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1

Evolutionary Optimization of a Geometrically Refined Truss  

NASA Technical Reports Server (NTRS)

Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection, and stress on a benchmark cantilever truss problem. Predominantly traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This Technical Publication (TP) presents a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation: genetic algorithms and differential evolution to successfully optimize a benchmark structural optimization problem. A nontraditional solution to the benchmark problem is presented in this TP, specifically a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization toolset.

Hull, P. V.; Tinker, M. L.; Dozier, G. V.

2007-01-01

2

Optimization of biotechnological systems through geometric programming  

PubMed Central

Background In the past, tasks of model based yield optimization in metabolic engineering were either approached with stoichiometric models or with structured nonlinear models such as S-systems or linear-logarithmic representations. These models stand out among most others, because they allow the optimization task to be converted into a linear program, for which efficient solution methods are widely available. For pathway models not in one of these formats, an Indirect Optimization Method (IOM) was developed where the original model is sequentially represented as an S-system model, optimized in this format with linear programming methods, reinterpreted in the initial model form, and further optimized as necessary. Results A new method is proposed for this task. We show here that the model format of a Generalized Mass Action (GMA) system may be optimized very efficiently with techniques of geometric programming. We briefly review the basics of GMA systems and of geometric programming, demonstrate how the latter may be applied to the former, and illustrate the combined method with a didactic problem and two examples based on models of real systems. The first is a relatively small yet representative model of the anaerobic fermentation pathway in S. cerevisiae, while the second describes the dynamics of the tryptophan operon in E. coli. Both models have previously been used for benchmarking purposes, thus facilitating comparisons with the proposed new method. In these comparisons, the geometric programming method was found to be equal or better than the earlier methods in terms of successful identification of optima and efficiency. Conclusion GMA systems are of importance, because they contain stoichiometric, mass action and S-systems as special cases, along with many other models. Furthermore, it was previously shown that algebraic equivalence transformations of variables are sufficient to convert virtually any types of dynamical models into the GMA form. Thus, efficient methods for optimizing GMA systems have multifold appeal. PMID:17897440

Marin-Sanguino, Alberto; Voit, Eberhard O; Gonzalez-Alcon, Carlos; Torres, Nestor V

2007-01-01

3

Ligand Binding to the Pregnane X Receptor by Geometric Matching of Hydrogen Bonds  

E-print Network

Ligand Binding to the Pregnane X Receptor by Geometric Matching of Hydrogen Bonds Robert ¢ Keywords: ligand-protein docking, hydrogen bonds, pregnane X receptor, geometric matching. 1 Introduction Hydrogen bonds are important in protein-ligand interactions. We describe a geometric model of hydrogen

North Carolina at Chapel Hill, University of

4

Geometric optimization of flow systems with irreversibilities  

NASA Astrophysics Data System (ADS)

This dissertation is based on several studies of the geometric optimization of flow systems. Chapter 1 reports the solution to the fundamental problem of how to maximize the mechanical power extracted from a hot single-phase stream when the total heat transfer area bathed by the stream is constrained. The optimal stream temperature distribution is exponential in x, and so is the temperature distribution along the hot end of the system that converts the heat transfer into mechanical power. Similar conclusions are reached for the cold end heat exchanger, when the power system rejects heat to a cold single-phase stream. Chapter 2 outlines a strategy for constructing the architecture of the volume-to-point path such that the flow resistance is minimal (constructal theory1). The given volume is viewed as an assembly of volume elements of various sizes. The main discovery is that the shape of each element can be optimized subject to fixed volume, such that the elemental volume-to-point flow resistance is minimal. The flow integrated over each new assembly is channeled through a high-permeability path to a point on the side of the assembly. Most of the main hypotheses are relaxed in the next chapter. Chapter 3 describes an analytical and numerical study of the geometric minimization of the resistance to Darcy flow between a finite-size volume and one point. The volume is two-dimensional and contains materials with several permeabilities. At the end it yields the same conclusions reached in chapter 2 regarding the methodology and the results. Chapter 4 shows that the dendritic patterns formed by low-resistance channels in a river drainage basin are reproducible and can be deduced from a single principle that acts at every step in the development of the pattern: the constrained minimization of global resistance in area-to-point flow. Chapter 5 describes the geometric optimization of the internal structure of a volume that generates heat at every point and is cooled by a single stream. It is shown that in the end the fluid channels form a tree network that cools every point of the given volume.

Errera, Marcelo Risso

1999-11-01

5

Ligand Binding to the Pregnane X Receptor by Geometric Matching of Hydrogen Bonds  

E-print Network

Ligand Binding to the Pregnane X Receptor by Geometric Matching of Hydrogen Bonds Robert; Ryan Watkins x 1 Introduction Hydrogen bonds are important in protein­ligand interactions. We describe a geometric model of hydrogen bonds, which we use to study ligand binding to the Pregnane X Receptor (PXR

Kettner, Lutz

6

Optimization in Geometric Graphs: Complexity and Approximation  

E-print Network

solution procedures for several problems using geometrical properties of these graphs. We outline a matching-based branch and bound solution procedure for the maximum k-clique problem in unit disk graphs and demonstrate its effectiveness through...

Kahruman-Anderoglu, Sera

2011-02-22

7

Water Resource System Optimization by Geometric Programming  

E-print Network

Water resources planners and systems analysts are continually confronted with many complex optimization problems. Two major factors contribute to this problem. Firstly, mathematical modeling and system description capabilities in water resources...

Meier, W. L.; Shih, C. S.; Wray, D. J.

8

Accelerating method of global optimization for signomial geometric programming  

NASA Astrophysics Data System (ADS)

Signomial geometric programming (SGP) has been an interesting problem for many authors recently. Many methods have been provided for finding locally optimal solutions of SGP, but little progress has been made for global optimization of SGP. In this paper we propose a new accelerating method for global optimization algorithm of SGP using a suitable deleting technique. This technique offers a possibility to cut away a large part of the currently investigated region in which the globally optimal solution of SGP does not exist, and can be seen as an accelerating device for global optimization algorithm of SGP problem. Compared with the method of Shen and Zhang [Global optimization of signomial geometric programming using linear relaxation, Appl. Math. Comput. 150 (2004) 99-114], numerical results show that the computational efficiency is improved obviously by using this new technique in the number of iterations, the required saving list length and the execution time of the algorithm.

Shen, Pei-Ping; Li, Xiao-Ai; Jiao, Hong-Wei

2008-04-01

9

Improved bond-orbital calculations of rotation barriers and geometrical isomerism  

NASA Astrophysics Data System (ADS)

Rotational barriers in 19 molecules possessing a single internal rotation angle around a B-N, C-C, C-N, C-O, N-N, N-O, O-O central bond and geometrical isomerism in 3 molecules possessing a N=N double bond have been studied ab initio by the improved bond-orbital method. The first approximation, where the chemical groups occurring in these molecules are described in terms of non-orthogonal SCF bond-orbitals constructed from energy-optimized bond hybrids and polarities, is improved in second order of perturbation theory by admitting single excitations from bonding to antibonding orbitals and accounting for induction including exchange (polarization and delocalization). The molecules studied possess 16 to 34 electrons and a variety of functional groups differing in their chemical structure (CH3, NH2, OH, NO, CHO, CH=CH2, NH= and some of their F-derivatives). The overall results obtained using a STO-3G basis, rigid rotation and experimental geometries, are close to experiment and to the corresponding MO-SCF calculations in the same basis, but individual energy components allow us to establish a clear correlation between barriers and chemical structure, grouping the 22 molecules into 4 classes. In the first class (CH3-X molecules and 1,2-difluoroethane) barriers are dominated by steric interactions (Pauli repulsions) which are sufficiently well described in first order. In the second class (N2H4, NH2OH, NH=NH and its fluoroderivatives, molecules all possessing lone pairs adjacent to the central bond) barriers are due to competition between first-order Pauli repulsion and characteristic geminal ?-?* delocalization occurring in second order. In the third class (1,3-butadiene, glyoxal, formamide and formic acid, molecules possessing double bonds and/or ?-lone pairs at both ends of the rotation axis) barriers are dominated by large ?-?* vicinal delocalization. In the fourth class (HNO2, H2O2 and its fluoroderivatives, molecules presenting both previous structural features) barriers result from competition between all preceding effects.

Musso, Gian Franco; Magnasco, Valerio

10

Testing Geometrical Discrimination within an Enzyme Active Site: Constrained Hydrogen Bonding in the Ketosteroid  

E-print Network

Testing Geometrical Discrimination within an Enzyme Active Site: Constrained Hydrogen Bonding and Rosenstiel Basic Medical Sciences Research Center, Brandeis UniVersity, Waltham, Massachusetts 02454 Received-chain reorientation and prevent hydrogen bond shortening by 0.1 ? or less. Further, this constraint has substantial

Herschlag, Dan

11

Optimal control of underactuated mechanical systems: A geometric approach  

NASA Astrophysics Data System (ADS)

In this paper, we consider a geometric formalism for optimal control of underactuated mechanical systems. Our techniques are an adaptation of the classical Skinner and Rusk approach for the case of Lagrangian dynamics with higher-order constraints. We study a regular case where it is possible to establish a symplectic framework and, as a consequence, to obtain a unique vector field determining the dynamics of the optimal control problem. These developments will allow us to develop a new class of geometric integrators based on discrete variational calculus.

Colombo, Leonardo; Martn De Diego, David; Zuccalli, Marcela

2010-08-01

12

Ligand Binding to the Pregnane X Receptor by Geometric Matching of Hydrogen Bonds  

E-print Network

Hydrogen bonds are important in protein-ligand interactions. We describe a geometric model of hydrogen bonds, which we use to study ligand binding to the pregnane X receptor (PXR). PXR binds drug ligands promiscuously. The recently determined structure of PXR in humans (hPXR) reveals that its binding pocket is large, smooth, and uniformly hydrophobic [5], leading to the hypothesis that hydrogen bonds are the main

Robert-paul Berretty; David Hsu; Lutz Kettner; Ajith Mascarenhas; Matthew R. Redinbo; Jack Snoeyink; Ryan Watkins

13

Valence bond liquids and solids in geometrically frustrated magnets  

NASA Astrophysics Data System (ADS)

Frustrated magnets are models of strongly interacting systems. Frustration reveals itself through a vast degeneracy of the classical ground state and is responsible for a large number of soft modes that destroy spin order. Possible alternative phases that could emerge in place of the Nel state are: (a) The valence-bond solid (VBS), in which bond averages < Si ot Sj >, rather than spins themselves, form a periodic structure. (b) The valence-bond liquid (VBL), in which any bond order is absent, but there is hidden topological order, similar to that in the fractional quantum Hall effect. In recent years particular attention has been paid to the Heisenberg antiferromagnet on the pyrochlore lattice---a 3D network of corner-sharing tetrahedra---and its 2D analogs. It has been established that a spin-lattice coupling stabilizes the VBS in the pyrochlores (Yamashita and Ueda, Tchernyshyov et al.); the related spin-Peierls phase transition has been observed in ZnCr_2O4 (S.-H. Lee et al.). Fouet et al. have found numerically that quantum spins (S=1/2) on the checkerboard lattice form a VBS. Until recently, systematic approaches---such as the 1/S and 1/N expansions---to the problem of the ground state in the pyrochlore have met with little success: the remaining degeneracy in the first nontrivial order is still very large. New technical developments (Henley) have allowed us to construct explicitly all ground states at order 1/S and characterize the resulting phases for two pyrochlore-like lattices. We find a VBS---resembling that of Fouet et al.---on the checkerboard lattice and a VBL in a 2D pyrochlore slab. A study of the 3D pyrochlore is in progress.

Tchernyshyov, Oleg

2003-03-01

14

Energy Optimal Routing in Radio Networks Using Geometric Data Structures ?  

E-print Network

the transmission cost be­ tween two sites is the square of their Euclidean distance plus a constant offset. We give an O(kn log n) time algorithm that finds an optimal path with at most k hops, and an O \\Gamma n 1+ffl on geometric data structures ranging from simple 2­dimensional Delaunay triangula­ tions to more sophisticated

Schmitt, Peter H.

15

Comparison between first geometric-arithmetic index and atom-bond connectivity index  

NASA Astrophysics Data System (ADS)

The first geometric-arithmetic index ( GA) [1] and atom-bond connectivity index ( ABC) [2] that are recently introduced, are found to be useful tools in QSPR and QSAR studies. In this letter we compare the GA and ABC indices for chemical trees and molecular graphs. Moreover, we also compare these two indices for general graphs.

Das, Kinkar Ch.; Trinajsti?, N.

2010-09-01

16

Geometrical parameters optimization for tube hydroforming using response surface method  

NASA Astrophysics Data System (ADS)

In tube hydroforming (THF) the optimal thickness variation of a product is influenced by the geometrical, material and process parameters. In this study different values of initial tube length combined with various fillet and entry radii of the die are taken into account to predict an acceptable T-shaped tube of which the minimum wall thickness fulfills the industrial demand. To reach this goal, an integrated optimization approach, using the classical explicit dynamic (ED) incremental approach using ABAQUS commercial code together with an optimization algorithm was developed. This latter consists in constructing an explicit form of the objective function by response surface methodology (RSM) based on diffuse approximation (DA) according to the design variables. To search the global optimum of the objective function, the sequential quadratic programming (SQP) algorithm has been used.

Chebbah, M. S.; Azaouzi, M.

2014-10-01

17

A geometric analysis of mastectomy incisions: Optimizing intraoperative breast volume  

PubMed Central

INTRODUCTION: The advent of acellular dermis-based tissue expander breast reconstruction has placed an increased emphasis on optimizing intraoperative volume. Because skin preservation is a critical determinant of intraoperative volume expansion, a mathematical model was developed to capture the influence of incision dimension on subsequent tissue expander volumes. METHODS: A mathematical equation was developed to calculate breast volume via integration of a geometrically modelled breast cross-section. The equation calculates volume changes associated with excised skin during the mastectomy incision by reducing the arc length of the cross-section. The degree of volume loss is subsequently calculated based on excision dimensions ranging from 35 mm to 60 mm. RESULTS: A quadratic relationship between breast volume and the vertical dimension of the mastectomy incision exists, such that incrementally larger incisions lead to a disproportionally greater amount of volume loss. The vertical dimension of the mastectomy incision more so than the horizontal dimension is of critical importance to maintain breast volume. Moreover, the predicted volume loss is more profound in smaller breasts and primarily occurs in areas that affect breast projection on ptosis. CONCLUSIONS: The present study is the first to model the relationship between the vertical dimensions of the mastectomy incision and subsequent volume loss. These geometric principles will aid in optimizing intra-operative volume expansion during expander-based breast reconstruction. PMID:22654531

Chopp, David; Rawlani, Vinay; Ellis, Marco; Johnson, Sarah A; Buck, Donald W; Khan, Seema; Bethke, Kevin; Hansen, Nora; Kim, John YS

2011-01-01

18

C(Ar)-HO hydrogen bonds in substituted isobenzofuranone derivatives: geometric, topological, and NMR characterization.  

PubMed

Substituted isobenzofuranone derivatives 1a-3a and bindone 4 are characterized by the presence of an intramolecular C(Ar)-HO hydrogen bond in the crystal (X-ray), solution ((1)H NMR and specific and nonspecific IEF-PCM solvation model combined with MP2 and B3LYP methods), and gas (MP2 and B3LYP) phases. According to geometric and AIM criteria, the C(Ar)-HO interaction weakens in 1a-3a (independent of substituent nature) and in 4 with the change in media in the following order: gas phase > CHCl(3) solution > DMSO solution > crystal. The maximum value of hydrogen bond energy is 4.6 kcal/mol for 1a-3a and 5.6 kcal/mol for 4. Both in crystals and in solutions, hydrogen bond strength increases in the order 1a < 2a < 3a with the rising electronegativity of the ring substituents (H < OMe < Cl). The best method for calculating (1)H NMR chemical shifts (?(calcd) - ?(expl) < 0.7 ppm) of hydrogen bonded and nonbonded protons in 1a-3a and 1b-3b (isomers without hydrogen bonds) is the GIAO method at the B3LYP level with the 6-31G** and 6-311G** basis sets. For the C-H moiety involved in the hydrogen bond, the increase of the spin-spin coupling constant (1)J((13)C-(1)H) by about 7.5 Hz is in good agreement with calculations for C-H bond shortening and for blue shifts of C-H stretching vibrations (by 55-75 cm(-1)). PMID:22734703

Sigalov, Mark V; Doronina, Evgeniya P; Sidorkin, Valery F

2012-07-26

19

Optimization Evaluation of Geometric Error Based on Correctional Simplex Method  

Microsoft Academic Search

This paper researches the theory of geometric error evaluation and its application. On the basis of the geometric model of error evaluation, the features of the geometric error enclosure evaluation are analyzed, and the paper has founded the linear programming model of minimum zone association, maximum inscribed association and minimum circumscribed association. By taking the minimum conditions criterion and the

P Zheng; L N Zhang; H D Zheng; M Y Chen

2006-01-01

20

Optimization of position of geometrical frame by SNV  

NASA Astrophysics Data System (ADS)

The geometrical frame moves in different directions and areas when its tolerance zones and (or) location dimensions are determined in defferent ways. In this paper, by means of the measured coordinate values of the toleranced features, vectors are used to study the translations and (or) rotations of the geometrical frame, and further to judge if the errors are minimum and up to standard when the constraining conditions are satisfied. The diameter of the minimum envelope circle of error is the value of the error being searched. During translation and (or) rotation of the geometrical frame, if there are any the same name vectors (SNV for short) on the envelope circle of error which envelops the measured elements, or, in spite of SNVs , the envelope circle of error cannot be further reduced because of the constraint of the reference, such an envelope circle of error is called the minimum one. The results obtained show that 1 . the minimum envelope circle of position error can be found using SNV technique; 2. on the circle there may be 4, 3, 2 even just 1 point because of the constraint of the reference; 3 . the SNV technique can describe the change of the geometrical frame visually and is convenient for on-the-spot technological analysis; 4. whether the geometrical frame has compensation of reference or not, the position errors can be evaluated; 5. this technique is suitable for judging the measured results of a hole group distributed on a rectangle or a circumference.

Chen, Long-De; Zhao, Fu-Ling; Li, Man

1993-09-01

21

Proving strong duality for geometric optimization using a conic formulation  

E-print Network

is organized as follows: Section 2 introduces conic optimization and outlines the associated duality theory based on conic duality. Finally, we provide in Section 5 some hints on how to establish the link between Conic optimization In this section, we describe conic optimization and the associated duality theory

Glineur, François

22

Proving strong duality for geometric optimization using a conic formulation  

E-print Network

is organized as follows: Section 2 introduces conic optimization * *and outlines the associated duality theory theorems based on conic duality. Finally* *, we provide in Section 5 some hints on how to establish concluding remarks. 2 Conic optimization In this section, we describe conic optimization

Glineur, François

23

Multi-objective Optimization of Geometric Dimensions and Material Composition of  

E-print Network

optimization of a metal/metal functionally graded material active cooling component. The plane stress transient]), CP973, Multiscale andFunctionally GradedMaterials 2006 edited by G. H. Paulino, M.-J. Pmdera, R. HMulti-objective Optimization of Geometric Dimensions and Material Composition of Functionally

Vel, Senthil

24

Integrated multidisciplinary design optimization using discrete sensitivity analysis for geometrically complex aeroelastic configurations  

Microsoft Academic Search

The first two steps in the development of an integrated multidisciplinary design optimization procedure capable of analyzing the nonlinear fluid flow about geometrically complex aeroelastic configurations have been accomplished in the present work. For the first step, a three-dimensional unstructured grid approach to aerodynamic shape sensitivity analysis and design optimization has been developed. The advantage of unstructured grids, when compared

James Charles Newman III

1997-01-01

25

Efficient Algorithms for Geometric Optimization Pankaj K. Agarwal  

E-print Network

, including facility location, proximity problems, statistical estimators and metrology, placement.g. [97]), the full-scale technique was presented by Megiddo in the late 1970's and early 1980's [179, 180 optimization, and did not receive much attention by the computational geometry community until the late 1980's

Sharir, Micha

26

Geometric Programming for Aircraft Design Optimization Warren Hoburg  

E-print Network

[N] Wfuel,out = fuel burned, outbound [N] Wfuel,ret = fuel burned, return [N] WMTO = maximum takeoff = inviscid propeller efficiency v = viscous propeller efficiency eng = engine efficiency prop = propeller opened new doors for system-wide optimization, creating the possibility of quantifying and exploiting

Abbeel, Pieter

27

Geometrical optimization of organic microlasers for microfluidic chemical sensing  

NASA Astrophysics Data System (ADS)

We report the design, fabrication, and demonstration of a chemical sensor-based on the spectral shift of organic microcavity lasers. The shape of the cavity contour is used as a parameter and is optimized to improve the sensitivity. Analytical and numerical predictions are in good agreement with experiments performed in a microfluidic environment, showing sensitivities of up to 100 nm per refractive index unit for stadium-shaped microlasers on pedestal. Selective sensing of Hg2+ at a concentration down to 200 ppb is then demonstrated with cavities functionalized by ligands that are known to bind mercuric cations.

Lozenko, Sergey; Faye, Djibril; Zhang, Haitao; Lebental, Mlanie; Lautru, Joseph; Zyss, Joseph; Lefevre, Jean-Pierre; Leray, Isabelle

2014-10-01

28

Parabolic movement primitives and cortical states: merging optimality with geometric invariance  

Microsoft Academic Search

Previousstudieshavesuggestedthatseveraltypes of rules govern the generation of complex arm movements. One class of rules consists of optimizing an objective func- tion (e.g., maximizing motion smoothness). Another class consists of geometric and kinematic constraints, for instance the coupling between speed and curvature during drawing movements as expressed by the two-thirds power law. It has also been suggested that complex movements are

Felix Polyakov; Eran Stark; Rotem Drori; Moshe Abeles; Tamar Flash

2009-01-01

29

Fluence Map Optimization in IMRT Cancer Treatment Planning and A Geometric Approach  

E-print Network

therapy (IMRT) is a state-of-the-art technique for administering radiation to cancer patients. The goal radiation therapy, Optimal treatment planning, Fluence map op- timization, A geometric Approach eventually recover. Therefore, research in radiation therapy seeks methods of delivering a sufficient dose

Zhang, Yin

30

Geometric Algorithms for Optimal Airspace Design and Air Traffic Controller Workload Balancing  

E-print Network

Geometric Algorithms for Optimal Airspace Design and Air Traffic Controller Workload Balancing America. For purposes of workload limitations for air traffic controllers, the airspace is partitioned by one or more air traffic controllers (or a small team of 1-3 controllers) at any given time of the day

Mitchell, Joseph S.B.

31

A Wafer-Bonded, Floating Element Shear-Stress Sensor Using a Geometric Moire Optical Transduction Technique  

NASA Technical Reports Server (NTRS)

This paper presents a geometric Moir optical-based floating-element shear stress sensor for wind tunnel turbulence measurements. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Measured results indicate a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.

Horowitz, Stephen; Chen, Tai-An; Chandrasekaran, Venkataraman; Tedjojuwono, Ken; Cattafesta, Louis; Nishida, Toshikazu; Sheplak, Mark

2004-01-01

32

Optimization of the blade trailing edge geometric parameters for a small scale ORC turbine  

NASA Astrophysics Data System (ADS)

In general, the method proposed by Whitfield and Baines is adopted for the turbine preliminary design. In this design procedure for the turbine blade trailing edge geometry, two assumptions (ideal gas and zero discharge swirl) and two experience values (WR and ?) are used to get the three blade trailing edge geometric parameters: relative exit flow angle ?6, the exit tip radius R6t and hub radius R6h for the purpose of maximizing the rotor total-to-static isentropic efficiency. The method above is established based on the experience and results of testing using air as working fluid, so it does not provide a mathematical optimal solution to instruct the optimization of geometry parameters and consider the real gas effects of the organic, working fluid which must be taken into consideration for the ORC turbine design procedure. In this paper, a new preliminary design and optimization method is established for the purpose of reducing the exit kinetic energy loss to improve the turbine efficiency ?ts, and the blade trailing edge geometric parameters for a small scale ORC turbine with working fluid R123 are optimized based on this method. The mathematical optimal solution to minimize the exit kinetic energy is deduced, which can be used to design and optimize the exit shroud/hub radius and exit blade angle. And then, the influence of blade trailing edge geometric parameters on turbine efficiency ?ts are analysed and the optimal working ranges of these parameters for the equations are recommended in consideration of working fluid R123. This method is used to modify an existing ORC turbine exit kinetic energy loss from 11.7% to 7%, which indicates the effectiveness of the method. However, the internal passage loss increases from 7.9% to 9.4%, so the only way to consider the influence of geometric parameters on internal passage loss is to give the empirical ranges of these parameters, such as the recommended ranges that the value of ? is at 0.3 to 0.4, and the value of ? is at 0.5 to 0.6.

Zhang, L.; Zhuge, W. L.; Peng, J.; Liu, S. J.; Zhang, Y. J.

2013-12-01

33

IEEE TRANSACTIONS ON ROBOTICS, VOL. 27, NO. 4, AUGUST 2011 641 Discrete Geometric Optimal Control on Lie Groups  

E-print Network

on Lie Groups Marin B. Kobilarov and Jerrold E. Marsden Abstract--We consider the optimal control of mechanical sys- tems on Lie groups and develop numerical methods that exploit the structure of the state--Discrete mechanics, geometric optimization, Lie groups, optimal control, underactuated systems. I. INTRODUCTION WE

Kobilarov, Marin

34

IMRT optimization including random and systematic geometric errors based on the expectation of TCP and NTCP  

SciTech Connect

The purpose of this work was the development of a probabilistic planning method with biological cost functions that does not require the definition of margins. Geometrical uncertainties were integrated in tumor control probability (TCP) and normal tissue complication probability (NTCP) objective functions for inverse planning. For efficiency reasons random errors were included by blurring the dose distribution and systematic errors by shifting structures with respect to the dose. Treatment plans were made for 19 prostate patients following four inverse strategies: Conformal with homogeneous dose to the planning target volume (PTV), a simultaneous integrated boost using a second PTV, optimization using TCP and NTCP functions together with a PTV, and probabilistic TCP and NTCP optimization for the clinical target volume without PTV. The resulting plans were evaluated by independent Monte Carlo simulation of many possible treatment histories including geometrical uncertainties. The results showed that the probabilistic optimization technique reduced the rectal wall volume receiving high dose, while at the same time increasing the dose to the clinical target volume. Without sacrificing the expected local control rate, the expected rectum toxicity could be reduced by 50% relative to the boost technique. The improvement over the conformal technique was larger yet. The margin based biological technique led to toxicity in between the boost and probabilistic techniques, but its control rates were very variable and relatively low. During evaluations, the sensitivity of the local control probability to variations in biological parameters appeared similar for all four strategies. The sensitivity to variations of the geometrical error distributions was strongest for the probabilistic technique. It is concluded that probabilistic optimization based on tumor control probability and normal tissue complication probability is feasible. It results in robust prostate treatment plans with an improved balance between local control and rectum toxicity, compared to conventional techniques.

Witte, Marnix G.; Geer, Joris van der; Schneider, Christoph; Lebesque, Joos V.; Alber, Markus; Herk, Marcel van [Department of Radiation Oncology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands); Sektion fuer Biomedizinische Physik, Universitaetsklinik fuer Radioonkologie, Universitaet Tuebingen (Germany); Department of Radiation Oncology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)

2007-09-15

35

Topology optimization of geometrically nonlinear structures including thermo-mechanical coupling  

NASA Astrophysics Data System (ADS)

The goal of this research is to develop an efficient and robust methodology for the topology optimization of geometrically nonlinear structures actuated by thermal expansion. The corotational finite element method is used to model the geometric nonlinearity because its element independent nature and linear elastic element core provide a flexibility to introduce thermal loads and formulate analytical sensitivities for any element type. To create thermal expansion, this work uses both prescribed temperature changes and localized heat generation via Joule heating, where electrical and thermal conduction are additionally considered. In this coupled multi-physics problem, emphasis is put on material models and coupling to maintain accuracy and efficiency. One-way coupling is shown to be equivalent to a small strain assumption, and the proper modeling of convection properties in topology optimization is addressed. To model the thermal and electrical conduction in planar layered materials, an averaged (smeared) model based on the smoothed properties of the individual layers is introduced. Large displacement structures are prone to exhibit buckling and limit point behavior. To include instabilities in topology optimization, specialized techniques are introduced to overcome inherent numerical difficulties. A nodal density transformation is introduced to isolate structurally relevant eigenmodes, and a homotopy between linear and nonlinear finite elements is provided to limit the effects of mesh distortion. The proposed methodology is successfully applied to micro-mechanism applications capable of a three-dimensional range of motion, including novel designs reflective of the manufacturing technology used in the micro-electro-mechanical (MEMS) community.

Pajot, Joseph M.

36

Implementation and Optimization of miniGMG - a Compact Geometric Multigrid Benchmark  

SciTech Connect

Multigrid methods are widely used to accelerate the convergence of iterative solvers for linear systems used in a number of different application areas. In this report, we describe miniGMG, our compact geometric multigrid benchmark designed to proxy the multigrid solves found in AMR applications. We explore optimization techniques for geometric multigrid on existing and emerging multicore systems including the Opteron-based Cray XE6, Intel Sandy Bridge and Nehalem-based Infiniband clusters, as well as manycore-based architectures including NVIDIA's Fermi and Kepler GPUs and Intel's Knights Corner (KNC) co-processor. This report examines a variety of novel techniques including communication-aggregation, threaded wavefront-based DRAM communication-avoiding, dynamic threading decisions, SIMDization, and fusion of operators. We quantify performance through each phase of the V-cycle for both single-node and distributed-memory experiments and provide detailed analysis for each class of optimization. Results show our optimizations yield significant speedups across a variety of subdomain sizes while simultaneously demonstrating the potential of multi- and manycore processors to dramatically accelerate single-node performance. However, our analysis also indicates that improvements in networks and communication will be essential to reap the potential of manycore processors in large-scale multigrid calculations.

Williams, Samuel; Kalamkar, Dhiraj; Singh, Amik; Deshpande, Anand M.; Straalen, Brian Van; Smelyanskiy, Mikhail; Almgren, Ann; Dubey, Pradeep; Shalf, John; Oliker, Leonid

2012-12-01

37

Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization  

NASA Technical Reports Server (NTRS)

Joining and integration methods are critically needed as enabling technologies for the full utilization of advanced ceramic components in aerospace and aeronautics applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. In the application, several SiC substrates with different hole patterns to form fuel and combustion air channels are bonded to form the injector. Diffusion bonding is a joining approach that offers uniform bonds with high temperature capability, chemical stability, and high strength. Diffusion bonding was investigated with the aid of titanium foils and coatings as the interlayer between SiC substrates to aid bonding. The influence of such variables as interlayer type, interlayer thickness, substrate finish, and processing time were investigated. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

38

CMOS Operational Ampli er Design and Optimization via Geometric Programming Maria del Mar Hershenson, Stephen Boyd, Thomas H. Lee  

E-print Network

1 CMOS Operational Ampli er Design and Optimization via Geometric Programming Maria del Mar| We describe a general method for optimized design of CMOS operational ampli ers. We observe functions of the de- sign variables. As a result, the ampli er design problem can be expressed as a special

Lee, Thomas H.

39

CMOS Operational Ampli er Design and Optimization via Geometric Programming Maria del Mar Hershenson, Stephen Boyd, Thomas H. Lee  

E-print Network

15 CMOS Operational Ampli er Design and Optimization via Geometric Programming Maria del Mar| We describe a general method for optimized design of CMOS operational ampli ers. We observe functions of the de- sign variables. As a result, the ampli er design problem can be expressed as a special

40

Macronutrient optimization and seasonal diet mixing in a large omnivore, the grizzly bear: a geometric analysis.  

PubMed

Nutrient balance is a strong determinant of animal fitness and demography. It is therefore important to understand how the compositions of available foods relate to required balance of nutrients and habitat suitability for animals in the wild. These relationships are, however, complex, particularly for omnivores that often need to compose balanced diets by combining their intake from diverse nutritionally complementary foods. Here we apply geometric models to understand how the nutritional compositions of foods available to an omnivorous member of the order Carnivora, the grizzly bear (Ursus arctos L.), relate to optimal macronutrient intake, and assess the seasonal nutritional constraints on the study population in west-central Alberta, Canada. The models examined the proportion of macronutrients that bears could consume by mixing their diet from food available in each season, and assessed the extent to which bears could consume the ratio of protein to non-protein energy previously demonstrated using captive bears to optimize mass gain. We found that non-selective feeding on ungulate carcasses provided a non-optimal macronutrient balance with surplus protein relative to fat and carbohydrate, reflecting adaptation to an omnivorous lifestyle, and that optimization through feeding selectively on different tissues of ungulate carcasses is unlikely. Bears were, however, able to dilute protein intake to an optimal ratio by mixing their otherwise high-protein diet with carbohydrate-rich fruit. Some individual food items were close to optimally balanced in protein to non-protein energy (e.g. Hedysarum alpinum roots), which may help explain their dietary prevalence. Ants may be consumed particularly as a source of lipids. Overall, our analysis showed that most food available to bears in the study area were high in protein relative to lipid or carbohydrate, suggesting the lack of non-protein energy limits the fitness (e.g. body size and reproduction) and population density of grizzly bears in this ecosystem. PMID:24841821

Coogan, Sean C P; Raubenheimer, David; Stenhouse, Gordon B; Nielsen, Scott E

2014-01-01

41

Macronutrient Optimization and Seasonal Diet Mixing in a Large Omnivore, the Grizzly Bear: A Geometric Analysis  

PubMed Central

Nutrient balance is a strong determinant of animal fitness and demography. It is therefore important to understand how the compositions of available foods relate to required balance of nutrients and habitat suitability for animals in the wild. These relationships are, however, complex, particularly for omnivores that often need to compose balanced diets by combining their intake from diverse nutritionally complementary foods. Here we apply geometric models to understand how the nutritional compositions of foods available to an omnivorous member of the order Carnivora, the grizzly bear (Ursus arctos L.), relate to optimal macronutrient intake, and assess the seasonal nutritional constraints on the study population in west-central Alberta, Canada. The models examined the proportion of macronutrients that bears could consume by mixing their diet from food available in each season, and assessed the extent to which bears could consume the ratio of protein to non-protein energy previously demonstrated using captive bears to optimize mass gain. We found that non-selective feeding on ungulate carcasses provided a non-optimal macronutrient balance with surplus protein relative to fat and carbohydrate, reflecting adaptation to an omnivorous lifestyle, and that optimization through feeding selectively on different tissues of ungulate carcasses is unlikely. Bears were, however, able to dilute protein intake to an optimal ratio by mixing their otherwise high-protein diet with carbohydrate-rich fruit. Some individual food items were close to optimally balanced in protein to non-protein energy (e.g. Hedysarum alpinum roots), which may help explain their dietary prevalence. Ants may be consumed particularly as a source of lipids. Overall, our analysis showed that most food available to bears in the study area were high in protein relative to lipid or carbohydrate, suggesting the lack of non-protein energy limits the fitness (e.g. body size and reproduction) and population density of grizzly bears in this ecosystem. PMID:24841821

Coogan, Sean C. P.; Raubenheimer, David; Stenhouse, Gordon B.; Nielsen, Scott E.

2014-01-01

42

GNSS tomography and optimal geometrical setting to retrieve water vapour density of the neutral atmosphere  

NASA Astrophysics Data System (ADS)

Day by day, the number of GNSS satellites, ground receivers and slant observations are increasing. From these measurements a better monitoring of the water vapour of the neutral atmosphere is expected using tomographic imaging. For the moment the limitation of GNSS tomography is still due to a weak geometric representation. For this reason, this study will present some tests about the sensitivity of tomographic retrievals to different geometry of network and to different vertical and horizontal distributions of the adjusted volumic pixels (voxels). Using a synthetic approach (slant water vapour contents simulated from numerical atmospheric model outputs, e.g. ERA-interim and BASCOE) to retrieve information about the water vapour of different layers of the neutral atmosphere, this study will show the respective optimal geometrical setting of GNSS tomography. A validation of these configurations will be shown using real GNSS observations of SIWV (established from ZTD and gradients) and tomographic retrievals compared to profiles from radiosondes and sun-synchronous satellites sensors (i.e. IASI on MetOp-A and MLS on Aura).

Brenot, Hugues; Errera, Quentin; Champollion, Cdric; Verhoelst, Tijl; Kumps, Nicolas; Van Malderen, Roeland; Van Roozendael, Michel

2014-05-01

43

Towards the geometric optimization of potential field models - A new spatial operator tool and applications  

NASA Astrophysics Data System (ADS)

We present a new method for automated geometric modifications of potential field models. Computational developments and the increasing amount of available potential field data, especially gradient data from the satellite missions, lead to increasingly complex models and integrated modelling tools. Editing of these models becomes more difficult. Our approach presents an optimization tool that is designed to modify vertex-based model geometries (e.g. polygons, polyhedrons, triangulated surfaces) by applying spatial operators to the model that use an adaptive, on-the-fly model discretization. These operators deform the existing model via vertex-dragging, aiming at a minimized misfit between measured and modelled potential field anomaly. The parameters that define the operators are subject to an optimization process. This kind of parametrization provides a means for the reduction of unknowns (dimensionality of the search space), allows a variety of possible modifications and ensures that geometries are not destroyed by crossing polygon lines or punctured planes. We implemented a particle swarm optimization as a global searcher with restart option for the task of finding optimal operator parameters. This approach provides us with an ensemble of model solutions that allows a selection and geologically reasonable interpretations. The applicability of the tool is demonstrated in two 2D case studies that provide models of different extent and with different objectives. The first model is a synthetic salt structure in a horizontally layered background model. Expected geometry modifications are considerably small and localized and the initial models contain rather little information on the intended salt structure. A large scale example is given in the second study. Here, the optimization is applied to a sedimentary basin model that is based on seismic interpretation. With the aim to evaluate the seismically derived model, large scale operators are applied that mainly cause depth adjustments to the model horizons.

Haase, Claudia; Gtze, Hans-Jrgen

2014-05-01

44

On the geometrical and mechanical multi-aspect optimization of PPy/MWCNT actuators  

NASA Astrophysics Data System (ADS)

Polypyrrole (PPy) conducting polymers as one of the most well-known actuation materials have shown numerous applications in a variety of fields such as biomedical devices as well as biomimetic robotics. This study investigates the multiobjective optimization of a PPy/MWCNTs actuator through an electrochemomechanical model. The multilayer actuator is composed of a PVDF layer, as the core membrane and an electrolyte reservoir, as well as two one layer of a conjugated polymer and one layer of multiwalled carbon nanotubes deposited on each side of the PVDF layer. In order to obtain the optimum values for each decision variable (i.e., geometrical and electrochemical), the two main outputs of the bending actuator, the tip displacement and blocking force, have been mathematically modeled and formulated as the objective functions. A multiobjective optimization algorithm is applied to simultaneously maximize the blocking force and tip displacement generated by the actuator. Furthermore, a range for each design variable is defined within which none of the objective functions of the film-type actuator dominates the other one while they are both kept within an acceptable range. The results obtained from the mathematical model are experimentally verified. Moreover, in order to determine the performance of the fabricated actuator, its outputs are compared with their counterparts of a neat PPy actuator.

Khalili, Nazanin; Naguib, Hani E.; Kwon, Roy H.

2014-03-01

45

Optimization of the Geometric Beta for the SSR2 Cavities of the Project X  

SciTech Connect

Project X based on the 3 GeV CW superconducting Linac and is currently in the R&D phase. The CW SC Linac starts from a low-energy SCRF section (2.1 - 165 MeV) containing three different types of resonators. HWR f = 162.5 MHz (2.1 - 11 MeV) having beta= 0.11, SSR1 f = 325 MHz (11 - 35 MeV) having beta = 0.21. In this paper we present the analysis that lead to the final design of SSR2 f = 325 MHz cavity (35 - 165 MeV). We present the results of optimization of the geometric beta and the comparison between single, double and triple spoke resonators used in Project X frontend. A {beta} optimization has been carried out for the last spoke cavity section of Project X front end. The optimization process of {beta}{sub opt} for a single spoke resonator family SSR2 shown that {beta}{sub opt} = 0.47 looks better than the previous choice, which is {beta}{sub opt} = 0.4. This change can save some cavities and provide the same final energy for this section, 160 MeV. Single double and triple spoke resonator performances have been compared. The best option is the single spoke resonator SSR2 because the NTTF of a multi-spoke resonator is much narrower than a single one. In the energy range considered (40-160 MeV) the most efficient resonator is the single spoke one.

Solyak, N.; Vostrikov, A.; Yakovlev, V.P.; /Fermilab; Awida, M.H.; Berrutti, P.; Gonin, I.V.; /Fermilab

2012-05-01

46

Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer  

NASA Astrophysics Data System (ADS)

Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ?(r) and Laplacian ?2?(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ?(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems.

Paul, Bijan Kumar; Guchhait, Nikhil

2013-02-01

47

Integrated multidisciplinary design optimization using discrete sensitivity analysis for geometrically complex aeroelastic configurations  

NASA Astrophysics Data System (ADS)

The first two steps in the development of an integrated multidisciplinary design optimization procedure capable of analyzing the nonlinear fluid flow about geometrically complex aeroelastic configurations have been accomplished in the present work. For the first step, a three-dimensional unstructured grid approach to aerodynamic shape sensitivity analysis and design optimization has been developed. The advantage of unstructured grids, when compared with a structured-grid approach, is their inherent ability to discretize irregularly shaped domains with greater efficiency and less effort. Hence, this approach is ideally suited for geometrically complex configurations of practical interest. In this work the time-dependent, nonlinear Euler equations are solved using an upwind, cell-centered, finite-volume scheme. The discrete, linearized systems which result from this scheme are solved iteratively by a preconditioned conjugate-gradient-like algorithm known as GMRES for the two-dimensional cases and a Gauss-Seidel algorithm for the three-dimensional; at steady-state, similar procedures are used to solve the accompanying linear aerodynamic sensitivity equations in incremental iterative form. As shown, this particular form of the sensitivity equation makes large-scale gradient-based aerodynamic optimization possible by taking advantage of memory efficient methods to construct exact Jacobian matrix-vector products. Various surface parameterization techniques have been employed in the current study to control the shape of the design surface. Once this surface has been deformed, the interior volume of the unstructured grid is adapted by considering the mesh as a system of interconnected tension springs. Grid sensitivities are obtained by differentiating the surface parameterization and the grid adaptation algorithms with ADIFOR, an advanced automatic-differentiation software tool. To demonstrate the ability of this procedure to analyze and design complex configurations of practical interest, the sensitivity analysis and shape optimization has been performed for several two- and three-dimensional cases. In twodimensions, an initially symmetric NACA-0012 airfoil and a high-lift multielement airfoil were examined. For the three-dimensional configurations, an initially rectangular wing with uniform NACA-0012 cross-sections was optimized; in addition, a complete Boeing 747-200 aircraft was studied. Furthermore, the current study also examines the effect of inconsistency in the order of spatial accuracy between the nonlinear fluid and linear shape sensitivity equations. The second step was to develop a computationally efficient, high-fidelity, integrated static aeroelastic analysis procedure. To accomplish this, a structural analysis code was coupled with the aforementioned unstructured grid aerodynamic analysis solver. The use of an unstructured grid scheme for the aerodynamic analysis enhances the interaction compatibility with the wing structure. The structural analysis utilizes finite elements to model the wing so that accurate structural deflections may be obtained. In the current work, parameters have been introduced to control the interaction of the computational fluid dynamics and structural analyses; these control parameters permit extremely efficient static aeroelastic computations. To demonstrate and evaluate this procedure, static aeroelastic analysis results for a flexible wing in low subsonic, high subsonic (subcritical), transonic (supercritical), and supersonic flow conditions are presented.

Newman, James Charles, III

1997-10-01

48

Scaling of swim speed and stroke frequency in geometrically similar penguins: they swim optimally to minimize cost of transport  

PubMed Central

It has been predicted that geometrically similar animals would swim at the same speed with stroke frequency scaling with mass?1/3. In the present study, morphological and behavioural data obtained from free-ranging penguins (seven species) were compared. Morphological measurements support the geometrical similarity. However, cruising speeds of 1.82.3 m s?1 were significantly related to mass0.08 and stroke frequencies were proportional to mass?0.29. These scaling relationships do not agree with the previous predictions for geometrically similar animals. We propose a theoretical model, considering metabolic cost, work against mechanical forces (drag and buoyancy), pitch angle and dive depth. This new model predicts that: (i) the optimal swim speed, which minimizes the energy cost of transport, is proportional to (basal metabolic rate/drag)1/3 independent of buoyancy, pitch angle and dive depth; (ii) the optimal speed is related to mass0.05; and (iii) stroke frequency is proportional to mass?0.28. The observed scaling relationships of penguins support these predictions, which suggest that breath-hold divers swam optimally to minimize the cost of transport, including mechanical and metabolic energy during dive. PMID:19906666

Sato, Katsufumi; Shiomi, Kozue; Watanabe, Yuuki; Watanuki, Yutaka; Takahashi, Akinori; Ponganis, Paul J.

2010-01-01

49

Optimized Cu-Sn Wafer-Level Bonding Using Intermetallic Phase Characterization  

NASA Astrophysics Data System (ADS)

The objective of this study is to optimize the Cu/Sn solid-liquid interdiffusion process for wafer-level bonding applications. To optimize the temperature profile of the bonding process, the formation of intermetallic compounds (IMCs) which takes place during the bonding process needs to be well understood and characterized. In this study, a simulation model for the development of IMCs and the unreacted remaining Sn thickness as a function of the bonding temperature profile was developed. With this accurate simulation model, we are able to predict the parameters which are critical for bonding process optimization. The initial characterization focuses on a kinetics model of the Cu3Sn thickness growth and the amount of Sn thickness that reacts with Cu to form IMCs. As-plated Cu/Sn samples were annealed using different temperatures (150C to 300C) and durations (0 min to 320 min). The kinetics model is then extracted from the measured thickness of IMCs of the annealed samples.

Luu, Thi-Thuy; Duan, Ani; Aasmundtveit, Knut E.; Hoivik, Nils

2013-12-01

50

A Geometric Characterization of the Power of Finite Adaptability in Multistage Stochastic and Adaptive Optimization  

E-print Network

In this paper, we show a significant role that geometric properties of uncertainty sets, such as symmetry, play in determining the power of robust and finitely adaptable solutions in multistage stochastic and adaptive ...

Bertsimas, Dimitris J.

51

GEOMETRIC CHARACTERIZATION AND OPTIMIZATION OF 3D ORGANIC FLEXIBLE SOLAR CELLS  

E-print Network

for her constant encouragement and motivation at all times. #12;v ABSTRACT OF THE THESIS Geometric 3D organic solar cell is first micro-fabricated using negative photolithography procedure followed .........................................................................................................1 1.1 Motivation for Research

Kassegne, Samuel Kinde

52

On the Distance to Optimality of the Geometric Approximate Minimum-Energy Attitude Filter  

E-print Network

Zamani1 and Jochen Trumpf2 and Robert Mahony3 Abstract-- This paper studies the near `Geometric observer theory for mechanical control systems'. 1Mohammad Zamani is with Faculty of Electrical Engineering, UNSW, Canberra, Australia m.zamani@adfa.edu.au 2Jochen Trumpf is with the Research School

Trumpf, Jochen

53

Improving the quality factor of microwave compact resonators by optimizing their geometrical parameters  

E-print Network

of dielectric loaded surface plasmon waveguide structures: Transfer matrix method for plasmonic devices J. Appl: A comprehensive study towards practical terahertz filters and sensors AIP Advances 2, 022109 (2012) Analysis have tested the surface-dominated loss hypothesis by systematically studying the role of geometrical

Devoret, Michel H.

54

Geometric parametrization and constrained optimization techniques in the design of salient pole synchronous machines  

Microsoft Academic Search

The shape optimization of magnetic devices is efficiently performed with field calculation and sensitivity analysis based on the finite element method. Several sequential unconstrained optimization techniques are discussed and evaluated with respect to their application in engineering design. The optimization of the geometry of a salient pole generator so as to achieve a desired field configuration in the airgap is

Konrad Weeber; S. R. H. Hoole

1992-01-01

55

Optimal Unicast Capacity of Random Geometric Graphs: Impact of Multipacket Transmission and Reception  

Microsoft Academic Search

We establish a tight max-flow min-cut theorem for multi-commodity routing in random geometric graphs. We show that, as the number of nodes in the network n tends to infinity, the maximum concurrent flow (MCF) and the minimum cut-sparsity scale as (n2r3(n)\\/k), for a random choice of k = (n) source-destination pairs, where n and r(n) are the number of nodes

Jose Joaquin Garcia-luna-aceves; Zheng Wang; Hamid R. Sadjadpour; Shirish S. Karande

2009-01-01

56

Soft chelating irrigation protocol optimizes bonding quality of Resilon/Epiphany root fillings.  

PubMed

This study was designed to test the impact of either a strong (MTAD) or a soft (1-hydroxyethylidene-1, 1-bisphosphonate [HEPB]) chelating solution on the bond strength of Resilon/Epiphany root fillings. Both 17% EDTA and the omission of a chelator in the irrigation protocol were used as reference treatments. Forty extracted human upper lateral incisors were prepared using different irrigation protocols (n = 10): G1: NaOCl, G2: NaOCl + 17% EDTA, G3: NaOCl + BioPure MTAD (Dentsply/Tulsa, Tulsa, OK), and G4: NaOCl + 18% HEPB. The teeth were obturated and then prepared for micropush-out assessment using root slices of 1 mm thickness. Loading was performed on a universal testing machine at a speed of 0.5 mm/min. One-way analysis of variance and Tukey multiple comparisons were used to compare the results among the experimental groups. EDTA- and MTAD-treated samples revealed intermediate bond strength (0.3-3.6 MPa). The lowest bond strengths were achieved in NaOCl-treated samples (0.3-1.2 MPa, p < 0.05). The highest bond strength was reached in the HEBP-treated samples (3.1-6.1 MPa, p < 0.05). Under the present in vitro conditions, the soft chelating irrigation protocol (18% HEBP) optimized the bonding quality of Resilon/Epiphany (Resilon Research LLC, Madison, CT) root fillings. PMID:18498893

De-Deus, Gustavo; Namen, Ftima; Galan, Joo; Zehnder, Matthias

2008-06-01

57

OPTIMAL SELECTION OF STEAM TURBINE EXHAUST ANNULUS AND CONDENSER SIZES BY GEOMETRIC PROGRAMMING  

Microsoft Academic Search

In this paper, a posynomial programming model is developed for the optimal selection of steam turbine exhaust annulus and condenser sizes. After formulating the general model, a numerical example is presented and sensitivity analysis is considered. A simple formula expressing the optimal cost of the condensing system as a function of selected parameters is obtained.

J. G. ECKER; R. D. WIEBKING

1976-01-01

58

A Geometric Analysis of Bang-Bang Extremals in Optimal Control Problems for Combination Cancer Chemotherapy*  

E-print Network

Chemotherapy* Heinz Sch¨attler Dept. of Electrical and Systems Engineering, Washington University, St. Louis of cancer cells under combination chemotherapies are considered as multi-input optimal control problems over for chemotherapy over a fixed therapy interval. For these problems, and consistent with medical practice, optimal

Ledzewicz, Urszula

59

A Single-Lap Joint Adhesive Bonding Optimization Method Using Gradient and Genetic Algorithms  

NASA Technical Reports Server (NTRS)

A natural process for any engineer, scientist, educator, etc. is to seek the most efficient method for accomplishing a given task. In the case of structural design, an area that has a significant impact on the structural efficiency is joint design. Unless the structure is machined from a solid block of material, the individual components which compose the overall structure must be joined together. The method for joining a structure varies depending on the applied loads, material, assembly and disassembly requirements, service life, environment, etc. Using both metallic and fiber reinforced plastic materials limits the user to two methods or a combination of these methods for joining the components into one structure. The first is mechanical fastening and the second is adhesive bonding. Mechanical fastening is by far the most popular joining technique; however, in terms of structural efficiency, adhesive bonding provides a superior joint since the load is distributed uniformly across the joint. The purpose of this paper is to develop a method for optimizing single-lap joint adhesive bonded structures using both gradient and genetic algorithms and comparing the solution process for each method. The goal of the single-lap joint optimization is to find the most efficient structure that meets the imposed requirements while still remaining as lightweight, economical, and reliable as possible. For the single-lap joint, an optimum joint is determined by minimizing the weight of the overall joint based on constraints from adhesive strengths as well as empirically derived rules. The analytical solution of the sin-le-lap joint is determined using the classical Goland-Reissner technique for case 2 type adhesive joints. Joint weight minimization is achieved using a commercially available routine, Design Optimization Tool (DOT), for the gradient solution while an author developed method is used for the genetic algorithm solution. Results illustrate the critical design variables as a function of adhesive properties and convergences of different joints based on the two optimization methods.

Smeltzer, Stanley S., III; Finckenor, Jeffrey L.

1999-01-01

60

Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization  

E-print Network

Dispersion engineering in silicon nitride (SiX NY ) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multi-cladding arrangement. Ultra-flat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during the fabrication of the SiX NY waveguides are a limitation for obtaining ultra-flat dispersion profiles. Single- and multi-cladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in both single-cladding waveguides and multi-cladding waveguides with small refractive index contrast (3 %). A flat dispersion profile with 3.2 ps/nm/km variation over 500 nm is obtained ...

Boggio, J M Chavez; Fremberg, T; Haynes, R; Roth, M M; Eisermann, R; Lisker, M; Zimmermann, L; Boehm, M

2014-01-01

61

Geometric optimization of a step bearing for a hydrodynamically levitated centrifugal blood pump for the reduction of hemolysis.  

PubMed

A hydrodynamically levitated centrifugal blood pump with a semi-open impeller has been developed for mechanical circulatory assistance. However, a narrow bearing gap has the potential to cause hemolysis. The purpose of the present study is to optimize the geometric configuration of the hydrodynamic step bearing in order to reduce hemolysis by expansion of the bearing gap. First, a numerical analysis of the step bearing, based on lubrication theory, was performed to determine the optimal design. Second, in order to assess the accuracy of the numerical analysis, the hydrodynamic forces calculated in the numerical analysis were compared with those obtained in an actual measurement test using impellers having step lengths of 0%, 33%, and 67% of the vane length. Finally, a bearing gap measurement test and a hemolysis test were performed. As a result, the numerical analysis revealed that the hydrodynamic force was the largest when the step length was approximately 70%. The hydrodynamic force calculated in the numerical analysis was approximately equivalent to that obtained in the measurement test. In the measurement test and the hemolysis test, the blood pump having a step length of 67% achieved the maximum bearing gap and reduced hemolysis, as compared with the pumps having step lengths of 0% and 33%. It was confirmed that the numerical analysis of the step bearing was effective, and the developed blood pump having a step length of approximately 70% was found to be a suitable configuration for the reduction of hemolysis. PMID:23834855

Kosaka, Ryo; Yada, Toru; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

2013-09-01

62

Discrete-Time Pricing and Optimal Exercise of American Perpetual Warrants in the Geometric Random Walk Model  

SciTech Connect

An American option (or, warrant) is the right, but not the obligation, to purchase or sell an underlying equity at any time up to a predetermined expiration date for a predetermined amount. A perpetual American option differs from a plain American option in that it does not expire. In this study, we solve the optimal stopping problem of a perpetual American option (both call and put) in discrete time using linear programming duality. Under the assumption that the underlying stock price follows a discrete time and discrete state Markov process, namely a geometric random walk, we formulate the pricing problem as an infinite dimensional linear programming (LP) problem using the excessive-majorant property of the value function. This formulation allows us to solve complementary slackness conditions in closed-form, revealing an optimal stopping strategy which highlights the set of stock-prices where the option should be exercised. The analysis for the call option reveals that such a critical value exists only in some cases, depending on a combination of state-transition probabilities and the economic discount factor (i.e., the prevailing interest rate) whereas it ceases to be an issue for the put.

Vanderbei, Robert J., E-mail: rvdb@princeton.edu [Princeton University, Department of Operations Research and Financial Engineering (United States); P Latin-Small-Letter-Dotless-I nar, Mustafa C., E-mail: mustafap@bilkent.edu.tr [Bilkent University, Department of Industrial Engineering (Turkey); Bozkaya, Efe B. [Sabanc Latin-Small-Letter-Dotless-I University, Faculty of Administrative Sciences (Turkey)] [Sabanc Latin-Small-Letter-Dotless-I University, Faculty of Administrative Sciences (Turkey)

2013-02-15

63

Geometrical optimization of an ellipsoidal plasma mirror toward tight focusing of ultra-intense laser pulse  

NASA Astrophysics Data System (ADS)

We developed for the first time, very compact (<1 cm3) extremely low f-number (f/# = 0.4) confocal ellipsoid focusing systems. Direct measurement of the laser focal spot using a low-energy laser beam indicates 1/5 reduction of the spot size compared to standard focusing (using a f/2.7 optics). Such mirror is thus able to achieve significant enhancement of the focused laser intensity without modifying the laser system itself. The mirror is then used under plasma mirror regime which enables us to compactify the size, to liberate us from the anxiety of protecting the optics from target debris after shots, and to enhance the temporal contrast. In this paper, we focus our attention to designing and optimizing the geometry of such innovative plasma optics.

Kon, A.; Nakatsutsumi, M.; Buffechoux, S.; Chen, Z. L.; Fuchs, J.; Jin, Z.; Kodama, R.

2010-08-01

64

A simple geometric algorithm to predict optimal starting gantry angles using equiangular-spaced beams for intensity modulated radiation therapy of prostate cancer  

Microsoft Academic Search

A fast, geometric beam angle optimization (BAO) algorithm for clinical intensity-modulated radiation therapy (IMRT) was implemented on ten localized prostate cancer patients on the Radiation Therapy Oncology Group (RTOG) 0126 protocol. The BAO algorithm computed the beam intersection volume (BIV) within the rectum and bladder using five and seven equiangular-spaced beams as a function of starting gantry angle for comparison

Zoann Nugent; Adel S. El-Gubtan; James B. Butler; Boyd M. C. McCurdy; Peter S. Potrebko

2007-01-01

65

SHORTEST PATHS FOR THE REEDS-SHEPP CAR: A WORKED OUT EXAMPLE OF THE USE OF GEOMETRIC TECHNIQUES IN NONLINEAR OPTIMAL CONTROL. 1  

Microsoft Academic Search

We illustrate the use of the techniques of modern geometric optimal control theory by studying the shortest paths for a model of a car that can move forwards and backwards. This problem was discussed in recent work by Reeds and Shepp who showed, by special methods, (a) that shortest path motion could always be achieved by means of trajectories of

J. Sussmann; Guoqing Tang

1991-01-01

66

Optimizing Diffusion Bonding Parameters in AA6061-T6 Aluminum and AZ80 Magnesium Alloy Dissimilar Joints  

NASA Astrophysics Data System (ADS)

The main difficulty when joining magnesium (Mg) and aluminum (Al) alloys by fusion welding lies in the formation of oxide films and brittle intermetallic in the bond region which affects the integrity of the joints. However, diffusion bonding is a suitable process to join these two materials as no such characteristic defects are produced at the joints. The diffusion bonding process parameters such as bonding temperature, bonding pressure, holding time, and surface roughness of the specimen play a major role in determining the joint strength. In this investigation, an attempt was made to develop empirical relationships to predict the strengths of diffusion bonded AZ80 magnesium and AA6061 aluminum alloys dissimilar joints from the process parameters based on central composite factorial design. Response surface methodology was applied to optimize the process parameters to attain the maximum shear strength and bonding strength of the joint. From this investigation, it was found that the bonds produced with the temperature of 405.87 C, pressure of 7.87 MPa, holding time of 29.02 min and surface roughness of 0.10 ?m exhibited maximum shear strength and bonding strength of 57.70 and 76.90 MPa, respectively. The intermetallic formation at the interface was identified.

Joseph Fernandus, M.; Senthilkumar, T.; Balasubramanian, V.; Rajakumar, S.

2012-11-01

67

Why is NBe distance of NH3H(+)DBeH shorter than that of NH3D(+)HBeH? Paradoxical geometrical isotope effects for partially isotope-substituted dihydrogen-bonded isotopomers.  

PubMed

The partial isotope substitution for the change of geometrical parameters, interaction energies, and nuclear magnetic shielding tensors (?) of dihydrogen-bonded NH3X(+)YBeH (X, Y?=?H, D, and T) systems is analyzed. Based on the theoretical calculation, the distance between heavy atoms RNBe of NH3H(+) DBeH is clearly found to be shorter than that in NH3D(+)HBeH. Such apparently paradoxical geometrical isotope effect (GIE) on RNBe is revealed by the cooperative effect of two kinds of (1) primary covalent-bonded GIE and (2) secondary dihydrogen-bonded one. We have demonstrated that (1) the covalent bond lengths become shorter by heavier isotope-substitution and (2) the dihydrogen-bonded distance RXY becomes shorter by heavier Y and lighter X isotope-substitution due to the difference of electronic structure reflected by the nuclear distribution. We have also found that interaction energy of NH3H(+)DBeH is stronger than that of NH3D(+)HBeH and isotopic deshielding effect of magnetic shielding becomes large in lighter isotope. PMID:24323845

Udagawa, Taro; Tachikawa, Masanori

2014-02-01

68

Geometric analysis of the b-dependent effects of Rician signal noise on DTI estimates and determining an optimal b-value  

PubMed Central

The optimal diffusion weighting (DW) factor, b, for use in DTI studies remains uncertain. In this study, the geometric relations of DW quantities are examined, in particular the effects of Rician noise in the measured MR signal. This geometric analysis is used to make theoretical predictions for selecting a b-value to reduce the influence of noise. It is shown that the optimal b-value for DTI studies is healthy human parenchyma is approximately b = 1200 s mm?2, with a simple relation given as well for a given expected apparent diffusion coeffcient (ADC). Monte Carlo simulations on sets of realistic DTI measures are then performed, verifying the optimal DW for minimizing estimate errors. The effects of noise on various DTI parameters such as anisotropy indices (FA and sRA), mean diffusivity (MD), radial diffusivity (RD), eigenvalues and the direction of the first eigenvector are investigated as well. PMID:21550747

Taylor, Paul A.; Biswal, Bharat

2011-01-01

69

Synthesis and structural optimization of multiple H-bonding region of diarylalkyl (thio)amides as novel TRPV1 antagonists  

E-print Network

focused on optimization of the multiple H-bonding part A to improve potency and metabolic potency enhancement by structural optimization of A-region of diarylalkyl amides or thioamides as well.10.043 * Corresponding author. E-mail address: ygsuh@snu.ac.kr (Y.-G. Suh). N H N H S NHMs SC-0030 F N H S NHMs R2 R3 ABC

Suh, Young-Ger

70

Design Optimization of Energy-Efficient Hydrophobic Wafer-bonded III-V/Si Semiconductor Optical Amplifiers  

E-print Network

of Electrical and Computer Engineering, University of California, One Shields Ave., Davis, California 95616 USA) (b) energy band diagram of optimal In(1-x)GaxAsyP(1-y) composition bonding interface (c) current flow transport, optical gain computation, and optical wave-guiding are considered. The energy band diagram shows

Yoo, S. J. Ben

71

Conic Geometric Programming Venkat Chandrasekaranc  

E-print Network

Conic Geometric Programming Venkat Chandrasekaranc and Parikshit Shahw c Departments of Computing introduce and study conic geometric programs (CGPs), which are convex optimiza- tion problems that unify geometric programs (GPs) and conic optimization problems such as semidefinite programs (SDPs). A CGP

72

Anatomy-based inverse optimization in high-dose-rate brachytherapy combined with hypofractionated external beam radiotherapy for localized prostate cancer: Comparison of incidence of acute genitourinary toxicity between anatomy-based inverse optimization and geometric optimization  

SciTech Connect

Purpose: To evaluate the advantages of anatomy-based inverse optimization (IO) in planning high-dose-rate (HDR) brachytherapy. Methods and Materials: A total of 114 patients who received HDR brachytherapy (9 Gy in two fractions) combined with hypofractionated external beam radiotherapy (EBRT) were analyzed. The dose distributions of HDR brachytherapy were optimized using geometric optimization (GO) in 70 patients and by anatomy-based IO in the remaining 44 patients. The correlation between the dose-volume histogram parameters, including the urethral dose and the incidence of acute genitourinary (GU) toxicity, was evaluated. Results: The averaged values of the percentage of volume receiving 80-150% of the prescribed minimal peripheral dose (V{sub 8}-V{sub 15}) of the urethra generated by anatomy-based IO were significantly lower than the corresponding values generated by GO. Similarly, the averaged values of the minimal dose received by 5-50% of the target volume (D{sub 5}-D{sub 5}) obtained using anatomy-based IO were significantly lower than those obtained using GO. Regarding acute toxicity, Grade 2 or worse acute GU toxicity developed in 23% of all patients, but was significantly lower in patients for whom anatomy-based IO (16%) was used than in those for whom GO was used (37%), consistent with the reduced urethral dose (p <0.01). Conclusion: The results of this study suggest that anatomy-based IO is superior to GO for dose optimization in HDR brachytherapy for prostate cancer.

Akimoto, Tetsuo [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan)]. E-mail: takimoto@showa.gunma-u.ac.jp; Katoh, Hiroyuki [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Kitamoto, Yoshizumi [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Shirai, Katsuyuki [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Shioya, Mariko [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Nakano, Takashi [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan)

2006-04-01

73

CORRESPONDENCE PROBLEMS IN GEOMETRIC VISION  

E-print Network

- Dimensional Vision, submitted to SIAM Journal on Imaging Sciences ­ Special Issue on Optimization in ImagingCORRESPONDENCE PROBLEMS IN GEOMETRIC VISION OLOF ENQVIST Faculty of Engineering CentreTryck, Lund 2009 #12;Preface This thesis concerns optimal methods for geometric vision problems. Two important

Lunds Universitet

74

A simple geometric algorithm to predict optimal starting gantry angles using equiangular-spaced beams for intensity modulated radiation therapy of prostate cancer  

SciTech Connect

A fast, geometric beam angle optimization (BAO) algorithm for clinical intensity-modulated radiation therapy (IMRT) was implemented on ten localized prostate cancer patients on the Radiation Therapy Oncology Group (RTOG) 0126 protocol. The BAO algorithm computed the beam intersection volume (BIV) within the rectum and bladder using five and seven equiangular-spaced beams as a function of starting gantry angle for comparison to the V 75 Gy and V 70 Gy. A mathematical theory was presented to explain the correlation of BIV with dose and dose-volume metrics. The class solution 'W' pattern in the rectal V 75 Gy and V 70 Gy as a function of starting gantry angle using five equiangular-spaced beams (with two separate minima centered near 20 deg. and 50 deg. ) was reproduced by the 5 BIV within the rectum. A strong correlation was found between the rectal 5 BIV and the rectal V 75 Gy and V 70 Gy as a function of starting gantry angle. The BAO algorithm predicted the location of the two dosimetric minima in rectal V 75 Gy and V 70 Gy (optimal starting gantry angles) to within 5 deg. . It was demonstrated that the BIV geometric variations for seven equiangular-spaced beams were too small to translate into a strong dosimetric effect in the rectal V 75 Gy and V 70 Gy. The relatively flat distribution with starting gantry angle of the bladder V 75 Gy and V 70 Gy was reproduced by the bladder five and seven BIV for each patient. A geometric BAO method based on BIV has the advantage over dosimetric BAO methods of simplicity and rapid computation time. This algorithm can be used as a standalone optimization method or act as a rapid calculation filter to reduce the search space for a dosimetric BAO method. Given the clinically infeasible computation times of many dosimetric beam orientation optimization algorithms, this robust geometric BIV algorithm has the potential to facilitate beam angle selection for prostate IMRT in clinical practice.

Potrebko, Peter S.; McCurdy, Boyd M. C.; Butler, James B.; El-Gubtan, Adel S.; Nugent, Zoann [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada) and Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada); Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada); Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada) and Department of Radiology, University of Manitoba, Winnipeg, Manitoba R3A 1R9 (Canada); Department of Radiation Oncology, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada) and Department of Radiology, University of Manitoba, Winnipeg, Manitoba R3A 1R9 (Canada); Department of Epidemiology, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada)

2007-10-15

75

Optimization of direct currents to enhance dentine bonding of simplified one-step adhesive.  

PubMed

The aim of this study was to investigate the effects of different direct current intensities on dentine bonding effectiveness of Clearfil S(3) Bond and on cell viability of human dental pulp cells (HDPCs). Thirty-five-third molars were sectioned and ground to provide flat surfaces. Clearfil S(3) Bond was applied under different current conditions for 30 s and then resin composite was built up. Specimens were processed for microtensile bond strength (TBS) testing and for nanoleakage investigation using scanning electron microscopy. Primary HDPCs isolated from premolars were stimulated with different intensities of electric current for 30 s. Then, cell viability was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Specimens bonded with application of electrical current intensities of 50, 60, 70, and 90 A exhibited a significant increase in immediate TBS compared with all other groups. Bonded interfaces prepared using electrically assisted current application showed reduced interfacial nanoleakage upon scanning electron microscopy. Electric current application, from 20 to 70 A, had no effect on the viability of HDPCs. This study provides further evidence for its future clinical use. PMID:24965668

Chen, Hongfei; Fu, Dongjie; Yang, Hongye; Liu, Yinchen; Huang, Yanyu; Huang, Cui

2014-08-01

76

Optimization of the Second Order Logarithmic Machining Economics Problem by Extended Geometric Programming Part IUnconstrained  

Microsoft Academic Search

An extended theory of geometric programming is applied to the machining economics problem utilizing a more accurate tool-life equation that is quadratic in the logarithms of the machining variables. The tool-life equation and corresponding unit cost or productivity functions are classified as quadratic posylognomials (QPL). By comparison, the extended Taylor tool-life equation and corresponding objective functions are classified as posynomials.

Clarence I. Hough Jr; Ramon E. Goforth

1981-01-01

77

Optimization of magnesia-based, cement-free, spinel bonded castables  

NASA Astrophysics Data System (ADS)

The optimization of magnesia-based, cement-free and spinel bonded MgO-Al2O3 castables with more than 70% magnesia and 5% hydratable alumina as binder has been conducted. The major aspects which have been covered during this study are: flowability, volume stability, physical and mechanical properties and corrosion resistance. Flowability tests have been carried out to determine the appropriate deflocculant type and addition level. Volume stability study is divided into two parts, one emphases on the effects of pre-reacted spinel addition on thermal expansion behaviors, the other focuses on the effect of silica fume additions. For the first part, three series have been tested with additions of 0%, 5%, 10% pre-reacted spinel. The starting temperature of in-situ spinel formed is around 1100C. The reversible thermal expansion coefficient of MgO-Al 2O3 castable corresponds to the expansion of the magnesia for temperature up to 1100C. Above 1100C, the thermal expansion of MgO-Al2O3 castable is consistent with phenomenological model with three distinct contributions: the reversible thermal expansion of MgO aggregate, the volume exchange due to the formation of spinel from the reaction of MgO, Al2O3 and the high temperature shrinkage from fine powders sintering. For the second part, silica fume was added at 0--3% to two series, with or without pre-reacted spinel AR78 addition. With silica fume addition, the in-situ spinel formation is enhanced. Adding silica fume into castable doesn't change the thermal expansion behavior below 1100C, but does at higher temperature, increasing the maximum thermal expansion and decreasing the temperature at maximum thermal expansion. The additional level also remarkably affects thermal expansion of MgO-Al2O3 castable at high temperature. Adding pre-reacted spinel AR78 still can control the expansion. The effects of pre-reacted spinel and SiO2 fume addition on physical and mechanical properties of MgO-Al2O3 castable are discussed. The MgO to Al2O3 ratio in the mix, the amount of pre-reacted spinel and the silica fume used significantly influence the porosity, the bulk density and the cold modulus of rupture. Corrosion resistance measurement in highly ferritic basic slag was conducted through rotary slag testing. The erosion resistance are improved by adding 5% of AR78. Adding 5% MR66 is beneficial for the penetration resistance, however, AR90 is not appropriate for MgO-Al2O 3 castable. The microstructural characteristics of corroded MgO-Al2O 3 castable have been analyzed. Three different layers, a slag layer, a penetrated layer and an unattacked layer are distinguishable in the castable. The microstructural analyses showed that both MgO and MA capture FeO from slag to form solid solutions. (Abstract shortened by UMI.)

Xing, Cheng

78

A Probabilistic Approach to the Air Traffic Management in The Next Generation Air Transportation System: Optimal Routing Decision With Geometric Recourse Model  

NASA Astrophysics Data System (ADS)

There has been growing interest in air transportation community to develop a routing decision model based on probabilistic characterization of severe weather. In the probabilistic air traffic management (PATM), decisions are made based on the stochastic weather information in the expected total cost sense. Probabilistic approach aims to enhance routing flexibility and reduce the risks associated with uncertainty of the future weather. In this research, a geometric model is adopted to generate optimal route choice when the future weather is stochastic. The geometric recourse model (GRM) is a strategic PATM model that incorporates route hedging and en-route recourse options to respond to weather change. Hedged routes are routes other than the nominal or detour route, and aircraft is re-routed to fly direct to the destination, which is called recourse, when the weather restricted airspace become flyable. Aircraft takes either the first recourse or the second recourse: The first recourse occurs when weather clears before aircraft reaches it flying on the initial route. The second recourse occurs when the aircraft is at the weather region. There are two variations of GRM: Single Recourse Model (SRM) with first recourse only and Dual Recourse Model (DRM) with both the first and second recourse options. When the weather clearance time follows a uniform distribution, SRM becomes convex with optimal route being either the detour or a hedged route. The DRM has a special property when the maximum storm duration time is less than the flight time to the tip of the storm on the detour route: it is always optimal to take the nominal route. The performance study is conducted by measuring the cost saving from either SRM or DRM. The result shows that there are cases with substantial cost saving, reaching nearly 30% with DRM. The ground-airborne hybrid model is an extension of the GRM, where both ground holding as well as route hedging are considered. The optimal combination of ground delay and route choice is determined by weather characteristics as well as the ground-airborne cost ratio. The numerical analysis reveals that whenever ground delay is required, the optimal route choice is the nominal one, while a non-nominal route is optimal when the ground delay is zero. There exists a unique critical cost ratio associated with given weather condition, which determines whether ground holding is optimal or not.

Yoon, Yoonjin

79

Optimization of thermal assisted direct bonding of soda-lime glasses for lab-on chip application  

Microsoft Academic Search

Surface treatment on glass before thermal assisted direct bonding (TADB) is an issue for lab-on chip fabrication. Surface\\u000a cleaning for obtaining good quality TADB on soda-lime glass are studied and tested in this paper. The optimized cleaning solution\\u000a for soda lime glass samples is NH4OHH2O2H2O (0.5:1:5 volume ratio) and it can be considered as the optimised solution for cleaning soda-lime

Qiuping Chen; Qiuling Chen; Monica Ferraris

2010-01-01

80

Geometric Solids  

NSDL National Science Digital Library

This tool lets learners explore various geometric solids and their properties. Learners can manipulate and color each shape to explore the faces, edges, and vertices, and they can use this tool to investigate the relationship among the number of faces, vertices, and edges. This tool supports the 5-lesson unit "Geometric Solids and Their Properties" (cataloged separately).

2011-01-01

81

Geometric Solids  

NSDL National Science Digital Library

This math activity exposes early learners to a variety of three-dimensional objects. Learners bring geometric solids (everyday objects) from home. Learners sort and graph the objects on a Floor Graphing Mat. After the activity, learners can explore the geometric shapes in centers (see Extensions).

Lessonplans, Utah

2012-09-18

82

Geometric Mechanics  

Microsoft Academic Search

Mechanics for the nonmathematician-a modern approach For physicists, mechanics is quite obviously geometric, yet the classical approach typically emphasizes abstract, mathematical formalism. Setting out to make mechanics both accessible and interesting for nonmathematicians, Richard Talman uses geometric methods to reveal qualitative aspects of the theory. He introduces concepts from differential geometry, differential forms, and tensor analysis, then applies them to

Richard Talman

1999-01-01

83

Rational introduction of disulfide bond to enhance optimal temperature of Lipomyces starkeyi alpha-dextranase expressed in Pichia pastoris.  

PubMed

Alpha-dextranase, which can hydrolyze dextran, is largely used in the sugar industry. However, a thermostable alpha- dextranase is needed to alleviate the viscosity of syrups and clean blocked machines. Thus, to improve the optimal temperature of Lipomyces starkeyi alpha-dextranase expressed by Pichia pastoris, the rational introduction of a de novo designed disulfide bond was investigated. Based on the known structure of Penicillium minioluteum dextranase, L. starkeyi alpha-dextranase was constructed using homology modeling. Four amino acids residues were then selected for site-directed mutagenesis to cysteine. When compared with the wildtype dextranase, the mutant DexM2 (D279C/S289C) showed a more than 13oC improvement on its optimal temperature. DexM2 and DexM12 (T245C/N248C, D279C/S289C) also showed a better thermal stability than the wild-type dextranase. After the introduction of two disulfide bonds, the specific activity of DexM12 was evaluated and found to be two times higher than that of the wild-type. Moreover, DexM12 also showed the highest Vmax. PMID:20075611

Chen, Lin; Yu, Chao; Zhou, Xiangshan; Zhang, Yuanxing

2009-12-01

84

Soft Chelating Irrigation Protocol Optimizes Bonding Quality of Resilon\\/Epiphany Root Fillings  

Microsoft Academic Search

This study was designed to test the impact of either a strong (MTAD) or a soft (1-hydroxyethylidene-1, 1-bisphosphonate [HEPB]) chelating solution on the bond strength of Resilon\\/Epiphany root fillings. Both 17% EDTA and the omission of a chelator in the irrigation protocol were used as reference treatments. Forty extracted human upper lateral incisors were prepared using different irrigation protocols (n

Gustavo De-Deus; Ftima Namen; Joo Galan; Matthias Zehnder

2008-01-01

85

Geometric and Electronic Structure of [{Cu(MeAN)}2(?-?2:?2(O22?))]2+ with an Unusually Long OO Bond: OO Bond Weakening vs Activation for Reductive Cleavage  

PubMed Central

Certain side-on peroxo dicopper(II) species with particularly low ?OO (710730 cm?1) have been found in equilibrium with their bis-?-oxo dicopper(III) isomer. An issue is whether such side-on peroxo bridges are further activated for OO cleavage. In a previous study (Liang, H.-C., et al., J. Am. Chem. Soc. 2002, 124, 41704171), we showed that oxygenation of the three-coordinate complex [CuI(MeAN)]+ (MeAN=N-methyl-N,N-bis[3-(dimethylamino)propyl]amine) leads to a low-temperature stable [{CuII(MeAN)}2(?-?2:?2-O22?)]2+ peroxo species with low ?OO (721 cm?1), as characterized by UV-Vis absorption and resonance Raman (rR) spectroscopies. Here, this complex has been crystallized as its SbF6? salt and an X-ray structure indicates the presence of an unusually long OO bond (1.540(5) ) consistent with the low ?OO. EXAFS and rR spectroscopic and reactivity studies indicate the exclusive formation of [{CuII(MeAN)}2(?-?2:?2-O22?)]2+ without any bis-?-oxo-dicopper(III) isomer present. This is the first structure of a side-on peroxo dicopper(II) species with a significantly long and weak OO bond. DFT calculations show that the weak OO bond results from strong ? donation from the MeAN ligand to Cu that is compensated by a decrease in the extent of peroxo to Cu charge transfer. Importantly, the weak OO bond does not reflect an increase in backbonding into the ?* orbital of the peroxide. Thus, although the OO bond is unusually weak, this structure is not further activated for reductive cleavage to form a reactive bis-?-oxo-dicopper(III) species. These results highlight the necessity of understanding electronic structure changes associated with spectral changes for correlations to reactivity. PMID:22571744

Park, Ga Young; Qayyum, Munzarin F.; Woertink, Julia; Hodgson, Keith O.; Hedman, Britt; Narducci Sarjeant, Amy A.; Solomon, Edward I.; Karlin, Kenneth D.

2012-01-01

86

Selective bond breakage within the HOD molecule using optimized femtosecond ultraviolet laser pulses  

NASA Astrophysics Data System (ADS)

With the HOD molecule initially in its vibrational ground state, we theoretically analyze the laser-induced control of the OD/OH branching ratio D+OH?HOD?H+OD in the first absorption band. In the weak-field limit, any form of UV-pulse shaping control leads to a branching ratio larger than 2 . We obtain in the strong-field limit (peak intensities 10TW/cm2 ) a branching ratio significantly less than 2. The optimized pulses operate by a pump-dump-pump mechanism, where the dumping to the electronic ground state creates nonstationary vibrational states in HOD.

Tiwari, Ashwani Kumar; Mller, Klaus B.; Henriksen, Niels E.

2008-12-01

87

Geometric Solids  

NSDL National Science Digital Library

This tool allows you to learn about various geometric solids and their properties. You can manipulate each solid, seeing it from every angle. You can also color each shape to explore the number of faces, edges, and vertices. With that information, you are challenged to investigate the following question: For any polyhedron, what is the relationship between the number of faces, vertices, and edges?

Illuminations, Nctm

2000-01-01

88

Geometric Mechanics  

NASA Astrophysics Data System (ADS)

Mechanics for the nonmathematician-a modern approach For physicists, mechanics is quite obviously geometric, yet the classical approach typically emphasizes abstract, mathematical formalism. Setting out to make mechanics both accessible and interesting for nonmathematicians, Richard Talman uses geometric methods to reveal qualitative aspects of the theory. He introduces concepts from differential geometry, differential forms, and tensor analysis, then applies them to areas of classical mechanics as well as other areas of physics, including optics, crystal diffraction, electromagnetism, relativity, and quantum mechanics. For easy reference, Dr. Talman treats separately Lagrangian, Hamiltonian, and Newtonian mechanics-exploring their geometric structure through vector fields, symplectic geometry, and gauge invariance respectively. Practical perturbative methods of approximation are also developed. Geometric Mechanics features illustrative examples and assumes only basic knowledge of Lagrangian mechanics. Of related interest . . . APPLIED DYNAMICS With Applications to Multibody and Mechatronic Systems Francis C. Moon A contemporary look at dynamics at an intermediate level, including nonlinear and chaotic dynamics. 1998 (0-471-13828-2) 504 pp. MATHEMATICAL PHYSICS Applied Mathematics for Scientists and Engineers Bruce Kusse and Erik Westwig A comprehensive treatment of the mathematical methods used to solve practical problems in physics and engineering. 1998 (0-471-15431-8) 680 pp.

Talman, Richard

1999-10-01

89

Optimization of HIP bonding conditions for ITER shielding blanket/first wall made from austenitic stainless steel and dispersion strengthened copper alloy  

NASA Astrophysics Data System (ADS)

Optimum bonding conditions were studied on the Hot Isostatic Pressing (HIP) bonded joints of type 316L austenitic stainless steel and Dispersion Strengthened Copper alloy (DSCu) for application to the ITER shielding blanket / first wall. HIP bonded joints were fabricated at temperatures in a 980-1050C range, and a series of mechanical tests and metallurgical observations were conducted on the joints. Also, bondability of two grades of DSCu (Glidcop Al-25 and Al-15 ) with SS316L was examined in terms of mechanical properties of the HIP bonded joints. From those studies it was concluded that the HIP temperature of 1050C was an optimal condition for obtaining higher ductility, impact values and fatigue strength. Also, SS316L/Al-15 joints showed better results in terms of ductility and impact values compared with SS316L/Al-25 joints.

Sato, S.; Hatano, T.; Kuroda, T.; Furuya, K.; Hara, S.; Enoeda, M.; Takatsu, H.

1998-10-01

90

Geometric Intersection Problems  

Microsoft Academic Search

We develop optimal algorithms for forming the intersection of geometric objects in the plane and apply them to such diverse problems as linear programming, hidden-line elimination, and wire layout. Given N line segments in the plane, finding all intersecting pairs requires O(N2) time. We give an O(N log N) algorithm to determine whether any two intersect and use it to

Michael Ian Shamos; Dan Hoey

1976-01-01

91

Influence of optimized leading-edge deflection and geometric anhedral on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration. [langley 7 by 10 foot tunnel  

NASA Technical Reports Server (NTRS)

An investigation conducted in the Langley 7 by 10 foot tunnel to determine the influence of an optimized leading-edge deflection on the low speed aerodynamic performance of a configuration with a low aspect ratio, highly swept wing. The sensitivity of the lateral stability derivative to geometric anhedral was also studied. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to spanwise variation of unwash, the resulting optimized leading edge was a smooth, continuously warped surface for which the deflection varied from 16 deg at the side of body to 50 deg at the wing tip. For the particular configuration studied, levels of leading-edge suction on the order of 90 percent were achieved. The results of tests conducted to determine the sensitivity of the lateral stability derivative to geometric anhedral indicate values which are in reasonable agreement with estimates provided by simple vortex-lattice theories.

Coe, P. L., Jr.; Huffman, J. K.

1979-01-01

92

Chemical Distribution and Bonding of Lithium in Intercalated Graphite: Identification with Optimized Electron Energy Loss Spectroscopy  

SciTech Connect

Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer.

Zhu, Y.; Wang, F.; Graetz, J.; Moreno, M.S.; Ma, C.; Wu, L.; Volkov, V.

2011-02-01

93

Chemical distribution and bonding of lithium in intercalated graphite: identification with optimized electron energy loss spectroscopy.  

PubMed

Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer. PMID:21218844

Wang, Feng; Graetz, Jason; Moreno, M Sergio; Ma, Chao; Wu, Lijun; Volkov, Vyacheslav; Zhu, Yimei

2011-02-22

94

Geometric Models  

NSDL National Science Digital Library

Created by Kyle Siegrist of the University of Alabama-Huntsville, this is an online, interactive lesson on geometric models. The author provides examples, exercises, and applets which include Buffon's problems, Bertrand's paradox, and random triangles. Additionally, the author provides links to external resources for students wanting to engage further in this topic. This is simply one lesson in a series of seventeen. They are all easily accessible as the author has formated his site much like an online textbook.

Siegrist, Kyle

2009-02-23

95

Geometric Algebra  

E-print Network

This is an introduction to geometric algebra, an alternative to traditional vector algebra that expands on it in two ways: 1. In addition to scalars and vectors, it defines new objects representing subspaces of any dimension. 2. It defines a product that's strongly motivated by geometry and can be taken between any two objects. For example, the product of two vectors taken in a certain way represents their common plane. This system was invented by William Clifford and is more commonly known as Clifford algebra. It's actually older than the vector algebra that we use today (due to Gibbs) and includes it as a subset. Over the years, various parts of Clifford algebra have been reinvented independently by many people who found they needed it, often not realizing that all those parts belonged in one system. This suggests that Clifford had the right idea, and that geometric algebra, not the reduced version we use today, deserves to be the standard "vector algebra." My goal in these notes is to describe geometric algebra from that standpoint and illustrate its usefulness. The notes are work in progress; I'll keep adding new topics as I learn them myself.

Eric Chisolm

2012-05-27

96

HNCO-based measurement of one-bond amide 15N-1H couplings with optimized precision.  

PubMed

A pair of 3D HNCO-based experiments have been developed with the aim of optimizing the precision of measurement of (1)J(NH) couplings. Both pulse sequences record (1)J(NH) coupling evolution during the entire constant time interval that (15)N magnetization is dephasing or rephasing with respect to the directly bonded (13)C' nucleus, with (15)N(13)C' multiple quantum coherence maintained during the (13)C' evolution period. The first experiment, designed for smaller proteins, produces an apparent doubling of the (1)J(NH) coupling without any accompanying increases in line width. The second experiment is a J-scaled TROSY-HNCO experiment in which the (1)J(NH) coupling is measured by frequency difference between resonances offset symmetrically about the position of the downfield component of the (15)N doublet (i.e. the TROSY resonance). This experiment delivers significant gains in precision of (1)J(NH) coupling measurement compared to existing J-scaled TROSY-HNCO experiments. With the proper choice of acquisition parameters and sufficient sensitivity to acquire a 3D TROSY-HNCO experiment, it is shown that (1)J(NH) couplings can be measured with a precision which approaches or exceeds the precision of measurement with which the frequency of the TROSY resonance itself can be determined. PMID:20012159

Arbogast, Luke; Majumdar, Ananya; Tolman, Joel R

2010-02-01

97

HNCO-based measurement of one-bond amide 15N-1H couplings with optimized precision  

PubMed Central

A pair of 3D HNCO-based experiments have been developed with the aim of optimizing the precision of measurement of 1JNH couplings. Both pulse sequences record 1JNH coupling evolution during the entire constant time interval that 15N magnetization is dephasing or rephasing with respect to the directly bonded 13C? nucleus, with 15N13C? multiple quantum coherence maintained during the 13C? evolution period. The first experiment, designed for smaller proteins, produces an apparent doubling of the 1JNH coupling without any accompanying increases in line width. The second experiment is a J-scaled TROSY-HNCO experiment in which the 1JNH coupling is measured by frequency difference between resonances offset symmetrically about the position of the downfield component of the 15N doublet (i.e. the TROSY resonance). This experiment delivers significant gains in precision of 1JNH coupling measurement compared to existing J-scaled TROSY-HNCO experiments. With the proper choice of acquisition parameters and sufficient sensitivity to acquire a 3D TROSY-HNCO experiment, it is shown that 1JNH couplings can be measured with a precision which approaches or exceeds the precision of measurement with which the frequency of the TROSY resonance itself can be determined. PMID:20012159

Arbogast, Luke; Majumdar, Ananya; Tolman, Joel R.

2010-01-01

98

Labyrinth stepped seal geometric optimization  

E-print Network

. . . . . . . . . . . . . . . . 35 Influence of distance-to-contact on seal loss coefficient 38 Influence of radial step size on seal loss coefficient for smaller distance-to-contact and pitch values . . . . . . . . . . . . . . . . . . . 13 Influence of radial step size on seal... loss coefficient for larger distance-to-contact and pitch values . . . . . . . . . . . . . . . . . . . . . 41 14 Influence of radius size on seal loss coefficient for constant pitch 43 15 Influence of radius size on seal loss coefficient for small...

Wernig, Marcus Daniel

2012-06-07

99

Calculation of intramolecular hydrogen bonding strength and natural bond orbital (NBO) analysis of naphthazarin with chlorine substitution  

Microsoft Academic Search

The hydrogen bond strength, geometry optimization and 1H NMR for naphthazarin (NZ) and its chlorine substitutions have been calculated at the B3LYP\\/6-31G** theoretical level.The calculated chemical shifts of the chelated proton for all molecules, using GIAO method, are well correlate with the calculated geometrical parameters results.According to the calculated results, substitutions near the hydroxyl groups and near the carbonyl groups

M. Zahedi-Tabrizi; R. Farahati

2011-01-01

100

Excited-state hydrogen-bonding dynamics of camphorsulfonic acid doped polyaniline: a theoretical study.  

PubMed

First-principles calculations were performed to study the hydrogen bond in the camphorsulfonic (CSA) acid-doped polyaniline system. The density functional theory (DFT) method was used to calculate the ground-state geometric structure optimization. Meanwhile, the electronic excitation energies and corresponding oscillation strengths of the low-lying electronically excited states were investigated by the time-dependent density functional theory (TDDFT) method. In the acid-doped system, S[double bond, length as m-dash]OH-N type intermolecular hydrogen bonds were formed. The band lengths at the hydrogen bond formation point were elongated, and the stronger hydrogen-bond interaction causes longer bond stretching. DPA-DMSO was photoexcited to the S2 state which possessed the largest oscillator strength, and the ICPA-DMSO was photoexcited to the S3 state in a similar way. In addition, we also discussed the frontier molecular orbitals and the electron density transition. PMID:25363721

Zhang, Yahong; Duan, Yuping; Wang, Tongmin

2014-12-21

101

Exploitation of spatiotemporal information and geometric optimization of signal\\/noise performance using arrays of carbon black-polymer composite vapor detectors  

Microsoft Academic Search

We have investigated various aspects of the geometric and spatiotemporal response properties of an array of sorption-based vapor detectors. The detectors of specific interest are composites of insulating organic polymers filled with electrical conductors, wherein the detector film provides a reversible dc electrical resistance change upon the sorption of an analyte vapor. An analytical expression derived for the signal\\/noise performance

Shawn M. Briglin; Michael S. Freund; Phil Tokumaru; Nathan S. Lewis

2002-01-01

102

Natural bond orbital analysis, electronic structure, non-linear properties and vibrational spectral analysis of l-histidinium bromide monohydrate: A density functional theory  

Microsoft Academic Search

The spectroscopic properties of the crystallized nonlinear optical molecule l-histidinium bromide monohydrate (abbreviated as l-HBr-mh) have been recorded and analyzed by FT-IR, FT-Raman and UV techniques. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the crystal were calculated with the help of density functional theory computations. The optimized geometric bond lengths and bond angles obtained by using

D. Sajan; Lynnette Joseph; N. Vijayan; M. Karabacak

2011-01-01

103

REMO: A New Protocol to Refine Full Atomic Protein Models from C-alpha Traces by Optimizing Hydrogen-Bonding Networks  

PubMed Central

Protein structure prediction approaches usually perform modeling simulations based on reduced representation of protein structures. For biological utilizations, it is an important step to construct full atomic models from the reduced structure decoys. Most of the current full-atomic model reconstruction procedures have defects which either could not completely remove the steric clashes among backbone atoms or generate final atomic models with worse topology similarity relative to the native structures than the reduced models. In this work, we develop a new protocol, called REMO, to generate full atomic protein models by optimizing the hydrogen-bonding network with basic fragments matched from a newly constructed backbone isomer library of solved protein structures. The algorithm is benchmarked on 230 non-homologous proteins with reduced structure decoys generated by I-TASSER simulations. The results show that REMO has a significant ability to remove steric clashes, and meanwhile retains good topology of the reduced model. The hydrogen-bonding network of the final models is dramatically improved during the procedure. The REMO algorithm has been exploited in the recent CASP8 experiment which demonstrated significant improvements of the I-TASSER models in both atomic-level structural refinement and hydrogen-bonding network construction. PMID:19274737

Li, Yunqi; Zhang, Yang

2009-01-01

104

Optimization of bond strength between gold alloy and porcelain through a composite interlayer obtained by powder metallurgy  

Microsoft Academic Search

The purpose of this study was to evaluate the influence of a composite interlayer (at the metalceramic interface) on the shear bond strength of a metalceramic composite when compared with a conventional porcelain fused to metal (PFM).Several metalceramic composites specimens were produced by hot pressing. To identify which was the best composition for the interlayer several composites, with different relations

B. Henriques; D. Soares; F. S. Silva

2011-01-01

105

Theory of chemical bonds in metalloenzymes XI: Full geometry optimization and vibration analysis of porphyrin iron-oxo species  

NASA Astrophysics Data System (ADS)

Physiochemical properties of compound I and II intermediate states for heme enzymes (catalase, peroxidase, P450) and inorganic models are investigated by hybrid density functional theory. Used theoretical models are composed of an oxoferryl porphyrin and an axial ligand, which are cresol, methylimidazole, methylthiol, and chloride for catalase, peroxidase, P450, and inorganic models, respectively. The oxoferryl bonds are characterized in terms of bond lengths and vibration frequencies. It is found that the oxoferryl bond lengths (the stretching frequency) are shorter (higher) than those of the X-ray crystal structures of enzymes, on the other hand for inorganic models, they are comparable with the experimental values. Spin density distributions showed that radical state at the compound I can be classified into two types: (1) porphyrin radical state and (2) axial ligand radical state. Peroxidase and inorganic model are in the former case and Catalase and P450 are in the later case at the present calculation models. Magnetic interactions between oxoferryl and ligand radical moieties are analyzed by the natural orbital analysis and it is showed that the effective exchange integral (J) values are strongly related to the radical spin density distributions: axial ligand radical tends to increase the antiferromagnetic interaction. Mssbauer shift parameters are also evaluated and it is shown that iron charge states are similar for these models.

Shoji, Mitsuo; Isobe, Hiroshi; Saito, Toru; Kitagawa, Yasutaka; Yamanaka, Shusuke; Kawakami, Takashi; Okumura, Mitsutaka; Yamaguchi, Kizashi

106

Optimal acidulated phosphate fluoride gel etching time for surface treatment of feldspathic porcelain: on shear bond strength to resin composite  

PubMed Central

Objectives: This in vitro study evaluated the shear bond strength (SBS) of resin composite to feldspathic porcelain after acidulated phosphate fluoride (APF) gel treatment over different periods of time. Methods: One hundred and fifty-six feldspathic specimens were divided into 12 groups. Group C received no treatment (control group). Groups APF1 through APF10, ten experimental groups, were treated with 1.23% APF gel. Each group obtained 1 to 10 minutes of etching time in 1 minute increments, respectively. Group HF2 was treated with 9.6% hydrofluoric acid (HF) for 2 minutes. All specimens were then bonded to a resin composite cylinder using Adper Scotchbond Multi-purpose (3M ESPE) after silane (Monobond-S, Ivoclar Vivadent AG) application. Specimens were stored at 37C for 24 hours before the SBS was performed and were recorded in MPa at fracture. Data were analyzed using one-way ANOVA and Tukeys test (?=.05). Results: HF etching yielded the highest SBS (18.0 1.5 MPa), which was not significantly different from APF gel etching for 6 to 10 minutes (16.0 2.1 to 17.2 1.6 MPa) (P>.05). Conclusions: APF gel etching for 6 minutes might be used as an alternative etchant to HF acid for bonding resin composite to silanized feldspathic porcelain. PMID:22229009

Kukiattrakoon, Boonlert; Thammasitboon, Kewalin

2012-01-01

107

PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism  

Microsoft Academic Search

Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon

Jason S. Gardner

2011-01-01

108

Cooperativity in beryllium bonds.  

PubMed

A theoretical study of the beryllium bonded clusters of the (iminomethyl)beryllium hydride and (iminomethyl)beryllium fluoride [HC(BeX)=NH, X = H, F] molecules has been carried out at the B3LYP/6-311++G(3df,2p) level of theory. Linear and cyclic clusters have been characterized up to the decamer. The geometric, energetic, electronic and NMR properties of the clusters clearly indicate positive cooperativity. The evolution of the molecular properties, as the size of the cluster increases, is similar to those reported in polymers held together by hydrogen bonds. PMID:24452820

Alkorta, Ibon; Elguero, Jos; Yez, Manuel; M, Otilia

2014-03-01

109

Atomic and electronic structure of diamond (111) surfaces I. Reconstruction and hydrogen-induced de-reconstruction of the one dangling-bond surface  

Microsoft Academic Search

We present ab-initio local-density functional calculations of the atomic and electronic structure of the clean and hydrogen-covered one dangling-bond diamond (111) surfaces. The calculations are based on a finite-temperature local-density approximation, optimized ultrasoft pseudopotentials, and an exact calculation of the electronic ground state and Hellmann-Feynman forces before each step in the geometrical optimization of the surface. We find that the

G. Kern; J. Hafner; G. Kresse

1996-01-01

110

Shape design sensitivity analysis and optimization of three dimensional elastic solids using geometric modeling and automatic regridding. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

An automatic regridding method and a three dimensional shape design parameterization technique were constructed and integrated into a unified theory of shape design sensitivity analysis. An algorithm was developed for general shape design sensitivity analysis of three dimensional eleastic solids. Numerical implementation of this shape design sensitivity analysis method was carried out using the finite element code ANSYS. The unified theory of shape design sensitivity analysis uses the material derivative of continuum mechanics with a design velocity field that represents shape change effects over the structural design. Automatic regridding methods were developed by generating a domain velocity field with boundary displacement method. Shape design parameterization for three dimensional surface design problems was illustrated using a Bezier surface with boundary perturbations that depend linearly on the perturbation of design parameters. A linearization method of optimization, LINRM, was used to obtain optimum shapes. Three examples from different engineering disciplines were investigated to demonstrate the accuracy and versatility of this shape design sensitivity analysis method.

Yao, Tse-Min; Choi, Kyung K.

1987-01-01

111

Optimization of HIP bonding conditions for ITER shielding blanket\\/first wall made from austenitic stainless steel and dispersion strengthened copper alloy  

Microsoft Academic Search

Optimum bonding conditions were studied on the Hot Isostatic Pressing (HIP) bonded joints of type 316L austenitic stainless steel and Dispersion Strengthened Copper alloy (DSCu) for application to the ITER shielding blanket \\/ first wall. HIP bonded joints were fabricated at temperatures in a 9801050C range, and a series of mechanical tests and metallurgical observations were conducted on the joints.

S. Sato; T Hatano; T Kuroda; K Furuya; S Hara; M Enoeda; H Takatsu

1998-01-01

112

Geometrization of Quantum Mechanics  

E-print Network

We show that it is possible to represent various descriptions of Quantum Mechanics in geometrical terms. In particular we start with the space of observables and use the momentum map associated with the unitary group to provide an unified geometrical description for the different pictures of Quantum Mechanics. This construction provides an alternative to the usual GNS construction for pure states.

J. F. Carinena; J. Clemente-Gallardo; G. Marmo

2007-01-19

113

Hierarchies of Geometric Entanglement  

E-print Network

We introduce and discuss a class of generalized geometric measures of entanglement. For pure quantum states of N elementary subsystems, these extended measures are defined as the distances from the sets of K-separable states (K = 2,...,N). In principle, the entire set of these geometric measures provides a complete quantification and a hierarchical ordering of the different bipartite and multipartite components of the global geometric entanglement, and allows to discriminate among the different contributions. The extended measures are applied in the study of entanglement for different classes of N-qubit pure states, including W, GHZ, and cluster states. In all these cases we introduce a general method for the computation of the different geometric entanglement com- ponents. The entire set of geometric measures establishes an ordering among the different types of bipartite and multipartite entanglement. In particular, it determines a consistent hierarchy between GHZ and W states, clarifying the original result...

Blasone, M; De Siena, S; Illuminati, F

2007-01-01

114

On a novel rate theory for transport in narrow ion channels and its application to the study of flux optimization via geometric effects  

NASA Astrophysics Data System (ADS)

We present a novel rate theory based on the notions of splitting probability and mean first passage time to describe single-ion conduction in narrow, effectively one-dimensional membrane channels. In contrast to traditional approaches such as transition state theory or Kramers theory, transitions between different conduction states in our model are governed by rates which depend on the full geometry of the potential of mean force (PMF) resulting from the superposition of an equilibrium free energy profile and a transmembrane potential induced by a nonequilibrium constraint. If a detailed theoretical PMF is available (e.g., from atomistic molecular dynamics simulations), it can be used to compute characteristic conductance curves in the framework of our model, thereby bridging the gap between the atomistic and the mesoscopic level of description. Explicit analytic solutions for the rates, the ion flux, and the associated electric current can be obtained by approximating the actual PMF by a piecewise linear potential. As illustrative examples, we consider both a theoretical and an experimental application of the model. The theoretical example is based on a hypothetical channel with a fully symmetric sawtooth equilibrium PMF. For this system, we explore how changes in the spatial extent of the binding sites affect the rate of transport when a linear voltage ramp is applied. Already for the case of a single binding site, we find that there is an optimum size of the site which maximizes the current through the channel provided that the applied voltage exceeds a threshold value given by the binding energy of the site. The above optimization effect is shown to arise from the complex interplay between the channel structure and the applied electric field, expressed by a nonlinear dependence of the rates with respect to the linear size of the binding site. In studying the properties of current-voltage curves, we find a double crossover between sublinear and superlinear behaviors as the size of the binding site is varied. The ratio of unidirectional fluxes clearly deviates from the Ussing limit and can be characterized by a flux ratio exponent which decreases below unity as the binding site becomes wider. We also explore effects arising from changes in the ion bulk concentration under symmetric ionic conditions and the presence of additional binding sites in the hypothetical channel. As for the experimental application, we show that our rate theory is able to provide good fits to conductance data for sodium permeation through the gramicidin A channel. Possible extensions of the theory to treat the case of an asymmetric equilibrium PMF, fluctuations in the mean number of translocating ions, the case of fluctuating energy barriers, and multi-ion conductance are briefly discussed.

Abad, E.; Reingruber, J.; Sansom, M. S. P.

2009-02-01

115

A Survey of Geometric Algebra  

E-print Network

A Survey of Geometric Algebra and Geometric Calculus c Alan Macdonald Luther College, Decorah, IA is always available at my web page.) The principal argument for the adoption of geometric algebra and Geometric Algebra: http://faculty.luther.edu/~macdonal/laga/ Vector and Geometric Calculus: http

Harrington, J. Patrick

116

Geometric Reasoning for Automated Planning  

NASA Technical Reports Server (NTRS)

An important aspect of mission planning for NASA s operation of the International Space Station is the allocation and management of space for supplies and equipment. The Stowage, Configuration Analysis, and Operations Planning teams collaborate to perform the bulk of that planning. A Geometric Reasoning Engine is developed in a way that can be shared by the teams to optimize item placement in the context of crew planning. The ISS crew spends (at the time of this writing) a third or more of their time moving supplies and equipment around. Better logistical support and optimized packing could make a significant impact on operational efficiency of the ISS. Currently, computational geometry and motion planning do not focus specifically on the optimized orientation and placement of 3D objects based on multiple distance and containment preferences and constraints. The software performs reasoning about the manipulation of 3D solid models in order to maximize an objective function based on distance. It optimizes for 3D orientation and placement. Spatial placement optimization is a general problem and can be applied to object packing or asset relocation.

Clement, Bradley J.; Knight, Russell L.; Broderick, Daniel

2012-01-01

117

Geometric methods in quantum computation  

NASA Astrophysics Data System (ADS)

Recent advances in the physical sciences and engineering have created great hopes for new computational paradigms and substrates. One such new approach is the quantum computer, which holds the promise of enhanced computational power. Analogous to the way a classical computer is built from electrical circuits containing wires and logic gates, a quantum computer is built from quantum circuits containing quantum wires and elementary quantum gates to transport and manipulate quantum information. Therefore, design of quantum gates and quantum circuits is a prerequisite for any real application of quantum computation. In this dissertation we apply geometric control methods from differential geometry and Lie group representation theory to analyze the properties of quantum gates and to design optimal quantum circuits. Using the Cartan decomposition and the Weyl group, we show that the geometric structure of nonlocal two-qubit gates is a 3-Torus. After further reducing the symmetry, the geometric representation of nonlocal gates is seen to be conveniently visualized as a tetrahedron. Each point in this tetrahedron except on the base corresponds to a different equivalent class of nonlocal gates. This geometric representation is one of the cornerstones for the discussion on quantum computation in this dissertation. We investigate the properties of those two-qubit operations that can generate maximal entanglement. It is an astonishing finding that if we randomly choose a two-qubit operation, the probability that we obtain a perfect entangler is exactly one half. We prove that given a two-body interaction Hamiltonian, it is always possible to explicitly construct a quantum circuit for exact simulation of any arbitrary nonlocal two-qubit gate by turning on the two-body interaction for at most three times, together with at most four local gates. We also provide an analytic approach to construct a universal quantum circuit from any entangling gate supplemented with local gates. Closed form solutions have been derived for each step in this explicit construction procedure. Moreover, the minimum upper bound is found to construct a universal quantum circuit from any Controlled-Unitary gate. A near optimal explicit construction of universal quantum circuits from a given Controlled-Unitary is provided. For the Controlled-NOT and Double-CNOT gate, we then develop simple analytic ways to construct universal quantum circuits with exactly three applications, which is the least possible for these gates. We further discover a new quantum gate (named B gate) that achieves the desired universality with minimal number of gates. Optimal implementation of single-qubit quantum gates is also investigated. Finally, as a real physical application, a constructive way to implement any arbitrary two-qubit operation on a spin electronics system is discussed.

Zhang, Jun

118

A Bayesian framework for geometric uncertainties handling  

E-print Network

in physics, in artificial intelligence [4], as well as in mobile robotics [5, 6] and computer vision [7 simulation results using the implemented CAD modeler. INTRODUCTION The use of geometric models in robotics method. The accuracy of this estimation is controlled by the optimization process to reduce computation

Paris-Sud XI, Université de

119

Hydrogen bonding, halogen bonding and lithium bonding: an atoms in molecules and natural bond orbital perspective towards conservation of total bond order, inter- and intra-molecular bonding.  

PubMed

One hundred complexes have been investigated exhibiting D-XA interactions, where X = H, Cl or Li and DX is the 'X bond' donor and A is the acceptor. The optimized structures of all these complexes have been used to propose a generalized 'Legon-Millen rule' for the angular geometry in all these interactions. A detailed Atoms in Molecules (AIM) theoretical analysis confirms an important conclusion, known in the literature: there is a strong correlation between the electron density at the XA bond critical point (BCP) and the interaction energy for all these interactions. In addition, we show that extrapolation of the fitted line leads to the ionic bond for Li-bonding (electrostatic) while for hydrogen and chlorine bonding, it leads to the covalent bond. Further, we observe a strong correlation between the change in electron density at the D-X BCP and that at the XA BCP, suggesting conservation of the bond order. The correlation found between penetration and electron density at BCP can be very useful for crystal structure analysis, which relies on arbitrary van der Waals radii for estimating penetration. Various criteria proposed for shared- and closed-shell interactions based on electron density topology have been tested for H/Cl/Li bonded complexes. Finally, using the natural bond orbital (NBO) analysis it is shown that the D-X bond weakens upon X bond formation, whether it is ionic (DLi) or covalent (DH/DCl) and the respective indices such as ionicity or covalent bond order decrease. Clearly, one can think of conservation of bond order that includes ionic and covalent contributions to both D-X and XA bonds, for not only X = H/Cl/Li investigated here but also any atom involved in intermolecular bonding. PMID:25127185

Shahi, Abhishek; Arunan, Elangannan

2014-10-01

120

Bond stretching phonon softening and angle-resolved photoemission kinks in optimally doped Bi2Sr1:6La0:4Cu2O6+sigma superconductors  

SciTech Connect

We report the first measurement of the Cu-O bond stretching phonon dispersion in optimally doped Bi2Sr1.6La0.4Cu2O6+delta using inelastic x-ray scattering. We found a softening of this phonon at q=(0.25,0,0) from 76 to 60 meV, similar to the one reported in other cuprates. A comparison with angle-resolved photoemission data on the same sample revealed an excellent agreement in terms of energy and momentum between the angle-resolved photoemission nodal kink and the soft part of the bond stretching phonon. Indeed, we find that the momentum space where a 63+-5 meV kink is observed can be connected with a vector q=(xi,0,0) with xi>= 0.22, corresponding exactly to the soft part of the bond stretching phonon.

Graf, Jeff; d'Astuto, M.; Jozwiak, C.; Garcia, D.R.; Saini, N.L.; Krisch, M.; Ikeuchi, K.; Baron, A.Q.R.; Eisaki, H.; Lanzara, Alessandra

2008-05-08

121

Bond Stretching Phonon Softening And Kinks in the Angle-Resolved Photoemission Spectra of Optimally Doped Bi(2)Sr(1.6)La(0.4)Cu(2)O(6)+-Delta Superconductors  

SciTech Connect

We report the first measurement of the Cu-O bond stretching phonon dispersion in optimally doped Bi{sub 2}Sr{sub 1.6}La{sub 0.4}Cu{sub 2}O{sub 6+{delta}} using inelastic x-ray scattering. We found a softening of this phonon at q = ({approx} 0.25, 0, 0) from 76 to 60 meV, similar to the one reported in other cuprates. A comparison with angle-resolved photoemission data on the same sample revealed an excellent agreement in terms of energy and momentum between the angle-resolved photoemission nodal kink and the soft part of the bond stretching phonon. Indeed, we find that the momentum space where a 63 {+-} 5 meV kink is observed can be connected with a vector q = ({zeta}, 0, 0) with {zeta} {ge} 0.22, corresponding exactly to the soft part of the bond stretching phonon.

Graf, J.; d'Astuto, M.; Jozwiak, C.; Garcia, D.R.; Saini, N.L.; Krisch, M.; Ikeuchi, K.; Baron, A.Q.R.; Eisaki, H.; Lanzara, A.

2009-05-19

122

AJ Geometric Formulas Calculator  

NSDL National Science Digital Library

Solve various attributes of shapes and solids. Includes calculations for circle, parallelogram, rectangle, square, trapezoid, right circular cone, right circular cylinder, rectangular solid, and sphere geometric formulas. Geometry attributes include volume, area, perimeter, surface area, radius, length and circumference.

Raymond, Jimmy

123

Discover Geometric Dimensioning & Tolerancing  

NSDL National Science Digital Library

Learn about Geometric Dimensioning & Tolerancing (GD&T) basics before applying it to DT-1200 course projects Geometric Dimensioning & Tolerancing is the science of size, shape, and form control. It is used in mechanical design to ensure proper fit and function of mating parts in mechanical assemblies. It addresses the following mechanical design challenges: 1. How does feature form, and not just size and location, affect ...

Manning, David

2005-11-21

124

Greedy Fans: A geometric approach to dual greedy algorithms  

E-print Network

Greedy Fans: A geometric approach to dual greedy algorithms Hiroshi HIRAI Research Institute and Okamoto's models. Keywords: submodularity, greedy algorithms, regular triangulations 1 Introduction investigated greedily solvable linear programs, where so-called dual greedy algorithms construct a dual optimal

125

Geometric optimization for radiation hardness assurance  

NASA Astrophysics Data System (ADS)

The probability of a single event effect occurring is generally a function of the energy deposited in a sensitive volume, which is typically expressed as the absorbed dose in that volume. For short segments of high energy particle tracks, the dose due to a single event is proportional to the chord length through the sensitive volume. Thus, the distribution of dose in chord length is likely to relate to the probability of single event effects. For various geometries, a differential chord length distribution was generated and from this the dose distribution, frequency mean chord length, and dose mean chord length were calculated. In every case, the dose mean chord length was greater than the frequency mean chord length by a minimum of 26% and increased with the eccentricity of the volume. The large value of the dose mean chord length relative to the frequency mean chord length demonstrates the need to consider rare, long-chord-length crossings in radiation hardness testing, despite their relatively low probability of occurrence.

Northum, J.; Guetersloh, S.

126

Water filtration optimization by geometric programming  

E-print Network

plant capacity at minimal cost. For example, the water plant at Minnetka, Illinois was converted from 6. 0 to 12. 0 million gallons per day (mgd) at less than 25 per cent of the cost of adding either new rapid sarid or diatomaceous-earth filters... plant capacity at minimal cost. For example, the water plant at Minnetka, Illinois was converted from 6. 0 to 12. 0 million gallons per day (mgd) at less than 25 per cent of the cost of adding either new rapid sarid or diatomaceous-earth filters...

Wray, Duane Jimmy

2012-06-07

127

Halogen bond tunability I: the effects of aromatic fluorine substitution on the strengths of halogen-bonding interactions involving chlorine, bromine, and iodine.  

PubMed

In the past several years, halogen bonds have been shown to be relevant in crystal engineering and biomedical applications. One of the reasons for the utility of these types of noncovalent interactions in the development of, for example, pharmaceutical ligands is that their strengths and geometric properties are very tunable. That is, substitution of atoms or chemical groups in the vicinity of a halogen can have a very strong effect on the strength of the halogen bond. In this study we investigate halogen-bonding interactions involving aromatically-bound halogens (Cl, Br, and I) and a carbonyl oxygen. The properties of these halogen bonds are modulated by substitution of aromatic hydrogens with fluorines, which are very electronegative. It is found that these types of substitutions have dramatic effects on the strengths of the halogen bonds, leading to interactions that can be up to 100% stronger. Very good correlations are obtained between the interaction energies and the magnitudes of the positive electrostatic potentials (?-holes) on the halogens. Interestingly, it is seen that the substitution of fluorines in systems containing smaller halogens results in electrostatic potentials resembling those of systems with larger halogens, with correspondingly stronger interaction energies. It is also shown that aromatic fluorine substitutions affect the optimal geometries of the halogen-bonded complexes, often as the result of secondary interactions. PMID:21369930

Riley, Kevin E; Murray, Jane S; Fanfrlk, Jind?ich; Rez?, Jan; Sol, Ricardo J; Concha, Monica C; Ramos, Felix M; Politzer, Peter

2011-12-01

128

Geometric Quantum Computation  

E-print Network

We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.

A. Ekert; M. Ericsson; P. Hayden; H. Inamori; J. A. Jones; D. K. L. Oi; V. Vedral

2000-04-04

129

Algebraic geometric codes  

NASA Technical Reports Server (NTRS)

The performance characteristics are discussed of certain algebraic geometric codes. Algebraic geometric codes have good minimum distance properties. On many channels they outperform other comparable block codes; therefore, one would expect them eventually to replace some of the block codes used in communications systems. It is suggested that it is unlikely that they will become useful substitutes for the Reed-Solomon codes used by the Deep Space Network in the near future. However, they may be applicable to systems where the signal to noise ratio is sufficiently high so that block codes would be more suitable than convolutional or concatenated codes.

Shahshahani, M.

1991-01-01

130

Wave function as geometric entity  

E-print Network

A new approach to the geometrization of the electron theory is proposed. The particle wave function is represented by a geometric entity, i.e., Clifford number, with the translation rules possessing the structure of Dirac equation for any manifold. A solution of this equation is obtained in terms of geometric treatment. Interference of electrons whose wave functions are represented by geometric entities is considered. New experiments concerning the geometric nature of electrons are proposed.

B. I. Lev

2011-02-10

131

Effect of intermolecular hydrogen bonding, vibrational analysis and molecular structure of a biomolecule: 5-Hydroxymethyluracil.  

PubMed

In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400cm(-1)) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the NH stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular NH?O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented. PMID:24632154

?rak, a?r?; Sert, Yusuf; Ucun, Fatih

2014-06-01

132

Geometric Series via Probability  

ERIC Educational Resources Information Center

Infinite series is a challenging topic in the undergraduate mathematics curriculum for many students. In fact, there is a vast literature in mathematics education research on convergence issues. One of the most important types of infinite series is the geometric series. Their beauty lies in the fact that they can be evaluated explicitly and that

Tesman, Barry

2012-01-01

133

Nonlinear Geometrical Acoustics.  

National Technical Information Service (NTIS)

The development of the theory of nonlinear wave propagation in both bounded and semi-infinite dissipative media is followed from its origins in the theories of linear geometrical acoustics, simple waves, and acceleration fronts. In Part I, Sections 2 to 5...

B. R. Seymour, M. P. Mortell

1975-01-01

134

Tournaments and Geometric Sequences.  

ERIC Educational Resources Information Center

Proposes a novel method of introducing and promoting the topic of geometric sequences through the problem of calculating the number of games necessary to determine the winner of a single elimination tournament in which two, three, or more teams compete at a time. (MDH)

Schielack, Vincent P., Jr.

1993-01-01

135

A Geometric Scavenger Hunt  

ERIC Educational Resources Information Center

Children possess a genuine curiosity for exploring the natural world around them. One third grade teacher capitalized on this inherent trait by leading her students on "A Geometric Scavenger Hunt." The four-lesson inquiry investigation described in this article integrates mathematics and science. Among the students' discoveries was the fact that

Smart, Julie; Marshall, Jeff

2007-01-01

136

PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism  

NASA Astrophysics Data System (ADS)

Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry based on triangles and tetrahedra. Most studies have centred around the kagom and pyrochlore based magnets but recent work has looked at other structures including the delafossite, langasites, hyper-kagom, garnets and Laves phase materials to name a few. Personally, I hope this issue serves as a great reference to scientist both new and old to this field, and that we all continue to have fun in this very frustrated playground. Finally, I want to thank the HFM 2010 organizers and all the sponsors whose contributions were an essential part of the success of the meeting in Baltimore. Geometrically frustrated magnetism contents Spangolite: an s = 1/2 maple leaf lattice antiferromagnet? T Fennell, J O Piatek, R A Stephenson, G J Nilsen and H M Rnnow Two-dimensional magnetism and spin-size effect in the S = 1 triangular antiferromagnet NiGa2S4 Yusuke Nambu and Satoru Nakatsuji Short range ordering in the modified honeycomb lattice compound SrHo2O4 S Ghosh, H D Zhou, L Balicas, S Hill, J S Gardner, Y Qi and C R Wiebe Heavy fermion compounds on the geometrically frustrated Shastry-Sutherland lattice M S Kim and M C Aronson A neutron polarization analysis study of moment correlations in (Dy0.4Y0.6)T2 (T = Mn, Al) J R Stewart, J M Hillier, P Manuel and R Cywinski Elemental analysis and magnetism of hydronium jarositesmodel kagome antiferromagnets and topological spin glasses A S Wills and W G Bisson The Herbertsmithite Hamiltonian: ?SR measurements on single crystals Oren Ofer, Amit Keren, Jess H Brewer, Tianheng H Han and Young S Lee Classical topological order in kagome ice Andrew J Macdonald, Peter C W Holdsworth and Roger G Melko Magnetic phase diagrams of classical triangular and kagome antiferromagnets M V Gvozdikova, P-E Melchy and M E Zhitomirsky The ordering of XY spin glasses Hikaru Kawamura Dynamic and thermodynamic properties of the generalized diamond chain model for azurite Andreas Honecker, Shijie Hu, Robert Peters and Johannes Richter Classical height models with topological order Christopher L Henley A search for disorder in the spin glass double perovskites Sr2CaReO6 and Sr2MgReO6 using neutron diffraction and neutron pair distribution function analysis J E Greedan, Shahab Derakhshan, F Ramezanipour, J Siewenie and Th Proffen Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb2Mo2O7 Yu Jiang, Ashfia Huq, Corwin H Booth, Georg Ehlers, John E Greedan and Jason S Gardner The magnetic phase diagram of Gd2Sn2O7 R S Freitas and J S Gardner Calculation of the expected zero-field muon relaxation rate in the geometrically frustrated rare earth pyrochlore Gd2Sn2O7 antiferromagnet P A McClarty, J N Cosman, A G Del Maestro and M J P Gingras Magnetic frustration in the disordered pyrochlore Yb2GaSbO7 J A Hodges, P Dalmas de Rotier, A Yaouanc, P C M Gubbens, P J C King and C Baines Titanium pyrochlore magnets: how much can be learned from magnetization measurements? O A Petrenko, M R Lees and G Balakrishnan Local susceptibility of the Yb2Ti2O7 rare earth pyrochlore computed from a Hamiltonian with anisotropic exchange J D Thompson, P A McClarty and M J P Gingras Slow and static spin correlations in Dy2 + xTi2 - xO7 - ? J S Gardner, G Ehlers, P Fouquet, B Farago and J R Stewart The spin ice Ho2Ti2O7 versus the spin liquid Tb2Ti2O7: field-induced magnetic structures A P Sazonov, A Gukasov and I Mirebeau Magnetic monopole dynamics in spin ice L D C Jaubert and P C W Holdsworth

Gardner, Jason S.

2011-04-01

137

Geometric simulation of flexible motion in proteins.  

PubMed

This chapter describes the use of physically simplified analysis and simulation methods-pebble-game rigidity analysis, coarse-grained elastic network modeling, and template-based geometric simulation-to explore flexible motion in protein structures. Substantial amplitudes of flexible motion can be explored rapidly in an all-atom model, retaining realistic covalent bonding, steric exclusion, and a user-defined network of noncovalent polar and hydrophobic interactions, using desktop computing resources. Detailed instructions are given for simulations using FIRST/FRODA software installed on a UNIX/Linux workstation. Other implementations of similar methods exist, particularly NMSim and FRODAN, and are available online. Topics covered include rigidity analysis and constraints, geometric simulation of flexible motion, targeting between known structures, and exploration of motion along normal mode eigenvectors. PMID:24061922

Wells, Stephen A

2014-01-01

138

Gaussian states and geometrically uniform symmetry  

NASA Astrophysics Data System (ADS)

Quantum Gaussian states can be considered as the majority of the practical quantum states used in quantum communications and more generally in quantum information. Here we consider their properties in relation to the geometrically uniform symmetry, a property of quantum states that greatly simplifies the derivation of the optimal decision by means of the square root measurements. In a general framework of the N-mode Gaussian states we show the general properties of this symmetry and the application of the optimal quantum measurements. An application example is presented to quantum communication systems employing pulse position modulation. We prove that the geometrically uniform symmetry can be applied to the general class of multimode Gaussian states.

Cariolaro, Gianfranco; Corvaja, Roberto; Pierobon, Gianfranco

2014-10-01

139

Gaussian states and geometrically uniform symmetry  

E-print Network

Quantum Gaussian states can be considered as the majority of the practical quantum states used in quantum communications and more generally in quantum information. Here we consider their properties in relation with the geometrically uniform symmetry, a property of quantum states that greatly simplifies the derivation of the optimal decision by means of the square root measurements. In a general framework of the $N$-mode Gaussian states we show the general properties of this symmetry and the application of the optimal quantum measurements. An application example is presented, to quantum communication systems employing pulse position modulation. We prove that the geometrically uniform symmetry can be applied to the general class of multimode Gaussian states.

Gianfranco Cariolaro; Roberto Corvaja; Gianfranco Pierobon

2014-10-20

140

Geometric Direct Search Algorithms for Image Registration  

Microsoft Academic Search

A widely used approach to image registration involves finding the general linear transformation that maximizes the mutual information between two images, with the transformation being rigid-body [i.e., belonging to SE(3)] or volume-preserving [i.e., belonging to SL(3)]. In this paper, we present coordinate-invariant, geometric versions of the Nelder-Mead optimization algorithm on the groups SL(3), SE(3), and their various subgroups, that are

Seok Lee; Minseok Choi; Hyungmin Kim; Frank Chongwoo Park

2007-01-01

141

A generative geometric kernel  

Microsoft Academic Search

We present the design and implementation of a generative geometric kernel. The kernel generator is generic, type-safe, parametrized by many design-level choices and extensible. The resulting code has minimal traces of the design abstractions. We achieve genericity through a layered design deriving concepts from affine geometry, linear algebra and abstract algebra. We achieve parametrization and type-safety by using OCaml's module

Jacques Carette; Mustafa Elsheikh; Spencer Smith

2011-01-01

142

Methods and apparatuses for signaling with geometric constellations  

NASA Technical Reports Server (NTRS)

Communication systems are described that use signal constellations, which have unequally spaced (i.e. geometrically shaped) points. In many embodiments, the communication systems use specific geometric constellations that are capacity optimized at a specific SNR. In addition, ranges within which the constellation points of a capacity optimized constellation can be perturbed and are still likely to achieve a given percentage of the optimal capacity increase compared to a constellation that maximizes d.sub.min, are also described. Capacity measures that are used in the selection of the location of constellation points include, but are not limited to, parallel decode (PD) capacity and joint capacity.

Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)

2012-01-01

143

Limits: Geometric and Harmonic Series  

NSDL National Science Digital Library

A geometric series is a sum of numbers such that the ratio between consecutive terms is constant. For instance, 1/2 + 1/4 + 1/8 + … is a geometric series. In this resource you can set up various geometric series and see a visual representation of the successive terms and the corresponding sum of those terms.

Mathematics, Illuminations N.

2010-05-26

144

Compiler Generation and Autotuning of Communication-Avoiding Operators for Geometric  

E-print Network

Compiler Generation and Autotuning of Communication-Avoiding Operators for Geometric Multigrid--This paper describes a compiler approach to intro- ducing communication-avoiding optimizations in geometric. Communication-avoiding optimizations re- duce vertical communication through the memory hierarchy and horizontal

145

Representing geometrical knowledge.  

PubMed Central

This paper introduces perspex algebra which is being developed as a common representation of geometrical knowledge. A perspex can currently be interpreted in one of four ways. First, the algebraic perspex is a generalization of matrices, it provides the most general representation for all of the interpretations of a perspex. The algebraic perspex can be used to describe arbitrary sets of coordinates. The remaining three interpretations of the perspex are all related to square matrices and operate in a Euclidean model of projective space-time, called perspex space. Perspex space differs from the usual Euclidean model of projective space in that it contains the point at nullity. It is argued that the point at nullity is necessary for a consistent account of perspective in top-down vision. Second, the geometric perspex is a simplex in perspex space. It can be used as a primitive building block for shapes, or as a way of recording landmarks on shapes. Third, the transformational perspex describes linear transformations in perspex space that provide the affine and perspective transformations in space-time. It can be used to match a prototype shape to an image, even in so called 'accidental' views where the depth of an object disappears from view, or an object stays in the same place across time. Fourth, the parametric perspex describes the geometric and transformational perspexes in terms of parameters that are related to everyday English descriptions. The parametric perspex can be used to obtain both continuous and categorical perception of objects. The paper ends with a discussion of issues related to using a perspex to describe logic. PMID:9304680

Anderson, J A

1997-01-01

146

Constructing matrix geometric means  

E-print Network

In this paper, we analyze the process of assembling new matrix geometric means from existing ones, and show what new means can be found, and what cannot be done because of group-theoretical obstructions. We show that for n = 4 a new matrix mean exists which is simpler to compute than the existing ones. Moreover, we show that for n> 4 the existing strategies of composing matrix means and taking limits of iterations cannot provide a mean computationally simpler than the existing ones.

Federico Poloni

147

Causal And Geometric Relations  

E-print Network

, for one, rejoiced in Einstein's treatment of gravitation. With the adoption of non- Euclidean geometry, he observed, we no longer need to assume that the sun somehow "makes" the earth travel in an ellipse about it; the earth simply travels along... the natural geodesic prescribed by the geometry; no "forces" or "little pushes" are required to keep it on its orbit.7 It is not that we have excused ourselves from giving a causal explanation of the orbitwe are using geometrical considerations as our...

Shrader, Douglas W. Jr.

1977-06-01

148

Geometric phase in Bohmian mechanics  

SciTech Connect

Using the quantum kinematic approach of Mukunda and Simon, we propose a geometric phase in Bohmian mechanics. A reparametrization and gauge invariant geometric phase is derived along an arbitrary path in configuration space. The single valuedness of the wave function implies that the geometric phase along a path must be equal to an integer multiple of 2{pi}. The nonzero geometric phase indicates that we go through the branch cut of the action function from one Riemann sheet to another when we locally travel along the path. For stationary states, quantum vortices exhibiting the quantized circulation integral can be regarded as a manifestation of the geometric phase. The bound-state Aharonov-Bohm effect demonstrates that the geometric phase along a closed path contains not only the circulation integral term but also an additional term associated with the magnetic flux. In addition, it is shown that the geometric phase proposed previously from the ensemble theory is not gauge invariant.

Chou, Chia-Chun, E-mail: chiachun@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Wyatt, Robert E., E-mail: wyattre@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States)

2010-10-15

149

Efficient Geometric Routing in Three Dimensional Ad Hoc Networks  

Microsoft Academic Search

Efficient geometric routing algorithms have been studied extensively in two-dimensional ad hoc networks, or simply 2D networks. These algorithms are efficient and they have bee n proven to be the worst-case optimal, localized routing algorithms. However, few prior works have focused on efficient geometric routing in 3D networks due to the lack of an efficient method to limit the search

Cong Liu; Jie Wu

2009-01-01

150

Halogen bonds in crystal engineering: like hydrogen bonds yet different.  

PubMed

The halogen bond is an attractive interaction in which an electrophilic halogen atom approaches a negatively polarized species. Short halogen atom contacts in crystals have been known for around 50 years. Such contacts are found in two varieties: type I, which is symmetrical, and type II, which is bent. Both are influenced by geometric and chemical considerations. Our research group has been using halogen atom interactions as design elements in crystal engineering, for nearly 30 years. These interactions include halogenhalogen interactions (XX) and halogenheteroatom interactions (XB). Many XX and almost all XB contacts can be classified as halogen bonds. In this Account, we illustrate examples of crystal engineering where one can build up from previous knowledge with a focus that is provided by the modern definition of the halogen bond. We also comment on the similarities and differences between halogen bonds and hydrogen bonds. These interactions are similar because the protagonist atoms-halogen and hydrogen-are both electrophilic in nature. The interactions are distinctive because the size of a halogen atom is of consequence when compared with the atomic sizes of, for example, C, N, and O, unlike that of a hydrogen atom. Conclusions may be drawn pertaining to the nature of XX interactions from the Cambridge Structural Database (CSD). There is a clear geometric and chemical distinction between type I and type II, with only type II being halogen bonds. Cl/Br isostructurality is explained based on a geometric model. In parallel, experimental studies on 3,4-dichlorophenol and its congeners shed light on the nature of halogenhalogen interactions and reveal the chemical difference between Cl and Br. Variable temperature studies also show differences between type I and type II contacts. In terms of crystal design, halogen bonds offer a unique opportunity in the strength, atom size and interaction gradation; this may be used in the design of ternary cocrystals. Structural modularity in which an entire crystal structure is defined as a combination of modules is rationalized on the basis of the intermediate strength of a halogen bond. The specific directionality of the halogen bond makes it a good tool to achieve orthogonality in molecular crystals. Mechanical properties can be tuned systematically by varying these orthogonally oriented halogenhalogen interactions. In a further development, halogen bonds are shown to play a systematic role in organization of LSAMs (long range synthon aufbau module), which are bigger structural units containing multiple synthons. With a formal definition in place, this may be the right time to look at differences between halogen bonds and hydrogen bonds and exploit them in more subtle ways in crystal engineering. PMID:25134974

Mukherjee, Arijit; Tothadi, Srinu; Desiraju, Gautam R

2014-08-19

151

Geometric Brownian Motion Consider the geometric Brownian motion process  

E-print Network

Geometric Brownian Motion · Consider the geometric Brownian motion process Y (t) eX(t) ­ X(t) is a (µ, ) Brownian motion. · As Y/X = Y and 2 Y/X2 = Y , Ito's formula (51) on p. 453 implies dY Y = µ-Dauh Lyuu, National Taiwan University Page 459 Product of Geometric Brownian Motion Processes · Let d

Lyuu, Yuh-Dauh

152

Determination of the optimal position of adjacent proton-donor centers for the activation or inhibition of peptide bond formation--a computational model study.  

PubMed

The study reports a computational analysis of the influence of proton donor group adjacent to the reaction center during ester ammonolysis of an acylated diol as a model reaction for peptide bond formation. This analysis was performed using catalytic maps constructed after a detailed scanning of the available space around the reaction centers in different transition states, a water molecule acting as a typical proton donor. The calculations suggest that an adjacent proton donor center can reduce the activation barrier of the rate determining transition states by up to 7.2 kcal/mol, while no inhibition of the reaction can be achieved by such a group. PMID:21775181

Rangelov, Miroslav A; Petrova, Galina P; Yomtova, Vihra M; Vayssilov, Georgi N

2011-09-01

153

Geometrical pattern learning  

SciTech Connect

In this paper we consider the problem of learning the positions of spheres in metric spaces, given as data randomly drawn points classified according to whether they are internal or external to an unknown sphere. The particular metrics under consideration are geometrical shape metrics, and the results are intended to be applicable to the problem of learning to identify a shape from related shapes classified according to whether they resemble it visually. While it is typically NP-hard to locate a central point for a hypothesis sphere, we find that it is however often possible to obtain a non-spherical hypothesis which can accurately predict whether further random points lie within the unknown sphere. We exhibit algorithms which achieve this, and in the process indicate useful general techniques for computational learning. Finally we exhibit a natural shape metric and show that it defines a class of spheres not predictable in this sense, subject to standard cryptographic assumptions.

Goldberg, P.W.

1993-04-01

154

Bonded Lubricants  

NASA Technical Reports Server (NTRS)

Another spinoff to the food processing industry involves a dry lubricant developed by General Magnaplate Corp. of Linden, N.J. Used in such spacecraft as Apollo, Skylab and Viking, the lubricant is a coating bonded to metal surfaces providing permanent lubrication and corrosion resistance. The coating lengthens equipment life and permits machinery to be operated at greater speed, thus increasing productivity and reducing costs. Bonded lubricants are used in scores of commercia1 applications. They have proved particularly valuable to food processing firms because, while increasing production efficiency, they also help meet the stringent USDA sanitation codes for food-handling equipment. For example, a cookie manufacturer plagued production interruptions because sticky batter was clogging the cookie molds had the brass molds coated to solve the problem. Similarly, a pasta producer faced USDA action on a sanitation violation because dough was clinging to an automatic ravioli-forming machine; use of the anti-stick coating on the steel forming plates solved the dual problem of sanitation deficiency and production line downtime.

1977-01-01

155

Geometrical scaling law for laser shock processing  

NASA Astrophysics Data System (ADS)

Scaling approach to laser shock processing is studied by dimensional analysis and numerical simulation. The essential dimensionless parameters controlling the shock effect are studied, and a geometrical scaling law correlating the input laser parameters and the output strengthening effect parameters is presented. The numerical results show that there is a competition controlling mechanism between thickness of confined overlay and laser duration for the surface residual stress; the plastically affected depth increases linearly with increasing laser duration, increases quadratically with increasing laser power density, and is almost independent with the thickness of confined overlay. Based on the results, a window of the optimal working parameters is presented.

Wu, Xianqian; Tan, Qingming; Huang, Chenguang

2013-07-01

156

Compass routing on geometric networks  

Microsoft Academic Search

this paper we study local routing algorithms on geometric networks. Formally speaking, suppose that we want to travel from a vertex s to a vertex t of a geometric network. A routing algorithm is called a local routing algorithm if it satisfies the following conditions:

Evangelos Kranakis; Harvinder Singh; Jorge Urrutia

1999-01-01

157

Geometric Relations Among Voronoi Diagrams  

Microsoft Academic Search

Two general classes of Voronoi diagrams are introduced and, along with their modifications to higher order, are shown to be geometrically related. This geometric background, on one hand, serves to analyze the size and the combinatorial structure, and on the other hand, implies general and efficient methods of construction, for various important types of Voronoi diagrams considered in the literature.

Franz Aurenhammer; Hiroshi Imai

1987-01-01

158

A Primer on Geometric Mechanics  

E-print Network

Geometric mechanics is usually studied in applied mathematics and most introductory texts are hence aimed at a mathematically minded audience. The present note tries to provide the intuition of geometric mechanics and to show the relevance of the subject for an understanding of "mechanics".

Christian Lessig

2012-06-14

159

Encoding geometric and non-geometric information: a study with evolved agents  

Microsoft Academic Search

Vertebrate species use geometric information and non-geometric or featural cues to orient. Under some circumstances, when\\u000a both geometric and non-geometric information are available, the geometric information overwhelms non-geometric cues (geometric\\u000a primacy). In other cases, we observe the inverse tendency or the successful integration of both cues. In past years, modular\\u000a explanations have been proposed for the geometric primacy: geometric and

Michela Ponticorvo; Orazio Miglino

2010-01-01

160

Basics of Fidelity Bonding.  

ERIC Educational Resources Information Center

Fidelity bonds are important for an agency to hold to protect itself against any financial loss that can result from dishonest acts by its employees. Three types of fidelity bonds are available to an agency: (1) public official bonds; (2) dishonesty bonds; and (3) faithful performance bonds. Public official bonds are required by state law to be

Kahn, Steven P.

161

Reactive interatomic potentials and their geometrical features  

E-print Network

We discuss various approaches to modeling the interatomic interactions for molecular dynamics with special focus on the geometrical structural properties. The type of interactions considered are so called reactive force fields, i.e. interactions without predefined bonds and structures. The discussed cases cover the well known Stillinger-Weber, Tersoff-Brenner, EDIP, ReaxFF and ABOP interaction models as well as some additional examples. We discuss also a recently published synthesis of diamond-like structures by isotropic pair potential with multiple minima and use this concepts to propose a sort of classification scheme for interactions with respect to the geometry modeling. In most details we discuss the Tersoff-Brenner potentials and also Stillinger-Weber potential, since these models still appear quite popular in recent research, even though the newer models are more efficient in most respects, except of simplicity. We also propose simple modifications of the basically three-body interactions in order to ...

Kocbach, Ladislav

2009-01-01

162

Geometric frustration in small colloidal clusters  

E-print Network

We study the structure of clusters in a model colloidal system with competing interactions using Brownian dynamics simulations. A short-ranged attraction drives clustering, while a weak, long-ranged repulsion is used to model electrostatic charging in experimental systems. The former is treated with a short-ranged Morse attractive interaction, the latter with a repulsive Yukawa interaction. We consider the yield of clusters of specific structure as a function of the strength of the interactions, for clusters with m=3,4,5,6,7,10 and 13 colloids. At sufficient strengths of the attractive interaction (around 10 kT), the average bond lifetime approaches the simulation timescale and the system becomes nonergodic. For small clusters m<=5 where geometric frustration is not relevant, despite nonergodicity, for sufficient strengths of the attractive interaction the yield of clusters which maximise the number of bonds approaches 100%. However for $m=7$ and higher, in the nonergodic regime we find a lower yield of these structures where we argue geometric frustration plays a significant role. $m=6$ is a special case, where two structures, of octahedral and C2v symmetry compete, with the latter being favoured by entropic contributions in the ergodic regime and by kinetic trapping in the nonergodic regime. We believe that our results should be valid as far as the one-component description of the interaction potential is valid. A system with competing electrostatic repulsions and van der Waals attractions may be such an example. However, in some cases, the one-component description of the interaction potential may not be appropriate.

Alex Malins; Stephen R. Williams; Jens Eggers; Hajime Tanaka; C. Patrick Royall

2009-09-17

163

Protein Folding: A New Geometric Analysis  

E-print Network

A geometric analysis of protein folding, which complements many of the models in the literature, is presented. We examine the process from unfolded strand to the point where the strand becomes self-interacting. A central question is how it is possible that so many initial configurations proceed to fold to a unique final configuration. We put energy and dynamical considerations temporarily aside and focus upon the geometry alone. We parameterize the structure of an idealized protein using the concept of a ribbon from differential geometry. The deformation of the ribbon is described by introducing a generic twisting Ansatz. The folding process in this picture entails a change in shape guided by the local amino acid geometry. The theory is reparamaterization invariant from the start, so the final shape is independent of folding time. We develop differential equations for the changing shape. For some parameter ranges, a sine-Gordon torsion soliton is found. This purely geometric waveform has properties similar to dynamical solitons. Namely: A threshold distortion of the molecule is required to initiate the soliton, after which, small additional distortions do not change the waveform. In this analysis, the soliton twists the molecule until bonds form. The analysis reveals a quantitative relationship between the geometry of the amino acids and the folded form.

Walter A. Simmons; Joel L. Weiner

2008-09-11

164

Geometric Effects on Electron Cloud  

SciTech Connect

The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit the machine performances by inducing beam instabilities, beam emittance increase, beam loss, vacuum pressure increases and increased heat load on the vacuum chamber wall. The electron multipacting is a kind of geometric resonance phenomenon and thus is sensitive to the geometric parameters such as the aperture of the beam pipe, beam shape and beam bunch fill pattern, etc. This paper discusses the geometric effects on the electron cloud build-up in a beam chamber and examples are given for different beams and accelerators.

Wang, L

2007-07-06

165

DISCRETE GEOMETRIC MOTION CONTROL OF AUTONOMOUS Marin Kobilarov  

E-print Network

#12;Acknowledgments This work would not have been possible were I not surrounded by many great people of the reasons why I continued pursuing my dream and passion for robotics with the hope to contribute to science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Chapter 2: A Discrete Geometric Framework for Optimal Control on Lie groups 8 2.1 Introduction

Kobilarov, Marin

166

Algebraic, geometric, and stochastic aspects of genetic operators  

NASA Technical Reports Server (NTRS)

Genetic algorithms for function optimization employ genetic operators patterned after those observed in search strategies employed in natural adaptation. Two of these operators, crossover and inversion, are interpreted in terms of their algebraic and geometric properties. Stochastic models of the operators are developed which are employed in Monte Carlo simulations of their behavior.

Foo, N. Y.; Bosworth, J. L.

1972-01-01

167

Some Lower Bounds on Geometric Separability Problems Esther M. Arkin  

E-print Network

Some Lower Bounds on Geometric Separability Problems Esther M. Arkin Ferran Hurtado Joseph S. B. Mitchell§ Carlos Seara¶ Steven S. Skiena December 31, 2005 Abstract We obtain lower bounds in the algebraic, and therefore prove their optimality. Key Words: Lower bounds; separation; maximum gap. 1 Introduction Let B

Mitchell, Joseph S.B.

168

Geometric Programming and Mechanism Design for Air Traffic Conflict Resolution  

E-print Network

Geometric Programming and Mechanism Design for Air Traffic Conflict Resolution Jerome Le Ny and George J. Pappas Abstract-- We develop certain extensions of optimization- based conflict resolution research activity in the past decade to develop automated systems for air traffic conflict detection

Pappas, George J.

169

Waldyr Muniz Oliva Geometric Mechanics  

E-print Network

Waldyr Muniz Oliva Geometric Mechanics February 1, 2002 Springer Berlin Heidelberg New mechanics : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 51 4.1 Galilean space-time structure and Newton equations . . . . . . . . 51 4.2 Critical remarks on Newtonian mechanics

Natário, José

170

Geometrical optics in general relativity  

E-print Network

General relativity includes geometrical optics. This basic fact has relevant consequences that concern the physical meaning of the discontinuity surfaces propagated in the gravitational field - as it was first emphasized by Levi-Civita.

A. Loinger

2006-09-19

171

GEOMETRIC FOKKER-PLANCK EQUATIONS  

Microsoft Academic Search

We study the large deviation function and small time asymptotics near the diagonal for the heat equation associated to Geometric Fokker-Planck equations (GFK) on the cotangent bundle ? = TX of a Riemannian smooth compact connected variety X.

Gilles Lebeau

2005-01-01

172

Geometric Analysis and General Relativity  

E-print Network

This article discusses methods of geometric analysis in general relativity, with special focus on the role of "critical surfaces" such as minimal surfaces, marginal surface, maximal surfaces and null surfaces.

Lars Andersson

2005-12-23

173

Crystal-Like geometric modeling  

E-print Network

geometry. The tiered extrusion method, along with a face grouping technique, simplifies the creation of complex, intricate faceted shapes. In combination with remeshing, these methods provide the capability to generate geometric shapes exhibiting planar...

Landreneau, Eric Benjamin

2006-08-16

174

Guitars, Violins, and Geometric Sequences  

ERIC Educational Resources Information Center

This article describes middle school mathematics activities that relate measurement, ratios, and geometric sequences to finger positions or the placement of frets on stringed musical instruments. (Contains 2 figures and 2 tables.)

Barger, Rita; Haehl, Martha

2007-01-01

175

Geometric Exponents of Dilute Loop Models  

NASA Astrophysics Data System (ADS)

The fractal dimensions of the hull, the external perimeter and of the red bonds are measured through Monte Carlo simulations for dilute minimal models, and compared with predictions from conformal field theory and SLE methods. The dilute models used are those first introduced by Nienhuis. Their loop fugacity is ?=-2 \\cos(?/bar{kappa}) where the parameter bar{kappa} is linked to their description through conformal loop ensembles. It is also linked to conformal field theories through their central charges c(bar{kappa})=13-6(bar{kappa}+bar{kappa}^{-1}) and, for the minimal models of interest here, bar{kappa}=p/p' where p and p' are two coprime integers. The geometric exponents of the hull and external perimeter are studied for the pairs ( p, p')=(1,1),(2,3),(3,4),(4,5),(5,6),(5,7), and that of the red bonds for ( p, p')=(3,4). Monte Carlo upgrades are proposed for these models as well as several techniques to improve their speeds. The measured fractal dimensions are obtained by extrapolation on the lattice size H, V??. The extrapolating curves have large slopes; despite these, the measured dimensions coincide with theoretical predictions up to three or four digits. In some cases, the theoretical values lie slightly outside the confidence intervals; explanations of these small discrepancies are proposed.

Provencher, Guillaume; Saint-Aubin, Yvan; Pearce, Paul A.; Rasmussen, Jrgen

2012-04-01

176

Algorithms of NCG geometrical module  

NASA Astrophysics Data System (ADS)

The methods and algorithms of the versatile NCG geometrical module used in the MCU code system are described. The NCG geometrical module is based on the Monte Carlo method and intended for solving equations of particle transport. The versatile combinatorial body method, the grid method, and methods of equalized cross sections and grain structures are used for description of the system geometry and calculation of trajectories.

Gurevich, M. I.; Pryanichnikov, A. V.

2012-12-01

177

Geometric and electronic structures of V 2C 2- and V 2C 2 studied by photoelectron spectroscopy and density-functional calculations  

NASA Astrophysics Data System (ADS)

The electronic and geometric structures of V 2C 2- were investigated by photoelectron spectroscopy (PES) and density-functional theory (DFT). The experimental PES spectrum was compared with the simulated ones for several low-energy isomers obtained by the structural optimization procedure. The spectrum is found to be best reproduced by the most stable isomer, which has a doublet spin multiplicity and a planar distorted four-membered-ring geometry with a transannular V-C bonding. The VC 2 subunit in V 2C 2- is almost identical with the optimized structure of free VC 2. The DFT study of V 2C 2 shows that it has the singlet ground state with a geometry similar to that of the anion.

Tono, Kensuke; Terasaki, Akira; Ohta, Toshiaki; Kondow, Tamotsu

2002-01-01

178

Electron transfer in pnicogen bonds.  

PubMed

As a new type of noncovalent interactions, pnicogen bond between a VA group element (N, P, and As) and an electron donor (Lewis base) has grabbed attention in recent several years. Here we employ the block-localized wave function (BLW) based energy decomposition scheme to probe the bonding nature in a series of substituted phosphines XnPH3-n complexed with ammonia. As the BLW method can derive the optimal monomer orbitals in a complex with the electron transfer among monomers quenched, we can effectively examine the HOMO-LUMO interaction in these pnicogen bonding systems. Among various energy components, electron transfer energy together with the polarization energy dominates the pnicogen bonding energy. Although usually it is assumed that the electron transfer from ammonia to substituted phosphines occurs in the form of n ? ?*(XP) hyperconjugative interaction, we identify a kind of new pathway when X = NO2 and CN, i.e., n ? d?*, which results from the interaction between the ? orbital of cyano or nitro substituent and d orbitals on P. But still this picture of electron transfer using a single pair of orbitals is greatly simplified, as the electron density difference (EDD) maps corresponding to the overall electron transfer processes show the accumulation of electron density on the P side opposite to the X-P bond, with insignificant or even negligible gain of electron density on the substituent group side. Thus, the EDD maps tend to support the concept of ?-hole in pnicogen bonds. PMID:24588109

Guan, Liangyu; Mo, Yirong

2014-10-01

179

Characteristics of hydrogen bond revealed from water clusters  

NASA Astrophysics Data System (ADS)

The hydrogen bond network is responsible for the exceptional physical and chemical properties of water, however, the description of hydrogen bond remains a challenge for the studies of condensed water. The investigation of structural and binding properties of water clusters provides a key for understanding the H-bonds in bulk water. In this paper, a new set of geometric parameters are defined to describe the extent of the overlap between the bonding orbital of the donor OH and the nonbonding orbital of the lone-pair of the acceptor molecule. This orbital overlap plays a dominant role for the strength of H-bonds. The dependences of the binding energy of the water dimer on these parameters are studied. The results show that these parameters properly describe the H-bond strength. The ring, book, cage and prism isomers of water hexamer form 6, 7, 8 and 9 H-bonds, and the strength of the bonding in these isomers changes markedly. The internally-solvated and the all-surface structures of (H2O)n for n = 17, 19 and 21 are nearly isoenergetic. The internally-solvated isomers form fewer but stronger H-bonds. The hydrogen bonding in the above clusters are investigated in detail. The geometric parameters can well describe the characters of the H-bonds, and they correlate well with the H-bond strength. For the structures forming stronger H-bonds, the H-bond lengths are shorter, the angle parameters are closer to the optimum values, and their rms deviations are smaller. The H-bonds emanating from DDAA and DDA molecules as H-donor are relatively weak. The vibrational spectra of (H2O)n (n = 17, 19 and 21) are studied as well. The stretching vibration of the intramolecular OH bond is sensitive to its bonding environment. The H-bond strength judged from the geometric parameters is in good agreement with the bonding strength judged from the stretching frequencies. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2014-50027-5

Song, Yan; Chen, Hongshan; Zhang, Cairong; Zhang, Yan; Yin, Yuehong

2014-09-01

180

Diffusion Bonding of Metals.  

National Technical Information Service (NTIS)

The need to reduce the cost and weight of aerospace metallic structures has led to increased interest in solid state and liquid phase diffusion bonding processes, especially in combination with superplastic forming. The bonding mechanisms and bonding tech...

P. G. Partridge

1989-01-01

181

Students' Perceptions of Parental Bonding Styles and Their Academic Burnout  

ERIC Educational Resources Information Center

This study investigated how parental bonding style affects academic burnout in Korean adolescents. Participants were 447 middle school students, who completed the Parental Bonding Instrument and the Maslach Burnout Inventory-Student Survey. MANCOVA results confirmed that adolescents reporting the optimal bonding parental style, for both mother and

Shin, Hyojung; Lee, Jayoung; Kim, Boyoung; Lee, Sang Min

2012-01-01

182

Effect of bonding variables on TLP bonding of oxide dispersion strengthened superalloy  

Microsoft Academic Search

Transient liquid phase (TLP) bonding has evolved as a successful alternative joining technique for high service temperature\\u000a components (e.g., vanes and blades for aircraft gas turbine engines) made from superalloys when neither fusion welding nor\\u000a solid-state bonding techniques are successful. However, study shows that the optimization of bonding variables is critical\\u000a to achieve a metallurgically sound joint free from deleterious

Ratan Kumar Saha; Tahir I. Khan

2007-01-01

183

Bond order analysis based on the Laplacian of electron density in fuzzy overlap space.  

PubMed

Bond order is an important concept for understanding the nature of a chemical bond. In this work, we propose a novel definition of bond order, called the Laplacian bond order (LBO), which is defined as a scaled integral of negative parts of the Laplacian of electron density in fuzzy overlap space. Many remarkable features of LBO are exemplified by numerous structurally diverse molecules. It is shown that LBO has a direct correlation with the bond polarity, the bond dissociation energy, and the bond vibrational frequency. The dissociation behavior of LBO of the N-N bond in N2 has been studied. Effects of the basis sets, theoretic methods, and geometrical conformations on LBO have also been investigated. Through comparisons, we discussed in details similarities and discrepancies among LBO, Mayer bond order, natural localized molecular orbital bond order, fuzzy overlap population, and electron density at bond critical points. PMID:23514314

Lu, Tian; Chen, Feiwu

2013-04-11

184

Ideally Glassy Hydrogen Bonded Networks  

E-print Network

The axiomatic theory of ideally glassy networks, which has proved effective in describing phase diagrams and properties of chalcogenide and oxide glasses and their foreign interfaces, is broadened here to include intermolecular interactions in hydrogen-bonded polyalcohols such as glycerol, monosaccharides (glucose), and the optimal bioprotective hydrogen-bonded disaccharide networks formed from trehalose. The methods of Lagrangian mechanics and Maxwellian scaffolds are useful at the molecular level when bonding hierarchies are characterized by constraint counting similar to the chemical methods used by Huckel and Pauling. Whereas Newtonian molecular dynamical methods are useful for simulating large-scale interactions for times of order 10 ps, constraint counting describes network properties on glassy (almost equilibrated) time scales, which may be of cosmological order for oxide glasses, or years for trehalose. The ideally glassy network of trehalose may consist of extensible tandem sandwich arrays.

J. C. Phillips

2005-08-05

185

29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.  

Code of Federal Regulations, 2013 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

2013-07-01

186

29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.  

Code of Federal Regulations, 2010 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

2010-07-01

187

29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.  

Code of Federal Regulations, 2011 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

2011-07-01

188

29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.  

Code of Federal Regulations, 2012 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

2012-07-01

189

Correlated valence-bond states  

NASA Astrophysics Data System (ADS)

We study generalizations of the singlet-sector amplitude-product (AP) states in the valence-bond basis of S=1/2 quantum spin systems. In the standard AP states, the weight of a tiling of the system into valence bonds (singlets of two spins) is a product of amplitudes depending on the length of the bonds. We here introduce correlated AP (CAP) states, in which the AP is further multiplied by factors depending on two bonds connected to a pair of sites (here nearest neighbors). While the standard AP states can describe a phase transition between an antiferromagnetic (Nel) state and a valence-bond solid (VBS) in one dimension (which we also study here), in two dimensions it cannot describe VBS order. With the CAP states, Nel-VBS transitions are realized as a function of some parameter describing the bond correlations. We here study such phase transitions of CAP wave functions on the square lattice. We find examples of direct first-order Nel-VBS transitions, as well as cases where there is an extended U(1) spin liquid phase intervening between the Nel and VBS states. In the latter case the transitions are continuous and we extract critical exponents and address the issue of a possible emergent U(1) symmetry in the near-critical VBS. We also consider variationally optimized CAP states for the standard Heisenberg model in one and two dimensions and the J-Q model in two dimensions, with the latter including four-spin interactions (Q) in addition to the Heisenberg exchange (J) and harboring VBS order for large Q/J. The optimized CAP states lead to significantly lower variational energies than the simple AP states for these models.

Lin, Yu-Cheng; Tang, Ying; Lou, Jie; Sandvik, Anders W.

2012-10-01

190

Geometric modeling basic examples Toric surface patches  

E-print Network

Tutorial John B. Little Department of Mathematics and Computer Science College of the Holy Cross July 29-31, 2013 John B. Little Toric Varieties in Geometric Modeling #12;Geometric modeling ­ basic examples Toric and connections with statistics John B. Little Toric Varieties in Geometric Modeling #12;Geometric modeling

Little, John B.

191

Geometric structures of vectorial type  

NASA Astrophysics Data System (ADS)

We study geometric structures of W4-type in the sense of A. Gray on a Riemannian manifold. If the structure group G?SO(n) preserves a spinor or a non-degenerate differential form, its intrinsic torsion ? is a closed 1-form (Proposition 2.1 and Theorem 2.1). Using a G-invariant spinor we prove a splitting theorem (Proposition 2.2). The latter result generalizes and unifies a recent result obtained in [S. Ivanov, M. Parton, P. Piccinni, Locally conformal parallel G- and Spin(7)-structures, mathdg/0509038], where this splitting has been proved in dimensions n=7,8 only. Finally we investigate geometric structures of vectorial type and admitting a characteristic connection ?. An interesting class of geometric structures generalizing Hopf structures are those with a ?-parallel intrinsic torsion ?. In this case, ? induces a Killing vector field (Proposition 4.1) and for some special structure groups it is even parallel.

Agricola, I.; Friedrich, T.

2006-12-01

192

Bond valence at mixed occupancy sites. I. Regular polyhedra.  

PubMed

Bond valence sum calculations at mixed occupancy sites show the occurrence of systematic errors leading to apparent violations of the Valence Sum Rule (bond valence theory) in regular and unstrained bonding environments. The systematic deviation of the bond valence from the expected value is observed in the long-range structure, and is discussed from geometric and algebraic viewpoints. In the valence-length diagram, such a deviation arises from discrepancies between the intersection points of the long-range bond valences and the theoretical bond valences with the valence-length curves of involved cations. Three factors cause systematic errors in the bond valences: difference in atomic valences, bond valence parameters Ri (the length of a bond of unit valence) and bond valence parameters bi (the bond softness) between the involved cations over the same crystallographic site. One important consequence strictly related to the systematic errors is that they lead to erroneous bond strain values for mixed occupancy sites indicating underbonding or overbonding that actually does not exist. PMID:25274520

Bosi, Ferdinando

2014-10-01

193

Geometrical Optics of Dense Aerosols  

SciTech Connect

Assembling a free-standing, sharp-edged slab of homogeneous material that is much denser than gas, but much more rare ed than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed fi eld, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the nite particle density reduces the eff ective Stokes number of the flow, a critical result for controlled focusing. __________________________________________________

Hay, Michael J.; Valeo, Ernest J.; Fisch, Nathaniel J.

2013-04-24

194

Geometrical spin symmetry and spin  

SciTech Connect

Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.

Pestov, I. B., E-mail: pestov@theor.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)

2011-07-15

195

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

196

Savings Bonds Value Calculator  

NSDL National Science Digital Library

From the Federal Reserve Bank of New York, this site computes the redemption value of users's US savings bonds. Easy-to-use pull-down menus allow visitors to enter information such as the date of issue and face value of their Series E bonds, Series EE bonds, and Series S bonds. After entering the information, the Calculator will then show a chart of issue dates and denominations and actual worth of the bonds, if cashed within a set period of time.

197

Celestial mechanics with geometric algebra  

NASA Technical Reports Server (NTRS)

Geometric algebra is introduced as a general tool for Celestial Mechanics. A general method for handling finite rotations and rotational kinematics is presented. The constants of Kepler motion are derived and manipulated in a new way. A new spinor formulation of perturbation theory is developed.

Hestenes, D.

1983-01-01

198

Sublinear Geometric Algorithms # Bernard Chazelle  

E-print Network

University and NEC Laboratories America, Inc. chazelle@cs.princeton.edu Ding Liu Department of Computer for geo­ metric problems in two and three dimensions. We give opti­ mal algorithms for intersection.5 [Computational Geometry and Object Modeling]: Geometric algorithms, languages, and systems General Terms

Magen, Avner

199

Geometrical Methods in Gauge Theory  

E-print Network

In this work we explore the geometrical interpretation of gauge theories through the formalism of fiber bundles. Moreover, we conduct an investigation in the topology of fiber bundles, providing a proof of the Classification Theorem. In the last chapter we present some applications, such as electromagnetism and generalized Kaluza-Klein Theory.

Henrique de A. Gomes

2006-10-25

200

Exploring young children's geometrical strategies  

Microsoft Academic Search

This study explores young children's strategies while transforming polygons, through the use of geometrical models. Data were collected from 291 children ranging from 4 to 8 years of age in Cyprus. Children were asked to draw a stairway of specific poly- gons, with each shape being bigger or smaller than its preceding one. Relationships between children's responses in the transformation

ATHANASIOS GAGATSIS; BHARATH SRIRAMAN; ILIADA ELIA; MODESTINA MODESTOU

201

Vergence, Vision, and Geometric Optics  

ERIC Educational Resources Information Center

Provides a definition of vergence in terms of the curvature of the wave fronts, and gives examples to illustrate the advantages of this approach. The vergence treatment of geometrical optics provides both conceptual and algebraic advantages, particularly for the life science student, over the traditional object distance-image distance-focal length

Keating, Michael P.

1975-01-01

202

Algorithmic + Geometric characterization of CAR  

E-print Network

Algorithmic + Geometric characterization of CAR (Coarsening at Random) Richard Gill - Utrecht but independent) CCAR 3 door problem X=door with car behind Y=two doors still closed = {your first choice, other door left closed} 3 door problem X=door with car behind Y=(your first choice, other door left closed

Gill, Richard D.

203

Hydrogen-bond dynamics for the extended simple point-charge model of water Francis W. Starr,1,  

E-print Network

Hydrogen-bond dynamics for the extended simple point-charge model of water Francis W. Starr,1 1999; revised manuscript received 22 February 2000 We study hydrogen-bond dynamics in liquid water and geometric definitions of a hydrogen bond, and employ two analysis methods: i a history-dependent correlation

Stanley, H. Eugene

204

LET'S BOND! A Chemical Bonding Webquest  

NSDL National Science Digital Library

Today we are going to use the internet to explore chemical bonding! Even though there are just a few questions for each website, you need to read the entire content. Don't worry about understanding all of it, but make sure that you are familiar with it! Stay on task and have fun! Let's start with some basics. Click on the link below and answer the questions on your worksheet under "Bonding Basics". Bonding Basics Good job! Lets move on and talk about ions. Ions are a big part of bonding, so make sure you get this section down pat! Click on the ...

Hicken, Mrs.

2009-04-08

205

Investing in Bonds.com  

NSDL National Science Digital Library

Investing in Bonds was created by the Bond Market Association to educate investors about the benefits of bonds investing. The Investor's Guide to Bond Basics educates investors about the types of bonds available, criteria for evaluating a bond, a guide to buying bonds, bond investment strategies and a glossary of bond market terms. The Bond Market section provides an overview of the U.S. bond market while the Investor's Checklist section takes the investor step-by-step through the bond investment decision process. Investors will also find sections with information on municipal bonds, corporate bonds, mortgage securities and U.S. Inflation-Indexed Securities.

206

Numerical simulation of biological base pairs considering geometric and energetic criteria  

Microsoft Academic Search

The aim of this work is the numerical simulation of the formation of hydrogen-bonded base pairs between adenine, thymine, guanine and cytosine. We use a Monte Carlo diffusion simulation with geometric (molecular distances and orientation) and energetic (acceptance proportional to the Boltzmann factor) criteria. Our results show that the occurrence of the different types of base pairs is strongly influenced

Sani De C. R. Da Silva; Dimitrios Samios; P. A. Netz; Dagoberto A. R. Justo; A. L. De Bortoli

2008-01-01

207

The verdict geometric quality library.  

SciTech Connect

Verdict is a collection of subroutines for evaluating the geometric qualities of triangles, quadrilaterals, tetrahedra, and hexahedra using a variety of metrics. A metric is a real number assigned to one of these shapes depending on its particular vertex coordinates. These metrics are used to evaluate the input to finite element, finite volume, boundary element, and other types of solvers that approximate the solution to partial differential equations defined over regions of space. The geometric qualities of these regions is usually strongly tied to the accuracy these solvers are able to obtain in their approximations. The subroutines are written in C++ and have a simple C interface. Each metric may be evaluated individually or in combination. When multiple metrics are evaluated at once, they share common calculations to lower the cost of the evaluation.

Knupp, Patrick Michael; Ernst, C.D. (Elemental Technologies, Inc., American Fork, UT); Thompson, David C. (Sandia National Laboratories, Livermore, CA); Stimpson, C.J. (Elemental Technologies, Inc., American Fork, UT); Pebay, Philippe Pierre

2006-03-01

208

Bouncing Balls and Geometric Series  

NSDL National Science Digital Library

The introduction to this intriguing exercise and article begins "If a ball bounces an infinite number of times, it must take an infinite amount of time to finish bouncing!" This piece appeared in The Journal of Online Mathematics and Its Applications in May 2007, and it was authored by Robert Styer and Morgan Besson of Villanova University. This particular article and its accompanying teaching module "explore the time and distance of a bouncing ball and leads to a study of the geometric series." Along with the actual article, this site also includes a video clip and several interactive Flash mathlets. It's a fun way to get students thinking about geometric series, and mathematics educators will definitely want to tell colleagues about the site as well. [KMG

Besson, Morgan; Styer, Robert

2007-05-01

209

Geometrical modelling of textile reinforcements  

NASA Technical Reports Server (NTRS)

The mechanical properties of textile composites are dictated by the arrangement of yarns contained within the material. Thus, to develop a comprehensive understanding of the performance of these materials, it is necessary to develop a geometrical model of the fabric structure. This task is quite complex, as the fabric is made from highly flexible yarn systems which experience a certain degree of compressibility. Furthermore there are tremendous forces acting on the fabric during densification typically resulting in yarn displacement and misorientation. The objective of this work is to develop a methodology for characterizing the geometry of yarns within a fabric structure including experimental techniques for evaluating these models. Furthermore, some applications of these geometric results to mechanical property predictions models are demonstrated.

Pastore, Christopher M.; Birger, Alexander B.; Clyburn, Eugene

1995-01-01

210

Geometric Modeling and Industrial Geometry  

NSDL National Science Digital Library

The Geometric Modeling and Industrial Geometry group is part of the Institute of Discrete Mathematics and Geometry at the Vienna University of Technology. The group's goal is "to bridge the gap between academic and industrial research in geometry" by "performing application oriented fundamental research and industrial research closely connected to geometry." Its work currently emphasizes the recognition, inspection, manipulation, and design of geometric shapes. Short descriptions of the group's work and some articles are available on the academic research, covering topics such as Computational Line Geometry, Laguerre Geometry, approximation in the space of planes, the isophotic metric, and swept volumes. Visitors can also read about the group's industrial research on 3-D Computer Vision, reverse Engineering, and Industrial Inspection. The Application Areas section includes more articles and provides actual data from some of the objects it has scanned along with the resulting 3-D images.

2005-11-03

211

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations  

NASA Technical Reports Server (NTRS)

A methodology is presented for determining the fatigue life of bonded composite skin/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange/skin specimens to verify the approach.

Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin

2000-01-01

212

Fatigue Life Methodology for Bonded Composite Skin\\/Stringer Configurations  

Microsoft Academic Search

A methodology is presented for determining the fatigue life of bonded composite skin\\/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange\\/skin specimens to verify the approach.

Ronald Krueger; Isabelle L. Paris; T. Kevin O'Brien; Pierre J. Minguet

2000-01-01

213

Realization of ultrafast and high-quality anodic bonding using a non-contact scanning electrode  

NASA Astrophysics Data System (ADS)

The anodic bonding technique, which is primarily used in glass to silicon wafer bonding, has been extensively used in microelectromechanical systems (MEMS) for the packaging of microsensors and microactuators. When the bonding voltage is applied, the bonded region instantly occurs at the contact point of the cathode with the glass. The geometric shape or arranged pattern of the cathode electrode significantly affects the bonding quality, particularly the gas-trapping at the bonded interface and the bonding time. This paper presents a novel anodic bonding process, in which the non-contacting and rotating electrode with radial lines is used as the cathode for scan bonding with arc-discharge assistance. The experimental results show that a bonding ratio of 99.98% and an average bonding strength of 15.45 MPa for a 4-inch silicon/glass bonded pair can be achieved in a 17 s bonding time by using a cathode electrode with eight 45 included-angle radial lines at a rotation speed of 0.45 rpm, a non-contact gap of 120 m, a bonding voltage of 900 V and a bonding temperature of 400 C. This ultrafast and high-quality anodic bonding has been synchronously realized under this scan bonding technique.

Wu, Jim-Wei; Yang, Chii-Rong; Huang, Mao-Jung; Yang, Cheng-Hao; Huang, Che-Yi

2013-07-01

214

Parametric FEM for geometric biomembranes  

NASA Astrophysics Data System (ADS)

We consider geometric biomembranes governed by an L2-gradient flow for bending energy subject to area and volume constraints (Helfrich model). We give a concise derivation of a novel vector formulation, based on shape differential calculus, and corresponding discretization via parametric FEM using quadratic isoparametric elements and a semi-implicit Euler method. We document the performance of the new parametric FEM with a number of simulations leading to dumbbell, red blood cell and toroidal equilibrium shapes while exhibiting large deformations.

Bonito, Andrea; Nochetto, Ricardo H.; Sebastian Pauletti, M.

2010-05-01

215

Geometric compression through topological surgery  

Microsoft Academic Search

The abundance and importance of complex 3-D data bases in major industry segments, the affordability of interactive 3-D rendering for office and consumer use, and the exploitation of the Internet to distribute and share 3-D data have intensified the need for an effective 3-D geometric compression technique that would significantly reduce the time required to transmit 3-D models over digital

Gabriel Taubin; Jarek Rossignac

1998-01-01

216

Geometric structures of vectorial type  

Microsoft Academic Search

We study geometric structures of W4-type in the sense of A. Gray on a Riemannian manifold. If the structure group G?SO(n) preserves a spinor or a non-degenerate differential form, its intrinsic torsion ? is a closed 1-form (Proposition 2.1 and Theorem 2.1). Using a G-invariant spinor we prove a splitting theorem (Proposition 2.2). The latter result generalizes and unifies a

Ilka Agricola; Thomas Friedrich

2006-01-01

217

Geometric phases of water waves  

E-print Network

Recently, Banner et al. (2014) highlighted a new fundamental property of open ocean wave groups, the so-called crest slowdown. For linear narrowband waves, this is related to the geometric phase associated with the parallel transport through the principal fiber bundle of the wave motion with U(1) group symmetry. The theoretical predictions are shown to be in fair agreement with ocean field observations.

Fedele, Francesco

2014-01-01

218

Geometrical methods in learning theory  

NASA Astrophysics Data System (ADS)

The methods of information theory provide natural approaches to learning algorithms in the case of stochastic formal neural networks. Most of the classical techniques are based on some extremization principle. A geometrical interpretation of the associated algorithms provides a powerful tool for understanding the learning process and its stability and offers a framework for discussing possible new learning rules. An illustration is given using sequential and parallel learning in the Boltzmann machine.

Burdet, G.; Combe, Ph.; Nencka, H.

2001-02-01

219

Scaling properties of geometric parallelization  

NASA Astrophysics Data System (ADS)

We present a universal scaling law for all geometrically parallelized computer simulation algorithms. For algorithms with local interaction laws we calculate the scaling exponents for zero and infinite lattice size. The scaling is tested on local (cellular automata, Metropolis Ising) as well as cluster (Swendsen-Wang) algorithms. The practical aspects of the scaling properties lead to a simple recipe for finding the optimum number of processors to be used for the parallel simulation of a particular system.

Jakobs, A.; Gerling, R. W.

1992-01-01

220

Great Gobs of Geometric Games!  

NSDL National Science Digital Library

These games help you review shapes, make shapes, and transform shapes! First, use the online Geoboard to make your own shapes, just for fun. Now, review your geometric vocabulary and match the shape with its name in the memory game Matching Shapes. Transformational Geometry is loads of fun. You'll have to use your knowledge of translation and rotation for this game. Can you make the ...

Hearne, Miss

2009-04-30

221

Geometrical content of Leslie coefficients  

NASA Astrophysics Data System (ADS)

In this work, we will study how the effective geometry acquired by nematic molecules under thermal vibration contribute to the determination of the Leslie coefficients. To do this, we will divide this work in two sections. In the first section, we present the geometrical fundamentals of the so-called Hess-Baalss (HB) approach [D. Baalss and S. Hess, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.57.86 57, 86 (1986)] where we show that its basic assumptions can be understood as a geometrical interpretation of de Gennes passage from the microscopic to the macroscopic order parameter. In the second section, we use an extended version of the HB approach [M. Simes, K. Yamaguti, and A. J. Palangana, Phys. Rev. EPHRVAO1539-375510.1103/PhysRevE.80.061701 80, 061701 (2009)] to obtain the geometrical contribution to each Leslie coefficient. Our results will be compared with experimental data, and we will show that the Miesowiczs coefficients are connected as long as the ratio ?3/?4 between these Leslie coefficients can be considered small.

Simes, M.; da Silva, J. L. Correia

2011-05-01

222

Geometric mean for subspace selection.  

PubMed

Subspace selection approaches are powerful tools in pattern classification and data visualization. One of the most important subspace approaches is the linear dimensionality reduction step in the Fisher's linear discriminant analysis (FLDA), which has been successfully employed in many fields such as biometrics, bioinformatics, and multimedia information management. However, the linear dimensionality reduction step in FLDA has a critical drawback: for a classification task with c classes, if the dimension of the projected subspace is strictly lower than c - 1, the projection to a subspace tends to merge those classes, which are close together in the original feature space. If separate classes are sampled from Gaussian distributions, all with identical covariance matrices, then the linear dimensionality reduction step in FLDA maximizes the mean value of the Kullback-Leibler (KL) divergences between different classes. Based on this viewpoint, the geometric mean for subspace selection is studied in this paper. Three criteria are analyzed: 1) maximization of the geometric mean of the KL divergences, 2) maximization of the geometric mean of the normalized KL divergences, and 3) the combination of 1 and 2. Preliminary experimental results based on synthetic data, UCI Machine Learning Repository, and handwriting digits show that the third criterion is a potential discriminative subspace selection method, which significantly reduces the class separation problem in comparing with the linear dimensionality reduction step in FLDA and its several representative extensions. PMID:19110492

Tao, Dacheng; Li, Xuelong; Wu, Xindong; Maybank, Stephen J

2009-02-01

223

GEOMETRIC HOMOGENEITY AND STABILIZATION MATTHIAS KAWSKI \\Lambda  

E-print Network

GEOMETRIC HOMOGENEITY AND STABILIZATION MATTHIAS KAWSKI \\Lambda \\Lambda Center for Systems Science of homogeneity, for vector fields (differential equations and control systems), functions, differential forms and endomorphisms. The fundamental observation is that homogeneity is an intrinsic, geometric property. Accordingly

Kawski, Matthias

224

SEARCH OPTIMIZATION USING HYBRID PARTICLE SUB SWARMS AND EVOLUTIONARY ALGORITHMS  

Microsoft Academic Search

Particle Swarm Optimization (PSO) technique proved its ability to deal with very complicated optimization and search problems. Several variants of the original algorithm have been proposed. This paper proposes a variant of the PSO technique named Independent Neighborhoods Particle Swarm Optimization (INPSO) dealing with sub-swarms for solving the well known geometrical place problems. Finding the geometrical place can be sometimes

CRINA GROSAN; AJITH ABRAHAM; MONICA NICOARA

2005-01-01

225

Accurate Structure and Dynamics of the Metal-Site of Paramagnetic Metalloproteins from NMR Parameters Using Natural Bond Orbitals  

PubMed Central

A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metalligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metalligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for 15N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of 15N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of 15N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site. PMID:22329704

2012-01-01

226

A Common Eurozone Bond  

Microsoft Academic Search

Introduction\\u000aThe sovereign bond yields of the Eurozone, or more correctly the euro area, have since the introduction of the Euro undergone a bond yield compression. However, as can be seen in table 1, these bond yields started to diverge considerably around mid 2008 following the recent financial crisis and increased sovereign risk. Yields on Greek, Irish, and Portuguese bond

Erik Welin

2010-01-01

227

Geometric Algebra and Physics Anthony Lasenby  

E-print Network

Geometric Algebra and Physics Anthony Lasenby Astrophysics Group, Cavendish Laboratory, Cambridge Microwave Background, and early universe Why am I here talking about `Geometric Algebra'? Came across effectively extends them to the relativistic domain And via `conformal geometric algebra' gives a whole new

Hart, Gus

228

CRYSTAL-LIKE GEOMETRIC MODELING ERIC LANDRENEAU  

E-print Network

CRYSTAL-LIKE GEOMETRIC MODELING A Thesis by ERIC LANDRENEAU Submitted to the Office of Graduate OF SCIENCE May 2005 Major Subject: Computer Science #12;CRYSTAL-LIKE GEOMETRIC MODELING A Thesis by ERIC Science #12;iii ABSTRACT Crystal-Like Geometric Modeling. (May 2005) Eric Landreneau, B.S., Texas A

Keyser, John

229

Introduction to Pauli Geometric Algebra M. Berrondo  

E-print Network

Introduction to Pauli Geometric Algebra M. Berrondo May 9, 2009 #12;Pauli Algebra Geometric Algebras Geometric algebras (also called Cliord algebras) are used to endow physical spaces with a useful algebraic structure. By analyzing the physical system within this context, we can nd alternate

Hart, Gus

230

GEOMETRIC MEASUREMENT COMPARISONS FOR ROCKWELL DIAMOND INDENTERS  

Microsoft Academic Search

In the uncertainty budget of Rockwell C hardness (HRC) tests, geometric error of the Rockwell diamond indenter is a major contributor. The geometric calibration of Rockwell diamond indenters has been a key issue for Rockwell hardness standardization. The National Institute of Standards and Technology (NIST) developed a microform calibration system based on a stylus instrument for the geometric calibration of

John Song; Samuel Low; Alan Zheng

231

Geometrically frustrated magnets Arnab Sen, TIFR  

E-print Network

, 10786 (1992) f= |cw|/T* Arnab Sen, TIFR Geometrically frustrated magnets #12;Materials TriangularGeometrically frustrated magnets Arnab Sen, TIFR Theoretical Physics Colloquium Collaborators: K and A. Vishwanath, PRL 100, 097202 (2008). July 7, 2009 Arnab Sen, TIFR Geometrically frustrated magnets

232

Rapid adhesive bonding concepts  

NASA Technical Reports Server (NTRS)

Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process is often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid adhesive bonding concepts were developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens are cut by a factor of 10 to 100 compared to standard press bonding. The development of rapid adhesive bonding for lap shear specimens (per ASTM D1003 and D3163), for aerospace panel bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric matrix composite structures are reviewed.

Stein, B. A.; Tyeryar, J. R.; Hodges, W. T.

1984-01-01

233

Making and Breaking Bonds  

NSDL National Science Digital Library

Atoms collide and, under certain circumstances, react to form bonds with one another. The process of association is the bonding of atoms into a molecule while dissociation is the process by which a molecule breaks apart into simpler groups of atoms, individual atoms, or ions. Students interact with a molecular dynamics model to explore the making and breaking of bonds.

Consortium, The C.

2011-12-11

234

A conic approach for separable convex optimization  

E-print Network

' & $ % A conic approach for separable convex optimization Fran#24;cois Glineur Aspirant F programmation math#19;ematique Han-sur-Lesse, February 2, 2001 #12; A conic approach for separable convex optimization ' & $ % #11; #8; Outline Introduction #5; Conic optimization #5; Geometric optimization

Glineur, François

235

Prospective bonding applications  

NASA Astrophysics Data System (ADS)

Adhesive bonding in industry and in the laboratory is surveyed and prospects for its wider utilization are assessed. The economic impact of bonding technology on industry is discussed. Research is reviewed, centering on the development of nondestructive testing and inspection techniques. Traditional (wood) as well as new materials susceptible to bonding are considered. Applications in construction and civil engineering, in aeronautics, and in the automobile industry are covered. The use of glues in mechanical constructions, in assembling cylindrical parts, and in metal-metal bonding are examined. Hybrid assembling and bonding of composite materials are included.

Ancenay, H.; Benazet, D.

1981-07-01

236

Geometric parameter inverse model for drawbeads based on grey relational analysis and GA-BP  

NASA Astrophysics Data System (ADS)

In sheet metal forming, the wrinkling and fracture can be eliminated via an appropriate drawbead design. Proper drawbead design method to reduce time and cost is highly required. In the paper, the geometric parameters influencing semi-circular drawbead force are firstly analyzed making use of grey relational analysis, and the main parameters are obtained. The main parameters are sampled making use of Latin hypercube. The box forming is simulated with DYNAFORM, and the sample data are obtained. In the back propagation (BP) neural network, the thinning, thickening and major strains are selected as input parameters, and drawbead geometric parameters are selected as output objective. The inverse model of drawbead geometric parameters is established. The BP neural network weights are optimized with genetic algorithm (GA). Compared with the predictive values by BP, the parameters values by GA-BP are more accurate. Based on the GA-BP, the nonlinear relationship of the forming quality and drawbead geometric parameters is obtained making use of the optimized BP weights. Finally the optimum geometric parameters of drawbeads are obtained based on GA. The numerical simulations of box forming are compared before optimization and after optimization. The results show the optimized drawbeads can greatly improve the formability of sheet metal forming.

Xie, Yanmin

2013-12-01

237

Categorical geometric skew Howe duality  

E-print Network

We categorify the R-matrix isomorphism between tensor products of minuscule representations of U_q(sl(n)) by constructing an equivalence between the derived categories of coherent sheaves on the corresponding convolution products in the affine Grassmannian. The main step in the construction is a categorification of representations of U_q(sl(2)) which are related to representations of U_q(sl(n)) by quantum skew Howe duality. The resulting equivalence is part of the program of algebro-geometric categorification of Reshitikhin-Turaev tangle invariants developed by the first two authors.

Cautis, Sabin; Licata, Anthony

2009-01-01

238

Science, art and geometrical imagination  

NASA Astrophysics Data System (ADS)

From the geocentric, closed world model of Antiquity to the wraparound universe models of relativistic cosmology, the parallel history of space representations in science and art illustrates the fundamental rle of geometric imagination in innovative findings. Through the analysis of works of various artists and scientists like Plato, Drer, Kepler, Escher, Grisey or the author, it is shown how the process of creation in science and in the arts rests on aesthetical principles such as symmetry, regular polyhedra, laws of harmonic proportion, tessellations, group theory, etc., as well as on beauty, conciseness and an emotional approach of the world.

Luminet, Jean-Pierre

2011-06-01

239

Geometrical setting of solid mechanics  

NASA Astrophysics Data System (ADS)

The starting point in the geometrical setting of solid mechanics is to represent deformation process of a solid body as a trajectory in a convenient space with Riemannian geometry, and then to use the corresponding tools for its analysis. Based on virtual power of internal stresses, we show that such a configuration space is the (globally) symmetric space of symmetric positive-definite real matrices. From this unifying point of view, we shall analyse the logarithmic strain, the stress rate, as well as linearization and intrinsic integration of corresponding evolution equation.

Fiala, Zden?k

2011-08-01

240

Geometric phases of water waves  

NASA Astrophysics Data System (ADS)

Recently, Banner et al. (Phys. Rev. Lett., 112 (2014) 114502) highlighted a new fundamental property of open ocean wave groups, the so-called crest slowdown. For linear narrow-band waves, this is related to the geometric and dynamical phase velocities Ud and Ug associated with the parallel transport through the principal fiber bundle of the wave dynamics with U(1) symmetry. The theoretical predictions are shown to be in fair agreement with ocean field observations, from which the average crest speed c=U_d+Ug with c/U_d?0.8 and Ug/U_d?-0.2 .

Fedele, Francesco

2014-09-01

241

Geometric analysis of wing sections  

NASA Technical Reports Server (NTRS)

This paper describes a new geometric analysis procedure for wing sections. This procedure is based on the normal mode analysis for continuous functions. A set of special shape functions is introduced to represent the geometry of the wing section. The generators of the NACA 4-digit airfoils were included in this set of shape functions. It is found that the supercritical wing section, Korn airfoil, could be well represented by a set of ten shape functions. Preliminary results showed that the number of parameters to define a wing section could be greatly reduced to about ten. Hence, the present research clearly advances the airfoil design technology by reducing the number of design variables.

Chang, I.-CHUNG; Torres, Francisco J.; Tung, Chee

1995-01-01

242

Buildings, spiders, and geometric Satake  

E-print Network

Let G be a simple algebraic group. Labelled trivalent graphs called webs can be used to product invariants in tensor products of minuscule representations. For each web, we construct a configuration space of points in the affine Grassmannian. Via the geometric Satake correspondence, we relate these configuration spaces to the invariant vectors coming from webs. In the case G = SL(3), non-elliptic webs yield a basis for the invariant spaces. The non-elliptic condition, which is equivalent to the condition that the dual diskoid of the web is CAT(0), is explained by the fact that affine buildings are CAT(0).

Fontaine, Bruce; Kuperberg, Greg

2011-01-01

243

Graphene with geometrically induced vorticity  

E-print Network

At half filling, the electronic structure of graphene can be modelled by a pair of free two-dimensional Dirac fermions. We explicitly demonstrate that in the presence of a geometrically induced gauge field, an everywhere-real Kekule modulation of the hopping matrix elements can correspond to a non-real Higgs field with non-trivial vorticity. This provides a natural setting for fractionally charged vortices with localized zero modes. For fullerene-like molecules we employ the index theorem to demonstrate the existence of six low-lying states that do not depend strongly on the Kekule-induced mass gap.

Jiannis K. Pachos; Michael Stone; Kristan Temme

2007-10-03

244

Geometric phases of water waves  

E-print Network

Recently, Banner et al. (2014) highlighted a new fundamental property of open ocean wave groups, the so-called crest slowdown. For linear narrowband waves, this is related to the geometric and dynamical phase velocities $U_d$ and $U_g$ associated with the parallel transport through the principal fiber bundle of the wave motion with $\\mathit{U}(1)$ symmetry. The theoretical predictions are shown to be in fair agreement with ocean field observations, from which the average crest speed $c=U_d+U_g$ with $c/U_d\\approx0.8$ and $U_{g}/U_d\\approx-0.2$.

Francesco Fedele

2014-05-31

245

Constrained ballistics and geometrical optics  

E-print Network

The problem of constant-speed ballistics is studied under the umbrella of non-linear non-holonomic constrained systems. The Newtonian approach is shown to be equivalent to the use of Chetaev's rule to incorporate the constraint within the initially unconstrained formulation. Although the resulting equations are not, in principle, obtained from a variational statement, it is shown that the trajectories coincide with those of geometrical optics in a medium with a suitably chosen refractive index, as prescribed by Fermat's principle of least time. This fact gives rise to an intriguing mechano-optical analogy. The trajectories are further studied and discussed.

Epstein, Marcelo

2014-01-01

246

Optimal bird migration revisited  

Microsoft Academic Search

Using optimality perspectives is now regarded as an essential way of analysing and understanding adaptations and behavioural\\u000a strategies in bird migration. Optimization analyses in bird migration research have diversified greatly during the two recent\\u000a decades with respect to methods used as well as to topics addressed. Methods range from simple analytical and geometric models\\u000a to more complex modeling by stochastic

Thomas Alerstam

247

Geometric effects of Circumbinary Planets  

NASA Astrophysics Data System (ADS)

The largest fraction of random observers will never see a planet transit. Multiple systems contain a planet orbiting two sun-like stars that orbit and eclipse each other, creating unique effects for the planet and its transits. In the case of a perfectly coplanar binary and planet system looked upon exactly edge on, there is a transit every time the planet comes by. In between, there are a wide variety of possibilities. To understand the complicated geometry, probability of transits, and true frequency in these systems, determining bias in transits is essential. In looking at these possibilities, random observers from any location are considered for the most likely transits. We use three- body integration and we find the geometric probability depending on the number of random observations within a short interval in our model of transiting system. We will explore how these geometric effects vary as a function of binary and planetary orbital parameters, which will allow for a characterization of the unknown intrinsic properties of the circumbinary planet population.

Shahady, Anna K.; Ragozzine, Darin

2014-11-01

248

Photothermoelastic analysis of bonded propellant grains  

Microsoft Academic Search

A two-dimensional model of the transversal cross section of a bonded rocket propellant grain was subjected to uniform and steady thermal loading and, alternatively, to mechanically applied uniform radial displacements on the outer boundary. The optimization of perforation contours (attained in previous research programs by applying uniform pressure on the outer boundary of the grain model) was confirmed for both

I. M. Daniel; A. J. Durelli

1961-01-01

249

Gear optimization  

NASA Technical Reports Server (NTRS)

The use of formal numerical optimization methods for the design of gears is investigated. To achieve this, computer codes were developed for the analysis of spur gears and spiral bevel gears. These codes calculate the life, dynamic load, bending strength, surface durability, gear weight and size, and various geometric parameters. It is necessary to calculate all such important responses because they all represent competing requirements in the design process. The codes developed here were written in subroutine form and coupled to the COPES/ADS general purpose optimization program. This code allows the user to define the optimization problem at the time of program execution. Typical design variables include face width, number of teeth and diametral pitch. The user is free to choose any calculated response as the design objective to minimize or maximize and may impose lower and upper bounds on any calculated responses. Typical examples include life maximization with limits on dynamic load, stress, weight, etc. or minimization of weight subject to limits on life, dynamic load, etc. The research codes were written in modular form for easy expansion and so that they could be combined to create a multiple reduction optimization capability in future.

Vanderplaats, G. N.; Chen, Xiang; Zhang, Ning-Tian

1988-01-01

250

System analysis through bond graph modeling  

NASA Astrophysics Data System (ADS)

Modeling and simulation form an integral role in the engineering design process. An accurate mathematical description of a system provides the design engineer the flexibility to perform trade studies quickly and accurately to expedite the design process. Most often, the mathematical model of the system contains components of different engineering disciplines. A modeling methodology that can handle these types of systems might be used in an indirect fashion to extract added information from the model. This research examines the ability of a modeling methodology to provide added insight into system analysis and design. The modeling methodology used is bond graph modeling. An investigation into the creation of a bond graph model using the Lagrangian of the system is provided. Upon creation of the bond graph, system analysis is performed. To aid in the system analysis, an object-oriented approach to bond graph modeling is introduced. A framework is provided to simulate the bond graph directly. Through object-oriented simulation of a bond graph, the information contained within the bond graph can be exploited to create a measurement of system efficiency. A definition of system efficiency is given. This measurement of efficiency is used in the design of different controllers of varying architectures. Optimal control of a missile autopilot is discussed within the framework of the calculated system efficiency.

McBride, Robert Thomas

251

Geometric Effects on the Amplification of First Mode Instability Waves  

NASA Technical Reports Server (NTRS)

The effects of geometric changes on the amplification of first mode instability waves in an external supersonic boundary layer were investigated using numerical techniques. Boundary layer stability was analyzed at Mach 6 conditions similar to freestream conditions obtained in quiet ground test facilities so that results obtained in this study may be applied to future test article design to measure first mode instability waves. The DAKOTA optimization software package was used to optimize an axisymmetric geometry to maximize the amplification of the waves at first mode frequencies as computed by the 2D STABL hypersonic boundary layer stability analysis tool. First, geometric parameters such as nose radius, cone half angle, vehicle length, and surface curvature were examined separately to determine the individual effects on the first mode amplification. Finally, all geometric parameters were allowed to vary to produce a shape optimized to maximize the amplification of first mode instability waves while minimizing the amplification of second mode instability waves. Since first mode waves are known to be most unstable in the form of oblique wave, the geometries were optimized using a broad range of wave frequencies as well as a wide range of oblique wave angles to determine the geometry that most amplifies the first mode waves. Since first mode waves are seen most often in flows with low Mach numbers at the edge of the boundary layer, the edge Mach number for each geometry was recorded to determine any relationship between edge Mach number and the stability of first mode waves. Results indicate that an axisymmetric cone with a sharp nose and a slight flare at the aft end under the Mach 6 freestream conditions used here will lower the Mach number at the edge of the boundary layer to less than 4, and the corresponding stability analysis showed maximum first mode N factors of 3.

Kirk, Lindsay C.; Candler, Graham V.

2013-01-01

252

Geometric Programming optimization of deterministic inventory systems under multiple constraints  

E-print Network

. , and the previous 1. 1. i expression becomes u + u '+, , + u & fu " u 4 . d '~ n 16~' which may be more compactly written as n i=1 i=1 Id. 1. The left side of this expression is termed the PRIM, function g and the right side the PRE-DUAL function y, where.... , and the previous 1. 1. i expression becomes u + u '+, , + u & fu " u 4 . d '~ n 16~' which may be more compactly written as n i=1 i=1 Id. 1. The left side of this expression is termed the PRIM, function g and the right side the PRE-DUAL function y, where...

Foster, Ralph Emerson

2012-06-07

253

Application of separable programming to optimization by geometric programming  

E-print Network

) = H d [j Xk(d) where the components 6. of the vector 6 are the dual variables and i (6) =- 6 , k=1, 2, . . . dp icJ[kj The vector variable 6 is subject to the following three condt. tions: th ~t' ' dttt 6 & 0, i=1, 2, . . . , n the nor...~malit condition, isJ[0] :, . d . h ~th? 1' dt. n Q. , d, . = d, j=1, 2, . . . , m Collectively, these constraints are called the dual constraints. To make the function v(6) continuous over its domain of definition, define x x x=x=1, ifx=0 Either problem...

Humber, Joseph Barker

2012-06-07

254

A Geometric Optimization Approach to Detecting and Intercepting Dynamic Targets  

E-print Network

-pursuit problem considered in this paper is analogous to the Marco Polo game, in which the pursuer must capture is inspired by the game Marco Polo described in [13] and is motivated by many applications i

Ferrari, Silvia

255

Optimal Strokes for Driftless Swimmers: A General Geometric Approach  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . 53 2 hal-00969259,version1-2Apr2014 #12;1 Introduction Understanding the mechanics of swimming has an attrac- tive model for the design of biomimetic robots. Significant contributions to this matter are due

Paris-Sud XI, Université de

256

Parameterization and Geometric Optimization of Balloon Launched Sensorcraft for Atmospheric  

E-print Network

and manufacturing of balloon launched, high altitude gliders. The purpose of these gliders is to conduct di- rected that can protect the payload, ensure recoverability and ex- tend sampling times. A manufacturing technique American Institute of Aeronautics and Astronautics #12;Potential applications for this technology include

Sóbester, András

257

Optimal Navigation and Object Finding without Geometric Maps or Localization  

E-print Network

such as surveillance, search- and-rescue, fire-fighting, law enforcement, and re- mote visual presence. Classical Engineering ITESM CCM Mexico City Mexico Dept. of Computer Science University of Illinois Urbana, IL 61801

LaValle, Steven M.

258

Optimal Navigation and Object Finding without Geometric Maps or Localization  

E-print Network

such as surveillance, search­ and­rescue, fire­fighting, law enforcement, and re­ mote visual presence. Classical@robotics.stanford.edu # Dept. of Electrical Engineering ITESM CCM Mexico City Mexico + Dept. of Computer Science University

LaValle, Steven M.

259

Application of generalized geometric programming to optimizing polynomials  

E-print Network

, 2325054E 0 ' 2205/06F 0. 224*73UF A. 22088'3Ht 21T2017E 0 & 213621i&E 0 ~ 2101378E 0 206/51/t 0. 2G34554F A. ZUn?i, 0&, E 0 19712 51F 0 ~ 194{&026E 0. 1911195E U 15!323?9{. 0 1 85 i& 1 79 F 0 ~ 1 H? 6 7 '5 II C 0 1HUonnbF 0 & 1773926E U 1 14... Hi&. 73 F. O. 17? 3b36F n. 1699399 E 0 e 1. 6 7 '& 74 0 t. 0& 16'5? 63 5 F 0 1630063E 02 Q? 02 A? 02 02 CZ 02 UZ 02 0? C2 02 n? C? 0? 02 A? 02 Ci 2 Oi 0? 02 02 A2 A2 0? 02 02 02 ac -0&120 -0. 171 ? A 1?2 -0 1?3 -0...

Gibson, Robert Engel

2012-06-07

260

Geometric view of adaptive optics control  

NASA Astrophysics Data System (ADS)

The objective of an astronomical adaptive optics control system is to minimize the residual wave-front error remaining on the science-object wave fronts after being compensated for atmospheric turbulence and telescope aberrations. Minimizing the mean square wave-front residual maximizes the Strehl ratio and the encircled energy in pointlike images and maximizes the contrast and resolution of extended images. We prove the separation principle of optimal control for application to adaptive optics so as to minimize the mean square wave-front residual. This shows that the residual wave-front error attributable to the control system can be decomposed into three independent terms that can be treated separately in design. The first term depends on the geometry of the wave-front sensor(s), the second term depends on the geometry of the deformable mirror(s), and the third term is a stochastic term that depends on the signal-to-noise ratio. The geometric view comes from understanding that the underlying quantity of interest, the wave-front phase surface, is really an infinite-dimensional vector within a Hilbert space and that this vector space is projected into subspaces we can control and measure by the deformable mirrors and wave-front sensors, respectively. When the control and estimation algorithms are optimal, the residual wave front is in a subspace that is the union of subspaces orthogonal to both of these projections. The method is general in that it applies both to conventional (on-axis, ground-layer conjugate) adaptive optics architectures and to more complicated multi-guide-star- and multiconjugate-layer architectures envisaged for future giant telescopes. We illustrate the approach by using a simple example that has been worked out previously [J. Opt. Soc. Am. A73, 1171 (1983)] for a single-conjugate, static atmosphere case and follow up with a discussion of how it is extendable to general adaptive optics architectures.

Wiberg, Donald M.; Max, Claire E.; Gavel, Donald T.

2005-05-01

261

Energy pulse bonding  

NASA Technical Reports Server (NTRS)

To eliminate many of the present termination problems a technique called energy pulse bonding (EPB) was developed. The process demonstrated the capability of: (1) joining conductors without prior removal of insulations, (2) joining conductors without danger of brittle intermetallics, (3) increased joint temperature capability, (4) simultaneous formation of several bonds, (5) capability of higher joint density, and (6) a production oriented process. The following metals were successfully bonded in the solid state: copper, beryllium copper, phosphor bronze, aluminum, brass, and Kovar.

Smith, G. C.

1972-01-01

262

Chemical bonding technology  

NASA Technical Reports Server (NTRS)

Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.

Plueddemann, E.

1986-01-01

263

Hydrogen bonding and anaesthesia  

NASA Astrophysics Data System (ADS)

General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

Sndorfy, C.

2004-12-01

264

Mathematical Optimization  

NSDL National Science Digital Library

Some of the most fundamental problems in engineering, science, and mathematics would take the most powerful computer in the world several lifetimes to find an optimal solution. However, near-optimal solutions to many of these problems have been discovered thanks to various methods of mathematical optimization. This Topic in Depth looks at some optimization techniques and the areas to which they have been applied.Argonne National Laboratory hosts an online guide (1) to some of the most well known optimization problems and algorithms. People who are new to the subject can find a wealth of introductory material in the Optimization Tree section, and several applications are illustrated with interactive demonstrations in the Case Studies section. Optimization has roots in operations research, and this tutorial (2) covers many topics within OR. A fun applet requires the user to place as many queens on a chess board as possible without any two being in direct line-of-sight, and an accompanying discussion shows how linear programming can be used to solve this problem; this is one of many resources contained within the tutorial. Two chemical engineering professors at Carnegie Mellon University are the authors of Retrospective on Optimization (3), a fairly comprehensive paper chronicling the history of optimization problems and the development of solution methods. The 51-page document is divided into two main parts; the first outlines some of the most significant advances in the field, and the second looks ahead toward key areas of research needed to evolve optimization further. Highway planning and development is the focus of this paper (4), which proposes using, among other things, genetic algorithms to optimize highway alignment. The authors state that this technique could be used to avoid delays and added costs due to changing plans later in the construction process. Another use of genetic algorithms in optimization is highlighted in this document from the German Aerospace Center (5). The document describes how a novel method for robot design, which involves formulating mathematical representations of robotic constraints and kinematics. These figures can then be used as parameters in a genetic algorithm that would optimize component placement while maintaining the desired functionality. A joint effort between architecture and mechanical engineering researchers at the University of Michigan (6) applied geometrical and topological optimization techniques to building floorplan layout. In the course of their research, they developed an optimization tool that is briefly described and can be downloaded from a Web site given in the paper. The Mathematical Programming Glossary (7) contains short discussions of hundreds of terms related to optimization theory. Each entry includes a clear definition and hyperlinks to other terms, and some of the entries are accompanied by a more in-depth supplement. One of the best sources for current research papers and reports is Optimization Online (8). This repository receives numerous submissions each month, and papers can be browsed by data added or category.

Leske, Cavin.

265

Geometrical setting of solid mechanics  

SciTech Connect

Highlights: > Solid mechanics within the Riemannian symmetric manifold GL (3, R)/O (3, R). > Generalized logarithmic strain. > Consistent linearization. > Incremental principle of virtual power. > Time-discrete approximation. - Abstract: The starting point in the geometrical setting of solid mechanics is to represent deformation process of a solid body as a trajectory in a convenient space with Riemannian geometry, and then to use the corresponding tools for its analysis. Based on virtual power of internal stresses, we show that such a configuration space is the (globally) symmetric space of symmetric positive-definite real matrices. From this unifying point of view, we shall analyse the logarithmic strain, the stress rate, as well as linearization and intrinsic integration of corresponding evolution equation.

Fiala, Zdenek, E-mail: fiala@itam.cas.cz [Institute of Theoretical and Applied Mechanics, ASCR, v. v. i., Prosecka 809/76, 190 00 Praha 9 (Czech Republic)

2011-08-15

266

Leonardo da Vinci's Geometric Sketches  

NSDL National Science Digital Library

How do you solve a problem like solids, mathematically speaking? Well, you could use this rather fascinating resource provided by the Convergence magazine. Offered as an educational resource by the Mathematical Association of America (MAA), this particular resource brings together the work of the Franciscan friar Luca Pacioli (c.1445-1509) and the geometric sketches of Leonardo Da Vinci. Both men were interested in geometry, and this piece offers up a number of plate facsimiles of illustrations created by Da Vinci. Here visitors will find an introduction to this educational resource, along with illustrations of cubes, octahedrons, and cylinders. The accompanying article was written by Frank J. Swetz, and it is easy to see how these materials could be incorporated into a classroom discussion about the history of mathematics.

267

Leonardo da Vinci's Geometric Sketches  

NSDL National Science Digital Library

How do you solve a problem like solids, mathematically speaking? Well, you could use this rather fascinating resource provided by the Convergence magazine. Offered as an educational resource by the Mathematical Association of America (MAA), this particular resource brings together the work of the Franciscan friar Luca Pacioli (c.1445-1509) and the geometric sketches of Leonardo Da Vinci. Both men were interested in geometry, and this piece offers up a number of plate facsimiles of illustrations created by Da Vinci. Here visitors will find an introduction to this educational resource, along with illustrations of cubes, octahedrons, and cylinders. The accompanying article was written by Frank J. Swetz, and it is easy to see how these materials could be incorporated into a classroom discussion about the history of mathematics.

2008-09-15

268

Geometric analysis of transient bursts  

NASA Astrophysics Data System (ADS)

We consider the effect of a brief stimulation from the rest state of a minimal neuronal model with multiple time scales. Such transient dynamics brings out the intrinsic bursting capabilities of the system. Our main goal is to show that a minimum of three dimensions is enough to generate spike-adding phenomena in transient responses, and that the onset of a new spike can be tracked using existing continuation packages. We take a geometric approach to illustrate how the underlying fast subsystem organises the spike adding in much the same way as for spike adding in periodic bursts, but the bifurcation analysis for spike onset is entirely different. By using a generic model, we further strengthen claims made in our earlier work that our numerical method for spike onset can be used for a broad class of systems.

Osinga, Hinke M.; Tsaneva-Atanasova, Krasimira T.

2013-12-01

269

Geometric asymmetry driven Janus micromotors.  

PubMed

The production and application of nano-/micromotors is of great importance. In order for the motors to work, asymmetry in their chemical composition or physical geometry must be present if no external asymmetric field is applied. In this paper, we present a "coconut" micromotor made of platinum through the partial or complete etching of the silica templates. It was shown that although both the inner and outer surfaces are made of the same material (Pt), motion of the structure can be observed as the convex surface is capable of generating oxygen bubbles. This finding shows that not only the chemical asymmetry of the micromotor, but also its geometric asymmetry can lead to fast propulsion of the motor. Moreover, a considerably higher velocity can be seen for partially etched coconut structures than the velocities of Janus or fully etched, shell-like motors. These findings will have great importance on the design of future micromotors. PMID:25122607

Zhao, Guanjia; Pumera, Martin

2014-10-01

270

Engineering geometric phase in semiconductor microcavities  

NASA Astrophysics Data System (ADS)

We present rigorous investigations of the geometric phase in semiconductor microcavities. The effects of excitonic spontaneous emission, initial state setting and cavity dissipation have been discussed. It is shown that the geometric phase decays exponentially due to the presence of excitonic spontaneous emission. More importantly, the inclusion of the phase shift leads to an enhanced sensitivity for the control of the geometric phase evolution and system dynamics.

Abdel-Khalek, S.; Berrada, K.; Eleuch, H.; Abdel-Aty, M.

2014-11-01

271

Animation of Geometric Algorithms: A Video Review  

Microsoft Academic Search

Geometric algorithms and data structures are often easiest to understand visually,in terms of the geometric objects they manipulate. Indeed, most papers in computationalgeometry rely on diagrams to communicate the intuition behind the results.Algorithm animation uses dynamic visual images to explain algorithms. Thus it isnatural to present geometric algorithms, which are inherently dynamic, via algorithmanimation.The accompanying videotape presents a video review

Marc H. Brown; John Hershberger

1993-01-01

272

Encoding geometric and non-geometric information: a study with evolved agents.  

PubMed

Vertebrate species use geometric information and non-geometric or featural cues to orient. Under some circumstances, when both geometric and non-geometric information are available, the geometric information overwhelms non-geometric cues (geometric primacy). In other cases, we observe the inverse tendency or the successful integration of both cues. In past years, modular explanations have been proposed for the geometric primacy: geometric and non-geometric information are processed separately, with the geometry module playing a dominant role. The modularity issue is related to the recent debate on the encoding of geometric information: is it innate or does it depend on environmental experience? In order to get insight into the mechanisms that cause the wide variety of behaviors observed in nature, we used Artificial Life experiments. We demonstrated that agents trained mainly with a single class of information oriented efficiently when they were exposed to one class of information (geometric or non-geometric). When they were tested in environments that contained both classes of information, they displayed a primacy for the information that they had experienced more during their training phase. Encoding and processing geometric and non-geometric information was run in a single cognitive neuro-representation. These findings represent a theoretical proof that the exposure frequency to different spatial information during a learning/adaptive history could produce agents with no modular neuro-cognitive systems that are able to process different types of spatial information and display various orientation behaviors (geometric primacy, non-geometric primacy, no primacy at all). PMID:19582489

Ponticorvo, Michela; Miglino, Orazio

2010-01-01

273

Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin  

NASA Astrophysics Data System (ADS)

In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the ?* and ?* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

2013-01-01

274

Excited-state intramolecular hydrogen bonding of compounds based on 2-(2-hydroxyphenyl)-1,3-benzoxazole in solution: a TDDFT study.  

PubMed

The excited-state properties of intramolecular hydrogen bonding in the compounds based on 2-(2-hydroxyphenyl)-1,3-benzoxazole (6 and its tautomers 6a and 6b) have been investigated using theoretical methods. According to the geometric optimization and IR spectra in the ground and excited states calculated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods respectively, the type of intramolecular hydrogen bonding N?HO in 6 and 6a is demonstrated to be significantly strengthened, while NH?O in the tautomers 6a and 6b are proved to be sharply weakened upon excitation to excited state S1. The calculated absorption peaks of 6 are in good accordance with the experimental results. Moreover, other compounds based on 6 that R1 and R2 are both substituted as well as that only R1 is substituted are investigated to understand the effect of substituent on intramolecular hydrogen bonding. It is found that the hydrogen bond strength can be controlled by the inductive field effect of the substituent. In addition, the intramolecular charge transfers (ICT) of the S1 state for 6 and its tautomers 6a and 6b were theoretically investigated by analyses of molecular orbital. PMID:25000569

Li, Hui; Liu, Yufang; Yang, Yonggang; Yang, Dapeng; Sun, Jinfeng

2014-12-10

275

Geometric and Electronic Structures of Manganese-substituted Iron Superoxide Dismutase  

PubMed Central

The active-site structures of the oxidized and reduced forms of manganese-substituted iron superoxide dismutase (Mn(Fe)SOD) are examined, for the first time, using a combination of spectroscopic and computational methods. On the basis of electronic absorption, circular dichrosim (CD), magnetic CD (MCD), and variable-temperature variable-field MCD data obtained for oxidized Mn(Fe)SOD, we propose that the active site of this species is virtually identical to that of wild-type manganese SOD (MnSOD), both containing a metal ion that resides in a trigonal bipyramidal ligand environment. This proposal is corroborated by quantum mechanical / molecular mechanical (QM/MM) computations performed on complete protein models of Mn(Fe)SOD in both its oxidized and reduced states and, for comparison, wild-type (WT) MnSOD. The major differences between the QM/MM optimized active sites of WT MnSOD and Mn(Fe)SOD are a smaller (His)NMnN(His) equatorial angle and a longer (Gln146(69))NH?O(sol) H-bond distance in the metal-substituted protein. Importantly, these modest geometric differences are consistent with our spectroscopic data obtained for the oxidized proteins and high-field electron paramagnetic resonance spectra reported previously for reduced Mn(Fe)SOD and MnSOD. As Mn(Fe)SOD exhibits a reduction midpoint potential (Em) almost 700 mV higher than that of MnSOD, which has been shown to be sufficient for explaining the lack of SOD activity displayed by the metal-subtituted species (Vance, C. K.; Miller, A. F. Biochemistry 2001, 40, 1307913087), Ems were computed for our experimentally validated QM/MM optimized models of Mn(Fe)SOD and MnSOD. These computations properly reproduce the experimental trend and reveal that the drastically elevated Em of the metal substituted protein stems from a larger separation between the second-sphere Gln residue and the coordinated solvent in Mn(Fe)SOD relative to MnSOD, which causes a weakening of the corresponding H-bond interaction in the oxidized state and alleviates steric crowding in the reduced state. PMID:23461587

Jackson, Timothy A.; Gutman, Craig T.; Maliekal, James; Miller, Anne-Frances; Brunold, Thomas C.

2013-01-01

276

Anodic bonded graphene  

Microsoft Academic Search

We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the

Adrian Balan; Rakesh Kumar; Mohamed Boukhicha; Olivier Beyssac; Jean-Claude Bouillard; Dario Taverna; William Sacks; Massimiliano Marangolo; Emanuelle Lacaze; Roger Gohler; Walter Escoffier; Jean-Marie Poumirol; Abhay Shukla

2010-01-01

277

The Sibling Bond.  

ERIC Educational Resources Information Center

The relationships among brothers and sisters are infinitely varied, but whatever their characteristics, these bonds last throughout life. This book examines the sibling relationship as a distinctive emotional, passionate, painful, and solacing power. Chapter 1, "Unraveling the Sibling Bond," addresses research on siblings and development of the

Bank, Stephen P.; Kahn, Michael D.

278

Measuring Abnormal Bond Performance  

Microsoft Academic Search

We analyze the empirical power and specification of test statistics designed to detect abnormal bond returns in corporate event studies, using monthly and daily data. We find that test statistics based on frequently used methods of calculating abnormal monthly bond returns are biased. Most methods implemented in monthly data also lack power to detect abnormal returns. We also consider unique

Hendrik Bessembinder; Kathleen M. Kahle; William F. Maxwell; Danielle Xu

2009-01-01

279

Water's Hydrogen Bond Strength  

Microsoft Academic Search

Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less

Martin Chaplin

2007-01-01

280

Interactive Pi Bonding Effects  

NSDL National Science Digital Library

This application demonstrates the effect of pi bonding on the one-electron ligand field splitting in an octahedral. By clicking on the appropriate buttons students can see how D changes when you move from ligands with no pi bonding capability to pi donor and pi acceptor ligands.

281

Mirror profile optimization for nano-focusing KB mirror  

SciTech Connect

A KB focusing mirror width profile has been optimized to achieve nano-focusing for the nano-imaging end-station ID22NI at the ESRF. The complete mirror and flexure bender assembly has been modeled in 3D with finite element analysis using ANSYS. Bender stiffness, anticlastic effects and geometrical non-linear effects have been considered. Various points have been studied: anisotropy and crystal orientation, stress in the mirror and bender, actuator resolution and the mirror-bender adhesive bonding... Extremely high performance of the mirror is expected with residual slope error smaller than 0.6 {mu}rad, peak-to-valley, compared to the bent slope of 3000 {mu}rad.

Zhang Lin; Baker, Robert; Barrett, Ray; Cloetens, Peter; Dabin, Yves [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex (France)

2010-06-23

282

Wood Bond Testing  

NASA Astrophysics Data System (ADS)

A joint development program between Hartford Steam Boiler Inspection Technologies and The Weyerhaeuser Company resulted in an internal bond analyzer (IBA), a device which combines ultrasonics with acoustic emission testing techniques. It is actually a spinoff from a spinoff, stemming from a NASA Lewis invented acousto-ultrasonic technique that became a system for testing bond strength of composite materials. Hartford's parent company, Acoustic Emission Technology Corporation (AET) refined and commercialized the technology. The IBA builds on the original system and incorporates on-line process control systems. The IBA determines bond strength by measuring changes in pulsar ultrasonic waves injected into a board. Analysis of the wave determines the average internal bond strength for the panel. Results are displayed immediately. Using the system, a mill operator can adjust resin/wood proportion, reduce setup time and waste, produce internal bonds of a consistent quality and automatically mark deficient products.

1989-01-01

283

Ultrasonically bonded value assembly  

NASA Technical Reports Server (NTRS)

A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.

Salvinski, R. J. (inventor)

1975-01-01

284

Optimal domain decomposition strategies  

NASA Technical Reports Server (NTRS)

The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.

Yoon, Yonghyun; Soni, Bharat K.

1995-01-01

285

Geometric Quantization and Foliation Reduction  

NASA Astrophysics Data System (ADS)

A standard question in the study of geometric quantization is whether symplectic reduction interacts nicely with the quantized theory, and in particular whether "quantization commutes with reduction." Guillemin and Sternberg first proposed this question, and answered it in the affirmative for the case of a free action of a compact Lie group on a compact Kahler manifold. Subsequent work has focused mainly on extending their proof to non-free actions and non-Kahler manifolds. For realistic physical examples, however, it is desirable to have a proof which also applies to non-compact symplectic manifolds. In this thesis we give a proof of the quantization-reduction problem for general symplectic manifolds. This is accomplished by working in a particular wavefunction representation, associated with a polarization that is in some sense compatible with reduction. While the polarized sections described by Guillemin and Sternberg are nonzero on a dense subset of the Kahler manifold, the ones considered here are distributional, having support only on regions of the phase space associated with certain quantized, or "admissible", values of momentum. We first propose a reduction procedure for the prequantum geometric structures that "covers" symplectic reduction, and demonstrate how both symplectic and prequantum reduction can be viewed as examples of foliation reduction. Consistency of prequantum reduction imposes the above-mentioned admissibility conditions on the quantized momenta, which can be seen as analogues of the Bohr-Wilson-Sommerfeld conditions for completely integrable systems. We then describe our reduction-compatible polarization, and demonstrate a one-to-one correspondence between polarized sections on the unreduced and reduced spaces. Finally, we describe a factorization of the reduced prequantum bundle, suggested by the structure of the underlying reduced symplectic manifold. This in turn induces a factorization of the space of polarized sections that agrees with its usual decomposition by irreducible representations, and so proves that quantization and reduction do indeed commute in this context. A significant omission from the proof is the construction of an inner product on the space of polarized sections, and a discussion of its behavior under reduction. In the concluding chapter of the thesis, we suggest some ideas for future work in this direction.

Skerritt, Paul

286

Geometric asymmetry driven Janus micromotors  

NASA Astrophysics Data System (ADS)

The production and application of nano-/micromotors is of great importance. In order for the motors to work, asymmetry in their chemical composition or physical geometry must be present if no external asymmetric field is applied. In this paper, we present a ``coconut'' micromotor made of platinum through the partial or complete etching of the silica templates. It was shown that although both the inner and outer surfaces are made of the same material (Pt), motion of the structure can be observed as the convex surface is capable of generating oxygen bubbles. This finding shows that not only the chemical asymmetry of the micromotor, but also its geometric asymmetry can lead to fast propulsion of the motor. Moreover, a considerably higher velocity can be seen for partially etched coconut structures than the velocities of Janus or fully etched, shell-like motors. These findings will have great importance on the design of future micromotors.The production and application of nano-/micromotors is of great importance. In order for the motors to work, asymmetry in their chemical composition or physical geometry must be present if no external asymmetric field is applied. In this paper, we present a ``coconut'' micromotor made of platinum through the partial or complete etching of the silica templates. It was shown that although both the inner and outer surfaces are made of the same material (Pt), motion of the structure can be observed as the convex surface is capable of generating oxygen bubbles. This finding shows that not only the chemical asymmetry of the micromotor, but also its geometric asymmetry can lead to fast propulsion of the motor. Moreover, a considerably higher velocity can be seen for partially etched coconut structures than the velocities of Janus or fully etched, shell-like motors. These findings will have great importance on the design of future micromotors. Electronic supplementary information (ESI) available: Additional SEM images, data analysis, Videos S-1 and S-2. See DOI: 10.1039/c4nr02393e

Zhao, Guanjia; Pumera, Martin

2014-09-01

287

Optical bonding reinforced by femtosecond laser welding  

NASA Astrophysics Data System (ADS)

Previous work on welding of optical materials with ultrashort laser pulses demonstrated that the ability to achieve good contact between components limits the applicability of the technology to only very small components. We have overcome this limitation and demonstrated the capability to weld similar and dissimilar materials using femtosecond laser pulses over several mm2 areas between intimately contacted surfaces. Our joining process is realised in two steps. Firstly, the two pieces which must be joined are direct bonded, thereby inducing optical contact throughout the whole potentially bondable surface. Subsequently, the direct bond is reinforced by the inscription of femtosecond laser weld seams in a sealing pattern in order to enclose the central region of the direct bond. We demonstrated the applicability of this process to identical glass, dissimilar glass and glass-semiconductor. We also measured a mean threefold increase in joint strength for such bonds between fused silica windows with only a few welding seams. The final assembly is free from macroscopic surface deformations. Furthermore, by optimizing the laser exposure parameters, we can avoid microscopic defects inside and around weld seams. Finally, the bonding method does not alter the optical transmission properties at the center of the sealed region. As opposed to the use of adhesives, such bonds resist to important thermal constraints and are free from chemical contaminants, degassing and ageing. Potential applications may be considered in the fields of aerospace, laser manufacturing, semiconductor industry, solar cell protection, precision manufacturing and many more.

Lacroix, Fabrice; Hlie, David; Valle, Ral

2011-09-01

288

Design Optimization and Development of Linear Brushless Permanent Magnet Motor  

Microsoft Academic Search

A method of design optimization for minimization of force ripple and maximization of thrust force in a linear brushless permanent magnet motor without finite element analysis is represented. The design optimization method calculated the driving force in the function of electric and geometric parameters of a linear brushless PM motor using the sequential quadratic programming method. Using electric and geometric

Myung-Jin Chung; Dae-Gab Gweon

2003-01-01

289

Hybrid Particle Swarm - Evolutionary Algorithm for Search and Optimization  

Microsoft Academic Search

Particle Swarm Optimization (PSO) technique has proved its ability to deal with very complicated optimization and search prob- lems. Several variants of the original algorithm have been proposed. This paper proposes a novel hybrid PSO - evolutionary algorithm for solving the well known geometrical place problems. Finding the geometrical place could be sometimes a hard task. In almost all situations

Crina Grosan; Ajith Abraham; Sangyong Han; Alexander F. Gelbukh

2005-01-01

290

GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES  

E-print Network

GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES A.N. LASENBY AND C.J.L. DORAN Astrophysics describe some applications of geometric algebra to the field of black hole physics. Our main focus is on the proper- ties of Dirac wavefunctions around black holes. We show the existence of normalised bound state

Cambridge, University of

291

Early Sex Differences in Weighting Geometric Cues  

ERIC Educational Resources Information Center

When geometric and non-geometric information are both available for specifying location, men have been shown to rely more heavily on geometry compared to women. To shed insight on the nature and developmental origins of this sex difference, we examined how 18- to 24-month-olds represented the geometry of a surrounding (rectangular) space when

Lourenco, Stella F.; Addy, Dede; Huttenlocher, Janellen; Fabian, Lydia

2011-01-01

292

Geometric Phases for Mixed States in Interferometry  

Microsoft Academic Search

We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed state reduces to well

Erik Sjqvist; Arun K. Pati; Artur Ekert; Jeeva S. Anandan; Marie Ericsson; Daniel K. L. Oi; Vlatko Vedral

2000-01-01

293

Geometric Information Criterion for Model Selection  

Microsoft Academic Search

In building a 3-D model of the environment from image and sensor data, one must fit to the data an appropriate class of models, which can be regarded as a parametrized manifold, or geometric model, defined in the data space. In this paper, we present a statistical framework for detecting degeneracies of a geometric model by evaluating its predictive capability

Kenichi Kanatani

1998-01-01

294

Parabolas: Connection between Algebraic and Geometrical Representations  

ERIC Educational Resources Information Center

A parabola is an interesting curve. What makes it interesting at the secondary school level is the fact that this curve is presented in both its contexts: algebraic and geometric. Being one of Apollonius' conic sections, the parabola is basically a geometric entity. It is, however, typically known for its algebraic characteristics, in particular

Shriki, Atara

2011-01-01

295

Sensor alignment using rotors in Geometric Algebra  

Microsoft Academic Search

This paper uses rotors in Geometric Algebra to formulate a stable adaptive identifier on the group of rigid body rotations. This identifier is intended to estimate the alignment offsets between independent sensors. The approach provides a straightforward geometric interpretation based on first-order rotor kinematics. Lyapunov theory is used to prove the sta- bility of the identifier, and numerical simulations illustrate

M. Jordan Stanway; James C. Kinsey

2011-01-01

296

Geometrical Spinoptics and the Optical Hall Effect  

E-print Network

Geometrical optics is extended so as to provide a model for spinning light rays via the coadjoint orbits of the Euclidean group characterized by color and spin. This leads to a theory of ``geometrical spinoptics'' in refractive media. Symplectic scattering yields generalized Snell-Descartes laws that include the recently discovered optical Hall effect.

Christian Duval; Zalan Horvath; Peter Horvathy

2005-09-14

297

LOCALLY HOMOGENEOUS RIGID GEOMETRIC STRUCTURES ON SURFACES  

E-print Network

LOCALLY HOMOGENEOUS RIGID GEOMETRIC STRUCTURES ON SURFACES SORIN DUMITRESCU Abstract. We study locally homogeneous rigid geometric structures on surfaces. We show that a locally homogeneous projective connection on a compact surface is flat. We also show that a locally homogeneous unimodular affine connection

Boyer, Edmond

298

Geometric frustration in compositionally modulated ferroelectrics  

Microsoft Academic Search

Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry. Geometric frustration gives rise to new fundamental phenomena and is known to yield intriguing effects such as the formation of exotic states like spin ice, spin liquids and spin glasses. It has also led to interesting findings of fractional

Narayani Choudhury; Laura Walizer; Sergey Lisenkov; L. Bellaiche

2011-01-01

299

Geometric frustration in buckled colloidal monolayers  

Microsoft Academic Search

Geometric frustration arises when lattice structure prevents simultaneous minimization of local interaction energies. It leads to highly degenerate ground states and, subsequently, to complex phases of matter, such as water ice, spin ice, and frustrated magnetic materials. Here we report a simple geometrically frustrated system composed of closely packed colloidal spheres confined between parallel walls. Diameter-tunable microgel spheres are self-assembled

Yilong Han; Yair Shokef; Ahmed M. Alsayed; Peter Yunker; Tom C. Lubensky; Arjun G. Yodh

2008-01-01

300

Hierarchical geometric models for visible surface algorithms  

Microsoft Academic Search

The geometric structure inherent in the definition of the shapes of three-dimensional objects and environments is used not just to define their relative motion and placement, but also to assist in solving many other problems of systems for producing pictures by computer. By using an extension of traditional structure information, or a geometric hierarchy, five significant improvements to current techniques

James H. Clark

1976-01-01

301

Monotonicity and its analytic and geometric implications  

PubMed Central

In this expository article, we discuss various monotonicity formulas for parabolic and elliptic operators and explain how the analysis of function spaces and the geometry of the underlining spaces are intertwined. After briefly discussing some of the well-known analytical applications of monotonicity for parabolic operators, we turn to their elliptic counterparts, their geometric meaning, and some geometric consequences.

Colding, Tobias Holck; Minicozzi, William P.

2013-01-01

302

Mobile robot localization by tracking geometric beacons  

Microsoft Academic Search

The application of the extended Kaman filter to the problem of mobile robot navigation in a known environment is presented. An algorithm for, model-based localization that relies on the concept of a geometric beacon, a naturally occurring environment feature that can be reliably observed in successive sensor measurements and can be accurately described in terms of a concise geometric parameterization,

John J. Leonard; Hugh F. Durrant-Whyte

1991-01-01

303

Geometric algebra and particle dynamics  

E-print Network

In a recent publication the I showed how the geometric algebra ${G}_{4,1}$, the algebra of 5-dimensional space-time, can generate relativistic dynamics from the simple principle that only null geodesics should be allowed. The same paper showed also that Dirac equation could be derived from the condition that a function should be monogenic in that algebra; this construction of the Dirac equation allows a choice for the imaginary unit and it was suggested that different imaginary units could be assigned to the various elementary particles. An earlier paper had already shown the presence of standard model gauge group symmetry in complexified ${G}_{1,3}$, an algebra isomorphic to ${G}_{4,1}$. In this presentation I explore the possible choices for the imaginary unit in the Dirac equation to show that SU(3) and SU(2) symmetries arise naturally from such choices. The quantum numbers derived from the imaginary units are unusual but a simple conversion allows the derivation of electric charge and isospin, quantum numbers for two families of particles. This association to elementary particles is not final because further understanding of the role played by the imaginary unit is needed.

Jose B. Almeida

2005-04-01

304

Geometrical aspects of quantum spaces  

SciTech Connect

Various geometrical aspects of quantum spaces are presented showing the possibility of building physics on quantum spaces. In the first chapter the authors give the motivations for studying noncommutative geometry and also review the definition of a Hopf algebra and some general features of the differential geometry on quantum groups and quantum planes. In Chapter 2 and Chapter 3 the noncommutative version of differential calculus, integration and complex structure are established for the quantum sphere S{sub 1}{sup 2} and the quantum complex projective space CP{sub q}(N), on which there are quantum group symmetries that are represented nonlinearly, and are respected by all the aforementioned structures. The braiding of S{sub q}{sup 2} and CP{sub q}(N) is also described. In Chapter 4 the quantum projective geometry over the quantum projective space CP{sub q}(N) is developed. Collinearity conditions, coplanarity conditions, intersections and anharmonic ratios is described. In Chapter 5 an algebraic formulation of Reimannian geometry on quantum spaces is presented where Riemannian metric, distance, Laplacian, connection, and curvature have their quantum counterparts. This attempt is also extended to complex manifolds. Examples include the quantum sphere, the complex quantum projective space and the two-sheeted space. The quantum group of general coordinate transformations on some quantum spaces is also given.

Ho, P.M. [Lawrence Berkeley Lab., CA (United States). Theoretical Physics Group

1996-05-11

305

Geometric precipices in string cosmology  

SciTech Connect

We consider the effects of graviton multiplet fields on transitions between string gas phases. Focusing on the dilaton field, we show that it may obstruct transitions between different thermodynamic phases of the string gas, because the sign of its dimensionally reduced, T-duality invariant, part is conserved when the energy density of the Universe is positive. Thus, many interesting solutions for which this sign is positive end up in a future curvature singularity. Because of this, some of the thermodynamic phases of the usual gravitating string gases behave like superselection sectors. For example, a past-regular Hagedorn phase and an expanding Friedmann-Robertson-Walker (FRW) phase dominated by string momentum modes cannot be smoothly connected in the framework of string cosmology with positive sources. The singularity separates them like a geometric precipice in the moduli space, preventing the dynamics of the theory from bridging across. Sources which simultaneously violate the positivity of energy and null energy condition (NEC) could modify these conclusions. We provide a quantitative measure of positivity of energy and NEC violations that would be necessary for such transitions. These effects must dominate the Universe at the moment of transition, altering the standard gas pictures. At present, it is not known how to construct such sources from first principles in string theory.

Kaloper, Nemanja [Department of Physics, University of California, Davis, California 95616 (United States); Watson, Scott [Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2008-03-15

306

Geometric morphology of cellular solids  

SciTech Connect

We demonstrate how to derive morphological information from micrographs, i.e., grey-level images, of polymeric foams. The segmentation of the images is performed by applying a pulse-coupled neural network. This processing generates blobs of the foams walls/struts and voids, respectively. The contours of the blobs and their corresponding points form the input to a constrained Delaunay tessellation, which provides an unstructured grid of the material under consideration. The subsequently applied Chordal Axis Transform captures the intrinsic shape characteristics, and facilitates the identification and localization of key morphological features. While stochastic features of the polymeric foams struts/walls such as areas, aspect ratios, etc., already can be computed at this stage, the foams voids require further geometric processing. The voids are separated into single foam cells. This shape manipulation leads to a refinement of the initial blob contours, which then requires the repeated application of the constrained Delaunay tessellation and Chordal Axis Transform, respectively. Using minimum enclosing rectangles for each foam cell, finally the stochastic features of the foam voids are computed.

Schlei, B. R. (Bernd R.); Prasad, L. (Lakshaman); Skourikhine, A. N. (Alexei N.)

2001-01-01

307

Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications  

NASA Technical Reports Server (NTRS)

A robust joining approach is critically needed for a Micro-Electro-Mechanical Systems-Lean Direct Injector (MEMS-LDI) application which requires leak free joints with high temperature mechanical capability. Diffusion bonding is well suited for the MEMS-LDI application. Diffusion bonds were fabricated using titanium interlayers between silicon carbide substrates during hot pressing. The interlayers consisted of either alloyed titanium foil or physically vapor deposited (PVD) titanium coatings. Microscopy shows that well adhered, crack free diffusion bonds are formed under optimal conditions. Under less than optimal conditions, microcracks are present in the bond layer due to the formation of intermetallic phases. Electron microprobe analysis was used to identify the reaction formed phases in the diffusion bond. Various compatibility issues among the phases in the interlayer and substrate are discussed. Also, the effects of temperature, pressure, time, silicon carbide substrate type, and type of titanium interlayer and thickness on the microstructure and composition of joints are discussed.

Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, J. Douglas

2007-01-01

308

Geometric Analogue of Holographic Reduced Representation  

E-print Network

Holographic reduced representations (HRR) are based on superpositions of convolution-bound $n$-tuples, but the $n$-tuples cannot be regarded as vectors since the formalism is basis dependent. This is why HRR cannot be associated with geometric structures. Replacing convolutions by geometric products one arrives at reduced representations analogous to HRR but interpretable in terms of geometry. Variable bindings occurring in both HRR and its geometric analogue mathematically correspond to two different representations of $Z_2\\times...\\times Z_2$ (the additive group of binary $n$-tuples with addition modulo 2). As opposed to standard HRR, variable binding performed by means of geometric product allows for computing exact inverses of all nonzero vectors, a procedure even simpler than approximate inverses employed in HRR. The formal structure of the new reduced representation is analogous to cartoon computation, a geometric analogue of quantum computation.

Aerts, Diederik; De Moor, Bart

2007-01-01

309

Geometric Analogue of Holographic Reduced Representation  

E-print Network

Holographic reduced representations (HRR) are based on superpositions of convolution-bound $n$-tuples, but the $n$-tuples cannot be regarded as vectors since the formalism is basis dependent. This is why HRR cannot be associated with geometric structures. Replacing convolutions by geometric products one arrives at reduced representations analogous to HRR but interpretable in terms of geometry. Variable bindings occurring in both HRR and its geometric analogue mathematically correspond to two different representations of $Z_2\\times...\\times Z_2$ (the additive group of binary $n$-tuples with addition modulo 2). As opposed to standard HRR, variable binding performed by means of geometric product allows for computing exact inverses of all nonzero vectors, a procedure even simpler than approximate inverses employed in HRR. The formal structure of the new reduced representation is analogous to cartoon computation, a geometric analogue of quantum computation.

Diederik Aerts; Marek Czachor; Bart De Moor

2007-10-15

310

Chemical Bonding, again ionic bonding (in salts): transfer of e-  

E-print Network

Chemical Bonding, again · ionic bonding (in salts): transfer of e- · covalent bonding (organicJ/mol Li+ (g) + F¯ (g) #12;The Covalent Bond H H HH+ HHH · + · H ! H : H Lewis electron-dot structures single bond, a shared pair of electrons The Covalent Bond H H HH+ HH #12;E N E R G Y kJ/mol distance 74

Zakarian, Armen

311

Bonding and solvation preferences of nickel complexes [Ni(S 2PR 2) 2] (R=H, Me, OMe) according a natural bond orbital analysis  

Microsoft Academic Search

Calculations based on density functional methods (DFT) are carried out for the dithiophosphorus nickel complexes of the type [Ni(S2PR2)2] where R=H, Me and OMe. Geometrical parameters obtained by the calculation are in good agreement with reported X-ray structure. A Natural Bond Orbital analysis indicates that the NiS bond is mainly governed by charge transfer via a strong delocalization of the

Alexis Otero-Calvi; Gabriel Aullon; Santiago Alvarez; Luis A. Montero; Wolf-Dieter Stohrer

2006-01-01

312

Kissing bonds A kissing bond is adhesively bonded but holds little of the strength usually  

E-print Network

Kissing bonds · A kissing bond is adhesively bonded but holds little of the strength usually weight saving and excellent stress transfer. · The ability to reliably assess defects in adhesive bonds · To develop a non destructive method to assess the integrity of adhesive bonds using pulsed phase thermography

Sóbester, András

313

Recognition of Watson-Crick base pairs: constraints and limits due to geometric selection and tautomerism  

PubMed Central

The natural bases of nucleic acids have a strong preference for one tautomer form, guaranteeing fidelity in their hydrogen bonding potential. However, base pairs observed in recent crystal structures of polymerases and ribosomes are best explained by an alternative base tautomer, leading to the formation of base pairs with Watson-Crick-like geometries. These observations set limits to geometric selection in molecular recognition of complementary Watson-Crick pairs for fidelity in replication and translation processes. PMID:24765524

Yusupov, Marat; Yusupova, Gulnara

2014-01-01

314

Predicting Crystalline Packing Arrangements of Molecules That Form Hydrogen-Bonded Tapes  

E-print Network

Predicting Crystalline Packing Arrangements of Molecules That Form Hydrogen-Bonded Tapes Donovan N Monte Carlo (SAMC) was used to predict the crystal structures of hydrogen-bonded organic molecules that form molecular tapes. This procedure was optimized to select structures with good hydrogen-bond

Prentiss, Mara

315

Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC Donald J. Siegel  

E-print Network

Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC Donald J. Siegel yield substantial adhesion energies in the range 4­6 J/m¢ , bonding at the optimal C of an interface is the ideal work of adhesion,£¥¤§¦ [1], which is defined as the bond energy needed (per unit area

Adams, James B

316

Gold Thermocompression Wafer Bonding  

E-print Network

Thermocompression bonding of gold is a promising technique for the fabrication and packaging microelectronic and MEMS devices. The use of a gold interlayer and moderate temperatures and pressures results in a hermetic, ...

Spearing, S. Mark

317

Characterization of anodic bonding  

E-print Network

Anodic bonding is a common process used in MicroElectroMechanical Systems (MEMS) device fabrication and packaging. Polycrystalline chemical vapor deposited (CVD) silicon carbide (SiC) is emerging as a new MEMS device and ...

Tudryn, Carissa Debra, 1978-

2004-01-01

318

Diffusion Bonding of Silicon Carbide Ceramics using Titanium Interlayers  

NASA Technical Reports Server (NTRS)

Robust joining approaches for silicon carbide ceramics are critically needed to fabricate leak free joints with high temperature mechanical capability. In this study, titanium foils and physical vapor deposited (PVD) titanium coatings were used to form diffusion bonds between SiC ceramics using hot pressing. Silicon carbide substrate materials used for bonding include sintered SiC and two types of CVD SiC. Microscopy results show the formation of well adhered diffusion bonds. The bond strengths as determined from pull tests are on the order of several ksi, which is much higher than required for a proposed application. Microprobe results show the distribution of silicon, carbon, titanium, and other minor elements across the diffusion bond. Compositions of several phases formed in the joint region were identified. Potential issues of material compatibility and optimal bond formation will also be discussed.

Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, James D.

2006-01-01

319

Ideally glassy hydrogen-bonded networks  

NASA Astrophysics Data System (ADS)

The axiomatic theory of ideally glassy networks, which has proved effective in describing phase diagrams and properties of chalcogenide and oxide glasses and their foreign interfaces, is broadened here to include intermolecular interactions in hydrogen-bonded polyalcohols such as glycerol, monosaccharides (glucose), and the optimal bioprotective hydrogen-bonded disaccharide networks formed from trehalose. The methods of Lagrangian mechanics and Maxwellian scaffolds are useful at the molecular level when bonding hierarchies are characterized by constraint counting similar to the chemical methods used by Huckel and Pauling. Whereas Newtonian molecular dynamical methods are useful for simulating large-scale interactions for times of order 10ps , constraint counting describes network properties on glassy (almost equilibrated) time scales which may be of cosmological order for oxide glasses or years for trehalose. The ideally glassy network of trehalose may consist of extensible tandem sandwich arrays.

Phillips, J. C.

2006-01-01

320

All about Chemical Bonding  

NSDL National Science Digital Library

Stephen Lower, a retired professor at Simon Fraser University, created this expansive and instructive website as a supplement to formal chemistry education for undergraduate students. Visitors will find in-depth descriptions along with several diagrams dealing with chemical bonding issues including their properties, shared-electron covalent bonds, hybrid orbitals, coordination complexes, and metals and semiconductors. General chemistry students looking for assistance should visit this well-developed educational site.

Lower, Stephen

321

On geometric factors for neutral particle analyzersa)  

NASA Astrophysics Data System (ADS)

Neutral particle analyzers (NPA) detect neutralized energetic particles that escape from plasmas. Geometric factors relate the counting rate of the detectors to the intensity of the particle source. Accurate geometric factors enable quick simulation of geometric effects without the need to resort to slower Monte Carlo methods. Previously derived expressions [G. R. Thomas and D. M. Willis, "Analytical derivation of the geometric factor of a particle detector having circular or rectangular geometry," J. Phys. E: Sci. Instrum. 5(3), 260 (1972); J. D. Sullivan, "Geometric factor and directional response of single and multi-element particle telescopes," Nucl. Instrum. Methods 95(1), 5-11 (1971)] for the geometric factor implicitly assume that the particle source is very far away from the detector (far-field); this excludes applications close to the detector (near-field). The far-field assumption does not hold in most fusion applications of NPA detectors. We derive, from probability theory, a generalized framework for deriving geometric factors that are valid for both near and far-field applications as well as for non-isotropic sources and nonlinear particle trajectories.

Stagner, L.; Heidbrink, W. W.

2014-11-01

322

Geometric frustration in compositionally modulated ferroelectrics.  

PubMed

Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry. Geometric frustration gives rise to new fundamental phenomena and is known to yield intriguing effects such as the formation of exotic states like spin ice, spin liquids and spin glasses. It has also led to interesting findings of fractional charge quantization and magnetic monopoles. Mechanisms related to geometric frustration have been proposed to understand the origins of relaxor and multiferroic behaviour, colossal magnetocapacitive coupling, and unusual and novel mechanisms of high-transition-temperature superconductivity. Although geometric frustration has been particularly well studied in magnetic systems in the past 20 years or so, its manifestation in the important class formed by ferroelectric materials (which are compounds with electric rather than magnetic dipoles) is basically unknown. Here we show, using a technique based on first principles, that compositionally graded ferroelectrics possess the characteristic 'fingerprints' associated with geometric frustration. These systems have a highly degenerate energy surface and display critical phenomena. They further reveal exotic orderings with novel stripe phases involving complex spatial organization. These stripes display spiral states, topological defects and curvature. Compositionally graded ferroelectrics can thus be considered the 'missing link' that brings ferroelectrics into the broad category of materials able to exhibit geometric frustration. Our ab initio calculations allow deep microscopic insight into this novel geometrically frustrated system. PMID:21307851

Choudhury, Narayani; Walizer, Laura; Lisenkov, Sergey; Bellaiche, L

2011-02-24

323

Brachytherapy seed localization using geometric and linear programming techniques.  

PubMed

We propose an optimization algorithm to solve the brachytherapy seed localization problem in prostate brachytherapy. Our algorithm is based on novel geometric approaches to exploit the special structure of the problem and relies on a number of key observations which help us formulate the optimization problem as a minimization integer program (IP). Our IP model precisely defines the feasibility polyhedron for this problem using a polynomial number of half-spaces; the solution to its corresponding linear program is rounded to yield an integral solution to our task of determining correspondences between seeds in multiple projection images. The algorithm is efficient in theory as well as in practice and performs well on simulation data (approximately 98% accuracy) and real X-ray images (approximately 95% accuracy). We present in detail the underlying ideas and an extensive set of performance evaluations based on our implementation. PMID:17896600

Singh, Vikas; Mukherjee, Lopamudra; Xu, Jinhui; Hoffmann, Kenneth R; Dinu, Petru M; Podgorsak, Matthew

2007-09-01

324

Water's Hydrogen Bond Strength  

E-print Network

Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures. The overall conclusion of this investigation is that water's hydrogen bond strength is poised centrally within a narrow window of its suitability for life.

Martin Chaplin

2007-06-10

325

Orthodontic bonded retainers.  

PubMed

Retention is usually necessary following orthodontic treatment to overcome the elastic recoil of the periodontal supporting fibres and to allow remodelling of the alveolar bone. The degree of change is variable and largely unpredictable. Bonded lingual retainers have been shown to be an effective means of retaining aligned anterior teeth in the post-treatment position in the long term. Two basic designs of lingual bonded retainers are currently in use. Rigid mandibular canine-to-canine retainers are attached to the canines only. They are effective in maintaining intercanine width but less so in preventing individual tooth rotations. Flexible spiral wire retainers are bonded to each tooth in the segment, their flexibility allowing for physiological movement of the teeth. This design is more effective at preventing rotation of the bonded teeth. Failure of bonded retainers may occur at the wire-composite interface, at the adhesive-enamel interface or as a stress fracture of the wire. Failure of a retainer may lead to unwanted tooth movement. In many cases it will be possible to repair the appliance in the mouth. However, in some instances it will be necessary to replace the retainer. A disadvantage of fixed retainers is that they complicate oral hygiene procedures, and favour the accumulation of plaque and calculus. Despite this, the presence of a bonded retainer appears to cause no increase in incidence of caries or periodontal disease. Use of interdental cleaning aids is required to ensure adequate oral hygiene. PMID:15789987

Butler, Jonathan; Dowling, Paul

2005-01-01

326

Geometric Particle Swarm Optimisation on Binary and Real Spaces: from Theory to Practice  

E-print Network

Chio Department of Computer Science University of Essex, UK cdichi@essex.ac.uk Alberto Moraglio Department of Computer Science University of Essex, UK amoragn@essex.ac.uk Riccardo Poli Department of Computer Science University of Essex, UK rpoli@essex.ac.uk ABSTRACT Geometric particle swarm optimization

Yao, Xin

327

The role of geometric constraints in amphiphilic self-assembly: A Brownian dynamics study  

E-print Network

The role of geometric constraints in amphiphilic self-assembly: A Brownian dynamics study Geuorgui simulation method to investigate the effect of optimal head group area in amphiphilic self temperatures. Likewise, for a given concentration, amphiphiles with the larger effective head group exhibit

Bhattacharya, Aniket

328

A Fast Method to Minimize L Error Norm for Geometric Vision Problems  

Microsoft Academic Search

Minimizing L? error norm for some geometric vision problems provides global optimization using the well- developed algorithm called SOCP (second order cone programming). Because the error norm belongs to quasi- convex functions, bisection method is utilized to attain the global optimum. It tests the feasibility of the intersection of all the second order cones due to measurements, repeatedly adjusting the

Yongduek Seo; Richard Hartley

2007-01-01

329

Fluxless eutectic bonding of GaAs-on-Si by using Ag/Sn solder  

NASA Astrophysics Data System (ADS)

Fluxless GaAs-on-Si wafer bonding using Ag/Sn solder was investigated to realize uniform and void-free heterogeneous material integration. The effects of the diffusion barrier, Ag/Sn thickness, and Ar plasma treatment were studied to achieve the optimal fluxless bonding process. Pt on a GaAs wafer and Mo on a Si wafer act as diffusion barriers by preventing the flow of Ag/Sn solder into both the wafers. The bonding strength is closely related to the Ag/Sn thickness and Ar plasma treatment. A shear strength test was carried out to investigate the bonding strength. Under identical bonding conditions, the Ag/Sn thickness was optimized to achieve higher bonding strength and to avoid the formation of voids due to thermal stress. An Ar plasma pretreatment process improved the bonding strength because the Ar plasma removed carbon contaminants and metal-oxide bonds from the metal surface.

Eo, Sung-Hwa; Kim, Dae-Seon; Jeong, Ho-Jung; Jang, Jae-Hyung

2013-11-01

330

True stabilization energies for the optimal planar hydrogen-bonded and stacked structures of guanine...cytosine, adenine...thymine, and their 9- and 1-methyl derivatives: complete basis set calculations at the MP2 and CCSD(T) levels and comparison with experiment.  

PubMed

Planar H-bonded and stacked structures of guanine...cytosine (G.C), adenine...thymine (A...T), 9-methylguanine...1-methylcytosine (mG...mC), and 9-methyladenine...1-methylthymine (mA...mT) were optimized at the RI-MP2 level using the TZVPP ([5s3p2d1f/3s2p1d]) basis set. Planar H-bonded structures of G...C, mG...mC, and A...T correspond to the Watson-Crick (WC) arrangement, in contrast to mA...mT for which the Hoogsteen (H) structure is found. Stabilization energies for all structures were determined as the sum of the complete basis set limit of MP2 energies and a (DeltaE(CCSD(T)) - DeltaE(MP2)) correction term evaluated with the cc-pVDZ(0.25,0.15) basis set. The complete basis set limit of MP2 energies was determined by two-point extrapolation using the aug-cc-pVXZ basis sets for X = D and T and X = T and Q. This procedure is required since the convergency of the MP2 interaction energy for the present complexes is rather slow, and it is thus important to include the extrapolation to the complete basis set limit. For the MP2/aug-cc-pVQZ level of theory, stabilization energies for all complexes studied are already very close to the complete basis set limit. The much cheaper D-->T extrapolation provided a complete basis set limit close (by less than 0.7 kcal/mol) to the more accurate T-->Q term, and the D-->T extrapolation can be recommended for evaluation of complete basis set limits of more extended complexes (e.g. larger motifs of DNA). The convergency of the (DeltaE(CCSD(T)) - DeltaE(MP2)) term is known to be faster than that of the MP2 or CCSD(T) correlation energy itself, and the cc-pVDZ(0.25,0.15) basis set provides reasonable values for planar H-bonded as well as stacked structures. Inclusion of the CCSD(T) correction is essential for obtaining reliable relative values for planar H-bonding and stacking interactions; neglecting the CCSD(T) correction results in very considerable errors between 2.5 and 3.4 kcal/mol. Final stabilization energies (kcal/mol) for the base pairs studied are very substantial (A...T WC, 15.4; mA...mT H, 16.3; A...T stacked, 11.6; mA...mT stacked, 13.1; G...C WC, 28.8; mG...mC WC, 28.5; G...C stacked, 16.9; mG...mC stacked, 18.0), much larger than published previously. On the basis of comparison with experimental data, we conclude that our values represent the lower boundary of the true stabilization energies. On the basis of error analysis, we expect the present H-bonding energies to be fairly close to the true values, while stacked energies are still expected to be about 10% too low. The stacking energy for the mG...mC pair is considerably lower than the respective H-bonding energy, but it is larger than the mA...mT H-bonding energy. This conclusion could significantly change the present view on the importance of specific H-bonding interactions and nonspecific stacking interactions in nature, for instance, in DNA. Present stabilization energies for H-bonding and stacking energies represent the most accurate and reliable values and can be considered as new reference data. PMID:14664608

Jurecka, Petr; Hobza, Pavel

2003-12-17

331

Double-bond defect modelling in As-S glasses  

NASA Astrophysics Data System (ADS)

Ab initio calculations with the RHF/6-311G* basis set are used for geometrical optimization of regular pyramidal and defect quasi-tetrahedral clusters in binary As-S glasses. It is shown that quasi-tetrahedral S=AsS3/2 structural units are impossible as main network-building blocks in these glasses.

Boyko, V.; Shpotyuk, O.; Hyla, M.

2010-11-01

332

The construction of spinors in geometric algebra  

SciTech Connect

The relationship between spinors and Clifford (or geometric) algebra has long been studied, but little consistency may be found between the various approaches. However, when spinors are defined to be elements of the even subalgebra of some real geometric algebra, the gap among algebraic, geometric, and physical methods is closed. Spinors are developed in any number of dimensions from a discussion of spin groups, followed by the specific cases of U(1), SU(2), and SL(2,C) spinors. The physical observables in Schrodinger-Pauli theory and Dirac theory are found, and the relationship between Dirac, Lorentz, Weyl, and Majorana spinors is made explicit. The use of a real geometric algebra, as opposed to one defined over the complex numbers, provides a simpler construction and advantages of conceptual and theoretical clarity not available in other approaches.

Francis, Matthew R. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)]. E-mail: mfrancis@physics.rutgers.edu; Kosowsky, Arthur [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)]. E-mail: kosowsky@physics.rutgers.edu

2005-06-01

333

Geometric axioms for existentially closed Hasse fields  

E-print Network

Geometric axioms for existentially closed Hasse fields for existentially closed Hasse fields. We prove a quantifier elimination result for existentially closed n- truncated Hasse fields and characterize them as reducts of existentially closed Hasse fields. 0

Kowalski, Piotr

334

Curve sampling and geometric conditional simulation  

E-print Network

The main objective of this thesis is the development and exploitation of techniques to generate geometric samples for the purpose of image segmentation. A sampling-based approach provides a number of benefits over existing ...

Fan, Ayres C. (Ayres Chee), 1978-

2008-01-01

335

Geometric Mechanics -Part I January 13, 2009  

E-print Network

Geometric Mechanics - Part I Bob Rink January 13, 2009 Contents 1 Mechanical systems 4 1.1 Two Lagrangian mechanics 9 2.1 New position variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-Lagrange equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 Natural mechanical systems

Hanssmann, Heinz

336

A Pure Geometric Approach to Stellar Structure  

E-print Network

The present work represents a step to deal with stellar structure using a pure geometric approach. A geometric field theory is used to construct a model for a spherically symmetric configuration. The model obtained can be considered as a pure geometric one in the sense that the tensor describing the material distributions is not a phenomenological object, but a part of the geometric structure used. A general equation of state is obtained from, and not imposed on, the model. The solution obtained shows that there are different zones characterizing the configuration: a central radiation dominant zone, a probable convection zone as a physical interpretation of the singularity of the model and a corona like zone. The model may represent a type of main sequence stars. The present work shows that Einstein's geometerization scheme can be extended to gain more physical information within material distribution, with some advantages.

M. I. Wanas; Samah A. Ammar

2009-06-25

337

Geometric Photonic Spin Hall Effect with Metapolarization  

E-print Network

We develop a geometric photonic spin Hall effect (PSHE) which manifests as spin-dependent shift in momentum space. It originates from an effective space-variant Pancharatnam-Berry (PB) phase created by artificially engineering the polarization distribution of the incident light. Unlikely the previously reported PSHE involving the light-matter interaction, the resulting spin-dependent splitting in the geometric PSHE is purely geometrically depend upon the polarization distribution of light which can be tailored by assembling its circular polarization basis with suitably magnitude and phase. This metapolarization idea enables us to manipulate the geometric PSHE by suitably tailoring the polarization geometry of light. Our scheme provides great flexibility in the design of various polarization geometry and polarization-dependent application, and can be extrapolated to other physical system, such as electron beam or atom beam, with the similar spin-orbit coupling underlying.

Ling, Xiaohui; Yi, Xunong; Luo, Hailu; Wen, Shuangchun

2014-01-01

338

Lecture notes on "Geometric Mechanics and Dynamics"  

E-print Network

Lecture notes on "Geometric Mechanics and Dynamics" Bob Rink December 14, 2007 Contents 1 Mechanical systems 3 1.1 Two classical examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 One degree of freedom mechanical systems . . . . . . . . . . . . . . . . . . 5 1.3 More degrees

Rink, Bob

339

Geometrically robust perceptual fingerprinting: an asymmetric case  

E-print Network

Geometrically robust perceptual fingerprinting: an asymmetric case Oleksiy Koval, Sviatoslav investigate the impact of the fingerprint length on the error performance of these protocols relaxing. INTRODUCTION Recent advances in modern networking and multimedia technologies have open an access

Genève, Université de

340

Optimizing electrostatic field calculations with the Adaptive Poisson-Boltzmann Solver to predict electric fields at protein-protein interfaces II: explicit near-probe and hydrogen-bonding water molecules.  

PubMed

We have examined the effects of including explicit, near-probe solvent molecules in a continuum electrostatics strategy using the linear Poisson-Boltzmann equation with the Adaptive Poisson-Boltzmann Solver (APBS) to calculate electric fields at the midpoint of a nitrile bond both at the surface of a monomeric protein and when docked at a protein-protein interface. Results were compared to experimental vibrational absorption energy measurements of the nitrile oscillator. We examined three methods for selecting explicit water molecules: (1) all water molecules within 5 of the nitrile nitrogen; (2) the water molecule closest to the nitrile nitrogen; and (3) any single water molecule hydrogen-bonding to the nitrile. The correlation between absolute field strengths with experimental absorption energies were calculated and it was observed that method 1 was only an improvement for the monomer calculations, while methods 2 and 3 were not significantly different from the purely implicit solvent calculations for all protein systems examined. Upon taking the difference in calculated electrostatic fields and comparing to the difference in absorption frequencies, we typically observed an increase in experimental correlation for all methods, with method 1 showing the largest gain, likely due to the improved absolute monomer correlations using that method. These results suggest that, unlike with quantum mechanical methods, when calculating absolute fields using entirely classical models, implicit solvent is typically sufficient and additional work to identify hydrogen-bonding or nearest waters does not significantly impact the results. Although we observed that a sphere of solvent near the field of interest improved results for relative field calculations, it should not be consider a panacea for all situations. PMID:24446740

Ritchie, Andrew W; Webb, Lauren J

2014-07-17

341

Statistical Template Matching under Geometric Transformations  

Microsoft Academic Search

We present a novel template matching framework for detecting geometrically transformed objects. A template is a simplified\\u000a representation of the object of interest by a set of pixel groups of any shape, and the similarity between the template and\\u000a an image region is derived from the F-test statistic. The method selects a geometric transformation from a discrete set of\\u000a transformations,

Alexander Sibiryakov

2008-01-01

342

Machine Learning and Geometric Technique for SLAM  

NASA Astrophysics Data System (ADS)

This paper describes a new approach for building 3D geometric maps using a laser rangefinder, a stereo camera system and a mathematical system the Conformal Geometric Algebra. The use of a known visual landmarks in the map helps to carry out a good localization of the robot. A machine learning technique is used for recognition of objects in the environment. These landmarks are found using the Viola and Jones algorithm and are represented with their position in the 3D virtual map.

Bernal-Marin, Miguel; Bayro-Corrochano, Eduardo

343

Strength of Chemical Bonds  

NASA Technical Reports Server (NTRS)

Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.

Christian, Jerry D.

1973-01-01

344

Geometric phase in NMR interferometry experiment  

NASA Astrophysics Data System (ADS)

Experimental detection of geometric phase effects is based on interferometry techniques. The observation of a nonadiabatic geometric phase in nuclear magnetic resonance has been reported by D. Suter, K. T. Mueller, and A. Pines (1988, Phys. Rev. Lett., 60, 1218). A rigorous interpretation of their results is presented here. The experiment exploits the concept of fictitious spin-1/2 subsystems embedded in a spin system of higher order. A relevant expression for the geometric phase is derived here using the Euler rotation representation for the SU(2) group. In order to correlate the experimental data to the geometric phase, a decomposition of the density matrix in a basis of pure states is used and the isomorphism between the cyclic evolution of pure states and mixed states is constructed. Rigorous treatment of the dynamic phase, along with technical aspects of the experiment, shows that the observed echo shift is related directly to the geometric phase, in agreement with Suter et al. The observed geometric phase is classified as a frame-related phase.

Skrynnikov, N. R.; Sanctuary, B. C.

345

Graphene geometric diodes for terahertz rectennas  

NASA Astrophysics Data System (ADS)

We demonstrate a new thin-film graphene diode called a geometric diode that relies on geometric asymmetry to provide rectification at 28 THz. The geometric diode is coupled to an optical antenna to form a rectenna that rectifies incoming radiation. This is the first reported graphene-based antenna-coupled diode working at 28 THz, and potentially at optical frequencies. The planar structure of the geometric diode provides a low RC time constant, on the order of 10-15 s, required for operation at optical frequencies, and a low impedance for efficient power transfer from the antenna. Fabricated geometric diodes show asymmetric current-voltage characteristics consistent with Monte Carlo simulations for the devices. Rectennas employing the geometric diode coupled to metal and graphene antennas rectify 10.6 m radiation, corresponding to an operating frequency of 28 THz. The graphene bowtie antenna is the first demonstrated functional antenna made using graphene. Its response indicates that graphene is a suitable terahertz resonator material. Applications for this terahertz diode include terahertz-wave and optical detection, ultra-high-speed electronics and optical power conversion.

Zhu, Zixu; Joshi, Saumil; Grover, Sachit; Moddel, Garret

2013-05-01

346

Free vibration of functionally graded material beams with surface-bonded piezoelectric layers in thermal environment  

Microsoft Academic Search

Free vibration of statically thermal postbuckled functionally graded material (FGM) beams with surface-bonded piezoelectric\\u000a layers subject to both temperature rise and voltage is studied. By accurately considering the axial extension and based on\\u000a the Euler-Bernoulli beam theory, geometrically nonlinear dynamic governing equations for FGM beams with surface-bonded piezoelectric\\u000a layers subject to thermo-electromechanical loadings are formulated. It is assumed that the

Shi-rong Li; Hou-de Su; Chang-jun Cheng

2009-01-01

347

Relationship between fiber orientation distribution function and mechanical anisotropy of thermally point-bonded nonwovens  

Microsoft Academic Search

Current efforts to establish links between geometrical features and mechanical performance of nonwoven fabrics in general,\\u000a and of point-bonded (spot-bonded) nonwovens in particular has been made using the measurements of Fiber Orientation Distribution\\u000a Function (ODF) and tensile modulus which occurs during controlled-deformation experiments. Image analysis technique (using\\u000a the Fast Fourier Transform) was used to quantify the fiber orientation distribution. The

Han Seong Kim

2004-01-01

348

Insulation bonding test system  

NASA Technical Reports Server (NTRS)

A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (inventors)

1984-01-01

349

Geometrical criteria for characterizing open and closed states of WPD-loop in PTP1B  

NASA Astrophysics Data System (ADS)

Distinctive movement of WPD-loop occurs during the catalysis of phosphotyrosine by protein tyrosine phosphatase 1B (PTP1B). This loop is in the "open" state in apo-form whereas it is catalytically competent in the "closed" state. During the closure of this loop, unique hydrogen bond interactions are formed between different residues of the PTP1B. Present study examines such interactions from the available 118 crystal structures of PTP1B. It gives insights into the five novel hydrogen bonds essentially formed in the "closed" loop structures. Additionally, the study provides distance ranges between the atoms involved in the hydrogen bonds. This information can be used as a geometrical criterion in the characterization of conformational state of the WPD-loop especially in the molecular dynamics simulations.

Shinde, Ranajit Nivrutti; Elizabeth Sobhia, M.

2012-06-01

350

Solid-Liquid Interdiffusion Bonding of Silicon Carbide to Steel for High Temperature MEMS Sensor Packaging and Bonding  

NASA Astrophysics Data System (ADS)

Complex engineering systems ranging from automobile engines to geothermal wells require specialized sensors to monitor conditions such as pressure, acceleration and temperature in order to improve efficiency and monitor component lifetime in what may be high temperature, corrosive, harsh environments. Microelectromechanical systems (MEMS) have demonstrated their ability to precisely and accurately take measurements under such conditions. The systems being monitored are typically made from metals, such as steel, while the MEMS sensors used for monitoring are commonly fabricated from silicon, silicon carbide and aluminum nitride, and so there is a sizable thermal expansion mismatch between the two. For these engineering applications the direct bonding of MEMS sensors to the components being monitored is often required. This introduces several challenges, namely the development of a bond that is capable of surviving high temperature harsh environments while mitigating the thermally induced strains produced during bonding. This project investigates the development of a robust packaging and bonding process, using the gold-tin metal system and the solid-liquid interdiffusion (SLID) bonding process, to join silicon carbide substrates directly to type-316 stainless steel. The SLID process enables bonding at lower temperatures while producing a bond capable of surviving higher temperatures. Finite element analysis was performed to model the thermally induced strains generated in the bond and to understand the optimal way to design the bond. The cross-sectional composition of the bonds has been analyzed and the bond strength has been investigated using die shear testing. The effects of high temperature aging on the bond's strength and the metallurgy of the bond were studied. Additionally, loading of the bond was performed at temperatures over 415 C, more than 100 C, above the temperature used for bonding, with full survival of the bond, thus demonstrating the benefit of SLID bonding for high temperature applications. Lastly, this dissertation provides recommendations for improving the strength and durability of the bond at temperatures of 400 C and provides the framework for future work in the area of high temperature harsh environment MEMS packaging that would take directly bonded MEMS to temperatures of 600 C and beyond.

Chan, Matthew Wei-Jen

351

Teachers' Domain: Ionic Bonding  

NSDL National Science Digital Library

This Flash interactive tutorial explores ionic bondinga type of chemical bond formed between two ions with opposite charges. Learners investigate how the transfer of electrons between atoms creates ions and how the mutual attraction of these charged particles forms ionic bonds. It also discusses trends in the periodic table to help learners comprehend how the structure of an ionic compound relates to its formula. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

352

Investing in Bonds  

E-print Network

, also known as strips, are fixed-income securi- ties that do not pay any periodic interest, or ?coupon,? like regular bonds. Instead, the bond is sold at a deep discount from its face value and at maturity the bondholder collects all of the compounded... or the par amount, whichever is greater. Like other Treasury securi- ties, they?re safe and are guaran- teed by the full faith and credit of the U.S. government. Inflation- Indexed securities are exempt from state and local taxes, although fed- eral income...

Johnson, Jason; Polk, Wade

2002-08-12

353

19 CFR 113.12 - Bond application.  

Code of Federal Regulations, 2010 CFR

...Duties 1 2010-04-01 2010-04-01 false Bond application. 113.12 Section 113.12 Customs...HOMELAND SECURITY; DEPARTMENT OF THE TREASURY CUSTOMS BONDS Bond Application and Approval of Bond 113.12 Bond...

2010-04-01

354

Hyperconjugation-mediated solvent effects in phosphoanhydride bonds  

PubMed Central

Density functional theory and Natural Bond Orbital analysis are used to explore the impact of solvent on hyperconjugation in methyl triphosphate, a model for energy rich phosphoanhydride bonds, such as found in ATP. As expected, dihedral rotation of a hydroxyl group vicinal to the phosphoanhydride bond reveals that the conformational dependence of the anomeric effect involves modulation of the orbital overlap between the donor and acceptor orbitals. However, a conformational independence was observed in the rotation of a solvent hydrogen bond. As one lone pair orbital rotates away from an optimal anti-periplanar orientation, the overall magnitude of the anomeric effect is compensated approximately by the other lone pair as it becomes more anti-periplanar. Furthermore, solvent modulation of the anomeric effect is not restricted to the anti-periplanar lone pair; hydrogen bonds involving gauche lone pairs also affect the anomeric interaction and the strength of the phosphoanhydride bond. Both gauche and anti solvent hydrogen bonds lengthen non-bridging OP bonds, increasing the distance between donor and acceptor orbitals, and decreasing orbital overlap which leads to a reduction of the anomeric effect. Solvent effects are additive with greater reduction in the anomeric effect upon increasing water coordination. By controlling the coordination environment of substrates in an active site, kinases, phosphatases and other enzymes important in metabolism and signaling, may have the potential to modulate the stability of individual phosphoanhydride bonds through stereoelectronic effects. PMID:23009395

Summerton, Jean C.; Evanseck, Jeffrey D.; Chapman, Michael S.

2012-01-01

355

Hydrogen bond dynamics in the active site of photoactive yellow protein  

PubMed Central

Hydrogen bonds play major roles in biological structure and function. Nonetheless, hydrogen-bonded protons are not typically observed by X-ray crystallography, and most structural studies provide limited insight into the conformational plasticity of individual hydrogen bonds or the dynamical coupling present within hydrogen bond networks. We report the NMR detection of the hydrogen-bonded protons donated by Tyr-42 and Glu-46 to the chromophore oxygen in the active site of the bacterial photoreceptor, photoactive yellow protein (PYP). We have used the NMR resonances for these hydrogen bonds to probe their conformational properties and ability to rearrange in response to nearby electronic perturbation. The detection of geometric isotope effects transmitted between the Tyr-42 and Glu-46 hydrogen bonds provides strong evidence for robust coupling of their equilibrium conformations. Incorporation of a modified chromophore containing an electron-withdrawing cyano group to delocalize negative charge from the chromophore oxygen, analogous to the electronic rearrangement detected upon photon absorption, results in a lengthening of the Tyr-42 and Glu-46 hydrogen bonds and an attenuated hydrogen bond coupling. The results herein elucidate fundamental properties of hydrogen bonds within the complex environment of a protein interior. Furthermore, the robust conformational coupling and plasticity of hydrogen bonds observed in the PYP active site may facilitate the larger-scale dynamical coupling and signal transduction inherent to the biological function that PYP has evolved to carry out and may provide a model for other coupled dynamic systems. PMID:19470452

Sigala, Paul A.; Tsuchida, Mark A.; Herschlag, Daniel

2009-01-01

356

Photochemical tissue bonding  

DOEpatents

Photochemical tissue bonding methods include the application of a photosensitizer to a tissue and/or tissue graft, followed by irradiation with electromagnetic energy to produce a tissue seal. The methods are useful for tissue adhesion, such as in wound closure, tissue grafting, skin grafting, musculoskeletal tissue repair, ligament or tendon repair and corneal repair.

Redmond, Robert W. (Brookline, MA); Kochevar, Irene E. (Charlestown, MA)

2012-01-10

357

Bonding without Tears.  

ERIC Educational Resources Information Center

Discusses merits of using sigma-pi model of ethylene as a teaching aid in introductory organic chemistry. The nonmathematical treatment of sigma-pi bonding is then extended to such phenomena as conjugation, hyperconjugation, Markovnikoff addition, aromaticity, and aromatic substitution. (SK)

Akeroyd, F. Michael

1982-01-01

358

Nodal free geometric phases: Concept and application to geometric quantum computation  

E-print Network

Nodal free geometric phases are the eigenvalues of the final member of a parallel transporting family of unitary operators. These phases are gauge invariant, always well-defined, and can be measured interferometrically. Nodal free geometric phases can be used to construct various types of quantum phase gates.

Marie Ericsson; David Kult; Erik Sjqvist; Johan Aberg

2007-08-06

359

Geometric Algebra: A Powerful Tool for Solving Geometric Problems in Visual Computing  

Microsoft Academic Search

Geometric problems in visual computing (computer graphics, computer vision, and image processing) are typically modeled and solved using linear algebra (LA). Thus, vectors are used to represent directions and points in space, while matrices are used to model transformations. LA, however, presents some well-known limitations for performing geometric computations. As a result, one often needs to aggregate different formalisms (e.g.,

Leandro A. F. Fernandes; Manuel M. Oliveira

2009-01-01

360

A Differential Geometric Approach to the Geometric Mean of Symmetric Positive-Definite Matrices  

Microsoft Academic Search

In this paper we introduce metric-based means for the space of positive-definite matrices. The mean associated with the Euclidean metric of the ambient space is the usual arithmetic mean. The mean associated with the Riemannian metric corresponds to the geometric mean. We discuss some invariance properties of the Riemannian mean and we use dierential geometric tools to give a characterization

Maher Moakher

2005-01-01

361

Chemical bond descriptors from molecular information channels in orbital resolution  

NASA Astrophysics Data System (ADS)

The inter and intraorbital flows of the Fisher and Shannon informations in the molecular communication networks defined in the condensed atomic orbital (AO) resolution are investigated, and the effect of the basis set overlap is examined. The Schrdinger equation is interpreted as solution of the variation principle for the extreme Fisher information, subject to the wave-function-normalization (geometric) and potential-energy (physical) constraints. Its orbital contributions determine the information scattering of the underlying Fisher channel in the adopted AO basis set. This communication network is compared with the associated information system of the Shannon theory of communication. The new set of conditional probabilities between orbitals is compared to that used in the previous, sequential-cascade approach to the effective information promotion of AO in the molecular environment. Both geometrical and physical probabilities are reexamined using the quantum-mechanical superposition principle. The former characterizes the whole orbital space, whereas the latter describes only its occupied part, which determines the system chemical bonds. It is argued that the squares of corresponding elements of the charge and bond-order (CBO) matrix of the LCAO MO theory replace in the physical set of conditional probabilities the corresponding squares of the overlap integrals, which determine the geometrical set. The chain-rule interpretation of conditional probabilities is given. The modified 2-AO channel reproduces fully the earlier predictions from the molecular information channel in atomic resolution. The familiar bond criteria for an effective mixing of AO into molecular orbitals (MO) are shown to remain valid in the communication theory of the chemical bond (CTCB).

Nalewajski, Roman F.

362

Control Chart Tests Based on Geometric Moving Averages  

Microsoft Academic Search

A geometrical moving average gives the most recent observation the greatest weight, and all previous observations weights decreasing in geometric progression from the most recent back to the first. A graphical procedure for generating geometric moving averages is described in which the most recent observation is assigned a weight r. The properties of control chart tests based on geometric moving

S. W. Roberts

1959-01-01

363

Primary School Teacher Candidates' Geometric Habits of Mind  

ERIC Educational Resources Information Center

Geometric habits of mind are productive ways of thinking that support learning and using geometric concepts. Identifying primary school teacher candidates' geometric habits of mind is important as they affect the development of their future students' geometric thinking. Therefore, this study attempts to determine primary school

Kse, Nilufer Y.; Tanisli, Dilek

2014-01-01

364

The Calculation of Accurate Metal-Ligand Bond Energies  

NASA Technical Reports Server (NTRS)

The optimization of the geometry and calculation of zero-point energies are carried out at the B3LYP level of theory. The bond energies are determined at this level, as well as at the CCSD(T) level using very large basis sets. The successive OH bond energies to the first row transition metal cations are reported. For most systems there has been an experimental determination of the first OH. In general, the CCSD(T) values are in good agreement with experiment. The bonding changes from mostly covalent for the early metals to mostly electrostatic for the late transition metal systems.

Bauschlicher, Charles W.; Partridge, Harry, III; Ricca, Alessandra; Arnold, James O. (Technical Monitor)

1997-01-01

365

Advanced Bonding\\/Joining Techniques  

Microsoft Academic Search

\\u000a In this chapter, three advanced bonding\\/joining techniques, adhesive bonding, direct bonding, and lead-free soldering, are\\u000a presented. For each technique, we first review the bonding principles and applications in electronic industries, followed\\u000a by novel bonding materials and processes.\\u000a \\u000a \\u000a For adhesive bonding, four popular adhesives, epoxy resins, silicon resins, polymides, and acrylics, are reviewed. Two new\\u000a adhesives, liquid crystal polymer (LCP) and

Chin C. Lee; Pin J. Wang; Jong S. Kim

366

The effect of photometric and geometric context on photometric and geometric lightness effects  

PubMed Central

We measured the lightness of probe tabs embedded at different orientations in various contextual images presented on a computer-controlled stereo display. Two background context planes met along a horizontal roof-like ridge. Each plane was a graphic rendering of a set of achromatic surfaces with the simulated illumination for each plane controlled independently. Photometric context was varied by changing the difference in simulated illumination intensity between the two background planes. Geometric context was varied by changing the angle between them. We parsed the data into separate photometric effects and geometric effects. For fixed geometry, varying photometric context led to linear changes in both the photometric and geometric effects. Varying geometric context did not produce a statistically reliable change in either the photometric or geometric effects. PMID:24464163

Lee, Thomas Y.; Brainard, David H.

2014-01-01

367

Amalgam shear bond strength to dentin using different bonding agents.  

PubMed

This study evaluated the shear bond strength of amalgam to dentin using five different bonding agents: Amalgambond Plus, Optibond, Imperva Dual, All-Bond 2, and Clearfil Liner Bond. Flat dentin surfaces obtained by grinding the occlusal portion of 50 human third molars were used for this study. To contain the amalgam on the tooth surface, cylindrical plastic molds were placed on the dentin and secured with sticky wax. The bonding agents were then applied according to the manufacturers' instructions or light activated and Tytin amalgam was condensed into the plastic molds. The samples were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. Analysis by one-way ANOVA indicated significant difference between the five groups (P < 0.05). The bond strength of amalgam to dentin was significantly higher with Amalgambond Plus using the High-Performance Additive than with the other four bonding agents. PMID:9028242

Vargas, M A; Denehy, G E; Ratananakin, T

1994-01-01

368

Geometric inequalities for axially symmetric black holes  

E-print Network

A geometric inequality in General Relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman black hole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical black holes. This kind of inequalities play an important role in the characterization of the gravitational collapse, they are closed related with the cosmic censorship conjecture. Axially symmetric black holes are the natural candidates to study these inequalities because the quasi-local angular momentum is well defined for them. We review recent results in this subject and we also describe the main ideas behind the proofs. Finally, a list of relevant open problem is presented.

Sergio Dain

2011-11-15

369

Gender recognition based on face geometric features  

NASA Astrophysics Data System (ADS)

Automatic gender recognition based on face images plays an important role in computer vision and machine vision. In this paper, a novel and simple gender recognition method based on face geometric features is proposed. The method is divided in three steps. Firstly, Pre-processing step provides standard face images for feature extraction. Secondly, Active Shape Model (ASM) is used to extract geometric features in frontal face images. Thirdly, Adaboost classifier is chosen to separate the two classes (male and female). We tested it on 2570 pictures (1420 males and 1150 females) downloaded from the internet, and encouraging results were acquired. The comparison of the proposed geometric feature based method and the full facial image based method demonstrats its superiority.

Xiao, Jie; Guo, Zhaoli; Cai, Chao

2013-10-01

370

Information-geometric aspects of Hawking radiation  

E-print Network

This paper illustrates the resemblance between the information-geometric structures of probability spaces and that of the discrete spectrum for Hawking radiation. The information geometry gives rise to a reconstruction of the standard formalism of quantum mechanics, while the discrete spectrum of Hawking radiation contributes to the semiclassical unitary evolution of Hawking radiation. If more realistic models of Hawking radiation are chosen, the information-geometric structures of the probability space for Hawking radiation can be constructed from some physical considerations. The constructed quantum formalism is consistent with both the unitary evolution of Hawking radiation in the semiclassical picture and the topology change of fuzzy horizon. These aspects of Hawking radiation can be connected to some general convictions of quantum gravity such as holography. A comparison with fuzzball propasal shows the limiation and effectiveness of this construction. We conclude that the infromation-geometric aspects show some possible ways bridging the gap between semiclassical models and quantum gravity.

Xiao-Kan Guo

2014-10-04

371

Intrinsic geometric scale space by shape diffusion.  

PubMed

This paper formalizes a novel, intrinsic geometric scale space (IGSS) of 3D surface shapes. The intrinsic geometry of a surface is diffused by means of the Ricci flow for the generation of a geometric scale space. We rigorously prove that this multiscale shape representation satisfies the axiomatic causality property. Within the theoretical framework, we further present a feature-based shape representation derived from IGSS processing, which is shown to be theoretically plausible and practically effective. By integrating the concept of scale-dependent saliency into the shape description, this representation is not only highly descriptive of the local structures, but also exhibits several desired characteristics of global shape representations, such as being compact, robust to noise and computationally efficient. We demonstrate the capabilities of our approach through salient geometric feature detection and highly discriminative matching of 3D scans. PMID:19834189

Zou, Guangyu; Hua, Jing; Lai, Zhaoqiang; Gu, Xianfeng; Dong, Ming

2009-01-01

372

Neurogenetic optimization of micro compact heat exchanger  

Microsoft Academic Search

Purpose This paper seeks to introduce an optimization method for maximizing the effectiveness of the micro compact heat exchanger (MHE) under various geometrical parameters. Design\\/methodology\\/approach Optimization is realized using the neuro-genetic methodology which combines the application of artificial neural network (ANN) together with genetic algorithms (GA). The analyses are divided into two main sections; the first being the

H. W. Lee; Y. J. Teng; I. A. Azid; K. N. Seetharamu

2007-01-01

373

Semionic resonating valence-bond states  

NASA Astrophysics Data System (ADS)

The nature of the kagome Heisenberg antiferromagnet (HAFM) is under ongoing debate. While recent evidence points towards a Z2 topological spin liquid, the exact nature of the topological phase is still unclear. In this paper, we introduce semionic resonating valence-bond (RVB) states, this is, resonating valence-bond states which are in the Z2-ordered double-semion phase, and study them using projected entangled pair states. We investigate their physics and study their suitability as an ansatz for the HAFM, as compared to a conventional RVB state which is in the toric-code Z2 topological phase. In particular, we find that a suitably optimized "semionic simplex RVB" outperforms the equally optimized conventional "simplex RVB" state, and that the entanglement spectrum (ES) of the semionic RVB behaves very differently from the ES of the conventional RVB, which suggests using the ES to discriminate the two phases. Finally, we also discuss the possible relevance of space-group symmetry breaking in valence-bond wave functions with double-semion topological order.

Iqbal, Mohsin; Poilblanc, Didier; Schuch, Norbert

2014-09-01

374

Geometric Effects and Computation in Spin Networks  

E-print Network

When initially introduced, a Hamiltonian that realises perfect transfer of a quantum state was found to be analogous to an x-rotation of a large spin. In this paper we extend the analogy further to demonstrate geometric effects by performing rotations on the spin. Such effects can be used to determine properties of the chain, such as its length, in a robust manner. Alternatively, they can form the basis of a spin network quantum computer. We demonstrate a universal set of gates in such a system by both dynamical and geometrical means.

Alastair Kay; Marie Ericsson

2005-04-08

375

Persisting topological order via geometric frustration  

NASA Astrophysics Data System (ADS)

We introduce a toric code model on the dice lattice which is exactly solvable and displays topological order at zero temperature. In the presence of a magnetic field, the flux dynamics is mapped to the highly frustrated transverse field Ising model on the kagome lattice. This correspondence suggests an intriguing disorder by disorder phenomenon in a topologically ordered system implying that the topological order is extremely robust due to the geometric frustration. Furthermore, a connection between fully frustrated transverse field Ising models and topologically ordered systems is demonstrated which opens an exciting physical playground due to the interplay of topological quantum order and geometric frustration.

Schmidt, Kai Phillip

2013-07-01

376

Geometric Distance Measurement using Light Echo Polarization  

NASA Astrophysics Data System (ADS)

By imaging the polarization distribution of a light echo and finding the angular size of the ring of maximum polarization, the geometric distance to the echo may be inferred. The technique may be used for extragalactic geometric distance measurement with observations of supernova light echoes. We have obtained such observations using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The recent spectacular light echo around the Galactic nova V838 Mon has also been observed with ACS and is providing valuable insights into the technique as well as an estimate of the distance of that object.

Sparks, W. B.

2005-12-01

377

Classical light beams and geometric phases.  

PubMed

We present a study of geometric phases in classical wave and polarization optics using the basic mathematical framework of quantum mechanics. Important physical situations taken from scalar wave optics, pure polarization optics, and the behavior of polarization in the eikonal or ray limit of Maxwell's equations in a transparent medium are considered. The case of a beam of light whose propagation direction and polarization state are both subject to change is dealt with, attention being paid to the validity of Maxwell's equations at all stages. Global topological aspects of the space of all propagation directions are discussed using elementary group theoretical ideas, and the effects on geometric phases are elucidated. PMID:24977351

Mukunda, N; Chaturvedi, S; Simon, R

2014-06-01

378

Geometrical aspects in optical wave-packet dynamics.  

PubMed

We construct a semiclassical theory for propagation of an optical wave packet in a nonconducting medium with a periodic structure of dielectric permittivity and magnetic permeability, i.e., a nonconducting photonic crystal. We employ a quantum-mechanical formalism in order to clarify its link to those of electronic systems. It involves the geometrical phase, i.e., Berry's phase, in a natural way, and describes an interplay between orbital motion and internal rotation. Based on the above theory, we discuss the geometrical aspects of the optical Hall effect. We also consider a reduction of the theory to a system without periodic structure and apply it to the transverse shift of an optical beam at an interface reflection or refraction. For a generic incident beam with an arbitrary polarization, an identical result for the transverse shift of each reflected or transmitted beam is given by the following different approaches: (i) analytic evaluation of wave-packet dynamics, (ii) total angular momentum (TAM) conservation for individual photons, and (iii) numerical simulation of wave-packet dynamics. It is consistent with a result by classical electrodynamics. This means that the TAM conservation for individual photons is already taken into account in wave optics, i.e., classical electrodynamics. Finally, we show an application of our theory to a two-dimensional photonic crystal, and propose an optimal design for the enhancement of the optical Hall effect in photonic crystals. PMID:17280165

Onoda, Masaru; Murakami, Shuichi; Nagaosa, Naoto

2006-12-01

379

Mechanics of Tunable Helices and Geometric Frustration in Biomimetic Seashells  

E-print Network

Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, adds to the variety of this family of aesthetic beauty. Here we develop a comprehensive theoretical framework for tunable helical morphologies, and report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves equilibrium. In this work, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessarily be locally optimized. This novel approach can be applied to develop materials and devices of tunable geometries with a range of applications in nano/biotechnology.

Qiaohang Guo; Zi Chen; Wei Li; Pinqiang Dai; Kun Ren; Junjie Lin; Larry A. Taber; Wenzhe Chen

2013-12-03

380

Enzymatic functionalization of carbon-hydrogen bonds.  

PubMed

The development of new catalytic methods to functionalize carbon-hydrogen (C-H) bonds continues to progress at a rapid pace due to the significant economic and environmental benefits of these transformations over traditional synthetic methods. In nature, enzymes catalyze regio- and stereoselective C-H bond functionalization using transformations ranging from hydroxylation to hydroalkylation under ambient reaction conditions. The efficiency of these enzymes relative to analogous chemical processes has led to their increased use as biocatalysts in preparative and industrial applications. Furthermore, unlike small molecule catalysts, enzymes can be systematically optimized via directed evolution for a particular application and can be expressed in vivo to augment the biosynthetic capability of living organisms. While a variety of technical challenges must still be overcome for practical application of many enzymes for C-H bond functionalization, continued research on natural enzymes and on novel artificial metalloenzymes will lead to improved synthetic processes for efficient synthesis of complex molecules. In this critical review, we discuss the most prevalent mechanistic strategies used by enzymes to functionalize non-acidic C-H bonds, the application and evolution of these enzymes for chemical synthesis, and a number of potential biosynthetic capabilities uniquely enabled by these powerful catalysts (110 references). PMID:21079862

Lewis, Jared C; Coelho, Pedro S; Arnold, Frances H

2011-04-01

381

An integrated approach to the synthesis of geometrically non-linear structures  

NASA Technical Reports Server (NTRS)

An integrated approach to the minimum weight design of geometrically nonlinear three-dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The nonlinear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the constraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically nonlinear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.

Smaoui, H.; Schmit, L. A.

1988-01-01

382

Kernel density estimation applied to bond length, bond angle, and torsion angle distributions.  

PubMed

We describe the method of kernel density estimation (KDE) and apply it to molecular structure data. KDE is a quite general nonparametric statistical method suitable even for multimodal data. The method generates smooth probability density function (PDF) representations and finds application in diverse fields such as signal processing and econometrics. KDE appears to have been under-utilized as a method in molecular geometry analysis, chemo-informatics, and molecular structure optimization. The resulting probability densities have advantages over histograms and, importantly, are also suitable for gradient-based optimization. To illustrate KDE, we describe its application to chemical bond length, bond valence angle, and torsion angle distributions and show the ability of the method to model arbitrary torsion angle distributions. PMID:24746022

McCabe, Patrick; Korb, Oliver; Cole, Jason

2014-05-27

383

The Illiquidity of Corporate Bonds  

E-print Network

This paper examines the illiquidity of corporate bonds and its asset-pricing implications. Using transactions data from 2003 to 2009, we show that the illiquidity in corporate bonds is substantial, significantly greater ...

Bao, Jack

384

On the Geometric Interpretation of the Nonnegative Rank  

E-print Network

The nonnegative rank of a nonnegative matrix is the minimum number of nonnegative rank-one factors needed to reconstruct it exactly. The problem of determining this rank and computing the corresponding nonnegative factors is difficult; however it has many potential applications, e.g., in data mining, graph theory and computational geometry. In particular, it can be used to characterize the minimal size of any extended reformulation of a given combinatorial optimization program. In this paper, we introduce and study a related quantity, called the restricted nonnegative rank. We show that computing this quantity is equivalent to a problem in polyhedral combinatorics, and fully characterize its computational complexity. This in turn sheds new light on the nonnegative rank problem, and in particular allows us to provide new improved lower bounds based on its geometric interpretation. We apply these results to slack matrices and linear Euclidean distance matrices and obtain counter-examples to two conjectures of B...

Gillis, Nicolas

2010-01-01

385

Low temperature reactive bonding  

DOEpatents

The joining technique requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process.

Makowiecki, Daniel M. (Livermore, CA); Bionta, Richard M. (Livermore, CA)

1995-01-01

386

Disulfide bonds of acetylcholinesterase  

SciTech Connect

The positions of the inter- and intrasubunit disulfide bridges were established for the 11S form of acetylcholinesterase (AChE) isolated from Torpedo californica. A major form of AChE localized within the basal lamina of the synapse is a dimensionally asymmetric molecule which contains either two (13S) or three (17S) sets of catalytic subunits linked to collagenous and non-collagenous structural subunits. Limited proteolysis yields a tetramer of catalytic subunits which sediments at 11S. Each catalytic subunit contains 8 cysteine residues. Initially, these Cys residues were identified following trypsin digestion of the reduced protein alkylated with (/sup 14/C)-iodoacetate. Peptides were resolved by gel filtration followed by reverse phase HPLC. To determine the disulfide bonding profile, native non-reduced 11S AChE was treated with a fluorescent, sulfhydryl-specific reagent, monobromobimane, prior to proteolytic digestion. One fluorescent Cys peptide was identified indicating that a single sulfhydryl residue was present in its reduced form. Three pairs of disulfide bonded peptides were identified, sequenced, and localized in the polypeptide chain. The Cys residue that is located in the C-terminal tryptic peptide was disulfide bonded to an identical peptide and thus forms the intersubunit crosslink. Finally, the cysteine positions have been compared with the sequence of the homologous protein, thyroglobulin. Both likely share a common pattern of folding.

MacPhee-Quigley, K.; Vedvick, T.; Taylor, P.; Taylor, S.

1986-05-01

387

Electronic configuration and bond energy  

Microsoft Academic Search

ConclusionsThe original interpretation of the method of molecular orbitals as a theory of valency, in which the single electron possesses\\u000a bonding power was based on the assumption that non-premoted electrons are bonding and premoted ones are anti-bonding or non-bonding.\\u000a This assumption is not the outcome of any requirements of theory but is an empirical postulate, which seeks justification\\u000a in experimental

R. K. Asundi; R. Samuel

1936-01-01

388

Average bond energies between boron and elements of the fourth, fifth, sixth, and seventh groups of the periodic table  

NASA Technical Reports Server (NTRS)

The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.

Altshuller, Aubrey P

1955-01-01

389

An Orientation-dependent Hydrogen Bonding Potential Improves Prediction of Specificity and Structure for Proteins and ProteinProtein Complexes  

E-print Network

Hydrogen bonding is a key contributor to the specificity of intramolecular and intermolecular interactions in biological systems. Here, we develop an orientation-dependent hydrogen bonding potential based on the geometric characteristics of hydrogen bonds in high-resolution protein crystal structures, and evaluate it using four tests related to the prediction and design of protein structures and proteinprotein complexes. The new potential is superior to the widely used Coulomb model of hydrogen bonding in prediction of the sequences of proteins and proteinprotein interfaces from their structures, and improves discrimination of correctly docked proteinprotein complexes from large sets of alternative structures.

Tanja Kortemme A; Re V. Morozov A; David Baker A; Howard Hughes Medical

390

Entanglement capacity of nonlocal Hamiltonians: A geometric approach  

NASA Astrophysics Data System (ADS)

We develop a geometric approach to quantify the capability of creating entanglement for a general physical interaction acting on two qubits. We use the entanglement measure proposed by us for N -qubit pure states [Ali Saif M. Hassan and Pramod S. Joag, Phys. Rev. A 77, 062334 (2008)]. This geometric method has the distinct advantage that it gives the experimentally implementable criteria to ensure the optimal entanglement production rate without requiring a detailed knowledge of the state of the two qubit system. For the production of entanglement in practice, we need criteria for optimal entanglement production, which can be checked in situ without any need to know the state, as experimentally finding out the state of a quantum system is generally a formidable task. Further, we use our method to quantify the entanglement capacity in higher level and multipartite systems. We quantify the entanglement capacity for two qutrits and find the maximal entanglement generation rate and the corresponding state for the general isotropic interaction between qutrits, using the entanglement measure of N -qudit pure states proposed by us [Ali Saif M. Hassan and Pramod S. Joag, Phys. Rev. A 80, 042302 (2009)]. Next we quantify the genuine three qubit entanglement capacity for a general interaction between qubits. We obtain the maximum entanglement generation rate and the corresponding three qubit state for a general isotropic interaction between qubits. The state maximizing the entanglement generation rate is of the Greenberger-Horne-Zeilinger class. To the best of our knowledge, the entanglement capacities for two qutrit and three qubit systems have not been reported earlier.

Lari, Behzad; Hassan, Ali Saif M.; Joag, Pramod S.

2009-12-01

391

Continuing Conversation about Continuing Bonds  

ERIC Educational Resources Information Center

The article is a response to the contributions the special issue of Death Studies on continuing bonds. The contributions indicate that the conversation among scholars has clarified our thinking on how bonds function in individual grief. The author discussed two issues to help keep the conversation moving: (a) the relationship of continuing bonds

Klass, Dennis

2006-01-01

392

Rapid Adhesive Bonding of Composites  

NASA Technical Reports Server (NTRS)

Strong bonds created in less time and with less power than use of conventional bonding methods. Rapid adhesive bonding (RAB) technique for composites uses high-frequency induction heating toroids to quickly heat metallic susceptor impregnated with thermoplastic adhesive or sandwiched between thermoset or thermoplastic adhesive cloths or films. Susceptor steel screen or perforated steel foil.

Stein, B. A.; Tyeryar, J. R.; Fox, R. L.; Sterling, S. Elmo, Jr.; Buckley, J. D.; Inge, Spencer V., Jr.; Burcher, L. G.; Wright, Robert E., Jr.

1986-01-01

393

Bond financing in volatile times.  

PubMed

A competitive landscape for providers and changing market conditions require an understanding of key capital sources: tax-exempt bonds remain an attractive capital source. Credit enhancement for bonds is more expensive and more difficult to find than it was in years past. Direct bond purchases by commercial banks mitigate the traditional risks. PMID:24701850

Gould, Kenneth A; Blanda, Christopher M

2014-03-01

394

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2013 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2013-10-01

395

Geometric performance of ENVISAT ASAR products  

Microsoft Academic Search

We describe validation measurements of the geometric accuracy of ASAR images, measured redundantly via independent methods. Our tests include image (IM), alternating polarization (AP), and wide swath (WS) mode acquisitions over a variety of test sites. ASAR's slant range products (IMS\\/APS) require a slightly different validation methodology than ground range precision (IMP, APP) and medium resolution products (IMM, APM, WSM).

David Small; Jrgen Holzner; Hannes Raggam; Detlev Kosmann; Adrian Schubert

2003-01-01

396

One-Point Geometric Crossover Alberto Moraglio  

E-print Network

One-Point Geometric Crossover Alberto Moraglio School of Computing and Center for Reasoning, University of Kent, Canterbury, UK A.Moraglio@kent.ac.uk Abstract. Uniform crossover for binary strings has of combination operators acting on the neighborhood structure (e.g., path- relinking). Early studies

Yao, Xin

397

Geometric Mean--What Does It Mean?  

ERIC Educational Resources Information Center

The National Council of Teachers of Mathematics and numerous mathematics educators promote the combination of conceptual understanding and procedural learning in the successful instruction of mathematics. Despite this, when geometric mean is taught in a typical American geometry class, it is taught as a process only despite the many connections

Kalder, Robin S.

2012-01-01

398

More Meaning from the Geometric Mean.  

ERIC Educational Resources Information Center

Provides classroom suggestions for combining numerical, algebraic, and geometric techniques with the understanding of a simple method for computing square roots. Historical origins of the method illustrate the debt owed to ancient minds living in what are now India, Pakistan, Iraq, and Egypt. (Author/NB)

Dorner, Bryan C.

2003-01-01

399

Transportation Networks and Location A Geometric Approach  

E-print Network

Transportation Networks and Location A Geometric Approach Belén Palop1,2 1Departamento de March 2009 Florida State University #12;Belén Palop, UVa, SUNY Outline Transportation Network Model;Transportation Network Model Belén Palop, UVa, SUNY Outline Transportation Network Model Network placement

Palop del Río, Belén

400

A GEOMETRIC STUDY OF WASSERSTEIN SPACES: ULTRAMETRICS  

E-print Network

. Introduction Given a metric space X, that we shall always assume to be compact, one can define its Lp for precise definitions). In some sense, Wp(X) can be thought of as a geometric measure theory analogue of Lp space, although its geometry is finely governed by the geometry of X as Wp involves the metric on X

Paris-Sud XI, Université de

401

The integral of geometric Brownian motion  

Microsoft Academic Search

This paper is about the probability law of the integral of geometric Brownian motion over a finite time interval. A partial differential equation is derived for the Laplace transform of the law of the reciprocal integral, and is shown to yield an expression for the density of the distribution. This expression has some advantages over the ones obtained previously, at

Daniel Dufresne

2001-01-01

402

Geometric calibration of ERS satellite SAR images  

Microsoft Academic Search

Geometric calibration of the European Remote Sensing (ERS) Satellite synthetic aperture radar (SAR) slant range images is important in relation to mapping areas without ground reference points and also in relation to automated processing. The relevant SAR system parameters are discussed and calibrated by using the European Space Agency (ESA) transponders at Flevoland. The resulting accuracy of the slant range

Johan Jacob Mohr; Sren Nrvang Madsen

2001-01-01

403

Geometric Interpretation of the Pauli Spinor.  

ERIC Educational Resources Information Center

Presents a reexamination of an intuitively geometric view of the nonrelativistic Pauli spinor in a simplified discussion of the connection between the rotation group and special transformations in the plane of projection. This view of the spinor is related to those based on the existence of an istropic or null vector. (SK)

Frescura, F. A. M.; Hiley, B. J.

1981-01-01

404

Geometric axioms for existentially closed Hasse elds  

E-print Network

Geometric axioms for existentially closed Hasse #12;elds Piotr Kowalski #3; Wroc law University for existentially closed Hasse #12;elds. We prove a quanti#12;er elimination result for existentially closed n- truncated Hasse #12;elds and characterize them as reducts of existentially closed Hasse #12;elds. 0

Kowalski, Piotr

405

Gaigen 2: a geometric algebra implementation generator  

Microsoft Academic Search

Geometric Algebra (GA) is an algebra that encodes geometry much better than standard techniques, which are mainly based on linear algebra with various extensions. Compared to standard techniques, GA has clearer semantics and a richer, more consistent language. This expresses itself, among others, in a much greater genericity of functions over the algebra. Exploiting this genericity efficiently is a problem

Daniel Fontijne

2006-01-01

406

Magnetic bottles on geometrically finite hyperbolic surfaces  

E-print Network

We consider a magnetic Laplacian on a geometrically finite hyperbolic surface, when the corresponding magnetic field is infinite at the boundary at infinity. We prove that the counting function of the eigenvalues has a particular asymptotic behaviour when the surface has an infinite area.

Abderemane Morame; Francoise Truc

2008-09-05

407

Geometrically Frustrated Antiferromagnets: Statistical Mechanics and Dynamics  

Microsoft Academic Search

\\u000a These lecture notes provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical\\u000a and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in\\u000a which the results provide an understanding of some of the main observed properties of these systems.

John T. Chalker

408

Geometrically frustrated antiferromagnets: statistical mechanics and dynamics  

Microsoft Academic Search

These lecture notes are intended to provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in which the results provide an understanding of some of the main observed properties of these systems.

J. T. Chalker

2009-01-01

409

Fractal Geometric Characterization of Functionally Graded Materials  

E-print Network

Fractal Geometric Characterization of Functionally Graded Materials A. Saharan1 ; M. Ostoja. Author keywords: Fractal; Fractal dimension; Functionally graded materials (FGM); Scale dependence, since the 1980s, there has been a major research effort on the so-called functionally graded materials

Ostoja-Starzewski, Martin

410

A Geometric Model for Cortical Magnification  

Microsoft Academic Search

A Riemannian manifold endowed with a conformal metric is proposed as a geometric model for the cortical magnification that\\u000a characterises foveal systems. The eccentricity scaling of receptive fields, the relative size of the foveola, as well as the\\u000a fraction of receptive fields involved in foveal vision can all be deduced from it.

Luc Florack

2000-01-01

411

Processing Textured Surfaces via Anisotropic Geometric Diffusion  

E-print Network

. Also from medical image generation methods such as CT and MRI devices or 3D ultrasound, certain flow (top right) and by the new anisotropic diffusion method (bottom right). Fur- thermoreProcessing Textured Surfaces via Anisotropic Geometric Diffusion U. Clarenz, U. Diewald, M. Rumpf

Rumpf, Martin

412

Gradient Vector Flow Fast Geometric Active Contours  

E-print Network

for boundary extraction. To this end, we combine the geodesic active contour flow [3] and the gradient vector Terms--Boundary extraction, image segmentation, gradient vector flow, geodesic active contours, level-level geometric components such as lines, circles, and ellipses [15]. Point Distribution Models: A step further

Paragios, Nikos

413

Neutron Studies of Geometrically Frustrated Magnets  

Microsoft Academic Search

Antiferromagnetically coupled spins residing on a network of corner sharing triangles (Kagome) or tetrahedra (pyrochlore) have attracted much attention in recent years [1-4] and often display phenomena known broadly as geometrical frustration. Because of their low propensity to order, even for classical spins, antiferromagnetic materials based on a pyrochlore lattice appear to be excellent systems for studying exotic ground states.

Jason Gardner

2004-01-01

414

Chemical control of geometrically frustrated magnets  

Microsoft Academic Search

The chemistry of geometrically frustrated magnets - materials which are composed of networks of spins which typically cannot find conventional ordered ground states - has in the past been largely restricted to a few archetypes, including the pyrochlore lattice, the spinel lattice, and variants of the perovskite lattice. Even though these compounds have exhibited a rich variety of low-temperature ground

Christopher Wiebe

2010-01-01

415

Fast Wind Turbine Design via Geometric Programming  

E-print Network

Fast Wind Turbine Design via Geometric Programming Warren Hoburg and Pieter Abbeel UC Berkeley the application of GP to large wind turbine design problems a promising approach. Nomenclature (·)a, (·)t axial According to the World Wind Energy Association, wind turbine installations supply approximately 3

Abbeel, Pieter

416

GEOMETRIC TOMOGRAPHY OF CONVEX CONES GABRIELE BIANCHI  

E-print Network

relative of computerised tomography, which reconstructs an image from X-rays of a human patient. The book convex bodies has been widely studied in geometric tomography. In this paper we are interested-rays. Let K Rn be a convex body, let u Sn-1 and let u denote the (n - 1)-dimensional subspace orthogonal

Bianchi, Gabriele

417

Geometrical analysis of catalogs of galaxies  

Microsoft Academic Search

A method is developed for analyzing catalogs of galaxies based on the plotting of contours of density, separating regions of high and low density, and conducting a statistical analysis of the geometrical parameters of these regions. Algorithms are developed for separating the regions and for determining their parameters. Four catalogs of galaxies are investigated using this method: the stochastic catalog

Sh. A. Guberman; A. G. Doroshkevich; E. V. Kotok; S. F. Shandarin

1983-01-01

418

Curves and Surfaces In Geometric Modeling  

E-print Network

.2 Infinite Knot Sequences, Open B-Spline Curves . . . . . . . . . . . . . . . . 194 6.3 Finite Knot Sequences, Finite B-Spline Curves . . . . . . . . . . . . . . . . . 206 6.4 Cyclic Knot Sequences, Closed (Cyclic) B-SplineCurves and Surfaces In Geometric Modeling: Theory And Algorithms Jean Gallier Department

Gallier, Jean

419

GEOMETRIC MODELLING WITH MULTIVARIATE B-SPLINES  

E-print Network

GEOMETRIC MODELLING WITH MULTIVARIATE B-SPLINES by Timothy Irwin Mueller A dissertation submitted Mueller 1986 All Rights Reserved #12;ABSTRACT The tensor product B-spline surface, while regarded in CAGD. In recent years, the theory of univariate B-splines has been extended to multidimen- sional

Utah, University of

420

Curves and Surfaces In Geometric Modeling  

E-print Network

.2 Infinite Knot Sequences, Open B-Spline Curves . . . . . . . . . . . . . . . . 196 6.3 Finite Knot Sequences, Finite B-Spline Curves . . . . . . . . . . . . . . . . . 209 6.4 Cyclic Knot Sequences, Closed (Cyclic) B-Spline#12;#12;Curves and Surfaces In Geometric Modeling: Theory And Algorithms Jean Gallier Department

Gallier, Jean

421

Lecture notes on "Geometric Dynamics and Symmetry"  

E-print Network

Lecture notes on "Geometric Dynamics and Symmetry" Bob Rink December 2, 2009 Contents 1 Mechanical systems 4 1.1 Two classical examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 One degree of freedom mechanical systems . . . . . . . . . . . . . . . . . . 6 1.3 More degrees of freedom

Rink, Bob

422

Lecture notes on "Geometric Dynamics and Symmetry"  

E-print Network

Lecture notes on "Geometric Dynamics and Symmetry" Bob Rink May 9, 2012 Contents 1 Mechanical systems 4 1.1 Two classical examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 One degree of freedom mechanical systems . . . . . . . . . . . . . . . . . . 6 1.3 More degrees of freedom

Rink, Bob

423

Geometrically Frustrated Antiferromagnets: Statistical Mechanics and Dynamics  

NASA Astrophysics Data System (ADS)

These lecture notes provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in which the results provide an understanding of some of the main observed properties of these systems.

Chalker, John T.

424

A historical survey geometric computer vision  

E-print Network

A historical survey of geometric computer vision Peter Sturm, INRIA hal-00646071,version1-29Nov2011-00646071,version1-29Nov2011 #12;Outline · Introduction · 1st Flashback: Invention of Photography applications of photography hal-00646071,version1-29Nov2011 #12;1st Flashback: Invention of Photography

Boyer, Edmond

425

Geometric Avatar Problems Mario E. Consuegra1  

E-print Network

Geometric Avatar Problems Mario E. Consuegra1 and Giri Narasimhan1 1 School of Computing introduce the concept of Avatar problems that deal with situations where each entity has multiple copies or "avatars" and the solutions are constrained to use exactly one of the avatars. The resulting set

Narasimhan, Giri

426

Original Articles Geometric Control of Cardiomyogenic Induction  

E-print Network

Original Articles Geometric Control of Cardiomyogenic Induction in Human Pluripotent Stem Cells influences extraembryonic endoderm (ExE) commitment and cardiac inductive properties. hESC aggregates were-free cardiac induction system, that robust and efficient cardiac differentiation is a function of endogenous Ex

Zandstra, Peter W.

427

Thermal assisted ultrasonic bonding method for poly(methyl methacrylate) (PMMA) microfluidic devices.  

PubMed

A thermal assisted ultrasonic bonding method for poly(methyl methacrylate) (PMMA) microfluidic devices has been presented. The substrates were preheated to 20-30 degrees C lower than glass transition temperature (T(g)) of the polymer. Then low amplitude ultrasonic vibration was employed to generate facial heat at the interface of PMMA substrates. PMMA microfluidic chips were successfully bonded with bulk temperature well below T(g) of the material and with pressure two orders lower than conventional thermal bonding, which was of great benefit to reduce the deformation of microstructures. The bonding process was optimized by Taguchi method. This bonding technique showed numerous superiorities including high bonding strength (0.95MPa), low dimension loss (0.3-0.8%) and short bonding time. Finally, a micromixer was successfully bonded by this method and its performance was demonstrated. PMID:20441903

Zhang, Zongbo; Wang, Xiaodong; Luo, Yi; He, Shengqiang; Wang, Liding

2010-06-15

428

Evolutionary optimization of a Genetically Refined Truss  

NASA Technical Reports Server (NTRS)

Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection and stress on a benchmark cantilever truss problem. Predominantly traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This paper will present a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation: Genetic Algorithms and Differential Evolution to successfully optimize a benchmark structural optimization problem. An non-traditional solution to the benchmark problem is presented in this paper, specifically a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization toolset.

Hull, Patrick V.; Tinker, Michael L.; Dozier, Gerry

2005-01-01

429

582 J. Am. Chem. SOC.1986, 108, 582-584 Theoretical Studies of Transition-Metal Hydrides. 1. Bond  

E-print Network

: We present here consistent ab initio calculations (generalized valence bond plus configuration calculations involve all-electron ab initio wave functions with a basis consistingof an optimized valence calculation was a generalized valence bond (GVB) wave function with the valence bond spin eigenfunction [GVB

Goddard III, William A.

430

A differential geometric approach to the geometric mean of symmetric positive-definite matrices  

E-print Network

Abstract. In this paper we introduce metric-based means for the space of positive-definite matrices. The mean associated with the Euclidean metric of the ambient space is the usual arithmetic mean. The mean associated with the Riemannian metric corresponds to the geometric mean. We discuss some invariance properties of the Riemannian mean and we use differential geometric tools to give a characterization of this mean. Key words. Geometric mean, Positive-definite symmetric matrices, Riemannian distance, Geodesics. AMS subject classifications. 47A64, 26E60, 15A48, 15A57

Maher Moakher

431

A GEOMETRICAL HEIGHT SCALE FOR SUNSPOT PENUMBRAE  

SciTech Connect

Inversions of spectropolarimetric observations of penumbral filaments deliver the stratification of different physical quantities in an optical depth scale. However, without establishing a geometrical height scale, their three-dimensional geometrical structure cannot be derived. This is crucial in understanding the correct spatial variation of physical properties in the penumbral atmosphere and to provide insights into the mechanism capable of explaining the observed penumbral brightness. The aim of this work is to determine a global geometrical height scale in the penumbra by minimizing the divergence of the magnetic field vector and the deviations from static equilibrium as imposed by a force balance equation that includes pressure gradients, gravity, and the Lorentz force. Optical depth models are derived from the inversion of spectropolarimetric data of an active region observed with the Solar Optical Telescope on board the Hinode satellite. We use a genetic algorithm to determine the boundary condition for the inference of geometrical heights. The retrieved geometrical height scale permits the evaluation of the Wilson depression at each pixel and the correlation of physical quantities at each height. Our results fit into the uncombed penumbral scenario, i.e., a penumbra composed of flux tubes with channeled mass flow and with a weaker and more horizontal magnetic field as compared with the background field. The ascending material is hotter and denser than their surroundings. We do not find evidence of overturning convection or field-free regions in the inner penumbral area analyzed. The penumbral brightness can be explained by the energy transfer of the ascending mass carried by the Evershed flow, if the physical quantities below z = -75 km are extrapolated from the results of the inversion.

Puschmann, K. G.; Ruiz Cobo, B.; MartInez Pillet, V., E-mail: kgp@iac.e, E-mail: brc@iac.e, E-mail: vmp@iac.e [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)

2010-09-10

432

Can EPR non-locality be geometrical?  

SciTech Connect

The presence in Quantum Mechanics of non-local correlations is one of the two fundamentally non-intuitive features of that theory. The non-local correlations themselves fall into two classes: EPR and Geometrical. The non-local characteristics of the geometrical type are well-understood and are not suspected of possibly generating acausal features, such as faster-than-light propagation of information. This has especially become true since the emergence of a geometrical treatment for the relevant gauge theories, i.e. Fiber Bundle geometry, in which the quantum non-localities are seen to correspond to pure homotopy considerations. This aspect is reviewed in section 2. Contrary-wise, from its very conception, the EPR situation was felt to be paradoxical. It has been suggested that the non-local features of EPR might also derive from geometrical considerations, like all other non-local characteristics of QM. In[7], one of the authors was able to point out several plausibility arguments for this thesis, emphasizing in particular similarities between the non-local correlations provided by any gauge field theory and those required by the preservation of the quantum numbers of the original EPR state-vector, throughout its spatially-extended mode. The derivation was, however, somewhat incomplete, especially because of the apparent difference between, on the one hand, the closed spatial loops arising in the analysis of the geometrical non-localities, from Aharonov-Bohm and Berry phases to magnetic monopoles and instantons, and on the other hand, in the EPR case, the open line drawn by the positions of the two moving decay products of the disintegrating particle. In what follows, the authors endeavor to remove this obstacle and show that as in all other QM non-localities, EPR is somehow related to closed loops, almost involving homotopy considerations. They develop this view in section 3.

Ne`eman, Y. [Tel-Aviv Univ. (Israel). Raymond and Beverly Sackler Faculty of Exact Sciences]|[Univ. of Texas, Austin, TX (United States). Center for Particle Physics; Botero, A. [Texas Univ., Austin, TX (United States)

1995-10-01

433

Rapid bond rearrangement in molecules after core-electron excitation  

NASA Astrophysics Data System (ADS)

Experimental studies of core-excited molecules using three-dimensional multi particle momentum imaging are presented where bond rearrangement processes in dication species are analysed. The aim of the study is to understand the relation between the geometric changes associated with core-excited states and the kinetic energy released in particular molecular dissociation processes. The kinematics of individual fragmentation channels are studied by fully three-dimensional momentum imaging of fragments in coincidence. Examples are presented where the high efficiency of the instrument and the fully three-dimensional momentum capabilities are exploited to understand nuclear motion leading to bond rearrangement in core-excited states. We identify bond-rearrangement processes in water, carbonyl sulphide and acetylene which are initiated in the core-excited state. In water this is evidenced by the H+2/O+ ion pair, and in carbonyl sulphide the OS++C+ pair is the fingerprint of this reaction. In acetylene the H+2 + C+2 ion pair indicates a molecular geometry that changes from linear to strongly bent. We measure the angular distribution of all fragments and fragment pairs and for the bond rearrangement processes in water and in core-excited acetylene the angular distribution of fragments suggests that the bond rearrangement is very rapid.

Sorensen, S. L.; Gisselbrecht, M.; Laksman, J.; Mnsson, E. P.; Colin, D.; Sankari, A.; Afaneh, F.

2014-04-01

434

Effect of quantum nuclear motion on hydrogen bonding.  

PubMed

This work considers how the properties of hydrogen bonded complexes, X-H?Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H?O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 , i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends. PMID:24811647

McKenzie, Ross H; Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G

2014-05-01

435

Methodology and method and appartus for signaling with capacity optimized constellations  

NASA Technical Reports Server (NTRS)

Communication systems are described that use geometrically shaped constellations that have increased capacity compared to conventional constellations operating within a similar SNR band. In several embodiments, the geometrically shaped is optimized based upon a capacity measure such as parallel decoding capacity or joint capacity. In many embodiments, a capacity optimized geometrically shaped constellation can be used to replace a conventional constellation as part of a firmware upgrade to transmitters and receivers within a communication system. In a number of embodiments, the geometrically shaped constellation is optimized for an Additive White Gaussian Noise channel or a fading channel.

Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)

2012-01-01

436

Geometric global quantum discord of two-qubit X states  

E-print Network

Xu [Jianwei Xu, J. Phys. A: Math. Theor. 45 405304 (2012)] generalized geometric quantum discord [B.Dakic, V. Vedral, and C . Brukner, Phys. Rev. Lett. 105 190502 (2010)] to multipartite states and proposed the geometric global quantum discord. In this paper, we first derive the analytical formulas of the geometric global quantum discord and geometric quantum discord for two-qubit X states, respectively. Second, we give five concrete examples to demonstrate the use of our formulas. Finally, we prove that the geometric quantum discord is a tight lower bound of the geometric global quantum discord.

Wen-Chao Qiang; Hua-Ping Zhanga; Lei Zhang

2014-06-08

437

Qualifying Energy Conservation Bonds  

E-print Network

1Qualified Energy Construction Bonds (QECBs) CATEE Conference December 18, 2013 ESL-KT-13-12-39 CATEE 2013: Clean Air Through Energy Efficiency Conference, San Antonio, Texas Dec. 16-18 Originally authorized by the Energy Improvement & Extension... are QECBs ESL-KT-13-12-39 CATEE 2013: Clean Air Through Energy Efficiency Conference, San Antonio, Texas Dec. 16-18 70% of allocation must be for public use, 30% of allocation MAY be used for a private activity Representative projects include school...

Briggs, J.

2013-01-01

438

Low temperature reactive bonding  

DOEpatents

The joining technique is disclosed that requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process. 5 figures.

Makowiecki, D.M.; Bionta, R.M.

1995-01-17

439

Where's the Orange? Geometric and Extra-Geometric Influences on English Children's Descriptions of Spatial Locations  

ERIC Educational Resources Information Center

The effect of both geometric and extra-geometric factors on children's production of "in" is reported (free-response paradigm). Eighty children across four age groups (means 4;1, 5;5, 6;1, and 7;1) were shown video scenes of puppets placing real objects in various positions with reference to a bowl and a plate. Located objects were placed at three

Richards, Lynn V.; Coventry, Kenny R.; Clibbens, John

2004-01-01

440

Diffusion bonding of the oxide dispersion strengthened steel PM2000  

NASA Astrophysics Data System (ADS)

Ferritic oxide dispersion strengthened (ODS) steels are well suited as structural materials, e.g. for claddings in fission reactors and for plasma facing components in fusion power plants due to their high mechanical and oxidation stability at high temperatures and their high irradiation resistance. PM2000 is an iron based ODS ferritic steel with homogeneously distributed nanometric yttria particles. Melting joining techniques are not suitable for such ODS materials because of the precipitation and agglomeration of the oxide particles and hence the loss of their strengthening effect. Solid state diffusion bonding is thus chosen to join PM2000 and is investigated in this work with a focus on oxide particles. The diffusion bonding process is aided by the computational modeling, including the influence of the ODS particles. For modeling the microstructure stability and the creep behavior of PM2000 at various, diffusion bonding relevant temperatures (50-80% Tm) are investigated. Particle distribution (TEM), strength (tensile test) and toughness (Charpy impact test) obtained at temperatures relevant for bonding serve as input for the prediction of optimal diffusion bonding parameters. The optimally bonded specimens show comparable strength and toughness relative to the base material.

Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir

2013-11-01

441

27 CFR 17.107 - Strengthening bonds.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Strengthening bonds. 17.107 Section 17.107 Alcohol...USED IN MANUFACTURING NONBEVERAGE PRODUCTS Bonds and Consents of Sureties 17.107 Strengthening bonds. Whenever the amount of a bond on...

2010-04-01

442

27 CFR 25.96 - Superseding bond.  

Code of Federal Regulations, 2010 CFR

... Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS BEER Bonds and Consents of Surety 25.96 Superseding bond. When the principal submits a new bond to supersede a bond...

2010-04-01

443

6.253 Convex Analysis and Optimization, Spring 2010  

E-print Network

This course will focus on fundamental subjects in (deterministic) optimization, connected through the themes of convexity, geometric multipliers, and duality. The aim is to develop the core analytical and computational ...

Bertsekas, Dimitri

444

A Micromachined Geometric Moire Interferometric Floating-Element Shear Stress Sensor  

NASA Technical Reports Server (NTRS)

This paper presents the development of a floating-element shear stress sensor that permits the direct measurement of skin friction based on geometric Moir interferometry. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Experimental characterization indicates a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.

Horowitz, S.; Chen, T.; Chandrasekaran, V.; Tedjojuwono, K.; Nishida, T.; Cattafesta, L.; Sheplak, M.

2004-01-01

445

Geometrical defects in two-dimensional melting of many-particle Yukawa systems  

NASA Astrophysics Data System (ADS)

We present a theoretical polygon construction analysis of two-dimensional melting and freezing transitions in many-particle Yukawa systems. Two-dimensional melting transitions can be characterized as proliferation of geometrical defectsnontriangular polygons, obtained by removing unusually long bonds in the triangulation of particle positions. A liquid state is characterized by the temperature-independent number of quadrilaterals and linearly increasing number of pentagons. We analyze specific types of vertices, classified by the type and distribution of polygons surrounding them, and determine temperature dependencies of their concentrations. Solid-liquid phase transitions are followed by the peaks in the abundances of certain types of vertices.

Radzvilavi?ius, Ar?nas

2012-11-01

446

Functionally important segments in proteins dissected using Gene Ontology and geometric clustering of peptide fragments  

PubMed Central

We have developed a geometric clustering algorithm using backbone ?,? angles to group conformationally similar peptide fragments of any length. By labeling each fragment in the cluster with the level-specific Gene Ontology 'molecular function' term of its protein, we are able to compute statistics for molecular function-propensity and p-value of individual fragments in the cluster. Clustering-cum-statistical analysis for peptide fragments 8 residues in length and with only trans peptide bonds shows that molecular function propensities ?20 and p-values ?0.05 can dissect fragments within a protein linked to the molecular function. PMID:18331637

Manikandan, Karuppasamy; Pal, Debnath; Ramakumar, Suryanarayanarao; Brener, Nathan E; Iyengar, Sitharama S; Seetharaman, Guna

2008-01-01

447

Geometric Attributes of Retaining Glycosyltransferase Enzymes Favor an Orthogonal Mechanism  

PubMed Central

Retaining glycosyltransferase enzymes retain the stereochemistry of the donor glycosidic linkage after transfer to an acceptor molecule. The mechanism these enzymes utilize to achieve retention of the anomeric stereochemistry has been a matter of much debate. Re-analysis of previously released structural data from retaining and inverting glycosyltransferases allows competing mechanistic proposals to be evaluated. The binding of metal-nucleotide-sugars between inverting and retaining enzymes is conformationally unique and requires the donor substrate to occupy two different orientations in the two types of glycosyltransferases. The available structures of retaining glycosyltransferases lack appropriately positioned enzymatic dipolar residues to initiate or stabilize the intermediates of a dissociative mechanism. Further, available structures show that the acceptor nucleophile and anomeric carbon of the donor sugar are in close proximity. Structural features support orthogonal (front-side) attack from a position lying ?90 from the C1-O phosphate bond for retaining enzymes. These structural conclusions are consistent with the geometric conclusions of recent kinetic and computational studies. PMID:23936487

Schuman, Brock; Evans, Stephen V.; Fyles, Thomas M.

2013-01-01

448

Advanced Stress, Strain And Geometrical Analysis In Semiconductor Devices  

SciTech Connect

High stresses and defect densities increases the risk of semiconductor device failure. Reliability studies on potential failure sources have an impact on design and are essential to assure the long term functioning of the device. Related to the dramatically smaller volume of semiconductor devices and new bonding techniques on such devices, new methods in testing and qualification are needed. Reliability studies on potential failure sources have an impact on design and are essential to assure the long term functioning of the device. In this paper, the applications of advanced High Resolution X-ray Diffraction (HRXRD) methods in strain, defect and deformation analysis on semiconductor devices are discussed. HRXRD with Rocking Curves (RC's) and Reciprocal Space Maps (RSM's) is used as accurate, non-destructive experimental method to evaluate the crystalline quality, and more precisely for the given samples, the in-situ strain, defects and geometrical parameters such as tilt and bending of device. The combination with advanced FEM simulations gives the possibility to support efficiently semiconductor devices design.

Neels, Antonia; Dommann, Alex; Niedermann, Philippe [Centre Suisse d'Electronique et de Microtechnique, CSEM, Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland); Farub, Claudiu; Kaenel, Hans von [Laboratorium f. Festkoerperphysik, ETH Zuerich (Switzerland)

2010-11-24

449

A study of improvements in silicon solar cell efficiency due to various geometrical and doping modifications  

NASA Technical Reports Server (NTRS)

This paper presents the results of continued studies of silicon solar cell operation and limitations. The objective of this paper is to report on geometrical and doping changes in silicon solar cells which result in predictions of high efficiencies. Efficiencies as high as 20 per cent (uncorrected for metal coverage and ohmic sheet resistance) have been calculated for optimized cells. The conditions required to achieve these efficiency values are discussed.

Dunbar, P. M.; Hauser, J. R.

1976-01-01

450

Geometrical layout of a Mars balloon and precalculation of the thermal control system  

Microsoft Academic Search

A solar-balloon (SB) system was geometrically optimized using published data on the ambient conditions on Mars, yielding, as a result, a design of a one-body SB system with an integrated hermetically sealed helium lifting balloon. The SB shape is similar to a Cassinian curve. The maximum diameter is 93.6 m, and maximum height is 122.3 m. Kapton with golden, black,

D. Brockhagen; W. Hallmann; M. Reinartz

1990-01-01

451

27 CFR 19.241 - Operations bond-distilled spirits plant and adjacent bonded wine cellar.  

Code of Federal Regulations, 2010 CFR

...false Operations bond-distilled spirits plant and adjacent bonded wine cellar. 19...TREASURY LIQUORS DISTILLED SPIRITS PLANTS Bonds and Consents of Surety 19.241 Operations bonddistilled spirits plant and adjacent bonded wine cellar....

2010-04-01

452

77 FR 32128 - Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of Qualified...  

Federal Register 2010, 2011, 2012, 2013

...Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of...amount was calculated pursuant to enhanced bonding requirements (EBR bond) upon the agency's...INFORMATION: Background I. Enhanced Bonding Requirements In 2004, U.S....

2012-05-31

453

27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.  

Code of Federal Regulations, 2013 CFR

... Operations bond for distilled spirits plant and adjacent bonded wine cellar. 19...TREASURY ALCOHOL DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Requirements... Operations bond for distilled spirits plant and adjacent bonded wine cellar....

2013-04-01

454

27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.  

... Operations bond for distilled spirits plant and adjacent bonded wine cellar. 19...TREASURY ALCOHOL DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Requirements... Operations bond for distilled spirits plant and adjacent bonded wine cellar....

2014-04-01

455

27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.  

Code of Federal Regulations, 2012 CFR

... Operations bond for distilled spirits plant and adjacent bonded wine cellar. 19...TREASURY LIQUORS DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Requirements... Operations bond for distilled spirits plant and adjacent bonded wine cellar....

2012-04-01

456

27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.  

Code of Federal Regulations, 2011 CFR

... Operations bond for distilled spirits plant and adjacent bonded wine cellar. 19...TREASURY LIQUORS DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Requirements... Operations bond for distilled spirits plant and adjacent bonded wine cellar....

2011-04-01

457

Production of Disulfide-Bonded Proteins in Escherichia coli.  

PubMed

Production of recombinant proteins at high yields in Escherichia coli requires extensive optimization of expression conditions. Production is further complicated for proteins that require specific post-translational modifications for their eventual folding. One common and particularly important post-translational modification is oxidation of the correct pair of cysteines to form a disulfide bond. This unit describes methods to produce disulfide-bonded proteins in E. coli in either the naturally oxidizing periplasm or the cytoplasm of appropriately engineered cells. The focus is on variables key to improving the oxidative folding of disulfide-bonded proteins, with the aim of helping the researcher optimize expression conditions for a protein of interest. Curr. Protoc. Mol. Biol. 108:16.1B.1-16.1B.21. 2014 by John Wiley & Sons, Inc. PMID:25271713

Ke, Na; Berkmen, Mehmet

2014-01-01

458

A micro energy harvester with 3D wire bonded microcoils  

Microsoft Academic Search

We developed the first micro energy harvester with optimized wire bonded microcoils. The coils were fabricated with a fully automated process on PCB. The 3D coils enable to effectively use the magnetic field and generate an output power of 0.62 !W at 1 ms -2 within a total harvester volume of 0.46 cm 3 . With the coil wire thickness

C. Cepnik; U. Wallrabe

2011-01-01

459

Rational trigonometry via projective geometric algebra  

E-print Network

We show that main results of rational trigonometry (as developed by NJ Wildberger, "Divine Proportions", 2005) can be succinctly expressed using projective (aka homogeneous) geometric algebra (PGA). In fact, the PGA representation exhibits distinct advantages over the original vector-based approach. These include the advantages intrinsic to geometric algebra: it is coordinate-free, treats lines and points in a unified framework, and handles many special cases in a uniform and seamless fashion. It also reveals structural patterns not visible in the original formulation, for example, the exact duality of spread and quadrance. The current article handles only a representative (euclidean) subset of the full content of Wildberger's work, but enough to establish the value of this approach for further development. The metric-neutral framework of PGA makes it especially promising also to handle universal geometry, which extends rational trigonometry to the hyperbolic plane.

Charles Gunn

2014-01-08

460

Velocity coordinate spectrum: geometrical aspects of observations  

E-print Network

We analyze a technique of obtaining turbulence power spectrum using spectral line data along the velocity coordinate, which we refer to as Velocity Coordinate Spectrum (VCS). We formalize geometrical aspects of observation through a single factor, "geometric term". We find that all variety of particular observational configurations can be described using correspondent variants of this term, which we explicitly calculate. This allows us to obtain asymptotics for both parallel lines of sight and crossing lines of sight. The latter case is especially important for studies of turbulence within diffuse ISM in Milky Way. For verification of our results, we use direct calculation of VCS spectra, while the numerical simulations are presented in a companion paper.

A. Chepurnov; A. Lazarian

2006-11-15

461

Universal geometrical scaling of the elliptic flow  

E-print Network

The presence of scaling variables in experimental observables provide very valuable indications of the dynamics underlying a given physical process. In the last years, the search for geometric scaling, that is the presence of a scaling variable which encodes all geometrical information of the collision as well as other external quantities as the total energy, has been very active. This is motivated, in part, for being one of the genuine predictions of the Color Glass Condensate formalism for saturation of partonic densities. Here we extend these previous findings to the case of experimental data on elliptic flow. We find an excellent scaling for all centralities and energies, from RHIC to LHC, with a simple generalization of the scaling previously found for other observables and systems. Interestingly the case of the photons, difficult to reconcile in most formalisms, nicely fit the scaling curve. We discuss on the possible interpretations of this finding in terms of initial or final state effects.

C. Andrs; J. Dias de Deus; A. Moscoso; C. Pajares; Carlos A. Salgado

2014-05-09

462

Geometric modeling for computer aided design  

NASA Technical Reports Server (NTRS)

Over the past several years, it has been the primary goal of this grant to design and implement software to be used in the conceptual design of aerospace vehicles. The work carried out under this grant was performed jointly with members of the Vehicle Analysis Branch (VAB) of NASA LaRC, Computer Sciences Corp., and Vigyan Corp. This has resulted in the development of several packages and design studies. Primary among these are the interactive geometric modeling tool, the Solid Modeling Aerospace Research Tool (smart), and the integration and execution tools provided by the Environment for Application Software Integration and Execution (EASIE). In addition, it is the purpose of the personnel of this grant to provide consultation in the areas of structural design, algorithm development, and software development and implementation, particularly in the areas of computer aided design, geometric surface representation, and parallel algorithms.

Schwing, James L.

1993-01-01

463

Topological Minimally Entangled States via Geometric Measure  

E-print Network

Here we show how the Minimally Entangled States (MES) of a 2d system with topological order can be identified using the geometric measure of entanglement. We show this by minimizing this measure for the doubled semion, doubled Fibonacci and toric code models on a torus with non-trivial topological partitions. Our calculations are done either quasi-exactly for small system sizes, or using the tensor network approach in [R. Orus, T.-C. Wei, O. Buerschaper, A. Garcia-Saez, arXiv:1406.0585] for large sizes. As a byproduct of our methods, we see that the minimisation of the geometric entanglement can also determine the number of quasiparticle excitations in a given model. The results in this paper provide a very efficient and accurate way of extracting the full topological information of a 2d quantum lattice model from the multipartite entanglement structure of its ground states.

Buerschaper, Oliver; Orus, Roman; Wei, Tzu-Chieh

2014-01-01

464

Topological Minimally Entangled States via Geometric Measure  

E-print Network

Here we show how the Minimally Entangled States (MES) of a 2d system with topological order can be identified using the geometric measure of entanglement. We show this by minimizing this measure for the doubled semion, doubled Fibonacci and toric code models on a torus with non-trivial topological partitions. Our calculations are done either quasi-exactly for small system sizes, or using the tensor network approach in [R. Orus, T.-C. Wei, O. Buerschaper, A. Garcia-Saez, arXiv:1406.0585] for large sizes. As a byproduct of our methods, we see that the minimisation of the geometric entanglement can also determine the number of Abelian quasiparticle excitations in a given model. The results in this paper provide a very efficient and accurate way of extracting the full topological information of a 2d quantum lattice model from the multipartite entanglement structure of its ground states.

Oliver Buerschaper; Artur Garcia-Saez; Roman Orus; Tzu-Chieh Wei

2014-10-02

465

Geometrical Aspects in Optical Wavepacket Dynamics  

E-print Network

We construct a semiclassical theory for propagation of an optical wavepacket in non-conducting media with periodic structures of dielectric permittivity and magnetic permeability, i.e., non-conducting photonic crystals. We employ a quantum-mechanical formalism in order to clarify its link to those of electronic systems. It involves the geometrical phase, i.e., Berry phase, in a natural way, and describes an interplay between orbital motion and the internal rotation. Based on the above theory, we discuss the geometrical aspects of the optical Hall effect. We also consider a reduction of the theory to a system without periodic structure and apply it to the transverse shift at an interface reflection/refraction. For generic incident beams with elliptic polarizations, an identical result for the transverse shift of each reflected/transmitted beam is given by the following different approaches; (i) analytic evaluation of wavepacket dynamics, (ii) total angular momentum (TAM) conservation {\\it for individual photon...

Onoda, M; Nagaosa, N; Onoda, Masaru; Murakami, Shuichi; Nagaosa, Naoto

2006-01-01

466

Geometric phase shifts in biological oscillators.  

PubMed

Many intracellular processes continue to oscillate during the cell cycle. Although it is not well-understood how they are affected by discontinuities in the cellular environment, the general assumption is that oscillations remain robust provided the period of cell divisions is much larger than the period of the oscillator. Here, I will show that under these conditions a cell will in fact have to correct for an additional quantity added to the phase of oscillation upon every repetition of the cell cycle. The resulting phase shift is an analogue of the geometric phase, a curious entity first discovered in quantum mechanics. In this letter, I will discuss the theory of the geometric phase shift and demonstrate its relevance to biological oscillations. PMID:24769251

Tourigny, David S

2014-08-21

467

Geometric Frustration in Buckled Colloidal Monolayers  

E-print Network

Geometric frustration arises when lattice structure prevents simultaneous minimization of local interactions. It leads to highly degenerate ground states and, subsequently, complex phases of matter such as water ice, spin ice and frustrated magnetic materials. Here we report a simple geometrically frustrated system composed of closely packed colloidal spheres confined between parallel walls. Diameter-tunable microgel spheres are self-assembled into a buckled triangular lattice with either up or down displacements analogous to an antiferromagnetic Ising model on a triangular lattice. Experiment and theory reveal single-particle dynamics governed by in-plane lattice distortions that partially relieve frustration and produce ground-states with zigzagging stripes and subextensive entropy, rather than the more random configurations and extensive entropy of the antiferromagnetic Ising model. This tunable soft matter system provides an uncharted arena in which the dynamics of frustration, thermal excitations and defects can be directly visualized.

Yilong Han; Yair Shokef; Ahmed M. Alsayed; Peter Yunker; Tom C. Lubensky; Arjun G. Yodh

2008-07-24

468

Geometric frustration in buckled colloidal monolayers.  

PubMed

Geometric frustration arises when lattice structure prevents simultaneous minimization of local interaction energies. It leads to highly degenerate ground states and, subsequently, to complex phases of matter, such as water ice, spin ice, and frustrated magnetic materials. Here we report a simple geometrically frustrated system composed of closely packed colloidal spheres confined between parallel walls. Diameter-tunable microgel spheres are self-assembled into a buckled triangular lattice with either up or down displacements, analogous to an antiferromagnetic Ising model on a triangular lattice. Experiment and theory reveal single-particle dynamics governed by in-plane lattice distortions that partially relieve frustration and produce ground states with zigzagging stripes and subextensive entropy, rather than the more random configurations and extensive entropy of the antiferromagnetic Ising model. This tunable soft-matter system provides a means to directly visualize the dynamics of frustration, thermal excitations and defects. PMID:19092926

Han, Yilong; Shokef, Yair; Alsayed, Ahmed M; Yunker, Peter; Lubensky, Tom C; Yodh, Arjun G

2008-12-18

469

The Fractal Geometrical Properties of Nuclei  

E-print Network

We present a new idea to understand the structure of nuclei, which is comparing to the liquid drop model. After discussing the probability that the nuclear system may be a fractal object with the characteristic of self-similarity, the nuclear irregular structure properties and the self-similarity characteristic are considered to be an intrinsic aspects of nuclear structure properties. For the description of nuclear geometric properties, nuclear fractal dimension is an irreplaceable variable similar to the nuclear radius. In order to determine these two variables, a new nuclear potential energy formula which is related to the fractal dimension is put forward and the phenomenological semi-empirical Bethe-Weizsacker binding energy formula is modified using the fractal geometric theory. And one important equation set with two equations is obtained, which is related to the conception that the fractal dimension should be a dynamical parameter in the process of nuclear synthesis. The fractal dimensions of the light ...

Ma, W H; Wang, Q; Mukherjee, S; Yang, L; Yang, Y Y; Huang, M R; Zhou, Y J

2014-01-01

470

Effects of bonding layer on the available strain measuring range of fiber Bragg gratings.  

PubMed

Stress-induced birefringence can lead to distortion in the reflection spectra of fiber Bragg grating (FBG) sensors, thereby resulting in the loss of accuracy and stability of strain measurements. The bonding layer is a direct factor in producing stress birefringence within FBGs. To assess the impacts quantitatively, a theoretical model that links the bonding layer and the reflection spectrum was established. At the same time, the finite element method, based on the theoretical model, was used to study the relationships between characteristics of the bonding layer and reflection spectrum in detail. The analytical results indicate that high elastic modulus and mismatched Poisson's ratio of bonding layer decrease the available strain measuring range of FBGs remarkably, and that unreasonable geometric parameters of the bonding layer should be avoided. In addition, a validation experiment was conducted and experimental results proved the prediction of the theoretical analysis. It can be concluded from the results that the bonding layer is the major limiting factor for the application of surface-bonded FBG sensors in large strain measurements. The bonding materials and bonding processes used in producing FBG sensors deserve serious consideration. PMID:24663267

Zhang, Wei; Chen, Weimin; Shu, Yuejie; Lei, Xiaohua; Liu, Xianming

2014-02-10

471

Geometric Perturbation Theory and Plasma Physics  

Microsoft Academic Search

Modern differential geometric techniques are used to unify the physical asymptotics underlying mechanics, wave theory and statistical mechanics. The approach gives new insights into the structure of physical theories and is suited to the needs of modern large-scale computer simulation and symbol manipulation systems. A coordinate-free formulation of non-singular perturbation theory is given, from which a new Hamiltonian perturbation structure

Stephen Malvern Omohundro

1985-01-01

472

Expander flows, geometric embeddings and graph partitioning  

Microsoft Academic Search

We give a O(?log n)-approximation algorithm for sparsest cut, balanced separator, and graph conductance problems. This improves the O(log n)-approximation of Leighton and Rao (1988). We use a well-known semidefinite relaxation with triangle inequality constraints. Central to our analysis is a geometric theorem about projections of point sets in Rd, whose proof makes essential use of a phenomenon called measure

Sanjeev Arora; Satish Rao; Umesh V. Vazirani

2004-01-01

473

Geometric Effects in an Elastic Tensegrity Structure  

Microsoft Academic Search

Tensegrity structures are under-constrained, 3-dimensional, self-stressing structural systems. They demonstrate an infinitesimal flex and when loaded they display a nonlinear geometric stiffening. In earlier work many examples of the resulting forcedisplacement relationship have been demonstrated numerically, and some aspects of the forcedisplacement relationship have been derived analytically. In this article an energy formulation is presented for the case of a

I. J. Oppenheim; W. O. Williams

2000-01-01

474

Paper Folding: Unfurling Geometric Paper Shapes  

NSDL National Science Digital Library

Use geometry, a ruler, and a steady hand to create these amazing unfurling paper folds! Be sure to check out Simon Guest's folded "super structure" link, and to see great paper folding examples, check out Margaret Pezalla-Granlund's website. This activity works really well with learners interested in origami, or learners wanting to transform plain old geometric shapes into pop-up masterpieces. This activity could last from one to three hours.

Minnesota, Science M.

2012-06-26

475

GEOMETRICAL AND VARIATIONAL ISSUES ON FLAGS  

Microsoft Academic Search

Abstract. We intend to describe the interplay of some results derived in [4], with the ones obtained in [2] which describe new invariant Einstein non-Kahler metrics on geometrical flag manifold F(n,n1,...,nk) with n1 +... +nk = n, and the maximal,one denoted by F(n). According to [3], the almost Hermitian structures are classified into 16 classes. But in the case of

CAIO JOSE; COLLETTI NEGREIROS

2006-01-01

476