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1

Implementation and Verification of a Nodally-Integrated Tetrahedral Element in FEBio  

E-print Network

Implementation and Verification of a Nodally-Integrated Tetrahedral Element in FEBio Steve A. Maas Abstract: Finite element simulations in computational biomechanics commonly require the discretization and time consuming using hexahedral elements. Automatic meshing algorithms exist for tetrahedral elements

Utah, University of

2

A computational study of nodal-based tetrahedral element behavior.  

SciTech Connect

This report explores the behavior of nodal-based tetrahedral elements on six sample problems, and compares their solution to that of a corresponding hexahedral mesh. The problems demonstrate that while certain aspects of the solution field for the nodal-based tetrahedrons provide good quality results, the pressure field tends to be of poor quality. Results appear to be strongly affected by the connectivity of the tetrahedral elements. Simulations that rely on the pressure field, such as those which use material models that are dependent on the pressure (e.g. equation-of-state models), can generate erroneous results. Remeshing can also be strongly affected by these issues. The nodal-based test elements as they currently stand need to be used with caution to ensure that their numerical deficiencies do not adversely affect critical values of interest.

Gullerud, Arne S.

2010-09-01

3

Comparison of linear strain triangular and tetrahedral elements with isoparametric elements in two- and three-dimensional finite element analyses  

E-print Network

COMPARISON OF LINEAR STRAIN TRIANGULAR AND TETRAHEDRAL ELEMENTS WITH ISOPARAMETRIC ELEMENTS IN TWO- AND THREE-DIMENSIONAL FINITE ELEMENT ANALYSES A Thesis by Philip Wai-Sun Ho Submitted to the Graduate College of Texas A&M University...-DIMENSIONAL FINITE ELEMENT ANALYSES A Thesis by Philip Wai-Sun Ho Approved as to style and content by: (Chairman of Committee) (Head of Department (Mes r) (Member) December 1977 ABSTRACT Comparison of Linear Strain Triangular and Tetrahedral Elements...

Ho, Philip Wai-Sun

2012-06-07

4

Elemental matrices for the finite element method in electromagnetics with quadratic triangular elements  

E-print Network

The finite element method has become a preeminent simulation technique in electromagnetics. For problems involving anisotropic media and metamaterials, proper algorithms should be developed. It has been proved that discretizing in quadratic triangular elements may lead to an improved accuracy. Here we present a collection of elemental matrices evaluated analytically for quadratic triangular elements. They could be useful for the finite element method in advanced electromagnetics.

E. Cojocaru

2009-10-20

5

On Interpolation Errors over Quadratic Nodal Triangular Finite Elements  

E-print Network

On Interpolation Errors over Quadratic Nodal Triangular Finite Elements Shankar P. Sastry to interpolate a solution (within an element) of a partial differential equation obtained by the finite element the bounds on the error of the interpolated solution. For linear elements, the error bounds at a point have

Kirby, Mike

6

QUADRATIC SERENDIPITY FINITE ELEMENTS ON POLYGONS USING GENERALIZED BARYCENTRIC COORDINATES  

PubMed Central

We introduce a finite element construction for use on the class of convex, planar polygons and show it obtains a quadratic error convergence estimate. On a convex n-gon, our construction produces 2n basis functions, associated in a Lagrange-like fashion to each vertex and each edge midpoint, by transforming and combining a set of n(n + 1)/2 basis functions known to obtain quadratic convergence. The technique broadens the scope of the so-called ‘serendipity’ elements, previously studied only for quadrilateral and regular hexahedral meshes, by employing the theory of generalized barycentric coordinates. Uniform a priori error estimates are established over the class of convex quadrilaterals with bounded aspect ratio as well as over the class of convex planar polygons satisfying additional shape regularity conditions to exclude large interior angles and short edges. Numerical evidence is provided on a trapezoidal quadrilateral mesh, previously not amenable to serendipity constructions, and applications to adaptive meshing are discussed.

RAND, ALEXANDER; GILLETTE, ANDREW; BAJAJ, CHANDRAJIT

2013-01-01

7

Quadratic  

NSDL National Science Digital Library

Shows how the roots of a quadratic change as the b term in the equation changes. The equation was chosen to illustrate the fact that only real roots are seen as points where the curve crosses the x-axis. This can lead to a useful discussion of what is meant by a physically meaningful solution.

8

Geometric multigrid to accelerate the solution of the quasi-static electric field problem by tetrahedral finite elements.  

PubMed

The acceleration of the solution of the quasi-static electric field problem considering anisotropic complex conductivity simulated by tetrahedral finite elements of first order is investigated by geometric multigrid. PMID:15005314

Hollaus, K; Weiss, B; Magele, Ch; Hutten, H

2004-02-01

9

Wave Propagation in QuadraticFiniteElement Approximations to Hyperbolic Equations #  

E-print Network

Wave Propagation in Quadratic­Finite­Element Approximations to Hyperbolic Equations # Dale R. Durran # University of Washington, USA October 8, 1999 SUMMARY Eigenmodes for the quadratic­finite­element arise as part of the conventional analysis. KEYWORDS: 65P25 Finite Elements 76M10 Finite Element Methods

10

The quarter-point quadratic isoparametric element as a singular element for crack problems  

NASA Technical Reports Server (NTRS)

The quadratic isoparametric elements which embody the inverse square root singularity are used for calculating the stress intensity factors at tips of cracks. The strain singularity at a point or an edge is obtained in a simple manner by placing the mid-side nodes at quarter points in the vicinity of the crack tip or an edge. These elements are implemented in NASTRAN as dummy elements. The method eliminates the use of special crack tip elements and in addition, these elements satisfy the constant strain and rigid body modes required for convergence.

Hussain, M. A.; Lorensen, W. E.; Pflegel, G.

1976-01-01

11

Deformation Expression for Elements of Algebras (III) --Generic product formula for *-exponentials of quadratic forms--  

E-print Network

In a noncommutative algebra there is no canonical way to express elements in univalent way, which is often called "ordering problem". In this note we give product formula of the Weyl algebra in generic ordered expression. In particular, the generic product formula of *-exponential functions of quadratic forms will be given.

Hideki Omori; Yoshiaki Maeda; Naoya Miyazaki; Akira Yoshioka

2011-07-13

12

Fast calculation of the sensitivity matrix in magnetic induction tomography by tetrahedral edge finite elements and the reciprocity theorem.  

PubMed

Magnetic induction tomography of biological tissue is used to reconstruct the changes in the complex conductivity distribution by measuring the perturbation of an alternating primary magnetic field. To facilitate the sensitivity analysis and the solution of the inverse problem a fast calculation of the sensitivity matrix, i.e. the Jacobian matrix, which maps the changes of the conductivity distribution onto the changes of the voltage induced in a receiver coil, is needed. The use of finite differences to determine the entries of the sensitivity matrix does not represent a feasible solution because of the high computational costs of the basic eddy current problem. Therefore, the reciprocity theorem was exploited. The basic eddy current problem was simulated by the finite element method using symmetric tetrahedral edge elements of second order. To test the method various simulations were carried out and discussed. PMID:15005313

Hollaus, K; Magele, C; Merwa, R; Scharfetter, H

2004-02-01

13

Geometrically nonlinear analysis of hyperelastic solids by high-order tetrahedral finite elements  

Microsoft Academic Search

The purpose of this study is to develop a computer code for accurate prediction of the mechanical behavior of hyperelastic solids under large deformation and finite strains. It is used, in the present work, the Lagrangian positional version of the Finite Element Method, in which the degrees of freedom are current positions instead of displacements. The main mechanical variables are

João P Pascon; Humberto B Coda

2010-01-01

14

Parallel Anisotropic Tetrahedral Adaptation  

NASA Technical Reports Server (NTRS)

An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.

Park, Michael A.; Darmofal, David L.

2008-01-01

15

Building Tetrahedral Kites  

NSDL National Science Digital Library

Working in teams of four, students build tetrahedral kites following specific instructions and using specific materials. They use the basic processes of manufacturing systems â cutting, shaping, forming, conditioning, assembling, joining, finishing, and quality control â to manufacture complete tetrahedral kites within a given time frame. Project evaluation takes into account team efficiency and the quality of the finished product.

Center For Engineering Educational Outreach

16

Building Tetrahedral Kites  

NSDL National Science Digital Library

Working in teams of four, learners build tetrahedral kites following specific instructions and using specific materials. They use the basic processes of manufacturing systems--cutting, shaping, forming, conditioning, assembling, joining, finishing, and quality control--to manufacture complete tetrahedral kites within a given time frame. Investigating questions encourage learners to reflect about the engineering and manufacturing process. Activity contains recommended resources about the history of kites and their construction.

University, Tufts

2013-01-01

17

Building Tetrahedral Kites  

NSDL National Science Digital Library

Working in teams of four, you and your team will build a tetrahedral kite following a specific set of directions and using specific provided materials. You will use basic processes of manufacturing systems - cutting, shaping, forming, conditioning, assembling, joining, finishing, and quality control - to manufacture a complete tetrahedral kite within a given time frame. Evaluation of your project will involve the efficiency of your team as well as your finished product.

18

Strongly cumulative second harmonic generation in a plate with quadratic nonlinearity: Finite element simulation  

NASA Astrophysics Data System (ADS)

A comprehensive analysis for guided wave preferred fundamental excitation that satisfies cumulative conditions of second harmonic generation in a weakly nonlinear plate has been carried out and then confirmed by finite element modeling for selected cases. The properties of nonlinear forcing terms and secondary mode shapes are manipulated to determine the cumulative second harmonics. Analysis shows that the synchronism points with higher power flux intensity are the preferred fundamental excitations that are suitable for nonlinear guided wave NDE. Finite element modeling of SH mode and Lamb mode fundamental excitation has been conducted on the excitation points selected by the co-analysis method. A linear increase of qualitative nonlinear parameter over the propagation distance has been observed for both Lamb wave and SH wave fundamental excitations.

Liu, Yang; Lissenden, Cliff J.; Rose, J. L.

2013-01-01

19

Variational Delaunay Approach to the Generation of Tetrahedral  

E-print Network

Variational Delaunay Approach to the Generation of Tetrahedral Finite Element Meshes Petr Krysl of arbitrarily complex three-dimensional solids into tetrahe- dral finite elements (tetrahedrization) is a very is easy to achieve), lack of robustness in three-dimensional geometries is a serious impediment

Krysl, Petr

20

Quadratic elongation: A quantitative measure of distortion in coordination polyhedra  

USGS Publications Warehouse

Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrahedral coordination complexes, both of which show variations in bond length and bond angle. The quadratic elonga tion is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.

Robinson, K.; Gibbs, G.V.; Ribbe, P.H.

1971-01-01

21

QUADRATIC RECIPROCITY JORDAN SCHETTLER  

E-print Network

is a quadratic residue mod p -1 if n is a quadratic nonresidue mod p 0 if p|n. The law of quadratic reciprocityQUADRATIC RECIPROCITY JORDAN SCHETTLER Abstract. The goals of this project are to have the reader proof of Gauss's Theorema Aureum of quadratic reciprocity. 1. Quadratic Residues and Legendre Symbols

Bigelow, Stephen

22

Quadratic double centralizers and quadratic multipliers  

Microsoft Academic Search

In this paper, we establish stability of quadratic double centralizers and quadratic multipliers on Banach algebras. We also\\u000a prove the super stability of quadratic double centralizers on Banach algebras which are weakly commutative and weakly without\\u000a order, and of quadratic multipliers on Banach algebras which are weakly without order.

M. Eshaghi Gordji; M. Ramezani; A. Ebadian

2011-01-01

23

Parallel tetrahedral mesh refinement with MOAB.  

SciTech Connect

In this report, we present the novel functionality of parallel tetrahedral mesh refinement which we have implemented in MOAB. This report details work done to implement parallel, edge-based, tetrahedral refinement into MOAB. The theoretical basis for this work is contained in [PT04, PT05, TP06] while information on design, performance, and operation specific to MOAB are contained herein. As MOAB is intended mainly for use in pre-processing and simulation (as opposed to the post-processing bent of previous papers), the primary use case is different: rather than refining elements with non-linear basis functions, the goal is to increase the number of degrees of freedom in some region in order to more accurately represent the solution to some system of equations that cannot be solved analytically. Also, MOAB has a unique mesh representation which impacts the algorithm. This introduction contains a brief review of streaming edge-based tetrahedral refinement. The remainder of the report is broken into three sections: design and implementation, performance, and conclusions. Appendix A contains instructions for end users (simulation authors) on how to employ the refiner.

Thompson, David C.; Pebay, Philippe Pierre

2008-12-01

24

Streaming simplification of tetrahedral meshes.  

PubMed

Unstructured tetrahedral meshes are commonly used in scientific computing to represent scalar, vector, and tensor fields in three dimensions. Visualization of these meshes can be difficult to perform interactively due to their size and complexity. By reducing the size of the data, we can accomplish real-time visualization necessary for scientific analysis. We propose a two-step approach for streaming simplification of large tetrahedral meshes. Our algorithm arranges the data on disk in a streaming, I/O-efficient format that allows coherent access to the tetrahedral cells. A quadric-based simplification is sequentially performed on small portions of the mesh in-core. Our output is a coherent streaming mesh which facilitates future processing. Our technique is fast, produces high quality approximations, and operates out-of-core to process meshes too large for main memory. PMID:17093343

Vo, Huy T; Callahan, Steven P; Lindstrom, Peter; Pascucci, Valerio; Silva, Cláudio T

2007-01-01

25

Feature-Sensitive Tetrahedral Mesh Generation with Guaranteed Quality.  

PubMed

Tetrahedral meshes are being extensively used in finite element methods (FEM). This paper proposes an algorithm to generate feature-sensitive and high-quality tetrahedral meshes from an arbitrary surface mesh model. A top-down octree subdivision is conducted on the surface mesh and a set of tetrahedra are constructed using adaptive body-centered cubic (BCC) lattices. Special treatments are given to the tetrahedra near the surface such that the quality of the resulting tetrahedral mesh is provably guaranteed: the smallest dihedral angle is always greater than 5.71°. The meshes generated by our method are not only adaptive from the interior to the boundary, but also feature-sensitive on the surface with denser elements in high-curvature regions where geometric feature most likely reside. A variety of experimental results are presented to demonstrate the effectiveness and robustness of this algorithm. PMID:22328787

Wang, Jun; Yu, Zeyun

2012-05-01

26

Self-Replicating Quadratics  

ERIC Educational Resources Information Center

We show that there are exactly four quadratic polynomials, Q(x) = x [superscript 2] + ax + b, such that (x[superscript 2] + ax + b) (x[superscript 2] - ax + b) = (x[superscript 4] + ax[superscript 2] + b). For n = 1, 2, ..., these quadratic polynomials can be written as the product of N = 2[superscript n] quadratic polynomials in x[superscript…

Withers, Christopher S.; Nadarajah, Saralees

2012-01-01

27

Lesson 14: Quadratic Formula  

NSDL National Science Digital Library

Completing the square is applied to the general quadratic to derive the quadratic formula. Before an area application example is given there is a quick review of the four methods that have been presented for solving quadratic equations. Complex numbers are introduced before the discriminant is presented.

2011-01-01

28

Robust solutions of uncertain quadratic and conic-quadratic problems  

E-print Network

Robust solutions of uncertain quadratic and conic-quadratic problems A. Ben-Tal y#3; A. Nemirovski birthday. Abstract We consider a conic-quadratic (and in particular a quadratically constrained conic-quadratic problem. Keywords: Semide#12;nite relaxation of NP-hard problems, (conic) quadratic

Roos, Kees

29

PRIMES AND QUADRATIC RECIPROCITY  

Microsoft Academic Search

We discuss number theory with the ultimate goal of understanding quadratic reciprocity. We begin by discussing Fermat's Little Theorem, the Chinese Remainder Theorem, and Carmichael numbers. Then we dene the Legendre symbol and prove Gauss's Lemma. Finally, using Gauss's Lemma we prove the Law of Quadratic Reciprocity.

ANGELICA WONG

30

Au40: A Large Tetrahedral Magic Cluster  

E-print Network

40 is a magic number for tetrahedral symmetry predicted in both nuclear physics and the electronic jellium model. We show that Au40 could be such a a magic cluster from density functional theory-based basin hopping for global minimization. The putative global minimum found for Au40 has a twisted pyramid structure, reminiscent of the famous tetrahedral Au20, and a sizable HOMO-LUMO gap of 0.69 eV, indicating its molecular nature. Analysis of the electronic states reveals that the gap is related to shell closings of the metallic electrons in a tetrahedrally distorted effective potential.

Jiang, De-en

2011-01-01

31

Structure of 152Sm via Deuteron Inelastic Scattering to Probe the Tetrahedral Symmetry  

NASA Astrophysics Data System (ADS)

The structure of 152Sm is investigated in search of the tetrahedral symmetry, which would represent a new quantum effect in the nucleus. The information for the existence of such exotic symmetry may reside in the transition matrix elements of the excited 152Sm nucleus, which are probed through a deuteron inelastic scattering experiment. The tetrahedral band candidates (low-lying negative-parity bands) are observed to be strongly populated, and preliminary coupled-channel calculations have been performed.

Chagnon-Lessard, S.; Garrett, P. E.; Bangay, J. C.; Bianco, L.; Leach, K. G.; Phillips, A. A.; Rand, E. T.; Svensson, C. E.; Ball, G.; Faestermann, T.; Krücken, R.; Hertenberger, R.; Wirth, H. F.; Hertenberger, R.; Wirth, H. F.

2013-03-01

32

Interactive isosurface ray tracing of time-varying tetrahedral volumes.  

PubMed

We describe a system for interactively rendering isosurfaces of tetrahedral finite-element scalar fields using coherent ray tracing techniques on the CPU. By employing state-of-the art methods in polygonal ray tracing, namely aggressive packet/frustum traversal of a bounding volume hierarchy, we can accomodate large and time-varying unstructured data. In conjunction with this efficiency structure, we introduce a novel technique for intersecting ray packets with tetrahedral primitives. Ray tracing is flexible, allowing for dynamic changes in isovalue and time step, visualization of multiple isosurfaces, shadows, and depth-peeling transparency effects. The resulting system offers the intuitive simplicity of isosurfacing, guaranteed-correct visual results, and ultimately a scalable, dynamic and consistently interactive solution for visualizing unstructured volumes. PMID:17968131

Wald, Ingo; Friedrich, Heiko; Knoll, Aaron; Hansen, Charles D

2007-01-01

33

Quadratic Functions: Workshop 4  

NSDL National Science Digital Library

Lesson 1 of two lessons requires students to explore quadratic functions by examining the family of functions described by y = a (x - h)squared+ k. In Lesson 2 students explore quadratic functions by using a motion detector known as a Calculator Based Ranger (CBR) to examine the heights of the different bounces of a ball. Students will represent each bounce with a quadratic function of the form y = a (x - h)squared + k. Background information, resources, references and videos of the lessons are included. Students work in teams of four.

Annenberg Media, Insights into Algebra, Teaching for Learning

2009-12-23

34

NASA Tetrahedral Unstructured Software System (TETRUSS).  

National Technical Information Service (NTIS)

The NASA Tetrahedral Unstructured Software System (TetrUSS) was developed during the 1990's to provide a rapid aerodynamic analysis and design capability to applied aerodynamicists. The system is comprised of loosely integrated, user-friendly software tha...

M. J. Pandya, M. K. Bhat, N. T. Frink, P. C. Parikh, S. Z. Pirzadeh

2000-01-01

35

A velocity-pressure integrated, mixed interpolation, Galerkin finite element method for high Reynolds number laminar flows  

NASA Technical Reports Server (NTRS)

A velocity-pressure integrated, mixed interpolation, Galerkin finite element method for the Navier-Stokes equations is presented. In the method, the velocity variables were interpolated using complete quadratic shape functions and the pressure was interpolated using linear shape functions. For the two dimensional case, the pressure is defined on a triangular element which is contained inside the complete biquadratic element for velocity variables; and for the three dimensional case, the pressure is defined on a tetrahedral element which is again contained inside the complete tri-quadratic element. Thus the pressure is discontinuous across the element boundaries. Example problems considered include: a cavity flow for Reynolds number of 400 through 10,000; a laminar backward facing step flow; and a laminar flow in a square duct of strong curvature. The computational results compared favorable with those of the finite difference methods as well as experimental data available. A finite elememt computer program for incompressible, laminar flows is presented.

Kim, Sang-Wook

1988-01-01

36

Multistage quadratic stochastic programming  

NASA Astrophysics Data System (ADS)

Quadratic stochastic programming (QSP) in which each subproblem is a convex piecewise quadratic program with stochastic data, is a natural extension of stochastic linear programming. This allows the use of quadratic or piecewise quadratic objective functions which are essential for controlling risk in financial and project planning. Two-stage QSP is a special case of extended linear-quadratic programming (ELQP). The recourse functions in QSP are piecewise quadratic convex and Lipschitz continuous. Moreover, they have Lipschitz gradients if each QP subproblem is strictly convex and differentiable. Using these properties, a generalized Newton algorithm exhibiting global and superlinear convergence has been proposed recently for the two stage case. We extend the generalized Newton algorithm to multistage QSP and show that it is globally and finitely convergent under suitable conditions. We present numerical results on randomly generated data and modified publicly available stochastic linear programming test sets. Efficiency schemes on different scenario tree structures are discussed. The large-scale deterministic equivalent of the multistage QSP is also generated and their accuracy compared.

Lau, Karen K.; Womersley, Robert S.

2001-04-01

37

Robust solutions of uncertain quadratic and conic-quadratic problems  

E-print Network

Robust solutions of uncertain quadratic and conic-quadratic problems A. Ben-Tal A. Nemirovski C. Abstract We consider a conic-quadratic (and in particular a quadratically constrained) optimization problem on the quality of the approximation, which is essentially independent of the dimensions of the underlying conic

Nemirovski, Arkadi

38

Robust solutions of uncertain quadratic and conic-quadratic problems  

E-print Network

Robust solutions of uncertain quadratic and conic-quadratic problems A. Ben-Tal A. Nemirovski C. Abstract We consider a conic-quadratic (and in particular a quadratically constrained) optimization problem on the quality of the approximation, which is independent of the dimensions of the underlying conic

Roos, Kees

39

ROBUST SOLUTIONS OF UNCERTAIN QUADRATIC AND CONIC-QUADRATIC PROBLEMS  

E-print Network

ROBUST SOLUTIONS OF UNCERTAIN QUADRATIC AND CONIC-QUADRATIC PROBLEMS A. BEN-TAL, A. NEMIROVSKI­560 Dedicated to Jochem Zowe on the occasion of his 60th birthday. Abstract. We consider a conic-quadratic (and, which is essentially independent of the dimensions of the underlying conic-quadratic problem. Key words

Nemirovski, Arkadi

40

Optical Quadratic Measure Eigenmodes  

E-print Network

We report a mathematically rigorous technique which facilitates the optimization of various optical properties of electromagnetic fields. The technique exploits the linearity of electromagnetic fields along with the quadratic nature of their interaction with matter. In this manner we may decompose the respective fields into optical quadratic measure eigenmodes (QME). Key applications include the optimization of the size of a focused spot, the transmission through photonic devices, and the structured illumination of photonic and plasmonic structures. We verify the validity of the QME approach through a particular experimental realization where the size of a focused optical field is minimized using a superposition of Bessel beams.

Michael Mazilu; Joerg Baumgartl; Sebastian Kosmeier; Kishan Dholakia

2010-07-13

41

Evidence for tetrahedral symmetry in 16O  

E-print Network

We derive the rotation-vibration spectrum of a 4-alpha configuration with tetrahedral symmetry, T_d, and show evidence for the occurrence of this symmetry in the low-lying spectrum of 16O. All vibrational states with A, E and F symmetry appear to have been observed, as well as the rotational bands with L(P)=0(+), 3(-), 4(+), 6(+) on the A states, and part of the rotational bands built on the E, F states. We derive analytic expressions for the form factors and B(EL) values of the ground state rotational band and show that the measured values support the tetrahedral symmetry of this band.

R. Bijker; F. Iachello

2014-03-26

42

Evidence for tetrahedral symmetry in 16O  

E-print Network

We derive the rotation-vibration spectrum of a 4-alpha configuration with tetrahedral symmetry, T_d, and show evidence for the occurrence of this symmetry in the low-lying spectrum of 16O. All vibrational states with A, E and F symmetry appear to have been observed, as well as the rotational bands with L(P)=0(+), 3(-), 4(+), 6(+) on the A states, and part of the rotational bands built on the E, F states. We derive analytic expressions for the form factors and B(EL) values of the ground state rotational band and show that the measured values support the tetrahedral symmetry of this band.

Bijker, R

2014-01-01

43

The NASA Tetrahedral Unstructured Software System (TETRUSS)  

NASA Technical Reports Server (NTRS)

The NASA Tetrahedral Unstructured Software System (TetrUSS) was developed during the 1990's to provide a rapid aerodynamic analysis and design capability to applied aerodynamicists. The system is comprised of loosely integrated, user-friendly software that enables the application of advanced Euler and Navier-Stokes tetrahedral finite volume technology to complex aerodynamic problems. TetrUSS has matured well because of the generous feedback from many willing users representing a broad cross-section of background and skill levels. This paper presents an overview of the current capabilities of the TetrUSS system along with some representative results from selected applications.

Frink, Neal T.; Pirzadeh, Shahyar Z.; Parikh, Paresh C.; Pandya, Mohagna J.; Bhat, M. K.

2000-01-01

44

The Mystical "Quadratic Formula."  

ERIC Educational Resources Information Center

Uses projectile motion to explain the two roots found when using the quadratic formula. An example is provided for finding the time of flight for a projectile which has a negative root implying a negative time of flight. This negative time of flight also has a useful physical meaning. (MVL)

March, Robert H.

1993-01-01

45

A finite element computational method for high Reynolds number laminar flows  

NASA Technical Reports Server (NTRS)

A velocity-pressure integrated, mixed interpolation, Galerkin finite element method for the Navier-Stokes equations is presented. In the method, the velocity variables are interpolated using complete quadratic shape functions, and the pressure is interpolated using linear shape functions which are defined on a triangular element for the two-dimensional case and on a tetrahedral element for the three-dimensional case. The triangular element and the tetrahedral element are contained inside the complete bi- and tri-quadratic elements for velocity variables for two and three dimensional cases, respectively, so that the pressure is discontinuous across the element boundaries. Example problems considered include: a cavity flow of Reynolds numbers 400 through 10,000; a laminar backward facing step flow; and a laminar flow in a square duct of strong curvature. The computational results compared favorably with the finite difference computational results and/or experimental data available. It was found that the present method can capture the delicate pressure driven recirculation zones, that the method did not yield any spurious pressure modes, and that the method requires fewer grid points than the finite difference methods to obtain comparable computational results.

Kim, Sang-Wook

1987-01-01

46

Tetrahedral boron in naturally occurring tourmaline  

SciTech Connect

Evidence for boron in both trigonal and tetrahedral coordination has been found in {sup 11}B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectra of natural, inclusion-free specimens of aluminum-rich lithian tourmaline from granitic pregmatites.

Tagg, S.L.; Cho, H. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.; Dyar, M.D. [Mount Holyoke Coll., South Hadley, MA (United States). Dept. of Geology and Geography; Grew, E.S. [Univ. of Maine, Orono, ME (United States). Dept. of Geological Sciences

1999-09-01

47

Small Power Technology for Tetrahedral Rovers  

Microsoft Academic Search

The Small Power Technology (SPOT) being studied at GSFC has the potential to be an efficient and compact radioisotope based electrical power system. Such a system would provide power for innovative tetrahedral robotic arms and walkers to support the lunar exploration initiative within the next decade. Presently, NASA has designated two flight qualified Radioisotope Power Supplies (RPS): the Multi-Mission RTG

P. E. Clark; S. R. Floyd; C. D. Butler; Y. Flom

2006-01-01

48

Small Power Technology Systems for Tetrahedral Rovers  

Microsoft Academic Search

The Small Power Technology (SPOT) being studied at GSFC has the potential to be an efficient and compact radioisotope based power system. Such a system would provide power for innovative tetrahedral robotic arms and walkers to support the lunar exploration initiative within the next decade. Presently, NASA has designated two flight qualified Radioisotope Power Supplies (RPS): the Multi-Mission RTG (MMRTG)

P. E. Clark; S. R. Floyd; C. D. Butler; Y. Flom

49

Extreme Mobility: Next Generation Tetrahedral Rovers  

Microsoft Academic Search

This paper describes the development and testing of a patented rover concept called Tetrahedral Explorer Technologies (TET), designed to provide extreme mobility and plug-and-play utility through reconfigurable addressable architecture. Here, we present the results of preliminary lab and field tests of Prototype III. Reconfigurable architecture is essential in exploration because reaching features of the great potential interest will require crossing

P. E. Clark; S. A. Curtis; M. L. Rilee; C. Y. Cheung; R. Wesenberg; G. Brown; C. Cooperrider

2007-01-01

50

Efficient query processing on unstructured tetrahedral meshes  

Microsoft Academic Search

Modern scientific applications consume massive volumes of data produced by computer simulations. Such applications require new data management capabilities in order to scale to terabyte-scale data volumes (25, 10). The most common way to discretize the application domain is to decompose it into pyramids, forming an unstructured tetrahedral mesh. Modern simulations generate meshes of high resolution and precision, to be

Stratos Papadomanolakis; Anastassia Ailamaki; Julio C. López; Tiankai Tu; David R. O'hallaron; Gerd Heber

2006-01-01

51

Electron phonon interaction in tetrahedral semiconductors  

NASA Astrophysics Data System (ADS)

Considerable progress has been made in recent years in the field of ab initio calculations of electronic band structures of semiconductors and insulators. The one-electron states (and the concomitant two-particle excitations) have been obtained without adjustable parameters, with a high degree of reliability. Also, more recently, the electron-hole excitation frequencies responsible for optical spectra have been calculated. These calculations, however, are performed with the constituent atoms fixed in their crystallographic positions and thus neglect the effects of the lattice vibrations (i.e. electron-phonon interaction) which can be rather large, even larger than the error bars assumed for ab initio calculations. Effects of electron-phonon interactions on the band structure can be experimentally investigated in detail by measuring the temperature dependence of energy gaps or critical points (van Hove singularities) of the optical excitation spectra. These studies have been complemented in recent years by observing the dependence of such spectra on isotopic mass whenever different stable isotopes of a given atom are available at affordable prices. In crystals composed of different atoms, the effect of the vibration of each separate atom can thus be investigated by isotopic substitution. Because of the zero-point vibrations, such effects are present even at zero temperature ( T=0). In this paper, we discuss state-of-the-art calculations of the dielectric function spectra and compare them with experimental results, with emphasis on the differences introduced by the electron-phonon interaction. The temperature dependence of various optical parameters will be described by means of one or two (in a few cases three) Einstein oscillators, except at the lowest temperatures where the T4 law (contrary to the Varshni T2 result) will be shown to apply. Increasing an isotopic mass increases the energy gaps, except in the case of monovalent Cu (e.g. CuCl) and possibly Ag (e.g. AgGaS 2). It will be shown that the gaps of tetrahedral materials containing an element of the first row of the periodic table (C,N,O) are strongly affected by the electron-phonon interaction. It will be conjectured that this effect is related to the superconductivity recently observed in heavily boron-doped carbon.

Cardona, Manuel

2005-01-01

52

Algebraic cluster model with tetrahedral symmetry  

SciTech Connect

We propose an algebraic treatment of a four-body system in terms of a U(10) spectrum generating algebra. The formalism for the case of four identical objects is developed in detail. This includes a discussion of the permutation symmetry, a study of special solutions which are shown to correspond to the harmonic oscillator, the deformed oscillator and the spherical top with tetrahedral symmetry.

Bijker, Roelof [ICN-UNAM, AP 70-543, 04510 Mexico, DF (Mexico)

2010-12-23

53

Lattice Cleaving: Conforming Tetrahedral Meshes of Multimaterial Domains with Bounded Quality  

PubMed Central

Summary We introduce a new algorithm for generating tetrahedral meshes that conform to physical boundaries in volumetric domains consisting of multiple materials. The proposed method allows for an arbitrary number of materials, produces high-quality tetrahedral meshes with upper and lower bounds on dihedral angles, and guarantees geometric fidelity. Moreover, the method is combinatoric so its implementation enables rapid mesh construction. These meshes are structured in a way that also allows grading, in order to reduce element counts in regions of homogeneity. PMID:25309969

Bronson, Jonathan R.; Levine, Joshua A.; Whitaker, Ross T.

2013-01-01

54

Quadratic spatial solitons  

NASA Astrophysics Data System (ADS)

Quadratic spatial solitons, beams that propagate unchanged in shape and magnitude, are supported by second order optical nonlinearities and can occur in all wave mixing processes under appropriate conditions. They are multi-component, consisting of all the frequency components that are coupled by a second order nonlinear interaction near a phase-matching condition. They have been observed in a number of bulk crystalline media, in LiNbO 3 slab waveguides and in arrays of parallel, weakly coupled, LiNbO 3 channel waveguides. The properties of the solitons and their excitation will be reviewed. To cite this article: G.I. Stegeman, C. R. Physique 8 (2007).

Stegeman, George I.

2007-03-01

55

Quadratic spatial soliton interactions  

NASA Astrophysics Data System (ADS)

Quadratic spatial soliton interactions were investigated in this Dissertation. The first part deals with characterizing the principal features of multi-soliton generation and soliton self-reflection. The second deals with two beam processes leading to soliton interactions and collisions. These subjects were investigated both theoretically and experimentally. The experiments were performed by using potassium niobate (KNBO 3) and periodically poled potassium titanyl phosphate (KTP) crystals. These particular crystals were desirable for these experiments because of their large nonlinear coefficients and, more importantly, because the experiments could be performed under non-critical-phase-matching (NCPM) conditions. The single soliton generation measurements, performed on KNBO3 by launching the fundamental component only, showed a broad angular acceptance bandwidth which was important for the soliton collisions performed later. Furthermore, at high input intensities multi-soliton generation was observed for the first time. The influence on the multi-soliton patterns generated of the input intensity and beam symmetry was investigated. The combined experimental and theoretical efforts indicated that spatial and temporal noise on the input laser beam induced multi-soliton patterns. Another research direction pursued was intensity dependent soliton routing by using of a specially engineered quadratically nonlinear interface within a periodically poled KTP sample. This was the first time demonstration of the self-reflection phenomenon in a system with a quadratic nonlinearity. The feature investigated is believed to have a great potential for soliton routing and manipulation by engineered structures. A detailed investigation was conducted on two soliton interaction and collision processes. Birth of an additional soliton resulting from a two soliton collision was observed and characterized for the special case of a non-planar geometry. A small amount of spiraling, up to 30 degrees rotation, was measured in the experiments performed. The parameters relevant for characterizing soliton collision processes were also studied in detail. Measurements were performed for various collision angles (from 0.2 to 4 degrees), phase mismatch, relative phase between the solitons and the distance to the collision point within the sample (which affects soliton formation). Both the individual and combined effects of these collision variables were investigated. Based on the research conducted, several all-optical switching scenarios were proposed.

Jankovic, Ladislav

56

Measure of disorder in tetrahedrally bonded semiconductors  

SciTech Connect

A measure of crystalline order in tetrahedrally bonded semiconductors is proposed based on optical response. This measure is obtained from the <111> critical point structure in the dielectric spectra. This descriptor is sensitive to the nature and extent of disorder in specimens and distinguishes differences in medium and short-order present in amorphous materials. Application to Ar{sup +}-irradiated Si specimens yields the threshold amorphization dose and this technique is sensitive to structural changes which occur as a function of irradiation fluence both above and beyond the amorphization threshhold. Systematic variations are also obtained in hydrogenated amorphous-Si. The general validity of the method is indicated.

Sundari, S. Tripura; Raghavan, G. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2005-06-13

57

Theory of prospective tetrahedral perovskite ferroelectrics  

E-print Network

Using first-principles methods, we predict the energy landscape and ferroelectric states of double perovskites of the form AA$'$BB$'$O$_6$ in which the atoms on both the A and B sites are arranged in rock-salt order. While we are not aware of compounds that occur naturally in this structure, we argue that they might be realizable by directed synthesis. The high-symmetry structure formed by this arrangement belongs to the tetrahedral $F\\bar{4}3m$ space group. If a ferroelectric instability occurs, the energy landscape will tend to have minima with the polarization along tetrahedral directions, leading to a rhombohedral phase, or along Cartesian directions, leading to an orthorhombic phase. We find that the latter scenario applies to CaBaTiZrO$_6$ and KCaZrNbO$_6$, which are weakly ferroelectric, and the former one applies to PbSnTiZrO$_6$, which is strongly ferroelectric. The results are modeled with a fourth- or fifth-order Landau-Devonshire expansion, providing good agreement with the first-principles calcul...

Roy, Anindya

2010-01-01

58

A bicontinuous tetrahedral structure in a liquid-crystalline lipid  

NASA Astrophysics Data System (ADS)

The structure of most lipid-water phases can be visualized as an ordered distribution of two liquid media, water and hydrocarbons, separated by a continuous surface covered by the polar groups of the lipid molecules1. In the cubic phases in particular, rod-like elements are linked into three-dimensional networks1,2. Two of these phases (space groups Ia3d and Pn3m) contain two such three-dimensional networks mutually inter-woven and unconnected. Under the constraints of energy minimization3, the interface between the components in certain of these `porous fluids' may well resemble one of the periodic minimal surface structures of the type described mathematically by Schwarz4,5. A structure of this sort has been proposed for the viscous isotropic (cubic) form of glycerol monooleate (GMO) by Larsson et al.6 who suggested that the X-ray diagrams of Lindblom et al.7 indicated a body-centred crystal structure in which lipid bilayers might be arranged as in Schwarz's octahedral surface4. We have now found that at high water contents, a primitive cubic lattice better fits the X-ray evidence with the material in the crystal arranged in a tetrahedral way. The lipid appears to form a single bilayer, continuous in three dimensions, separating two continuous interlinked networks of water. Each of the water networks has the symmetry of the diamond crystal structure and the bilayer lies in the space between them following a surface resembling Schwarz's tetrahedral surface4.

Longley, William; McIntosh, Thomas J.

1983-06-01

59

A Sequential Quadratically Constrained Quadratic Programming Method of Feasible Directions  

SciTech Connect

In this paper, a sequential quadratically constrained quadratic programming method of feasible directions is proposed for the optimization problems with nonlinear inequality constraints. At each iteration of the proposed algorithm, a feasible direction of descent is obtained by solving only one subproblem which consist of a convex quadratic objective function and simple quadratic inequality constraints without the second derivatives of the functions of the discussed problems, and such a subproblem can be formulated as a second-order cone programming which can be solved by interior point methods. To overcome the Maratos effect, an efficient higher-order correction direction is obtained by only one explicit computation formula. The algorithm is proved to be globally convergent and superlinearly convergent under some mild conditions without the strict complementarity. Finally, some preliminary numerical results are reported.

Jian Jinbao [Guangxi University, College of Mathematics and Informatics Science (China)], E-mail: jianjb@gxu.edu.cn; Hu Qingjie [Hunan Business College, Department of Information (China); Tang Chunming; Zheng Haiyan [Guangxi University, College of Mathematics and Informatics Science (China)

2007-12-15

60

Robust Solutions of Uncertain Quadratic and Conic-Quadratic Problems  

Microsoft Academic Search

We consider a conic-quadratic (and in particular a quadratically constrained) optimization problem with uncertain data, known only to reside in some uncertainty set U . The robust counterpart of such a problem leads usually to an NP-hard semidefinite problem; this is the case for example when U is given as intersection of ellipsoids, or as an n-dimensional box. For these

Aharon Ben-Tal; Arkadi Nemirovski; Cees Roos

2002-01-01

61

The Rise and Fall of Anomalies in Tetrahedral Liquids  

E-print Network

The thermodynamic liquid-state anomalies and associated structural changes of the Stillinger-Weber family of liquids are mapped out as a function of the degree of tetrahedrality of the interaction potential, focusing in particular on tetrahedrality values suitable for modeling C, H2O, Si, Ge and Sn. We show that the density anomaly, associated with a rise in molar volume on isobaric cooling, emerges at intermediate tetrahedralities (e.g. Ge, Si and H2O) but is absent in the low (e.g. Sn) and high (e.g. C) tetrahedrality liquids. The rise in entropy on isothermal compression associated with the density anomaly is related to the structural changes in the liquid using the pair correlation entropy. An anomalous increase in the heat capacity on isobaric cooling exists at high tetrahedralities but is absent at low tetrahedralities (e.g. Sn). Structurally, this heat capacity anomaly originates in a sharp rise in the fraction of four-coordinated particles and local tetrahedral order in the liquid as its structure approaches that of the tetrahedral crystal.

Waldemar Hujo; B. Shadrack Jabes; Varun K. Rana; Charusita Chakravarty; Valeria Molinero

2011-07-28

62

Tetrahedral Mesh Generation with Good Dihedral Angles Using Point Lattices  

E-print Network

Tetrahedral Mesh Generation with Good Dihedral Angles Using Point Lattices by Franc¸ois Labelle B Tetrahedral Mesh Generation with Good Dihedral Angles Using Point Lattices by Franc¸ois Labelle Doctor of Philosophy in Computer Science University of California, Berkeley Professor Jonathan Shewchuk, Chair Three-dimensional

O'Brien, James F.

63

Tetrahedral Mesh Generation with Good Dihedral Angles Using Point Lattices  

E-print Network

Shewchuk, Chair Three-dimensional meshes are frequently used to perform physical simulations in sci- enceTetrahedral Mesh Generation with Good Dihedral Angles Using Point Lattices Francois Labelle, requires prior specific permission. #12;Tetrahedral Mesh Generation with Good Dihedral Angles Using Point

O'Brien, James F.

64

An Investigation on Quadratic Equations.  

ERIC Educational Resources Information Center

Argues that exploring a familiar topic or examination question in a novel manner is a useful way to find topics for mathematical investigation in the classroom. The example used to illustrate the premise is a quadratic equation. (PK)

Hirst, Keith

1988-01-01

65

regularized sequential quadratic programming methods  

E-print Network

Oct 2, 2011 ... Research supported in part by National Science Foundation grants DMS- .... in the formulation of algorithms since the early 1960s (for a seminal reference, see .... is the solution (when it exists) of the convex quadratic program.

2011-10-30

66

ADAPTIVE TETRAHEDRAL GRID REFINEMENT AND COARSENING IN MESSAGE-PASSING ENVIRONMENTS  

SciTech Connect

A grid refinement and coarsening scheme has been developed for tetrahedral and triangular grid-based calculations in message-passing environments. The element adaption scheme is based on an edge bisection of elements marked for refinement by an appropriate error indicator. Hash-table/linked-list data structures are used to store nodal and element formation. The grid along inter-processor boundaries is refined and coarsened consistently with the update of these data structures via MPI calls. The parallel adaption scheme has been applied to the solution of a transient, three-dimensional, nonlinear, groundwater flow problem. Timings indicate efficiency of the grid refinement process relative to the flow solver calculations.

Hallberg, J.; Stagg, A. [and others

2000-10-01

67

Streaming Compression of Tetrahedral Volume Meshes  

SciTech Connect

Geometry processing algorithms have traditionally assumed that the input data is entirely in main memory and available for random access. This assumption does not scale to large data sets, as exhausting the physical memory typically leads to IO-inefficient thrashing. Recent works advocate processing geometry in a 'streaming' manner, where computation and output begin as soon as possible. Streaming is suitable for tasks that require only local neighbor information and batch process an entire data set. We describe a streaming compression scheme for tetrahedral volume meshes that encodes vertices and tetrahedra in the order they are written. To keep the memory footprint low, the compressor is informed when vertices are referenced for the last time (i.e. are finalized). The compression achieved depends on how coherent the input order is and how many tetrahedra are buffered for local reordering. For reasonably coherent orderings and a buffer of 10,000 tetrahedra, we achieve compression rates that are only 25 to 40 percent above the state-of-the-art, while requiring drastically less memory resources and less than half the processing time.

Isenburg, M; Lindstrom, P; Gumhold, S; Shewchuk, J

2005-11-21

68

Periodic superstructures in tetrahedrally bonded homopolymers  

NASA Astrophysics Data System (ADS)

Using a lattice sum over single bipolaron potentials displaced by periodicity d, we have analytically obtained a solution for a bipolaron lattice for a tetrahedrally bonded homopolymer within the continuum model of Rice and Phillpot. This solution is used to derive the band structure, which consists of two bipolaron bands symmetrically located about the middle of the band gap in addition to the conduction and valence bands. The electronic density of states, chemical potential ?, and the energy of formation of a bipolaron lattice are also calculated as a function of the bipolaron density ?b. The bipolaron chemical potential lies between the conduction-band edge and the upper edge of the upper bipolaron band, indicating that the bipolaron lattice is energetically the most favorable charge configuration at low ?b. In the strict weak-coupling limit (infinite momentum cutoff ?) the bipolaron-bipolaron interaction is found to be repulsive and varies with bipolaron density as (1/?b)exp(-2/?b?p), ?p being the bipolaron characteristic length. Thus, the bipolaron lattice is stable only in the range 0

Saxena, Avadh; Cao, Wenwu

1988-10-01

69

More About the Tetrahedral Unstructured Software System  

NASA Technical Reports Server (NTRS)

TetrUSS is a comprehensive suite of computational fluid dynamics (CFD) programs that won the Software of the Year award in 1996 and has found increasing use in government, academia, and industry for solving realistic flow problems (especially in aerodynamics and aeroelastics of aircraft having complex shapes). TetrUSS includes not only programs for solving basic equations of flow but also programs that afford capabilities for efficient generation and utilization of computational grids and for graphical representation of computed flows (see figure). The 2004 version of the Tetrahedral Unstructured Software System (TetrUSS), which is one of two software systems reported in "NASA s 2004 Software of the Year," NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 18, has been improved greatly since 1996. These improvements include (1) capabilities to simulate viscous flow by solving the Navier-Stokes equations on unstructured grids, (2) portability to personal computers from diverse manufacturers, (3) advanced models of turbulence, (4) a parallel-processing version of one of the unstructured-grid Navier-Stokes-equation-solving programs, and (5) advanced programs for generating unstructured grids.

Abdol-Hamid, Khaled S.; Frink, Neal T.; Hunter, Craig A.; Parikh, Paresh C.; Pizadeh, Shalyar Z.; Samareh, Jamshid A.; Bhat, Maharaj K.; Pandya, Mohagna J.; Grismer, Matthew J.

2006-01-01

70

Preliminary design of a large tetrahedral truss/hexagonal heatshield panel aerobrake  

NASA Technical Reports Server (NTRS)

An aerobrake structural concept is introduced which consists of two primary components: (1) a lightweight erectable tetrahedral support truss; and (2) sandwich hexagonal heatshield panels which, when attached to the truss, form a continuous impermeable aerobraking surface. Generic finite element models and a general analysis procedure to design tetrahedral truss/hexagonal heatshield panel aerobrakes is developed, and values of the aerobrake design parameters which minimize mass and packaging volume for a 120-foot-diameter aerobrake are determined. Sensitivity of the aerobrake design to variations in design parameters is also assessed. The results show that a 120-foot-diameter aerobrake is viable using the concept presented (i.e., the aerobrake mass is less than or equal to 15 percent of the payload spacecraft mass). Minimizing the aerobrake mass (by increasing the number of rings in the support truss) however, leads to aerobrakes with the highest part count.

Dorsey, John T.; Mikulas, Martin M., Jr.

1989-01-01

71

Solving Quadratic Equations by Factoring  

NSDL National Science Digital Library

This video explains how to solve quadratic equations with the factoring method. In 4 minutes 23 seconds, the two narrators explain in detail the steps required. Additionally, how these equations relate to objects and events in the real world such as roller coasters is covered.

2012-08-06

72

QUADRATIC RECIPROCITY IN ODD CHARACTERISTIC KEITH CONRAD  

E-print Network

+ T + 1? The answer to questions like this can be found with the quadratic reciprocity law in F[T]. It has a strong resemblance to the quadratic reciprocity law in Z. We restrict to F with odd characteristic the quadratic reciprocity law. The proof of the law is in Section 3. Some applications are given in Section 4

Lozano-Robledo, Alvaro

73

QUADRATIC RECIPROCITY IN CHARACTERISTIC 2 KEITH CONRAD  

E-print Network

. When F has odd characteristic, the quadratic reciprocity law in F[T] lets us decide whether . This is similar to the quadratic reciprocity law in Z. We want to develop an analogous reciprocity law when F has properties, and state the quadratic reciprocity law on F[T]. Section 3 defines the trace on finite fields

Lozano-Robledo, Alvaro

74

The generation of tetrahedral mesh models for neuroanatomical MRI.  

PubMed

In this article, we describe a detailed method for automatically generating tetrahedral meshes from 3D images having multiple region labels. An adaptively sized tetrahedral mesh modeling approach is described that is capable of producing meshes conforming precisely to the voxelized regions in the image. Efficient tetrahedral mesh improvement is then performed minimizing an energy function containing three terms: a smoothing term to remove the voxelization, a fidelity term to maintain continuity with the image data, and a novel elasticity term to prevent the tetrahedra from becoming flattened or inverted as the mesh deforms while allowing the voxelization to be removed entirely. The meshing algorithm is applied to structural MR image data that has been automatically segmented into 56 neuroanatomical sub-divisions as well as on two other examples. The resulting tetrahedral representation has several desirable properties such as tetrahedra with dihedral angles away from 0 and 180 degrees, smoothness, and a high resolution. Tetrahedral modeling via the approach described here has applications in modeling brain structure in normal as well as diseased brain in human and non-human data and facilitates examination of 3D object deformations resulting from neurological illness (e.g. Alzheimer's disease), development, and/or aging. PMID:21073968

Lederman, Carl; Joshi, Anand; Dinov, Ivo; Vese, Luminita; Toga, Arthur; Van Horn, John Darrell

2011-03-01

75

The law of quadratic reciprocity  

Microsoft Academic Search

Which famous mathematical theorem has been proved most often? Pythagoras would certainly be a good candidate or the fundamental\\u000a theorem of algebra, but the champion is without doubt the law of quadratic reciprocity in number theory. In an admirable monograph\\u000a Franz Lemmermeyer lists as of the year 2000 no fewer than 196 proofs. Many of them are of course only

Martin Aigner; Günter M. Ziegler

76

ORTHOGONAL POLYNOMIALS AND QUADRATIC TRANSFORMATIONS  

Microsoft Academic Search

Starting from a sequencefPngn‚0 of monic polynomials orthogonal with respect to a linear functional u, we flnd a linear functional v such that fQng‚0, with either Q2n(x) = Pn(T(x)) or Q2n+1(x) = (x¡a)Pn(T(x)) where T is a monic quadratic polynomial and a 2 C, is a sequence of monic orthogonal polynomials with respect to v. In particular, we discuss the

PORTUGALIAE MATHEMATICA; F. Marcellan; J. Petronilho

77

Quadratic Residues a is a quadratic residue mod m if x2  

E-print Network

a reciprocity law.) The law of quadratic reciprocity says: The congruences are either both solvable or both, a is a quadratic nonresidue. · Quadratic Reciprocity relates the solvability of the congruence x2 = p (mod q gave of quadratic reciprocity one of his crowning achievements; in fact, he gave 6 distinct proofs

Ikenaga, Bruce

78

Compatible quadratic Poisson brackets related to a family of elliptic curves  

NASA Astrophysics Data System (ADS)

We construct nine pairwise compatible quadratic Poisson structures such that a generic linear combination of them is associated with an elliptic algebra in n generators. Explicit formulas for Casimir elements of this elliptic Poisson structure are obtained.

Odesskii, Alexander; Wolf, Thomas

2013-01-01

79

HIGH QUALITY ANISOTROPIC TETRAHEDRAL MESH GENERATION VIA ELLIPSOIDAL BUBBLE PACKING  

E-print Network

the behavior of soap bubbles in nature. If we pack soap bubbles in a volumetric domain, the bubblesHIGH QUALITY ANISOTROPIC TETRAHEDRAL MESH GENERATION VIA ELLIPSOIDAL BUBBLE PACKING Soji Yamakawa1 through a physically based particle simulation, which we call 'bubble packing.' Ellipsoidal bubbles

Shimada, Kenji

80

Selective refinement queries for volume visualization of unstructured tetrahedral meshes.  

PubMed

In this paper, we address the problem of the efficient visualization of large irregular volume data sets by exploiting a multiresolution model based on tetrahedral meshes. Multiresolution models, also called Level-Of-Detail (LOD) models, allow encoding the whole data set at a virtually continuous range of different resolutions. We have identified a set of queries for extracting meshes at variable resolution from a multiresolution model, based on field values, domain location, or opacity of the transfer function. Such queries allow trading off between resolution and speed in visualization. We define a new compact data structure for encoding a multiresolution tetrahedral mesh built through edge collapses to support selective refinement efficiently and show that such a structure has a storage cost from 3 to 5.5 times lower than standard data structures used for tetrahedral meshes. The data structures and variable resolution queries have been implemented together with state-of-the art visualization techniques in a system for the interactive visualization of three-dimensional scalar fields defined on tetrahedral meshes. Experimental results show that selective refinement queries can support interactive visualization of large data sets. PMID:15382696

Cignoni, Paolo; De Floriani, Leila; Magillo, Paola; Puppo, Enrico; Scopigno, Roberto

2004-01-01

81

Constrained Delaunay Tetrahedralizations and Provably Good Boundary Recovery  

E-print Network

Constrained Delaunay Tetrahedralizations and Provably Good Boundary Recovery Jonathan Richard recovery: it usually requires fewer additional vertices to be inserted, it yields provably good bounds on edge lengths (i.e. edges are not made unnecessarily short), and it interacts well with provably good

California at Berkeley, University of

82

Hardware-Based Ray Casting for Tetrahedral Meshes  

Microsoft Academic Search

We present the first implementation of a volume ray casting algorithm for tetrahedral meshes running on off-the-shelf programmable graphics hardware. Our implementation avoids the memory transfer bottleneck of the graphics bus since the complete mesh data is stored in the local memory of the graphics adapter and all computations, in particular ray traversal and ray integration, are performed by the

Manfred Weiler; Martin Kraus; Markus Merz; Thomas Ertl

2003-01-01

83

Quadratic algebra contractions and 2nd order superintegrable systems  

E-print Network

Quadratic algebras are generalizations of Lie algebras; they include the symmetry algebras of 2nd order superintegrable systems in 2 dimensions as special cases. The superintegrable systems are exactly solvable physical systems in classical and quantum mechanics. For constant curvature spaces we show that the free quadratic algebras generated by the 1st and 2nd order elements in the enveloping algebras of their Euclidean and orthogonal symmetry algebras correspond one-to-one with the possible superintegrable systems with potential defined on these spaces. We describe a contraction theory for quadratic algebras and show that for constant curvature superintegrable systems, ordinary Lie algebra contractions induce contractions of the quadratic algebras of the superintegrable systems that correspond to geometrical pointwise limits of the physical systems. One consequence is that by contracting function space realizations of representations of the generic superintegrable quantum system on the 2-sphere (which give the structure equations for Racah/Wilson polynomials) to the other superintegrable systems one obtains the full Askey scheme of orthogonal hypergeometric polynomials.

Ernest G. Kalnins; Willard Miller Jr

2014-01-04

84

Single-photon quadratic optomechanics  

PubMed Central

We present exact analytical solutions to study the coherent interaction between a single photon and the mechanical motion of a membrane in quadratic optomechanics. We consider single-photon emission and scattering when the photon is initially inside the cavity and in the fields outside the cavity, respectively. Using our solutions, we calculate the single-photon emission and scattering spectra, and find relations between the spectral features and the system's inherent parameters, such as: the optomechanical coupling strength, the mechanical frequency, and the cavity-field decay rate. In particular, we clarify the conditions for the phonon sidebands to be visible. We also study the photon-phonon entanglement for the long-time emission and scattering states. The linear entropy is employed to characterize this entanglement by treating it as a bipartite one between a single mode of phonons and a single photon. PMID:25200128

Liao, Jie-Qiao; Nori, Franco

2014-01-01

85

Quality Tetrahedral Mesh Smoothing via Boundary-Optimized Delaunay Triangulation  

PubMed Central

Despite its great success in improving the quality of a tetrahedral mesh, the original optimal Delaunay triangulation (ODT) is designed to move only inner vertices and thus cannot handle input meshes containing “bad” triangles on boundaries. In the current work, we present an integrated approach called boundary-optimized Delaunay triangulation (B-ODT) to smooth (improve) a tetrahedral mesh. In our method, both inner and boundary vertices are repositioned by analytically minimizing the error between a paraboloid function and its piecewise linear interpolation over the neighborhood of each vertex. In addition to the guaranteed volume-preserving property, the proposed algorithm can be readily adapted to preserve sharp features in the original mesh. A number of experiments are included to demonstrate the performance of our method. PMID:23144522

Gao, Zhanheng; Yu, Zeyun; Holst, Michael

2012-01-01

86

Quadratic Equations: From Factored to Standard Form  

NSDL National Science Digital Library

This activity leads students to understand the utility in the factored form of a quadratic equation. Students then express quadratic equations in standard form in the corresponding factored form. The activity is concluded with four critical-thinking questions. website: http://www.mathedpage.org/ copyright information: http://www.mathedpage.org/rights.html

2011-01-01

87

Binary Quadratic Forms: A Historical View  

ERIC Educational Resources Information Center

We present an expository account of the development of the theory of binary quadratic forms. Beginning with the formulation and proof of the Two-Square Theorem, we show how the study of forms of the type x[squared] + ny[squared] led to the discovery of the Quadratic Reciprocity Law, and how this theorem, along with the concept of reduction relates…

Khosravani, Azar N.; Beintema, Mark B.

2006-01-01

88

Another Look at the Quadratic Formula.  

ERIC Educational Resources Information Center

An exploration of a problem called solving quadratic congruences modulo p is detailed and is built around an alternate method of deriving the quadratic formula. Three practical pedagogical values that have been experienced by students and instructor when the material was presented to classes are noted. (MP)

Obermeyer, Dean D.

1982-01-01

89

Dynamics of quadratic polynomials II: rigidity  

Microsoft Academic Search

This is a continuation of the series of notes on the dynamics of quadratic polynomials. We show the following Rigidity Theorem: Any combinatorial class contains at most one quadratic polynomial satisfying the secondary limbs condition with a-priori bounds. As a corollary, such maps are combinatorially and topologically rigid, and as a consequence, the Mandelbrot set is locally connected at the

Mikhail Lyubich

1995-01-01

90

An Unexpected Influence on a Quadratic  

ERIC Educational Resources Information Center

Using technology to explore the coefficients of a quadratic equation can lead to an unexpected result. This article describes an investigation that involves sliders and dynamically linked representations. It guides students to notice the effect that the parameter "a" has on the graphical representation of a quadratic function in the form…

Davis, Jon D.

2013-01-01

91

Search for Fingerprints of Tetrahedral Symmetry in $^{156}Gd$  

E-print Network

Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2-transitions at the bottom of the odd-spin negative parity band in $^{156}Gd$. The present study reports on experiment performed to address this phenomenon. It allowed to determine the intra-band E2 transitions and branching ratios B(E2)/B(E1) of two of the negative-parity bands in $^{156}Gd$.

Q. T. Doan; D. Curien; O. Stezowski; J. Dudek; K. Mazurek; A. Gozdz; J. Piot; G. Duchene; B. Gall; H. Molique; M. Richet; P. Medina; D. Guinet; N. Redon; C. Schmitt; P. Jones; R. Julin; P. Peura; S. Ketelhut; M. Nyman; U. Jakobsson; A. Maj; K. Zuber; P. Bednarczyk; N. Schunck; J. Dobaczewski; A. Astier; I. Deloncle; D. Verney; G. De Angelis; J. Gerl

2008-11-08

92

Tetrahedral Sn-silsesquioxane: synthesis, characterization and catalysis.  

PubMed

A tetrahedral stannasilsesquioxane complex was synthesized as a racemic mixture using Sn(O(i)Pr)4 and silsesquioxanediol, and its structure was confirmed with X-ray crystallography, NMR, and EXAFS. The complex was a Lewis acid, and both anti and syn-binding with Lewis bases were possible with the formation of octahedral Sn complexes. It was also a Lewis acid catalyst active for epoxide ring opening and hydride transfer. PMID:25360661

Beletskiy, Evgeny V; Shen, Zhongliang; Riofski, Mark V; Hou, Xianliang; Gallagher, James R; Miller, Jeffrey T; Wu, Yuyang; Kung, Harold H; Kung, Mayfair C

2014-12-25

93

A quadratically convergent VBSCF method.  

PubMed

A quadratically convergent valence bond self-consistent field method is described where the simultaneous optimisation of orbitals and the coefficients of the configurations (VB structures) is based on a Newton-Raphson scheme. The applicability of the method is demonstrated in actual calculations. The convergence and efficiency are compared with the Super-CI method. A necessary condition to achieve convergence in the Newton-Raphson method is that the Hessian is positive definite. When this is not the case, a combination of the Super-CI and Newton-Raphson methods is shown to be an optimal choice instead of shifting the eigenvalues of the Hessian to make it positive definite. In the combined method, the first few iterations are performed with the Super-CI method and then the Newton-Raphson scheme is switched on based on an internal indicator. This approach is found computationally a more economical choice than using either the Newton-Raphson or Super-CI method alone to perform a full optimisation of the nonorthogonal orbitals. PMID:23406096

Rashid, Zahid; van Lenthe, Joop H

2013-02-01

94

A quadratically convergent VBSCF method  

NASA Astrophysics Data System (ADS)

A quadratically convergent valence bond self-consistent field method is described where the simultaneous optimisation of orbitals and the coefficients of the configurations (VB structures) is based on a Newton-Raphson scheme. The applicability of the method is demonstrated in actual calculations. The convergence and efficiency are compared with the Super-CI method. A necessary condition to achieve convergence in the Newton-Raphson method is that the Hessian is positive definite. When this is not the case, a combination of the Super-CI and Newton-Raphson methods is shown to be an optimal choice instead of shifting the eigenvalues of the Hessian to make it positive definite. In the combined method, the first few iterations are performed with the Super-CI method and then the Newton-Raphson scheme is switched on based on an internal indicator. This approach is found computationally a more economical choice than using either the Newton-Raphson or Super-CI method alone to perform a full optimisation of the nonorthogonal orbitals.

Rashid, Zahid; van Lenthe, Joop H.

2013-02-01

95

Seven Wonders of the Ancient and Modern Quadratic World.  

ERIC Educational Resources Information Center

Presents four methods for solving a quadratic equation using graphing calculator technology: (1) graphing with the CALC feature; (2) quadratic formula program; (3) table; and (4) solver. Includes a worksheet for a lab activity on factoring quadratic equations. (KHR)

Taylor, Sharon E.; Mittag, Kathleen Cage

2001-01-01

96

A stabilized mixed finite element method for shear-rate dependent non-Newtonian fluids: 3D benchmark problems and application to blood flow in bifurcating arteries  

NASA Astrophysics Data System (ADS)

This paper presents a stabilized mixed finite element method for shear-rate dependent fluids. The nonlinear viscosity field is a function of the shear-rate and varies uniformly in space and in time. The stabilized form is developed via application of Variational Multiscale (VMS) framework to the underlying generalized Navier-Stokes equation. Linear and quadratic tetrahedral and hexahedral elements are employed with equal-order interpolations for the velocity and pressure fields. A variety of benchmark problems are solved to assess the stability and accuracy properties of the resulting method. The method is then applied to non-Newtonian shear-rate dependent flows in bifurcating artery geometry, and significant non-Newtonian fluid effects are observed. A comparative study of the proposed method shows that the additional computational costs due to the nonlinear shear-rate dependent viscosity are only ten percent more than the computational cost for a Newtonian model.

Kwack, JaeHyuk; Masud, Arif

2014-04-01

97

An assessment of the adaptive unstructured tetrahedral grid, Euler Flow Solver Code FELISA  

NASA Technical Reports Server (NTRS)

A three-dimensional solution-adaptive Euler flow solver for unstructured tetrahedral meshes is assessed, and the accuracy and efficiency of the method for predicting sonic boom pressure signatures about simple generic models are demonstrated. Comparison of computational and wind tunnel data and enhancement of numerical solutions by means of grid adaptivity are discussed. The mesh generation is based on the advancing front technique. The FELISA code consists of two solvers, the Taylor-Galerkin and the Runge-Kutta-Galerkin schemes, both of which are spacially discretized by the usual Galerkin weighted residual finite-element methods but with different explicit time-marching schemes to steady state. The solution-adaptive grid procedure is based on either remeshing or mesh refinement techniques. An alternative geometry adaptive procedure is also incorporated.

Djomehri, M. Jahed; Erickson, Larry L.

1994-01-01

98

Delaunay Tetrahedralization of the Heart Based on Integration of Open Source Codes  

NASA Astrophysics Data System (ADS)

The Finite Element Method (FEM) is a way of numerical solution applied in different areas, as simulations used in studies to improve cardiac ablation procedures. For this purpose, the meshes should have the same size and histological features of the focused structures. Some methods and tools used to generate tetrahedral meshes are limited mainly by the use conditions. In this paper, the integration of Open Source Softwares is presented as an alternative to solid modeling and automatic mesh generation. To demonstrate its efficiency, the cardiac structures were considered as a first application context: atriums, ventricles, valves, arteries and pericardium. The proposed method is feasible to obtain refined meshes in an acceptable time and with the required quality for simulations using FEM.

Pavarino, E.; Neves, L. A.; Machado, J. M.; de Godoy, M. F.; Shiyou, Y.; Momente, J. C.; Zafalon, G. F. D.; Pinto, A. R.; Valêncio, C. R.; do Nascimento, M. Z.

2014-03-01

99

Search for Fingerprints of Tetrahedral Symmetry in ^{156}Gd  

SciTech Connect

Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2 transitions at the bottom of the odd-spin negative-parity band in ^{156}Gd. The present study reports on experiment performed to address this phenomenon. It allowed to remove certain ambiguities related to the intra-band E2 transitions in the negative-parity bands to determine the new inter-band transitions and reduced probability ratios B(E2)/B(E1) and, for the first time, to determine the experimental uncertainties related to the latter observable.

Doan, Q. T. [Universite Lyon 1, Villeurbanne, France; Curien, D. [CNRS, Strasbourg, France; Stezowski, O. [Universite Lyon 1, Villeurbanne, France; Dudek, J. [CNRS, Strasbourg, France; Mazurek, K. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Gozdz, A. [Maria Curie-Sklodowskiej, Lublin, Poland; Piot, J. [CNRS, Strasbourg, France; Duchene, G. [CNRS, Strasbourg, France; Gall, B. [CNRS, Strasbourg, France; Molique, H. [CNRS, Strasbourg, France; Richet, M. [CNRS, Strasbourg, France; Medina, P. [CNRS, Strasbourg, France; Guinet, D. [Universite Lyon 1, Villeurbanne, France; Redon, N. [Universite Lyon 1, Villeurbanne, France; Schmitt, Ch. [Universite Lyon 1, Villeurbanne, France; Jones, P. [University of Jyvaskyla; Peura, P. [University of Jyvaskyla; Ketelhut, S. [University of Jyvaskyla; Nyman, M. [University of Jyvaskyla; Jakobsson, U. [University of Jyvaskyla; Greenlees, P. T. [University of Jyvaskyla; Julin, R. [University of Jyvaskyla; Juutinen, S. [University of Jyvaskyla; Rahkila, P. [University of Jyvaskyla; Maj, A. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Zuber, K. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Bednarczyk, P. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Schunck, Nicolas F [ORNL; Dobaczewski, J. [Warsaw University; Astier, A. [CNRS, Orsay, France; Deloncle, I. [CNRS, Orsay, France; Verney, D. [CNRS/IN2P3, Orsay, France; De Angelis, G. [INFN, Laboratori Nazionali di Legnaro, Italy; Gerl, J. [Gesellschaft fur Schwerionenforschung (GSI), Germany

2009-01-01

100

Novel biomedical tetrahedral mesh methods: algorithms and applications  

NASA Astrophysics Data System (ADS)

Tetrahedral mesh generation algorithm, as a prerequisite of many soft tissue simulation methods, becomes very important in the virtual surgery programs because of the real-time requirement. Aiming to speed up the computation in the simulation, we propose a revised Delaunay algorithm which makes a good balance of quality of tetrahedra, boundary preservation and time complexity, with many improved methods. Another mesh algorithm named Space-Disassembling is also presented in this paper, and a comparison of Space-Disassembling, traditional Delaunay algorithm and the revised Delaunay algorithm is processed based on clinical soft-tissue simulation projects, including craniofacial plastic surgery and breast reconstruction plastic surgery.

Yu, Xiao; Jin, Yanfeng; Chen, Weitao; Huang, Pengfei; Gu, Lixu

2007-12-01

101

Practical implementation of tetrahedral mesh reconstruction in emission tomography  

NASA Astrophysics Data System (ADS)

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio projection datasets. The results demonstrate that the reconstructed images represented as tetrahedral meshes based on point clouds offer image quality comparable to that achievable using a standard voxel grid while allowing substantial reduction in the number of unknown intensities to be reconstructed and reducing the noise.

Boutchko, R.; Sitek, A.; Gullberg, G. T.

2013-05-01

102

Practical implementation of tetrahedral mesh reconstruction in emission tomography.  

PubMed

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio projection datasets. The results demonstrate that the reconstructed images represented as tetrahedral meshes based on point clouds offer image quality comparable to that achievable using a standard voxel grid while allowing substantial reduction in the number of unknown intensities to be reconstructed and reducing the noise. PMID:23588373

Boutchko, R; Sitek, A; Gullberg, G T

2013-05-01

103

Quadratic Functionals with General Boundary Conditions  

SciTech Connect

The purpose of this paper is to give the Reid 'Roundabout Theorem' for quadratic functionals with general boundary conditions. In particular, we describe the so-called coupled point and regularity condition introduced in terms of Riccati equation solutions.

Dosla, Z.; Dosly, O. [Department of Mathematics, Masaryk University, Janackovo nam. 2a, 66295 Brno (Czech Republic)

1997-11-15

104

RELIABLE SOLUTION OF CONVEX QUADRATIC PROGRAMS ...  

E-print Network

lems in Sequential Quadratic Programming (SQP), a state-of-the-art method for ...... Support by the German Federal Ministry of Education and Research (BMBF) under ... sults has received funding from the European Union Seventh Framework ...

2011-01-28

105

Improved semidefinite programming bounds for quadratic ...  

E-print Network

Sep 15, 2009 ... gramming Relaxations for the Quadratic Assignment Problem. Journal ... a partial assignment of facilities to locations leads to a smaller QAP problem ...... Society for Industrial and Applied Mathematics, 12(1): 131–135, 1964.

2009-09-15

106

BLOCK STRUCTURED QUADRATIC PROGRAMMING FOR THE ...  

E-print Network

brid null–space range–space approach to exploit the block sparse structure of the quadratic ... ment of the theoretical run time complexity reveals significant advantages of the proposed ... complementary condensing, based on work by [35

2009-09-11

107

Remarks on Quadratic Hamiltonians in Spaceflight Mechanics  

E-print Network

Remarks on Quadratic Hamiltonians in Spaceflight Mechanics Bernard Bonnard1 , Jean-Baptiste Caillau in spaceflight mechanics when the averaged system of energy minimizing trajectories of the Kepler equation

Caillau, Jean-Baptiste

108

sensitivity analysis in convex quadratic optimization: simultaneous ...  

E-print Network

of using optimal bases in parametric LO showing by an example that different ...... maximization game correspond to optimal solutions of the following quadratic minimization .... mization, Springer Science+Business Media, New York, USA.

2007-08-30

109

Weight of quadratic forms and graph states  

E-print Network

We prove a connection between Schmidt-rank and weight of quadratic forms. This provides a new tool for the classification of graph states based on entanglement. Our main tool arises from a reformulation of previously known results concerning the weight of quadratic forms in terms of graph states properties. As a byproduct, we obtain a straightforward characterization of the weight of functions associated with pivot-minor of bipartite graphs.

Alessandro Cosentino; Simone Severini

2009-06-13

110

Linear and quadratic programming neural network analysis  

Microsoft Academic Search

Neural networks for linear and quadratic programming are analyzed. The network proposed by M.P. Kennedy and L.O. Chua (IEEE Trans. Circuits Syst., vol.35, pp.554-562, May 1988) is justified from the viewpoint of optimization theory and the technique is extended to solve optimization problems, such as the least-squares problem. For quadratic programming, the network converges either to an equilibrium or to

Chia-Yiu Maa; Michael A. Shanblatt

1992-01-01

111

The Factorability of Quadratics: Motivation for More Techniques  

ERIC Educational Resources Information Center

Typically, secondary and college algebra students attempt to utilize either completing the square or the quadratic formula as techniques to solve a quadratic equation only after frustration with factoring has arisen. While both completing the square and the quadratic formula are techniques which can determine solutions for all quadratic equations,…

Bosse, Michael J.; Nandakumar, N. R.

2005-01-01

112

Interpenetrating metal-organic frameworks formed by self-assembly of tetrahedral and octahedral building blocks  

NASA Astrophysics Data System (ADS)

To investigate the relationship between topological types and molecular building blocks (MBBs), we have designed and synthesized a series of three-dimensional (3D) interpenetrating metal-organic frameworks based on different polygons or polyhedra under hydrothermal conditions, namely [Cd(bpib) 0.5(L 1)] ( 1), [Cd(bpib) 0.5(L 2)]·H 2O ( 2), [Cd(bpib) 0.5(L 3)] ( 3) and [Cd(bib) 0.5(L 1)] ( 4), where bpib=1,4-bis(2-(pyridin-2-yl)-1 H-imidazol-1-yl)butane, bib=1,4-bis(1 H-imidazol-1-yl)butane, H 2L 1=4-(4-carboxybenzyloxy)benzoic acid, H 2L 2=4,4'-(ethane-1,2-diylbis(oxy))dibenzoic acid and H 2L 3=4,4'-(1,4-phenylenebis(methylene))bis(oxy)dibenzoic acid, respectively. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compounds 1- 3 display ?-Po topological nets with different degrees of interpenetration based on the similar octahedral [Cd 2(-COO) 4] building blocks. Compound 4 is a six-fold interpenetrating diamondoid net based on tetrahedral MBBs. By careful inspection of these structures, we find that various carboxylic ligands and N-donor ligands with different coordination modes and conformations, and metal centers with different geometries are important for the formation of the different MBBs. It is believed that different topological types lie on different MBBs with various polygons or polyhedra. Such as four- and six-connected topologies are formed by tetrahedral and octahedral building blocks. In addition, with the increase of carboxylic ligands' length, the degrees of interpenetration have been changed in the ?-Po topological nets. And the luminescent properties of these compounds have been investigated in detail.

Lu, Yong-Ming; Lan, Ya-Qian; Xu, Yan-Hong; Su, Zhong-Min; Li, Shun-Li; Zang, Hong-Ying; Xu, Guang-Juan

2009-11-01

113

Mechanical dissipation at elevated temperatures in tetrahedral amorphous carbon.  

SciTech Connect

We have measured the temperature dependence of mechanical dissipation in tetrahedral amorphous carbon flexural and torsional resonators over the temperature range from 300 to 1023 K. The mechanical dissipation was found to be controlled by defects within the material, and the magnitude and temperature dependence of the dissipation were found to depend on whether flexural or torsional vibrational modes were excited. The defects that were active under flexural stresses have a relatively flat concentration from 0.4 to 0.7 eV with an ever increasing defect concentration up to 1.9 eV. Under shear stresses (torsion), the defect activation energies increase immediately beginning at 0.4 eV, with increasing defect concentration at higher energies.

Sullivan, John P.; Friedmann, Thomas Aquinas; Czaplewski, David A.; Wendt, Joel Robert

2005-05-01

114

Grid-characteristic method on unstructured tetrahedral meshes  

NASA Astrophysics Data System (ADS)

The goal of this paper is to develop a grid-characteristic method intended for high-performance computer systems and implemented on unstructured tetrahedral hierarchical meshes with the use of a multiple time step and high-order interpolation, including interpolation with a limiter, piecewise parabolic interpolation, and monotone interpolation. The method is designed for simulating complex three-dimensional dynamical processes in heterogeneous media. It involves accurately stated contact conditions and produces physically correct solutions of problems in seismology and seismic exploration. Hierarchical meshes make it possible to take into account numerous inhomogeneous inclusions (cracks, cavities, etc.) and to solve problems in a real-life formulation. The grid-characteristic method enables the use of a multiple time step. As a result, the computation time is considerably reduced and the efficiency of the method is raised. The method is parallelized on a computer cluster with an optimal use of system resources.

Muratov, M. V.; Petrov, I. B.; Sannikov, I. V.; Favorskaya, A. V.

2014-05-01

115

Half-solidity of tetrahedral-like Al(55) clusters.  

PubMed

A new dynamic melting state, which has both solid and liquid characteristics, is revealed from first-principles molecular dynamics simulations of Al(55) clusters. In thermal fluctuations near the melting point, the low-energy tetrahedral-like Al(55) survives through rapid, collective surface transformations-such as parity conversions and correlated diffusion of two distant vacancies-without losing its structural orders. The emergence of the collective motions is solely due to efficient thermal excitation of soft phonon modes at nanoscale. A series of spontaneous surface reconfigurations result in a mixture or effective flow of surface atoms as is random color shuffling of a Rubik's cube. This novel flexible solid state (termed as half-solidity) provides useful insights into understanding stability, flexibility, and functionality of nanosystems near or below melting temperatures. PMID:20055435

Kang, Joongoo; Kim, Yong-Hyun

2010-02-23

116

Optimization of Time-Dependent Particle Tracing Using Tetrahedral Decomposition  

NASA Technical Reports Server (NTRS)

An efficient algorithm is presented for computing particle paths, streak lines and time lines in time-dependent flows with moving curvilinear grids. The integration, velocity interpolation and step-size control are all performed in physical space which avoids the need to transform the velocity field into computational space. This leads to higher accuracy because there are no Jacobian matrix approximations or expensive matrix inversions. Integration accuracy is maintained using an adaptive step-size control scheme which is regulated by the path line curvature. The problem of cell-searching, point location and interpolation in physical space is simplified by decomposing hexahedral cells into tetrahedral cells. This enables the point location to be done analytically and substantially faster than with a Newton-Raphson iterative method. Results presented show this algorithm is up to six times faster than particle tracers which operate on hexahedral cells yet produces almost identical particle trajectories.

Kenwright, David; Lane, David

1995-01-01

117

Nuclear Tetrahedral Symmetry: Possibly Present Throughout the Periodic Table  

E-print Network

More than half a century after the fundamental, spherical shell structure in nuclei has been established, theoretical predictions indicate that the shell-gaps comparable or even stronger than those at spherical shapes may exist. Group-theoretical analysis supported by realistic mean-field calculations indicate that the corresponding nuclei are characterized by the $T_d^D$ ('double-tetrahedral') group of symmetry, exact or approximate. The corresponding strong shell-gap structure is markedly enhanced by the existence of the 4-dimensional irreducible representations of the group in question and consequently it can be seen as a geometrical effect that does not depend on a particular realization of the mean-field. Possibilities of discovering the corresponding symmetry in experiment are discussed.

J. Dudek; A. Gozdz; N. Schunck; M. Miskiewicz

2002-05-21

118

Quadratic Integrate-and-Fire Model  

NSDL National Science Digital Library

The Quadratic Integrate-and-Fire model is a slight modification of the integrate-and-fire model. This slight modification has some drastic changes on the dynamics, although the equation is still solvable analytically in order to determine the period of a continuously-spiking neuron. Because of its simplicity, the Quadratic Integrate-and-Fire model and its variations are favorites for mathematical treatments of neural networks. The Quadratic Integrate-and-Fire model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Thomson, Colin F.

2012-11-06

119

Guises and Disguises of Quadratic Divergences  

E-print Network

In this contribution, we present a new perspective on the control of quadratic divergences in quantum field theory, in general, and in the Higgs naturalness problem, in particular. Our discussion is essentially based on an approach where UV divergences are parameterized, after being reduced to basic divergent integrals (BDI) in one internal momentum, as functions of a cutoff and a renormalization group scale $\\lambda$. We illustrate our proposal with well-known examples, such as the gluon vacuum self energy of QCD and the Higgs decay in two photons within this approach. We also discuss frameworks in effective low-energy QCD models, where quadratic divergences are indeed fundamental.

Cherchiglia, A L; Hiller, Brigitte; Scarpelli, A P Baêta; Sampaio, Marcos

2014-01-01

120

Guises and Disguises of Quadratic Divergences  

E-print Network

In this contribution, we present a new perspective on the control of quadratic divergences in quantum field theory, in general, and in the Higgs naturalness problem, in particular. Our discussion is essentially based on an approach where UV divergences are parameterized, after being reduced to basic divergent integrals (BDI) in one internal momentum, as functions of a cutoff and a renormalization group scale $\\lambda$. We illustrate our proposal with well-known examples, such as the gluon vacuum self energy of QCD and the Higgs decay in two photons within this approach. We also discuss frameworks in effective low-energy QCD models, where quadratic divergences are indeed fundamental.

A. L. Cherchiglia; A. R. Vieira; Brigitte Hiller; A. P. Baêta Scarpelli; Marcos Sampaio

2014-10-04

121

Optical power flow with sequential quadratic programming  

NASA Astrophysics Data System (ADS)

Newton's method as an approach to solve the optimal power flow problem in electric power plants is presented. A general formulation of the optimal flow problem is given. Newton's method is applied to solve the nonlinear Kuhn-Tucker conditions by iteration. Every Newton step is calculated by solving a quadratic programming problem. Variations of the sequential quadratic programming method are presented. Byproducts of the optimization, namely the Lagrange multipliers and their interpretation as marginal costs and shadow prices, are outlined. The most important computer programs are enclosed.

Vanamerongen, R. A. M.

1985-01-01

122

Robust linear quadratic designs with respect to parameter uncertainty  

NASA Technical Reports Server (NTRS)

The authors derive a linear quadratic regulator (LQR) which is robust to parametric uncertainty by using the overbounding method of I. R. Petersen and C. V. Hollot (1986). The resulting controller is determined from the solution of a single modified Riccati equation. It is shown that, when applied to a structural system, the controller gains add robustness by minimizing the potential energy of uncertain stiffness elements, and minimizing the rate of dissipation of energy through uncertain damping elements. A worst-case disturbance in the direction of the uncertainty is also considered. It is proved that performance robustness has been increased with the robust LQR when compared to a mismatched LQR design where the controller is designed on the nominal system, but applied to the actual uncertain system.

Douglas, Joel; Athans, Michael

1992-01-01

123

Thermal conductivity of ultrathin tetrahedral amorphous carbon films A. A. Balandin,1,a  

E-print Network

materials.1 Carbon has a variety of allotropes, including graphene, carbon nano- tubes, diamondThermal conductivity of ultrathin tetrahedral amorphous carbon films A. A. Balandin,1,a M. Shamsa,1 tetrahedral amorphous carbon ta-C films on silicon, down to subnanometer thickness. For films with an initial

124

Why Is the Tetrahedral Bond Angle 109 Degrees? The Tetrahedron-in-a-Cube  

ERIC Educational Resources Information Center

The common question of why the tetrahedral angle is 109.471 degrees can be answered using a tetrahedron-in-a-cube, along with some Year 10 level mathematics. The tetrahedron-in-a-cube can also be used to demonstrate the non-polarity of tetrahedral molecules, the relationship between different types of lattice structures, and to demonstrate that…

Lim, Kieran F.

2012-01-01

125

Quadratic reciprocity and the sign of the Gauss sum via the finite Weil representation  

Microsoft Academic Search

We give new proofs of two basic results in number theory: The law of quadratic reciprocity and the sign of the Gauss sum. We show that these results are encoded in the relation between the discrete Fourier transform and the action of the Weyl element in the Weil representation modulo p,q and pq.

Shamgar Gurevich; Ronny Hadani; Roger Howe

2008-01-01

126

A Streaming Language Implementation of the Discontinuous Galerkin Finite Element Method  

E-print Network

StreamFEM A Streaming Language Implementation of the Discontinuous Galerkin Finite Element Method(MHD)Linear(Euler)Linear(MHD) Quadratic(Euler) Quadratic(MHD)Cubic(Euler)Cubic(MHD) Element Type (Equation Type) Sustained GFLOPS LRF BW(MHD)Linear(Euler)Linear(MHD)Quadratic(Euler)Quadratic(MHD) Cubic(Euler) Cubic(MHD) Element Type (Equation Type) Sustained GFLOPS Ops / mem access A DG Finite

Dally, William J.

127

High order Godunov mixed methods on tetrahedral meshes for density driven flow simulations in porous media  

NASA Astrophysics Data System (ADS)

Two-dimensional Godunov mixed methods have been shown to be effective for the numerical solution of density-dependent flow and transport problems in groundwater even when concentration gradients are high and the process is dominated by density effects. This class of discretization approaches solves the flow equation by means of the mixed finite element method, thus guaranteeing mass conserving velocity fields, and discretizes the transport equation by mixed finite element and finite volumes techniques combined together via appropriate time splitting. In this paper, we extend this approach to three dimensions employing tetrahedral meshes and introduce a spatially variable time stepping procedure that improves computational efficiency while preserving accuracy by adapting the time step size according to the local Courant-Friedrichs-Lewy (CFL) constraint. Careful attention is devoted to the choice of a truly three-dimensional limiter for the advection equation in the time-splitting technique, so that to preserve second order accuracy in space (in the sense that linear functions are exactly interpolated). The three-dimensional Elder problem and the saltpool problem, recently introduced as a new benchmark for testing three-dimensional density models, provide assessments with respect to accuracy and reliability of this numerical approach.

Mazzia, Annamaria; Putti, Mario

2005-09-01

128

Quadratic and Hilbert Reciprocity Timothy Curry  

E-print Network

. . . . . . . . . . . . . . . . . . . . . 17 3.5 Hilbert Reciprocity Law on Q . . . . . . . . . . . . . . . . . . . . . . 24 Ch. 4. The Hilbert vi #12;Chapter 1 Introduction The law of quadratic reciprocity provides conditions that tell whether . The Hilbert symbol satisfies the Hilbert reciprocity law, which we will show is equivalent to the law

Lozano-Robledo, Alvaro

129

SELMER GROUPS AND QUADRATIC RECIPROCITY FRANZ LEMMERMEYER  

E-print Network

typical for early class field theory, and were used for proving explicit reciprocity laws. Hecke, on the other hand, first proved (a large part of) the quadratic reciprocity law in number fields using his essentially is just the calculation of the order of a certain Selmer group) from the reciprocity law

Lemmermeyer, Franz

130

Uncertain Conic Quadratic and Semidefinite Optimization  

E-print Network

Uncertain Conic Quadratic and Semidefinite Optimization "Canonical" Conic problem: min x cT xI KI (CP) Uncertain canonical conic problem P: a collec- tion of canonical conic programsI) : Z Robust Counterpart of uncertain canonical conic problem P: the problem min t,x t : t - c[]T x

Nemirovski, Arkadi

131

Robust Conic Quadratic and Semidefinite Optimization  

E-print Network

Lecture 3 Robust Conic Quadratic and Semidefinite Optimization In this lecture, we extend the RO methodology onto non-linear convex optimization problems, specifically, conic ones. 3.1 Uncertain Conic Optimization: Preliminaries 3.1.1 Conic Programs A conic optimization (CO) problem (also called conic program

Nemirovski, Arkadi

132

Global quadratic optimization via conic relaxation  

Microsoft Academic Search

We present a convex conic relaxation for a problem of maximizing an indefinite quadratic form over a set of convex constraints on the squared variables. We show that for all these problems we get at least 12\\/37-relative accuracy of the approximation. In the second part of the paper we derive the conic relaxation by another approach based on the second

Yurii NESTEROV

1998-01-01

133

A Practical Approach to Quadratic Equations.  

ERIC Educational Resources Information Center

The usual methods for solving quadratic equations are noted to require either the use of numerical formula or curve plotting on graph paper. The method described here enables pupils to solve equations using only a 45 degree setsquare, graph paper, and a pencil for those which have both real roots and real coefficients. (Author/MP)

Light, Peter

1983-01-01

134

Theory of the Quadratic Zeeman Effect  

Microsoft Academic Search

The experiments of Jenkins and Segrè, reported in the accompanying paper, are considered theoretically. The quadratic Zeeman effect observed in absorption to large orbits in strong magnetic fields is due to the diamagnetic term in the Hamiltonian, which is proportional to the square of the vector potential and hence to the square of the magnetic field. For the alkalis, the

L. I. Schiff; H. Snyder

1939-01-01

135

Inhomogeneous quadratic forms and triangular numbers  

Microsoft Academic Search

We prove an explicit formula for the number of representations of an integer as the sum of n triangular numbers for each n in the range 2 ? n ? 8 as special cases of a more general formula applicable to an inhomogeneous quadratic form over a totally real number field. The formula can be derived by calculating explicitly the

Goro Shimura

2004-01-01

136

Globally Solving Nonconvex Quadratic Programming Problems via ...  

E-print Network

Mar 7, 2011 ... the new algorithm with existing codes on a diverse set of test instances, ... We consider the problem of optimizing a general quadratic function ... in Matlab's Optimization Toolbox (MathWorks, 2010) is a widely ..... Quadprogbb does, we were unsuccessful due to CPLEX run-time errors that we could not fix.

2011-08-15

137

ESTIMATION OF QUADRATIC FUNCTIONS: NONINFORMATIVE PRIORS FOR  

E-print Network

ESTIMATION OF QUADRATIC FUNCTIONS: NONINFORMATIVE PRIORS FOR NON­CENTRALITY PARAMETERS by James O­Centrality Parameters \\Lambda James O. Berger 1 , Anne Philippe 2 and Christian P. Robert 2;3 1 ISDS, Duke University 2 sets arising from these reference priors. Starting with Welch and Peers (1963) and Peers (1965

Berger, Jim

138

Natural frequency of uniform and optimized tetrahedral truss platforms  

NASA Technical Reports Server (NTRS)

Qualitative and quantitative estimates for the fundamental frequency of uniform and optimized tetrahedral truss platforms are determined. A semiempirical equation is developed for the frequency of free-free uniform trusses as a function of member material properties, truss dimensions, and parasitic (nonstructural) mass fraction Mp/Mt. Optimized trusses with frequencies approximately two times those of uniform trusses are determined by varying the cross-sectional areas of member groups. Trusses with 3 to 8 rings, no parasitic mass, and member areas up to 25 times the minimum area are optimized. Frequencies computed for ranges of both Mp/Mt and the ratio of maximum area to minimum area are normalized to the frequency of a uniform truss with no parasitic mass. The normalized frequency increases with the number of rings, and both frequency and the ratio of maximum area to minimum area decrease with increasing Mp/Mt. Frequency improvements that are achievable with a limited number of member areas are estimated for a 3-ring truss by using Taguchi methods. Joint stiffness knockdown effects are also considered. Comparison of optimized and baseline uniform truss frequencies indicates that tailoring can significantly increase structural frequency; maximum gains occur for trusses with low values of Mp/Mt. This study examines frequency trends for ranges of structural parameters and may be used as a preliminary design guide.

Wu, K. Chauncey; Lake, Mark S.

1994-01-01

139

Theoretical Studies of Routes to Synthesis of Tetrahedral N4  

NASA Technical Reports Server (NTRS)

A paper [Chem. Phys. Lett. 345, 295 (2001)] describes theoretical studies of excited electronic states of nitrogen molecules, with a view toward utilizing those states in synthesizing tetrahedral N4, or Td N4 a metastable substance under consideration as a high-energy-density rocket fuel. Several ab initio theoretical approaches were followed in these studies, including complete active space self-consistent field (CASSCF), state-averaged CASSCF (SA-CASSCF), singles configuration interaction (CIS), CIS with second-order and third-order correlation corrections [CIS(D) and CIS(3)], and linear response singles and doubles coupled-cluster (LRCCSD). Standard double zeta polarized and triple zeta double polarized one-particle basis sets were used. The CASSCF calculations overestimated the excitation energies, while SACASSCF calculations partly corrected these overestimates. The accuracy of the CIS calculations varied, depending on the particular state, while the CIS(D), CIS(3), and LRCCSD results were in generally good agreement. The energies of the lowest six excited singlet states of Td N4 as calculated by the LRCCSD were compared with the energies of possible excited states of N2 + N2 fragments, leading to the conclusion that the most likely route for synthesis of Td N4 would involve a combination of two bound quintet states of N2.

Lee, Timothy J.; Dateo, Christopher E.

2007-01-01

140

Structural stability of boron clusters with octahedral and tetrahedral symmetries.  

PubMed

The structural stability of cagelike boron clusters with octahedral and tetrahedral symmetries has been investigated by means of first-principles calculations. Twenty-eight cluster models, ranging from B(10) to B(66), were systematically constructed using regular and semiregular polyhedra as prototypes. The binding energies per atom were, on the whole, slightly lower than those of icosahedral clusters B(80) and B(100), which are supposed to be the most stable in the icosahedral group. The larger clusters did not always have higher binding energies. Isothermal molecular dynamics simulations were performed to determine the deformation temperatures at which clusters began to break or change their structures. We found eight clusters that had nonzero deformation temperatures, indicating that they are in metastable states. The octahedral cluster B(18) had the highest deformation temperature among these, similar to that of icosahedral B(80) and B(100). The analysis of the electronic structure of B(18) showed that it attained this high stability owing to Jahn-Teller distortion. PMID:21675744

Hayami, Wataru; Otani, Shigeki

2011-07-28

141

Quadratic RK shooting solution for a environmental parameter prediction boundary value problem  

NASA Astrophysics Data System (ADS)

Using tools of Information Geometry, the minimum distance between two elements of a statistical manifold is defined by the corresponding geodesic, e.g. the minimum length curve that connects them. Such a curve, where the probability distribution functions in the case of our meteorological data are two parameter Weibull distributions, satisfies a 2nd order Boundary Value (BV) system. We study the numerical treatment of the resulting special quadratic form system using Shooting method. We compare the solutions of the problem when we employ a classical Singly Diagonally Implicit Runge Kutta (SDIRK) 4(3) pair of methods and a quadratic SDIRK 5(3) pair . Both pairs have the same computational costs whereas the second one attains higher order as it is specially constructed for quadratic problems.

Famelis, Ioannis Th.; Tsitouras, Ch.

2014-10-01

142

Geometric Approaches to Quadratic Equations from Other Times and Places.  

ERIC Educational Resources Information Center

Focuses on geometric solutions of quadratic problems. Presents a collection of geometric techniques from ancient Babylonia, classical Greece, medieval Arabia, and early modern Europe to enhance the quadratic equation portion of an algebra course. (KHR)

Allaire, Patricia R.; Bradley, Robert E.

2001-01-01

143

THE EFFECTIVENESS OF QUADRATS FOR MEASURING VASCULAR PLANT DIVERSITY  

EPA Science Inventory

Quadrats are widely used for measuring characteristics of vascular plant communities. It is well recognized that quadrat size affects measurements of frequency and cover. The ability of quadrats of varying sizes to adequately measure diversity has not been established. An exha...

144

QUADRATIC RECIPROCITY VIA LINEAR ALGEBRA M. RAM MURTY  

E-print Network

from this, the law of quadratic reciprocity. 1.Introduction Let p to determine trA when n is an odd number and this allows us to deduce the law of quadratic reciprocity QUADRATIC RECIPROCITY VIA LINEAR ALGEBRA M. RAM MURTY

Murty, Ram

145

Applications: Quadratic Formulas Up to NCTM's Curriculum Standards.  

ERIC Educational Resources Information Center

Discusses an alternative form of the quadratic formula to solve quadratic equations. Presents an application to chemistry to illustrate the need for quadratic formulas better suited to approximations obtained using hand-held calculators. Addresses the problems of rounding errors, accuracy of solutions, and factoring as a method of solution. (MDH)

Nievergelt, Yves

1992-01-01

146

Linear and quadratic time-frequency signal representations  

Microsoft Academic Search

A tutorial review of both linear and quadratic representations is given. The linear representations discussed are the short-time Fourier transform and the wavelet transform. The discussion of quadratic representations concentrates on the Wigner distribution, the ambiguity function, smoothed versions of the Wigner distribution, and various classes of quadratic time-frequency representations. Examples of the application of these representations to typical problems

F. Hlawatsch; G. F. Boudreaux-Bartels

1992-01-01

147

Interface solitons in quadratic nonlinear photonic lattices  

SciTech Connect

We study the properties of two-color nonlinear localized modes which may exist at the interfaces separating two different periodic photonic lattices in quadratic media, focusing on the impact of phase mismatch of the photonic lattices on the properties, stability, and threshold power requirements for the generation of interface localized modes. We employ both an effective discrete model and continuum model with periodic potential and find good qualitative agreement between both models. Dynamic excitation of interface modes shows that a two-color interface twisted mode splits into two beams with different escaping angles and carrying different energies when entering a uniform medium from the quadratic photonic lattice. The output position and energy contents of each two-color interface solitons can be controlled by judicious tuning of the lattice parameters.

Xu Zhiyong; Kivshar, Yuri S. [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Molina, Mario I. [Departmento de Fisica, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, 7800024 Nunoa, Santiago (Chile)

2009-07-15

148

A Mechanical Proof of Quadratic Reciprocity  

Microsoft Academic Search

We describe the use of the Boyer-Moore theorem prover in mechanically generating a proof of the Law of Quadratic Reciprocity: for distinct odd primes p and q, the congruences x2=q (mod p) and x2=p (mod q) are either both solvable or both unsolvable, unless p=q=3 (mod 4). The proof is a formalization of an argument due to Eisenstein, based on

David M. Russinoff

1992-01-01

149

Stochastic Linear Quadratic Optimal Control Problems  

SciTech Connect

This paper is concerned with the stochastic linear quadratic optimal control problem (LQ problem, for short) for which the coefficients are allowed to be random and the cost functional is allowed to have a negative weight on the square of the control variable. Some intrinsic relations among the LQ problem, the stochastic maximum principle, and the (linear) forward-backward stochastic differential equations are established. Some results involving Riccati equation are discussed as well.

Chen, S. [Department of Mathematics, Zhejiang University, Hangzhou 310027 (China); Yong, J. [Laboratory of Mathematics for Nonlinear Sciences, Department of Mathematics, and Institute of Mathematical Finance, Fudan University, Shanghai 200433 (China)

2001-07-01

150

Characterization of a Quadratic Function in Rn  

ERIC Educational Resources Information Center

It is proved that a scalar-valued function "f"(x) defined in "n"-dimensional space must be quadratic, if the intersection of tangent planes at x[subscript 1] and x[subscript 2] always contains the midpoint of the line joining x[subscript 1] and x[subscript 2]. This is the converse of a result of Stenlund proved in this JOURNAL in 2001.

Xu, Conway

2010-01-01

151

Extended Decentralized Linear-Quadratic-Gaussian Control  

NASA Technical Reports Server (NTRS)

A straightforward extension of a solution to the decentralized linear-Quadratic-Gaussian problem is proposed that allows its use for commonly encountered classes of problems that are currently solved with the extended Kalman filter. This extension allows the system to be partitioned in such a way as to exclude the nonlinearities from the essential algebraic relationships that allow the estimation and control to be optimally decentralized.

Carpenter, J. Russell

2000-01-01

152

Quadratic Programming for Allocating Control Effort  

NASA Technical Reports Server (NTRS)

A computer program calculates an optimal allocation of control effort in a system that includes redundant control actuators. The program implements an iterative (but otherwise single-stage) algorithm of the quadratic-programming type. In general, in the quadratic-programming problem, one seeks the values of a set of variables that minimize a quadratic cost function, subject to a set of linear equality and inequality constraints. In this program, the cost function combines control effort (typically quantified in terms of energy or fuel consumed) and control residuals (differences between commanded and sensed values of variables to be controlled). In comparison with prior control-allocation software, this program offers approximately equal accuracy but much greater computational efficiency. In addition, this program offers flexibility, robustness to actuation failures, and a capability for selective enforcement of control requirements. The computational efficiency of this program makes it suitable for such complex, real-time applications as controlling redundant aircraft actuators or redundant spacecraft thrusters. The program is written in the C language for execution in a UNIX operating system.

Singh, Gurkirpal

2005-01-01

153

Optimal Approximation of Quadratic Interval Functions  

NASA Technical Reports Server (NTRS)

Measurements are never absolutely accurate, as a result, after each measurement, we do not get the exact value of the measured quantity; at best, we get an interval of its possible values, For dynamically changing quantities x, the additional problem is that we cannot measure them continuously; we can only measure them at certain discrete moments of time t(sub 1), t(sub 2), ... If we know that the value x(t(sub j)) at a moment t(sub j) of the last measurement was in the interval [x-(t(sub j)), x + (t(sub j))], and if we know the upper bound D on the rate with which x changes, then, for any given moment of time t, we can conclude that x(t) belongs to the interval [x-(t(sub j)) - D (t - t(sub j)), x + (t(sub j)) + D (t - t(sub j))]. This interval changes linearly with time, an is, therefore, called a linear interval function. When we process these intervals, we get an expression that is quadratic and higher order w.r.t. time t, Such "quadratic" intervals are difficult to process and therefore, it is necessary to approximate them by linear ones. In this paper, we describe an algorithm that gives the optimal approximation of quadratic interval functions by linear ones.

Koshelev, Misha; Taillibert, Patrick

1997-01-01

154

Assessment of the Adaptive Unstructured Tetrahedral Grid, Euler Flow Solver Code Felisa.  

National Technical Information Service (NTIS)

A three-dimensional solution-adaptive Euler flow solver for unstructured tetrahedral meshes is assessed, and the accuracy and efficiency of the method for predicting sonic boom pressure signatures about simple generic models are demonstrated. Comparison o...

M. J. Djomehri, L. L. Erickson

1994-01-01

155

Multi-Dimensional, Inviscid flux Reconstruction for Simulation of Hypersonic Heating on Tetrahedral Grids.  

National Technical Information Service (NTIS)

The quality of simulated hypersonic stagnation region heating on tetrahedral meshes is investigated by using a three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. Two test problems are investigated: hypersonic flow over a thre...

P. A. Gnoffo

2009-01-01

156

Tetrahedrality and structural order for hydrophobic interactions in a coarse-grained water model  

NASA Astrophysics Data System (ADS)

The hydrophobic interaction manifests two separate regimes in terms of size: Small nonpolar bodies exhibit a weak oscillatory force (versus distance) while large nonpolar surfaces exhibit a strong monotonic one. This crossover in hydrophobic behavior is typically explained in terms of water's tetrahedral structure: Its tetrahedrality is enhanced near small solutes and diminished near large planar ones. Here, we demonstrate that water's tetrahedral correlations signal this switch even in a highly simplified, isotropic, "core-softened" water model. For this task, we introduce measures of tetrahedrality based on the angular distribution of water's nearest neighbors. On a quantitative basis, the coarse-grained model of course is only approximate: (1) While greater than simple Lennard-Jones liquids, its bulk tetrahedrality remains lower than that of fully atomic models; and (2) the decay length of the large-scale hydrophobic interaction is less than has been found in experiments. Even so, the qualitative behavior of the model is surprisingly rich and exhibits numerous waterlike hydrophobic behaviors, despite its simplicity. We offer several arguments for the manner in which it should be able to (at least partially) reproduce tetrahedral correlations underlying these effects.

Chaimovich, Aviel; Shell, M. Scott

2014-02-01

157

Using a Mixed Integer Quadratic Programming Solver for the Unconstrained Quadratic 0-1 Problem  

Microsoft Academic Search

In this paper, we consider problem (P) of minimizing a quadratic function q(x)=x\\u000a \\u000a t\\u000a \\u000a Qx+c\\u000a \\u000a t\\u000a \\u000a x of binary variables. Our main idea is to use the recent Mixed Integer Quadratic Programming (MIQP) solvers. But, for this,\\u000a we have to first convexify the objective function q(x). A classical trick is to raise up the diagonal entries of Q by a

Alain Billionnet; Sourour Elloumi

2007-01-01

158

Discrete wave propagation in quadratically nonlinear media  

NASA Astrophysics Data System (ADS)

Discrete models are used in describing various microscopic phenomena in many branches of science, ranging from biology through chemistry to physics. Arrays of evanescently coupled, equally spaced, identical waveguides are prime examples of optical structures in which discrete dynamics can be easily observed and investigated. As a result of discretization, these structures exhibit unique diffraction properties with no analogy in continuous systems. Recently nonlinear discrete optics has attracted a growing interest, triggered by the observation of discrete solitons in AlGaAs waveguide arrays reported by Eisenberg et al. in 1998. So far, the following experiments involved systems with third order nonlinearities. In this work, an experimental investigation of discrete nonlinear wave propagation in a second order nonlinear medium is presented. This system deserves particular attention because the nonlinear process involves two or three components at different frequencies mutually locked by a quadratic nonlinearity, and new degrees of freedom enter the dynamical process. In the first part of dissertation, observation of the discrete Talbot effect is reported. In contrast to continuous systems, where Talbot self-imaging effect occurs irrespective of the pattern period, in discrete configurations this process is only possible for a specific set of periodicities. The major part of the dissertation is devoted to the investigation of soliton formation in lithium niobate waveguide arrays with a tunable cascaded quadratic nonlinearity. Soliton species with different topology (unstaggered---all channels in-phase, and staggered---neighboring channels with a pi relative phase difference) are identified in the same array. The stability of the discrete solitons and plane waves (modulational instability) are experimentally investigated. In the last part of the dissertation, a phase-insensitive, ultrafast, all-optical spatial switching and frequency conversion device based on quadratic waveguide array is demonstrated. Spatial routing and wavelength conversion of milliwatt signals is achieved without pulse distortions.

Iwanow, Robert

159

Complex modes in unstable quadratic bosonic forms  

E-print Network

We discuss the necessity of using non-standard boson operators for diagonalizing quadratic bosonic forms which are not positive definite and its convenience for describing the temporal evolution of the system. Such operators correspond to non-hermitian coordinates and momenta and are associated with complex frequencies. As application, we examine a bosonic version of a BCS-like pairing Hamiltonian, which, in contrast with the fermionic case, is stable just for limited values of the gap parameter and requires the use of the present extended treatment for a general diagonal representation. The dynamical stability of such forms and the occurrence of non-diagonalizable cases are also discussed.

R. Rossignoli; A. M. Kowalski

2014-04-17

160

Complex modes in unstable quadratic bosonic forms  

SciTech Connect

We discuss the necessity of using nonstandard boson operators for diagonalizing quadratic bosonic forms which are not positive definite and its convenience for describing the temporal evolution of the system. Such operators correspond to non-Hermitian coordinates and momenta and are associated with complex frequencies. As application, we examine a bosonic version of a BCS-like pairing Hamiltonian, which, in contrast with the fermionic case, is stable just for limited values of the gap parameter and requires the use of the present extended treatment for a general diagonal representation. The dynamical stability of such forms and the occurrence of nondiagonalizable cases are also discussed.

Rossignoli, R.; Kowalski, A.M. [Departamento de Fisica, Universidad Nacional de La Plata, C.C.67, La Plata (1900) (Argentina)

2005-09-15

161

An interface capturing method with a continuous function: The THINC method on unstructured triangular and tetrahedral meshes  

NASA Astrophysics Data System (ADS)

A novel interface-capturing method is proposed to compute moving interfaces on unstructured grids with triangular (2D) and tetrahedral (3D) elements. Different from the conventional VOF (volume of fluid) method which involves geometric reconstructions of the interface, the present method is based on the algebraic reconstruction approach originally developed in the THINC (tangent of hyperbola interface capturing) scheme by Xiao et al. (2005) [17]. A continuous multidimensional hyperbolic tangent function is employed for retrieving the jump-like distribution of the indicator function, which avoids the explicit geometric representation of the interface and thus substantially reduces the algorithmic complexity in unstructured grids. Numerical diffusion and smearing are effectively eliminated, and the compact thickness of the jump transition layer in the volume fraction is retained throughout the computation even for largely deformed interface. The solution quality of the present scheme is comparable to the VOF method with PLIC (piecewise linear interface calculation) algorithm.

Ii, Satoshi; Xie, Bin; Xiao, Feng

2014-02-01

162

Quadratic Scaling Local Canonical Transformation Method.  

NASA Astrophysics Data System (ADS)

Canonical transformation theory [1] can be used to describe the detailed dynamic correlation in bonding situations where there is significant non-dynamic, i.e. multireference character. This theory uses an exponential ansatz and is size-consistent. The computational cost of this method scales as N^6 which is about the same as in a single reference coupled cluster theory. We have devised a local Canonical transformation method for large systems. For large systems, we have been able to obtain quadratic scaling with the size of the system. Reduced and linear scaling algorithms for methods like MP2 and coupled cluster are well known. However, all these reduced scaling algorithms have been primarily developed for single reference correlation calculations. By combining the local canonical transformation method with, e.g. the quadratic scaling ab-initio Density Matrix Renormalization Group theory, we can now obtain a reduced-scaling description of dynamical and non-dynamical correlation in large multireference problems. [1] Takeshi Yanai, Garnet K.L. Chan, J. Chem. Phys. 124, 194106, 2006.

Ghosh, Debashree; Yanai, Takeshi; Kin-Lic Chan, Garnet

2007-03-01

163

A quadratic pulse height analyzer for space applications.  

NASA Technical Reports Server (NTRS)

A flight-worthy pulse height analyzer that has a quadratic transfer function is described. This quadratic function permits optimum usage of the entire PHA dynamic range due to the quadratic nature of the gamma ray spectrometer's resolution vs energy. After the theoretical design discussion, the implementation of the design is examined and test results described. The analyzer is part of the University of New Hampshire gamma ray monitor for OSO-H.

Burtis, D. W.; Aalami, D.; Evelyn-Veere, R. H.; Sarkady, A. A.

1972-01-01

164

Tetrahedral Mesh Improvement Using Swapping and Smoothing Lori A. Freitag  

E-print Network

in Int. J. for Numerical Methods in Engineering 2 Abstract. Automatic mesh generation and adaptive re nement methods for complex three-dimensional domains have proven to be very successful tools for the e elements. This decomposition can be accomplished by using available automatic mesh generation tools

California at Berkeley, University of

165

Steller Structure Treatment of Quadratic Gravity  

NASA Astrophysics Data System (ADS)

A scheme for considering stellar structure by taking advantage of the quadratic theory of gravitation in four-dimensions is proposed, citing the fact that the possible deviation of gravity in astrophysical systems from the Newtonian inverse square law can be explained through the use of this theory. A modified Lane-Emden equation is derived by making use of the linearized static field equation of quadratic gravity and the polytropic equation of state for a fluid. The influence on stellar structure of the additional force included in quadratic gravity is investigated. It is shown that the additional force can be treated as a perturbation of a bound system by solutions of the modified Lane-Emden equation and an order-of-magnitude analysis. %ZY. Fujii, Nature (London) 234 (1971), 5; Phys. Rev. D9 (1974), 874. D. R. Long, Phys. Rev. D 9 (1974), 850. J. O'Hanlon, Phys. Rev. Lett. 29 (1972), 137. D. R. Mikkelson and M. J. Newman, Phys. Rev. D 16 (1977), 919. R. V. Wagoner, Phys. Rev. D 1 (1970), 3209. J. Z. Xu and Y. H. Chen, Gen. Relat. Gravit. J. 23 (1991), 169. K. S. Stelle, Gen. Relat. Gravit. J. 8 (1978), 631. C. Xu and G. F. R. Ellis, Class. Quant. Grav. 8 (1991), 1747. A. Eddington, The Mathematical Theory of Relativity, 2nd ed. (Cambridge University Press, Cambridge, 1924). W. Pauli, Theory of Relativity (Pergamon Press, New York, 1921). H. A. Buchdahl, Proc. Edinburgh Math. Soc. 8 (1948), 89. J. D. Barrow and A. C. Ottewill, J. of Phys. A 16 (1983), 2757. M. B. Mijic, M. S. Morris and W. M. Suen, Phys. Rev. D 34 (1986), 2934. A. L. Berkin, Phys. Rev. D 42 (1990), 1017. N. D. Birrell and P. C. W. Davies, Quantum Field in Curved Space (Cambridge University Press, 1982). E. T. Tomboulis, Quantum Theory of Gravity, ed. S. M. Christensen (Bristol: Adam Hilger 1984). H. J. Treder, Ann. der Phys. 32 (1975), 383. S. Weinberg, Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity (Wiley, New York 1972). E. N. Glass and G. Szamosi, Phys. Rev. D 35 (1987), 1205.

Chen, Y.; Shao, C.; Chen, X.

2001-07-01

166

Quadratic dynamical decoupling with nonuniform error suppression  

SciTech Connect

We analyze numerically the performance of the near-optimal quadratic dynamical decoupling (QDD) single-qubit decoherence errors suppression method [J. West et al., Phys. Rev. Lett. 104, 130501 (2010)]. The QDD sequence is formed by nesting two optimal Uhrig dynamical decoupling sequences for two orthogonal axes, comprising N{sub 1} and N{sub 2} pulses, respectively. Varying these numbers, we study the decoherence suppression properties of QDD directly by isolating the errors associated with each system basis operator present in the system-bath interaction Hamiltonian. Each individual error scales with the lowest order of the Dyson series, therefore immediately yielding the order of decoherence suppression. We show that the error suppression properties of QDD are dependent upon the parities of N{sub 1} and N{sub 2}, and near-optimal performance is achieved for general single-qubit interactions when N{sub 1}=N{sub 2}.

Quiroz, Gregory; Lidar, Daniel A. [Department of Physics and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States); Departments of Electrical Engineering, Chemistry, and Physics, and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States)

2011-10-15

167

The suggested presence of the tetrahedral-symmetry in the ground-state configuration of the $^{96}$Zr nucleus  

E-print Network

We discuss the predictions of the large scale calculations using the realistic realisation of the phenomenological nuclear mean-field theory. Calculations indicate that certain Zirconium nuclei are tetrahedral-symmetric in their ground-states. After a short overview of the research of the nuclear tetrahedral symmetry in the past we analyse the predictive capacities of the method and focus on the $^{96}$Zr nucleus expected to be tetrahedral in its ground-state.

Jerzy Dudek; Dominique Curien; David Rouvel; Katarzyna Mazurek; Yoshifumi Shimizu; Shingo Tagami

2014-04-23

168

From Fischer projections to quantum mechanics of tetrahedral molecules: new perspectives in chirality  

E-print Network

The algebraic structure of central molecular chirality can be achieved starting from the geometrical representation of bonds of tetrahedral molecules, as complex numbers in polar form, and the empirical Fischer projections used in organic chemistry. A general orthogonal O(4) algebra is derived from which we obtain a chirality index related to the classification of a molecule as achiral, diastereoisomer or enantiomer. Consequently, the chiral features of tetrahedral chains can be predicted by means of a molecular Aufbau. Moreover, a consistent Schroedinger equation is developed, whose solutions are the bonds of tetrahedral molecules in complex number representation. Starting from this result, the O(4) algebra can be considered as a quantum chiral algebra. It is shown that the operators of such an algebra preserve the parity of the whole system.

S. Capozziello; A. Lattanzi

2004-11-04

169

Tetrahedral-mesh-based computational human phantom for fast Monte Carlo dose calculations  

NASA Astrophysics Data System (ADS)

Although polygonal-surface computational human phantoms can address several critical limitations of conventional voxel phantoms, their Monte Carlo simulation speeds are much slower than those of voxel phantoms. In this study, we sought to overcome this problem by developing a new type of computational human phantom, a tetrahedral mesh phantom, by converting a polygonal surface phantom to a tetrahedral mesh geometry. The constructed phantom was implemented in the Geant4 Monte Carlo code to calculate organ doses as well as to measure computation speed, the values were then compared with those for the original polygonal surface phantom. It was found that using the tetrahedral mesh phantom significantly improved the computation speed by factors of between 150 and 832 considering all of the particles and simulated energies other than the low-energy neutrons (0.01 and 1 MeV), for which the improvement was less significant (17.2 and 8.8 times, respectively).

Yeom, Yeon Soo; Jeong, Jong Hwi; Han, Min Cheol; Kim, Chan Hyeong

2014-06-01

170

Reordering between tetrahedral and octahedral sites in ultrathin magnetite films grown on MgO(001)  

SciTech Connect

Magnetite ultrathin films were grown using different deposition rates and substrate temperatures. The structure of these films was studied using (grazing incidence) x-ray diffraction, while their surface structure was characterized by low energy electron diffraction. In addition to that, we performed x-ray photoelectron spectroscopy and magneto optic Kerr effect measurements to probe the stoichiometry of the films as well as their magnetic properties. The diffraction peaks of the inverse spinel structure, which originate exclusively from Fe ions on tetrahedral sites are strongly affected by the preparation conditions, while the octahedral sites remain almost unchanged. With both decreasing deposition rate as well as decreasing substrate temperature, the integrated intensity of the diffraction peaks originating exclusively from Fe on tetrahedral sites is decreasing. We propose that the ions usually occupying tetrahedral sites in magnetite are relocated to octahedral vacancies. Ferrimagnetic behaviour is only observed for well ordered magnetite films.

Bertram, F.; Deiter, C. [Hamburger Synchrotronstrahlungslabor am Deutschen Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg (Germany)] [Hamburger Synchrotronstrahlungslabor am Deutschen Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg (Germany); Schemme, T.; Jentsch, S.; Wollschlaeger, J. [Fachbereich Physik, Universitaet Osnabrueck, Barbarastr. 7, 49069 Osnabrueck (Germany)] [Fachbereich Physik, Universitaet Osnabrueck, Barbarastr. 7, 49069 Osnabrueck (Germany)

2013-05-14

171

Influence of Patch-Size Variability on the Crystallization of Tetrahedral Patchy Particles  

NASA Astrophysics Data System (ADS)

The understanding of disorder effects on crystallization is of fundamental and technological importance. It is well established by both theory and experiment that particle-size polydispersity hinders crystallization for isotropically interacting particles. Here, we address the effects of patch variability in a model for tetrahedral colloids, where polydispersity is introduced independently on the size, position, and strength of the attractive patches. Our simulations indicate that, unlike particle-size polydispersity, angular polydispersity has a minor impact on the crystallization properties of tetrahedral colloidal particles. Particles with angular polydispersity well within current experimental possibilities fully retain their crystallization properties, a result which should encourage the realization of colloidal crystals in experiment.

Romano, Flavio; Russo, John; Tanaka, Hajime

2014-09-01

172

Interatomic potential for the structure and energetics of tetrahedrally coordinated silica polymorphs  

SciTech Connect

We introduce a many-body fixed-charge potential optimized for tetrahedral silica. The potential is used to investigate the crystal structures and energetics of six tetrahedrally coordinated silica polymorphs ({alpha}- and {beta}-quartz, {alpha}- and {beta}-cristobalite, {beta}-tridymite, and coesite). The structural parameters of the different phases are found to be well-reproduced. Most importantly, the ground state of the silica polymorphs is reproduced correctly. The results are compared with previous electronic structure calculations and with the results of other empirical potentials.

Yu Jianguo; Phillpot, Simon R.; Sinnott, Susan B. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400 (United States)

2007-06-15

173

A Public Key Block Cipher Based on Multivariate Quadratic Quasigroups  

E-print Network

- formations using a specific class of quasigroups called multivariate quadratic quasigroups (MQQ). Our public key algorithm is a bijective mapping, it does not perform message expansions and can be used both for encryption and signatures. The public key consist of n quadratic polynomials with n variables where n = 140

174

High order approximation of conic sections by quadratic splines  

E-print Network

High order approximation of conic sections by quadratic splines Michael Floater SINTEF P.O. Box 124, Blindern 0314 Oslo Norway December 1993. Revised, October 1994 Abstract. Given a segment of a conic section and cylinder. Keywords. approximation, conic sections, quadratic splines §1. Introduction The approximate

Floater, Michael S.

175

Sketching the General Quadratic Equation Using Dynamic Geometry Software  

ERIC Educational Resources Information Center

This paper explores a geometrical way to sketch graphs of the general quadratic in two variables with Geometer's Sketchpad. To do this, a geometric procedure as described by De Temple is used, bearing in mind that this general quadratic equation (1) represents all the possible conics (conics sections), and the fact that five points (no three of…

Stols, G. H.

2005-01-01

176

Some Paradoxical Results for the Quadratically Weighted Kappa  

ERIC Educational Resources Information Center

The quadratically weighted kappa is the most commonly used weighted kappa statistic for summarizing interrater agreement on an ordinal scale. The paper presents several properties of the quadratically weighted kappa that are paradoxical. For agreement tables with an odd number of categories "n" it is shown that if one of the raters uses the same…

Warrens, Matthijs J.

2012-01-01

177

The explicit linear quadratic regulator for constrained systems  

Microsoft Academic Search

We present a technique to compute the explicit state-feedback solution to both the xnite and inxnite horizon linear quadratic optimal control problem subject to state and input constraints. We show that this closed form solution is piecewise linear and continuous. As a practical consequence of the result, constrained linear quadratic regulation becomes attractive also for systems with high sampling rates,

Alberto Bemporad; Manfred Morari; Vivek Dua; Efstratios N. Pistikopoulos

2002-01-01

178

Analytical placement: A linear or a quadratic objective function?  

Microsoft Academic Search

This paper addresses the problem of cell placement which is considered crucial for layout quality. Based on the combined analytical and partitioning strategy successfully applied in the GORDIAN placement tool, we discuss the consequences of using linear or quadratic ob- jective functions. By joining the linear objective with an efficient quadratic programming approach, and by applying a refined iterative partitioning

Georg Sigl; Konrad Doll; Frank M. Johannes

1991-01-01

179

Clock Distribution Network Optimization by Sequential Quadratic Programing  

E-print Network

. Quasi-Newton Approximation of Hessian . . . . . . . 18 III SENSITIVITY ANALYSIS : : : : : : : : : : : : : : : : : : : : : 20 IV RESULTS AND CONCLUSIONS : : : : : : : : : : : : : : : : : 24 A. Experimental Setup... of quadratic approximations. We use the Karush-Kuhn-Tucker (KKT) conditions to improve the computational e ciency. A quadratic delay formula used in our problem improves the accuracy compared to a linear delay approximation used in [6]. So, we use the quasi-newton...

Mekala, Venkata

2010-07-14

180

Quadratic divergences and quantum gravitational contributions to gauge coupling constants  

SciTech Connect

The calculation of quadratic divergences in Einstein-Maxwell theory with a possible cosmological constant is considered. We describe a method of calculation, using the background-field method, that is sensitive to quadratic divergences, is respectful of gauge invariance, and is independent of gauge conditions. A standard renormalization group analysis is applied to the result where it is shown that the quadratic divergences do lead to asymptotic freedom as found in the original paper of Robinson and Wilczek. The role and nature of these quadratic divergences is critically evaluated in light of recent criticism. Within the context of the background-field method, it is shown that it is possible to define the charge in a physically motivated way in which the quadratic divergences do not play a role. This latter view is studied in more depth in a toy model described in an appendix.

Toms, David J. [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)

2011-10-15

181

Quadratic divergences and quantum gravitational contributions to gauge coupling constants  

NASA Astrophysics Data System (ADS)

The calculation of quadratic divergences in Einstein-Maxwell theory with a possible cosmological constant is considered. We describe a method of calculation, using the background-field method, that is sensitive to quadratic divergences, is respectful of gauge invariance, and is independent of gauge conditions. A standard renormalization group analysis is applied to the result where it is shown that the quadratic divergences do lead to asymptotic freedom as found in the original paper of Robinson and Wilczek. The role and nature of these quadratic divergences is critically evaluated in light of recent criticism. Within the context of the background-field method, it is shown that it is possible to define the charge in a physically motivated way in which the quadratic divergences do not play a role. This latter view is studied in more depth in a toy model described in an appendix.

Toms, David J.

2011-10-01

182

Optimal and suboptimal quadratic forms for noncentered Gaussian processes.  

PubMed

Individual random trajectories of stochastic processes are often analyzed by using quadratic forms such as time averaged (TA) mean square displacement (MSD) or velocity auto-correlation function (VACF). The appropriate quadratic form is expected to have a narrow probability distribution in order to reduce statistical uncertainty of a single measurement. We consider the problem of finding the optimal quadratic form that minimizes a chosen cumulant moment (e.g., the variance) of the probability distribution, under the constraint of fixed mean value. For discrete noncentered Gaussian processes, we construct the optimal quadratic form by using the spectral representation of cumulant moments. Moreover, we obtain a simple explicit formula for the smallest achievable cumulant moment that may serve as a quality benchmark for other quadratic forms. We illustrate the optimality issues by comparing the optimal variance with the variances of the TA MSD and TA VACF of fractional Brownian motion superimposed with a constant drift and independent Gaussian noise. PMID:24125246

Grebenkov, Denis S

2013-09-01

183

Optimal and suboptimal quadratic forms for noncentered Gaussian processes  

NASA Astrophysics Data System (ADS)

Individual random trajectories of stochastic processes are often analyzed by using quadratic forms such as time averaged (TA) mean square displacement (MSD) or velocity auto-correlation function (VACF). The appropriate quadratic form is expected to have a narrow probability distribution in order to reduce statistical uncertainty of a single measurement. We consider the problem of finding the optimal quadratic form that minimizes a chosen cumulant moment (e.g., the variance) of the probability distribution, under the constraint of fixed mean value. For discrete noncentered Gaussian processes, we construct the optimal quadratic form by using the spectral representation of cumulant moments. Moreover, we obtain a simple explicit formula for the smallest achievable cumulant moment that may serve as a quality benchmark for other quadratic forms. We illustrate the optimality issues by comparing the optimal variance with the variances of the TA MSD and TA VACF of fractional Brownian motion superimposed with a constant drift and independent Gaussian noise.

Grebenkov, Denis S.

2013-09-01

184

Lattice thermal expansion for normal tetrahedral compound semiconductors  

SciTech Connect

The cubic root of the deviation of the lattice thermal expansion from that of the expected value of diamond for group IV semiconductors, binary compounds of III-V and II-VI, as well as several ternary compounds from groups I-III-VI{sub 2}, II-IV-V{sub 2} and I-IV{sub 2}V{sub 3} semiconductors versus their bonding length are given straight lines. Their slopes were found to be 0.0256, 0.0210, 0.0170, 0.0259, 0.0196, and 0.02840 for the groups above, respectively. Depending on the valence electrons of the elements forming these groups, a formula was found to correlate all the values of the slopes mentioned above to that of group IV. This new formula which depends on the melting point and the bonding length as well as the number of valence electrons for the elements forming the compounds, will gives best calculated values for lattice thermal expansion for all compounds forming the groups mentioned above. An empirical relation is also found between the mean ionicity of the compounds forming the groups and their slopes mentioned above and that gave the mean ionicity for the compound CuGe{sub 2}P{sub 3} in the range of 0.442.

Omar, M.S. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)]. E-mail: dr_m_s_omar@yahoo.com

2007-02-15

185

Finite element analyses of three dimensional fully plastic solutions using quasi-nonsteady algorithm and tetrahedral elements  

Microsoft Academic Search

To estimate entire elastic-plastic behaviors of cracked bodies, fully plastic solutions are utilized with linear elastic solutions in the engineering approach. Some numerical algorithms such as the Selective Reduced Integration\\/Penalty Function (SRI\\/PF) method have been developed and utlized to calculate various two-dimensional fully plastic solutions. However, only a few three-dimensional solutions have been obtained because of their numerical instability caused

S. Yoshimura; C.-R. Pyo; G. Yagawa; H. Kawai

1994-01-01

186

Elastic Model Transitions Using Quadratic Inequality Constrained Least Squares  

NASA Technical Reports Server (NTRS)

A technique is presented for initializing multiple discrete finite element model (FEM) mode sets for certain types of flight dynamics formulations that rely on superposition of orthogonal modes for modeling the elastic response. Such approaches are commonly used for modeling launch vehicle dynamics, and challenges arise due to the rapidly time-varying nature of the rigid-body and elastic characteristics. By way of an energy argument, a quadratic inequality constrained least squares (LSQI) algorithm is employed to e ect a smooth transition from one set of FEM eigenvectors to another with no requirement that the models be of similar dimension or that the eigenvectors be correlated in any particular way. The physically unrealistic and controversial method of eigenvector interpolation is completely avoided, and the discrete solution approximates that of the continuously varying system. The real-time computational burden is shown to be negligible due to convenient features of the solution method. Simulation results are presented, and applications to staging and other discontinuous mass changes are discussed

Orr, Jeb S.

2012-01-01

187

A Streaming Language Implementation of the Discontinuous Galerkin Finite Element Method  

E-print Network

StreamFEM A Streaming Language Implementation of the Discontinuous Galerkin Finite Element Method(MHD)Linear(Euler)Linear(MHD)Quadratic(Euler)Quadratic(MHD) Cubic(Euler) Cubic(MHD) Element Type (Equation Type) Sustained GFLOPS Ops / mem access A DG Finite Element Method for Conservation Laws ·Scalar Advection (1 PDE) ·Euler Equations (4 PDEs

Dally, William J.

188

Local classifier weighting by quadratic programming.  

PubMed

It has been widely accepted that the classification accuracy can be improved by combining outputs of multiple classifiers. However, how to combine multiple classifiers with various (potentially conflicting) decisions is still an open problem. A rich collection of classifier combination procedures -- many of which are heuristic in nature -- have been developed for this goal. In this brief, we describe a dynamic approach to combine classifiers that have expertise in different regions of the input space. To this end, we use local classifier accuracy estimates to weight classifier outputs. Specifically, we estimate local recognition accuracies of classifiers near a query sample by utilizing its nearest neighbors, and then use these estimates to find the best weights of classifiers to label the query. The problem is formulated as a convex quadratic optimization problem, which returns optimal nonnegative classifier weights with respect to the chosen objective function, and the weights ensure that locally most accurate classifiers are weighted more heavily for labeling the query sample. Experimental results on several data sets indicate that the proposed weighting scheme outperforms other popular classifier combination schemes, particularly on problems with complex decision boundaries. Hence, the results indicate that local classification-accuracy-based combination techniques are well suited for decision making when the classifiers are trained by focusing on different regions of the input space. PMID:18842488

Cevikalp, Hakan; Polikar, Robi

2008-10-01

189

Are ghost surfaces quadratic-flux-minimizing?  

E-print Network

Two candidates for "almost-invariant" toroidal surfaces passing through magnetic islands, namely quadratic-flux-minimizing (QFMin) surfaces and ghost surfaces, use families of periodic pseudo-orbits (i.e. paths for which the action is not exactly extremal). QFMin pseudo-orbits, which are coordinate-dependent, are field lines obtained from a modified magnetic field, and ghost-surface pseudo-orbits are obtained by displacing closed field lines in the direction of steepest descent of magnetic action, $\\oint \\vec{A}\\cdot\\mathbf{dl}$. A generalized Hamiltonian definition of ghost surfaces is given and specialized to the usual Lagrangian definition. A modified Hamilton's Principle is introduced that allows the use of Lagrangian integration for calculation of the QFMin pseudo-orbits. Numerical calculations show QFMin and Lagrangian ghost surfaces give very similar results for a chaotic magnetic field perturbed from an integrable case, and this is explained using a perturbative construction of an auxiliary poloidal angle for which QFMin and Lagrangian ghost surfaces are the same up to second order. While presented in the context of 3-dimensional magnetic field line systems, the concepts are applicable to defining almost-invariant tori in other $1{1/2}$ degree-of-freedom nonintegrable Lagrangian/Hamiltonian systems.

S. R. Hudson; R. L. Dewar

2009-09-11

190

A Quadratic Closure for Compressible Turbulence  

SciTech Connect

We have investigated a one-point closure model for compressible turbulence based on third- and higher order cumulant discard for systems undergoing rapid deformation, such as might occur downstream of a shock or other discontinuity. In so doing, we find the lowest order contributions of turbulence to the mean flow, which lead to criteria for Adaptive Mesh Refinement. Rapid distortion theory (RDT) as originally applied by Herring closes the turbulence hierarchy of moment equations by discarding third order and higher cumulants. This is similar to the fourth-order cumulant discard hypothesis of Millionshchikov, except that the Millionshchikov hypothesis was taken to apply to incompressible homogeneous isotropic turbulence generally, whereas RDT is applied only to fluids undergoing a distortion that is 'rapid' in the sense that the interaction of the mean flow with the turbulence overwhelms the interaction of the turbulence with itself. It is also similar to Gaussian closure, in which both second and fourth-order cumulants are retained. Motivated by RDT, we develop a quadratic one-point closure for rapidly distorting compressible turbulence, without regard to homogeneity or isotropy, and make contact with two equation turbulence models, especially the K-{var_epsilon} and K-L models, and with linear instability growth. In the end, we arrive at criteria for Adaptive Mesh Refinement in Finite Volume simulations.

Futterman, J A

2008-09-16

191

Tetrahedral symmetry in Zr nuclei: Calculations of low-energy excitations with Gogny interaction  

E-print Network

We report on the results of the calculations of the low energy excitation patterns for three Zirconium isotopes, viz. $^{80}$Zr$_{40}$, $^{96}$Zr$_{56}$ and $^{110}$Zr$_{70}$, reported by other authors to be doubly-magic tetrahedral nuclei (with tetrahedral magic numbers $Z$=40 and $N$=40, 56 and 70). We employ the realistic Gogny effective interactions using three variants of their parametrisation and the particle-number, parity and the angular-momentum projection techniques. We confirm quantitatively that the resulting spectra directly follow the pattern expected from the group theory considerations for the tetrahedral symmetric quantum objects. We also find out that, for all the nuclei studied, the correlation energy obtained after the angular momentum projection is very large for the tetrahedral deformation as well as other octupole deformations. The lowering of the energies of the resulting configurations is considerable, i.e. by about 10 MeV or even more, once again confirming the significance of the an...

Tagami, Shingo; Dudek, Jerzy

2014-01-01

192

Tetrahedral symmetry in Zr nuclei: Calculations of low-energy excitations with Gogny interaction  

E-print Network

We report on the results of the calculations of the low energy excitation patterns for three Zirconium isotopes, viz. $^{80}$Zr$_{40}$, $^{96}$Zr$_{56}$ and $^{110}$Zr$_{70}$, reported by other authors to be doubly-magic tetrahedral nuclei (with tetrahedral magic numbers $Z$=40 and $N$=40, 56 and 70). We employ the realistic Gogny effective interactions using three variants of their parametrisation and the particle-number, parity and the angular-momentum projection techniques. We confirm quantitatively that the resulting spectra directly follow the pattern expected from the group theory considerations for the tetrahedral symmetric quantum objects. We also find out that, for all the nuclei studied, the correlation energy obtained after the angular momentum projection is very large for the tetrahedral deformation as well as other octupole deformations. The lowering of the energies of the resulting configurations is considerable, i.e. by about 10 MeV or even more, once again confirming the significance of the angular-momentum projections techniques in the mean-field nuclear structure calculations.

Shingo Tagami; Yoshifumi R Shimizu; Jerzy Dudek

2014-10-24

193

Compressive-stress-induced formation of thin-film tetrahedral amorphous carbon  

Microsoft Academic Search

Thin tetrahedrally coordinated amorphous carbon (ta-C) films have been grown using a filtered vacuum arc. ta-C is a new allotrope of carbon whose existence was previously thought to be unlikely. A model is proposed which accounts for the formation and structure of these films on the basis of the compressive stress generated by the shallow implantation of carbon ions. An

D. R. McKenzie; D. Muller; B. A. Pailthorpe

1991-01-01

194

A New Species of Streptocephalus Fairy Shrimp (Crustacea, Anostraca) with Tetrahedral Cysts from Central Thailand  

NASA Astrophysics Data System (ADS)

A new species of fairy shrimp, Streptocephalus siamensis n. sp., is described from five temporary pools in Suphan Buri and Kanchana Buri Provinces, central Thailand. It sometimes co-occurs with its congener, S. sirindhornae . This new species belongs to the subgenus Parastreptocephalus which is defined by bearing tetrahedral cysts. This is the third anostracan species reported from Thailand.

Sanoamuang, La-Orsri; Saengphan, Nukul

2006-06-01

195

Automated Tetrahedral Mesh Generation for CFD Analysis of Aircraft in Conceptual Design  

NASA Technical Reports Server (NTRS)

The paper introduces an automation process of generating a tetrahedral mesh for computational fluid dynamics (CFD) analysis of aircraft configurations in early conceptual design. The method was developed for CFD-based sonic boom analysis of supersonic configurations, but can be applied to aerodynamic analysis of aircraft configurations in any flight regime.

Ordaz, Irian; Li, Wu; Campbell, Richard L.

2014-01-01

196

Optical absorption from polarons and bipolarons in a tetrahedrally bonded homopolymer  

NASA Astrophysics Data System (ADS)

The optical absorption associated with polarons and bipolarons in a tetrahedrally bonded homopolymer is studied within the Rice-Phillpot continuum model. Analytical expressions for the absorption coefficients are obtained and compared with those of polyenes. Both the intragap transitions involving the localized and extended states exhibit square-root singularities at their respective absorption edges.

Cao, Wenwu; Saxena, Avadh

1988-07-01

197

Crystal-chemical examination of natural diopsides: Some geometrical indications of Si-Ti tetrahedral substitution  

Microsoft Academic Search

Summary The crystal structures of 20 natural diopsides have been refined. For some samples, microprobe analyses show a Si deficiency in the tetrahedron with no A1 present; this suggests that some Ti4+ may enter the tetrahedral site. Geometrical variations in these samples with respect to the others are discussed in the light of this Si ? Ti4+ substitution. The volumes

Susanna Carbonin; Gabriella Salviulol; Rosalba Munno; Mirella Desiderio; A. Dal Negro

1989-01-01

198

Aging of Tetrahedral Structure in a Lennard-Jones Glass1 Gianguido C. CIANCI2  

E-print Network

Aging of Tetrahedral Structure in a Lennard-Jones Glass1 Gianguido C. CIANCI2 and Eric R. WEEKS3,4 Summary We study the aging of a glassy Lennard-Jones binary mixture with molecular dy- namics simulations. We follow the evolution of the packing as a function of the system's age tw, the time passed since

Weeks, Eric R.

199

Extended orientational correlation study for molecular liquids containing distorted tetrahedral molecules: Application to methylene halides  

NASA Astrophysics Data System (ADS)

The method of Rey [Rey, J. Chem. Phys. 126, 164506 (2007)] for describing how molecules orient toward each other in systems with perfect tetrahedral molecules is extended to the case of distorted tetrahedral molecules of c2v symmetry by means of introducing 28 subgroups. Additionally, the original analysis developed for perfect tetrahedral molecules, based on six groups, is adapted for molecules with imperfect tetrahedral shape. Deriving orientational correlation functions have been complemented with detailed analyses of dipole-dipole correlations. This way, (up to now) the most complete structure determination can be carried out for such molecular systems. In the present work, these calculations have been applied for particle configurations resulting from reverse Monte Carlo computer modeling. These particle arrangements are fully consistent with structure factors from neutron and x-ray diffraction measurements. Here we present a complex structural study for methylene halide (chloride, bromide, and iodide) molecular liquids, as possibly the best representative examples. It has been found that the most frequent orientations of molecules are of the 2:2 type over the entire distance range in these liquids. Focusing on the short range orientation, neighboring molecules turn toward each other with there ``H,Y''-``H,Y'' (Y: Cl, Br, I) edges, apart from CH2Cl2 where the H,H-H,Cl arrangement is the most frequent. In general, the structure of methylene chloride appears to be different from the structure of the other two liquids.

Pothoczki, Szilvia; Temleitner, László; Pusztai, László

2010-04-01

200

Mixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment.  

PubMed

The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], , and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(?-H){Os3(CO)9}S], , and [Cp*Ru(?-H){Os3(CO)11}], . In a similar fashion, the reaction of [(Cp*Mo)2B5H9], , with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(?-H){Ru3(CO)9}S], , and conjuncto-[(Cp*Mo)2B5H8(?-H){Ru3(CO)9}S], . Both compounds and can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds and possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and (1)H, (11)B and (13)C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds , and . PMID:25317933

Yuvaraj, K; Roy, Dipak Kumar; Anju, V P; Mondal, Bijnaneswar; Varghese, Babu; Ghosh, Sundargopal

2014-10-28

201

Mechanical response of single-layer tetrahedral trusses under shear loading  

Microsoft Academic Search

It has been demonstrated by analytical and numerical studies that lattice core panels may be structurally more efficient than other lightweight structures that are currently available. This paper addresses the mechanical performance of single-layer tetrahedral trusses under shear loading. The truss specimens were fabricated by rapid prototyping and investment casting. Casting defects can contribute significantly to the deviation of the

Yuki Sugimura

2004-01-01

202

A novel coupled level set and volume of fluid method for sharp interface capturing on 3D tetrahedral grids  

E-print Network

2009 Available online 14 December 2009 Keywords: VOF Level set Free surface Tetrahedral grid Finite of fluid (VOF) method for free surface flow simulations on tetrahedral grids. At each time step, we evolve used for such a purpose. Nichols et al. [1] developed the volume of fluid (VOF) method to track

Frey, Pascal

203

A decentralized linear quadratic control design method for flexible structures  

NASA Technical Reports Server (NTRS)

A decentralized suboptimal linear quadratic control design procedure which combines substructural synthesis, model reduction, decentralized control design, subcontroller synthesis, and controller reduction is proposed for the design of reduced-order controllers for flexible structures. The procedure starts with a definition of the continuum structure to be controlled. An evaluation model of finite dimension is obtained by the finite element method. Then, the finite element model is decomposed into several substructures by using a natural decomposition called substructuring decomposition. Each substructure, at this point, still has too large a dimension and must be reduced to a size that is Riccati-solvable. Model reduction of each substructure can be performed by using any existing model reduction method, e.g., modal truncation, balanced reduction, Krylov model reduction, or mixed-mode method. Then, based on the reduced substructure model, a subcontroller is designed by an LQ optimal control method for each substructure independently. After all subcontrollers are designed, a controller synthesis method called substructural controller synthesis is employed to synthesize all subcontrollers into a global controller. The assembling scheme used is the same as that employed for the structure matrices. Finally, a controller reduction scheme, called the equivalent impulse response energy controller (EIREC) reduction algorithm, is used to reduce the global controller to a reasonable size for implementation. The EIREC reduced controller preserves the impulse response energy of the full-order controller and has the property of matching low-frequency moments and low-frequency power moments. An advantage of the substructural controller synthesis method is that it relieves the computational burden associated with dimensionality. Besides that, the SCS design scheme is also a highly adaptable controller synthesis method for structures with varying configuration, or varying mass and stiffness properties.

Su, Tzu-Jeng; Craig, Roy R., Jr.

1990-01-01

204

Fully Consistent Diffusion Synthetic Acceleration of Linear Discontinuous S{sub N} Transport Discretizations on Unstructured Tetrahedral Meshes  

SciTech Connect

We recently presented a method for efficiently solving linear discontinuous discretizations of the two-dimensional P{sub 1} equations on rectangular meshes. The linear system was efficiently solved with Krylov iterative methods and a novel two-level preconditioner based on a linear continuous finite element discretization of the diffusion equation. Here, we extend the preconditioned solution method to three-dimensional, unstructured tetrahedral meshes. Solution of the P{sub 1} equations forms the basis of a diffusion synthetic acceleration (DSA) scheme for three-dimensional S{sub N} transport calculations with isotropic scattering. The P{sub 1} equations and the transport equation are both discretized with isoparametric linear discontinuous finite elements so that the DSA method is fully consistent. Fourier analysis in three dimensions and computational results show that this DSA scheme is stable and very effective. The fully consistent method is compared to other 'partially consistent' DSA schemes. Results show that the effectiveness of the partially consistent schemes can degrade for skewed or optically thick mesh cells. In fact, one such scheme can degrade to the extent of being unstable even though it is both unconditionally stable and effective on rectangular grids. Results for a model application show that our fully consistent DSA method can outperform the partially consistent DSA schemes under certain circumstances.

Warsa, James S.; Wareing, Todd A.; Morel, Jim E. [Los Alamos National Laboratory (United States)

2002-07-15

205

Models for the 3D singular isotropic oscillator quadratic algebra  

SciTech Connect

We give the first explicit construction of the quadratic algebra for a 3D quantum superintegrable system with nondegenerate (4-parameter) potential together with realizations of irreducible representations of the quadratic algebra in terms of differential-differential or differential-difference and difference-difference operators in two variables. The example is the singular isotropic oscillator. We point out that the quantum models arise naturally from models of the Poisson algebras for the corresponding classical superintegrable system. These techniques extend to quadratic algebras for superintegrable systems in n dimensions and are closely related to Hecke algebras and multivariable orthogonal polynomials.

Kalnins, E. G., E-mail: math0236@waikato.ac.n [University of Waikato, Department of Mathematics (New Zealand); Miller, W.; Post, S. [University of Minnesota, School of Mathematics (United States)

2010-02-15

206

Controlling the disorder properties of quadratic nonlinear photonic crystals  

E-print Network

Controlling the disorder properties of quadratic nonlinear photonic crystals Idith Varon,* Gil demonstrate a modulation scheme for disordered nonlinear crystals that combines periodic modulation and disordered sections. The crystal is divided into a set of identical periodically poled building blocks

Arie, Ady

207

On the Convergence of Successive Linear-Quadratic Programming Algorithms  

E-print Network

. M. Gould Jorge Nocedal Richard A. Waltz April 12, 2005 (revised) Abstract The global convergence-quadratic programming approach presented by Byrd, Gould, Nocedal and Waltz (Math. Programming 100(1):27­48, 2004). Every

Waltz, Richard A.

208

INDEFINITE STOCHASTIC LINEAR QUADRATIC CONTROL AND GENERALIZED DIFFERENTIAL RICCATI EQUATION  

E-print Network

INDEFINITE STOCHASTIC LINEAR QUADRATIC CONTROL AND GENERALIZED DIFFERENTIAL RICCATI EQUATION M. AIT in finance. However, there remains an outstanding open problem, which is to identify an appropriate Riccati Riccati equation, called the generalized (differential) Riccati equation, is introduced, which involves

Moore, John Barratt

209

Quadratic discrete Fourier transform and mutually unbiased bases  

E-print Network

The present chapter [submitted for publication in "Fourier Transforms, Theory and Applications", G. Nikolic (Ed.), InTech (Open Access Publisher), Vienna, 2011] is concerned with the introduction and study of a quadratic discrete Fourier transform. This Fourier transform can be considered as a two-parameter extension, with a quadratic term, of the usual discrete Fourier transform. In the case where the two parameters are taken to be equal to zero, the quadratic discrete Fourier transform is nothing but the usual discrete Fourier transform. The quantum quadratic discrete Fourier transform plays an important role in the field of quantum information. In particular, such a transformation in prime dimension can be used for obtaining a complete set of mutually unbiased bases.

Maurice Robert Kibler

2010-10-28

210

Geometric Procedures for Graphing the General Quadratic Equation.  

ERIC Educational Resources Information Center

How tedious algebraic manipulations for simplifying general quadratic equations can be supplemented with simple geometric procedures is discussed. These procedures help students determine the type of conic and its axes and allow a graph to be sketched quickly. (MNS)

DeTemple, Duane W.

1984-01-01

211

Good Numerical Technique in Chemistry: The Quadratic Equation.  

ERIC Educational Resources Information Center

Discusses the loss of precision that normally results in solving equilibrium problems, particularly as presented through the use of quadratic formulas in most introductory college chemistry textbooks. Provides examples of demonstrations. (TW)

Thompson, H. Bradford

1987-01-01

212

Regular zeros of quadratic maps and their application  

SciTech Connect

Sufficient conditions for the existence of regular zeros of quadratic maps are obtained. Their applications are indicated to certain problems of analysis related to the inverse function theorem in a neighbourhood of an abnormal point. Bibliography: 13 titles.

Arutyunov, Aram V; Karamzin, Dmitry Yu

2011-06-30

213

A Sequential Quadratic Optimization Algorithm with Rapid Infeasibility Detection  

E-print Network

, Frank E. Curtis, and Hao Wang Lehigh Industrial and Systems Engineering COR@L Technical Report 2012T-12, FRANK E. CURTIS, AND HAO WANG Abstract. We present a sequential quadratic optimization (SQO) algorithm

Snyder, Larry

214

Adaptive continuous-time linear quadratic Gaussian control  

E-print Network

The adaptive linear quadratic Gaussian control problem, where the linear transformation of the state A and the linear transformation of the control B are unknown, is solved assuming only that (A, B) is controllable and (A, ...

Duncan, Tyrone E.; Guo, L.; Pasik-Duncan, Bozenna

1999-09-01

215

Contingency Simulation Using Single Phase Quadratized Power Flow  

E-print Network

Contingency Simulation Using Single Phase Quadratized Power Flow Fang Yang, Student Member, IEEE, A, Student Member, IEEE Abstract -- Contingency simulation is an essential but computationally demanding procedure for power system security assessment, reliability evaluation, and real time operation. Simulation

216

A method of Weil sum in multivariate quadratic cryptosystem  

E-print Network

A new cryptanalytic application is proposed for a number theoretic tool Weil sum to the birthday attack against multivariate quadratic trapdoor function. This new customization of the birthday attack is developed by evaluating the explicit Weil sum...

Harayama, Tomohiro

2007-09-17

217

Estimation of wildlife populations using the quadrat method of sampling  

E-print Network

ESTIMATION OF WILDLIFE POPULATIONS USING THE QUADRAT METHOD OF SAMPLING A Thesis by JOHN RICHARD HRIBAR Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... May 1970 Major Subject: Statistics ESTIMATION OF WILDLIFE POPUIATIONS USING THE QUADRAT METHOD OF SAMPLING A Thesis by JOHN RICHARD HRZBAR Approved as to style and content by: ( airman of Committee (Member Head of Departme t Member, May 1970...

Hribar, John Richard

2012-06-07

218

On the Convergence of Successive Linear-Quadratic Programming Algorithms  

Microsoft Academic Search

The global convergence properties of a class of penalty methods for nonlinear pro- gramming are analyzed. These methods include successive linear programming ap- proaches, and more specically , the successive linear-quadratic programming approach presented by Byrd, Gould, Nocedal and Waltz (Math. Programming 100(1):27{48, 2004). Every iteration requires the solution of two trust-region subproblems involving piecewise linear and quadratic models, respectively.

Richard H. ByrdNicholas; I. M. Gould; Jorge Nocedalz; Richard A. Waltz

219

The classical bi-Poisson process: An invertible quadratic harness  

Microsoft Academic Search

We give an elementary construction of a time-invertible Markov process which is discrete except at one instance. The process is one of the quadratic harnesses studied in Bryc and Weso?owski [2005. Conditional moments of q-Meixner processes. Probab. Theory Related Fields 131, 415–441 ?arxiv.org\\/abs\\/math.PR\\/0403016?], Bryc et al. [2005b. Quadratic harnesses, q-commutations, and orthogonal martingale polynomials. Trans. Amer. Math. Soc. ?arxiv.org\\/abs\\/math.PR\\/0504194?, to

W?odzimierz Bryc; Jacek Weso?owski

2006-01-01

220

Parallel Higher-order Finite Element Method for Accurate Field Computations in Wakefield and PIC Simulations  

SciTech Connect

Over the past years, SLAC's Advanced Computations Department (ACD), under SciDAC sponsorship, has developed a suite of 3D (2D) parallel higher-order finite element (FE) codes, T3P (T2P) and Pic3P (Pic2P), aimed at accurate, large-scale simulation of wakefields and particle-field interactions in radio-frequency (RF) cavities of complex shape. The codes are built on the FE infrastructure that supports SLAC's frequency domain codes, Omega3P and S3P, to utilize conformal tetrahedral (triangular)meshes, higher-order basis functions and quadratic geometry approximation. For time integration, they adopt an unconditionally stable implicit scheme. Pic3P (Pic2P) extends T3P (T2P) to treat charged-particle dynamics self-consistently using the PIC (particle-in-cell) approach, the first such implementation on a conformal, unstructured grid using Whitney basis functions. Examples from applications to the International Linear Collider (ILC), Positron Electron Project-II (PEP-II), Linac Coherent Light Source (LCLS) and other accelerators will be presented to compare the accuracy and computational efficiency of these codes versus their counterparts using structured grids.

Candel, A.; Kabel, A.; Lee, L.; Li, Z.; Limborg, C.; Ng, C.; Prudencio, E.; Schussman, G.; Uplenchwar, R.; Ko, K.; /SLAC

2009-06-19

221

Atomic Scale Picture of the Ion Conduction Mechanism in Tetrahedral Network of Lanthanum Barium Gallate  

SciTech Connect

Combined experimental study of impedance spectroscopy, neutron powder diffraction and quasielastic neutron scattering was performed to shed light into the atomic scale ion migration processes in proton and oxide ion conductor; La0.8Ba1.2GaO3.9 . This material consist of tetrahedral GaO4 units, which are rather flexible and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along c axis, involving a single elementary step, which occurs between adjacent tetrahedron (inter-tetrahedron jump). The proton conduction mechanism consists of intra-tetrahedron and inter-tetrahedron elementary processes. The intra-tetrahedron proton transport is the rate-limiting process, with activation energy of 0.44 eV. The rocking motion of the GaO4 tetrahedron aids the inter-tetrahedral proton transport, which has the activation energy of 0.068 eV.

Jalarvo, Niina H [ORNL] [ORNL; Gourdon, Olivier [ORNL] [ORNL; Bi, Zhonghe [ORNL] [ORNL; Gout, Delphine J [ORNL] [ORNL; Ohl, Michael E [ORNL] [ORNL; Paranthaman, Mariappan Parans [ORNL] [ORNL

2013-01-01

222

Near-field testing of the 5-meter model of the tetrahedral truss antenna  

NASA Technical Reports Server (NTRS)

This report documents the technical results from near-field testing of the General Dynamics 5-meter model of the tetrahedral truss antenna at the Martin Marietta Denver Aerospace facility. A 5-meter square side of the tetrahedral served as the perimeter of the antenna, and a mesh surface and extensive surface contouring cord network was used to create a parabolic aperture shape to within an rms accuracy of 30 mils or better. Pattern measurements were made with offset feed systems radiating at frequencies of 7.73, 11.60, 2.27, and 4.26 (all in GHz). This report discusses the method of collecting the data, system measurement accuracy, the test data compiled, and diagostics and isolation of causes of pattern results. The technique of using near-field phase for measuring surface mechanical tolerances is included. Detailed far field antenna patterns and their implications are provided for all tests conducted.

Kefauver, Neill; Cencich, Tom; Osborn, Jim; Osmanski, J. T.

1986-01-01

223

Low symmetry tetrahedral nematic liquid crystal phases: Ambidextrous chirality and ambidextrous helicity.  

PubMed

We discuss the symmetry properties as well as the dynamic behavior of various non-polar nematic liquid crystal phases with tetrahedral order. We concentrate on systems that show biaxial nematic order coexisting with octupolar (tetrahedral) order. Non-polar examples are phases with D2 and S4 symmetries, which can be characterized as biaxial nematics lacking inversion symmetry. It is this combination that allows for new features in the statics and dynamics of these phases. The D2-symmetric phase is chiral, even for achiral molecules, and shows ambidextrous chirality in all three preferred directions. The achiral S4-symmetric phase allows for ambidextrous helicity, similar to the higher-symmetric D2d-symmetric phase. Such phases are candidates for nematic phases made from banana-shaped molecules. PMID:24566665

Pleiner, Harald; Brand, Helmut R

2014-02-01

224

Fostering Teacher Development to a Tetrahedral Orientation in the Teaching of Chemistry  

NASA Astrophysics Data System (ADS)

This paper reports on the initial outcomes from the end of the fourth year of a 5 year research and professional development project to improve chemistry teaching among three cohorts of chemistry teachers in Manitoba, Canada. The project responds to a new curriculum introduction advocating a tetrahedral orientation (Mahaffy, Journal of Chemical Education 83(1), 49-55, 2006) to the teaching of chemistry. The project in its entirety is based upon several theoretical models in fostering chemistry teacher development (in particular Bronfenbrenner's bio-ecological model). These models are described, as is the progress made by teachers based upon the use of a Chemistry Teacher Inventory and associated teacher responses. Overall, statistical analysis of perceptions of their own teaching and comments made by teachers suggests they are showing limited development towards a tetrahedral orientation, albeit in a manner consistent with the curriculum. Ongoing research-based activities in this project are also described.

Lewthwaite, Brian; Wiebe, Rick

2011-11-01

225

Numerical approximation for the infinite-dimensional discrete-time optimal linear-quadratic regulator problem  

NASA Technical Reports Server (NTRS)

An abstract approximation framework is developed for the finite and infinite time horizon discrete-time linear-quadratic regulator problem for systems whose state dynamics are described by a linear semigroup of operators on an infinite dimensional Hilbert space. The schemes included the framework yield finite dimensional approximations to the linear state feedback gains which determine the optimal control law. Convergence arguments are given. Examples involving hereditary and parabolic systems and the vibration of a flexible beam are considered. Spline-based finite element schemes for these classes of problems, together with numerical results, are presented and discussed.

Gibson, J. S.; Rosen, I. G.

1988-01-01

226

Photoelectron emission and Raman scattering studies of nitrogenated tetrahedral amorphous carbon films  

Microsoft Academic Search

Nitrogenated tetrahedral amorphous carbon (N:ta-C) films prepared by the filtered cathodic vacuum arc technique were studied by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, spectroscopic ellipsometry, ultraviolet photoelectron spectroscopy and temperature dependent resistance measurement. As the nitrogen flow rate varies from 0 to 20 sccm, the nitrogen content in the deposited film increases from 0 to 4.6 at. %. Curve fitting

J. R. Shi; J. P. Wang; A. T. S. Wee; C. B. Yeo; C. T. Cheng; M. Ueda; S. Tomioka; J. Ohsako

2002-01-01

227

Steady tetrahedral and cubic patterns of spherical shell convection with temperature-dependent viscosity  

Microsoft Academic Search

Steady thermal convection of an infinite Prandtl number, Boussinesq fluid with temperature-dependent viscosity is systematically examined in a three-dimensional, basally heated spherical shell with isothermal and stress-free boundaries. Convective flows exhibiting cubic (l=2, m={0,4}) and tetrahedral (l=3, m=2) symmetry are generated with a finite-volume numerical model for various combinations of Rayleigh number Ra (defined with viscosity based on the average

James Todd Ratcliff; Gerald Schubert; Abdelfattah Zebib

1996-01-01

228

Structure and mechanical properties of low stress tetrahedral amorphous carbon films prepared by pulsed laser deposition  

Microsoft Academic Search

:   Tetrahedral amorphous carbon films have been produced by pulsed laser deposition, at a wavelength of 248 nm, ablating highly\\u000a oriented pyrolytic graphite at room temperature, in a 10-2 Pa vacuum, at fluences ranging between 0.5 and 35 Jcm-2. Both (100) Si wafers and wafers covered with a SiC polycrystalline interlayer were used as substrates. Film structure was\\u000a investigated by

M. Bonelli; A. C. Ferrari; A. Fioravanti; A. Li Bassi; A. Miotello; P. M. Ossi

2002-01-01

229

Comparing hardness and wear data for tetrahedral amorphous carbon and hydrogenated amorphous carbon thin films  

Microsoft Academic Search

We compared nanoindentation and nanoscratch testing of 10 and 50nm thick tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H). Raman spectroscopy shows the expected spectral features for the two carbon forms, however, luminescence from the ceramic substrate can alter the spectra. We find that hard ta-C films can blunt the diamond tip and hence use a tip area function

P. Lemoine; J. P. Quinn; P. Maguire; J. A. McLaughlin

2004-01-01

230

Pulsed photothermal measurement of tetrahedral amorphous carbon (taC) film  

Microsoft Academic Search

Pulsed photothermal reflection technique is developed to measure the thermal conductivity of tetrahedral amorphous carbon (ta-C) films. This technique is basically a pump and probe type. The pump source is Nd YAG laser, pulse width 8 ns, is operated at 532 nm with 1 mJ. The sample is deposited on silicon wafer and over-coated with a gold layer for heat

George Chen; Ping Hui

1999-01-01

231

Tetrahedral Amorphous Carbon (taC) Ultra Thin Films for Slider Overcoat Application  

Microsoft Academic Search

Tetrahedral Amorphous Carbon (ta-C) thin film by using Filtered Cathodic Vacuum Arc (FCVA) technique has proven to be wear-resistive and corrosion resistant for a wide range of electrical, optical, and mechanical applications. Many investigations have shown that the ta-C film prepared by the FCVA technique can provide a superior ultra thin overcoat for the sliders and media compared to ECR-CVD

X. Shi; Y. H. Hu; L. Hu

2002-01-01

232

Thermally induced sp2 clustering in tetrahedral amorphous carbon (taC) films  

Microsoft Academic Search

Tetrahedral amorphous carbon films with 70%–88% sp3 content are studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy as a function of annealing temperature in the range 25–1100 °C. Using a high-resolution AFM current imaging, we directly image the formation and growth of conducting graphitic (sp2-bonded) nanoclusters in the ta-C films. Overall results from all the

J. O. Orwa; I. Andrienko; J. L. Peng; S. Prawer; Y. B. Zhang; S. P. Lau

2004-01-01

233

Electronic properties of tetrahedral amorphous carbon (taC) films containing nanotube regions  

Microsoft Academic Search

The electronic and optical properties of nitrogen doped tetrahedral amorphous carbon (ta-C:N) are compared with those of a new form of carbon ta-C film in which nanotube regions are included (ta-C:(NT)). It is found that nanotubes in ta-C inhibit the N doping effect in ta-C and leads to a reduction in conductivity. The results point to the nanotube regions acting

G. A. J. Amaratunga; M. Chhowalla; K. G. Lim; D. A. I. Munindradasa; S. D. Pringle; M. Baxendale; I. Alexandrou; C. J. Kiely; B. Keyse

1998-01-01

234

Thermally induced sp2 clustering in tetrahedral amorphous carbon (taC) films  

Microsoft Academic Search

Tetrahedral amorphous carbon films with 70%-88% sp3 content are studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy as a function of annealing temperature in the range 25-1100 °C. Using a high-resolution AFM current imaging, we directly image the formation and growth of conducting graphitic (sp2-bonded) nanoclusters in the ta-C films. Overall results from all the

J. O. Orwa; I. Andrienko; J. L. Peng; S. Prawer; Y. B. Zhang; S. P. Lau

2004-01-01

235

Tetrahedral Finite-Volume Solutions to the Navier-Stokes Equations on Complex Configurations  

NASA Technical Reports Server (NTRS)

A review of the algorithmic features and capabilities of the unstructured-grid flow solver USM3Dns is presented. This code, along with the tetrahedral grid generator, VGRIDns, is being extensively used throughout the U.S. for solving the Euler and Navier-Stokes equations on complex aerodynamic problems. Spatial discretization is accomplished by a tetrahedral cell-centered finite-volume formulation using Roe's upwind flux difference splitting. The fluxes are limited by either a Superbee or MinMod limiter. Solution reconstruction within the tetrahedral cells is accomplished with a simple, but novel, multidimensional analytical formula. Time is advanced by an implicit backward-Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the near-wall region of the boundary layer. The issues of accuracy and robustness of USM3Dns Navier-Stokes capabilities are addressed for a flat-plate boundary layer, and a full F-16 aircraft with external stores at transonic speed.

Frink, Neal T.; Pirzadeh, Shahyar Z.

1998-01-01

236

Ultrahigh-Resolution {gamma}-Ray Spectroscopy of {sup 156}Gd: A Test of Tetrahedral Symmetry  

SciTech Connect

Tetrahedral symmetry in strongly interacting systems would establish a new class of quantum effects at subatomic scale. Excited states in {sup 156}Gd that could carry the information about the tetrahedral symmetry were populated in the {sup 155}Gd(n,{gamma}){sup 156}Gd reaction and studied using the GAMS4/5 Bragg spectrometers at the Institut Laue-Langevin. We have identified the 5{sub 1}{sup -{yields}}3{sub 1}{sup -} transition of 131.983(12) keV in {sup 156}Gd and determined its intensity to be 1.9(3)x10{sup -6} per neutron capture. The lifetime {tau}=220{sub -30}{sup +180}fs of the 5{sub 1}{sup -} state in {sup 156}Gd has been measured using the GRID technique. The resulting B(E2)=293{sub -134}{sup +61}Weisskopf unit rate of the 131.983 keV transition provides the intrinsic quadrupole moment of the 5{sub 1}{sup -} state in {sup 156}Gd to be Q{sub 0}=7.1{sub -1.6}{sup +0.7} b. This large value, comparable to the quadrupole moment of the ground state in {sup 156}Gd, gives strong evidence against tetrahedral symmetry in the lowest odd-spin, negative-parity band of {sup 156}Gd.

Jentschel, M.; Krempel, J. [Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, F-38042 Grenoble (France); Urban, W. [Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, F-38042 Grenoble (France); Faculty of Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw (Poland); Tonev, D.; Petkov, P. [Institute for Nuclear Research and Nuclear Energy, BAS, BG-1784 Sofia (Bulgaria); Dudek, J.; Curien, D. [Departement de Recherches Subatomiques, Institut Pluridisciplinaire Hubert Curien, DRS-IPHC, 23 rue du Loess, BP 28, F-67037 Strasbourg (France); Lauss, B. [Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Angelis, G. de [Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy)

2010-06-04

237

Ultrahigh-Resolution ?-Ray Spectroscopy of Gd156: A Test of Tetrahedral Symmetry  

NASA Astrophysics Data System (ADS)

Tetrahedral symmetry in strongly interacting systems would establish a new class of quantum effects at subatomic scale. Excited states in Gd156 that could carry the information about the tetrahedral symmetry were populated in the Gd155(n,?)Gd156 reaction and studied using the GAMS4/5 Bragg spectrometers at the Institut Laue-Langevin. We have identified the 51-?31- transition of 131.983(12) keV in Gd156 and determined its intensity to be 1.9(3)x10-6 per neutron capture. The lifetime ?=220-30+180fs of the 51- state in Gd156 has been measured using the GRID technique. The resulting B(E2)=293-134+61Weisskopf unit rate of the 131.983 keV transition provides the intrinsic quadrupole moment of the 51- state in Gd156 to be Q0=7.1-1.6+0.7b. This large value, comparable to the quadrupole moment of the ground state in Gd156, gives strong evidence against tetrahedral symmetry in the lowest odd-spin, negative-parity band of Gd156.

Jentschel, M.; Urban, W.; Krempel, J.; Tonev, D.; Dudek, J.; Curien, D.; Lauss, B.; de Angelis, G.; Petkov, P.

2010-06-01

238

Simulation of Stagnation Region Heating in Hypersonic Flow on Tetrahedral Grids  

NASA Technical Reports Server (NTRS)

Hypersonic flow simulations using the node based, unstructured grid code FUN3D are presented. Applications include simple (cylinder) and complex (towed ballute) configurations. Emphasis throughout is on computation of stagnation region heating in hypersonic flow on tetrahedral grids. Hypersonic flow over a cylinder provides a simple test problem for exposing any flaws in a simulation algorithm with regard to its ability to compute accurate heating on such grids. Such flaws predominantly derive from the quality of the captured shock. The importance of pure tetrahedral formulations are discussed. Algorithm adjustments for the baseline Roe / Symmetric, Total-Variation-Diminishing (STVD) formulation to deal with simulation accuracy are presented. Formulations of surface normal gradients to compute heating and diffusion to the surface as needed for a radiative equilibrium wall boundary condition and finite catalytic wall boundary in the node-based unstructured environment are developed. A satisfactory resolution of the heating problem on tetrahedral grids is not realized here; however, a definition of a test problem, and discussion of observed algorithm behaviors to date are presented in order to promote further research on this important problem.

Gnoffo, Peter A.

2007-01-01

239

A FAST ITERATIVE METHOD FOR SOLVING THE EIKONAL EQUATION ON TETRAHEDRAL DOMAINS  

PubMed Central

Generating numerical solutions to the eikonal equation and its many variations has a broad range of applications in both the natural and computational sciences. Efficient solvers on cutting-edge, parallel architectures require new algorithms that may not be theoretically optimal, but that are designed to allow asynchronous solution updates and have limited memory access patterns. This paper presents a parallel algorithm for solving the eikonal equation on fully unstructured tetrahedral meshes. The method is appropriate for the type of fine-grained parallelism found on modern massively-SIMD architectures such as graphics processors and takes into account the particular constraints and capabilities of these computing platforms. This work builds on previous work for solving these equations on triangle meshes; in this paper we adapt and extend previous two-dimensional strategies to accommodate three-dimensional, unstructured, tetrahedralized domains. These new developments include a local update strategy with data compaction for tetrahedral meshes that provides solutions on both serial and parallel architectures, with a generalization to inhomogeneous, anisotropic speed functions. We also propose two new update schemes, specialized to mitigate the natural data increase observed when moving to three dimensions, and the data structures necessary for efficiently mapping data to parallel SIMD processors in a way that maintains computational density. Finally, we present descriptions of the implementations for a single CPU, as well as multicore CPUs with shared memory and SIMD architectures, with comparative results against state-of-the-art eikonal solvers.

Fu, Zhisong; Kirby, Robert M.; Whitaker, Ross T.

2014-01-01

240

Relativistic Jahn-Teller effects in the photoelectron spectra of tetrahedral P{sub 4}, As{sub 4}, Sb{sub 4}, and Bi{sub 4}  

SciTech Connect

The group-V tetrahedral cluster cations P{sub 4}{sup +}, As{sub 4}{sup +}, Sb{sub 4}{sup +}, and Bi{sub 4}{sup +} are known to exhibit exceptionally strong Jahn-Teller (JT) effects of electrostatic origin in their {sup 2}E ground states and {sup 2}T{sub 2} excited states. It has been predicted that there exist, in addition, JT couplings of relativistic origin (arising from the spin-orbit (SO) operator) in {sup 2}E and {sup 2}T{sub 2} states of tetrahedral systems, which should become relevant for the heavier elements. In the present work, the JT and SO couplings in the group-V tetramer cations have been analyzed with ab initio relativistic electronic structure calculations. The vibronic line spectra and the band shapes of the photoelectron spectra were simulated with time-dependent quantum wave-packet methods. The results provide insight into the interplay of electrostatic and relativistic JT couplings and SO splittings in the complex photoelectron spectra of these systems.

Opalka, Daniel; Domcke, Wolfgang [Department of Chemistry, Technische Universitaet Muenchen, D-85747 Garching (Germany); Poluyanov, Leonid V. [Institute of Chemical Physics, Academy of Sciences, Chernogolovka, Moscow 142432 (Russian Federation)

2011-09-14

241

Quadratic 0-1 programming: Geometric methods and duality analysis  

NASA Astrophysics Data System (ADS)

The unconstraint quadratic binary problem (UBQP), as a classical combinatorial problem, finds wide applications in broad field and human activities including engineering, science, finance, etc. The NP-hardness of the combinatorial problems makes a great challenge to solve the ( UBQP). The main purpose of this research is to develop high performance solution method for solving (UBQP) via the geometric properties of the objective ellipse contour and the optimal solution. This research makes several contributions to advance the state-of-the-art of geometric approach of (UBQP). These contributions include both theoretical and numerical aspects as stated below. In part I of this dissertation, certain rich geometric properties hidden behind quadratic 0-1 programming are investigated. Especially, we derive new lower bounding methods and variable fixation techniques for quadratic 0-1 optimization problems by investigating geometric features of the ellipse contour of a (perturbed) convex quadratic function. These findings further lead to some new optimality conditions for quadratic 0-1 programming. Integrating these novel solution schemes into a proposed solution algorithm of a branch-and-bound type, we obtain promising preliminary computational results. In part II of this dissertation, we present new results of the duality gap between the binary quadratic optimization problem and its Lagrangian dual. We first derive a necessary and sufficient condition for the zero duality gap and discuss its relationship with the polynomial solvability of the problem. We then characterize the zeroness of duality gap by the distance, delta, between the binary set and certain affine space C. Finally, we discuss a computational procedure of the distance delta. These results provide new insights into the duality gap and polynomial solvability of binary quadratic optimization problems.

Liu, Chunli

242

A transient, quadratic nodal method for triangular-Z geometry  

SciTech Connect

Many systematically-derived nodal methods have been developed for Cartesian geometry due to the extensive interest in Light Water Reactors. These methods typically model the transverse-integrated flux as either an analytic or low order polynomial function of position within the node. Recently, quadratic nodal methods have been developed for R-Z and hexagonal geometry. A static and transient quadratic nodal method is developed for triangular-Z geometry. This development is particularly challenging because the quadratic expansion in each node must be performed between the node faces and the triangular points. As a consequence, in the 2-D plane, the flux and current at the points of the triangles must be treated. Quadratic nodal equations are solved using a non-linear iteration scheme, which utilizes the corrected, mesh-centered finite difference equations, and forces these equations to match the quadratic equations by computing discontinuity factors during the solution. Transient nodal equations are solved using the improved quasi-static method, which has been shown to be a very efficient solution method for transient problems. Several static problems are used to compare the quadratic nodal method to the Coarse Mesh Finite Difference (CMFD) method. The quadratic method is shown to give more accurate node-averaged fluxes. However, it appears that the method has difficulty predicting node leakages near reactor boundaries and severe material interfaces. The consequence is that the eigenvalue may be poorly predicted for certain reactor configurations. The transient methods are tested using a simple analytic test problem, a heterogeneous heavy water reactor benchmark problem, and three thermal hydraulic test problems. Results indicate that the transient methods have been implemented correctly.

DeLorey, T.F.

1993-06-01

243

On implementing a primal-dual interior-point method for conic quadratic optimization  

Microsoft Academic Search

Conic quadratic optimization is the problem of minimizing a linear function subject to the intersection of an ane set and the product of quadratic cones. The problem is a convex optimization problem and has numerous applications in engineering, economics, and other areas of science. Indeed, linear and convex quadratic optimization is a special case. Conic quadratic optimization problems can in

Erling D. Andersen; Cornelis Roos; Tamás Terlaky

2003-01-01

244

Tetrahedral lander  

NASA Astrophysics Data System (ADS)

An apparatus and method is disclosed for decelerating and absorbing impact of a re-entry vehicle suitable for payloads that are relatively light as well as payloads weighing several tons or more. The apparatus includes four inflatable legs displaced equidistantly from each other around a capsule or housing which contains a payload. The legs are inflated at a designated altitude after entering Earth's atmosphere to slow the descent of the re-entry vehicle. Connected between each of the four legs are drag inducing surfaces that deploy as the legs inflate. The drag inducing surfaces are triangularly shaped with one such surface being connected between each pair of legs for a total of six drag inducing surfaces. The legs have drag inducing outer surfaces which act to slow the descent of the re-entry vehicle.

Nyberg, Karen L.

1993-02-01

245

Tetrahedral lander  

NASA Technical Reports Server (NTRS)

An apparatus and method is disclosed for decelerating and absorbing impact of a re-entry vehicle suitable for payloads that are relatively light as well as payloads weighing several tons or more. The apparatus includes four inflatable legs displaced equidistantly from each other around a capsule or housing which contains a payload. The legs are inflated at a designated altitude after entering earth's atmosphere to slow the descent of the re-entry vehicle. Connected between each of the four legs are drag inducing surfaces that deploy as the legs inflate. The drag inducing surfaces are triangularly shaped with one such surface being connected between each pair of legs for a total of six drag inducing surfaces. The legs have drag inducing outer surfaces which act to slow the descent of the re-entry vehicle.

Roberts, Michael L. (inventor)

1993-01-01

246

Recent Development in the CESE Method for the Solution of the Navier-Stokes Equations Using Unstructured Triangular or Tetrahedral Meshes With High Aspect Ratio  

NASA Technical Reports Server (NTRS)

In the multidimensional CESE development, triangles and tetrahedra turn out to be the most natural building blocks for 2D and 3D spatial meshes. As such the CESE method is compatible with the simplest unstructured meshes and thus can be easily applied to solve problems with complex geometries. However, because the method uses space-time staggered stencils, solution decoupling may become a real nuisance in applications involving unstructured meshes. In this paper we will describe a simple and general remedy which, according to numerical experiments, has removed any possibility of solution decoupling. Moreover, in a real-world viscous flow simulation near a solid wall, one often encounters a case where a boundary with high curvature or sharp corner is surrounded by triangular/tetrahedral meshes of extremely high aspect ratio (up to 106). For such an extreme case, the spatial projection of a space-time compounded conservation element constructed using the original CESE design may become highly concave and thus its centroid (referred to as a spatial solution point) may lie far outside of the spatial projection. It could even be embedded beyond a solid wall boundary and causes serious numerical difficulties. In this paper we will also present a new procedure for constructing conservation elements and solution elements which effectively overcomes the difficulties associated with the original design. Another difficulty issue which was addressed more recently is the wellknown fact that accuracy of gradient computations involving triangular/tetrahedral grids deteriorates rapidly as the aspect ratio of grid cells increases. The root cause of this difficulty was clearly identified and several remedies to overcome it were found through a rigorous mathematical analysis. However, because of the length of the current paper and the complexity of mathematics involved, this new work will be presented in another paper.

Chang, Sin-Chung; Chang, Chau-Lyan; Yen, Joseph C.

2013-01-01

247

Mixed finite element formulation in large deformation frictional contact problem  

E-print Network

Mixed finite element formulation in large deformation frictional contact problem Laurent Baillet using the 2D finite element code PLAST21 . The first contact algorithm is the classical node and compared for linear and quadratic elements. KEY WORDS: contact, mixed finite element, friction, dynamic

Paris-Sud XI, Université de

248

Quadratic Integrate-and-Fire Neuron Network Model  

NSDL National Science Digital Library

The Quadratic Integrate-and-Fire Neuron Network Model uses a network of Quadratic Integrate-and-Fire neurons to demonstrate how connectivity influences network synchrony. The user selects the number of neurons and the degree of connectivity, and can see how the neurons synchronize over time. In addition, the user can watch the potential of a single neuron. Although the dynamics of a single neuron do not change, the network architecture has a dramatic effect on how quickly the neurons will synchronize. The Quadratic Integrate-and-Fire Neuron Network Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Thomson, Colin F.

2012-12-22

249

Quadratic algebra approach to relativistic quantum Smorodinsky-Winternitz systems  

SciTech Connect

There exists a relation between the Klein-Gordon and the Dirac equations with scalar and vector potentials of equal magnitude and the Schroedinger equation. We obtain the relativistic energy spectrum for the four relativistic quantum Smorodinsky-Winternitz systems from their quasi-Hamiltonian and the quadratic algebras studied by Daskaloyannis in the nonrelativistic context. We also apply the quadratic algebra approach directly to the initial Dirac equation for these four systems and show that the quadratic algebras obtained are the same than those obtained from the quasi-Hamiltonians. We point out how results obtained in context of quantum superintegrable systems and their polynomial algebras can be applied to the quantum relativistic case.

Marquette, Ian [Department of Mathematics, University of York, Heslington, York YO10 5DD (United Kingdom)

2011-04-15

250

Quadratically consistent nodal integration for second order meshfree Galerkin methods  

NASA Astrophysics Data System (ADS)

Robust and efficient integration of the Galerkin weak form only at the approximation nodes for second order meshfree Galerkin methods is proposed. The starting point of the method is the Hu-Washizu variational principle. The orthogonality condition between stress and strain difference is satisfied by correcting nodal derivatives. The corrected nodal derivatives are essentially linear functions which can exactly reproduce linear strain fields. With the known area moments, the stiffness matrix resulting from these corrected nodal derivatives can be exactly evaluated using only the nodes as quadrature points. The proposed method can exactly pass the quadratic patch test and therefore is named as quadratically consistent nodal integration. In contrast, the stabilized conforming nodal integration (SCNI) which prevails in the nodal integrations for meshfree Galerkin methods fails to pass the quadratic patch test. Better accuracy, convergence, efficiency and stability than SCNI are demonstrated by several elastostatic and elastodynamic examples.

Duan, Qinglin; Wang, Bingbing; Gao, Xin; Li, Xikui

2014-08-01

251

Homotopy approach to optimal, linear quadratic, fixed architecture compensation  

NASA Technical Reports Server (NTRS)

Optimal linear quadratic Gaussian compensators with constrained architecture are a sensible way to generate good multivariable feedback systems meeting strict implementation requirements. The optimality conditions obtained from the constrained linear quadratic Gaussian are a set of highly coupled matrix equations that cannot be solved algebraically except when the compensator is centralized and full order. An alternative to the use of general parameter optimization methods for solving the problem is to use homotopy. The benefit of the method is that it uses the solution to a simplified problem as a starting point and the final solution is then obtained by solving a simple differential equation. This paper investigates the convergence properties and the limitation of such an approach and sheds some light on the nature and the number of solutions of the constrained linear quadratic Gaussian problem. It also demonstrates the usefulness of homotopy on an example of an optimal decentralized compensator.

Mercadal, Mathieu

1991-01-01

252

On volumes of hyperbolic Coxeter polytopes and quadratic forms  

E-print Network

In this paper, we compute the covolume of the group of units of the quadratic form f_d^n(x) = x_1^2 + x_2^2 + . . . + x_n^2 - d x_{n+1}^2 with d an odd, positive, square-free integer. Mcleod has determined the hyperbolic Coxeter fundamental domain of the reflection subgroup of the group of units of the quadratic form f_3^n. We apply our covolume formula to compute the volumes of these hyperbolic Coxeter polytopes.

Ratcliffe, John G

2012-01-01

253

Illitization by tetrahedral exchange: Evidence from the laboratory flow-through experiments  

SciTech Connect

The authors have reacted natural smectite in a hydrothermal flow-through apparatus in order to investigate the mechanism and kinetics of the smectite-to-illite reaction. Experiments were conducted from 150-300C and 150 bars, and input fluids consisted of near-neutral pH, Si- and Al-bearing, KCl solutions. The unique design of the apparatus allows periodic sampling of solids as well as fluids during the course of a single experiment. Reaction progress is monitored by following changes in clay composition (XRD, microprobe) with time. By controlling input fluid composition, they have been able to simulate all stages of illitization; from smectite to illite through a progression of mixed-layered smectite/illite phases. Chemical analysis of extracted solids show that illitization is accompanied by stoichiometric enrichment in K and Al and depletion in Si in the tetrahedral sheet. The cation content of the octahedral sheet remains essentially constant. These results provide clear experimental evidence for a tetrahedral exchange reaction. Such a reaction may also involve a solid-solution in smectite-illite series; extent of illitization in these experiments systematically decreases with increasing aqueous silica concentration. While a illitization by tetrahedral exchange does not exclude other pathways for illitization, the compositional changes observed here are consistent with those observed in many diagenetic settings. The results of these experiments further suggest that extent of illitization in nature may be strongly influenced by factors which affect aqueous silica concentrations in the host rock environment (e.g., local mineralogy, permeability, and fluid flow conditions).

Kacandes, G.H.; Barnes, H.L.; Kump, L.R. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Geosciences)

1992-01-01

254

Surface characterisation of spinels with Ti(IV) distributed in tetrahedral and octahedral sites  

Microsoft Academic Search

The differences of the binding energy of the Ti 2p3\\/2 electron obtained by X-ray photoelectron spectroscopy (XPS) in ternary spinels such as LiFeTiO4, LiMnTiO4 and LiCrTiO4 have been studied. X-ray diffraction patterns for these spinels and neutron powder diffraction data for LiFeTiO4, LiMnTiO4 and LiCrTiO4 reveal that Fe(III) is in octahedral and tetrahedral sites, and Cr(III) and Mn(III) are exclusively

M. A. Arillo; M. L. López; C. Pico; M. L. Veiga; A. Jiménez-López; E. Rodr??guez-Castellón

2001-01-01

255

Metal-Organic Framework Isomers with Diamondoid Networks Constructed of a Semi-Rigid Tetrahedral Linker  

SciTech Connect

Solvothermal assembly of a semi-rigid tetrahedral carboxylate ligand tetrakis[4-(carboxyphenyl)oxamethyl]methane acid (H4X) with Cd(II) ion in different solvent systems yields three novel metal-organic framework isomers (1-3) based on different secondary building units (SBUs). Although all three frameworks have the same dia (diamondoid) topology, complex 1 and 3 are chiral and complex 2 is achiral. One of the networks, 3 shows cross-linked three-fold interpenetration of the single dia net and exhibits permanent porosities, as confirmed by BET and selective CO2 adsorption.

Tian, Jian; Motkuri, Radha K.; Thallapally, Praveen K.; McGrail, B. Peter

2010-10-19

256

A new three-dimensional interface finite element to simulate fracture in composites  

Microsoft Academic Search

A new three-dimensional quadratic interface finite element is developed. The element is made up by two 6-noded triangular surfaces which initially lie together and connect the faces of adjacent quadratic tetrahedra, the only elements supported by automatic meshing algorithms. The element is introduced within the framework of implicit analysis and large displacements, and can include any traction–separation law at the

Javier Segurado; Javier LLorca

2004-01-01

257

Inertia-Controlling Methods for General Quadratic Programming  

Microsoft Academic Search

Active-set quadratic programming (QP) methods use a working set to define the search direction and multiplier estimates. In the method proposed by Fletcher in 1971, and in several subsequent mathematically equivalent methods, the working set is chosen to control the inertia of the reduced Hessian, which is never permitted to have more than one nonpositive eigenvalue. (We call such methods

PHILIP E. GILL; WALTER MURRAY; MICHAEL A. SAUNDERS

1991-01-01

258

Rocket ascent trajectory optimization via recursive quadratic programming  

Microsoft Academic Search

An algorithm for solving parameterized optimal control problems such as the ascent trajectory optimization problem of a multistage launch vehicle is developed. The implementation of this algorithm, designated as the Recursive Quadratic Programming Approach, for the pitch and yaw optimization of a multistage launch vehicle is discussed, and results are given for injection into a polar orbit from the Indian

K. H. Well; S. R. Tandon

1982-01-01

259

Indefinite Stochastic Linear Quadratic Control and Generalized Differential Riccati Equation  

E-print Network

Indefinite Stochastic Linear Quadratic Control and Generalized Differential Riccati Equation M. Ait is to identify an appro- priate Riccati-type equation whose solvability is equivalent to the solvability of this possibly in- definite LQ problem. In this paper we intro- duce a new type of differential Riccati equation

Moore, John Barratt

260

Homotopy analysis method for quadratic Riccati differential equation  

Microsoft Academic Search

In this paper, the quadratic Riccati differential equation is solved by means of an analytic technique, namely the homotopy analysis method (HAM). Comparisons are made between Adomian’s decomposition method (ADM), homotopy perturbation method (HPM) and the exact solution and the homotopy analysis method. The results reveal that the proposed method is very effective and simple.

Yue Tan; Saeid Abbasbandy

2008-01-01

261

Finding Optimal Gains In Linear-Quadratic Control Problems  

NASA Technical Reports Server (NTRS)

Analytical method based on Volterra factorization leads to new approximations for optimal control gains in finite-time linear-quadratic control problem of system having infinite number of dimensions. Circumvents need to analyze and solve Riccati equations and provides more transparent connection between dynamics of system and optimal gain.

Milman, Mark H.; Scheid, Robert E., Jr.

1990-01-01

262

The eccentricity of conic sections formulated as rational Bézier quadratics  

Microsoft Academic Search

The eccentricity of rational quadratic Bézier curves is formulated directly in terms of their control-points and weights. Based on this expression, we analyze the range and extreme values of the eccentricity of conic sections expressed in this form. We also provide an explicit expression for the eccentricity of the osculating conic of a rational Bézier curve of high degree.

Chendong Xu; Tae-wan Kim; Gerald E. Farin

2010-01-01

263

Linear Quadratic State Feedback Optimal Control against Actuator Failures  

Microsoft Academic Search

This paper is concerned with the synthesis of a robust and optimal controller for open-loop unstable systems possessing actuator redundancy. The designed linear quadratic state feedback regulator can maintain the close-loop stability in the presence of some certain actuator failures. At the first design stage, a discriminance of actuator functional redundancy is given, which is the precondition to design the

Zhizhou Zhang; Zhiqiang Long; Longhua She; Wensen Chang

2007-01-01

264

Finding the Best Quadratic Approximation of a Function  

ERIC Educational Resources Information Center

This article examines the question of finding the best quadratic function to approximate a given function on an interval. The prototypical function considered is f(x) = e[superscript x]. Two approaches are considered, one based on Taylor polynomial approximations at various points in the interval under consideration, the other based on the fact…

Yang, Yajun; Gordon, Sheldon P.

2011-01-01

265

Information-Theoretic Learning Using Renyi's Quadratic Entropy  

E-print Network

to offer to learning theory since it is a deep mathematical theory concerned with the very essenceInformation-Theoretic Learning Using Renyi's Quadratic Entropy Jose C. Principe, Dongxin Xu of Florida, Gainesville, FL 32611, USA ABSTRACT Learning from examples has been traditionally based

Slatton, Clint

266

Near-optimal placement using a quadratic objective function  

Microsoft Academic Search

Placement algorithms for IC layout which are optimal are known to be NP-complete 5. As a result, heuristics such as pairwise-interchange techniques must be employed to generate satisfactory placements. Unfortunately, with these algorithms, there is generally no way of knowing just how far away the result is from optimum. With the quadratic metric used in this study, however, a useful

John P. Blanks

1985-01-01

267

On Quadratic g-Evaluations/Expectations and Related Analysis  

E-print Network

On Quadratic g-Evaluations/Expectations and Related Analysis Jin Ma, Song Yao Abstract In this paper we extend the notion of g-evaluation, in particular g-expectation, of Peng [9, 10] to the case of the g-expectations, including a representation theorem between the generator and the corresponding g-expectation

Zhang, Jianfeng

268

Solving the quadratic assignment problem by means of general ...  

E-print Network

The Quadratic Assignment Problem (QAP) can be solved by linearization, where one ... locations j and l, and cij denotes the cost of locating facility i at location j. xij = 1 if facility ...... Journal of the Society for Industrial and Applied Mathematices, ...

2010-04-19

269

ON THE GEOMETRY OF BIFURCATION CURRENTS FOR QUADRATIC RATIONAL MAPS.  

E-print Network

ON THE GEOMETRY OF BIFURCATION CURRENTS FOR QUADRATIC RATIONAL MAPS. FRANÃ?OIS BERTELOOT AND THOMAS current. 1. Introduction. For any holomorphic family (f)M of degree d rational maps on P1, the bifurcation GAUTHIER Abstract. We describe the behaviour at infinity of the bifurcation current in the mod- uli space

Paris-Sud XI, Université de

270

Nonlinear Quadratic Pricing for Concavifiable Utilities in Network Rate Control  

E-print Network

with the non-elastic applications. Such applications, for example, voice/video over IP, have certain data rateNonlinear Quadratic Pricing for Concavifiable Utilities in Network Rate Control Quanyan Zhu objective function. We use a game- theoretical framework as well as a centralized optimization approach

Boutaba, Raouf

271

A Greedy Genetic Algorithm for the Quadratic Assignment Problem  

Microsoft Academic Search

The Quadratic Assignment Problem (QAP) is one of the classical combinatorial optimizationproblems and is known for its diverse applications. In this paper, we suggest a genetic algorithm for theQAP and report its computational behavior. The genetic algorithm incorporates many greedyprinciples in its design and, hence, is called the greedy genetic algorithm. The ideas we incorporate inthe greedy genetic algorithm include

Ravindra K. Ahuja; James B. Orlin

1997-01-01

272

A greedy genetic algorithm for the quadratic assignment problem  

Microsoft Academic Search

The Quadratic Assignment Problem (QAP) is one of the classical combinatorial optimization problems and is known for its diverse applications. In this paper, we suggest a genetic algorithm for the QAP and report its computational behavior. The genetic algorithm incorporates many greedy principles in its design and, hence, we refer to it as a greedy genetic algorithm. The ideas we

Ravindra K. Ahuja; James B. Orlin; Ashish Tiwari

2000-01-01

273

Solving the Quadratic Capacitated Facilities Location Problem by Computer.  

ERIC Educational Resources Information Center

Several computer programs were developed to solve various versions of the quadratic capacitated facilities location problem. Matrices, which represent various business costs, are defined for the factors of sites, facilities, customers, commodities, and production units. The objective of the program is to find an optimization matrix for the lowest…

Cote, Leon C.; Smith, Wayland P.

274

Quadratic Approximation-Based Coordinate Change in Genetic Algorithms  

Microsoft Academic Search

This paper proposes a procedure for space coordinate change, inside genetic algorithms, based on convex quadratic approximations of the general nonlinear objective function. It is shown that in the transformed coordinates the genetic algorithm is able to And the problem optimum in less iterations and with greater proportion of successful attempts. The proposed procedure employs only the objective function samples

Elizabeth F. Wanner; Frederico G. Guimaraes; Ricardo H. C. Takahashi; Peter J. Fleming

2006-01-01

275

Analysis of Quadratic Diophantine Equations with Fibonacci Number Solutions  

ERIC Educational Resources Information Center

An analysis is made of the role of Fibonacci numbers in some quadratic Diophantine equations. A general solution is obtained for finding factors in sums of Fibonacci numbers. Interpretation of the results is facilitated by the use of a modular ring which also permits extension of the analysis.

Leyendekkers, J. V.; Shannon, A. G.

2004-01-01

276

Delay Robustness of Interconnected Passive Systems: An Integral Quadratic Constraint  

E-print Network

consider networks of passive systems with time delays in the interconnections, and present a stability1 Delay Robustness of Interconnected Passive Systems: An Integral Quadratic Constraint Approach that depend on the duration of delay. Since the effect of delay depends on its duration relative to the time

Arcak, Murat

277

Confidence set interference with a prior quadratic bound. [in geophysics  

NASA Technical Reports Server (NTRS)

Neyman's (1937) theory of confidence sets is developed as a replacement for Bayesian interference (BI) and stochastic inversion (SI) when the prior information is a hard quadratic bound. It is recommended that BI and SI be replaced by confidence set interference (CSI) only in certain circumstances. The geomagnetic problem is used to illustrate the general theory of CSI.

Backus, George E.

1989-01-01

278

Improving the Performance of MIQP Solvers for Quadratic Programs ...  

E-print Network

doctrine, a mean-variance optimizer should solve the following quadratic problem: min xT Qx ... with different risk measures and tracking error control. ...... the CVX Matlab codes and the C program codes in our numerical tests are available at.

2013-09-07

279

Clustered Self Organising Migrating Algorithm for the Quadratic Assignment Problem  

NASA Astrophysics Data System (ADS)

An approach of population dynamics and clustering for permutative problems is presented in this paper. Diversity indicators are created from solution ordering and its mapping is shown as an advantage for population control in metaheuristics. Self Organising Migrating Algorithm (SOMA) is modified using this approach and vetted with the Quadratic Assignment Problem (QAP). Extensive experimentation is conducted on benchmark problems in this area.

Davendra, Donald; Zelinka, Ivan; Senkerik, Roman

2009-08-01

280

Confidence set interference with a prior quadratic bound  

Microsoft Academic Search

Neyman's (1937) theory of confidence sets is developed as a replacement for Bayesian interference (BI) and stochastic inversion (SI) when the prior information is a hard quadratic bound. It is recommended that BI and SI be replaced by confidence set interference (CSI) only in certain circumstances. The geomagnetic problem is used to illustrate the general theory of CSI.

George E. Backus

1989-01-01

281

Quadratic Expressions by Means of "Summing All the Matchsticks"  

ERIC Educational Resources Information Center

This note presents demonstrations of quadratic expressions that come about when particular problems are posed with respect to matchsticks that form regular triangles, squares, pentagons and so on. Usually when such "matchstick" problems are used as ways to foster algebraic thinking, the expressions for the number of matchstick quantities are…

Gierdien, M. Faaiz

2012-01-01

282

Word Alignment via Quadratic Assignment Simon Lacoste-Julien  

E-print Network

in various dic- tionaries, the similarity of the frequency of its two words, choices made by other alignmentWord Alignment via Quadratic Assignment Simon Lacoste-Julien UC Berkeley, Berkeley, CA 94720@cs.berkeley.edu Abstract Recently, discriminative word alignment methods have achieved state-of-the-art accuracies

Plotkin, Joshua B.

283

An Attempt to Remove Quadratic Divergences in the Standard Theory  

E-print Network

The quadratic divergences caused by Yukawa interactions in the standard theory of elementary particle physics is shown to be removed by introducing finite-mass complex-ghost regulator fields. In this modification of the standard theory, its manifest covariance, renormalizability, gauge invariance and unitarity are retained, and no new observable particles are introduced.

Noboru Nakanishi

2007-11-29

284

A Unified Approach to Teaching Quadratic and Cubic Equations.  

ERIC Educational Resources Information Center

Presents a simple method for teaching the algebraic solution of cubic equations via completion of the cube. Shows that this method is readily accepted by students already familiar with completion of the square as a method for quadratic equations. (Author/KHR)

Ward, A. J. B.

2003-01-01

285

Direct atomic imaging and dynamical fluctuations of the tetrahedral Au20 cluster  

NASA Astrophysics Data System (ADS)

We report real-space, atomic-resolution images of Au20 clusters obtained with the aberration-corrected Scanning Transmission Electron Microscopy. The proposed tetrahedral (FCC segment) pyramid structure is confirmed. The clusters cycle between isomers under the electron beam in the time-lapse images acquired. Disordered variants on the high symmetry forms are commonly observed. We believe that the direct experimental identification of these kinds of atomic structure, and the fluctuations between them, is fundamental to our understanding of nanoparticle structures, as well as applications such as heterogeneous catalysis.We report real-space, atomic-resolution images of Au20 clusters obtained with the aberration-corrected Scanning Transmission Electron Microscopy. The proposed tetrahedral (FCC segment) pyramid structure is confirmed. The clusters cycle between isomers under the electron beam in the time-lapse images acquired. Disordered variants on the high symmetry forms are commonly observed. We believe that the direct experimental identification of these kinds of atomic structure, and the fluctuations between them, is fundamental to our understanding of nanoparticle structures, as well as applications such as heterogeneous catalysis. Electronic supplementary information (ESI) available: The full-size images corresponding to Fig. 1(a) and (d). See DOI: 10.1039/c2nr31071f

Wang, Z. W.; Palmer, R. E.

2012-07-01

286

Structure and mechanical properties of low stress tetrahedral amorphous carbon films prepared by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Tetrahedral amorphous carbon films have been produced by pulsed laser deposition, at a wavelength of 248 nm, ablating highly oriented pyrolytic graphite at room temperature, in a 10-2 Pa vacuum, at fluences ranging between 0.5 and 35 Jcm-2. Both (100) Si wafers and wafers covered with a SiC polycrystalline interlayer were used as substrates. Film structure was investigated by Raman spectroscopy at different excitation wavelength from 633 nm to 229 nm and by transmission Electron Energy Loss Spectroscopy. The films, which are hydrogen-free, as shown by Fourier Transform Infrared Spectroscopy, undergo a transition from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C) above a threshold laser fluence of 5 J cm-2. By X-ray reflectivity roughness, density and cross-sectional layering of selected samples were studied. Film hardness as high as 70 GPa was obtained by nanoindentation on films deposited with the SiC interlayer. By scratch test film adhesion and friction coefficients between 0.06 and 0.11 were measured. By profilometry we obtained residual stress values not higher than 2 GPa in as-deposited 80% sp3 ta-C films.

Bonelli, M.; Ferrari, A. C.; Fioravanti, A.; Li Bassi, A.; Miotello, A.; Ossi, P. M.

2002-02-01

287

Approximation theory for LQG (Linear-Quadratic-Gaussian) optimal control of flexible structures  

NASA Technical Reports Server (NTRS)

An approximation theory is presented for the LQG (Linear-Quadratic-Gaussian) optimal control problem for flexible structures whose distributed models have bounded input and output operators. The main purpose of the theory is to guide the design of finite dimensional compensators that approximate closely the optimal compensator. The optimal LQG problem separates into an optimal linear-quadratic regulator problem and an optimal state estimation problem. The solution of the former problem lies in the solution to an infinite dimensional Riccati operator equation. The approximation scheme approximates the infinite dimensional LQG problem with a sequence of finite dimensional LQG problems defined for a sequence of finite dimensional, usually finite element or modal, approximations of the distributed model of the structure. Two Riccati matrix equations determine the solution to each approximating problem. The finite dimensional equations for numerical approximation are developed, including formulas for converting matrix control and estimator gains to their functional representation to allow comparison of gains based on different orders of approximation. Convergence of the approximating control and estimator gains and of the corresponding finite dimensional compensators is studied. Also, convergence and stability of the closed-loop systems produced with the finite dimensional compensators are discussed. The convergence theory is based on the convergence of the solutions of the finite dimensional Riccati equations to the solutions of the infinite dimensional Riccati equations. A numerical example with a flexible beam, a rotating rigid body, and a lumped mass is given.

Gibson, J. S.; Adamian, A.

1988-01-01

288

FIBER OPTIC POINT QUADRAT SYSTEM FOR IMPROVED ACCURACY IN VEGETATION SAMPLING  

EPA Science Inventory

An automated, fiber optic point quadrat system for vegetation sampling is described. Because the effective point diameter of the system never exceeds 25um it minimizes the substantial errors which can arise with conventional point quadrats. Automatic contact detection eliminates ...

289

GONII: UNIVERSAL QUATERNARY QUADRATIC FORMS PETE L. CLARK, JACOB HICKS, KATHERINE THOMPSON, AND NATHAN WALTERS  

E-print Network

, AND NATHAN WALTERS Contents 1. Introduction 1 2. Review of Quadratic Forms 2 2.1. Quadratic forms over a ring;2 PETE L. CLARK, JACOB HICKS, KATHERINE THOMPSON, AND NATHAN WALTERS and include a link to the C++ code

Smith, Roy

290

Effect of Lithium Absorption at Tetrahedral Site and Isomorphic Substitution on Montmorillonite Properties: A Density Functional Theory Study  

NASA Astrophysics Data System (ADS)

This study deals with the effect of the isomorphic substitution on the sorption of two Li atoms on montmorillonite using density functional theory (DFT). The isomorphic substitution is carried out by modifying the atomic composition of the upper tetrahedral layer of the montmorillonite by replacing one Si atom with one Al atom on the said position. Note that in the conventional structure, Si atom is located at the upper tetrahedral layer of montmorillonite. Results show that one Li atom is likely to be situated in the vacant tetrahedral site and the other one is in the vacant octahedral site, for both of the two montmorillonite systems (isomorphic substitution and conventional structure). The sorption energy was found to be -6.31 eV at the most stable configuration, that is for the isomorphic substitution.

Wungu, Triati Dewi Kencana; Diño, Wilson Agerico; Dipojono, Hermawan Kresno; Kasai, Hideaki

2011-05-01

291

A unified multigrid solver for the Navier-Stokes equations on mixed element meshes  

NASA Technical Reports Server (NTRS)

A unified multigrid solution technique is presented for solving the Euler and Reynolds-averaged Navier-Stokes equations on unstructured meshes using mixed elements consisting of triangles and quadrilaterals in two dimensions, and of hexahedra, pyramids, prisms, and tetrahedra in three dimensions. While the use of mixed elements is by no means a novel idea, the contribution of the paper lies in the formulation of a complete solution technique which can handle structured grids, block structured grids, and unstructured grids of tetrahedra or mixed elements without any modification. This is achieved by discretizing the full Navier-Stokes equations on tetrahedral elements, and the thin layer version of these equations on other types of elements, while using a single edge-based data-structure to construct the discretization over all element types. An agglomeration multigrid algorithm, which naturally handles meshes of any types of elements, is employed to accelerate convergence. An automatic algorithm which reduces the complexity of a given triangular or tetrahedral mesh by merging candidate triangular or tetrahedral elements into quadrilateral or prismatic elements is also described. The gains in computational efficiency afforded by the use of non-simplicial meshes over fully tetrahedral meshes are demonstrated through several examples.

Mavriplis, D. J.; Venkatakrishnan, V.

1995-01-01

292

On the time-weighted quadratic sum of linear discrete systems  

NASA Technical Reports Server (NTRS)

A method is proposed for obtaining the time-weighted quadratic sum for linear discrete systems. The formula of the weighted quadratic sum is obtained from matrix z-transform formulation. In addition, it is shown that this quadratic sum can be derived in a recursive form for several useful weighted functions. The discussion presented parallels that of MacFarlane (1963) for weighted quadratic integral for linear continuous systems.

Jury, E. I.; Gutman, S.

1975-01-01

293

Synthesis, evaluation and defect compensation of tetrahedral glasses as possible solar cell materials. Final report, February 1, 1979-April 30, 1980  

SciTech Connect

The work reported was directed towards evaluation of new amorphous compounds for application in solar cells. The ternary A/sup II/B/sup IV/C/sub 2//sup V/ chalcopyrite systems were selected because of their inexpensive constituent elements and tetrahedral geometry. Polycrystalline samples of the ternary arsenides with Cd and Zn as the group II element and Ge, Si, Sn as the group IV element were synthesized. Thin films were deposited by vacuum evaporation of the bulk ternary arsenides. The stoichiometries of the films were irreproducible and were usually deficient in the lower vapor pressure group IV element. Films made by evaporating polycrystalline ZnAs/sub 2/, which also has a tetrahedral bonding structure, had stoichiometries generally in the range from Zn/sub 3/As/sub 2/ to ZnAs/sub 2/. The former compound is formed by the decomposition of ZnAs/sub 2/ to Zn/sub 3/As/sub 2/ and As/sub 4/. The intermediate stoichiometries are thought to be mixtures of the decomposition products. Preliminary results from annealing of the films indicate that heat treatment produces the stoichiometries expected for one of the two forms of zinc arsenide. The as-deposited films are amorphous when the substrate temperature is kept below 100/sup 0/C. The a-ZnAs/sub x/ films were characterized. EDAX and Auger analysis showed that films were homogeneous in the plane of the substrate, but that some variation occurred in the depth profile of the films. This change in composition is consistent with the sample decomposition which occurs during the evaporation. The as-prepared films were p-type with room temperature resistivities on the order of 10/sup 2/-10/sup 4/..cap omega..-cm. Optical absorption measurements gave optical band gap values of 1.2 eV for a-Zn/sub 3/As/sub 2/ and 1.5 eV for a-ZnAs/sub 2/. The ZnAs/sub x/ films were photoconductive.

Rauh, R.D.; Rose, T.L.; Scoville, A.N.

1980-04-01

294

Gauss Sums and Quadratic Reciprocity c W W L Chen, 1981, 2013.  

E-print Network

, where q = 1, if q 1 mod 4, i, if q -1 mod 4. To deduce the Law of quadratic reciprocity, note the proof of the Law of quadratic reciprocity, it remains to establish Theorem 7.3, which we do in Section 7CHAPTER 7 Gauss Sums and Quadratic Reciprocity c W W L Chen, 1981, 2013. This chapter originates

Chen, William

295

On Approximate Robust Counterparts of Uncertain Semidefinite and Conic Quadratic Programs  

E-print Network

On Approximate Robust Counterparts of Uncertain Semidefinite and Conic Quadratic Programs Aharon conditions for the validity of specific NP-hard semi-infinite systems of semidefinite and conic quadratic as robust counterparts of uncertain conic quadratic and semidefinite problems. We start with specifying

Nemirovski, Arkadi

296

A Lifted Linear Programming Branch-and-Bound Algorithm for Mixed Integer Conic Quadratic Programs  

E-print Network

A Lifted Linear Programming Branch-and-Bound Algorithm for Mixed Integer Conic Quadratic Programs develops a linear programming based branch-and-bound algorithm for mixed in- teger conic quadratic programs. The algorithm is based on a higher dimensional or lifted polyhedral relaxation of conic quadratic constraints

Ahmed, Shabbir

297

An Attribute Weight Setting Method for k-NN Based Binary Classification using Quadratic Programming  

E-print Network

An Attribute Weight Setting Method for k-NN Based Binary Classification using Quadratic Programming. In this paper, we propose a new attribute weight setting method for k-NN based classifiers using quadratic the attribute weight setting problem as a quadratic programming problem and exploits commercial software

Coenen, Frans

298

Genetic\\/quadratic search algorithm for plant economic optimizations using a process simulator  

Microsoft Academic Search

The genetic\\/quadratic search algorithm (GQSA) is a hybrid genetic algorithms (GA) for optimizing plant economics when a process simulator models the plant. By coupling a regular GA with an algorithm based upon a quadratic search, the required number of objective function evaluations for obtaining an acceptable solution decreases significantly in most cases. The GQSA combines advantages of GA and quadratic

Won-hyouk Jang; Juergen Hahn; Kenneth R. Hall

2005-01-01

299

Symmetry-breaking instability of quadratic soliton bound states  

SciTech Connect

We study both numerically and experimentally two-dimensional soliton bound states in quadratic media and demonstrate their symmetry-breaking instability. The experiment is performed in a potassium titanyl phosphate crystal in a type-II configuration. The bound state is generated by the copropagation of the antisymmetric fundamental beam locked in phase with the symmetrical second harmonic one. Experimental results are in good agreement with numerical simulations of the nonlinear wave equations.

Delque, Michaeel [Service OPERA-photonique, CP194/5, Universite Libre de Bruxelles U.L.B. Avenue F.D. Roosevelt, B-1050 Bruxelles (Belgium); Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon (France); Fanjoux, Gil; Maillotte, Herve; Kockaert, Pascal; Sylvestre, Thibaut; Haelterman, Marc [Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon (France)

2011-01-15

300

Design of Linear Quadratic Regulators and Kalman Filters  

NASA Technical Reports Server (NTRS)

AESOP solves problems associated with design of controls and state estimators for linear time-invariant systems. Systems considered are modeled in state-variable form by set of linear differential and algebraic equations with constant coefficients. Two key problems solved by AESOP are linear quadratic regulator (LQR) design problem and steady-state Kalman filter design problem. AESOP is interactive. User solves design problems and analyzes solutions in single interactive session. Both numerical and graphical information available to user during the session.

Lehtinen, B.; Geyser, L.

1986-01-01

301

Quadratic Reciprocity and the Group Orders of Particle States  

Microsoft Academic Search

The construction of inverse states in a finite field F{sub P{sub Pα}} enables the organization of the mass scale by associating particle states with residue class designations. With the assumption of perfect flatness (Ωtotal = 1.0), this approach leads to the derivation of a cosmic seesaw congruence which unifies the concepts of space and mass. The law of quadratic reciprocity

YANG DAI; ALEXEY B. BORISOV; JAMES W. LONGWORTH; KEITH BOYER; CHARLES K. RHODES

2001-01-01

302

High-order approximation of conic sections by quadratic splines  

Microsoft Academic Search

Given a segment of a conic section in the form of a rational Bezier curve, a quadratic spline approximation is constructed and an explicit error bound is derived. The convergence order of the error bound is shown to be O(h4) which is optimal, and the spline curve is both C1 and G2. The approximation method is very efficient as it

Michael Floater

1995-01-01

303

Quadratic thermal terms in the deconfined phase from holography  

E-print Network

Recent lattice simulation has uncovered many interesting properties of SU(N) gauge theory at finite temperature. Especially, above the deconfinement phase transition all the thermodynamics quantities acquire significant quadratic contributions in inverse temperature. Such a term is also found to dominate the logarithmic of the renormalized Polyakov loop. Using the Hawking-Page transition in Anti-de Sitter space as an example, we show how such contributions can be naturally generated in the holographic approach.

Zuo, Fen

2014-01-01

304

Quadratic thermal terms in the deconfined phase from holography  

E-print Network

Recent lattice simulation has uncovered many interesting properties of SU(N) gauge theory at finite temperature. Especially, above the deconfinement phase transition all the thermodynamics quantities acquire significant quadratic contributions in inverse temperature. Such a term is also found to dominate the logarithmic of the renormalized Polyakov loop. Using the Hawking-Page transition in Anti-de Sitter space as an example, we show how such contributions can be naturally generated in the holographic approach.

Fen Zuo; Yi-Hong Gao

2014-03-10

305

Quadratic Volume-Preserving Maps: Invariant Circles and Bifurcations  

E-print Network

We study the dynamics of the five-parameter quadratic family of volume-preserving diffeomorphisms of R^3. This family is the unfolded normal form for a bifurcation of a fixed point with a triple-one multiplier and also is the general form of a quadratic three-dimensional map with a quadratic inverse. Much of the nontrivial dynamics of this map occurs when its two fixed points are saddle-foci with intersecting two-dimensional stable and unstable manifolds that bound a spherical ``vortex-bubble''. We show that this occurs near a saddle-center-Neimark-Sacker (SCNS) bifurcation that also creates, at least in its normal form, an elliptic invariant circle. We develop a simple algorithm to accurately compute these elliptic invariant circles and their longitudinal and transverse rotation numbers and use it to study their bifurcations, classifying them by the resonances between the rotation numbers. In particular, rational values of the longitudinal rotation number are shown to give rise to a string of pearls that creates multiple copies of the original spherical structure for an iterate of the map.

Holger R. Dullin; James D. Meiss

2008-07-04

306

Quadratic constrained mixed discrete optimization with an adiabatic quantum optimizer  

E-print Network

We extend the family of problems that may be implemented on an adiabatic quantum optimizer (AQO). When a quadratic optimization problem has at least one set of discrete controls and the constraints are linear, we call this a quadratic constrained mixed discrete optimization (QCMDO) problem. QCMDO problems are NP-hard, and no efficient classical algorithm for their solution is known. Included in the class of QCMDO problems are combinatorial optimization problems constrained by a linear partial differential equation (PDE) or system of linear PDEs. An essential complication commonly encountered in solving this type of problem is that the linear constraint may introduce many intermediate continuous variables into the optimization while the computational cost grows exponentially with problem size. We resolve this difficulty by developing a constructive mapping from QCMDO to quadratic unconstrained binary optimization (QUBO) such that the size of the QUBO problem depends only on the number of discrete control variables. With a suitable embedding, taking into account the physical constraints of the realizable coupling graph, the resulting QUBO problem can be implemented on an existing AQO. The mapping itself is efficient, scaling cubically with the number of continuous variables in the general case and linearly in the PDE case if an efficient preconditioner is available.

Rishabh Chandra; N. Tobias Jacobson; Jonathan E. Moussa; Steven H. Frankel; Sabre Kais

2013-10-07

307

Revisiting the naturalness problem: Who is afraid of quadratic divergences?  

NASA Astrophysics Data System (ADS)

It is widely believed that quadratic divergences severely restrict natural constructions of particle physics models beyond the standard model (SM). Supersymmetry provides a beautiful solution, but the recent LHC experiments have excluded large parameter regions of supersymmetric extensions of the SM. It will now be important to reconsider whether we have been misinterpreting the quadratic divergences in field theories. In this paper, we revisit the problem from the viewpoint of the Wilsonian renormalization group and argue that quadratic divergences—which can always be absorbed into a position of the critical surface—should be simply subtracted in model constructions. Such a picture gives another justification to the argument [W. A. Bardeen, Report No. FERMILAB-CONF-95-391-T] that the scale invariance of the SM, except for the soft-breaking terms, is an alternative solution to the naturalness problem. It also largely broadens possibilities of model constructions beyond the SM since we just need to take care of logarithmic divergences, which cause mixings of various physical scales and runnings of couplings.

Aoki, Hajime; Iso, Satoshi

2012-07-01

308

Released Plasmonic Electric Field of Ultrathin Tetrahedral-Amorphous-Carbon Films Coated Ag Nanoparticles for SERS  

NASA Astrophysics Data System (ADS)

We have demonstrated the plasmonic characteristics of an ultrathin tetrahedral amorphous carbon (ta-C) film coated with Ag nanoparticles. The simulation result shows that, under resonant and non-resonant excitations, the strongest plasmonic electric field of 1 nm ta-C coated Ag nanoparticle is not trapped within the ta-C layer but is released to its outside surface, while leaving the weaker electric field inside ta-C layer. Moreover, this outside plasmonic field shows higher intensity than that of uncoated Ag nanoparticle, which is closely dependent on the excitation wavelength and size of Ag particles. These observations are supported by the SERS measurements. We expect that the ability for ultrathin ta-C coated Ag nanoparticles as the SERS substrates to detect low concentrations of target biomolecules opens the door to the applications where it can be used as a detection tool for integrated, on-chip devices.

Liu, Fanxin; Tang, Chaojun; Zhan, Peng; Chen, Zhuo; Ma, Hongtao; Wang, Zhenlin

2014-03-01

309

Released Plasmonic Electric Field of Ultrathin Tetrahedral-Amorphous-Carbon Films Coated Ag Nanoparticles for SERS  

PubMed Central

We have demonstrated the plasmonic characteristics of an ultrathin tetrahedral amorphous carbon (ta-C) film coated with Ag nanoparticles. The simulation result shows that, under resonant and non-resonant excitations, the strongest plasmonic electric field of 1?nm ta-C coated Ag nanoparticle is not trapped within the ta-C layer but is released to its outside surface, while leaving the weaker electric field inside ta-C layer. Moreover, this outside plasmonic field shows higher intensity than that of uncoated Ag nanoparticle, which is closely dependent on the excitation wavelength and size of Ag particles. These observations are supported by the SERS measurements. We expect that the ability for ultrathin ta-C coated Ag nanoparticles as the SERS substrates to detect low concentrations of target biomolecules opens the door to the applications where it can be used as a detection tool for integrated, on-chip devices. PMID:24675437

Liu, Fanxin; Tang, Chaojun; Zhan, Peng; Chen, Zhuo; Ma, Hongtao; Wang, Zhenlin

2014-01-01

310

"Crystal-clear" liquid-liquid transition in a tetrahedral fluid.  

PubMed

For a model known to exhibit liquid-liquid transitions, we examine how varying the bond orientational flexibility affects the stability of the liquid-liquid transition relative to that of the crystal phases. For very rigidly oriented bonds, the crystal is favored over all amorphous phase transitions. We find that increasing the bond flexibility decreases both the critical temperature Tc for liquid-liquid phase separation and the melting temperature Tm. The effect of increasing flexibility is much stronger for melting, so that the distance between Tc and Tm progressively reduces and inverts sign. Under these conditions, a "naked" liquid-liquid critical point bulges out in the liquid phase and becomes accessible, without the possibility of crystallization. These results confirm that a crystal-clear, liquid-liquid transition can occur as a genuine, thermodynamically stable phenomenon for tetrahedral coordinated particles with flexible bond orientation, but that such a transition is hidden by crystallization when bonds are highly directional. PMID:25349962

Starr, Francis W; Sciortino, Francesco

2014-12-21

311

Self-assembly of tetrahedral CdSe nanocrystals: effective "patchiness" via anisotropic steric interaction.  

PubMed

Controlling the spontaneous organization of nanoscale objects remains a fundamental challenge of materials design. Here we present the first characterization of self-assembled superlattices (SLs) comprised of tetrahedral nanocrystal (NCs). We observe self-assembly of CdSe nanotetrahedra into an open structure (estimated space-filling fraction ? ? 0.59) which has not been anticipated by many recent theoretical studies and simulations of tetrahedron packings. This finding highlights a gap in the understanding of the hierarchy of energy scales acting on colloidal NCs during self-assembly. We propose a strong dependence of ligand-ligand interaction potential on NC surface curvature. This effect favors spatial proximity of vertices in the dense colloidal crystal and may be considered an emergent "patchiness" acting through chemically identical ligand molecules. PMID:24655011

Boles, Michael A; Talapin, Dmitri V

2014-04-23

312

Comparative morphology of configurations with reduced part count derived from the octahedral-tetrahedral truss  

NASA Technical Reports Server (NTRS)

Morphology (the study of structure and form) of the octahedral-tetrahedral (octet) truss is described. Both the geometry and symmetry of the octet truss are considered. Morphological techniques based on symmetry operations are presented which enable the derivation of reduced-part-count truss configurations from the octet truss by removing struts and nodes. These techniques are unique because their Morphological origination and they allow for the systematic generation and analysis of a large variety of structures. Methods for easily determining the part count and redundancy of infinite truss configurations are presented. Nine examples of truss configurations obtained by applying the derivation techniques are considered. These configurations are structurally stable while at the same time exhibiting significant reductions in part count. Some practical and analytical considerations, such as structural performance, regarding the example reduced-part-count truss geometries are briefly discussed.

Lalvani, Haresh; Collins, Timothy J.

1991-01-01

313

FRET lasing from self-assembled DNA tetrahedral nanostructures suspended in optofluidic droplet resonators  

NASA Astrophysics Data System (ADS)

We demonstrate Förster resonance energy transfer (FRET) lasing from self-assembled tetrahedral DNA complexes labeled with Cy3 and Cy5 dyes and suspended as a gain medium in aqueous microdroplet cavities deposited on a superhydrophobic surface. Threshold fluence and differential efficiency are characterized for DNA complexes containing 1Cy3-3Cy5 and 3Cy3-1Cy5. We demonstrate that at a constant Cy5 concentration, average threshold fluence is reduced 3 to 8 times and average differential efficiency is enhanced 6 to 30 times for 3Cy3-1Cy5 as compared to 1Cy3-3Cy5. Using 3Cy3-1Cy5 nanostructures, FRET lasing is observed at very low concentrations down to ˜ 1 ?M. This work shows that optofluidic microlasers based on droplet resonators can be combined with DNA nanotechnology to explore applications in bio/chemical sensing and novel photonic devices.

Aas, M.; Özelci, E.; Jonáš, A.; Kiraz, A.; Liu, H.; Fan, C.; Chen, Q.; Fan, X.

2014-09-01

314

First-principles calculation of vibrational Raman spectra of tetrahedral amorphous carbon  

NASA Astrophysics Data System (ADS)

The nonresonant vibrational Raman spectra of tetrahedral amorphous carbon are calculated from first principles. The structural model was generated using Car-Parinello molecular dynamics, the vibrational modes are determined using the linear response approach and Raman tensors are calculated using the finite electric field method. Our theoretical visible and reduced Raman spectra show an overall good agreement with experimental spectra, and better than previous calculated results. The analysis in terms of atomic vibrations shows that the Raman spectrum mainly comes from sp 2 contribution, G peak is due to the stretching vibration of any pair of sp 2 atoms and only a small sp 3 contribution can be noticed. The differences between peak intensities of reduced theoretical and experimental results mainly come from defects and the high sp 3 content in our simulated structure.

Niu, Li; Zhu, Jiaqi; Gao, Wei; Liu, Aiping; Han, Xiao; Du, Shanyi

2008-10-01

315

Non-Axial Octupole Deformations and Tetrahedral Symmetry in Heavy Nuclei  

NASA Astrophysics Data System (ADS)

The total energies of about 120 nuclei in the Thorium region have been calculated within the macroscopic-microscopic method in the 5-dimensional space of deformation parameters ?20, ?22, ?30, ?32 and ?40. The macroscopic energy term contains the nuclear surface-curvature dependence as proposed within the LSD approach. The microscopic energies are calculated with the Woods-Saxon single particle potential employing the universal set of parameters. We study a possible presence of the octupole axial and non-axial degrees of freedom all-over in the (?, ?)-plane focussing on the ground-states, secondary minima and in the saddle points. In fact, a competition between axial and tri-axial octupole deformation parameters is obtained at the saddle points and in the secondary minima for many isotones with N > 136. The presence of the tetrahedral symmetry minima is predicted in numerous nuclei in the discussed region, although most of the time at relatively high excitation energies.

Mazurek, Katarzyna; Dudek, Jerzy

2005-11-01

316

Near-field supersonic flow predictions by an adaptive unstructured tetrahedral grid solver  

NASA Technical Reports Server (NTRS)

Applicability of a three-dimensional solution adaptive unstructured tetrahedral Euler flow solver about generic models for near-field sonic boom pressure signature predictions is evaluated. Comparisons of computational and experimental data demonstrates the capability of the method for predicting inviscid solutions useful for high speed calculations about simple 3-D geometries. The approach has promising features and results indicate potential for application to more complex configurations. The mesh generation is based on the advancing front technique, and steady state solutions of the Euler equations are achieved by explicit time integration. Spatial discretization uses the Taylor-Galerkin approach; an alternate time integration, based on the Runge-Kutta method, is also included. The solution-adaptive grid procedure is based on either remeshing or mesh refinement techniques. An alternative geometry-adaptive grid procedure has also been incorporated.

Djomehri, M. J.; Erickson, Larry L.

1993-01-01

317

Upwind scheme for solving the Euler equations on unstructured tetrahedral meshes  

NASA Technical Reports Server (NTRS)

An upwind scheme is presented for solving the three-dimensional Euler equations on unstructured tetrahedral meshes. Spatial discretization is accomplished by a cell-centered finite-volume formulation using flux-difference splitting. Higher-order differences are formed by a multidimensional linear reconstruction process. The solution gradients required for the higher-order differenes are computed by a novel approach that yields highly resolved solutions in regions of smooth flow while avoiding oscillations across shocks without explicitly applying a limiter. Solutions are advanced in time by a three-stage Runge-Kutta time-stepping scheme with convergence accelerated to steady state by local time stepping and implicit residual smoothing. Transonic solutions are presented for two meshes around the ONERA M6 wing and demonstrate substantial accuracy and insensitivity to mesh size.

Frink, Neal T.

1992-01-01

318

Epitaxially stabilized iridium spinel oxide without cations in the tetrahedral site  

NASA Astrophysics Data System (ADS)

Single-crystalline thin film of an iridium dioxide polymorph Ir2O4 has been fabricated by the pulsed laser deposition of LixIr2O4 precursor and the subsequent Li-deintercalation using soft chemistry. Ir2O4 crystallizes in a spinel (AB2O4) without A cations in the tetrahedral site, which is isostructural to ?-MnO2. Ir ions form a pyrochlore sublattice, which is known to give rise to a strong geometrical frustration. This Ir spinel was found to be a narrow gap insulator, in remarkable contrast to the metallic ground state of rutile-type IrO2. We argue that an interplay of a strong spin-orbit coupling and a Coulomb repulsion gives rise to an insulating ground state as in a layered perovskite Sr2IrO4.

Kuriyama, Hiromichi; Matsuno, Jobu; Niitaka, Seiji; Uchida, Masaya; Hashizume, Daisuke; Nakao, Aiko; Sugimoto, Kunihisa; Ohsumi, Hiroyuki; Takata, Masaki; Takagi, Hidenori

2010-05-01

319

Conversion of Osculating Orbital Elements to Mean Orbital Elements  

NASA Technical Reports Server (NTRS)

Orbit determination and ephemeris generation or prediction over relatively long elapsed times can be accomplished with mean elements. The most simple and efficient method for orbit determination, which is also known as epoch point conversion, performs the conversion of osculating elements to mean elements by iterative procedures. Previous epoch point conversion methods are restricted to shorter elapsed times with linear convergence. The new method presented in this paper calculates an analytic initial guess of the unknown mean elements from a first order theory of secular perturbations and computes a transition matrix with accurate numerical partials. It thereby eliminates the problem of an inaccurate initial guess and an identity transition matrix employed by previous methods. With a good initial guess of the unknown mean elements and an accurate transition matrix, converging osculating elements to mean elements can be accomplished over long elapsed times with quadratic convergence.

Der, Gim J.; Danchick, Roy

1996-01-01

320

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method.  

PubMed

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated. PMID:20736496

Pereira, N F; Sitek, A

2010-09-21

321

Microstructure and tribological performance of self-lubricating diamond/tetrahedral amorphous carbon composite film  

NASA Astrophysics Data System (ADS)

In order to smooth the rough surface and further improve the wear-resistance of coarse chemical vapor deposition diamond films, diamond/tetrahedral amorphous carbon composite films were synthesized by a two-step preparation technique including hot-filament chemical vapor deposition for polycrystalline diamond (PCD) and subsequent filtered cathodic vacuum arc growth for tetrahedral amorphous carbon (ta-C). The microstructure and tribological performance of the composite films were investigated by means of various characterization techniques. The results indicated that the composite films consisted of a thick well-grained diamond base layer with a thickness up to 150 ?m and a thin covering ta-C layer with a thickness of about 0.3 ?m, and sp3-C fraction up to 73.93%. Deposition of a smooth ta-C film on coarse polycrystalline diamond films was proved to be an effective tool to lower the surface roughness of the polycrystalline diamond film. The wear-resistance of the diamond film was also enhanced by the self-lubricating effect of the covering ta-C film due to graphitic phase transformation. Under dry pin-on-disk wear test against Si3N4 ball, the friction coefficients of the composite films were much lower than that of the single PCD film. An extremely low friction coefficient (?0.05) was achieved for the PCD/ta-C composite film. Moreover, the addition of Ti interlayer between the ta-C and the PCD layers can further reduce the surface roughness of the composite film. The main wear mechanism of the composite films was abrasive wear.

Chen, Xinchun; Peng, Zhijian; Yu, Xiang; Fu, Zhiqiang; Yue, Wen; Wang, Chengbiao

2011-02-01

322

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method  

PubMed Central

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated. PMID:20736496

Pereira, N F; Sitek, A

2011-01-01

323

EUROGRAPHICS 2005 / J. Dingliana and F. Ganovelli Short Presentations Efficient, physically plausible finite elements  

E-print Network

to recompute the strain-displacement matrix of each element at each time step to avoid ghost torques. Based tetrahedrized viscoelastic solids. Background can be found in standard texts [ZC67]. The force applied "ghost forces" which make the element artificially in- flate. A possible approach to solve this problem

Payan, Yohan

324

A correlation between solid solubility and tetrahedral radius of III, IV and V group impurities in silicon  

Microsoft Academic Search

The strain entropy of substitutional Group III, IV and V impurities in silicon has been calculated from the experimental solid solubility taking into account the electronic, vibrational and polarization contributions. A correlation between differences of tetrahedral radii and strain entropy is found.Silicon is perhaps the most studied substance after water. In spite of this, there is, at present, no unified

P. Cappelletti; G. F. Cerofolini; G. U. Pignatel

1982-01-01

325

Defect density and atomic bond structure of tetrahedral amorphous carbon (taC) films prepared by filtered vacuum arc process  

Microsoft Academic Search

Defect density of tetrahedral amorphous carbon (ta-C) film prepared by filtered vacuum arc process was investigated in a wide range of fraction of sp3 hybridized bond. We could observe a close relationship between unpaired spin density measured by electron spin resonance spectroscopy and their atomic bond structure: the defect density was proportional to the content of sp3 hybridized bond in

Churl Seung Lee; Jin-Koog Shin; Kwang Yong Eun; Kwang-Ryeol Lee; Ki Hyun Yoon

2004-01-01

326

Generation of 2D and 3D (PtS, Adamantanoid) Nets with a Flexible Tetrahedral Building Block  

SciTech Connect

The self-assembly of a flexible tetrahedral linker tetrakis[4-(carboxyphenyl)oxamethyl]methane acid with various transition metals (Cu, Co and Mg) results in a 2D layered structure and 3D frameworks with PtS and adamantanoid topology. The PtS net exhibits permanent porosity as confirmed by BET and gas adsorption experiments.

Tian, Jian; Motkuri, Radha K.; Thallapally, Praveen K.

2010-09-01

327

Electronic Transitions as a Probe of Tetrahedral versus Octahedral Coordination in Nickel(II) Complexes: An Undergraduate Inorganic Chemistry Experiment.  

ERIC Educational Resources Information Center

Discusses procedures, theoretical considerations, and results of an experiment involving the preparation of a tetrahedral nickel(II) complex and its transformation into an octahedral species. Suggests that fundamental aspects of coordination chemistry can be demonstrated by simple experiments performed in introductory level courses. (Author/JN)

Filgueiras, Carlos A. L.; Carazza, Fernando

1980-01-01

328

Optimization of structures to satisfy a flutter velocity constraint by use of quadratic equation fitting. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Using the first and the second derivative of flutter velocity with respect to the parameters, the velocity hypersurface is made quadratic. This greatly simplifies the numerical procedure developed for determining the values of the design parameters such that a specified flutter velocity constraint is satisfied and the total structural mass is near a relative minimum. A search procedure is presented utilizing two gradient search methods and a gradient projection method. The procedure is applied to the design of a box beam, using finite-element representation. The results indicate that the procedure developed yields substantial design improvement satisfying the specified constraint and does converge to near a local optimum.

Motiwalla, S. K.

1973-01-01

329

Creepers: Real quadratic orders with large class number  

NASA Astrophysics Data System (ADS)

Shanks's sequence of quadratic fields Q(sqrt{S_{n}}) where S_{n}=(2^n+1)^2 + 2^{n+2} instances a class of quadratic fields for which the class number is large and, therefore, the continued fraction period is relatively short. Indeed, that period length increases linearly with n, that is: in arithmetic progression. The fields have regulator O(n^2). In the late nineties, these matters intrigued Irving Kaplansky, and led him to compute period length of the square root of sequences a^2x^{2n}+bx^{n}+c for integers a, b, c, and x. In brief, Kap found unsurprisingly that, generically, triples (a,b,c) are `leapers': they yield sequences with period length increasing at exponential rate. But there are triples yielding sequences with constant period length, Kap's `sleepers'. Finally, there are triples, as exemplified by the Shanks's sequence, for which the period lengths increase in arithmetic progression. Felicitously, Kaplansky called these `creepers'. It seems that the sleepers and creepers are precisely those for which one is able to detail the explicit continued fraction expansion for all n. Inter alia, this thesis noticeably extends the known classes of creepers and finds that not all are `kreepers' (of the shape identified by Kaplansky) and therefore not of the shape of examples studied by earlier authors looking for families of quadratic number fields with explicitly computable unit and of relatively large regulator. The work of this thesis includes the discovery of old and new families of hyperelliptic curves of increasing genus g and torsion divisor of order O(g^2). It follows that the apparent trichotomy leaper/sleeper/creeper coincides with the folk belief that the just-mentioned torsion is maximum possible.

Patterson, Roger

2007-03-01

330

Neural network for solving convex quadratic bilevel programming problems.  

PubMed

In this paper, using the idea of successive approximation, we propose a neural network to solve convex quadratic bilevel programming problems (CQBPPs), which is modeled by a nonautonomous differential inclusion. Different from the existing neural network for CQBPP, the model has the least number of state variables and simple structure. Based on the theory of nonsmooth analysis, differential inclusions and Lyapunov-like method, the limit equilibrium points sequence of the proposed neural networks can approximately converge to an optimal solution of CQBPP under certain conditions. Finally, simulation results on two numerical examples and the portfolio selection problem show the effectiveness and performance of the proposed neural network. PMID:24333480

He, Xing; Li, Chuandong; Huang, Tingwen; Li, Chaojie

2014-03-01

331

Deterministic macroscopic quantum superpositions of motion via quadratic optomechanical coupling  

E-print Network

We propose a scheme to prepare macroscopic quantum superpositions of motion in optomachanical nano- or micromechanical oscillators quadratically coupled to an intracavity field. The nonlinear optomechanical coupling leads to an effective degenerate three-wave mixing interaction between the mechanical and cavity modes. The quantum superpositions result from the combined effects of the interaction and cavity dissipation. We show analytically and confirm numerically that various deterministic quantum superpositions can be achieved, depending on initial mechanical state. The effect of mechanical damping is also studied in detail via the negativity of the Wigner function. The present scheme can be realized in various optomechanical systems with current technology.

Huatang Tan; F. Bariani; Gaoxiang Li; P. Meystre

2013-02-28

332

Rocket ascent trajectory optimization via recursive quadratic programming  

NASA Astrophysics Data System (ADS)

An algorithm for solving parameterized optimal control problems such as the ascent trajectory optimization problem of a multistage launch vehicle is developed. The implementation of this algorithm, designated as the Recursive Quadratic Programming Approach, for the pitch and yaw optimization of a multistage launch vehicle is discussed, and results are given for injection into a polar orbit from the Indian launch site where in order to satisfy safety conditions curved ascent trajectories are necessary. It is concluded that the algorithm provides relatively fast optimization, is easy to implement, and has a large convergence region.

Well, K. H.; Tandon, S. R.

1982-06-01

333

Negative-frequency dispersive wave generation in quadratic media  

NASA Astrophysics Data System (ADS)

We show that the extremely blueshifted dispersive wave emitted in Kerr media owing to the coupling with the negative-frequency branch [E. Rubino , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.253901 108, 253901 (2012)] can be observed in quadratic media via second-harmonic generation. Not only is such a phenomenon thus independent of the specific nonlinear mechanism, but it is shown to occur regardless of the fact that the process is pumped by a pulse which exhibits soliton-like features or vice versa undergoes wave breaking. A simple unified formula gives the frequencies of the emitted dispersive waves in both cases.

Conforti, Matteo; Westerberg, Niclas; Baronio, Fabio; Trillo, Stefano; Faccio, Daniele

2013-07-01

334

Strange Quark Star Model with Quadratic Equation of State  

E-print Network

In this paper, we studied the behaviour of compact relativistic objects with anisotropic matter distribution considering quadratic equation of state of Feroze and Siddiqui (2011). We specify the gravitational potential Z(x) in order to integrate the fields equations and there has been calculated the energy density, the radial pressure, the anisotropy and the mass function. The new solutions to the Einstein-Maxwell system of equations are found in term of elementary functions. For n=2, we have obtained the expressions for mass function, energy density, radius and metric functions of the model of Thirukkanesh and Ragel (2012) with polytropic equation of state.

Manuel Malaver

2014-07-03

335

Analysis of electroperforated materials using the quadrat counts method  

NASA Astrophysics Data System (ADS)

The electroperforation distribution in thin porous materials is investigated using the quadrat counts method (QCM), a classical statistical technique aimed to evaluate the deviation from complete spatial randomness (CSR). Perforations are created by means of electrical discharges generated by needle-like tungsten electrodes. The objective of perforating a thin porous material is to enhance its air permeability, a critical issue in many industrial applications involving paper, plastics, textiles, etc. Using image analysis techniques and specialized statistical software it is shown that the perforation locations follow, beyond a certain length scale, a homogeneous 2D Poisson distribution.

Miranda, E.; Garzón, C.; Martínez-Cisneros, C.; Alonso, J.; García-García, J.

2011-06-01

336

Rigorous performance bounds for quadratic and nested dynamical decoupling  

SciTech Connect

We present rigorous performance bounds for the quadratic dynamical decoupling pulse sequence which protects a qubit from general decoherence, and for its nested generalization to an arbitrary number of qubits. Our bounds apply under the assumptions of instantaneous pulses and of bounded perturbing environment and qubit-environment Hamiltonians such as those realized by baths of nuclear spins in quantum dots. We prove that if the total sequence time is fixed then the trace-norm distance between the unperturbed and protected system states can be made arbitrarily small by increasing the number of applied pulses.

Xia, Yuhou; Uhrig, Goetz S.; Lidar, Daniel A. [Department of Mathematics and Department of Physics, Haverford College, Haverford, Pennsylvania 19041 (United States); Lehrstuhl fuer Theoretische Physik I, Technische Universitaet Dortmund, Otto-Hahn Strasse 4, D-44221 Dortmund (Germany); Department of Electrical Engineering, Department of Chemistry, and Department of Physics, Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States)

2011-12-15

337

A-REI A Linear and Quadratic System  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Consider the linear and quadratic functions appearing in the figure below. What are the coordinates of the point Q? Show step-by-step algebra work. Wha...

338

The quadratic phase factor of tightly focused wavefronts  

NASA Astrophysics Data System (ADS)

The phase structure is investigated at the focal plane of an aplanatic, high numerical aperture focusing optical system. The tightly focused field is numerically evaluated using combination of the Richards-Wolf approach and the Stratton-Chu diffraction integral. An investigation is performed for both 2D and 3D geometries for a number of different illumination structures, having piecewise quasi-constant phase at the entrance pupil and different polarization states. For the investigated illumination structures, the quadratic phase term of the focused field was found to depend on the structure of the incident illumination contrary to the paraxial case where it depends solely on the optical system parameters.

Normatov, Alexander; Spektor, Boris; Shamir, Joseph

2010-10-01

339

Relativistic Stellar Model Admitting a Quadratic Equation of State  

NASA Astrophysics Data System (ADS)

A class of solutions describing the interior of a static spherically symmetric compact anisotropic star is reported. The analytic solution has been obtained by utilizing the Finch and Skea [Class. Quantum Grav.6 (1989) 467] ansatz for the metric potential grr which has a clear geometric interpretation for the associated background spacetime. Based on physical grounds, appropriate bounds on the model parameters have been obtained and it has been shown that the model admits an equation of state (EOS) which is quadratic in nature.

Sharma, R.; Ratanpal, B. S.

2013-11-01

340

Rolling element bearing diagnosis using convex hull  

Microsoft Academic Search

In this paper, we compare traditional classifiers, such as Linear and Quadratic Discriminant Classifiers and neural networks, with a one-class classifier, namely, convex hull. With reference to rolling element bearing diagnosis, we show that convex hull outperforms traditional classifiers in the classification of faults and different levels of fault severity not known during the training phase.

Sara Lioba Volpi; Marco Cococcioni; Beatrice Lazzerini; Dan Stefanescu

2010-01-01

341

EVA assembly of large space structure element  

NASA Technical Reports Server (NTRS)

The results of a test program to assess the potential of manned extravehicular activity (EVA) assembly of erectable space trusses are described. Seventeen tests were conducted in which six "space-weight" columns were assembled into a regular tetrahedral cell by a team of two "space"-suited test subjects. This cell represents the fundamental "element" of a tetrahedral truss structure. The tests were conducted under simulated zero-gravity conditions. Both manual and simulated remote manipulator system modes were evaluated. Articulation limits of the pressure suit and zero gravity could be accommodated by work stations with foot restraints. The results of this study have confirmed that astronaut EVA assembly of large, erectable space structures is well within man's capabilities.

Bement, L. J.; Bush, H. G.; Heard, W. L., Jr.; Stokes, J. W., Jr.

1981-01-01

342

Cr1/3Zr2P3O12 with unusual tetrahedral coordination of Cr(iii): peculiarities of the formation, thermal stability and application as a pigment.  

PubMed

All the known chromium(iii) NASICON-related phosphates are considered to be solid solutions. In these compounds chromium atoms share their position in the basic framework of the crystal lattice with other structure forming elements such as zirconium. In our study, we have hypothesised a completely new way of structural organisation of the chromium(iii) zirconium(iv) NASICON framework, consisting in the distribution of chromium over the charge-compensating atom sites with tetrahedral oxygen coordination. The possibility of formation of the corresponding phosphate, Cr1/3Zr2P3O12, was studied using a classical ceramic route and a sol-gel method. Structural affiliation of the obtained pure phase product was studied using XRD analysis. The results confirmed that the Cr1/3Zr2P3O12 phosphate belongs to monoclinic SW-subtype of the NASICON family. In this structure, chromium atoms occupy charge-compensating sites with a strongly distorted tetrahedral oxygen environment. To the best of our knowledge, it is the first example of tetrahedral coordination of chromium(iii) in phosphates. Along with the unusual crystallographic characteristics of chromium, special attention in this paper is devoted to the thermal stability of this phosphate and to its performance as an inorganic pigment. The sample was characterised by heating microscopy and DTA study, particle size distribution analysis, and IR- and VIS-spectroscopy. The stability of the obtained powder in a glaze environment, its colouring performance and lightfastness are discussed as well. PMID:25189199

Gorodylova, Nataliia; Kosinová, Veronika; Sulcová, Petra; B?lina, Petr; Vl?ek, Milan

2014-09-30

343

Quadratic Reciprocity and the Group Orders of Particle States  

SciTech Connect

The construction of inverse states in a finite field F{sub P{sub P{alpha}}} enables the organization of the mass scale by associating particle states with residue class designations. With the assumption of perfect flatness ({Omega}total = 1.0), this approach leads to the derivation of a cosmic seesaw congruence which unifies the concepts of space and mass. The law of quadratic reciprocity profoundly constrains the subgroup structure of the multiplicative group of units F{sub P{sub {alpha}}}* defined by the field. Four specific outcomes of this organization are (1) a reduction in the computational complexity of the mass state distribution by a factor of {approximately}10{sup 30}, (2) the extension of the genetic divisor concept to the classification of subgroup orders, (3) the derivation of a simple numerical test for any prospective mass number based on the order of the integer, and (4) the identification of direct biological analogies to taxonomy and regulatory networks characteristic of cellular metabolism, tumor suppression, immunology, and evolution. It is generally concluded that the organizing principle legislated by the alliance of quadratic reciprocity with the cosmic seesaw creates a universal optimized structure that functions in the regulation of a broad range of complex phenomena.

DAI,YANG; BORISOV,ALEXEY B.; LONGWORTH,JAMES W.; BOYER,KEITH; RHODES,CHARLES K.

2001-06-01

344

Linear-Quadratic-Gaussian Regulator Developed for a Magnetic Bearing  

NASA Technical Reports Server (NTRS)

Linear-Quadratic-Gaussian (LQG) control is a modern state-space technique for designing optimal dynamic regulators. It enables us to trade off regulation performance and control effort, and to take into account process and measurement noise. The Structural Mechanics and Dynamics Branch at the NASA Glenn Research Center has developed an LQG control for a fault-tolerant magnetic bearing suspension rig to optimize system performance and to reduce the sensor and processing noise. The LQG regulator consists of an optimal state-feedback gain and a Kalman state estimator. The first design step is to seek a state-feedback law that minimizes the cost function of regulation performance, which is measured by a quadratic performance criterion with user-specified weighting matrices, and to define the tradeoff between regulation performance and control effort. The next design step is to derive a state estimator using a Kalman filter because the optimal state feedback cannot be implemented without full state measurement. Since the Kalman filter is an optimal estimator when dealing with Gaussian white noise, it minimizes the asymptotic covariance of the estimation error.

Choi, Benjamin B.

2002-01-01

345

Confidence set inference with a prior quadratic bound  

NASA Technical Reports Server (NTRS)

In the uniqueness part of a geophysical inverse problem, the observer wants to predict all likely values of P unknown numerical properties z=(z sub 1,...,z sub p) of the earth from measurement of D other numerical properties y (sup 0) = (y (sub 1) (sup 0), ..., y (sub D (sup 0)), using full or partial knowledge of the statistical distribution of the random errors in y (sup 0). The data space Y containing y(sup 0) is D-dimensional, so when the model space X is infinite-dimensional the linear uniqueness problem usually is insoluble without prior information about the correct earth model x. If that information is a quadratic bound on x, Bayesian inference (BI) and stochastic inversion (SI) inject spurious structure into x, implied by neither the data nor the quadratic bound. Confidence set inference (CSI) provides an alternative inversion technique free of this objection. Confidence set inference is illustrated in the problem of estimating the geomagnetic field B at the core-mantle boundary (CMB) from components of B measured on or above the earth's surface.

Backus, George E.

1989-01-01

346

An Instability Index Theory for Quadratic Pencils and Applications  

NASA Astrophysics Data System (ADS)

Primarily motivated by the stability analysis of nonlinear waves in second-order in time Hamiltonian systems, in this paper we develop an instability index theory for quadratic operator pencils acting on a Hilbert space. In an extension of the known theory for linear pencils, explicit connections are made between the number of eigenvalues of a given quadratic operator pencil with positive real parts to spectral information about the individual operators comprising the coefficients of the spectral parameter in the pencil. As an application, we apply the general theory developed here to yield spectral and nonlinear stability/instability results for abstract second-order in time wave equations. More specifically, we consider the problem of the existence and stability of spatially periodic waves for the "good" Boussinesq equation. In the analysis our instability index theory provides an explicit, and somewhat surprising, connection between the stability of a given periodic traveling wave solution of the "good" Boussinesq equation and the stability of the same periodic profile, but with different wavespeed, in the nonlinear dynamics of a related generalized Korteweg-de Vries equation.

Bronski, Jared; Johnson, Mathew A.; Kapitula, Todd

2014-04-01

347

Chiral and achiral imidazole-linked tetrahedral zinc phosphonate frameworks with photoluminescent properties.  

PubMed

Presented here are three imidazole-linked tetrahedral zinc phosphonate frameworks based on a special ligand 2-(1-imidazole)-1-hydroxyl-1,1'-ethylidenediphosphonic acid (= ImhedpH4) with both an organic imidazole linker and inorganic phosphonate groups. Three new compounds, namely, [Zn2(ImhedpH2)2(ox)](H2ppz) (1), Zn3(ImhedpH)2(H2O)4 (2) and [Zn3(Imhedp)2](H2ppz) (3) (ox = oxalate and ppz = piperazine), were obtained by hydrothermal synthesis and structurally characterized by single-crystal X-ray diffraction. Compound 1 shows a chain structure with the ox ligands linking the [Zn2(ImhedpH2)2] units, and the resulting chains are further connected to form a 3D structure through the strong N-H···O and O-H···O hydrogen bonds between the neighboring chains. Compound 2 displays an inorganic layer structure with dangling imidazole units, where these protonated imidazoles also act as pillars between adjacent inorganic layers. Compound 3 features an unusual chiral three-dimensional (3D) Zn-Imhedp framework with guest H2ppz(2+) cations. It can be topologically represented as a 4-connected qtz network. Furthermore, the luminescent properties of the three compounds were investigated in the solid state. PMID:24100382

Zhang, Xiu-Ling; Cheng, Kai; Wang, Fei; Zhang, Jian

2014-01-01

348

Simulation of pressure-driven phase transitions from tetrahedral crystal structures  

NASA Astrophysics Data System (ADS)

Pressure-driven transitions of ionic materials from the zinc-blende to rocksalt and ?-ZnCl2 to CdCl2 crystal structures are studied using constant-stress molecular dynamics with a polarizable-ion potential model. Both transformations are characterized by a change in cation coordination environment from tetrahedral to octahedral and are nonmartensitic. Transformation mechanisms are identified and characterized and similarities discussed. The blende to rocksalt transformation is observed to proceed via a diatomic ?-tin-like structure, though this is shown to be a transition state and not a true intermediate phase in this system. The relationship of the observed mechanisms to those deduced from experiments on halide systems is discussed. The development of displacive motion across the simulation cell is discussed. The ZnCl2 system is a layered structure, and while the coordination changes are highly cooperative within each layer, the overall transformation takes place on a layer-by-layer basis. In the blende, the interlayer correlations required to produce a grain-boundary-free final structure are associated with a shearing motion which propagates across the cell. These differences have characteristic effects on the kinetics of the transformations.

Wilson, Mark; Hutchinson, Francis; Madden, Paul A.

2002-03-01

349

Dynamics in a tetrahedral network glassformer: Vibrations, network rearrangements, and diffusion  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulation on a tetrahedral network glassformer using a model for viscous SiO2 by Coslovich and Pastore [J. Phys.: Condens. Matter 21, 285107 (2009)]. In this system, Si and O particles form a random network at low temperature T. We attach an ellipsoid to each particle to represent its time-averaged vibration tensor. We then examine the anisotropic vibrations of Si and O, where the ellipsoid orientations are correlated with the network. The ellipsoids exhibit marked vibrational heterogeneity. The configuration changes occur as breakage and reorganization of the network, where only one or two particles undergo large jumps at each rearrangement leading to diffusion. To the time-correlation functions, however, the particles surrounding these largely displaced ones yield significantly T-dependent contributions, resulting in a weak violation of the Stokes-Einstein relation. This crossover is mild in silica due to the small Si-O bond numbers per particle, while it is strong in fragile glassformers with large coordination numbers. On long timescales, jump events tend to occur in the same regions forming marked dynamic heterogeneity. We also calculate the diffusion constants and the viscosity. The diffusion obeys activation dynamics and may be studied by short-time analysis of irreversible jumps.

Kawasaki, Takeshi; Kim, Kang; Onuki, Akira

2014-05-01

350

Output-Adaptive Tetrahedral Cut-Cell Validation for Sonic Boom Prediction  

NASA Technical Reports Server (NTRS)

A cut-cell approach to Computational Fluid Dynamics (CFD) that utilizes the median dual of a tetrahedral background grid is described. The discrete adjoint is also calculated, which permits adaptation based on improving the calculation of a specified output (off-body pressure signature) in supersonic inviscid flow. These predicted signatures are compared to wind tunnel measurements on and off the configuration centerline 10 body lengths below the model to validate the method for sonic boom prediction. Accurate mid-field sonic boom pressure signatures are calculated with the Euler equations without the use of hybrid grid or signature propagation methods. Highly-refined, shock-aligned anisotropic grids were produced by this method from coarse isotropic grids created without prior knowledge of shock locations. A heuristic reconstruction limiter provided stable flow and adjoint solution schemes while producing similar signatures to Barth-Jespersen and Venkatakrishnan limiters. The use of cut-cells with an output-based adaptive scheme completely automated this accurate prediction capability after a triangular mesh is generated for the cut surface. This automation drastically reduces the manual intervention required by existing methods.

Park, Michael A.; Darmofal, David L.

2008-01-01

351

Insights into Substrate Specificity and Metal Activation of Mammalian Tetrahedral Aspartyl Aminopeptidase*  

PubMed Central

Aminopeptidases are key enzymes involved in the regulation of signaling peptide activity. Here, we present a detailed biochemical and structural analysis of an evolutionary highly conserved aspartyl aminopeptidase called DNPEP. We show that this peptidase can cleave multiple physiologically relevant substrates, including angiotensins, and thus may play a key role in regulating neuron function. Using a combination of x-ray crystallography, x-ray absorption spectroscopy, and single particle electron microscopy analysis, we provide the first detailed structural analysis of DNPEP. We show that this enzyme possesses a binuclear zinc-active site in which one of the zinc ions is readily exchangeable with other divalent cations such as manganese, which strongly stimulates the enzymatic activity of the protein. The plasticity of this metal-binding site suggests a mechanism for regulation of DNPEP activity. We also demonstrate that DNPEP assembles into a functionally relevant tetrahedral complex that restricts access of peptide substrates to the active site. These structural data allow rationalization of the enzyme's preference for short peptide substrates with N-terminal acidic residues. This study provides a structural basis for understanding the physiology and bioinorganic chemistry of DNPEP and other M18 family aminopeptidases. PMID:22356908

Chen, Yuanyuan; Farquhar, Erik R.; Chance, Mark R.; Palczewski, Krzysztof; Kiser, Philip D.

2012-01-01

352

Quantitative measure of tetrahedral-sp3 geometries in amorphous phase-change alloys  

NASA Astrophysics Data System (ADS)

Phase change or Ovonic memory technology has gained much interest in the past decade as a viable solution for the rapid increase in the demand for memory storage. This unique technology, first proposed by S. Ovshinsky in 1968, is based on storing information on the crystalline and amorphous phases of a material. The most common phase-change materials (PCMs) use chalcogenide alloys such as the Ge2Sb2Te5 (GST225). However, while the structure of its crystalline phase is relatively well characterized as consisting of a rhombohedrally distorted rock-salt lattice, the corresponding amorphous phase remains still poorly understood. Here, we show that Sn119 Mössbauer spectroscopy and angular constraint counting of simulated structures can provide a quantitative measure of the sp3 tetrahedral fraction of Ge or Si cation in amorphous phase-change binary tellurides GexTe1-x and SixTe1-x. This represents the first quantitative estimate of such local structures, and reveals the fraction to be nearly 50%, while also revealing implications for the phase-change mechanism itself.

Micoulaut, M.; Gunasekera, K.; Ravindren, S.; Boolchand, P.

2014-09-01

353

Zintl-phase compounds with SnSb4 tetrahedral anions: Electronic structure and thermoelectric properties  

SciTech Connect

We report the investigation of Zintl-phase Na(K){sub 8}SnSb{sub 4} and related compounds that contain SnSb{sub 4} tetrahedral anions using first principles electronic structure, Boltzmann transport, and density functional phonon calculations. We find that these compounds are narrow-gap semiconductors and there is a combination of heavy and light bands at valence band edge, which may lead to a combination of high thermopower and reasonable conductivity. High values of the thermopower are found for p-type doping within the Boltzmann transport theory. Furthermore, these materials are expected to have low thermal conductivity due to their structures that consist of a network of weakly coupled SnSb{sub 4} clusters, which leads to low phonon frequencies. In particular, we find low-frequency optical phonons that should effectively scatter the heat-carrying acoustic phonons. These results are discussed in terms of the structure, which consists of anionic clusters. Based on the results, it is suggested that such compounds may represent a useful paradigm for finding new thermoelectric materials.

Zhang, Lijun; Du, Mao-Hua; Singh, David J.

2010-01-01

354

Scaling Laws for the Multidimensional Burgers Equation with Quadratic External Potential  

Microsoft Academic Search

The reordering of the multidimensional exponential quadratic operator in coordinate-momentum space (see X. Wang, C.H. Oh and L.C. Kwek (1998). J. Phys. A.: Math. Gen.\\u000a 31:4329–4336) is applied to derive an explicit formulation of the solution to the multidimensional heat equation with quadratic external potential and random initial conditions. The solution to the multidimensional Burgers equation with quadratic external potential

N. N. Leonenko; M. D. Ruiz-Medina

2006-01-01

355

Tetrahedral magnetic order and the metal-insulator transition in the pyrochlore lattice of Cd2Os2O7.  

PubMed

Cd2Os2O7 shows a peculiar metal-insulator transition at 227 K with magnetic ordering in a frustrated pyrochlore lattice, but its magnetic structure in the ordered state and the transition origin are yet uncovered. We observed a commensurate magnetic peak by resonant x-ray scattering in a high-quality single crystal. X-ray diffraction and Raman scattering experiments confirmed that the transition is not accompanied with any spatial symmetry breaking. We propose a noncollinear all-in-all-out spin arrangement on the tetrahedral network made of Os atoms. Based on this we suggest that the transition is not caused by the Slater mechanism as believed earlier but by an alternative mechanism related to the formation of the specific tetrahedral magnetic order on the pyrochlore lattice in the presence of strong spin-orbit interactions. PMID:23004317

Yamaura, J; Ohgushi, K; Ohsumi, H; Hasegawa, T; Yamauchi, I; Sugimoto, K; Takeshita, S; Tokuda, A; Takata, M; Udagawa, M; Takigawa, M; Harima, H; Arima, T; Hiroi, Z

2012-06-15

356

Efficient calculation of the quasi-static electrical potential on a tetrahedral mesh and its implementation in STEPS  

PubMed Central

We describe a novel method for calculating the quasi-static electrical potential on tetrahedral meshes, which we call E-Field. The E-Field method is implemented in STEPS, which performs stochastic spatial reaction-diffusion computations in tetrahedral-based cellular geometry reconstructions. This provides a level of integration between electrical excitability and spatial molecular dynamics in realistic cellular morphology not previously achievable. Deterministic solutions are also possible. By performing the Rallpack tests we demonstrate the accuracy of the E-Field method. Efficient node ordering is an important practical consideration, and we find that a breadth-first search provides the best solutions, although principal axis ordering suffices for some geometries. We discuss potential applications and possible future directions, and predict that the E-Field implementation in STEPS will play an important role in the future of multiscale neural simulations. PMID:24194715

Hepburn, Iain; Cannon, Robert; De Schutter, Erik

2013-01-01

357

Efficient calculation of the quasi-static electrical potential on a tetrahedral mesh and its implementation in STEPS.  

PubMed

We describe a novel method for calculating the quasi-static electrical potential on tetrahedral meshes, which we call E-Field. The E-Field method is implemented in STEPS, which performs stochastic spatial reaction-diffusion computations in tetrahedral-based cellular geometry reconstructions. This provides a level of integration between electrical excitability and spatial molecular dynamics in realistic cellular morphology not previously achievable. Deterministic solutions are also possible. By performing the Rallpack tests we demonstrate the accuracy of the E-Field method. Efficient node ordering is an important practical consideration, and we find that a breadth-first search provides the best solutions, although principal axis ordering suffices for some geometries. We discuss potential applications and possible future directions, and predict that the E-Field implementation in STEPS will play an important role in the future of multiscale neural simulations. PMID:24194715

Hepburn, Iain; Cannon, Robert; De Schutter, Erik

2013-01-01

358

Unraveling the voltage fade mechanism in layer Li-Mn-rich electrode: formation of the tetrahedral cations for spinel conversion  

SciTech Connect

Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.

Mohanty, Debasish [ORNL; Li, Jianlin [ORNL; Abraham, Daniel P [Argonne National Laboratory (ANL); Huq, Ashfia [ORNL; Payzant, E Andrew [ORNL; Wood III, David L [ORNL; Daniel, Claus [ORNL

2014-01-01

359

Photovoltaic characteristics of amorphous silicon solar cells using boron doped tetrahedral amorphous carbon films as p-type window materials  

Microsoft Academic Search

Boron doped tetrahedral amorphous carbon (ta-C:B) was prepared by filtered cathodic vacuum arc deposition. A band gap of 2.0 eV and a conductivity of 1.42×10-7 S\\/cm were obtained at the doping ratio of 2.13 at. %. A device structure was deduced from the conventional amorphous silicon (a-Si:H) solar cell using the ta-C:B window layer. Photovoltaic parameters of the cells were

Jiecai Han; Manlin Tan; Jiaqi Zhu; Songhe Meng; Binsheng Wang; Shaojun Mu; Dawei Cao

2007-01-01

360

Influence of the incident angle of energetic carbon ions on the properties of tetrahedral amorphous carbon (taC) films  

Microsoft Academic Search

Tetrahedral amorphous carbon (ta-C) films have been grown on Ar+-beam-cleaned silicon substrates by changing the incident angle of energetic carbon ions produced in the plasma of pulsed cathodic vacuum arc discharge. Their surface roughness, deposition rate, composition, and mechanical and frictional properties as a function of the incident angle of energetic carbon ions were reported. The substrate holder can be

Dongping Liu; Günther Benstetter; Edgar Lodermeier; Johann Vancea

2003-01-01

361

The use of tetrahedral mesh geometries in Monte Carlo simulation of applicator based brachytherapy dose distributions.  

PubMed

Accounting for brachytherapy applicator attenuation is part of the recommendations from the recent report of AAPM Task Group 186. To do so, model based dose calculation algorithms require accurate modelling of the applicator geometry. This can be non-trivial in the case of irregularly shaped applicators such as the Fletcher Williamson gynaecological applicator or balloon applicators with possibly irregular shapes employed in accelerated partial breast irradiation (APBI) performed using electronic brachytherapy sources (EBS). While many of these applicators can be modelled using constructive solid geometry (CSG), the latter may be difficult and time-consuming. Alternatively, these complex geometries can be modelled using tessellated geometries such as tetrahedral meshes (mesh geometries (MG)). Recent versions of Monte Carlo (MC) codes Geant4 and MCNP6 allow for the use of MG. The goal of this work was to model a series of applicators relevant to brachytherapy using MG. Applicators designed for (192)Ir sources and 50?kV EBS were studied; a shielded vaginal applicator, a shielded Fletcher Williamson applicator and an APBI balloon applicator.All applicators were modelled in Geant4 and MCNP6 using MG and CSG for dose calculations. CSG derived dose distributions were considered as reference and used to validate MG models by comparing dose distribution ratios.In general agreement within 1% for the dose calculations was observed for all applicators between MG and CSG and between codes when considering volumes inside the 25% isodose surface. When compared to CSG, MG required longer computation times by a factor of at least 2 for MC simulations using the same code. MCNP6 calculation times were more than ten times shorter than Geant4 in some cases.In conclusion we presented methods allowing for high fidelity modelling with results equivalent to CSG. To the best of our knowledge MG offers the most accurate representation of an irregular APBI balloon applicator. PMID:25210788

Fonseca, Gabriel Paiva; Landry, Guillaume; White, Shane; D'Amours, Michel; Yoriyaz, Hélio; Beaulieu, Luc; Reniers, Brigitte; Verhaegen, Frank

2014-10-01

362

The stability of a crystal with diamond structure for patchy particles with tetrahedral symmetry  

E-print Network

The phase diagram of model anisotropic particles with four attractive patches in a tetrahedral arrangement has been computed at two different values for the range of the potential, with the aim of investigating the conditions under which a diamond crystal can be formed. We find that the diamond phase is never stable for our longer-ranged potential. At low temperatures and pressures, the fluid freezes into a body-centred-cubic solid that can be viewed as two interpenetrating diamond lattices with a weak interaction between the two sublattices. Upon compression, an orientationally ordered face-centred-cubic crystal becomes more stable than the body-centred-cubic crystal, and at higher temperatures a plastic face-centered-cubic phase is stabilized by the increased entropy due to orientational disorder. A similar phase diagram is found for the shorter-ranged potential, but at low temperatures and pressures, we also find a region over which the diamond phase is thermodynamically favored over the body-centred-cubic phase. The higher vibrational entropy of the diamond structure with respect to the body-centred-cubic solid explains why it is stable even though the enthalpy of the latter phase is lower. Some preliminary studies on the growth of the diamond structure starting from a crystal seed were performed. Even though the diamond phase is never thermodynamically stable for the longer-ranged model, direct coexistence simulations of the interface between the fluid and the body-centred-cubic crystal and between the fluid and the diamond crystal show that, at sufficiently low pressures, it is quite probable that in both cases the solid grows into a diamond crystal, albeit involving some defects. These results highlight the importance of kinetic effects in the formation of diamond crystals in systems of patchy particles.

Eva G. Noya; Carlos Vega; Jonathan P. K. Doye; Ard A. Louis

2010-05-27

363

The use of tetrahedral mesh geometries in Monte Carlo simulation of applicator based brachytherapy dose distributions  

NASA Astrophysics Data System (ADS)

Accounting for brachytherapy applicator attenuation is part of the recommendations from the recent report of AAPM Task Group 186. To do so, model based dose calculation algorithms require accurate modelling of the applicator geometry. This can be non-trivial in the case of irregularly shaped applicators such as the Fletcher Williamson gynaecological applicator or balloon applicators with possibly irregular shapes employed in accelerated partial breast irradiation (APBI) performed using electronic brachytherapy sources (EBS). While many of these applicators can be modelled using constructive solid geometry (CSG), the latter may be difficult and time-consuming. Alternatively, these complex geometries can be modelled using tessellated geometries such as tetrahedral meshes (mesh geometries (MG)). Recent versions of Monte Carlo (MC) codes Geant4 and MCNP6 allow for the use of MG. The goal of this work was to model a series of applicators relevant to brachytherapy using MG. Applicators designed for 192Ir sources and 50?kV EBS were studied; a shielded vaginal applicator, a shielded Fletcher Williamson applicator and an APBI balloon applicator. All applicators were modelled in Geant4 and MCNP6 using MG and CSG for dose calculations. CSG derived dose distributions were considered as reference and used to validate MG models by comparing dose distribution ratios. In general agreement within 1% for the dose calculations was observed for all applicators between MG and CSG and between codes when considering volumes inside the 25% isodose surface. When compared to CSG, MG required longer computation times by a factor of at least 2 for MC simulations using the same code. MCNP6 calculation times were more than ten times shorter than Geant4 in some cases. In conclusion we presented methods allowing for high fidelity modelling with results equivalent to CSG. To the best of our knowledge MG offers the most accurate representation of an irregular APBI balloon applicator.

Paiva Fonseca, Gabriel; Landry, Guillaume; White, Shane; D'Amours, Michel; Yoriyaz, Hélio; Beaulieu, Luc; Reniers, Brigitte; Verhaegen, Frank

2014-10-01

364

Discriminative learning quadratic discriminant function for handwriting recognition.  

PubMed

In character string recognition integrating segmentation and classification, high classification accuracy and resistance to noncharacters are desired to the underlying classifier. In a previous evaluation study, the modified quadratic discriminant function (MQDF) proposed by Kimura et al. was shown to be superior in noncharacter resistance but inferior in classification accuracy to neural networks. This paper proposes a discriminative learning algorithm to optimize the parameters of MQDF with aim to improve the classification accuracy while preserving the superior noncharacter resistance. We refer to the resulting classifier as discriminative learning QDF (DLQDF). The parameters of DLQDF adhere to the structure of MQDF under the Gaussian density assumption and are optimized under the minimum classification error (MCE) criterion. The promise of DLQDF is justified in handwritten digit recognition and numeral string recognition, where the performance of DLQDF is comparable to or superior to that of neural classifiers. The results are also competitive to the best ones reported in the literature. PMID:15384535

Liu, Cheng-Lin; Sako, Hiroshi; Fujisawa, Hiromichi

2004-03-01

365

Dissipative quadratic solitons supported by a localized gain  

E-print Network

We propose two models for the creation of stable dissipative solitons in optical media with the $\\chi^{(2)}$ (quadratic) nonlinearity. To compensate spatially uniform loss in both the fundamental-frequency (FF) and second-harmonic (SH) components of the system, a strongly localized "hot spot", carrying the linear gain, is added, acting either on the FF component, or on the SH one. In both systems, we use numerical methods to find families of dissipative $\\chi^{(2)}$ solitons pinned to the "hot spot". The shape of the existence and stability domains may be rather complex. An existence boundary for the solitons, which corresponds to the guided mode in the linearized version of the systems, is obtained in an analytical form. The solitons demonstrate noteworthy features, such as spontaneous symmetry breaking (of spatially symmetric solitons) and bistability.

Lobanov, Valery E; Malomed, Boris A

2014-01-01

366

Lensless imaging by entangled photons from quadratic nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

Lenses play a key role in quantum imaging but inevitably constrain the spatial resolution and working wavelength. In this work we develop and demonstrate a lensless quantum ghost imaging by engineering quadratic nonlinear photonic crystals. With a transverse parabolic domain modulation introduced into the lithium tantalate crystal, the entangled photon pairs generated from parametric down-conversion will self-focus. Therefore we can dispense with additional lenses to construct imaging in a nonlocal way. The lensless imaging is found to follow a specific imaging formula where the effective focal length is determined by the domain modulation and pump wavelength. Additionally, two nonlocal images can be retrieved when the entangled photon pair is generated under two concurrent noncollinear phase-matching geometries. Our work provides a principle and method to realize lensless ghost imaging, which may be extended to other wavelengths and stimulate new types of practical quantum technologies.

Xu, P.; Leng, H. Y.; Zhu, Z. H.; Bai, Y. F.; Jin, H.; Gong, Y. X.; Yu, X. Q.; Xie, Z. D.; Mu, S. Y.; Zhu, S. N.

2012-07-01

367

Exact Nonnull Wavelike Solutions to Gravity with Quadratic Lagrangians  

E-print Network

Solutions to gravity with quadratic Lagrangians are found for the simple case where the only nonconstant metric component is the lapse $N$ and the Riemann tensor takes the form $R^{t}_{.itj}=-k_{i}k_{j}, i,j=1,2,3$; thus these solutions depend on cross terms in the Riemann tensor and therefore complement the linearized theory where it is the derivatives of the Riemann tensor that matter. The relationship of this metric to the null gravitational radiation metric of Peres is given. Gravitaional energy Poynting vectors are construcetd for the solutions and one of these, based on the Lanczos tensor, supports the indication in the linearized theory that nonnull gravitational radiation can occur.

Mark D. Roberts

1999-04-04

368

Multiscale analysis for stochastic partial differential equations with quadratic nonlinearities  

NASA Astrophysics Data System (ADS)

In this paper we derive rigorously amplitude equations for stochastic partial differential equations with quadratic nonlinearities, under the assumption that the noise acts only on the stable modes and for an appropriate scaling between the distance from bifurcation and the strength of the noise. We show that, due to the presence of two distinct timescales in our system, the noise (which acts only on the fast modes) gets transmitted to the slow modes and, as a result, the amplitude equation contains both additive and multiplicative noise. As an application we study the case of the one-dimensional Burgers equation forced by additive noise in the orthogonal subspace to its dominant modes. The theory developed in the present paper thus allows us to explain theoretically some recent numerical observations on stabilization with additive noise.

Blömker, D.; Hairer, M.; Pavliotis, G. A.

2007-07-01

369

A Fixed-Point Iteration Method with Quadratic Convergence  

SciTech Connect

The fixed-point iteration algorithm is turned into a quadratically convergent scheme for a system of nonlinear equations. Most of the usual methods for obtaining the roots of a system of nonlinear equations rely on expanding the equation system about the roots in a Taylor series, and neglecting the higher order terms. Rearrangement of the resulting truncated system then results in the usual Newton-Raphson and Halley type approximations. In this paper the introduction of unit root functions avoids the direct expansion of the nonlinear system about the root, and relies, instead, on approximations which enable the unit root functions to considerably widen the radius of convergence of the iteration method. Methods for obtaining higher order rates of convergence and larger radii of convergence are discussed.

Walker, Kevin P. [Engineering Science Software, Inc.; Sham, Sam [ORNL

2012-01-01

370

An experiment in rotational motion with linear and quadratic drag  

NASA Astrophysics Data System (ADS)

We describe a study of velocity-dependent drag in rotational motion that is suitable for an undergraduate laboratory experiment. Using standard teaching-laboratory equipment to obtain the data, we found that a drag force that is linear in the angular speed describes the data very well; however, the model residuals reveal that quadratic drag is also present. When a combined model is used, the residuals are reduced to the level of measurement uncertainties. An investigation of the effect of airflow on the air bearing used in the experiment confirms that there is a turbine effect on the disk and that the drag is dependent on the airflow suspending the disk. The experiment is simple to perform and analyze, yet reveals interesting physical and analytical complexity with deeper investigation.

Thompson, B. G.; Smith, P. A.

2004-06-01

371

Impact of a global quadratic potential on galactic rotation curves.  

PubMed

We present a conformal gravity fit to the 20 largest of a sample of 110 spiral galaxies. We identify the presence of a universal quadratic potential V(?)(r)=-?c²r²/2 with ?=9.54×10??? cm?² induced by cosmic inhomogeneities. When V(?)(r) is taken in conjunction with both a universal linear potential V(??)(r)=??c²r/2 with ??=3.06×10?³? cm?¹ generated by the homogeneous cosmic background and the contribution generated by the local luminous matter in galaxies, the theory then accounts for the rotation curve systematics observed in the entire 110 galaxies, without the need for any dark matter whatsoever. Our study suggests that using dark matter may be nothing more than an attempt to describe global effects in purely local galactic terms. With V(?)(r) being negative, galaxies can only support bound orbits up to distances of order ??/?=100kpc, with global physics imposing a limit on the size of galaxies. PMID:21517292

Mannheim, Philip D; O'Brien, James G

2011-03-25

372

Confidence set inference with a prior quadratic bound  

NASA Technical Reports Server (NTRS)

In the uniqueness part of a geophysical inverse problem, the observer wants to predict all likely values of P unknown numerical properties z = (z sub 1,...,z sub p) of the earth from measurement of D other numerical properties y(0)=(y sub 1(0),...,y sub D(0)) knowledge of the statistical distribution of the random errors in y(0). The data space Y containing y(0) is D-dimensional, so when the model space X is infinite-dimensional the linear uniqueness problem usually is insoluble without prior information about the correct earth model x. If that information is a quadratic bound on x (e.g., energy or dissipation rate), Bayesian inference (BI) and stochastic inversion (SI) inject spurious structure into x, implied by neither the data nor the quadratic bound. Confidence set inference (CSI) provides an alternative inversion technique free of this objection. CSI is illustrated in the problem of estimating the geomagnetic field B at the core-mantle boundary (CMB) from components of B measured on or above the earth's surface. Neither the heat flow nor the energy bound is strong enough to permit estimation of B(r) at single points on the CMB, but the heat flow bound permits estimation of uniform averages of B(r) over discs on the CMB, and both bounds permit weighted disc-averages with continous weighting kernels. Both bounds also permit estimation of low-degree Gauss coefficients at the CMB. The heat flow bound resolves them up to degree 8 if the crustal field at satellite altitudes must be treated as a systematic error, but can resolve to degree 11 under the most favorable statistical treatment of the crust. These two limits produce circles of confusion on the CMB with diameters of 25 deg and 19 deg respectively.

Backus, George E.

1988-01-01

373

Adaptive mesh refinement for time-domain electromagnetics using vector finite elements :a feasibility study.  

SciTech Connect

This report investigates the feasibility of applying Adaptive Mesh Refinement (AMR) techniques to a vector finite element formulation for the wave equation in three dimensions. Possible error estimators are considered first. Next, approaches for refining tetrahedral elements are reviewed. AMR capabilities within the Nevada framework are then evaluated. We summarize our conclusions on the feasibility of AMR for time-domain vector finite elements and identify a path forward.

Turner, C. David; Kotulski, Joseph Daniel; Pasik, Michael Francis

2005-12-01

374

Numerical simulation of BSDEs with drivers of quadratic growth Adrien Richou  

E-print Network

]. But in all these works, the driver of the BSDE is a Lipschitz function with respect to z and this assumption. To the best of our knowledge, the only work where the time approxima- tion of a BSDE with a quadratic growthNumerical simulation of BSDEs with drivers of quadratic growth Adrien Richou IRMAR, Université

375

Model selection in high dimensions: a quadratic-risk-based approach  

Microsoft Academic Search

We propose a general class of risk measures which can be used for data-based evaluation of parametric models. The loss function is defined as the generalized quadratic distance between the true density and the model proposed. These distances are characterized by a simple quadratic form structure that is adaptable through the choice of a non-negative definite kernel and a bandwidth

Surajit Ray; Bruce G. Lindsay

2008-01-01

376

Exploration of Quadratic Expressions through Multiple Representations for Students with Mathematics Difficulties  

ERIC Educational Resources Information Center

The current study focuses on the effects of incorporating multiple visual representations on students' conceptual understanding of quadratic expressions embedded within area word problems and students' procedural fluency of transforming quadratic expressions in standard form to factored-form and vice versa. The intervention included the…

Strickland, Tricia K.; Maccini, Paula

2013-01-01

377

Are ghost-surfaces quadratic-flux minimizing? S.R. Hudsona  

E-print Network

Are ghost-surfaces quadratic-flux minimizing? S.R. Hudsona and R.L. Dewarb aPrinceton Plasma through magnetic islands, namely quadratic-flux-minimizing (QFMIN) surfaces and ghost surfaces, use, and ghost-surface pseudo-orbits are obtained by displacing closed field lines in the direction of steepest

Hudson, Stuart

378

Applications of the Quadratic Covariation Differentiation Theory: Variants of the Clark-Ocone and Stroock's Formulas  

Microsoft Academic Search

In a 2006 article [1], Allouba gave his quadratic covariation differentiation theory for Itô's integral calculus. In it, he defined the derivative of a semimartingale with respect to a Brownian motion as the time derivative of their quadratic covariation and a generalization thereof. He then obtained a systematic pathwise stochastic differentiation theory that comes complete with a fundamental theorem of

Hassan Allouba; Ramiro Fontes

2011-01-01

379

BIFURCATION MEASURES AND QUADRATIC RATIONAL MAPS LAURA DE MARCO, XIAOGUANG WANG, AND HEXI YE  

E-print Network

BIFURCATION MEASURES AND QUADRATIC RATIONAL MAPS LAURA DE MARCO, XIAOGUANG WANG, AND HEXI YE Abstract. We study critical orbits and bifurcations in the curves Per1() within the moduli space M2 of quadratic rational maps, f : P1 P1 . For each C, the curve Per1() is defined by the condition

DeMarco, Laura

380

Single-photon spontaneous parametric down-conversion in quadratic nonlinear waveguide arrays  

E-print Network

Single-photon spontaneous parametric down-conversion in quadratic nonlinear waveguide arrays Diana-conversion Single-photon pump Correlation function Waveguide array a b s t r a c t We describe spontaneous parametric down-conversion of a single-photon pump in quadratic nonlinear waveguides and waveguide arrays

381

A Tighter Piecewise Linear Approximation of Quadratic Cost Curves for Unit Commitment Problems  

Microsoft Academic Search

This letter provides a tighter piecewise linear ap- proximation of generating units' quadratic cost curves (QCCs) for unit commitment (UC) problems. In order to facilitate the UC optimization process with efficient mixed-integer linear programing (MILP) solvers, QCCs are piecewise linearized for converting the original mixed-integer quadratic programming (MIQP) problem into an MILP problem. Traditionally, QCCs are piecewise linearized by evenly

Lei Wu

2011-01-01

382

On-Line Geometric Modeling Notes QUADRATIC UNIFORM B-SPLINE CURVE REFINEMENT  

E-print Network

On-Line Geometric Modeling Notes QUADRATIC UNIFORM B-SPLINE CURVE REFINEMENT Kenneth I. Joy subdivision of uniform B-spline curves. The uniform B-spline curves, surfaces and solids have been extensively the refinement method for a quadratic uniform B-spline curve and show that the refinement is exactly

California at Davis, University of

383

ECS 178 Course Notes QUADRATIC UNIFORM B-SPLINE CURVE REFINEMENT  

E-print Network

ECS 178 Course Notes QUADRATIC UNIFORM B-SPLINE CURVE REFINEMENT Kenneth I. Joy Institute for Data of uniform B-spline curves. The uniform B-spline curves, surfaces and solids have been extensively studied method for a quadratic uniform B-spline curve and show that the refinement is exactly that speci- fied

California at Davis, University of

384

Computing the Partial Fraction Decomposition of Rational Functions with Irreducible Quadratic Factors in the Denominators  

ERIC Educational Resources Information Center

In this note, a new method for computing the partial fraction decomposition of rational functions with irreducible quadratic factors in the denominators is presented. This method involves polynomial divisions and substitutions only, without having to solve for the complex roots of the irreducible quadratic polynomial or to solve a system of linear…

Man, Yiu-Kwong

2012-01-01

385

Global Models for the Orientation Field of Fingerprints: An Approach Based on Quadratic Differentials  

Microsoft Academic Search

Quadratic differentials naturally define analytic orientation fields on planar surfaces. We propose to model orientation fields of fingerprints by specifying quadratic differentials. Models for all fingerprint classes such as arches, loops and whorls are laid out. These models are parametrised by few, geometrically interpretable parameters which are invariant under Euclidean motions. We demonstrate their ability in adapting to given, observed

Stephan Huckemann; Thomas Hotz; Axel Munk

2008-01-01

386

A direct Arbitrary-Lagrangian-Eulerian ADER-WENO finite volume scheme on unstructured tetrahedral meshes for conservative and non-conservative hyperbolic systems in 3D  

NASA Astrophysics Data System (ADS)

In this paper we present a new family of high order accurate Arbitrary-Lagrangian-Eulerian (ALE) one-step ADER-WENO finite volume schemes for the solution of nonlinear systems of conservative and non-conservative hyperbolic partial differential equations with stiff source terms on moving tetrahedral meshes in three space dimensions. A WENO reconstruction technique is used to achieve high order of accuracy in space, while an element-local space-time Discontinuous Galerkin finite element predictor on moving curved meshes is used to obtain a high order accurate one-step time discretization. Within the space-time predictor the physical element is mapped onto a reference element using a high order isoparametric approach, where the space-time basis and test functions are given by the Lagrange interpolation polynomials passing through a predefined set of space-time nodes. Since our algorithm is cell-centered, the final mesh motion is computed by using a suitable node solver algorithm. A rezoning step as well as a flattener strategy are used in some of the test problems to avoid mesh tangling or excessive element deformations that may occur when the computation involves strong shocks or shear waves. The ALE algorithm presented in this article belongs to the so-called direct ALE methods because the final Lagrangian finite volume scheme is based directly on a space-time conservation formulation of the governing PDE system, with the rezoned geometry taken already into account during the computation of the fluxes. We apply our new high order unstructured ALE schemes to the 3D Euler equations of compressible gas dynamics, for which a set of classical numerical test problems has been solved and for which convergence rates up to sixth order of accuracy in space and time have been obtained. We furthermore consider the equations of classical ideal magnetohydrodynamics (MHD) as well as the non-conservative seven-equation Baer-Nunziato model of compressible multi-phase flows with stiff relaxation source terms.

Boscheri, Walter; Dumbser, Michael

2014-10-01

387

Parallel finite element solutions of nonlinear aeroelastic and aeroservoelastic problems in three-dimensional transonic flows  

Microsoft Academic Search

In this dissertation, computational solutions of three-dimensional aeroelastic and aeroservoelastic problems of flexible wings in the transonic flow regime are presented. The aeroelastic solutions are based on the Galerkin finite element method, implemented on a tetrahedral unstructured mesh. A new flutter suppression scheme based on dynamic twist control is also explored. The results show that this scheme is both robust

Guang-Yaw Hwang

1997-01-01

388

Discontinuous Finite Element S{sub N} Methods on Three-Dimensional Unstructured Grids  

SciTech Connect

Discontinuous finite element methods for the S{sub N} equations on three-dimensional unstructured tetrahedral and hexahedral meshes are presented. Solution techniques including source iteration and diffusion-synthetic acceleration are described. Numerical results are presented that demonstrate the accuracy and efficiency of these methods.

Wareing, Todd A.; McGhee, John M.; Morel, Jim E.; Pautz, Shawn D. [Los Alamos National Laboratory (United States)

2001-07-15

389

Part I. Nanostructured semiconductor photoelectrochemical cells. Part II. Electrodes of tetrahedral amorphous carbon containing nitrogen  

NASA Astrophysics Data System (ADS)

In Part I, preparation of CdS and CdSe films on various electrode materials including nanoporous TiO2 and their photoresponses were demonstrated. Both electrochemical and chemical deposition methods successfully produced Cd-chalcogenide films and post-thermal treatment was done to develop respectable photoactivity. Chemical and photo-electrochemical etching were also performed to remove impurities and increase film stability. Transparency issues for a sandwich type of a solar cell based on semiconductor thin films on a TiO 2 porous nanostructure were examined by measuring transmittances of different wavelengths of laser light. Porous TiO2 films were made from both Degussa P25 TiO2 and Ti(IV) isopropoxide sol-gels. CdSe films on both TiO2 substrates showed comparable photospectra, but the sol-gel one is more transparent and shows better net response. In Part II, electrodes of conductive nitrogen-incorporated tetrahedral amorphous carbon films (taC:N) deposited at ambient temperatures were shown to possess an extraordinary combination of the stability associated with boron-doped diamonds, yet with much enhanced electrocatalytic properties. In this study on the electrochemistry of deposited thin films of taC:N, we showed that this material demonstrates more active charge transfer properties on a variety of systems relative to the H-terminated, highly boron-doped diamond (B-diamond). Stability was shown by chlorine evolution from HCl solution for >104 times the coulombs necessary for 4e/C-atom oxidation to CO2 of a 40 nm thick taC:N film without noticeable change of the voltammetry. Cu deposition and stripping on taC:N electrodes have revealed several distinctive features comparative to other electrodes. From stationary and rotating disk voltammograms, we observed a larger nucleation overpotential of Cu deposition on a taC:N electrode, and the extraordinary Cu stripping pattern, two peak or shoulder-peak, at the position about a higher (more positive) potential than normal bulk Cu stripping peak potential, in the region of the Cu(I)/Cu(II) process. RRDE evidence clearly showed a mixed process of oxidation of Cu(0) to Cu(I) or Cu(0) to Cu(II), and, especially, the presence of Cu(II) in the product stream.

Yoo, Kwangsun

390

Three isoparametric solid elements for NASTRAN. [for static, dynamic, buckling, and heat transfer analyses  

NASA Technical Reports Server (NTRS)

Linear, quadratic, and cubic isoparametric hexahedral solid elements have been added to the element library of NASTRAN. These elements are available for static, dynamic, buckling, and heat-transfer analyses. Because the isoparametric element matrices are generated by direct numerical integration over the volume of the element, variations in material properties, temperatures, and stresses within the elements are represented in the computations. In order to compare the accuracy of the new elements, three similar models of a slender cantilever were developed, one for each element. All elements performed well. As expected, however, the linear element model yielded excellent results only when shear behavior predominated. In contrast, the results obtained from the quadratic and cubic element models were excellent in both shear and bending.

Johnson, S. E.; Field, E. I.

1973-01-01

391

AESOP- INTERACTIVE DESIGN OF LINEAR QUADRATIC REGULATORS AND KALMAN FILTERS  

NASA Technical Reports Server (NTRS)

AESOP was developed to solve a number of problems associated with the design of controls and state estimators for linear time-invariant systems. The systems considered are modeled in state-variable form by a set of linear differential and algebraic equations with constant coefficients. Two key problems solved by AESOP are the linear quadratic regulator (LQR) design problem and the steady-state Kalman filter design problem. AESOP is designed to be used in an interactive manner. The user can solve design problems and analyze the solutions in a single interactive session. Both numerical and graphical information are available to the user during the session. The AESOP program is structured around a list of predefined functions. Each function performs a single computation associated with control, estimation, or system response determination. AESOP contains over sixty functions and permits the easy inclusion of user defined functions. The user accesses these functions either by inputting a list of desired functions in the order they are to be performed, or by specifying a single function to be performed. The latter case is used when the choice of function and function order depends on the results of previous functions. The available AESOP functions are divided into several general areas including: 1) program control, 2) matrix input and revision, 3) matrix formation, 4) open-loop system analysis, 5) frequency response, 6) transient response, 7) transient function zeros, 8) LQR and Kalman filter design, 9) eigenvalues and eigenvectors, 10) covariances, and 11) user-defined functions. The most important functions are those that design linear quadratic regulators and Kalman filters. The user interacts with AESOP when using these functions by inputting design weighting parameters and by viewing displays of designed system response. Support functions obtain system transient and frequency responses, transfer functions, and covariance matrices. AESOP can also provide the user with open-loop system information including stability, controllability, and observability. The AESOP program is written in FORTRAN IV for interactive execution and has been implemented on an IBM 3033 computer using TSS 370. As currently configured, AESOP has a central memory requirement of approximately 2 Megs of 8 bit bytes. Memory requirements can be reduced by redimensioning arrays in the AESOP program. Graphical output requires adaptation of the AESOP plot routines to whatever device is available. The AESOP program was developed in 1984.

Lehtinen, B.

1994-01-01

392

Self-consistent linearization of non-linear BEM formulations with quadratic convergence  

NASA Astrophysics Data System (ADS)

In this work, a general technique to obtain the self-consistent linearization of non-linear formulations of the boundary element method (BEM) is presented. In the incremental-iterative procedure required to solve the non-linear problem the convergence is quadratic, being the solution obtained from the consistent tangent operator. This technique is applied to non-linear BEM formulations for plates where two independent problems are discussed: the plate bending and the stretching problem. For both problems an equilibrium equation is written in terms of strains and internal forces and then the consistent tangent operator is derived by applying the Newton-Raphson’s scheme. The Von Mises criterion is adopted to govern the elasto-plastic material behaviour checked at points along the plate thickness, although the presented formulations can be used with any non-linear model. Numerical examples are presented showing the accuracy of the results as well as the high convergence rate of the iterative procedure.

Fernandes, G. R.; de Souza Neto, E. A.

2013-11-01

393

Profile-Following Entry Guidance Using Linear Quadratic Regulator Theory  

NASA Technical Reports Server (NTRS)

This paper describes one of the entry guidance concepts that is currently being tested as part of Marshall Space Flight Center's Advance Guidance and Control Project. The algorithm is of the reference profile tracking type. The reference profile consists of the reference states, range-to-go, altitude, and flight path angle, and reference controls, bank angle and angle of attack, versus energy. A linear control law using state feedback is used with energy-scheduled gains. The gains are obtained offline using Matlab's steady state linear quadratic regulator function. Lateral trajectory control is effected by performing periodic bank sign reversals based on a heading error corridor. A description and results of the AG&C test cases on which it has been tested are given. Although it is not anticipated that the algorithm will be quite as robust as algorithms with onboard trajectory re-generation capability, the results nevertheless show it to be very robust with respect to varying initial conditions and works satisfactorily even for entries from widely different orbits than that of the reference profile. Moreover, the commanded bank and angle of attack histories are very smooth, making it easier for the attitude control system to implement the guidance commands. Finally, results indicate that the guidance gains are more or less trajectory-independent which is a potentially useful property.

Dukeman, Greg A.; Fogle, Frank (Technical Monitor)

2002-01-01

394

Time-averaged quadratic functionals of a Gaussian process.  

PubMed

The characterization of a stochastic process from its single random realization is a challenging problem for most single-particle tracking techniques which survey an individual trajectory of a tracer in a complex or viscoelastic medium. We consider two quadratic functionals of the trajectory: the time-averaged mean-square displacement (MSD) and the time-averaged squared root mean-square displacement (SRMS). For a large class of stochastic processes governed by the generalized Langevin equation with arbitrary frictional memory kernel and harmonic potential, the exact formulas for the mean and covariance of these functionals are derived. The formula for the mean value can be directly used for fitting experimental data, e.g., in optical tweezers microrheology. The formula for the variance (and covariance) allows one to estimate the intrinsic fluctuations of measured (or simulated) time-averaged MSD or SRMS for choosing the experimental setup appropriately. We show that the time-averaged SRMS has smaller fluctuations than the time-averaged MSD, in spite of much broader applications of the latter one. The theoretical results are successfully confirmed by Monte Carlo simulations of the Langevin dynamics. We conclude that the use of the time-averaged SRMS would result in a more accurate statistical analysis of individual trajectories and more reliable interpretation of experimental data. PMID:21797312

Grebenkov, Denis S

2011-06-01

395

Quadratic isothermal amplification for the detection of microRNA.  

PubMed

This protocol describes an isothermal amplification approach for ultrasensitive detection of specific microRNAs (miRNAs). It achieves this level of sensitivity through quadratic amplification of the target oligonucleotide by using a Bst DNA polymerase-induced strand-displacement reaction and a lambda exonuclease-aided recycling reaction. First, the target miRNA binds to a specifically designed molecular beacon, causing it to become a fluorescence emitter. A primer then binds to the activated beacon, and Bst polymerase initiates the synthesis of a double-stranded DNA segment templated on the molecular beacon. This causes the concomitant release of the target miRNA from the beacon--the first round of 'recycling'. Second, the duplex beacon thus produced is a suitable substrate for a nicking enzyme present in solution. After the duplex beacon is nicked, the lambda exonuclease digests the beacon and releases the DNA single strand just synthesized, which is complementary to the molecular beacon, inducing the second round of recycling. The miRNA detection limit of this protocol is 10 fmol at 37 °C and 1 amol at 4 °C. This approach also affords high selectivity when applied to miRNA extracted from MCF-7 and PC3 cell lines and even from breast cancer tissue samples. Upon isolation of miRNA, the detection process can be completed in ?2 h. PMID:24525753

Duan, Ruixue; Zuo, Xiaolei; Wang, Shutao; Quan, Xiyun; Chen, Dongliang; Chen, Zhifei; Jiang, Lei; Fan, Chunhai; Xia, Fan

2014-03-01

396

Generation and dynamics of quadratic birefringent spatial gap solitons  

SciTech Connect

A method is proposed to generate and study the dynamics of spatial light solitons in a birefringent medium with quadratic nonlinearity. Although no analytical expression for propagating solitons has been obtained, our numerical simulations show the existence of stable localized spatial solitons in the frequency forbidden band gap of the medium. The dynamics of these objects is quite rich and manifests for instance elastic reflections, or inelastic collisions where two solitons merge and propagate as a single solitary wave. We derive the dynamics of the slowly varying envelopes of the three fields (second harmonic pump and two-component signal) and study this new system theoretically. We show that it does present a threshold for nonlinear supratransmission that can be calculated from a series expansion approach with a very high accuracy. Specific physical implications of our theoretical predictions are illustrated on LiGaTe{sub 2} (LGT) crystals. Once irradiated by a cw laser beam of 10 {mu}m wavelength, at an incidence beyond the extinction angle, such crystals will transmit light, in the form of spatial solitons generated in the nonlinear regime above the nonlinear supratransmission threshold.

Anghel-Vasilescu, P. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, D-01187 Dresden (Germany); Dorignac, J.; Geniet, F.; Leon, J. [Laboratoire Charles Coulomb, Departement de Physique Theorique, UMR 5221 CNRS-UM2, Universite Montpellier 2, F-34095 Montpellier Cedex 5 (France); Taki, A. [Laboratoire de Physique des Lasers, Atomes et Molecules, CNRS-INP-UMR8523, Universite des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq (France)

2011-04-15

397

Phase Transitions in the Quadratic Contact Process on Complex Networks  

NASA Astrophysics Data System (ADS)

The quadratic contact process (QCP) is a natural extension of the well studied linear contact process where a single infected (1) individual can infect a susceptible (0) neighbor and infected individuals are allowed to recover (1 ->0). In the QCP, a combination of two 1's is required to effect a 0 ->1 change. We extend the study of the QCP, which so far has been limited to lattices, to complex networks as a model for the change in a population via sexual reproduction and death. We define two versions of the QCP -- vertex centered (VQCP) and edge centered (EQCP) with birth events 1-0-1 ->1-1-1 and 1-1-0 ->1-1-1 respectively, where `-' represents an edge. We investigate the effects of network topology by considering the QCP on regular, Erdos-Rényi and power law random graphs. We perform mean field calculations as well as simulations to find the steady state fraction of occupied vertices as a function of the birth rate. We find that on the homogeneous graphs (regular and Erdos-Rényi ) there is a discontinuous phase transition with a region of bistability, whereas on the heavy tailed power law graph, the transition is continuous. The critical birth rate is found to be positive in the former but zero in the latter.

Varghese, Chris; Durrett, Rick

2013-03-01

398

Structure preserving integrators for solving linear quadratic optimal control problems with applications to describe the flight of a quadrotor  

E-print Network

Structure preserving integrators for solving linear quadratic optimal control problems Valencia, Spain. Abstract We present structure preserving integrators for solving linear quadratic optimal control problems. This problem requires the numerical integration of matrix Riccati differential equations

Blanes, Sergio

399

Math. Res. Lett. 14 (2007), no. 2, 333341 c International Press 2007 THICK-THIN DECOMPOSITION FOR QUADRATIC  

E-print Network

FOR QUADRATIC DIFFERENTIALS Kasra Rafi 1. Introduction Quadratic differentials arise naturally in the study;334 KASRA RAFI a subsurface Y , which provides the scale factor in the main theorem. We show in Lemma 3

Rafi, Kasra

400

Elucidation of a low spin cobalt(II) system in a distorted tetrahedral geometry.  

PubMed

We have prepared a series of divalent cobalt(II) complexes supported by the [PhBP(3)] ligand ([PhBP(3)] = [PhB(CH(2)PPh(2))(3)](-)) to probe certain structural and electronic phenomena that arise from this strong field, anionic tris(phosphine) donor ligand. The solid-state structure of the complex [PhBP(3)]CoI (1), accompanied by SQUID, EPR, and optical data, indicates that it is a pseudotetrahedral cobalt(II) species with a doublet ground state-the first of its type. To our knowledge, all previous examples of 4-coordinate cobalt(II) complexes with doublet ground states have adopted square planar structure types. Complex 1 provided a useful precursor to the corresponding bromide and chloride complexes, ([PhBP(3)]Co(mu-Br))(2), (2), and ([PhBP(3)]Co(mu-Cl))(2), (3). These complexes were similarly characterized and shown to be dimeric in the solid-state. In solution, however, the monomeric low spin form of 2 and 3 dominates at 25 degrees C. There is spectroscopic evidence for a temperature-dependent monomer/dimer equilibrium in solution for complex 3. Furthermore, the dimers 2 and 3 did not display appreciable antiferromagnetic coupling that is typical of halide and oxo-bridged copper(II) and cobalt(II) dimers. Rather, the EPR and SQUID data for solid samples of 2 and 3 suggest that they have triplet ground states. Complexes 1, 2, and 3 are extremely oxygen sensitive. Thus, stoichiometric oxidation of 1 by dioxygen produced the 4-coordinate, high spin complex [PhB(CH(2)P(O)Ph(2))(2)(CH(2)PPh(2))]CoI, (4), in which the [PhBP(3)] ligand had undergone a 4-electron oxidation. Reaction of 1 with TlOAr (Ar = 2,6-Me(2)Ph) afforded an example of a 4-coordinate, high spin complex, [PhBP(3)]Co(O-2,6-Me(2)Ph) (5), with an intact [PhBP(3)] ligand. The latter two complexes were spectroscopically and structurally characterized for comparison to complexes 1, 2, and 3. Our data for these complexes collectively suggest that the [PhBP(3)] ligand provides an unusually strong ligand-field to these divalent cobalt complexes that is chemically distinct from typical tris(phosphine) donor ligand sets, and distinct from tridentate borato ligands that have been previously studied. Coupling this strong ligand-field with a pronounced axial distortion away from tetrahedral symmetry, a geometric consequence that is enforced by the [PhBP(3)] ligand, provides access to monomeric [PhBP(3)]CoX complexes with doublet rather than quartet ground states. PMID:12487609

Jenkins, David M; Di Bilio, Angel J; Allen, Matthew J; Betley, Theodore A; Peters, Jonas C

2002-12-25

401

Electrical and Electrochemical Properties of Nitrogen-Containing Tetrahedral Amorphous Carbon (ta-C) Thin Films  

NASA Astrophysics Data System (ADS)

Tetrahedral amorphous carbon (ta-C) is a diamond-like carbon (DLC) material comprised of a mixture of sp2 (˜40%) and sp3-bonded (˜60%) carbon domains. The physicochemical structure and electrochemical properties depend strongly on the sp2/sp3 bonding ratio as well as the incorporation of impurities, such as hydrogen or nitrogen. The ability to grow ta-C films at lower temperatures (25-100 °C) on a wider variety of substrates is a potential advantage of these materials as compared with diamond films. In this project, the basic structural and electrochemical properties of nitrogen-incorporated ta-C thin films will be discussed. The major goal of this work was to determine if the ta-C:N films exhibit electrochemical properties more closely aligned with those of boron-doped diamond (sp 3 carbon) or glassy carbon (amorphous sp2 carbon). Much like diamond, ta-C:N thin-film electrodes are characterized by a low background voltammetric current, a wide working potential window, relatively rapid electron-transfer kinetics for aqueous redox systems, such as Fe(CN) 6-3/-4 and Ru(NH3)6+3/+2 , and weak adsorption of polar molecules from solution. For example, negligible adsorption of methylene blue was found on the ta-C:N films in contrast to glassy carbon; a surface on which this molecule strongly adsorbs. The film microstructure was studied with x-ray photoelectron microscopy (XPS), visible Raman spectroscopy and electron-energy loss spectroscopy (EELS); all of which revealed the sp2-bonded carbon content increased with increasing nitrogen. The electrical properties of ta-C:N films were studied by four-point probe resistance measurement and conductive-probe AFM (CP-AFM). The incorporation of nitrogen into ta-C films increased the electrical conductivity primarily by increasing the sp2-bonded carbon content. CP-AFM showed the distribution of the conductive sp2-carbon on the film surface was not uniform. These films have potential to be used in field emission area. The heterogeneous electrochemical properties were studied with scanning electron microscopy (SECM). If was found that more electrically conducting sites were isolated by less conducting or even insulating sites. Consistent with the heterogeneous electrical properties, heterogeneous electrochemical activity was observed for different aqueous redox analytes. Flow injection analysis with electrochemical detection (EC-FIA) of dopamine and norepinephrine were carried out using the N-ta:C films. Detection figures of merit for these biomolecules were determined. These biomolecules can be detected stably and reproducible in PBS buffer at constant potential by N-ta:C film. The N-ta:C films provide good limits of detection for these biomolecules. N-ta:C films show great promise in the electroanalytical field. Compared with the diamond, the growth condition is much milder. These N-ta:C films are commercially available and could be produced in large scale. All of these virtues make N-ta:C films excellent choices for electroanalytical measurements.

Yang, Xingyi

402

Gurevich, S. et al. (2010) "Quadratic Reciprocity and the Sign of the Gauss Sum via the Finite Weil Representation,"  

E-print Network

constant. More specifically, the law of quadratic reciprocity follows from basic properties of the Weil known proofs of the law of quadratic reciprocity in terms of the Weil representation of some coverGurevich, S. et al. (2010) "Quadratic Reciprocity and the Sign of the Gauss Sum via the Finite Weil

Gurevich, Shamgar

403

A Bifurcation Analysis of the Quadratically Damped Mathieu Equation and Its Applications to the Dynamics of Submarine  

E-print Network

A Bifurcation Analysis of the Quadratically Damped Mathieu Equation and Its Applications behind a vessel. The LFD satisfies the non-dimensional quadratically damped Mathieu equation ¨x + ( + cos analysis of the quadratic Mathieu equation and a nonlinear analysis for small values of . The goal

Rand, Richard H.

404

Linear and quadratic static response functions and structure functions in Yukawa liquids.  

PubMed

We compute linear and quadratic static density response functions of three-dimensional Yukawa liquids by applying an external perturbation potential in molecular dynamics simulations. The response functions are also obtained from the equilibrium fluctuations (static structure factors) in the system via the fluctuation-dissipation theorems. The good agreement of the quadratic response functions, obtained in the two different ways, confirms the quadratic fluctuation-dissipation theorem. We also find that the three-point structure function may be factorizable into two-point structure functions, leading to a cluster representation of the equilibrium triplet correlation function. PMID:25215834

Magyar, Péter; Donkó, Zoltán; Kalman, Gabor J; Golden, Kenneth I

2014-08-01

405

Linear and quadratic static response functions and structure functions in Yukawa liquids  

E-print Network

We compute linear and quadratic static density response functions of three-dimensional Yukawa liquids by applying an external perturbation potential in molecular dynamics simulations. The response functions are also obtained from the equilibrium fluctuations (static structure factors) in the system via the fluctuation-dissipation theorems. The good agreement of the quadratic response functions, obtained in the two different ways confirms the quadratic fluctuation-dissipation theorem. We also find that the three-point structure function may be factorizable into two-point structure functions, leading to a cluster representation of the equilibrium triplet correlation function.

Magyar, P; Kalman, G J; Golden, K I

2014-01-01

406

1.2A-resolution crystal structures reveal the second tetrahedral intermediates of streptogrisin B (SGPB).  

PubMed

Streptogrisin B (SGPB) has served as one of the models for studying the catalytic activities of serine peptidases. Here we report its native crystal structures at pH 4.2 at a resolution of 1.18A, and at pH 7.3 at a resolution of 1.23A. Unexpectedly, outstanding electron density peaks occurred in the active site and the substrate-binding region of SGPB in the computed maps at both pHs. The densities at pH 4.2 were assigned as a tetrapeptide, Asp-Ala-Ile-Tyr, whereas those at pH 7.3 were assigned as a tyrosine molecule and a leucine molecule existing at equal occupancies in both of the SGPB molecules in the asymmetric unit. Refinement with relaxed geometric restraints resulted in molecular structures representing mixtures of the second tetrahedral intermediates and the enzyme-product complexes of SGPB existing in a pH-dependent equilibrium. Structural comparisons with the complexes of SGPB with turkey ovomucoid third domain (OMTKY3) and its variants have shown that, upon the formation of the tetrahedral intermediate, residues Glu192A to Gly193 of SGPB move towards the alpha-carboxylate O of residue P1 of the bound species, and adjustments in the side-chain conformational angles of His57 and Ser195 of SGPB favor the progression of the catalytic mechanism of SGPB. PMID:18157955

Lee, Ting-Wai; James, Michael N G

2008-02-01

407

Hydrogeniridate(VI) anion and the geometries of tetrahedral oxo-anions.  

PubMed

The compound KHIrO4, potassium hydrogentetraoxidoiridate(VI)(1-), crystallizes in a Scheelite-type structure containing discrete, slightly flattened, [Ir(O3OH)](-) tetrahedra--the first observation of a group 9 element in the 6+ oxidation state as an oxoanion. PMID:24819546

Weller, Mark T; Galati, Rosa

2014-06-01

408

Stability of the equilibrium positions of an engine with nonlinear quadratic springs  

NASA Astrophysics Data System (ADS)

Our paper realizes a study of the equilibrium positions for an engine supported by four identical nonlinear springs of quadratic characteristic. The systems with quadratic characteristic are generally avoided because they lead to mathematical complications. Our goal is to realize such a study for an engine supported on quadratic springs. For the model purposed, we established the equations of motion and we discussed the possibilities for the equilibrium positions. Because of the quadratic characteristic of the springs and of the approximations made for the small rotations, the equations obtained for the equilibrium lead us to a paradox, which consists in the existence of an open neighborhood in which there exists an infinity of positions of indifferent equilibrium, or a curve where the equilibrium positions are situated. Moreover, the study of the stability shows that the stability is assured for the position at which the springs are not compressed. Finally, a numerical example is presented and completely solved.

St?nescu, Nicolae-Doru; Popa, Dinel

2014-06-01

409

Nonparametric Estimation of Quadratic Regression Functionals LiShan Huang Jianqing Fan  

E-print Network

Nonparametric Estimation of Quadratic Regression Functionals Li­Shan Huang Jianqing Fan Department noise model are obtained in Donoho and Nussbaum (1990) and Fan (1991). In the context of nonparametric

Fan, Jianqing

410

Semidefinite relaxation based branch-and-bound method for nonconvex quadratic programming  

E-print Network

In this thesis, we use a semidefinite relaxation based branch-and-bound method to solve nonconvex quadratic programming problems. Firstly, we show an interval branch-and-bound method to calculate the bounds for the minimum ...

Hu, Sha, S.M. Massachusetts Institute of Technology

2006-01-01

411

Separation of quadratic and linear external field effects in high J quantum beats  

E-print Network

frequency harmonic modulation. A special geometry was found in which the quadratic beats are fully absent the magnetic, or Zee- man quantum beats yield Land6 factor values. Let us address quantum beats between

Auzinsh, Marcis

412

Sequential design of discrete linear quadratic regulators via optimal root-locus techniques  

NASA Technical Reports Server (NTRS)

A sequential method employing classical root-locus techniques has been developed in order to determine the quadratic weighting matrices and discrete linear quadratic regulators of multivariable control systems. At each recursive step, an intermediate unity rank state-weighting matrix that contains some invariant eigenvectors of that open-loop matrix is assigned, and an intermediate characteristic equation of the closed-loop system containing the invariant eigenvalues is created.

Shieh, Leang S.; Yates, Robert E.; Ganesan, Sekar

1989-01-01

413

A Branch-and-Bound Algorithm to Solve Large Scale Integer Quadratic Multi-Knapsack Problems  

Microsoft Academic Search

The separable quadratic multi-knapsack problem (QMKP) consists in maximizing a concave separable quadratic integer (non pure binary) function subject to m linear capacity constraints. In this paper we develop a branch-and-bound algorithm to solve (QMKP) to optimality. This method is based on the computation of a tight upper bound for (QMKP) which is derived from a linearization and a surrogate

Dominique Quadri; Éric Soutif; Pierre Tolla

2007-01-01

414

Robustness results in linear-quadratic Gaussian based multivariable control designs  

NASA Technical Reports Server (NTRS)

The robustness of control systems with respect to model uncertainty is considered using simple frequency domain criteria. Available and new results are derived under a common framework in which the minimum singular value of the return difference transfer matrix is the key quantity. In particular, robustness results associated with multivariable control systems designed on the basis of linear-quadratic (LQ) and the linear-quadratic Gaussian (LQG) design methodologies are presented.

Lehtomaki, N. A.; Athans, M.; Sandell, N. R., Jr.

1981-01-01

415

Applications of the quadratic covariation differentiation theory: variants of the Clark-Ocone and Stroock's formulas  

Microsoft Academic Search

In a 2006 article (\\\\cite{A1}), Allouba gave his quadratic covariation differentiation theory for It\\\\^o's integral calculus. He defined the derivative of a semimartingale with respect to a Brownian motion as the time derivative of their quadratic covariation and a generalization thereof. He then obtained a systematic differentiation theory containing a fundamental theorem of stochastic calculus relating this derivative to It\\\\^o's

Hassan Allouba; Ramiro Fontes

2010-01-01

416

Use of a Quadrat Rotenone Technique and Bioenergetics Modeling to Evaluate Prey Availability to Stocked Piscivores  

Microsoft Academic Search

Young-of-year gizzard shad Dorosoma cepedianum, the primary prey for piscivores in Ohio impoundments, are difficult to sample by conventional techniques. We developed a technique for sampling littoral zone quadrats with rotenone and compared this method to other gear. To sample, we isolated 0.15-hectare shoreline areas (N = 28 quadrats) with a plastic barrier, which confined the rotenone and even small

Brett M. Johnson; Roy A. Stein; Robert F. Carline

1988-01-01

417

A STRUCTURED METHOD FOR THE REAL QUADRATIC EIGENVALUE PROBLEM FOR SPECIFIC GYROSCOPIC SYSTEMS  

E-print Network

1 A Structured Method for the real Quadratic Eigenvalue Problem for speciflc Gyroscopic Systems BY Wade D. Rush Submitted to the graduate degree program in Mathematics and the Graduate Faculty of the University of Kansas in partial fulflllment... Version of the following thesis: A STRUCTURED METHOD FOR THE REAL QUADRATIC EIGENVALUE PROBLEM FOR SPECIFIC GYROSCOPIC SYSTEMS Committee: Chairperson: Dr. Hongguo Xu, Math Dept. Dr. Erik Van Vleck, Math Dept. Dr. Weizhang Huang, Math Dept. Date approved: 3...

Rush, Wade

2008-12-15

418

Induction of Quadratic Decision Trees using Genetic Algorithms and k-D Trees  

Microsoft Academic Search

Genetic Algorithm-based Quadratic Decision Tree (GA-based QDT) has been applied successfully in various classification problems with non-linear class boundaries. However, the execution time of GA-based QDT is quite long. In this paper, a new version of GA-based QDT, called Genetic Algorithm-based Quadratic Decision Tree with k-D Tree (GA-based QDT with k-D Tree), is proposed. In the proposed algorithm, a k-D

SAI-CHEONG NG; KWONG-SAK LEUNG

419

The Triangular Theorem of the Primes: Binary Quadratic Forms and Primitive Pythagorean Triples  

E-print Network

This article reports the occurrence of binary quadratic forms in primitive Pythagorean triangles and their geometric interpretation. In addition to the well-known fact that the hypotenuse, z, of a right triangle, with sides of integral (relatively prime) length, can be expressed as the sum of two squares, z=a^2+b^2, where a and b are positive integers of opposite parity such that a>b>0 and gcd(a,b)=1, it is shown that the sum of the two sides, x and y, can also be expressed as a binary quadratic form, x+y=(a+b)^2-2b^2. Similarly, when the radius of the inscribed circle is taken into account, r=b(a-b), a third binary quadratic form is found, namely (x+y)-4r=z-2r=(a-b)^2+2b^2. The three quadratic representations accommodate positive integers whose factorizations can only include primes p represented by the same type of binary quadratic forms, i.e. p=1,5(mod8), p=1,7(mod8), and p=1,3(mod8), respectively. For all three types of binary quadratic forms, when the positive integers represented are prime, such representations are unique. This implies that all odd primes can be geometrically incorporated into primitive Pythagorean triangles.

J. A. Perez

2011-02-21

420

Finite Element Flux-Corrected Transport (FEM-FCT) for the Euler and Navier-Stokes equations  

NASA Technical Reports Server (NTRS)

A high resolution finite element method for the solution of problems involving high speed compressible flows is presented. The method uses the concepts of flux-corrected transport and is presented in a form which is suitable for implementation on completely unstructured triangular or tetrahedral meshes. Transient and steady state examples are solved to illustrate the performance of the algorithm.

Loehner, Rainald; Morgan, Ken; Peraire, Jaime; Vahdati, Mehdi

1987-01-01

421

ASC Report No. 32/2011 Numerical quadratic energy minimization  

E-print Network

, M. Karkulik, JM. Melenk, D. Praetorius Quasi-optimal convergence rate for an adaptive boundary element method 27/2011 N. Happenhofer, O. Koch, F. Kupka IMEX Methods for the ANTARES Code 26/2011 Michael, Markus Mayr, Dirk Praetorius HILBERT-A MATLAB Implementation of Adaptive 2D-BEM 23/2011 JinMyong Kim

Melenk, Jens Markus

422

Automatic parallel generation of tetrahedral grids by using a domain decomposition approach  

NASA Astrophysics Data System (ADS)

An algorithm for the automatic parallel generation of three-dimensional unstructured grids based on geometric domain decomposition is proposed. A software package based on this algorithm is described. Examples of generating meshes for some application problems on a multiprocessor computer are presented. It is shown that the parallel algorithm can significantly (by a factor of several tens) reduce the mesh generation time. Moreover, it can easily generate meshes with as many as 5 × 107 elements, which can hardly be generated sequentially. Issues concerning the speedup and the improvement of the efficiency of the computations and of the quality of the resulting meshes are discussed.

Andrä, H.; Gluchshenko, O. N.; Ivanov, E. G.; Kudryavtsev, A. N.

2008-08-01

423

Water Adsorption at the Tetrahedral Titania Surface Layer of SrTiO3(110)-(4 x 1)  

PubMed Central

The interaction of water with oxide surfaces is of great interest for both fundamental science and applications. We present a combined theoretical (density functional theory (DFT)) and experimental (scanning tunneling microscopy (STM) and photoemission spectroscopy (PES)) study of water interaction with the two-dimensional titania overlayer that terminates the SrTiO3(110)-(4 × 1) surface and consists of TiO4 tetrahedra. STM and core-level and valence band PES show that H2O neither adsorbs nor dissociates on the stoichiometric surface at room temperature, whereas it does dissociate at oxygen vacancies. This is in agreement with DFT calculations, which show that the energy barriers for water dissociation on the stoichiometric and reduced surfaces are 1.7 and 0.9 eV, respectively. We propose that water weakly adsorbs on two-dimensional, tetrahedrally coordinated overlayers. PMID:24353755

2013-01-01

424

Computing secular motion under slowly rotating quadratic perturbation  

E-print Network

We consider secular perturbations of nearly Keplerian two-body motion under a perturbing potential that can be approximated to sufficient accuracy by expanding it to second order in the coordinates. After averaging over time to obtain the secular Hamiltonian, we use angular momentum and eccentricity vectors as elements. The method of variation of constants then leads to a set of equations of motion that are simple and regular, thus allowing efficient numerical integration. Some possible applications are briefly described.

S. Mikkola; P. Nurmi

2006-06-09

425

Chemical Elements  

NSDL National Science Digital Library

To find quick facts on elements The Photographic Periodic Table of Elements-shows a photograhpic representation of most of the elements (remember some are invisible gases) The Element Song Click on the following links to find quick facts about the elements and peridoic table: Periodic Table of Elements: LANL - Originally this resource, the Periodic Table, was created by Robert Husted at Los Alamos National Laboratory during his time ...

Schultz, Ms.

2007-03-08

426

MGGHAT: ELLIPTIC PDE SOFTWARE WITH ADAPTIVE REFINEMENT, MULTIGRID AND HIGH ORDER FINITE ELEMENTS  

E-print Network

MGGHAT: ELLIPTIC PDE SOFTWARE WITH ADAPTIVE REFINEMENT, MULTIGRID AND HIGH ORDER FINITE ELEMENTS. It is a finite element method with linear, quadratic or cubic ele­ ments over triangles. The adaptive refinement via newest vertex bisection and the multigrid iteration are both based on a hierarchical basis

427

A Wavelet Bicoherence-Based Quadratic Nonlinearity Feature for Translational Axis Condition Monitoring  

PubMed Central

The translational axis is one of the most important subsystems in modern machine tools, as its degradation may result in the loss of the product qualification and lower the control precision. Condition-based maintenance (CBM) has been considered as one of the advanced maintenance schemes to achieve effective, reliable and cost-effective operation of machine systems, however, current vibration-based maintenance schemes cannot be employed directly in the translational axis system, due to its complex structure and the inefficiency of commonly used condition monitoring features. In this paper, a wavelet bicoherence-based quadratic nonlinearity feature is proposed for translational axis condition monitoring by using the torque signature of the drive servomotor. Firstly, the quadratic nonlinearity of the servomotor torque signature is discussed, and then, a biphase randomization wavelet bicoherence is introduced for its quadratic nonlinear detection. On this basis, a quadratic nonlinearity feature is proposed for condition monitoring of the translational axis. The properties of the proposed quadratic nonlinearity feature are investigated by simulations. Subsequently, this feature is applied to the real-world servomotor torque data collected from the X-axis on a high precision vertical machining centre. All the results show that the performance of the proposed feature is much better than that of original condition monitoring features. PMID:24473281

Li, Yong; Wang, Xiufeng; Lin, Jing; Shi, Shengyu

2014-01-01

428

Efficient optical resolution of water-soluble self-assembled tetrahedral M4L6 cages with 1,1'-bi-2-naphthol.  

PubMed

In this paper, a water-soluble racemic self-assembled tetrahedral cage [Fe4L6](4-) was successfully resolved into their ???? and ???? enantiomers by (R)-/(S)-1,1'-bi-2-naphthol. The enantiomeric excess of the resolved Fe(ii) cage was 99%. PMID:25076461

Wan, Shigang; Lin, Li-Rong; Zeng, Lili; Lin, Yiji; Zhang, Hui

2014-12-18

429

Tetrahedral Displacement: The Molecular Mechanism behind the Debye Relaxation Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew UniVersity,  

E-print Network

time, D, and possesses a smaller activation energy. It governs the abnormally fast proton mobility agreement with the activation energy for water reorientation and, in the framework of a two- dimensionalTetrahedral Displacement: The Molecular Mechanism behind the Debye Relaxation in Water Noam Agmon

Agmon, Noam

430

Detection of code spread OFDM based on 0-1 integer quadratic programming  

NASA Astrophysics Data System (ADS)

In this paper we introduce Integer Quadratic Programming (MIQP) approach to optimally detect QPSK Code Spread OFDM (CS-OFDM) by formulating the problem as a combinatorial optimization problem. The Branch and Bound (BB) algorithm is utilized to solve this integer quadratic programming problem. Furthermore, we propose combined preprocessing steps that can be applied prior to BB so that the computational complexity of the optimum receiver is reduced. The first step in this combination is to detect as much as possible symbols using procedures presented in [9], which is basically based on the gradient of quadratic function. The second step detects the undetected symbols from the first step using MMSE estimator. The result of the latter step will be used to predict the initial upper bound of the BB algorithm. Simulation results show that the proposed preprocessing combination when applied prior to BB provides optimal performance with a significantly reduced computational complexity.

Elghariani, Ali; Zoltowski, Michael D.

2012-05-01

431

An accelerated proximal gradient algorithm for singly linearly constrained quadratic programs with box constraints.  

PubMed

Recently, the existed proximal gradient algorithms had been used to solve non-smooth convex optimization problems. As a special nonsmooth convex problem, the singly linearly constrained quadratic programs with box constraints appear in a wide range of applications. Hence, we propose an accelerated proximal gradient algorithm for singly linearly constrained quadratic programs with box constraints. At each iteration, the subproblem whose Hessian matrix is diagonal and positive definite is an easy model which can be solved efficiently via searching a root of a piecewise linear function. It is proved that the new algorithm can terminate at an ?-optimal solution within [Formula: see text] iterations. Moreover, no line search is needed in this algorithm, and the global convergence can be proved under mild conditions. Numerical results are reported for solving quadratic programs arising from the training of support vector machines, which show that the new algorithm is efficient. PMID:24223028

Han, Congying; Li, Mingqiang; Zhao, Tong; Guo, Tiande

2013-01-01

432

Application of penalized least-squares algorithm in PET image reconstruction based a nonlocal quadratic prior  

NASA Astrophysics Data System (ADS)

In this paper, we present a novel image reconstruction method based on penalized least squares (PLS) objective function for positron emission tomography (PET). Unlike usual PLS algorithm, the proposed method, which is called NL-PLS, combines a novel nonlocal quadratic prior with the classical least squares algorithm. The novel prior can not only solve the unfavorable oversmoothing effect produced by the simple quadratic membrane (QM) smoothing prior, but also partly eliminate blocky piecewise regions or so-called staircase artifacts produced by edge-preserving nonquadratic priors. What's more, we can easily confirm the convergence of the NL-PLS as the objective function' quadratic characteristic. The performance of the proposed NL-PLS method is evaluated in experiments using simulated data. The results show that the method is advantageous, compared with the Filter Back Projection (FBP) reconstruction and Maximum Likelihood (MLEM) reconstruction, and Bayesian constructions using the normal local priors.

Gui, Zhiguo; He, Jiawei; Ma, Xiaobo

2011-10-01

433

Theoretical analysis of integral neutron transport equation using collision probability method with quadratic flux approach  

NASA Astrophysics Data System (ADS)

Theoretical analysis of integral neutron transport equation using collision probability (CP) method with quadratic flux approach has been carried out. In general, the solution of the neutron transport using the CP method is perfomed with the flat flux approach. In this research, the CP method is implemented in the cylindrical nuclear fuel cell with the spatial of mesh being conducted into non flat flux approach. It means that the neutron flux at any point in the nuclear fuel cell are considered different each other followed the distribution pattern of quadratic flux. The result is presented here in the form of quadratic flux that is better understanding of the real condition in the cell calculation and as a starting point to be applied in computational calculation.

Shafii, Mohammad Ali; Meidianti, Rahma; Wildian, Fitriyani, Dian; Tongkukut, Seni H. J.; Arkundato, Artoto

2014-09-01

434

Quadratic optomechanics in a cryogenic membrane-in-the-middle system  

E-print Network

Optomechanical experiments in the quantum regime have mostly been limited to the study of Gaussian states. This limitation is largely due to the linearity of the optomechanical coupling that is realized in most devices. In contrast, theoretical proposals show that non-Gaussian states and other striking quantum phenomena (such as quantum jumps between phonon number eigenstates) can be observed in optomechanical systems with large nonlinear coupling, provided that they operate in the resolved sideband regime, with very low damping, and in a sufficiently cold environment. Here we describe a device that meets these requirements. Specifically, we demonstrate a cryogenic, resolved sideband membrane-in-the-middle device with large quadratic optomechanical coupling. We present a thorough characterization of the classical dynamics that result from the quadratic coupling and find that these results agree with a simple model. We also use the quadratic coupling to monitor fluctuations of the intracavity laser power, in a...

Lee, Donghun; Mason, David; Shkarin, Alexey B; Hoch, Scott W; Harris, Jack G E

2014-01-01

435

An Accelerated Proximal Gradient Algorithm for Singly Linearly Constrained Quadratic Programs with Box Constraints  

PubMed Central

Recently, the existed proximal gradient algorithms had been used to solve non-smooth convex optimization problems. As a special nonsmooth convex problem, the singly linearly constrained quadratic programs with box constraints appear in a wide range of applications. Hence, we propose an accelerated proximal gradient algorithm for singly linearly constrained quadratic programs with box constraints. At each iteration, the subproblem whose Hessian matrix is diagonal and positive definite is an easy model which can be solved efficiently via searching a root of a piecewise linear function. It is proved that the new algorithm can terminate at an ?-optimal solution within O(1/?) iterations. Moreover, no line search is needed in this algorithm, and the global convergence can be proved under mild conditions. Numerical results are reported for solving quadratic programs arising from the training of support vector machines, which show that the new algorithm is efficient. PMID:24223028

Han, Congying; Zhao, Tong; Guo, Tiande

2013-01-01

436

Design of a two-dimensional metamaterial cloak with minimum scattering using a quadratic transformation function  

NASA Astrophysics Data System (ADS)

The presence of extreme material properties and undesired scattering make practical implementation of transformation optics based cloaks an extremely challenging issue. To overcome these problems, a simplified quadratic cloak has been proposed which provides finite material properties at the inner radius of the cloak and impedance match with the free space at the outer radius of the cloak simultaneously. The simultaneous occurrence of finite material properties and impedance match with the free space at the respective boundaries reduces the scattering cross section significantly. The material properties of the proposed simplified quadratic cloak can be realized with two dimensional (2D) metamaterials. The performance of the proposed cloak is examined by plotting the normalized total scattering cross section (SCSt,norm), and the scattering patterns in azimuthal plane. The proposed simplified quadratic cloak shows 10 dB reduction of the scattered field in both the forward and backward directions with respect to the perfect electric conductor (PEC) cylinder.

Rajput, Archana; Srivastava, Kumar Vaibhav

2014-09-01

437

Soliton compression to high-quality few-cycle pulses by engineering cascaded quadratic nonlinearities  

E-print Network

We propose an efficient approach to improve few-cycle soliton compression with cascaded quadratic nonlinearities by using an engineered multi-section structure of the nonlinear crystal. By exploiting engineering of the cascaded quadratic nonlinearities, in each section soliton compression with a low effective order is realized, and high-quality few-cycle pulses with large compression factors are feasible. Each subsequent section is designed so that the compressed pulse exiting the previous section experiences an overall effective self-defocusing cubic nonlinearity corresponding to a modest soliton order, which is kept larger than unity to ensure further compression. This is done by increasing the cascaded quadratic nonlinearity in the new section with an engineered reduced residual phase mismatch. The low soliton orders in each section ensure excellent pulse quality and high efficiency. Numerical results show that compressed pulses with less than three-cycle duration can be achieved even when the compression ...

Zeng, Xianglong; Zhou, Binbin; Bache, Morten

2012-01-01

438

Directional passability and quadratic steering logic for pyramid-type single gimbal control moment gyros  

NASA Astrophysics Data System (ADS)

Singularity analysis and the steering logic of pyramid-type single gimbal control moment gyros are studied. First, a new concept of directional passability in a specified direction is introduced to investigate the structure of an elliptic singular surface. The differences between passability and directional passability are discussed in detail and are visualized for 0H, 2H, and 4H singular surfaces. Second, quadratic steering logic (QSL), a new steering logic for passing the singular surface, is investigated. The algorithm is based on the quadratic constrained quadratic optimization problem and is reduced to the Newton method by using Gröbner bases. The proposed steering logic is demonstrated through numerical simulations for both constant torque maneuvering examples and attitude control examples.

Yamada, Katsuhiko; Jikuya, Ichiro

2014-09-01

439

Sequential design of linear quadratic state regulators via the optimal root-locus techniques  

NASA Technical Reports Server (NTRS)

The use of well-known root-locus techniques for sequentially finding the weighting matrices and the linear quadratic state regulators of multivariable control systems in the frequency domain is considered. This sequential design method permits the retention of some stable open-loop poles and the associated eigenvectors in the closed-loop system; it also allows some optimal closed-loop poles to be placed in a specific region of the complex plane. In addition, it provides a design procedure for determining the weighting matrices and linear quadratic state regulators for the optimal control of multivariable systems in the frequency domain.

Shieh, L. S.; Dib, H. M.; Yates, R. E.

1988-01-01

440

Generation of Knot Net for Calculation of Quadratic Triangular B-spline Surface of Human Head  

NASA Astrophysics Data System (ADS)

This paper deals with calculation of the quadratic triangular B-spline surface of the human head for the purpose of its modeling in the standard videocodec MPEG-4 SNHC. In connection with this we propose an algorithm of generation of the knot net and present the results of its application for triangulation of the 3D polygonal model Candide. Then for the model and generated knot net as well as an established distribution of control points we show the results of the calculated quadratic triangular B-spline surface of the human head including its textured version for the texture of the selected avatar.

Mihalík, Ján

2011-09-01

441

Design of linear quadratic regulators with eigenvalue placement in a specified region  

NASA Technical Reports Server (NTRS)

Two linear quadratic regulators are developed for placing the closed-loop poles of linear multivariable continuous-time systems within the common region of an open sector, bounded by lines inclined at +/- pi/2k (for a specified integer k not less than 1) from the negative real axis, and the left-hand side of a line parallel to the imaginary axis in the complex s-plane, and simultaneously minimizing a quadratic performance index. The design procedure mainly involves the solution of either Liapunov equations or Riccati equations. The general expression for finding the lower bound of a constant gain gamma is also developed.

Shieh, Leang-San; Zhen, Liu; Coleman, Norman P.

1990-01-01

442

Contractions and deformations of quasiclassical Lie algebras preserving a nondegenerate quadratic Casimir operator  

SciTech Connect

By means of contractions of Lie algebras, we obtain new classes of indecomposable quasiclassical Lie algebras that satisfy the Yang-Baxter equations in its reformulation in terms of triple products. These algebras are shown to arise naturally from noncompact real simple algebras with nonsimple complexification, where we impose that a nondegenerate quadratic Casimir operator is preserved by the limiting process. We further consider the converse problem and obtain sufficient conditions on integrable cocycles of quasiclassical Lie algebras in order to preserve nondegenerate quadratic Casimir operators by the associated linear deformations.

Campoamor-Stursberg, R., E-mail: rutwig@mat.ucm.e [Universidad Complutense, Departamento de Geometria y Topologia (Spain)

2008-05-15

443

Convex relaxations of non-convex mixed integer quadratically constrained programs: projected formulations  

Microsoft Academic Search

A common way to produce a convex relaxation of a Mixed Integer Quadratically Constrained Program (MIQCP) is to lift the problem\\u000a into a higher-dimensional space by introducing variables Y\\u000a \\u000a ij\\u000a to represent each of the products x\\u000a \\u000a i\\u000a \\u000a x\\u000a \\u000a j\\u000a of variables appearing in a quadratic form. One advantage of such extended relaxations is that they can be efficiently strengthened

Anureet Saxena; Pierre Bonami; Jon Lee

444

Non-Quadratic Gauge Fixing and Ghosts for Gauge Theories on the Hypersphere  

E-print Network

It has been suggested that using a gauge fixing Lagrangian that is not quadratic in a gauge fixing condition is most appropriate for gauge theories formulated on a hypersphere. We reexamine the appropriate ghost action that is to be associated with gauge fixing, applying a technique that has been used for ensuring that the propagator for a massless spin-two field is transverse and traceless. It is shown that this non-quadratic gauge fixing Lagrangian leads to two pair of complex Fermionic ghosts and two Bosonic real ghosts.

F. T. Brandt; D. G. C. McKeon

2011-10-07

445

Toward Verification of USM3D Extensions for Mixed Element Grids  

NASA Technical Reports Server (NTRS)

The unstructured tetrahedral grid cell-centered finite volume flow solver USM3D has been recently extended to handle mixed element grids composed of hexahedral, prismatic, pyramidal, and tetrahedral cells. Presently, two turbulence models, namely, baseline Spalart-Allmaras (SA) and Menter Shear Stress Transport (SST), support mixed element grids. This paper provides an overview of the various numerical discretization options available in the newly enhanced USM3D. Using the SA model, the flow solver extensions are verified on three two-dimensional test cases available on the Turbulence Modeling Resource website at the NASA Langley Research Center. The test cases are zero pressure gradient flat plate, planar shear, and bump-inchannel. The effect of cell topologies on the flow solution is also investigated using the planar shear case. Finally, the assessment of various cell and face gradient options is performed on the zero pressure gradient flat plate case.

Pandya, Mohagna J.; Frink, Neal T.; Ding, Ejiang; Parlette, Edward B.

2013-01-01

446

Importance of tetrahedral coordination for high-valent transition-metal oxides: YCrO4 as a model system  

NASA Astrophysics Data System (ADS)

We have investigated the electronic structure of the high oxidation state material YCrO4 within the framework of the Zaanen-Sawatzky-Allen phase diagram. While Cr4+-based compounds such as SrCrO3/CaCrO3 and CrO2 can be classified as small-gap or metallic negative-charge-transfer systems, we find using photoelectron spectroscopy that YCrO4 is a robust insulator despite the fact that its Cr ions have an even higher formal valence state of 5+. We reveal using band-structure calculations that the tetrahedral coordination of the Cr5+ ions in YCrO4 plays a decisive role, namely to diminish the bonding of the Cr 3d states with the top of the O 2p valence band. This finding not only explains why the charge-transfer energy remains effectively positive and the material stable, but also opens up a new route to create doped carriers with symmetries different from those of other transition-metal ions.

Tsirlin, A. A.; Rabie, M. G.; Efimenko, A.; Hu, Z.; Saez-Puche, R.; Tjeng, L. H.

2014-08-01

447

Effects of tetrahedral Fe2+ on the structural, magnetic and electronic properties of solution-based titanomagnetite thin films  

NASA Astrophysics Data System (ADS)

Polycrystalline titanomagnetite (Ti x Fe3- x O4) thin films prepared by using a sol-gel process exhibited a phase-pure spinel structure for Ti compositions up to x = 0.6. An X-ray photoelectron spectroscopy (XPS) investigation disclosed an increase of the Fe2+ concentration with increasing x, indicating a reduction in ionic valence, Fe3+ ? Fe2+, induced by Ti4+ occupation of the cationic sublattice. Analyses on XPS and X-ray diffraction spectra of the Ti x Fe3- x O4 samples suggest that the Fe2+ ions prefer the tetrahedral sites while the Ti4+ ions prefer the octahedral sites of the sublattice. Magnetic hysteresis measurements on the Ti x Fe3- x O4 films revealed significant loss of the saturation magnetization (M s ) with increasing x: M s is reduced to 50% that of Fe3O4 for x = 0.10 and to 10% for x = 0.60. The big loss of M s caused by small Ti doping suggests a significant disruption of the inter-site Fe3+-Fe3+ super-exchange interaction in thin-film titanomagnetites.

Kim, Kwang Joo; Koh, Tae Young; Kim, Chul Sung; Lee, Young Bae

2014-01-01

448

Shape distribution and correlation between size and shape of star-branched tetrahedral lattice chains in athermal and theta systems  

NASA Astrophysics Data System (ADS)

By means of Monte Carlo simulation, linear (F=2) and star-branched tetrahedral lattice chains with F=3-12 arms of length n=480 connected to a hard core consisting of MIN(5,F+1) segments (the total number of segments thus ranging from 963 to 5765) were produced for athermal and theta conditions. Nonreversal random walks (random walks without backfolding bonds) were generated as a reference. Several quantities (asphericity factor ?*, prolateness factor S*, and shape factors sfi*) characteristic of the instantaneous shape of molecules—being based on the orthogonal components of the squared radius of gyration taken along the principal axes of inertia—were computed. The probability distributions of these quantities were calculated and their interdependence as well as their correlation with quantities characteristic of the size of configurations was analyzed. Shape and size of star-branched chains for athermal as well as for theta conditions are highly correlated as earlier found for linear chains and random walk stars. The broadness of distribution functions decreases with increasing number of arms, but remains appreciably for F=12, the system with the largest functionality evaluated.

Zifferer, Gerhard

1999-03-01

449

sp3-rich deposition conditions and growth mechanism of tetrahedral amorphous carbon films deposited using filtered arc  

NASA Astrophysics Data System (ADS)

Tetrahedral amorphous carbon (ta-C) films with many superior properties approaching those of diamond crystal were prepared using filtered cathodic vacuum arc technology. To ascertain the sp3-rich deposition condition, the dependence of the film microstructure on the deposition energy was investigated by means of visible Raman spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, x-ray reflectivity, and nanoindentation. The maximum hardness and Young's modulus are achieved at a bias of -80V, at which the maximum sp3 fraction of about 82% is obtained. Under this condition, the most symmetric Raman line shape, the highest x-ray photoemission C 1s core level position and a ?* transition peak with the smallest integral area in the K-edge spectra are simultaneously achieved. The structural properties are found to be strongly correlated with the mass density of the films. At the optimal substrate bias of -80V, the film mass density reaches its maximum value. The cross section of the films is characterized with a layered distribution in mass density. A surface layer with low density is an intrinsic feature and experimental evidence of the subplantation growth of the films.

Zhu, Jiaqi; Han, Jiecai; Han, Xiao; Schlaberg, H. Inaki; Wang, Jiazhi

2008-07-01

450

Final Report - High-Order Spectral Volume Method for the Navier-Stokes Equations On Unstructured Tetrahedral Grids  

SciTech Connect

The overriding objective for this project is to develop an efficient and accurate method for capturing strong discontinuities and fine smooth flow structures of disparate length scales with unstructured grids, and demonstrate its potentials for problems relevant to DOE. More specifically, we plan to achieve the following objectives: 1. Extend the SV method to three dimensions, and develop a fourth-order accurate SV scheme for tetrahedral grids. Optimize the SV partition by minimizing a form of the Lebesgue constant. Verify the order of accuracy using the scalar conservation laws with an analytical solution; 2. Extend the SV method to Navier-Stokes equations for the simulation of viscous flow problems. Two promising approaches to compute the viscous fluxes will be tested and analyzed; 3. Parallelize the 3D viscous SV flow solver using domain decomposition and message passing. Optimize the cache performance of the flow solver by designing data structures minimizing data access times; 4. Demonstrate the SV method with a wide range of flow problems including both discontinuities and complex smooth structures. The objectives remain the same as those outlines in the original proposal. We anticipate no technical obstacles in meeting these objectives.

Wang, Z J

2012-12-06

451

Effects and thermal stability of hydrogen microwave plasma treatment on tetrahedral amorphous carbon films by in situ ultraviolet photoelectron spectroscopy  

SciTech Connect

This paper reports a comprehensive experimental study on the effects of hydrogen microwave plasma treatment on nonhydrogenated high sp{sup 3} content tetrahedral amorphous carbon (ta-C) film. In this study, a surface C-H dipole layer was first observed by high resolution electron energy loss spectroscopy, showing the presence of C-H bonding states. This resulted in the enhancement of electron field emission of the plasma treated films by largely lowering the turn-on field. Thermal stability tests using in situ ultraviolet photoelectron spectroscopy confirm that the C-H dipole layer not only reduces the work function of the films, it is extremely stable in both ambient and vacuum conditions and can sustain up to 600 deg. C annealing in vacuum. Atomic force microscopy studies also show minimal modifications to the surface morphology, leading to the conclusion that the C-H dipole layer is responsible for lowering the work function. This has improved the electron emission properties which can lead to potential applications such as electron emission displays.

Chua, Daniel H. C.; Hsieh, Jovan [Department of Materials Science and Engineering, National University of Singapore, Science Drive 3, Singapore 119260 (Singapore); Gao Xingyu; Qi Dongchen; Chen Shi; Varghese, Binni; Sow, Chorng Haur; Wee, A. T. S. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Lu Jiong; Loh, Kian Ping [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Yu Xiaojiang; Moser, Herbert O. [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore)

2009-07-15

452

One-pot, water-based and high-yield synthesis of tetrahedral palladium nanocrystal decorated graphene  

NASA Astrophysics Data System (ADS)

This paper reports a facile, water-based and one-pot synthesis of tetrahedral Pd nanocrystals (Pd-TNPs) with high yield and good size monodispersity supported on reduced graphene oxide (RGO) nanosheets via a co-chemical reduction method. The key synthetic strategy employed a positively charged polyallylamine-PdII complex (PAH-PdII) with un-coordinated amine groups as a linker molecule to immobilize PdII species on the negatively charged graphene oxide (GO) surface through electrostatic interaction. As characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) techniques, well-defined Pd-TNPs with an average size of 9 nm were uniformly distributed on the RGO surface. The as-prepared Pd-TNPs/RGO nanohybrid with excellent colloidal stability in aqueous solution exhibits superior catalytic activity towards the degradation of methylene blue (MB) compared to both unsupported Pd-TNPs and Pd black. Thus, the resultant Pd-TNPs/RGO nanohybrid, as a promising heterogeneous catalyst, might have wide potential applications in water-based catalysis systems for the future.

Fu, Gengtao; Tao, Lin; Zhang, Min; Chen, Yu; Tang, Yawen; Lin, Jun; Lu, Tianhong

2013-08-01

453

Erasing no-man’s land by thermodynamically stabilizing the liquid-liquid transition in tetrahedral particles  

NASA Astrophysics Data System (ADS)

One of the most controversial hypotheses for explaining the origin of the thermodynamic anomalies characterizing liquid water postulates the presence of a metastable second-order liquid-liquid critical point located in the `no-man’s land’. In this scenario, two liquids with distinct local structure emerge near the critical temperature. Unfortunately, as spontaneous crystallization is rapid in this region, experimental support for this hypothesis relies on significant extrapolations, either from the metastable liquid or from amorphous solid water. Although the liquid-liquid transition is expected to feature in many tetrahedrally coordinated liquids, including silicon, carbon and silica, even numerical studies of atomic and molecular models have been unable to conclusively prove the existence of this transition. Here we provide such evidence for a model in which it is possible to continuously tune the softness of the interparticle interaction and the flexibility of the bonds, the key ingredients controlling the existence of the critical point. We show that conditions exist where the full coexistence is thermodynamically stable with respect to crystallization. Our work offers a basis for designing colloidal analogues of water exhibiting liquid-liquid transitions in equilibrium, opening the way for experimental confirmation of the original hypothesis.

Smallenburg, Frank; Filion, Laura; Sciortino, Francesco

2014-09-01

454

New approaches to relaxed quadratic stability condition of fuzzy control systems  

Microsoft Academic Search

This paper deals with the quadratic stability conditions of fuzzy control systems that relax the existing conditions reported in the previous literatures. Two new conditions are proposed and shown to be useful in analyzing and designing fuzzy control systems. The first one employs the S-procedure to utilize information regarding the premise parts of the fuzzy systems. The next one enlarges

Euntai Kim; Heejin Lee

2000-01-01

455

Human-Inspired Control of Bipedal Robots via Control Lyapunov Functions and Quadratic Programs  

E-print Network

Human-Inspired Control of Bipedal Robots via Control Lyapunov Functions and Quadratic Programs walking through controller synthesis inspired by human locomotion. Motivated by the hierarchical con- trol present in humans, we begin by viewing the human as a "black box" and describe outputs, or virtual

Ames, Aaron

456

A tutorial on the LQG/LTR method. [Linear Quadratic Gaussian/Loop Transfer Recovery  

NASA Technical Reports Server (NTRS)

In this paper the so-called Linear-Quadratic-Gaussian method with Loop-Transfer-Recovery is surveyed. The objective is to provide a pragmatic exposition, with special emphasis on the step-by-step characteristics for designing multivariable feedback control systems.

Athans, M.

1986-01-01

457

A Hybrid Dynamic/Quadratic Programming Algorithm for Interconnect Tree Optimization  

E-print Network

in determining the system performance of the 0.25 m technology. Even with the help of copper and low dielectric constant () materials, interconnect delay is still likely to dominate the chip performance beyond 0.18 m/Quadratic Programming (DQP) to refer to our hybrid algorithm. In addition, we present a constant reusing technique

Chu, Chris C.-N.

458

On some dynamical and geometrical properties of the Maxwell-Bloch equations with a quadratic control  

E-print Network

In this paper, we analyze the stability of the real-valued Maxwell-Bloch equations with a control that depends on state variables quadratically. We also investigate the topological properties of the energy-Casimir map, as well as the existence of periodic orbits and explicitly construct the heteroclinic orbits.

Tudor Binzar; Cristian Lazureanu

2014-02-24

459

http://www.jstor.org The Simplex Method for Quadratic Programming  

E-print Network

http://www.jstor.org The Simplex Method for Quadratic Programming Author(s): Philip Wolfe Source: Econometrica, Vol. 27, No. 3, (Jul., 1959), pp. 382-398 Published by: The Econometric Society Stable URL: http://www.jstor.org/stable/1909468 Accessed: 22/07/2008 04:45 Your use of the JSTOR archive indicates your acceptance of JSTOR

Recht, Ben

460

Annihilating polynomials for quadratic forms and Stirling numbers of the second kind  

E-print Network

Annihilating polynomials for quadratic forms and Stirling numbers of the second kind Stefan De valuation of Stirling numbers of the second kind. 1 Introduction In 1937, Witt already observed out to be related to the Stirling numbers of the second kind. The result about the (torsion

461

Annihilating polynomials for quadratic forms and Stirling numbers of the second kind  

E-print Network

Annihilating polynomials for quadratic forms and Stirling numbers of the second kind Stefan De valuation of Stirling numbers of the second kind. 1 Introduction In 1937, Witt already observed of sums of m­fold Pfis­ ter forms and the coe#cients that appear turn out to be related to the Stirling

462

Annihilating polynomials for quadratic forms and Stirling numbers of the second kind  

E-print Network

Annihilating polynomials for quadratic forms and Stirling numbers of the second on the 2-adic valuation of Stirling numbers of the second kind. 1 Introduction In 1937, Witt obtaining a new lower bound for the 2-adic valuation of all Stirling numbers S(n, k) of the second kind

463

Two-color surface solitons in two-dimensional quadratic photonic lattices  

E-print Network

lattice, and we analyze the impact of the phase mismatch on their properties, stability, and the threshold power for their generation. © 2009 Optical Society of America OCIS codes: 190.4350, 190.4410, 190 for cubic or saturable nonlinear media. However, multicolor discrete solitons in quadratically nonlinear

464

Brief note on Ashtekar-Magnon-Das conserved quantities in quadratic curvature theories  

SciTech Connect

In this note, we correct a mistake in the mass formula in [N. Okuyama and J. i. Koga, Phys. Rev. D 71, 084009 (2005).] which generalizes the Ashtekar-Magnon-Das method to incorporate extended gravities with quadratic curvature terms. The corrected mass formula confirms that the black hole masses for recently discovered critical gravities vanish.

Pang Yi [Kavli Institute for Theoretical Physics, Key Laboratory of Frontiers in Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2011-04-15

465

Homotopy perturbation method for quadratic Riccati differential equation and comparison with Adomian's decomposition method  

Microsoft Academic Search

In this paper, a homotopy perturbation method is proposed to solve quadratic Riccati differential equation. Comparisons are made between Adomian’s decomposition method (ADM) and the exact solution and the proposed method. The results reveal that the proposed method is very effective and simple.

Saeid Abbasbandy

2006-01-01

466

Linear matrix inequalities, Riccati equations, and indefinite stochastic linear quadratic controls  

Microsoft Academic Search

This paper deals with an optimal stochastic linear-quadratic (LQ) control problem in infinite time horizon, where the diffusion term in dynamics depends on both the state and the control variables. In contrast to the deterministic case, we allow the control and state weighting matrices in the cost functional to be indefinite. This leads to an indefinite LQ problem, which may

Mustapha Ait Rami; Xun Yu Zhou

2000-01-01

467

QUADRATIC ALTERNATING DIRECTION IMPLICIT ITERATION FOR THE FAST SOLUTION OF ALGEBRAIC RICCATI EQUATIONS  

E-print Network

QUADRATIC ALTERNATING DIRECTION IMPLICIT ITERATION FOR THE FAST SOLUTION OF ALGEBRAIC RICCATI@ecn.purdue.edu ABSTRACT Algebraic Riccati equations (AREs) spread over many branches of signal processing and system of an algebraic Riccati equation (ARE) plays an im- portant role in many engineering and scientific applications

Balakrishnan, Venkataramanan "Ragu"

468

Iterated He’s homotopy perturbation method for quadratic Riccati differential equation  

Microsoft Academic Search

In this paper, iterated He’s homotopy perturbation method is proposed to solving quadratic Riccati differential equation. Comparisons are made between Adomian’s decomposition method (ADM) and the exact solution and the proposed method. The results reveal that the method is very effective and simple.

S. Abbasbandy

2006-01-01

469

An Efficient Sequential Linear Quadratic Algorithm for Solving Nonlinear Optimal Control Problems  

E-print Network

sequence of linear quadratic subproblems. Each subproblem is solved efficiently using the Riccati complex to compute analytically. Our algorithm is based on linearizing the system dynamics about a input by solving a Riccati difference equation. Algorithms similar in spirit are reported in [6], [7], [8], [9

Bobrow, James E.

470

QUADRATIC JULIA SETS WITH POSITIVE AREA. XAVIER BUFF AND ARNAUD CHERITAT  

E-print Network

QUADRATIC JULIA SETS WITH POSITIVE AREA. XAVIER BUFF AND ARNAUD CH´ERITAT Abstract. We prove.7. The proof 44 2. The linearizable case 49 3. The infinitely renormalizable case 51 Appendix A. Parabolic to J(P) the methods of Borel-Lebesgue for the measure of sets. It is known that the area (Lebesgue

Buff, Xavier

471

Augmented Lagrangians with Adaptive Precision Control for Quadratic Programming with Equality Constraints  

Microsoft Academic Search

In this paper we introduce an augmented Lagrangian type algorithm for strictly convex quadratic programming problems with equality constraints. The new feature of the proposed algorithm is the adaptive precision control of the solution of auxiliary problems in the inner loop of the basic algorithm. Global convergence and boundedness of the penalty parameter are proved and an error estimate is

Z. Dostál; A. Friedlander; S. A. Santos

1999-01-01

472

[Quadratic formula: a new pediatric advance for glomerular filtration rate estimation].  

PubMed

A new formula for glomerular filtration rate estimation in pediatric population from 2 to 18 years has been developed by the University Unit of Pediatric Nephrology. This Quadratic formula, accessible online, allows pediatricians to adjust drug dosage and/or follow-up renal function more precisely and in an easy manner. PMID:24558910

Chehade, Hassib; Cachat, Françoise; Parvex, Paloma; Girardin, Eric

2014-01-15

473

Are ghost surfaces and quadratic-flux-minimizing surfaces the same?  

E-print Network

Are ghost surfaces and quadratic-flux-minimizing surfaces the same? Dr. Stuart Hudson CEMM Workshop, - and - are almost identical the "easy method" of constructing the "best surfaces" may be possible! ghost surfaces is solved by chaotic-coordinates. ghost-surfaces for high-order periodic orbits "fill

Hudson, Stuart

474

A hybrid linear equation solver and its application in quadratic placement  

Microsoft Academic Search

This paper presents a new hybrid linear equation solver for quadratic placement. The new solver is a combination of stochastic solver and iterative solver: it is proven in this paper that an approximate LDL factorization can be obtained from random walks, and used as a preconditioner for conjugate gradient solver. Testing on real-life placement benchmarks shows a speedup of up

Haifeng Qian; Sachin S. Sapatnekar

2005-01-01

475

Application of the dual active set algorithm to quadratic network optimization  

Microsoft Academic Search

A new algorithm, the dual active set algorithm, is presented for solving a minimization problem with equality constraints and bounds on the variables. The algorithm identifies the active bound constraints by maximizing an unconstrained dual function in a finite number of iterations. Convergence of the method is established, and it is applied to convex quadratic programming. In its implementable form,

William W. Hager; Donald W. Hearn

1993-01-01

476

Advanced Nonlinear Latent Variable Modeling: Distribution Analytic LMS and QML Estimators of Interaction and Quadratic Effects  

ERIC Educational Resources Information Center

Interaction and quadratic effects in latent variable models have to date only rarely been tested in practice. Traditional product indicator approaches need to create product indicators (e.g., x[superscript 2] [subscript 1], x[subscript 1]x[subscript 4]) to serve as indicators of each nonlinear latent construct. These approaches require the use of…

Kelava, Augustin; Werner, Christina S.; Schermelleh-Engel, Karin; Moosbrugger, Helfried; Zapf, Dieter; Ma, Yue; Cham, Heining; Aiken, Leona S.; West, Stephen G.

2011-01-01

477

Stability of generalized mixed type additive-quadratic-cubic functional equation in non-Archimedean spaces  

Microsoft Academic Search

In this paper, we prove generalized Hyres--Ulam--Rassias stability of the\\u000amixed type additive, quadratic and cubic functional equation\\u000a$$f(x+ky)+f(x-ky)=k^2f(x+y)+k^2f(x-y)+2(1-k^2)f(x)$$ for fixed integers $k$\\u000awith $k\\\

M. Eshaghi Gordji; M. Bavand Savadkouhi; Th. M. Rassias

2009-01-01

478

Stability of generalized mixed type additive-quadratic-cubic functional equation in non-Archimedean spaces  

Microsoft Academic Search

In this paper, we prove generalized Hyres--Ulam--Rassias stability of the mixed type additive, quadratic and cubic functional equation $$f(x+ky)+f(x-ky)=k^2f(x+y)+k^2f(x-y)+2(1-k^2)f(x)$$ for fixed integers $k$ with $k\\\

M. Eshaghi Gordji; M. Bavand Savadkouhi; Th. M. Rassias

2009-01-01

479

A Comparison of Methods for Estimating Quadratic Effects in Nonlinear Structural Equation Models  

ERIC Educational Resources Information Center

Two Monte Carlo simulations were performed to compare methods for estimating and testing hypotheses of quadratic effects in latent variable regression models. The methods considered in the current study were (a) a 2-stage moderated regression approach using latent variable scores, (b) an unconstrained product indicator approach, (c) a latent…

Harring, Jeffrey R.; Weiss, Brandi A.; Hsu, Jui-Chen

2012-01-01

480

Linear-quadratic-regulator pointing control system design for a high-altitude balloon payload  

Microsoft Academic Search

A pointing control system design for the science package of a NASA high-altitude research balloon is described. The balloon assembly consists of a single helium balloon connected to a payload recovery parachute, payload gondola, and ballast hopper. Pointing of the scientific payload is accomplished via an arrangement of drive motors and a flywheel. Linear quadratic regulator (LQR) synthesis techniques are

J. E. White; J. R. Etter

1987-01-01

481

Rigorous derivation of the nonlinear Schrodinger equation and Davey-Stewartson systems from quadratic hyperbolic systems  

Microsoft Academic Search

In this paper, we derive rigorously the nonlinear Schrodinger equation and Davey-Stewartson systems from quadratic hyperbolic systems using nonlinear diractive geometric optics. We construct approximate solutions and prove the convergence of the asymptotic expansion. The keys of this work is to consider only systems of a particular form introduced in (20), which includes Maxwell-Bloch system, and which satisfy a \\

Thierry Colin

482

Designing microstructured polymer optical fibers for cascaded quadratic nonlinear interaction of short pulses  

E-print Network

The dispersion of index-guiding microstructured polymer optical fibers is calculated for second-harmonic generation, where the quadratic nonlinearity is assumed to come from poling of the polymer. Since the phase mismatch is very large, the potential for cascaded quadratic second-harmonic generation is investigated in particular for soliton compression of fs pulses. We find that excitation of cascaded quadratic temporal solitons requires an effective quadratic nonlinearity around 5-7 pm/V, and around 10 pm/V if higher-order solitons should be efficiently generated. This might be reduced if a polymer with a low Kerr nonlinear refractive index is used. Almost all combinations of fiber design parameters (relative hole diameter and hole pitch) resulted in cascaded effects in the stationary regime, where efficient and clean soliton compression can be found. We therefore did not see any benefit from choosing a fiber design where the group-velocity mismatch was minimized (by having a large relative hole size and a h...

Bache, M

2008-01-01

483

Critical Sets and Properties of Endomorphisms Built by Coupling of Two Identical Quadratic Mappings  

Microsoft Academic Search

In this paper, it is shown that there are parameter values such that endomorphisms built by coupling of two identical 1-dimensional quadratic mappings (a) have two kinds of trapping regions in the phase space: a large simply-connected domain inside of which there is a smaller trapping subregion consisting of two disjoint domains; (b) restrictions of the main diagonal y =

V. A. Dobrynskii

1999-01-01

484

Gap-free computation of Pareto-points by quadratic scalarizations  

Microsoft Academic Search

In multicriteria optimization, several objective functions have to be minimized simultaneously. For this kind of problem, approximations to the whole solution set are of particular importance to decision makers. Usually, approximating this set involves solving a family of parameterized optimization problems. It is the aim of this paper to argue in favour of parameterized quadratic objective functions, in contrast to

Jörg Fliege

2004-01-01

485

A Discrete Linear Adaptive Controller with a Linear Quadratic Regulator Derived Proportional Derivative Controller  

Microsoft Academic Search

Recently, a linear adaptive control strategy based on Discrete Disturbance Accommodating Control theory (DAC) has appeared in the literature. This approach permits an entirely linear controller with constant parameters. The adaptive DAC approach is combined with a Linear-Quadratic Regulator (LQR) derived Proportional-Derivative (PD) controller for setpoint control of a simulated Thermal Control System on board the Space Station Freedom (SSF).

Steve Rogers; Haik Biglari

1992-01-01

486

A parametric model for the quadratic sampling of a bandlimited signal  

Microsoft Academic Search

The paper treats the problem of ambiguity resolution using non-uniform sampling. This problem occurs for Doppler estimation in coherent pulsed Doppler radar. In the paper, the authors study the case where the duration between two samples is a linear function of time: quadratic sampling. Assuming that the continuous signal is stationary, the sampled signal will be non-stationary. The autocorrelation of

A. Ferrari; R. Lorion; G. Alengrin

1995-01-01

487

Generating Hard Test Instances with Known Optimal Solution for the Rectilinear Quadratic Assignment Problem  

Microsoft Academic Search

In this paper we consider the rectilinear version of the quadratic assignment problem (QAP). We define a class of edge-weighted graphs with nonnegatively valued bisections. For one important type of such graphs we provide a characterization of point sets on the plane for which the optimal value of the related QAP is zero. These graphs are used in the algorithms

G. Palubeckis

1999-01-01

488

A Quadratic Regulator-Based Heuristic for Rapidly Exploring State Space Elena Leah Glassman  

E-print Network

A Quadratic Regulator-Based Heuristic for Rapidly Exploring State Space by Elena Leah Glassman S.B., E.E. M.I.T., 2008 Submitted to the Department of Electrical Engineering and Computer Science Regulator-Based Heuristic for Rapidly Exploring State Space by Elena Leah Glassman Submitted

Tedrake, Russ

489

Inexact fuzzy-stochastic quadratic programming approach for waste management under multiple uncertainties  

Microsoft Academic Search

In this study, an inexact fuzzy-stochastic quadratic programming (IFSQP) method is developed for effectively allocating waste to available facilities. The IFSQP approach is an extension of the conventional inexact linear programming for handling nonlinear programming in the objective function and multiple uncertainties on parameters in the constraints. The developed IFSQP is applied to a municipal solid waste management system. The

P. Guo; G. H. Huang

2011-01-01

490

Sparsity based sub-wavelength imaging with partially incoherent light via quadratic  

E-print Network

light microscopes with the additional knowledge of the light source spectrum. ©2011 Optical Society A spatial resolution light microscope: I. light is efficiently transmitted through /16 diameter aperturesSparsity based sub-wavelength imaging with partially incoherent light via quadratic compressed

Eldar, Yonina

491

Quadratic Model for Reservoir Management: Application to the Central Valley Project  

NASA Astrophysics Data System (ADS)

A quadratic optimization model is applied to a large-scale reservoir system to obtain operation schedules. The model has the minimum possible dimensionality, treats spillage and penstock releases as decision variables and takes advantage of system-dependent features to reduce the size of the decision space. An efficient and stable quadratic programming active set algorithm is used to solve for the optimal release policies. The stability and convergence of the solution algorithm are ensured by the factorization of the reduced Hessian matrix and the accurate computation of the Lagrange multipliers. The quadratic model is compared with a simplified linear model and it is found that optimal release schedules are robust to the choice of model, both yielding an increase of nearly 27% in the total annual energy production with respect to conventional operation procedures, although the quadratic model is more flexible and of general applicability. The adequate fulfillment of other system functions such as flood control and water supply is guaranteed via constraints on storage and spillage variables.

MariñO, Miguel A.; Loaiciga, Hugo A.

1985-05-01

492

CREATED ON MAY 31, 2013 1 Linear Quadratic Gaussian (LQG) Control of Wind  

E-print Network

navigation control systems, medical porocesses controllers and even nuclear power plants. It combines both wind trubines. Such control theories are not only capable of increasing the energy capture efficiency and maintenance costs associated with the system. In this paper, the general formulation of the Linear Quadratic