generating station response for electrical grid islanding  

Microsoft Academic Search

A description of problems associated with the performance characteristics of nuclear generating stations which do not have their overall plant control design functions coordinated with the other grid controls is presented. Also presented are some design changes to typical nuclear plant controls which result in a significant improvement in both the performance of the grid island and the chances of

Q. B. Chou; P. Kundur; P. N. Acchione; B. Lautsch

1989-01-01

288

Improving Nuclear Generating Station Response for Electrical Grid Islanding  

Microsoft Academic Search

This paper describes problems associated with the performance characteristics of nuclear generating stations which do not have their overall plant control design functions co-ordinated with the other grid controls. Some design changes to typical nuclear plant controls are presented which can result in a significant improvement in both the performance of the grid island and reduce the need to isolate

Q. B. Chou; P. Kundur; P. N. Acchione; B. Lautsch

1989-01-01

289

MIT Physics 8.02: Vector Fields Visualizations - Coordinate Systems  

NSDL National Science Digital Library

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

2010-03-31

290

The Transverse Systems of Coordinates for the Arctic.  

National Technical Information Service (NTIS)

The application of a cartographic grid network of coordinates for the solution of certain geophysical problems associated with the plotting of fields for meteorological and hydrological magnitudes in Polar areas is discussed, and the method is illustrated...

D. A. Drogaitsev

1971-01-01

291

The fast marching method in Spherical coordinates: SEG\\/EAGE salt-dome model  

Microsoft Academic Search

Applying the fast marching method to solve the eikonal equation on the 3-D SEG\\/EAGE salt-dome model demonstrates two key features of the method, sta- bility and eciency . Such an application, also reveals some of the accuracy de- ciencies of the Cartesian-coordinate implementation of the fast marching method. The accuracy is improved by applying the fast marching method in spherical

Tariq Alkhalifah

1998-01-01

292

Validating and Scaling the MicroGrid: A Scientific Instrument for Grid Dynamics  

Microsoft Academic Search

Large-scale grids that aggregate and share resources over wide-area networks present major challenges in understanding dynamic application and resource behavior for performance, stability, and reliability. Accurate study of the dynamic behavior of applications, middleware, resources, and networks depends on coordinated and accurate modeling of all four of these elements simultaneously. We have designed and implemented a tool called the MicroGrid

Xin Liu; Huaxia Xia; Andrew A. Chien

2004-01-01

293

Wavelets in curvilinear coordinate quantum calculations: H2+ electronic states  

NASA Astrophysics Data System (ADS)

Multiscale wavelets are used to solve the quantum eigenvalue equations for the hydrogen molecular ion H2+ in the Born-Oppenheimer approximation. Normally restricted to Cartesian systems, "wavelets on the interval" (a normal wavelet family augmented by special edge functions) have recently been applied to such boundary value problems as the hydrogen atom in spherical polar coordinates [J. Mackey, J. L. Kinsey, and B. R. Johnson, J. Comp. Phys. 168, 356 (2001)]. These methods are extended here to ground and excited electronic states of the simplest molecule, for which the electronic Hamiltonian is separable in confocal elliptic coordinates. The set of curvilinear coordinate quantum systems for which wavelet bases have been applied is thus enlarged.

Maloney, A.; Kinsey, James L.; Johnson, Bruce R.

2002-08-01

294

Application of wall functions to generalized nonorthogonal curvilinear coordinate systems  

Microsoft Academic Search

A method has been developed for the application of wall functions to generalized curvilinear coordinate systems with nonorthogonal grids. Two test cases have been computed using this method with the k-epsilon turbulence model: flow over a flat plate at 0-deg angle of attack using a nonorthogonal grid at the wall and flow over a prolate hemispheroid with a hemispherical nose

Douglas L. Sondak; Richard H. Pletcher

1995-01-01

295

Grid generation and its application to separated flows  

NASA Astrophysics Data System (ADS)

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.

1992-04-01

296

An Automaton Model on Curvilinear Grids for the Simulation of Pedestrian Flow  

NASA Astrophysics Data System (ADS)

The geometry of cellular automata models for the simulation of pedestrian flow models is usually defined on a two-dimensional regular grid. We present a new model in which the underlying curvilinear grid is constructed on a path-oriented coordinate system. The basic idea of our model is generally applicable for grid-based methods for the simulation of pedestrian flow.

Schwandt, Hartmut; Chen, Minjie; Bärwolff, Günter

2009-09-01

297

Geoboard : coordinate (grades 6-8)  

NSDL National Science Digital Library

This virtual manipulative features an interactive grid where the student can mouse over points on the grid to display their coordinates and form shapes using virtual rubber bands. The online geoboard has a measure function that displays area and perimeter for shapes and, for single bands connected to two virtual pegs, distance and slope. Shapes may be colored as a way to sort or enhance them. The site features activities to explore slopes, construct reflections, and find an inscribed parallelogram. Also found on the site are instructions for using the manipulative, a brief lesson plan for using coordinates to locate shapes on a grid, and a link to the NCTM standard for geometry. Copyright 2005 Eisenhower National Clearinghouse

Mathematics, Utah S.

2003-01-01

298

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

PubMed

The analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral-equation-based methods, for which traditional iterative methods require O(N2) operations, N being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectric structures. The crux of our method is the accelerated Cartesian expansion algorithm, which is used to evaluate the requisite potentials in O(N) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications. PMID:22472831

Baczewski, Andrew D; Miller, Nicholas C; Shanker, Balasubramaniam

2012-04-01

299

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

300

Construction of freeforms in illumination systems via generalized Cartesian oval representation  

NASA Astrophysics Data System (ADS)

Freeforms in illumination systems are directly constructed by adapting some ideas of Oliker and co-workers [1]. The freeform is created by a set of primitive surface elements which are generalized Cartesian ovals including the optical response of the residual system. Hamiltonian theory of ray optics can be used to determine the family of primitives which is in particular a simple task if the freeform is the exit surface of the illumination system. For simple optical systems an analytical description of the primitives is possible. Contrarily, for more complex optics a conventional raytracer is additionally utilized to determine the required system's information, like the optical path lengths or mixed characteristics. To this end a discrete set of rays is traced through the residual systems and the required relations are interpolated to obtain a quasi-analytic representation of the primitives. The potential of this approach is demonstrated by some examples, e.g. freeform optics including collimating or deflection elements.

Michaelis, D.; Schreiber, P.; Li, Chen; Bräuer, A.

2011-09-01

301

Studies of charge neutral FCC Lattice Gas with Yukawa Interaction and Accelerated Cartesian Expansion method  

NASA Astrophysics Data System (ADS)

In this thesis, I present the results of studies of the structural properties and phase transition of a charge neutral FCC Lattice Gas with Yukawa Interaction and discuss a novel fast calculation algorithm---Accelerated Cartesian Expansion (ACE) method. In the first part of my thesis, I discuss the results of Monte Carlo simulations carried out to understand the finite temperature (phase transition) properties and the ground state structure of a Yukawa Lattice Gas (YLG) model. In this model the ions interact via the potential q iqjexp(-kappar> ij)/rij where qi,j are the charges of the ions located at the lattice sites i and j with position vectors R i and Rj; rij = Ri-Rj, kappa is a measure of the range of the interaction and is called the screening parameter. This model approximates an interesting quaternary system of great current thermoelectric interest called LAST-m, AgSbPbmTem+2. I have also developed rapid calculation methods for the potential energy calculation in a lattice gas system with periodic boundary condition bases on the Ewald summation method and coded the algorithm to compute the energies in MC simulation. Some of the interesting results of the MC simulations are: (i) how the nature and strength of the phase transition depend on the range of interaction (Yukawa screening parameter kappa) (ii) what is the degeneracy of the ground state for different values of the concentration of charges, and (iii) what is the nature of two-stage disordering transition seen for certain values of x. In addition, based on the analysis of the surface energy of different nano-clusters formed near the transition temperature, the solidification process and the rate of production of these nano-clusters have been studied. In the second part of my thesis, we have developed two methods for rapidly computing potentials of the form R-nu. Both these methods are founded on addition theorems based on Taylor expansions. Taylor's series has a couple of inherent advantages: (i) it forms a natural framework for developing addition theorem based computational schemes for a range of potentials; (ii) only Cartesian tensors (or products of Cartesian quantities) are used as opposed to special functions. This makes creating a fast scheme possible for potential of the form R-nu . Indeed, it is also possible to generalize the proposed methods to several potentials that are important in mathematical physics. An interesting consequence of the approach has been the demonstration of the equivalence of FMMs that are based on traceless Cartesian tensors to those based on spherical expansions for nu = 1. Two methods are introduced; the first relies on exact translation of the origin of the multipole whereas the second relies on cascaded Taylor's approximations. Finally, we have shown the application of this methodology to computing Coulombic, Lennard-Jones, Yukawa potentials and etc. We have also demonstrated the efficacy of this scheme for other (non-integer) potential functions.

Huang, He

302

ALGEBRAIC GRID FRONT MARCHING METHODS  

Microsoft Academic Search

The transfinite interpolation formula of grid generation that employs the Hermite interpolation formula is improved by the addition of a grid front marching method embedded with a simple grid smoother. In the test cases, the proposed method preserved approximate grid orthogonality around all the boundaries and eliminates grid nonsmooth-ness, grid slope discontinuity, and grid overlapping that occurred with the original

Yuan Chang Liou; Yih Nen Jeng

1995-01-01

303

TEM simulation with topography using boundary-fitted grid  

NASA Astrophysics Data System (ADS)

Finite-Difference Time-Domain (FDTD) method has been successfully used in transient electromagnetic (TEM) simulation. Until recently, however, topography seems to be commonly neglected. To assess the topographic effect in TEM, some authors used a staircase approximation to the earth-air interface. But this approach might have two problems: first, its error might be very large; second, since air layer is explicitly included in FDTD computation, a very small time step is necessary to maintain the stability condition, which makes it inefficient. Another method to account for the tomography is using a non-Cartesian grid which is conformed to the boundary. In fact such boundary-fitted grids have been widely used in computational fluid dynamics to approximate the irregular boundary. In this study, we use a FDTD method combining boundary-fitted grids with the classical staggered grid, unconditional stable DuFort-Frankel scheme to discrete the quasi-static Maxwell equation. Since TEM simulation needs to step to a very late time, air layer had better not be included in FDTD computation. Instead, the boundary condition at the earth-air interface is handled via upward continuation. As the interface is generally not flat, the traditional FFT approach in upward continuation needs some modification. We use a method similar to the equivalent source method in gravity upward continuation, which required several FFT iterations to refine the results. We will report the preliminary results of our method and test its accuracy and efficiency with other methods.

Li, D.; Huang, Q.

2009-12-01

304

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

305

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

Microsoft Academic Search

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

Steven Dubowsky; Constantinos Mavroidis

1999-01-01

306

An efficient hierarchical optical path network design algorithm based on a traffic demand expression in a cartesian product space  

Microsoft Academic Search

We propose a hierarchical optical path network design algorithm. In order to efficiently accommodate wavelength paths in each waveband path, we define a source-destination Cartesian product space that allows the 'closeness' among wavelength paths to be assessed. By grouping 'close' wavelength paths, found by searching for clusters in the space, we iteratively create waveband paths that efficiently accommodate the wavelength

Isao Yagyu; Hiroshi Hasegawa; Ken-ichi Sato

2008-01-01

307

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

Microsoft Academic Search

This paper is concerned with the analysis and the numerical evaluation from experimental measurements of the static, Cartesian stiffness of wrist joints, in particular the human wrist. The primary aim is to extend from Euclidean spaces to so(3), the group of rigid body rotations, previous methods for assessing the end-point stiffness of the human arm, typically performed via a robotic

Domenico Campolo

2011-01-01

308

Advancing Smart Grid Interoperability and Implementing NIST's Interoperability Roadmap  

SciTech Connect

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

Basso,T.; DeBlasio, R.

2010-04-01

309

Anharmonic state counts and partition functions for molecules via classical phase space integrals in curvilinear coordinates  

NASA Astrophysics Data System (ADS)

An algorithm is presented for calculating fully anharmonic vibrational state counts, state densities, and partition functions for molecules using Monte Carlo integration of classical phase space. The algorithm includes numerical evaluations of the elements of the Jacobian and is general enough to allow for sampling in arbitrary curvilinear or rectilinear coordinate systems. Invariance to the choice of coordinate system is demonstrated for vibrational state densities of methane, where we find comparable sampling efficiency when using curvilinear z-matrix and rectilinear Cartesian normal mode coordinates. In agreement with past work, we find that anharmonicity increases the vibrational state density of methane by a factor of ~2 at its dissociation threshold. For the vinyl radical, we find a significant (~10×) improvement in sampling efficiency when using curvilinear z-matrix coordinates relative to Cartesian normal mode coordinates. We attribute this improved efficiency, in part, to a more natural curvilinear coordinate description of the double well associated with the H2C-C-H wagging motion. The anharmonicity correction for the vinyl radical state density is ~1.4 at its dissociation threshold. Finally, we demonstrate that with trivial parallelizations of the Monte Carlo step, tractable calculations can be made for the vinyl radical using direct ab initio potential energy surface evaluations and a composite QCISD(T)/MP2 method.

Kamarchik, Eugene; Jasper, Ahren W.

2013-05-01

310

Anharmonic state counts and partition functions for molecules via classical phase space integrals in curvilinear coordinates.  

PubMed

An algorithm is presented for calculating fully anharmonic vibrational state counts, state densities, and partition functions for molecules using Monte Carlo integration of classical phase space. The algorithm includes numerical evaluations of the elements of the Jacobian and is general enough to allow for sampling in arbitrary curvilinear or rectilinear coordinate systems. Invariance to the choice of coordinate system is demonstrated for vibrational state densities of methane, where we find comparable sampling efficiency when using curvilinear z-matrix and rectilinear Cartesian normal mode coordinates. In agreement with past work, we find that anharmonicity increases the vibrational state density of methane by a factor of ?2 at its dissociation threshold. For the vinyl radical, we find a significant (?10×) improvement in sampling efficiency when using curvilinear z-matrix coordinates relative to Cartesian normal mode coordinates. We attribute this improved efficiency, in part, to a more natural curvilinear coordinate description of the double well associated with the H2C-C-H wagging motion. The anharmonicity correction for the vinyl radical state density is ?1.4 at its dissociation threshold. Finally, we demonstrate that with trivial parallelizations of the Monte Carlo step, tractable calculations can be made for the vinyl radical using direct ab initio potential energy surface evaluations and a composite QCISD(T)/MP2 method. PMID:23697411

Kamarchik, Eugene; Jasper, Ahren W

2013-05-21

311

Numerical relativity in spherical polar coordinates: Evolution calculations with the BSSN formulation  

NASA Astrophysics Data System (ADS)

In the absence of symmetry assumptions most numerical relativity simulations adopt Cartesian coordinates. While Cartesian coordinates have some desirable properties, spherical polar coordinates appear better suited for certain applications, including gravitational collapse and supernova simulations. Development of numerical relativity codes in spherical polar coordinates has been hampered by the need to handle the coordinate singularities at the origin and on the axis, for example by careful regularization of the appropriate variables. Assuming spherical symmetry and adopting a covariant version of the Baumgarte-Shapiro-Shibata-Nakamura equations, Montero and Cordero-Carrión recently demonstrated that such a regularization is not necessary when a partially implicit Runge-Kutta method is used for the time evolution of the gravitational fields. Here we report on an implementation of the Baumgarte-Shapiro-Shibata-Nakamura equations in spherical polar coordinates without any symmetry assumptions. Using a partially implicit Runge-Kutta method we obtain stable simulations in three spatial dimensions without the need to regularize the origin or the axis. We perform and discuss a number of tests to assess the stability, accuracy and convergence of the code, namely weak gravitational waves, “hydro-without-hydro” evolutions of spherical and rotating relativistic stars in equilibrium, and single black holes.

Baumgarte, Thomas W.; Montero, Pedro J.; Cordero-Carrión, Isabel; Müller, Ewald

2013-02-01

312

A Grid Cataloging System  

NASA Astrophysics Data System (ADS)

Grid computing typically involves a large number of grid and scientific research collaborations with different computing needs. In grid computing, the needs are provided by distributed computing sites with computing resources and storage resources for participating research collaborations. In each site which provides such grid resources, it is necessary for the distributed computing resources to be monitored constantly. Then, the status of the monitored site information needs to be accurately presented to the collaborators. The monitored site information can be presented in the form of catalog for each site in a single web page which summarizes the status of each participating sites. Then, based on the information presented in the cataloging system, computing can be scheduled or participating grid site's status can be checked easily. We have designed a grid site status cataloging system to be used for such purpose. We present a grid cataloging system called the Gridcat. The Gridcat stores monitored information to a database using the back-end scripts. The back-end scripts are used to access to information on the grid computing resources, perform grid tests proactively, query against each grid site, and finally store all the information gathered to a database. The web front-end scripts presents a summary of site status at a certain time. The Gridcat can be easily plugged into existing web servers that serves grid site status and can provide an easy grid cataloging with combination of other grid monitoring components.

Kim, Bockjoo; Prescott, Craig; Rodrigue, Jorge; Avery, Paul

2004-11-01

313

A generalized implicit algorithm for multi-dimensional particle-in-cell simulations in Cartesian geometry  

NASA Astrophysics Data System (ADS)

An implicit multi-dimensional particle-in-cell (PIC) code is developed to study the interaction of ultrashort pulse lasers with matter. The algorithm is based on current density decomposition and is only marginally more complicated compared to explicit PIC codes, but it completely eliminates grid heating and possesses good energy conserving properties with relaxed time step and grid resolution. This is demonstrated in a test case study, in which high-energy protons are generated from a thin carbon foil at solid density using linear and circular polarizations. The grid heating rate is estimated to be 1-10 eV/ps.

Petrov, G. M.; Davis, J.

2011-07-01

314

A generalized implicit algorithm for multi-dimensional particle-in-cell simulations in Cartesian geometry  

SciTech Connect

An implicit multi-dimensional particle-in-cell (PIC) code is developed to study the interaction of ultrashort pulse lasers with matter. The algorithm is based on current density decomposition and is only marginally more complicated compared to explicit PIC codes, but it completely eliminates grid heating and possesses good energy conserving properties with relaxed time step and grid resolution. This is demonstrated in a test case study, in which high-energy protons are generated from a thin carbon foil at solid density using linear and circular polarizations. The grid heating rate is estimated to be 1-10 eV/ps.

Petrov, G. M.; Davis, J. [Naval Research Laboratory, Plasma Physics Division, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)

2011-07-15

315

Data Grids, Collections, and Grid Bricks  

Microsoft Academic Search

Data grids federate storage resources. They provide a logical name space that can be used to register digital entities, a storage repository abstraction for manipulating data, and a high level abstraction for supporting user-selected interfaces. Data grids can be used to build persistent collections. Data can be stored across multiple types of storage systems with persistent copies kept in archives.

Arcot Rajasekar; Michael Wan; Reagan Moore; George Kremenek; Tom Guptil

2003-01-01

316

Equations of laminar and turbulent flows in general curvilinear coordinates  

Microsoft Academic Search

Recent developments in computational fluid mechanics and grid generation have made it possible to consider complex three dimensional laminar and turbulent flows using nonorthogonal coordinates. However, the necessary equations in generalized nonorthogonal coordinates are not readily available in a single reference. The purpose of this report is to present these equations for an incompressible fluid. Methods of curvilinear tensor analysis

M. C. Richmond; H. C. Chen; V. C. Patel

1986-01-01

317

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

318

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 nationâs electric power grid and what it means for a residential home to be âoff the grid

Integrated Teaching And Learning Program

319

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

320

Building a Biodiversity GRID  

Microsoft Academic Search

In the BiodiversityWorld project we are building a GRID to support scientific biodiversity-related research. The requirements as- sociated with such a GRID are somewhat different from other GRIDs, and this has influenced the architecture that we have developed. In this paper we outline these requirements, most notably the need to inter- operate over a diverse set of legacy databases and

Andrew C. Jones; Richard J. White; W. Alex Gray; Frank A. Bisby; Neil Caithness; Nick Pittas; Xuebiao Xu; Tim Sutton; Nick J. Fiddian; Alastair Culham; Malcolm Scoble; Paul Williams; Oliver Bromley; Peter Brewer; Chris Yesson; Shonil Bhagwat

2004-01-01

321

Plasma-Grid Interaction  

Microsoft Academic Search

Plasma interaction with a grid is important in a number of applications. In neutral beam etching, for example, a grid is used to neutralize ions and generate collimated beams of energetic neutrals for anisotropic etch without charge damage. Also, many ion sources and satellite thrusters are based on extraction of an ion beam from a plasma through a grid. The

Chang-Koo Kim; Demetre Economou; Justine Johannes; Timothy Bartel

1999-01-01

322

Approach for Dynamic Grids.  

National Technical Information Service (NTIS)

An approach is presented for the generation of two-dimensional, structured, dynamic grids. The grid motion may be due to the motion of the boundaries of the computational domain or to the adaptation of the grid to the transient, physical solution. A time-...

J. W. Slater M. Liou R. G. Hindman

1994-01-01

323

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

324

Hyperboloidal coordinates: transformations and applications in special constructions  

NASA Astrophysics Data System (ADS)

The vector-based algorithms for biaxial and triaxial ellipsoidal coordinates presented by Feltens (J Geod 82:493-504, 2008; 83:129-137, 2009) have been extended to hyperboloids of one sheet. For the backward transformation from Cartesian to hyperboloidal coordinates, of two iterative process candidates one was identified to be well suited. It turned out that a careful selection of the center of curvature is essential for the establishment of a stable and reliable iteration process. In addition, for zero hyperboloidal heights a closed solution is presented. The hyperboloid algorithms are again based on simple formulae and have been successfully tested for various theoretical hyperboloids. The paper concludes with a practical application example on a cooling tower construction.

Feltens, J.

2011-04-01

325

Variational formulation of curved beams in global coordinates  

NASA Astrophysics Data System (ADS)

In this paper we derive a variational formulation for the static analysis of a linear curved beam natively expressed in global Cartesian coordinates. Using an implicit description of the beam midline during derivation we eliminate the need for local coordinates. The only geometrical information appearing in the final expressions for the governing equations is the tangential direction. As a consequence, zero or discontinuous curvature, for example at inflection points, pose no difficulty in this formulation. Kinematic assumptions encompassing both Timoshenko and Euler-Bernoulli beam theories are considered. With the exception of truly three-dimensional formulations, models for curved beams found in the literature are typically derived in the local Frenet frame. We implement finite element methods with global degrees of freedom and discuss curvature coupling effects and locking. Numerical comparisons with classical solutions for straight and curved cantilever beams under tip load are given, as well as numerical examples illustrating curvature coupling effects.

Hansbo, Peter; Larson, Mats G.; Larsson, Karl

2013-09-01

326

On Adaptive Aspect-Oriented Coordination for Critical Infrastructures  

Microsoft Academic Search

The future EU power grid must rely on a flexible hierarchy of coordi- nation mechanisms. To that end, we propose a top-down approach to coordina- tion which enables us to introduce meta-coordination as a viable approach. We describe several important aspects of meta -coordination. Software adaptation and aspect-oriented approaches may be a suitable venue for use in meta- coordination. Consequently,

Björn Törnqvis; Rune Gustavsson

327

Wind-driven spin-up in eddy-resolving ocean models formulated in isopycnic and isobaric coordinates  

NASA Astrophysics Data System (ADS)

Wind-driven spin-up of the four-layer, quasi-isopycnic, eddy-resolving primitive equation model of Bleck and Boudra (1981) is compared with that obtained with a (numerically dissimilar) "pure" isopycnic coordinate model and an isobaric (i.e., quasi-Cartesian) coordinate model. In particular, the onset of hydrodynamic instabilities in the flow forced by a double-gyre wind stress pattern is studied. The spin-up processes associated with the isopycnic and quasi-isopycnic model are found to be similar, whereas the flow pattern produced by the quasi-Cartesian model deviates in the direction of Holland's (1978) and Holland and Lin's (1975a, b) two-layer solutions.

Bleck, Rainer; Boudra, Douglas

1986-06-01

328

Grid Quality Measures  

NASA Astrophysics Data System (ADS)

The third chapter discusses very important issues of grid generation, connected with a description of grid quality measures in forms suitable for formulating grid techniques. The definitions of the grid quality measures are based on the metric tensors and on the relations between the metric elements considered in Chap. 2. Special attention is paid to the invariants of the metric tensors, which are the basic elements for the definition of many important grid quality measures. Clear algebraic and geometric interpretations of the invariants are presented.

Liseikin, Vladimir D.

329

The Grid in INAF  

NASA Astrophysics Data System (ADS)

This paper presents an overview of the Grid-related projects in which Insitutes of INAF (Istituto Nazionale di Astrofisica) were involved, starting from the GRID.IT project until the recent and currently in progress participation to EGEE (Enabling Grids for E-sciencE), the main project for the setup of a Grid Infrastructure for Science in Europe. The paper will give an overview of these activities putting particular emphasis on some key pilot projects, like the simulations of the Planck mission and the development of tools to widen the Grid capabilities to meet the needs of astrophysical applications.

Vuerli, C.; Taffoni, G.; Sponza, M.; Pasian, F.

330

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

331

Representation of protein 3D structures in spherical (?, ?, ?) coordinates and two of its potential applications.  

PubMed

Three-dimensional objects can be represented using cartesian, spherical or cylindrical coordinate systems, among many others. Currently all protein 3D structures in the PDB are in cartesian coordinates. We wanted to explore the possibility that protein 3D structures, especially the globular type (spheroproteins), when represented in spherical coordinates might find useful novel applications. A Fortran program was written to transform protein 3D structure files in cartesian coordinates (x,y,z) to spherical coordinates (?, ?, ?), with the centroid of the protein molecule as origin. We present here two applications, namely, (1) separation of the protein outer layer (OL) from the inner core (IC); and (2) identifying protrusions and invaginations on the protein surface. In the first application, ? and ? were partitioned into suitable intervals and the point with maximum ? in each such '?-? bin' was determined. A suitable cutoff value for ? is adopted, and for each ?-? bin, all points with ? values less than the cutoff are considered part of the IC, and those with ? values equal to or greater than the cutoff are considered part of the OL. We show that this separation procedure is successful as it gives rise to an OL that is significantly more enriched in hydrophilic amino acid residues, and an IC that is significantly more enriched in hydrophobic amino acid residues, as expected. In the second application, the point with maximum ? in each ?-? bin are sequestered and their frequency distribution constructed (i.e., maximum ?'s sorted from lowest to highest, collected into 1.50Å-intervals, and the frequency in each interval plotted). We show in such plots that invaginations on the protein surface give rise to subpeaks or shoulders on the lagging side of the main peak, while protrusions give rise to similar subpeaks or shoulders, but on the leading side of the main peak. We used the dataset of Laskowski et al. (1996) to demonstrate both applications. PMID:21956738

Reyes, Vicente M

2011-09-29

332

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

PubMed

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 using 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 in the energy calculations amount to 36N - 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 (water dimer and trimer) are presented. In all cases the frequencies based on internal coordinates differ on average by <1 cm(-1) from those obtained from Cartesian coordinates. PMID:23406376

Miliordos, Evangelos; Xantheas, Sotiris S

2013-03-05

333

Observation Coverage Gridding for Infrared Sounding Instruments using Ray Casting  

NASA Astrophysics Data System (ADS)

Gridding in remote sensing is a process to re-project observations from their original coordinate system based on satellite orbit and attitude to a grid defined by Earth coordinates. Primitive methods assume that radiances are point measurements on Earth, and typically average all observations centered in grid cells, or perform nearest neighbor, bilinear, or other interpolation schemes between geolocated observations. A more accurate gridding approach exists using Observation Coverage (obscov), which is a statistic describing the percentage coverage of a footprint for a particular grid-cell. Obscov based gridding produces better results, because it takes into account the instrument's footprint geometry, and spatial response capability, and has been implemented for several instruments such as MODIS. We describe and implement a new ray-casting algorithm to accurately determine observation coverage (obscov) for each gridcell/footprint pair. The described algorithm can, ignoring atmospheric effects, determine obscov for footprints with any known spatial response function at any limb angle, and also works for grid sizes either coarser or finer than the footprint size. We discuss the algorithmic optimizations as well as accuracy/performance tradeoffs that allow this ray-casting algorithm to compute obscov at production speeds. We have integrated this obscov algorithm into our on demand gridding system for the Atmospheric Infra-Red Sounder (AIRS). AIRS has been recording Outgoing Longwave Radiation (OLR) since the launch of the Aqua satellite in September 2002. Our processing system has gridded all AIRS OLR observations between September 2002 to Jan 2008 using the 324 operational channels to a daily 1/2 by 1 degree latitude/longitude grid, and will accept on demand gridding at any grid resolution.

Chapman, D. R.; Halem, M.

2008-05-01

334

Understanding The Smart Grid  

SciTech Connect

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

NONE

2007-11-15

335

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

Microsoft Academic Search

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

Akihiko Konagaya

2006-01-01

336

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

PubMed

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

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

2011-02-18

337

VARIANT: VARIational anisotropic nodal transport for multidimensional Cartesian and hexadgonal geometry calculation  

SciTech Connect

The theoretical basis, implementation information and numerical results are presented for VARIANT (VARIational Anisotropic Neutron Transport), a FORTRAN module of the DIF3D code system at Argonne National Laboratory. VARIANT employs the variational nodal method to solve multigroup steady-state neutron diffusion and transport problems. The variational nodal method is a hybrid finite element method that guarantees nodal balance and permits spatial refinement through the use of hierarchical complete polynomial trial functions. Angular variables are expanded with complete or simplified P{sub 1}, P{sub 3} or P{sub 5}5 spherical harmonics approximations with full anisotropic scattering capability. Nodal response matrices are obtained, and the within-group equations are solved by red-black or four-color iteration, accelerated by a partitioned matrix algorithm. Fission source and upscatter iterations strategies follow those of DIF3D. Two- and three-dimensional Cartesian and hexagonal geometries are implemented. Forward and adjoint eigenvalue, fixed source, gamma heating, and criticality (concentration) search problems may be performed.

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

1995-10-01

338

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 resulting FORTRAN computer code is designed to handle an arbitrary number of spatial, energy, and angle subdivisions. Any degree of scattering anisotropy can be handled by the code for either external source or fission systems. The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. In the general case the calculation is iterative due to neutron sources which depend on the neutron density itself, such as scattering interactions.

Pevey, R.E.

1982-07-01

339

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

2006-10-17

340

Arbitrary order El'yashevich-Wilson B tensor formulas for the most frequently used internal coordinates in molecular vibrational analyses  

NASA Astrophysics Data System (ADS)

In recent years, internal coordinates have become the preferred means of expressing potential energy surfaces. The ability to transform quantities from chemically significant internal coordinates to primitive Cartesian coordinates and spectroscopically relevant normal coordinates is thus critical to the further development of computational chemistry. In the present work, general nth order formulas are presented for the Cartesian derivatives of the five most commonly used internal coordinates--bond stretching, bond angle, torsion, out-of-plane angle, and linear bending. To compose such formulas in a reasonably understandable fashion, a new notation is developed that is a generalization of that which has been used previously for similar purposes. The notation developed leads to easily programmable and reasonably understandable arbitrary order formulas, yet it is powerful enough to express the arbitrary order B tensor of a general, N-point internal coordinate, as is done herein. The techniques employed in the derivation of such formulas are relatively straightforward, and could presumably be applied to a number of other internal coordinates as needed.

Hollman, David S.; Schaefer, Henry F.

2012-10-01

341

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.

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

2013-04-01

342

Choice of coordinates on a toroidal magnetic surface  

SciTech Connect

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

Skovoroda, A. A. [Russian Research Centre Kurchatov Institute, Nuclear Fusion Institute (Russian Federation)

2008-11-15

343

Securing smart grid technology  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

344

Study on Retrieving Three-Dimensional Wind Using Simulated Dual-Doppler Radar Data in the Cartesian Space  

Microsoft Academic Search

This paper investigates a technique of retrieving three-dimensional wind elds from the dual-Doppler weather radar radial wind which is based on the Cartesian space using variational method. This technology provides a simultaneous resolution of three wind components and satises both the minimal dual-equation system and the continuity equation. The main advantage of this method is that it can remove the

ZHOU Haiguang; ZHANG Peiyuan

2005-01-01

345

Developmental coordination disorder  

MedlinePLUS

Developmental coordination disorder is a childhood disorder that leads to poor coordination and clumsiness. ... of school-age children have some kind of developmental coordination disorder. Children with this disorder may: Have ...

346

Science on the TeraGrid  

Microsoft Academic Search

The TeraGrid is an advanced, integrated, nationally-distributed, open, user-driven, US cyberinfrastructure that enables and supports leading edge scientific discovery and promotes science and technology education. It comprises supercomputing resources, storage systems, visualization re- sources, data collections, software, and science gateways, integrated by software systems and high bandwidth networks, coordinated through com- mon policies and operations, and supported by technology experts.

Daniel S. Katz; Scott Callaghan; Robert Harkness; Sudhakar Pamidighantam; Marlon Pierce; Beth Plale; Carol Song; John Towns

2010-01-01

347

A fast algorithm for grid generation  

SciTech Connect

The need for fast grid generation has become an important part of solving large complex computational fluid dynamic problems. A new algorithm is developed for this purpose. The two-dimensional system of equations for coordinate generation includes a procedure to force the line spacing in the interior field to reflect the adjacent boundary point distribution. The coordinate generation equations, in Newton's iteration form, are solved with a modified strongly implicit (MSI) procedure. The algorithm is applied to typical H-, O-, and C-type grids and a practical problem configured as a forward facing cavity. The grid generation equations were initialized with their Laplacian counterpart. All computations were performed on a MicroVAX 3400 computer. Based on the numerical studies, the proposed solution scheme is faster than the more common point SOR and ADI methods for large grid generation problems of practical interest. The degree of computational savings however is highly problem dependent. Extensions of the solution scheme to problems involving three-dimensions, including surfaces in three-dimensional space, are described.

Jordan, S.A. (Naval Undersea Warfare Center, Newport, RI (United States)); Spaulding, M.L. (Univ. of Rhode Island, Kingston (United States))

1993-01-01

348

Challenges facing production grids  

SciTech Connect

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

Pordes, Ruth; /Fermilab

2007-06-01

349

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

350

Grid Computing Planet  

NSDL National Science Digital Library

Grid computing is a way of achieving high computational power by using the collective resources of many networked computers. This Web site serves as a news source for some of the latest breakthroughs in grid technology, major project announcements and milestones, and governmental initiatives. In addition to the regular news updates, the site offers many other resources. For example, the Frequently Asked Questions list defines grid computing and briefly touches on its importance and applications. Feature articles are added periodically and categorized into background information, grid implementations, standards, and other issues.

2003-01-01

351

Solar System Data Access and Analysis with AstroGrid  

Microsoft Academic Search

AstroGrid is the UK's contribution to a global Virtual Observatory (VO). This paper emphasizes the Solar System aspects of the 2006.3 AstroGrid release. The HelioScope service is presented, providing access to solar image data from the Virtual Solar Observatory, and to time series data from a variety of heliospheric and magnetospheric datasets part of the NASA Coordinated Data Analysis Workshops

S. Dalla; A. M. S. Richards; E. Gonzalez-Solares; N. A. Walton; J. A. Tedds

2007-01-01

352

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

NASA Astrophysics Data System (ADS)

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

Slowik, Edward Steven

353

Research on the comparison of extension mechanism of cellular automaton based on hexagon grid and rectangular grid  

NASA Astrophysics Data System (ADS)

Historically, cellular automata (CA) is a discrete dynamical mathematical structure defined on spatial grid. Research on cellular automata system (CAS) has focused on rule sets and initial condition and has not discussed its adjacency. Thus, the main focus of our study is the effect of adjacency on CA behavior. This paper is to compare rectangular grids with hexagonal grids on their characteristics, strengths and weaknesses. They have great influence on modeling effects and other applications including the role of nearest neighborhood in experimental design. Our researches present that rectangular and hexagonal grids have different characteristics. They are adapted to distinct aspects, and the regular rectangular or square grid is used more often than the hexagonal grid. But their relative merits have not been widely discussed. The rectangular grid is generally preferred because of its symmetry, especially in orthogonal co-ordinate system and the frequent use of raster from Geographic Information System (GIS). However, in terms of complex terrain, uncertain and multidirectional region, we have preferred hexagonal grids and methods to facilitate and simplify the problem. Hexagonal grids can overcome directional warp and have some unique characteristics. For example, hexagonal grids have a simpler and more symmetric nearest neighborhood, which avoids the ambiguities of the rectangular grids. Movement paths or connectivity, the most compact arrangement of pixels, make hexagonal appear great dominance in the process of modeling and analysis. The selection of an appropriate grid should be based on the requirements and objectives of the application. We use rectangular and hexagonal grids respectively for developing city model. At the same time we make use of remote sensing images and acquire 2002 and 2005 land state of Wuhan. On the base of city land state in 2002, we make use of CA to simulate reasonable form of city in 2005. Hereby, these results provide a proof of concept for hexagonal which has great dominance.

Zhai, Xiaofang; Zhu, Xinyan; Xiao, Zhifeng; Weng, Jie

2009-10-01

354

Astronomical data reduction in DATA-GRID  

NASA Astrophysics Data System (ADS)

The DRACO (Datagrid for Italian Research in Astrophysics and Coordination with the Virtual Observatory) project is meant to create a Grid distributed system of resources with multi-functionalities combined with the Virtual Obervatory approach. The final aim is the porting on DataGrid of all main astrophysical applications within a National calculation infrastructure. Partecipans to the DRACO project are the National Observatories of Rome, Trieste, Padua, Catania, Naples, Bologne and the University of study of Salern. An astronomical software package has been developed to make all main astronomical tools availables on Data Grid (Astrosoft_v1.0Jan2005, Gallozzi et al., 2005, ref. http://grid006.mporzio.astro.it) starting from the ESO-Scisoft package. This software package contains the ESO-MIDAS, IRAF, IDL, SEXTRACOTR, etc. Here we present a standard astronomical data reduction test performed with the ESO MIDAS component of the Astrosoft package. This data reduction test was submitted with a web Grid Portal developed within the same DRACO project. All tests and simulations were performed on the Gilda testbed.

Gallozzi, Stefano

355

Scripting Coordination Styles  

Microsoft Academic Search

The fact that so many different kinds of coordination models and lan- guages have been proposed suggests that no one single approach will be the best for all coordination problems. Different coordination styles exhibiting different properties may be more suitable for some problems than others. Like other archi- tectural styles, coordination styles can be expressed in terms of components, con-

Franz Achermann; Stefan Kneubuehl; Oscar Nierstrasz

2000-01-01

356

The MammoGrid Virtual Organisation - Federating Distributed Mammograms.  

PubMed

The MammoGrid project aims to deliver a prototype which enables the effective collaboration between radiologists using grid, service-orientation and database solutions. The grid technologies and service-based database management solution provide the platform for integrating diverse and distributed resources, creating what is called a 'virtual organisation'. The MammoGrid Virtual Organisation facilitates the sharing and coordinated access to mammography data, medical imaging software and computing resources of participating hospitals. Hospitals manage their local database of mammograms, but in addition, radiologists who are part of this organisation can share mammograms, reports, results and image analysis software. The MammoGrid Virtual Organisation is a federation of autonomous multi-centres sites which transcends national boundaries. This paper outlines the service-based approach in the creation and management of the federated distributed mammography database and discusses the role of virtual organisations in distributed image analysis. PMID:16160378

Estrella, Florida; McClatchey, Richard; Rogulin, Dmitry

2005-01-01

357

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

358

Visualizing the electric grid  

Microsoft Academic Search

In the new world of competition, power traders, grid managers, public service boards, and the public itself all need to take in what's happening at a glance. Visualization software enables viewers to interpret the data more rapidly and more accurately than ever before. This kind of software will become still more useful, even indispensable, as electricity grids are integrated over

T. J. Overbye; J. D. Weber

2001-01-01

359

Datums, Ellipsoids, Grids, and Grid Reference Systems.  

National Technical Information Service (NTIS)

This manual describes the basic principles of the Military Grid Reference System and the non-standard reference systems. It describes the method for determining references on maps and charts at scales of 1:1,000,000 and larger. It contains identifications...

J. W. Hager L. L. Fry S. S. Jacks D. R. Hill

1992-01-01

360

An Optimal Magnetic Coordinate system for High-Beta ST configurations  

NASA Astrophysics Data System (ADS)

In the study of magnetohydrodynamics of magnetically confined systems, it is well known that both analysis and computation are facilitated by an appropriate coordinate system. Specifically, a magnetic coordinate system,(,),where ? is a flux label, ? a poloidal angle and ? a generalized toroidal angle, such that magnetic field lines are straight in (,) space. The generalized toroidal angle, ?, can be related to the Cartesian angle ?, by introducing a periodic function ?(,). This function depends on the choice of Jacobian, and is identically zero when the Jacobian is proportional to x^2. This coordinate is commonly referred to as PEST coordinates. A more general approach to straight field line coordinates is obtained when the Jacobian is defined as J = X^i/?(?) |??|^j. Commonly used coordinate systems are: PEST, with i=2 , j=0; Equal Arcs, with i=j=1; and Hamada with i=j=0. Each of these coordinates has its own merits, but for high beta spherical tori, we identify a new coordinate system, i=0, j=1, which is optimal to this regime. We present results comparing the different coordinate systems in different parameter regimes.

Manickam, Janardhan

2007-11-01

361

CaGrid Workflow Toolkit: A taverna based workflow tool for cancer grid  

PubMed Central

Background In biological and medical domain, the use of web services made the data and computation functionality accessible in a unified manner, which helped automate the data pipeline that was previously performed manually. Workflow technology is widely used in the orchestration of multiple services to facilitate in-silico research. Cancer Biomedical Informatics Grid (caBIG) is an information network enabling the sharing of cancer research related resources and caGrid is its underlying service-based computation infrastructure. CaBIG requires that services are composed and orchestrated in a given sequence to realize data pipelines, which are often called scientific workflows. Results CaGrid selected Taverna as its workflow execution system of choice due to its integration with web service technology and support for a wide range of web services, plug-in architecture to cater for easy integration of third party extensions, etc. The caGrid Workflow Toolkit (or the toolkit for short), an extension to the Taverna workflow system, is designed and implemented to ease building and running caGrid workflows. It provides users with support for various phases in using workflows: service discovery, composition and orchestration, data access, and secure service invocation, which have been identified by the caGrid community as challenging in a multi-institutional and cross-discipline domain. Conclusions By extending the Taverna Workbench, caGrid Workflow Toolkit provided a comprehensive solution to compose and coordinate services in caGrid, which would otherwise remain isolated and disconnected from each other. Using it users can access more than 140 services and are offered with a rich set of features including discovery of data and analytical services, query and transfer of data, security protections for service invocations, state management in service interactions, and sharing of workflows, experiences and best practices. The proposed solution is general enough to be applicable and reusable within other service-computing infrastructures that leverage similar technology stack.

2010-01-01

362

Standardized UXO Technology Demonstration Site Blind Grid Scoring Record Number 691.  

National Technical Information Service (NTIS)

This scoring record documents the efforts of ARM Group Inc., to detect and discriminate inert unexploded ordnance (UXO) utilizing the APG Standardized UXO Technology Demonstration Site blind grid. Scoring Records have been coordinated by Larry Overbay and...

J. L. Overbay K. Watts R. Fling C. McClung M. Banta

2006-01-01

363

Orthogonal grid generation  

NASA Astrophysics Data System (ADS)

A technique is presented for the generation of two-dimensional orthogonal grids which is accurate, rapid, conceptually simple, relatively robust, and general enough to be applicable to a wide range of applications when coupled with modern flow solvers. A novel application of the hinge point transformation is used to map a contour onto a half plane, which is thereby transformed into an open rectangle, where the points added to close the rectangle and grid boundary point locations are specified according to preselected stretchings. Exponential spline interpolation determines the physical plane locations corresponding to the grid boundary point locations on three sides of the rectangle, and physical locations corresponding to the fourth side are obtained by inverting the transformations. A fast Poisson solver is then used to determine the physical location of the interior grid nodes. A method for building complex multiple region grids through the matching of simpler grids at common boundaries is illustrated. Suitable grids can be produced for a wide range of nonperiodic geometries.

Ives, D. C.; Siddons, W. D., Jr.

1984-06-01

364

The DESY Grid Centre  

NASA Astrophysics Data System (ADS)

DESY is one of the world-wide leading centers for research with particle accelerators, synchrotron light and astroparticles. DESY participates in LHC as a Tier-2 center, supports on-going analyzes of HERA data, is a leading partner for ILC, and runs the National Analysis Facility (NAF) for LHC and ILC in the framework of the Helmholtz Alliance, Physics at the Terascale. For the research with synchrotron light major new facilities are operated and built (FLASH, PETRA-III, and XFEL). DESY furthermore acts as Data-Tier1 centre for the Neutrino detector IceCube. Established within the EGI-project DESY operates a grid infrastructure which supports a number of virtual Organizations (VO), incl. ATLAS, CMS, and LHCb. Furthermore, DESY hosts some of HEP and non-HEP VOs, such as the HERA experiments and ILC as well as photon science communities. The support of the new astroparticle physics VOs IceCube and CTA is currently set up. As the global structure of the grid offers huge resources which are perfect for batch-like computing, DESY has set up the National Analysis Facility (NAF) which complements the grid to allow German HEP users for efficient data analysis. The grid infrastructure and the NAF use the same physics data which is distributed via the grid. We call the conjunction of grid and NAF the DESY Grid Centre. In the contribution to CHEP2012 we will in depth discuss the conceptional and operational aspects of our multi-VO and multi-community Grid Centre and present the system setup. We will in particular focus on the interplay of Grid and NAF and present experiences of the operations.

Haupt, A.; Gellrich, A.; Kemp, Y.; Leffhalm, K.; Ozerov, D.; Wegner, P.

2012-12-01

365

A transformation-free HOC scheme for steady convection-diffusion on non-uniform grids  

NASA Astrophysics Data System (ADS)

A higher order compact (HOC) finite difference solution procedure has been proposed for the steady two-dimensional (2D) convection-diffusion equation on non-uniform orthogonal Cartesian grids involving no transformation from the physical space to the computational space. Effectiveness of the method is seen from the fact that for the first time, an HOC algorithm on non-uniform grid has been extended to the Navier-Stokes (N-S) equations. Apart from avoiding usual computational complexities associated with conventional transformation techniques, the method produces very accurate solutions for difficult test cases. Besides including the good features of ordinary HOC schemes, the method has the advantage of better scale resolution with smaller number of grid points, with resultant saving of memory and CPU time. Gain in time however may not be proportional to the decrease in the number of grid points as grid non-uniformity imparts asymmetry to some of the associated matrices which otherwise would have been symmetric. The solution procedure is also highly robust as it computes complex flows such as that in the lid-driven square cavity at high Reynolds numbers (Re), for which no HOC results have so far been seen.

Kalita, Jiten C.; Dass, Anoop K.; Dalal, D. C.

2004-01-01

366

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

367

Grid Architecture Storage - Utilising Grid Computing for Dynamic Data Storage  

Microsoft Academic Search

Grid architecture storage (GAS) is based on the concept that the grid computing architecture can be manipulated in order to facilitate data storage on the grid. This paper describes the software that has been developed to prove this concept. The software utilises volatile resources on distributed grid nodes - primarily random access memory - to store data dynamically by shifting

P. Koszek; K. Sandrasegaran

2005-01-01

368

Digital Grid: Communicative Electrical Grids of the Future  

Microsoft Academic Search

To support a high penetration of intermittent solar and wind power generation, many regions are planning to add new high capacity transmission lines. These additional transmis- sion lines strengthen grid synchronization, but will also increase the grid's short circuit capacity, and furthermore will be very costly. With a highly interconnected grid and variable renewable generation, a small grid failure can

Rikiya Abe; Hisao Taoka; David McQuilkin

2011-01-01

369

Weaving computational grids: how analogous are they with electrical grids?  

Microsoft Academic Search

Can computational grids make as great an impact in the 21st century as electrical grids did in the 20th? A comparison of the two technologies could provide clues about how to make computational grids pervasive, dependable, and convenient. In this article, we describe how computational grids developed, their layered structure, and their emerging operational model, which we envisage as providing

MADHU CHETTY; RAJKUMAR BUYYA

2002-01-01

370

Numerical Generation of Orthogonal and Nonorthogonal Coordinates in Two Dimensional Simply and Doubly Connected Regions.  

National Technical Information Service (NTIS)

Techniques of mathematical modeling and numerical solution for grid generation in two dimensional simply and doubly connected regions are outlined. Four computer program listings and examples of the generation of nonorthogonal and orthogonal coordinates a...

Z. U. A. Warsi

1984-01-01

371

General Curvilinear Coordinate Systems.  

National Technical Information Service (NTIS)

The basic ideas of the construction and use of numerically-generated boundary-fitted coordinate systems for the numerical solution of partial differential equations are discussed. With such coordinate systems, all computation can be done on a fixed square...

J. F. Thompson

1982-01-01

372

Molecular Grid Membranes.  

National Technical Information Service (NTIS)

Regular two-dimensional covalent grids of monolayer thickness with molecular-size openings, reminiscent of a tennis net or chickenwire, will have many useful applications, among others as selective barrier materials and efficient passive or active separat...

J. Michl T. Magnera

2008-01-01

373

CMS Intergration Grid Testbed.  

National Technical Information Service (NTIS)

The CMS Integration Grid Testbed (IGT) comprises USCMS Tier-1 and Tier-2 hardware at the following sites: the California Institute of Technology, Fermi National Accelerator Laboratory, the University of California at San Diego, and the University of Flori...

G. E. Graham M. Anzar S. Aziz L. A. T. Bauserdick M. Ernst

2004-01-01

374

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.

375

Optimal population codes for space: grid cells outperform place cells.  

PubMed

Rodents use two distinct neuronal coordinate systems to estimate their position: place fields in the hippocampus and grid fields in the entorhinal cortex. Whereas place cells spike at only one particular spatial location, grid cells fire at multiple sites that correspond to the points of an imaginary hexagonal lattice. We study how to best construct place and grid codes, taking the probabilistic nature of neural spiking into account. Which spatial encoding properties of individual neurons confer the highest resolution when decoding the animal's position from the neuronal population response? A priori, estimating a spatial position from a grid code could be ambiguous, as regular periodic lattices possess translational symmetry. The solution to this problem requires lattices for grid cells with different spacings; the spatial resolution crucially depends on choosing the right ratios of these spacings across the population. We compute the expected error in estimating the position in both the asymptotic limit, using Fisher information, and for low spike counts, using maximum likelihood estimation. Achieving high spatial resolution and covering a large range of space in a grid code leads to a trade-off: the best grid code for spatial resolution is built of nested modules with different spatial periods, one inside the other, whereas maximizing the spatial range requires distinct spatial periods that are pairwisely incommensurate. Optimizing the spatial resolution predicts two grid cell properties that have been experimentally observed. First, short lattice spacings should outnumber long lattice spacings. Second, the grid code should be self-similar across different lattice spacings, so that the grid field always covers a fixed fraction of the lattice period. If these conditions are satisfied and the spatial "tuning curves" for each neuron span the same range of firing rates, then the resolution of the grid code easily exceeds that of the best possible place code with the same number of neurons. PMID:22594833

Mathis, Alexander; Herz, Andreas V M; Stemmler, Martin

2012-05-17

376

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

377

Grid in Geosciences  

NASA Astrophysics Data System (ADS)

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

Petitdidier, Monique; Schwichtenberg, Horst

2010-05-01

378

Random array grid collimator  

DOEpatents

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

Fenimore, E.E.

1980-08-22

379

MicroGrids  

Microsoft Academic Search

The MicroGrid concept assumes a cluster of loads and microsources (<100 kW) operating as a single controllable system that provides both power and heat to its local area. This concept provides a new paradigm for defining the operation of distributed generation. To the utility the MicroGrid can be thought of as a controlled cell of the power system. For example

R. H. Lasseter

2002-01-01

380

Algorithms and the Grid  

Microsoft Academic Search

We review the impact of Grid Computing and Web Services on scientific computing, stressing the importance of the “data-deluge”\\u000a that is driven by deployment of new instruments, sensors and satellites. This implies the need to integrate the naturally\\u000a distributed data sources with large simulation engines offering parallel low latency communication and so to integrate parallel\\u000a and Grid computing paradigms. We

Geoffrey C. Fox; Mehmet S. Aktas; Galip Aydin; Harshawardhan Gadgil; Shrideep Pallickara; Marlon E. Pierce; Ahmet Sayar

2009-01-01

381

GRIDs and Ambient Computing  

Microsoft Academic Search

GRIDs are both a new and an old concept. Many of the components have been the subject of R&D and some exist as commercial\\u000a products. The GRIDs concept represents many different things to different people: metacomputing, distributed computing, advanced\\u000a networking, distributed database, information retrieval, digital libraries, hypermedia, cooperative working, knowledge management,\\u000a advanced user interfaces, mobile and pervasive computing and many

Keith G. Jeffery; Oxfordshire OX

2002-01-01

382

Cook-Coordinate Plane  

NSDL National Science Digital Library

Become familiar with the coordinate plane. Learn the quadrants and how to graph points and read points on a coordinate plane. You are required to do the assignment and take the quiz. The other resources are to help prepare you for the quiz and book assignment. This is a quick review of the lesson.The Coordinate Plane This is a game to practice plotting and reading points.coordinates game *Assignment: Watch Powerpoint 3.3 and fill in your ...

Cook, Miss

2010-10-12

383

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

384

Coordinates, Conversions, and Kinematics  

Microsoft Academic Search

This is a guide to coordinate systems, representations, and geometric relationships between them, for components of the Rochester Robotics Laboratory. The main entities at issue are the joint angles, location variables, and coordinate systems of the Puma, the camera angles and coordinate systems associated with the head, the spatial location of three-dimensional points, and the kinematic and inverse kinematic relationships

Christopher M. Brown; Raymond D. Rimey

385

Literacy Coordinators' Handbook.  

ERIC Educational Resources Information Center

|This handbook is designed to provide support for England's National Literacy Strategy's Literacy Coordinators leading and coordinating literacy across the school. The handbook is designed as a working document and will contain additional materials, LEA (local education authorities) guidance, and additional papers which Coordinators may choose to…

Department for Education and Skills, London (England).

386

LCLS Undulator Coordinate System  

SciTech Connect

This note defines the LCLS undulator coordinate system and relates that coordinate system to the linear accelerator coordinate system. The slight downward pitch of the SLAC linac and the finite radius of the Earth necessitate some choices and definitions for the undulator layout which is described here. The layout described is consistent with the LCLS optics MAD file ''LCLS13APR04''.

Bong, E.

2005-01-31

387

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

388

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

389

Robust Controller for DFIGs of Grid-Connected Wind Turbines  

Microsoft Academic Search

This paper proposes a new robust controller in a stationary reference frame for doubly fed induction generators (DFIGs) of grid-connected wind turbines. Initially, a DFIG dy- namic model is derived from the voltage and flux equations in ?? coordinates, where uncertainties and disturbances intrinsic to the system are accounted for as perturbation terms are added to the nominal model. Then,

Jean Patric da Costa; Humberto Pinheiro; Thomas Degner; Gunter Arnold

2011-01-01

390

Characterizing and Correcting Gradient Errors in Non-Cartesian Imaging: Are Gradient Errors Linear-Time-Invariant?  

PubMed Central

Non-Cartesian and rapid imaging sequences are more sensitive to scanner imperfections such as gradient delays and eddy currents. These imperfections vary between scanners and over time and can be a significant impediment towards successful implementation and eventual adoption of non-Cartesian techniques by scanner manufacturers. Differences between the k-space trajectory desired and the trajectory actually acquired lead to misregistration and reduction in image quality. While early calibration methods required considerable scan time, more recent methods can work more quickly by making certain approximations. We examine a rapid gradient calibration procedure applied to multi-echo 3DPR acquisitions where the calibration runs as part of every scan. After measuring the trajectories traversed for excitations on each of the orthogonal gradient axes, trajectories for the oblique projections actually acquired during the scan are synthesized as linear combinations of these measurements. The ability to do rapid calibration depends on the assumption that gradient errors are linear and time-invariant. This work examines the validity of these assumptions and shows that the assumption of linearity is reasonable, but that gradient errors can vary over short time periods (due to changes in gradient coil temperature) and thus it is important to use calibration data matched to the scan data.

Brodsky, Ethan K.; Samsonov, Alexey A.; Block, Walter F.

2010-01-01

391

Environment-Based Coordination Through Coordination Artifacts  

Microsoft Academic Search

\\u000a In the context of human organisations, environment plays a fundamental role for supporting cooperative work and, more generally,\\u000a complex coordination activities. Support is realised through services, tools, artifacts shared and exploited by the collectivity of individuals for achieving individual as well as global objectives.\\u000a \\u000a \\u000a The conceptual framework of coordination artifacts is meant to bring the same sort of approach to

Alessandro Ricci; Mirko Viroli; Andrea Omicini

2004-01-01

392

Generation of curvilinear coordinates on multiply connected regions with boundary singularities  

Microsoft Academic Search

A new algorithm to generate smooth two-dimensional boundary conforming coordinates, with grid lines control, on multiply connected regions including boundary singularities, is devised. The technique fits into the category of elliptic grid generators, since it is based on the numerical solution of Poisson equations. The physical domain D is transformed into a topologically equivalent connected rectangular domain D? by defining

Vianey Villamizar; Otilio Rojas; Joseph Mabey

2007-01-01

393

Consistent discretization for simulations of flows with moving generalized curvilinear coordinates  

Microsoft Academic Search

SUMMARY We develop a consistent discretization of conservative momentum and scalar transport for the numerical simulation of flow using a generalized moving curvilinear coordinate system. The formulation guarantees consistency between the discrete transport equation and the discrete mass conservation equation due to grid motion. This enables simulation of conservative transport using generalized curvilinear grids that move arbitrarily in three dimensions

Y. J. Chou; O. B. Fringer

2009-01-01

394

Smart Grid Integration Laboratory  

SciTech Connect

The initial federal funding for the Colorado State University Smart Grid Integration Laboratory is through a Congressionally Directed Project (CDP), DE-OE0000070 Smart Grid Integration Laboratory. The original program requested in three one-year increments for staff acquisition, curriculum development, and instrumentation â?? all which will benefit the Laboratory. This report focuses on the initial phase of staff acquisition which was directed and administered by DOE NETL/ West Virginia under Project Officer Tom George. Using this CDP funding, we have developed the leadership and intellectual capacity for the SGIC. This was accomplished by investing (hiring) a core team of Smart Grid Systems engineering faculty focused on education, research, and innovation of a secure and smart grid infrastructure. The Smart Grid Integration Laboratory will be housed with the separately funded Integrid Laboratory as part of CSUâ??s overall Smart Grid Integration Center (SGIC). The period of performance of this grant was 10/1/2009 to 9/30/2011 which included one no cost extension due to time delays in faculty hiring. The Smart Grid Integration Laboratoryâ??s focus is to build foundations to help graduate and undergraduates acquire systems engineering knowledge; conduct innovative research; and team externally with grid smart organizations. Using the results of the separately funded Smart Grid Workforce Education Workshop (May 2009) sponsored by the City of Fort Collins, Northern Colorado Clean Energy Cluster, Colorado State University Continuing Education, Spirae, and Siemens has been used to guide the hiring of faculty, program curriculum and education plan. This project develops faculty leaders with the intellectual capacity to inspire its students to become leaders that substantially contribute to the development and maintenance of Smart Grid infrastructure through topics such as: (1) Distributed energy systems modeling and control; (2) Energy and power conversion; (3) Simulation of electrical power distribution system that integrates significant quantities of renewable and distributed energy resources; (4) System dynamic modeling that considers end-user behavior, economics, security and regulatory frameworks; (5) Best practices for energy management IT control solutions for effective distributed energy integration (including security with the underlying physical power systems); (6) Experimental verification of effects of various arrangements of renewable generation, distributed generation and user load types along with conventional generation and transmission. Understanding the core technologies for enabling them to be used in an integrated fashion within a distribution network remains is a benefit to the future energy paradigm and future and present energy engineers.

Wade Troxell

2011-09-30

395

Moving Overlapping Grids with Adaptive Mesh Refinement for High-Speed Reactive and Non-reactive Flow  

SciTech Connect

We consider the solution of the reactive and non-reactive Euler equations on two-dimensional domains that evolve in time. The domains are discretized using moving overlapping grids. In a typical grid construction, boundary-fitted grids are used to represent moving boundaries, and these grids overlap with stationary background Cartesian grids. Block-structured adaptive mesh refinement (AMR) is used to resolve fine-scale features in the flow such as shocks and detonations. Refinement grids are added to base-level grids according to an estimate of the error, and these refinement grids move with their corresponding base-level grids. The numerical approximation of the governing equations takes place in the parameter space of each component grid which is defined by a mapping from (fixed) parameter space to (moving) physical space. The mapped equations are solved numerically using a second-order extension of Godunov's method. The stiff source term in the reactive case is handled using a Runge-Kutta error-control scheme. We consider cases when the boundaries move according to a prescribed function of time and when the boundaries of embedded bodies move according to the surface stress exerted by the fluid. In the latter case, the Newton-Euler equations describe the motion of the center of mass of the each body and the rotation about it, and these equations are integrated numerically using a second-order predictor-corrector scheme. Numerical boundary conditions at slip walls are described, and numerical results are presented for both reactive and non-reactive flows in order to demonstrate the use and accuracy of the numerical approach.

Henshaw, W D; Schwendeman, D W

2005-08-30

396

Coordinated control of FACTS devices based on optimal power flow  

Microsoft Academic Search

Flexible AC transmission systems (FACTS) are an option to mitigate the problem of overloaded lines due to increased electric power transmission by controlling power flows and voltages. To avoid mutual influences among several devices placed in the same grid, a coordinated control is indispensable. In this paper, a supervisory controller based on optimal power flow (OPF) with multiple objectives is

G. Glanzmann; G. Andersson

2005-01-01

397

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

398

An arbitrary curvilinear coordinate particle in cell method  

NASA Astrophysics Data System (ADS)

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

Fichtl, Christopher A.

399

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

400

The Computing Grids  

NASA Astrophysics Data System (ADS)

Since the beginning of the millennium, High Energy Physics research institutions like CERN and INFN pioneered several projects aimed at exploiting the synergy among computing power, storage and network resources, and creating an infrastructure of distributed computing on a worldwide scale. In the year 2000, after the Monarch project [http://monarc.web.cern.ch/MONARC/], DataGrid started [http://eu-datagrid.web.cern.ch/eu-datagrid/] aimed at providing High Energy Physics with the computing power needed for the LHC enterprise. This program evolved into the EU DataGrid project, that implemented the first actual prototype of a Grid middleware running on a testbed environment. The next step consisted in the application to the LHC experiments, with the LCG project [http://lcg.web.cern.ch/LCG/], in turn followed by the EGEE [http://www.eu-egee.org/] and EGEE II programs.

Govoni, P.

2009-12-01

401

Well-balanced shallow water flow simulation on quadtree cut cell grids  

NASA Astrophysics Data System (ADS)

A well-balanced shallow water flow model on quadtree cut cell grids is presented. The Cartesian cut cell method is applied due to its flexibility in treating curvilinear boundaries. In order to preserve a lake-at-rest and the positivity of water depths in drying/wetting zones, the hydrostatic reconstruction proposed by Audusse et al. [1] is implemented on cut cell grids. In addition, the gradient construction method on cut cells proposed by Causon et al. [8] is modified due to the spurious calculation when a solid boundary is nearly parallel to grids. The numerical schemes mentioned above are employed in Gerris which is open source free software and provides a shallow water solver on adaptive quadtree grids. The applied numerical schemes are validated using four test simulations: still water in an inclined domain; oscillation in a parabolic container; shock reflection by a circular cylinder; flash flood experiment in a model city. The simulation results are compared with analytical solutions, experiment data and the results simulated by other researchers.

An, Hyunuk; Yu, Soonyoung

2012-04-01

402

Grids in mammography  

SciTech Connect

A special soft-tissue grid reduced scattered radiation to the receptor and resulted in improved contrast and visibility of small structures to the degree that increased kVp could be used during screen-film mammography. The reduction in radiation to the skin that is associated with the more penetrating higher kVp technique more than compensated for the Bucky factor of the grid. This technique allowed for better penetration of the base of large, dense breasts without the use of vigorous compression. Results that were obtained with a faster (2X) film are also presented and discussed.

Egan, R.L.; McSweeney, M.B.; Sprawls, P.

1983-02-01

403

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

404

Tax Coordination and Unemployment  

Microsoft Academic Search

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

Clemens Fuest; Bernd Huber

1999-01-01

405

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

SciTech Connect

The IEEE American National Standards smart grid publications and standards development projects IEEE 2030, which addresses smart grid interoperability, and IEEE 1547TM, which addresses distributed resources interconnection with the grid, have made substantial progress since 2009. The IEEE 2030TM and 1547 standards series focus on systems-level aspects and cover many of the technical integration issues involved in a mature smart grid. The status and highlights of these two IEEE series of standards, which are sponsored by IEEE Standards Coordinating Committee 21 (SCC21), are provided in this paper.

Basso, T.; DeBlasio, R.

2012-04-01

406

Evaluating the Information Power Grid using the NAS Grid Benchmarks.  

National Technical Information Service (NTIS)

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 NA...

M. A. Frumkin

2004-01-01

407

Changing from computing grid to knowledge grid in life-science grid.  

PubMed

Grid computing has a great potential to become a standard cyber infrastructure for life sciences that often require high-performance computing and large data handling, which exceeds the computing capacity of a single institution. Grid computer applies the resources of many computers in a network to a single problem at the same time. It is useful to scientific problems that require a great number of computer processing cycles or access to a large amount of data.As biologists,we are constantly discovering millions of genes and genome features, which are assembled in a library and distributed on computers around the world.This means that new, innovative methods must be developed that exploit the re-sources available for extensive calculations - for example grid computing.This survey reviews the latest grid technologies from the viewpoints of computing grid, data grid and knowledge grid. Computing grid technologies have been matured enough to solve high-throughput real-world life scientific problems. Data grid technologies are strong candidates for realizing a "resourceome" for bioinformatics. Knowledge grids should be designed not only from sharing explicit knowledge on computers but also from community formulation for sharing tacit knowledge among a community. By extending the concept of grid from computing grid to knowledge grid, it is possible to make use of a grid as not only sharable computing resources, but also as time and place in which people work together, create knowledge, and share knowledge and experiences in a community. PMID:19579217

Talukdar, Veera; Konar, Amit; Datta, Ayan; Choudhury, Anamika Roy

2009-09-01

408

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

PubMed

The research presented in this paper uses memory work as a method to explore six women's collective constructions of two embodied practices, sweating and pain. The paper identifies limitations in the ways in which social constructionist research has theorized the relationship between discourse and materiality, and it proposes an approach to the study of embodiment which enjoins, rather than bridges, the discursive and the non-discursive. The paper presents an analysis of 25 memories of sweating and pain which suggests that Cartesian dualism is central to the women's accounts of their experiences. However, such dualism does not operate as a stable organizing principle. Rather, it offers two strategies for the performance of a split between mind and body. The paper traces the ways in which dualism can be both functional and restrictive, and explores the tensions between these two forms. The paper concludes by identifiying opportunities and limitations associated with memory work as a method for studying embodiment. PMID:15035700

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

2004-03-01

409

Code Development of Linearized Euler Equation on Block-Structured Cartesian Mesh Combined with Immersed Boundary Method  

NASA Astrophysics Data System (ADS)

Recently, acoustic analysis using the Linearized Euler Equation (LEE) on multi-block structured or unstructured mesh is focused. However, mesh generation around complicated geometries takes time on structured mesh and cost of high order calculation gets larger on unstructured mesh. In this research, a LEE code for aeroacoustic analysis is developed on block structured Cartesian mesh of Building-Cube Method. To make an accurate calculation, the Immersed Boundary Method is implemented for wall boundary treatment and high order Lagrange interpolation is implemented at the Cube boundary for data exchange. This code is validated through acoustics scattering problems around cylinders and the calculational errors are compared. The results show good agreement with analytical solutions and the usability of these methods.

Fukushima, Yuuma; Sasaki, Daisuke; Nakahashi, Kazuhiro

410

Robustness and coordination in voltage control of large-scale power systems  

Microsoft Academic Search

In this paper it is shown how the robustness and the coordination of the voltage regulation actions for the transmission grid can be improved. Simpler approaches which ensure higher robustness and performances can be used if the control objectives are pursued at two hierarchical levels of different nature. Also, this is a way to coordinate means of control of different

Bogdan Marinescu

2008-01-01

411

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

412

Times Tables Grid Game  

NSDL National Science Digital Library

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

2013-01-01

413

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

414

Unlocking the smart grid  

SciTech Connect

The country has progressed in a relatively short time from rotary dial phones to computers, cell phones, and iPads. With proper planning and orderly policy implementation, the same will happen with the Smart Grid. Here are some suggestions on how to proceed. (author)

Rokach, Joshua Z.

2010-10-15

415

Piloting the smart grid  

SciTech Connect

To address the likely impact of the smart grid on customers, utilities, and society as a whole, it may be necessary to conduct a pilot. When should a pilot be conducted and how should it be conducted? What validity criteria should the pilot satisfy? Here are issues to consider. (author)

Faruqui, Ahmad; Hledik, Ryan; Sergici, Sanem

2009-08-15

416

Cartesian-Hyperspherical Hartree-Fock method for numerical observation of stabilized Langmuir states  

NASA Astrophysics Data System (ADS)

Based on the fact that hyperspherical radial dynamics of the Helium atom can be slow comparing to other coordinates we formulate adiabatic Hartree-Fock equations for the Hydrogen atom in both circularly polarized and the magnetic fields for the Langmuir states both in the circularly polarized and magnetic fields. The time-dependent Hartree-Fock equations are solved as functions of the effective parameter z (approximately the hyperspherical radius of the suspected configuration) and then the time-averaged energy is minimized to obtained the electron equilibrium in third spatial direction. The transverse part of the wave function is then found by solving two-dimensional Schr"odinger equation with the effective potential found from the minimalization.

Kalinski, Matt

2005-05-01

417

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

418

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

419

Current Grid operation and future role of the Grid  

NASA Astrophysics Data System (ADS)

Grid-like technologies and approaches became an integral part of HEP experiments. Some other scientific communities also use similar technologies for data-intensive computations. The distinct feature of Grid computing is the ability to federate heterogeneous resources of different ownership into a seamless infrastructure, accessible via a single log-on. Like other infrastructures of similar nature, Grid functioning requires not only technologically sound basis, but also reliable operation procedures, monitoring and accounting. The two aspects, technological and operational, are closely related: weaker is the technology, more burden is on operations, and other way around. As of today, Grid technologies are still evolving: at CERN alone, every LHC experiment uses an own Grid-like system. This inevitably creates a heavy load on operations. Infrastructure maintenance, monitoring and incident response are done on several levels, from local system administrators to large international organisations, involving massive human effort worldwide. The necessity to commit substantial resources is one of the obstacles faced by smaller research communities when moving computing to the Grid. Moreover, most current Grid solutions were developed under significant influence of HEP use cases, and thus need additional effort to adapt them to other applications. Reluctance of many non-HEP researchers to use Grid negatively affects the outlook for national Grid organisations, which strive to provide multi-science services. We started from the situation where Grid organisations were fused with HEP laboratories and national HEP research programmes; we hope to move towards the world where Grid will ultimately reach the status of generic public computing and storage service provider and permanent national and international Grid infrastructures will be established. How far will we be able to advance along this path, depends on us. If no standardisation and convergence efforts will take place, Grid will become limited to HEP; if however the current multitude of Grid-like systems will converge to a generic, modular and extensible solution, Grid will become true to its name.

Smirnova, O.

2012-12-01

420

Grid Plate Calibration.  

National Technical Information Service (NTIS)

To achieve an optimum Analytical Photogrammetric System, it becomes necessary to attain as high an accuracy in the coordinate measurements on comparators as is practicable. Comparators are normally adjusted by the manufacturer to meet a particular level o...

R. C. Malhotra

1968-01-01

421

Orthographic star coordinates.  

PubMed

Star coordinates is a popular projection technique from an nD data space to a 2D/3D visualization domain. It is defined by setting n coordinate axes in the visualization domain. Since it generally defines an affine projection, strong distortions can occur: an nD sphere can be mapped to an ellipse of arbitrary size and aspect ratio. We propose to restrict star coordinates to orthographic projections which map an nD sphere of radius r to a 2D circle of radius r. We achieve this by formulating conditions for the coordinate axes to define orthographic projections, and by running a repeated non-linear optimization in the background of every modification of the coordinate axes. This way, we define a number of orthographic interaction concepts as well as orthographic data tour sequences: a scatterplot tour, a principle component tour, and a grand tour. All concepts are illustrated and evaluated with synthetic and real data. PMID:24051828

Lehmann, Dirk J; Theisel, Holger

2013-12-01

422

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.

Russell, Michael.; Radke, Thomas.; Seidel, Ed.; Nabrzyski, Jarek.; Pukacki, Juliusz.; Shalf, John.

2003-01-01

423

Microwave absorbing composite lattice grids  

Microsoft Academic Search

Stretching dominated lattice grids reinforced by glass fibers and carbon fibers filled with spongy materials were designed and manufactured to achieve multifunctional structures with microwave absorbing abilities. The reflectivity of the GFRC and CFRC grid panels was measured in the darkroom at normal and oblique incidences, respectively. GFRC grid panels of 20mm thickness and CFRC panels of 18mm thickness displayed

H. L. Fan; W. Yang; Z. M. Chao

2007-01-01

424

Evolution of Data Grid Concepts  

Microsoft Academic Search

The goal of the Global Grid Forum is to develop a common set of services for access to distributed resources. The goal of the digital library and persistent archive communities is to organize, publish, and preserve digital entities. A Data Grid is the software infrastructure that maps from access mechanisms provided by grids to management functions provided by digital libraries.

Reagan W. Moore

425

Smart grid customer domain analysis  

Microsoft Academic Search

Smart Grid Initiative aims to use the current energy resources more efficiently by providing a more resilient and reliable infrastructure. One of the main targets of this initiative is the increased customer participation and interaction with the overall grid. In this paper, we analyse the customer domain in order to increase the understanding of this domain within smart grid and

Nauman Zafar; Emine G. Aydal Phillips; Husam Suleiman; Davor Svetinovic

2010-01-01

426

Continuous Localization Using Evidence Grids  

Microsoft Academic Search

Evidence grids provide a uniform representation for fusing temporally and spatially distinct sensor readings. However, the use of evidence grids requires that the robot be localized within its environment. Odometry errors typically accumulate over time, making localization estimates degrade, and introducing significant errors into evidence grids as they are built. We have addressed this problem by developing a method for

Alan C. Schultz; William Adams

1998-01-01

427

Spectral methods on arbitrary grids  

SciTech Connect

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. 9 refs., 3 figs.

Carpenter, M.H. [NASA Langley Research Center, Hampton, VA (United States); Gottlieb, D. [Brown Univ., Providence, RI (United States)

1996-11-01

428

Collaborative Learning through Wireless Grids  

Microsoft Academic Search

In this paper, we describe wireless grids, an emerging technology that enables ad hoc sharing of resources (such as screen, services and microphone) on edge devices (such as mobile Internet devices, laptops and mobile phones). As wireless devices have become common, and “smart,” wireless grids have become practical. To highlight the capabilities of wireless grids to support collaborative learning, projects

Angela Usha Ramnarine-Rieks; Lee W. McKnight; Ruth V. Small

2011-01-01

429

Kentucky Smart Grid roadmap initiative  

Microsoft Academic Search

Smart Grid refers to the modernization of the electric grid through the integration of advanced technologies with an intelligent information infrastructure to offer numerous benefits to both electricity providers and consumers. The Kentucky Public Service Commission, the University of Kentucky, and the University of Louisville have partnered to develop a technical roadmap for the development and deployment of Smart Grid

Y. Du; M. Turner; Y. Liao; M. Sunkara; J. DeRouen; A. Greenwell; J. Rogness; K. Cole; J. Gardner

2012-01-01

430

Traceability, reproducibility, and comparability of grid calibrations  

NASA Astrophysics Data System (ADS)

The national metrology institute of Germany, PTB, offers traceable, two-dimensional pattern placement calibrations of microstructures on masks. Whereas the measurement uncertainty for the calibrated pattern positions in terms of traceable coordinate values is only comparable to the position tolerances actually required for mask patterning, i.e. about 35 nm, the deviations from the design grid can be determined with smaller uncertainties. In calibration certificates offered by PTB, these differences are taken into account and the uncertainties for the length of the grid and the uncertainties for the position deviations from the design grid are quoted separately as 30 nm and 10 nm respectively. Developments to further reduce the uncertainties are under way. An analysis of photomask recalibration results shows the long-term reproducibility of PTB length calibrations to be better than 15 nm or 1*10-7, including substrate stability effects. Details of the recalibration results will be given. Leica Microsystems Lithography runs a laboratory for two-dimensional pattern placement calibrations, formally accredited by PTB within DKD, the German calibration service. Results of recent comparison measurements between the DKD laboratory and PTB on masks of different size will be given and discussed as an example of the process of dissemination of the length unit to industry.

Bosse, Harald; Haessler-Grohne, Wolfgang; Brendel, Bernd

1999-12-01

431

Quantum instanton evaluation of the thermal rate constants and kinetic isotope effects for SiH4+H-->SiH3+H2 reaction in full Cartesian space.  

PubMed

The quantum instanton calculations of thermal rate constants for the gas-phase reaction SiH4+H-->SiH3+H2 and its deuterated analogs are presented, using an analytical potential energy surface. The quantum instanton approximation is manipulated by full dimensionality in Cartesian coordinate path integral Monte Carlo approach, thereby taking explicitly into account the effects of the whole rotation, the vibrotational coupling, and anharmonicity of the reaction system. The rates and kinetic isotope effects obtained for the temperature range of 200-1000 K show good agreements with available experimental data, which give support to the accuracy of the underlying potential surface used. In order to investigate the sole quantum effect to the rates, the authors also derive the classical limit of the quantum instanton and find that it can be exactly expressed as the classical variation transition state theory. Comparing the quantum quantities with their classical analogs in the quantum instanton formula, the authors demonstrate that the quantum correction of the prefactor is more important than that of the activation energy at the transition state. PMID:17381206

Wang, Wenji; Feng, Shulu; Zhao, Yi

2007-03-21

432

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

NASA Astrophysics Data System (ADS)

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

Commer, M.; Newman, G. A.

2005-12-01

433

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

434

A research of security architecture in grid  

NASA Astrophysics Data System (ADS)

Grid architecture is the frame of the grid environment, and the grid security architecture is the indemnity of the grid architecture. The reasonable grid architecture is the core of the establishment of good grid. Only could they establish the reasonable grid architecture, they can design and build the good grid system. In this paper we put the security architecture into the small grid environment which is set up in a school's lab. This experiment provides the useful experience for us to put the security architecture into the actual grid environment and make the big contribution for the further study of grid.

Zhu, Youchan; Zhang, Xiaofang

2013-03-01

435

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

PubMed Central

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

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

2010-01-01

436

Power Grid Issues  

NSDL National Science Digital Library

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

Leske, Cavin.

437

Sliding-Mode-Based Direct Power Control of Grid-Connected Wind-Turbine-Driven Doubly Fed Induction Generators Under Unbalanced Grid Voltage Conditions  

Microsoft Academic Search

This paper proposes an improved direct power control (DPC) strategy of grid-connected wind-turbine-driven doubly fed induction generators (DFIGs) when the grid voltage is unbalanced. The DPC scheme is based on the sliding mode control (SMC) approach, which directly regulates the instantaneous active and reactive powers in the stator stationary reference frame without the requirement of either synchronous coordinate transformation or

Lei Shang; Jiabing Hu

2012-01-01

438

An Environment for Enabling Interactive Grids  

Microsoft Academic Search

Traditional use of grid computing allows a user to sub- mit batch jobs in a grid environment. We believe, next gen- eration grids will extend the application domain to include interactive graphical sessions. We term such grids interac- tive grids. In this paper, we describe some of the challenges involved in building interactive grids. These include fine grain access control,

Vanish Talwar; Sujoy Basu; Raj Kumar

2003-01-01

439

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

440

The BioGRID Interaction Database: 2008 update.  

PubMed

The Biological General Repository for Interaction Datasets (BioGRID) database (http://www.thebiogrid.org) was developed to house and distribute collections of protein and genetic interactions from major model organism species. BioGRID currently contains over 198 000 interactions from six different species, as derived from both high-throughput studies and conventional focused studies. Through comprehensive curation efforts, BioGRID now includes a virtually complete set of interactions reported to date in the primary literature for both the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. A number of new features have been added to the BioGRID including an improved user interface to display interactions based on different attributes, a mirror site and a dedicated interaction management system to coordinate curation across different locations. The BioGRID provides interaction data with monthly updates to Saccharomyces Genome Database, Flybase and Entrez Gene. Source code for the BioGRID and the linked Osprey network visualization system is now freely available without restriction. PMID:18000002

Breitkreutz, Bobby-Joe; Stark, Chris; Reguly, Teresa; Boucher, Lorrie; Breitkreutz, Ashton; Livstone, Michael; Oughtred, Rose; Lackner, Daniel H; Bähler, Jürg; Wood, Valerie; Dolinski, Kara; Tyers, Mike

2007-11-13

441

Uranyl ion coordination  

USGS Publications Warehouse

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

Evans, Jr. , H. T.

1963-01-01

442

Grid pulse generator  

NASA Astrophysics Data System (ADS)

A fast pulse generator was designed for the grid of the injector of the electron accelerator MEA in order to shoot the electrons emitted by the cathode into the bundle pipe where they are accelerated. The generator delivers a high voltage pulse of maximum 6000 V with a rise tile smaller than 50 ns. This results in a slow rate of more than 120,000 V/microsecond. A current of 8 A is required to charge the 60 pF capacity of the grid up to 6000 V is 50 ns. The maximul pulse length is 50 microseconds with a 500 Hz pulse repetition frequency. During these 5 microseconds the pulse amplitude stability is better than 0.1 percent.

Jansweijer, P. P. M.; Vanes, J. T.

443

Power control of a grid-connected hybrid generation system with photovoltaic\\/wind turbine\\/battery sources  

Microsoft Academic Search

A grid-connected hybrid distributed generation system, composed of PV(photovoltaic) array, wind turbine and BESS (battery energy storage system), is proposed for various power transfer functions to the distribution network. The proposed system has several operation modes which are normal operation, power dispatching, and power averaging, according to coordinate control of the BESS and grid inverter. PV array and wind turbine

Jinhong Jeon; Seulki Kim; Changhee Cho; Jonbo Ahn; Jangmok Kim

2007-01-01

444

Position Paper: An Agent-Based Quality of Service Negotiation Framework for Grid Environments - Semi Automatic Service Level Agreement Adaptation  

Microsoft Academic Search

As a result of ever-increasing network performance, and growing needs in the science community for large-scale computations on huge data sets, the research fields of parallel computing and distributed computing merged into what became known as Grid computing. A Grid is a system that coordinates decentralized resources, such as CPU, disk space and bandwidth, while leveraging ubiquitous communication protocols to

Thomas Sandholm

2004-01-01

445

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

446

GridFTP pipelining.  

SciTech Connect

GridFTP is an exceptionally fast transfer protocol for large volumes of data. Implementations of it are widely deployed and used on well-connected Grid environments such as those of the TeraGrid because of its ability to scale to network speeds. However, when the data is partitioned into many small files instead of few large files, it suffers from lower transfer rates. The latency between the serialized transfer requests of each file directly detracts from the amount of time data pathways are active, thus lowering achieved throughput. Further, when a data pathway is inactive, the TCP window closes, and TCP must go through the slow-start algorithm. The performance penalty can be severe. This situation is known as the 'lots of small files' problem. In this paper we introduce a solution to this problem. This solution, called pipelining, allows many transfer requests to be sent to the server before any one completes. Thus, pipelining hides the latency of each transfer request by sending the requests while a data transfer is in progress. We present an implementation and performance study of the pipelining solution.

Bresnahan, J.; Link, M.; Kettimuthu, R.; Fraser, D.; Foster, I.; Mathematics and Computer Science; Univ. of Chicago

2007-01-01

447

Advanced techniques for constrained internal coordinate molecular dynamics.  

PubMed

Internal coordinate molecular dynamics (ICMD) methods provide a more natural description of a protein by using bond, angle, and torsional coordinates instead of a Cartesian coordinate representation. Freezing high-frequency bonds and angles in the ICMD model gives rise to constrained ICMD (CICMD) models. There are several theoretical aspects that need to be developed to make the CICMD method robust and widely usable. In this article, we have designed a new framework for (1) initializing velocities for nonindependent CICMD coordinates, (2) efficient computation of center of mass velocity during CICMD simulations, (3) using advanced integrators such as Runge-Kutta, Lobatto, and adaptive CVODE for CICMD simulations, and (4) cancelling out the "flying ice cube effect" that sometimes arises in Nosé-Hoover dynamics. The Generalized Newton-Euler Inverse Mass Operator (GNEIMO) method is an implementation of a CICMD method that we have developed to study protein dynamics. GNEIMO allows for a hierarchy of coarse-grained simulation models based on the ability to rigidly constrain any group of atoms. In this article, we perform tests on the Lobatto and Runge-Kutta integrators to determine optimal simulation parameters. We also implement an adaptive coarse-graining tool using the GNEIMO Python interface. This tool enables the secondary structure-guided "freezing and thawing" of degrees of freedom in the molecule on the fly during molecular dynamics simulations and is shown to fold four proteins to their native topologies. With these advancements, we envision the use of the GNEIMO method in protein structure prediction, structure refinement, and in studying domain motion. PMID:23345138

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

2013-01-23

448

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

449

Unapproved Drugs Coordinator  

Center for Drug Evaluation (CDER)

Text Version... Nancy Smith Office of New Drugs John Jenkins ... and Research (CDER) Office of Counter- Terrorism and Emergency Coordination ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

450

Testing the coordination predicate  

SciTech Connect

A collection of parallel processors is said to be coordinated if each write from one processing element (PE) to another is answered by a read. The authors report on an efficient algorithm to test coordination for parallel programs in which the code for each PE is a loop. They also test a weaker predicate for parallel algorithms with oblivious PE codes, and they show that the general problem is pspace-hard. 6 references.

Cuny, J.E.; Snyder, L.

1984-03-01

451

Advances Towards Automatic Surface Domain Decomposition and Grid Generation for Overset Grids.  

National Technical Information Service (NTIS)

An algorithm for surface domain decomposition and grid generation for overset grids is described. A complex surface domain is covered by two types of grids: seam grids and block grids. Seam grids are grids used to wrap around surface crease lines and regi...

R. L. Meakin W. M. Chan

1997-01-01

452

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

453

Viscous waves and wave-structure interaction in a tank using adapting quadtree grids  

NASA Astrophysics Data System (ADS)

Viscous waves and waves over a submerged cylinder in a stationary tank are simulated using a volume-of-fluid numerical scheme on adaptive hierarchical grids. A high resolution interface-capturing method is used to advect the free surface interface and the Navier Stokes equations are discretised using finite volumes with collocated primitive variables and solved using a Pressure Implicit with Splitting of Operators (PISO) algorithm. The cylinder is modelled by using the technique of Cartesian cut cells. Results of flow of a single fluid past a cylinder at Reynolds number Re=100 are presented and found to agree well with experimental and other numerical data. Viscous free surface waves in a tank are simulated using uniform and quadtree grids for Reynolds numbers in the range from 2 to 2000, and the results compared against analytical solutions where available. The quadtree-based results are of the same accuracy as those on the equivalent uniform grids, and retain a sharp interface at the free surface while leading to considerable savings in both storage and CPU requirements. The nonlinearity in the wave is investigated for a selection of initial wave amplitudes. A submerged cylinder is positioned in the tank and its influence on the waves as well as the hydrodynamic loading on the cylinder is investigated.

Greaves, D. M.

2007-11-01

454

Grid alignment in entorhinal cortex.  

PubMed

The spatial responses of many of the cells recorded in all layers of rodent medial entorhinal cortex (mEC) show mutually aligned grid patterns. Recent experimental findings have shown that grids can often be better described as elliptical rather than purely circular and that, beyond the mutual alignment of their grid axes, ellipses tend to also orient their long axis along preferred directions. Are grid alignment and ellipse orientation aspects of the same phenomenon? Does the grid alignment result from single-unit mechanisms or does it require network interactions? We address these issues by refining a single-unit adaptation model of grid formation, to describe specifically the spontaneous emergence of conjunctive grid-by-head-direction cells in layers III, V, and VI of mEC. We find that tight alignment can be produced by recurrent collateral interactions, but this requires head-direction (HD) modulation. Through a competitive learning process driven by spatial inputs, grid fields then form already aligned, and with randomly distributed spatial phases. In addition, we find that the self-organization process is influenced by any anisotropy in the behavior of the simulated rat. The common grid alignment often orients along preferred running directions (RDs), as induced in a square environment. When speed anisotropy is present in exploration behavior, the shape of individual grids is distorted toward an ellipsoid arrangement. Speed anisotropy orients the long ellipse axis along the fast direction. Speed anisotropy on its own also tends to align grids, even without collaterals, but the alignment is seen to be loose. Finally, the alignment of spatial grid fields in multiple environments shows that the network expresses the same set of grid fields across environments, modulo a coherent rotation and translation. Thus, an efficient metric encoding of space may emerge through spontaneous pattern formation at the single-unit level, but it is coherent, hence context-invariant, if aided by collateral interactions. PMID:22892761

Si, Bailu; Kropff, Emilio; Treves, Alessandro

2012-08-15

455

Gridding advisor: an expert system for selecting gridding algorithms  

SciTech Connect

Gridding Advisor is a small expert system designed to aid in selecting gridding algorithms. The program's selection is based on rules for six gridding algorithms: triangles, polygonal, inverse distance squared, polynomial trend surface, double Fourier, and kriging. The program proceeds by asking the user questions about the data set and its intended use. An explanation of why each question is being asked is displayed with the question. Once the program reaches a conclusion, both the conclusion and the supporting reasoning are displayed.

Maslyn, R.M.

1987-11-01

456

The fabrication of fuel rod support grids for the Shippingport Light Water Breeder Reactor: LWBR Development Program  

SciTech Connect

The fabrication of grids to support fuel rods in a close-packed hexagonal array for the Light Water Breeder Reactor (LWBR) is described. A variety of manufacturing and inspection processes, many of which were developed specifically for LWBR, were used in the grid fabrication process sequence. Among the unique operations performed were precision stamping of AM-350 stainless steel components, brazing of the components into the grid geometry, decarburization of the grids to the desired carbon level, and the measurement of grid dimensional characteristics utilizing a Coordinate Measuring Machine (CMM) with associated computerized data recording equipment. These processes, from basic component fabrication to final grid inspection, are described in detail and the significant problems encountered during the course of grid manufacture and inspection are dis cussed. 7 refs., 33 figs., 4 tabs.

Wittmann, R.P. (ed.); Cioletti, O.J.; Ebejer, L.P.; Glass, R.M.; Lynch, M.F.; Matchett, R.L.; Nilsen, R.J.; Payne, L.R.; Pitcairn, G.W.; Scharf, A.

1987-10-01

457

Cartesian theories on the passions, the pineal gland and the pathogenesis of affective disorders: an early forerunner.  

PubMed

The relationship between physical and functional alterations in the pineal gland, the 'passions' (emotions or feelings) and psychopathology has been a constant throughout the history of medicine. One of the most influential authors on this subject was René Descartes, who discussed it in his work The Treatise on the Passions of the Soul (1649). Descartes believed that 'passions' were sensitive movements that the soul, located in the pineal gland, experienced due to its union with the body, by circulating animal spirits. Descartes described sadness as one of the six primitive passions of the soul, which leads to melancholy if not remedied. Cartesian theories had a great deal of influence on the way that mental pathologies were considered throughout the entire 17th century and during much of the 18th century, but the link between the pineal gland and psychiatric disorders it was definitively highlighted in the 20th century, with the discovery of melatonin in 1958. The recent development of a new pharmacological agent acting through melatonergic receptors (agomelatine) has confirmed the close link between the pineal gland and affective disorders. PMID:20836904

López-Muñoz, F; Alamo, C

2010-09-14

458

Accelerated Cartesian expansion (ACE) based framework for the rapid evaluation of diffusion, lossy wave, and Klein-Gordon potentials  

NASA Astrophysics Data System (ADS)

Diffusion, lossy wave, and Klein-Gordon equations find numerous applications in practical problems across a range of diverse disciplines. The temporal dependence of all three Green’s functions are characterized by an infinite tail. This implies that the cost complexity of the spatio-temporal convolutions, associated with evaluating the potentials, scales as ONs2Nt2, where Ns and Nt are the number of spatial and temporal degrees of freedom, respectively. In this paper, we discuss two new methods to rapidly evaluate these spatio-temporal convolutions by exploiting their block-Toeplitz nature within the framework of accelerated Cartesian expansions (ACE). The first scheme identifies a convolution relation in time amongst ACE harmonics and the fast Fourier transform (FFT) is used for efficient evaluation of these convolutions. The second method exploits the rank deficiency of the ACE translation operators with respect to time and develops a recursive numerical compression scheme for the efficient representation and evaluation of temporal convolutions. It is shown that the cost of both methods scales as O(NsNtlog2Nt). Several numerical results are presented for the diffusion equation to validate the accuracy and efficacy of the fast algorithms developed here.

Vikram, M.; Baczewski, A.; Shanker, B.; Kempel, L.

2010-12-01

459

Gemini world coordinates  

NASA Astrophysics Data System (ADS)

The Gemini World Coordinate Systems (WCS) facilities support various types of astrometric coordinates as well as instrument-specific quantities such as wavelengths or times. The astrometric facilities are based on the principle that, for sky-imaging applications, users are concerned only with (i) positions in the focal plane and (ii) celestial coordinates. All intermediate calculations, for example involving the position of the tip/tilt secondary mirror, the orientation of the instrument rotator, the selection of focal station, differential refraction and atmospheric dispersion, and field rotation effects caused by misalignments in the telescope mount, are encapsulated in the WCS transformation. We have implemented a library of C functions which support Gemini astrometric world coordinates. Most of them can be run off-line, and are applicable to other telescopes. More general WCS problems, involving data coordinates as well as astrometry, are treated by breaking the telescope, instrument and detector into a set of 'agents' each of which manages its own local transformations. The individual transformations can then be combined to provide the end-to-end transformations needed by data display and analysis facilities.

Wallace, Patrick T.

1998-05-01

460

DNS of vibrating grid turbulence  

Microsoft Academic Search

Direct numerical simulation of the turbulence generated at a grid vibrating normally to itself using spectral code [1] is presented. Due to zero mean shear there is no production of turbulence apart from the grid. Action of the grid is mimiced by the function implemented in the middle of the simulation box:f_i (x_1 ,x_2 ) = {n^2 S}\\/2left{ {left| {{delta

G. Khujadze; M. Oberlack

2009-01-01

461

Discovering HealthGrid Services  

Microsoft Academic Search

HealthGrids represent the next generation of advanced healthcare IT and hold the promise to resolve complex healthcare problems by integrating health information systems and healthcare entities. Healthcare could benefit from a new delivery approach using HealthGrids to better meet the bio-medical and health-related needs. Specialized services are needed to provide unified discovery of and ubiquitous access to available HealthGrid resources.

Aisha Naseer; Lampros K. Stergioulas

2006-01-01

462

Coordination: a vector-matrix description of transformations of overcomplete CNS coordinates and a tensorial solution using the Moore-Penrose generalized inverse.  

PubMed

Neuronal organisms express their function, such as a movement, by multicomponental actions. Thus, the problem of how the central nervous system (CNS) coordinates the elements of a single action is fundamental to our understanding of brain function. Coordinated activation of multijointed "limbs" has also become an acute problem in modern multivariable control theory and engineering, such as robotics. Thus, a coherent interdisciplinary approach is expected, one that arrives at concepts and formalisms applicable to this problem both in living and man-made organisms. By treating coordination with coordinates, tensor network theory of the CNS, which explains transformations through the neuronal networks of natural non-orthogonal coordinates that are intrinsic to living organisms, may successfully integrate the diverse approaches to this general problem. A link between tensor network theory of the CNS and multivariable control engineering can be established if the latter is formulated in generalized non-orthogonal coordinates, rather than in conventional Cartesian expressions. In general terms, the problem of coordinating an overcomplete (more than necessary) number of components of an action can be resolved by a three-step tensorial scheme. A key operation is a covariant-to-contravariant transformation executed by the Moore-Penrose generalized inverse when, in an overcomplete manifold, the covariant metric tensor is singular. In the neuronal organization of the CNS, it is assumed that the cerebellum plays this role of acting as a contravariant metric. A quantitative example is also provided, in order to demonstrate the viability of the numerical and network-implementations. PMID:6503306

Pellionisz, A J

1984-10-01

463

A WDM method on a generalized curvilinear grid for calculation of storm surge flooding  

Microsoft Academic Search

In this paper, the wet-dry grid point method (WDM) with generalized curvilinear computation grids is introduced with the aim of presenting a kind of effective numerical model for real-time forecasting of storm surge flooding. To realize this general WDM method, generalized 2-D shallow sea dynamic equations in curvilinear co-ordinates are derived, and the contravariant components of the velocity vector are

Fengyan Shi; Wenxin Sun; Gengsheng Wei

1997-01-01

464

DEVELOPMENT OF A GRID-CONNECTEDED WIND\\/PV\\/BESS HYBRID DISTRIBUTED GENERATION SYSTEM  

Microsoft Academic Search

A grid-connected hybrid distributed generation system, composed of PV(photovoltaic) array, wind turbine and battery, is proposed for various power transfer functions to the distribution network. The proposed system has several operation modes which are normal operation, power dispatching, and power averaging, according to coordinate control of the BESS(Battery Energy Storage System) and grid inverter. PV array and wind turbine are

Jinhong JEON; Seulki KIM; Changhee CHO; Jongbo AHN

2007-01-01

465

Evaluating a High-Level Parallel Language (GpH) for Computational GRIDs  

Microsoft Academic Search

Computational GRIDs potentially offer low-cost, readily available, and large-scale high-performance platforms. For the parallel execution of programs, however, computational GRIDs pose serious challenges: they are heterogeneous and have hierarchical and often shared interconnects, with high and variable latencies between clusters. This paper investigates whether a programming language with high-level parallel coordination and a Distributed Shared Memory (DSM) model can deliver

Abdallah D. Al Zain; Philip W. Trinder; Greg J. Michaelson; Hans-wolfgang Loidl

2008-01-01

466

Direct recordings of grid-like neuronal activity in human spatial navigation.  

PubMed

Grid cells in the entorhinal cortex appear to represent spatial location via a triangular coordinate system. Such cells, which have been identified in rats, bats and monkeys, are believed to support a wide range of spatial behaviors. Recording neuronal activity from neurosurgical patients performing a virtual-navigation task, we identified cells exhibiting grid-like spiking patterns in the human brain, suggesting that humans and simpler animals rely on homologous spatial-coding schemes. PMID:23912946

Jacobs, Joshua; Weidemann, Christoph T; Miller, Jonathan F; Solway, Alec; Burke, John F; Wei, Xue-Xin; Suthana, Nanthia; Sperling, Michael R; Sharan, Ashwini D; Fried, Itzhak; Kahana, Michael J

2013-08-04

467

Grid-Enabled Measures  

PubMed Central

Scientists are taking advantage of the Internet and collaborative web technology to accelerate discovery in a massively connected, participative environment —a phenomenon referred to by some as Science 2.0. As a new way of doing science, this phenomenon has the potential to push science forward in a more efficient manner than was previously possible. The Grid-Enabled Measures (GEM) database has been conceptualized as an instantiation of Science 2.0 principles by the National Cancer Institute with two overarching goals: (1) Promote the use of standardized measures, which are tied to theoretically based constructs; and (2) Facilitate the ability to share harmonized data resulting from the use of standardized measures. This is done by creating an online venue connected to the Cancer Biomedical Informatics Grid (caBIG®) where a virtual community of researchers can collaborate together and come to consensus on measures by rating, commenting and viewing meta-data about the measures and associated constructs. This paper will describe the web 2.0 principles on which the GEM database is based, describe its functionality, and discuss some of the important issues involved with creating the GEM database, such as the role of mutually agreed-on ontologies (i.e., knowledge categories and the relationships among these categories— for data sharing).

Moser, Richard P.; Hesse, Bradford W.; Shaikh, Abdul R.; Courtney, Paul; Morgan, Glen; Augustson, Erik; Kobrin, Sarah; Levin, Kerry; Helba, Cynthia; Garner, David; Dunn, Marsha; Coa, Kisha

2011-01-01

468

Coordinating overcurrent protection devices  

SciTech Connect

Distribution, substation, and plant engineers can benefit from using an overcurrent protection program in commercial, industrial, and utility applications to aid in clearing temporary faults and isolating permanent faults. In the time it normally takes to check one coordination scheme manually, dozens of alternatives can be evaluated using a graphics-oriented program, because the engineer receives immediate feedback for quick decision-making. It is well known that accurately coordinating overcurrent protection devices can minimize or pre