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1

Geometric entanglement in valance-bond-solid state

NASA Astrophysics Data System (ADS)

Multipartite entanglement, measured by the geometric entanglement (GE), is discussed for integer spin Valance-Bond-Solid (VBS) state respectively with periodic boundary condition (PBC) and open boundary condition (OBC) in this paper. The optimization in the definition of geometric entanglement can be reduced greatly by exploring the symmetry of VBS state, and then the fully separable state can be determined explicitly. Numerical evaluation for GE by the random simulation is also implemented in order to demonstrate the validity of the reductions. Our calculations show that GE is saturated by a finite value with the increment of particle number, that means that the total entanglement for VBS state would be divergent under the thermodynamic limit. Moreover it is found that the scaling behavior of GE with spin number s is fitted as ? log(s + ?/s + ?)+?, in which the values of the parameters ?, ?, ?, ? are only dependent on the parity of spin s. A comparison with entanglement entropy of VBS state is also made, in order to demonstrate the essential differences between multipartite and bipartite entanglement in this model.

Cui, H. T.; Wang, C. M.; Yuan, S. Z.

2010-04-01

2

Water Resource System Optimization by Geometric Programming

resources optimization problems. This new and potentially powerful technique is called geometric programming. It is one of a class of mathematical programming techniques. Mathematical programming discussed extensively elsewhere [56,23] refers to a class...

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

3

Geometrically nonlinear analysis of adhesively bonded joints

NASA Technical Reports Server (NTRS)

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-relase rates (G1/G2) was found to be strongly affected by he 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.

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

1982-01-01

4

Evolutionary Optimization of a Geometrically Refined Truss

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

5

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

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

North Carolina at Chapel Hill, University of

6

Interplay between Peptide Bond Geometrical Parameters in Nonglobular Structural Contexts

Several investigations performed in the last two decades have unveiled that geometrical parameters of protein backbone show a remarkable variability. Although these studies have provided interesting insights into one of the basic aspects of protein structure, they have been conducted on globular and water-soluble proteins. We report here a detailed analysis of backbone geometrical parameters in nonglobular proteins/peptides. We considered membrane proteins and two distinct fibrous systems (amyloid-forming and collagen-like peptides). Present data show that in these systems the local conformation plays a major role in dictating the amplitude of the bond angle N-C?-C and the propensity of the peptide bond to adopt planar/nonplanar states. Since the trends detected here are in line with the concept of the mutual influence of local geometry and conformation previously established for globular and water-soluble proteins, our analysis demonstrates that the interplay of backbone geometrical parameters is an intrinsic and general property of protein/peptide structures that is preserved also in nonglobular contexts. For amyloid-forming peptides significant distortions of the N-C?-C bond angle, indicative of sterical hidden strain, may occur in correspondence with side chain interdigitation. The correlation between the dihedral angles ??/? in collagen-like models may have interesting implications for triple helix stability. PMID:24455689

Esposito, Luciana; De Simone, Alfonso; Vitagliano, Luigi

2013-01-01

7

Kanatani's Statistical Optimization for Geometric Computation

the covariance of {h, R} given V[x]'s and V[x]'s results in: ¯V(^h) ¯V(^h, ^R) ¯V(^R, ^h) ¯V(^R) = W(¯h, ¯R) ¯aKanatani's Statistical Optimization for Geometric Computation Chapter 11: 3-D Motion Analysis Olaf) Throughout the chapter: 3-D Motion Analysis -> 3-D Motion and Scene Reconstruction Analysis -> #12

Dorst, Leo

8

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

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

Kettner, Lutz

9

Introduction to geometric processing through optimization.

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

Taubin, Gabriel

2012-01-01

10

A geometric representation scheme suitable for shape optimization

NASA Technical Reports Server (NTRS)

A geometric representation scheme is outlined which utilizes the natural design variable concept. A base configuration with distinct topological features is created. This configuration is then deformed to define components with similar topology but different geometry. The values of the deforming loads are the geometric entities used in the shape representation. The representation can be used for all geometric design studies; it is demonstrated here for structural optimization. This technique can be used in parametric design studies, where the system response is defined as functions of geometric entities. It can also be used in shape optimization, where the geometric entities of an original design are modified to maximize performance and satisfy constraints. Two example problems are provided. A cantilever beam is elongated to meet new design specifications and then optimized to reduce volume and satisfy stress constraints. A similar optimization problem is presented for an automobile crankshaft section. The finite element method is used to perform the analyses.

Tortorelli, Daniel A.

1990-01-01

11

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

Herschlag, Dan

12

Geometrical features of hydrogen bonded complexes involving sterically hindered pyridines.

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

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

2006-09-21

13

Geometric constructions of optimal optical orthogonal codes

We provide a variety of constructions of (n,w,?)-optical orthog- onal codes using special sets of points and Singer groups in finite projective spaces. In several of the constructions, we are able to prove that the result- ing codes are optimal with respect to the Johnson bound. The optimal codes exhibited have ? = 1,2 and w 1 (where w is

T. L. Alderson; K. E. Mellinger

2008-01-01

14

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...

15

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

Wolfgang Kabsch; Christian Sander

1983-01-01

16

Geometrical parameters optimization for tube hydroforming using response surface method

NASA Astrophysics Data System (ADS)

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

Chebbah, M. S.; Azaouzi, M.

2014-10-01

17

Adhesive selection and bonding parameter optimization for hybrid bonding in 3D integration.

Hybrid bonding, an emerging bonding approach with high yield and reliability, can achieve vertical interconnection with adhesive serving reinforcement of the mechanical stability between stacked ICs. To develop metal/adhesive hybrid bonding technology, four kinds of polymer materials, BCB, SU-8, AL-Polymer, and PI, were evaluated as the bonding adhesive. The compatibility between each polymer and metal was investigated, and the application range of each material was established thereof. Furthermore, the scheme of Cu-Sn-Cu interconnection hybridized with patterned BCB was designed and evaluated. Two key factors were discussed and optimized to perform the bonding integrity. The evaluation results and successful metal/adhesive hybrid bonding demonstration are disclosed in the paper. PMID:22754986

Chen, Kuan-Neng; Ko, Cheng-Ta; Hsiao, Zhi-Cheng; Fu, Huan-Chun; Lo, Wei-Chung

2012-03-01

18

Bonding temperature optimization of SU-8 material for metal/adhesive hybrid bonding was investigated. The good bond quality of SU-8 adhesive can be achieved with the bonding temperature between 150 degrees C and 250 degrees C, while bond failures of SU-8 wafers are observed starting from 275 degrees C. IR transmittance spectra measurements indicate the crosslinks inside SU-8 break and further bond failure is observed due to the large decomposition of epoxy rings and phenyl in plane bending above 275 degrees C. This research provides guidelines of material selection and bonding parameters for heterogeneous integration, 3DIC and MEMS applications using metal/adhesive hybrid bonding. PMID:22103107

Chen, K N; Cheng, C A; Huang, W C; Ko, C T

2011-08-01

19

Optimal prefix codes for some families of two-dimensional geometric distributions

Optimal prefix codes for some families of two-dimensional geometric distributions Fr case turn out not to hold in the two-dimensional case. Specifically, the codes described in [1] and [3 prediction residuals, which are well-modeled by two-sided geometric distributions. Optimal prefix codes

Bassino, Frédérique

20

Optimal prefix codes for some families of two-dimensional geometric distributions

Optimal prefix codes for some families of two-dimensional geometric distributions Fr prediction residuals, which are well-modeled by two-sided geometric distributions. Optimal prefix codes Compression Conference (DCC'06), United States (2006)" #12;We refer to this distribution as a two-dimensional

Paris-Sud XI, Université de

21

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.

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

22

Optimal Allocation of Local Feedback in Multistage Amplifiers via Geometric Programming

Optimal Allocation of Local Feedback in Multistage Amplifiers via Geometric Programming Joel L of optimally allocating local feedback to the stages of a multistage amplifier. The local feedback gains affect INTRODUCTION The use of linear feedback around an amplifier stage was pi- oneered by Black [1], Bode [2

23

Application of separable programming to optimization by geometric programming

is said to be consistent if there is at least one vector that satisfies its constraints. The primal program is idt b~'r tcf h*' tl t 1'*0 such that gk(T*) ' I ~ The following two theorems are called the Duality Theorems and are stated here without... be solved quickly and easily using the computer. The course of this research proceded in three phases: First, the computer solution of geometric programming problems, by the technique described, was examined. Only limited success was obtained...

Humber, Joseph Barker

1971-01-01

24

Optimization of the geometrical stability in square ring laser gyroscopes

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.

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

2014-11-12

25

Geometrical optimization of a local ballistic magnetic sensor

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.

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

26

COORDINATION AND GEOMETRIC OPTIMIZATION VIA DISTRIBUTED DYNAMICAL SYSTEMS

unknown. What are the critical points of such dynam- ical systems? What is their asymptotic behavior? Are these systems optimizing any aggregate function? In what way do these local interactions give rise was supported in part by DARPA/AFOSR MURI Award F49620-02-1-0325 and ONR YIP Award N00014

Bullo, Francesco

27

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

28

Optimal geometric design of monolithic thin-film solar modules: Architecture of polymer solar cells

In this study the geometrical optimization of monolithically integrated solar cells into serially connected solar modules is reported. Based on the experimental determination of electrodes? sheet and intermittent contact resistances, the overall series resistance of individual solar cells and interconnected solar modules is calculated. Taking a constant photocurrent generation density into account, the total Joule respectively resistive power losses are

Harald Hoppe; Marco Seeland; Burhan Muhsin

29

Optimal prefix codes for pairs of geometrically-distributed random variables

-called two-dimensional geometric distributions are parameter-singular, in the sense that a prefix code contrast to the one-dimensional case, where codes are optimal for positive-length intervals of the parameter q. Thus, in the two-dimensional case, it is infeasible to give a compact characterization

Bassino, Frédérique

30

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

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

Mitchell, Joseph S.B.

31

A 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

Paris-Sud XI, Université de

32

NASA Astrophysics Data System (ADS)

Finite element models have been successfully used to analyze adhesive bonds in actual structures, but this takes a considerable amount of time and a high computational cost. The objective of this study is to develop a simple and cost-effective finite element model for adhesively bonded joints which could be used in industry. Stress and durability analyses of crack patch geometries are possible applications of this finite element model. For example, the lifetime of aging aircraft can be economically extended by the application of patches bonded over the flaws located in the wings or the fuselage. Special two- and three-dimensional adhesive elements have been developed for stress and displacement analyses in adhesively bonded joints. Both the 2-D and 3-D elements are used to model the whole adhesive system: adherends and adhesive layer. In the 2-D elements, adherends are represented by Bernoulli beam elements with axial deformation and the adhesive layer by plane stress or plane strain elements. The nodes of the plane stress-strain elements that lie in the adherend-adhesive interface are rigidly linked with the nodes of the beam elements. The 3-D elements consist of shell elements that represent the adherends and solid brick elements to model the adhesive. This technique results in smaller models with faster convergence than ordinary finite element models. The resulting mesh can represent arbitrary geometries of the adhesive layer and include cracks. Since large displacements are often observed in adhesively bonded joints, geometric nonlinearity is modeled. 2-D and 3-D stress analyses of single lap joints are presented. Important 3-D effects can be appreciated. Fracture mechanics parameters are computed for both cases. A stress analysis of a crack patch geometry is presented. A numerical simulation of the debonding of the patch is also included.

Andruet, Raul Horacio

33

Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization

NASA Technical Reports Server (NTRS)

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

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

34

NASA Astrophysics Data System (ADS)

With the development of remote sensing satellites, the data quantity of remote sensing image is increasing tremendously, which brings a huge workload to the image geometric rectification through manual ground control point (GCP) selections. GCP database is one of the effective methods to cut down manual operation. The GCP loaded from database is generally redundant, which may result in a rectification slowdown. How to automatically optimize these ground control points is a problem that should be resolved urgently. According to the basic theory of geometric rectification and the principle of GCP selection, this paper deeply comprehends some existing methods about automatic optimization of GCP, and puts forward a new method of automatic optimization of GCP based on voronoi diagram to filter ground control points from the overfull ones without manual subjectivity for better accuracy. The paper is organized as follows: First, it clarifies the basic theory of remote sensing image multinomial geometric rectification and the arithmetic of how to get the GCP error. Second, it particularly introduces the voronoi diagram including its origin, development and characteristics, especially the creating process. Third, considering the deficiencies of existing methods about automatic optimization of GCP, the paper presents the idea of applying voronoi diagram to filter GCP in order to complete automatic optimization. During this process, it advances the conception of single GCP's importance value based on voronoi diagram. Then by integrating the GCP error and GCP's importance value, the paper gives the theory and the flow of automatic optimization of GCPs as well. It also presents an example of the application of this method. In the conclusion, it points out the advantages of automatic optimization of GCP based on the voronoi diagram.

Li, Ying; Cheng, Bo

2009-10-01

35

We develop a simple elastic model to study the conformation of DNA in the nucleosome core particle. In this model, the changes in the energy of the covalent bonds that connect the base pairs of each strand of the DNA double helix, as well as the lateral displacements and the rotation of adjacent base pairs are considered. We show that because of the rigidity of the covalent bonds in the sugar-phosphate backbones, the base pair parameters are highly correlated, especially, strong twist-roll-slide correlation in the conformation of the nucleosomal DNA is vividly observed in the calculated results. This simple model succeeds to account for the detailed features of the structure of the nucleosomal DNA, particularly, its more important base pair parameters, roll and slide, in good agreement with the experimental results. PMID:20972223

Ghorbani, Maryam; Mohammad-Rafiee, Farshid

2011-03-01

36

NSDL National Science Digital Library

Bonding Purpose: To review the 3 Types of Bonds and the 4 Intermolecular Forces. Assignment: Answer the following questions on a separate piece of paper: 1) List the 3 types of bonding, give descriptions and one example of each 2) List the 4 intermolecular forces and draw examples of each. Be ...

Cutting, Mrs.

2008-03-08

37

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

38

Plasmonic sensors based on ordered arrays of nanoprisms are optimized in terms of their geometric parameters like size, height, aspect ratio for Au, Ag or Au0.5-Ag0.5 alloy to be used in the visible or near IR spectral range. The two figures of merit used for the optimization are the bulk and the surface sensitivity: the first is important for optimizing the sensing to large volume analytes whereas the latter is more important when dealing with small bio-molecules immobilized in close proximity to the nanoparticle surface. A comparison is made between experimentally obtained nanoprisms arrays and simulated ones by using Finite Elements Methods (FEM) techniques. PMID:25461180

Michieli, Niccol; Kalinic, Boris; Scian, Carlo; Cesca, Tiziana; Mattei, Giovanni

2014-10-31

39

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

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

2014-01-01

40

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

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

2014-01-01

41

Optimal Design Method for SRC Frame Structures Based on Bond-Slip Theory

1. Abstract Based on the experimental study on bond-slip behavior between shaped steel and concrete, an optimal design scheme of single objective and discrete variables is proposed to design shaped steel reinforced concrete (SRC) frame structures. In the optimum scheme, design variables include the layout dimensions of SRC frame structure, structural member sections, the dimensions and distribution of shaped steel;

Shansuo ZHENG; Guozhuan DENG; Weihong ZHANG; Chunguang ZHA

42

NASA Astrophysics Data System (ADS)

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

Haase, Claudia; Gtze, Hans-Jrgen

2014-05-01

43

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

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

2012-11-26

44

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...

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

2010-01-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

46

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

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

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

2012-05-01

47

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

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

2000-01-01

48

NASA Astrophysics Data System (ADS)

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

Newman, James Charles, III

1997-10-01

49

Finite element models have been successfully used to analyze adhesive bonds in actual structures, but this takes a considerable amount of time and a high computational cost. The objective of this study is to develop a simple and cost-effective finite element model for adhesively bonded joints which could be used in industry. Stress and durability analyses of crack patch geometries

Raul Horacio Andruet

1998-01-01

50

Purpose and background: Intensity modulated arc therapy (IMAT) is a rotational variant of Intensity modulated radiation therapy (IMRT) that is achieved by allowing the multileaf collimator (MLC) positions to vary as the gantry rotates around the patient. This work describes a method to generate an IMAT plan through the use of a fast ray tracing technique based on dosimetric and geometric information for setting initial MLC leaf positions prior to final IMAT optimization. Methods and materials: Three steps were used to generate an IMAT plan. The first step was to generate arcs based on anatomical contours. The second step was to generate ray importance factor (RIF) maps by ray tracing the dose distribution inside the planning target volume (PTV) to modify the MLC leaf positions of the anatomical arcs to reduce the maximum dose inside the PTV. The RIF maps were also segmented to create a new set of arcs to improve the dose to low dose voxels within the PTV. In the third step, the MLC leaf positions from all arcs were put through a leaf position optimization (LPO) algorithm and brought into a fast Monte Carlo dose calculation engine for a final dose calculation. The method was applied to two phantom cases, a clinical prostate case and the Radiological Physics Center (RPC)'s head and neck phantom. The authors assessed the plan improvements achieved by each step and compared plans with and without using RIF. They also compared the IMAT plan with an IMRT plan for the RPC phantom. Results: All plans that incorporated RIF and LPO had lower objective function values than those that incorporated LPO only. The objective function value was reduced by about 15% after the generation of RIF arcs and 52% after generation of RIF arcs and leaf position optimization. The IMAT plan for the RPC phantom had similar dose coverage for PTV1 and PTV2 (the same dose volume histogram curves), however, slightly lower dose to the normal tissues compared to a six-field IMRT plan. Conclusion: The use of a ray importance factor can generate initial IMAT arcs efficiently for further MLC leaf position optimization to obtain more favorable IMAT plan.

Oliver, Mike; Gladwish, Adam; Craig, Jeff; Chen, Jeff; Wong, Eugene [Department of Medical Biophysics, University of Western Ontario, London, Ontario, N6A 5C1 (Canada); Department of Physics and Engineering, London Regional Cancer Program, London Health Sciences Centre, London, Ontario, N6A 4L6 (Canada); Department of Medical Biophysics, University of Western Ontario, London, Ontario, N6A 5C1 (Canada); Department of Oncology, University of Western Ontario, London, Ontario, N6A 4L6 (Canada) and Department of Physics and Engineering, London Regional Cancer Program, London Health Sciences Centre, London, Ontario, N6A 4L6 (Canada); Department of Medical Biophysics, University of Western Ontario, London, Ontario, N6A 5C1 (Canada); Department of Oncology, University of Western Ontario, London, Ontario, N6A 4L6 (Canada); Department of Physics and Engineering, London Regional Cancer Program, London Health Sciences Centre, London, Ontario, N6A 4L6 (Canada) and Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 (Canada)

2008-07-15

51

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

52

NASA Astrophysics Data System (ADS)

A novel type of Compton camera, called a double-scattering Compton imager (DOCI), is under development for nuclear medicine and molecular imaging applications. Two plane-type position-sensitive semiconductor detectors are employed as the scatterer detectors, and a 3?3? cylindrical NaI(Tl) scintillation detector is employed as the absorber detector. This study determined the optimal geometrical configuration of these component detectors to maximize the performance of the Compton camera in imaging resolution and sensitivity. To that end, the Compton camera was simulated very realistically, with the GEANT4 detector simulation toolkit, including various detector characteristics such as energy resolution, spatial resolution, energy discrimination, and Doppler energy broadening. According to our simulation results, the Compton camera is expected to show its maximum performance when the two scatterer detectors are positioned in parallel, with 8 cm of separation. The Compton camera will show the maximum performance also when the gamma-ray energy is about 500 keV, which suggests that the Compton camera is a suitable device to image the distribution of the positron emission tomography (PET) isotopes in the human body.

Seo, Hee; Lee, Se Hyung; Kim, Chan Hyeong; An, So Hyun; Lee, Ju Hahn; Lee, Chun Sik

2008-06-01

53

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

54

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

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

2010-01-01

55

The geometrical and vibrational characteristics of isolated H-bonded anionic complexes [FHFDF](-), [FHFTF](-), and [FDFTF](-) are calculated quantum-mechanically. The four-dimensional anharmonic vibrational problems are solved by the variational method using the potential energy and dipole moment surfaces calculated in the MP2/6-311++G(3df,3pd) approximation with the basis set superposition error taken into account. Changes in the bond lengths of molecular fragments LF (L = H, D, T) and in the distances between the F(-) anion and the centers of mass of LF are used as the vibrational coordinates. For each isotopologue, the vibrational energy levels, the transition frequencies and absolute intensities for the H-bond and L-F stretching vibrations are determined. To study the isotope effects on the geometrical parameters, the values of internuclear separations and the asymmetry parameter of the F(-)L-F bridges, averaged over the ground state and several excited vibrational states, are calculated, as well as their standard deviations. The calculations revealed an extremely strong influence of anharmonic coupling between different vibrations on the absorption intensities and a significant mass-dependence of spectroscopic and structural parameters. The geometry and harmonic frequencies of KH(2)F(3), KD(2)F(3), and KHDF(3) are also calculated at a lower ab initio level. The results obtained for [FHFDF](-), [FHFTF](-), and [FDFTF](-) are compared with the available experimental data and the results of earlier calculations of the symmetric complexes [F(HF)(2)](-), [F(DF)(2)](-), and [F(TF)(2)](-) and complexes containing a positive K-meson. PMID:21695326

Bulychev, V P; Buturlimova, M V; Tokhadze, K G

2011-08-21

56

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

57

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

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

2014-11-01

58

NASA Astrophysics Data System (ADS)

A new heuristic algorithm based on the so-called geometric distance sorting technique is proposed for solving the fluence map optimization with dose-volume constraints which is one of the most essential tasks for inverse planning in IMRT. The framework of the proposed method is basically an iterative process which begins with a simple linear constrained quadratic optimization model without considering any dose-volume constraints, and then the dose constraints for the voxels violating the dose-volume constraints are gradually added into the quadratic optimization model step by step until all the dose-volume constraints are satisfied. In each iteration step, an interior point method is adopted to solve each new linear constrained quadratic programming. For choosing the proper candidate voxels for the current dose constraint adding, a so-called geometric distance defined in the transformed standard quadratic form of the fluence map optimization model was used to guide the selection of the voxels. The new geometric distance sorting technique can mostly reduce the unexpected increase of the objective function value caused inevitably by the constraint adding. It can be regarded as an upgrading to the traditional dose sorting technique. The geometry explanation for the proposed method is also given and a proposition is proved to support our heuristic idea. In addition, a smart constraint adding/deleting strategy is designed to ensure a stable iteration convergence. The new algorithm is tested on four cases including head-neck, a prostate, a lung and an oropharyngeal, and compared with the algorithm based on the traditional dose sorting technique. Experimental results showed that the proposed method is more suitable for guiding the selection of new constraints than the traditional dose sorting method, especially for the cases whose target regions are in non-convex shapes. It is a more efficient optimization technique to some extent for choosing constraints than the dose sorting method. By integrating a smart constraint adding/deleting scheme within the iteration framework, the new technique builds up an improved algorithm for solving the fluence map optimization with dose-volume constraints.

Lan, Yihua; Li, Cunhua; Ren, Haozheng; Zhang, Yong; Min, Zhifang

2012-10-01

59

Task Based Optimal Geometric Design and Positioning of Serial Robotic Manipulators

This paper devises a multi-objective cost function which elaborates different constraints as well as an optimality criterion for design of serial robotic manipulators. In practice, inclusion of different constraints drastically limits the possible range of design parameters. The result of minimizing this multi-objective cost function is compared with another method which locates an optimal solution using a graphical representation. The

S. Barissi; H. D. Taghirad

2008-01-01

60

A reliability-based design optimization method is developed to apply to topology design problems. Using the total Lagrangian formulation, the spatial domain is discretized using Mindlin plate elements with the von Krmn straindisplacement relation. The topology optimization problem is reformulated as a volume minimization problem having probabilistic displacement constraints using the performance measure approach. For the efficient computation of the sensitivity

Hyun-Seung Jung; Seonho Cho

2004-01-01

61

Optimal prefix codes for sources with two-sided geometric distributions

Abstract: A complete characterization of optimal prefix codes for off-centered, two-sided geometricdistributions of the integers is presented. These distributions are often encountered in losslessimage compression applications, as probabilistic models for image prediction residuals.

Neri Merhav; Gadiel Seroussi; Marcelo J. Weinberger

2000-01-01

62

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

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 ...

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

2014-01-01

63

Applications in quantum information processing and photon detectors are stimulating a race to produce the highest possible quality factor on-chip superconducting microwave resonators. We have tested the surface-dominated loss hypothesis by systematically studying the role of geometrical parameters on the internal quality factors of compact resonators patterned in Nb on sapphire. Their single-photon internal quality factors were found to increase with the distance between capacitor fingers, the width of the capacitor fingers, and the impedance of the resonator, achieving quality factors as high as 500,000. With no ion-milling of the sapphire, the internal quality factors drop by roughly a factor of four. All of these results are consistent with our starting hypothesis.

Geerlings, K; Edwards, E; Frunzio, L; Schoelkopf, R J; Devoret, M H

2012-01-01

64

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

J. Sussmann; Guoqing Tang

1991-01-01

65

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

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

2013-02-15

66

Valuation and Optimal Exercise of the Wild Card Option in the Treasury Bond Futures Market

The Chicago Board of Trade Treasury Bond Futures Contract allows the short position several delivery options as to when and with which bond the contract will be settled. The timing option allows the short position to choose any business day in the delivery month to make delivery. In addition, the contract settlement price is locked in at 2:00 p.m. when

Alex Kane; Alan J. Marcus

1986-01-01

67

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

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

Kokiopoulou, Effrosyni; Kressner, Daniel; Frossard, Pascal

2011-06-01

68

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

69

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

Taylor, Paul A.; Biswal, Bharat

2011-01-01

70

NASA Astrophysics Data System (ADS)

A thermoelectric stack composed of arrays of Bi-Te alloy thermoelectric converter (TEC) modules is considered for geothermal heat conversion. The TEC modules consist of Al2O3 plates with surface 3030 mm2 and 127 p-type (Bi0.2Sb0.8)2Te3 and n-type Bi2(Te0.96Se0.04)3 thermoelement pairs, each having a cross-section of 1.051.05 mm2, and with a figure-of-merit of 1 and a heat-to-electricity conversion efficiency of 5%. A heat transfer model is formulated to couple conduction in the thermoelements with convection between the Al2O3 plates and the water flow in counter-flow channel configuration. The calculated open-circuit voltages are compared to those resulting from the mean temperature differences across the TEC modules computed by CFD. The investigated parameters are: hot water inlet and outlet temperatures (373 - 413 K and 323 - 363 K, respectively), stack length (300 - 1500 mm), thermoelement length (1 - 4 mm) and hot channel heights (0.2 - 2 mm). The heat transfer model is then applied to optimize a 1 kWel stack with hot water inlet at 393 K and outlet at 353 K for either maximum heat-to-electricity conversion efficiency of 2.9% or minimum size of 0.0044 m3.

Suter, C.; Jovanovic, Z.; Steinfeld, A.

2012-06-01

71

This paper describes the NMR observation of 15N15N and 1H15N scalar couplings across the hydrogen bonds in WatsonCrick 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 14-mer DNA duplex was used to measure hJNN, which is in the range 67 Hz, and the two-dimensional hJNN-correlation-[15N,1H]-TROSY experiment was used to correlate the chemical shifts of pairs of hydrogen bond-related 15N spins and to observe, for the first time, hJHN scalar couplings, with values in the range 23.6 Hz. TROSY-based studies of scalar couplings across hydrogen bonds should be applicable for large molecular sizes, including protein-bound nucleic acids. PMID:9826668

Pervushin, Konstantin; Ono, Akira; Fernndez, Csar; Szyperski, Thomas; Kainosho, Masatsune; Wthrich, Kurt

1998-01-01

72

Optimal specimen geometry in bonded-disk shrinkage-strain measurements on light-cured biomaterials

Objectives: The aim was to determine the effect on apparent shrinkage-strain values of varying specimen aspect ratio in the bonded-disk configuration. Thereby one source of possible inter-laboratory variation might be understood and eliminated.Methods: The bonded-disk procedure was followed and applied to three representative resin-composites. However, specimen sub-groups were examined, each of different diameters (3.5, 5.0, 7.0 and 9.0mm), corresponding to

D. C Watts; A. S Marouf

2000-01-01

73

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

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

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

74

Optimization of the effect of corrosion on bond behaviour between steel and concrete

This research program consists of laboratory study of corrosion phenomenon in reinforced concrete and further analytical study of the experimental results obtained by Amleh (2000). The laboratory study examined the influence of increasing levels of corrosion on the progressive deterioration of bond between the steel and concrete and determined the extent to which the various water to cement (w\\/c) ratio

Zahir Aldulaymi

2007-01-01

75

Localisation of Geometric Anisotropy

The class of 2-D nonseparable geometrically anisotropic localisation operators is defined, containing highly anisotropic nearly unidirectional localisation operator s, as well as isotropic localisation operators. A continuum of anisotropic operators between the extremes of near unidirectionality and isotropy are treated in a single class. The eigensystem of any given operator in this family is determined, thus specifying geometrically anisotropic optimally

Sofia C. Olhede

2008-01-01

76

CORRESPONDENCE PROBLEMS IN GEOMETRIC VISION

CORRESPONDENCE PROBLEMS IN GEOMETRIC VISION OLOF ENQVIST Faculty of Engineering CentreTryck, Lund 2009 #12;Preface This thesis concerns optimal methods for geometric vision problems. Two important and branch and bound to handle the correspon- dence problems arising in geometric vision. The thesis consists

Lunds Universitet

77

NASA Astrophysics Data System (ADS)

Creation of three-dimensional representations of surfaces from images taken at two or more view angles is a well-established technique applied to optical images and is frequently used in combination with scanning electron microscopy (SEM). The present work describes specific steps taken to optimize and enhance the repeatability of three-dimensional surfaces reconstructed from SEM images. The presented steps result in an approximately tenfold improvement in the repeatability of the surface reconstruction compared to more standard techniques. The enhanced techniques presented can be used with any SEM friendly samples. In this work the modified technique was developed in order to accurately quantify surface geometry changes in metallic bond coats used with thermal barrier coatings (TBCs) to provide improved turbine hot part durability. Bond coat surfaces are quite rough, and accurate determination of surface geometry change (rumpling) requires excellent repeatability. Rumpling is an important contributor to TBC failure, and accurate quantification of rumpling is important to better understanding of the failure behavior of TBCs.

Shahbazmohamadi, Sina; Jordan, Eric H.

2012-12-01

78

The surfaces of 63 extracted premolar teeth were processed with intense ultrashort laser pulses (??=?795nm; pulse duration, 120fs; repetition rate, 1kHz) to produce cross patterns with different pitches (s) in the micrometer range in order to evaluate the influence of such microstructures on the shear bond strengths of orthodontic brackets to enamel. The samples were classified in nine groups corresponding to the control group (raw samples) and eight different laser-processed groups (cross patterns with s increasing from 15 to 180?m). Brackets were luted with Transbond(TM) XT adhesive resin to all the samples; after 72h, they all were submitted to strength test in a universal testing machine. Additionally, a third of the samples underwent morphological analysis of the debonded surface by means of scanning electron microscope microscopy and an analysis of the failure mode based on the adhesive remnant index. The results showed that enamel microstructuring with ultrashort laser pulses remarkably increase the bond strength of brackets. Dense cross patterns (s?bond strengths as compared to control group whereas light ones (s?>?90?m) give rise to smaller improvements of the bond strength. A strong correlation of this behavior with the predominant failure mode in both scenarios was found. So far, the best compromise between suitable adhesive efficiency, processing time minimization, and enamel surface preservation suggests the performance of cross patterns with pitches in the order of 90?m. PMID:24249356

Lorenzo, M C; Portillo, M; Moreno, P; Montero, J; Garca, A; Santos-Del Riego, S E; Albaladejo, A

2015-02-01

79

Charge-assisted intramolecular hydrogen bonds in disubstituted cyclohexane derivatives.

In this paper, the N(+)-HN, N(+)-HO, and O-HO(-) charge-assisted intramolecular hydrogen bonds (CAHBs) are investigated using different theoretical approaches. Monocharged cyclohexyldiamines (CHDA), aminocyclohexanols (ACHO), and cyclohexanediols (CHDO) are used as model compounds. Geometry optimizations at the MP2/aug-cc-pVDZ level are used to find the equilibrium structures for all possible H-bonded conformers. CAHBs are characterized geometrically and spectroscopically, and their energy is evaluated by means of homodesmic reactions. By comparison with the neutral forms, the presence of the charge is found to have a deep influence on the geometric and energetic H-bond parameters. In addition, these parameters are strongly dependent on the type of the groups involved as well as on their relative position in the cyclohexyl ring. For the systems under study, the H-bond energies vary from -23 to -113 kJ mol(-1), being classified from moderate to strong H-bonds. These H-bonds are also characterized by the application of the NBO and AIM theories. NBO analysis reveals that the energy corresponding to the charge transfer between the lone-pairs of the electron donor group and the antibonding orbitals of the acceptor group represents an important contribution in the H-bond stabilization. From the application of the AIM theory it is possible to see that these H-bonds possess some covalence which varies according to the type and relative position of the intervenient groups. PMID:22026642

Lopes Jesus, A J; Redinha, J S

2011-12-01

80

This paper shows the analysis and design of feedforward neural networks using the coordinate-free system of Clifford or geometric algebra. It is shown that real-, complex-, and quaternion-valued neural networks are simply particular cases of the geometric algebra multidimensional neural networks and that some of them can also be generated using support multivector machines (SMVMs). Particularly, the generation of radial basis function for neurocomputing in geometric algebra is easier using the SMVM, which allows one to find automatically the optimal parameters. The use of support vector machines in the geometric algebra framework expands its sphere of applicability for multidimensional learning. Interesting examples of nonlinear problems show the effect of the use of an adequate Clifford geometric algebra which alleviate the training of neural networks and that of SMVMs. PMID:18249926

Bayro-Corrochano, E J

2001-01-01

81

Among the many applications of molecular modeling, drug design is probably the one with the highest demands on the accuracy of the underlying structures. During lead optimization, the position of every atom in the binding site should ideally be known with high precision to identify those chemical modifications that are most likely to increase drug affinity. Unfortunately, X-ray crystallography at common resolution yields an electron density map that is too coarse, since the chemical elements and their protonation states cannot be fully resolved.This chapter describes the steps required to fill in the missing knowledge, by devising an algorithm that can detect and resolve the ambiguities. First, the pK (a) values of acidic and basic groups are predicted. Second, their potential protonation states are determined, including all permutations (considering for example protons that can jump between the oxygens of a phosphate group). Third, those groups of atoms are identified that can adopt alternative but indistinguishable conformations with essentially the same electron density. Fourth, potential hydrogen bond donors and acceptors are located. Finally, all these data are combined in a single "configuration energy function," whose global minimum is found with the SCWRL algorithm, which employs dead-end elimination and graph theory. As a result, one obtains a complete model of the protein and its bound ligand, with ambiguous groups rotated to the best orientation and with protonation states assigned considering the current pH and the H-bonding network. An implementation of the algorithm has been available since 2008 as part of the YASARA modeling & simulation program. PMID:22183550

Krieger, Elmar; Dunbrack, Roland L; Hooft, Rob W W; Krieger, Barbara

2012-01-01

82

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

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

2012-01-01

83

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.

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

2011-01-01

84

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

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

2011-02-01

85

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

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

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

2010-01-01

86

Gaalop -High Performance Parallel Computing based on Conformal Geometric Algebra

Gaalop - High Performance Parallel Computing based on Conformal Geometric Algebra Dietmar Hildenbrand, Joachim Pitt, Andreas Koch Abstract We present Gaalop (Geometric algebra algorithms optimizer), our tool for high performance computing based on conformal geometric algebra. The main goal of Gaalop

87

NASA Astrophysics Data System (ADS)

We report the optimized geometrical structures using the ab initio method, and the calculated frequency dependence of the third-order nonlinear optical polarizabilities ? in the different optical processes of the third-harmonic generation, electric-field induced second-harmonic generation, and degenerate four-wave mixing using the INDO/SDCI method coupled with the sum-over-states method for C59Si and two isomers of C58Si2 heterofullerenes. The optimized structures show that the stabilization of the para isomer of C58Si2 is larger than that of the dia isomer of C58Si2, and the geometrical modifications of C59Si and C58Si2 isomers occur in the vicinity of the Si-doped atom after the replacement of one or two C atoms by Si atoms in the C60 fullerene. The calculated hyperpolarizabilities at nonresonant frequency show the varied trends in the order of C59Si~ dia isomer of C58Si2< para isomer of C58Si2 at ground state and the charge transfers of two-photon states make significant contributions to third-order optical polarizabilities for the para isomer of C58Si2. The enhancement of first excited singlet state is about one or two order of magnitude at nonresonant frequency. The susceptibilities of ?(-??,?,-?) of these Si-doped fullerene films are estimated to be about 10-10 esu at first excited state and 10-11 esu at ground state in nonresonant frequency.

Cheng, W.-D.; Wu, D.-S.; Zhang, H.; Chen, D.-G.; Wang, H.-X.

2002-08-01

88

NSDL National Science Digital Library

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

2011-01-01

89

NSDL National Science Digital Library

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

Lessonplans, Utah

2012-09-18

90

Reducing scanning time is significantly important for MRI. Compressed sensing has shown promising results by undersampling the k-space data to speed up imaging. Sparsity of an image plays an important role in compressed sensing MRI to reduce the image artifacts. Recently, the method of patch-based directional wavelets (PBDW) which trains geometric directions from undersampled data has been proposed. It has better performance in preserving image edges than conventional sparsifying transforms. However, obvious artifacts are presented in the smooth region when the data are highly undersampled. In addition, the original PBDW-based method does not hold obvious improvement for radial and fully 2D random sampling patterns. In this paper, the PBDW-based MRI reconstruction is improved from two aspects: 1) An efficient non-convex minimization algorithm is modified to enhance image quality; 2) PBDW are extended into shift-invariant discrete wavelet domain to enhance the ability of transform on sparsifying piecewise smooth image features. Numerical simulation results on vivo magnetic resonance images demonstrate that the proposed method outperforms the original PBDW in terms of removing artifacts and preserving edges. PMID:23992629

Ning, Bende; Qu, Xiaobo; Guo, Di; Hu, Changwei; Chen, Zhong

2013-11-01

91

High-energy, beta-delayed gamma-ray spectroscopy is under investigation as part of the Next Generation Safeguard Initiative effort to develop non-destructive assay instruments for plutonium mass quantification in spent nuclear fuel assemblies. Results obtained to date indicate that individual isotope-specific signatures contained in the delayed gamma-ray spectra can potentially be used to quantify the total fissile content and individual weight fractions of fissile and fertile nuclides present in spent fuel. Adequate assay precision for inventory analysis can be obtained using a neutron generator of sufficient strength and currently available detection technology. In an attempt to optimize the geometric configuration and material composition for a delayed gamma measurement on spent fuel, the current study applies MCNPX, a Monte Carlo radiation transport code, in order to obtain the best signal-to-noise ratio. Results are presented for optimizing the neutron spectrum tailoring material, geometries to maximize thermal or fast fissions from a given neutron source, and detector location to allow an acceptable delayed gamma-ray signal while achieving a reasonable detector lifetime while operating in a high-energy neutron field. This work is supported in part by the Next Generation Safeguards Initiative, Office of Nuclear Safeguards and Security, National Nuclear Security Administration.

Kulisek, Jonathan A.; Campbell, Luke W.; Rodriguez, Douglas C.

2012-06-07

92

Engineering Graphics in Geometric Algebra

NASA Astrophysics Data System (ADS)

We illustrate the suitability of geometric algebra for representing structures and developing algorithms in computer graphics, especially for engineering applications. A number of example applications are reviewed. Geometric algebra unites many underpinning mathematical concepts in computer graphics such as vector algebra and vector fields, quaternions, kinematics and projective geometry, and it easily deals with geometric objects, operations, and transformations. Not only are these properties important for computational engineering, but also for the computational point-of-view they provide. We also include the potential of geometric algebra for optimizations and highly efficient implementations.

Rockwood, Alyn; Hildenbrand, Dietmar

93

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

94

We comment on the paper [Song et al., J. Comput. Chem. 2009, 30, 399]. and discuss the efficiency of the orbital optimization and gradient evaluation in the Valence Bond Self Consistent Field (VBSCF) method. We note that Song et al. neglect to properly reference Broer et al., who published an algorithm [Broer and Nieuwpoort, Theor. Chim. Acta 1988, 73, 405] to use a Fock matrix to compute a matrix element between two different determinants, which can be used for an orbital optimization. Further, Song et al. publish a misleading comparison with our VBSCF algorithm [Dijkstra and van Lenthe, J. Chem. Phys. 2000, 113, 2100; van Lenthe et al., Mol. Phys. 1991, 73, 1159] to enable them to favorably compare their algorithm with ours. We give detail timings in terms of different orbital types in the calculation and actual timings for the example cases. PMID:22278948

van Lenthe, J H; Broer-Braam, H B; Rashid, Z

2012-03-30

95

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...

96

Bent Bonds and Multiple Bonds.

ERIC Educational Resources Information Center

Considers carbon-carbon multiple bonds in terms of Pauling's bent bond model, which allows direct calculation of double and triple bonds from the length of a CC single bond. Lengths of these multiple bonds are estimated from direct measurements on "bent-bond" models constructed of plastic tubing and standard kits. (CS)

Robinson, Edward A.; Gillespie, Ronald J.

1980-01-01

97

NSDL National Science Digital Library

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

NCTM Illuminations

2000-01-01

98

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

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

2011-01-01

99

The SmI2\\/H2O\\/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and found to be a viable alternative to the Birch reduction yielding the corresponding deoxygenated product in excellent yield. The reaction has been investigated by kinetic methods, and a mechanism involving a pre-complexation of the alcohol to SmI2 followed by an amine mediated electron transfer and subsequent bond

Tobias Ankner; Gran Hilmersson

2009-01-01

100

Geometric Algebra: the framework for geometric computations

Geometric Algebra: the framework for geometric computations Leo Dorst Intelligent Autonomous and in computation. Q: How do they relate? A: They are all aspects of geometric algebra! This connection can unify and simplify geometric programs. 2 #12; 2 What's new in geometric algebra? The uni#12;cation is achieved

Dorst, Leo

101

Relative Entropy Relaxations for Signomial Optimization Venkat Chandrasekaranc

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

102

NSDL National Science Digital Library

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

Siegrist, Kyle

103

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

Eric Chisolm

2012-05-27

104

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 al...

Chisolm, Eric

2012-01-01

105

This manuscript discusses microwave-assisted solid-phase synthesis of hydrogen-bond surrogate based alpha-helices and analogues by ring-closing metathesis (RCM). Microwave-mediated RCM allows access to a greater variety of amino acid residues in the macrocycles in shorter reaction times and higher yields compared to conventional heating. Surprisingly, we discovered that the Grubbs II catalyst is highly active under the influence of microwaves but catalytically dead under oil-bath conditions for the metathesis of these peptide bisolefins. [reaction: see text] PMID:17134282

Chapman, Ross N; Arora, Paramjit S

2006-12-01

106

Cooperativity in beryllium bonds.

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

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

2014-03-01

107

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

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

2014-01-01

108

Theoretical study of the S bond HO blue-shifted hydrogen bond

NASA Astrophysics Data System (ADS)

Theoretical calculations were performed to study the nature of the hydrogen bonds in the complexes HCHOHSO, HCOOHHSO, HCHOHOO, and HCOOHHOO. The geometric structures and vibrational frequencies of these four complexes at the MP2/6-31G(d,p) and MP2/6-311+G(d,p) levels are calculated by standard and counterpoise-corrected methods, respectively. The results indicate that in the complexes HCHOHSO and HCOOHHSO the S bond H bond is strongly contracted. In the S bond HO hydrogen bonds, the calculated blue shifts for the S bond H stretching frequencies are in the vicinity of 50 cm-1. While in the complexes HCHOHOO and HCOOHHOO, the O bond H bond is elongated and O bond HO red-shifted hydrogen bonds are found. From the natural bond orbital analysis it can be seen that the X bond H bond length in the X bond HY hydrogen bond is controlled by a balance of four main factors in the opposite directions: hyperconjugation, electron density redistribution, rehybridization, and structural reorganization. Among them hyperconjugation has the effect of elongating the X bond H bond. Electron density redistribution and rehybridization belong to the bond shortening effects, while structural reorganization has an uncertain influence on the X bond H bond length. In the complexes HCHOHSO and HCOOHHSO, the shortening effects dominate which lead to the blue shift of the S bond H stretching frequencies. In the complexes HCHOHOO and HCOOHHOO where elongating effects are dominant, the O bond HO hydrogen bonds are red-shifted.

Yang, Yong

109

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.

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

110

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 c(12) 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 R(2+n)T2X(2+n), previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm-Wyckoff sequence f(5)c(2). 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. PMID:24745932

Ponou, Simon; Lidin, Sven; Zhang, Yuemei; Miller, Gordon J

2014-05-01

111

Brachytherapy 3 (2004) 147152 Comparison of inverse planning simulated annealing and geometrical

optimization for prostate high-dose-rate brachytherapy I-Chow J. Hsu1,*, Etienne Lessard1 , Vivian Weinberg2. In this study, IPSA is compared with geometrical optimization (GO) for prostate brachytherapy. METHODS: Optimization; Inverse planning; Simulated annealing; Geometric optimization; HDR prostate brachytherapy

Pouliot, Jean

112

Pauling bond strength, bond length and electron density distribution

A power law regression equation, ~~/r)-0.21, determined for a large number of oxide crystals at ambient conditions and ~~~~/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)/~~

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

2014-01-18

113

Reconciling Geometric Planners with

Hierarchical Planning People Detection Structure Discovery Collaborative Manipulation Skill Learning #12Reconciling Geometric Planners with Physical Manipulation Siddhartha Srinivasa Senior Research Geometric Planners with Physical Manipulation Siddhartha Srinivasa Senior Research Scientist Intel

North Carolina at Chapel Hill, University of

114

Characteristics of hydrogen bond revealed from water clusters

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

115

Hybrid Matrix Geometric Algebra

\\u000a The structures of matrix algebra and geometric algebra are completely compatible and in many ways complimentary, each having\\u000a their own advantages and disadvantages. We present a detailed study of the hybrid 2 2 matrix geometric algebra M(2,IG) with elements in the 8 dimensional geometric algebra IG=IG\\u000a 3 of Euclidean space. The resulting hybrid structure, isomorphic to the geometric algebra

Garret Sobczyk; Gordon Erlebacher

2004-01-01

116

Geometric Systems in Architecture

NSDL National Science Digital Library

Lessons that include deriving formulas for volume by building rectangular prisms, identifying geometric solids by constructing cubes, tetrahedrons, and octahedrons, and identifying geometric patterns found in ceiling and wall tiles. Additional lessons deal with geometric systems manifested in the crystal structure of minerals. Students are introduced to three-dimensional figures in nature, in the classroom, and in architecture.

Decaprio, Sheryl A.

2007-04-09

117

ArithmeticGeometric Progression

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

Feret, Jérôme

118

Objective: The aim of this study was to identify sources of anatomical misrepresentation due to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimise the 4DCT scan protocol and improve geometrical-temporal accuracy. Methods: A phantom with an imaging insert was driven with a sinusoidal superior-inferior motion of varying amplitude and period for 4DCT scanning. The length of a high density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested. Results: No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall mounted or couch mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5s rather than 1.0s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose. Conclusions: 4DCT accuracy may be increased by optimising scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace leads to spatial artefacts and this risk can be reduced by using a couch mounted infrared camera. Advances in knowledge: This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed. PMID:25470359

O'Connell, Barry; Irvine, Denise M; Cole, Aidan J; Hanna, Gerard G; McGarry, Conor K

2014-12-01

119

An Orientation-dependent Hydrogen Bonding Potential Improves Prediction of Specificity and

An Orientation-dependent Hydrogen Bonding Potential Improves Prediction of Specificity of Washington Box 351560, Seattle WA 98195-1560, USA Hydrogen bonding is a key contributor to the specificity-dependent hydrogen bonding potential based on the geometric characteristics of hydrogen bonds in high

Morozov, Alexandre V.

120

Pauling bond strength, bond length and electron density distribution

NASA Astrophysics Data System (ADS)

The power law regression equation, ~~/r)-0.21 determined for oxide crystals at ambient conditions and ~~~~/r)-0.22 determined for geometry-optimized hydroxyacid molecules that relate the geometry-optimized bond lengths to the average Pauling bond strength, ~~~~, for the M-O bonded interactions. On the basis of the correspondence between the equations relating and ~~~~ with bond length, it seems plausible that the Pauling bond strength might serve a rough estimate of the accumulation of the electron density between M-O bonded pairs of atoms. Similar expressions, relating bond length and bond strength hold for fluoride, nitride and sulfide molecules and crystals. The similarity of the expressions for the crystals and molecules is compelling evidence that molecular and crystalline M-O bonded interactions are intrinsically related. The value of = r[(1.41)/~~

Gibbs, G. V.; Ross, N. L.; Cox, D. F.; Rosso, K. M.; Iversen, B. B.; Spackman, M. A.

2014-01-01

121

NASA Technical Reports Server (NTRS)

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

Yao, Tse-Min; Choi, Kyung K.

1987-01-01

122

Characterisation of sorbate geometrical isomers.

trans,trans Isomers of sorbic acid, its potassium salt and ethyl sorbate isomerise under UV irradiation. All four geometrical isomers of the acid, salt and ester were separated using high-performance liquid chromatography on a nonpolar reversed-phase column (C18) and the ester also by gas chromatography on a VOCOL capillary column. The limit of detection and the interval of linearity were determined for all chromatographic methods. Individual isomers were identified with NMR analysis. Resolved chemical shifts of protons adjacent to the double bonds enabled qualitative and quantitative determination of isomers in the mixture. Antimicrobial activity of potassium sorbate isomers was tested on yeast Saccharomyces cerevisiae. Results show that the pure trans,trans isomer has a higher antimicrobial activity than the mixture of isomers. PMID:11206806

Cigi?, I K; Plavec, J; Mozina, S S; Zupancic-Kralj, L

2001-01-01

123

Fast Wind Turbine Design via Geometric Programming

Fast Wind Turbine Design via Geometric Programming Warren Hoburg and Pieter Abbeel UC Berkeley the application of GP to large wind turbine design problems a promising approach. Nomenclature (·)a, (·)t axial the wind sector's annual turnover of $65 Billion, optimal design of wind turbines is a problem of great

Abbeel, Pieter

124

Geometric Reasoning for Automated Planning

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

125

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

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

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

2014-08-19

126

Geometric Algebra for Physicists

As leading experts in geometric algebra, Chris Doran and Anthony Lasenby have led many new developments in the field over the last ten years. This book provides an introduction to the subject, covering applications such as black hole physics and quantum computing. Suitable as a textbook for graduate courses on the physical applications of geometric algebra, the volume is also

Chris Doran; Anthony Lasenby

2003-01-01

127

Geometric Shapes in Architecture

NSDL National Science Digital Library

A unit designed to improve students' understanding and appreciation of basic geometric shapes used in architecture. It describes various plane geometric figures and discusses in detail the properties of several of these figures. Perimeters and areas of polygons and circles are computed.

Fox, Lauretta J.

2007-02-22

128

Hierarchies of Geometric Entanglement

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

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

2007-01-01

129

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

Harrington, J. Patrick

130

Geometric sensitivity of ClearPET Neuro

NASA Astrophysics Data System (ADS)

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.

Gundlich, Brigitte; Weber, Simone

2007-02-01

131

Three-dimensional hydrogen-bond geometry and probability information from a crystal survey

An extensive crystal survey of the Cambridge Structural Database has been carried out to provide hydrogen-bond data for use in drug-design strategies. Previous crystal surveys have generated 1D frequency distributions of hydrogen-bond distances and angles, which are not sufficient to model the hydrogen bond as a ligand-receptor interaction. For each hydrogen-bonding group of interest to the drug designer, geometric hydrogen-bond

J. E. J. Mills; Philip M. Dean

1996-01-01

132

NASA Technical Reports Server (NTRS)

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

1977-01-01

133

Optimization in Geometric Graphs: Complexity and Approximation

independent neighbors if the graph is a unit disk graph. Thus, G cannot contain K1;6 as an induced subgraph either. a0 a1 a2 a3 a4 a5 Fig. 1 Intersection of 2 unit disks centered at points v and u. Lemma 5. If G is a unit ball graph, then it does not contain... induced subgraphs isomorphic to K1;13, K2;6 and K3;4. Proof. Let G be a unit ball graph. It is easy to see that G cannot contain K1;13 as an induced subgraph by Lemma 1. Let u and v be two non-adjacent vertices in G. Consider the intersection of the unit...

Kahruman-Anderoglu, Sera

2011-02-22

134

A Babylonian Geometrical Algebra.

ERIC Educational Resources Information Center

A possible method of derivation of prescriptions for solving problems, found in Babylonian cuneiform texts, is presented. It is a kind of "geometric algebra" based mainly on one figure and the manipulation of or within various areas and segments. (MNS)

Bidwell, James K.

1986-01-01

135

AJ Geometric Formulas Calculator

NSDL National Science Digital Library

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

Jimmy Raymond

136

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...

137

MM Algorithms for Geometric and Signomial Programming.

This paper derives new algorithms for signomial programming, a generalization of geometric programming. The algorithms are based on a generic principle for optimization called the MM algorithm. In this setting, one can apply the geometric-arithmetic mean inequality and a supporting hyperplane inequality to create a surrogate function with parameters separated. Thus, unconstrained signomial programming reduces to a sequence of one-dimensional minimization problems. Simple examples demonstrate that the MM algorithm derived can converge to a boundary point or to one point of a continuum of minimum points. Conditions under which the minimum point is unique or occurs in the interior of parameter space are proved for geometric programming. Convergence to an interior point occurs at a linear rate. Finally, the MM framework easily accommodates equality and inequality constraints of signomial type. For the most important special case, constrained quadratic programming, the MM algorithm involves very simple updates. PMID:24634545

Lange, Kenneth; Zhou, Hua

2014-02-01

138

Geometric algebra: a computation framework for geometrical applications

Abstract Geometric algebra is a consistent computational,framework,in which to define geometric primitives and their relationships. This algebraic approach contains all geometric operators and permits specification of constructions in a coordinate-free manner. Thus, the ideas of geometric algebra are important for developers of CAD systems. This paper gives an introduction to the elements of geometric algebra, which contains primitives of any

L. Dorst; S. Mann

2001-01-01

139

Geometric algebra: a computational framework

Geometric algebra: a computational framework for geometrical applications (part I: algebra) Leo Dorst and Stephen Mann Abstract Geometric algebra is a consistent computational framework in which of geometric algebra are important for developers of CAD systems. This paper gives an introduction

Waterloo, University of

140

Geometric algebra: a computational framework

Geometric algebra: a computational framework for geometrical applications (part II: applications) Leo Dorst and Stephen Mann Abstract Geometric algebra is a consistent computational framework in which. It shows how using well-chosen geometric algebra models, we can eliminate special cases in incidence

Dorst, Leo

141

Geometric simulation of flexible motion in proteins.

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

Wells, Stephen A

2014-01-01

142

Students' Perceptions of Parental Bonding Styles and Their Academic Burnout

ERIC Educational Resources Information Center

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

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

2012-01-01

143

Inflation from geometrical tachyons

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.

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

2005-10-15

144

... the child's social and cognitive development. Why Is Bonding Important? Bonding is essential for a baby. Studies ... as biological parents and their children. Back Continue Bonding With Daddy Men these days spend more time ...

145

What Determines Bond Costs. Municipal Bonds Series.

ERIC Educational Resources Information Center

Public officials in small towns who participate infrequently in the bond market need information about bond financing. This publication, one in a series of booklets published by the Western Rural Development Center using research gathered between 1967-77, discusses factors influencing the marketability and cost of bond financing for towns and

Young, Douglas; And Others

146

Ideally Glassy Hydrogen Bonded Networks

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

J. C. Phillips

2005-08-05

147

A comparative study of semiempirical bond dissociation energy calculations

Anderson's modified version of the extended Hueckel molecular orbital method and the MNDO and AM1 methods of Dewar are used to study bond cleavage in molecular fragments of interest in coal liquefaction. Geometric conformations, molecular orbital coefficients for the HOMO's and LUMO's, and bond dissociation energies are computed and compared for the three methods. Qualitative agreement with experiment for bond cleavage is observed for the three methods for the neutral molecule. However the ASED-MO method appears to best describe the bond cleavage in the presence of an electron-accepting catalyst.

Ades, H.F.; Companion, A.L.; Subbaswamy, K.R. (Univ. of Kentucky, Lexington (United States))

1991-08-22

148

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

149

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

150

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

Code of Federal Regulations, 2012 CFR

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

2012-07-01

151

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

Code of Federal Regulations, 2011 CFR

2011-07-01

152

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

Code of Federal Regulations, 2014 CFR

2014-07-01

153

ERIC Educational Resources Information Center

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

Smart, Julie; Marshall, Jeff

2007-01-01

154

Geometric Series via Probability

ERIC Educational Resources Information Center

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

Tesman, Barry

2012-01-01

155

Geometric computing in computer graphics using conformal geometric algebra

Abstract Early in the development,of Computer Graphics it was realized that projective geometry,was well suited for the representation of transformations. Now, it seems that another change of paradigm is lying ahead of us based on Geometric Computing using Conformal Geometric Algebra. Due to its geometric intuitiveness, elegance and simplicity, the underlying Conformal Geometric Algebra appears to be a promising mathematical,tool

Dietmar Hildenbrand

2005-01-01

156

Geometric Algebra: A Computational Framework for Geometrical Applications (Part 1)

Geometric algebra is a consistent computational framework in which to de- fine geometric primitives and their relationships. This algebraic approach con- tains all geometric operators and permits specification of constructions in a totally coordinate-free manner. Since it contains primitives of any dimensionality (rather than just vectors) it has no special cases: all intersections of primitives are com- puted with one

Leo Dorst; Stephen Mann

2002-01-01

157

Real-Time Nondestructive Contact Resistance Method to Estimate Wire Bond Pull Force

NASA Astrophysics Data System (ADS)

We estimate microelectronic wire bond quality nondestructively by measuring the contact resistance (CR) of the bond in situ during the bonding process. This measurement employs a Kelvin cross setup contacting the wedge, 25 um Al wire and an Au substrate. The results verify that the method can identify the bond process phases and predict whether the bonding was successful (94% classification accuracy). The method can be used for process control and optimization to create stronger bonds and higher yield.

Kurppa, R.; Seppnen, H.; Merilinen, A.; Oinonen, M.; Hggstrm, E.

2010-02-01

158

Bond University Queensland, Australia

Bond University Queensland, Australia About: Bond University is a private university located institutions, Bond has a strong component of international students who hail from some 80 countries worldwide. Bond's small size, internationalized-student body, 14-week trimesters, and fabulous Gold Coast location

Duchowski, Andrew T.

159

Foundations of Geometric Algebra computing

NASA Astrophysics Data System (ADS)

Geometric Algebra has the power to lead easily from the geometric intuition of solving an engineering application to its efficient implementation on current and future computing platforms. It is easy to develop new algorithms in areas such as computer graphics, robotics, computer animation and computer simulation. Owing to its geometric intuitiveness, compactness and simplicity, algorithms based on Geometric Algebra can lead to enhanced quality, a reduction in development time and solutions that are more easily understandable and maintainable. Often, a clear structure and greater elegance result in lower runtime performance. However, based on our computing technology, Geometric Algebra implementations can even be faster and more robust than conventional ones. We present an example on how easy it is to describe algorithms in Geometric Algebra and introduce our technology for the integration of Geometric Algebra into standard programming languages. We really do hope that this technology can support the widespread use of Geometric Algebra Computing technology in many engineering fields.

Hildenbrand, Dietmar

2012-09-01

160

Geometric Phases for Coherent States

We explore geometric phases of coherent states and some of their properties. A better and elegant expression of geometric phase for coherent state is derived. It is used to obtain the explicit form of the geometric phase for entangled coherent states, several interesting results followed by considering different cases for the parameters. The effects of entanglement and harmonic potential on the geometric phase are discussed.

Da-Bao Yang; Jing-Ling Chen; Chunfeng Wu; C. H. Oh

2011-10-19

161

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.

162

The classical geometrization electromagnetism

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.

C. A. Duarte

2015-02-11

163

NSDL National Science Digital Library

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

164

LET'S BOND! A Chemical Bonding Webquest

NSDL National Science Digital Library

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

Hicken, Mrs.

2009-04-08

165

NASA Technical Reports Server (NTRS)

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.

Gwo, Dz-Hung (Inventor)

2003-01-01

166

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

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

Stanley, H. Eugene

167

The authors address the problem of planning optimal grasps. Two general optimality criteria that consider the total finger force and the maximum finger force are introduced and discussed. Their formalization using various metrics on a space of generalized forces is detailed. The geometric interpretation of the two criteria leads to an efficient planning algorithm. An example of its use in

Carlo Ferrari; John Canny

1992-01-01

168

Geometric phase in Bohmian mechanics

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

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

2010-10-15

169

Channel Bonding Notes 03/25/2004 Channel Bonding Notes

Channel Bonding Notes 03/25/2004 Channel Bonding Notes Luke Hindman Department of Computer Science by attempting to use the Linux kernel bonding driver (bonding.o) to implement channel bonding on the master node. However, each time I would bring up the bonded interface (bond0) I would loose communication

Jain, Amit

170

NSDL National Science Digital Library

The Bond Market Association "represents securities firms and banks that underwrite, trade and sell debt securities." Their web site is divided into several sections. The Research Desk presents the results of research conducted by the association, including forecasts of economic growth and analysis of bond market trends. The Legislative Issues and Regulatory sections provide a summary of legislative and regulatory developments of interest to the bond market community. Market Practices contains guidelines and procedures to be followed in the bond market. The site also provides information to investors on how to invest in corporate bonds, tax-exempt municipal bonds, and mortgage securities.

171

Representing geometrical knowledge.

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

Anderson, J A

1997-01-01

172

NASA Astrophysics Data System (ADS)

Integer sequences where each element is determined by a previous randomly chosen element are investigated analytically. In particular, the random geometric series xn = 2xp with 0 les p les n - 1 is studied. At large n, the moments grow algebraically, langxsnrang ~ nbgr(s) with bgr(s) = 2s - 1, while the typical behaviour is xn ~ nln 2. The probability distribution is obtained explicitly in terms of the Stirling numbers of the first kind and it approaches a log-normal distribution asymptotically.

Ben-Naim, E.; Krapivsky, P. L.

2004-06-01

173

NASA Astrophysics Data System (ADS)

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.

Zhou, Pan-Pan; Qiu, Wen-Yuan

2009-08-01

174

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 ...

Bao, Jack (Jack C.)

2009-01-01

175

Bonding silicones with epoxies

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.

Tira, J.S.

1980-01-01

176

Geometric phase analysis of lattice images from algal cellulose microfibrils

A geometric phase analysis has been applied to high-resolution transmission electron microscopy images from algal cellulose microcrystals. The pictures were decomposed into images containing selectively the amplitude or phase information associated to selected Bragg reflections. Compared with I? (monoclinic)-rich cellulose microfibrils, I?(triclinic)-rich microfibrils were found to be more heterogeneous when viewed along the H-bonding sheets. As a microfibril twist and

Tomoya Imai; Jean-Luc Putaux; Junji Sugiyama

2003-01-01

177

Rapid adhesive bonding concepts

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

178

This paper analyzes the development of 49 local bond markets. The main finding is that policies and laws matter: countries with stable inflation rates and strong creditor rights have more developed local bond markets and rely less on foreign- currency-denominated bonds. The results suggest that \\

FRANCIS E. WARNOCK

2006-01-01

179

The tensile strength of bonded acrylic is tested as a function of bond joint thickness. 0.125 in. thick bond joints were found to posses the maximum strength while the acceptable range of joints varied from 0.063 in. to almost 0.25 in. Such joints are used in the Sudbury Neutrino Observatory.

Wouters, J.M.; Doe, P.J.

1991-02-01

180

GAMNAS- GEOMETRIC AND MATERIAL NONLINEAR ANALYSIS OF STRUCTURES

NASA Technical Reports Server (NTRS)

GAMNAS (Geometric and Material Nonlinear Analysis of Structures) is a two-dimensional finite element stress analysis program developed to support fracture mechanics studies of debonding and delamination. GAMNAS options include linear, geometric nonlinear, material nonlinear, and combined geometric and material nonlinear analysis. GAMNAS can analyze plastic deformations of isotropic materials. GAMNAS can calculate strain energy release rates using a virtual crack extension technique. The element available to the GAMMNAS user is a four-node isoparametric quadrilateral with full or reduced integration. GAMNAS has been used to investigate debonding and delamination of adhesively bonded composites. GAMNAS is written in FORTRAN 77 for batch execution and has been implemented on a PRIME 700 series computer. As currently dimensioned for a maximum global stiffness matrix of 1300 degrees of freedom and a bandwidth of 70, GAMNAS has a central memory requirement of approximately 603K of 16 bit words. GAMNAS was developed in 1983.

Whitcomb, J. D.

1994-01-01

181

Geometrical scaling law for laser shock processing

NASA Astrophysics Data System (ADS)

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

Wu, Xianqian; Tan, Qingming; Huang, Chenguang

2013-07-01

182

Aerospace plane guidance using geometric control theory

NASA Technical Reports Server (NTRS)

A reduced-order method employing decomposition, based on time-scale separation, of the 4-D state space in a 2-D slow manifold and a family of 2-D fast manifolds is shown to provide an excellent approximation to the full-order minimum-fuel ascent trajectory. Near-optimal guidance is obtained by tracking the reduced-order trajectory. The tracking problem is solved as regulation problems on the family of fast manifolds, using the exact linearization methodology from nonlinear geometric control theory. The validity of the overall guidance approach is indicated by simulation.

Van Buren, Mark A.; Mease, Kenneth D.

1990-01-01

183

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

184

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

2012-01-01

185

Geometric integration in Born-Oppenheimer molecular dynamics.

Geometric integration schemes for extended Lagrangian self-consistent Born-Oppenheimer molecular dynamics, including a weak dissipation to remove numerical noise, are developed and analyzed. The extended Lagrangian framework enables the geometric integration of both the nuclear and electronic degrees of freedom. This provides highly efficient simulations that are stable and energy conserving even under incomplete and approximate self-consistent field (SCF) convergence. We investigate three different geometric integration schemes: (1) regular time reversible Verlet, (2) second order optimal symplectic, and (3) third order optimal symplectic. We look at energy conservation, accuracy, and stability as a function of dissipation, integration time step, and SCF convergence. We find that the inclusion of dissipation in the symplectic integration methods gives an efficient damping of numerical noise or perturbations that otherwise may accumulate from finite arithmetics in a perfect reversible dynamics. PMID:22168678

Odell, Anders; Delin, Anna; Johansson, Brje; Cawkwell, Marc J; Niklasson, Anders M N

2011-12-14

186

Computer optimized design of electron guns

Calabazas Creek Research, Inc. (CCR) and North Carolina State University are developing optimization techniques for advanced, 3D, electron guns. Our approach uses advanced solid modeling CAD programs capable of controlling geometrical parameters with design tables manipulated by an optimization control program. Geometrical and parametric changes are simulated using a 3D, finite element, adaptive meshing charged particle program. Results of the

R. L. Ives; Thuc Bui; M. Read; J. David; A. Attarian; H. Tran

2008-01-01

187

Prospective bonding applications

NASA Astrophysics Data System (ADS)

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

Ancenay, H.; Benazet, D.

1981-07-01

188

Bonding thermoplastic polymers

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.

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

189

Geometric Design and Comparison of Multifaceted Antenna Arrays for Hemispherical Coverage

We address the optimization of the geometric design of two classes of multifaceted antenna arrays, namely, pyramids and pyramidal frusta. The optimization involves choosing the face elevation and the number of arrays. The optimal face elevation minimizes the maximum scan angle encountered by the arrays, given a general hemispherical coverage requirement. Firstly, an approach is presented to compute the face

Inas Khalifa; Rodney G. Vaughan

2009-01-01

190

On the nature of blueshifting hydrogen bonds.

The block-localized wave function (BLW) method can derive the energetic, geometrical, and spectral changes with the deactivation of electron delocalization, and thus provide a unique way to elucidate the origin of improper, blueshifting hydrogen bonds versus proper, redshifting hydrogen bonds. A detailed analysis of the interactions of F(3)CH with NH(3) and OH(2) shows that blueshifting is a long-range phenomenon. Since among the various energy components contributing to hydrogen bonds, only the electrostatic interaction has long-range characteristics, we conclude that the contraction and blueshifting of a hydrogen bond is largely caused by electrostatic interactions. On the other hand, lengthening and redshifting is primarily due to the short-range n(Y)??*(X-H) hyperconjugation. The competition between these two opposing factors determines the final frequency change direction, for example, redshifting in F(3)CH???NH(3) and blueshifting in F(3)CH???OH(2). This mechanism works well in the series F(n)Cl(3)-n CH???Y (n=0-3, Y=NH(3), OH(2), SH(2)) and other systems. One exception is the complex of water and benzene. We observe the lengthening and redshifting of the O-H bond of water even with the electron transfer between benzene and water completely quenched. A distance-dependent analysis for this system reveals that the long-range electrostatic interaction is again responsible for the initial lengthening and redshifting. PMID:24862363

Mo, Yirong; Wang, Changwei; Guan, Liangyu; Brada, Benot; Hiberty, Philippe C; Wu, Wei

2014-07-01

191

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

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

Michela Ponticorvo; Orazio Miglino

2010-01-01

192

An algorithm for converting a virtual-bond chain into a complete polypeptide backbone chain

NASA Technical Reports Server (NTRS)

A systematic analysis is presented of the algorithm for converting a virtual-bond chain, defined by the coordinates of the alpha-carbons of a given protein, into a complete polypeptide backbone. An alternative algorithm, based upon the same set of geometric parameters used in the Purisima-Scheraga algorithm but with a different "linkage map" of the algorithmic procedures, is proposed. The global virtual-bond chain geometric constraints are more easily separable from the loal peptide geometric and energetic constraints derived from, for example, the Ramachandran criterion, within the framework of this approach.

Luo, N.; Shibata, M.; Rein, R.

1991-01-01

193

Reactive interatomic potentials and their geometrical features

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

Kocbach, Ladislav

2009-01-01

194

Geometric and algebraic algorithms for modelling yarn in woven fabrics

This paper presents geometric and algebraic algorithms and relevant optimizing operators for 3D computer modelling of yarns in fabric. New algorithms and approaches are successfully employed to create more realistic and flexible geometry models with consideration of the differential and topological structure of yarns. By using asymptotic iterative approximation, we have developed a new algorithm for creating B-spline curves using

Y. Jiang; X. Chen

2005-01-01

195

Geometric Design of Pyramidal Antenna Arrays for Hemispherical Scan Coverage

An approach is presented for optimizing the geometry of pyramidal antenna arrays, given a full azimuth and a full or limited elevation scan requirement. It involves choosing the best face elevation and number of faces of the pyramid, which minimize the maximum scan angle while maximizing the geometric directivity. The analysis shows that the 4-face pyramid is the best choice.

Inas Khalifa; Rodney Vaughan

2007-01-01

196

Algebraic, geometric, and stochastic aspects of genetic operators

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

197

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

Goldberg, P.W.

1993-04-01

198

Geometric algebra: a computational framework for geometrical applications. 2

Every vector space with an inner product has a geometric algebra, whether or not you choose to use it. This article shows how to call on this structure to define common geometrical constructs, ensuring a consistent computational framework. The goal is to show you that this can be done and that it is compact, directly computational, and transcends the dimensionality

Stephen Mann; Leo Dorst

2002-01-01

199

Geometric frustration in small colloidal clusters.

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 10k(B)T), the average bond lifetime approaches the simulation timescale and the system becomes nonergodic. For small clusters, m?5, where geometric frustration is not relevant, despite nonergodicity, for sufficient strengths of the attractive interaction the yield of clusters which maximize 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 C(2v) 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 long 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. PMID:21715858

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

2009-10-21

200

Photothermoelastic analysis of bonded propellant grains

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

I. M. Daniel; A. J. Durelli

1961-01-01

201

A Novel Geometric Flow-Driven Approach for Quality Improvement of Segmented

A Novel Geometric Flow-Driven Approach for Quality Improvement of Segmented Tetrahedral Meshes: Segmented tetrahedral mesh, quality improvement, geometric flow-driven, optimization-based mesh smoothing-manifold boundaries, are needed for partitioned regions. In this paper, we focus on quality improvement of segmented

Xu, Guo-liang

202

Protein Folding: A New Geometric Analysis

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

Walter A. Simmons; Joel L. Weiner

2008-09-11

203

System analysis through bond graph modeling

NASA Astrophysics Data System (ADS)

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

McBride, Robert Thomas

2005-07-01

204

Characterization of transfer-bonded silicon bolometer arrays

In this paper we present the design, fabrication and characterization of arrays of boron doped polycrystalline silicon bolometers. The bolometer arrays have been fabricated using CMOS compatible wafer-level transfer bonding. The transfer bonding technique allows the bolometer materials to be deposited and optimized on a separate substrate and then, in a subsequent integration step to be transferred to the read-out

Frank Niklaus; Johan Pejnefors; Matteo Dainese; Michael Haggblad; Per-Erik Hellstrom; Ulf J. Wallgren; Goran Stemme

2004-01-01

205

Geometric Algebra for Subspace Operations

The set theory relations ?, \\\\,?,n, and ? have corollaries in subspace relations. Geometric algebra is introduced as a useful framework to explore these subspace operations. The relations ?, \\\\, and ? are easily subsumed by geometric algebra for Euclidean metrics. A short computation shows that the meet (n) and join (?) are resolved in a projection operator representation with

T. A. Bouma; L. Dorst; H. G. J. Pijls

2002-01-01

206

Thematic Mapper geometric correction processing

NASA Technical Reports Server (NTRS)

The Thematic Mapper Image Processing System is described from the point of view of geometric correction. The system performance requirements are discussed, and the Landsat-D flight segment is described. The ground processing and overall geometric system performance is addressed. Those aspects of the Thematic Mapper Image Processing System that differ significantly from those of the MSS System are emphasized.

Beyer, E. P.

1984-01-01

207

Circle actions in geometric quantisation

NASA Astrophysics Data System (ADS)

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.

Solha, Romero

2015-01-01

208

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

209

Bonded semiconductor substrate

Ge/Si and other nonsilicon film heterostructures are formed by hydrogen-induced exfoliation of the Ge film which is wafer bonded to a cheaper substrate, such as Si. A thin, single-crystal layer of Ge is transferred to Si substrate. The bond at the interface of the Ge/Si heterostructures is covalent to ensure good thermal contact, mechanical strength, and to enable the formation of an ohmic contact between the Si substrate and Ge layers. To accomplish this type of bond, hydrophobic wafer bonding is used, because as the invention demonstrates the hydrogen-surface-terminating species that facilitate van der Waals bonding evolves at temperatures above 600.degree. C. into covalent bonding in hydrophobically bound Ge/Si layer transferred systems.

Atwater, Jr.; Harry A. (South Pasadena, CA), Zahler; James M. (Pasadena, CA)

2010-07-13

210

Multidisciplinary optimization for gas turbine airfoil design

A multidisciplinary optimization procedure for gas turbine airfoil design has been developed and demonstrated on a generic blade. Aerodynamic and heat transfer design objectives are integrated along with various constraints on the airfoil geometry. Heat transfer optimization and external aerodynamic shape optimization has been performed on a generic blade. Shape optimization is performed using geometric parameters associated with film cooling

S. S. Talya; J. N. Rajadas; A. Chattopadhyay

2000-01-01

211

NASA Technical Reports Server (NTRS)

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

Plueddemann, E.

1986-01-01

212

NASA Technical Reports Server (NTRS)

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

Smith, G. C.

1972-01-01

213

Geometric algebra, qubits, geometric evolution, and all that

The earlier approach is used for description of qubits and geometric phase parameters, the things critical in the area of topological quantum computing. The used tool, Geometric (Clifford) Algebra is the most convenient formalism for that case. Generalization of formal complex plane to an an arbitrary plane in three dimensions and of usual Hopf fibration to the map generated by an arbitrary unit value element of even sub-algebra of the three-dimensional Geometric Algebra are resulting in more profound description of qubits compared to quantum mechanical Hilbert space formalism.

Soiguine, Alexander M

2015-01-01

214

Teachers' Domain: Covalent Bonding

NSDL National Science Digital Library

This Flash interactive tutorial explores covalent bonding, a type of chemical bond that involves sharing of electrons. Learners investigate the attractive and repulsive forces that act on atomic particles and how the sharing of electrons can keep atoms together. See how two hydrogen atoms interact with each other to create a covalent bond. Learn about patterns in the periodic table and how electrostatic potential energy determines the bond length. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

215

Hydrogen bonding and anaesthesia

NASA Astrophysics Data System (ADS)

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

Sndorfy, C.

2004-12-01

216

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

217

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

218

Geometrically frustrated magnets Arnab Sen, TIFR

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 (virtual hoppings). Arnab Sen, TIFR Geometrically frustrated magnets #12;Unfrustrated magnets Usually

219

Repeating Decimals and Geometric Series

NSDL National Science Digital Library

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.

2011-01-01

220

Antenna with Dielectric Having Geometric Patterns

NASA Technical Reports Server (NTRS)

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.

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

221

Geometrical method of decoupling

NASA Astrophysics Data System (ADS)

The computation of tunes and matched beam distributions are essential steps in the analysis of circular accelerators. If certain symmetrieslike midplane symmetryare present, then it is possible to treat the betatron motion in the horizontal, the vertical plane, and (under certain circumstances) the longitudinal motion separately using the well-known Courant-Snyder theory, or to apply transformations that have been described previously as, for instance, the method of Teng and Edwards. In a preceding paper, it has been shown that this method requires a modification for the treatment of isochronous cyclotrons with non-negligible space charge forces. Unfortunately, the modification was numerically not as stable as desired and it was still unclear, if the extension would work for all conceivable cases. Hence, a systematic derivation of a more general treatment seemed advisable. In a second paper, the author suggested the use of real Dirac matrices as basic tools for coupled linear optics and gave a straightforward recipe to decouple positive definite Hamiltonians with imaginary eigenvalues. In this article this method is generalized and simplified in order to formulate a straightforward method to decouple Hamiltonian matrices with eigenvalues on the real and the imaginary axis. The decoupling of symplectic matrices which are exponentials of such Hamiltonian matrices can be deduced from this in a few steps. It is shown that this algebraic decoupling is closely related to a geometric decoupling by the orthogonalization of the vectors E?, B?, and P?, which were introduced with the so-called electromechanical equivalence. A mathematical analysis of the problem can be traced down to the task of finding a structure-preserving block diagonalization of symplectic or Hamiltonian matrices. Structure preservation means in this context that the (sequence of) transformations must be symplectic and hence canonical. When used iteratively, the decoupling algorithm can also be applied to n-dimensional systems and requires O(n2) iterations to converge to a given precision.

Baumgarten, C.

2012-12-01

222

Bond energy effects on strength, cooperativity and robustness of molecular structures.

A fundamental challenge in engineering biologically inspired materials and systems is the identification of molecular structures that define fundamental building blocks. Here, we report a systematic study of the effect of the energy of chemical bonds on the mechanical properties of molecular structures, specifically, their strength and robustness. By considering a simple model system of an assembly of bonds in a cluster, we demonstrate that weak bonding, as found for example in H-bonds, results in a highly cooperative behaviour where clusters of bonds operate synergistically to form relatively strong molecular clusters. The cooperative effect of bonding results in an enhanced robustness since the drop of strength owing to the loss of a bond in a larger cluster only results in a marginal reduction of the strength. Strong bonding, as found in covalent interactions such as disulphide bonds or in the backbone of proteins, results in a larger mechanical strength. However, the ability for bonds to interact cooperatively is lost, and, as a result, the overall robustness is lower since the mechanical strength hinges on individual bonds rather than a cluster of bonds. The systematic analysis presented here provides general insight into the interplay of bond energy, robustness and other geometric parameters such as bond spacing. We conclude our analysis with a correlation of structural data of natural protein structures, which confirms the conclusions derived from our study. PMID:23050078

Chou, Chia-Ching; Buehler, Markus J

2011-10-01

223

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

224

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

225

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. PMID:23123244

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

2013-01-15

226

NASA Technical Reports Server (NTRS)

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.

Boerio, J.

1984-01-01

227

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

Gordon, Nirit

2013-01-01

228

Visionlearning: Chemical Bonding

NSDL National Science Digital Library

This digital learning module provides an easily-understood overview of chemical bonding for users with little formal background in chemistry or physics. It explores ionic bonding through the example of sodium (an alkali metal) reacting with chlorine gas to produce common table salt. A concept simulation further illustrates the process.

Carpi, Anthony

2011-07-12

229

ERIC Educational Resources Information Center

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

Bank, Stephen P.; Kahn, Michael D.

230

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.

231

NASA Technical Reports Server (NTRS)

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

1989-01-01

232

NASA Technical Reports Server (NTRS)

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.

Pontius, James T. (Inventor)

2010-01-01

233

Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

234

Optical bonding reinforced by femtosecond laser welding

NASA Astrophysics Data System (ADS)

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

Lacroix, Fabrice; Hlie, David; Valle, Ral

2011-09-01

235

Guitars, Violins, and Geometric Sequences

ERIC Educational Resources Information Center

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

Barger, Rita; Haehl, Martha

2007-01-01

236

Geometric algorithms for reconfigurable structures

In this thesis, we study three problems related to geometric algorithms of reconfigurable structures. In the first problem, strip folding, we present two universal hinge patterns for a strip of material that enable the ...

Benbernou, Nadia M

2011-01-01

237

Current Concept of Geometrical Accuracy

NASA Astrophysics Data System (ADS)

Within the solving VEGA 1/0615/12 research project "Influence of 5-axis grinding parameters on the shank cutte?s geometric accuracy", the research team will measure and evaluate geometrical accuracy of the produced parts. They will use the contemporary measurement technology (for example the optical 3D scanners). During the past few years, significant changes have occurred in the field of geometrical accuracy. The objective of this contribution is to analyse the current standards in the field of geometric tolerance. It is necessary to bring an overview of the basic concepts and definitions in the field. It will prevent the use of outdated and invalidated terms and definitions in the field. The knowledge presented in the contribution will provide the new perspective of the measurement that will be evaluated according to the current standards.

Grg, Augustn; Grgov, Ingrid

2014-06-01

238

Algorithms of NCG geometrical module

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

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

2012-12-15

239

Geometric Algebra for Subspace Operations

The set theory relations \\\\in, \\\\backslash, \\\\Delta, \\\\cap, and \\\\cup have\\u000acorollaries in subspace relations. Geometric Algebra is introduced as the ideal\\u000aframework to explore these subspace operations. The relations \\\\in, \\\\backslash,\\u000aand \\\\Delta are easily subsumed by Geometric Algebra for Euclidean metrics. A\\u000ashort computation shows that the meet (\\\\cap) and join (\\\\cup) are resolved in a\\u000aprojection operator

T. A. Bouma; L. Dorst; H. G. J. Pijls

2001-01-01

240

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

Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC Donald J. Siegel yield substantial adhesion energies in the range 46 J/m¢ , bonding at the optimal C of an interface is the ideal work of adhesion,£¥¤§¦ [1], which is defined as the bond energy needed (per unit area

Adams, James B

241

Extent of Hydrogen-Bond Protection in Folded Proteins: A Constraint on Packing Architectures

Extent of Hydrogen-Bond Protection in Folded Proteins: A Constraint on Packing Architectures Ariel structuring and ultimately exclusion of water by hydrophobes surrounding backbone hydrogen bonds turn hydrophobes yields an optimal hydrogen-bond stabilization. This motif is shown to be nearly ubiquitous

Berry, R. Stephen

242

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

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

Prentiss, Mara

243

Optimal bird migration revisited

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

Thomas Alerstam

244

Quadratic 0-1 programming: Geometric methods and duality analysis

NASA Astrophysics Data System (ADS)

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

Liu, Chunli

245

Geometric quantum discord through the Schatten 1-norm

NASA Astrophysics Data System (ADS)

It has recently been pointed out that the geometric quantum discord, as defined by the Hilbert-Schmidt norm (2-norm), is not a good measure of quantum correlations, since it may increase under local reversible operations on the unmeasured subsystem. Here, we revisit the geometric discord by considering general Schatten p-norms, explicitly showing that the 1-norm is the only p-norm able to define a consistent quantum correlation measure. In addition, by restricting the optimization to the tetrahedron of two-qubit Bell-diagonal states, we provide an analytical expression for the 1-norm geometric discord, which turns out to be equivalent to the negativity of quantumness. We illustrate the measure by analyzing its monotonicity properties.

Paula, F. M.; de Oliveira, Thiago R.; Sarandy, M. S.

2013-06-01

246

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

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

Sóbester, András

247

Wafer-Level Thermocompression Bonds

Thermocompression bonding of gold is a promising technique for achieving low temperature, wafer-level bonding without the application of an electric field or complicated pre-bond cleaning procedure. The presence of a ductile ...

Tsau, Christine H.

248

A geometric view of quantum cellular automata

Nielsen, et al. [1, 2] proposed a view of quantum computation where determining optimal algorithms is equivalent to extremizing a geodesic length or cost functional. This view of optimization is highly suggestive of an action principle of the space of N-qubits interacting via local operations. The cost or action functional is given by the cost of evolution operators on local qubit operations leading to causal dynamics, as in Blute et. al. [3] Here we propose a view of information geometry for quantum algorithms where the inherent causal structure determines topology and information distances [4, 5] set the local geometry. This naturally leads to geometric characterization of hypersurfaces in a quantum cellular automaton. While in standard quantum circuit representations the connections between individual qubits, i.e. the topology, for hypersurfaces will be dynamic, quantum cellular automata have readily identifiable static hypersurface topologies determined via the quantum update rules. We demonstrate construction of quantum cellular automata geometry and discuss the utility of this approach for tracking entanglement and algorithm optimization.

Jonathan R. McDonald; Paul M. Alsing; Howard A. Blair

2012-08-15

249

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

250

Cryogenic evaluation of epoxy bond strength

NASA Astrophysics Data System (ADS)

The purpose of the work presented here was to determine methods of optimizing the adhesion of a particular epoxy (CTD-101K, Composite Technology Development Inc.) to a particular nickel-based alloy substrate (Incoloy 908, Inco Alloys International) for cryogenic applications. Initial efforts were focused on surface preparation of the substrate material via various mechanical and chemical cleaning techniques. Test samples, fabricated to simulate the conduit-to-insulation interface, were put through a mock heat treat and vacuum/pressure impregnation process. Samples were compression/shear load tested to compare the bond strengths at room temperature and liquid nitrogen temperature. The resulting data indicate that acid etching creates a higher bond strength than the other tested techniques and that the bond formed is stronger at cryogenic temperatures than at room temperature. A description of the experiment along with the resulting data is presented here.

Albritton, N.; Young, W.

251

Geometric algebra, spacetime physics and gravitation

Geometric algebra, spacetime physics and gravitation By S. F. GUL L, A. N. LASENBY AND C. J. L Clifford's `geometric algebra' is presented as the natural language for expressing geometrical ideas are discussed. 1. Introduction For some time we have been convinced that geometric algebra is the best available

Cambridge, University of

252

Geometric Context from a Single Image

Many computer vision algorithms limit their performance by ignoring the underlying 3D geometric structure in the image. We show that we can estimate the coarse geometric properties of a scene by learning appearance-based mod- els of geometric classes, even in cluttered natural scenes. Geometric classes describe the 3D orientation of an image region with respect to the camera. We provide

Derek Hoiem; Alexei A. Efros; Martial Hebert

2005-01-01

253

ERIC Educational Resources Information Center

Describes how a long-predicted decline in the fortunes of small private colleges is beginning to show up in the bond market, as the number of colleges now rated in the junk category has nearly doubled. (EV)

Van Der Werf, Martin

2003-01-01

254

Gold Thermocompression Wafer Bonding

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

Spearing, S. Mark

255

NSDL National Science Digital Library

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

Leske, Cavin.

256

Mirror profile optimization for nano-focusing KB mirror

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

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

2010-06-23

257

Comparison of the copper and gold wire bonding processes for LED packaging

NASA Astrophysics Data System (ADS)

Wire bonding is one of the main processes of the LED packaging which provides electrical interconnection between the LED chip and lead frame. The gold wire bonding process has been widely used in LED packaging industry currently. However, due to the high cost of gold wire, copper wire bonding is a good substitute for the gold wire bonding which can lead to significant cost saving. In this paper, the copper and gold wire bonding processes on the high power LED chip are compared and analyzed with finite element simulation. This modeling work may provide guidelines for the parameter optimization of copper wire bonding process on the high power LED packaging.

Zhaohui, Chen; Yong, Liu; Sheng, Liu

2011-02-01

258

Water's Hydrogen Bond Strength

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

Martin Chaplin

2007-06-10

259

Who Should Buy Long-Term Bonds?

According to conventional wisdom, long-term bonds are appropriate for conservative long-term investors. This paper develops a model of optimal consumption and portfolio choice for infinite-lived investors with recursive utility who face stochastic interest rates, solves the model using an approximate analytical method, and evaluates conventional wisdom. As risk aversion increases, the myopic component of risky asset demand disappears but the

John Y. Campbell; Luis M. Viceira

2001-01-01

260

Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups

Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups Gongbing Hong, James for providing weighted sharing of aggregate capacity in networks having parallel bonded channels in which a single channel may simultaneously be a member of multiple bonding groups. Our work is motivated

Martin, Jim

261

30 CFR 581.33 - Bonds and bonding requirements.

Code of Federal Regulations, 2013 CFR

...Resources 2 2013-07-01 2013-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2013-07-01

262

Leave with Pay Bond/Waiver of Bond Form

Leave with Pay Bond/Waiver of Bond Form Submit to: The Office of Faculty Affairs and Professional Development, ADM 451 I. As you were granted a leave with pay, you must either post a bond in the amount of the salary to be paid during the leave or be granted a waiver of the bond. Most faculty members request

263

30 CFR 281.33 - Bonds and bonding requirements.

Code of Federal Regulations, 2011 CFR

...Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 281.33 Bonds and bonding requirements. (a) When the leasing notice...

2011-07-01

264

30 CFR 581.33 - Bonds and bonding requirements.

Code of Federal Regulations, 2014 CFR

...Resources 2 2014-07-01 2014-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2014-07-01

265

30 CFR 581.33 - Bonds and bonding requirements.

Code of Federal Regulations, 2012 CFR

...Resources 2 2012-07-01 2012-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2012-07-01

266

30 CFR 281.33 - Bonds and bonding requirements.

Code of Federal Regulations, 2010 CFR

...Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 281.33 Bonds and bonding requirements. (a) When the leasing notice...

2010-07-01

267

Geometrical modelling of textile reinforcements

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

268

Geometric scalar theory of gravity

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.

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

269

Geometric and Electronic Properties of Edge-decorated Graphene Nanoribbons

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

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

2014-01-01

270

Geometrical Optics of Dense Aerosols

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

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

2013-04-24

271

Star products and geometric algebra

The formalism of geometric algebra can be described as deformed super analysis. The deformation is done with a fermionic star product, that arises from deformation quantization of pseudoclassical mechanics. If one then extends the deformation to the bosonic coefficients of superanalysis one obtains quantum mechanics for systems with spin. This approach clarifies on the one hand the relation between Grassmann and Clifford structures in geometric algebra and on the other hand the relation between classical mechanics and quantum mechanics. Moreover it gives a formalism that allows to handle classical and quantum mechanics in a consistent manner.

Henselder, Peter [Fachbereich Physik, Universitaet Dortmund 44221, Dortmund (Germany)]. E-mail: henselde@dilbert.physik.uni-dortmund.de; Hirshfeld, Allen C. [Fachbereich Physik, Universitaet Dortmund 44221, Dortmund (Germany)]. E-mail: hirsh@physik.uni-dortmund.de; Spernat, Thomas [Fachbereich Physik, Universitaet Dortmund 44221, Dortmund (Germany)]. E-mail: tspernat@zylon.physik.uni-dortmund.de

2005-05-01

272

Star Products and Geometric Algebra

The formalism of geometric algebra can be described as deformed super analysis. The deformation is done with a fermionic star product, that arises from deformation quantization of pseudoclassical mechanics. If one then extends the deformation to the bosonic coefficient part of superanalysis one obtains quantum mechanics for systems with spin. This approach clarifies on the one hand the relation between Grassmann and Clifford structures in geometric algebra and on the other hand the relation between classical mechanics and quantum mechanics. Moreover it gives a formalism that allows to handle classical and quantum mechanics in a consistent manner.

Peter Henselder; Allen C. Hirshfeld; Thomas Spernat

2004-09-28

273

Geometrical Modeling of Steel Ropes

NASA Astrophysics Data System (ADS)

The paper deals with the mathematical geometric modeling of the ropes of circular cross- section. Such rope can be formed from strands of different shapes. There is considered steel rope made up of six strands, whose crosssection has oval, triangular or circular profil in this paper. The wires of these types of the strands are presented by parametric equations of the wire axis. The equations are implemented in the Pro/Engineer Wildfire V5 software for creating the geometrical model of the strand.

Stanov, Eva

2013-11-01

274

Geometric design of compound reflectors

NASA Astrophysics Data System (ADS)

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.

Downs, J. W.

1985-05-01

275

Geometrical and FEA study on Millipede Forming

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

276

Geometric nomenclature and classification of RNA base pairs.

Non-Watson-Crick base pairs mediate specific interactions responsible for RNA-RNA self-assembly and RNA-protein recognition. An unambiguous and descriptive nomenclature with well-defined and nonoverlapping parameters is needed to communicate concisely structural information about RNA base pairs. The definitions should reflect underlying molecular structures and interactions and, thus, facilitate automated annotation, classification, and comparison of new RNA structures. We propose a classification based on the observation that the planar edge-to-edge, hydrogen-bonding interactions between RNA bases involve one of three distinct edges: the Watson-Crick edge, the Hoogsteen edge, and the Sugar edge (which includes the 2'-OH and which has also been referred to as the Shallow-groove edge). Bases can interact in either of two orientations with respect to the glycosidic bonds, cis or trans relative to the hydrogen bonds. This gives rise to 12 basic geometric types with at least two H bonds connecting the bases. For each geometric type, the relative orientations of the strands can be easily deduced. High-resolution examples of 11 of the 12 geometries are presently available. Bifurcated pairs, in which a single exocyclic carbonyl or amino group of one base directly contacts the edge of a second base, and water-inserted pairs, in which single functional groups on each base interact directly, are intermediate between two of the standard geometries. The nomenclature facilitates the recognition of isosteric relationships among base pairs within each geometry, and thus facilitates the recognition of recurrent three-dimensional motifs from comparison of homologous sequences. Graphical conventions are proposed for displaying non-Watson-Crick interactions on a secondary structure diagram. The utility of the classification in homology modeling of RNA tertiary motifs is illustrated. PMID:11345429

Leontis, N B; Westhof, E

2001-04-01

277

Hydrogen bonding is a key contributor to the specificity of intramolecular and intermolecular interactions in biological systems. Here, we develop an orientation-dependent hydrogen bonding potential based on the geometric characteristics of hydrogen bonds in high-resolution protein crystal structures, and evaluate it using four tests related to the prediction and design of protein structures and proteinprotein complexes. The new potential is

Tanja Kortemme; Alexandre V. Morozov; David Baker

2003-01-01

278

NASA Astrophysics Data System (ADS)

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

Chan, Matthew Wei-Jen

279

Bond Markets with Stochastic Volatility

Bond Markets with Stochastic Volatility Rafael DeSantiago Jean-Pierre Fouque Knut Sølna September 27, 2007 Abstract We analyze stochastic volatility effects in the context of the bond market- nection to defaultable bonds. Contents 1 Introduction 2 2 Pricing Bonds 3 2.1 The Term Structure Equation

Solna, Knut

280

Optimal domain decomposition strategies

NASA Technical Reports Server (NTRS)

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

Yoon, Yonghyun; Soni, Bharat K.

1995-01-01

281

Surface analysis in composite bonding

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

282

Shear bond strength of four orthodontic bonding systems.

Recently new orthodontic bonding systems have been developed for attachment of brackets to the etched facial surfaces of teeth. Two of these new systems use bonding agents that contain solvents. It is claimed that this improves the polymerization of the unfilled resin primer and may increase bond strength. A new light-cured restorative enamel/dentin-bonding agent has also recently been introduced. Its value in orthodontic bonding has not been determined. The aim of this investigation was to evaluate the shear bond strengths of the three new bonding systems and to compare these with a conventional orthodontic bonding system. Forty-eight enamel specimens were prepared with 600-grit silicone carbide paper, acid etched with 37% phosphoric acid, and assigned to four enamel-bonding treatment groups: (A) Saga sealant; (B) Maximum Cure; (C) Scotchbond-2; and (D) Concise enamel bond. After enamel priming, the specimens were bonded to Concise orthodontic bonding resin. The bonded specimens were thermocycled (15 degrees C to 45 degrees C) and then stored in distilled water at 37 degrees C for 7 days. Shear bond strength was tested with an Instron testing machine at a strain rate of 0.02 in/min. The mean shear bond strengths and standard deviations reported in MN/m2 were (A) 20.34 (5.37); (B) 25.33 (5.96); (C) 14.59 (5.25); and (D) 20.13 (4.98). The mean shear bond strengths for groups A, B, and D were significantly greater (p less than 0.05) than that for group C. The addition of solvents to the new orthodontic bonding systems does not appear to have a clinically significant effect. The new restorative bonding resin does not provide comparable enamel bond strengths. PMID:2405634

Coreil, M N; McInnes-Ledoux, P; Ledoux, W R; Weinberg, R

1990-02-01

283

Platonic Symmetry and Geometric Thinking

ERIC Educational Resources Information Center

Cubic symmetry is used to build the other four Platonic solids and some formalism from classical geometry is introduced. Initially, the approach is via geometric construction, e.g., the "golden ratio" is necessary to construct an icosahedron with pentagonal faces. Then conventional elementary vector algebra is used to extract quantitative

Zsombor-Murray, Paul

2007-01-01

284

CRYSTAL CELLS IN GEOMETRIC ALGEBRA

This paper focuses on the symmetries of space lattice crystal cells. All 32 point groups of three dimensional crystal cells are exclusively described by vectors (three for one particular cell) taken from the physical cell. Geometric multiplication of these vectors completely generates all symmetries, including reflections, rotations, inversions, rotary-reflections and rotary-inversions. The sets of vectors necessary are illustrated in drawings

Eckhard Hitzer; Christian Perwass

285

Spacetime physics with geometric algebra

This is an introduction to spacetime algebra (STA) as a unified mathematical language for physics. STA simplifies, extends, and integrates the mathematical methods of classical, relativistic, and quantum physics while elucidating geometric structure of the theory. For example, STA provides a single, matrix-free spinor method for rotational dynamics with applications from classical rigid body mechanics to relativistic quantum theory-thus significantly

David Hestenes

2003-01-01

286

Geometric Multigrid Susanne C. Brenner

guess z0 Output = MGV(k, , z0, m) For k = 0, we solve A0z = exactly to obtaiGeometric Multigrid Susanne C. Brenner Department of Mathematics and Center for Computation Analysis VII, North-Holland, 2000. 4 U. Trottenberg, C. Oosterlee and A. Schüller Multigrid, Academic Press

Jensen, Max

287

Geometrical Methods in Gauge Theory

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

Henrique de A. Gomes

2006-10-25

288

Geometric theory of meromorphic functions

Then X is of hyperbolic type and ? is a univalent function in U. An example of the .... We have B(C,?) = B, where ? is the Weierstrass function of a hexagonal .... However a geometric characterization of K-singularities is known only for a very.

2009-11-11

289

The geometric structure of color.

Color is commonly described in terms of the three perceptual attributes-hue, saturation, and brightness-of which only hue has a qualitative nature, saturation and brightness being of a quantitative nature. A possible reason for such a phenomenological structure of the color manifold, and its geometric representation, are discussed. PMID:25589300

Logvinenko, Alexander D

2015-01-01

290

Vergence, Vision, and Geometric Optics

ERIC Educational Resources Information Center

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

Keating, Michael P.

1975-01-01

291

Since high temperatures can lead to broadening of absorption spectra, ambient temperature chloride melts were used; the system used was AlCl{sub 3}-1-ethyl-3-methyl-imidazolium chloride (EMIC). The uv-visible spectrum of UCl{sub 4} in basic melt had many peaks with the most intense (triplet) ones around 2000 nm, similar to these at high temperature and indicating the same species. The electronic transition is allowed by a static rather than a vibronic mechanism. The central peak in the UCl{sub 6}{sup 2-} spectrum indicates distortion of geometry from the O{sub h} symmetry by the solvent medium. Very strong hydrogen bonding between UCl{sub 6}{sup 2-} and solvent EMI is suggested.

Dai, S.; Toth, L.M.; Del Cul, G.D.; Metcalf, D.H.

1994-09-01

292

Insulation bonding test system

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

293

Hyperconjugation-mediated solvent effects in phosphoanhydride bonds

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

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

2012-01-01

294

Hyperconjugation-mediated solvent effects in phosphoanhydride bonds.

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 antiperiplanar orientation, the overall magnitude of the anomeric effect is compensated approximately by the other lone pair as it becomes more antiperiplanar. Furthermore, solvent modulation of the anomeric effect is not restricted to the antiperiplanar 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 nonbridging O-P bonds, increasing the distance between donor and acceptor orbitals and decreasing orbital overlap, which leads to a reduction of the anomeric effect. Solvent effects are additive with greater reduction in the anomeric effect upon increasing water coordination. By controlling the coordination environment of substrates in an active site, kinases, phosphatases, and other enzymes important in metabolism and signaling may have the potential to modulate the stability of individual phosphoanhydride bonds through stereoelectronic effects. PMID:23009395

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

2012-10-18

295

Quantal trajectories and geometric phase

NASA Astrophysics Data System (ADS)

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.

Carlsen, Olav Henrik

296

Teachers' Domain: Ionic Bonding

NSDL National Science Digital Library

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

2011-08-16

297

Universal prediction of intramolecular hydrogen bonds in organic crystals.

A complete exploration of intramolecular hydrogen bonds (IHBs) has been undertaken using a combination of statistical analyses of the Cambridge Structural Database and computation of ab initio interaction energies for prototypical hydrogen-bonded fragments. Notable correlations have been revealed between computed energies, hydrogen-bond geometries, donor and acceptor chemistry, and frequencies of occurrence. Significantly, we find that 95% of all observed IHBs correspond to the five-, six- or seven-membered rings. Our method to predict a propensity for hydrogen-bond occurrence in a crystal has been adapted for such IHBs, applying topological and chemical descriptors derived from our findings. In contrast to intermolecular hydrogen bonding, it is found that IHBs can be predicted across the complete chemical landscape from a single optimized probability model, which is presented. Predictivity of 85% has been obtained for generic organic structures, which can exceed 90% for discrete classes of IHB. PMID:20305358

Galek, Peter T A; Fbin, Lszl; Allen, Frank H

2010-04-01

298

DYNAMIC MANIPULATION SCHEMES OF GEOMETRICAL CONSTRUCTIONS

DYNAMIC MANIPULATION SCHEMES OF GEOMETRICAL CONSTRUCTIONS: INSTRUMENTAL GENESIS AS AN ABSTRACTION: Dynamic manipulation of geometrical constructions enabled by a specially designed computational tool abstraction. The Dynamic Manipulation Schemes (DMS) developed by 13-year-old students based on the use

Paris-Sud XI, Université de

299

Testing multifield inflation: A geometric approach

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 ...

Peterson, Courtney M.

300

Unusual chemical bonds are proposed. Each bond is almost covalent but is characterized by the thread of a small radius $\\sim 0.6\\times 10^{-11}$cm, between two nuclei in a molecule. The main electron density is concentrated outside the thread as in a covalent bond. The thread is formed by the electron wave function which has a tendency to be singular on it. The singularity along the thread is cut off by electron "vibrations" due to the interaction with zero point electromagnetic oscillations. The electron energy has its typical value of (1-10)eV. Due to the small tread radius the uncertainty of the electron momentum inside the thread is large resulting in a large electron kinetic energy $\\sim 1 MeV$. This energy is compensated by formation of a potential well due to the reduction of the energy of electromagnetic zero point oscillations. This is similar to formation of a negative van der Waals potential. Thread bonds are stable and cannot be created or destructed in chemical or optical processes.

Ivlev, B

2015-01-01

301

Bonded Retainers - Clinical Reliability

Bonded retainers have become a very important retention appliance in orthodontic treatment. They are popular because they are considered reliable, independent of patient cooperation, highly efficient, easy to fabricate, and almost invisible. Of these traits, reliability is the subject of this clinical study. A total of 549 patients with retainers were analyzed with regard to wearing time, extension of the

Dietmar Segner; Bettina Heinrici

2000-01-01

302

Dialogic Bonds and Boundaries.

ERIC Educational Resources Information Center

A study of literature cannot be divorced from cultural contexts, nor can it ignore the humanist vision in interpreting literary texts. To discover dialogic bonds and boundaries between the reader and the text, or the writer and the audience, English classes should have two objectives: (1) to explore the diversity of perspectives, and (2) to relate

Khawaja, Mabel

303

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

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

2012-01-10

304

Flax Fiber - Interfacial Bonding

Technology Transfer Automated Retrieval System (TEKTRAN)

Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...

305

ERIC Educational Resources Information Center

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

Akeroyd, F. Michael

1982-01-01

306

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

NASA Astrophysics Data System (ADS)

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.

Wikfeldt, K. T.

2014-12-01

307

Geometric uncertainty relation for quantum ensembles

NASA Astrophysics Data System (ADS)

Geometrical structures of quantum mechanics provide us with new insightful results about the nature of quantum theory. In this work we consider mixed quantum states represented by finite rank density operators. We review our geometrical framework that provide the space of density operators with Riemannian and symplectic structures, and we derive a geometric uncertainty relation for observables acting on mixed quantum states. We also give an example that visualizes the geometric uncertainty relation for spin-\\frac{1}{2} particles.

Heydari, Hoshang; Andersson, Ole

2015-02-01

308

Geometric Algebras for Euclidean Geometry

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.

Charles Gunn

2015-01-26

309

The verdict geometric quality library.

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

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

2006-03-01

310

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.

311

Geometrical frustration in colloidal ``antiferromanget''

NASA Astrophysics Data System (ADS)

We report experiments about a self-organized colloidal system that exhibits geometrical frustration similar to that of antiferromagnetic Ising spins on a triangular lattice. Novel thermally sensitive microgel NIPA (N-isopropyl acrylamide) spheres are close packed between two parallel flat walls with a vertical separation of about 1.5-particle diameters. The particles form an approximate in-plane triangular lattice. Neighboring particles tend to push each other toward opposite walls leading to out-of-plane local up and down buckling. We tune the strength of such effective antiferromagnetic interactions by varying temperature-tunable diameter of spheres. ``Spin'' flipping was directly visualized with video microscopy. We investigated the static structures, the dynamics of particles with different degrees of frustration and the degenerated ground state. This experiment is the first dynamic measurement in a geometrical frustrated system at single-particle resolution.

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

2008-03-01

312

The Arithmetic-Geometric Progression Abstract Domain

VMCAI'05 The Arithmetic-Geometric Progression Abstract Domain Jérôme Feret ?cole Normale Supérieure;Overview 1. Introduction 2. Case study 3. Arithmetic-geometric progressions 4. Benchmarks 5. Conclusion-geometric progressions 4. Benchmarks 5. Conclusion Jérôme Feret, LIENS 13 January, 2005 #12;Arithmetic

Feret, Jérôme

313

Geometric Algebra and Physics Anthony Lasenby

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

Hart, Gus

314

Surface Evolution and Representation using Geometric Algebra

Surface Evolution and Representation using Geometric Algebra Anthony Lasenby 1 and Joan Lasenby 2 1 such surfaces. 1 Introduction The mathematical language we will use throughout will be that of geometric algebra no more here than outline some aspects used in the problems we will discuss. In a geometric algebra of n

Cambridge, University of

315

Recent Applications of Conformal Geometric Anthony Lasenby

Recent Applications of Conformal Geometric Algebra Anthony Lasenby Cavendish Laboratory, University://www.mrao.cam.ac.uk/?anthony Abstract. We discuss a new covariant approach to geometry, called conformal geometric algebra vectors. In the final sections, we discuss a new approach to the area of conformal geometric algebra

Cambridge, University of

316

Recent Applications of Conformal Geometric Anthony Lasenby

Recent Applications of Conformal Geometric Algebra Anthony Lasenby Cavendish Laboratory, University://www.mrao.cam.ac.uk/~anthony Abstract. We discuss a new covariant approach to geometry, called conformal geometric algebra refer the reader to [3] (this volume), for a summary of the conformal geometric algebra approach

Cambridge, University of

317

Introduction to Pauli Geometric Algebra M. Berrondo

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

Hart, Gus

318

Geometric Algebra and Particle Dynamics

.In a recent publication [1] it was shown how the geometric algebra G\\u000a 4,1, the algebra of 5-dimensional space-time, can generate relativistic dynamics from the simple principle that only null geodesics\\u000a should be allowed. The same paper showed also that Dirac equation could be derived from the condition that a function should\\u000a be monogenic in that algebra; this construction of

Jos B. Almeida

2008-01-01

319

Simplicial Calculus with Geometric Algebra

We construct geometric calculus on an oriented k-surface embedded in Eu- clidean space by utilizing the notion of an oriented k-surface as the limit set of a sequence of k-chains. This method provides insight into the relationship between the vector derivative, and the Fundamental Theorem of Calculus and Residue Theorem It should be of practical value in numerical flnite difierence

Garret Sobczyk

320

Geometrical Methods in Gauge Theory

In this work we explore the geometrical interpretation of gauge theories\\u000athrough the formalism of fiber bundles. Moreover, we conduct an investigation\\u000ain the topology of fiber bundles, providing a proof of the Classification\\u000aTheorem. In the last chapter we present some applications, such as\\u000aelectromagnetism and generalized Kaluza-Klein Theory.

Henrique de Andrade Gomes

2006-01-01

321

Geometric compression through topological surgery

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

Gabriel Taubin; Jarek Rossignac

1998-01-01

322

ERROR PROPAGATION THROUGH GEOMETRIC TRANSFORMATIONS

investigate the propagation of errors through geometric trans- formations, such as reflections, rotations m23 m42 l1 l2 l3 l4 A A B B m13 m23 m42 l1 l2 l3 l4 A A B B Figure 1. Fat lines with butterflies defining |A B|. 2. Preliminaries 2.1. Fat points and fat lines. In Euclidean geometry, points are the most

Wallner, Johannes

323

Enzymatic functionalization of carbon-hydrogen bonds.

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

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

2011-04-01

324

Orthodontic bonding to porcelain: A comparison of bonding systems

Statement of problem. Direct bonding of orthodontic brackets to porcelain surfaces has been plagued by failure. Purpose. The purpose of this study was to compare the bond strengths of several different bonding systems when bonding orthodontic brackets to porcelain-fused-to-metal surfaces. Material and methods. Fifty natural glazed feldspathic porcelain-fused-to-noble metal disks 6 mm in diameter and 3 mm in height (1

Dianne D. Pannes; Daniel K. Bailey; Jeffrey Y. Thompson; Daniel M. Pietz

2003-01-01

325

Geometric Tachyon and Warm Inflation

The inflationary models developed in presence of a background radiation can be a solution to the reheating problem faced by common cold (isentropic) inflationary scenario. A D-brane system comprising of k Neuvo-Schwarz(NS) 5-branes with a transverse circle and BPS D3-branes with world volume parallel to the NS 5-branes, placed at a point on the transverse circle diametrically opposite to the NS 5-branes has a point of unstable equilibrium and the D3 brane has a geometric tachyonic mode associated with displacement of the brane along the circle. Cold inflationary scenario has been studied in connection with this geometric tachyon \\cite{PA1} where it was found that one needs a background of minimum $10^4$ branes to realize a viable inflationary model. In this piece of work, we have tried to study a model of inflation driven by this geometric tachoyn in presence of radiation. We have found that compared to the isentropic scenario, to satisfy the observational bounds, the number of background branes required in this case reduces drastically and a viable model can be obtained with even six to seven NS 5-branes in the background.In this context, we have also analyzed the non-gaussianity associated with the model and observed that the concerned parameter lies well within the observation limit.

Anindita Bhattacharjee; Atri Deshamukhya

2014-02-27

326

Geometric endoscopy and mirror symmetry

NASA Astrophysics Data System (ADS)

The geometric Langlands correspondence has been interpreted as the mirror symmetry of the Hitchin fibrations for two dual reductive groups. This mirror symmetry, in turn, reduces to T-duality on the generic Hitchin fibers, which are smooth tori. In this paper, we study what happens when the Hitchin fibers on the B-model side develop orbifold singularities. These singularities correspond to local systems with finite groups of automorphisms. In the classical Langlands program, local systems of this type are called endoscopic. They play an important role in the theory of automorphic representations, in particular, in the stabilization of the trace formula. Our goal is to use the mirror symmetry of the Hitchin fibrations to expose the special role played by these local systems in the geometric theory. The study of the categories of A-branes on the dual Hitchin fibers allows us to uncover some interesting phenomena associated with the endoscopy in the geometric Langlands correspondence. We then follow our predictions back to the classical theory of automorphic functions. This enables us to test and confirm them. The geometry we use is similar to that which is exploited in recent work by Ng, a fact which could be significant for understanding the trace formula.

Frenkel, Edward; Witten, Edward

327

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

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

McCabe, Patrick; Korb, Oliver; Cole, Jason

2014-05-27

328

Improving humidity bond reliability of copper bonding wires

There is growing interest in Cu wire bonding for LSI interconnection due to cost savings and better electrical and mechanical properties. Conventional bare Cu bonding wires, in general, are severely limited in their use compared to Au wires. A coated Cu bonding wire (EX1) has been developed for LSI application. EX1 is a Pd-coated Cu wire to enhance the bondability.

Tomohiro Uno; Takashi Yamada

2010-01-01

329

hp calculators HP 50g Bond Yield

rate the bond pays is fixed when the bond is first sold or issued, but changes in the market interesthp calculators HP 50g Bond Yield The FINANCE menu Bond Yield Practice solving for the yield of a bond #12;hp calculators HP 50g Bond Yield hp calculators - 2 - HP 50g Bond Yield The FINANCE menu

Vetter, Frederick J.

330

NSDL National Science Digital Library

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

2011-01-01

331

NSDL National Science Digital Library

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.

2011-01-01

332

The Illiquidity of Corporate Bonds

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

Bao, Jack

333

Geometric programming prediction of design trends for OMV protective structures

NASA Technical Reports Server (NTRS)

The global optimization trends of protective honeycomb structural designs for spacecraft subject to hypervelocity meteroid and space debris are presented. This nonlinear problem is first formulated for weight minimization of the orbital maneuvering vehicle (OMV) using a generic monomial predictor. Five problem formulations are considered, each dependent on the selection of independent design variables. Each case is optimized by considering the dual geometric programming problem. The dual variables are solved for in terms of the generic estimated exponents of the monomial predictor. The primal variables are then solved for by conversion. Finally, parametric design trends are developed for ranges of the estimated regression parameters. Results specify nonmonotonic relationships for the optimal first and second sheet mass per unit areas in terms of the estimated exponents.

Mog, R. A.; Horn, J. R.

1990-01-01

334

GaalopHigh Performance Parallel Computing Based on Conformal Geometric Algebra

NASA Astrophysics Data System (ADS)

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.

Hildenbrand, Dietmar; Pitt, Joachim; Koch, Andreas

335

On the bond distance in methane

NASA Technical Reports Server (NTRS)

The equilibrium bond distance in methane has been optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valance correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers.

Bowen-Jenkins, Philippa; Pettersson, Lars G. M.; Siegbahn, Per; Almlof, Jan; Taylor, Peter R.

1988-01-01

336

On the bond distance in methane

NASA Technical Reports Server (NTRS)

The equilibrium bond distance in methane was optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valence correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers.

Bowen-Jenkins, Philippa; Pettersson, Lars G. M.; Siegbahn, Per; Almloef, Jan; Taylor, Peter R.

1987-01-01

337

Isoelectronic C=F(+) and C=O bonds contained in fluoro-substituted carbenium ions, aldehydes, and ketones are investigated with regard to their bond properties by utilizing the vibrational spectra of these molecules. It is demonstrated that bond dissociation energies (BDEs), bond lengths, vibrational stretching frequencies, and bond densities are not reliable descriptors of the bond strength. The latter is related to the intrinsic BDE, which corresponds to nonrelaxed dissociation products retaining the electronic structure and geometry they have in the molecule. It is shown that the harmonic stretching force constants k(a) of the localized internal coordinate vibrations (adiabatic vibrational modes) reflect trends in the intrinsic BDEs. The k(a) values of both CO and CF bonds are related to the bond lengths through a single exponential function. This observation is used to derive a common bond order n for 46 CO- and CF-containing molecules that reliably describes differences in bonding. CF bonds in fluorinated carbenium ions possess bond orders between 1.3 and 1.7 as a result of significant pi back-bonding from F to C, which is sensitive to electronic effects caused by substituents at the carbenium center. Therefore, the strength of the C=F(+) bond can be used as a sensor for (hyper)conjugation and other electronic effects influencing the stability of the carbenium ion. The diatomic C=F(+) ion has a true double bond due to pi donation from the F atom. The characterization of CF bonds with the help of adiabatic stretching modes is also applied to fluoronium ions (n = 0.3-0.6) and transition states involving CF cleavage and HF elimination (n = 0.7-0.8). PMID:19152353

Kraka, Elfi; Cremer, Dieter

2009-03-01

338

EFFICIENT INVERSE KINEMATICS ALGORITHM BASED ON CONFORMAL GEOMETRIC ALGEBRA

EFFICIENT INVERSE KINEMATICS ALGORITHM BASED ON CONFORMAL GEOMETRIC ALGEBRA Using Reconfigurable@esa.informatik.tu-darmstadt.de Keywords: geometric algebra, geometric computing, computer animation, inverse kinematics, hardware approach for algorithms developed based on conformal geometric algebra using reconfigurable hardware. We

339

Cyclic Bonds in Branched Polymers

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.

Kazumi Suematsu

2015-02-12

340

Bond financing in volatile times.

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

Gould, Kenneth A; Blanda, Christopher M

2014-03-01

341

Rapid Adhesive Bonding of Composites

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

342

New Materials for Bonding Wire

In this paper, Insulated wire for Fine pad pitch bonding and 3D PKG technology, Cu wire and Au-Ag wire for cost reduction, and Ag wire in response to bond pad metallization change are reviewed from technology aspect. With only few tens of nanometers thick coating layer, insulated wire forms stable free air ball with good 1 st bond bondability. As

Jeong Tak Moon; June Sub Hwang; Jong Su Cho; Seong Hyoun Kim

343

Code of Federal Regulations, 2010 CFR

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

2010-10-01

344

Code of Federal Regulations, 2011 CFR

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

2011-10-01

345

Code of Federal Regulations, 2012 CFR

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

2012-10-01

346

Code of Federal Regulations, 2014 CFR

2014-10-01

347

Code of Federal Regulations, 2013 CFR

2013-10-01

348

Solder Bonded Optoelectronic Transceiver Components

solder bonded optical modulator and detector arrays on silicon VLSI circuits, together with solder bonded lasers and micro-fabricated silicon packaging are described. These approaches are being used for integrated components for optical interconnect applications. Introduction. integration using solder bonding enables optimised optoelectronic and electronic components to be combined for a wide range of applications, particularly in optical interconnect where the

A. J. Moseley; M. J. Goodwin

1993-01-01

349

Global-Local Finite Element Analysis for Thermo-Mechanical Stresses in Bonded Joints

NASA Technical Reports Server (NTRS)

An analysis of adhesively bonded joints using conventional finite elements does not capture the singular behavior of the stress field in regions where two or three dissimilar materials form a junction with or without free edges. However, these regions are characteristic of the bonded joints and are prone to failure initiation. This study presents a method to capture the singular stress field arising from the geometric and material discontinuities in bonded composites. It is achieved by coupling the local (conventional) elements with global (special) elements whose interpolation functions are constructed from the asymptotic solution.

Shkarayev, S.; Madenci, Erdogan; Camarda, C. J.

1997-01-01

350

The equilibrium geometry, ring-inversion pathway barriers for analogues of cyclohexene with an exocyclic double bond have been studied using the MP2/6-311 G(d,p) level of theory. The equilibrium conformation of the ring depends on conjugation between the endocyclic and exocyclic double bonds. Interactions between conjugated double bonds include the pi-pi conjugation and interactions between the lone pair of the heteroatom of the exocyclic double bond and the sigma-antibonding orbital of the endocyclic single bond. In the case of the tetrahydrocycles with double bonds separated by a methylene group the balance between the pi --> sigma* hyperconjugation interactions between the exocyclic double bond and the neighboring methylene group and the n --> sigma* interaction between the lone pair of the heteroatom and the sigma-antibonding orbitals of the C(sp(2))-C(sp(3)) bond determine the geometrical parameters of the ring. The character of the potential-energy surface around the saddle point depends on the position of the exocyclic double bond and the orientation of the hydrogen atom attached to the heteroatom of the V group of the periodic table in the tetrahydrocycles with double bonds separated by a methylene group. PMID:18613653

Shishkina, Svetlana V; Shishkin, Oleg V; Desenko, Sergey M; Leszczynski, Jerzy

2008-07-31

351

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

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

Kuzkin, Vitaly A; Asonov, Igor E

2012-11-01

352

hcp metal nanoclusters with hexagonal A-A bilayer stacking stabilized by enhanced covalent bonding

hcp metal nanoclusters with hexagonal A-A bilayer stacking stabilized by enhanced covalent bonding theory have been performed to study the geometric and electronic structures of Run nanoclusters of fullerenes1 and their subsequent bulk synthesis,2 the structure and stability of nanoclusters have been

Gong, Xingao

353

Chemical bond effects on the low energy electronic stopping power: theory

We discuss the applicability of a modified version of the Firsov model to account for the low-energy electronic stopping cross section (Se) due to molecular targets. We employ floating spherical Gaussian orbitals (FSGO), which reproduce major trends in electronic and geometrical structure of molecules. Two advantages of using FSGO are: i) each localized orbital is classified as inner shell, bonding

S. A. Cruz; J. Soullard

1991-01-01

354

Steelconcrete bond in lightweight fiber reinforced concrete under monotonic and cyclic actions

Experimental results of the local bond stressslip relationship of reinforcing bars embedded in lightweight fiber reinforced concrete with expanded clay aggregates are presented. The effect of the following parameters were investigated: dimension of specimens; anchorage length; percentages of hooked steel fibers; geometrical ratio of transverse reinforcement; confinement external transverse pressure. Prismatic specimens with deformed steel

G. Campione; C. Cucchiara; L. La Mendola; M. Papia

2005-01-01

355

NASA Technical Reports Server (NTRS)

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

Altshuller, Aubrey P

1955-01-01

356

Geometric Programming optimization of deterministic inventory systems under multiple constraints

, can be written as d b(o) ) b(j) j=l and (o) + ( (j) 1 j=l j i where b is the normality vector, b are the null vectors, and (o) (j) the subscript i indicates the ith component of the vector. Nullity of the v ctors b , j = 1, 2, (j) d, guarantees...'. variations o f tllc. G, ivc. tile trade ? o f fs be meen o'oj ective=. to re. ?l in SL 1 hQ optllllulll. 37 Lillv ' s1Ly Pl'*s ') ' 131!cLLoil !tais Jc 'scv& j9 Prziic'' cr. Unrv rs' ty ' css7 'r i1cetoc, 1em ~era& y, 196 '. 3. !!vr 7' cl, iv. '. , 7...

Foster, Ralph Emerson

2012-06-07

357

Geometric optimization methods for the analysis of gene expression data

experiments, which correspond, e.g., to different patients, tissues or environmental conditions. Gene expres are also detailed in [5, 6, 7]. These studies identified independent components and used the Gene Ontology

Absil, Pierre-Antoine

358

Parameterization and Geometric Optimization of Balloon Launched Sensorcraft for Atmospheric

the output of the Monte Carlo based balloon trajectory program for a balloon payload with a parachute descent to a ground control station. In addition, these technologies improve the chances of recovery, as more position

Sóbester, András

359

Protein Structures and Optimal Folding from a Geometrical Variational Principle

NASA Astrophysics Data System (ADS)

A novel approach, validated by an analysis of barnase and chymotrypsin inhibitor, is introduced to elucidate the paramount role played by the geometry of the protein backbone in steering the folding to the native state. It is found that native states of proteins, compared with compact artificial backbones, have an exceedingly large number of conformations with a given amount of structural overlap with them; moreover, the density of overlapping conformations, at a given overlap, of unrelated proteins of the same length are nearly equal. These results suggest an extremality principle underlying protein evolution, which, in turn, is shown to be possibly associated with the emergence of secondary structures.

Micheletti, Cristian; Banavar, Jayanth R.; Maritan, Amos; Seno, Flavio

1999-04-01

360

Diffusion bonding of the oxide dispersion strengthened steel PM2000

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

361

Science, art and geometrical imagination

NASA Astrophysics Data System (ADS)

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

Luminet, Jean-Pierre

2011-06-01

362

Graphene with geometrically induced vorticity

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

Jiannis K. Pachos; Michael Stone; Kristan Temme

2007-10-03

363

Geometric phases of water waves

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

Francesco Fedele

2014-05-31

364

SQCD Vacua and Geometrical Engineering

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.

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

2008-11-23

365

Geometric analysis of wing sections

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

366

Effect of quantum nuclear motion on hydrogen bonding

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

367

Effect of quantum nuclear motion on hydrogen bonding

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.

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

368

Federal Register 2010, 2011, 2012, 2013, 2014

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

2012-05-31

369

NPP VIIRS Geometric Performance Status

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

370

Geometric effects of Circumbinary Planets

NASA Astrophysics Data System (ADS)

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

Shahady, Anna K.; Ragozzine, Darin

2014-11-01

371

Form, function, and geometric morphometrics.

Geometric morphometrics (GM) has increasingly become an important tool in assessing and studying shape variation in a wide variety of taxa. While the GM toolkit has unparalleled power to quantify shape, its use in studies of functional morphology have been questioned. Here, we assess the state of the field of GM and provide an overview of the techniques available to assess shape, including aspects of visualization, statistical analysis, phylogenetic control, and more. Additionally, we briefly review the history of functional morphology and summarize the main tools available to the functional morphologist. We explore the intersection of geometric morphometrics and functional morphology and we suggest ways that we may be able to move forward in profitably combining these two research areas. Finally, this paper provides a brief introduction to the papers in this special issue and highlights the ways in which the contributing authors have approached the intersection of GM and functional morphology. Anat Rec, 298:5-28, 2015. 2014 Wiley Periodicals, Inc. PMID:25339616

Cooke, Siobhn B; Terhune, Claire E

2015-01-01

372

Movie admissions and rental income: the case of James Bond

This paper addresses the issue of optimal movie design with respect to a single series of feature films, the James Bond movies. This is in contrast to previous studies where analysis has been primarily confined to samples of record box office earning movies. With respect to US admissions and rental income four separate models are estimated examining economic factors, the

Mark Baimbridge

1997-01-01

373

Further developments in gold-stud bump bonding

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

374

Packing: A Geometric Analysis of Feature Selection and Category Formation

This paper presents a geometrical analysis of how local interactions in a large population of categories packed into a feature space create a global structure of feature relevance. The theory is a formal proof that the joint optimization of discrimination and inclusion creates a smooth space of categories such that near categories in the similarity space have similar generalization gradients. Packing theory offers a unified account of several phenomena in human categorization including the differential importance of different features for different kinds of categories, the dissociation between judgments of similarity and judgments of category membership, and childrens ability to generalize a category from very few examples. PMID:21442046

Hidaka, Shohei; Smith, Linda B.

2011-01-01

375

Geometric solitons of Hamiltonian flows on manifolds

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.

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

376

Computer optimization of electron gun designs

Computer optimization is applied to three dimensional design of electron guns. The resulting designs exhibit improved performance with significantly reduced design cost compared to manual design. Design tables update geometric parameters in a solid modeling program, including dimensions for points defining spline surfaces. Algorithms then modified the geometry and other parameters based on goal functions defining the desired performance. Optimal

R. L. Ives; Thuc Bui; J. David; Hien Tran; M. Read

2007-01-01

377

SPACE SHUTTLE EXTERNAL FUEL TANK DESIGN OPTIMIZATION

A design optimization study of the Space Shuttle External Fuel Tank (SSEFT) is performed using a model that, although simplified, captures some of the important aspects of the system's attributes and behavior. The goal of the optimization is to determine the values of the geometric characteristics of the system that maximize the ROI of the project and the payload that

Massimo Usan

378

ERIC Educational Resources Information Center

A computational experiment is devised for advanced inorganic laboratory course that allows the students to explore the structure and bonding patterns of ethene and some heavier analogues. The HOMO-LUMO gaps, double bond dissociation energetics, and optimized geometries of ethene, disilene, and digermene are explored.

Streit, Bennett R.; Geiger, David K.

2005-01-01

379

Engineering geometric phase in semiconductor microcavities

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

380

Geometric Algebra in Quantum Information Processing

This paper develops a geometric model for coupled two-state quantum systems\\u000a(qubits), which is formulated using geometric (aka Clifford) algebra. It begins\\u000aby showing how Euclidean spinors can be interpreted as entities in the\\u000ageometric algebra of a Euclidean vector space. This algebra is then lifted to\\u000aMinkowski space-time and its associated geometric algebra, and the insights\\u000athis provides into

Timothy F. Havel; Chris J. L. Doran

2000-01-01

381

Geometr a Computacional Bel en Palop

Geometr#19;#16;a Computacional Bel#19;en Palop Universidad Rey Juan Carlos 15 de Marzo de 2001 http://www.escet.urjc.es/~bpalop/geoc.ps.gz 1 #12; La Geometr#19;#16;a Computacional en el Web Principal BD de art#19;#16;culos relacionados con://www.ti.com/calc/docs/cabri.htm http://www.cinderella.de/ #12; La Geometr#19;#16;a Computacional en revistas Editorial T#19;#16;tulo

Palop del Río, Belén

382

Solder extrusion pressure bonding process and bonded products produced thereby

Production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about -40.degree. C. and 110.degree. C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Beavis, Leonard C. (Albuquerque, NM); Karnowsky, Maurice M. (Albuquerque, NM); Yost, Frederick G. (Ceder Crest, NM)

1992-01-01

383

Geometrical and Graphical Solutions of Quadratic Equations.

ERIC Educational Resources Information Center

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)

Hornsby, E. John, Jr.

1990-01-01

384

Multiqubit symmetric states with high geometric entanglement

We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric entanglement and how their entanglement behaves asymptotically for large N. We show that much higher geometric entanglement with improved asymptotical behavior can be obtained in comparison with the highly entangled balanced Dicke states studied previously. We also derive an upper bound for the geometric measure of entanglement of symmetric states. The connection with the quantumness of a state is discussed.

Martin, J.; Bastin, T. [Institut de Physique Nucleaire, Atomique et de Spectroscopie, Universite de Liege, B-4000 Liege (Belgium); Giraud, O. [Universite de Toulouse, UPS, Laboratoire de Physique Theorique (IRSAMC), F-31062 Toulouse (France); CNRS, LPT (IRSAMC), F-31062 Toulouse (France); Universite Paris-Sud, LPTMS, UMR8626, Ba circumflex t. 100, Universite Paris-Sud, F-91405 Orsay (France); CNRS, LPTMS, UMR8626, Ba circumflex t. 100, Universite Paris-Sud, F-91405 Orsay (France); Braun, P. A. [Fachbereich Physik, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Institute of Physics, Saint-Petersburg University, 198504 Saint-Petersburg (Russian Federation); Braun, D. [Universite de Toulouse, UPS, Laboratoire de Physique Theorique (IRSAMC), F-31062 Toulouse (France); CNRS, LPT (IRSAMC), F-31062 Toulouse (France)

2010-06-15

385

Computer Aided Geometric Design 19 (2002) 4364 www.elsevier.com/locate/comaid

Computer Aided Geometric Design 19 (2002) 4364 www.elsevier.com/locate/comaid Optimal slicing Received March 2001; revised August 2001 Abstract Many applications, such as contour machining, rapid prototyping, and reverse engineering by laser scanner or coordinate measuring machine, involve sampling

Pottmann, Helmut

386

, multi-way transportation, and multi-commodity b-matching: with linear or nonlinear, congestion optimization problems where the feasible solutions are the integer points satisfying a system of linear and geometric methods, we were able to show that Graver bases enable to solve linear and nonlinear integer

Onn, Shmuel

387

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

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

Bhattacharya, Aniket

388

Geometric algebra in plasma electrodynamics

NASA Astrophysics Data System (ADS)

Geometric algebra (GA) is a recent broad mathematical framework incorporating synthetic and coordinate geometry, complex variables, quarternions, vector analysis, matrix algebra, spinors, tensors, and differential forms. It has been claimed to be a unified language for physics. GA is presented in the context of the Maxwell-Plasma system. In this formalism the divergence and curl differential operators are united in a single vector derivative, which is invertible, in the form of a first-order Green function. The four Maxwell equations can be combined into a single equation (for homogeneous and constant media) or into two equations involving the invertible vector derivative for more complex media. GA is applied to simple examples to illustrate the compactness of the notation and coordinate-free computations.

Resendes, D. P.

2013-10-01

389

Geometric effects on blackbody radiation

NASA Astrophysics Data System (ADS)

Planck's formula for blackbody radiation was formulated subject to the assumption that the radiating body is much larger than the emitted wavelength. We demonstrate that thermal radiation exceeding Planck's law may occur in a narrow spectral range when the local radius of curvature is comparable with the wavelength of the emitted radiation. Although locally the spectral enhancement may be of several orders of magnitude, the deviation from the Stefan-Boltzmann law is less than one order of magnitude. The fluctuation-dissipation theorem needs to be employed for adequate assessment of the spectrum in this regime. Several simple examples are presented as well as experimental results demonstrating the effect. For each configuration a geometric form factor needs to be incorporated into Planck's formula in order to properly describe the emitted radiation.

Reiser, Ariel; Schchter, Levi

2013-03-01

390

Leonardo da Vinci's Geometric Sketches

NSDL National Science Digital Library

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

2008-09-15

391

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.

392

Autophoretic locomotion from geometric asymmetry

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.

Michelin, Sebastien

2015-01-01

393

Autophoretic locomotion from geometric asymmetry

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.

Sebastien Michelin; Eric Lauga

2015-01-16

394

Geometrical setting of solid mechanics

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

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

2011-08-15

395

Bond Sensitivity to Silicone Contamination

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

396

Better Bonded Ethernet Load Balancing

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.

Gabler, Jason

2006-09-29

397

Anion Transport with Halogen Bonds.

This review covers the application of halogen bonds to transport anions across lipid bilayer membranes. The introduction provides a brief description of biological and synthetic transport systems. Emphasis is on examples that explore interactions beyond the coordination with lone pairs or hydrogen bonds for the recognition of cations and anions, particularly cation-? and anion-? interactions, and on structural motifs that are relevant for transport studies with halogen bonds. Section 2 summarizes the use of macrocyclic scaffolds to achieve transport with halogen bonds, focusing on cyclic arrays of halogen-bond donors of different strengths on top of calixarene scaffolds. This section also introduces methods to study anion binding in solution and anion transport in fluorogenic vesicles. In Sect. 3, transport studies with monomeric halogen bond-donors are summarized. This includes the smallest possible organic anion transporter, trifluoroiodomethane, a gas that can be bubbled through a suspension of vesicles to turn on transport. Anion transport with a gas nicely illustrates the power of halogen bonds for anion transport. Like hydrogen bonds, they are directional and strong, but compared to hydrogen-bond donors, halogen-bond donors are more lipophilic. Section 3 also offers a concise introduction to the measurement of ion selectivity in fluorogenic vesicles and conductance experiments in planar bilayer membranes. Section 4 introduces the formal unrolling of cyclic scaffolds into linear scaffolds that can span lipid bilayers. As privileged transmembrane scaffolds, the importance of hydrophobically matching fluorescent p-oligophenyl rods is fully confirmed. The first formal synthetic ion channel that operates by cooperative multiion hopping along transmembrane halogen-bonding cascades is described. Compared to homologs for anion-? interactions, transport with halogen bonds is clearly more powerful. PMID:24696354

Jentzsch, Andreas Vargas; Matile, Stefan

2014-04-01

398

Evolutionary optimization of a Genetically Refined Truss

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

399

Geometric algebra: A computational framework for geometrical applications ({Part II: Applications})

Geometric algebra is a consistent computational framework in which to de- fine geometric primitives and their relationships. This algebraic approach contains all geometric operators and permits coordinate-free specification of computational constructions. It contains primitives of any dimensionality (rather than just vec- tors). This second paper on the subject uses the basic products to represent ro- tations (naturally incorporating quaternions), intersections,

Leo Dorst; S. A. Mann

2002-01-01

400

Blue-shifted and red-shifted hydrogen bonds: Theoretical study of the CH3CHO HNO complexes

NASA Astrophysics Data System (ADS)

The blue-shifted and red-shifted H-bonds have been studied in complexes CH3CHO?HNO. At the MP2/6-31G(d), MP2/6-31+G(d,p) MP2/6-311++G(d,p), B3LYP/6-31G(d), B3LYP/6-31+G(d,p) and B3LYP/6-311++G(d,p) levels, the geometric structures and vibrational frequencies of complexes CH3CHO?HNO are calculated by both standard and CP-corrected methods, respectively. Complex A exhibits simultaneously red-shifted C bond H?O and blue-shifted N bond H?O H-bonds. Complex B possesses simultaneously two blue-shifted H-bonds: C bond H?O and N bond H?O. From NBO analysis, it becomes evident that the red-shifted C bond H?O H-bond can be explained on the basis of the two opposite effects: hyperconjugation and rehybridization. The blue-shifted C bond H?O H-bond is a result of conjunct C bond H bond strengthening effects of the hyperconjugation and the rehybridization due to existence of the significant electron density redistribution effect. For the blue-shifted N bond H?O H-bonds, the hyperconjugation is inhibited due to existence of the electron density redistribution effect. The large blue shift of the N bond H stretching frequency is observed because the rehybridization dominates the hyperconjugation.

Yang, Yong; Zhang, Weijun; Gao, Xiaoming

401

Thomas Young's contributions to geometrical optics.

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

Atchison, David A; Charman, W Neil

2011-07-01

402

Early Sex Differences in Weighting Geometric Cues

ERIC Educational Resources Information Center

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

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

2011-01-01

403

Geometric Algebra in Linear Algebra and Geometry

This article explores the use of geometric algebra in linear and multilinear algebra, and in affine, projective and conformal geometries. Our principal objective is to show how the rich algebraic tools of geometric algebra are fully compatible with and augment the more traditional tools of matrix algebra. The novel concept of an h-twistor makes possible a simple new proof of

Jos Mara Pozo; Garret Sobczyk

2002-01-01

404

Computer Graphics Using Conformal Geometric Algebra

Using the algebra developed by Cliord (1878) from the work of Gramann (1877) and the mapping introduced by Hestenes & Sobczyk (1984), which we call the conformal model, certain geometric objects (e.g. spheres, lines, circles, etc) may be conveniently represented as multivectors in a higher dimension space. Furthermore, geometric operations on these objects (e.g. intersections, rotations, inversions etc.) may be

Richard Wareham; Joan Lasenby; Anthony Lasenby

405

Minkowski Geometric Algebra of Complex Sets

A geometric algebra of point sets in the complex plane is proposed, based on two fundamental operations: Minkowski sums and products. Although the (vector) Minkowski sum is widely known, the Minkowski product of two-dimensional sets (induced by the multiplication rule for complex numbers) has not previously attracted much attention. Many interesting applications, interpretations, and connections arise from the geometric algebra

Rida T. Farouki; Hwan Pyo Moon; Bahram Ravani

2001-01-01

406

Mobile robot localization by tracking geometric beacons

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

John J. Leonard; Hugh F. Durrant-Whyte

1991-01-01

407

Geometric Comparison of Clarifications and Rule Sets

We present a technique for evaluating classifications by geometric com- parison of rule sets, Rules ~e represented as objects in an n-dimensional hyperspace. The similarity of classes is computed from the overlap of the geometric class descriptions, The system produces a correlation matrix that indicates the degree of similarity between each pair of classes. The tech- nique can be

T. J. Monk; R. S. Mitchell; L. A. Smith; G. Holmes

1994-01-01

408

A Geometric Construction of Multivariate Sinc Functions

We present a geometric framework for explicit derivation of multivariate sampling functions (sinc) on multidimensional lattices. The approach leads to a generalization of the link between sinc functions and the Lagrange interpolation in the multivariate setting. Our geometric approach also provides a frequency partition of the spectrum that leads to a nonseparable extension of the 1-D Shannon (sinc) wavelets to

Wenxing Ye; Alireza Entezari

2012-01-01

409

Geometric quantization on symplectic fiber bundles

Consider a fiber bundle in which the total space, the base space and the fiber are all symplectic manifolds. We study the relations between the quantization of these spaces. In particular, we discuss the geometric quantization of a vector bundle, as oppose to a line bundle, over the base space that recovers the standard geometric quantization of the total space.

Yihren Wu

1997-11-15

410

Geometric interpretation of the characteristic polarizations

The scattering mechanism can be analyzed from the geometrical point of view using the polar decomposition which decomposes the normalized scattering matrix in a unitary matrix and in a Hermitian (positive definite) one. Each of them can be built using parameters (polar parameters) such as vectors, angles and scalars which have geometrical meaning in the Stokes space. In this work

Laura Carrea; Gerd Wanielik; Madhu Chandra

2004-01-01

411

Monotonicity and its analytic and geometric implications

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

Colding, Tobias Holck; Minicozzi, William P.

2013-01-01

412

Geometric Derivation of Radial Acceleration Magnitude.

ERIC Educational Resources Information Center

Standard treatments of uniform circular motion generally employ a combination of geometric and kinematic arguments to obtain the magnitude of radial acceleration. Presents a novel approach to the geometric portion of the derivation that uses the property that vectors can be translated parallel to themselves. (JRH)

Kraft, David W.; Motz, Lloyd

1995-01-01

413

GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES

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

Cambridge, University of

414

GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES

GEOMETRIC ALGEBRA, DIRAC WAVEFUNCTIONS AND BLACK HOLES A.N. LASENBY AND C.J.L. DORAN Astrophysics describe some applications of geometric algebra to the #12;eld of black hole physics. Our main focus is on the proper- ties of Dirac wavefunctions around black holes. We show the existence of normalised bound state

Cambridge, University of

415

Geometrical scaling, furry branching and minijets

Scaling properties and their violations in hadronic collisions are discussed in the framework of the geometrical branching model. Geometrical scaling supplemented by Furry branching characterizes the soft component, while the production of jets specifies the hard component. Many features of multiparticle production processes are well described by this model. 21 refs.

Hwa, R.C.

1988-01-01

416

Geometric heat comparison criteria for Riemannian manifolds

The main results of this article are small time heat comparison results for two points in two manifolds with characteristic functions as initial temperature distributions (Theorems 1 and 2). These results are based on the geometric concepts of (essential) distance from the complement and spherical area function. We also discuss some other geometric results about the heat development and illustrate them by examples.

Leon Karp; Norbert Peyerimhoff

2005-06-10

417

Geometric pattern generation by sewing machine

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

Yasumichi Hasegawa; Kihachi Takeichi; Tsuyoshi Matsuo

1996-01-01

418

Geometrical Music Theory Rachel Wells Hall1

in modeling musical objects such as chords, rhythms, and scales; however, no unified geometric perspective hasGeometrical Music Theory Rachel Wells Hall1 Music theorists have frequently invoked geometry musical terms can be understood as expressing symmetries of n-dimensional space. Identifying-- "gluing

Hall, Rachel W.

419

Bond strengths of ceramic brackets using different bonding techniques.

A series of laboratory investigations was carried out to compare the shear-type bond strengths and site of bond failure of ceramic orthodontic brackets bonded to etched enamel. When light-cured composite resin was used as the luting agent, there was no reduction in bond strength when using 2.5 per cent nitric acid to etch the enamel, compared to 37 per cent phosphoric acid. The use of the two resin modified glass ionomer cements were found to give rise to significantly lower bond strengths than composite resin when used for placing ceramic brackets. Significantly less composite resin remained on the enamel surface following bracket removal in those samples etched with nitric acid. PMID:7786864

Blight, S J; Lynch, E

1995-02-01

420

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

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.

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

421

On the basis of recently synthesized calix[4]hydroquinone (CHQ) nanotubes which were self-assembled with infinitely long one-dimensional (1-D) short hydrogen bonds (SHB), we have investigated the nature of 1-D SHB using first-principles calculations for all the systems including the solvent water. The H-bonds relay (i.e., contiguous H-bonds) effect in CHQs shortens the H...O bond distances significantly (by more than 0.2 A) and increases the bond dissociation energy to a large extent (by more than approximately 4 kcal/mol) due to the highly enhanced polarization effect along the H-bond relay chain. The H-bonds relay effect shows a large increase in the chemical shift associated with the SHB. The average binding energies for the infinite 1-D H-bond arrays of dioles and dions increase by approximately 4 and approximately 9 kcal/mol per H-bond, respectively. The solvent effect (due to nonbridging water molecules) has been studied by explicitly adding water molecules in the CHQ tube crystals. This effect is found to be small with slight weakening of the SHB strength; the H...O bond distance increases only by 0.02 A, and the average binding energy decreases by approximately 1 kcal/mol per H-bond. All these results based on the first-principles calculations are the first detailed analysis of energy gain by SHB and energy loss by solvent effect, based on a partitioning scheme of the interaction energy components. These reliable results elucidate not only the self-assembly phenomena based on the H-bond relay but also the solvent effect on the SHB strength. PMID:14971954

Suh, Seung Bum; Kim, Jong Chan; Choi, Young Cheol; Yun, Sunggoo; Kim, Kwang S

2004-02-25

422

Methodology and method and appartus for signaling with capacity optimized constellations

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

423

Geometric Algebra in Quantum Information Processing

This paper develops a geometric model for coupled two-state quantum systems (qubits), which is formulated using geometric (aka Clifford) algebra. It begins by showing how Euclidean spinors can be interpreted as entities in the geometric algebra of a Euclidean vector space. This algebra is then lifted to Minkowski space-time and its associated geometric algebra, and the insights this provides into how density operators and entanglement behave under Lorentz transformations are discussed. The direct sum of multiple copies of space-time induces a tensor product structure on the associated algebra, in which a suitable quotient is isomorphic to the matrix algebra conventionally used in multi-qubit quantum mechanics. Finally, the utility of geometric algebra in understanding both unitary and nonunitary quantum operations is demonstrated on several examples of interest in quantum information processing.

Timothy F. Havel; Chris J. L. Doran

2001-06-27

424

Temperature effects on mixed state geometric phase

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.

A. T. Rezakhani; P. Zanardi

2005-12-29

425

On Geometrical Aspects of Dynamical Stability

Geometrization of dynamics consists of representing trajectories by geodesics on a suitably defined metric. Previously, efforts were made to show that the analysis of dynamical stability can also be carried out within geometrical frameworks, by measuring the broadening rate of a bundle of geodesics. Two known formalisms are via Jacobi and Eisenhart metrics. We find that this geometrical analysis measures the actual stability when the length of any geodesic is proportional to the corresponding time interval. We prove that the Jacobi metric is not an appropriate parametrization by showing that it predicts chaotic behavior for a system of harmonic oscillators. Furthermore, we show, by explicit calculation, that the correspondence between dynamical- and geometrical-spread is ill-defined for the Jacobi metric. We find that the Eisenhart dynamics corresponds to the actual tangent dynamics and is therefore an appropriate geometrization scheme.

Eduardo Cuervo-Reyes; Ramis Movassagh

2008-11-02

426

GEOMETRIC REASONING IN THE ANALYSIS OF ASSEMBLIES AND MECHANISMS

Geometric Reasoning ability is central to many applications in CAD \\/ CAM \\/ CAPP environments. An increasing demand exists for Geometric Reasoning systems which evaluate the feasibility of virtual scenes specified by geometric relations. Thus, the Geometric Constraint Satisfaction or Scene Feasibility (GCS\\/SF) problem consists of a basic scenario containing geometric entities, whose context is used to propose constraining relations

O. E. Ruiz; P. M. Ferreira

427

Geometric asymmetry driven Janus micromotors

NASA Astrophysics Data System (ADS)

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

Zhao, Guanjia; Pumera, Martin

2014-09-01

428

Microwave bonding of MEMS component

NASA Technical Reports Server (NTRS)

Bonding of MEMs materials is carried out using microwave. High microwave absorbing films are placed within a microwave cavity, and excited to cause selective heating in the skin of the material. This causes heating in one place more than another. Thereby minimizing the effects of the bonding microwave energy.

Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)

2005-01-01

429

Computational Chemistry of Adhesive Bonds

NASA Technical Reports Server (NTRS)

This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

Phillips, Donald H.

1999-01-01

430

Ultrasonic phosphate bonding of nanoparticles.

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

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

2013-11-01

431

Coulombic Models in Chemical Bonding.

ERIC Educational Resources Information Center

Describes a bonding theory which provides a framework for the description of a wide range of substances and provides quantitative information of remarkable accuracy with far less computational effort than that required of other approaches. Includes applications, such as calculation of bond energies of two binary hydrides (methane and diborane).

Sacks, Lawrence J.

1986-01-01

432

Weld-bonded titanium structures

NASA Technical Reports Server (NTRS)

Structurally stronger titanium articles are produced by a weld-bonding technique comprising fastening at least two plates of titanium together using spotwelding and curing an adhesive interspersed between the spot-weld nuggets. This weld-bonding may be employed to form lap joints or to stiffen titanium metal plates.

Vaughan, R. W.; Creedon, J. F. (inventors)

1976-01-01

433

Application of geometric algebra for the description of polymer conformations.

In this paper a Clifford algebra-based method is applied to calculate polymer chain conformations. The approach enables the calculation of the position of an atom in space with the knowledge of the bond length (l), valence angle (theta), and rotation angle (phi) of each of the preceding bonds in the chain. Hence, the set of geometrical parameters {l(i),theta(i),phi(i)} yields all the position coordinates p(i) of the main chain atoms. Moreover, the method allows the calculation of side chain conformations and the computation of rotations of chain segments. With these features it is, in principle, possible to generate conformations of any type of chemical structure. This method is proposed as an alternative for the classical approach by matrix algebra. It is more straightforward and its final symbolic representation considerably simpler than that of matrix algebra. Approaches for realistic modeling by means of incorporation of energetic considerations can be combined with it. This article, however, is entirely focused at showing the suitable mathematical framework on which further developments and applications can be built. PMID:18345877

Chys, Pieter

2008-03-14

434

Optimal design of nonimaging solar concentrators with wedge receivers

The geometric characteristics of a general class of nonimaging solar energy concentrators with wedge-shaped receivers are investigated. For concentrators with fixed receiver area and fixed geometric concentration ratio, an analytic solution is derived for the concentrator configuration that minimizes reflector area (often a key element in solar collector optimization). The configuration with minimal reflector area is not an ideal concentrator

H. P. Baum; J. M. Gordon

1985-01-01

435

Quantum Confinement in Hydrogen Bond

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.

Santos, Carlos da Silva dos; Ricotta, Regina Maria

2015-01-01

436

?-Hole Bonding: A Physical Interpretation.

The anisotropic electronic densities of covalently-bonded GroupIV-VII atoms frequently give rise to regions of positive electrostatic potential on the extensions of single covalent bonds to these atoms. Through such positive "?-holes," the atoms can interact attractively and highly directionally with negative sites such as the lone pairs of Lewis bases, anions, ? electrons, etc. In the case of GroupVII this is called "halogen bonding." Hydrogen bonding can be viewed as a less directional subset of ?-hole interactions. Since positive ?-holes often exist in conjunction with regions of negative potential, the atoms can also interact favorably with positive sites. In accordance with the Hellmann-Feynman theorem, all of these interactions are purely Coulombic in nature (which encompasses polarization and dispersion). The strength of ?-hole bonding increases with the magnitudes of the potentials of the positive ?-hole and the negative site; their polarizabilities must sometimes also be taken explicitly into account. PMID:25467532

Politzer, Peter; Murray, Jane S; Clark, Timothy

2014-12-01

437

Anti-electrostatic hydrogen bonds.

Ab?initio and hybrid density functional techniques were employed to characterize a surprising new class of H-bonded complexes between ions of like charge. Representative H-bonded complexes of both anion-anion and cation-cation type exhibit appreciable kinetic stability and the characteristic theoretical, structural, and spectroscopic signatures of hydrogen bonding, despite the powerful opposition of Coulomb electrostatic forces. All such "anti-electrostatic" H-bond (AEHB) species confirm the dominance of resonance-type covalency ("charge transfer") interactions over the inessential (secondary or opposing) "ionic" or "dipole-dipole" forces that are often presumed to be essential for numerical modeling or conceptual explanation of the H-bonding phenomenon. PMID:25196556

Weinhold, Frank; Klein, Roger A

2014-10-13

438

Explosive bonding of 316L to C18150 CuCrZr alloy for ITER applications.

Recent developments in the ITER experimental fusion reactor require that a 316L stainless steel substructure be bonded to a precipitation strengthened CuCrZr heat sink alloy, C18150. This bond defines the cooling water pressure boundary. Given the importance of this interface, a variety of experiments with fusion welding and solid-state joining techniques have been performed. Analysis of the joints includes mechanical measurements of bond strength and microstructural analysis using optical and electron microscopy techniques. A particular emphasis was placed on the mechanical properties of the CuCrZr, since it undergoes additional thermal processing and cannot be solutionized and aged hardened per standard heat treatments. It was determined that the explosion bonding, of all the techniques examined, maximized the residual mechanical strength of the CuCrZr. The bonding parameters were optimized to minimize the amount of mixing and porosity at the interface. The details of these results and the optimization will be discussed.

Puskar, Joseph David; Butler, Don J. (High Energy Metals, Inc., Sequim, WA); Goods, Steven Howard (Sandia National Laboratories, Livermore, CA); Brasher, Dave G. (High Energy Metals, Inc., Sequim, WA)

2010-10-01

439

The application of diffusion bonding in the manufacture of aeroengine components

NASA Astrophysics Data System (ADS)

Rolls-Royce has developed and optimized diffusion bonding processes for the manufacture of advanced titanium alloy aeroengine structures and components. Both categories of the joining technique - 'liquid-phase' and 'solid-state' - are being applied in the production of both static fabrications and complex rotating parts. In order to utilize diffusion bonding processes in a production environment, the process parameters which contribute to consistent formation of joints of the required strength have been critically examined. Process variables include temperature, pressure, time, surface roughness and, in the case of liquid-phase diffusion bonding, interlayer composition, density and thickness. Mechanical testing (tensile, impact and fatigue) complemented by metallography has predominantly been used to identify the permitted variations in the processes for the realistic and economical production manufacture of high quality lightweight aeroengine fabrications. The development of a high integrity bond via optimized diffusion bonding processes has been fundamental to the development of Rolls-Royce's unique wide chord fan design concept.

Fitzpatrick, J. A.

440

Bonding and Integration Technologies for Silicon Carbide Based Injector Components

NASA Technical Reports Server (NTRS)

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.

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

441

Geometric algebra and particle dynamics

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

Jose B. Almeida

2005-07-12

442

Geometric reasoning about assembly tools

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.

Wilson, R.H.

1997-01-01

443

Oregon School Bond Manual. Sixth Edition.

ERIC Educational Resources Information Center

Given that purchasers of Oregon school bonds rely on recommendations of accredited bond attorneys, this document is designed to assist school districts in complying with state statutes regulating the issuance of school bond issues in order that attorney opinions may be favorable. Six initial steps toward a bond sale and Oregon laws regarding bonds

Oregon State Dept. of Education, Salem. Office of School District Services.

444

On geometric factors for neutral particle analyzers

NASA Astrophysics Data System (ADS)

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

Stagner, L.; Heidbrink, W. W.

2014-11-01

445

On geometric factors for neutral particle analyzers.

Neutral particle analyzers (NPA) detect neutralized energetic particles that escape from plasmas. Geometric factors relate the counting rate of the detectors to the intensity of the particle source. Accurate geometric factors enable quick simulation of geometric effects without the need to resort to slower Monte Carlo methods. Previously derived expressions [G. R. Thomas and D. M. Willis, "Analytical derivation of the geometric factor of a particle detector having circular or rectangular geometry," J. Phys. E: Sci. Instrum. 5(3), 260 (1972); J. D. Sullivan, "Geometric factor and directional response of single and multi-element particle telescopes," Nucl. Instrum. Methods 95(1), 5-11 (1971)] for the geometric factor implicitly assume that the particle source is very far away from the detector (far-field); this excludes applications close to the detector (near-field). The far-field assumption does not hold in most fusion applications of NPA detectors. We derive, from probability theory, a generalized framework for deriving geometric factors that are valid for both near and far-field applications as well as for non-isotropic sources and nonlinear particle trajectories. PMID:25430216

Stagner, L; Heidbrink, W W

2014-11-01

446

GRAVITY, GAUGE THEORIES AND GEOMETRIC Anthony Lasenby, Chris Doran and

GRAVITY, GAUGE THEORIES AND GEOMETRIC ALGEBRA Anthony Lasenby, Chris Doran and Stephen Gull MRAO and powerful physical insights. The language of `geometric algebra' best expresses the physical of Geometric Algebra 5 2.1 The Spacetime Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2

Cambridge, University of

447

Contemporary Mathematics Geometric Algebra in Quantum Information Processing

Contemporary Mathematics Geometric Algebra in Quantum Information Processing-time and its associated geometric algebra, and the insights this p* *rovides into how density operators quantum mechanics. Finally, the utility of geometric algebra in understa* *nding both unitary

Lomonaco Jr., Samuel J.

448

Geometric Gyrokinetic Theory for Edge Plasma

It turns out that gyrokinetic theory can be geometrically formulated as special cases of a geometrically generalized Vlasov-Maxwell system. It is proposed that the phase space of the spacetime is a 7-dimensional fiber bundle P over the 4-dimensional spacetime M, and that a Poincare-Cartan-Einstein 1-form {gamma} on the 7-dimensional phase space determines particles worldlines in the phase space. Through Liouville 6-form {Omega} and fiber integral, the 1-form {gamma} also uniquely defines a geometrically generalized Vlasov-Maxwell system as a field theory for the collective electromagnetic field. The geometric gyrokinetic theory is then developed as a special case of the geometrically generalized Vlasov-Maxwell system. In its most general form, gyrokinetic theory is about a symmetry, called gyro-symmetry, for magnetized plasmas, and the 1-form {gamma} again uniquely defines the gyro-symmetry. The objective is to decouple the gyro-phase dynamics from the rest of particle dynamics by finding the gyro-symmetry in {gamma}. Compared with other methods of deriving the gyrokinetic equations, the advantage of the geometric approach is that it allows any approximation based on mathematical simplification or physical intuition to be made at the 1-form level, and yet the field theories still have the desirable exact conservation properties such as phase space volume conservation and energy-momentum conservation if the 1-form does not depend on the spacetime coordinate explicitly. A set of generalized gyrokinetic equations valid for the edge plasmas is then derived using this geometric method. This formalism allows large-amplitude, time-dependent background electromagnetic fields to be developed fully nonlinearly in addition to small-amplitude, short-wavelength electromagnetic perturbations. The fact that we adopted the geometric method in the present study does not necessarily imply that the major results reported here can not be achieved using classical methods. What the geometric method offers is a systematic treatment and simplified calculations.

Qin, H; Cohen, R H; Nevins, W M; Xu, X Q

2007-01-18

449

29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

Code of Federal Regulations, 2012 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules 2580...section 13, if, with respect to bonding coverage required under section...

2012-07-01

450

29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

Code of Federal Regulations, 2014 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules 2580...section 13, if, with respect to bonding coverage required under section...

2014-07-01

451

29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

Code of Federal Regulations, 2010 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules 2580...section 13, if, with respect to bonding coverage required under section...

2010-07-01

452

Detecting Image Forgeries using Geometric Cues

This chapter presents a framework for detecting fake regions by using various methods including watermarking technique and blind approaches. In particular, we describe current categories on blind approaches which can be divided into five: pixel-based techniques, format-based techniques, camera-based techniques, physically-based techniques and geometric-based techniques. Then we take a second look on the geometric-based techniques and further categorize them in detail. In the following section, the state-of-the-art methods involved in the geometric technique are elaborated.

Wu, Lin

2010-01-01

453

Geometric flows and black hole entropy

NASA Astrophysics Data System (ADS)

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 note 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.

Samuel, Joseph; Chowdhury, Sutirtha Roy

2007-06-01

454

27 CFR 19.152 - Types of bonds.

Code of Federal Regulations, 2011 CFR

...DEPARTMENT OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Bonding Requirements for A Dsp 19.152 Types of bonds. (a) Basic Bonds. There are two basic types of bonds: the operations bond, and the...

2011-04-01

455

NASA Astrophysics Data System (ADS)

This article presents a study of the deformation mechanisms and failure behavior of punch bonding technology for dissimilar sheet metals. Using theoretical and numerical methods, the simulation of the punch bonding process is presented and the results show that to realize effective punch bonding, the sheets with higher elastic modulus and yield strength should be located at the punch side. It is also shown that when the boss height of the female die ( X 1) is too small, it is liable to induce excessive stress concentration under the punch blade, whereas when X 1 is too large, the embedded depth of the sheets and the bonding reliability decrease significantly. Punch bonding experiments were performed and the results showed that for the configuration tested an X 1 value of 10 mm was optimal for connection strength. The failure behavior of the punch bonding joint was joint cracking with smaller female die boss height and joint pull-off with larger female die boss height.

Li, Feng; Li, Jian Hui; Li, Chao; Wang, L. L.

2012-05-01

456

Smart interfacial bonding alloys

The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

R. Q. Hwang; J. C. Hamilton; J. E. Houston

1999-04-01

457

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.

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

458

Method for vacuum fusion bonding

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.

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

2001-01-01

459

Fusion bonding and alignment fixture

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.

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

2000-01-01

460

43 CFR 3904.10 - Bonding requirements.

Code of Federal Regulations, 2011 CFR

...Interior 2 2011-10-01 2011-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2011-10-01

461

43 CFR 3904.10 - Bonding requirements.

Code of Federal Regulations, 2012 CFR

...Interior 2 2012-10-01 2012-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2012-10-01

462

43 CFR 3904.10 - Bonding requirements.

Code of Federal Regulations, 2014 CFR

...Interior 2 2014-10-01 2014-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2014-10-01

463

43 CFR 3904.10 - Bonding requirements.

Code of Federal Regulations, 2013 CFR

...Interior 2 2013-10-01 2013-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2013-10-01

464

Enamel-dentin crown fractures bonded with various bonding agents.

A method is described, by which the fracture strength of bonded, previously fractured incisors can be measured. The study employed incisors from sheep, which could be obtained in suitable numbers and with limited variation in size. The incisors were fractured parallel to the incisal edge. The mean fracture area +/- SD of central incisors was 8.45 +/- 0.89 mm2 and of lateral incisors 6.50 +/- 0.64 mm2. The enamel area constituted about 30% of the total fracture area. Acid etching of the enamel and bonding of the fractures with an unfilled resin yielded a fracture strength, which was approximately 38% of the fracture strength of fractured teeth restored with acid etching of enamel, Gluma treatment of dentin and bonding with the unfilled resin. Teeth restored in this way, but using the dentin bonding agent Tenure or Scotchbond2 instead of Gluma, exhibited mean fracture strengths which were not significantly different from that obtained when Gluma was employed as the bonding agent. The mean fracture strength by using one of the three bonding agents in combination with acid etching of enamel was about 8 MPa, which is approximately 50% of the fracture strength of intact teeth. PMID:1782898

Munksgaard, E C; Hjtved, L; Jrgensen, E H; Andreasen, J O; Andreasen, F M

1991-04-01

465

Curve sampling and geometric conditional simulation

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

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

2008-01-01

466

Geometrical and Instrumental Optics I Class Policies

location Image size Image quality Image brightness will teach the student four main factors relating to image formation in geometrical optics: Image spatial all cell phones and pagers. No talking during class, unless for class participation! No food

Arizona, University of

467

The Construction of Spinors in Geometric Algebra

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

Matthew R. Francis; Arthur Kosowsky

2004-10-18

468

The construction of spinors in geometric algebra

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

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

2005-06-01

469

The Inner Products of Geometric Algebra

Abstract: Making derived products out of the geometric product requires care in consistency. We show how a split based on outer product and scalar product necessitates a slightly different inner product than usual. We demonstrate the use of...

L. Dorst

2002-01-01

470

Geometric symmetries in superfluid vortex dynamics

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.

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

471

Fractal Geometric Characterization of Functionally Graded Materials

Fractal Geometric Characterization of Functionally Graded Materials A. Saharan1 ; M. Ostoja graded materials (FGM) is studied from the standpoint of fractal geometry. First, upon introducing fractals, and an interfacial fractal dimension is estimated for varying degrees of fineness. Avariation

Ostoja-Starzewski, Martin

472

Geometric Feature Estimators for Noisy Discrete Surfaces

functions able to sort objects by shape or by size. In bioinformatics, in the protein-protein docking framework, one tries to associate two proteins according to their geometrical complementarity. Thus

Paris-Sud XI, Université de

473

The perception of geometrical structure from congruence

NASA Technical Reports Server (NTRS)

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.

Lappin, Joseph S.; Wason, Thomas D.

1989-01-01

474

Environmental Effects on the Geometric Phase

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.

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

2009-12-25

475

Method to improve commercial bonded SOI material

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.

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

2000-07-11

476

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

NSDL National Science Digital Library

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 ...

Camp, Mrs

2007-11-28

477

Energetics of short hydrogen bonds in photoactive yellow protein

Recent neutron diffraction studies of photoactive yellow protein (PYP) proposed that the H bond between protonated Glu46 and the chromophore [ionized p-coumaric acid (pCA)] was a low-barrier H bond (LBHB). Using the atomic coordinates of the high-resolution crystal structure, we analyzed the energetics of the short H bond by two independent methods: electrostatic pKa calculations and a quantum mechanical/molecular mechanical (QM/MM) approach. (i) In the QM/MM optimized geometry, we reproduced the two short H-bond distances of the crystal structure: Tyr42-pCA (2.50?) and Glu46-pCA (2.57?). However, the H atoms obviously belonged to the Tyr or Glu moieties, and were not near the midpoint of the donor and acceptor atoms. (ii) The potential-energy curves of the two H bonds resembled those of standard asymmetric double-well potentials, which differ from those of LBHB. (iii) The calculated pKa values for Glu46 and pCA were 8.6 and 5.4, respectively. The pKa difference was unlikely to satisfy the prerequisite for LBHB. (iv) The LBHB in PYP was originally proposed to stabilize the ionized pCA because deprotonated Arg52 cannot stabilize it. However, the calculated pKa of Arg52 and QM/MM optimized geometry suggested that Arg52 was protonated on the protein surface. The short H bond between Glu46 and ionized pCA in the PYP ground state could be simply explained by electrostatic stabilization without invoking LBHB. PMID:22173632

Saito, Keisuke; Ishikita, Hiroshi

2012-01-01

478

NASA Astrophysics Data System (ADS)

We show that a new glassy phase can emerge in the presence of strong magnetic frustration and quantum fluctuations. It is a valence bond glass (VBG). We study its properties solving the Hubbard-Heisenberg model on a Bethe lattice within the large-N limit introduced by Affleck and Marston. We work out the phase diagram that contains Fermi liquid, dimer and valence bond glass phases. This new glassy phase has no electronic or spin gap (although a pseudo-gap is observed), it is characterized by long-range critical valence bond correlations and is not related to any magnetic ordering. As a consequence, it is quite different from both valence bond crystals and spin glasses.

Tarzia, M.; Biroli, G.

2008-06-01

479

Double Wells and Covalent Bonds

NSDL National Science Digital Library

Explore tunneling splitting in double well potentials. This classic problem describes many physical systems, including covalent bonds, Josephson junctions, and two-state systems such as spin 1/2 particles and ammonia molecules.

Simulations, Phet I.; Malley, Chris; Mckagan, Sam; Perkins, Kathy; Wieman, Carl

2006-07-01

480

Are Government Bonds Net Wealth?

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 \\

Robert J. Barro

1974-01-01

481

Bond Illiquidity and Excess Volatility

We find that the empirical volatilities of corporate bond and CDS returns are higher than implied by equity return volatilities and the Merton model. This excess volatility may arise because structural models inadequately ...

Bao, Jack

482

Time-resolved Faraday rotation spectroscopy is currently exploited as a powerful technique to probe spin dynamics in semiconductors. We propose here an all-optical approach to geometrically manipulate electron spin and to detect the geometric phase by this type of extremely sensitive experiment. The global nature of the geometric phase can make the quantum manipulation more stable, which may find interesting application in quantum devices.

Li Xue Qian; Cen, L X; Zheng, H Z; Yan, Y J; Li, Xin-Qi; Hu, Cheng-Yong; Cen, Li-Xiang; Zheng, Hou-Zhi; Yan, YiJing

2002-01-01

483

Time-resolved Faraday rotation spectroscopy is currently exploited as a powerful technique to probe spin dynamics in semiconductors. We propose here an all-optical approach to geometrically manipulate electron spin and to detect the geometric phase by this type of extremely sensitive experiment. The global nature of the geometric phase can make the quantum manipulation more stable, which may find interesting application in quantum devices.

Xin-Qi Li; Cheng-Yong Hu; Li-Xiang Cen; Hou-Zhi Zheng; YiJing Yan

2002-10-17

484

Adhesive bonding of aluminum alloys

The topics concerned with the European chromic acid anodize process, the sealed chromic acid anodize, the phosphoric acid anodize, surface analysis, and adhesive selection are discussed. Consideration is given to epoxy adhesives, elevated-temperature-resistant adhesives, the mechanical properties of adhesives, environmental/durability testing, and coatings. Data on the use of chemical analysis for control, the structural analysis of adhesive-bonded joints, tooling design and inspection, nondestructive inspection, and adhesive-bonded aluminum structure repair are presented.

Thrall, E.W.; Shannon, R.W.

1985-01-01

485

Surface analysis in composite bonding

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

486

Geometric frustration on a 1/9^th site depleted triangular lattice

NASA Astrophysics Data System (ADS)

In the searches both for new spin liquid and spin ice (artificial and macroscopic) candidates, geometrically frustrated two-dimensional spin systems have played a prominent role. Here we present a study of the classical antiferromagnetic Ising (AFI) model on the sorrel net, a 1/9^th site depleted and 1/7^th bond depleted triangular lattice. The AFI model on this corner-shared triangle net is found to have a large residual entropy per spin SN = 0.48185 0.00008, indicating the sorrel net is highly geometrically frustrated. Anticipating that it may be difficult to achieve perfect bond depletion, we investigate the physics resulting from turning back on the depleted bonds (J2). We present the phase diagram, analytic expressions for the long range partially ordered ground state spin structure for antiferromagnetic J2 and the short range ordered ground state spin structure for ferromagnetic J2, the magnetic susceptibility and the static structure factor. We briefly comment on the possibility that artificial spin ice on the sorrel lattice could by made, and on a recent report [T. D. Keene et al., Dalton Trans. 40 2983 (2011)] of the creation of a 1/9^th depleted cobalt hydroxide oxalate.

Hopkinson, John; Beck, Jarrett

2013-03-01

487

Fatigue aging of adhesive bonds

A year-long study has been made of the effect of fatigue on the bond between two epoxy encapsulant formulations and a fused alumina disc. The variables studied included isothermal aging at temperatures up to and including the cure temperature and cyclic thermal aging from +74/sup 0/C to -54/sup 0/C. The encapsulants were glass microballoon filled epoxies differing only in curing agents. One was cured with an aromatic amine eutectic (Shell Curing Agent Z). The other was cured with diethanolamine. The Z cured encapsulant bond failed completely at the bond interface with little or no aging; infrared evidence indicated a soluable interlayer as a possible cause of failure. The diethanolamine cured encapsulant survived a year of isothermal aging with little or no evidence of bond degradation. Cyclic thermal aging resulted in gradual bond failure with time. An extrapolation of the cyclic aging data indicates that the stresses induced by thermal cycling would result in complete bond failure in about 1200 days.

DeLollis, N.J.

1981-10-01

488

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

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

2014-09-15

489

NASA Astrophysics Data System (ADS)

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 oscillators 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.

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

2014-09-01

490

The probability of improvement in Fisher's geometric model: a probabilistic approach.

Fisher developed his geometric model to support the micro-mutationalism hypothesis which claims that small mutations are more likely to be beneficial and therefore to contribute to evolution and adaptation. While others have provided a general solution to the model using geometric approaches, we derive an equivalent general solution using a probabilistic approach. Our approach to Fisher's geometric model provides alternative intuition and interpretation of the solution in terms of the model's parameters: for mutation to improve a phenotype, its relative beneficial effect must be larger than the ratio of its total effect and twice the difference between the current phenotype and the optimal one. Our approach provides new insight into this classical model of adaptive evolution. PMID:25453607

Ram, Yoav; Hadany, Lilach

2015-02-01

491

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

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, h