Sample records for optimized geometric bond

  1. Geometric optimization of thermal systems

    NASA Astrophysics Data System (ADS)

    Alebrahim, Asad Mansour

    2000-10-01

    The work in chapter 1 extends to three dimensions and to convective heat transfer the constructal method of minimizing the thermal resistance between a volume and one point. In the first part, the heat flow mechanism is conduction, and the heat generating volume is occupied by low conductivity material (k 0) and high conductivity inserts (kp) that are shaped as constant-thickness disks mounted on a common stem of kp material. In the second part the interstitial spaces once occupied by k0 material are bathed by forced convection. The internal and external geometric aspect ratios of the elemental volume and the first assembly are optimized numerically subject to volume constraints. Chapter 2 presents the constrained thermodynamic optimization of a cross-flow heat exchanger with ram air on the cold side, which is used in the environmental control systems of aircraft. Optimized geometric features such as the ratio of channel spacings and flow lengths are reported. It is found that the optimized features are relatively insensitive to changes in other physical parameters of the installation and relatively insensitive to the additional irreversibility due to discharging the ram-air stream into the atmosphere, emphasizing the robustness of the thermodynamic optimum. In chapter 3 the problem of maximizing exergy extraction from a hot stream by distributing streams over a heat transfer surface is studied. In the first part, the cold stream is compressed in an isothermal compressor, expanded in an adiabatic turbine, and discharged into the ambient. In the second part, the cold stream is compressed in an adiabatic compressor. Both designs are optimized with respect to the capacity-rate imbalance of the counter-flow and the pressure ratio maintained by the compressor. This study shows the tradeoff between simplicity and increased performance, and outlines the path for further conceptual work on the extraction of exergy from a hot stream that is being cooled gradually. The aim of chapter 4 was to optimize the performance of a boot-strap air cycle of an environmental control system (ECS) for aircraft. New in the present study was that the optimization refers to the performance of the entire ECS system, not to the performance of an individual component. Also, there were two heat exchangers, not one, and their relative positions and sizes were not specified in advance. This study showed that geometric optimization can be identified when the optimization procedure refers to the performance of the entire ECS system, not to the performance of an individual component. This optimized features were robust relative to some physical parameters. This robustness may be used to simplify future optimization of similar systems.

  2. Water filtration optimization by geometric programming

    E-print Network

    Wray, Duane Jimmy

    1970-01-01

    MATER FILTRATION OPTIMIZATION BY GEOMETRIC PROGRAMMING A Thesis by DUANE JIMMY WRAY Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1970 Major... Subject: Industrial Engineering WATER FILTRATION OPTIMIZATION BY GEOMETRIC PROGRAMMING A Thesis by DUANE JIMMY WRAY Chairman of Committee) (Head of Department) (Member) M p, ~ (Member)' December 1970 ABSTRACT Water Fi 1 trati on Optimization...

  3. Geometrically nonlinear analysis of adhesively bonded joints

    NASA Technical Reports Server (NTRS)

    Dattaguru, B.; Everett, R. A., Jr.; Whitcomb, J. D.; Johnson, W. S.

    1984-01-01

    A geometrically nonlinear finite element analysis of cohesive failure in typical joints is presented. Cracked-lap-shear joints were chosen for analysis. Results obtained from linear and nonlinear analysis show that nonlinear effects, due to large rotations, significantly affect the calculated mode 1, crack opening, and mode 2, inplane shear, strain-energy-release rates. The ratio of the mode 1 to mode 2 strain-energy-release rates (G1/G2) was found to be strongly affected by the adhesive modulus and the adherend thickness. The ratios between 0.2 and 0.8 can be obtained by varying adherend thickness and using either a single or double cracked-lap-shear specimen configuration. Debond growth rate data, together with the analysis, indicate that mode 1 strain-energy-release rate governs debond growth. Results from the present analysis agree well with experimentally measured joint opening displacements. Previously announced in STAR as N83-13497

  4. ORIGINAL ARTICLE Geometrical and mechanical aspects of fabric bonding

    E-print Network

    Mobasher, Barzin

    ORIGINAL ARTICLE Geometrical and mechanical aspects of fabric bonding and pullout in cement Abstract Fabric reinforced cement composites are a new class of cementitious materials with enhanced tensile strength and ductility. The reinforcing mecha- nisms of 2-D fabric structures in cement matrix

  5. Evolutionary Optimization of a Geometrically Refined Truss

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

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

    E-print Network

    North Carolina at Chapel Hill, University of

    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

  7. Optimization of inductor circuits via geometric programming

    Microsoft Academic Search

    Maria del Mar Hershenson; Sunderarajan S. Mohan; Stephen P. Boyd; Thomas H. Lee

    1999-01-01

    We present an efficient method for optimal design and synthe- sis of CMOS inductors for use in RF circuits. This method uses the the physical dimensions of the inductor as the design pa- rameters and handles a variety of specifications including fixed value of inductance, minimum self-resonant frequency, mini- mum quality factor, etc. Geometric constraints that can be han- dled

  8. Optimization of biotechnological systems through geometric programming

    PubMed Central

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

    2007-01-01

    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

  9. Optimization of measurement configurations for geometrical calibration of industrial robot

    E-print Network

    Paris-Sud XI, Université de

    Optimization of measurement configurations for geometrical calibration of industrial robot Alexandr of industrial robots employed in precise manufacturing. To identify geometric parameters, an advanced is illustrated by several examples. Keywords: industrial robot, calibration, design of experiments, industry

  10. Geometric optimization of flow systems with irreversibilities

    NASA Astrophysics Data System (ADS)

    Errera, Marcelo Risso

    1999-11-01

    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.

  11. Introduction to geometric processing through optimization.

    PubMed

    Taubin, Gabriel

    2012-01-01

    As an introduction to the field, this article shows how to formulate several geometry-processing operations to solve systems of equations in the "least-squares" sense. The equations are derived from local geometric relations using elementary concepts from analytic geometry, such as points, lines, planes, vectors, and polygons. Simple and useful tools for interactive polygon mesh editing result from the most basic descent strategies to solve these optimization problems. Throughout the article, the author develops the mathematical formulations incrementally, keeping in mind that the objective is to implement simple software for interactive editing applications that works well in practice. Readers can implement higher-performance versions of these algorithms by replacing the simple solvers proposed here with more advanced ones. PMID:24806636

  12. Optimal Strokes for Driftless Swimmers: A General Geometric Approach

    E-print Network

    Paris-Sud XI, Universit de

    Optimal Strokes for Driftless Swimmers: A General Geometric Approach Thomas Chambrion Laetitia . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Outline and Main Achievements . . . . . . . . . . . . . . . . 4 2 Seeking of optimal strokes 5 2.4 Firsts Properties of the Optimal Strokes . . . . . . . . . . . . 12 2.5 Further Properties

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

    E-print Network

    Herschlag, Dan

    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

  14. Geometric Programming optimization of deterministic inventory systems under multiple constraints

    E-print Network

    Foster, Ralph Emerson

    1967-01-01

    GEOMETRIC PROGRAivdqING OPTIMIZATION OF DETERMINISTIC INVENTORY SYSTEMS UNDER MULTIPLE CONSTRAINTS A Thesis By RALPH EMERSON FOSTER Submitted to the Graduate College of the Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE August, 1967 Major Subject: Industrial Engineering GEOMETRIC PROGRAMING OPTIMIZATION 01' DETERMTNI. , 'I'IC INVLNTORY SYSTLstS UNDER )1i, LTIY! E CONSTRAI, 'TS A Thesis By RALPH EMERSON I'OSTER Approved as to style...

  15. Geometrical features of hydrogen bonded complexes involving sterically hindered pyridines.

    PubMed

    Andreeva, Daria V; Ip, Brenda; Gurinov, Andrey A; Tolstoy, Peter M; Denisov, Gleb S; Shenderovich, Ilja G; Limbach, Hans-Heinrich

    2006-09-21

    The ability of strongly sterically hindered pyridines to form hydrogen bonded complexes was inspected using low-temperature 1H and 15N NMR spectroscopy in a liquefied Freon mixture. The proton acceptors were 2,6-di(tert-butyl)-4-methyl- and 2,6-di(tert-butyl)-4-diethylaminopyridine; the proton donors were hydrogen tetrafluoroborate, hydrogen chloride, and hydrogen fluoride. The presence of the tert-butyl groups in the ortho positions dramatically perturbed the geometry of the forming hydrogen bonds. As revealed by experiment, the studied crowded pyridines could form hydrogen bonded complexes with proton donors exclusively through their protonation. Even the strongest small proton acceptor, anion F-, could not be received by the protonated base. Instead, the simplest hydrogen bonded complex involved the [FHF]- anion. This complex was characterized by the shortest possible N...F distance of about 2.8 A. Because the ortho tert-butyl groups did not prevent the hydrogen bond interaction between the protonated center and the anion completely, an increase of the pyridine basicity caused a further shortening of the N-H distance and a weakening of the hydrogen bond to the counterion. PMID:16970384

  16. Water Resource System Optimization by Geometric Programming

    E-print Network

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

    of the applicability and usefulness of optimization methods in water resources analyses [38]. Linear programming [53], dynamic programming [41,40], and nonlinear programming [19] have been shown to be useful in water resource optimization problems. These techniques...

  17. Optimization in Geometric Graphs: Complexity and Approximation

    E-print Network

    Kahruman-Anderoglu, Sera

    2011-02-22

    geometry, facility location and, particularly, wireless communication networks. Efficient operation of wireless networks involves several decision problems that can be reduced to well known optimization problems in graph theory. For instance, the notion...

  18. Optimal Control of Underactuated Mechanical Systems: A Geometric Approach

    E-print Network

    L. Colombo; D. Martin de Diego; M. Zuccalli

    2009-12-10

    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.

  19. Optimal Execution Problem for Geometric Ornstein-Uhlenbeck Price Process

    E-print Network

    Kato, Takashi

    2011-01-01

    We study the optimal execution problem in the presence of market impact and give a generalization of the main result of Kato(2009). Then we consider an example where the security price follows a geometric Ornstein-Uhlenbeck process which has the so-called mean-reverting property, and then show that an optimal strategy is a mixture of initial/terminal block liquidation and intermediate gradual liquidation. When the security price has no volatility, the form of our optimal strategy is the same as results of Obizhaeva and Wang(2005) and Alfonsi et al.(2010), who studied the optimal execution in a limit-order-book model.

  20. THP-1 macrophage lipid accumulation unaffected by fatty acid double bond geometric or positional configuration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dietary fatty acid type alters atherosclerotic lesion progression and macrophage lipid accumulation. Incompletely elucidated are the mechanisms by which fatty acids differing in double-bond geometric or positional configuration alter arterial lipid accumulation. The objective of this study was to ev...

  1. Optimal source codes for geometrically distributed integer alphabets

    NASA Technical Reports Server (NTRS)

    Gallager, R. G.; Van Voorhis, D. C.

    1975-01-01

    An approach is shown for using the Huffman algorithm indirectly to prove the optimality of a code for an infinite alphabet if an estimate concerning the nature of the code can be made. Attention is given to nonnegative integers with a geometric probability assignment. The particular distribution considered arises in run-length coding and in encoding protocol information in data networks. Questions of redundancy of the optimal code are also investigated.

  2. Stiffness design of geometrically nonlinear structures using topology optimization

    Microsoft Academic Search

    T. Buhl; C. B. W. Pedersen; O. Sigmund

    2000-01-01

    . The paper deals with topology optimization of structures undergoing large deformations. The geometrically nonlinear behaviour\\u000a of the structures are modelled using a total Lagrangian finite element formulation and the equilibrium is found using a Newton-Raphson\\u000a iterative scheme. The sensitivities of the objective functions are found with the adjoint method and the optimization problem\\u000a is solved using the Method of

  3. Geometric Parameterization and Multiobjective Shape Optimization of Convective Periodic Channels

    Microsoft Academic Search

    E. Nobile; F. Pinto; G. Rizzetto

    2006-01-01

    In this article we describe a general procedure for the geometric parameterization and multiobjective shape optimization of periodic wavy channels, representative of the repeating module of an ample variety of heat exchangers. The two objectives considered are the maximization of heat transfer rate and the minimization of friction factor. Since there is no single optimum to be found, we use

  4. Global laminate optimization on geometrically partitioned shell structures

    Microsoft Academic Search

    David Keller

    2011-01-01

    A method aimed at the optimization of locally varying laminates is investigated. The structure is partitioned into geometrical\\u000a sections. These sections are covered by global plies. A variable-length representation scheme for an evolutionary algorithm\\u000a is developed. This scheme encodes the number of global plies, their thickness, material, and orientation. A set of genetic\\u000a variation operators tailored to this particular representation

  5. Dictionary of protein secondary structure: pattern recognition of hydrogen-bonded and geometrical features

    Microsoft Academic Search

    Wolfgang Kabsch; Christian Sander

    1983-01-01

    For a successful analysis of the relation between amino acid sequence and protein structure, an unambiguous and physically meaningful definition of secondary structure is essential. We have developed a set of simple and physically motivated criteria for secondary structure, programmed as a pattern-recognition process of hydrogen-bonded and geometrical features extracted from x-ray coordinates. Cooperative secondary structure is recognized as repeats

  6. Geometrical parameters optimization for tube hydroforming using response surface method

    NASA Astrophysics Data System (ADS)

    Chebbah, M. S.; Azaouzi, M.

    2014-10-01

    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.

  7. Geometrical optimization of helical flow in grooved micromixers

    PubMed Central

    Lynn, N. Scott; Dandy, David S.

    2010-01-01

    Owing to the enhancement of surface effects at the micro-scale, patterned grooves on a micro-channel floor remain a powerful method to induce helical flows within a pressure driven system. Although there have been a number of numerical studies on geometrical effects concerning fluid mixing within the staggered herringbone mixer, all have focused mainly on the groove angle and depth, two factors that contribute greatly to the magnitude of helical flow. Here we present a new geometrical factor that significantly affects the generation of helical flow over patterned grooves. By varying the ratio of the length of the grooves to the neighboring ridges, helical flow can be optimized for a given groove depth and channel aspect ratio, with up to 50% increases in transverse flow possible. A thorough numerical study of over 700 cases details the magnitude of helical flow over unsymmetrical patterned grooves in a slanted groove micro-mixer, where the optimized parameters for the slanted groove mixer can be translated to the staggered herringbone mixer. The optimized groove geometries are shown to have a large dependence on the channel aspect ratio, the groove depth ratio, and the ridge length. PMID:17476376

  8. Testing Geometrical Discrimination within an Enzyme Active Site: Constrained Hydrogen Bonding in the Ketosteroid Isomerase Oxyanion Hole

    PubMed Central

    Sigala, Paul A.; Kraut, Daniel A.; Caaveiro, Jose M. M.; Pybus, Brandon; Ruben, Eliza A.; Ringe, Dagmar; Petsko, Gregory A.; Herschlag, Daniel

    2009-01-01

    Enzymes are classically proposed to accelerate reactions by binding substrates within active site environments that are structurally preorganized to optimize binding interactions with reaction transition states rather than ground states. This is a remarkably formidable task considering the limited 0.1 1 scale of most substrate rearrangements. The flexibility of active site functional groups along the coordinate of substrate rearrangement, the distance scale on which enzymes can distinguish structural rearrangement, and the energetic significance of discrimination on that scale remain open questions that are fundamental to a basic physical understanding of enzyme active sites and catalysis. We bring together high resolution X-ray crystallography, 1H and 19F NMR spectroscopy, quantum mechanical calculations, and transition state analog binding measurements to test the distance scale on which non-covalent forces can constrain side chain and ligand relaxation or translation along a specific coordinate and the energetic consequences of such geometric constraints within the active site of bacterial ketosteroid isomerase (KSI). Our results strongly suggest that packing and binding interactions within the KSI active site can constrain local side chain reorientation and prevent hydrogen bond shortening by 0.1 or less. Further, this constraint has substantial energetic effects on ligand binding and stabilization of negative charge within the oxyanion hole. These results provide evidence that subtle geometric effects, indistinguishable in most X-ray crystallographic structures, can have significant energetic consequences and highlight the importance of using synergistic experimental approaches to dissect enzyme function. PMID:18808119

  9. Tubular occlusion optimizes bonding of hydrophobic resins to dentin.

    PubMed

    Sadek, F T; Pashley, D H; Ferrari, M; Tay, F R

    2007-06-01

    Although hydrophobic resins may be bonded to acid-etched dentin with an ethanol wet-bonding technique, the protocol is sensitive to moisture contamination when bonding is performed in deep dentin. This study tested the hypothesis that the use of oxalate or poly(glutamic) acid-modified, diluted ceramicrete (PADC) for dentinal tubule occlusion prevents fluid contamination and improves the bonding of an experimental hydrophobic adhesive to acid-etched, ethanol-dehydrated dentin. Mid-coronal and deep acid-etched moist dentin pre-treated with oxalate or PADC was dehydrated by ethanol wet-bonding and infiltrated with the experimental three-step etch-and-rinse hydrophobic adhesive under simulated pulpal pressure. Tensile bond strengths to deep dentin without pre-treatment were severely compromised. Conversely, oxalate and PADC pre-treatments reduced dentin permeability, prevented water contamination, and improved bond strengths. Minimal nanoleakage was identified within hybrid layers created in the oxalate- and PADC-pre-treated deep dentin. The use of tubular occluding agents optimized bonding of hydrophobic resins to dentin. PMID:17525351

  10. Empirical corrections for anharmonic zero-point vibrations of hydrogen and deuterium in geometric hydrogen bond correlations

    Microsoft Academic Search

    Hans-Heinrich Limbach; Mariusz Pietrzak; Hans Benedict; Peter M. Tolstoy; Nikolai S. Golubev; Gleb S. Denisov

    2004-01-01

    In this paper, empirical corrections for anharmonic ground-state vibrations of hydrogen and deuterium in the hydrogen bridges AL?B, L=H, D are introduced into the geometric hydrogen bond correlation analysis based on the empirical Pauling valence bond orders. The method is verified using the examples of the hydrogen bonded anions in [(CO)5CrC?N?H?N?CCr(CO)5]? As(Ph)4+ (1h), in [(CO)5CrC?N?H?N?CCr(CO)5]? N(n-propyl)4+ (2h), in the model

  11. Communication: Ab initio simulations of hydrogen-bonded ferroelectrics: Collective tunneling and the origin of geometrical isotope effects

    SciTech Connect

    Wikfeldt, K. T., E-mail: wikfeldt@hi.is [Science Institute, University of Iceland, Nordita, Stockholm, Sweden and University College London, London WC1E 6BT (United Kingdom); Michaelides, A. [Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1E 6BT (United Kingdom)] [Thomas Young Centre, London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1E 6BT (United Kingdom)

    2014-01-28

    Ab initio simulations that account for nuclear quantum effects have been used to examine the order-disorder transition in squaric acid, a prototypical H-bonded antiferroelectric crystal. Our simulations reproduce the >100 K difference in transition temperature observed upon deuteration as well as the strong geometrical isotope effect observed on intermolecular separations within the crystal. We find that collective transfer of protons along the H-bonding chains facilitated by quantum mechanical tunneling is critical to the order-disorder transition and the geometrical isotope effect. This sheds light on the origin of isotope effects and the importance of tunneling in squaric acid which likely extends to other H-bonded ferroelectrics.

  12. Application of separable programming to optimization by geometric programming

    E-print Network

    Humber, Joseph Barker

    1971-01-01

    of geometric programming. The scaling technique nas, in practice, produced a much more accurate approximate solution. The primal function, g , and each of the constraints, g , can 0 be written in general form as 1 isJ[k] where subject to the restrictions... in Chapter II. The geometric inequality may be. written generally as 6. where the 6. are subject to the normality condition. i However, the geometric inequality may be written in more generalized form in terms of unuormalized weights, A, : First denote i...

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

    E-print Network

    Ledzewicz, Urszula

    , such as cytotoxic (killing) and cytostatic (blocking) drugs or recruiting agents. Singular controls are not optimal interlaced with rest periods when no drugs are given. We describe a geometric approach that is based

  14. Geometric Optimization of Relative Link Lengths for Biomimetic Robotic Fish

    Microsoft Academic Search

    Junzhi Yu; Long Wang; Min Tan

    2007-01-01

    This paper focuses on the design of fishlike underwater robots using an optimization approach to choose relative link lengths. Considering both ichthyologic characteristics and mechatronic constraints, the optimal link-length ratios are numerically calculated by an improved constrained cyclic variable method. Comparative results, before and after the optimization, demonstrate the enhanced performance

  15. Optimization of the geometrical stability in square ring laser gyroscopes

    E-print Network

    R. Santagata; A. Beghi; J. Belfi; N. Beverini; D. Cuccato; A. Di Virgilio; A. Ortolan; A. Porzio; S. Solimeno

    2014-11-12

    Ultra sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth: the project name is GINGER (Gyroscopes IN GEneral Relativity), a ground-based triaxial array of ring lasers aiming at measuring the Earth rotation rate with an accuracy of 10^-14 rad/s. Such ambitious goal is now within reach as large area ring lasers are very close to the necessary sensitivity and stability. However, demanding constraints on the geometrical stability of the laser optical path inside the ring cavity are required. Thus we have started a detailed study of the geometry of an optical cavity, in order to find a control strategy for its geometry which could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions which allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.

  16. Optimization of the geometrical stability in square ring laser gyroscopes

    NASA Astrophysics Data System (ADS)

    Santagata, R.; Beghi, A.; Belfi, J.; Beverini, N.; Cuccato, D.; Di Virgilio, A.; Ortolan, A.; Porzio, A.; Solimeno, S.

    2015-03-01

    Ultra-sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth. Our project for this goal is called GINGER (gyroscopes in general relativity), and consists of a ground-based triaxial array of ring lasers aimed at measuring the rotation rate of the Earth with an accuracy of {{10}-14} rad {{s}-1}. Such an ambitious goal is now within reach, as large-area ring lasers are very close to the required sensitivity and stability. However, demanding constraints on the geometrical stability of the optical path of the laser inside the ring cavity are required. Thus, we have begun a detailed study of the geometry of an optical cavity in order to find a control strategy for its geometry that could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions that allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.

  17. Geometric Factors Affecting Dentin Bonding in Root Canals: A Theoretical Modeling Approach

    Microsoft Academic Search

    Franklin R. Tay; Robert J. Loushine; Paul Lambrechts; R. Norman Weller; David H. Pashley

    2005-01-01

    Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded surface area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses to debond the material from dentin, thereby

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  19. Geometrical optimization of a local ballistic magnetic sensor

    NASA Astrophysics Data System (ADS)

    Kanda, Yuhsuke; Nomura, Tatsuya; Kimura, Takashi; Hara, Masahiro

    2014-04-01

    We have developed a highly sensitive local magnetic sensor by using a ballistic transport property in a two-dimensional conductor. A semiclassical simulation reveals that the sensitivity increases when the geometry of the sensor and the spatial distribution of the local field are optimized. We have also experimentally demonstrated a clear observation of a magnetization process in a permalloy dot whose size is much smaller than the size of an optimized ballistic magnetic sensor fabricated from a GaAs/AlGaAs two-dimensional electron gas.

  20. Geometrical optimization of a local ballistic magnetic sensor

    SciTech Connect

    Kanda, Yuhsuke; Hara, Masahiro [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Nomura, Tatsuya [Advanced Electronics Research Division, INAMORI Frontier Research Center, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Kimura, Takashi [Advanced Electronics Research Division, INAMORI Frontier Research Center, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan)

    2014-04-07

    We have developed a highly sensitive local magnetic sensor by using a ballistic transport property in a two-dimensional conductor. A semiclassical simulation reveals that the sensitivity increases when the geometry of the sensor and the spatial distribution of the local field are optimized. We have also experimentally demonstrated a clear observation of a magnetization process in a permalloy dot whose size is much smaller than the size of an optimized ballistic magnetic sensor fabricated from a GaAs/AlGaAs two-dimensional electron gas.

  1. Optimal Resource Allocation for Network Protection: A Geometric Programming Approach

    E-print Network

    Plotkin, Joshua B.

    ]. Designing strategies to contain spreading processes in networks is a central problem in public health the problem of containing spreading processes in arbitrary directed networks by distributing pro- tection cost and study the problem of finding the cost-optimal distribution of resources throughout the nodes

  2. Optimization of Phase-Locked Loop Circuits via Geometric Programming

    E-print Network

    an optimal PLL design. For the power consumption trade-off curve, the maximum VCO frequency is constant while ¢ and Maria del Mar Hershenson Barcelona Design, Inc., Newark, CA 94560, Email: dave requirements, companies have focused on design reuse, cre- ating a small library of individual phase

  3. Tubular Occlusion Optimizes Bonding of Hydrophobic Resins to Dentin

    Microsoft Academic Search

    F. T. Sadek; D. H. Pashley; M. Ferrari; F. R. Tay

    2007-01-01

    Although hydrophobic resins may be bonded to acid-etched dentin with an ethanol wet-bonding technique, the protocol is sensitive to moisture contamination when bonding is performed in deep dentin. This study tested the hypothesis that the use of oxalate or poly(glutamic) acid-modified, diluted ceramicrete (PADC) for dentinal tubule occlusion prevents fluid contamination and improves the bonding of an experimental hydrophobic adhesive

  4. A new optimization method of the geometric distance in an automatic recognition system for bird vocalisations

    E-print Network

    Paris-Sud XI, Université de

    A new optimization method of the geometric distance in an automatic recognition system for bird an automatic recognition system for bird vocalisations. Many biologists have been using the early 32 bit of the bird vocalisation from a three-hour continuous recording and ex- tracts the sound spectrum pattern from

  5. Discrete Geometric Optimal Control on Lie Groups Marin Kobilarov and Jerrold E. Marsden

    E-print Network

    Kobilarov, Marin

    1 Discrete Geometric Optimal Control on Lie Groups Marin Kobilarov and Jerrold E. Marsden Abstract discretization or approximation. This Marin Kobilarov and Jerrold Marsden are with the Department of Control@cds.caltech.edu, marsden@cds.caltech.edu). Manuscript received June 11, 2010; revised March 29, 2011. is achieved

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

    E-print Network

    Zhang, Yin

    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

  7. Design Sensitivity Analysis and Optimization of Geometrically Nonlinear Finite-Dimensional Structures

    Microsoft Academic Search

    M. Ohsaki

    The purpose of this review paper is to summarize the results of design sensi- tivity analysis and optimization methods of elastic conservative systems considering geo- metrical nonlinearity. Although those results are presented mainly for finite dimensional structures, they are applicable to continua discretized by finite element methods. Difficul- ties related to geometrical nonlinearity are discussed in detains by using small

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

    E-print Network

    Mitchell, Joseph S.B.

    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

  9. Geometrical optimization of organic microlasers for microfluidic chemical sensing

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  10. Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2008-01-01

    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.

  11. Geometric versus numerical optimal control of a dissipative spin-(1/2) particle

    SciTech Connect

    Lapert, M.; Sugny, D. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 5209 CNRS-Universite de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Zhang, Y.; Braun, M.; Glaser, S. J. [Department of Chemistry, Technische Universitaet Muenchen, Lichtenbergstrasse 4, D-85747 Garching (Germany)

    2010-12-15

    We analyze the saturation of a nuclear magnetic resonance (NMR) signal using optimal magnetic fields. We consider both the problems of minimizing the duration of the control and its energy for a fixed duration. We solve the optimal control problems by using geometric methods and a purely numerical approach, the grape algorithm, the two methods being based on the application of the Pontryagin maximum principle. A very good agreement is obtained between the two results. The optimal solutions for the energy-minimization problem are finally implemented experimentally with available NMR techniques.

  12. Computational modeling and optimization for wire bonding process on Cu\\/low-K wafers

    Microsoft Academic Search

    Weidong Huang

    2009-01-01

    A methodology is developed to use the explicit dynamic analysis results to reflect the real impact responses of wire bonding under different CV (constant velocity) settings. The optimal ranges of the process parameter settings for wire bonding on Cu\\/low-K wafers are determined by this way. The KNS Maxum bonder is selected as the vehicle for mapping the process settings into

  13. Optimal Design of the Adhesively-Bonded Tubular Single Lap Joint

    Microsoft Academic Search

    Su Jeong Lee; Dai Gil Lee

    1995-01-01

    In this paper, a method for the optimal design of the adhesively-bonded tubular single lap joint was proposed based on the failure model of the adhesively-bonded tubular single lap joint. The failure model incorporated the nonlinear mechanical behavior of the adhesive as well as the different failure modes in which the adhesive failure mode changed from bulk shear failure, via

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  15. A topology optimization method for geometrically nonlinear structures with meshless analysis and independent density field interpolation

    NASA Astrophysics Data System (ADS)

    He, Qizhi; Kang, Zhan; Wang, Yiqiang

    2014-09-01

    Based on the element-free Galerkin (EFG) method, an analysis-independent density variable approach is proposed for topology optimization of geometrically nonlinear structures. This method eliminates the mesh distortion problem often encountered in the finite element analysis of large deformations. The topology optimization problem is formulated on the basis of point-wise description of the material density field. This density field is constructed by a physical meaning-preserving interpolation with the density values of the design variable points, which can be freely positioned independently of the field points used in the displacement analysis. An energy criterion of convergence is used to resolve the well-known convergence difficulty, which would be usually encountered in low density regions, where displacements oscillate severely during the optimization process. Numerical examples are given to demonstrate the effectiveness of the developed approach. It is shown that relatively clear optimal solutions can be achieved, without exhibiting numerical instabilities like the so-called "layering" or "islanding" phenomena even in large deformation cases. This study not only confirms the potential of the EFG method in topology optimization involving large deformations, but also provides a novel topology optimization framework based on element-free discretization of displacement and density fields, which can also easily incorporate other meshless analysis methods for specific purposes.

  16. Implementation and Optimization of miniGMG - a Compact Geometric Multigrid Benchmark

    SciTech Connect

    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

    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.

  17. Optimal design of micro-force sensor for wire bonding with high acceleration and frequent movement

    Microsoft Academic Search

    Yuehong Yin; Chunlin Zhou; Shiyi Chen; Hui Hu; Zhongqin Lin

    2006-01-01

    The wire bonding is the mostly used process in chip packaging, which requires micro-force sensor and micro-force control to perform the bonding task with high frequency no less than 15Hz. This paper presents a new strategy of active control methodology based on the linear motor (used as actuator). The novel methodology of optimal design for the 0.001N-resolution micro-force sensor under

  18. Geometrical optimization of sensors for eddy currents nondestructive testing and evaluation

    SciTech Connect

    Thollon, F.; Burais, N. [Ecole Centrale de Lyon, Ecully (France). Dept. Electrotechnique] [Ecole Centrale de Lyon, Ecully (France). Dept. Electrotechnique

    1995-05-01

    Design of Non Destructive Testing (NDT) and Non Destructive Evaluation (NDE) sensors is possible by solving Maxwell`s relations with FEM or BIM. But the large number of geometrical and electrical parameters of sensor and tested material implies many results that don`t give necessarily a well adapted sensor. The authors have used a genetic algorithm for automatic optimization. After having tested this algorithm with analytical solution of Maxwell`s relations for cladding thickness measurement, the method has been implemented in finite element package.

  19. Cooperative Effects and Optimal Halogen Bonding Motifs for Self-Assembling Systems

    PubMed Central

    2015-01-01

    Halogen bonding, due to its directionality and tunable strength, is being increasingly utilized in self-assembling materials and crystal engineering. Using density functional theory (DFT) and molecular mechanics (OPLS/CM1Ax) calculations, multiply halogen bonded complexes of brominated imidazole and pyridine are investigated along with their potential in construction of self-assembling architectures. Dimers with 110 halogen bonds are considered and reveal maximal binding energies of 336 kcal/mol. Cooperative (nonadditive) effects are found in complexes that extend both along and perpendicular to the halogen bonding axes, with interaction energies depending on polarization, secondary interactions, and ring spacers. Four structural motifs were identified to yield optimal halogen bonding. For the largest systems, the excellent agreement found between the DFT and OPLS/CM1Ax results supports the utility of the latter approach for analysis and design of self-assembling supramolecular structures. PMID:24678636

  20. 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)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2013-02-01

    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.

  1. Bonding

    MedlinePLUS

    ... between teeth Make teeth look longer Change the shape or color of teeth Sometimes, bonding also is used to ... a color that will most closely match the color of the tooth. He or she will shape the tooth with a drill (handpiece) if necessary, ...

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

    PubMed

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

    2014-01-01

    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

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

    PubMed Central

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

    2014-01-01

    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

  4. NMR studies of solid pentachlorophenol-4-methylpyridine complexes exhibiting strong OHN hydrogen bonds: geometric H/D isotope effects and hydrogen bond coupling cause isotopic polymorphism.

    PubMed

    Ip, Brenda C K; Shenderovich, Ilya G; Tolstoy, Peter M; Frydel, Jaroslaw; Denisov, Gleb S; Buntkowsky, Gerd; Limbach, Hans-Heinrich

    2012-11-26

    We have studied the hydrogen bond interactions of (15)N labeled 4-methylpyridine (4-MP) with pentachlorophenol (PCP) in the solid state and in polar solution using various NMR techniques. Previous spectroscopic, X-ray, and neutron crystallographic studies showed that the triclinic 1:1 complex (4-MPPCP) exhibits the strongest known intermolecular OHN hydrogen bond in the solid state. By contrast, deuteration of the hydrogen bond gives rise to the formation of a monoclinic structure exhibiting a weaker hydrogen bond. By performing NMR experiments at different deuterium fractions and taking advantage of dipolar (1)H-(15)N recoupling under combined fast MAS and (1)H decoupling, we provide an explanation of the origin of the isotopic polymorphism of 4-MPPCP and improve previous chemical shift correlations for OHN hydrogen bonds. Because of anharmonic ground state vibrations, an ODN hydrogen bond in the triclinic form exhibits a shorter oxygen-hydron and a longer oxygen-nitrogen distance as compared to surrounding OHN hydrogen bonds, which also implies a reduction of the local dipole moment. The dipole-dipole interaction between adjacent coupled OHN hydrogen bonds which determines the structure of triclinic 4-MPPCP is then reduced by deuteration, and other interactions become dominant, leading to the monoclinic form. Finally, the observation of stronger OHN hydrogen bonds by (1)H NMR in polar solution as compared to the solid state is discussed. PMID:22861155

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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).

  6. The manufacture and geometric optics optimization of a double-curved broadband reflector antenna

    NASA Astrophysics Data System (ADS)

    Jelloul, M.; Dubost, G.

    1985-06-01

    A numerical model was developed for a double curved antenna sensitive to signals in the 1-5 GHz range. The two distinct orthogonal linear polarizations of the antenna were achieved using a broadband, pyramid shaped log-period primary feed. Expressions are presented for predicting the patterns and phase characteristics of the feed horn at different frequencies. The design effort included separate descriptions of the center of the antenna, which emits elevation diffraction patterns, and the transverse sections, which emit the azimuthal patterns. A geometric optics approach (Dunbar's method) was applied to optimize the central fiber spacing and the flat curves of the transverse sections. Measurements made of the radiation patterns, isotropic gain and output power of a prototype antenna were closely predicted with the model.

  7. Optimal allocation of stratified samples with several variance constraints and equal workloads over time by geometric programming

    Microsoft Academic Search

    Miles Davis; Robert H. Finch Jr

    1989-01-01

    We apply geometric programming, developed by Duffin, Peterson and Zener (1967), to the optimal allocation of stratified samples with several variance constraints arising from several estimates of deficiency rates in the quality control of administrative decisions. We develop also a method for imposing constraints on sample sizes to equalize workloads over time, as required by the practicalities of clerical work

  8. Geometric Construction of Eighth-Order Optimal Families of Ostrowski's Method

    PubMed Central

    Motsa, S. S.

    2015-01-01

    Based on well-known fourth-order Ostrowski's method, we proposed many new interesting optimal families of eighth-order multipoint methods without memory for obtaining simple roots. Its geometric construction consists in approximating f n? at zn in such a way that its average with the known tangent slopes f n? at xn and yn is the same as the known weighted average of secant slopes and then we apply weight function approach. The adaptation of this strategy increases the convergence order of Ostrowski's method from four to eight and its efficiency index from 1.587 to 1.682. Finally, a number of numerical examples are also proposed to illustrate their accuracy by comparing them with the new existing optimal eighth-order methods available in the literature. It is found that they are very useful in high precision computations. Further, it is also noted that larger basins of attraction belong to our methods although the other methods are slow and have darker basins while some of the methods are too sensitive upon the choice of the initial value.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  10. Optimal bounded trigonometry control of N-level quantum systems based on the geometrical parametrization

    E-print Network

    Zhang, Ming; Dai, Hong-Yi; Xi, Zairong; Schirmer, S G

    2010-01-01

    Based on the observation that the pure states of $N-$level quantum systems can be expressed in terms of $2(N-1)$ real geometric parameters, we make full use of distinguished properties of generalized pauli operators to construct $(4N-5)$ local trigonometry control Hamiltonian to transform $N-$level quantum systems from an arbitrary initial pure state to another arbitrary target pure state. The optimal bounded local trigonometry controls are further exploited in terms of both time performance $J_{t}=\\int^{t_{f}}_{t_{0}}dt$ and time-energy performance $J_{te}=\\int^{t_{f}}_{t_{0}}[\\lambda+E(t)]dt$ with a ratio $\\lambda>0$. It is underlined that the whole control time is inverse-proportional to the control magnitude bound $L_{B}$ for optimal time control and the product of the whole control time and energy is a constance independent of $\\lambda$ and $L_{B}$. It is exemplified that one can construct control Hamiltonian to generate entanglement of two-qubit systems by applying the main results proposed in this pape...

  11. Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method

    SciTech Connect

    Oudjene, M.; Ben-Ayed, L. [Institut Superieur d'Ingenierie de la Conception (GIP-InSIC), 27 rue d'Hellieule, 88100 Saint-Die-des-Vosges (France); Batoz, J.-L. [Universite de Technologie de Compiegne (UTC), BP 20529, 60205 Compiegne Cedex (France)

    2007-05-17

    The determination of optimum tool shapes in clinch forming process is needed to achieve the required high quality of clinch joints. The design of the tools (punch and die) is crucial since the strength of the clinch joints is closely correlated to the tools geometry. To increase the strength of clinch joints, an automatic optimization procedure is developed. The objective function is defined in terms of the maximum value of the tensile force, obtained by separation of the sheets. Feasibility constraints on the geometrical parameters are also taken into account. First, a Python Script is used to generate the ABAQUS finite element model, to run the computations and post-process results, which are exported in an ASCII file. Then, this ASCII file is read by a FORTRAN program, in which the response surface approximation and SQP algorithm are implemented. The results show the potential interest of the developed optimization procedure towards the improvement of the strength of the clinch forming joints to tensile loading.

  12. Condition optimization, reliability evaluation of SiO 2SiO 2 HF bonding and its application for UV detection micro flow cell

    Microsoft Academic Search

    H Nakanishi; T Nishimoto; M Kanai; T Saitoh; R Nakamura; T Yoshida; S Shoji

    2000-01-01

    In order to apply SiO2SiO2 bonding with hydrofluoric acid (HF bonding) for micro-electro-mechanical systems (MEMS) fabrication, the optimal bonding conditions were examined under different temperature, HF concentration and bonding time. The necessary HF concentration and the necessary time for bonding are reduced by elevating the bonding temperature. The time for bonding was reduced from 24 h at room temperature to

  13. Geometrical effects of phospholipid olefinic bonds on the structure and dynamics of membranes: A molecular dynamics study.

    PubMed

    Tsai, Hui-Hsu Gavin; Lee, Jian-Bin; Li, Hung-Sheng; Hou, Tsai-Yi; Chu, Wen-Yuan; Shen, Po-Chuan; Chen, Ying-Yu; Tan, Chun-Jui; Hu, Jia-Cheng; Chiu, Chih-Chiang

    2015-05-01

    The trans isomers of fatty acids are found in human adipose tissue. These isomers have been linked with deleterious health effects (e.g., coronary artery disease). In this study, we performed molecular dynamics simulations to investigate the structures and dynamic properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and 1-palmitoyl-2-elaidoyl sn-glycero-3-phosphatidylcholine (PEPC) lipid bilayers. The geometry of the olefinic bond and membrane packing effects significantly influenced the conformations and dynamics of the two CC single bonds adjacent to the olefinic bond. For the PEPC lipid, the two CC single bonds adjacent to the olefinic bond adopted mainly nonplanar skew-trans and planar cis-trans motifs; although the cis conformation featured relatively strong steric repulsion, it was stabilized through membrane packing because its planar structure is more suitable for membrane packing. Moreover, membrane packing effects stabilized the planar transition state for conformational conversion to a greater extent than they did with the nonplanar transition state, thereby affecting the dynamics of conformational conversion. The rotational motions of the first neighboring CC single bonds were much faster than those of typical saturated CC single bonds; in contrast, the rotational motions of the second neighboring CC single bonds were significantly slower than those of typical saturated torsion angles. The packing of PEPC lipids is superior to that of POPC lipids, leading to a smaller area per lipid, a higher order parameter and a smaller diffusion coefficient. The distinct properties of POPC and PEPC lipids result in PEPC lipids forming microdomains within a POPC matrix. PMID:25732027

  14. Performance improvement for optimization of the non-linear geometric fitting problem in manufacturing metrology

    NASA Astrophysics Data System (ADS)

    Moroni, Giovanni; Syam, Wahyudin P.; Petr, Stefano

    2014-08-01

    Product quality is a main concern today in manufacturing; it drives competition between companies. To ensure high quality, a dimensional inspection to verify the geometric properties of a product must be carried out. High-speed non-contact scanners help with this task, by both speeding up acquisition speed and increasing accuracy through a more complete description of the surface. The algorithms for the management of the measurement data play a critical role in ensuring both the measurement accuracy and speed of the device. One of the most fundamental parts of the algorithm is the procedure for fitting the substitute geometry to a cloud of points. This article addresses this challenge. Three relevant geometries are selected as case studies: a non-linear least-squares fitting of a circle, sphere and cylinder. These geometries are chosen in consideration of their common use in practice; for example the sphere is often adopted as a reference artifact for performance verification of a coordinate measuring machine (CMM) and a cylinder is the most relevant geometry for a pin-hole relation as an assembly feature to construct a complete functioning product. In this article, an improvement of the initial point guess for the Levenberg-Marquardt (LM) algorithm by employing a chaos optimization (CO) method is proposed. This causes a performance improvement in the optimization of a non-linear function fitting the three geometries. The results show that, with this combination, a higher quality of fitting results a smaller norm of the residuals can be obtained while preserving the computational cost. Fitting an incomplete-point-cloud, which is a situation where the point cloud does not cover a complete feature e.g. from half of the total part surface, is also investigated. Finally, a case study of fitting a hemisphere is presented.

  15. Optimal tubular adhesive-bonded lap joint of the carbon fiber epoxy composite shaft

    NASA Astrophysics Data System (ADS)

    Kim, Ki S.; Kim, Won T.; Lee, Dai G.; Jun, Eui J.

    The effects of the adhesive thickness and the adherend surface roughness on the fatigue strength of a tubular adhesive-bonded single lap joint were investigated using fatigue test specimens whose adherends were made of S45C carbon steel. Results of fatigue tests showed that the optimal arithmetic surface roughness of the adherends is about 2 microns and the optimal adhesive thickness is about 0.15 mm. Using these values, the prototype torsional adhesive joints were manufactured for power transmission shafts of an automotive vehicle or a small helicopter, and static tests under torque were performed on a single-lap joint, a single-lap joint with scarf, a double-lap joint, and a double-lap joint with scarf. It was found that the double-lap joint was superior among the joints, in terms of torque capacity and manufacturing cost.

  16. An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms

    NASA Astrophysics Data System (ADS)

    Panetta, D.; Belcari, N.; DelGuerra, A.; Moehrs, S.

    2008-07-01

    In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving the capability of the proposed calibration method. In principle, the method can be adapted to other cone-beam imaging modalities (e.g., single photon emission computed tomography).

  17. Optimization of Stability Constrained Geometrically Nonlinear Shallow Trusses Using an Arc Length Sparse Method with a Strain Energy Density Approach

    NASA Technical Reports Server (NTRS)

    Hrinda, Glenn A.; Nguyen, Duc T.

    2008-01-01

    A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.

  18. NMR Scalar Couplings across Watson-Crick Base Pair Hydrogen Bonds in DNA Observed by Transverse Relaxation-Optimized Spectroscopy

    Microsoft Academic Search

    Konstantin Pervushin; Akira Ono; Cesar Fernandez; Thomas Szyperski; Masatsune Kainosho; Kurt Wuthrich

    1998-01-01

    This paper describes the NMR observation of 15N--15N and 1H--15N scalar couplings across the hydrogen bonds in Watson-Crick base pairs in a DNA duplex, hJNN and hJHN. These couplings represent new parameters of interest for both structural studies of DNA and theoretical investigations into the nature of the hydrogen bonds. Two dimensional [15N, 1H]-transverse relaxation-optimized spectroscopy (TROSY) with a 15N-labeled

  19. Investigation of optimized end-bonding magnetoelectric heterostructure for sensitive magnetic field sensor.

    PubMed

    Lu, Caijiang; Xu, Changbao; Wang, Lei; Gao, Jipu; Gui, Junguo; Lin, Chenghui

    2014-11-01

    This paper reports an optimized end-bonding magnetoelectric (ME) heterostructure FeCuNbSiB-PZT-FeCuNbSiB (FPF) for sensitive magnetic field sensor. The heterostructure is made by attaching magnetostrictive Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB) foils at the free ends of piezoelectric Pb(Zr1-x,Tix)O3 (PZT) plates. Due to the structural advantages, the FPF has ?3.12 times larger resonance voltage coefficient (?ME,r) than traditional FeCuNbSiB/PZT laminate. And compared with the Metglas-PZT-Metglas heterostructure, the FPF heterostructure has stronger ME responses for the excellent magnetic characteristics of FeCuNbSiB. In experiments, the FPF heterostructure is optimal designed through adjusting the thickness of PZT plate (tp) and the length of FeCuNbSiB foil (L). The results demonstrate that the maximum ?ME,r of 662.1 (V/cm Oe) is observed at 13 Oe DC bias magnetic field when L = 15 mm and tp = 0.6 mm. Based on the giant ME coupling, the DC magnetic field sensitivity for the optimized FPF heterostructure is 3.89 nT at resonant frequency. These results are very promising for the cheap room-temperature magnetic field sensing technology. PMID:25430140

  20. Extremal Optimization for Ground States of the Sherrington-Kirkpatrick Spin Glass with Levy Bonds

    NASA Astrophysics Data System (ADS)

    Boettcher, Stefan

    2013-03-01

    Using the Extremal Optimization heuristic (EO),footnotetextS. Boettcher & A.G. Percus, PRL 86, 5211 (2001) ground states of the SK-spin glass are studied with bonds J distributed according to a Levy distribution P(J)1/|J|^1+? with |J|>1 and 1bonds.footnotetextS. Boettcher, Philosophical Magazine 92, 34 (2012) We find that the energies attain universally the Parisi-energy of the SK when the second moment of P(J) exists (?>2). They compare favorably with recent one-step replica symmetry breaking predictions well below ?=2. Near ?=2, the simulations deviate significantly from theoretical expectations. The finite-size corrections exponent ? decays from the putative SK value ?SK=23 already well above ?=2. The exponent ? for the scaling of ground state energy fluctuations with system size decays linearly from its SK value for decreasing ? and vanishes at ?=1.

  1. Searching optimal shapes for blades of a fan

    E-print Network

    Gianluca Argentini

    2008-03-26

    A nonlinear differential equation about optimal shapes for blades of a fan. A boundary value differential problem from engineering, geometrical or physical bonds. A relation between linear profiles and constant speed along the side under flow.

  2. Geometric modeling and optimization in 3D solar cells : implementation and algorithms

    E-print Network

    Wan, Jin Hao, M. Eng. Massachusetts Institute of Technology

    2014-01-01

    Conversion of solar energy in three-dimensional (3D) devices has been essentially untapped. In this thesis, I design and implement a C++ program that models and optimizes a 3D solar cell ensemble embedded in a given ...

  3. Multi-objective Optimization of Geometric Dimensions and Material Composition of

    E-print Network

    Vel, Senthil

    and shape parameters that will minimize multiple objectives subject to nonlinear constraints. Keywords: FGM designing a high-temperature FGM since optimal designs based on static and transient analysis may be quite-objective genetic algorithms (GAs) [4]. Numerical results are presented for a tungsten/copper (W/Cu) FGM

  4. Geometric Optimization for 3D Pose Estimation of Quadratic Surfaces Pei Yean Lee, John B. Moore

    E-print Network

    Moore, John Barratt

    for arbitrary rotations and translations and the algorithm iteration is data independent. Section II presents on pose estimation of such surfaces. Our optimization is of an error measure between the CAD model and the measured data. Most existing algorithms are sensitive to noise and occlusion or only converge linearly. Our

  5. A LINEARIZED APPROACH TO WORST-CASE DESIGN IN PARAMETRIC AND GEOMETRIC SHAPE OPTIMIZATION

    E-print Network

    Paris-Sud XI, Universit de

    DREAM-DELT'A Guyancourt, France. Abstract The purpose of this article is to propose a deterministic visions of reality, most optimization frameworks assume a complete knowledge of the param- eters and data, these external stresses are affected by the outer medium, which may itself undergo unknown pertur- bations

  6. OPTIMAL GROWTH IN A TWO-SECTOR RSS MODEL WITHOUT DISCOUNTING: A GEOMETRIC INVESTIGATION

    Microsoft Academic Search

    M. ALI KHAN; TAPAN MITRA

    2007-01-01

    This essay reports results on optimal growth in a two-sector model with fixed coefficients, irreversible investment and no discounting. Under normalization, the model can be represented by two real numbers, but despite its deceptive simplicity, it admits rich transition dynamics and apparent pathologies that seem to have been missed in earlier work. From a methodological point of view, and in

  7. A geometric approach to the optimal control of nonholnomic mechanical systems

    E-print Network

    Anthony Bloch; Leonardo Colombo; Rohit Gupta; David Martin de Diego

    2014-12-23

    In this paper, we describe a constrained Lagrangian and Hamiltonian formalism for the optimal control of nonholonomic mechanical systems. In particular, we aim to minimize a cost functional, given initial and final conditions where the controlled dynamics is given by nonholonomic mechanical system. In our paper, the controlled equations are derived using a basis of vector fields adapted to the nonholonomic distribution and the Riemannian metric determined by the kinetic energy. Given a cost function, the optimal control problem is understood as a constrained problem or equivalently, under some mild regularity conditions, as a Hamiltonian problem on the cotangent bundle of the nonholonomic distribution. A suitable Lagrangian submanifold is also shown to lead to the correct dynamics. We demonstrate our techniques in several examples including a continuously variable transmission problem and motion planning for obstacle avoidance problems.

  8. Optimal Power Allocation for Type II H-ARQ via Geometric Programming

    Microsoft Academic Search

    Hongbo Liu; Leonid Razoumov; Narayan Mandayam

    2005-01-01

    In mobile wireless data communications, it is very important to reduce the average energy consumption while maintaining a target frame-error-rate (FER) and frame latency. These goals can be achieved by means of Hybrid-ARQ (re)transmission power con- trol. By allocating different symbol energy for each (re)transmission, the average energy consumption can be optimized. For a type-II Hybrid-ARQ scheme over an i.i.d.

  9. Discounted optimal growth in the two-sector RSS model: a geometric investigation

    Microsoft Academic Search

    M. Ali Khan; Tapan Mitra

    This paper initiates a comprehensive investigation of discounted optimal growth in the two-sector RSS model as a specific\\u000a instance of the general theory of resource allocation associated with Brock, Gale and McKenzie. For an interval of values\\u000a of a parameter ? formalizing the marginal technical rate of transformation, under zero consumption, of machines from one period\\u000a to the next, we

  10. Region Detection by Minimizing Intraclass Variance With Geometric Constraints, Global Optimality, and Efficient Approximation

    PubMed Central

    Wu, Xiaodong; Dou, Xin; Wahle, Andreas; Sonka, Milan

    2011-01-01

    Efficient segmentation of globally optimal surfaces in volumetric images is a central problem in many medical image analysis applications. Intraclass variance has been successfully utilized for object segmentation, for instance, in the ChanVese model, especially for images without prominent edges. In this paper, we study the optimization problem of detecting a region (volume) between two coupled smooth surfaces by minimizing the intraclass variance using an efficient polynomial-time algorithm. Our algorithm is based on the shape probing technique in computational geometry and computes a sequence of minimum-cost closed sets in a derived parametric graph. The method has been validated on computer-synthetic volumetric images and in X-ray CT-scanned datasets of plexiglas tubes of known sizes. Its applicability to clinical data sets was also demonstrated. In all cases, the approach yielded highly accurate results. We believe that the developed technique is of interest on its own. We expect that it can shed some light on solving other important optimization problems arising in medical imaging. Furthermore, we report an approximation algorithm which runs much faster than the exact algorithm while yielding highly comparable segmentation accuracy. PMID:21118766

  11. 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

    J. Sussmann; Guoqing Tang

    1991-01-01

    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

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

    PubMed

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

    2013-09-01

    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

  13. Geometrical optimization of an annulus Compton suppression system using Monte Carlo simulation.

    PubMed

    Han, Jubong; Lee, K B; Park, T S; Lee, J M; Lee, S H

    2013-11-01

    We are planning to construct a Compton-suppression system permitting accurate and precise determinations of radioactivity of low-level environmental samples. An annulus guard detector (NaI) and a plug-in detector (NaI) are being used as suppression detectors with an HPGe primary detector. The geometry of the Compton suppression spectrometer was optimized by simulation with PENELOPE for obtaining the highest suppression factor (SF) for a point source. The results of the simulations show that the ultimate value of the suppression factor is 7.87 0.18, obtained when the source is located at 57% of an annuls guard detector. PMID:23583087

  14. Optimal image alignment with random projections of manifolds: algorithm and geometric analysis.

    PubMed

    Kokiopoulou, Effrosyni; Kressner, Daniel; Frossard, Pascal

    2011-06-01

    This paper addresses the problem of image alignment based on random measurements. Image alignment consists of estimating the relative transformation between a query image and a reference image. We consider the specific problem where the query image is provided in compressed form in terms of linear measurements captured by a vision sensor. We cast the alignment problem as a manifold distance minimization problem in the linear subspace defined by the measurements. The transformation manifold that represents synthesis of shift, rotation, and isotropic scaling of the reference image can be given in closed form when the reference pattern is sparsely represented over a parametric dictionary. We show that the objective function can then be decomposed as the difference of two convex functions (DC) in the particular case where the dictionary is built on Gaussian functions. Thus, the optimization problem becomes a DC program, which in turn can be solved globally by a cutting plane method. The quality of the solution is typically affected by the number of random measurements and the condition number of the manifold that describes the transformations of the reference image. We show that the curvature, which is closely related to the condition number, remains bounded in our image alignment problem, which means that the relative transformation between two images can be determined optimally in a reduced subspace. PMID:21189239

  15. Geometric modeling of space-optimal unit-cell-based tissue engineering scaffolds

    NASA Astrophysics Data System (ADS)

    Rajagopalan, Srinivasan; Lu, Lichun; Yaszemski, Michael J.; Robb, Richard A.

    2005-04-01

    Tissue engineering involves regenerating damaged or malfunctioning organs using cells, biomolecules, and synthetic or natural scaffolds. Based on their intended roles, scaffolds can be injected as space-fillers or be preformed and implanted to provide mechanical support. Preformed scaffolds are biomimetic "trellis-like" structures which, on implantation and integration, act as tissue/organ surrogates. Customized, computer controlled, and reproducible preformed scaffolds can be fabricated using Computer Aided Design (CAD) techniques and rapid prototyping devices. A curved, monolithic construct with minimal surface area constitutes an efficient substrate geometry that promotes cell attachment, migration and proliferation. However, current CAD approaches do not provide such a biomorphic construct. We address this critical issue by presenting one of the very first physical realizations of minimal surfaces towards the construction of efficient unit-cell based tissue engineering scaffolds. Mask programmability, and optimal packing density of triply periodic minimal surfaces are used to construct the optimal pore geometry. Budgeted polygonization, and progressive minimal surface refinement facilitate the machinability of these surfaces. The efficient stress distributions, as deduced from the Finite Element simulations, favor the use of these scaffolds for orthopedic applications.

  16. Optimizing dentin bond durability: strategies to prevent hydrolytic degradation of the hybrid layer

    PubMed Central

    Tjderhane, Leo; Nascimento, Fabio D.; Breschi, Lorenzo; Mazzoni, Annalisa; Tersariol, Ivarne L.S.; Geraldeli, Saulo; Tezvergil-Mutluay, Arzu; Carrilho, Marcela; Carvalho, Ricardo M.; Tay, Franklin R.; Pashley, David H.

    2014-01-01

    Objectives Endogenous dentin collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, are responsible for the time-related hydrolysis of collagen matrix of the hybrid layers. As the integrity of the collagen matrix is essential for the preservation of long-term dentin bond strength, inhibition or inactivation of endogenous dentin proteases is necessary for durable resin-bonded composite resin restorations. Methods Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface. Several tentative approaches to prevent enzyme function either directly or indirectly have been proposed in the literature. Results Chlorhexidine, a general inhibitor of both MMPs and cysteine cathepsins, applied before primer/adhesive application is the most tested method. In general, these experiments have shown that enzyme inhibition is a promising scheme to improve hybrid layer preservation and bond strength durability. Other enzyme inhibitors, e.g. enzyme-inhibiting monomers and antimicrobial compounds, may be considered promising alternatives that would allow more simple clinical application than chlorhexidine. Cross-linking collagen and/or dentin organic matrix-bound enzymes could render hybrid layer organic matrix resistant to degradation, and complete removal of water from the hybrid layer with ethanol wet bonding or biomimetic remineralization should eliminate hydrolysis of both collagen and resin components. Significance Identification of the enzymes responsible for the hydrolysis of hybrid layer collagen and understanding their function has prompted several innovative approaches to retain the hybrid layer integrity and strong dentin bonding. The ultimate goal, prevention of collagen matrix degradation with techniques and commercially available materials that are simple and effective in clinical settings may be achievable in several ways, and will likely become reality in the near future. PMID:23953737

  17. Extremal Optimization for Ground States of the Sherrington-Kirkpatrick Spin Glass with Levy Bonds

    NASA Astrophysics Data System (ADS)

    Boettcher, Stefan

    Ground states of Ising spin glasses on fully connected graphs are studied for a broadly distributed bond family. In particular, bonds J distributed according to a Levy distribution P(J) / 1/|J|1+?; |J| > 1; are investigated for a range of powers ?. We determine ground state energy density variation with ? and their finite-size corrections. We find that the energies attain universally the Parisi-energy of the SK as long as the second moment of P (J) exists (? > 2). They compare favorably with recent one-step replica symmetry breaking predictions well below ? = 2. At and just below ? = 2, the simulations deviate significantly from theoretical expectations. The finite-size investigation reveals that the corrections exponent ? decays from the putative SK value ?SK = = 2/3 already well above ? = 2, at which point it reaches a minimum.

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

    Microsoft Academic Search

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

    2008-01-01

    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

  19. Design of laser pulses for selective vibrational excitation of the N6-H bond of adenine and adenine-thymine base pair using optimal control theory

    Microsoft Academic Search

    Sitansh Sharma; Purshotam Sharma; Harjinder Singh; Gabriel G. Balint-Kurti

    2009-01-01

    Time dependent quantum dynamics and optimal control theory are used for selective vibrational excitation of the N6-H (amino\\u000a N-H) bond in free adenine and in the adenine-thymine (A-T) base pair. For the N6-H bond in free adenine we have used a one\\u000a dimensional model while for the hydrogen bond, N6-H(A)...O4(T), present in the A-T base pair, a two mathematical dimensional

  20. Optimal mortgage refinancing: application of bond valuation tools to household risk management

    Microsoft Academic Search

    Andrew J. Kalotay; Deane Yang; Frank J. Fabozzi

    2008-01-01

    Despite the enormous volume of refinancing activity in conventional residential mortgages, reaching record levels during recent years of historically low interest rates, the solution to the problem of how to time refinancing decisions optimally has remained elusive. It is recognized that the decision should depend, among other factors, on the call options of the outstanding and the new mortgage. Determining

  1. Direct bonding and beyond

    NASA Astrophysics Data System (ADS)

    Haisma, Jan; Hattu, Nico; (Dook) Pulles, J. T. C. M.; Steding, Esther; Vervest, Jan C. G.

    2007-09-01

    We present a number of recent evaluations of direct bonding, a glueless bonding technology, performed under ambient conditions. If combined with bond-strengthening, this geometry-conserving technology is well suited for an application in far ultraviolet immersion lithography. Our term beyond direct bonding refers to taking at least one additional technological step beyond direct bonding, involving chemical interface engineering, advanced silicon-on-insulator (SOI) technology, whereby the unwanted influence of dilatation mismatch is obviated. The combination of successive direct bonding, nanopillar lattice structures and silicon-technological engineering makes it possible for us to arrange quantum dots, wires, and planes in a transversal cascade. We also address the interrelationship between direct bonding and elasticity, as well as plasticity; the latter is in relation to direct bonded glass wafers that are thermally treated to create the geometric shape, e.g., required for specific lab-on-a-chip components with a three-dimensional overall configuration.

  2. Electronic structure and bonding of ozone

    NASA Astrophysics Data System (ADS)

    Kalemos, Apostolos; Mavridis, Aristides

    2008-08-01

    The ground and low-lying states of ozone (O3) have been studied by multireference variational methods and large basis sets. We have constructed potential energy curves along the bending coordinate for (1,2) 1A', (1,2) 1A'', (1,2) 3A', and (1,2) 3A'' symmetries, optimizing at the same time the symmetric stretching coordinate. Thirteen minima have been located whose geometrical and energetic characteristics are in very good agreement with existing experimental data. Special emphasis has been given to the interpretation of the chemical bond through valence-bond-Lewis diagrams; their appropriate use captures admirably the bonding nature of the O3 molecule. The biradical character of its ground state, adopted long ago by the scientific community, does not follow from a careful analysis of its wave function.

  3. 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

    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

    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

  4. Geometric travel planning

    Microsoft Academic Search

    Stefan Edelkamp; Shahid Jabbar; Thomas Willhalm

    2005-01-01

    This paper provides a novel approach for optimal route planning making efficient use of the underlying geometrical structure. It combines classical AI exploration with computa- tional geometry. Given a set of global positioning system (GPS) trajectories, the input is refined by geometric filtering and rounding algorithms. For constructing the graph and the according point localization structure, fast scan-line and divide-and-conquer

  5. Disorder-order structural transformation in electron-poor Sr3Au8Sn3 driven by chemical bonding optimization.

    PubMed

    Lin, Qisheng; Vetter, Jordan; Corbett, John D

    2013-06-01

    Sr3Au8Sn3 was synthesized through fusion of a stoichiometric amount of pure metals at 800 C and annealing treatments at lower temperatures. Single-crystal X-ray diffraction analyses revealed that Sr3Au8Sn3 has a La3Al11-type Immm structure (a = 4.6767(8) , b = 9.646(2) , c = 14.170(2) , Z = 2) if annealed at 550 C and above but a Ca3Au8Ge3-type structure (Pnnm, a = 9.6082(8) , b = 14.171(1) , c = 4.6719(4) , Z = 2) if annealed at 400 C. The transition occurs at about 454 C according to DTA data. Both structures feature columns of Sr-centered pentagonal and hexagonal prisms of Au and Sn stacked along the respective longest axial directions, but different "colorings" of the polyhedra are evident. In the high-temperature phase (Immm) all sites shared between the two prisms adopt 50:50 mixtures of Au/Sn atoms, whereas in the low-temperature phase (Pnnm) Au or Sn are completely ordered. A Klassengleiche group-subgroup relationship was established between these two structures. LMTO-ASA calculations reveal that ?E for the disorder-to-order transformation on cooling is driven mainly by optimization of the Au-Au and Au-Sn bond populations around the former mixed Au/Sn sites, particularly those with extremely short bonds at the higher temperature. These gains also overcome the smaller effect of ordering on the entropy decrease. PMID:23679918

  6. 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)

    Yoon, Yoonjin

    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.

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

    Microsoft Academic Search

    M. Zahedi-Tabrizi; R. Farahati

    2011-01-01

    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

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

    SciTech Connect

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

    2011-02-01

    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.

  9. Geometric Solids

    NSDL National Science Digital Library

    2012-09-18

    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).

  10. Geometric Solids

    NSDL National Science Digital Library

    2011-01-01

    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).

  11. Optimization of bonded joints

    NASA Technical Reports Server (NTRS)

    Ojalvo, I. U.

    1983-01-01

    A procedure for minimizing the elastic shear stress concentration in adhesive lap joints is presented. The proposed method is based upon tapering the adherends to achieve smooth stiffness transitions and uniform shear stresses. Both single and double lap splices are considered, but numerical examples are restricted to the case of double lap joints. Nonisotropic materials and nonoptimum design limitations, such as minimum and maximum thickness adherends, load-line eccentricity, and peel stresses are treated, and typical results are presented.

  12. Copper ion mediated selective cleavage of C-S bond in ferrocenylthiosemicarbazone forming mixed geometrical [(PPh3)Cu(?-S)2Cu(PPh3)2] having Cu2S2 core: toward a new avenue in copper-sulfur chemistry.

    PubMed

    Prabhakaran, Rathinasabapathi; Kalaivani, Palaniappan; Renukadevi, Somanur V; Huang, Rui; Senthilkumar, Kittusamy; Karvembu, Ramasamy; Natarajan, Karuppannan

    2012-03-19

    Unprecedented selective cleavage of the carbon-sulfur bond of the ferrocenylthiosemicarbazone moiety has been observed for the first time, resulting in the formation of mixed geometrical binuclear copper complex [(PPh(3))Cu(?-S)(2)Cu(PPh(3))(2)]. Upon trying direct synthesis of the title complex, an unusual tetranuclear [Cu(4)(?(3)-Cl)(4)(PPh(3))(4)] cubane resulted. PMID:22376179

  13. Intramolecular hydrogen-bonding interactions in 2-nitrosophenol and nitrosonaphthols: ab initio, density functional, and nuclear magnetic resonance theoretical study.

    PubMed

    Shchavlev, Andrew E; Pankratov, Alexei N; Enchev, Venelin

    2007-08-01

    Intramolecular hydrogen bonding (IHB) interactions and molecular structures of 2-nitrosophenol, nitrosonaphthols, and their quinone-monooxime tautomers were investigated at ab initio and density functional theory (DFT) levels. The geometry optimization of the structures studied was performed without any geometrical restrictions. Possible conformations with different types of the IHB of the tautomers were considered to understand the nature of the HB among these conformers. The effect of solvent on hydrogen bond energies, conformational equilibria, and tautomerism in aqueous solution were studied. Natural bond orbital analysis was performed to study the IHB in the gaseous phase and in aqueous medium. The NMR 1H, 13C, 15N, and 17O chemical shifts in the gaseous phase and in solution for the studied compounds were calculated using the gauge-including atomic orbitals approach implemented in the Gaussian 03 program package. The optimized geometrical parameters and 1H NMR chemical shifts are in good agreement with previous theoretical and experimental data. PMID:17616175

  14. 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

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

    2011-01-01

    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

  15. Comparison of insect kinin analogs with cis-peptide bond motif 4-aminopyroglutamate identifies optimal stereochemistry for diuretic activity.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The insect kinins are present in a wide variety of insects and function as potent diuretic peptides, though they are subject to rapid degradation by internal peptidases. Insect kinin analogs incorporating stereochemical variants of (2S,4S)-4-aminopyroglutamate (APy), a cis-peptide bond motif, demon...

  16. Geometric Mechanics

    NASA Astrophysics Data System (ADS)

    Talman, Richard

    1999-10-01

    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.

  17. Geometric Solids

    NSDL National Science Digital Library

    NCTM Illuminations

    2000-01-01

    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?

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

    NASA Astrophysics Data System (ADS)

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

    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.

  19. Geometric Shapes

    NSDL National Science Digital Library

    Mr. Hoskins

    2005-11-21

    We will be learning the names and properties (# of sides, vertices, parallel sides, etc.) of several different geometric shapes. By now, everybody should know how many sides a square has and be able to recognize a circle. But, do you know how many vertices a parallelogram has, or how many sides to a rhombus? After completing the following exercies, you should be able to answer those questions and many ...

  20. Geometric Algebra

    E-print Network

    Eric Chisolm

    2012-05-27

    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.

  1. Relative Entropy Relaxations for Signomial Optimization Venkat Chandrasekaranc

    E-print Network

    with efficiently computable nonnegativity certificates via the arithmetic-geometric- mean inequality. By appealing numerical experiments. Keywords: arithmetic-geometric-mean inequality; convex optimization; geometric

  2. Optimal Investment Problems with Marked Point Processes

    Microsoft Academic Search

    Claudia Ceci

    \\u000a Optimal investment problems in an incomplete financial market with pure jump stock dynamics are studied. An investor with\\u000a Constant Relative Risk Aversion (CRRA) preferences, including the logarithmic utility, wants to maximize her\\/his expected\\u000a utility of terminal wealth by investing in a bond and in a risky asset. The risky asset price is modeled as a geometric marked\\u000a point process, whose

  3. Conic Geometric Programming - Optimization Online

    E-print Network

    2013-10-03

    Oct 2, 2013 ... A basic restriction is that the constraint sets in SDPs have algebraic ..... are specified in terms of exponential/linear functions, it is natural to expect the ... Here e is the Euler constant, K? ? Rn is the dual of the cone K (2), and Q,R .... This simple observation yields a number of interesting CGP lift-and-project.

  4. Geometric and electronic structure of Ti2AlX (X=V, Nb, or Ta)

    NASA Astrophysics Data System (ADS)

    Hu, Q. M.; Yang, R.; Xu, D. S.; Hao, Y. L.; Li, D.; Wu, W. T.

    2003-08-01

    Using a first-principles plane-wave pseudopotential method, the geometric and electronic structures of Ti2AlX (X=V, Nb, or Ta) are investigated. The supercells of Ti2AlX are constructed by replacing certain Ti atoms in ?2-Ti3Al with X, and then the cell geometry is fully optimized. The geometric structure of the optimized Ti2AlNb supercell agrees well with that of the experimentally identified O phase in Ti3Al-Nb alloys. The optimized geometric structures of Ti2AlV and Ti2AlTa indicate that V and Ta may also induce the ?2 to O phase transformation. The calculations of density of states and valence charge density indicate that the strength of the p-d covalent bond in Ti2AlX changes in the order Ti2AlVbond changes in the order Ti3Albond. The calculated heat of formation of Ti2AlNb is very close to that of Ti3Al, but is about 17% larger than those of Ti2AlV and Ti2AlTa, significantly different from some other reports in the literature. The calculated geometric and electronic structures of the O phase are related to the beneficial effect of the alloying elements on the mechanical properties of Ti3Al.

  5. A geometric approach to Support Vector Machine (SVM) classification

    Microsoft Academic Search

    Michael E. Mavroforakis; Sergios Theodoridis

    2006-01-01

    The geometric framework for the support vector machine (SVM) classification problem provides an intuitive ground for the understanding and the application of geometric optimization algorithms, leading to practical solutions of real world classification problems. In this work, the notion of \\

  6. Geometric mouldability analysis by geometric reasoning and fuzzy decision making

    Microsoft Academic Search

    Zhou-ping Yin; Han Ding; Han-xiong Li; You-lun Xiong

    2004-01-01

    This paper presents a methodology for mouldability analysis by finding the optimal cavity design scheme (CDS) based on manufacturing and cost considerations using part geometry, where a CDS refers to a combination of the parting direction, parting line (PL), and undercut features (UF). The methodology takes advantage of geometric reasoning and fuzzy evaluation, and consists of two main stages: (1)

  7. Biomolecular halogen bonds.

    PubMed

    Ho, P Shing

    2015-01-01

    Halogens are atypical elements in biology, but are common as substituents in ligands, including thyroid hormones and inhibitors, which bind specifically to proteins and nucleic acids. The short-range, stabilizing interactions of halogens - now seen as relatively common in biology - conform generally to halogen bonds characterized in small molecule systems and as described by the ?-hole model. The unique properties of biomolecular halogen bonds (BXBs), particularly in their geometric and energetic relationship to classic hydrogen bonds, make them potentially powerful tools for inhibitor design and molecular engineering. This chapter reviews the current research on BXBs, focusing on experimental studies on their structure-energy relationships, how these studies inform the development of computational methods to model BXBs, and considers how BXBs can be applied to the rational design of more effective inhibitors against therapeutic targets and of new biological-based materials. PMID:25326832

  8. Integrating nutrition: a geometrical approach

    Microsoft Academic Search

    D. Raubenheimer; S. J. Simpson

    1999-01-01

    We present and illustrate using data from insects an integrative approach to modelling animal nutrition. This framework enables the unification within simple geometrical models of several nutritionally relevant measures. These include: the optimal balance and amounts of nutrients required to be ingested and allocated to growth by an animal over a given time period (the intake and growth targets, respectively);

  9. Parallel Search Algorithm for Geometric Constraints Solving

    Microsoft Academic Search

    Kong Zhao; Hua Yuan; Wenhui Li; Rongqin Yi

    2007-01-01

    In this paper, we propose a hybrid algorithm -(parallel search algorithm) to solve geometric constraint problems. First, particle swarm optimization is employed to gain parallelization while solution diversity is maintained. Second, simplex method reduces the number of infeasible solutions while solution quality is improved with an operation order search. Performance results on geometric constraint problems show that parallel search algorithm

  10. Chemical Bonds

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    Electrons are key to forming the two broad categories of chemical bonds: covalent and ionic. Atoms, which have a nucleus surrounded by electrons, are represented in several different ways. In the Chemical Bonds activity, students explore the different kinds of chemical bonds that can form, ranging from non-polar covalent to ionic. In the model depicted above students adjust the electronegativity of two atoms and see the effect it has on electron distribution and bond type.

  11. 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

    Shahi, Abhishek; Arunan, Elangannan

    2014-11-14

    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

  12. Effect of Geometric Distance on Agreement Dynamics of Naming Game

    NASA Astrophysics Data System (ADS)

    Hao, Jia-Bo; Yang, Han-Xin; Liu, Run-Ran; Wang, Bing-Hong; Zhang, Zhi-Yuan

    2010-09-01

    We investigate the naming game on geometric networks. The geometric networks are constructed by adding geometric links to two-dimensional regular lattices. It is found that the agreement time is a non-monotonic function of the geometric distance and there exists an optimal value of the geometric distance resulting in the shortest agreement time. All these results show that the geometric distance plays an important role in the evolutionary process of the language game. Our results also show that the convergence time strongly depends on the number of adding links.

  13. Combining Immune with Ant Colony Algorithm for Geometric Constraint Solving

    Microsoft Academic Search

    Hua Yuan; Yi Li; Wenhui Li; Kong Zhao; Duo Wang; Rongqin Yi

    2008-01-01

    Geometric constraint problem can be transformed to an optimization problem which the objective function and constraints are non-convex functions. In this paper an evolutionary algorithm based on ant colony optimization algorithm and the immune system model is proposed to provide solution to the geometric constraints problem. In the new algorithm, affinity calculation process and pheromone trail lying is embedded to

  14. Optimizing Evaluation of Split Renal Function in a Living Kidney Donor Using Scintigraphy and Calculation of the Geometric Mean: A Case Report

    PubMed Central

    Weinberger, S.; Bder, M.; Scheurig-Mnkler, C.; Hinz, S.; Neymeyer, J.; Miller, K.; Kempkensteffen, C.

    2014-01-01

    Within the evaluation process of living kidney donors, split renal function is usually evaluated by renal scintigraphy. Since split renal function measured by conventional posterior scans depends on the position of the kidney, actual suitable donors may be rejected because of an inaccurate examination technique. We report the case of a 28-year-old male living kidney donor. Due to a complex vascular anatomy of the right kidney, only his left kidney was considered eligible for transplantation. In conventional posterior Tc99m-mercapto-acetyltriglycine scintigraphy, the left kidney had a relative function of 60%. A second scintigraphy using anterior and posterior dimercaptosuccinic acid scans with calculation of the geometric mean showed an adapted relative function of the left kidney of 53%, now meeting the inclusion criteria for living kidney donation. This case shows that the geometric mean method using simultaneous anterior and posterior views obtained with a dual-head gamma camera can be a very helpful approach to determine split renal function of potential living kidney donors. Further investigation is necessary to prove the benefit of a general bilateral scan before living kidney donation. PMID:24575115

  15. Low-Stress Thermosonic Copper Ball Bonding

    Microsoft Academic Search

    Aashish Shah; Michael Mayer; Y. Norman Zhou; S. J. Hong; J. T. Moon

    2009-01-01

    Thermosonic ball bonding processes on test chips with Al metallized bonding pads are optimized with one Au and two Cu wire types, all 25 mum diameter, obtaining average shear strengths of more than 120 MPa. The process temperature is ~110degC. Ball bonds made with Cu wire show at least 15% higher shear strength than those made with Au wire. The

  16. Valence State Driven Site Preference in the Quaternary Compound Ca5MgAgGe5: An Electron-Deficient Phase with Optimized Bonding

    SciTech Connect

    Ponou, Simeon [Centre for Analysis and Synthesis, Lund University; Lidin, Sven [Centre for Analysis and Synthesis, Lund University; Zhang, Yuemei [Ames Laboratory; Miller, Gordon J. [Ames Laboratory

    2014-04-18

    The quaternary phase Ca5Mg0.95Ag1.05(1)Ge5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma Wyckoff sequence c12 with a = 23.1481(4) , b = 4.4736(1) , c = 11.0128(2) , V = 1140.43(4) 3, Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R2+nT2X2+n, previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm Wyckoff sequence f5c2. The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed.

  17. Pauling bond strength, bond length and electron density distribution

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.

    2014-01-18

    A power law regression equation, = 1.46(/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, , between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(?(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ?(rc) and the Pauling bond strength s with bond length, it appears that Paulings simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, ?, power law expression ? = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M-O bonded interactions for a relatively wide range of M atoms of the periodic table. The power law equation determined for the oxide crystals at ambient conditions is similar to the power law expression = r[1.46/]5.26 determined for the perovskites at pressures as high as 80 GPa, indicating that the intrinsic connection between R(M-O) and ?(rc) that holds at ambient conditions also holds, to a first approximation, at high pressures.

  18. Parallel Search Algorithm for Geometric Constraints Solving

    Microsoft Academic Search

    Hua Yuan; Wenhui Li; Kong Zhao; Rongqin Yi

    2007-01-01

    We propose a hybrid algorithm (Parallel Search Algorithm) between PSO and simplex methods to approximate optimal solution\\u000a for the Geometric Constraint problems. Locally, simplex is extended to reduce the number of infeasible solutions while solution\\u000a quality is improved with an operation order search. Globally, PSO is employed to gain parallelization while solution diversity\\u000a is maintained. Performance results on Geometric

  19. ArithmeticGeometric Progression

    E-print Network

    Feret, Jrme

    VMCAI'05 The ArithmeticGeometric Progression Abstract Domain Jrme Feret cole Normale Suprieure; Overview 1. Introduction 2. Case study 3. Arithmeticgeometric progressions 4. Benchmarks 5. Conclusiongeometric progressions 4. Benchmarks 5. Conclusion Jrme Feret, LIENS 13 January, 2005 #12; Arithmetic

  20. Optimism

    PubMed Central

    Carver, Charles S.; Scheier, Michael F.; Segerstrom, Suzanne C.

    2010-01-01

    Optimism is an individual difference variable that reflects the extent to which people hold generalized favorable expectancies for their future. Higher levels of optimism have been related prospectively to better subjective well-being in times of adversity or difficulty (i.e., controlling for previous well-being). Consistent with such findings, optimism has been linked to higher levels of engagement coping and lower levels of avoidance, or disengagement, coping. There is evidence that optimism is associated with taking proactive steps to protect one's health, whereas pessimism is associated with health-damaging behaviors. Consistent with such findings, optimism is also related to indicators of better physical health. The energetic, task-focused approach that optimists take to goals also relates to benefits in the socioeconomic world. Some evidence suggests that optimism relates to more persistence in educational efforts and to higher later income. Optimists also appear to fare better than pessimists in relationships. Although there are instances in which optimism fails to convey an advantage, and instances in which it may convey a disadvantage, those instances are relatively rare. In sum, the behavioral patterns of optimists appear to provide models of living for others to learn from. PMID:20170998

  1. Geometric Optimization of 2D Cellular Metals Cooled by Forced Convection Subjected to Fixed Pumping Power, Pressure Drop or Mass Flowrate

    Microsoft Academic Search

    T. Wen; F. Xu; T. J. Lu; N. Collings

    2007-01-01

    An analytical approach for the optimal design of 2D cellular metallic structures for heat sink applications is proposed. By integrating fin analogy model into intersection-of-asymptotes method, both the conjugate conduction-convection heat transfer mechanism and the developing flow\\/temperature fields are considered in this approach. Results are reported nondimensionally for three different flow configurations: fixed mass flowrate, fixed pressure drop and fixed

  2. 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)

    Yao, Tse-Min; Choi, Kyung K.

    1987-01-01

    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.

  3. Geometric Reasoning for Automated Planning

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  4. DISCRETE GEOMETRIC MOTION CONTROL OF AUTONOMOUS Marin Kobilarov

    E-print Network

    Kobilarov, Marin

    DISCRETE GEOMETRIC MOTION CONTROL OF AUTONOMOUS VEHICLES by Marin Kobilarov A Dissertation 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

  5. Geometric description of vakonomic and nonholonomic dynamics. Comparison of solutions

    Microsoft Academic Search

    Jorge Cortes; Manuel de Leon; David Mart; Sonia Mart nez

    We treat the vakonomic dynamics with general constraints within a new geometric framework which will be appropriate to study optimal control problems. We compare our formulation with Vershik-Gershkovich one in the case of linear constraints. We show how nonholonomic mechanics also admits a new geometrical description wich en- ables us to develop an algorithm of comparison between the solutions of

  6. Geometrization of Quantum Mechanics

    E-print Network

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

    2007-03-23

    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.

  7. Adaptive Source Coding Schemes for Geometrically Distributed Integer Alphabets

    NASA Technical Reports Server (NTRS)

    Cheung, K-M.; Smyth, P.

    1993-01-01

    Revisit the Gallager and van Voorhis optimal source coding scheme for geometrically distributed non-negative integer alphabets and show that the various subcodes in the popular Rice algorithm can be derived from the Gallager and van Voorhis code.

  8. A Survey of Geometric Algebra

    E-print Network

    Harrington, J. Patrick

    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

  9. Investing in Bonds

    E-print Network

    Johnson, Jason; Polk, Wade

    2002-08-12

    Bonds, which are issued by governments and corporations, can be an important part of one's investment portfolio. U.S. government bonds, municipal bonds, zero-coupon bonds and other types are described. Also learn strategies for coping with inflation...

  10. Quantifying weak hydrogen bonding in uracil and 4-cyano-4'-ethynylbiphenyl: a combined computational and experimental investigation of NMR chemical shifts in the solid state.

    PubMed

    Uldry, Anne-Christine; Griffin, John M; Yates, Jonathan R; Prez-Torralba, Marta; Mara, M Dolores Santa; Webber, Amy L; Beaumont, Maximus L L; Samoson, Ago; Claramunt, Rosa Mara; Pickard, Chris J; Brown, Steven P

    2008-01-23

    Weak hydrogen bonding in uracil and 4-cyano-4'-ethynylbiphenyl, for which single-crystal diffraction structures reveal close CH...O=C and C[triple bond]CH...N[triple bond]C distances, is investigated in a study that combines the experimental determination of 1H, 13C, and 15N chemical shifts by magic-angle spinning (MAS) solid-state NMR with first-principles calculations using plane-wave basis sets. An optimized synthetic route, including the isolation and characterization of intermediates, to 4-cyano-4'-ethynylbiphenyl at natural abundance and with 13C[triple bond]13CH and 15N[triple bond]C labeling is described. The difference in chemical shifts calculated, on the one hand, for the full crystal structure and, on the other hand, for an isolated molecule depends on both intermolecular hydrogen bonding interactions and aromatic ring current effects. In this study, the two effects are separated computationally by, first, determining the difference in chemical shift between that calculated for a plane (uracil) or an isolated chain (4-cyano-4'-ethynylbiphenyl) and that calculated for an isolated molecule and by, second, calculating intraplane or intrachain nucleus-independent chemical shifts that quantify the ring current effects caused by neighboring molecules. For uracil, isolated molecule to plane changes in the 1H chemical shift of 2.0 and 2.2 ppm are determined for the CH protons involved in CH...O weak hydrogen bonding; this compares to changes of 5.1 and 5.4 ppm for the NH protons involved in conventional NH...O hydrogen bonding. A comparison of CH bond lengths for geometrically relaxed uracil molecules in the crystal structure and for geometrically relaxed isolated molecules reveals differences of no more than 0.002 A, which corresponds to changes in the calculated 1H chemical shifts of at most 0.1 ppm. For the C[triple bond]CH...N[triple bond]C weak hydrogen bonds in 4-cyano-4'-ethynylbiphenyl, the calculated molecule to chain changes are of similar magnitude but opposite sign for the donor 13C and acceptor 15N nuclei. In uracil and 4-cyano-4'-ethynylbiphenyl, the CH hydrogen-bonding donors are sp2 and sp hybridized, respectively; a comparison of the calculated changes in 1H chemical shift with those for the sp3 hybridized CH donors in maltose (Yates et al. J. Am. Chem. Soc. 2005, 127, 10216) reveals no marked dependence on hybridization for weak hydrogen-bonding strength. PMID:18166050

  11. Geometric sensitivity of ClearPET Neuro

    NASA Astrophysics Data System (ADS)

    Gundlich, Brigitte; Weber, Simone

    2007-02-01

    ClearPET Neuro is a small-animal positron emission tomography (PET) scanner dedicated to brain studies on rats and primates. The design of ClearPET Neuro leads to a specific geometric sensitivity, characterized by inhomogeneous and, depending on the measurement setup, even incomplete data. With respect to reconstruction techniques, homogeneous and complete data sets are a 'must' for analytical reconstruction methods, whereas iterative methods take the geometrical sensitivity into account during the reconstruction process. Nevertheless, here a homogeneous geometric sensitivity over the field of view is highly desirable. Therefore, this contribution aims at studying the impact of different scanner geometries and measurement setups on the geometric sensitivity. A data set of coincident events is computed for certain settings that contains each possible crystal combination once. The lines of response are rebinned into normalizing sinograms and backprojected into sensitivity images. Both, normalizing sinograms and sensitivity images mirror the geometric sensitivity and therefore, provide information which setting enables most complete and homogeneous data sets. An optimal measurement setup and scanner geometry in terms of homogeneous geometric sensitivity is found by analyzing the sensitivity images.

  12. Bonded Lubricants

    NASA Technical Reports Server (NTRS)

    1977-01-01

    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.

  13. OPTIMIZATION OPTIMIZATION

    E-print Network

    Stanford University

    CONVEX OPTIMIZATION & EUCLIDEAN DISTANCE GEOMETRY DATTORRO M #12;Dattorro CONVEX OPTIMIZATION & EUCLIDEAN DISTANCE GEOMETRY Meboo #12;Convex Optimization & Euclidean Distance Geometry Jon Dattorro Moo & Euclidean Distance Geometry, Moo, 2005, v2014.04.08. ISBN 0976401304 (English) ISBN 9780615193687

  14. Geometrizing Relativistic Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Falciano, F. T.; Novello, M.; Salim, J. M.

    2010-12-01

    We propose a new approach to describe quantum mechanics as a manifestation of non-Euclidean geometry. In particular, we construct a new geometrical space that we shall call Qwist. A Qwist space has a extra scalar degree of freedom that ultimately will be identified with quantum effects. The geometrical properties of Qwist allow us to formulate a geometrical version of the uncertainty principle. This relativistic uncertainty relation unifies the position-momentum and time-energy uncertainty principles in a unique relation that recover both of them in the non-relativistic limit.

  15. Arithmetic and Geometric Sequences

    NSDL National Science Digital Library

    2007-12-12

    Find the value of individual terms in an arithmetic or geometric sequence using graphs of the sequence and direct computation. Vary the common difference and common ratio and examine how the sequence changes in response.

  16. Geometric intrinsic symmetries

    SciTech Connect

    Gozdz, A., E-mail: Andrzej.Gozdz@umcs.lublin.pl; Szulerecka, A.; Pedrak, A. [University of Maria Curie-Sklodowska, Institute of Physics, Department of Mathematical Physics (Poland)] [University of Maria Curie-Sklodowska, Institute of Physics, Department of Mathematical Physics (Poland)

    2013-08-15

    The problem of geometric symmetries in the intrinsic frame of a many-body system (nucleus) is considered. An importance of symmetrization group notion is discussed. Ageneral structure of the intrinsic symmetry group structure is determined.

  17. AJ Geometric Formulas Calculator

    NSDL National Science Digital Library

    Jimmy Raymond

    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.

  18. Hierarchies of Geometric Entanglement

    E-print Network

    M. Blasone; F. Dell'Anno; S. De Siena; F. Illuminati

    2008-05-28

    We introduce a class of generalized geometric measures of entanglement. For pure quantum states of $N$ elementary subsystems, they are defined as the distances from the sets of $K$-separable states ($K=2,...,N$). The entire set of generalized geometric measures provides a quantification and 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 to the study of entanglement in different classes of $N$-qubit pure states. These classes include $W$ and $GHZ$ states, and their symmetric superpositions; symmetric multi-magnon states; cluster states; and, finally, asymmetric generalized $W$-like superposition states. We discuss in detail a general method for the explicit evaluation of the multipartite components of geometric entanglement, and we show that 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 of Wei and Goldbart that $W$ states possess a larger global entanglement than $GHZ$ states. Furthermore, we show that all multipartite components of geometric entanglement in symmetric states obey a property of self-similarity and scale invariance with the total number of qubits and the number of qubits per party.

  19. Cis Peptide Bonds in Proteins: Residues Involved, their Conformations, Interactions and Locations

    E-print Network

    Pal, Debnath

    Cis Peptide Bonds in Proteins: Residues Involved, their Conformations, Interactions and Locations bonding and other stabilizing interactions involving cis peptide bonds. This has led to a reclassi®cation of turns mediated by cis peptides, and their average geometrical par- ameters have been evaluated

  20. Robust Truss Topology Optimization under Geometric Uncertainties

    E-print Network

    Kanno, Yoshihiro

    ] #12;uncertainty in boundary shape of continuum · uniform manufacturing error · SIMP [Sigmund 09], [Wang, Lazarov, & Sigmund 11] · level-set method [Jang, van Dijk, van Keulen 12] · probabilistic model · SIMP [Schevenels, Lazarov, & Sigmund 11] [Lazarov, Schevenels, & Sigmund 12] · level-set method [Chen

  1. Optimization of Inductor Circuits via Geometric Programming

    E-print Network

    -cost radio-frequency integrated circuits (RF-ICs) has generated tremendous interest in on-chip spiral in and handles a variety of specifications including fixed value of inductance, minimum self-resonant frequency the experimental data and the specifications predicted by our method. 1 Introduction The rising demand for low

  2. DFT OPTIMIZATION STUDIES OF ALPHA-MALTOSE: ISO-ENERGETIC AND INTERNAL COORDINATE CONTOUR MAPS UPON ROTATION ABOUT THE GLYCOSIDIC BONDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The disaccharide alpha-maltose is a molecular template for amylose. Our previous DFT work on maltose is expanded to a set of 63 fully optimized (B3LYP/6-311++G**) conformations. All clockwise, and counter clockwise hydroxyl groups, as well as 'kink' and band-slip conformers, are studied. Adiabati...

  3. Geometric simulation of flexible motion in proteins.

    PubMed

    Wells, Stephen A

    2014-01-01

    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

  4. Students' Perceptions of Parental Bonding Styles and Their Academic Burnout

    ERIC Educational Resources Information Center

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

    2012-01-01

    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

  5. Mutual influence between anion-? and pnicogen bond interactions: The enhancement of P?N and P?O interactions by an anion-? bond.

    PubMed

    Esrafili, Mehdi D; Mohammadian-Sabet, Fariba; Solimannejad, Mohammad

    2015-04-01

    In this work, the interplay between anion-? and pnicogen bond interactions is investigated by ab initio calculations. Cooperative effects are observed in the studied complexes in which anion-? and pnicogen bond interactions coexist. These effects are analyzed in detail in terms of the energetic, geometric, charge-transfer and electron density properties of the complexes. The cooperative energy ranges from -1.8 to -4.1kcalmol(-1). The effect of an anion-? bond on a pnicogen bond is more pronounced than that of a pnicogen bond on an anion-? bond. The enhancing mechanism is analyzed in views with the charge-transfer, electrostatic potential and electron density analysis. PMID:25698102

  6. Inflation from geometrical tachyons

    SciTech Connect

    Thomas, Steven; Ward, John [Department of Physics, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)

    2005-10-15

    We propose an alternative formulation of tachyon inflation using the geometrical tachyon arising from the time dependent motion of a BPS D3-brane in the background geometry due to k parallel NS5-branes arranged around a ring of radius R. Because of the fact that the mass of this geometrical tachyon field is {radical}(2/k) times smaller than the corresponding open-string tachyon mass, we find that the slow-roll conditions for inflation and the number of e-foldings can be satisfied in a manner that is consistent with an effective 4-dimensional model and with a perturbative string coupling. We also show that the metric perturbations produced at the end of inflation can be sufficiently small and do not lead to the inconsistencies that plague the open-string tachyon models. Finally we argue for the existence of a minimum of the geometrical tachyon potential which could give rise to a traditional reheating mechanism.

  7. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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 ...

  8. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...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 ...

  9. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...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 ...

  10. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...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 ...

  11. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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 ...

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

    PubMed

    Lu, Tian; Chen, Feiwu

    2013-04-11

    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

  13. Dynamic Asset Allocation for Stocks, Bonds, and Cash

    Microsoft Academic Search

    Roland Portait

    2003-01-01

    Closed-form solutions for HARA optimal portfolios are obtained in a dynamic portfolio optimization model in three assets (stocks, bonds, and cash) in a Vasicek-type model of stochastic interest rates with correlated stock prices. The HARA is a buy-and-hold combination of a zero-coupon bond with maturity matching the investor's horizon and a \\

  14. Semiconductor wafer bonding

    NASA Astrophysics Data System (ADS)

    Reiche, M.

    2006-03-01

    When mirror-polished, flat, and clean wafers are brought into contact, they are locally attracted to each other and adhere or bond. This phenomenon is known as semiconductor wafer bonding. Different adhesion forces (van der Waals forces, hydrogen bonding) are the reason for the bonding effect at room temperature. The different bonding mechanisms acting in dependence on the surface conditions (hydrophilic, hydrophobic) are reviewed. Variations of the properties of bonded interfaces (structural, mechanical, electrical) during annealing are discussed. The focus is on low-temperature bonding techniques. Reasons for the formation of interface defects are presented. Applications of semiconductor wafer bonding for future developments are briefly summarized.

  15. Geometric Sound Propagation

    E-print Network

    North Carolina at Chapel Hill, University of

    Some sound is absorbed Multiply bands by some absorption coefficient A[2] Coefficient is basedGeometric Sound Propagation Micah Taylor #12;Sound propagation Given a sound source in a scene arrive at the listener #12;Sound propagation Sound travels slow 344 m/s Specular reflections Perfect

  16. Geometric grid generation

    NASA Technical Reports Server (NTRS)

    Ives, David

    1995-01-01

    This paper presents a highly automated hexahedral grid generator based on extensive geometrical and solid modeling operations developed in response to a vision of a designer-driven one day turnaround CFD process which implies a designer-driven one hour grid generation process.

  17. Geometrization of quantum mechanics

    Microsoft Academic Search

    T. W. B. Kibble

    1979-01-01

    Quantum mechanics is cast into a classical Hamiltonian form in terms of a symplectic structure, not on the Hilbert space of state-vectors but on the more physically relevant infinite-dimensional manifold of instantaneous pure states. This geometrical structure can accommodate generalizations of quantum mechanics, including the nonlinear relativistic models recently proposed. It is shown that any such generalization satisfying a few

  18. Untangling Geometric Ideas

    ERIC Educational Resources Information Center

    Burgess, Claudia R.

    2014-01-01

    Designed for a broad audience, including educators, camp directors, afterschool coordinators, and preservice teachers, this investigation aims to help individuals experience mathematics in unconventional and exciting ways by engaging them in the physical activity of building geometric shapes using ropes. Through this engagement, the author

  19. A Geometric Scavenger Hunt

    ERIC Educational Resources Information Center

    Smart, Julie; Marshall, Jeff

    2007-01-01

    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

  20. LABORATORY I: GEOMETRIC OPTICS

    E-print Network

    Minnesota, University of

    Lab I - 1 LABORATORY I: GEOMETRIC OPTICS In this lab, you will solve several problems related to the formation of optical images. Most of us have a great deal of experience with the formation of optical images this laboratory, you should be able to: · Describe features of real optical systems in terms of ray diagrams

  1. Geometric Series via Probability

    ERIC Educational Resources Information Center

    Tesman, Barry

    2012-01-01

    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

  2. Geometric Modelling Dagstuhl 2002

    E-print Network

    Hahmann, Stefanie

    , simulation, and medical imaging, and it attracts researchers with backgrounds in computer science as well, Houston Editorial Geometric Modeling is the branch of Computer Science concerned with the efficient to the following diverse topics: · curve and surface modeling · non-manifold modeling in CAD · multiresolution

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

    PubMed

    Bosi, Ferdinando

    2014-10-01

    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

  4. PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism

    NASA Astrophysics Data System (ADS)

    Gardner, Jason S.

    2011-04-01

    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

  5. 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.

  6. The classical geometrization electromagnetism

    E-print Network

    C. A. Duarte

    2015-02-11

    Following the line of the history, if by one side the electromagnetic theory was consolidated on the 19th century, the emergence of the special and the general relativity theories on the 20th century opened possibilities of further developments, with the search for the unification of the gravitation and the electromagnetism on a single unified theory. Some attempts to the geometrization of the electromagnetism emerged in this context, where these first models resided strictly on a classical basis. Posteriorly, they were followed by more complete and embracing quantum field theories. The present work reconsiders the classical viewpoint, with the purpose of showing that in a first order of approximation the electromagnetism constitutes a geometric structure aside other phenomena as gravitation. Even though being limited, the model is consistent and offers the possibility of an experimental test of validity.

  7. MESHLESS GEOMETRIC SUBDIVISION Carsten Moenning

    E-print Network

    Minnesota, University of

    MESHLESS GEOMETRIC SUBDIVISION By Carsten Moenning Facundo M´emoli Guillermo Sapiro Nira Dyn­0436 Phone: 612/624-6066 Fax: 612/626-7370 URL: http://www.ima.umn.edu #12;Meshless Geometric Subdivision by introducing the notion of meshless, or point cloud, geometric subdivision. Our meshless subdivision approach

  8. Limits: Geometric and Harmonic Series

    NSDL National Science Digital Library

    Illuminations National Council of Teachers of Mathematics

    2010-05-26

    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.

  9. Geometric Solids and Their Properties

    NSDL National Science Digital Library

    Illuminations; National Council of Teachers of Mathematics (NCTM)

    2000-01-01

    Explore geometric solids and their properties with these interactive tools, beginning with an introduction to the faces of basic polyhedra; counting the number of faces, edges, and corners (vertices) in various solids; discovering Euler's Formula; constructing physical models of geometric solids; and identifying which geometric solids can be made from given nets.

  10. LET'S BOND! A Chemical Bonding Webquest

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-04-08

    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 ...

  11. Compatible Geometric Matchings

    Microsoft Academic Search

    Oswin Aichholzer; Sergey Bereg; Adrian Dumitrescu; Alfredo Garca; Clemens Huemer; Ferran Hurtado; Mikio Kano; Alberto Mrquez; David Rappaport; Shakhar Smorodinsky; Diane L. Souvaine; Jorge Urrutia; David R. Wood

    2008-01-01

    This paper studies non-crossing geometric perfect matchings. Two such perfect matchings are compatible if they have the same vertex set and their union is also non-crossing. Our first result states that for any two perfect matchings M and M0 of the same set of n points, for some k 2 O(logn), there is a sequence of perfect matchings M =

  12. Geometrical theory of diffraction

    Microsoft Academic Search

    P B Sunil Kumar; G S Ranganath

    1991-01-01

    Geometrical theory of diffraction (GTD) is an alternative model of diffraction propounded first by Thomas Young in 1802. GTD\\u000a has a long history of nearly 150 years over which many eminent people enriched this model which has now become an accepted\\u000a tool in the calculation of diffraction patterns. In the conventional Helmholtz-Kirchhoff theory the diffracted field is obtained\\u000a by computing

  13. Random Geometric Identification

    Microsoft Academic Search

    Gyula O. H. Katona

    2008-01-01

    The practical problem can be described in the following way. Physical objects (credit cards, important documents) should be\\u000a identified using geometric labels. An optical device reads the label and a simple computation checks whether the label belongs\\u000a to the given object or not. This could be done by asking an authority which stores certain data (e.g. the reading of the

  14. Hydroxide-catalyzed bonding

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2003-01-01

    A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

  15. Specificity of the juvenile hormone binding protein: The geometrical isomers of juvenile hormone I

    PubMed Central

    Goodman, Walter; Schooley, David A.; Gilbert, Lawrence I.

    1978-01-01

    The binding of the geometrical isomers (?99% pure) of juvenile hormone I to the hemolymph juvenile hormone binding protein of Manduca sexta (Lepidoptera, Sphingidae) was analyzed. A technique is described for isomer separation by micropreparative high-resolution liquid chromatography. Analysis of competition was performed by using a batch adsorption hydroxylapatite binding assay. Competition studies indicate that the naturally occurring isomer, 2E,6E,10cis, is bound with the highest affinity. Optimal binding appears to depend most heavily upon the configuration of the 2,3 double bond. Juvenile hormone binding protein shows a higher affinity for the 2E than for the 2Z configuration. The 6,7 double bond is of less importance in determining binding activity, and isomerism about the epoxide appears least important in conferring binding activity. The binding site may be a groove along the surface of the binding protein interacting with the side chains of juvenile hormone, including the ester methyl group. The grouping of the side chains and the ester methyl group thus constitutes a distinct hydrophobic face, and the hydrophobic interactions are essential in maintenance of the bound ligand. PMID:16592479

  16. Geometric Exponents, SLE and Logarithmic Minimal Models

    E-print Network

    Yvan Saint-Aubin; Paul A. Pearce; Jorgen Rasmussen

    2008-10-10

    In statistical mechanics, observables are usually related to local degrees of freedom such as the Q < 4 distinct states of the Q-state Potts models or the heights of the restricted solid-on-solid models. In the continuum scaling limit, these models are described by rational conformal field theories, namely the minimal models M(p,p') for suitable p, p'. More generally, as in stochastic Loewner evolution (SLE_kappa), one can consider observables related to nonlocal degrees of freedom such as paths or boundaries of clusters. This leads to fractal dimensions or geometric exponents related to values of conformal dimensions not found among the finite sets of values allowed by the rational minimal models. Working in the context of a loop gas with loop fugacity beta = -2 cos(4 pi/kappa), we use Monte Carlo simulations to measure the fractal dimensions of various geometric objects such as paths and the generalizations of cluster mass, cluster hull, external perimeter and red bonds. Specializing to the case where the SLE parameter kappa = 4p'/p is rational with p < p', we argue that the geometric exponents are related to conformal dimensions found in the infinitely extended Kac tables of the logarithmic minimal models LM(p,p'). These theories describe lattice systems with nonlocal degrees of freedom. We present results for critical dense polymers LM(1,2), critical percolation LM(2,3), the logarithmic Ising model LM(3,4), the logarithmic tricritical Ising model LM(4,5) as well as LM(3,5). Our results are compared with rigourous results from SLE_kappa, with predictions from theoretical physics and with other numerical experiments. Throughout, we emphasize the relationships between SLE_kappa, geometric exponents and the conformal dimensions of the underlying CFTs.

  17. Evidence for stereoelectronic effects in the N-C-N group of 8,10,12-triaza-1-azoniatetracyclo[8.3.1.1(8,12).0(2,7)]pentadecane 4-nitrophenolate 4-nitrophenol monosolvate from the protonation of aminal (2R,7R)-1,8,10,12-tetraazatetracyclo[8.3.1.1(8,12).0(2,7)]pentadecane: X-ray and natural bond orbital analysis.

    PubMed

    Rivera, Augusto; Uribe, Juan Manuel; Ros-Motta, Jaime; Osorio, Hector Jairo; Bolte, Michael

    2015-04-01

    The title molecular salt, C11H21N4(+)C6H4NO3(-)C6H5NO3, (II), crystallizes with two independent three-component aggregates in the asymmetric unit. In the cations, the cyclohexane rings fused to the cage azaadamantane systems both adopt a chair conformation. In the crystal structure, the aggregates are connected by C-H...O hydrogen bonds, forming a supramolecular unit enclosing an R4(4)(24) ring motif. These units are linked via C-H...O and C-H...N hydrogen bonds, forming a three-dimensional network. Even hydrogen-bond formation to one of the N atoms is enough to induce structural stereoelectronic effects in the normal donor?acceptor direction. The C-N bond distances provide structural evidence for a strong anomeric effect. The structure also displays O-H...O and N-H...O hydrogen bonding. Geometric optimization and natural bond orbital (NBO) analysis of (II) were undertaken by utilizing DFT/B3LYP with the 6-31+G(d,p) basis set. NBO second-order perturbation theory calculations indicate donor-acceptor interactions between nitrogen lone pairs and the antibonding orbital of the C-C and C-N bonds for the protonated polyamine, in agreement with the occurrence of bond-length and bond-angle changes within the aminal cage structure. PMID:25836286

  18. Geometric phase in Bohmian mechanics

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  20. Geometric mechanics of periodic pleated origami.

    PubMed

    Wei, Z Y; Guo, Z V; Dudte, L; Liang, H Y; Mahadevan, L

    2013-05-24

    Origami structures are mechanical metamaterials with properties that arise almost exclusively from the geometry of the constituent folds and the constraint of piecewise isometric deformations. Here we characterize the geometry and planar and nonplanar effective elastic response of a simple periodically folded Miura-ori structure, which is composed of identical unit cells of mountain and valley folds with four-coordinated ridges, defined completely by two angles and two lengths. We show that the in-plane and out-of-plane Poisson's ratios are equal in magnitude, but opposite in sign, independent of material properties. Furthermore, we show that effective bending stiffness of the unit cell is singular, allowing us to characterize the two-dimensional deformation of a plate in terms of a one-dimensional theory. Finally, we solve the inverse design problem of determining the geometric parameters for the optimal geometric and mechanical response of these extreme structures. PMID:23745895

  1. Geometric Mechanics of Periodic Pleated Origami

    NASA Astrophysics Data System (ADS)

    Wei, Z. Y.; Guo, Z. V.; Dudte, L.; Liang, H. Y.; Mahadevan, L.

    2013-05-01

    Origami structures are mechanical metamaterials with properties that arise almost exclusively from the geometry of the constituent folds and the constraint of piecewise isometric deformations. Here we characterize the geometry and planar and nonplanar effective elastic response of a simple periodically folded Miura-ori structure, which is composed of identical unit cells of mountain and valley folds with four-coordinated ridges, defined completely by two angles and two lengths. We show that the in-plane and out-of-plane Poissons ratios are equal in magnitude, but opposite in sign, independent of material properties. Furthermore, we show that effective bending stiffness of the unit cell is singular, allowing us to characterize the two-dimensional deformation of a plate in terms of a one-dimensional theory. Finally, we solve the inverse design problem of determining the geometric parameters for the optimal geometric and mechanical response of these extreme structures.

  2. Red-Shifted Hydrogen Bonds and Blue-Shifted van der Waals Contact in the Standard Watson-Crick Adenine-Thymine Base Pair

    NASA Astrophysics Data System (ADS)

    Zhou, Pan-Pan; Qiu, Wen-Yuan

    2009-08-01

    Standard Watson-Crick adenine-thymine (AT) base pair has been investigated by using the B3LYP functional with 6-31G(d, p) basis set, at which level of theory the geometrical characteristics of the AT base pair are the best in agreement with the experiment. It exhibits simultaneously red-shifted N-HO and N-HN hydrogen bonds as well as a blue-shifted C-HO contact. AIM analysis suggests that the blue-shifted C-HO contact exists as van der Waals interaction, and the electron density ? that reflects the strength of a bond has been used to explain the red- and blue-shifted. By means of NBO analysis, we report a method to estimate the effect of hyperconjugation quantitatively, which combines the electron density in the X-H (X = N, C) ? bonding orbital with that in the ?* antibonding orbital. The effect of structural reorganization on the origins of the red- and blue-shifted has been considered by the partial optimization, its behavior on the X-H (X = N, C) bond is quite different. Rehybridization and repolarization models are employed, and they act as bond-shortening effects. The competition between the electrostatic attractions and Pauli/nucleus repulsions is present in the two typical red-shifted N-HO and N-HN hydrogen bonds as well as in the blue-shifted C-HO van der Waals contact. Electrostatic attraction between H and Y atoms (Y = O, N) is an important reason for the red shift, while the nucleus-nucleus repulsion between H and O atoms may be a factor leading to the C-H bond contraction and its blue shift. The electric field effect induced by the acceptor O atom on the C-H bond is also discussed.

  3. Representing geometrical knowledge.

    PubMed Central

    Anderson, J A

    1997-01-01

    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

  4. Geometric Semigroup Theory

    E-print Network

    McCammond, Jon; Steinberg, Benjamin

    2011-01-01

    Geometric semigroup theory is the systematic investigation of finitely-generated semigroups using the topology and geometry of their associated automata. In this article we show how a number of easily-defined expansions on finite semigroups and automata lead to simplifications of the graphs on which the corresponding finite semigroups act. We show in particular that every finite semigroup can be finitely expanded so that the expansion acts on a labeled directed graph which resembles the right Cayley graph of a free Burnside semigroup in many respects.

  5. Essays on corporate bonds

    E-print Network

    Bao, Jack (Jack C.)

    2009-01-01

    This thesis consists of three empirical essays on corporate bonds, examining the role of both credit risk and liquidity. In the first chapter, I test the ability of structural models of default to price corporate bonds in ...

  6. Bonding silicones with epoxies

    SciTech Connect

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  7. Rapid adhesive bonding concepts

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  8. IMPROVED BONDING METHOD

    Microsoft Academic Search

    E. V. Jr. Padgett; D. H. Warf

    1964-01-01

    An improved process of bonding aluminum to aluminum without fusion by ; ultrasonic vibrations plus pressure is described. The surfaces to be bonded are ; coated with an aqueous solution of alkali metal stearate prior to assembling for ; bonding. (AEC) O H19504 Present information is reviewed on steady state ; proliferation, differentiation, and maturation of blood cells in mammals.

  9. Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  10. Hysteresis heating based induction bonding of composite materials

    Microsoft Academic Search

    Witchuda Suwanwatana

    2004-01-01

    The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni\\/PSU). An excellent

  11. Bonding thermoplastic polymers

    DOEpatents

    Wallow, Thomas I. (Fremont, CA); Hunter, Marion C. (Livermore, CA); Krafcik, Karen Lee (Livermore, CA); Morales, Alfredo M. (Livermore, CA); Simmons, Blake A. (San Francisco, CA); Domeier, Linda A. (Danville, CA)

    2008-06-24

    We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

  12. Prospective bonding applications

    NASA Astrophysics Data System (ADS)

    Ancenay, H.; Benazet, D.

    1981-07-01

    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.

  13. Hydrophobic silicon wafer bonding

    NASA Astrophysics Data System (ADS)

    Tong, Q.-Y.; Schmidt, E.; Gsele, U.; Reiche, M.

    1994-01-01

    Wafers prepared by an HF dip without a subsequent water rinse were bonded at room temperature and annealed at temperatures up to 1100 C. Based on substantial differences between bonded hydrophilic and hydrophobic Si wafer pairs in the changes of the interface energy with respect to temperature, secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM), we suggest that hydrogen bonding between Si-F and H-Si across two mating wafers is responsible for room temperature bonding of hydrophobic Si wafers. The interface energy of the bonded hydrophobic Si wafer pairs does not change appreciably with time up to 150 C. This stability of the bonding interface makes reversible room-temperature hydrophobic wafer bonding attractive for the protection of silicon wafer surfaces.

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

    Microsoft Academic Search

    Michela Ponticorvo; Orazio Miglino

    2010-01-01

    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

  15. An Image Inpainting Algorithm Based on Local Geometric Similarity

    Microsoft Academic Search

    Pan Qi; Xiaonan Luo; Jiwu Zhu

    2009-01-01

    \\u000a This paper proposes a novel noniterative orientation adaptive image inpainting algorithm. Assuming the image can be locally\\u000a modeled, the filling process is formulated as a linear optimization problem, which the optimal coefficients can be adapted\\u000a to match an arbitrary-oriented edge based on local geometric similarity. We provided A Weighted Least Square (WLS) method is provided to offer a convenient way

  16. Development of an Explosive Bonding Process for Producing High Strength Bonds between Niobium and 6061-T651 Aluminum

    SciTech Connect

    Palmer, T A; Elmer, J W; Brasher, D; Butler, D; Riddle, R

    2005-09-23

    An explosive bonding procedure for joining 9.5 mm thick niobium plate to 203 mm thick 6061-T651 Al plate has been developed in order to maximize the bond tensile and impact strengths and the amount of bonded material across the surface of the plate. This procedure improves upon previous efforts, in which the 9.5 mm thick niobium plate is bonded directly to 6061-T4 Al plate. In this improved procedure, thin Nb and Al interlayers are explosively clad between the thicker niobium and aluminum plates. Bonds produced using these optimized parameters display a tensile strength of approximately 255 MPa and an impact strength per unit area of approximately 0.148 J/mm{sup 2}. Specialized mechanical testing geometries and procedures are required to measure these bond properties because of the unique bond geometry. In order to ensure that differences in the thermal expansion coefficients of aluminum and niobium do not adversely affect the bond strength, the effects of thermal cycling at temperatures between -22 C and 45 C on the mechanical properties of these bonds have also been investigated by testing samples in both the as-received and thermal cycled conditions. Based on the results obtained from this series of mechanical tests, thermal cycling is shown to have no adverse effect on the resulting tensile and impact strengths of the bonds produced using the optimized bonding parameters.

  17. Algebraic, geometric, and stochastic aspects of genetic operators

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  18. Dynamic Allocation of Treasury and Corporate Bonds

    Microsoft Academic Search

    Roger Walder

    In this paper, we solve the intertemporal investment problem of an in- vestor holding a portfolio of default-free and defaultable bonds. Default- risk is modeled in an intensity based framework with state variables fol- lowing an affine diffusion. The structure of the optimal portfolio over time is investigated and compared to the static mean-variance portfolio. Furthermore, we describe the impact

  19. Towards a unified description of the hydrogen bond network of liquid water: a dynamics based approach.

    PubMed

    Ozkanlar, Abdullah; Zhou, Tiecheng; Clark, Aurora E

    2014-12-01

    The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the use of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed. PMID:25481129

  20. Towards a unified description of the hydrogen bond network of liquid water: A dynamics based approach

    NASA Astrophysics Data System (ADS)

    Ozkanlar, Abdullah; Zhou, Tiecheng; Clark, Aurora E.

    2014-12-01

    The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the use of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed.

  1. Protein Folding: A New Geometric Analysis

    E-print Network

    Walter A. Simmons; Joel L. Weiner

    2008-09-11

    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.

  2. 1.3-?m InP-InGaAsP lasers fabricated on Si substrates by wafer bonding

    Microsoft Academic Search

    Hiroshi Wada; Takeshi Kamijoh

    1997-01-01

    1.3-?m InP-InGaAsP lasers have been successfully fabricated on Si substrates by wafer bonding. InP-InGaAsP thin epitaxial films are prepared by selective etching of InP substrates and then bonded to Si wafers, after which the laser structures are fabricated on the bonded thin films. The bonding temperature has been optimized to be 400C by considering bonding strength, quality of the bonded

  3. Circle actions in geometric quantisation

    NASA Astrophysics Data System (ADS)

    Solha, Romero

    2015-01-01

    The aim of this article is to present unifying proofs for results in geometric quantisation with real polarisations by exploring the existence of symplectic circle actions. It provides an extension of Rawnsley's results on the Kostant complex, and gives a partial result for the focus-focus contribution to geometric quantisation; as well as, an alternative proof for theorems of ?niatycki and Hamilton.

  4. Computational Topology for Geometric Design

    E-print Network

    Peters, Thomas J.

    "mi03 2005/ page i i i i i i i i Computational Topology for Geometric Design and Molecular Design Edward L. F. Moore , Thomas J. Peters Abstract The nascent field of computational topology holds great. Commercial CAGD packages depend upon complementary geometric and topological algorithms. The emergence of geo

  5. Chemical bonding technology

    NASA Technical Reports Server (NTRS)

    Plueddemann, E.

    1986-01-01

    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.

  6. One Bond Strategy

    NSDL National Science Digital Library

    2001-01-01

    Provided by SmartMoney.com (see the May 20, 1999 Scout Report for Business & Economics), this quick and easy yet thorough guide takes readers through the process of developing a bond portfolio. At the site, users will find help on deciding how much to invest in bonds, how to divide their portfolio, and tips on investing for both income and profit. First, however, visitors might want to wet their feet in the bond primer section, which covers all the basics, explains the yield curve, offers a calculator and glossary, and throws in "ten things your broker won't tell you about bonds" for good measure.

  7. Mechanical stabilities of ultrasonic Al ribbon bonding on electroless nickel immersion gold finished Cu substrates

    NASA Astrophysics Data System (ADS)

    Park, Semin; Nagao, Shijo; Sugahara, Tohru; Suganuma, Katsuaki

    2014-01-01

    Metal ribbon wiring attracts much attention for next-generation power-electronics interconnection technology, which requires wider capacity of electrical current in smaller package. The bonding methods of metal ribbons are to be optimized suitable for the larger bonding area than conventional thin string wires. We here use ultrasonic bonding for Al ribbon (1500 200 m2) on to electroless nickel immersion gold (ENIG) finished copper substrate, and optimize the bonding process parameters to minimize the heat damage with sufficient bonding strength. The effect of the process parameters of ultrasonic power, bonding time and normal bonding force on bond formation at ambient temperatures have been investigated with field emission-scanning electron microscopy (FE-SEM) and energy-dispersive spectroscopy (EDS) analysis. Au-Al interfaces were characterized by FE-SEM following pull- and shear-test to effect separation of the bond joints. Bond stabilities were evaluated by lift-off phenomenon and fracture morphology after pull- and shear-test. The highest bonding strength indicated at 20 W (ultrasonic power), 1.8 s (bonding time), and 800 mN (normal bonding force). In this bonding condition, relative motion was occurred from center of gross sliding area over 60%. Based on those result, we confirmed the excellent ribbon bonding conditions and investigated bonding mechanism involved in relative motion.

  8. Substrate, Molecular Structure, and Solvent Effects in 2D Self-Assembly via Hydrogen and Halogen Bonding

    E-print Network

    )-1,3,5-triazine (TIPT) on both highly oriented pyrolytic graphite and the (111) facet of a gold double polarization of the carbon-halogen (C-X) bond, which permits the formation of geometrically stable

  9. November 2007, Orsay Geometrical Frustration 1/21 GeometricalGeometrical FrustrationFrustration

    E-print Network

    Paris-Sud 11, Université de

    3d N=4 U ~ -7 e U ~ -9 e N=5 #12;November 2007, Orsay Geometrical Frustration 9/21 PackingPacking Triangles : non frustrated case Pentagons : frustrated case Geometrical Frustration ! Possible extension tetrahedra - Local icosahedral coordination - Dense sphere packing Coxeter helices Symmetry group of order

  10. Compatible Geometric Matchings

    E-print Network

    Aichholzer, Oswin; Dumitrescu, Adrian; Garca, Alfredo; Huemer, Clemens; Hurtado, Ferran; Kano, Mikio; Mrquez, Alberto; Smorodinsky, Shakhar; Souvaine, Diane; Urrutia, Jorge; Wood, David R

    2007-01-01

    This paper studies non-crossing geometric perfect matchings. Two such perfect matchings are \\emph{compatible} if they have the same vertex set and their union is also non-crossing. Our first result states that for any two perfect matchings $M$ and $M'$ of the same set of $n$ points, for some $k\\in\\Oh{\\log n}$, there is a sequence of perfect matchings $M=M_0,M_1,...,M_k=M'$, such that each $M_i$ is compatible with $M_{i+1}$. This improves the previous best bound of $k\\leq n-2$. We then study the conjecture: \\emph{every perfect matching with an even number of edges has an edge-disjoint compatible perfect matching}. We introduce a sequence of stronger conjectures that imply this conjecture, and prove the strongest of these conjectures in the case of perfect matchings that consist of vertical and horizontal segments. Finally, we prove that every perfect matching with $n$ edges has an edge-disjoint compatible matching with approximately $3n/4$ edges.

  11. [Geometrical property of navigation].

    PubMed

    Watanabe, Toshio

    2003-08-01

    There is a tendency that a blind or a blind-folded subject fails to return to a starting point within the range of errors when he or she walks to a place, next turns to right or left, and then comes back to the starting point. We studied this tendency from a non-Euclidean geometrical point of view. In Experiment 1, total of 28 blind-folded subjects walked to construct a square, a regular triangle and a circle. The result showed that the location of the final reaching point was on the fronto-right side of the starting point in the square and triangle conditions and went over the starting point in the circle condition. In Experiment 2, 15 subjects judged visual properties (angles and distances) of a triangle and constructed the triangle by walking. The walking loci were compared with the visual properties. It was found that the walking loci were curved, differing from the visual properties. These results implied that the walking loci agree with the nature of elliptic geometry. PMID:14584253

  12. Void-free wafer-level adhesive bonding utilizing modified poly (diallyl phthalate)

    NASA Astrophysics Data System (ADS)

    Zhong, Fang; Dong, Tao; Yong, He; Yan, Su; Wang, Kaiying

    2013-12-01

    A new thermosetting polymer, modified poly (diallyl phthalate) (PDAP), is used as intermediate layer to realize a void-free wafer-level transfer bonding, in which the bonding interface contains patterned metal. Through glass-silicon bonding experiments, bonding defects are easily recognized with light microscopy. Three typical defect types are identified as: uneven flow defect, particle defect and bubble defect. The processing parameters, such as bonding pressure, pre-baking temperature, polymer thickness and coating conditions, have been optimized based on analysis of the defect formation. The optimized conditions have yielded a void-free wafer-level adhesive bonding. Then, the die shearing test indicates a good bonding strength. Additionally, the transfer bonding process is applied in SOI-silicon bonding as a practical example of MEMS fabrication.

  13. The role of bond tangency and bond gap in hard sphere crystallization of chains.

    PubMed

    Karayiannis, Nikos Ch; Foteinopoulou, Katerina; Laso, Manuel

    2015-02-18

    We report results from Monte Carlo simulations on dense packings of linear, freely-jointed chains of hard spheres of uniform size. In contrast to our past studies where bonded spheres along the chain backbone were tangent, in the present work a finite tolerance in the bond is allowed. Bond lengths are allowed to fluctuate in the interval [?, ? + dl], where ? is the sphere diameter. We find that bond tolerance affects the phase behaviour of hard-sphere chains, especially in the close vicinity of the melting transition. First, a critical dl(crit) exists marking the threshold for crystallization, whose value decreases with increasing volume fraction. Second, bond gaps enhance the onset of phase transition by accelerating crystal nucleation and growth. Finally, bond tolerance has an effect on crystal morphologies: in the tangent limit the majority of structures correspond to stack-faulted random hexagonal close packing (rhcp). However, as bond tolerance increases a wealth of diverse structures can be observed: from single fcc (or hcp) crystallites to random hcp/fcc stackings with multiple directions. By extending the simulations over trillions of MC steps (10(12)) we are able to observe crystal-crystal transitions and perfection even for entangled polymer chains in accordance to the Ostwald's rule of stages in crystal polymorphism. Through simple geometric arguments we explain how the presence of rigid or flexible constraints affects crystallization in general atomic and particulate systems. Based on the present results, it can be concluded that proper tuning of bond gaps and of the connectivity network can be a controlling factor for the phase behaviour of model, polymer-based colloidal and granular systems. PMID:25594158

  14. Repeating Decimals and Geometric Series

    NSDL National Science Digital Library

    2011-01-01

    This activity begins by reviewing conversions between fractions and decimals with an emphasis on repeating decimals. The formula for the partial sum of a geometric series is bypassed and students are directed to use find partial sums by using the multiply, subtract, and solve technique which mimics the derivation of the formula for the partial sum of a geometric series. This sets the stage for students to quickly find the fraction representation of a repeating decimal number. This activity would be well-suited as a prelude to introducing infinite and partial sums of geometric sequences.

  15. Optical traps with geometric aberrations

    SciTech Connect

    Roichman, Yael; Waldron, Alex; Gardel, Emily; Grier, David G

    2006-05-20

    We assess the influence of geometric aberrations on the in-plane performance of optical traps by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers. The lateral stiffness of the traps turns out to be insensitive to moderate amounts of coma, astigmatism, and spherical aberration. Moreover holographic aberration correction enables us to compensate inherent shortcomings in the optical train, thereby adaptively improving its performance. We also demonstrate the effects of geometric aberrations on the intensity profiles of optical vortices, whose readily measured deformations suggest a method for rapidly estimating and correcting geometric aberrations in holographic trapping systems.

  16. Optical traps with geometric aberrations.

    PubMed

    Roichman, Yael; Waldron, Alex; Gardel, Emily; Grier, David G

    2006-05-20

    We assess the influence of geometric aberrations on the in-plane performance of optical traps by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers. The lateral stiffness of the traps turns out to be insensitive to moderate amounts of coma, astigmatism, and spherical aberration. Moreover holographic aberration correction enables us to compensate inherent shortcomings in the optical train, thereby adaptively improving its performance. We also demonstrate the effects of geometric aberrations on the intensity profiles of optical vortices, whose readily measured deformations suggest a method for rapidly estimating and correcting geometric aberrations in holographic trapping systems. PMID:16708086

  17. Geometric Effects on Electron Cloud

    SciTech Connect

    Wang, L

    2007-07-06

    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.

  18. Antenna with Dielectric Having Geometric Patterns

    NASA Technical Reports Server (NTRS)

    Dudley, Kenneth L. (Inventor); Elliott, Holly A. (Inventor); Cravey, Robin L. (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Watson, Kent A. (Inventor); Smith, Jr., Joseph G. (Inventor)

    2013-01-01

    An antenna includes a ground plane, a dielectric disposed on the ground plane, and an electrically-conductive radiator disposed on the dielectric. The dielectric includes at least one layer of a first dielectric material and a second dielectric material that collectively define a dielectric geometric pattern, which may comprise a fractal geometry. The radiator defines a radiator geometric pattern, and the dielectric geometric pattern is geometrically identical, or substantially geometrically identical, to the radiator geometric pattern.

  19. 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.

  20. The dissociative bond.

    PubMed

    Gordon, Nirit

    2013-01-01

    Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other. PMID:23282044

  1. Planning Successful Bond Campaigns.

    ERIC Educational Resources Information Center

    North Carolina State Dept. of Public Instruction, Raleigh. Div. of School Support.

    This document contains specific recommendations for conducting bond campaigns. It outlines the three major considerations of any bond campaign: (1) committee organization and appointment; (2) time lines; and (3) getting out the vote. The publication focuses on the need for total community involvement and outlines some of the components for

  2. Chemical Bonds I

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)

  3. Interfacial bonding stability

    NASA Technical Reports Server (NTRS)

    Boerio, J.

    1984-01-01

    Interfacial bonding stability by in situ ellipsometry was investigated. It is found that: (1) gamma MPS is an effective primer for bonding ethylene vinyl acetate (EVA) to aluminum; (2) ellipsometry is an effective in situ technique for monitoring the stability of polymer/metal interfaces; (3) the aluminized back surface of silicon wafers contain significant amounts of silicon and may have glass like properties.

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

    PubMed

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

    2014-12-10

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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⋯Hsbnd O in 6 and 6a is demonstrated to be significantly strengthened, while Nsbnd H⋯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.

  6. 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)

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

    2013-01-01

    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.

  7. Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.

    PubMed

    Zins, Emilie-Laure; Silvi, Bernard; Alikhani, M Esmal

    2015-04-14

    Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the ? C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a ? X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A ? X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the ?X-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes. PMID:25760795

  8. Wood Bond Testing

    NASA Technical Reports Server (NTRS)

    1989-01-01

    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.

  9. Shape Bonding method

    NASA Technical Reports Server (NTRS)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  10. Ultrasonically bonded value assembly

    NASA Technical Reports Server (NTRS)

    Salvinski, R. J. (inventor)

    1975-01-01

    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.

  11. The variational subspace valence bond method.

    PubMed

    Fletcher, Graham D

    2015-04-01

    The variational subspace valence bond (VSVB) method based on overlapping orbitals is introduced. VSVB provides variational support against collapse for the optimization of overlapping linear combinations of atomic orbitals (OLCAOs) using modified orbital expansions, without recourse to orthogonalization. OLCAO have the advantage of being naturally localized, chemically intuitive (to individually model bonds and lone pairs, for example), and transferrable between different molecular systems. Such features are exploited to avoid key computational bottlenecks. Since the OLCAO can be doubly occupied, VSVB can access very large problems, and calculations on systems with several hundred atoms are presented. PMID:25854233

  12. Optical bonding reinforced by femtosecond laser welding

    NASA Astrophysics Data System (ADS)

    Lacroix, Fabrice; Hlie, David; Valle, Ral

    2011-09-01

    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.

  13. Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  14. Property Testing with Geometric Queries

    Microsoft Academic Search

    Artur Czumaj; Christian Sohler

    2001-01-01

    This paper investigates geometric problems in the context of property testing algorithms. Property testing is an emerging area in computer science in which one is aiming at verifying whether a given object has a predetermined property or is \\

  15. The promise of geometric morphometrics

    Microsoft Academic Search

    Joan T. Richtsmeier; Valerie Burke Deleon; Subhash R. Lele

    2002-01-01

    Nontraditional or geometric morphomet- ric methods have found wide application in the biological sciences, especially in anthropology, a field with a strong history of measurement of biological form. Controversy has arisen over which method is the \\

  16. Geometrical optics in general relativity

    E-print Network

    A. Loinger

    2006-09-19

    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.

  17. Algorithms of NCG geometrical module

    SciTech Connect

    Gurevich, M. I.; Pryanichnikov, A. V., E-mail: prianik@adis.vver.kiae.ru [National Research Centre Kurchatov Institute (Russian Federation)

    2012-12-15

    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.

  18. Algorithms of NCG geometrical module

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  19. Crystal structure and bonding of ordered C60

    NASA Astrophysics Data System (ADS)

    David, William I. F.; Ibberson, Richard M.; Matthewman, Judy C.; Prassides, Kosmas; Dennis, T. J. S.; Hare, Jonathan P.; Kroto, Harold W.; Taylor, Roger; Walton, David R. M.

    1991-09-01

    The results are presented of a neutron powder diffraction study of the low-temperature ordered structure which reveals the packing configuration of the C60 molecules. The C60 units are rotated in an anticlockwise manner around the 111-line direction by about 98 deg from the ideal Fm3(bar) configuration. This apparently arbitrary rotation in fact results from an optimized ordering scheme in which electron-rich short interpentagon bonds face the electron-poor pentagon centers of adjacent C60 units. The high symmetry of the C60 molecule allows these interactions to be optimized identically for all 12 nearest neighbors, a possibility that is by no means intuitively obvious. The bonds common to a given pentagon are somewhat longer. The high degree of bonding optimization and the absence of bonding frustration accounts for the high ordering temperature of 249 K.

  20. Geometric Phases, Noise and Non-adiabatic Effects in Multi-level Superconducting Systems

    NASA Astrophysics Data System (ADS)

    Berger, S.; Pechal, M.; Abdumalikov, A. A.; Steffen, L.; Fedorov, A.; Wallraff, A.; Filipp, S.

    2012-02-01

    Geometric phases depend neither on time nor on energy, but only on the trajectory of the quantum system in state space. In previous studies [1], we have observed them in a Cooper pair box qubit, a system with large anharmonicity. We now make use of a superconducting transmon-type qubit with low anharmonicity to study geometric phases in a multi-level system. We measure the contribution of the second excited state to the geometric phase and find very good agreement with theory treating higher levels perturbatively. Furthermore, we quantify non-adiabatic corrections by decreasing the manipulation time in order to optimize our geometric gate. Geometric phases have also been shown to be resilient against adiabatic field fluctuations [2]. Here, we analyze the effect of artificially added noise on the geometric phase for different system trajectories. [1] P. J. Leek et al., Science 318, 1889 (2007) [2] S. Filipp et al., Phys. Rev. Lett. 102, 030404 (2009)

  1. High speed touch screen panels (TSPs) assembly using anisotropic conductive adhesives (ACAs) vertical ultrasonic bonding method

    Microsoft Academic Search

    Seung-Ho Kim; Kiwon Lee; Kyung-Wook Paik

    2010-01-01

    In this study, the effects of vertical ultrasonic (VUS) bonding parameters such as vibration amplitudes and bonding pressures were investigated and optimized in terms of thermal deformation of TSP polymer substrates, electrical continuity, and pull adhesion strength of anisotropic conductive adhesive (ACA) joints. And the reliability of VUS bonded TSP ACA joints were evaluated at various test conditions. As the

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

    E-print Network

    Adams, James B

    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

  3. Novel approach to the concept of bond-valence vectors.

    PubMed

    Zachara, Janusz

    2007-11-12

    A new approach to the old idea of deriving a bond-valence vector from the well-known bond-valence concept has been proposed. The foundation of the proposal is the previous electrostatic model in which bond valences are interpreted as electric fluxes. The outcome of this approach is actual vectorial quantities whose magnitudes are strictly but nonlinearly related to the scalar bond valences and are directed along the bond lines. It has been proved that the sum of all these bond-valence vectors drawn from a coordination center to its ligating atoms will be close to zero for the complete coordination sphere. Therefore, unlike the scalar bond valences, the obtained vectors provide information about the spatial arrangement of ligands. The geometrical consequences of the proposed bond-valence vector (BVV) model are analyzed for the geometries of the carbonates, phosphates, and five-coordinated organoaluminum compounds with CO3, PO4, and AlCO4 skeletons, respectively, retrieved from the Cambridge Structural Database. For acyclic carbonates this BVV model allows one to predict the O-C-O angles with a mean absolute error of 1.0 degrees using the empirical C-O distances only. Furthermore, this BVV model is able to quantitatively describe the strains in cyclic carbonates. The preliminary studies for NO2E, PO3E, and SO3E systems with a strongly stereoactive lone electron pair (E) show that the model may serve as a quantitative description of the lone electron pair effect on the coordination sphere. A great advantage of the presented BVV approach is that the derived relation between a bond-valence vector, bond valence, and bond length is given by an uncomplicated equation allowing quick and simple computations, thus providing a new analytical tool for describing the geometry of a coordination sphere that may be applied for structure validation. PMID:17948986

  4. Field-assisted bonding of single crystal quartz

    NASA Astrophysics Data System (ADS)

    Watkins, Randall D.; Tuthill, Clinton D.; Curlee, Richard M.; Koehler, Dale R.; Joerg, Charles F.

    A technique to produce strong, hermetic bonds between plates of single crystal quartz using a modified field-assisted bonding process is presented. Field-assisted bonding is a technique traditionally used to join glass to metals at temperatures well below normal glass softening temperatures. To promote reactivity between quartz within an electrical field at temperatures well below quartz transformation temperatures, thin films of silicon metal and glass were vapor deposited onto adjacent quartz plates. Thermal stresses caused by expansion mismatch between the quartz and the films were of concern. These stresses were reduced by determining the minimum film thicknesses capable of yielding sufficient reactivity for bonding. Processing studies were conducted to optimize bond integrity, and bonds were characterized by hermeticity, thermal shock, and mechanical shock. Packages produced under the most ideal conditions were able to survive greater than 1000 psi shock loads.

  5. Diffusion Bonding of Silicon Carbide Ceramics using Titanium Interlayers

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  6. Critical appraisal. Resin bonding to zirconia.

    PubMed

    Piascik, Jeffrey R

    2012-12-01

    Research has focused on adhesion and bond strengths to zirconia, but the question is "what is the gold standard--what is the bond strength we are trying to achieve?" Clinical data are needed to further understand adhesion issues--and studies are just now being published. Preliminary clinical research indicates that some failures are due to loss of adhesion but more are due to chipping of veneer porcelain. Commercial adhesion products are continuously being developed and optimized for clinical use. It is anticipated that the use of zirconia in dentistry will increase in the future, so reliable clinical adhesion solutions are needed. Based on the literature and the commercial products available to clinicians today, using novel primers (e.g., Z-PrimePlus) coupled with low pressure air-abrasion would be more than sufficient for adequate bonding of resin cement. PMID:23342396

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  8. Geometrical interpretation and curvature distribution in nanocarbons

    NASA Astrophysics Data System (ADS)

    Gupta, Sanju; Saxena, Avadh

    2011-04-01

    Despite extensive research on microscopic structure and physical property characterization of advanced nanocarbon systems, they have not been viewed as topologically distinct nanoscale materials with various geometries (curvature). This work is motivated by our recent work [S. Gupta and A. Saxena, J. Raman Spectrosc. 40, 1127 (2009)] where we introduced the notion of "global" topology for novel nanocarbons and provided systematic trends by monitoring the phonon spectra via resonance Raman spectroscopy, which led to the paradigm of curvature/topology ? property ? functionality relationship in these materials. Here we determined the distribution of the mean (H) and Gaussian (K) curvatures as pertinent observables for geometric characterization taking into account the observed geometrical parameters, that is, radius, polar, azimuthal, or conical angle associated with tubular (single, double-, and multi-walled nanotubes; K = 0), spherical (hypo- and hyperfullerenes; K > 0) and complex (helical nanoribbons and nanotori/nanorings; K < 0) nanocarbon geometries to quantify the interplay of intrinsic surface curvature and topology, wherein global topology of the overall sp2-bonded carbon (sp2C) constrains local topology of the constituent carbon rings. We also studied various other structures such as catenoid and saddle-shaped surfaces as interesting nanocarbons. We compared these results with highly oriented pyrolytic graphite and monolayer graphene as layered and planar systems, respectively. Moreover, nanocarbons discussed herein are their derivatives. Curvature leads to nonlinearity that manifests itself in some form of symmetry breaking which can be extrapolated to topological variation due to nanoscale defects. Thus it may either close/open the bandgap leading to the introduction of new Raman spectroscopy signatures and optical absorption peaks, changes in mechanical properties, electrical behavior, and electronic density of states and possibly inducing magnetism. Finally, we elucidate the role of curved geometry in Casimir forces arising in carbon nanostructures.

  9. GEOMETRIC AND MATAPLECTIC QUANTIZATION ALEXANDER CARDONA

    E-print Network

    Cardona, Alexander

    and topological key ingredients of two approaches to this type of quantization, the original Kostant of this geometric quantization procedure with respect to geometrical and topological aspects of the symplectic DiracGEOMETRIC AND MATAPLECTIC QUANTIZATION ALEXANDER CARDONA Abstract. Geometric quantization gives

  10. Bonding with Your Baby

    MedlinePLUS

    ... baby feel the different textures of dad's face Building a Support System Of course, it's easier to ... can take nearly all of your attention and energy especially for a breastfeeding mom. Bonding will be ...

  11. Gold Thermocompression Wafer Bonding

    E-print Network

    Spearing, S. Mark

    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, ...

  12. Characterization of anodic bonding

    E-print Network

    Tudryn, Carissa Debra, 1978-

    2004-01-01

    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 ...

  13. Hydrogen bonds animation

    NSDL National Science Digital Library

    Northland Community and Technical College Biology Department

    2007-12-12

    This color animation of water molecules interacting and forming hydrogen bonds is a hybrid between a PowerPoint slide show an an animation. Students can replay portions or click next if they do not need to replay a segment.

  14. 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

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

    2006-01-01

    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

  15. Bonded Interactions and the Crystal Chemistry of Minerals: A Review

    SciTech Connect

    Gibbs, Gerald V.; Downs, R. T.; Cox, David F.; Ross, Nancy L.; Prewitt, C. T.; Rosso, Kevin M.; Lippmann, Thomas; Kirfel, Armin

    2008-02-26

    Connections established during the 20th century between bond length, radii, bond strength, bond valence and crystal and molecular chemistry are briefly reviewed followed with a survey of the physical properties of the electron density distributions for a variety of minerals and representative molecules, recently generated with first-principles local density based quantum mechanical methods. The structures for several minerals, geometry-optimized at ambient conditions and at a variety of pressures, match those determined experimentally within several percent. The structures and the physical properties of model experimental electron density distributions determined with high resolution and high energy synchrotron single crystal X-ray diffraction data also closely match those calculated with first principles methods. As the electron density is progressively accumulated and locally concentrated between pairs of bonded atoms, the nuclei are progressively shielded and the bond lengths and the bonded radii of the atoms decrease. Concomitant with the decrease in bond length, the local kinetic density energy increases while the potential energy and the electronic energy densities both decrease for intermediate and shared interactions with the potential energy dominating the local energy for the shorter bonded interactions. The shorter the bonds, the more negative the local electronic energy density, the greater the stabilization and the greater the shared character of the bonded interactions.

  16. All about Chemical Bonding

    NSDL National Science Digital Library

    Lower, Stephen

    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.

  17. Water's Hydrogen Bond Strength

    E-print Network

    Martin Chaplin

    2007-06-10

    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.

  18. Coherent Control of Bond Making

    E-print Network

    Liat Levin; Wojciech Skomorowski; Leonid Rybak; Ronnie Kosloff; Christiane P. Koch; Zohar Amitay

    2014-11-06

    We demonstrate for the first time coherent control of bond making, a milestone on the way to coherent control of photo-induced bimolecular chemical reactions. In strong-field multiphoton femtosecond photoassociation experiments, we find the yield of detected magnesium dimer molecules to be enhanced for positively chirped pulses and suppressed for negatively chirped pulses. Our ab initio model shows that control is achieved by purification via Franck-Condon filtering combined with chirp-dependent Raman transitions. Experimental closed-loop phase optimization using a learning algorithm yields an improved pulse that utilizes vibrational coherent dynamics in addition to chirp-dependent Raman transitions. Our results show that coherent control of binary photo-reactions is feasible even under thermal conditions.

  19. Optimal bird migration revisited

    Microsoft Academic Search

    Thomas Alerstam

    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

  20. Geometric frustration in small colloidal clusters

    E-print Network

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

    2010-01-01

    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 mfrustration 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.

  1. Relational Bonds and Loyalty: The Bonds that Tie

    Microsoft Academic Search

    Ahmad Shammout; Michael Polonsky; Michael Edwardson

    This paper explores the effect of financial, social and structural bonds on the loyalty of Arabic five star hotel guests. Three different measures of loyalty are used; attitudinal, behavioural and combined to identify how the three relational bonds affect loyalty. The results show that social and structural bonds increase all types of loyalty whereas financial bonds only increase attitudinal and

  2. Influence of bonding atmosphere on low-temperature wafer bonding

    Microsoft Academic Search

    Ying-Hui Wang; Tadatomo Suga

    2010-01-01

    The influence of bonding atmosphere was investigated for the wafer bonding at 25~200C using a surface activated bonding method. The results of the analysis of activated Si surfaces under different vacuum background and the residual gases in vacuum before and after Ar fast atom beam irradiation is reported. Based on the analysis, bonding of Si wafers in nitrogen atmosphere is

  3. Geometric and Electronic Properties of Edge-decorated Graphene Nanoribbons

    PubMed Central

    Chang, Shen-Lin; Lin, Shih-Yang; Lin, Shih-Kang; Lee, Chi-Hsuan; Lin, Ming-Fa

    2014-01-01

    Edge-decorated graphene nanoribbons are investigated with the density functional theory; they reveal three stable geometric structures. The first type is a tubular structure formed by the covalent bonds of decorating boron or nitrogen atoms. The second one consists of curved nanoribbons created by the dipole-dipole interactions between two edges when decorated with Be, Mg, or Al atoms. The final structure is a flat nanoribbon produced due to the repulsive force between two edges; most decorated structures belong to this type. Various decorating atoms, different curvature angles, and the zigzag edge structure are reflected in the electronic properties, magnetic properties, and bonding configurations. Most of the resulting structures are conductors with relatively high free carrier densities, whereas a few are semiconductors due to the zigzag-edge-induced anti-ferromagnetism. PMID:25123103

  4. Optimization of reactive mufflers

    NASA Astrophysics Data System (ADS)

    Komkin, A. I.

    2010-05-01

    A new approach to optimization of reactive mufflers, which is based on use of muffler prototype with nondimensional geometrical parameters and integral criterion of acoustic performance of mufflers, is proposed. Implementation of the approach using the example of chamber mufflers is considered.

  5. Geometrical modelling of textile reinforcements

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    The mechanical properties of textile composites are dictated by the arrangement of yarns contained with 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 form highly flexible yarn systems which experience a certain degree of compressability. 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 prediction models are demonstrated. Although more costly than its predecessors, the present analysis is based on the detailed architecture developed by one of the authors and his colleagues and accounts for many of the geometric complexities that other analyses ignore.

  6. Geometric scalar theory of gravity

    NASA Astrophysics Data System (ADS)

    Novello, M.; Bittencourt, E.; Moschella, U.; Goulart, E.; Salim, J. M.; Toniato, J. D.

    2013-06-01

    We present a geometric scalar theory of gravity. Our proposal will be described using the ``background field method" introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ``geometric" pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.

  7. Geometric scalar theory of gravity

    SciTech Connect

    Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D. [Instituto de Cosmologia Relatividade Astrofisica ICRA - CBPF Rua Dr. Xavier Sigaud 150 - 22290-180 Rio de Janeiro - Brazil (Brazil); Moschella, U., E-mail: novello@cbpf.br, E-mail: eduhsb@cbpf.br, E-mail: Ugo.Moschella@uninsubria.it, E-mail: egoulart@cbpf.br, E-mail: jsalim@cbpf.br, E-mail: toniato@cbpf.br [Universit degli Studi dell'Insubria - Dipartamento di Fisica e Matematica Via Valleggio 11 - 22100 Como - Italy (Italy)

    2013-06-01

    We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.

  8. Mirror profile optimization for nano-focusing KB mirror

    SciTech Connect

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

    2010-06-23

    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.

  9. Geometric Minimum Diameter Minimum Cost Spanning Tree Problem

    Microsoft Academic Search

    Dae Young Seo; D. T. Lee; Tien-ching Lin

    2009-01-01

    In this paper we consider bi-criteria geometric optimization problems, in particular, the minimum diameter minimum cost spanning\\u000a tree problem and the minimum radius minimum cost spanning tree problem for a set of points in the plane. The former problem\\u000a is to construct a minimum diameter spanning tree among all possible minimum cost spanning trees, while the latter is to construct

  10. Surface activation enhanced low temperature silicon wafer bonding

    NASA Astrophysics Data System (ADS)

    Gan, Qing

    Direct wafer bonding technology has received great attention since 1985. It enables to realize the novel combinations of different materials for expanded functionality and provides a versatile device technology for transferring device layers to another wafer for further processing or device integration onto one wafer. Silicon direct wafer bonding has found a wide range of applications including Silicon-on-Insulator (SOI) wafers, micromechanical devices, and sensors and actuators. One of the challenges facing this technology is to achieve strong bonding at low temperatures that can survive post-wafer bonding processing. This dissertation presents the results of developing new wafer bonding processes for achieving high bonding energy at low temperatures. For thermal oxide covered silicon wafer bonding, dilute HF solution has been used to etch the wafers prior to room temperature bonding. The bonding energy has been significantly enhanced which reached silicon fracture energy after annealed at 100C for 45 hours. For native oxide covered silicon wafers, the pre-treatment in dilute HNO3 and dilute HF mixtures has been found to be able to enhance the bonding energy at low temperatures. This is attributed to the incorporation of fluorine in native oxide during the pre-treatment. Various approaches have also been explored for hydrophobic silicon wafer bonding. Both boron doped surface layers and the amorphous surface layers have demonstrated an ability to significantly enhance the bonding energy at low temperatures, with silicon fracture energy achieved at 300--400C for hydrophobically bonded pairs. The thermal management of heterojunction bipolar transistor (HBT) circuits fabricated by Symmetric Intrinsic HBT (SIHBT) processing was also studied in this research project using simulation method. Design criteria of selecting the surrogate substrates, interconnection dimension, and dielectric materials for the optimization of thermal management have been obtained.

  11. Geometrical Optics of Dense Aerosols

    SciTech Connect

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

    2013-04-24

    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. __________________________________________________

  12. Geometric integration for particle accelerators

    NASA Astrophysics Data System (ADS)

    Forest, tienne

    2006-05-01

    This paper is a very personal view of the field of geometric integration in accelerator physicsa field where often work of the highest quality is buried in lost technical notes or even not published; one has only to think of Simon van der Meer Nobel prize work on stochastic coolingunpublished in any refereed journal. So I reconstructed the relevant history of geometrical integration in accelerator physics as much as I could by talking to collaborators and using my own understanding of the field. The reader should not be too surprised if this account is somewhere between history, science and perhaps even fiction.

  13. Geometrical spin symmetry and spin

    SciTech Connect

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

    2011-07-15

    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.

  14. Geometric design of compound reflectors

    NASA Astrophysics Data System (ADS)

    Downs, J. W.

    1985-05-01

    Geometric methods are reviewed for the generation of conic section design shapes for antennas. Examples are provided to demonstrate how elliptical, hyperbolic and parabolic curves suitable for figures of rotation can be generated without resorting to numerical values. The tools employed are a compass and drafting triangle. Emphasis is on the proportion inherent in each figure and the wide range of application of the Pythagorean Theorem. It is noted that ellipsoid reflectors concentrate energy on the location of the second focus. Hyperboloids are the bases for Cassegrain antennas. Paraboloids shapes are special cases of hyperboloidal and ellipsoidal shapes. Sample design geometrics are developed for Cassegrain and Gregorian reflectors.

  15. Crystal structure prediction via particle-swarm optimization

    NASA Astrophysics Data System (ADS)

    Wang, Yanchao; Lv, Jian; Zhu, Li; Ma, Yanming

    2010-09-01

    We have developed a method for crystal structure prediction from scratch through particle-swarm optimization (PSO) algorithm within the evolutionary scheme. PSO technique is different with the genetic algorithm and has apparently avoided the use of evolution operators (e.g., crossover and mutation). The approach is based on an efficient global minimization of free-energy surfaces merging total-energy calculations via PSO technique and requires only chemical compositions for a given compound to predict stable or metastable structures at given external conditions (e.g., pressure). A particularly devised geometrical structure parameter which allows the elimination of similar structures during structure evolution was implemented to enhance the structure search efficiency. The application of designed variable unit-cell size technique has greatly reduced the computational cost. Moreover, the symmetry constraint imposed in the structure generation enables the realization of diverse structures, leads to significantly reduced search space and optimization variables, and thus fastens the global structure convergence. The PSO algorithm has been successfully applied to the prediction of many known systems (e.g., elemental, binary, and ternary compounds) with various chemical-bonding environments (e.g., metallic, ionic, and covalent bonding). The high success rate demonstrates the reliability of this methodology and illustrates the promise of PSO as a major technique on crystal structure determination.

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

    NASA Astrophysics Data System (ADS)

    Chan, Matthew Wei-Jen

    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.

  17. SHM system using rectangular versus circular piezoceramic for the inspection within the bond of a composite bonded joint

    NASA Astrophysics Data System (ADS)

    Quaegebeur, Nicolas; Micheau, Philippe; Masson, Patrice; Castaings, Michel

    2012-04-01

    A bonded joint between an aluminum plate and CFRP plate (7 plies) is considered using a titanium spar. The bonding is ensured by double sided adhesive that is prone to degradation with aging structures. The problem is to detect the disbond occurring at the CFRP plate/titanium spar interface using guided waves generated by piezoceramic transducers (PZT) bonded on the CFRP plate. The objective of the present work is to optimize the SHM configuration (PZT location, Lamb wave mode, size and shape of the PZT) for pitch and catch measurements within the bond. 1D, 2D and 3D numerical simulations of the instrumented structure were performed to optimize the SHM configuration. It appears that the rectangular shape can ensure a plane wave front within the bond, since the circular shape generates complex wave fronts. For experimental investigation, coupon structure was manufactured with synthetic damages inserted using two hemispherical Teflon tapes between adhesive and titanium spar. The structure was instrumented for inspection within the bond by using rectangular PZT. Experimental validation of propagation characteristics and damage sensitivity are performed using LDV measurement within the bond line. Damage detectability using rectangular piezoceramics in pitch-catch configuration within the bond is validated.

  18. Incarcerated adolescents' distress and suicidality in relation to parental bonding styles.

    PubMed

    McGarvey, E L; Kryzhanovskaya, L A; Koopman, C; Waite, D; Canterbury, R J

    1999-01-01

    This study examines the relationships between the bonding style of an incarcerated adolescent with parents and his/her current feelings of self-esteem, hopelessness, and suicidal thoughts and attempts. It also investigates differences between bonding to mother and bonding to father. Some 296 incarcerated adolescents were interviewed using the Parental Bonding Instrument. Significant relationships were found between youths' self-esteem, hoplessness, and suicidal behavior and their bonding style. Youths whose parent(s) had a parental bonding style of affectionless control reported the greatest distress, and youths whose parent(s) had an optimal bonding style reported the least distress. Differences were found between bonding styles with the mother and with the father. Attachment theory may be useful in targeting incarcerated youths who have affectionless control bonding with parent(s) for special interventions since these youths are most at risk for psychosocial problems. PMID:10680283

  19. Geometrical and FEA study on Millipede Forming

    NASA Astrophysics Data System (ADS)

    Kong, Lingran; Tang, Di; Ding, Shichao; Zhang, Yuankun

    2013-12-01

    Millipede Forming is an innovative sheet metal forming approach that has been proposed and developed in Australia. U-channels, Z-channels or tubular products can be made by Millipede Forming. While a strip moves through an optimal transitional surface between the entry to exit of a forming stand, the redundant longitudinal membrane strain can be significantly reduced compared to the conventional roll forming, which is the essential principle to obtaining high quality products. The incremental forming process studied has demonstrated major advantages on space efficiency, power consumption and materials sensitivities. The purpose of this study is to investigate the effects of main geometrical parameters and their optimization, in order to minimize the redundant longitudinal strains into elastic to avoid the redundant plastic deformations at flange during forming. In this study, a mild-steel U-channel sample with 10 mm flange width, fabricated by Millipede Forming in a forming length of 200 mm has been studied. Theoretical longitudinal membrane strains at profile's edge of different transitional surfaces and downhill pass are also analyzed. The results showed that obtaining an optimal transitional surface is essential and necessary in controlling the peak longitudinal strain to an acceptable amount and that by increasing downhill pass, longitudinal strain can be significantly reduced. The optimized transitional surface and downhill pass flow were simulated by Abaqus, and the peak longitudinal strain was finally less than 0.2% through a very short forming length of 200 mm. The results prove that Millipede Forming can achieve a better product quality in a much shorter forming distance than conventional roll forming.

  20. Surface analysis in composite bonding

    NASA Technical Reports Server (NTRS)

    Messick, D. L.; Wightman, J. P.

    1982-01-01

    The role of the interfacial region in determining the bond strength and durability of composite bonds is discussed. The characterization of a variety of carbon fibers including Celion 6000 using both scanning electron microscopy and X-ray photoelectron spectroscopy is discussed. The emphasis is on composite bonding, that is, the adhesive bonding between composites in contrast to fiber-matrix interaction. The primary objective of the research is the characterization of composite surfaces before adhesive bonding and after fracture of bonded specimens. Work done on the analysis of composite samples pretreated in a number of ways prior to bonding is detailed.

  1. Strength of Chemical Bonds

    NASA Technical Reports Server (NTRS)

    Christian, Jerry D.

    1973-01-01

    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.

  2. Asymmetric bifurcated halogen bonds.

    PubMed

    Novk, Martin; Foroutan-Nejad, Cina; Marek, Radek

    2015-03-01

    Halogen bonding (XB) is being extensively explored for its potential use in advanced materials and drug design. Despite significant progress in describing this interaction by theoretical and experimental methods, the chemical nature remains somewhat elusive, and it seems to vary with the selected system. In this work we present a detailed DFT analysis of three-center asymmetric halogen bond (XB) formed between dihalogen molecules and variously 4-substituted 1,2-dimethoxybenzene. The energy decomposition, orbital, and electron density analyses suggest that the contribution of electrostatic stabilization is comparable with that of non-electrostatic factors. Both terms increase parallel with increasing negative charge of the electron donor molecule in our model systems. Depending on the orientation of the dihalogen molecules, this bifurcated interaction may be classified as '?-hole - lone pair' or '?-hole - ?' halogen bonds. Arrangement of the XB investigated here deviates significantly from a recent IUPAC definition of XB and, in analogy to the hydrogen bonding, the term bifurcated halogen bond (BXB) seems to be appropriate for this type of interaction. PMID:25656525

  3. Physical understanding through variational reasoning: electron sharing and covalent bonding.

    PubMed

    Ruedenberg, Klaus; Schmidt, Michael W

    2009-03-12

    Energy changes of stationary states resulting from geometric parameter changes in the Hamiltonian can be understood by variational reasoning in terms of the physical attributes of the kinetic and the potential energy functionals. In atoms as well as molecules, the energy minimization determines the ground state as the optimal compromise between the potential pull of the nuclear attractions and the localization-resisting kinetic pressure of the electron cloud. This variational competition is analyzed for the exact ab initio ground-state wave function of the hydrogen molecule ion to elucidate the formation of the bond. Its electronic wave function is shown to differ from the ground-state wave function of the hydrogen atom by polarization, sharing, and contraction, and the corresponding contributions to the binding energy are examined in detail. All told, the critical feature is that a molecular orbital, contracting (in the variational context) toward two nuclei simultaneously, can lower its potential energy while maintaining a certain degree of delocalization. As a consequence, its kinetic energy functional has a lower value than that of an orbital contracting toward a single nucleus equally closely. By contrast, the potential energy functional is lowered equally effectively whether the orbital contracts toward one nucleus or simultaneously toward two nuclei. Because of this weaker kinetic energy pressure, the electrostatic potential pull of the nuclei in the molecule is able to attach the orbital more tightly to each of the nuclei than the pull of the single nucleus in the atom is able to do. The role of the virial theorem is clarified. Generalizations to other molecules are discussed. PMID:19228050

  4. Mathematical Optimization

    NSDL National Science Digital Library

    Leske, Cavin.

    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.

  5. Geometric Mechanics 2009 H. Waalkens

    E-print Network

    Hanssmann, Heinz

    Geometric Mechanics 2009 H. Waalkens Exercise Sheet 2 Hamilton-Jacobi Equation. Note: this problem of the Hamilton-Jacobi equation for this problem. 2. Consider the motion of a particle on a 2-dimensional sphere x Hamilton-Jacobi equation is completely separable. 3. Consider the motion of a particle in the three

  6. Geometric Mechanics 2009 H. Waalkens

    E-print Network

    Hanssmann, Heinz

    Geometric Mechanics 2009 H. Waalkens Exercise Sheet 2 Hamilton­Jacobi Equation. Note: this problem solution of the Hamilton­Jacobi equation for this problem. 2. Consider the motion of a particle on a 2 that the corresponding Hamilton­Jacobi equation is completely separable. 3. Consider the motion of a particle

  7. Dexterous Manipulation: A Geometric Approach

    E-print Network

    Mishra, Bud

    Dexterous Manipulation: A Geometric Approach (A Survey Paper) Bhubaneswar Mishra Courant Institute the theory of dexterous manipulation. In particular, we discuss the models of robot hands and analysis connection between the problems of dexterous manipulation and some classical results in combinatorial

  8. Polymer representations and geometric quantization

    E-print Network

    Miguel Campiglia

    2011-11-02

    Polymer representations of the Weyl algebra of linear systems provide the simplest analogues of the representation used in loop quantum gravity. The construction of these representations is algebraic, based on the Gelfand-Naimark-Segal construction. Is it possible to understand these representations from a Geometric Quantization point of view? We address this question for the case of a two dimensional phase space.

  9. Celestial mechanics with geometric algebra

    NASA Technical Reports Server (NTRS)

    Hestenes, D.

    1983-01-01

    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.

  10. Algorithmic + Geometric characterization of CAR

    E-print Network

    Gill, Richard D.

    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

  11. Hyperconjugation-mediated solvent effects in phosphoanhydride bonds

    PubMed Central

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

    2012-01-01

    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

  12. Understanding mechanisms for C-H bond activation

    E-print Network

    Vastine, Benjamin Alan

    2009-05-15

    of 1 for the density functionals listed ........................................................................................... 106 4.7 Optimized geometric parameters for 1 optimized with four basis sets assigned to scandium... in a density functional theory 33 (DFT) study of the addition of H 2 and CH 4 to [Cp 2 ScX] (X = H, CH 3 ). The TSs for HT in these models are characterized by similar geometries and the distances between the scandium center and the transferring...

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

    NASA Astrophysics Data System (ADS)

    Xie, Yanmin

    2013-12-01

    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.

  14. Insurance and bonding

    SciTech Connect

    Katzman, M.T.

    1989-01-01

    Societal risk management in industrial democracies relies upon mechanisms of prior restraint rather than on responsibility for the consequence of accidents. The evolution of risk management from one based upon private, voluntary standard of risk management from one based upon private, voluntary standard setting to one based upon restraint is reviewed. While insurance and bonding historically have played a major role in private management of catastrophic risks, their role has been underutilized in the current, restraint-based mode. The conditions under the insurance and bonding that can serve as a tool for risk regulation are illustrated in the arena of toxic pollution risks. 45 refs., 1 fig.

  15. Quantal trajectories and geometric phase

    NASA Astrophysics Data System (ADS)

    Carlsen, Olav Henrik

    This thesis concerns the following topics: geometric phase in the context of Galilean invariance and quantum measurements, Rydberg states of hydrogen atoms, vibronic coupling in the E/otimes/epsilon Jahn-Teller system and realism in quantum computations. In the analyses the de Broglie-Bohm pilot-wave formulation of quantum mechanics is mainly used. It is shown that geometric phase is not Galilean invariant. Experimental implications are discussed and it is found that the experiments performed to date are frame independent. An experiment which is in principle able to detect the noninvariance is sketched. By adopting the measurement theory of the pilot-wave formulation it is shown how the measurement induced geometric phase continuously emerges. The Samuel-Bhandari geometric phase is identified as the nonrandom part of the total geometric phase induced in the measurement. Ensembles of particles for a circular Rydberg wave packet are studied. The trajectories of pilot-wave particles are shown to accurately imitate the behaviour of the wave packet in the high quantum number limit. The nonclassical features of the wave packet are intuitively explained by the nonvanishing quantum potential. Vibronic coupling in the Longuet-Higgins model of the E/otimes/epsilon Jahn-Teller system is investigated by means of quantal trajectories. The pilot-wave picture provides an intuitive tool for discussing time-scales. An argument based on ergodicity leads to an understanding of the averaging procedure over the electronic motion which provides the approximate nuclear motion. The existence of efficient quantum algorithms triggers questions on Natures ability of storing and processing information during quantum computations. The role of elements of reality in quantum computations is addressed using quantal trajectories. It is found that there is a many-to-one relationship between quantal trajectories and performed computations when quantum parallelism is utilized.

  16. Influence of transition metal coordination on halogen bonding: CSD survey and theoretical study

    NASA Astrophysics Data System (ADS)

    Wang, Yanhua; Wu, Weihong; Liu, Yingtao; Lu, Yunxiang

    2013-07-01

    Density functional theory calculations at the level of M06 have been carried out to investigate the influence of transition metal coordinate on halogen bonding. It was found that the introduction of coordination forces leads to much stronger halogen bonds. This effect has been analyzed in detail by the geometric, energetic, electrostatic potential, and AIM properties of the complexes. In addition, some crystal structures extracted from the Cambridge Structural Database were selected to provide experimental evidence of the combination of the two interactions.

  17. Double-bond defect modelling in As-S glasses

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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.

  18. Hydrogen bond dynamics in the active site of photoactive yellow protein

    PubMed Central

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

    2009-01-01

    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

  19. Hydroxide-catalysis bonding for stable optical systems for space

    NASA Astrophysics Data System (ADS)

    Elliffe, E. J.; Bogenstahl, J.; Deshpande, A.; Hough, J.; Killow, C.; Reid, S.; Robertson, D.; Rowan, S.; Ward, H.; Cagnoli, G.

    2005-05-01

    Space-based optical systems must be made from lightweight materials which can withstand significant acceleration and temperature changes. Materials such as ZERODUR, ULE (Ultra Low Expansion material) and silica are all potentially suitable. Depending on the specific requirements of the optical system and the transmissive or reflective nature of the optical layout these materials can be used by themselves or together to fabricate optical benches. The geometrical layouts of these optical systems are often very complicated and the requirements for mechanical stability very stringent, thus jointing components presents a challenge. In this paper we present developments of a novel chemical bonding process, originally invented at Stanford University for bonding silica components for the optical telescope for the Gravity Probe B mission. Colloquially called silicate bonding, this process utilizes hydroxide catalysis to join optical components to optical mounts to obtain high stability whilst accommodating the requirement for precise alignment procedures.

  20. The Calculation of Accurate Metal-Ligand Bond Energies

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  1. Nuclear quantum effects in a 1-D model of hydrogen bonded ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wikfeldt, K. T.

    2014-12-01

    A one dimensional model of a coupled hydrogen (H) bonding chain is developed and parametrized to density functional theory (DFT) calculations on squaric acid, a prototypical H-bonded antiferroelectric crystal. The energetics of single and collective proton jumps and its dependence on H-bond length, as obtained by DFT, is reproduced quite well in the model despite its simplicity where only hydrogen and oxygen atom positions in (O-H...O) H-bonds and nearest-neighbor coupling between H positions are explicitly included. Classical and path- integral molecular dynamics simulations are performed to shed light on nuclear quantum effects and how they influence the paraelectric phase transition. A large H/D isotope shift in the transition temperature TC as well as a geometric isotope effect is obtained in good agreement with experiment. Fixing the O-O bond length results in shifts of TC to higher temperature but a pronounced isotope shift of TC remains, highlighting the importance of quantum effects beyond the geometrical changes in H-bonds accompanying isotopic substitution. Intermediate between fully atomistic models and simpler Ising-type models, the proposed H-bond chain model is a useful toy model for investigating microscopic mechanisms behind phase transitions in H-bonded ferroelectrics and the detailed role of quantum fluctuations.

  2. Optimal domain decomposition strategies

    NASA Technical Reports Server (NTRS)

    Yoon, Yonghyun; Soni, Bharat K.

    1995-01-01

    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.

  3. Bonding with the Past.

    ERIC Educational Resources Information Center

    Common Ground: Archeology and Ethnography in the Public Interest, 1998

    1998-01-01

    An interview with Linda Mayro, archaeologist and cultural resources manager for Pima County, Arizona, discusses efforts of local groups to preserve local Native-American and Mexican cultural-heritage sites in oppositon to commercial land developers. A public information campaign led to passage of a $6.4 million historic preservation bond. (SAS)

  4. Bonding silicones with epoxies

    Microsoft Academic Search

    Tira

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone

  5. Parental Bonding Instrument

    Microsoft Academic Search

    L. C. Cavedo; G. Parker

    1994-01-01

    The view that those with obsessive compulsive disorder or obsessional personality have been exposed to overcontrolling and overcritical parenting is examined. Two measures of obsessionality (the Maudsley Obsessional-Compulsive Inventory and the Leyton Obsessionality Inventory) were completed by 344 nonclinical subjects. They also scored their parents on the Parental Bonding Instrument (PBI), a measure assessing perceived levels of parental care and

  6. Fluoroepoxy Adhesives Bond Fluoroplastics

    NASA Technical Reports Server (NTRS)

    Lee, Sheng Yen

    1989-01-01

    Etching or other special preparation unnecessary. Experiments show fluoroepoxy compounds of high fluorine content adhere to fluoroplastics, without prior etching or other treatment of fluoroplastic surfaces. Compounds mixed with each other in approximately stoichiometric amounts and react to produce fluoroepoxy compounds adhering to fluoroplastics. Advantageous in bonding polymers having fluorine contents of 55 percent or more.

  7. Photochemical tissue bonding

    DOEpatents

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

    2012-01-10

    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.

  8. Testing multifield inflation: A geometric approach

    E-print Network

    Peterson, Courtney M.

    We develop an approach for linking the power spectra, bispectrum, and trispectrum to the geometric and kinematical features of multifield inflationary Lagrangians. Our geometric approach can also be useful in determining ...

  9. 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

    Ritchie, Andrew W; Webb, Lauren J

    2014-07-17

    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

  10. Geometric and Electronic Structures of Manganese-substituted Iron Superoxide Dismutase

    PubMed Central

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

    2013-01-01

    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

  11. Geometric Algebras for Euclidean Geometry

    E-print Network

    Charles Gunn

    2015-01-26

    The article explores the question, which form of geometric algebra is best-suited for doing euclidean geometry? It begins with a review of mathematical prerequisites, including quaternions and biquaternions, dual exterior algebra, and the Cayley-Klein construction. These ingredients are combined into the dual projectivized Clifford algebra $\\mathbf{P(\\mathbb{R}^*_{n,0,1})}$ (PGA), as a geometric algebra for euclidean geometry. Next, a set of fundamental terms which carry multiple meanings in the existing literature, including $\\mathit{homogeneous model}$, $\\mathbb{R}^{n}$, $\\mathit{euclidean}$, and $\\mathit{duality}$ are clarified. This leads to the conclusion that PGA deserves the title of $\\mathit{standard}$ homogeneous model of euclidean geometry. This is followed by a comparison with the the conformal model for euclidean geometry (CGA). It is shown that these two algebras exhibit the same formal feature set for this task. The article ends with a comparison based on practical considerations.

  12. Bouncing Balls and Geometric Series

    NSDL National Science Digital Library

    Besson, Morgan

    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

  13. 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.

  14. Geometrical Visualisation--Epistemic and Emotional

    ERIC Educational Resources Information Center

    Rodd, Melissa

    2010-01-01

    A well-documented experience of students of elementary Euclidean geometry is "seeing" a geometric result and being sure about its truth; this sort of experience gives rise to the notion of geometrical visualisation that is developed here. In this essay a philosophical argument for the epistemic potential of geometrical visualisation is reviewed,

  15. Geometric Algebra and Physics Anthony Lasenby

    E-print Network

    Hart, Gus

    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

  16. Geometrically frustrated magnets Arnab Sen, TIFR

    E-print Network

    Geometrically 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 exclusion. How big is J? When is it positive? Difficult questions. Arnab Sen, TIFR Geometrically frustrated

  17. BFV approach to geometric quantization

    Microsoft Academic Search

    E. S. Fradkin; V. Ya. Linetsky

    1994-01-01

    A gauge-invariant approach to geometric quantization is developed. It yields a complete quantum description for dynamical systems with non-trivial geometry and topology of the phase space. The method is a global version of the gauge-invariant approach to quantization of second-class constraints developed by Batalin, Fradkin and Fradkina (BFF). Physical quantum states and quantum observables are respectively described by covariantly constant

  18. Great Gobs of Geometric Games!

    NSDL National Science Digital Library

    Miss Hearne

    2009-04-30

    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 ...

  19. Geometric compression through topological surgery

    Microsoft Academic Search

    Gabriel Taubin; Jarek Rossignac

    1998-01-01

    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

  20. Geometric aspects of particle segregation.

    PubMed

    Caulkin, R; Jia, X; Fairweather, M; Williams, R A

    2010-05-01

    Size segregation is a natural occurrence both in everyday life and in industrial processes. Understanding and research of the phenomenon has overwhelmingly been from a mechanistic point of view. This paper demonstrates through simulations that segregation can also be explained and trends predicted geometrically. The algorithm used in this study contains three simple elements: random walks combined with a rebounding probability to encourage particles to settle, plus the non-overlap constraint. It is implemented digitally in a regular lattice grid, to make it easy to deal with arbitrary shapes. It does not explicitly consider any particle interaction forces, and it does not include any rules specifically designed to promote or suppress segregation. Yet particle movement, which occurs within a digitized cubic grid, leads to shaking-induced segregation comparable to that observed in physical tests. The paper details the comparison of shaking-induced particle segregation between a series of computer based simulations and those of physical experiments undertaken in the laboratory. A range of mixtures, comprising nonspherical, arbitrary shaped/sized particles are investigated, having been packed into pseudo-two-dimensional containers. The simulation results suggest that segregation can be adequately explained, from a geometrical point of view, as a result of the relative motion between particles of different sizes and shapes. The geometrical algorithm thus provides a fast and qualitative prediction as to how likely segregation is to occur for any given mixture of arbitrary shapes. PMID:20866221

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

    PubMed

    McCabe, Patrick; Korb, Oliver; Cole, Jason

    2014-05-27

    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

  2. Palladium- and Nickel-Catalyzed CarbonCarbon Bond Insertion Reactions with Alkylidenesilacyclopropanes

    PubMed Central

    Buchner, Kay M.; Woerpel, K. A.

    2010-01-01

    Palladium and nickel catalysts promoted highly selective carboncarbon bond insertion reactions with di-tert-butyl-alkylidenesilacyclopropanes. Pd(PPh3)4 was demonstrated to be the optimal catalyst, allowing for a variety of carboncarbon ?-bond insertion reactions. Depending on the nature of the carboncarbon ? bond, the insertion reaction proceeded with either direct insertion into the carbon(sp2)silicon bond or with allylic transposition. Ring-substituted alkylidenesilacyclopropanes required a nickel catalyst to afford insertion products. Using Ni(cod)2 as the carboncarbon bond insertion catalyst, new double alkyne insertion products and alkene isomerization products were observed. PMID:20419110

  3. The Illiquidity of Corporate Bonds

    E-print Network

    Bao, Jack

    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 ...

  4. ChemTeacher: Ionic Bonds

    NSDL National Science Digital Library

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Ionic Bonds page includes resources for teaching students about ionic bonding.

  5. ChemTeacher: Covalent Bonds

    NSDL National Science Digital Library

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Covalent Bonds page includes resources for teaching students about covalent bonding.

  6. The concept of bond order

    NASA Astrophysics Data System (ADS)

    Elliott, Robert J.; Richards, W. Graham

    A method for obtaining precise charge densities in defined regions of space from ab initio molecular wavefunctions is employed to place the concept of bond order on a firm theoretical footing. The bond orders obtained for carboncarbon bonds in a range of organic compounds are assessed: those for buta-1,3-diene confirm that it consists of essentially localised double and single bonds.

  7. Geometric Effects on the Amplification of First Mode Instability Waves

    NASA Technical Reports Server (NTRS)

    Kirk, Lindsay C.; Candler, Graham V.

    2013-01-01

    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.

  8. Water lubricates hydrogen-bonded molecular machines.

    PubMed

    Panman, Matthijs R; Bakker, Bert H; den Uyl, David; Kay, Euan R; Leigh, David A; Buma, Wybren Jan; Brouwer, Albert M; Geenevasen, Jan A J; Woutersen, Sander

    2013-11-01

    The mechanical behaviour of molecular machines differs greatly from that of their macroscopic counterparts. This applies particularly when considering concepts such as friction and lubrication, which are key to optimizing the operation of macroscopic machinery. Here, using time-resolved vibrational spectroscopy and NMR-lineshape analysis, we show that for molecular machinery consisting of hydrogen-bonded components the relative motion of the components is accelerated strongly by adding small amounts of water. The translation of a macrocycle along a thread and the rotation of a molecular wheel around an axle both accelerate significantly on the addition of water, whereas other protic liquids have much weaker or opposite effects. We tentatively assign the superior accelerating effect of water to its ability to form a three-dimensional hydrogen-bond network between the moving parts of the molecular machine. These results may indicate a more general phenomenon that helps explain the function of water as the 'lubricant of life'. PMID:24153370

  9. Water lubricates hydrogen-bonded molecular machines

    NASA Astrophysics Data System (ADS)

    Panman, Matthijs R.; Bakker, Bert H.; den Uyl, David; Kay, Euan R.; Leigh, David A.; Buma, Wybren Jan; Brouwer, Albert M.; Geenevasen, Jan A. J.; Woutersen, Sander

    2013-11-01

    The mechanical behaviour of molecular machines differs greatly from that of their macroscopic counterparts. This applies particularly when considering concepts such as friction and lubrication, which are key to optimizing the operation of macroscopic machinery. Here, using time-resolved vibrational spectroscopy and NMR-lineshape analysis, we show that for molecular machinery consisting of hydrogen-bonded components the relative motion of the components is accelerated strongly by adding small amounts of water. The translation of a macrocycle along a thread and the rotation of a molecular wheel around an axle both accelerate significantly on the addition of water, whereas other protic liquids have much weaker or opposite effects. We tentatively assign the superior accelerating effect of water to its ability to form a three-dimensional hydrogen-bond network between the moving parts of the molecular machine. These results may indicate a more general phenomenon that helps explain the function of water as the lubricant of life.

  10. Bonding interactions through hydrogen

    Microsoft Academic Search

    Daniel J Goebbert

    2006-01-01

    Hydride reductions are some of the most important reactions in synthetic organic chemistry. Typically, a hydride transfer reagent, such as LiAlH 4 or NaBH4, is dissolved in solution and undergoes reactions with carbon-heteroatom unsaturated bonds. The classic example of such reactivity is the synthesis of alcohols from ketones. We have found, using experimental methods, that the hydride affinity of AIH3

  11. Continuing Conversation about Continuing Bonds

    ERIC Educational Resources Information Center

    Klass, Dennis

    2006-01-01

    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

  12. Cyclic Bonds in Branched Polymers

    E-print Network

    Kazumi Suematsu

    2015-02-19

    In the gelation theory it has been implicitly assumed that (I) a cyclic bond is a finite bond that returns to itself; (II) cyclic bonds distribute at random in network structures. In this paper these two assumptions are reexamined from a new point of view. The physical soundness of the assumptions are assessed through comparison with experimental observations.

  13. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...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...

  14. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...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...

  15. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...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...

  16. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...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...

  17. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...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...

  18. Vector-based model of elastic bonds for simulation of granular solids.

    PubMed

    Kuzkin, Vitaly A; Asonov, Igor E

    2012-11-01

    A model (further referred to as the V model) for the simulation of granular solids, such as rocks, ceramics, concrete, nanocomposites, and agglomerates, composed of bonded particles (rigid bodies), is proposed. It is assumed that the bonds, usually representing some additional gluelike material connecting particles, cause both forces and torques acting on the particles. Vectors rigidly connected with the particles are used to describe the deformation of a single bond. The expression for potential energy of the bond and corresponding expressions for forces and torques are derived. Formulas connecting parameters of the model with longitudinal, shear, bending, and torsional stiffnesses of the bond are obtained. It is shown that the model makes it possible to describe any values of the bond stiffnesses exactly; that is, the model is applicable for the bonds with arbitrary length/thickness ratio. Two different calibration procedures depending on bond length/thickness ratio are proposed. It is shown that parameters of the model can be chosen so that under small deformations the bond is equivalent to either a Bernoulli-Euler beam or a Timoshenko beam or short cylinder connecting particles. Simple analytical expressions, relating parameters of the V model with geometrical and mechanical characteristics of the bond, are derived. Two simple examples of computer simulation of thin granular structures using the V model are given. PMID:23214773

  19. Direct bonded space maintainers.

    PubMed

    Santos, V L; Almeida, M A; Mello, H S; Keith, O

    1993-01-01

    The aim of this study was to evaluate clinically a bonded space maintainer, which would reduce chair-side time and cost. Sixty appliances were fabricated from 0.7 mm stainless steel round wire and bonded using light-cured composite to the two teeth adjacent to the site of extraction of a posterior primary tooth. Twenty males and sixteen females (age range 5-9-years-old) were selected from the Pedodontic clinic of the State University of Rio de Janeiro. The sixty space maintainers were divided into two groups according to the site in which they were placed: a) absent first primary molar and b) absent second primary molar. Impressions and study models were obtained prior to and 6 months after bonding the appliances. During this period only 8.3% of failures were observed, most of them from occlusal or facial trauma. Student t-test did not show statistically significant alterations in the sizes of the maintained spaces during the trial period. PMID:8217886

  20. Disulfide bonds of acetylcholinesterase

    SciTech Connect

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

    1986-05-01

    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.

  1. GaalopHigh Performance Parallel Computing Based on Conformal Geometric Algebra

    NASA Astrophysics Data System (ADS)

    Hildenbrand, Dietmar; Pitt, Joachim; Koch, Andreas

    We present Gaalop (Geometric algebra algorithms optimizer), our tool for high-performance computing based on conformal geometric algebra. The main goal of Gaalop is to realize implementations that are most likely faster than conventional solutions. In order to achieve this goal, our focus is on parallel target platforms like FPGA (field-programmable gate arrays) or the CUDA technology from NVIDIA. We describe the concepts, current status, and future perspectives of Gaalop dealing with optimized software implementations, hardware implementations, and mixed solutions. An inverse kinematics algorithm of a humanoid robot is described as an example.

  2. On the bond graphs in the Delaunay-tetrahedra of the simplicial decomposition of spatial protein

    E-print Network

    Grolmusz, Vince

    On the bond graphs in the Delaunay-tetrahedra of the simplicial decomposition of spatial protein atoms of the protein structures in the PDB, and analyzed geometrical properties of the tetrahedra of the points are on the surface of a sphere), then all regions are tetrahedra (cf. Figure 1). We are interested

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

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1955-01-01

    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.

  4. Geometric feature extraction by a multimarked point process.

    PubMed

    Lafarge, Florent; Gimel'farb, Georgy; Descombes, Xavier

    2010-09-01

    This paper presents a new stochastic marked point process for describing images in terms of a finite library of geometric objects. Image analysis based on conventional marked point processes has already produced convincing results but at the expense of parameter tuning, computing time, and model specificity. Our more general multimarked point process has simpler parametric setting, yields notably shorter computing times, and can be applied to a variety of applications. Both linear and areal primitives extracted from a library of geometric objects are matched to a given image using a probabilistic Gibbs model, and a Jump-Diffusion process is performed to search for the optimal object configuration. Experiments with remotely sensed images and natural textures show that the proposed approach has good potential. We conclude with a discussion about the insertion of more complex object interactions in the model by studying the compromise between model complexity and efficiency. PMID:20634555

  5. 26 CFR 1.144-1 - Qualified small issue bonds, qualified student loan bonds, and qualified redevelopment bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...issue bonds, qualified student loan bonds, and qualified...144-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT...issue bonds, qualified student loan bonds, and qualified...limitation on capital expenditures) or under...

  6. Exclusive selectivity in the one-pot formation of C-C and C-Se bonds involving Ni-catalyzed alkyne hydroselenation: optimization of the synthetic procedure and a mechanistic study.

    PubMed

    Orlov, Nikolay V; Chistyakov, Igor V; Khemchyan, Levon L; Ananikov, Valentine P; Beletskaya, Irina P; Starikova, Zoya A

    2014-12-19

    A unique Ni-catalyzed transformation is reported for the one-pot highly selective synthesis of previously unknown monoseleno-substituted 1,3-dienes starting from easily available terminal alkynes and benzeneselenol. The combination of a readily available catalyst precursor, Ni(acac)2, and an appropriately tuned phosphine ligand, PPh2Cy, resulted in the exclusive assembly of the s-gauche diene skeleton via the selective formation of C-C and C-Se bonds. The unusual diene products were stable under regular experimental conditions, and the products maintained the s-gauche geometry both in the solid state and in solution, as confirmed by X-ray analysis and NMR spectroscopy. Thorough mechanistic studies using ESI-MS revealed the key Ni-containing species involved in the reaction. PMID:25288369

  7. Hydrogen bonding in ionic liquids.

    PubMed

    Hunt, Patricia A; Ashworth, Claire R; Matthews, Richard P

    2015-02-23

    Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (?BCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H ?* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak through to very strong H-bonds. PMID:25582457

  8. Diffusion bonding of the oxide dispersion strengthened steel PM2000

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  9. Effect of quantum nuclear motion on hydrogen bonding

    SciTech Connect

    McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au; Bekker, Christiaan [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia)] [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)] [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

    2014-05-07

    This work considers how the properties of hydrogen bonded complexes, XH?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 OH?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 XH 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.

  10. Graphene with geometrically induced vorticity

    E-print Network

    Jiannis K. Pachos; Michael Stone; Kristan Temme

    2008-03-26

    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.

  11. Constrained ballistics and geometrical optics

    E-print Network

    Epstein, Marcelo

    2014-01-01

    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.

  12. SQCD Vacua and Geometrical Engineering

    SciTech Connect

    Tatar, Radu; Wetenhall, Ben [Department of Mathematical Sciences, University of Liverpool, Liverpool L69 3BX (United Kingdom)

    2008-11-23

    We consider the geometrical engineering constructions for the N = 1 SQCD vacua. After one T-duality, these geometries with wrapped D5 branes become N = 1 brane configurations with NS-branes and D4-branes. After performing a flop, the geometries contain branes, antibranes and branes wrapped on non-holomorphic cycles. The various tachyon condensations between pairs of wrapped D5 branes and anti-D5 branes together with deformations of the cycles give rise to a variety of supersymmetric and metastable non-supersymmetric vacua.

  13. Science, art and geometrical imagination

    NASA Astrophysics Data System (ADS)

    Luminet, Jean-Pierre

    2011-06-01

    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.

  14. Geometric phases of water waves

    E-print Network

    Francesco Fedele

    2014-08-08

    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 $U_{g}/U_d\\approx-0.2$.

  15. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 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....

  16. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 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....

  17. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 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....

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

    PubMed Central

    Yusupov, Marat; Yusupova, Gulnara

    2014-01-01

    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

  19. An algorithm for the topology optimization of geometrically nonlinear structures

    E-print Network

    Gomes, Francisco A. M.

    and Senne [6], Sigmund [7], Kikuchi et al. [8], Nishiwaki et al. [9]) and the Sequential Quadratic those written by Jog [12], Buhl, Pedersen and Sigmund [13], Bruns and Tortorelli [14], Gea and Luo [15], Bruns, Sigmund and Tortorelli [16], Ohsaki and Nishiwaki [17], Luo and Tong [18], Lazarov, Schevenels

  20. Geometric Optimization of the Evaluation of Finite Element Matrices

    Microsoft Academic Search

    Robert C. Kirby; L. Ridgway Scott

    2007-01-01

    This paper continues earlier work on mathematical techniques for generating opti- mized algorithms for computing finite element stiffness matrices. These techniques start from rep- resenting the stiffness matrix for an affine element as a collection of contractions between reference tensors and an element-dependent geometry tensor. We go beyond the complexity-reducing binary relations explored in (R. C. Kirby, A. Logg, L.

  1. Geometric optimization of the supersonic stagnation-pressure probe

    NASA Technical Reports Server (NTRS)

    Couch, L. M.

    1975-01-01

    An investigation was conducted at Mach numbers of 1.41, 1.83, and 2.20 to determine the effects of parametric variations both in the height of the pitot-tube center line from the probe surface, by varying the pitot-tube diameter, and in the radius of surface curvature on the pressure recovery of a probe designed to measure free-stream stagnation pressure. The probe consists of a pitot tube mounted on the surface of a curved cylinder of circular cross section; the pitot tube senses the pressure of the stream tube which has been slowed to subsonic or near sonic velocity by isentropic compression along the curved surface. Pressure recovery - greater than or equal to 99.8 percent of free-stream stagnation pressure - was obtained for a wide range of both angle of attack and yaw for probes satisfying the optimum design criteria determined in this investigation.

  2. Structural and vibrational spectroscopic studies on charge transfer and ionic hydrogen bonding interactions of melaminium benzoate dihydrate.

    PubMed

    Kanagathara, N; Marchewka, M K; Drozd, M; Gunasekaran, S; Rajakumar, P R; Anbalagan, G

    2015-06-15

    Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by (1)H and (13)C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358K for heating and cooling, respectively. PMID:25796010

  3. Structure and electronic properties of the WatsonCrick base pairs: Role of hydrogen bonding

    Microsoft Academic Search

    Sairam S. Mallajosyula; Ayan Datta; Swapan K. Pati

    2005-01-01

    The hydrogen bonding patterns in the adeninethymine (AT) and guaninecytosine (GC) base pairs for B-DNA has been studied using the density functional theory. The H-bond for the crystal geometry is found to differ considerably from the geometry optimized structures for the free base pairs with larger deviation for the GC pair compared to the AT pair. Furthermore, the H-bonding patterns

  4. Low temperature reactive bonding

    DOEpatents

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

    1995-01-17

    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.

  5. Further developments in gold-stud bump bonding

    NASA Astrophysics Data System (ADS)

    Neher, C.; Lander, R. L.; Moskaleva, A.; Pasner, J.; Tripathi, M.; Woods, M.

    2012-02-01

    As silicon detectors in high energy physics experiments require increasingly complex assembly procedures, the availability of a wide variety of interconnect technologies provides more options for overcoming obstacles in generic R&D. Gold ball bonding has been a staple in the interconnect industry due to its ease of use and reliability. However, due to some limitations in the standard technique, alternate methods of gold-stud bonding are being developed. This paper presents recent progress and challenges faced in the development of double gold-stud bonding and 0.5 mil wire gold-stud bonding at the UC Davis Facility for Interconnect Technology. Advantages and limitations of each technique are analyzed to provide insight into potential applications for each method. Optimization of procedures and parameters is also presented.

  6. NPP VIIRS Geometric Performance Status

    NASA Technical Reports Server (NTRS)

    Lin, Guoqing; Wolfe, Robert E.; Nishihama, Masahiro

    2011-01-01

    Visible Infrared Imager Radiometer Suite (VIIRS) instrument on-board the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite is scheduled for launch in October, 2011. It is to provide satellite measured radiance/reflectance data for both weather and climate applications. Along with radiometric calibration, geometric characterization and calibration of Sensor Data Records (SDRs) are crucial to the VIIRS Environmental Data Record (EDR) algorithms and products which are used in numerical weather prediction (NWP). The instrument geometric performance includes: 1) sensor (detector) spatial response, parameterized by the dynamic field of view (DFOV) in the scan direction and instantaneous FOV (IFOV) in the track direction, modulation transfer function (MTF) for the 17 moderate resolution bands (M-bands), and horizontal spatial resolution (HSR) for the five imagery bands (I-bands); 2) matrices of band-to-band co-registration (BBR) from the corresponding detectors in all band pairs; and 3) pointing knowledge and stability characteristics that includes scan plane tilt, scan rate and scan start position variations, and thermally induced variations in pointing with respect to orbital position. They have been calibrated and characterized through ground testing under ambient and thermal vacuum conditions, numerical modeling and analysis. This paper summarizes the results, which are in general compliance with specifications, along with anomaly investigations, and describes paths forward for characterizing on-orbit BBR and spatial response, and for improving instrument on-orbit performance in pointing and geolocation.

  7. Bonding mechanism in ultrasonic gold ball bonds on copper substrate

    NASA Astrophysics Data System (ADS)

    Lum, I.; Jung, J. P.; Zhou, Y.

    2005-05-01

    The effects of process parameters on bond formation in thermosonic gold ball bonding on a copper substrate at ambient temperatures have been investigated with scanning electron microscopy (SEM). A model was developed based on classical microslip theory to explain the general phenomena observed in the evolution of bond footprints left on the substrate. The specific effects of ultrasonic energy and complex stress distributions arising from tool geometry must be taken into consideration and were incorporated into the model. It was shown that relative motion existed at the bonding interface as microslip at lower powers, transitioning into gross sliding at higher powers. With increased normal bonding forces, the transition point into gross sliding occurred at higher ultrasonic bonding powers.

  8. Silicon carbide wafer bonding by modified surface activated bonding method

    NASA Astrophysics Data System (ADS)

    Suga, Tadatomo; Mu, Fengwen; Fujino, Masahisa; Takahashi, Yoshikazu; Nakazawa, Haruo; Iguchi, Kenichi

    2015-03-01

    4H-SiC wafer bonding has been achieved by the modified surface activated bonding (SAB) method without any chemical-clean treatment and high temperature annealing. Strong bonding between the SiC wafers with tensile strength greater than 32 MPa was demonstrated at room temperature under 5 kN force for 300 s. Almost the entire wafer has been bonded very well except a small peripheral region and few voids. The interface structure was analyzed to verify the bonding mechanism. It was found an amorphous layer existed as an intermediate layer at the interface. After annealing at 1273 K in vacuum for 1 h, the bonding tensile strength was still higher than 32 MPa. The interface changes after annealing were also studied. The results show that the thickness of the amorphous layer was reduced to half after annealing.

  9. Geometric solitons of Hamiltonian flows on manifolds

    NASA Astrophysics Data System (ADS)

    Song, Chong; Sun, Xiaowei; Wang, Youde

    2013-12-01

    It is well-known that the LIE (Locally Induction Equation) admit soliton-type solutions and same soliton solutions arise from different and apparently irrelevant physical models. By comparing the solitons of LIE and Killing magnetic geodesics, we observe that these solitons are essentially decided by two families of isometries of the domain and the target space, respectively. With this insight, we propose the new concept of geometric solitons of Hamiltonian flows on manifolds, such as geometric Schrdinger flows and KdV flows for maps. Moreover, we give several examples of geometric solitons of the Schrdinger flow and geometric KdV flow, including magnetic curves as geometric Schrdinger solitons and explicit geometric KdV solitons on surfaces of revolution.

  10. Geometric solitons of Hamiltonian flows on manifolds

    SciTech Connect

    Song, Chong, E-mail: songchong@xmu.edu.cn [School of Mathematical Sciences, Xiamen University, Xiamen 361005 (China)] [School of Mathematical Sciences, Xiamen University, Xiamen 361005 (China); Sun, Xiaowei, E-mail: sunxw@cufe.edu.cn [School of Applied Mathematics, Central University of Finance and Economics, Beijing 100081 (China)] [School of Applied Mathematics, Central University of Finance and Economics, Beijing 100081 (China); Wang, Youde, E-mail: wyd@math.ac.cn [Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190 (China)] [Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190 (China)

    2013-12-15

    It is well-known that the LIE (Locally Induction Equation) admit soliton-type solutions and same soliton solutions arise from different and apparently irrelevant physical models. By comparing the solitons of LIE and Killing magnetic geodesics, we observe that these solitons are essentially decided by two families of isometries of the domain and the target space, respectively. With this insight, we propose the new concept of geometric solitons of Hamiltonian flows on manifolds, such as geometric Schrdinger flows and KdV flows for maps. Moreover, we give several examples of geometric solitons of the Schrdinger flow and geometric KdV flow, including magnetic curves as geometric Schrdinger solitons and explicit geometric KdV solitons on surfaces of revolution.

  11. Characterizing the geometrical edges of nonlocal two-qubit gates

    SciTech Connect

    Balakrishnan, S.; Sankaranarayanan, R. [Department of Physics, National Institute of Technology, Tiruchirappalli 620015 (India)

    2009-05-15

    Nonlocal two-qubit gates are geometrically represented by tetrahedron known as Weyl chamber within which perfect entanglers form a polyhedron. We identify that all edges of the Weyl chamber and polyhedron are formed by single parametric gates. Nonlocal attributes of these edges are characterized using entangling power and local invariants. In particular, SWAP{sup -{alpha}} family of gates with 0{<=}{alpha}{<=}1 constitutes one edge of the Weyl chamber with SWAP{sup -1/2} being the only perfect entangler. Finally, optimal constructions of controlled-NOT using SWAP{sup -1/2} gate and gates belong to three edges of the polyhedron are presented.

  12. Geometrical light transfer in optical waveguide arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xin-Ding; Liu, Wen-Jie; Yang, Guang-Fei

    2015-03-01

    We propose to simulate the four-level stimulated Raman adiabatic passage in a four-waveguide array. We find that an Abelian geometric phase factor emerges in this adiabatic passage, and the transfer of light between the waveguides can solely depend on the geometric phase. The robustness of geometric phase may bring additional benefits for high-precision light manipulation in some all-optical devices.

  13. Fracture behavior of masonry bond

    NASA Astrophysics Data System (ADS)

    Park, Cheolwoo

    In this study, three different mechanical tests and video microscopy experiments were preformed to characterize the fracture behavior of masonry bond. Mortars were fabricated under two different conditions: Mortars cast in plexiglass molds and; Mortars exposed to the interactions with dry masonry units. The mechanical properties of the mortar were significantly modified when the mortars experienced mortar/unit interactions. Also, different surface textures for the masonry units altered the strength of embedded mortar when identical mortars were used. It is strongly recommended that the in-situ mortar strength should be used rather than the cast mortar strength because dependence upon laboratory test results for determination of structural performance invites significant error. For masonry bond fracture, a test method was developed and used successfully to measure load-CMOD behavior until complete failure maintaining stable crack growth. It was found that the strength of in-situ mortar was an important indication of bond strength. Admixtures that had similar purposes for the bulk materials were dramatically different in bond strength. The bond strength was also significantly altered with different surface textures for the masonry. A new technique was performed to investigate the details of the fracture surface using video microscopy. Degree of bond was defined as an area fraction of the net bonded area. The bond strength was a strictly linear function of the degree of bond and when the bond strength was normalized with degree of bond. The applied fracture mechanics model, when both elastic and inelastic deformations were considered, always over-estimated the post-peak behavior. However, the post-peak behavior was successfully predicted when the model was modified to consider only elastic deformation. The analysis indicated that little toughening action took place during the fracture process and the fracture process zone at the crack tip was small relative to plain concrete and mortar. This was due to the highly brittle fracture nature associated with pre-determined weak crack path and relatively smooth crack surfaces. Using the relationship between degree of bond and bond strength, and the established fracture model, it was possible to describe the fracture behavior for an ideal perfect bond. As the degree of bond approaches 100%, bond strength increases but the work of fracture does not improve as a simple function of increase in the degree of bond.

  14. Geometrical and Graphical Solutions of Quadratic Equations.

    ERIC Educational Resources Information Center

    Hornsby, E. John, Jr.

    1990-01-01

    Presented are several geometrical and graphical methods of solving quadratic equations. Discussed are Greek origins, Carlyle's method, von Staudt's method, fixed graph methods and imaginary solutions. (CW)

  15. Original Articles Geometric Control of Cardiomyogenic Induction

    E-print Network

    Zandstra, Peter W.

    Original Articles Geometric Control of Cardiomyogenic Induction in Human Pluripotent Stem Cells Differentiating aggregates are thought to mimic the environment of the peri-implantation embryo where in

  16. The effect of non-bonded attractive electronic (anomeric) interactions on conformation and geometry of organic phosphates and thiophosphates

    NASA Astrophysics Data System (ADS)

    van Nuffel, P.; Van Alsenoy, C.; Lenstra, A. T. H.; Geise, H. J.

    1984-11-01

    Substituted 1,3,2-dioxaphosphorinane-2-oxides and -2-sulfides are classified according to the conformation of the ring and the orientation (axial or equatorial) of the P=O/P=S bond. Geometrical parameters (torsion angles, valence angles and bond lengths) of 37 compounds are analyzed and several systematic class differences are observed. The anomeric effect, with emphasis on the n?(O)? * (P-axial substituent) interaction, provides the basis for rationalizing conformational preferences as well as geometrical details. Mean experimental geometries are compared to ab initio calculated geometries for conformers of (HO) 2PH(O) and (HO) 2PH(S) mimicking the dioxaphosphorinanes.

  17. Bond Sensitivity to Silicone Contamination

    NASA Technical Reports Server (NTRS)

    Caldwell, G. A.; Hudson, W. D.; Hudson, W. D.; Cash, Stephen F. (Technical Monitor)

    2003-01-01

    Currently during fabrication of the Space Shuttle booster rocket motors, the use of silicone and silicone-containing products is prohibited in most applications. Many shop aids and other materials containing silicone have the potential, if they make contact with a bond surface, to transfer some of the silicone to the substrates being bonded. Such transfer could result in a reduction of the bond strength or even failure of the subsequent bonds. This concern is driving the need to understand the effect of silicones and the concentration needed to affect a given bond-line strength. Additionally, as silicone detection methods used for materials acceptance improve what may have gone unnoticed earlier is now being detected. Thus, realistic silicone limits for process materials (below which bond performance is satisfactory) are needed rather than having an absolute no silicone permitted policy.

  18. Better Bonded Ethernet Load Balancing

    SciTech Connect

    Gabler, Jason

    2006-09-29

    When a High Performance Storage System's mover shuttles large amounts of data to storage over a single Ethernet device that single channel can rapidly become saturated. Using Linux Ethernet channel bonding to address this and similar situations was not, until now, a viable solution. The various modes in which channel bonding could be configured always offered some benefit but only under strict conditions or at a system resource cost that was greater than the benefit gained by using channel bonding. Newer bonding modes designed by various networking hardware companies, helpful in such networking scenarios, were already present in their own switches. However, Linux-based systems were unable to take advantage of those new modes as they had not yet been implemented in the Linux kernel bonding driver. So, except for basic fault tolerance, Linux channel bonding could not positively combine separate Ethernet devices to provide the necessary bandwidth.

  19. Push-out bond strengths of two fiber post types bonded with different dentin bonding agents.

    PubMed

    Topcu, Fulya Toksoy; Erdemir, Ugur; Sahinkesen, Gunes; Mumcu, Emre; Yildiz, Esra; Uslan, Ibrahim

    2010-05-01

    The aim of this study was to evaluate the regional push-out bond strengths for two fiber-reinforced post types using three different dentin bonding agents. Sixty single-rooted extracted human first premolar teeth were sectioned below the cemento-enamel junction, and the roots were endodontically treated. Following standardized post space preparations, the roots were divided into two fiber-post groups (Glassix and Carbopost), and further divided into three subgroups of 10 specimens each for the bonding systems self-etching dentin bonding agents (Clearfil SE Bond and Optibond all-in-one), and total-etching dentin bonding agent (XP Bond). A dual-cure resin luting cement (Maxcem) was then placed in the post spaces and posts were then seated into the root canals polymerized through the cervical portion. The roots were then cut into 3-mm thick sections. Push-out tests were performed at a crosshead speed of 0.5 mm/min. The data were analyzed with multivariate ANOVA (alpha = 0.05). The morphology of interface between different dentin bonding agents from the cervical sections were analyzed with SEM. Glass fiber-reinforced posts demonstrated significantly higher push-out bond strengths than carbon fiber-reinforced posts (p < 0.001). Bond strength values decreased significantly from the cervical to the apical root canal regions (p < 0.001). Self-etching dentin adhesive Clearfil SE Bond and total-etching dentin adhesive XP Bond demonstrated similar bond strengths values and this was significantly higher compared with the Optibond all-in-one in cervical root canal region. In conclusion, in all root segments, the glass fiber-reinforced posts provided significantly increased post retention than the carbon fiber-reinforced posts, regardless of the adhesive used. PMID:20091920

  20. Autophoretic locomotion from geometric asymmetry

    E-print Network

    Sebastien Michelin; Eric Lauga

    2015-01-16

    Among the few methods which have been proposed to create small-scale swimmers, those relying on self-phoretic mechanisms present an interesting design challenge in that chemical gradients are required to generate net propulsion. Building on recent work, we propose that asymmetries in geometry are sufficient to induce chemical gradients and swimming. We illustrate this idea using two different calculations. We first calculate exactly the self-propulsion speed of a system composed of two spheres of unequal sizes but identically chemically homogeneous. We then consider arbitrary, small-amplitude, shape deformations of a chemically-homogeneous sphere, and calculate asymptotically the self-propulsion velocity induced by the shape asymmetries. Our results demonstrate how geometric asymmetries can be tuned to induce large locomotion speeds without the need of chemical patterning.

  1. Autophoretic locomotion from geometric asymmetry

    E-print Network

    Michelin, Sebastien

    2015-01-01

    Among the few methods which have been proposed to create small-scale swimmers, those relying on self-phoretic mechanisms present an interesting design challenge in that chemical gradients are required to generate net propulsion. Building on recent work, we propose that asymmetries in geometry are sufficient to induce chemical gradients and swimming. We illustrate this idea using two different calculations. We first calculate exactly the self-propulsion speed of a system composed of two spheres of unequal sizes but identically chemically homogeneous. We then consider arbitrary, small-amplitude, shape deformations of a chemically-homogeneous sphere, and calculate asymptotically the self-propulsion velocity induced by the shape asymmetries. Our results demonstrate how geometric asymmetries can be tuned to induce large locomotion speeds without the need of chemical patterning.

  2. Geometrical characteristics of uniportal VATS.

    PubMed

    Bertolaccini, Luca; Rocco, Gaetano; Viti, Andrea; Terzi, Alberto

    2013-08-01

    In terms of accuracy and efficacy Uniportal Video-Assisted Thoracic Surgery (VATS) resections are comparable to standard VATS. In standard three-ports VATS, the geometric configuration of a parallelogram generates interference with the optical source, creating a plane with a torsion angle not favorable on the flat two-dimensional vision of currently available monitors. The potential advantages of single-port VATS approach include not only the one intercostal space incision (reduction of postoperative pain) but also a translational approach of VATS instruments along a sagittal plane. Accordingly, the Uniportal approach enables VATS instruments to draw two parallel lines on the plane, bringing them to approach the target lesion from a caudo-cranial perspective thus achieving a projective plane. As a consequence, taking advantage of the unique spatial features specific to uniportal VATS, the surgeon is enabled to bring the operative fulcrum inside the chest to address the target lesion in a fashion similar to open surgery. PMID:24040527

  3. Geometric analysis of transient bursts

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  4. Autophoretic locomotion from geometric asymmetry.

    PubMed

    Michelin, Sbastien; Lauga, Eric

    2015-02-01

    Among the few methods which have been proposed to create small-scale swimmers, those relying on self-phoretic mechanisms present an interesting design challenge in that chemical gradients are required to generate net propulsion. Building on recent work, we propose that asymmetries in geometry are sufficient to induce chemical gradients and swimming. We illustrate this idea using two different calculations. We first calculate exactly the self-propulsion speed of a system composed of two spheres of unequal sizes but identically chemically homogeneous. We then consider arbitrary, small-amplitude, shape deformations of a chemically homogeneous sphere, and calculate asymptotically the self-propulsion velocity induced by the shape asymmetries. Our results demonstrate how geometric asymmetries can be tuned to induce large locomotion speeds without the need of chemical patterning. PMID:25676446

  5. 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.

  6. Bond failure patterns in vivo.

    PubMed

    Linklater, Rognvald A; Gordon, Peter H

    2003-05-01

    The aim of this study was to identify the presence and pattern of differences in bond failure between tooth types in vivo when bonding orthodontic brackets with the no-mix orthodontic composite adhesive Right-On. In vivo bond failure for a single operator was recorded for 108 consecutive patients undergoing fixed-appliance orthodontic treatment. The bond failure data were analyzed by survival analysis. Time to first failure or censorship was recorded for each bonded attachment. Overall failure in the sample matched previous clinical studies but conflicted with previous ex vivo bond strength data. Mandibular and posterior teeth had significantly higher rates of failure than did maxillary and anterior teeth. The type of attachment used had a significant effect on bond survival. The results of this study confirm that in vivo bond survival is not uniform for all teeth. Comparisons between the findings of this study and those of a previous ex vivo study by the same authors failed to validate ex vivo bond strength testing as clinically relevant. PMID:12750672

  7. Electrons and Hydrogen-Bond Connectivity in Liquid Water

    SciTech Connect

    Fernandez-Serra, M.V. [Laboratoire de Physique de la Matiere Condensee et Nanostructures (LPMCN) and UMR CNRS 5586, Universite Claude Bernard Lyon 1, 69622 Villeurbanne (France); Artacho, Emilio [Donostia International Physics Center, Universidad del Pais Vasco, 20080 San Sebastian (Spain); Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)

    2006-01-13

    The network connectivity in liquid water is revised in terms of electronic signatures of hydrogen bonds (HBs) instead of geometric criteria, in view of recent x-ray absorption studies. The analysis is based on ab initio molecular-dynamics simulations at ambient conditions. Even if instantaneous threadlike structures are observed in the electronic network, they continuously reshape in oscillations reminiscent of the r and t modes in ice ({tau}{approx}170 fs). However, two water molecules initially joined by a HB remain effectively bound over many periods regardless of its electronic signature.

  8. EXTRACTING GEOMETRIC FEATURES OF AORTIC VALVE ANNULUS MOTION FROM DYNAMIC MRI FOR GUIDING INTERVENTIONS

    E-print Network

    Deng, Zhigang

    of the geometric features such as the diameter, center and orien- tation of the aortic valve annulus (AVA). The method is based on finding an optimal fit for a circular ring mimicking AVA in the aortic root. Moreover, the presented approach provides dynamic tracking of the AVA in CINE MR images. This ap- proach can be used

  9. Tradeoff between delay and area in gate sizing using Geometric Programming

    Microsoft Academic Search

    Gracieli Posser; Guilherme Flach; Gustavo Wilke; Ricardo Reis

    2012-01-01

    A study about the tradeoff between delay and area (power) is presented in this work considering circuit gate sizing. We use a gate sizing tool based on Geometric Programming (GP), where delay is calculated by Elmore delay model. The optimization can be done targeting both delay and area (power) minimization. Tests were performed mapping ISCAS'85 benchmark circuits for 45nm technology.

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

    E-print Network

    Bhattacharya, Aniket

    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

  11. Geometric Approach to Statistical Learning Theory through Support Vector Machines (SVM)

    E-print Network

    Kouroupetroglou, Georgios

    Geometric Approach to Statistical Learning Theory through Support Vector Machines (SVM and non-separable, SVM optimization task. The contributions of this work are i) the extension were tested using public bench- mark datasets and outperformed the existing algebraic SVM algorithms

  12. Optimization of the geometry of the diphenylamine molecule by semiempirical quantum chemical methods

    SciTech Connect

    Pankratov, A.N.; Mushtakova, S.P.; Gribov, L.A.

    1986-03-01

    Available data on experimental study of the geometry of the diphenylamine molecule (I) in solution and in the crystal are fragmentary and not always reliable. Previously, they did a conformational analysis of molecule I using the atom-atom potential method. In order to refine the geometric parameters found for molecule I, optimization of its geometry is provided in the paper using the CNDO/2, INDO, MINDO/3 methods with the use of programs for the BESM-6 computer which are part of the VIKING program set. The angles of rotation for the phenyl rings relative to the CNC plane, the bond angles C/sub 2/N/sub 7/C/sub 8/ and C/sub 2/N/sub 7/H/sub 19/, and also the dihedral angle H/sub 19/N/sub 7/C/sub 8/C/sub 9/ were subjected to optimization. For any set of values for the indicated parameters, the bond angle C/sub 8/N/sub 7/H/sub 19/ is determined unambiguously. The results of the calculations are evidence that the MINDO/3 method is not suitable for optimization of the geometry for molecules of the indicated series; in particular, it leads to much too high a value for the CNC angles (135.9/sup 0/). The CNDO/2 method reproduces well the real value of the CNC angle (124.1/sup 0/) and confirms the known pyrimidal character of the nitrogen atom, the sum of the bond angles of which proved to be equal to 353.6/sup 0/. The calculation in the INDO approximation successfully gives the basic characteristics of the molecular geometry of (I); according to this approximation, the CNC angle is equal to 123.2/sup 0/, the CNH angles are equal to 118.0 and 118.8/sup 0/, the sum of the angles for the nitrogen atom is 360.0/sup 0/.

  13. Fatigue strength of a single lap joint SPR-bonded

    NASA Astrophysics Data System (ADS)

    Di Franco, G.; Fratini, L.; Pasta, A.

    2011-05-01

    In the last years, hybrid joints, meaning with this the joints which consist in combining a traditional mechanical joint to a layer of adhesive, are gradually attracting the attention of various sectors of the construction of vehicles and transportation industries, for their better performance compared to just mechanical joints (self-piercing riveting SPR, riveting, and so on) or just to bonded joints. The paper investigates the fatigue behavior of a single lap joint self-piercing riveted (SPR) and bonded throughout fatigue tests. The considered geometric configuration allowed the use of two rivets placed longitudinally; an epoxy resin was used as adhesive. In the first part of the work static characterization of the joints was carried out through tensile tests. Then fatigue tests were made with the application of different levels of load. The fatigue curves were also obtained at the varying the distance between the two rivets in order to better assess the joint strength for a given length of overlap.

  14. Mechanical and electrical characterization of BCB as a bond and seal material for cavities housing (RF)MEMS devices

    Microsoft Academic Search

    A Jourdain; P De Moor; K Baert; I De Wolf; H A C Tilmans

    2005-01-01

    This paper reports on the mechanical and electrical characterization of benzo-cyclo-butene (BCB) as a bonding and sealing material for 0-level packages (cavities) housing (RF-)MEMS devices. Shear strength and hermeticity of BCB-sealed cavities are experimentally investigated as functions of the geometrical parameters of the BCB sealing ring and the bonding conditions. The leak rate of BCB-sealed cavities strongly depends on the

  15. Optimal Investment Consumption Model with CIR Interest Rate

    Microsoft Academic Search

    Shuping Wan

    2007-01-01

    The optimal investment consumption problem for a single riskless bond, a zero-coupon bond and a risky stock modeled by the CIR interest process has been established. The investment objective is maximizing the utility of his consumption and terminal wealth. By the stochastic dynamic programming principle, the HJB equation for the optimal solution is given. In the case of constant relative

  16. Optimal Investment Consumption Model with Vasicek Interest Rate

    Microsoft Academic Search

    Dong Jiuying

    2007-01-01

    The optimal investment consumption problem for a single riskless bond, a zero-coupon bond and a risky stock modeled by the Vasicek interest process has been established. The investment objective is maximizing the utility of his consumption and terminal wealth. By the stochastic dynamic programming principle, the HJB equation for the optimal solution is given. In the case of constant relative

  17. Geometric estimates for the trace formula

    Microsoft Academic Search

    Werner Homann

    In order to study the asymptotic distribution of geometric or spectral data associated with quotients of a reductive group by a lattice, one needs a trace formula for test functions on that group with noncompact support. Arthur has proved a trace formula for compactly supported test functions on reductive groups of arbitrary rank. We show that the coarse geometric expansion

  18. Frequent Subgraph Retrieval in Geometric Graph Databases

    Microsoft Academic Search

    Sebastian Nowozin; Koji Tsuda

    2008-01-01

    Discovery of knowledge from geometric graph databases is of particular importance in chemistry and biology, be- cause chemical compounds and proteins are represented as graphs with 3D geometric coordinates. In such applica- tions, scientists are not interested in the statistics of the whole database. Instead they need information about a novel drug candidate or protein at hand, represented as a

  19. Thomas Young's contributions to geometrical optics.

    PubMed

    Atchison, David A; Charman, W Neil

    2011-07-01

    In addition to his work on physical optics, Thomas Young (1773-1829) made several contributions to geometrical optics, most of which received little recognition in his time or since. We describe and assess some of these contributions: Young's construction (the basis for much of his geometric work), paraxial refraction equations, oblique astigmatism and field curvature, and gradient-index optics. PMID:21214628

  20. Local Polyhedra and Geometric Graphs # Je# Erickson +

    E-print Network

    Erickson, Jeff

    Local Polyhedra and Geometric Graphs # Je# Erickson + University of Illinois at Urbana­Champaign je and nonconvex polyhedra. A geometric graph G is local if (1) the longest edge at every vertex v is only polyhedra in IR d , each with n vertices, can be computed in O(n log n) time, using a standard hierarchy

  1. Local Polyhedra and Geometric Graphs Jeff Erickson

    E-print Network

    Erickson, Jeff

    Local Polyhedra and Geometric Graphs Jeff Erickson University of Illinois at Urbana-Champaign jeffe and nonconvex polyhedra. A geometric graph G is local if (1) the longest edge at every vertex v is only polyhedra in IRd , each with n vertices, can be computed in O(n log n) time, using a standard hierarchy

  2. Local Polyhedra and Geometric Graphs # Je# Erickson +

    E-print Network

    Erickson, Jeff

    Local Polyhedra and Geometric Graphs # Je# Erickson + University of Illinois at Urbana­Champaign je form a local geometric graph. We show that any boolean combination of two local polyhedra in IR d # 3. Finally, we describe e#cient algorithms for computing Minkowski sums of local polyhedra in two

  3. Local Polyhedra and Geometric Graphs Jeff Erickson

    E-print Network

    Erickson, Jeff

    Local Polyhedra and Geometric Graphs Jeff Erickson University of Illinois at Urbana-Champaign jeffe form a local geometric graph. We show that any boolean combination of two local polyhedra in IRd , each. Finally, we describe efficient algorithms for computing Minkowski sums of local polyhedra in two and three

  4. The geometric semantics of algebraic quantum mechanics

    E-print Network

    John Alex Cruz Morales; Boris Zilber

    2014-10-27

    In this paper we will present an ongoing project which aims to use model theory as a suitable mathematical setting for studying the formalism of quantum mechanics. We will argue that this approach provides a geometric semantics for such formalism by means of establishing a (non-commutative) duality between certain algebraic and geometric objects.

  5. GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES

    E-print Network

    Cambridge, University of

    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

  6. Monotonicity and its analytic and geometric implications

    PubMed Central

    Colding, Tobias Holck; Minicozzi, William P.

    2013-01-01

    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.

  7. Geometric pattern generation by sewing machine

    Microsoft Academic Search

    Yasumichi Hasegawa; Kihachi Takeichi; Tsuyoshi Matsuo

    1996-01-01

    The authors propose a method for geometric pattern generation by using a sewing machine. Sewing machine equipment are mainly composed of mathematical models which may be constructed by computer programs or switching and other electric circuits. These models are called commutative linear representation systems and this method is a very different graphic generation scheme. Geometric pattern generation is a trial

  8. Mobile robot localization by tracking geometric beacons

    Microsoft Academic Search

    John J. Leonard; Hugh F. Durrant-Whyte

    1991-01-01

    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,

  9. Dynamic Geometric Graph Processes: Adjacency Operator Approach

    E-print Network

    Schott, René - Institut de Mathématiques ?lie Cartan, Université Henri Poincaré

    Dynamic Geometric Graph Processes: Adjacency Operator Approach Ren´e Schott and G. Stacey Staples's connectivity. Ad hoc networks are modeled by addition-deletion processes. Considering a geometric graph on n graph process is then associated with a random walk on a hypercube of appropriate dimension induced

  10. Early Sex Differences in Weighting Geometric Cues

    ERIC Educational Resources Information Center

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

    2011-01-01

    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

  11. Surface Reflection: Physical and Geometrical Perspectives

    Microsoft Academic Search

    Shree K. Nayar; Katsushi Ikeuchi; Takeo Kanade

    1991-01-01

    Reflectance models based on physical optics and geometrical optics are studied. Specifically, the authors consider the Beckmann-Spizzichino (physical optics) model and the Torrance-Sparrow (geometrical optics) model. These two models were chosen because they have been reported to fit experimental data well. Each model is described in detail, and the conditions that determine the validity of the model are clearly stated.

  12. Wafer level glass frit bonding for MEMS hermetic packaging

    Microsoft Academic Search

    Jin-Sheng Chang; Jing-Yuan Lin; Shu-Ching Ho; Yao-Jung Lee

    2010-01-01

    Wafer level bonding is widely applied in the manufacture of sensors, actuators and CMOS MEMS. Bonding technology includes direct bonding, anodic bonding, eutectic bonding, adhesive bonding and glass frit bonding. Glass frit bonding has pattern-able, excellent sealing performances, high bonding strength, don't need apply any voltage during bonding process and less CTE mismatch compared to glass and silicon is more

  13. Chemically bonded ceramic matrix composites: Densification and conversion to diffusion bonding

    SciTech Connect

    Johnson, B.R.; Guelguen, M.A.; Kriven, W.M. [Univ. of Illinois, Urbana, IL (United States). Dept. of Materials Science and Engineering

    1995-10-01

    Chemically bonded ceramics appear to be a promising alternative route for near-net shape fabrication of multi-phase ceramic matrix composites (CMC`s). The hydraulic (and refractory) properties of fine mono-calcium aluminate (CaAl{sub 2}O{sub 4}) powders were used as the chemically bonding matrix phase, while calcia stabilized zirconia powders were the second phase material. Samples containing up to 70 wt% (55 vol%) zirconia have been successfully compacted and sintered. Various processing techniques were evaluated. Processing was optimized based on material properties, dilatometry and simultaneous thermal analysis (DTA/TGA). The physical characteristics of this novel CMC were characterized by hardness, density, and fracture toughness testing. Microstructures were evaluated by SEM and phase identification was verified using XRD.

  14. Probing dark energy with the shear-ratio geometric test

    E-print Network

    A. N. Taylor; T. D. Kitching; D. J. Bacon; A. F. Heavens

    2006-11-15

    We adapt the Jain--Taylor (2003) shear-ratio geometric lensing method to measure the dark energy equation of state, and its time derivative from dark matter haloes in cosmologies with arbitrary spatial curvature. The full shear-ratio covariance matrix is calculated for lensed sources, including the intervening large-scale structure and photometric redshift errors as additional sources of noise, and a maximum likelihood method for applying the test is presented. Combining with the expected results from the CMB we design an optimal survey for probing dark energy. A targeted survey imaging 60 of the largest clusters in a hemisphere with 5-band optical photometric redshifts to a median galaxy depth of zm=0.9 could measure w0 to a marginal 1-sigma error of $\\Delta$w0=0.5. We marginalize over all other parameters including wa, where the equation of state is parameterized in terms of scale factor a as w(a)=w0+wa(1-a). For higher accuracy a large-scale photometric redshift survey is required. Such a near-future 5-band survey covering 10,000 square degrees to z_m=0.7 could measure w0 to $\\Delta$w0=0.075 and $\\Delta$wa=0.33. A stronger combined constraint is measured at a pivot redshift zp=0.27 of $\\Delta$w(zp)=0.0298. We compare and combine the geometric test with the cosmological and dark energy parameters measured from planned Baryon Acoustic Oscillation (BAO) and supernova Type Ia experiments, and find that the geometric test results combine with a significant reduction in errors due to different degeneracies. A combination of geometric lensing, CMB and BAO experiments could achieve a pivot redshift constraint of $\\Delta$w(zp)=0.020 at zp=0.62. Simple relations are presented that show how our lensing results can be scaled to other telescope classes and survey parameters.

  15. A geometric morphometric assessment of the optic cup in glaucoma.

    PubMed

    Sanfilippo, Paul G; Cardini, Andrea; Sigal, Ian A; Ruddle, Jonathan B; Chua, Brian E; Hewitt, Alex W; Mackey, David A

    2010-09-01

    The morphologic appearance of the optic disc is of interest in glaucoma. In contrast to descriptive classification systems that are currently used, a quantitative approach to the analysis of optic disc morphology is required. Our goal was to determine the optimal method for quantifying optic cup shape by comparing traditional (ovality, form-factor and neuroretinal rim (NRR) width ratio) and geometric morphometric approaches. Left optic disc stereophotographs of 160 (80 normal and 80 glaucomatous (stratified by severity)) subjects were examined. The optic cup margins were stereoscopically delineated with a custom tracing system and saved as a series of discrete points. The geometric morphometric methods of elliptic Fourier analysis (EFA) and sliding semi-landmark analysis (SSLA) were used to eliminate variation unrelated to shape (e.g. size) and yield a series of shape variables. Differences in optic cup shape between normal and glaucoma groups were investigated. Discriminant functions were computed and the sensitivity and specificity of each technique determined. Receiver operator characteristic (ROC) curves were calculated for all methods and evaluated in their potential to discriminate between normal and glaucomatous eyes based on the shape variables. All geometric morphometric methods revealed differences between normal and glaucomatous eyes in optic cup shape, in addition to the traditional parameters of ovality, form-factor and NRR width ratio (p<0.0005). SSLA (minimum bending energy criterion--18 points) had the best sensitivity (83%) and area under the curve (AUC) (0.91). EFA (72 points) performed similarly well (74%, 0.89) as did the set of traditional shape-based variables (76%, 0.86). This study demonstrated that a geometric morphometric approach for discriminating between normal and glaucomatous eyes in optic cup shape is superior to that provided by traditional single parameter shape measures. Such analytical techniques could be incorporated into future automated optic disc screening modalities. PMID:20599965

  16. Temperature effects on mixed state geometric phase

    E-print Network

    A. T. Rezakhani; P. Zanardi

    2006-05-31

    Geometric phase of an open quantum system that is interacting with a thermal environment (bath) is studied through some simple examples. The system is considered to be a simple spin-half particle which is weakly coupled to the bath. It is seen that even in this regime the geometric phase can vary with temperature. In addition, we also consider the system under an adiabatically time-varying magnetic field which is weakly coupled to the bath. An important feature of this model is that it reveals existence of a temperature-scale in which adiabaticity condition is preserved and beyond which the geometric phase is varying quite rapidly with temperature. This temperature is exactly the one in which the geometric phase vanishes. This analysis has some implications in realistic implementations of geometric quantum computation.

  17. Ultrasonic phosphate bonding of nanoparticles.

    PubMed

    Bassett, David C; Merle, Geraldine; Lennox, Bruce; Rabiei, Reza; Barthelat, Franois; Grover, Liam M; Barralet, Jake E

    2013-11-01

    Low intensity ultrasound-induced radicals interact with surface adsorbed orthophosphate to bond nanoparticles with high mechanical strength and surface area. Dissimilar materials could be bonded to form robust metallic, ceramic, and organic composite microparticles. 3D nanostructures of a hydrated and amorphous electrocatalyst with carbon nanotubes were also constructed which exceeded the resistance-limited efficiency of 2D electrodes. PMID:23893468

  18. Optimal Portfolio with Consumption Choice under Jump-Diffusion Process

    Microsoft Academic Search

    Shuping Wan

    2006-01-01

    The optimal portfolio problem for a single riskless bond and risky stock modeled by jump-diffusion process has been established. The investment objective is maximizing the utility of his consumption and terminal wealth. The problem is formulated as a stochastic optimal control problem. The verification theorem and HJB equation for the optimal trading strategies are given by stochastic optimal control theory.

  19. Efficient hyperspectral image segmentation using geometric active contour formulation

    NASA Astrophysics Data System (ADS)

    Albalooshi, Fatema A.; Sidike, Paheding; Asari, Vijayan K.

    2014-10-01

    In this paper, we present a new formulation of geometric active contours that embeds the local hyperspectral image information for an accurate object region and boundary extraction. We exploit self-organizing map (SOM) unsupervised neural network to train our model. The segmentation process is achieved by the construction of a level set cost functional, in which, the dynamic variable is the best matching unit (BMU) coming from SOM map. In addition, we use Gaussian filtering to discipline the deviation of the level set functional from a signed distance function and this actually helps to get rid of the re-initialization step that is computationally expensive. By using the properties of the collective computational ability and energy convergence capability of the active control models (ACM) energy functional, our method optimizes the geometric ACM energy functional with lower computational time and smoother level set function. The proposed algorithm starts with feature extraction from raw hyperspectral images. In this step, the principal component analysis (PCA) transformation is employed, and this actually helps in reducing dimensionality and selecting best sets of the significant spectral bands. Then the modified geometric level set functional based ACM is applied on the optimal number of spectral bands determined by the PCA. By introducing local significant spectral band information, our proposed method is capable to force the level set functional to be close to a signed distance function, and therefore considerably remove the need of the expensive re-initialization procedure. To verify the effectiveness of the proposed technique, we use real-life hyperspectral images and test our algorithm in varying textural regions. This framework can be easily adapted to different applications for object segmentation in aerial hyperspectral imagery.

  20. A geometric approach to shape from defocus.

    PubMed

    Favaro, Paolo; Soatto, Stefano

    2005-03-01

    We introduce a novel approach to shape from defocus, i.e., the problem of inferring the three-dimensional (3D) geometry of a scene from a collection of defocused images. Typically, in shape from defocus, the task of extracting geometry also requires deblurring the given images. A common approach to bypass this task relies on approximating the scene locally by a plane parallel to the image (the so-called equifocal assumption). We show that this approximation is indeed not necessary, as one can estimate 3D geometry while avoiding deblurring without strong assumptions on the scene. Solving the problem of shape from defocus requires modeling how light interacts with the optics before reaching the imaging surface. This interaction is described by the so-called point spread function (PSF). When the form of the PSF is known, we propose an optimal method to infer 3D geometry from defocused images that involves computing orthogonal operators which are regularized via functional singular value decomposition. When the form of the PSF is unknown, we propose a simple and efficient method that first learns a set of projection operators from blurred images and then uses these operators to estimate the 3D geometry of the scene from novel blurred images. Our experiments on both real and synthetic images show that the performance of the algorithm is relatively insensitive to the form of the PSF. Our general approach is to minimize the Euclidean norm of the difference between the estimated images and the observed images. The method is geometric in that we reduce the minimization to performing projections onto linear subspaces, by using inner product structures on both infinite and finite-dimensional Hilbert spaces. Both proposed algorithms involve only simple matrix-vector multiplications which can be implemented in real-time. PMID:15747795

  1. Geometric Quantization and Foliation Reduction

    NASA Astrophysics Data System (ADS)

    Skerritt, Paul

    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.

  2. Social bonding: regulation by neuropeptides

    PubMed Central

    Lieberwirth, Claudia; Wang, Zuoxin

    2014-01-01

    Affiliative social relationships (e.g., among spouses, family members, and friends) play an essential role in human society. These relationships affect psychological, physiological, and behavioral functions. As positive and enduring bonds are critical for the overall well-being of humans, it is not surprising that considerable effort has been made to study the neurobiological mechanisms that underlie social bonding behaviors. The present review details the involvement of the nonapeptides, oxytocin (OT), and arginine vasopressin (AVP), in the regulation of social bonding in mammals including humans. In particular, we will discuss the role of OT and AVP in the formation of social bonds between partners of a mating pair as well as between parents and their offspring. Furthermore, the role of OT and AVP in the formation of interpersonal bonding involving trust is also discussed. PMID:25009457

  3. Quantum Confinement in Hydrogen Bond

    E-print Network

    Carlos da Silva dos Santos; Elso Drigo Filho; Regina Maria Ricotta

    2015-02-09

    In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.

  4. Bonding and Integration Technologies for Silicon Carbide Based Injector Components

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2008-01-01

    Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding, titanium interlayers (PVD and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness (10, 20, and 50 microns), processing time and temperature, and cooling rates were investigated. Microprobe analysis was used to identify the phases in the bonded region. For bonds that were not fully reacted an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner titanium interlayers and/or longer processing times resulted in stable and compatible phases that did not contribute to microcracking and resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Non-destructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

  5. Excimer surface treatment to enhance bonding in coated steels

    NASA Astrophysics Data System (ADS)

    Mueller, Robert E.; Olfert, M.; Duley, Walter W.; North, T.; Hood, J.; Sakai, D.

    1996-04-01

    Zinc coated sheet steel in the form of temper rolled galvanize and galvanneal are used extensively in the automotive industry. Through a process of excimer laser surface treatment, we have succeeded in significantly enhancing the adhesion characteristics of these coated steels. The laser treatment is performed by scanning focused excimer laser radiation in a raster pattern over the surface to be bonded. Adhesion tests have been carried out in the form of T peel tests, using either a hot melt nylon resin or an epoxy as the adhesive. An increase in bond strength was observed over a substantial range of surface treatment conditions. The largest improvement observed was more than a factor of three greater than for untreated surfaces. With the improved surface condition, the bond strength became limited by the cohesive strength of the adhesive. The physical structure and chemical composition of the parent and excimer treated surfaces have been examined using scanning electron microscopy and X-ray photoelectron spectroscopy to determine the nature and extent of the changes caused by the surface treatment. The effects of the observed changes on the bonding performance will be discussed. Surfaces have been processed under an inert atmosphere to isolate the effects of physical surface modification and surface oxidation. An attempt will be made to correlate the surface changes with the bonding characteristics and thereby indicate which changes are most beneficial. The ultimate goal is to optimize the surface condition for bonding and maximize the process rate.

  6. Halogen bonding (X-bonding): A biological perspective

    PubMed Central

    Scholfield, Matthew R; Zanden, Crystal M Vander; Carter, Megan; Ho, P Shing

    2013-01-01

    The concept of the halogen bond (or X-bond) has become recognized as contributing significantly to the specificity in recognition of a large class of halogenated compounds. The interaction is most easily understood as primarily an electrostatically driven molecular interaction, where an electropositive crown, or ?-hole, serves as a Lewis acid to attract a variety of electron-rich Lewis bases, in analogous fashion to a classic hydrogen bonding (H-bond) interaction. We present here a broad overview of X-bonds from the perspective of a biologist who may not be familiar with this recently rediscovered class of interactions and, consequently, may be interested in how they can be applied as a highly directional and specific component of the molecular toolbox. This overview includes a discussion for where X-bonds are found in biomolecular structures, and how their structureenergy relationships are studied experimentally and modeled computationally. In total, our understanding of these basic concepts will allow X-bonds to be incorporated into strategies for the rational design of new halogenated inhibitors against biomolecular targets or toward molecular engineering of new biological-based materials. PMID:23225628

  7. Geometrical aspects of quantum spaces

    SciTech Connect

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

    1996-05-11

    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.

  8. Geometric algebra and particle dynamics

    E-print Network

    Jose B. Almeida

    2005-07-12

    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.

  9. Geometrical effects in protein nucleation.

    PubMed

    Kozak, John J; Basios, V; Nicolis, G

    2003-09-01

    To understand the importance of protein anisotropy and the influence of translational and rotational degrees of freedom on the nucleation event, we calculate numerically-exact values for the mean encounter time for two non-spherically symmetric molecules to form a cluster, regarded here as a precursor to nucleation. A lattice model is formulated in which the asymmetry of the molecules is accounted for by representing each as a 'dimer' in the sense that each molecule is specified to occupy two lattice sites. The two dimers undergo simultaneously translation and/or rotation, and the mean times for their encounter are determined. Exact numerical results are obtained for small lattices via application of the theory of finite Markov processes, and the results corroborated and extended to large lattices by performing Monte Carlo simulations. These calculations allow one to understand in a detailed way the interplay among geometrical anisotropy, translational and internal (rotational) degrees of freedom and system size in influencing the seminal nucleation event. PMID:14499913

  10. Geometric reasoning about assembly tools

    SciTech Connect

    Wilson, R.H.

    1997-01-01

    Planning for assembly requires reasoning about various tools used by humans, robots, or other automation to manipulate, attach, and test parts and subassemblies. This paper presents a general framework to represent and reason about geometric accessibility issues for a wide variety of such assembly tools. Central to the framework is a use volume encoding a minimum space that must be free in an assembly state to apply a given tool, and placement constraints on where that volume must be placed relative to the parts on which the tool acts. Determining whether a tool can be applied in a given assembly state is then reduced to an instance of the FINDPLACE problem. In addition, the author presents more efficient methods to integrate the framework into assembly planning. For tools that are applied either before or after their target parts are mated, one method pre-processes a single tool application for all possible states of assembly of a product in polynomial time, reducing all later state-tool queries to evaluations of a simple expression. For tools applied after their target parts are mated, a complementary method guarantees polynomial-time assembly planning. The author presents a wide variety of tools that can be described adequately using the approach, and surveys tool catalogs to determine coverage of standard tools. Finally, the author describes an implementation of the approach in an assembly planning system and experiments with a library of over one hundred manual and robotic tools and several complex assemblies.

  11. Strained-bond semiconductors

    NASA Astrophysics Data System (ADS)

    Dow, John D.

    1994-05-01

    Theories of strained-bond semiconductors and superconductors have been developed that promise to have significant impact on future electronic devices of interest to the Air Force. These include: (1) development of a theory of high-temperature superconductivity based on the idea of strained-layer superlattices, (2) elucidation of the physics of doping in Type-2 semiconductor superlattices, which is now central to the development of high-speed field-effect transistors, (3) a theory of dimerization and reconstruction on (001) semiconductor surfaces, (4) theory of Mobius transforms as applied to physics and remote sensing, (5) new understanding of how defects affect the vibrational properties of semiconductors, (6) new methods of efficiently computing the trajectories of atoms in semiconductors by a priori molecular dynamics, (7) elucidation of the criteria affecting quantum-well luminescence from Si, (8) models of the effects of vacancies in large-gap Al(x)Ga(1-x)N alloys, (9) physics of rare-earth-doped silicon, (10) models of Co adsorption to silicon surfaces, (11) theories of how defects affect the properties of large band-gap superlattices, and (12) models of the effects of electronic structure on the properties of semiconductors.

  12. Analytical and experimental investigation of vibratory response in adhesively bonded and composite structures

    SciTech Connect

    Nameung Kim.

    1991-01-01

    This thesis investigates the dynamic properties of adhesively bonded and composite beams. A preliminary set of experiments was conducted to qualify the damping in an overlap bonded beam. The results showed inconsistent values of damping and large scatter. Later it was found that damping is sensitive to small pre-deformation of the beam. To investigate this behavior, a finite element approach is developed for calculating modal parameters of adhesively bonded and composite beams. This approach uses special elements to represent composite and joint elements, and the modal strain energy method for estimating damping. The special element is derived using a generalization of the shape function method. The resulting element is well-suited for geometrically complex systems, such as a warped adhesively bonded or a composite beam. The modal strain energy approach for estimating damping is computationally efficient and provides an accurate estimate for lightly damped systems. Results obtained using this approach on sandwich beams compare well with published results.

  13. "Flex-activated" mechanophores: using polymer mechanochemistry to direct bond bending activation.

    PubMed

    Larsen, Michael B; Boydston, Andrew J

    2013-06-01

    We describe studies in mechanochemical transduction that probe the activation of bonds orthogonal to an elongated polymer main chain. Compression of mechanophore-cross-linked materials resulted in the release of small molecules via cleavage of covalent bonds that were not integral components of the elongated polymer segments. The reactivity is proposed to arise from the distribution of force through the cross-linking units of the polymer network and subsequent bond bending motions that are consistent with the geometric changes in the overall reaction. This departure from contemporary polymer mechanochemistry, in which activation is achieved primarily by force-induced bond elongation, is a first step toward mechanophores capable of releasing side-chain functionalities without inherently compromising the overall macromolecular architecture. PMID:23687904

  14. Optimization of a particle optical system in a mutilprocessor environment

    Microsoft Academic Search

    Lei Wei; Yin Hanchun; Wang Baoping; Tong Linsu

    2002-01-01

    In the design of a charged particle optical system, many geometrical and electric parameters have to be optimized to improve the performance characteristics. In every optimization cycle, the electromagnetic field and particle trajectories have to be calculated. Therefore, the optimization of a charged particle optical system is limited by the computer resources seriously. Apart from this, numerical errors of calculation

  15. Geometric frustration in compositionally modulated ferroelectrics.

    PubMed

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

    2011-02-24

    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

  16. On geometric factors for neutral particle analyzers

    SciTech Connect

    Stagner, L.; Heidbrink, W. W. [University of California-Irvine, Irvine, California 92697-4575 (United States)

    2014-11-15

    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), 511 (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.

  17. Results in computational geometry: Geometric embeddings and query-retrieval problems. Technical report

    SciTech Connect

    Hansen, M.D.

    1990-11-01

    Many fundamental questions in computational geometry arise from the consideration of distributions of points in euclidean space. This thesis explores two important areas of computational geometry in this setting: geometric embeddings and query-retrieval problems. Each area is addressed in a separate part of the thesis. Part I examines the geometric embedding problem for many of the graphs which are important in the study of parallel computation. Part II of this thesis examines query-retrieval problems concerning distributions of points in euclidean space. In this part, we describe a new technique for solving a variety of query-retrieval problems in optimal time with optimal or near optimal space. Our compaction technique incorporates planar separators, filtering search, and the probabilistic method for discrepancy problems.

  18. Optimization of the intensity enhancement in plasmonic nanoantennas

    NASA Astrophysics Data System (ADS)

    Hildebrandt, Andre; Reichelt, Matthias; Meier, Torsten; Frstner, Jens

    2012-09-01

    We design the geometrical shape of plasmonic nanostructures to achieve field patterns with desired properties. For this, we combine Maxwell simulations and automatic optimization techniques. By allowing variations of the geometrical shape, which can be based on either boxes or arbitrary polygons, we maximize the desired objective.

  19. Intensity modulation under geometrical uncertainty: a deconvolution approach to robust fluence

    NASA Astrophysics Data System (ADS)

    Fan, Yankhua; Nath, Ravinder

    2010-07-01

    A deconvolution algorithm has been developed to obtain robust fluence for external beam radiation treatment under geometrical uncertainties. Usually, the geometrical uncertainty is incorporated in the dose optimization process for inverse treatment planning to determine the additional intensity modulation of the beam to counter the geometrical uncertainty. Most of these approaches rely on dose convolution which is subject to the error caused by patient surface curvature and internal inhomogeneity. In this work, based on an 1D deconvolution algorithm developed by Ulmer and Kaissl, a fluence-deconvolution approach was developed to obtain robust fluence through the deconvolution of the nominal static one given by any treatment planning system. It incorporates the geometrical uncertainty outside the dose optimization procedure and therefore avoids the error of dose convolution. Robust fluences were calculated for a 4 4 cm flat field, a prostate IMRT and a head and neck IMRT plan in a commercial treatment planning system. The corresponding doses were simulated for 30 fractions with the random Gaussian distribution of the iso-centers showing good agreement with the nominal static doses. The feasibility of this deconvolution approach for clinical IMRT planning has been demonstrated. Because it is separated from the optimization procedure, this method is more flexible and easier to integrate into different existing treatment planning systems to obtain robust fluence.

  20. Geometric flows and black hole entropy

    E-print Network

    Joseph Samuel; Sutirtha Roy Chowdhury

    2007-11-03

    Perelman has given a gradient formulation for the Ricci flow, introducing an ``entropy function'' which increases monotonically along the flow.We pursue a thermodynamic analogy and apply Ricci flow ideas to general relativity. We investigate whether Perelman's entropy is related to (Bekenstein-Hawking)geometric entropy as familiar from black hole thermodynamics. From a study of the fixed points of the flow we conclude that Perelman entropy is not connected to geometric entropy. However, we notice that there is a very similar flow which DOES appear to be connected to geometric entropy. The new flow may find applications in black hole physics suggesting for instance, new approaches to the Penrose inequality.

  1. Hydrogen Bonded Arrays: The Power of Multiple Hydrogen Bonds

    SciTech Connect

    Shokri, Alireza; Schmidt, Jacob C.; Wang, Xue B.; Kass, Steven R.

    2012-02-01

    Hydrogen bond interactions in small covalent model compounds (i.e. deprotonated polyhydroxy alcohols) were measured by negative ion photoelectron spectroscopy. The experimentally determined vertical and adiabatic electron detachment energies for (HOCH2CH2)2CHO (2a), (HOCH2CH2) 3CO (3a) and (HOCH2CH2CH(OH)CH2)3CO (4a) reveal that hydrogen-bonded networks can provide enormous stabilizations, and that a single charge center not only can be stabilized by up to 3 hydrogen bonds but it can increase the interaction energy between non-charged OH groups by 5.8 kcal mol1 or more per hydrogen bond. This can lead to pKa values that are very different than in water, and provide some of the impetus for catalytic processes.

  2. Fabrication of nanoporous gold and the application for substrate bonding at low temperature

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Shan; Lin, Yu-Ching; Gessner, Thomas; Esashi, Masayoshi

    2015-03-01

    MEMS-compatible fabrication of nanoporous gold and the application for low temperature bonding are demonstrated. A cyanide-free electroplating solution is prepared for the AuSn alloy deposition. To investigate the influence of electroplating on AuSn alloy and nanoporous gold, different plating parameters and various sizes of patterns are designed and discussed. The optimized electroplating condition realizes 40 to 720 m line width patterns fabricated on the same substrate. Low temperature substrate bonding at 200 C is achieved with nanoporous gold and gold film, which has shear bond strength more than 60 MPa. The fracture inspection of the bonded area after shear tests verifies the bonding success. This study gives a study for fabricating on-chip nanostructure, and the results indicate the high feasibility of nanoporous gold for low temperature substrate bonding.

  3. Shape and layout optimization of structural systems and optimality criteria methods

    NASA Astrophysics Data System (ADS)

    Rozvany, G. I. N.

    Consideration is given to aims, problems, and methods of structural optimization; continuum-based optimality criteria (COC) methods; optimal layout theory; layout optimization using the iterative COC algorithm; simple solutions for optimal layout of trusses; CAD-integrated structural topology and design optimization; structural optimization of linearly elastic structures using a homogenization method; and mixed elements in shape optimal design of structures based on global criteria. Attention is also given to shape optimal design of axisymmetric shell structures, applications of artificial neural nets in structural mechanics, mathematical programming techniques for shape optimization of skeleton structures; exact and approximate static structural reanalysis; shape optimization with FEM; sensitivity analysis with BEM; and the theorems of structural and geometric variation for engineering structures. (No individual items are abstracted in this volume)

  4. Determination of optimum geometrical parameters of stators of turbine expansion engines

    SciTech Connect

    Sherstyuk, A.N.; Davydov, A.B.; Rozenoer, T.M.; Vasil'ev, M.Y.

    1986-05-01

    The efficiency of the stators of centripetal radial turbine expansion engines, characterized by the small dimensions of the flow section have been studied. The study is extended to obtain data on the variation of the losses in relation to the relative geometrical parameters. Investigations have been carried out into the level of the total losses in the wing-shaped small vane stator and its geometrical parameters are optimized. The processing method accepted for the calculations is based on the equations of the unidimensional theory of the gas flows which gives sufficiently reliable results.

  5. Method for vacuum fusion bonding

    DOEpatents

    Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

    2001-01-01

    An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

  6. Fusion bonding and alignment fixture

    DOEpatents

    Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

    2000-01-01

    An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all the components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

  7. Method of bonding

    DOEpatents

    Saller, deceased, Henry A. (late of Columbus, OH); Hodge, Edwin S. (Columbus, OH); Paprocki, Stanley J. (Columbus, OH); Dayton, Russell W. (Columbus, OH)

    1987-12-01

    1. A method of making a fuel-containing structure for nuclear reactors, comprising providing an assembly comprising a plurality of fuel units; each fuel unit consisting of a core plate containing thermal-neutron-fissionable material, sheets of cladding metal on its bottom and top surfaces, said cladding sheets being of greater width and length than said core plates whereby recesses are formed at the ends and sides of said core plate, and end pieces and first side pieces of cladding metal of the same thickness as the core plate positioned in said recesses, the assembly further comprising a plurality of second side pieces of cladding metal engaging the cladding sheets so as to space the fuel units from one another, and a plurality of filler plates of an acid-dissolvable nonresilient material whose melting point is above 2000.degree. F., each filler plate being arranged between a pair of said second side pieces and the cladding plates of two adjacent fuel units, the filler plates having the same thickness as the second side pieces; the method further comprising enclosing the entire assembly in an envelope; evacuating the interior of the entire assembly through said envelope; applying inert gas under a pressure of about 10,000 psi to the outside of said envelope while at the same time heating the assembly to a temperature above the flow point of the cladding metal but below the melting point of any material of the assembly, whereby the envelope is pressed against the assembly and integral bonds are formed between plates, sheets, first side pieces, and end pieces and between the sheets and the second side pieces; slowly cooling the assembly to room temperature; removing the envelope; and dissolving the filler plates without attacking the cladding metal.

  8. Nanoleakage patterns of four dentin bonding systems

    Microsoft Academic Search

    H. Li; M. F. Burrow; M. J. Tyas

    2000-01-01

    Objectives: The purpose of this study was to evaluate the nanoleakage patterns of four dentin bonding systems.Methods: The dentin bonding systems used in this study were: Single Bond, One Coat Bond, Prime & Bond NT\\/Non Rinse Conditioner (NRC), and PermaQuik. Flat occlusal dentin surfaces from extracted human molars were finished with wet 600-grit silicon carbide paper, and bonded with one

  9. Spontaneous direct bonding of thick silicon nitride

    NASA Astrophysics Data System (ADS)

    Snchez, S.; Gui, C.; Elwenspoek, M.

    1997-09-01

    Wafers with 0960-1317/7/3/007/img1 LPCVD silicon-rich nitride layers have been successfully direct bonded to silicon-rich nitride and boron-doped silicon surfaces. A chemical - mechanical polishing treatment was necessary to reduce the surface roughness of the nitride before bonding. The measured surface energies of the room-temperature bond were comparable to values found for Si - Si hydrophilic bonding. A mechanism similar to this bonding is suggested for silicon nitride bonding.

  10. Optimal Velocity Profile Generation for Given Acceleration Limits: Theoretical Analysis

    E-print Network

    Tsiotras, Panagiotis

    ]. The path in these references is designed using geometric principles, and an intuitively "optimal" velocity, and fn is the normal (centripetal) force such that the vehicle tracks the prescribed path. Consider now

  11. 6.253 Convex Analysis and Optimization, Spring 2010

    E-print Network

    Bertsekas, Dimitri

    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 ...

  12. Rapid and irreversible reduction of protein disulfide bonds.

    PubMed

    Lu, Bao-Yuan; Chang, Jui-Yoa

    2010-10-01

    This report describes the development of a method that enables a rapid (less than 20s), quantitative, and irreversible reduction and inactivation of disulfide-containing proteins at room temperature (20 to 25 degrees C). The formula comprises the ingredients of optimized concentrations of denaturant, reductant, and hydroxide ion. The novelty of this formula is the application of a potent hydroxide ion in the concoction. The component of hydroxide ion serves two major functions. (1) It accelerates the cleavage of disulfide bonds mediated by the reducing agent and denaturant, leading to an instant and quantitative reduction of disulfide proteins. (2) It triggers a rapid covalent destruction of sulfhydryl groups and disulfide bonds via the mechanism of base-catalyzed beta-elimination, thus leading to the irreversible and permanent abolition of disulfide bonds. The usefulness of this formula has been demonstrated here with the effective and rapid reduction of numerous highly stable disulfide-containing proteins, including cardiotoxin and prion aggregates. PMID:20488157

  13. Ionic Bonding (www.ia.usu.edu.)

    NSDL National Science Digital Library

    Mrs Camp

    2007-11-28

    Atoms can join together to form compounds. There are various ways atoms can bond which are determined by the types of elements that are involved in bonding. You are going to investigate why atoms bond and one of the ways they can bond together. Please take out your periodic tables. Bonding is not haphazard. There are definite reasons and ways that atoms can bond. Click on the bold question \\"Why Bond?\\" to find the reason why atoms join other atoms to form a compound. Why Bond? According to your periodic table, what type of elements are Na and Mg? According to ...

  14. Method to improve commercial bonded SOI material

    DOEpatents

    Maris, Humphrey John (Barrington, RI); Sadana, Devendra Kumar (Pleasantville, NY)

    2000-07-11

    A method of improving the bonding characteristics of a previously bonded silicon on insulator (SOI) structure is provided. The improvement in the bonding characteristics is achieved in the present invention by, optionally, forming an oxide cap layer on the silicon surface of the bonded SOI structure and then annealing either the uncapped or oxide capped structure in a slightly oxidizing ambient at temperatures greater than 1200.degree. C. Also provided herein is a method for detecting the bonding characteristics of previously bonded SOI structures. According to this aspect of the present invention, a pico-second laser pulse technique is employed to determine the bonding imperfections of previously bonded SOI structures.

  15. Geometric symmetries in superfluid vortex dynamics

    SciTech Connect

    Kozik, Evgeny [Institute for Theoretical Physics, ETH Zurich, CH-8093 Zurich (Switzerland); Svistunov, Boris [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Russian Research Center 'Kurchatov Institute', 123182 Moscow (Russian Federation)

    2010-10-01

    Dynamics of quantized vortex lines in a superfluid feature symmetries associated with the geometric character of the complex-valued field, w(z)=x(z)+iy(z), describing the instant shape of the line. Along with a natural set of Noether's constants of motion, which - apart from their rather specific expressions in terms of w(z) - are nothing but components of the total linear and angular momenta of the fluid, the geometric symmetry brings about crucial consequences for kinetics of distortion waves on the vortex lines, the Kelvin waves. It is the geometric symmetry that renders Kelvin-wave cascade local in the wave-number space. Similar considerations apply to other systems with purely geometric degrees of freedom.

  16. Curve sampling and geometric conditional simulation

    E-print Network

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

    2008-01-01

    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 ...

  17. LIE ALGEBROID GENERALIZATION OF GEOMETRIC MECHANICS

    Microsoft Academic Search

    E F. CARI; EDUARDO MARTINEZ

    Some recent progress in the geometric foundations of mechanics in Lie algebroids, and in particular in Lagrangian mechanics, are reported. We also develop the variational approach to Classical mechanics in Lie algebroids.

  18. Curves and Surfaces In Geometric Modeling

    E-print Network

    Gallier, Jean

    Curves and Surfaces In Geometric Modeling: Theory And Algorithms Jean Gallier Department@saul.cis.upenn.edu c Jean Gallier Please, do not reproduce without permission of the author November 8, 2008 #12;ii #12

  19. Curves and Surfaces In Geometric Modeling

    E-print Network

    Gallier, Jean

    #12;#12;Curves and Surfaces In Geometric Modeling: Theory And Algorithms Jean Gallier Department@cis.upenn.edu c Jean Gallier Please, do not reproduce without permission of the author June 8, 2013 #12;ii #12;iii

  20. The perception of geometrical structure from congruence

    NASA Technical Reports Server (NTRS)

    Lappin, Joseph S.; Wason, Thomas D.

    1989-01-01

    The principle function of vision is to measure the environment. As demonstrated by the coordination of motor actions with the positions and trajectories of moving objects in cluttered environments and by rapid recognition of solid objects in varying contexts from changing perspectives, vision provides real-time information about the geometrical structure and location of environmental objects and events. The geometric information provided by 2-D spatial displays is examined. It is proposed that the geometry of this information is best understood not within the traditional framework of perspective trigonometry, but in terms of the structure of qualitative relations defined by congruences among intrinsic geometric relations in images of surfaces. The basic concepts of this geometrical theory are outlined.

  1. Evolution of Geometrical Reasoning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Aaron Sloman

    E-print Network

    Sloman, Aaron

    Human engineering lags behind and jumps ahead of evolution . . . . 9 5.1 Kant on mathematicsContents Evolution of Geometrical Reasoning of a domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 14 Domains in the physical

  2. The Pentagon Problem: Geometric Reasoning with Technology.

    ERIC Educational Resources Information Center

    Zbiek, Rose Mary

    1996-01-01

    Presents an activity, involving pentagons and using a figure manipulator such as The Geometer's Sketchpad, that requires students to reason geometrically without making unsubstantiated assumptions based on diagrams. (MKR)

  3. Are Government Bonds Net Wealth?

    Microsoft Academic Search

    Robert J. Barro

    1974-01-01

    The assumption that government bonds are perceived as net wealth by the private sector is crucial in demonstrating real effects of shifts in the stock of public debt. In particular, the standard effects of \\

  4. Geometric Phase Atom Optics and Interferometry

    E-print Network

    Bernard Zygelman

    2015-01-08

    We illustrate how geometric gauge forces and topological phase effects emerge in quantum systems without employing assumptions that rely on adiabaticity. We show how geometric magnetism may be harnessed to engineer novel quantum devices including a velocity sieve, a component in mass spectrometers, for neutral atoms or neutrons. We outline a possible experimental setup that demonstrates topological interferometry for neutral spin 1/2 systems.

  5. Newton's superb theorem: An elementary geometric proof

    NASA Astrophysics Data System (ADS)

    Schmid, Christoph

    2011-05-01

    Newton's "superb theorem" for the gravitational 1/r2 force states that a spherically symmetric mass distribution attracts a body outside as if the entire mass were concentrated at the center. This theorem is crucial for Newton's comparison of the Moon's orbit with terrestrial gravity, which is evidence for the 1/r2 law. In this paper, we give an elementary geometric proof, which is simpler than Newton's geometric proof and more elementary than proofs using calculus.

  6. Environmental Effects on the Geometric Phase

    E-print Network

    A. C. Gnhan; S. Turgut; N. K. Pak

    2009-12-25

    The behavior of the geometric phase gained by a single spin-1/2 nucleus immersed into a thermal or a squeezed environment is investigated. Both the time dependence of the phase and its value at infinity are examined against several physical parameters. It is observed that for some intermediate ranges of the temperature and the coupling strength, the presence of squeezing enhances the geometric phase.

  7. Surface analysis in composite bonding

    NASA Technical Reports Server (NTRS)

    Messick, D. L.; Wightman, J. P.

    1983-01-01

    X ray photoelectron spectroscopy and contact angle measurements on graphite fiber composites pretreated in a number of different ways including mechanical, chemical, and light irradiation were analyzed. Data acquired on surface contamination as a result of fabrication techniques provides answers to the strength and durability of adhesively bonded composites. These techniques were shown to provide valuable information on surface analysis of pretreated composites prior to adhesive bonding and following lap shear fracture.

  8. Spectral decomposition of optimal assetliability management

    Microsoft Academic Search

    Marc Decamps; Ann De Schepper

    2009-01-01

    This paper concerns optimal assetliability management when the assets and the liabilities are modeled by means of correlated geometric Brownian motions as suggested in Gerber and Shiu [2003. Geometric Brownian motion models for assets and liabilities: from pension funding to optimal dividends. North American Actuarial Journal 7(3), 3751]. In a first part, we apply singular stochastic control techniques to derive

  9. Multispectral Image Correction for Geometric Measurements

    NASA Astrophysics Data System (ADS)

    Rosenberger, M.; Lin, G.

    2015-02-01

    Multispectral- and hyperspectral imaging technologies enable new possibilities in industrial measurement applications. Based on the knowledge of remote sensing a lot of investigations were made in the last decades of years. Nevertheless the demands on remote sensing versus technical multi spectral image processing are quite different. In the field of precise geometric measurement technics it is necessary to correct the image data between different spectral channels with a high accuracy, normally in the micron range. Otherwise the geometric absolute value of fail detection on edges can be become very large. State of the art in industrial imaging and detection of geometric features is the calibration of only one imaging channel. In this paper, the studies on a twelve channel multi spectral imager were presented. For the applied filter wheel system, investigations on the improvement of lens aberration as well as for the defocus problem were made. Therefore a calibrated high precision geometric test chart was used to calibrate the system geometrically. To correct the geometric errors on the image plane a special moving filter approach, based on linear convolution, was developed. For every channel a calibration matrix were calculated and applied on the image system output.

  10. Natural bond orbital analysis, electronic structure and vibrational spectral analysis of N-(4-hydroxyl phenyl) acetamide: a density functional theory.

    PubMed

    Govindasamy, P; Gunasekaran, S; Ramkumaar, G R

    2014-09-15

    The Fourier transform infrared (FT-IR) and FT-Raman spectra of N-(4-hydroxy phenyl) acetamide (N4HPA) of painkiller agent were recorded in the region 4000-450 cm(-1) and 4000-50 cm(-1) respectively. Density functional theory (DFT) has been used to calculate the optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations at DFT/B3LYP level with 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p) and 6-311++G(d,p) basis sets. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes calculated using Vibrational energy distribution analysis (VEDA 4) program. The oscillator's strength calculated by TD-DFT and N4HPA is approach complement with the experimental findings. The NMR chemical shifts 13C and 1H were recorded and calculated using the gauge independent atomic orbital (GIAO) method. The molecular electrostatic potential (MESP) and electron density surfaces of the molecule were constructed. The Natural charges and intermolecular contacts have been interpreted using Natural Bond orbital (NBO) analysis the HOMO-LUMO energy gap has been calculated. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated. PMID:24813292

  11. Optimization of selective hyperthermia.

    PubMed

    Bailey, Christopher A; Cowan, Thomas M; Liu, Vinson G; Lemley, Evan C; Chen, Wei R

    2004-01-01

    Selective hyperthermia can be a feasible treatment modality for deep tissue abnormalities. It is accomplished by using a laser or ultrasound noninvasively to transfer energy to a desired target causing tissue damage. This process has two potential benefits to medical professionals: simplicity of procedure and safety to patient. However, optimizing these selective interactions is difficult due to the number of variables. We propose an optimization coefficient relating the dynamic and geometric parameters of selective hyperthermia, and proceed to measure it in an experimental setup consisting of a near-infrared laser and laser-absorbing dye. To simulate tissue, gelatin phantoms are created using a combination of water, intralipid, and gelatin. Our experiments use a 1.00-cm-diam spherical phantom that is homogeneously enhanced with an indocyanine green (ICG) solution and placed inside a nontarget phantom and irradiated by an 805-nm diode laser. Temperature measurements taken at different locations are analyzed so optimization coefficients can be calculated for different parameters. This optimization coefficient compares the difference in temperatures from inside and outside the target. Analysis of the values after thermal equilibrium provides information about the best parameter selection. Our findings indicate that the optimal ICG concentration and power combination for our tested parameters are 0.083% and 0.97 W, respectively. Based on our analysis, optimization can be obtained by using this coefficient to compare the selectivity of several parameter combinations. PMID:15189104

  12. Halogen bond: its role beyond drug-target binding affinity for drug discovery and development.

    PubMed

    Xu, Zhijian; Yang, Zhuo; Liu, Yingtao; Lu, Yunxiang; Chen, Kaixian; Zhu, Weiliang

    2014-01-27

    Halogen bond has attracted a great deal of attention in the past years for hit-to-lead-to-candidate optimization aiming at improving drug-target binding affinity. In general, heavy organohalogens (i.e., organochlorines, organobromines, and organoiodines) are capable of forming halogen bonds while organofluorines are not. In order to explore the possible roles that halogen bonds could play beyond improving binding affinity, we performed a detailed database survey and quantum chemistry calculation with close attention paid to (1) the change of the ratio of heavy organohalogens to organofluorines along the drug discovery and development process and (2) the halogen bonds between organohalogens and nonbiopolymers or nontarget biopolymers. Our database survey revealed that (1) an obviously increasing trend of the ratio of heavy organohalogens to organofluorines was observed along the drug discovery and development process, illustrating that more organofluorines are worn and eliminated than heavy organohalogens during the process, suggesting that heavy halogens with the capability of forming halogen bonds should have priority for lead optimization; and (2) more than 16% of the halogen bonds in PDB are formed between organohalogens and water, and nearly 20% of the halogen bonds are formed with the proteins that are involved in the ADME/T process. Our QM/MM calculations validated the contribution of the halogen bond to the binding between organohalogens and plasma transport proteins. Thus, halogen bonds could play roles not only in improving drug-target binding affinity but also in tuning ADME/T property. Therefore, we suggest that albeit halogenation is a valuable approach for improving ligand bioactivity, more attention should be paid in the future to the application of the halogen bond for ligand ADME/T property optimization. PMID:24372485

  13. Dynamic Allocation of Treasury and Corporate Bond Portfolios

    Microsoft Academic Search

    Roger Walder

    2002-01-01

    In this paper, we solve the intertemporal investment problem of an investor holding a portfolio of default-free and defaultable bonds. Default-risk is modeled in an intensity based framework with state variables following an affine diffusion. The structure of the optimal portfolio over time is investigated and compared to the static mean-variance portfolio. Furthermore, we describe the impact of time varying

  14. Carbon nanotube-composite wafer bonding for ultra-high efficiency IIIV multijunction solar cells

    Microsoft Academic Search

    A. Boca; J. C. Boisvert; D. C. Law; S. Mesropian; N. H. Karam; W. D. Hong; R. L. Woo; D. M. Bhusari; E. Turevskaya; P. Mack; P. Glatkowski

    2010-01-01

    Device-wafer bonding provides a platform for the implementation of ultra-high-efficiency multijunction solar cell designs, by allowing optimal subcell bandgap combinations to be attained while using only high-quality materials lattice-matched to their growth substrates. One promising new method for achieving wafer bonding is to use carbon nanotube composite thin films as the bonding agent between subcells grown on dissimilar substrates. In

  15. Electronic structure and bonding at the Alterminated Al(111)/Al2O3(0001) interface: A first principles study

    E-print Network

    Adams, James B

    the mechanical properties of an interface, is the ideal work of adhesion, Ï ,[1] which is defined as the bondElectronic structure and bonding at the Al­terminated Al(111)/«­Al2O3(0001) interface: A first to determine the bonding character of the Al­terminated Al(111)/«­Al2O3(0001) interface. By using an optimized

  16. Geometric effects on stress wave propagation.

    PubMed

    Johnson, K L; Trim, M W; Horstemeyer, M F; Lee, N; Williams, L N; Liao, J; Rhee, H; Prabhu, R

    2014-02-01

    The present study, through finite element simulations, shows the geometric effects of a bioinspired solid on pressure and impulse mitigation for an elastic, plastic, and viscoelastic material. Because of the bioinspired geometries, stress wave mitigation became apparent in a nonintuitive manner such that potential real-world applications in human protective gear designs are realizable. In nature, there are several toroidal designs that are employed for mitigating stress waves; examples include the hyoid bone on the back of a woodpecker's jaw that extends around the skull to its nose and a ram's horn. This study evaluates four different geometries with the same length and same initial cross-sectional diameter at the impact location in three-dimensional finite element analyses. The geometries in increasing complexity were the following: (1) a round cylinder, (2) a round cylinder that was tapered to a point, (3) a round cylinder that was spiraled in a two dimensional plane, and (4) a round cylinder that was tapered and spiraled in a two-dimensional plane. The results show that the tapered spiral geometry mitigated the greatest amount of pressure and impulse (approximately 98% mitigation) when compared to the cylinder regardless of material type (elastic, plastic, and viscoelastic) and regardless of input pressure signature. The specimen taper effectively mitigated the stress wave as a result of uniaxial deformational processes and an induced shear that arose from its geometry. Due to the decreasing cross-sectional area arising from the taper, the local uniaxial and shear stresses increased along the specimen length. The spiral induced even greater shear stresses that help mitigate the stress wave and also induced transverse displacements at the tip such that minimal wave reflections occurred. This phenomenon arose although only longitudinal waves were introduced as the initial boundary condition (BC). In nature, when shearing occurs within or between materials (friction), dissipation usually results helping the mitigation of the stress wave and is illustrated in this study with the taper and spiral geometries. The combined taper and spiral optimized stress wave mitigation in terms of the pressure and impulse; thus providing insight into the ram's horn design and woodpecker hyoid designs found in nature. PMID:24362893

  17. Evidence for a Watson-Crick Hydrogen Bonding Requirement in DNA Synthesis by Human DNA Polymerase

    Microsoft Academic Search

    William T. Wolfle; M. Todd Washington; Eric T. Kool; Thomas E. Spratt; Sandra A. Helquist; Louise Prakash; Satya Prakash

    2005-01-01

    The efficiency and fidelity of nucleotide incorporation by high-fidelity replicative DNA polymerases (Pols) are governed by the geometric constraints imposed upon the nascent base pair by the active site. Consequently, these polymerases can efficiently and accurately replicate through the template bases which are isosteric to natural DNA bases but which lack the ability to engage in Watson-Crick (W-C) hydrogen bonding.

  18. The Role of Flexible Tethers in Multiple Ligand-Receptor Bond Formation between Curved Surfaces

    Microsoft Academic Search

    Nathan W. Moore; Tonya L. Kuhl

    2006-01-01

    Ligands mounted to surfaces via extensible tethers are present in nature and represent a growing class of molecules used to engineer adhesion in drug targeting, biosensing, self-assembling nanostructures, and in other biophysical research. Using a continuum approach with geometric and thermodynamic arguments, we derive a number of analytical expressions that relate key properties of single-tethered ligand-receptor interactions to multiple bond

  19. The structure of betaxolol from single crystal X-ray diffraction and natural bond orbital analysis

    Microsoft Academic Search

    Joo Canotilho; Ricardo A. E. Castro; Mrio T. S. Rosado; M. Ramos Silva; A. Matos Beja; J. A. Paixo; J. Simes Redinha

    2008-01-01

    The structure of betaxolol obtained from ethanol:water solution was studied by X-ray diffraction. The geometrical parameters needed to define the structure are tabulated. The X-ray data show the existence of two conformers in the unit cell differing only in the conformation of the cyclopropylmethoxy fragment. Differences in the bond lengths angles and dihedral between both conformations are observed. The cyclopropyl

  20. Extremal optimization for graph partitioning.

    PubMed

    Boettcher, S; Percus, A G

    2001-08-01

    Extremal optimization is a new general-purpose method for approximating solutions to hard optimization problems. We study the method in detail by way of the computationally hard (NP-hard) graph partitioning problem. We discuss the scaling behavior of extremal optimization, focusing on the convergence of the average run as a function of run time and system size. The method has a single free parameter, which we determine numerically and justify using a simple argument. On random graphs, our numerical results demonstrate that extremal optimization maintains consistent accuracy for increasing system sizes, with an approximation error decreasing over run time roughly as a power law t(-0.4). On geometrically structured graphs, the scaling of results from the average run suggests that these are far from optimal with large fluctuations between individual trials. But when only the best runs are considered, results consistent with theoretical arguments are recovered. PMID:11497658