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1

Geometric optimization  

SciTech Connect

An algorithm is presented which describes an application independent method for reducing the number of polygonal primitives required to faithfully represent an object. Reducing polygon count without a corresponding reduction in object detail is important for: achieving interactive frame rates in scientific visualization, reducing mass storage requirements, and facilitating the transmission of large, multi-timestep geometric data sets. This paper shows how coplanar and nearly coplanar polygons can be merged into larger complex polygons and re-triangulated into fewer simple polygons than originally required. The notable contributions of this paper are: (1) a method for quickly grouping polygons into nearly coplanar sets, (2) a fast approach for merging coplanar polygon sets and, (3) a simple, robust triangulation method for polygons created by 1 and 2. The central idea of the algorithm is the notion of treating polygonal data as a collection of segments and removing redundant segments to quickly form polygon hulls which represent the merged coplanar sets.

Hinker, P.; Hansen, C.

1993-09-01

2

OPTIMIZATION OF THE GEOMETRICAL PARAMETERS OF A BONDED STIFFENER: FINITE ELEMENT ANALYSIS  

Microsoft Academic Search

SUMMARY: A numerical study analyses important fabrication parameters for adhesive bonding of stiffened plates. The focus of this study lies on two parameters: the length and the thickness of the adhesive bond. Finite element analyses for four typical load cases are applied to a chosen test case, bonding two aluminium specimens. The analyses reveal most suitable values for the length

G. Mohamad; France V. Bertram; Germanischer Lloyd

3

Geometric optimization of thermal systems  

NASA Astrophysics Data System (ADS)

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

Alebrahim, Asad Mansour

2000-10-01

4

Optimal loading of molecular bonds.  

PubMed

A corollary of the Bell equation of bond rupture is that the bond transfers a maximal impulse during its lifetime when the applied force equals k(B)T/x*. It is proposed that the designs of biological systems converge toward loading bonds with this optimal force to minimize the need for self-healing and to optimize energy transfer. PMID:23025846

Hess, Henry

2012-10-03

5

Optimization of inductor circuits via geometric programming  

Microsoft Academic Search

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

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

1999-01-01

6

Geometric optimization on spaces of finite frames  

NASA Astrophysics Data System (ADS)

A finite (? S)-frame variety consists of the real or complex matrices F = [f1...fN] with frame operator FF* = S, and satisfying IIfiII = ?i for all i = 1,...,N. Here, S is a fixed Hermitian positive definite matrix and ? = [?1,..., ?N] is a fixed list of lengths. These spaces generalize the well-known spaces of finite unit norm tight frames. We explore the local geometry of these spaces and develop geometric optimization algorithms based on the resulting insights.

Strawn, Nate

2011-09-01

7

Geometric optimization for a thermal microfluidic chip  

Microsoft Academic Search

A geometric design for a microfluidic chip using numerical simulation is presented. Finite element method was employed in\\u000a order to design the microchannel configuration for a microfluidic chip array. The effect of geometry on the thermal response\\u000a at the interface between the microfluidic chips and an integrated system, such as a micro-electronic device, was investigated.\\u000a Dimensionless design charts, obtained from

Meysam Rahmat; Pascal Hubert

2010-01-01

8

Geometrical Optimization of a Cylindrical Plasma Lens  

NASA Astrophysics Data System (ADS)

Previous work by the authors have demonstrated the concept of an AC ``plasma lens'' for optical path difference (OPD) control of laser wavefronts. Plasma lenses feature no moving parts and a high frequency response, both of which are highly favorable for adaptive optics. This work investigates the geometrical constraints the plasma lens design, particularly the influence of the diameter of electrodes and gap distance between electrodes. A simplified electrostatic model for the plasma lens is developed and compared with experimental results. A good agreement is found between the experiments and theory. In regard to plasma lens design, the findings indicate (1) that there exists a critical gap-distance-to-diameter ratio, and (2) that the spatial efficiency of the device depends highly on the gap-distance-to-diameter ratio.

Neiswander, Brian; Matlis, Eric; Corke, Thomas

2011-11-01

9

Optimization of phase-locked loop circuits via geometric programming  

Microsoft Academic Search

We describe the global optimization of phase-locked loop (PLL) circuits using geometric programming (GP). Equations for the jitter, frequency range, and power of the PLL are presented in GP form. An array of PLL circuits was automatically generated using this technique in a 0.18 ?m, 1.8 V CMOS process. Silicon measurements show good agreement with the model. The results include

David M. Colleran; Clemenz Portmannt; Arash Hassibi; Cesar Crusius; Sunderarajan S. Mohan; Stephen Boyd; Thomas H. Leet; Maria del Mar Hershenson

2003-01-01

10

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

NASA Astrophysics Data System (ADS)

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

Das, Kinkar Ch.; Trinajsti?, N.

2010-09-01

11

Alternative Adhesive Strategies to Optimize Bonding to Radicular Dentin  

Microsoft Academic Search

This study tested the hypothesis that bond strengths of filling materials to radicular dentin might be optimized by using an indirect dentin bonding procedure with an acrylic core material. Roots of human teeth were end- odontically prepared and obturated with EndoREZ, Epiphany, or the bonding of an acrylic point with SE Bond by using a direct or an indirect bonding

Serge Bouillaguet; Bruno Bertossa; Ivo Krejci; John C. Wataha; Franklin R. Tay; David H. Pashley

12

Geometrical optimization of helical flow in grooved micromixers†  

PubMed Central

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

Lynn, N. Scott; Dandy, David S.

2010-01-01

13

A geometric analysis of mastectomy incisions: Optimizing intraoperative breast volume  

PubMed Central

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

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

2011-01-01

14

Geometrically based optimization of extracranial radiosurgery treatment planning  

NASA Astrophysics Data System (ADS)

Steterotactic radiosurgery (SRS) is a non-invasive surgical technique of using multiple high intensity external beams of x-rays to obliterate lesions. It has been successfully utilized for many intracranial diseases. There has been an interest in extending the technology to extraceanial treatment sites. Much effort has been made to improve the precision of tumor localization to make extracranial radiosurgery available for many centers. Ultrasound-guided extracranial radiosurgery, for example, has been used successfully at the University of Iowa. However, little effort has been made on extracranial radiosurgery treatment planning. For static conformal extracranial radiosurgery, a key component of a treatment plan is the selection of the number of beams and their orientations since the geometry of the beam arrangement dominates overall dose distribution. Maximizing beam separation in three dimensions decreases beam overlap, thus maximizing dose conformality and gradient outside the tumor volume. As a general rule, many centers place the beams manually in such a way that beam separations in the available space are maximal. The beam orientations are then modified to avoid the critical structure based on the planner's inspection of the beam's eye view. However manually placement and modification of beam orientations are impractical when a treatment uses a large number of beams. In this investigation, a geometrically based optimization of extracranial radiosurgery treatment planning system is developed. It begins with generating a maximally separated beam bouquets using a Monte Carlo process. These maximally separated beam bouquets are then optimized for a patient by considering the critical structure avoidances. Using this optimization process as a template, we have determined the optimal number of beams used in extracranial radiosurgery based on dose conformality, gradient, and biological indices. To evaluate the benefit of using non-coplanar beams in the treatment plan, a systematic comparison between conventional coplanar beam treatment plans and non-coplanar beam treatment plans is also addressed. Two beam shaping techniques, conformal and IMRT are used in this comparison. Decision and conclusion are made base on dose conformality, gradient, and biological indices.

Liu, Ruiguo

15

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

SciTech Connect

Enzymes are classically proposed to accelerate reactions by binding substrates within active-site environments that are structurally preorganized to optimize binding interactions with reaction transition states rather than ground states. This is a remarkably formidable task considering the limited 0.1--1 {angstrom} scale of most substrate rearrangements. The flexibility of active-site functional groups along the coordinate of substrate rearrangement, the distance scale on which enzymes can distinguish structural rearrangement, and the energetic significance of discrimination on that scale remain open questions that are fundamental to a basic physical understanding of enzyme active sites and catalysis. We bring together 1.2--1.5 {angstrom} resolution X-ray crystallography, {sup 1}H and {sup 19}F NMR spectroscopy, quantum mechanical calculations, and transition-state analogue binding measurements to test the distance scale on which noncovalent forces can constrain the structural relaxation or translation of side chains and ligands along a specific coordinate and the energetic consequences of such geometric constraints within the active site of bacterial ketosteroid isomerase (KSI). Our results strongly suggest that packing and binding interactions within the KSI active site can constrain local side-chain reorientation and prevent hydrogen bond shortening by 0.1 {angstrom} or less. Further, this constraint has substantial energetic effects on ligand binding and stabilization of negative charge within the oxyanion hole. These results provide evidence that subtle geometric effects, indistinguishable in most X-ray crystallographic structures, can have significant energetic consequences and highlight the importance of using synergistic experimental approaches to dissect enzyme function.

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

2008-11-03

16

Testing Geometrical Discrimination Within An Enzyme Active Site: Constrained Hydrogen Bonding in the Ketosteroid Isomerase Oxyanion Hole  

SciTech Connect

Enzymes are classically proposed to accelerate reactions by binding substrates within active-site environments that are structurally preorganized to optimize binding interactions with reaction transition states rather than ground states. This is a remarkably formidable task considering the limited 0.1--1 {angstrom} scale of most substrate rearrangements. The flexibility of active-site functional groups along the coordinate of substrate rearrangement, the distance scale on which enzymes can distinguish structural rearrangement, and the energetic significance of discrimination on that scale remain open questions that are fundamental to a basic physical understanding of enzyme active sites and catalysis. We bring together 1.2--1.5 {angstrom} resolution X-ray crystallography, {sup 1}H and {sup 19}F NMR spectroscopy, quantum mechanical calculations, and transition-state analogue binding measurements to test the distance scale on which noncovalent forces can constrain the structural relaxation or translation of side chains and ligands along a specific coordinate and the energetic consequences of such geometric constraints within the active site of bacterial ketosteroid isomerase (KSI). Our results strongly suggest that packing and binding interactions within the KSI active site can constrain local side-chain reorientation and prevent hydrogen bond shortening by 0.1 {angstrom} or less. Further, this constraint has substantial energetic effects on ligand binding and stabilization of negative charge within the oxyanion hole. These results provide evidence that subtle geometric effects, indistinguishable in most X-ray crystallographic structures, can have significant energetic consequences and highlight the importance of using synergistic experimental approaches to dissect enzyme function.

Sigala, P.A.; Kraut, D.A.; Caaveiro, J.M.M.; Pybus, B.; Ruben, E.A.; Ringe, D.; Petsko, G.A.; Herschlag, D.

2009-05-26

17

Printability Optimization For Fine Pitch Solder Bonding  

NASA Astrophysics Data System (ADS)

Effect of metal mask and pad design on solder printability was evaluated by DOE in this study. The process parameters were stencil thickness, squeegee angle, squeegee speed, mask separating speed, and pad angle of PCB. The main process parameters for printability were stencil thickness and squeegee angle. The response surface showed that maximum printability of 1005 chip was achieved at the stencil thickness of 0.12 mm while the maximum printability of 0603 and 0402 chip was obtained at the stencil thickness of 0.05 mm. The bonding strength of the MLCC chips was also directly related with the printability.

Kwon, Sang-Hyun; Lee, Chang-Woo; Yoo, Sehoon

2011-01-01

18

CONSTRUCTAL THEORY APPLIED TO THE GEOMETRIC OPTIMIZATION OF ELLIPTICAL CAVITIES INTO A SOLID CONDUCTING WALL  

Microsoft Academic Search

This work reports, according to Bejan's Constructal theory, the geometric optimization of an elliptical cavity that intrudes into a solid conducting wall. The objective is to minimize the global thermal resistance between the solid and the cavity. There is uniform heat generation on the solid wall. The cavity is optimized for two sets of thermal conditions: isothermal cavity and cavity

L. A. O. Rocha; C. Biserni; E. Lorenzini

2008-01-01

19

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

Microsoft Academic Search

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

James Charles Newman III

1997-01-01

20

Tubular occlusion optimizes bonding of hydrophobic resins to dentin.  

PubMed

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

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

2007-06-01

21

Design optimization of geometrically nonlinear truss structures considering cardinality constraints  

Microsoft Academic Search

The structural optimization problem of choosing the profile of each member belonging to a framed structure in order to minimize its weight while satisfying stress, displacement, stability, and other applicable constraints is often complicated by the requirement of considering non-linear structural behavior. The problem is further complicated if the members are to be chosen from a discrete set of commercially

Afonso C. C. Lemonge; Michelli M. Silva; Helio J. C. Barbosa

2011-01-01

22

Optimizing clinical performance and geometrical robustness of a new electrode device for intracranial tumor electroporation.  

PubMed

Current technology has limited applicability for electroporation based treatment of deep-seated tumors, and is in general, not optimized in terms of compliance with clinically relevant parameters. Here we present a novel electrode device developed for electrotransfer of antineoplastic drugs and genes to intracranial tumors in humans, and demonstrate a method to optimize the design (i.e. geometry) of the electrode device prototype to improve both clinical performance and geometrical tolerance (robustness). We have employed a semiempirical objective function based on constraints similar to those used in radiation oncology. The results show that small geometrical changes may yield a significant improvement. For example, a 2 mm displacement of 6 electrodes yields 14% better compliance with the clinical parameters, compared to the prototype, and additionally makes the electrode device less sensitive to random geometrical deviations. The method is readily applicable to other electrode configurations. PMID:21256816

Mahmood, Faisal; Gehl, Julie

2011-01-06

23

Optimal geometric design of robots for environments with obstacles  

NASA Astrophysics Data System (ADS)

The problem discussed is: given an environment with obstacles, what is the optimal design of a robot that can reach everywhere in this environment without collision with the obstacles. The main questions of concern are: what is the most appropriate type for the links of the robot; what is the minimum number of links that are needed to cover every point in the free space; and what is the best placement for the robot in the environment. The primary joint type employed is a one degree of freedom prismatic joint which folds into itself like a telescope to some minimal length. Our robot is formed by connecting each telescopically jointed link to a revolute joint at its other end. The revolute axes are perpendicular to the prismatic axes. The links thus formed are called 'telescoping links.' All links of the robots that are considered have telescoping structure. In the first part, some algorithms for finding the set of points in the environment (the link center) that can reach all other points with minimum number of telescoping links is discussed. The description and implementation of an algorithm that finds all visibility polygons from a given point when the obstacles are modeled as convex polygons are discussed. This algorithm is used in the implementation of algorithms for finding the link center and an approximate link center. The modifications and the additions that these algorithms require to cover curvilinear, non-convex and three-dimensional obstacles are discussed. In the second part, several theorems that establish upper and lower bounds on the number of links needed to cover the free space in both planar and spatial cases are derived. Some algorithms for minimizing the upper bounds to, hopefully, the optimal number of links for the environment are described. Finally, several generalizations to the basic problem for the cases when we design both the robot and the environment simultaneously, when we deal with moving robots and obstacles, multiple robots or robots with variable structure are considered.

Kolarov, Krasimir Dobromirov

1993-12-01

24

Optimal design of an automotive magnetorheological brake considering geometric dimensions and zero-field friction heat  

NASA Astrophysics Data System (ADS)

This paper presents an optimal design of a magnetorheological (MR) brake for a middle-sized passenger car which can replace a conventional hydraulic disc-type brake. In the optimization, the required braking torque, the temperature due to zero-field friction of MR fluid, the mass of the brake system and all significant geometric dimensions are considered. After describing the configuration, the braking torque of the proposed MR brake is derived on the basis of the field-dependent Bingham and Herschel-Bulkley rheological model of the MR fluid. The optimal design of the MR brake is then analyzed taking into account available space, mass, braking torque and steady heat generated by zero-field friction torque of the MR brake. The optimization procedure based on the finite element analysis integrated with an optimization tool is proposed to obtain optimal geometric dimensions of the MR brake. Based on the proposed procedure, optimal solutions of single and multiple disc-type MR brakes featuring different types of MR fluid are achieved. From the results, the most effective MR brake for the middle-sized passenger car is identified and some discussions on the performance improvement of the optimized MR brake are described.

Nguyen, Q. H.; Choi, S. B.

2010-11-01

25

Effects of geometric nonlinearities on the response of optimized box beam structures  

NASA Astrophysics Data System (ADS)

The present minimum-mass designs for a two-spar rectangular box beam were derived on the basis of linear-buckling FEM analysis constraints. In order to ascertain the effects of any geometric nonlinearities on these designs, each was subjected to a geometrically nonlinear FEM analysis. In all cases, the structure collapses below the design load, and does so in a mode which differs from that of linear theory. This discrepancy is attributable to such nonlinear panel-interaction mechanisms as rib-crusing loads. The optimized design is highly sensitive to crushing loads, relative to the nonoptimal design.

Ragon, S.; Gurdal, Z.

1993-04-01

26

Research on automatic optimization of ground control points in image geometric rectification based on Voronoi diagram  

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

27

Ureidobenzotriazine Multiple H-Bonding Arrays: The Importance of Geometrical Details on the Stability of H-Bonds  

Microsoft Academic Search

A 3-ureidobenzo-1,2,4-triazine 1-N-oxide (1) was synthesized successfully. The derivative displays an acceptor-donor-acceptor-acceptor (ADAA) hydrogen-bonding motif in CDCl3 and DMSO-d6 solution as well as in the solid state. Although moderately strong association of 1 was observed with DAD motifs, nonspecific binding is observed with ureidopyridines featuring a complementary DADD array. Density functional calculations of conformations 1a and 1b together with two

G. B. W. L. Ligthart; Dawei Guo; A. L. Spek; Huub Kooijman; Han Zuilhof; Rint P. Sijbesma

2008-01-01

28

Powder-neutron diffraction studies of geometric isotope and hydrogen-bonding effects in ?-CrOOH  

Microsoft Academic Search

Powder-neutron diffraction studies have been done on ?-CrOOH and ?-CrOOD to confirm whether or not the reported exceptionally large geometric isotope effect is real, and also to study hydrogen-bonding effects in ?-CrOOH compared to the prototype CrO2. The R(O?O) distance in the H-compound at room temperature is confirmed to be 2.472(3)Å, but in the D-compound it is significantly shorter, 2.518(3)Å,

Toshihiro Fujihara; Mizuhiko Ichikawa; Torbjörn Gustafsson; Ivar Olovsson; Takeshi Tsuchida

2002-01-01

29

Special two-dimensional and three-dimensional geometrically nonlinear finite elements for analysis of adhesively bonded joints  

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

30

Thermal and geometrically non-linear stress analyses of an adhesively bonded composite tee joint  

Microsoft Academic Search

Adhesive bonding technique is used successfully for joining the carbon fibre reinforced plastics to metals or composite structures. A good design of adhesive joint with either simple or more complex geometry requires its stress and deformation states to be known for different boundary conditions. In case the adhesive joint is subjected to thermal loads, the thermal and mechanical mismatches of

M. Kemal Apalak; Recep Gunes; M. Onder Turaman; A. Alper Cerit

2003-01-01

31

Geometrical correlations in the nucleosomal DNA conformation and the role of the covalent bonds rigidity  

PubMed Central

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.

Ghorbani, Maryam; Mohammad-Rafiee, Farshid

2011-01-01

32

Geometrical optimization of sensors for eddy currents nondestructive testing and evaluation  

SciTech Connect

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

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

1995-05-01

33

Geometrical and mechanical aspects of fabric bonding and pullout in cement composites  

Microsoft Academic Search

Fabric reinforced cement composites are a new class of cementitious materials with enhanced tensile strength and ductility.\\u000a The reinforcing mechanisms of 2-D fabric structures in cement matrix are studied using a fabric pullout model based on nonlinear\\u000a finite difference method. Three main aspects of the composite are evaluated: nonlinear bond slip characteristic at interface;\\u000a slack in longitudinal warp yarns, and

C. Soranakom; B. Mobasher

2009-01-01

34

Geometric parameter analysis to predetermine optimal radiosurgery technique for the treatment of arteriovenous malformation  

SciTech Connect

Purpose: To develop a method of predicting the values of dose distribution parameters of different radiosurgery techniques for treatment of arteriovenous malformation (AVM) based on internal geometric parameters. Methods and Materials: For each of 18 previously treated AVM patients, four treatment plans were created: circular collimator arcs, dynamic conformal arcs, fixed conformal fields, and intensity-modulated radiosurgery. An algorithm was developed to characterize the target and critical structure shape complexity and the position of the critical structures with respect to the target. Multiple regression was employed to establish the correlation between the internal geometric parameters and the dose distribution for different treatment techniques. The results from the model were applied to predict the dosimetric outcomes of different radiosurgery techniques and select the optimal radiosurgery technique for a number of AVM patients. Results: Several internal geometric parameters showing statistically significant correlation (p < 0.05) with the treatment planning results for each technique were identified. The target volume and the average minimum distance between the target and the critical structures were the most effective predictors for normal tissue dose distribution. The structure overlap volume with the target and the mean distance between the target and the critical structure were the most effective predictors for critical structure dose distribution. The predicted values of dose distribution parameters of different radiosurgery techniques were in close agreement with the original data. Conclusions: A statistical model has been described that successfully predicts the values of dose distribution parameters of different radiosurgery techniques and may be used to predetermine the optimal technique on a patient-to-patient basis.

Mestrovic, Ante [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia (Canada) and Department of Medical Physics, British Columbia Cancer Agency, Vancouver, British Columbia (Canada)]. E-mail: amestrovic@bccancer.bc.ca; Clark, Brenda G. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia (Canada); Department of Medical Physics, British Columbia Cancer Agency, Vancouver, British Columbia (Canada)

2005-11-01

35

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

NASA Astrophysics Data System (ADS)

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

Jelloul, M.; Dubost, G.

1985-06-01

36

Geometric optimization of the 56 MHz SRF cavity and its frequency table  

SciTech Connect

It is essential to know the frequency of a Superconducting Radio Frequency (SRF) cavity at its 'just being fabricated' stage because frequency is the key parameter in constructing the cavity. In this paper, we report our work on assessing it. We can estimate the frequency change from stage to stage theoretically and/or by simulation. At the operating stage, the frequency can be calculated accurately, and, from this value, we obtain the frequencies at other stages. They are listed in a table that serves to check the processes from stage to stage. Equally important is optimizing the geometric shape of the SRF cavity so that the peak electric-field and peak magnetic-field are as low as possible. It is particularly desirable in the 56MHz SRF cavity of RHIC to maximize the frequency sensitivity of the slow tuner. After undertaking such optimization, our resultant peak electric-field is only 44.1MV/m, and the peak magnetic-field is 1049G at 2.5MV of voltage across the cavity gap. To quench superconductivity in an SRF cavity, it is reported that the limit of the peak magnetic-field is 1800G [1], and that of the peak electric-field is more than l00MV/m for a SRF cavity [2]. Our simulations employed the codes Superfish and Microwave Studio.

Chang,X.; Ben-Zvi, I.

2008-10-01

37

Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method  

SciTech Connect

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

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

2007-05-17

38

Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method  

NASA Astrophysics Data System (ADS)

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

Oudjene, M.; Ben-Ayed, L.; Batoz, J.-L.

2007-05-01

39

Bonding Optimization on Composite Surfaces using Atmospheric Plasma Treatment  

Microsoft Academic Search

The effect of atmospheric plasma treatment (APT) on the bonding performance of a cyanate ester and an epoxy carbon fiber reinforced composite fabricated with a polyester peel ply was evaluated. A room temperature (RT) cured epoxy, an elevated temperature cured epoxy, and a cyanate ester resin, were used as the bonding adhesives. Only small increases in the carboxyl species concentration

R. J. Zaldivar; G. L. Steckel; B. A. Morgan; J. P. Nokes; H. I. Kim

2012-01-01

40

Empirical model based optimization of gearbox geometric design parameters to reduce rattle noise in an automotive transmission  

Microsoft Academic Search

The optimization of gearbox geometric design parameters to reduce rattle noise in an automotive transmission based on an empirical model approach is studied. Rattle noise is calculated and simulated based on the design parameters of a 5-speed gearbox, and all pinion gears and wheel gears are helical. The effect of the design parameters on rattle noise is analyzed. The observed

Mehmet Bozca; Peter Fietkau

2010-01-01

41

Torsional vibration model based optimization of gearbox geometric design parameters to reduce rattle noise in an automotive transmission  

Microsoft Academic Search

The optimization of gearbox geometric design parameters to reduce rattle noise in an automotive transmission based on a torsional vibration model approach is studied. Rattle noise is calculated and simulated based on the design parameters of a 5-speed gearbox, and all pinion gears and wheel gears are helical. The effect of the design parameters on rattle noise is analyzed. The

Mehmet Bozca

2010-01-01

42

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

NASA Astrophysics Data System (ADS)

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

Newman, James Charles, III

1997-10-01

43

Surface Femtochemistry: Investigation and Optimization of Bond-Forming Chemical Reactions  

NASA Astrophysics Data System (ADS)

We investigate femtosecond laser-induced surface reactions by varying the properties of the surface, the reactant gases, and the laser. In optimal control experiments, we selectively manipulate the bond-forming catalytic reactions.

Nuernberger, Patrick; Wolpert, Daniel; Weiss, Horst; Gerber, Gustav

44

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

NASA Astrophysics Data System (ADS)

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

Paul, Bijan Kumar; Guchhait, Nikhil

2013-02-01

45

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

PubMed

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

2012-08-23

46

Inter- and intra-chain disulfide bond prediction based on optimal feature selection.  

PubMed

Protein disulfide bond is formed during post-translational modifications, and has been implicated in various physiological and pathological processes. Proper localization of disulfide bonds also facilitates the prediction of protein three-dimensional (3D) structure. However, it is both time-consuming and labor-intensive using conventional experimental approaches to determine disulfide bonds, especially for large-scale data sets. Since there are also some limitations for disulfide bond prediction based on 3D structure features, developing sequence-based, convenient and fast-speed computational methods for both inter- and intra-chain disulfide bond prediction is necessary. In this study, we developed a computational method for both types of disulfide bond prediction based on maximum relevance and minimum redundancy (mRMR) method followed by incremental feature selection (IFS), with nearest neighbor algorithm as its prediction model. Features of sequence conservation, residual disorder, and amino acid factor are used for inter-chain disulfide bond prediction. And in addition to these features, sequential distance between a pair of cysteines is also used for intra-chain disulfide bond prediction. Our approach achieves a prediction accuracy of 0.8702 for inter-chain disulfide bond prediction using 128 features and 0.9219 for intra-chain disulfide bond prediction using 261 features. Analysis of optimal feature set indicated key features and key sites for the disulfide bond formation. Interestingly, comparison of top features between interand intra-chain disulfide bonds revealed the similarities and differences of the mechanisms of forming these two types of disulfide bonds, which might help understand more of the mechanisms and provide clues to further experimental studies in this research field. PMID:22591475

Niu, Shen; Huang, Tao; Feng, Kai-Yan; He, Zhisong; Cui, Weiren; Gu, Lei; Li, Haipeng; Cai, Yu-Dong; Li, Yixue

2013-03-01

47

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

PubMed

In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving the capability of the proposed calibration method. In principle, the method can be adapted to other cone-beam imaging modalities (e.g., single photon emission computed tomography). PMID:18583729

Panetta, D; Belcari, N; Del Guerra, A; Moehrs, S

2008-06-26

48

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

49

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

Microsoft Academic Search

The purpose of this work was the development of a probabilistic planning method with biological cost functions that does not require the definition of margins. Geometrical uncertainties were integrated in tumor control probability (TCP) and normal tissue complication probability (NTCP) objective functions for inverse planning. For efficiency reasons random errors were included by blurring the dose distribution and systematic errors

Marnix G. Witte; Joris van der Geer; Christoph Schneider; Joos V. Lebesque; Markus Alber; Marcel van Herk

2007-01-01

50

Radiation model for row crops: I. Geometric view factors and parameter optimization  

Technology Transfer Automated Retrieval System (TEKTRAN)

Row crops with partial cover result in different radiation partitioning to the soil and canopy compared with full cover; however, methods to account for partial cover have not been adequately investigated. The objectives of this study were to: (i) develop geometric view factors to account for the sp...

51

A numerical study on the optimal geometric design of speed control humps  

Microsoft Academic Search

The aim of the present paper is to find an optimum speed control hump geometric design by using the sequential quadratic programming method. Theoretical investigation of the dynamic behavior of the driver body components and the vehicle due to crossing speed control humps is presented. The vehicle–driver system represented as a mathematical model consists of 12 degrees of freedom (DOF).

Emad Khorshid; Mohammed Alfares

2004-01-01

52

The energy and geometric characteristics of the transition state in reactions of RO 2 • with carbonyl compound CH bonds  

Microsoft Academic Search

The energy and geometry of the transition state in reactions of the ethyl peroxyl radical with ethane, ethanol (its ? and\\u000a ? C-H bonds), acetone, butanone-2, and acetaldehyde were calculated by the density functional theory method. In all these\\u000a reactions (except EtO2\\/• + ethanol ? C-H bond), the C…H…O reaction center has an almost linear configuration (? = 176° ±

A. F. Shestakov; E. T. Denisov; N. S. Emel’yanova; T. G. Denisova

2009-01-01

53

The energy and geometric characteristics of the transition state in reactions of RO{2\\/•} with carbonyl compound CH bonds  

Microsoft Academic Search

The energy and geometry of the transition state in reactions of the ethyl peroxyl radical with ethane, ethanol (its alpha and beta C-H bonds), acetone, butanone-2, and acetaldehyde were calculated by the density functional theory method. In all these reactions (except EtO2\\/• + ethanol alpha C-H bond), the C...H...O reaction center has an almost linear configuration (phi = 176° ±

A. F. Shestakov; E. T. Denisov; N. S. Emel'Yanova; T. G. Denisova

2009-01-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

55

Optimizing geometrical design of superhydrophobic surfaces for prevention of microelectromechanical system (MEMS) stiction  

Microsoft Academic Search

Due to the surface smoothness of micromachined structures, strong adhesion forces between these fabricated structures and the substrate can be developed. The major adhesion mechanisms include capillary forces, hydrogen bonding, electrostatic forces and van der Waals forces. Once contact is made, the magnitude of these forces is in some cases sufficient to deform and pin these structures to the substrate,

Lingbo Zhu; Yonghao Xiu; Jianwen Xu; Dennis W. Hess; C. P. Wong

2006-01-01

56

Optimal prefix codes for sources with two-sided geometric distributions  

Microsoft Academic Search

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

57

Approximation schemes for NP-hard geometric optimization problems: A survey  

Microsoft Academic Search

gnpolynomial time algorithms to solve these problems optimally. However, wemight be able to design approximation algorithms: algorithms that computenear-optimal solutions in polynomial time for every problem instance. For1 we say that an algorithm approximates the problem within a factor# if it computes, for every instance I, a solution of cost at most #OPT(I),where OPT(I) is the cost of the optimum

Sanjeev Arora

2002-01-01

58

Doping an optimized resonance-valence-bond state: A picture of spin-charge separation  

Microsoft Academic Search

A systematic ``loop-gas'' formalism is developed for a general study of the resonance-valence-bond (RVB) states of a quantum antiferromagnet. At half-filling, we obtain analytic, parameter-free RVB amplitudes which reproduce virtually exact ground-state energy and spin excitation spectrum. A doped hole is then modeled by a holon-spinon pair moving on this optimized RVB background. Its energy is in excellent agreement with

Yong-Cong Chen; Zheng-Yu Weng

1996-01-01

59

Nearly Optimal Heuristics for Binary Search Trees with Geometric Generalizations (Extended Abstract)  

Microsoft Academic Search

Heuristics for optimal binary search trees with zero key access probabilities (with applications eg. in code theory and in point location) are considered. It is shown that for an arbitrarily small positive constant , there exists a linear-time heuristic for such search trees, producing solutions within the factor of 1+ from the optimum. Also, by using an interesting amortization argument,

Christos Levcopoulos; Andrzej Lingas; Jörg-rüdiger Sack

1987-01-01

60

Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method  

Microsoft Academic Search

The determination of optimum tool shapes in clinch forming process is needed to achieve the required high quality of clinch joints. The design of the tools (punch and die) is crucial since the strength of the clinch joints is closely correlated to the tools geometry. To increase the strength of clinch joints, an automatic optimization procedure is developed. The objective

M. Oudjene; L. Ben-Ayed; J.-L. Batoz

2007-01-01

61

Geometric Analysis and Manufacturing Considerations for Optimizing the Characteristics of a Twisted Pair  

Microsoft Academic Search

The geometry of a twisted pair largely determines its electrical characteristics. To improve and refine the value of these characteristics according to preset values, the optimization of the manufacturing processes requires comprehensive knowledge of twisted pair geometry and of how electrical magnitudes are affected by the construction features of the twisted pair. This paper studies the relation between the length

Alfonso Lago; Carlos M. Penalver; Jorge Marcos; JesÚs Doval-Gandoy; AndrÉs Melendez; Óscar Lopez; FÉlix Santiago; Francisco D. Freijedo; JosÉ Manuel Vilas; JosÉ Carlos Lorenzo

2009-01-01

62

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

PubMed

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

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

2013-07-03

63

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

PubMed

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

2010-12-23

64

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

65

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

Microsoft Academic Search

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

J. Sussmann; Guoqing Tang

1991-01-01

66

Analysis of Geometric Modifications to Optimize High-Power Tokamak Divertors  

NASA Astrophysics Data System (ADS)

Next generation tokamak experiments and fusion reactors will have to accommodate divertor power flux an order of magnitude higher than in the present day experiments, as measured by the characteristic parameter PLCFS/Rmaj. Due to the engineering and materials constraints designing a divertor for such environment poses a challenging and presently unresolved task. In the present study the MHD code Corsica and edge transport code UEDGE are used for quantitative assessment of performance of high-power tokamak divertors. A multi-parametric study is conducted where a range of options is explored: varying x-point flux expansion using regular or snowflake-like divertor configuration [1], choice of divertor leg length and shape, shape of target plates, options for the radiating impurity, and assumptions for the anomalous transport. Varying the parameters we analyze the trends to optimize the peak power flux density on the target plate in a high-power divertor. [1] D.D. Ryutov Physics of Plasmas 14, 064502

Umansky, M. V.; Bulmer, R. H.; Cohen, R. H.; Joseph, I.; Rognlien, T. D.; Ryutov, D. D.

2008-11-01

67

Determining the optimal PDMS–PDMS bonding technique for microfluidic devices  

Microsoft Academic Search

A number of polydimethysiloxane (PDMS) bonding techniques have been reported in the literature over the last several years as the focus on multilayer PDMS microfluidic devices has increased. Oxygen plasma bonding, despite cost, additional fabrication time and inconsistent bonding results, has remained a widely used method for bonding PDMS layers. A comparative study of four rapid, inexpensive alternative PDMS–PDMS bonding

Mark A Eddings; Michael A Johnson; Bruce K Gale

2008-01-01

68

Optimization of gold wire bonding on electroless nickel immersion gold for high temperature applications  

Microsoft Academic Search

Conventional gold (Au) wire bonding on aluminum (Al) bond pads leads to the formation of intermetallic compounds. During high temperature exposure, associated Kirkendall voids formed in the intermetallic phases (IMP) can degrade reliability of the interconnect. The advert of green molding compounds has exacerbated the ball bond reliability with Al bond pad. Thus there is a need for alternative bond

Beng Teck Ng; V. P. Ganesh; C. Lee

2006-01-01

69

Methodology for optimal configuration in structural health monitoring of composite bonded joints  

NASA Astrophysics Data System (ADS)

In this study, a structural health monitoring (SHM) strategy is proposed in order to detect disbonds in a composite lap-joint. The structure under study is composed of a carbon fiber reinforced polymer (CFRP) bonded to a titanium plate and artificial disbonds are simulated by inserting Teflon tapes of various dimensions within the joint. In situ inspection is ensured by piezoceramics bonded to the structure to generate and measure guided waves. Theoretical propagation and through-thickness stress distribution are first studied in order to determine damage sensitivity with respect to the mode and frequency of the generated guided wave. The optimal configuration of the system in terms of piezoceramic size, shape and inter-unit spacing is then validated using finite element modeling (FEM) in 3D. Experimental assessment of propagation characteristics is conducted using laser Doppler vibrometer (LDV) in order to justify theoretical and numerical assumptions and pitch-catch measurements are then performed to validate the efficient detection of the damage and accurate estimation of its size.

Quaegebeur, N.; Micheau, P.; Masson, P.; Castaings, M.

2012-10-01

70

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

NASA Astrophysics Data System (ADS)

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

Boettcher, Stefan

2013-03-01

71

Optimal Bond Trading with Personal Taxes: Implications for Bond Prices and Estimated Tax Brackets and Yield Curves  

Microsoft Academic Search

The assumption that bondholders follow either a buy-and-hold or a continuous realization trading policy, rather than the optimal trading policy,is at variance with reality and, as we demonstrate, may seriously bias the estimation of the yield curve and the implied tax bracket of the marginal investor. Tax considerations which govern a bondholder's optimal trading policy include the following: realization of

George M. Constantinides; Jonathan E. Ingersoll Jr.

1984-01-01

72

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

Microsoft Academic Search

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.

Luke Arbogast; Ananya Majumdar; Joel R. Tolman

2010-01-01

73

Optimization of interfacial bonding to enhance fracture toughness of ceramic matrix reinforced with metallic ribbon  

Microsoft Academic Search

The role of interface on the fracture toughness of ceramic glass reinforced with metallic ribbon was investigated. A strong interfacial bonding strength is essential for load transfer between the matrix and ribbon, and for utilization of the ductility of the reinforcement. However, weak interfacial bonding is considered to be important so that ribbon pull-out can improve the toughness of brittle

T. K. Lee; K. N. Subramanian

1995-01-01

74

Geometric Solids  

NSDL National Science Digital Library

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

Lessonplans, Utah

2012-09-18

75

Optimal Controller Gain Selection Using the Power Flow Information of Bond Graph Modeling  

Microsoft Academic Search

In the design of a controller, the selection of controller gains is the most time consuming and ad hoc of tasks. The difficulty lies in the fact that optimization tools cannot always find global optima, thus the solution found is more than likely sub-optimal. However, trying to find a more optimal solution quickly becomes cost ineffective. The controller gain selection

Robert T. McBride; François E. Cellier

76

Sublinear geometric algorithms  

Microsoft Academic Search

We initiate an investigation of sublinear algorithms for geometric problems in two and three dimensions. We give optimal algorithms for intersection detection of convex polygons and polyhedra, point location in two-dimensional Delaunay triangulations and Voronoi diagrams, and ray shooting in convex polyhedra, all of which run in time O(?n), where n is the size of the input. We also provide

Bernard Chazelle; Ding Liu; Avner Magen

2003-01-01

77

Optimizing hydrogen-bonding miscible binary polymer blends made by concentrated emulsion polymerization  

Microsoft Academic Search

Polystyrene\\/poly (n-butyl methacrylate) blends were prepared by concentrated emulsion polymerization using (2-hydroxy ethyl)\\u000a methacrylate and n-butyl methacrylate as hydrogen-bond donor and acceptor respectively. Two concentrated emulsions of styrene\\/(2-hydroxy\\u000a ethyl) methacrylate and n-butyl methacrylate monomers were prepared separately, and mixed mechanically after partial polymerization.\\u000a The products thus obtained consisted of compact particles. The specific formation of hydrogen bond between poly [styrene-co-

Zhongjie Du; Chen Zhang

2007-01-01

78

Magnetic resonance image reconstruction using trained geometric directions in 2D redundant wavelets domain and non-convex optimization.  

PubMed

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

2013-08-29

79

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

Microsoft Academic Search

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

80

Preliminary Simulations for Geometric Optimization of a High-Energy Delayed Gamma Spectrometer for Direct Assay of Pu in Spent Nuclear Fuel  

SciTech Connect

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

81

Structure Optimization of Au Wire Wedge-bond for High Temperature Applications  

Microsoft Academic Search

Thermo-mechanical performance of wirebonds is critical to the reliability of electrical interconnection systems of chip-level packaging for high temperature electronics because these devices are subject to a much wider temperature range compared with that for conventional electronics. The thermo-mechanical stress in wirebonds due to thermal expansion (CTE) mismatch between the metal wire, bond pads, chip and substrate materials may cause

Xiaodong Luo; Liang-Yu Chen

82

Laser assisted vessel anastomosis of coronary arteries in vitro: Optimization of bonding conditions  

Microsoft Academic Search

Laser-assisted anastomosis of pigs' coronary arteries has been investigated using an Argon laser and a technique of applying\\u000a an appropriate chromophore to the site of anastomosis. Remote infrared temperature measurements have shown that bonding was\\u000a achieved at temperatures between 65 and 80C corresponding to the collagen denaturation temperature and visual changes in\\u000a the appearance of the tissue. Further laser irradiation

C. A. Vance; J. Fisher; D. J. Wheatley; J. H. Evans; T. J. Spyt; H. Moseley; J. P. Paul

1988-01-01

83

Optimizing the performance characteristics of beams strengthened with bonded CFRP laminates  

Microsoft Academic Search

Ductility is of fundamental importance in the design of concrete structures. With structures using conventional materials\\u000a such as concrete and steel, ductility of a member as a whole can be satisfactorily defined in terms of deflection, curvature\\u000a or energy absorption capacity as examplified by the area under the load-deflection curve. However, when structural members\\u000a strengthened with externally bonded fibre reinforced

G. Spadea; F. Bencardino; R. N. Swamy

2000-01-01

84

Optimized Hydrophobic Interactions and Hydrogen Bonding at the Target-Ligand Interface Leads the Pathways of Drug-Designing  

PubMed Central

Background Weak intermolecular interactions such as hydrogen bonding and hydrophobic interactions are key players in stabilizing energetically-favored ligands, in an open conformational environment of protein structures. However, it is still poorly understood how the binding parameters associated with these interactions facilitate a drug-lead to recognize a specific target and improve drugs efficacy. To understand this, comprehensive analysis of hydrophobic interactions, hydrogen bonding and binding affinity have been analyzed at the interface of c-Src and c-Abl kinases and 4-amino substituted 1H-pyrazolo [3, 4-d] pyrimidine compounds. Methodology In-silico docking studies were performed, using Discovery Studio software modules LigandFit, CDOCKER and ZDOCK, to investigate the role of ligand binding affinity at the hydrophobic pocket of c-Src and c-Abl kinase. Hydrophobic and hydrogen bonding interactions of docked molecules were compared using LigPlot program. Furthermore, 3D-QSAR and MFA calculations were scrutinized to quantify the role of weak interactions in binding affinity and drug efficacy. Conclusions The in-silico method has enabled us to reveal that a multi-targeted small molecule binds with low affinity to its respective targets. But its binding affinity can be altered by integrating the conformationally favored functional groups at the active site of the ligand-target interface. Docking studies of 4-amino-substituted molecules at the bioactive cascade of the c-Src and c-Abl have concluded that 3D structural folding at the protein-ligand groove is also a hallmark for molecular recognition of multi-targeted compounds and for predicting their biological activity. The results presented here demonstrate that hydrogen bonding and optimized hydrophobic interactions both stabilize the ligands at the target site, and help alter binding affinity and drug efficacy.

Stanley, Ashley; Yadav, Lumbani; Sudhakar, Akulapalli; Varma, Ashok K.

2010-01-01

85

Geometric Mechanics  

NASA Astrophysics Data System (ADS)

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

Talman, Richard

1999-10-01

86

Correlation among the gas-phase, solution, and solid-phase geometrical and NMR parameters of dative bonds in the pentacoordinate silicon compounds. 1-Substituted silatranes.  

PubMed

Silatranes XSi(OCH2CH2)3N exhibit a good linear relationship between their experimental and calculated (IGLO and GIAO) values of the NMR chemical shifts of (15)N, ?N, and the lengths of dative bonds Si?N, dSiN, determined in the gas phase (ED, CCSD), solutions (COSMO PBE0, B3PW91), and crystals (X-ray). An aggregate of the obtained data provides strong evidence that the gas-phase value of dSiN in MeSi(OCH2CH2)3N should be greater by ?0.05 Å than that determined in the electron diffraction (ED) experiment (2.45 Å). Given this condition, a long-standing contradiction between the data of the structural (X-ray, ED) and NMR (15)N experiments for the molecules of 1-methyl- and 1-fluorosilatrane regarding the sensitivity of their coordination contact Si?N to the medium effect is resolved. PMID:23777391

Belogolova, Elena F; Sidorkin, Valery F

2013-06-18

87

H-bond network optimization in protein-protein complexes: are all-atom force field scores enough?  

PubMed

Structural prediction of protein-protein complexes given the structures of the two interacting compounds in their unbound state is a key problem in biophysics. In addition to the problem of sampling of near-native orientations, one of the modeling main difficulties is to discriminate true from false positives. Here, we present a hierarchical protocol for docking refinement able to discriminate near native poses from a group of docking candidates. The main idea is to combine an efficient sampling of the full system hydrogen bond network and side chains, together with an all-atom force field and a surface generalized born implicit solvent. We tested our method on a set of twenty two complexes containing a near-native solution within the top 100 docking poses, obtaining a near native solution as the top pose in 70% of the cases. We show that all atom force fields optimized H-bond networks do improve significantly state of the art scoring functions. PMID:22113891

Masone, Diego; Vaca, Israel Cabeza de; Pons, Carles; Recio, Juan Fernandez; Guallar, Victor

2011-11-24

88

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

89

3Drefine: consistent protein structure refinement by optimizing hydrogen bonding network and atomic-level energy minimization.  

PubMed

One of the major limitations of computational protein structure prediction is the deviation of predicted models from their experimentally derived true, native structures. The limitations often hinder the possibility of applying computational protein structure prediction methods in biochemical assignment and drug design that are very sensitive to structural details. Refinement of these low-resolution predicted models to high-resolution structures close to the native state, however, has proven to be extremely challenging. Thus, protein structure refinement remains a largely unsolved problem. Critical assessment of techniques for protein structure prediction (CASP) specifically indicated that most predictors participating in the refinement category still did not consistently improve model quality. Here, we propose a two-step refinement protocol, called 3Drefine, to consistently bring the initial model closer to the native structure. The first step is based on optimization of hydrogen bonding (HB) network and the second step applies atomic-level energy minimization on the optimized model using a composite physics and knowledge-based force fields. The approach has been evaluated on the CASP benchmark data and it exhibits consistent improvement over the initial structure in both global and local structural quality measures. 3Drefine method is also computationally inexpensive, consuming only few minutes of CPU time to refine a protein of typical length (300 residues). 3Drefine web server is freely available at http://sysbio.rnet.missouri.edu/3Drefine/. PMID:22927229

Bhattacharya, Debswapna; Cheng, Jianlin

2012-09-26

90

Halogen bonds as orthogonal molecular interactions to hydrogen bonds  

Microsoft Academic Search

Halogen bonds (X-bonds) are shown to be geometrically perpendicular to and energetically independent of hydrogen bonds (H-bonds) that share a common carbonyl oxygen acceptor. This orthogonal relationship is accommodated by the in-plane and out-of-plane electronegative potentials of the oxygen, which are differentially populated by H- and X-bonds. Furthermore, the local conformation of a peptide helps to define the geometry of

Andrea Regier Voth; Patricia Khuu; Keita Oishi; P. Shing Ho

2009-01-01

91

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

PubMed

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

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

2013-05-16

92

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

SciTech Connect

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

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

2011-02-01

93

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

PubMed Central

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

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

2010-01-01

94

Integrating nutrition: a geometrical approach  

Microsoft Academic Search

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

D. Raubenheimer; S. J. Simpson

1999-01-01

95

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

Microsoft Academic Search

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

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

2002-01-01

96

Differentialgeometriska Integrationsalforitmer. (Differential Geometrical Integration Algorithms).  

National Technical Information Service (NTIS)

This report describes the present status of the ongoing research in the field of differential geometric numerical methods done within the project Optimization of Missile Performance. These methods will plan an essential role in future guidance and simulat...

J. Hamberg A. Lennartsson

2001-01-01

97

Geometric theory of images  

NASA Astrophysics Data System (ADS)

This dissertation takes the first steps in the use of differential geometry in the study of images in pixel space. Unlike previous applications of geometry which focused on the surfaces of objects, this dissertation examines image manifolds. Previous work on image manifolds did not examine their intrinsic geometry. This work unifies many observations found in past work. Beyond that, many new results are obtained. In the first parts of this dissertation, the dimensions of some selected image manifolds are experimentally determined, yielding a ratio of pixel space dimension to image manifold dimension on the order of 100:1. This leads immediately to some new bounds on image source entropy. A novel approach to defining images as signals yields an analogous sampling theorem. The main repercussion of this approach is the discovery that sampling within reason is a geometric invariant. This work resurrects a classic signal interpolation method which has not been previously applied to images. With the geometric invariance of sampling in hand, more advanced aspects of image manifold geometry are explored. The first of these aspects is curvature, which is shown to be extremely high. The discovery of high curvature explains the well established but poorly understood fact that linear subspace coding methods applied to images are far from optimal. Some geometric theory concerning the use of geodesics to represent images is presented. More advanced aspects of image manifold structures are explored experimentally. Preliminary results in this area indicate that there may be a structural relation between images of crudely similar objects in similar poses. Supplementary to the theory, a novel approach to image warping is devised called multimorphing. Unlike traditional morphing, multimorphing allows one to combine several images.

Lu, Haw-Minn

1998-11-01

98

A tutorial on geometric programming  

Microsoft Academic Search

A geometric program (GP) is a type of mathematical optimization problem characterized by objective and constraint functions\\u000a that have a special form. Recently developed solution methods can solve even large-scale GPs extremely efficiently and reliably;\\u000a at the same time a number of practical problems, particularly in circuit design, have been found to be equivalent to (or well\\u000a approximated by) GPs.

Stephen P. Boyd; Seung-Jean Kim; Lieven Vandenberghe; Arash Hassibi

2007-01-01

99

Optimized Hydrophobic Interactions and Hydrogen Bonding at the Target-Ligand Interface Leads the Pathways of Drug-Designing  

Microsoft Academic Search

BackgroundWeak intermolecular interactions such as hydrogen bonding and hydrophobic interactions are key players in stabilizing energetically-favored ligands, in an open conformational environment of protein structures. However, it is still poorly understood how the binding parameters associated with these interactions facilitate a drug-lead to recognize a specific target and improve drugs efficacy. To understand this, comprehensive analysis of hydrophobic interactions, hydrogen

Rohan Patil; Suranjana Das; Ashley Stanley; Lumbani Yadav; Akulapalli Sudhakar; Ashok K. Varma; Sridhar Hannenhalli

2010-01-01

100

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

PubMed Central

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

Kukiattrakoon, Boonlert; Thammasitboon, Kewalin

2012-01-01

101

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

NASA Astrophysics Data System (ADS)

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

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

102

Geometric Algebra for Physicists  

Microsoft Academic Search

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

103

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

104

Geometric Dimensioning Sentence Structure.  

ERIC Educational Resources Information Center

Explanations of geometric dimensioning symbols are provided to assist in the comprehension of the implied basic sentence structure of modern geometric dimensioning and tolerance. The proper identification and interpretation of the substantive language within several exemplary engineering drawings, otherwise called feature control frames, is…

McCuistion, Patrick J.

1991-01-01

105

Geometrical modeling of fibrous materials under compression  

Microsoft Academic Search

Many fibrous materials such as nonwovens are consolidated via compaction rolls in a so-called calendering process. Hot rolls compress the fiber assembly and cause fiber-to-fiber bonding resulting in a strong yet porous structure. In this paper, we describe an algorithm for generating three dimensional virtual fiberwebs and simulating the geometrical changes that happen to the structure during the calendering process.

Benoit Maze; Hooman Vahedi Tafreshi; Behnam Pourdeyhimi

2007-01-01

106

Energy-Based Geometric Multi-model Fitting  

Microsoft Academic Search

Geometric model fitting is a typical chicken-&-egg problem: data points should be clustered based on geometric proximity to\\u000a models whose unknown parameters must be estimated at the same time. Most existing methods, including generalizations of RANSAC, greedily search for models with most inliers (within a threshold) ignoring overall classification of points. We formulate\\u000a geometric multi-model fitting as an optimal labeling

Hossam Isack; Yuri Boykov

107

Geometric Networks Analysis.  

National Technical Information Service (NTIS)

The main goal of the project was to develop and use algorithmic tools with a geometric underpinning to analyze large networks. For example, the Internet, social networks, connectivity properties between genes or proteins in a biological cell, and other ty...

G. Carlsson M. Mahoney

2012-01-01

108

Geometric ghosts and unitarity  

SciTech Connect

A review is given of the geometrical identification of the renormalization ghosts and the resulting derivation of Unitarity equations (BRST) for various gauges: Yang-Mills, Kalb-Ramond, and Soft-Group-Manifold.

Ne'eman, Y.

1980-09-01

109

AJ Geometric Formulas Calculator  

NSDL National Science Digital Library

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

Raymond, Jimmy

110

Geometric Retrieval Problems  

Microsoft Academic Search

A large class of geometric retrieval problems has the following form. Given a set X of geometric objects, preprocess to obtain a data structure D(X). Now use D(X) to rapidly answer queries on X. We say an algorithm for such a problem has (worst-case) space-time complexity O(f(n),g(n)) if the space requirement for D(X) is O(f) and the 'locate run-time' required

Richard Cole; Chee-keng Yap

1983-01-01

111

Geometric Algebra for Physicists  

NASA Astrophysics Data System (ADS)

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 a valuable reference for researchers working in the fields of relativity and quantum theory.

Doran, Chris; Lasenby, Anthony

2003-07-01

112

Information Intrinsic Geometric Flows  

NASA Astrophysics Data System (ADS)

Geometric Flow Theory is cross fertilized by diverse elements coming from Pure Mathematic and Mathematical Physic, but its foundation is mainly based on Riemannian Geometry, as explained by M. Berger in a recent panoramic view of this discipline, its extension to complex manifolds, the Erich Kähler's Geometry, vaunted for its unabated vitality by J.P. Bourguignon, and Minimal Surface Theory. This paper would like to initiate seminal studies for applying intrinsic geometric flows in the framework of information geometry theory. More specifically, after having introduced Information metric deduced for Complex Auto-Regressive (CAR) models from Fisher Matrix (Siegel Metric and Hyper-Abelian Metric from Entropic Kähler Potential), we study asymptotic behavior of reflection coefficients of CAR models driven by intrinsic Information geometric Kähler-Ricci and Calabi flows. These Information geometric flows can be used in different contexts to define distance between CAR models interpreted as geodesics of Entropy Manifold. We conclude with potential application of Intrinsic Geometric Flow on Gauss Map to transform Manifold of any dimension by mean of Generalized Weierstrass Formula introduced by Kenmotsu that can represent arbitrary surfaces with non-vanishing mean curvature in terms of the mean curvature function and the Gauss map. One of the advantages of the generalized formulae is that they allow to construct a new class of deformations of surfaces by use of Intrinsic Geometric Flow on Gauss Map. We conclude with the Heat equation interpretation in the framework of Information Geometry.

Barbaresco, Frédéric

2006-11-01

113

Geometrical frustration in the spin liquid ?'-Me3EtSb[Pd(dmit)2]2 and the valence-bond solid Me3EtP[Pd(dmit)2]2.  

PubMed

We show that the electronic structures of the title compounds predicted by density functional theory are well described by tight binding models. We determine the frustration ratio, J'/J, of the Heisenberg model on the anisotropic triangular lattice, which describes the spin degrees of freedom in the Mott insulating phase for a range of Pd(dmit)2 salts. All of the antiferromagnetic materials studied have J'/J is < or approximately equal to 0.5 or J'/J > or approximately equal to 0.9, and all salts with 0.5 < or approximately equal to J'/J < or approximately equal to 0.9 are known, experimentally, to be charge ordered valence-bond solids or spin liquids. PMID:23002879

Scriven, E P; Powell, B J

2012-08-29

114

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

115

Selectivity optimization of reversed-phase high-performance liquid chromatographic peptide and protein separations by varying bonded-phase functionality  

Microsoft Academic Search

Several chemical bonded-phase modified silicas were prepared using sterically protected monofunctional silane reagents which varied widely in structure and polarity. Since some of these bonded-phase packing materials are highly polar (hydrophilic), resistance to acid-catalyzed bonded-phase loss by hydrolysis was examined, and observed to remain high even for the highly polar Diol bonded-phase functionality. Modification of the surface of 300 Å

Barry E. Boyes; Douglas G. Walker

1995-01-01

116

Improvement of robot accuracy by calibrating kinematic model using a laser tracking system-compensation of non-geometric errors using neural networks and selection of optimal measuring points using genetic algorithm-  

Microsoft Academic Search

A laser tracking system is employed for measuring robot arm's tip with high accuracy. Geometric parameters in a robot kinematic model are calibrated by minimizing errors between measured positions and predicted ones based on the model. Residual errors caused by non-geometric parameters are further reduced by using neural networks, realizing high positioning accuracy of sub-millimeter order. To speed up the

Seiji Aoyagi; Atsushi Kohama; Yasutaka Nakata; Yuki Hayano; Masato Suzuki

2010-01-01

117

Toughness governs the rupture of the interfacial H-bond assemblies at a critical length scale in hybrid materials.  

PubMed

The geometry and material property mismatch across the interface of hybrid materials with dissimilar building blocks make it extremely difficult to fully understand the lateral chemical bonding processes and design nanocomposites with optimal performance. Here, we report a combined first-principles study, molecular dynamics modeling, and theoretical derivations to unravel the detailed mechanisms of H-bonding, deformation, load transfer, and failure at the interface of polyvinyl alcohol (PVA) and silicates, as an example of hybrid materials with geometry and property mismatch across the interface. We identify contributing H-bonds that are key to adhesion and demonstrate a specific periodic pattern of interfacial H-bond network dictated by the interface mismatch and intramolecular H-bonding. We find that the maximum toughness, incorporating both intra- and interlayer strain energy contributions, govern the existence of optimum overlap length and thus the rupture of interfacial (interlayer) H-bond assemblies in natural and synthetic hybrid materials. This universally valid result is in contrast to the previous reports that correlate shear strength with rupture of H-bonds assemblies at a finite overlap length. Overall, this work establishes a unified understanding to explain the interplay between geometric constraints, interfacial H-bonding, materials characteristics, and optimal mechanical properties in hybrid organic-inorganic materials. PMID:23713817

Sakhavand, Navid; Muthuramalingam, Prakash; Shahsavari, Rouzbeh

2013-06-11

118

Geometric optimization for prey–predator strategies  

Microsoft Academic Search

This paper investigates several strategies for prey and predator in both bounded and unbounded domains, assuming they have\\u000a the same speed. The work describes how the prey should move to escape from the predator and how predator should move to catch\\u000a the prey. The approach is agent-based and explicitly tracks movement of individuals as prey and predator. We show that

Bader Alshamary; Ovidiu Calin

119

Geometric optimization for prey-predator strategies.  

PubMed

This paper investigates several strategies for prey and predator in both bounded and unbounded domains, assuming they have the same speed. The work describes how the prey should move to escape from the predator and how predator should move to catch the prey. The approach is agent-based and explicitly tracks movement of individuals as prey and predator. We show that the prey escapes one or two competing predators, while might be caught in the case of three predators. The paper also describes a strategy for finding a well camouflaged static prey which emits signals. PMID:21221589

Alshamary, Bader; Calin, Ovidiu

2011-01-11

120

Geometric optimization for radiation hardness assurance  

NASA Astrophysics Data System (ADS)

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

Northum, J.; Guetersloh, S.

121

Optimal \\  

Microsoft Academic Search

This article describes optimal bankruptcy laws in a framework with asymmetric information. The key idea is that the financial distress of a firm is not observed by its lenders for quite a while. As early rescues are much cheaper than late rescues, it may pay if the creditors are forgiving in bankruptcy, thereby inducing the revelation of difficulties as early

Paul Povel

1999-01-01

122

Inflation from geometrical tachyons  

SciTech Connect

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

123

Chemical Bonds  

NSDL National Science Digital Library

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

Consortium, The C.

2011-12-11

124

Sticker Bonding.  

ERIC Educational Resources Information Center

|Introduces a science activity on the bonding of chemical compounds. Assigns students the role of either a cation or anion and asks them to write the ions they may bond with. Assesses students' understanding of charge, bonding, and other concepts. (YDS)|

Frazier, Laura Corbin

2000-01-01

125

Sticker Bonding.  

ERIC Educational Resources Information Center

Introduces a science activity on the bonding of chemical compounds. Assigns students the role of either a cation or anion and asks them to write the ions they may bond with. Assesses students' understanding of charge, bonding, and other concepts. (YDS)

Frazier, Laura Corbin

2000-01-01

126

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

SciTech Connect

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

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

2008-05-08

127

Levels of Geometric Understanding.  

ERIC Educational Resources Information Center

Three activities are presented to assess the level of students' geometric understanding according to van Hiele learning model. The activities--Descriptions, Minimum Properties, and Class Inclusion--are applied to the example of classifying quadrilaterals as squares, rectangles, rhombi, or parallelograms. Implications of this assessment are…

Pegg, John; Davey, Geoff

1991-01-01

128

Geometrical Adventures in Functionland.  

ERIC Educational Resources Information Center

Discussed is an approach in which algebra and geometry are interwoven in a series of problems that develop one from another. The two main concepts are the algebraic concept of function and the geometric concept of the "family of quadrilaterals." (MNS)

Hershkowitz, Rina; And Others

1987-01-01

129

A Geometric Scavenger Hunt  

ERIC Educational Resources Information Center

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

Smart, Julie; Marshall, Jeff

2007-01-01

130

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

131

Levels of Geometric Understanding.  

ERIC Educational Resources Information Center

|Three activities are presented to assess the level of students' geometric understanding according to van Hiele learning model. The activities--Descriptions, Minimum Properties, and Class Inclusion--are applied to the example of classifying quadrilaterals as squares, rectangles, rhombi, or parallelograms. Implications of this assessment are…

Pegg, John; Davey, Geoff

1991-01-01

132

Meshless geometric subdivision  

Microsoft Academic Search

Point-based surface processing has developed into an attractive alternative to mesh-based process- ing techniques for a number of geometric modeling applications. By working with point clouds directly, any processing is based on the given raw data and its underlying geometry rather than any arbitrary intermediate representations and generally artiflcial connectivity relations. We ex- tend this principle into the area of

C. Moenning; Facundo Mémoli; Guillermo Sapiro; Nira Dyn; Neil A. Dodgson

2007-01-01

133

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

134

Riemannian Geometrical Optics  

Microsoft Academic Search

The geometrical diffraction theory, in the sense of Keller, is here reconsidered as an obstacle problem in the Riemannian geometry. The first result is the proof of the existence and the analysis of the main properties of the ``diffracted rays'', which follow from the non-uniqueness of the Cauchy problem for geodesics in a Riemannian manifold with boundary. Then, the axial

E. de Micheli; G. Monti Bragadin; G. A. Viano

2000-01-01

135

Implementation of generalized valence bond-inspired coupled cluster theories  

NASA Astrophysics Data System (ADS)

We present an implementation of the recently proposed imperfect pairing (IP) and generalized valence bond restricted coupled cluster (GVB-RCC) methods. Our algorithm centers on repeated construction of Coulomb and exchange matrices. These operations are the computational bottleneck, scaling with the third power of system size for large systems. Robust optimization of the valence orbitals is attained using a geometrically consistent form of direct minimization. Analytic gradients of the IP and GVB-RCC energies are also obtained by a simple modification of the energy optimization scheme. As an illustration of the potential of these new methods, we use IP to compute the equilibrium geometry and energetics of a Si9H12 cluster that is a crude model for silicon dimerization on the Si(001) surface. We thus demonstrate a valuable role for IP and GVB-RCC as a diagnostic for the accuracy of reduced active space calculations as compared to their full valence analogs.

van Voorhis, Troy; Head-Gordon, Martin

2002-11-01

136

NMR spectroscopic parameters of molecular systems with strong hydrogen bonds.  

PubMed

A series of closed H-bonded molecules that have (or not) delocalized bonds were studied. The dependence of both NMR spectroscopic parameters sigma and J-couplings, and also the energy stability of such molecules with H-bond strength, were analyzed. The selected basic geometrical structure was that of malonaldehyde. From its full optimized geometry, the corresponding geometry of 3-OH propanal was obtained, fixing either the d(O-O) distance or a more extended local geometry and then optimizing the other part of the whole structure. Nitromalonaldehyde and nitromalonamide were also studied because they should have stronger H-bonds and their basic structure is also malonaldehyde. The last one also has electronic effects that may be varied by rotating the amino groups. By doing this it is possible to show that the effects on acidity of donors are more important than the equivalent effects on the basicity of acceptors. It is also shown that J-couplings that involve atoms close to the H-bond have important noncontact contributions that must be included in order to reproduce total J values. Noncontact contributions are more important than the Fermi contact (FC) one for J(O-O) in malonaldehyde. In nitromalonamide all three terms, FC, paramagnetic spin-orbital, and spin-dipolar are of the same order of magnitude when both amino groups are rotated. This does not happen for its planar configuration. Nuclear magnetic shielding of the hydrogen belonging to the H-bond is quite sensitive to it. The magnetic behavior of such hydrogen atom is modified when it is part of a closed H-bonded molecule. Then a relationship between the H-bond strength with the paramagnetic contributions of the shieldings of both atoms, C and O of the donor substructure, was obtained. We have found a cubic correlation between sigma(p) (C) of the C-O donor bond with sigma (H) of the H-bonded hydrogen. It is observed that both the noncontact J-coupling contributions and shieldings on atoms belonging to the donor substructure, give a clear evidence about the presence of the resonance phenomenon in the model compounds that have been studied, malonaldehyde, nitromalonaldehyde, and nitromalonamide. PMID:20553037

Zarycz, Natalia; Aucar, Gustavo A; Della Védova, Carlos O

2010-07-01

137

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

Microsoft Academic Search

A deconvolution algorithm has been developed to obtain robust fluence for external beam radiation treatment under geometrical uncertainties. Usually, the geometrical uncertainty is incorporated in the dose optimization process for inverse treatment planning to determine the additional intensity modulation of the beam to counter the geometrical uncertainty. Most of these approaches rely on dose convolution which is subject to the

Yankhua Fan; Ravinder Nath

2010-01-01

138

Geometric simulation of flexible motion in proteins.  

PubMed

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

Wells, Stephen A

2014-01-01

139

Geometric quantum discord with Bures distance  

NASA Astrophysics Data System (ADS)

We define a new measure of quantum correlations in bipartite quantum systems given by the Bures distance of the system state to the set of classical states with respect to one subsystem, that is, to the states with zero quantum discord. Our measure is a geometrical version of the quantum discord. As the latter it quantifies the degree of non-classicality in the system. For pure states it is identical to the geometric measure of entanglement. We show that for mixed states it coincides with the optimal success probability of an ambiguous quantum state discrimination task. Moreover, the closest zero-discord states to a state ? are obtained in terms of the corresponding optimal measurements.

Spehner, D.; Orszag, M.

2013-10-01

140

On the choice of “Geometric” thermodynamic models  

Microsoft Academic Search

A number of “geometric” models have been proposed for estimating the thermodynamic properties of a ternary solution from optimized\\u000a data for its binary subsystems. Among the most common of these are the Kohler, Muggianu, Kohler\\/Toop, and Muggianu\\/Toop models.\\u000a The latter two are “asymmetric” models in that one component is singled out and treated differently, whereas the first two\\u000a models are

Patrice Chartrand; Arthur D. Pelton

2000-01-01

141

Fuzzy geometric programming and its application  

Microsoft Academic Search

Fuzzy geometric programming (GP) is an important optimization type. In this paper, first the origin of fuzzy GP is introduced,\\u000a some recent research findings of its theory have been summarized. Then a lot of progress achieved in application is introduced\\u000a in fuzzy GP, including applications in power system, environmental engineering, economic management, etc. The range of its\\u000a application expects to

Ji-hui Yang; Bing-yuan Cao

2010-01-01

142

A Geometric Scavenger Hunt  

NSDL National Science Digital Library

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 geometry was no longer just an isolated concept in their math books; rather, it provided a tool that allowed them to examine their world in a completely different way.

Marshall, Jeff; Smart, Julie

2007-10-01

143

Advances in Geometric Morphometrics  

Microsoft Academic Search

Geometric morphometrics is the statistical analysis of form based on Cartesian landmark coordinates. After separating shape\\u000a from overall size, position, and orientation of the landmark configurations, the resulting Procrustes shape coordinates can\\u000a be used for statistical analysis. Kendall shape space, the mathematical space induced by the shape coordinates, is a metric\\u000a space that can be approximated locally by a Euclidean

Philipp Mitteroecker; Philipp Gunz

2009-01-01

144

IKONOS GEOMETRIC ACCURACY VALIDATION  

Microsoft Academic Search

ABSTRACT: Since its launch in September of 1999, the IKONOS satellite has been consistently providing high quality 1-meter panchromatic and 4-meter multispectral images. Accurate interior and exterior orientation enable IKONOS to achieve high geometric accuracy with or without ground control. Exterior orientation is determined by on-board GPS receivers, star trackers, gyros, and interlock angles. Post-processing of GPS data with software

J. Grodecki; G. Dial

2002-01-01

145

Geometric measures of entanglement  

SciTech Connect

The geometric measure of entanglement, which expresses the minimum distance to product states, has been generalized to distances to sets that remain invariant under the stochastic reducibility relation. For each such set, an associated entanglement monotone can be defined. The explicit analytical forms of these measures are obtained for bipartite entangled states. Moreover, the three-qubit case is discussed and it is argued that the distance to the W states is a new monotone.

Uyanik, K.; Turgut, S. [Department of Physics, Middle East Technical University, TR-06531, Ankara (Turkey)

2010-03-15

146

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

PubMed

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

Riley, Kevin E; Murray, Jane S; Fanfrlík, Jind?ich; Rezá?, Jan; Solá, Ricardo J; Concha, Monica C; Ramos, Felix M; Politzer, Peter

2011-03-04

147

GEOMETRIC OPERATIONS IN DIGITAL IMAGES  

Microsoft Academic Search

The geometrical transformations change the spatial relationship between objects in an image. One of the principle applications of geometric transformations concerns the possibility of correcting the digital images of the distortions introduced by the camera. Often the images produced by inexpensive cameras present geometric distortions of a very large nature. These images must be corrected in order to be used

Carlo Monti; Francesco Guerra; Caterina Balletti; Davide Miniutti

148

Geometrical Changes and Their Energies in the Formation of Donor–Acceptor Complexes  

Microsoft Academic Search

We have mapped the energy demands of the geometrical changes in donor–acceptor complexes BH3·NH3 and AlCl3·NH3 and in the course of their formation from their monomers. We have varied the individual geometrical parameters systematically and performed ab initio quantum chemical calculations for these structures. We investigated the energy requirements to change bond lengths and bond angles in both the monomers

Viktória Horváth; István Hargittai

2004-01-01

149

Effects of thermosonic bonding parameters on flip chip LEDs  

Microsoft Academic Search

The effects of thermosonic bonding parameters on GaN-based light emitting diodes (LEDs) with flip chip structure were investigated. Experiments with different thermosonic bonding parameters were conducted to optimize the flip chip process during production flow. These thermosonic bonding parameters on LEDs involved different bonding temperatures, different bonding force, and different ultrasonic power. This paper represents these parameters' effects on flip

Kun Zhao; Lei Jia; Ji'an Duan; Jianhua Zhanga

2006-01-01

150

Geometric phase in Bohmian mechanics  

NASA Astrophysics Data System (ADS)

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?. 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; Wyatt, Robert E.

2010-10-01

151

Riemannian Geometrical Optics  

NASA Astrophysics Data System (ADS)

The geometrical diffraction theory, in the sense of Keller, is here reconsidered as an obstacle problem in the Riemannian geometry. The first result is the proof of the existence and the analysis of the main properties of the ``diffracted rays'', which follow from the non-uniqueness of the Cauchy problem for geodesics in a Riemannian manifold with boundary. Then, the axial caustic is here regarded as a conjugate locus, in the sense of the Riemannian geometry, and the results of the Morse theory can be applied. The methods of the algebraic topology allow us to introduce the homotopy classes of diffracted rays. These geometrical results are related to the asymptotic approximations of a solution of a boundary value problem for the reduced wave equation. In particular, we connect the results of the Morse theory to the Maslov construction, which is used to obtain the uniformization of the asymptotic approximations. Then, the border of the diffracting body is the envelope of the diffracted rays and, instead of the standard saddle point method, use is made of the procedure of Chester, Friedman and Ursell to derive the damping factors associated with the rays which propagate along the boundary. Finally, the amplitude of the diffracted rays when the diffracting body is an opaque sphere is explicitly calculated.

de Micheli, E.; Bragadin, G. Monti; Viano, G. A.

152

Applications of geometric quantization  

SciTech Connect

Two applications of geometric quantization are described here. In the first, the classical system whose phase space is a two-sphere is quantized with an anti-holomorphic Kahler polarization. The result is an isolated quantum spin degree of freedom, with integral or half-integral total spin. A convenient formalism for handling geometric quantization with a Kahler polarization is exhibited. The second application is a discussion of several approaches to the quantization of classical systems with first class constraints. It is shown that there is a quantization procedure, called here the constrained polarization method, which is equivalent to quantizing (with a real polarization) the true classical degrees of freedom. This new method is often more convenient than directly quantizing the reduced phase space. In an example, it is shown that the time-honored procedure of imposing constraints as quantum operator equations can result in a mathematically non-viable quantum theory, if the chosen polarization is not compatible with the constraints. For this particular example, which is somewhat reminiscent of the canonical description of general relativity, there is a polarization compatible with constraints.

Stillerman, M.A.

1986-01-01

153

Optimizing rf Power for Preferential C?N Bond Formation in a-CNx Thin Films Prepared by rf-PECVD Technique  

NASA Astrophysics Data System (ADS)

Effects of rf power on the chemical bonding in carbon nitride films deposited using radio-frequency (rf) plasma enhanced chemical vapor deposition in pure methane and nitrogen gas mixtures were investigated. The rf power was varied from 60 to 100 W. The deposition rate of the films increased constantly with increasing rf power up to 80W, before saturating with further increase in rf power. Fourier transform infra-red spectroscopy (FTIR) studies showed a systematic change in the spectra and revealed three main peaks namely the G-peak, D-peak and C?N triple bond. This work showed that rf power has significant effects on the chemical bonding of the a-CNx films and the optimum rf power for the high C?N absorption intensity is 80 W.

Aziz, N. F. H.; Ritikos, R.; Kamal, S. A. A.; Awang, R.

2013-04-01

154

Geometric Mechanics of Periodic Pleated Origami  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

155

Chemical bonding for precision optical assemblies  

Microsoft Academic Search

We report on the optimization of precision optical component assemblies for space application with respect to mechanical resilience and retention of optical tolerances such as flatness and angles. Optimized parameters include: the cleaning method of the surfaces to be joined; type, concentration, and quantity of the chemical bonding agent; and post-bonding and curing conditions. Experimental studies and quality assurance are

Katie Green; Jan Burke; Bozenko Oreb

2011-01-01

156

Limits: Geometric and Harmonic Series  

NSDL National Science Digital Library

A geometric series is a sum of numbers such that the ratio between consecutive terms is constant. For instance, 1/2 + 1/4 + 1/8 + … is a geometric series. The harmonic series is the sum of all numbers 1/n for nn = 1, 2, 3, …. In this activity, you can see a representation of three geometric series and the harmonic series.

Mathematics, Illuminations N.

2010-05-26

157

Geometric measure of quantum discord  

SciTech Connect

Dakic, Vedral, and Brukner [arXiv:1004.0190 (2010)] introduced a geometric measure of quantum discord and derived an explicit formula for any two-qubit state. This measure is significant in capturing quantum correlations from a geometric perspective. In this brief report, we evaluate the geometric measure of quantum discord for an arbitrary state and obtain an explicit and tight lower bound. Furthermore, we reveal an intrinsic feature of geometric measure of quantum discord by showing that it actually coincides with a simpler quantity based on von Neumann measurements.

Luo Shunlong; Fu Shuangshuang [Academy of Mathematics and Systems Science, Chinese Academy of Sciences, 100190 Beijing (China)

2010-09-15

158

Mesh Generation and Optimal Triangulation.  

National Technical Information Service (NTIS)

The authors survey the computational geometry relevant to finite-element mesh generation. They especially focus on optimal triangulations of geometric domains in two- and three-dimensions. An optimal triangulation is a partition of the domain into triangl...

M. Bern D. Eppstein

1992-01-01

159

AUTOLOFT: The AUTOLOFT geometric processor  

Microsoft Academic Search

I'm going to talk about one phase of the design automation problem, that of the geometric computer processor, using as an example North American's AUTOLOFT system. Any design automation system requires a modicum of geometric ability, both in the analytic definition and manipulation areas. In the APT (Automatic Programmed Tool) system, both areas are well-developed, with many automatic features provided

R. Maier

1964-01-01

160

Regular Labelings and Geometric Structures  

Microsoft Academic Search

Three types of geometric structure|grid triangulations, rectangular subdivisions, and orthogonal polyhedra| can each be described combinatorially by a regular la- beling: an assignment of colors and orientations to the edges of an associated maximal or near-maximal planar graph. We briey survey the connections and analogies between these three kinds of labelings, and their uses in designing ecient geometric algorithms. algorithm

David Eppstein

2010-01-01

161

Compass routing on geometric networks  

Microsoft Academic Search

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

Evangelos Kranakis; Harvinder Singh; Jorge Urrutia

1999-01-01

162

Conifolds and geometric transitions  

NASA Astrophysics Data System (ADS)

Conifold geometries have recieved much attention in string theory and string-inspired cosmology recently, in particular the Klebanov-Strassler background that is known as the “warped throat.” This paper provides a pedagogical explanation for the singularity resolution in this geometry and emphasizes its connection to geometric transitions. The first part focuses on the gauge theory dual to the Klebanov-Strassler background, including the T-dual intersecting branes description. Then, a connection to the Gopakumar-Vafa conjecture for open-closed string duality is presented and a series of papers verifying this model on the supergravity level is summarized. An appendix provides extensive background material about conifold geometries. Special attention is given to their complex structures and the supersymmetry conditions on the background flux in constructions with fractional D3-branes on the singular (Klebanov-Tseytlin) and resolved (Pando Zayas-Tseytlin) conifolds are reevaluated. In agreement with earlier results, it is shown that only the singular solution allows a supersymmetric flux. However, the importance of using the correct complex structure to reach this conclusion is emphasized.

Gwyn, Rhiannon; Knauf, Anke

2008-10-01

163

Conifolds and geometric transitions  

SciTech Connect

Conifold geometries have recieved much attention in string theory and string-inspired cosmology recently, in particular the Klebanov-Strassler background that is known as the ''warped throat.'' This paper provides a pedagogical explanation for the singularity resolution in this geometry and emphasizes its connection to geometric transitions. The first part focuses on the gauge theory dual to the Klebanov-Strassler background, including the T-dual intersecting branes description. Then, a connection to the Gopakumar-Vafa conjecture for open-closed string duality is presented and a series of papers verifying this model on the supergravity level is summarized. An appendix provides extensive background material about conifold geometries. Special attention is given to their complex structures and the supersymmetry conditions on the background flux in constructions with fractional D3-branes on the singular (Klebanov-Tseytlin) and resolved (Pando Zayas-Tseytlin) conifolds are reevaluated. In agreement with earlier results, it is shown that only the singular solution allows a supersymmetric flux. However, the importance of using the correct complex structure to reach this conclusion is emphasized.

Gwyn, Rhiannon; Knauf, Anke [Department of Physics, McGill University, 3600 Rue Universite, Montreal, Quebec, H3A 2T8 (Canada)

2008-10-15

164

Low temperature Cu-Sn bonding by isothermal solidification technology  

Microsoft Academic Search

A low temperature wafer-to-wafer bonding technology for 3D packaging\\/integration based on Cu-Sn isothermal solidification (IS) technology is introduced in this paper. The fluxless bonding technique using Cu-Sn multilayer composites to produce higher re-melting temperature bonding layer is presented. The structure of the intermediate multilayers and bonding patterns are designed, and the bonding process is optimized. The microstructure of bonding layer

Yibo Rong; Jian Cai; Shuidi Wang; Songliang Jia

2009-01-01

165

Pauling bond strength, bond length and electron density distribution  

NASA Astrophysics Data System (ADS)

The power law regression equation, = 1.46(/r)-0.19, relating the average experimental bond lengths, , to the average accumulation of the electron density at the bond critical point, , between bonded pairs of metal and oxygen atoms (r is the row number of the M atom), determined at ambient conditions for oxide crystals, is similar to the regression equation R(M-O) = 1.41(?(r c)/r)-0.21 determined for three perovskite crystals at pressures as high as 80 GPa. The pair are also comparable with the equation = 1.43(/r)-0.21 determined for oxide crystals at ambient conditions and = 1.39(/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)/]4.76 determined for the average bond length for a given coordination polyhedron closely matches the Pauling's electrostatic bond strength reaching each the coordinating anions of the coordinated polyhedron. Despite the relative simplicity of the expression, it appears to be more general in its application in that it holds for the bulk of the M-O bonded pairs of atoms of the periodic table.

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

2013-08-01

166

Low-energy conformers of pamidronate and their intramolecular hydrogen bonds: a DFT and QTAIM study.  

PubMed

Extensive DFT and ab initio calculations were performed to characterize the conformational space of pamidronate, a typical pharmaceutical for bone diseases. Mono-, di- and tri-protic states of molecule, relevant for physiological pH range, were investigated for both canonical and zwitterionic tautomers. Semiempirical PM6 method were used for prescreening of the single bond rotamers followed by geometry optimizations at the B3LYP/6-31++G(d,p) and B3LYP/6-311++G(d,p) levels. For numerous identified low energy conformers the final electronic energies were determined at the MP2/6-311++G(2df,2p) level and corrected for thermal effects at B3LYP level. Solvation effects were also considered via the COSMO and C-PCM implicit models. Reasonable agreement was found between bond lengths and angle values in comparison with X-ray crystal structures. Relative equilibrium populations of different conformers were determined from molecular partition functions and the role of electronic, vibrational and rotational degrees of freedom on the stability of conformers were analyzed. For no level of theory is a zwitterionic structure stable in the gas-phase while solvation makes them available depending on the protonation state. Geometrically identified intramolecular hydrogen bonds were analyzed by QTAIM approach. All conformers exhibit strong inter-phosphonate hydrogen bonds and in most of them the alkyl-amine side chain is folded on the P-C-P backbone for further hydrogen bond formation. PMID:22940874

Arabieh, Masoud; Karimi-Jafari, Mohammad Hossein; Ghannadi-Maragheh, Mohammad

2012-09-02

167

The rotational spectrum and geometrical structure of thiozone, S3.  

PubMed

The rotational spectrum of thiozone, S3, has been observed for the first time. From the rotational constants of the normal and 34S isotopic species, a precise geometrical structure has been derived: S3 is a bent chain with a bond to the apex S of length 1.917(1) A and an apex angle of 117.36(6) degrees . The derived structural parameters indicate substantial double-bonding character in S3 and sp2 hybridization of the central sulfur atom. Thiozone is an excellent candidate for astronomical detection in the atmosphere of Io, the innermost Galilean moon of Jupiter, and in rich interstellar sources. PMID:15053585

McCarthy, Michael C; Thorwirth, Sven; Gottlieb, Carl A; Thaddeus, Patrick

2004-04-01

168

Intramolecular hydrogen bonding in 2-nitromalonaldehyde: Infrared spectrum and quantum chemical calculations  

NASA Astrophysics Data System (ADS)

2-Nitromalonaldehyde (NO2MA), a simple compound to study the intramolecular hydrogen bond, has been synthesized and deuterated at the enolated proton. Molecular structure and vibrational frequencies of NO2MA have been investigated by means of density functional theory (DFT) calculations. The geometrical parameters obtained in the B3LYP level using 6-31G**, 6-311G**, and 6-311++G** basis sets and compared with the corresponding parameters of malonaldehyde (MA). Frequencies calculated at B3LYP level using the 6-311G** and 6-311++G** basis sets are in good agreement with the corresponding experimental results for light and deuterated compounds in CCl4/CS2 solution. The percentage of deviation of the bond lengths and bond angles was used to give a picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. Theoretical calculations show that the hydrogen bond strength of NO2MA is slightly stronger than that of MA, which is in agreement with the spectroscopic results. The observed ?OH/?OD and ?OH/?OD appears at about 2880/2100 and 911/695 cm-1, respectively, are consistent with the calculated geometry and proton chemical shift results. To investigate the effect of NO2 group on the hydrogen bond strength, the charge distributions, steric effects, and electron delocalization in NO2MA and MA were studied by the Natural Bond Orbital (NBO) method for optimized model compounds at B3LYP/6-311++G** level of theory. The results of NBO analysis indicate that the electron-withdrawing effect of NO2 group decreases the hydrogen bond strength, but the steric and resonance effects increase the strength of the bond.

Tayyari, S. F.; Moosavi-Tekyeh, Z.; Zahedi-Tabrizi, M.; Eshghi, H.; Emampour, J. S.; Rahemi, H.; Hassanpour, M.

2006-01-01

169

Enhancing wire-composite bond strength of bonded retainers with wire surface treatment  

Microsoft Academic Search

Bonded orthodontic retainers with wires embedded in composite resin are commonly used for orthodontic retention. The purpose of this study was to test, in vitro, various wire surface treatments to determine the optimal method of enhancing the wire-composite bond strength. Coaxial wires and stainless steel wires with different surface treatments were bonded to bovine enamel and then pulled along their

Larry J. Oesterle; W. Craig Shellhart; Stacy Henderson

2001-01-01

170

GEOMETRICAL ISOMERS OF RETINENE  

PubMed Central

Five crystalline retinenes have been isolated, which have every appearance of being cis-trans isomers of one another. They are all-trans retinene; three apparently mono-cis isomers: neoretinenes a and b and isoretinene a; and isoretinene b, an apparently di-cis isomer. The absorption spectra of these substances display the relations expected of cis-trans isomers. The main absorption band is displaced 5.5 to 7 mµ toward shorter wave lengths for each presumptive cis linkage. Some of the presumptive cis isomers also display a cis peak at 255 to 260 mµ. All five substances yield an identical blue product on mixing with antimony chloride. All of them are converted by light to what appears to be an identical mixture of stereoisomers. Heat isomerizes them very slowly; only neoretinene b exhibits large changes on heating at 70°C. for 3 hours. The various isomers have been extensively interconverted by gentle procedures, and all of them have been converted to all-trans retinene. The present theory of cis-trans isomerism in carotenoids predicts the existence of four stable isomers of retinene. Instead we seem to have five—specifically three mono-cis forms where two are expected. There is no doubt that all these substances are closely related isomers of one another. The only point in question is whether they differ in part by something other than cis-trans configuration. One possibility, as yet little supported by evidence, is that isomerization between ?- and ?-ionone rings may be involved. If, however, as seems more likely, all these substances are geometrical isomers of one another, some modification is needed in the present theory of configurational relationships in this class of compounds.

Hubbard, Ruth; Gregerman, Robert I.; Wald, George

1953-01-01

171

Geometric integration in Born-Oppenheimer molecular dynamics  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

172

Optical traps with geometric aberrations  

SciTech Connect

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

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

2006-05-20

173

Multi-Objective Geometric Programming and Its Application in an Inventory Model  

Microsoft Academic Search

In this chapter, first the general multi-objective geometric programming problem is defined, then Pareto optimality, the fuzzy\\u000a geometric programming technique to solve a multi-objective geometric programming problem is discussed, and finally a multi-objective\\u000a marketing planning inventory problem is explained and formulated. Numerical examples are given for the inventory problem in\\u000a a multinational soft drink manufacturing company.

Tapan Kumar Roy

174

A general “geometric” thermodynamic model for multicomponent solutions  

Microsoft Academic Search

Several “geometric” models have been proposed for estimating thermodynamic properties of a ternary solution from optimized data for its binary subsystems. The most common are the Kohler, Muggianu, Kohler\\/Toop, and Muggianu\\/Toop models. The latter two are “asymmetric” in that one component is singled out, whereas the first two are “symmetric”. The use of a symmetric model when an asymetric model

Arthur D. Pelton

2001-01-01

175

Topology synthesis of geometrically nonlinear compliant mechanisms using meshless methods  

Microsoft Academic Search

This paper presents a new method for topology optimization of geometrical nonlinear compliant mechanisms using the element-free Galerkin method (EFGM). The EFGM is employed as an alternative scheme to numerically solve the state equations by fully taking advantage of its capability in dealing with large displacement problems. In the meshless method, the imposition of essential boundary conditions is also addressed.

Yixian Du; Liping Chen; Zhen Luo

2008-01-01

176

Diffusion bonding  

DOEpatents

1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

Anderson, Robert C. (Oak Ridge, TN)

1976-06-22

177

Computational geometric mechanics and control of rigid bodies  

NASA Astrophysics Data System (ADS)

This dissertation studies the dynamics and optimal control of rigid bodies from two complementary perspectives, by providing theoretical analyses that respect the fundamental geometric characteristics of rigid body dynamics and by developing computational algorithms that preserve those geometric features. This dissertation is focused on developing analytical theory and computational algorithms that are intrinsic and applicable to a wide class of multibody systems. A geometric numerical integrator, referred to as a Lie group variational integrator, is developed for rigid body dynamics. Discrete-time Lagrangian and Hamiltonian mechanics and Lie group methods are unified to obtain a systematic method for constructing numerical integrators that preserve the geometric properties of the dynamics as well as the structure of a Lie group. It is shown that Lie group variational integrators have substantial computational advantages over integrators that preserve either one of none of these properties. This approach is also extended to mechanical systems evolving on the product of two-spheres. A computational geometric approach is developed for optimal control of rigid bodies on a Lie group. An optimal control problem is discretized at the problem formulation stage by using a Lie group variational integrator, and discrete-time necessary conditions for optimality are derived using the calculus of variations. The discrete-time necessary conditions inherit the desirable computational properties of the Lie group variational integrator, as they are derived from a symplectic discrete flow. They do not exhibit the numerical dissipation introduced by conventional numerical integration schemes, and consequently, we can efficiently obtain optimal controls that respect the geometric features of the optimality conditions. The approach that combines computational geometric mechanics and optimal control is illustrated by various examples of rigid body dynamics, which include a rigid body pendulum on a cart, pure bending of an elastic rod, and two rigid bodies connected by a ball joint. Since all of the analytical and computational results developed in this dissertation are coordinate-free, they are independent of a specific choice of local coordinates, and they completely avoid any singularity, ambiguity, and complexity associated with local coordinates. This provides insight into the global dynamics of rigid bodies.

Lee, Taeyoung

178

Geometric phase around exceptional points  

SciTech Connect

A wave function picks up, in addition to the dynamic phase, the geometric (Berry) phase when traversing adiabatically a closed cycle in parameter space. We develop a general multidimensional theory of the geometric phase for (double) cycles around exceptional degeneracies in non-Hermitian Hamiltonians. We show that the geometric phase is exactly {pi} for symmetric complex Hamiltonians of arbitrary dimension and for nonsymmetric non-Hermitian Hamiltonians of dimension 2. For nonsymmetric non-Hermitian Hamiltonians of higher dimension, the geometric phase tends to {pi} for small cycles and changes as the cycle size and shape are varied. We find explicitly the leading asymptotic term of this dependence, and describe it in terms of interaction of different energy levels.

Mailybaev, Alexei A.; Kirillov, Oleg N.; Seyranian, Alexander P. [Institute of Mechanics, Moscow State Lomonosov University, Michurinskii pr. 1, 119192 Moscow, (Russian Federation)

2005-07-15

179

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

180

The promise of geometric morphometrics  

Microsoft Academic Search

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

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

2002-01-01

181

Pricing corporate bonds in structural models under CEV process  

Microsoft Academic Search

Much of the work on corporate bond pricing in structural models assumes that the firm value follows standard geometric Brownian\\u000a motion. This paper uses a more general assumption for firm value and derives an analytical formula for the corporate bond.\\u000a Specializing the formula to the so-called constant elasticity variance (CEV) process, we get a closed-form solution to the corporate bond.

Chang Qu

182

Infrared analysis of the bulk silicon-hydrogen bonds as an optimization tool for high-rate deposition of microcrystalline silicon solar cells  

NASA Astrophysics Data System (ADS)

It is demonstrated that the signature of bulk hydrogen stretching modes in the infrared of microcrystalline silicon (?c-Si:H) deposited at high deposition rates can be used for solar cell optimization in the high pressure depletion regime. A relation between the performance of a p-i-n solar cell and the hydride stretching modes corresponding to hydrogenated crystalline grain boundaries is observed. These crystalline surfaces show postdeposition oxidation and the absence of these surfaces in the ?c-Si:H matrix reflects device grade microcrystalline material.

Smets, A. H. M.; Matsui, T.; Kondo, M.

2008-01-01

183

Architectural Layout Design Optimization  

NSDL National Science Digital Library

This joint effort between architecture and mechanical engineering researchers at the University of Michigan 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.

Michalek, Jeremy J.; Choudhary, Ruchi; Papalambros, Panos Y.

2008-05-27

184

Planning optimal grasps  

Microsoft Academic Search

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

185

Basics of Fidelity Bonding.  

ERIC Educational Resources Information Center

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

Kahn, Steven P.

186

Geometric scalar theory of gravity  

NASA Astrophysics Data System (ADS)

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

2013-06-01

187

Geometrical response of multihole collimators  

NASA Astrophysics Data System (ADS)

A complete theory of camera multihole collimators is presented. The geometrical system response is determined in closed form in frequency space. This closed form accounts for the known efficiency and resolution formulae for parallel beam, fan beam, cone beam and astigmatic collimators as well as for the most frequent hole array patterns and hole shapes. The point spread function in the space domain for a certain collimator and source position can be calculated via a discrete fast Fourier transform. Beside the complete theoretical definition of the response of multihole collimators, this theory allows the definition of accurate models of the geometrical response for SPECT reconstruction and it is suitable for designing new collimators.

Formiconi, Andreas Robert

1998-11-01

188

Geometrical spin symmetry and spin  

SciTech Connect

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

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

2011-07-15

189

A geometric view of quantum cellular automata  

NASA Astrophysics Data System (ADS)

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 distances4, 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.

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

2012-05-01

190

FT-IR and Raman spectra, DFT and SQMFF calculations for geometrical interpretation and vibrational analysis of 3-nitro-p-toluic acid  

NASA Astrophysics Data System (ADS)

The Fourier transform infrared (FT-IR) and FT-Raman of 3-nitro-p-toluic acid (NTA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. 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 optimized geometric bond lengths and bond angles obtained by computation show good agreement with experimental data of the relative compound. The computed dimer parameters also show good agreement with experimental data. The first hyperpolarizability (?0) of this noval molecular system and related properties (?, ?0, and ??) of NTA are calculated using B3LYP/6-311++G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the ?\\midast and ?\\midast antibonding orbital and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The calculated HOMO and LUMO energies also show that charge transfer occurs within the molecule. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Nataraj, A.; Balachandran, V.; Karthick, T.

2012-08-01

191

Geometrical view of quantum entanglement  

Microsoft Academic Search

Although a precise description of microscopic physical problems requires a full quantum-mechanical treatment, physical quantities are generally discussed in terms of classical variables. One exception is quantum entanglement which apparently has no classical counterpart. We demonstrate here how quantum entanglement may be within the de Broglie-Bohm interpretation of quantum mechanics visualized in geometrical terms, giving new insight into this mysterious

A. Ramsak

2011-01-01

192

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

193

Surface Approximations in Geometric Modeling.  

National Technical Information Service (NTIS)

One of the major research efforts in the field of solid modeling focuses on extending the geometric coverage of modeling systems and on incorporating complex free-form surfaces. Some major obstacles to this goal include computing and rendering very comple...

J. H. Chuang

1990-01-01

194

Surface approximations in geometric modeling  

Microsoft Academic Search

One of the major research efforts in the field of solid modeling focuses on extending the geometric coverage of modeling systems and on incorporating complex free-form surfaces. Some major obstacles to this goal include computing and representing intersection curves of two general surfaces, and computing and rendering very complex surfaces, including offset, Voronoi, and blending surfaces. We present local and

Jung-Hong Chuang

1990-01-01

195

Geometric Modeling Using Octree Encoding.  

National Technical Information Service (NTIS)

Results are described of an effort to devise a new 3-D geometric modeling scheme and associated linear growth algorithms in which objects of arbitrary complexity can be encoded, manipulated, analyzed, and displayed interactively in real time or close to r...

D. Meagher

1981-01-01

196

Geometric Methods for Vortex Extraction  

Microsoft Academic Search

This paper presents two vortex detection methods which are based on the geometric properties of streamlines. Unlike traditional vortex detection meth- ods, which are based on point-samples of physical quantities, one of our methods is also effective in detecting weak vortices. In addition, it allows for quantitative feature extraction by calculating numerical attributes of vortices. Results are pre- sented of

I. Ari Sadarjoen; Frits H. Post

197

Parametric FEM for geometric biomembranes  

Microsoft Academic Search

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

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

2010-01-01

198

Modular optimization code package: MOZAIK  

Microsoft Academic Search

This dissertation addresses the development of a modular optimization code package, MOZAIK, for geometric shape optimization problems in nuclear engineering applications. MOZAIK's first mission, determining the optimal shape of the D2O moderator tank for the current and new beam tube configurations for the Penn State Breazeale Reactor's (PSBR) beam port facility, is used to demonstrate its capabilities and test its

Kursat B. Bekar

2008-01-01

199

Semiconductor wafer bonding  

Microsoft Academic Search

When mirror-polished, flat, and clean wafers are brought into contact, they are locally attracted to each other and adhere or bond. This phenomenon is known as semiconductor wafer bonding. Different adhesion forces (van der Waals forces, hydrogen bonding) are the reason for the bonding effect at room temperature. The different bonding mechanisms acting in dependence on the surface conditions (hydrophilic,

M. Reiche

2006-01-01

200

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

PubMed

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

Lu, Tian; Chen, Feiwu

2013-04-02

201

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…

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

2012-01-01

202

Geometrical response of multihole collimators.  

PubMed

A complete theory of camera multihole collimators is presented. The geometrical system response is determined in closed form in frequency space. This closed form accounts for the known efficiency and resolution formulae for parallel beam, fan beam, cone beam and astigmatic collimators as well as for the most frequent hole array patterns and hole shapes. The point spread function in the space domain for a certain collimator and source position can be calculated via a discrete fast Fourier transform. Beside the complete theoretical definition of the response of multihole collimators, this theory allows the definition of accurate models of the geometrical response for SPECT reconstruction and it is suitable for designing new collimators. PMID:9832021

Formiconi, A R

1998-11-01

203

The verdict geometric quality library.  

SciTech Connect

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

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

2006-03-01

204

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

205

Chemical Bonding Technology.  

National Technical Information Service (NTIS)

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 st...

E. Plueddemann

1986-01-01

206

Geometric Transition versus Cascading Solution  

Microsoft Academic Search

We study Vafa's geometric transition and Klebanov-Strassler solution from various points of view in M-theory. In terms of brane configurations, we show the detailed equivalences between the two models. In some limits, both models have an alternative realization as fourfolds in M-theory with appropriate G-fluxes turned on. We discuss some aspects of the fourfolds including how to see the transition

Keshav Dasgupta; Kyungho Oh; Radu Tatar

2002-01-01

207

Parametric FEM for geometric biomembranes  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

208

Geometric compression through topological surgery  

Microsoft Academic Search

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

Gabriel Taubin; Jarek Rossignac

1998-01-01

209

Geometrical interpretation of optical absorption  

SciTech Connect

We reinterpret the transfer matrix for an absorbing system in very simple geometrical terms. In appropriate variables, the system appears as performing a Lorentz transformation in a (1 + 3)-dimensional space. Using homogeneous coordinates, we map that action on the unit sphere, which is at the realm of the Klein model of hyperbolic geometry. The effects of absorption appear then as a loxodromic transformation, that is, a rhumb line crossing all the meridians at the same angle.

Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, E-28040 Madrid (Spain); Montesinos-Amilibia, J. M. [Departamento de Geometria y Topologia, Facultad de Matematicas, Universidad Complutense, E-28040 Madrid (Spain)

2011-08-15

210

Cortex registration: a geometric approach  

NASA Astrophysics Data System (ADS)

We have devised and implemented a novel method for calculating the high dimensional field relating the brain surfaces (cortex) of an arbitrary pair of subjects. This non-rigid registration method uses crest lines as anatomical landmarks and various geometrical techniques such as geodesic voronoi diagram, barycentric flattening and barycentric coordinates to partition the cortex into meaningful regions and achieve a spatially accurate matching. Finally, the multilevel B-splines method is used to compute a C2 continuous warping field.

Stylianou, Georgios

2005-04-01

211

Geometric characterization of planar regression  

Microsoft Academic Search

The geometric characterization of linear regression in terms of the ‘concentration ellipse’ by Galton [Galton, F., 1886, Family likeness in stature (with Appendix by Dickson, J.D.H.). Proceedings of the Royal Society of London, 40, 42–73.] and Pearson [Pearson, K., 1901, On lines and planes of closest fit to systems of points in space. Philosophical Magazine, 2, 559–572.] was extended to

Brian J. McCartin

2006-01-01

212

Uncertainties in Bayesian Geometric Models  

Microsoft Academic Search

Deformable geometric models fit very naturally into the context of Bayesian analysis. The prior proba- bility of boundary shapes is taken to proportional to the negative exponential of the deformation energy used to control the boundary. This probabilistic in- terpretation is demonstrated using a Markov-Chain Monte-Carlo (MCMC)technique, which permits one to generate configurations that populate the prior. One of many

Kenneth M. Hanson; Gregory S. Cunningham; Robert J. Mckee

1999-01-01

213

PALSAR Radiometric and Geometric Calibration  

Microsoft Academic Search

This paper summarizes the results obtained from geometric and radiometric calibrations of the Phased-Array L-Band Synthetic Aperture Radar (PALSAR) on the Advanced Land Observing Satellite, which has been in space for three years. All of the imaging modes of the PALSAR, i.e., single, dual, and full polarimetric strip modes and scanning synthetic aperture radar (SCANSAR), were calibrated and validated using

Masanobu Shimada; Osamu Isoguchi; Takeo Tadono; Kazuo Isono

2009-01-01

214

Scene analysis and geometric homology  

Microsoft Academic Search

During the last 10-12 years there has been a dramatic revival of interest in applied geometric problems. Geometers have reconsidered a number of questions in infinitesimal mechanics, questions treated by J.C. Maxwell and L. Cremona [6, 12, 13] in 1864-70, further developed under the banner of graphical statics [7, 11], but left largely untouched since the end of the nineteenth

Henry Crapo; Juliette Ryan

1986-01-01

215

Geometrical optics of moving media  

Microsoft Academic Search

The propagation of a monochromatic light wave in a medium moving at a spatially nonuniform velocity is described in terms\\u000a of geometrical optics. An eikonal equation is derived to the first order in the parameter v\\/c (where v is the velocity of the medium and c is the velocity of light). It is shown that the nonuniformity of the motion

N. N. Rozanov; G. B. Sochilin

2005-01-01

216

Geometrical content of Leslie coefficients.  

PubMed

In this work, we will study how the effective geometry acquired by nematic molecules under thermal vibration contribute to the determination of the Leslie coefficients. To do this, we will divide this work in two sections. In the first section, we present the geometrical fundamentals of the so-called Hess-Baalss (HB) approach [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 (1986)] where we show that its basic assumptions can be understood as a geometrical interpretation of de Gennes' passage from the microscopic to the macroscopic order parameter. In the second section, we use an extended version of the HB approach [M. Simões, K. Yamaguti, and A. J. Palangana, Phys. Rev. E 80, 061701 (2009)] to obtain the geometrical contribution to each Leslie coefficient. Our results will be compared with experimental data, and we will show that the Miesowicz's coefficients are connected as long as the ratio ?(3)/?(4) between these Leslie coefficients can be considered small. PMID:21728551

Simões, M; da Silva, J L Correia

2011-05-10

217

Geometrical content of Leslie coefficients  

NASA Astrophysics Data System (ADS)

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

Simões, M.; da Silva, J. L. Correia

2011-05-01

218

Geometric Tachyon and Warm Inflation  

NASA Astrophysics Data System (ADS)

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 to NS 5-brane 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 [S. Panda, M. Sami and S. Tsujikawa, Phys. Rev. D73, 023515 (2006)] where it was found that one needs a background of minimum 104 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 tachyon 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.

Bhattacharjee, Anindita; Deshamukhya, Atri

2013-03-01

219

Binding Energies of the Alpha Particle and the A=3 Isobars from a Theoretical Geometric Model  

Microsoft Academic Search

We assume a triple geometric structure for the electromagnetic nuclear interaction. This nuclear electromagnetism is used to calculate the binding energies of the alpha particle and the A=3 isobar nuclides. The approximation for the resultant wave equation which lead to the deuteron binding energy from the modified Mathieu equation for the radial eigenvalue equation also establishes proton-electron-proton magnetic bonds in

Gustavo R. Gonzalez-Martin

2008-01-01

220

Binding Energies of the ? Particle and the A=3 Isobars from a Theoretical Geometric Model  

Microsoft Academic Search

We assume a triple geometric structure for the electromagnetic nuclear interaction. This nuclear electromagnetism is used to calculate the binding energies of the alpha particle and the A=3 isobar nuclides. The approximation for the resultant wave equation which lead to the deuteron binding energy from the modified Mathieu equation for the radial eigenvalue equation also establishes pro- ton-electron-proton magnetic bonds

Gustavo R. González-Martín

221

Geometrical Visualisation--Epistemic and Emotional  

ERIC Educational Resources Information Center

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

Rodd, Melissa

2010-01-01

222

Development of a Geometric Spatial Visualization Tool  

ERIC Educational Resources Information Center

|This paper documents the development of the Geometric Spatial Assessment. We detail the development of this instrument which was designed to identify middle school students' strategies and advancement in understanding of four geometric concept domains (geometric spatial visualization, spatial projection, cardinal directions, and periodic…

Ganesh, Bibi; Wilhelm, Jennifer; Sherrod, Sonya

2009-01-01

223

Geometrical Visualisation--Epistemic and Emotional  

ERIC Educational Resources Information Center

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

Rodd, Melissa

2010-01-01

224

Multi-Objective Geometric Programming Problem Being Cost Coefficients as Continous Function with Weighted Mean Method  

Microsoft Academic Search

Geometric programming problems occur frequently in engineering design and management. In multiobjective optimization, the trade-off information between different objective functions is probably the most important piece of information in a solution process to reach the most preferred solution. In this paper we have discussed the basic concepts and principles of multiple objective optimization problems and developed a solution procedure to

A. K. Ojha; A. K. Das

2010-01-01

225

Topology synthesis of thermomechanical compliant mechanisms with geometrical nonlinearities using meshless method  

Microsoft Academic Search

The element-free Galerkin (EFG) method, one of the important meshless methods, is integrated into topology optimization and a new topology optimization method for designing thermomechanical actuated compliant mechanisms with geometrical nonlinearities is presented. The meshless method is employed to discretize the governing equations and the bulk density field. Using meshless method to analyze the thermomechanical model is better consistent with

Yi-xian Du; Li-ping Chen; Qi-hua Tian; Zheng-jia Wu

2009-01-01

226

Bond Paths Are Not Chemical Bonds  

NASA Astrophysics Data System (ADS)

This account takes to task papers that criticize the definition of a bond path as a criterion for the bonding between the atoms it links by mistakenly identifying it with a chemical bond. It is argued that the notion of a chemical bond is too restrictive to account for the physics underlying the broad spectrum of interactions between atoms and molecules that determine the properties of matter. A bond path on the other hand, as well as being accessible to experimental verification and subject to the theorems of quantum mechanics, is applicable to any and all of the interactions that account for the properties of matter. It is shown that one may define a bond path operator as a Dirac observable, making the bond path the measurable expectation value of a quantum mechanical operator. Particular attention is given to van der Waals interactions that traditionally are assumed to represent attractive interactions that are distinct from chemical bonding. They are assumed by some to act in concert with Pauli repulsions to account for the existence of condensed states of molecules. It is such dichotomies of interpretation that are resolved by the experimental detection of bond paths and the delineation of their properties in molecular crystals. Specific criticisms of the stabilization afforded by the presence of bond paths derived from spectroscopic measurements performed on dideuteriophenanthrene are shown to be physically unsound. The concept of a bond path as a "bridge of density" linking bonded atoms was introduced by London in 1928 following the definition of the electron density by Schrödinger in 1926. These papers marked the beginning of the theory of atoms in molecules linked by bond paths.

Bader, Richard F. W.

2009-09-01

227

On the geometrization of electrodynamics  

NASA Astrophysics Data System (ADS)

This paper develops the conjecture that the electromagnetic interaction is the manifestation of the torsion ?? of spacetime. This conjecture is made feasible by the natural separation of the connection ?{?/v} into “gravitational” and “electromagnetic” parts ?{?/v} and ?{?/v}, respectively, related to the metric and to the torsion. When ?{?/v} is neglected in front of ?{?/v}, the affine geodesics are shown to become the equations of motion of charged particles with Lorentz force, for an appropriate choice of ??. Since ?{?/v} contains the factor q/m, neutral particles do not see the torsional part of the connection and behave as if ?? were zero, i.e., as in Einstein's theory of gravity (the same effect is obviously obtained for charged particles when ?{?/v} ? ?{?/v}). In addition to the factor q/m, the velocity of the test particle appears in ??. This indicates that the appropriate context for this problem is to be found in velocity-dependent connections. The velocities are now coordinates and become the actual velocities of the test particles only in the system of equations that one solves for obtaining the affine geodesics in connections of this type. When written with differential forms, the combination of Maxwell's equations and of the pertinent form of the torsion suggests geometric field equations for electrodynamics. As for the gravitational part of the connection, it can be made to obey equations similar in form to the Einstein field equations. A unified geometric theory of electrodynamics and gravitation spontaneously emerges. The present state of the theory does not yet permit us to ascertain whether the right-hand side of the fully geometric, gravitational field equations corresponds to the energy-momentum tensor.

Vargas, Jose G.

1991-04-01

228

SQCD Vacua and Geometrical Engineering  

SciTech Connect

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

229

Categorical geometric skew Howe duality  

NASA Astrophysics Data System (ADS)

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

Cautis, Sabin; Kamnitzer, Joel; Licata, Anthony

230

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 rôle of geometric imagination in innovative findings. Through the analysis of works of various artists and scientists like Plato, Dürer, 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

231

Geometrization of Classical Wave Fields  

SciTech Connect

Geometrical interpretation of quantum physics is suggested. It is shown that the Dirac equation for free quantum particles can be considered as a relation describing propagation of the space topological defect with wave and corpuscular properties. This explains all ''strange'' properties of quantum formalism: appearance of probabilities, absence of the particles trajectories, unremovable influence of the measurement procedure, instantaneous nonlocal correlation in EPR-experiments. The same interpretation is suggested for the Maxwell equations for free electromagnetic waves. This interpretation explains independence of light velocity on the source movement.

Olkhov, Oleg A. [N.N. Semenov Institute of Chemical Physics, Kosygin str., 4, 119991 Moscow (Russian Federation)

2007-12-03

232

Geometrical view of quantum entanglement  

NASA Astrophysics Data System (ADS)

Although a precise description of microscopic physical problems requires a full quantum-mechanical treatment, physical quantities are generally discussed in terms of classical variables. One exception is quantum entanglement which apparently has no classical counterpart. We demonstrate here how quantum entanglement may be within the de Broglie-Bohm interpretation of quantum mechanics visualized in geometrical terms, giving new insight into this mysterious phenomenon and a language to describe it. On the basis of our analysis of the dynamics of a pair of qubits, quantum entanglement is linked to concurrent motion of angular momenta in the Bohmian space of hidden variables and to the average angle between these momenta.

Ramšak, A.

2011-11-01

233

Joint Strength Optimization of Adhesively Bonded Patches  

Microsoft Academic Search

Aircraft face damage from impact with objects or birds or due to ageing that leads to fatigue cracks. The conventional methods of repairing aircraft metallic structures generally include the use of a plate joined by screws or rivets. Although these methods are efficient in the short term, they introduce stress concentrations leading to the initiation of new cracks that are

E. A. S. Marques; Lucas F. M. da Silva

2008-01-01

234

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.

235

Image coding with geometric wavelets.  

PubMed

This paper describes a new and efficient method for low bit-rate image coding which is based on recent development in the theory of multivariate nonlinear piecewise polynomial approximation. It combines a binary space partition scheme with geometric wavelet (GW) tree approximation so as to efficiently capture curve singularities and provide a sparse representation of the image. The GW method successfully competes with state-of-the-art wavelet methods such as the EZW, SPIHT, and EBCOT algorithms. We report a gain of about 0.4 dB over the SPIHT and EBCOT algorithms at the bit-rate 0.0625 bits-per-pixels (bpp). It also outperforms other recent methods that are based on "sparse geometric representation." For example, we report a gain of 0.27 dB over the Bandelets algorithm at 0.1 bpp. Although the algorithm is computationally intensive, its time complexity can be significantely reduced by collecting a "global" GW n-term approximation to the image from a collection of GW trees, each constructed separately over tiles of the image. PMID:17283766

Alani, Dror; Averbuch, Amir; Dekel, Shai

2007-01-01

236

NPP VIIRS geometric performance status  

NASA Astrophysics Data System (ADS)

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

2011-09-01

237

Hyperbolic geometrical optics: Hyperbolic glass  

NASA Astrophysics Data System (ADS)

We study the geometrical optics generated by a refractive index of the form $n(x,y)=1/y$ $(y>0)$, where $y$ is the coordinate of the vertical axis in an orthogonal reference frame in $\\R^2$. We thus obtain what we call "hyperbolic geometrical optics" since the ray trajectories are geodesics in the Poincar\\'e-Lobachevsky half--plane $\\HH^2$. Then we prove that the constant phase surface are horocycles and obtain the \\emph{horocyclic waves}, which are closely related to the classical Poisson kernel and are the analogs of the Euclidean plane waves. By studying the transport equation in the Beltrami pseudosphere, we prove(i) the conservation of the flow in the entire strip $0

de Micheli, Enrico; Scorza, Irene; Viano, Giovanni Alberto

2006-02-01

238

Strong, high-yield and low-temperature thermocompression silicon wafer-level bonding with gold  

Microsoft Academic Search

A systematic variation of process parameters for wafer-level thermocompression bonding with gold is presented for the first time. The process was optimized for high bond strength and high bond yield. In addition, the impact of the process temperature was investigated. A bond strength of 10.7 ± 4.5 MPa and a bond yield of 89% was achieved when bonding a wafer

M. M. V. Taklo; P. Storås; K. Schjølberg-Henriksen; H. K. Hasting; H. Jakobsen

2004-01-01

239

Investing in Bonds.com  

NSDL National Science Digital Library

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

240

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

PubMed Central

A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal–ligand 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 metal–ligand 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.

2012-01-01

241

Optimal bird migration revisited  

Microsoft Academic Search

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

Thomas Alerstam

242

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

NASA Astrophysics Data System (ADS)

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-H···O and N-H···N hydrogen bonds as well as a blue-shifted C-H···O contact. AIM analysis suggests that the blue-shifted C-H···O 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-H···O and N-H···N hydrogen bonds as well as in the blue-shifted C-H···O 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

243

Acoustic-optic measurement of micromechanical resonance for adhesive bond integrity  

Microsoft Academic Search

Traditional nondestructive evaluation (NDE) of bonding flaws has generally used either ultrasound or x-rays as a directed energy source to image or otherwise detect the discontinuity of an improper bond. While this approach has broad applicability, it is inadequate where the material is highly attenuating or anisotropic, or when it is impossible to achieve an adequate interrogation due to geometrical

B. A. Barna; R. T. Allemeier; J. G. Rodriguez; D. M. Tow

1988-01-01

244

Cis peptide bonds in proteins: residues involved, their conformations, interactions and locations1  

Microsoft Academic Search

An analysis of a non-redundant set of protein structures from the Brook- haven Protein Data Bank has been carried out to find out the residue pre- ference, local conformation, hydrogen bonding and other stabilizing interactions involving cis peptide bonds. This has led to a reclassification of turns mediated by cis peptides, and their average geometrical par- ameters have been evaluated.

Debnath Pal; Pinak Chakrabarti

1999-01-01

245

Modified van der Waals atomic radii for hydrogen bonding based on electron density topology  

Microsoft Academic Search

Summation of van der Waals (VDW) atomic radii is commonly used as a criterion for whether donor and acceptor atoms, such as hydrogen and oxygen, nitrogen or fluorine, are close enough to form a hydrogen bond, being applied, together with a geometric constraint, as part of the parameterisation in determining whether or not a particular force-field ‘detects’ a hydrogen bond.

Roger A. Klein

2006-01-01

246

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

247

Operational geometric phase for mixed quantum states  

NASA Astrophysics Data System (ADS)

The geometric phase has found a broad spectrum of applications in both classical and quantum physics, such as condensed matter and quantum computation. In this paper, we introduce an operational geometric phase for mixed quantum states, based on spectral weighted traces of holonomies, and we prove that it generalizes the standard definition of the geometric phase for mixed states, which is based on quantum interferometry. We also introduce higher order geometric phases, and prove that under a fairly weak, generically satisfied, requirement, there is always a well-defined geometric phase of some order. Our approach applies to general unitary evolutions of both non-degenerate and degenerate mixed states. Moreover, since we provide an explicit formula for the geometric phase that can be easily implemented, it is particularly well suited for computations in quantum physics.

Andersson, O.; Heydari, H.

2013-05-01

248

Unifying geometric entanglement and geometric phase in a quantum phase transition  

NASA Astrophysics Data System (ADS)

Geometric measure of entanglement and geometric phase have recently been used to analyze quantum phase transition in the XY spin chain. We unify these two approaches by showing that the geometric entanglement and the geometric phase are respectively the real and imaginary parts of a complex-valued geometric entanglement, which can be investigated in typical quantum interferometry experiments. We argue that the singular behavior of the complex-value geometric entanglement at a quantum critical point is a characteristic of any quantum phase transition, by showing that the underlying mechanism is the occurrence of level crossings associated with the underlying Hamiltonian.

Azimi Mousolou, Vahid; Canali, Carlo M.; Sjöqvist, Erik

2013-07-01

249

The Bond Market Association  

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.

1998-01-01

250

Wrinkled flames and geometrical stretch  

NASA Astrophysics Data System (ADS)

Localized wrinkles of thin premixed flames subject to hydrodynamic instability and geometrical stretch of uniform intensity (S) are studied. A stretch-affected nonlinear and nonlocal equation, derived from an inhomogeneous Michelson-Sivashinsky equation, is used as a starting point, and pole decompositions are used as a tool. Analytical and numerical descriptions of isolated (centered or multicrested) wrinkles with steady shapes (in a frame) and various amplitudes are provided; their number increases rapidly with 1/S>0. A large constant S>0 weakens or suppresses all localized wrinkles (the larger the wrinkles, the easier the suppression), whereas S<0 strengthens them; oscillations of S further restrict their existence domain. Self-similar evolutions of unstable many-crested patterns are obtained. A link between stretch, nonlinearity, and instability with the cutoff size of the wrinkles in turbulent flames is suggested. Open problems are evoked.

Denet, Bruno; Joulin, Guy

2011-07-01

251

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.

252

Geometrical characteristics of uniportal VATS  

PubMed Central

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

Rocco, Gaetano; Viti, Andrea; Terzi, Alberto

2013-01-01

253

Geometric Mathematical Framework for Multibody System Dynamics  

NASA Astrophysics Data System (ADS)

The paper surveys geometric mathematical framework for computational modeling of multibody system dynamics. Starting with the configuration space of rigid body motion and analysis of it's Lie group structure, the elements of respective Lie algebra are addressed and basic relations pertinent to geometrical formulations of multibody system dynamics are surveyed. Dynamical model of multibody system on manifold introduced, along with the outline of geometric characteristics of holonomic and non-holonomic kinematical constraints.

Terze, Zdravko; Vrdoljak, Milan; Zlatar, Dario

2010-09-01

254

Splitting homomorphisms and the Geometrization Conjecture  

NASA Astrophysics Data System (ADS)

This paper gives an algebraic conjecture which is shown to be equivalent to Thurston's Geometrization Conjecture for closed, orientable 3-manifolds. It generalizes the Stallings-Jaco theorem which established a similar result for the Poincaré Conjecture. The paper also gives two other algebraic conjectures; one is equivalent to the finite fundamental group case of the Geometrization Conjecture and the other is equivalent to the union of the Geometrization Conjecture and Thurston's Virtual Bundle Conjecture.

Myers, Robert

2000-09-01

255

Geometric Routing in Wireless Sensor Networks  

Microsoft Academic Search

\\u000a This chapter surveys routing algorithms for wireless sensor networks that use geometric ideas and abstractions. Wireless sensor\\u000a networks have a unique geometric character as the sensor nodes are embedded in, and designed to monitor, the physical space.\\u000a Thus the geometric embedding of the network can be exploited for scalable and efficient routing algorithm design. This chapter\\u000a starts with geographical routing

Jie Gao

256

Registration of point cloud data from a geometric optimization perspective  

Microsoft Academic Search

We propose a framework for pairwise registration of shapes represented by point cloud data (PCD). We assume that the points are sampled from a surface and formulate the problem of aligning two PCDs as a minimization of the squared distance between the underlying surfaces. Local quadratic approximants of the squared distance function are used to develop a linear system whose

Niloy J. Mitra; Natasha Gelfand; Helmut Pottmann; Leonidas J. Guibas

2004-01-01

257

Energy Optimal Routing in Radio Networks Using Geometric Data Structures  

Microsoft Academic Search

Given the current position of n sites in a radio network, wediscuss the problem of finding routes between pairs of sites such thatthe energy consumption for this communication is minimized. Thoughthis can be done using Dijkstra's algorithm on the complete graph inquadratic tim, it is less clear how to do it in near linear time. We presentsuch algorithms for the

René Beier; Peter Sanders; Naveen Sivadasan

2002-01-01

258

Geometric phases in a scattering process  

SciTech Connect

The study of geometric phase in quantum mechanics has so far been confined to discrete (or continuous) spectra and trace-preserving evolutions. By considering only the transmission channel, a scattering process with internal degrees of freedom is neither a discrete spectrum problem nor a trace-preserving process. We explore the geometric phase in the scattering process by taking only the transmission process into account. We find that the geometric phase can be calculated by the same method as in unitary evolution. The interference visibility depends on the transmission amplitude. The dependence of the geometric phase on the barrier strength and the spin-spin coupling constant is also presented and discussed.

Liu, H. D.; Yi, X. X. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2011-08-15

259

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

PubMed

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

Ponticorvo, Michela; Miglino, Orazio

2009-07-07

260

Mathematical Optimization  

NSDL National Science Digital Library

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

Leske, Cavin.

261

Societal Bonding and Delinquency  

Microsoft Academic Search

Travis Hirschi's (1969) theory of control has amassed considerable empirical support since its development and has become one of the dominant explanations of delinquent behavior. Control theory's basic premise is that people with strong bonds to society are less likely to deviate from conventional behavior than those with weak bonds. In this article bonding theory is applied to a severely

Karen Witchcoff Knight; Tony Tripodi

1996-01-01

262

Bonded flexible pipe  

Microsoft Academic Search

This paper presents an overview of bonded flexible pipe improvements primarily driven by environmental safety as applied to offshore development using mobile production systems. Bonded pipe is a flexible pipe where the steel reinforcement is integrated and bonded to a vulcanized elastomeric material. Textile material is included in the structure to obtain additional structural reinforcement or to separate elastomeric layers.

Val M. Northcutt

2000-01-01

263

Thin die bonding techniques  

Microsoft Academic Search

Picking and bonding 50-micron thick chips presents new challenges to the die bonder industry. Extensive development efforts have identified a number of process challenges and solutions. This paper summarizes Esec's most recent learning's pertaining to the thin die bonding process. Problems with standard die bonding chip pick up and epoxy-dispensing techniques are discussed and solutions identified. Two novel pick solutions

J. Medding; R. Stalder; M. Niederhauser; P. Stoessel

2004-01-01

264

Hydrophobic silicon wafer bonding  

Microsoft Academic Search

Silicon wafers with hydrophilic surfaces can be bonded at room temperature (RT). This has been attributed to the presence of OH groups on the mating surfaces that form hydrogen bonds between the two wafers.19 Hydrophobic Si wafers prepared by a dip in diluted HF without subsequent water rinse have shown a similar RT bonding performance.3 Dispersion van der Waals forces

Q.-Y. Tong; E. Schmidt; U. Gösele; M. Reiche

1994-01-01

265

Geometric Dynamics of Calcium Oscillations ODEs Systems  

Microsoft Academic Search

From a difierential geometric point of view, this paper expresses in time dependent least squares Lagrangian terms that the solutions of any DEs sys- tems of order one are harmonic curves on 1-jet spaces. Natural time dependent electromagnetic flelds, together with their generalized Maxwell equations, are derived from the given DEs systems and suitable geometric structure. Impor- tant applications to

Mircea Neagu; Ileana Rodica Nicola

2004-01-01

266

Geometrical camera calibration with diffractive optical elements.  

PubMed

Traditional methods for geometrical camera calibration are based on calibration grids or single pixel illumination by collimated light. A new method for geometrical sensor calibration by means of diffractive optical elements (DOE) in connection with a laser beam equipment is presented. This method can be especially used for 2D-sensor array systems but in principle also for line scanners. PMID:19065162

Bauer, M; Griessbach, D; Hermerschmidt, A; Krüger, S; Scheele, M; Schischmanow, A

2008-12-01

267

Geometric Information Criterion for Model Selection  

Microsoft Academic Search

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

Kenichi Kanatani

1998-01-01

268

Frequent Subgraph Retrieval in Geometric Graph Databases  

Microsoft Academic Search

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

Sebastian Nowozin; Koji Tsuda

2008-01-01

269

Strapdown inertial navigation algorithm in geometric algebra  

Microsoft Academic Search

Geometric algebra(GA) is a very convenient re- presentational and computational system for geometry due to its clear geometrical meanings and simple notations. The rigid body motion is represented by motors in GA. We derive the kinematic equation of motors, and associate motors with specific force acceleration and angular rate which can be measured in strapdown inertial navigation system. The navigation

Dimin Wu; Zhengzhi Wang

2011-01-01

270

Towards a Geometric Theory of Hybrid Systems  

Microsoft Academic Search

We propose a framework for a geometric theory of hybrid systems. Given a deterministic, non-blocking hybrid system, we introduce the notion of its hybrifold with the associated hybrid flow on it. This enables us to study hybrid systems from a global geometric perspective as (generally non-smooth) dynamical systems. This point of view is adopted in studying the Zeno phenomenon. We

Slobodan N. Simic; Karl Henrik Johansson; John Lygeros; Shankar Sastry

2001-01-01

271

Towards a Geometric Theory of Hybrid Systems  

Microsoft Academic Search

We propose a framework for a geometric theory of hybrid systems. Given a deterministic, non-blocking hybrid system, we introduce the notion of its hybrifold with the associated hybrid o w on it. This enables us to study hybrid systems from a global geometric perspective as (generally non-smooth) dynamical systems. This point of view is adopted in studying the Zeno phenomenon.

Slobodan N. Simic; Karl Henrik Johansson; Shankar Sastry; John Lygeros

2000-01-01

272

State of the Union (of Geometric Objects)  

Microsoft Academic Search

Let C be a set of geometric objects in Rd. The combinatorial complexity of the union of C is the total number of faces of all dimensions on its boundary. We survey the known upper bounds on the complexity of the union of n geometric objects satisfying various natural conditions. These bounds play a central role in the analysis of

Pankaj K. Agarwal; Janos Pach; Micha Sharir

273

Kant on the Imagination and Geometrical Certainty  

Microsoft Academic Search

In what follows, I aim to develop our understanding of the role the imagination plays in Kant's Critical account of geometry and suggest, in particular, that the peculiar interpretation of the imagination that Kant forwards in the First Critique helps secure the certainty of geometrical knowledge. To make my case, I first consider the account of geometrical reasoning Kant presents

Mary Domski

2010-01-01

274

Surface Reflection: Physical and Geometrical Perspectives  

Microsoft Academic Search

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

Shree K. Nayar; Katsushi Ikeuchi; Takeo Kanade

1991-01-01

275

Hierarchical geometric models for visible surface algorithms  

Microsoft Academic Search

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

James H. Clark

1976-01-01

276

Applications of Geometric Algebra in Robot Vision  

Microsoft Academic Search

In this tutorial paper we will report on our experience in the use of geometric algebra (GA) in robot vision. The results could be reached in a long term research programme on modelling the perception- action cycle within geometric algebra. We will pick up three important applications from image processing, pattern recognition and computer vision. By presenting the problems and

Gerald Sommer

2004-01-01

277

Geometrical cluster growth models and kinetic gelation  

Microsoft Academic Search

Random percolation, self-avoiding walks or lattice animals can be regarded as static geometrical models where the different possible configurations are completely independent from each other and show no memory effects. These static geometrical models have extensively ben studied in the past. Certain configurations (clusters) were, for technical reasons, sometimes constructed by a growth process where computer time might be interpreted

H. J. Herrmann

1986-01-01

278

Geometric Error Measurement and Compensation of Machines  

Microsoft Academic Search

Methods for geometric error measurement are classified in direct and self-calibration, according to the use of calibrated or uncalibrated standard and to the strategy for the generation of information about errors. A vectorial equation for geometric error description is presented, which is independent from the machine structure. The evaluation of measurement effectiveness is discussed and error compensation methods and strategies

S. Sartori; G. X. Zhang

1995-01-01

279

Gaining Insights into Children's Geometric Knowledge  

ERIC Educational Resources Information Center

This article describes how research on children's geometric thinking was used in conjunction with the picture book "The Greedy Triangle" to gain valuable insights into children's prior geometric knowledge of polygons. Exercises focused on the names, visual appearance, and properties of polygons, as well as real-world connections for each, are…

Mack, Nancy K.

2007-01-01

280

Geometric Contact for Curves and Surfaces.  

National Technical Information Service (NTIS)

The notion of Frenet-contact of order p(F(sup p)) for parametric curves in the real space R(sup d) is defined in a new geometrical way which allows its extension to the case of surfaces. This notion is compared to geometric continuity of order p(G(sup p))...

M. Mazure

1992-01-01

281

Graph-based geometric-iconic guide-wire tracking.  

PubMed

In this paper we introduce a novel hybrid graph-based approach for Guide-wire tracking. The image support is captured by steerable filters and improved through tensor voting. Then, a graphical model is considered that represents guide-wire extraction/tracking through a B-spline control-point model. Points with strong geometric interest (landmarks) are automatically determined and anchored to such a representation. Tracking is then performed through discrete MRFs that optimize the spatio-temporal positions of the control points while establishing landmark temporal correspondences. Promising results demonstrate the potentials of our method. PMID:22003594

Honnorat, Nicolas; Vaillant, Régis; Paragios, Nikos

2011-01-01

282

Packing: A Geometric Analysis of Feature Selection and Category Formation  

PubMed Central

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 children’s ability to generalize a category from very few examples.

Hidaka, Shohei; Smith, Linda B.

2011-01-01

283

Geometric Phase of Unitary Evolution Operator  

NASA Astrophysics Data System (ADS)

The common geometric phase is understood in terms of curvature of the space of normalized quantum states (Berry-Simon and Aharonov-Anandan geometric phase). We demonstrate how the geometric phase can be self-consistently defined in the space of unitary operators if the dynamic group of a quantum system has physically meaningful partitioning into a subgroup and complimentary coset space. To motivate the introduction of a geometric phase of a unitary operator, we demonstrate that this phase does not vanish even if the quantum system is in a mixed state, described by a density matrix. Illustrative examples of calculating the geometric phase of a unitary operator are provided for SU(2) and SU(4) groups i.e. one- and two-qubit transformations.

Uskov, Dmitry

2005-05-01

284

Geometric reasoning about assembly tools  

SciTech Connect

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

285

Geometrical aspects of quantum spaces  

SciTech Connect

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

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

1996-05-11

286

Geometric morphology of cellular solids  

SciTech Connect

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

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

2001-01-01

287

Geometric precipices in string cosmology  

SciTech Connect

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

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

2008-03-15

288

Hydrogen multicentre bonds  

NASA Astrophysics Data System (ADS)

The concept of a chemical bond stands out as a major development in the process of understanding how atoms are held together in molecules and solids. Lewis' classical picture of chemical bonds as shared-electron pairs evolved to the quantum-mechanical valence-bond and molecular-orbital theories, and the classification of molecules and solids in terms of their bonding type: covalent, ionic, van der Waals and metallic. Along with the more complex hydrogen bonds and three-centre bonds, they form a paradigm within which the structure of almost all molecules and solids can be understood. Here, we present evidence for hydrogen multicentre bonds-a generalization of three-centre bonds-in which a hydrogen atom equally bonds to four or more other atoms. When substituting for oxygen in metal oxides, hydrogen bonds equally to all the surrounding metal atoms, becoming fourfold coordinated in ZnO, and sixfold coordinated in MgO. These multicentre bonds are remarkably strong despite their large hydrogen-metal distances. The calculated local vibration mode frequency in MgO agrees with infrared spectroscopy measurements. Multicoordinated hydrogen also explains the dependence of electrical conductivity on oxygen partial pressure, resolving a long-standing controversy on the role of point defects in unintentional n-type conductivity of ZnO (refs 8-10).

Janotti, Anderson; van de Walle, Chris G.

2007-01-01

289

Mirror profile optimization for nano-focusing KB mirror  

SciTech Connect

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

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

2010-06-23

290

Geometrical structure and spin order of Gd13 cluster.  

PubMed

The spin-polarized generalized gradient approximation to the density-functional theory has been used to determine the lowest energy structure, electronic structure, and magnetic property of Gd(13) cluster. Our results show that the ionic bonding is combined with the covalent characteristics in stabilizing the Gd cluster. The ferrimagnetic icosahedron is found to be the lowest energy configuration, in which the centered Gd atom couples antiferromagnetically with the rest Gd atoms surrounding it. No spin non-collinear evidence has been detected in our calculations. It is identified that the local magnetic moments of Gd atom are about 8 ?(B) regardless of geometrical structure. Finally, the comprehensive electronic structure analyses show that the indirect long-range magnetic coupling between the polarized 4f is mediated by the polarization of 5d, 6s, and 6p conduction electrons, which is the typical Ruderman-Kittel-Kasuya-Yosida interactions. PMID:21950876

Yuan, H K; Chen, H; Kuang, A L; Wu, B

2011-09-21

291

Geometric Gyrokinetic Theory for Edge Plasma  

SciTech Connect

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

292

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

293

A theoretical study of the geometrical structures of the hydrazones and their protonated complexes  

Microsoft Academic Search

1.N-N and N=C bond lengths and values of the NNC valence angles have been calculated for the hydrazones and their protonated complexes. Protonation does not lead to an essential alteration of the geometrical parameters of these compounds.2.The electrostatic potential map for the protonated complex shows two minima, these corresponding to the protons at the amine and imine nitrogen atoms.3.Study of

V. V. Zverev; Z. G. Bazhanova; L. V. Ermolaeva

1979-01-01

294

Binding Energies of the Alpha Particle and the A=3 Isobars from a Theoretical Geometric Model  

Microsoft Academic Search

We assume a triple geometric structure for the electromagnetic nuclear\\u000ainteraction. This nuclear electromagnetism is used to calculate the binding\\u000aenergies of the alpha particle and the A=3 isobar nuclides. The approximation\\u000afor the resultant wave equation which lead to the deuteron binding energy from\\u000athe modified Mathieu equation for the radial eigenvalue equation also\\u000aestablishes proton-electron-proton magnetic bonds in

Gustavo R. Gonzalez-Martin

2008-01-01

295

A geometric setting for moment tensors  

NASA Astrophysics Data System (ADS)

We describe a parametrization of moment tensors that is suitable for use in algorithms for moment tensor inversion. The parameters are conceptually natural and can be easily visualized. The ingredients of the parametrization are present in the literature; we have consolidated them into a concise statement in a geometric setting. We treat several familiar moment tensor topics in the same geometric setting as well. These topics include moment tensor decompositions, crack-plus-double-couple moment tensors, and the parameter ? that measures the difference between a deviatoric moment tensor and a double couple. The geometric approach clarifies concepts that are sometimes obscured by calculations.

Tape, Walter; Tape, Carl

2012-07-01

296

Interfacial modification of polymer blends—the emulsification curve: 2. Predicting the critical concentration of interfacial modifier from geometrical considerations  

Microsoft Academic Search

Geometrical considerations about macromolecular size have been used in order to make a critical analysis of the minimum amount of block copolymer needed to saturate the interface in the melt mixing of immiscible polymer blends. For the case of dispersed spherical domains an expression has been developed (Equation (8)) which contains only molecular parameters such as the number of bonds,

Mireya Matos; Basil D. Favis

1996-01-01

297

A novel modeling approach for multiple coupled wire bond interconnects  

Microsoft Academic Search

A novel approach for electrical modeling of multiple coupled wire bonds up to a frequency of 10GHz is presented. This paper describes a very easy way to get complex electrical model for complex structures like multiple coupled wire bonds. Electromagnetic field computation and compact model extraction using optimization algorithm is limited on few elements. A very efficient way is starting

Ingo Doerr; Grit Sommer; Herbert Reichl

2004-01-01

298

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

299

Tradeoff between delay and area in gate sizing using Geometric Programming  

Microsoft Academic Search

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

Gracieli Posser; Guilherme Flach; Gustavo Wilke; Ricardo Reis

2012-01-01

300

The hydrogen bond  

Microsoft Academic Search

The concept of the hydrogen bond is a century old but remains youthful because of its vital role in so many branches of science and because of continued advances in experiment, theory and simulation. We discuss the structural and energetic characteristics of normal hydrogen bonds X–H···Y as well as some exceptions to the normal, including proton-shared and ion-pair bonds. We

A. D. Buckingham; J. E. Del Bene; S. A. C. McDowell

2008-01-01

301

BONDING ALUMINUM METALS  

DOEpatents

A process is given for bonding aluminum to aluminum. Silicon powder is applied to at least one of the two surfaces of the two elements to be bonded, the two elements are assembled and rubbed against each other at room temperature whereby any oxide film is ruptured by the silicon crystals in the interface; thereafter heat and pressure are applied whereby an aluminum-silicon alloy is formed, squeezed out from the interface together with any oxide film, and the elements are bonded.

Noland, R.A.; Walker, D.E.

1961-06-13

302

Semiconductor Wafer Bonding  

Microsoft Academic Search

When mirror-polished, flat, and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces and adhere or bond. This phenomenon is referred to as wafer bonding. The most prominent applications of wafer bonding are silicon-on-insulator (SOI) devices, silicon-based sensors and actuators, as well as optical

U. Gosele; Q.-Y. Tong

1998-01-01

303

2-Step IMAT and 2-Step IMRT: a geometrical approach.  

PubMed

The purpose of this paper is to develop a method that reduces the number of segments for intensity modulated arc therapy (IMAT) and intensity modulated radiotherapy (IMRT) for concave target volumes (TV). The aim was to utilize no more than two intensity levels per organ at risk (OAR) and to derive both optimal segment widths and weights from geometric considerations. Brahme's model of an annular target surrounding a circular OAR was used as test model. Brahme's solution was substituted by a single segment added to a simple field blocking the OAR. Width and weight of the segment were the free parameters to optimize. The objective function to minimize was the root mean square (rms) error of the dose in the target volume. One boundary condition was--neglecting scatter--"zero-dose" to the OAR. The resulting rules for width and weight of the additive segment are referred to as "optimized 2-Step IMAT" and "2-Step IMRT." The recommendations were applied to some simplified plans representing clinical cases using a commercial planning system. Optimized 2-Step IMAT improved the rms by a factor of 4 with respect to techniques simply blocking the OAR. The additional segment reduced the rms below 3% for cases with gaps between OAR and TV larger than 8% of the TV diameter. The results for 2-Step IMAT are applicable to IMRT and aperture modulated arc therapy (AMAT). 2-Step IMAT can be utilized for noncylindrical cases and for more than one OAR. A geometrical and topological approach to IMAT and IMRT can be useful to understand fluence profiles. The results could be applied to ameliorate other topology-based procedures used in some planning systems. Basic mechanisms of 2-Step IMAT can assist with the creation of rules for adaptive IMRT to compensate for patient motion. PMID:15839350

Bratengeier, Klaus

2005-03-01

304

One Bond Strategy  

NSDL National Science Digital Library

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

2001-01-01

305

Effect of plasma treatment of Au-Ni-Cu bond pads on process windows of Au wire bonding  

Microsoft Academic Search

The wire bondability of Au-Ni-Cu bond pads with different Au plating schemes, including electrolytic and immersion plates, are evaluated after plasma treatment. The plasma cleaning conditions, such as cleaning power and time, are optimized based on the process window and wire pull strength measurements for different bond pad temperatures. Difference in the efficiency of plasma treatment in improving the wire

Yu Hin Chan; Jang-Kyo Kim; Deming Liu; P. C. K. Liu; Yiu-Ming Cheung; Ming Wai Ng

2005-01-01

306

Geometrical Origin of Supersymmetric Gauge Theories.  

National Technical Information Service (NTIS)

We show that the kinematical properties of any supersymmetric gauge theory may be obtained by mapping a geometric group structure of loops in superspace into some particular Lie group. The underlying group structure of the usual constrained supergauge the...

S. Caicedo R. Gambini

1988-01-01

307

Evaluating the geometric measure of quantum discord  

NASA Astrophysics Data System (ADS)

We derive analytic formulas for the geometric measure of quantum discord introduced by Dakic, Vedral, and Brukner for pure states and ( 2× n)-dimensional states and establish a general lower bound for arbitrary states.

Luo, Shunlong; Fu, Shuangshuang

2012-06-01

308

Geometric symmetries in superfluid vortex dynamics  

SciTech Connect

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

309

Geometric phases in open tripod systems  

SciTech Connect

We first consider stimulated Raman adiabatic passages in a closed four-level tripod system. In this case, the adiabatic eigenstates of the system acquire real geometric phases. When the system is open and subject to decoherence they acquire complex geometric phases that we determine by a Monte Carlo wave function approach. We calculate the geometric phases and the state evolution in the closed as well as in the open system cases and describe the deviation between these in terms of the phases acquired. When the system is closed, the adiabatic evolution implements a Hadamard gate. The open system implements an imperfect gate and hence has a fidelity below unity. We express this fidelity in terms of the acquired geometric phases.

Moeller, Ditte; Madsen, Lars Bojer; Moelmer, Klaus [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, DK-8000 (Denmark)

2008-02-15

310

A Geometric Interpretation of the Selberg Integral  

NASA Astrophysics Data System (ADS)

A geometric interpretation of the reciprocity relation of the Selberg integral is given. Combinatorial topological properties of the point-configuration spaces are used. It has an application to the conformal field theory.

Yoshida, Masaaki

311

Geometrically Frustrated Magnets as Model Systems.  

National Technical Information Service (NTIS)

The specific aim of this research program has been to understand the cooperative magnetic properties of geometrically frustrated antiferromagnets which are model frustrated systems. We have performed extensive thermal studies of one such material, gadolin...

P. Schiffer

2001-01-01

312

Using Proportional Reasoning to Solve Geometric Problems  

ERIC Educational Resources Information Center

Students solve a geometric problem of measuring polygons with the help of proportional reasoning. Thus the importance of conceptual reasoning is emphasized as a highly efficient technique for teaching and strengthening mathematical content.

Pandiscio, Eric A

2004-01-01

313

Geometric magnetism in open quantum systems  

NASA Astrophysics Data System (ADS)

An isolated classical chaotic system, when driven by the slow change in several parameters, responds with two reaction forces: geometric friction and geometric magnetism. By using the theory of quantum fluctuation relations, we show that this holds true also for open quantum systems and provide explicit expressions for those forces in this case. This extends the concept of Berry curvature to the realm of open quantum systems. We illustrate our findings by calculating the geometric magnetism of a damped charged quantum harmonic oscillator transported along a path in physical space in the presence of a magnetic field and a thermal environment. We find that, in this case, the geometric magnetism is unaffected by the presence of the heat bath.

Campisi, Michele; Denisov, Sergey; Hänggi, Peter

2012-09-01

314

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

PubMed

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

2011-07-27

315

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

PubMed Central

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.

Chou, Chia-Ching; Buehler, Markus J.

2011-01-01

316

Sulfur K-edge XAS and DFT calculations on nitrile hydratase: geometric and electronic structure of the non-heme iron active site.  

PubMed

The geometric and electronic structure of the active site of the non-heme iron enzyme nitrile hydratase (NHase) is studied using sulfur K-edge XAS and DFT calculations. Using thiolate (RS(-))-, sulfenate (RSO(-))-, and sulfinate (RSO(2)(-))-ligated model complexes to provide benchmark spectral parameters, the results show that the S K-edge XAS is sensitive to the oxidation state of S-containing ligands and that the spectrum of the RSO(-) species changes upon protonation as the S-O bond is elongated (by approximately 0.1 A). These signature features are used to identify the three cysteine residues coordinated to the low-spin Fe(III) in the active site of NHase as CysS(-), CysSOH, and CysSO(2)(-) both in the NO-bound inactive form and in the photolyzed active form. These results are correlated to geometry-optimized DFT calculations. The pre-edge region of the X-ray absorption spectrum is sensitive to the Z(eff) of the Fe and reveals that the Fe in [FeNO](6) NHase species has a Z(eff) very similar to that of its photolyzed Fe(III) counterpart. DFT calculations reveal that this results from the strong pi back-bonding into the pi antibonding orbital of NO, which shifts significant charge from the formally t(2)(6) low-spin metal to the coordinated NO. PMID:16402841

Dey, Abhishek; Chow, Marina; Taniguchi, Kayoko; Lugo-Mas, Priscilla; Davin, Steven; Maeda, Mizuo; Kovacs, Julie A; Odaka, Masafumi; Hodgson, Keith O; Hedman, Britt; Solomon, Edward I

2006-01-18

317

The Geometric Grids of the Hieratic Numeral.  

NASA Astrophysics Data System (ADS)

The paper discusses the geometrical designs of the hieratic numeral signs. It shows the regular-grid-patterns of squares upon which, the shapes of the already decoded hieratic numeral-signs, have been designed. Also, it shows the design of some hieratic numeral signs, based on subdividing the circle; and the hieratic signs of modular notation. It might reveal the basic geometrical level of understanding of anonymous ancient Egyptians who designed them some four thousand years ago.

Aboulfotouh, Hossam M. K.

318

Newton's superb theorem: An elementary geometric proof  

NASA Astrophysics Data System (ADS)

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

Schmid, Christoph

2011-05-01

319

Synchronization waves in geometric networks.  

PubMed

We report synchronization of networked excitable nodes embedded in a metric space, where the connectivity properties are mostly determined by the distance between units. Such a high clustered structure, combined with the lack of long-range connections, prevents full synchronization and yields instead the emergence of synchronization waves. We show that this regime is optimal for information transmission through the system, as it enhances the options of reconstructing the topology from the dynamics. Measurements of topological and functional centralities reveal that the wave-synchronization state allows detection of the most structurally relevant nodes from a single observation of the dynamics, without any a priori information on the model equations ruling the evolution of the ensemble. PMID:22304141

Leyva, I; Navas, A; Sendiña-Nadal, I; Buldú, J M; Almendral, J A; Boccaletti, S

2011-12-06

320

The quest for self-consistency in hydrogen bond definitions  

NASA Astrophysics Data System (ADS)

In the last decades several hydrogen-bond definitions were proposed by classical computer simulations. Aiming at validating their self-consistency on a wide range of conditions, here we present a comparative study of six among the most common hydrogen-bond definitions for temperatures ranging from 220 K to 400 K and six classical water models. Our results show that, in the interval of temperatures investigated, a generally weak agreement among definitions is present. Moreover, cutoff choice for geometrically based definitions depends on both temperature and water model. As such, analysis of the same water model at different temperatures as well as different water models at the same temperature would require the development of specific cutoff values. Interestingly, large discrepancies were found between two hydrogen-bond definitions which were recently introduced to improve on more conventional methods. Our results reinforce the idea that a more universal way to characterize hydrogen bonds in classical molecular systems is needed.

Prada-Gracia, Diego; Shevchuk, Roman; Rao, Francesco

2013-08-01

321

The quest for self-consistency in hydrogen bond definitions.  

PubMed

In the last decades several hydrogen-bond definitions were proposed by classical computer simulations. Aiming at validating their self-consistency on a wide range of conditions, here we present a comparative study of six among the most common hydrogen-bond definitions for temperatures ranging from 220 K to 400 K and six classical water models. Our results show that, in the interval of temperatures investigated, a generally weak agreement among definitions is present. Moreover, cutoff choice for geometrically based definitions depends on both temperature and water model. As such, analysis of the same water model at different temperatures as well as different water models at the same temperature would require the development of specific cutoff values. Interestingly, large discrepancies were found between two hydrogen-bond definitions which were recently introduced to improve on more conventional methods. Our results reinforce the idea that a more universal way to characterize hydrogen bonds in classical molecular systems is needed. PMID:24007012

Prada-Gracia, Diego; Shevchuk, Roman; Rao, Francesco

2013-08-28

322

Geometric estimates of heritability in biological shape.  

PubMed

The recently developed geometric morphometrics methods represent an important contribution of statistics and geometry to the study of biological shapes. We propose simple protocols using shape distances that incorporate geometric techniques into linear quantitative genetic models that should provide insights into the contribution of genetics to shape variation in organisms. The geometric approaches use Procrustes distances in a curved shape space and distances in tangent spaces within and among families to estimate shape heritability. We illustrate the protocols with an example of wing shape variation in the honeybee, Apis mellifera. The heritability of overall shape variation was small, but some localized components depicting shape changes on distal wing regions showed medium to large heritabilities. The genetic variance-covariance matrix of the geometric shape variables was significantly correlated with the phenotypic shape variance-covariance matrix. A comparison of the results of geometric methods with the traditional multivariate analysis of interlandmark distances indicated that even with a larger dimensionality, the interlandmark distances were not as rich in shape information as the landmark coordinates. Quantitative genetics studies of shape should greatly benefit from the application of geometric methods. PMID:11989686

Monteiro, Leandro R; Diniz-Filho, José Alexandre F; dos Reis, Sérgio F; Araújo, Edilson D

2002-03-01

323

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

324

Halogen bonding: Recent advances  

Microsoft Academic Search

Halogen bonding (XB), as a directional interaction between covalently bound halogen atoms (XB donor) and Lewis bases (A, XB acceptor), has been recently intensively investigated as a powerful tool in crystal engineering. After a short review on the origin and general features of halogen bonding, current developments towards (i) the elaboration of three-dimensional networks, (ii) the interaction with anionic XB

Marc Fourmigué

2009-01-01

325

The Sibling Bond.  

ERIC Educational Resources Information Center

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

Bank, Stephen P.; Kahn, Michael D.

326

The dissociative bond.  

PubMed

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

327

Planning Successful Bond Campaigns.  

ERIC Educational Resources Information Center

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

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

328

Bond-quality characterization of silicon-glass anodic bonding  

Microsoft Academic Search

A simple testing method is presented that allows the comparison of the bond quality for anodically bonded wafers. An array of parallel metal lines of predetermined thickness is formed on a glass wafer. The estimation of the bond quality can be performed by visual inspection after the bonding. This method enables comparison of the anodic-bonding process performance for different glasses,

Svetlana Tatic-Lucic; John Ames; Bill Boardman; David McIntyre; Paul Jaramillo; Larry Starr; Myoungho Lim

1997-01-01

329

Powder neutron diffraction studies on CrOOH-type zero-dimensional H-bonded crystals  

Microsoft Academic Search

Exceptionally large geometric isotope effects ?R(O…O) on deuteration, in the range of two to three times the maximum value in the other hydrogen-bonded crystals, have earlier been reported for ?-CrOOH, ?-CrOOH and ?-CoOOH. In order to reinvestigate these apparently anomalous large geometric isotope effects, powder neutron diffraction studies have been done. For ?-CrOOH and ?-CrOOH(D), the earlier reported R(O…O) distances

Toshihiro Fujihara; Mizuhiko Ichikawa; Torbjörn Gustafsson; Ivar Olovsson; Takeshi Tsuchida

2001-01-01

330

Wood Bond Testing  

NASA Astrophysics Data System (ADS)

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

1989-01-01

331

Ferroelectricity and Isotope Effects in Hydrogen-Bonded KDP Crystals  

NASA Astrophysics Data System (ADS)

Based on an accurate first principles description of the energetics in H-bonded potassium-dihydrogen-phosphate crystals, we conduct a first study of nuclear quantum effects and of the changes brought about by deuteration. Tunneling is allowed only for clusters involving correlated protons and heavy ion displacements, the main effect of deuteration being a depletion of the proton probability density at the O-H-O bridge center, which in turn weakens its proton-mediated covalent bonding. The ensuing lattice expansion couples self-consistently with the proton off-centering, thus explaining both the giant isotope effect and its close connection with geometrical effects.

Koval, S.; Kohanoff, J.; Migoni, R. L.; Tosatti, E.

2002-10-01

332

A new decomposition strategy for parallel bonded molecular dynamics  

SciTech Connect

A method is described for parallelizing molecular dynamics (MD) simulations by block-decomposing the matrix of bonded and non-bonded force computations. It is particularly useful for organic simulations (polymers, proteins) because unlike spatial-decomposition methods, it requires no geometric information about the simulation domain. Because its communication cost scales as N/{radical}P. rather than N as in the all-to-all broadcast or ring-exchange techniques commonly used in this type of MD simulation, larger numbers of processors can be used effectively, yielding greater parallel speed-ups.

Plimpton, S.; Hendrickson, B.; Heffelfinger, G.

1992-12-31

333

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; Hélie, David; Vallée, Réal

2011-09-01

334

Dilemmas in zirconia bonding: A review.  

PubMed

This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability.The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today. PMID:23858816

Dbradovi?-Djurici?, Kosovka; Medi?, Vesna; Dodi?, Slobodan; Gavrilov, Dragan; Antonijevi?, Djordje; Zrili?, Milorad

335

Scattering of obliquely incident guided waves by a stiffener bonded to a plate  

NASA Astrophysics Data System (ADS)

Nondestructive testing of aerospace structures often requires their immobilization or disassembly. Structural health monitoring (SHM) can overcome these problems; the use of guided elastic waves (GW) in SHM is of great interest, because they propagate long distance in the structure thickness. Structures being stiffened, optimally positioning sensors implies to determine the number of stiffeners a wave can go through while remaining detectable. Here, the diffraction of GW by a stiffener bonded to a plate is considered. Elastic and geometric invariances along stiffener axis lead to 2D computations involving the three components of wave particle displacement, whatever its incidence on stiffener. A hybrid model is developed combining the semi-analytical finite element method for GW propagation and a finite element method (FE) for the stiffener diffraction. Optimal hybridization is obtained thanks to the development of transparent boundaries of the FE domain. Such boundaries have been obtained for GW normally incident onto a scattering feature, thanks to Fraser's bi-orthogonality relation, which unfortunately does not hold for oblique incidence. A numerical approach is developed to numerically approximate it, then, to derive boundary conditions in the wanted form. Their use minimizes the size of the FE domain and avoids any artificial reflection. They provide a mean for projecting diffracted fields on modes reflected on or transmitted through the stiffener; corresponding coefficients are obtained as functions of the direction of incidence.

Taupin, L.; Lhémery, A.; Baronian, V.; Bonnet-BenDhia, A.-S.

2012-03-01

336

Bonded lap joints of composite laminates with tapered edges  

Microsoft Academic Search

This study presents a semi-analytical solution method to analyze the geometrically nonlinear response of bonded composite lap joints with tapered and\\/or non tapered adherend edges under uniaxial tension. The solution method provides the transverse shear and normal stresses in the adhesives and in-plane stress resultants and bending moments in the adherends. The method utilizes the principle of virtual work in

E. Oterkus; A. Barut; E. Madenci; S SMELTZERIII; D. R. Ambur

2006-01-01

337

NONLINEAR ANALYSIS OF BONDED COMPOSITE SINGLE-LAP JOINTS  

Microsoft Academic Search

Nomenclature This study presents a semi-analytical solution method to analyze the geometrically nonlinear response of bonded composite single-lap joints with tapered adherend edges under uniaxial tension. The solution method provides the transverse shear and normal stresses in the adhesive and in-plane stress resultants and bending moments in the adherends. The method utilizes the principle of virtual work in conjunction with

E. Oterkus; A. Barut; E. Madenci; S. S. Smeltzer; D. R. Ambur

338

27 CFR 24.147 - Operations bond or unit bond.  

Code of Federal Regulations, 2013 CFR

...TREASURY ALCOHOL WINE Establishment and Operations Bonds and Consents of Surety § 24.147 Operations bond or unit bond. Notwithstanding the provisions of § 24.146, each person intending to commence or to continue business...

2013-04-01

339

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

SciTech Connect

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

Hansen, M.D.

1990-11-01

340

Geometrical structures and probable dissociation channels of CrPm+ (m=2, 4, 6, 8) clusters  

NASA Astrophysics Data System (ADS)

A density functional theory study on the geometrical structures and probable dissociation channels of CrPm+ (m=2, 4, 6, 8) clusters has been performed. Our results reveal that the tetrahedral P4 structure and linear P2 structure are two stable units in CrPm+ clusters relatively. The lowest energy structures of CrPm+ clusters are constructed by bonding Cr with P4 unit or P2 unit. The bond between Cr and P4 unit or P2 unit is much weaker than the bond between P atoms in P4 or P2 unit. The most probable dissociation channel for CrP8+ cluster is the detachment of P4 unit or P2 unit. Our conclusions are consistent with the previous laser photodissociation experiments.

Kuang, Xiangjun; Wang, Xinqiang; Liu, Gaobin

2010-08-01

341

The role of geometric and non-geometric information in preschoolers' selective attention  

Microsoft Academic Search

This study was designed to examine preschoolers' reliance on geometric and non-geometric information for selective attention. Ninety early preschoolers and 90 late preschoolers were asked to remember the location of 1 of 2 sets of toys placed within a square box. One set was designated as relevant or important to remember and the other as irrelevant. Relevant items were placed

Meira Torenberg

2005-01-01

342

Geometrically deformed models: a method for extracting closed geometric models form volume data  

Microsoft Academic Search

We propose a new approach to the problem of generating a simple topologically-closed geometric model from a point-sampled volume data set. We call such a model a Geometrically Deformed Model or GDM. A GDM is created by placing a 'seed' model in the volume data set. The model is then deformed by a relaxation process that minimizes a set of

James V. Miller; David E. Breen; William E. Lorensen; Robert M. O'Bara; Michael J. Wozny

1991-01-01

343

Control Chart Tests Based on Geometric Moving Averages  

Microsoft Academic Search

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

S. W. Roberts

1959-01-01

344

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

Code of Federal Regulations, 2013 CFR

...long as a particular bond meets the requirements...this part as to the persons required to be bonded...c) Use of separate bonds. The choice of whether persons required to be bonded...separately or under the same bond, whether given...

2013-07-01

345

Structure and bonding in [M(6)O(19)](n-) isopolyanions.  

PubMed

The structure and bonding in [M(6)O(19)](n-) isopolyanions of Nb, Ta, Mo, and W have been investigated using density-functional methods. The computational-experimental agreement is good for the geometrical parameters of Mo and W species but less satisfactory for Nb and Ta clusters. The electronic structure of the anions has been probed with molecular-orbital, Mulliken-Mayer, and bonding-energy approaches. The results have indicated that M-O interactions are largely M d-O p in character and that sigma and pi bonds link the metal centers to terminal and bridging (O(b)) oxygen atoms. Some M-O(b) bonds exhibit a [M(4)O(4)] closed-loop structure, but this orbital-interaction mode has not been found to make a particularly outstanding contribution to the bonding stability of the molecules. Mayer indexes correspond to (fractional) multiple, approximately single, and low-order character for terminal, bridging, and internal bonds, respectively, and the valency analysis has yielded similar bonding capacities for the different oxygen atoms. A distribution of the negative charge over all types of oxygen sites and metal charges considerably smaller than the formal oxidation states have been obtained from the Mulliken analysis. Minimal structural changes have been detected on reduction of molybdates and tungstates, in accord with the general properties of the orbitals occupied by the added electrons. PMID:11925167

Bridgeman, Adam J; Cavigliasso, Germán

2002-04-01

346

Geometric inequalities for axially symmetric black holes  

NASA Astrophysics Data System (ADS)

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

Dain, Sergio

2012-04-01

347

Bonding aerogels with polyurethanes  

SciTech Connect

Aerogels, porous silica glasses with ultra-fine cell size (30nm), are made by a solution gelation (sol-gel) process. The resulting gel is critical point dried to densities from 0.15--0.60 g/cc. This material is machinable, homogeneous, transparent, coatable and bondable. To bond aerogel an adhesive should have long cure time, no attack on the aerogel structure, and high strength. Several epoxies and urethanes were examined to determine if they satisfied these conditions. Bond strengths above 13 psi were found with double bubble and DP-110 epoxies and XI-208/ODA-1000 and Castall U-2630 urethanes. Hardman Kalex Tough Stuff'' A-85 hardness urethane gave 18 psi bond strength. Hardman A-85, Tuff-Stuff'' was selected for further evaluation because it produced bond strengths comparable to the adherend cohesive strength. 5 refs., 2 figs.

Matthews, F.M.; Hoffman, D.M.

1989-11-01

348

Adhesive for composite bonding.  

National Technical Information Service (NTIS)

Adhesive bonding is a viable option for structural joining of carbon fiber reinforced epoxy composites. Recent examples from laboratory programs include a composite tube joined to a flared composite collar (skirt) to provide a means for mechanical attachm...

R. E. Lyon C. M. Walkup J. T. Matthews.

1989-01-01

349

Bonding Silicones with Epoxies.  

National Technical Information Service (NTIS)

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 sur...

J. S. Tira

1980-01-01

350

Structure and chemical bond characteristics of LaB6  

NASA Astrophysics Data System (ADS)

The structure and chemical bond characteristics of LaB6 have been achieved by means of the density functional theory using the state-of-the-art full-potential linearized augmented plane wave (FPLAPW) method, which are implemented within the EXCITING code. The results show our optimized lattice constant a (4.158 Å), parameter z (0.1981) and bulk modulus B (170.4 GPa) are in good agreement with the corresponding experimental data. Electron localization function (ELF) shows the La-La bond mainly is ionic bond, La-B bond is between ionic and covalent bond while the covalent bond between the nearest neighbor B atoms (B2 and B3) is a little stronger than that between the nearer neighbor B atoms (B1 and B4).

Bai, Lina; Ma, Ning; Liu, Fengli

2009-11-01

351

Field-assisted bonding of single crystal quartz  

SciTech Connect

A technique to produce strong, hermetic bonds between plates of single crystal quartz using a modified field-assisted bonding process is presented. Field-assisted bonding is a technique traditionally used to join glass to metals at temperatures well below normal glass softening temperatures. To promote reactivity between quartz within an electrical field at temperatures well below quartz transformation temperatures, thin films of silicon metal and glass were vapor deposited onto adjacent quartz plates. Thermal stresses caused by expansion mismatch between the quartz and the films were of concern. These stresses were reduced by determining the minimum film thicknesses capable of yielding sufficient reactivity for bonding. Processing studies were conducted to optimize bond integrity, and bonds were characterized by hermeticity, thermal shock, and mechanical shock. Packages produced under the most ideal conditions were able to survive greater than 1000 psi shock loads. 11 refs., 10 figs., 3 tabs.

Watkins, R.D.; Tuthill, C.D.; Curlee, R.M.; Koehler, D.R.; Joerg, C.F.

1989-01-01

352

Bonded wafer substrates for integrated detector arrays  

SciTech Connect

Bonded wafer substrates have been made which are optimized for integrating high energy particle detector arrays with their readout electronics. The detectors are processed in the handle wafer, which is a 300 [mu]m thick, high resistivity, <111> crystal orientation silicon wafer. This wafer is bonded to a primary wafer using a low temperature process that does not affect the detector material. The support electronics are processed in the remnant of the primary wafer, which is a submicron thick <100> crystal orientation silicon film formed by a bond-and-etchback procedure. These two device materials are isolated from each other by a radiation hardened dielectric film. The integrated process is based on a low temperature, radiation hardened VLSI CMOS process which is also shown not to seriously affect the detector material.

Wang, J.J.; King, E.E.; Leonov, P.; Huang, D.H. (Advanced Research and Applications Corp., Sunnyvale, CA (United States)); Thompson, P.; Godbey, D. (Naval Research Lab., Washington, DC (United States))

1993-10-01

353

Halogen bonding: the ?-hole  

Microsoft Academic Search

Halogen bonding refers to the non-covalent interactions of halogen atoms X in some molecules, RX, with negative sites on others.\\u000a It can be explained by the presence of a region of positive electrostatic potential, the ?-hole, on the outermost portion\\u000a of the halogen’s surface, centered on the R–X axis. We have carried out a natural bond order B3LYP analysis of

Timothy Clark; Matthias Hennemann; Jane S. Murray; Peter Politzer

2007-01-01

354

The geometric phase in quantum physics  

SciTech Connect

After an explanatory introduction, a quantum system in a classical time-dependent environment is discussed; an example is a magnetic moment in a classical magnetic field. At first, the general abelian case is discussed in the adiabatic approximation. Then the geometric phase for nonadiabatic change of the environment (Anandan--Aharonov phase) is introduced, and after that general cyclic (nonadiabatic) evolution is discussed. The mathematics of fiber bundles is introduced, and some of its results are used to describe the relation between the adiabatic Berry phase and the geometric phase for general cyclic evolution of a pure state. The discussion is restricted to the abelian, U(1) phase.

Bohm, A.

1993-03-01

355

Photometric and geometric rectification for stereoscopic images  

NASA Astrophysics Data System (ADS)

Stereoscopic images are captured by two cameras at different positions. In general, the two images often have geometric distortions including vertical misalignment, rotation and keystone as well as photometric distortions such as luminance or color differences. Even in case of a carefully designed parallel stereo camera configuration, the captured images pairs may have the distortions that cause uncomfortable 3D experiences to users. In this paper, we develop an algorithm to correct the captured image pairs to give a comfortable stereoscopic experience to users. The algorithm provides a practical method for compensating the photometric and geometrical distortions.

Han, Seung-Ryong; Min, Jongsul; Park, Taesung; Kim, Yongje

2012-02-01

356

Combining geometrical and dynamical disorder to enhance transport.  

PubMed

We look for the optimal way to distribute rectifiers in order to maximize their effect on the transport properties of Brownian particles. These rectifiers are introduced in the form of flashing asymmetric potentials distributed on a one dimensional lattice. We study the effects that different distributions of these rectifiers have on the generated current and on the energy cost of transport. Based on both analytical and numerical results, we observe an unexpected increase in the efficiency of the rectifiers and the magnitude of the current for the case in which geometrical and dynamical disorder are combined. We show that this effect is a direct consequence of the "hitchhiker" or "waiting time" paradox. PMID:15447551

Martinez, Hernan L; Parrondo, Juan M R

2004-08-25

357

Large mode area photonic crystal fibers with high geometrical birefringence  

NASA Astrophysics Data System (ADS)

We present the results of numerical analysis showing that high geometrical birefringence can be obtained in large mode area photonic crystal fibers. Simulations were carried out using Finite Element Method with Perfectly Matched Layer boundary conditions. To induce possibly high phase modal birefringence, we introduced a few small holes into the central region of the core, which breaks its hexagonal symmetry. Such modification of the fiber geometry is additionally responsible for increasing the effective area of the guided mode. For the optimized fiber design with a pitch distance ? = 8.8 ?m, the phase birefringence reaches B = 1.0×10-4 at wavelength ? = 1.3 ?m and B = 1.5×10-4 at ? = 1.5 ?m. In addition to high modal birefringence, an important advantage of the proposed fiber design is a single mode operation for wavelength greater than 1.3 ?m.

Golojuch, Grzegorz; Urba?czyk, Waclaw

2008-12-01

358

Geometrical optics approximation of light scattered by large spheroidal bubble  

NASA Astrophysics Data System (ADS)

The light scattering properties of bubbles are very important for exploration underwater. The shape of bubbles usually treated as spheres, are apparently nonspherical in turbulent flow. The present methods for calculating light scattered by nonspherical particles are lack of efficient computation due to the large size of bubble, where geometrical optics approximation is considered a better method for calculating light scattering patterns. In this paper, the large spheroidal bubble with end-on incidence in water are researched based on ray tracing method. The angular distribution of light scattered by prolate and oblate spheroidal bubbles are interpreted that both shapes of bubbles have strong forward and low backward scattering with rapid ripple structure. The types of ray paths permeating the bubble are calculated to explain the physical mechanisms that cause various prominent intensity features. The results could provide the theoretical foundation for optimizing the turbulent bubbly flow measurements.

He, Huiling; Yang, Kecheng; Li, Wei; Xia, Min; Li, Qing; Zhang, Xiaohui

2011-11-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

360

Bonded Interactions and the Crystal Chemistry of Minerals: A Review  

SciTech Connect

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

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

2008-02-26

361

Relational Bonds and Loyalty: The Bonds that Tie  

Microsoft Academic Search

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

Ahmad Shammout; Michael Polonsky; Michael Edwardson

362

Glycosidic bond cleavage in deoxynucleotides: effects of solvent and the DNA phosphate backbone in the computational model.  

PubMed

Density functional theory (B3LYP) was employed to examine the hydrolysis of the canonical 2'-deoxynucleotides in varied environments (gas phase or water) using different computational models for the sugar residue (methyl or phosphate group at C5') and nucleophile (water activated through full or partial proton abstraction). Regardless of the degree of nucleophile activation, our results show that key geometrical parameters along the reaction pathway are notably altered upon direct inclusion of solvent effects in the optimization routine, which leads to significant changes in the reaction energetics and better agreement with experiment. Therefore, despite the wide use of gas-phase calculations in the literature, small model computational work, as well as large-scale enzyme models, that strive to understand nucleotide deglycosylation must adequately describe the environment. Alternatively, although inclusion of the phosphate group at C5' also affects the geometries of important stationary points, the effects cancel to yield unchanged deglycosylation barriers, and therefore smaller computational models can be used to estimate the energy associated with nucleotide deglycosylation, with the 5' phosphate group included if full (geometric) details of the reaction are desired. Hydrogen-bonding interactions with the nucleobase can significantly reduce the barrier to deglycosylation, which supports suggestions that discrete hydrogen-bonding interactions with active-site amino acid residues can play a significant role in enzyme-catalyzed nucleobase excision. Taken together with previous studies, the present work provides vital clues about the components that must be included in future studies of the deglycosylation of isolated noncanonical nucleotides, as well as the corresponding enzyme-catalyzed reactions. PMID:23167947

Lenz, Stefan A P; Kellie, Jennifer L; Wetmore, Stacey D

2012-11-30

363

Geometric phase effects in the coherent control of the branching ratio of photodissociation products of phenol  

NASA Astrophysics Data System (ADS)

Optimal control simulation is used to examine the control mechanisms in the photodissociation of phenol within a two-dimensional, three-electronic-state model with two conical intersections. This model has two channels for H-atom elimination, which correspond to the 2? and 2? states of the phenoxyl radical. The optimal pulse that enhances 2? dissociation initially generates a wave packet on the S1 potential-energy surface of phenol. This wave packet is bifurcated at the S2-S1 conical intersection into two components with opposite phases because of the geometric phase effect. The destructive interference caused by the geometric phase effect reduces the population around the S1-S0 conical intersection, which in turn suppresses nonadiabatic transitions and thus enhances dissociation to the 2? limit. The optimal pulse that enhances S0 dissociation, on the other hand, creates a wave packet on the S2 potential-energy surface of phenol via an intensity borrowing mechanism, thus avoiding geometric phase effects at the S2-S1 conical intersection. This wave packet hits the S1-S0 conical intersection directly, resulting in preferred dissociation to the 2? limit. The optimal pulse that initially prepares the wave packet on the S1 potential-energy surface (PES) has a higher carrier frequency than the pulse that prepares the wave packet on the S2 PES. This counterintuitive effect is explained by the energy-level structure and the S2-S1 vibronic coupling mechanism.

Abe, Mayumi; Ohtsuki, Yukiyoshi; Fujimura, Yuichi; Lan, Zhenggang; Domcke, Wolfgang

2006-06-01

364

Entanglement capacity of nonlocal Hamiltonians: A geometric approach  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

365

Geometric Models for Collaborative Search and Filtering  

ERIC Educational Resources Information Center

|This dissertation explores the use of geometric and graphical models for a variety of information search and filtering applications. These models serve to provide an intuitive understanding of the problem domains and as well as computational efficiencies to our solution approaches. We begin by considering a search and rescue scenario where…

Bitton, Ephrat

2011-01-01

366

Can EPR non-locality be geometrical.  

National Technical Information Service (NTIS)

The presence in Quantum Mechanics of non-local correlations is one of the two fundamentally non-intuitive features of that theory. The non-local correlations themselves fall into two classes: EPR and Geometrical. The non-local characteristics of the geome...

Y. Ne'eman A. Botero

1995-01-01

367

Managing geometric complexity with enhanced procedural models  

Microsoft Academic Search

We illustrate two enhancements to procedural geometric models which allow autonomous procedures to jointly satisfy mutual constraints. One of the techniques adds communications paths between procedures which may affect one another. Conflicts are resolved by modifying communicating procedures as they execute.The second technique is a generalization of widely used subdivision procedures. The termination test of typical subdivision methods is replaced

Philip Amburn; Eric Grant; Turner Whitted

1986-01-01

368

Matrix models, geometric engineering and elliptic genera  

Microsoft Academic Search

We compute the prepotential of Script N = 2 supersymmetric gauge theories in four dimensions obtained by toroidal compactifications of gauge theories from 6 dimensions, as a function of Kähler and complex moduli of T2. We use three different methods to obtain this: matrix models, geometric engineering and instanton calculus. Matrix model approach involves summing up planar diagrams of an

Timothy J. Hollowood; Amer Iqbal; Cumrun Vafa

2008-01-01

369

Geometrical tile design for complex neighborhoods.  

PubMed

Recent research has showed that tile systems are one of the most suitable theoretical frameworks for the spatial study and modeling of self-assembly processes, such as the formation of DNA and protein oligomeric structures. A Wang tile is a unit square, with glues on its edges, attaching to other tiles and forming larger and larger structures. Although quite intuitive, the idea of glues placed on the edges of a tile is not always natural for simulating the interactions occurring in some real systems. For example, when considering protein self-assembly, the shape of a protein is the main determinant of its functions and its interactions with other proteins. Our goal is to use geometric tiles, i.e., square tiles with geometrical protrusions on their edges, for simulating tiled paths (zippers) with complex neighborhoods, by ribbons of geometric tiles with simple, local neighborhoods. This paper is a step toward solving the general case of an arbitrary neighborhood, by proposing geometric tile designs that solve the case of a "tall" von Neumann neighborhood, the case of the f-shaped neighborhood, and the case of a 3 x 5 "filled" rectangular neighborhood. The techniques can be combined and generalized to solve the problem in the case of any neighborhood, centered at the tile of reference, and included in a 3 x (2k + 1) rectangle. PMID:19956398

Czeizler, Eugen; Kari, Lila

2009-11-23

370

Congruence, Similarity, and Symmetries of Geometric Objects  

Microsoft Academic Search

We consider the problem of computing geometric transformations (rotation, translation, reflexion) that map a point setA exactly or approximately into a point setB. We derive efficient algorithms for various cases (Euclidean or maximum metric, translation or rotation, or general congruence).

Helmut Alt; Kurt Mehlhorn; Hubert Wagener; Emo Welzl

1988-01-01

371

Semiclassical Wigner Function and Geometrical Optics  

Microsoft Academic Search

We consider the problem of high-frequency asymptotics for the time-dependent one- dimensional Schrodinger equation with rapidly oscillating initial data. This problem is commonly studied via the WKB method. An alternative method is based on the limit Wigner measure. This approach recovers geometrical optics, but, like the WKB method, it fails at caustics. To remedy this deficiency we employ the semiclassical

Stathis Filippas; George N. Makrakis

2003-01-01

372

D.c. geometrical null arrays  

Microsoft Academic Search

The term geoelectric null array is used for D.C. electrode configurations where the measured or the interpreted potential difference is zero above a homogeneous halfspace. For D.C. geometrical null arrays this is achievable by convenient positioning of current and potential electrodes. Szalai et al. (2002) applied those geoelectric null arrays, which can be easily constructed from traditional arrays. The pairs

S. Szalai; L. Szarka; G. Marquis; P. Sailhac

2003-01-01

373

Geometric Interpretation of the Pauli Spinor.  

ERIC Educational Resources Information Center

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

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

1981-01-01

374

Discrete Surface Modeling using Geometric Flows  

Microsoft Academic Search

We use various nonlinear geometric partial dieren tial equations to ecien tly solve several surface modelling problems, including surface blending, N-sided hole lling and free-form surface tting. The nonlinear equations used include two second order o ws (mean curvature o w and average mean curvature o w), one fourth order o w (surface diusion o w) and a sixth order

Guoliang Xu; Qing Pan; Chandrajit L. Bajaj

2003-01-01

375

Geometric dispersion of unattached particles in foams  

Microsoft Academic Search

A sound understanding of the phenomena affecting the flow of unattached particles through the Plateau border network of a foam is essential for the accurate modelling of industrial flotation processes. One such phenomenon is the dispersion of liquid and particles perpendicular to the overall direction of flow, known as geometric dispersion. This dispersion is due to the interconnected nature of

J. R. Meloy; S. J. Neethling; J. J. Cilliers

2007-01-01

376

Dynamic Response of Geometrically Constrained Vapor Bubbles  

Microsoft Academic Search

Geometrically constrained vapor bubbles are important in many microelectromechanical systems (MEMS), such as actuators and micro-pumps. We consider a two-dimensional model of a vapor bubble between two horizontal parallel boundaries held at different temperatures. When the temperatures are constant, a steady state can be achieved such that evaporation near the contact lines at the hot bottom plate is balanced by

Vladimir S. Ajaev; G. M. Homsy

2001-01-01

377

More Meaning from the Geometric Mean.  

ERIC Educational Resources Information Center

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

Dorner, Bryan C.

2003-01-01

378

Geometric Mean--What Does It Mean?  

ERIC Educational Resources Information Center

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

Kalder, Robin S.

2012-01-01

379

Geometric approach to dislocation and disclination theory  

SciTech Connect

Cartan structure equations are used to create a four-dimensional geometric description of dislocations in continuum theory. It is shown that the dislocation distribution is determined by the torsion tensor, while the disclination distribution is determined by the curvature tensor. An analogy to electrodynamics is offered.

Nesterov, A.I.; Ovchinnikov, S.G.

1988-05-01

380

Geometric Transformations in Middle School Mathematics Textbooks  

ERIC Educational Resources Information Center

|This study analyzed treatment of geometric transformations in presently available middle grades (6, 7, 8) student mathematics textbooks. Fourteen textbooks from four widely used textbook series were evaluated: two mainline publisher series, Pearson (Prentice Hall) and Glencoe (Math Connects); one National Science Foundation (NSF) funded…

Zorin, Barbara

2011-01-01

381

On the Encoding of Arbitrary Geometric Configurations  

Microsoft Academic Search

A method is described which permits the encoding of arbitrary geometric configurations so as to facilitate their analysis and manipulation by means of a digital computer. It is shown that one can determine through the use of relatively simple numerical techniques whether a given arbitrary plane curve is open or closed, whether it is singly or multiply connected, and what

Herbert Freeman

1961-01-01

382

Geometric framework for fingerprint image classification  

Microsoft Academic Search

Given a digitized fingerprint image, we would like to classify it into one of several types already established in the literature. In this paper, we consider five types for classification: double loop, whorl, left loop, right loop, and arch. We illustrate the use of a geometric framework for a systematic top-down classification of the foregoing types. From the double-loop type

Michael M. S. Chong; Tan Han Ngee; Jun Liu; Robert K. L. Gay

1997-01-01

383

Which linear codes are algebraic-geometric?  

Microsoft Academic Search

An infinite series of curves is constructed in order to show that all linear codes can be obtained from curves using Goppa's construction. If one imposes conditions on the degree of the divisor used, then we derive criteria for linear codes to be algebraic-geometric. In particular, we investigate the family of q-ary Hamming codes, and prove that only those with

Ruud Pellikaan; Ba-zhong Shen; Gerhard J. M. Van Wee

1991-01-01

384

The geometrization of hydromagnetic fluid flows  

NASA Astrophysics Data System (ADS)

In this paper certain theorems of theoretical interest have been established with the help of the geometrical properties of Maxwellian surface (which is spanned by the flow and field lines). These theorems shed light on the behaviour of steady incompressible hydromagnetic flows. The complex-lamellar acceleration and simple geodesic motion admitted by such flows have also been studied.

Singh, S. N.; Choubey, K. R.; Singh, B. P.

1986-07-01

385

Geometric Mean--What Does It Mean?  

ERIC Educational Resources Information Center

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

Kalder, Robin S.

2012-01-01

386

A Characterization of Convoluted Geometric Distributions.  

National Technical Information Service (NTIS)

Let X be a nonnegative integer-valued random variable whose distribution is that of the sum of geometric variable Y with parameter theta and a nonnegative integer-valued random variable Z independent of Y whose distribution does not depend on theta. The c...

F. J. Samaniego

1977-01-01

387

Robot arm geometric link parameter estimation  

Microsoft Academic Search

A general method for estimating serial link manipulator geometric parameter errors is proposed in this paper. The positioning accuracy of the end-effector may be increased significantly by updating the nominal link parameters in the control software to represent the physical system more accurately. The proposed method is applicable for serial link manipulators with any combination of revolute or prismatic joints,

Samad A. Hayati

1983-01-01

388

RAGS: region-aided geometric snake  

Microsoft Academic Search

Abstract - An enhanced, region - aided, geometric active contour an Eulerian formulation that is more tolerant toward weak edges and noise in images is the theory of curve evolution in time according to intrinsic geo introduced The proposed method integrates gradient flow forces metric measures of the image and are numerically implemented with region constraints, composed of image region

Xianghua Xie; Majid Mirmehdi

2004-01-01

389

Modern Geometric Algebra: A (Very Incomplete!) Survey  

ERIC Educational Resources Information Center

|Geometric algebra is based on two simple ideas. First, the area of a rectangle is equal to the product of the lengths of its sides. Second, if a figure is broken apart into several pieces, the sum of the areas of the pieces equals the area of the original figure. Remarkably, these two ideas provide an elegant way to introduce, connect, and…

Suzuki, Jeff

2009-01-01

390

On Felix Klein's Geometric Model of Electromagnetism  

Microsoft Academic Search

In 1917 F. Klein proposed his work on projective geometry to A. Einstein for further developments of general relativity. Klein had a peculiar way to consider the relationship between mathematics and physics, based on his Erlanger Programm and geometrical modeling of physical phenomena. He was aiming at a physical foundation for non Euclidean geometry. However, the letters he wrote to

S. L. Vesely; A. A. Vesely

2006-01-01

391

Geometrical model of a waveguide transient  

Microsoft Academic Search

A nonstationary electromagnetic wave propagating down rectangular waveguide is represented as the superposition of a direct wave (in the case where cylindrical waves are excited) and its reflections from the guide side walls. This approach allows a geometric model of wave propagation and accounts for the properties of functions describing the transient in regular waveguide on the basis of physical

M. I. Efimchik; B. N. Levitas

1976-01-01

392

Clifford geometric parameterization of inequivalent vacua  

Microsoft Academic Search

We propose a geometric method to parameterize inequivalent vacua by dynamical data. Introducing quantum Clifford algebras with arbitrary bilinear forms we distinguish isomorphic algebras --as Clifford algebras-- by different filtrations resp. induced gradings. The idea of a vacuum is introduced as the unique algebraic projection on the base field embedded in the Clifford algebra, which is however equivalent to the

Bertfried Fauser

2001-01-01

393

Van Hiele Levels of Geometric Thought Revisited.  

ERIC Educational Resources Information Center

|Compared are the van Hiele levels of geometric thinking and the geometry curriculum recommended by the National Council of Teachers of Mathematics Curriculum and Evaluation Standards for School Mathematics. Activities which illustrate the various levels are provided by grade level with procedures. (CW)|

Teppo, Anne

1991-01-01

394

Dynamic analysis of geometrically nonlinear robot manipulators  

Microsoft Academic Search

In this paper, a method for the dynamic analysis of geometrically nonlinear elastic robot manipulators is presented. Robot arm elasticity is introduced using a finite element method which allows for the gross arm rotations. A shape function which accounts for the combined effects of rotary inertia and shear deformation is employed to describe the arm deformation relative to a selected

E. M. Bakp

1996-01-01

395

A Geometric Approach to Fair Division  

ERIC Educational Resources Information Center

|We wish to divide a cake among some collection of people (who may have very different notions of the comparative value of pieces of cake) in a way that is both "fair" and "efficient." We explore the meaning of these terms, introduce two geometric tools to aid our analysis, and present a proof (due to Dietrich Weller) that establishes the…

Barbanel, Julius

2010-01-01

396

Physical instability and geometric effects in frames  

Microsoft Academic Search

The interaction between physical instability and geometric (2nd-order) effects in plane frames is investigated herein within a finite element based mathematical programming framework, under the assumptions of quasistatic loading and lumped plasticity. The sources of physical instability consist of inelastic bending hinges characterized by softening nonholonomic (irreversible) moment versus rotation constitutive laws. The complex and insightful response spectrum which can

Gabriella Bolzon; Francis Tin-Loi

1999-01-01

397

Geometrical and Graphical Representations of Lissajous Figures  

Microsoft Academic Search

The fact that a sine curve, wrapped on the surface of a circular cylinder and projected orthogonally on a plane, will in certain cases produce Lissajous figures is used to develop a simple geometrical model which will demonstrate these curves. It is pointed out that natural generalizations of Lissajous figures can be obtained through this model. The use of sine-sine

Edward F. Fahy; Frank G. Karioris

1952-01-01

398

Geometric Partial Differential Equations and Image Analysis  

Microsoft Academic Search

This book provides an introduction to the use of geometric partial differential equations in image processing and computer vision. It brings a number of new concepts into the field, providing a very fundamental and formal approach to image processing. State-of-the-art practical results in a large number of real problems are achieved with the techniques described. Applications covered include image segmentation,

Guillermo Sapiro

2001-01-01

399

Geometrical Brownian Motion Driven by Color Noise  

NASA Astrophysics Data System (ADS)

The geometrical Brownian motion driven by Gaussian or dichotomous color noise is considered. The ordinary Malthusian evolution is observed for long times, however the initial values seem lowered and additionally, in the case of dichotomous noise, the rate of growth is decreased. In the latter case the possibility of arbitrage is shown explicitly.

Zygadlo, R.

2008-05-01

400

Geometrical approach to scattering in one dimension  

Microsoft Academic Search

The transfer matrix technique is much used to study one-dimensional scattering, such as electrons in semiconductor superlattices. We elaborate on the geometrical interpretation of the transfer matrix, in particular its relation to conformal mapping in the unit disc, and the analogy to Lorentz transformations on a Dirac spinor in 2 + 1 dimensions.

D. W. L. Sprung; G. V. Morozov; J. Martorell

2004-01-01

401

Geometrical setting for the classification of multilayers  

Microsoft Academic Search

We elaborate on the consequences of the factorization of the transfer matrix of any lossless multilayer in terms of three basic matrices of simple interpretation. By considering the bilinear transformation that this transfer matrix induces in the complex plane, we introduce the concept of multilayer transfer function and study its properties in the unit disk. In this geometrical setting, our

Juan J. Monzón; Teresa Yonte; Luis L. Sánchez-Soto

2002-01-01

402

Cumulative Arrays and Geometric Secret Sharing Schemes  

Microsoft Academic Search

Cumulative secret sharing schemes were introduced by Simmons et al (1991) based on the generalised secret sharing scheme of Ito et al (1987). A given monotone access structure together with a security level is associated with a unique cumulative scheme. Geometric secret sharing schemes form a wide class of secret sharing schemes which have many desirable properties including good information

Wen-ai Jackson; Keith M. Martin

1992-01-01

403

Framelet analysis of some geometrical illusions  

Microsoft Academic Search

In this paper we study a spiral illusion generated by fractal islands. Furthermore, by a neuro-scientific consideration we\\u000a present a new class of geometrical illusions. In order to analyse these illusions, we propose a new mathematical method.

Hitoshi Arai; Shinobu Arai

2010-01-01

404

Meshless analysis of geometrically nonlinear beams  

Microsoft Academic Search

The meshless method is applied to the response analysis of a geometrically nonlinear beam. The corresponding nonlinear strain operator matrix and tangent rigidity matrix are given. The computational results agree well with Holden's analytic solution. It is found that the meshless method is more efficient for large displacement.

J. M. Xia; D. M. Wei; R. H. Jin

2008-01-01

405

Meshless analysis of geometrically nonlinear beams  

NASA Astrophysics Data System (ADS)

The meshless method is applied to the response analysis of a geometrically nonlinear beam. The corresponding nonlinear strain operator matrix and tangent rigidity matrix are given. The computational results agree well with Holden's analytic solution. It is found that the meshless method is more efficient for large displacement.

Xia, J. M.; Wei, D. M.; Jin, R. H.

2008-02-01

406

Geometrical Methods for Equations of Hydrodynamical Type  

NASA Astrophysics Data System (ADS)

We describe some recent results for a class of nonlinear hydrodynamical approximation models where the geometric approach gives insight into a variety of aspects. The main contribution concerns analytical results for Euler equations on the diffeomorphism group of the circle for which the inertia operator is a nonlocal operator.

Escher, Joachim; Kolev, Boris

2012-10-01

407

Geometrizing the Quantum-A Toy Model  

NASA Astrophysics Data System (ADS)

It is shown that the equations of relativistic Bohmian mechanics for multiple bosonic particles have a dual description in terms of a classical theory of conformally ``curved'' space-time. This shows that it is possible to formulate quantum mechanics as a purely classical geometrical theory. The results are further generalized to interactions with an external electromagnetic field.

Koch, Benjamin

2009-12-01

408

Maintaining geometric dependencies in an assembly planner  

Microsoft Academic Search

The problem of generating assembly sequences strictly from the geometry of a goal assembly is addressed. The planner considers 2-D, polygonal parts and makes the usual assumptions about the monotony of partial assemblies, which allows an `and\\/or' graph representation to be used. The problem of decreasing the number of geometric checks which must be done to test candidate assembly operations

Randall H. Wilson; Jean-Fransois Rit

1990-01-01

409

Newton's superb theorem: An elementary geometric proof  

Microsoft Academic Search

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

Christoph Schmid

2011-01-01

410

Investigating geometric uncertainties in prostate cancer radiotherapy  

NASA Astrophysics Data System (ADS)

Geometric errors in prostate cancer radiotherapy can affect patient outcome. Target delineation error, patient positioning error and internal target motion are three major sources contributing to the overall geometric uncertainty. In this thesis the quality of prostate target delineation, the global geometric error (vector sum of systematic error, organ motion, positioning error and collimator calibration error) and the intra-fraction organ motion during radiation delivery are studied. The effect of internal target motion and patient setup error on the tumour control probability and the normal tissue complication probability are calculated. Anatomical images from the Visible Human Project were examined by an expert group who then segmented a gold standard volume for the subject prostate. On the corresponding CT images, six radiation oncologists were asked to each delineate the entire prostate organ twenty times, producing a total of 120 organ delineations. It was found that the physician delineated prostate volume is in general 30% larger than the "true" prostate volume, but this overestimate of volume only included 84% of the true prostate volume. It was also observed that there was a systematic error in the observer segmentations, such that none of the 120 segmentations ever included all of the posterior portion of the prostate, but all of the delineations extended past the anterior surface of the prostate. Global geometric error and intra-fraction prostate organ motion were measured using data from 1028 portal images acquired over 257 fractions delivered to a total of 21 patients. In each patient, fudcial markers implanted into the prostate prior to treatment surrogated the position of the prostate. The overall geometric uncertainty was found to have a standard deviation of 5.3 mm for all observed directions. If both target delineation and target deformation uncertainties are included, the overall geometric uncertainty would be 6.3 mm. The intra-fraction organ motion was found to have a standard deviation of 1 mm. The effect of these geometric uncertainties on tumour control probability is simulated for the combinations of two treatment margins and three treatment techniques.

Gao, Zhanrong

411

The fluoroform?ethylene oxide complex exhibits a C–H?O anti-hydrogen bond  

Microsoft Academic Search

A new, recently discovered type of intermolecular bond, called an anti-hydrogen bond, is found in the fluoroform?ethylene oxide complex. The complex structure and properties were predicted on the basis of counterpoise-corrected gradient optimization performed at a correlated ab initio level. Formation of the C–H?O anti-hydrogen bond is manifested by an 0.1 pm contraction of the C–H bond and a significant

Pavel Hobza; Zden?k Havlas

1999-01-01

412

High density Cu-Cu interconnect bonding for 3-D integration  

Microsoft Academic Search

The demand for more complex and multifunctional microsystems with enhanced performance characteristics is driving the electronics industry toward the use of best-of- breed materials and device technologies. Three-dimensional (3-D) integration enables building such high performance microsystems through bonding and interconnection of individually optimized device layers. Bonding of device layers can be achieved through polymer bonding or metal- metal interconnect bonding

J. Lannon Jr.; C. Gregory; M. Lueck; A. Huffman; D. Temple

2009-01-01

413

A Geometrical Height Scale for Sunspot Penumbrae  

NASA Astrophysics Data System (ADS)

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

Puschmann, K. G.; Ruiz Cobo, B.; Martínez Pillet, V.

2010-09-01

414

A GEOMETRICAL HEIGHT SCALE FOR SUNSPOT PENUMBRAE  

SciTech Connect

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

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

2010-09-10

415

Can EPR non-locality be geometrical?  

SciTech Connect

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

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

1995-10-01

416

Properties of chemically bonded phases  

Microsoft Academic Search

Retention on non-polar chemically-bonded stationary phases depends on the silica carrier, the kind of bonded silane, the surface concentration of bonded alkyl groups and the number of surface silanol groups before and after chemical modification. The influence of carbon content of bonded phases, column temperature and how the eluent mixture has been prepared on solute retention is demonstrated. For comparison

H. Engelhardt; G. Ahr

1981-01-01

417

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

418

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

Code of Federal Regulations, 2013 CFR

...small issue bonds, qualified student loan bonds, and qualified redevelopment...small issue bonds, qualified student loan bonds, and qualified redevelopment...bonds per taxpayer). (c) Effective dates. For effective dates of §§ 1.144-0...

2013-04-01

419

Insurance and bonding  

SciTech Connect

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

Katzman, M.T.

1989-01-01

420

Hydrogen bond dynamics in the active site of photoactive yellow protein  

PubMed Central

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

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

2009-01-01

421

Chemical bond descriptors from molecular information channels in orbital resolution  

NASA Astrophysics Data System (ADS)

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

Nalewajski, Roman F.

422

The Friction and Mechanical Properties of Powders Bonded by Synthetic Resins  

Microsoft Academic Search

The coefficient of friction and mechanical properties have been determined for a series of non-metallic materials formed by bonding mineral powders with resins. The manner in which the coefficient of friction varies with particle size has been studied, and a tentative explanation has been advanced involving certain geometrical parameters A correlation was observed between the coefficient of friction and the

R C Parker; E J W Whittaker

1951-01-01

423

Accurate geometric and physical response modelling for statistical image reconstruction in high resolution PET  

Microsoft Academic Search

Accurate modeling of the data formation and detection process in PET is essential for optimizing resolution. Here, the authors develop a model in which the following factors are explicitly included: depth dependent geometric sensitivity, photon pair non-colinearity, attenuation, intrinsic detector sensitivity, non-uniform sinogram sampling, crystal penetration and inter-crystal scatter. Statistical reconstruction methods can include these modeling factors in the system

Erkan U. Mumcuoglu; Richard M. Leahyt; Simon R. Cherry; Ed Hoffman

1996-01-01

424

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

Microsoft Academic Search

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

D. Brockhagen; W. Hallmann; M. Reinartz

1990-01-01

425

Hyperconjugation-mediated solvent effects in phosphoanhydride bonds  

PubMed Central

Density functional theory and Natural Bond Orbital analysis are used to explore the impact of solvent on hyperconjugation in methyl triphosphate, a model for “energy rich” phosphoanhydride bonds, such as found in ATP. As expected, dihedral rotation of a hydroxyl group vicinal to the phosphoanhydride bond reveals that the conformational dependence of the anomeric effect involves modulation of the orbital overlap between the donor and acceptor orbitals. However, a conformational independence was observed in the rotation of a solvent hydrogen bond. As one lone pair orbital rotates away from an optimal anti-periplanar orientation, the overall magnitude of the anomeric effect is compensated approximately by the other lone pair as it becomes more anti-periplanar. Furthermore, solvent modulation of the anomeric effect is not restricted to the anti-periplanar lone pair; hydrogen bonds involving gauche lone pairs also affect the anomeric interaction and the strength of the phosphoanhydride bond. Both gauche and anti solvent hydrogen bonds lengthen non-bridging 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.

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

2012-01-01

426

Conceptual design of aeroelastic structures by topology optimization  

Microsoft Academic Search

A topology optimization methodology is presented for the conceptual design of aeroelastic structures accounting for the fluid–structure interaction. The geometrical layout of the internal structure, such as the layout of stiffeners in a wing, is optimized by material topology optimization. The topology of the wet surface, that is, the fluid–structure interface, is not varied. The key components of the proposed

K. Maute; M. Allen

2004-01-01

427

19 CFR 113.11 - Bond approval.  

Code of Federal Regulations, 2013 CFR

...CUSTOMS BONDS Bond Application and Approval of Bond § 113.11 Bond approval. Each person who is required by law, regulation, or specific instruction to post a bond to secure a Customs transaction or multiple...

2013-04-01

428

?-Hole Bond Versus Hydrogen Bond: From Tetravalent to Pentavalent N, P, and As Atoms.  

PubMed

Ab initio calculations were performed on complexes of ZH4 (+) (Z=N, P, As) and their fluoro derivatives, ZFH3 (+) and ZF4 (+) , with a HCN (or LiCN) molecule acting as the Lewis base through the nitrogen electronegative center. It was found that the complexes are linked by the Z?H???N hydrogen bond or another type of noncovalent interaction in which the tetravalent heavy atom of the cation acts as the Lewis acid center, that is, when the Z???N link exists, which may be classified as the ?-hole bond. The formation of the latter interaction is usually preferable to the formation of the corresponding hydrogen bond. The Z???N interaction may be also considered as the preliminary stage of the SN 2 reaction. This is supported by the observation that for a short Z???N contact, the corresponding complex geometry coincides with the trigonal-bipyramidal geometry typical for the transition state of the SN 2 reaction. The Z???N interaction for some of complexes analyzed here possesses characteristics typical for covalent bonds. Numerous interrelations between geometrical, topological and energetic parameters are discussed. The natural bond orbital method as well as the Quantum Theory of "Atoms in Molecules" is applied to characterize interactions in the analyzed complexes. The experimental evidences of the existence of these interactions, based on the Cambridge Structure Database search, are also presented. In addition, it is justified that mechanisms of the formation of the Z???N interactions are similar to the processes occurring for the other noncovalent links. The formation of Z???N interaction as well as of other interactions may be explained with the use of the ?-hole concept. PMID:24038237

Grabowski, S?awomir J

2013-09-03

429

The transfer matrix: A geometrical perspective  

NASA Astrophysics Data System (ADS)

We present a comprehensive and self-contained discussion of the use of the transfer matrix to study propagation in one-dimensional lossless systems, including a variety of examples, such as superlattices, photonic crystals, and optical resonators. In all these cases, the transfer matrix has the same algebraic properties as the Lorentz group in a (2+1)-dimensional spacetime, as well as the group of unimodular real matrices underlying the structure of the abcd law, which explains many subtle details. We elaborate on the geometrical interpretation of the transfer-matrix action as a mapping on the unit disk and apply a simple trace criterion to classify the systems into three types with very different geometrical and physical properties. This approach is applied to some practical examples and, in particular, an alternative framework to deal with periodic (and quasiperiodic) systems is proposed.

Sánchez-Soto, Luis L.; Monzón, Juan J.; Barriuso, Alberto G.; Cariñena, José F.

2012-04-01

430

The Legendre transform in geometric calculus  

NASA Astrophysics Data System (ADS)

This paper explores the extension of the Legendre transform from scalar calculus to geometric calculus. In physics, the Legendre transform provides a change of variables to express equations of motion or other physical relationships in terms of the most convenient dynamical quantities for a given experimental or theoretical analysis. In classical mechanics and in field theory, the Legendre transform generates the Hamiltonian function of a system from the Lagrangian function or vice versa. In thermodynamics, the Legendre transform allows thermodynamic relationships to be written in terms of alternative sets of independent variables. In this paper, we review the properties of the Legendre transform in scalar calculus and show how an analogous transformation with similar properties may be constructed in geometric calculus.

McClellan, Gene E.

2013-10-01

431

Geometric superresolution using CCD-mask  

NASA Astrophysics Data System (ADS)

Resolution of any image taken by CCD camera is generally lower in resolution in comparison with original object. Assuming the imaging system as diffraction limited - the major component responsible for this resolution limitation is the pixel geometry in CCD. The area, shape of pixel and distance between them (inter-pixel spacing) together contributes in reduction of the resolution of the final electronic image. A number of techniques have been reported in the literature to overcome this geometric resolution limitation. We have proposed a novel geometric superresolution technique in which a CCD-mask is displaced over CCD-plane by one pixel in subpixel steps - both in x and y directions. The resultant processed superresolved image is improved in resolution by the subpixel steps factor. Simulation results in 2D have been presented which shows improvement in resolution. This superresolution technique can be applied to microscopy, medical imaging, satellite imaging and astronomy.

Haq, Ihtsham U.; Mudassar, Asloob A.

2010-08-01

432

Geometrical approach to gaussian beam propagation.  

PubMed

The curvature of the wavefront and the spot size of a propagating Gaussian beam may be determined from simple geometrical transformations of the lateral foci. The analysis starts from the construction of the lateral foci in the case of a spherical Fabry-Perot. Then the cases of Gaussian beam propagation through media with different refractive indices, lenses, and simple optical systems are treated. Constructions show how propagation in the image space is readily determined in each case. This analysis is the generalization of the technique outlined by Deschamps and Mast. The geometrical constructions developed for simple cases are applied to the design of some special cases of interest in laser optics: cavities by a lens, laser zoom telescope, and ring cavity. PMID:20057839

Laures, P

1967-04-01

433

Geometrical Description of fractional quantum Hall quasiparticles  

NASA Astrophysics Data System (ADS)

We examine a description of fractional quantum Hall quasiparticles and quasiholes suggested by a recent geometrical approach (F. D. M. Haldane, Phys. Rev. Lett. 108, 116801 (2011)) to FQH systems, where the local excess electric charge density in the incompressible state is given by a topologically-quantized ``guiding-center spin'' times the Gaussian curvature of a ``guiding-center metric tensor'' that characterizes the local shape of the correlation hole around electrons in the fluid. We use a phenomenological energy function with two ingredients: the shear distortion energy of area-preserving distortions of the fluid, and a local (short-range) approximation to the Coulomb energy of the fluctuation of charge density associated with the Gaussian curvature. Quasiparticles and quasiholes of the 1/3 Laughlin state are modeled as ``punctures'' in the incompressible fluid which then relax by geometric distortion which generates Gaussian curvature, giving rise to the charge-density profile around the topological excitation.

Park, Yeje; Yang, Bo; Haldane, F. D. M.

2012-02-01

434

A geometric construction of multivariate sinc functions.  

PubMed

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 the multivariate setting. Moreover, we propose a generalization of the Lanczos window function that provides a practical and unbiased approach for signal reconstruction on sampling lattices. While this framework is general for lattices of any dimension, we specifically characterize all 2-D and 3-D lattices and show the detailed derivations for 2-D hexagonal body-centered cubic (BCC) and face-centered cubic (FCC) lattices. Both visual and numerical comparisons validate the theoretical expectations about superiority of the BCC and FCC lattices over the commonly used Cartesian lattice. PMID:21775264

Ye, Wenxing; Entezari, Alireza

2011-07-18

435

Experimental evidence for the geometric clutch hypothesis.  

PubMed

The cilia and flagella of eukaryotic cells are complex filamentous organelles that undulate rapidly and produce propulsive force against the fluids that surround the living cell. They provide a number of important functions in the life cycle of higher organisms including humans. A flagellum propels the spermatozoa to the site of fertilization and cilia move the egg through the oviduct to the uterus and have a role in left-right asymmetry in the developing embryo and contribute to normal brain morphology. The geometric clutch hypothesis is a mechanistic explanation of how the repetitive bending of cilia and flagella is generated. This chapter recounts the events leading to the development of the geometric clutch hypothesis, explores the conceptual framework of the hypothesis as it relates to properties of the axoneme, and considers the experimental support for the existence of such a mechanism in real cilia and flagella. PMID:21501747

Lindemann, Charles B

2011-01-01

436

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…

Khawaja, Mabel

437

Bonding with the Past.  

ERIC Educational Resources Information Center

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

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

1998-01-01

438

Bonded Retainers - Clinical Reliability  

Microsoft Academic Search

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

439

Bonding without Tears.  

ERIC Educational Resources Information Center

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

Akeroyd, F. Michael

1982-01-01

440

Photochemical tissue bonding  

DOEpatents

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

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

2012-01-10

441

Geometric Hysteresis of Alveolated Ductal Architecture  

PubMed Central

Low Reynolds number airflow in the pulmonary acinus and aerosol particle kinetics therein are significantly conditioned by the nature of the tidal motion of alveolar duct geometry. At least two components of the ductal structure are known to exhibit stress-strain hysteresis: smooth muscle within the alveolar entrance rings, and surfactant at the air-tissue interface. We hypothesize that the geometric hysteresis of alveolar duct is largely determined by the interaction of the amount of smooth muscle & connective tissue in ductal rings, septal tissue properties, and surface tension-surface area characteristics of surfactant. To test this hypothesis, we have extended the well-known structural model of the alveolar duct by Wilson and Bachofen (J. Appl. Physiol. 52(4): 1064–1070, 1982) by adding realistic elastic and hysteretic properties of 1) the alveolar entrance ring, 2) septal tissue, and 3) surfactant. With realistic values for tissue and surface properties, we conclude that: 1) there is a significant, and underappreciated, amount of geometric hysteresis in alveolar ductal architecture; and 2) the contribution of smooth muscle and surfactant to geometric hysteresis are of opposite senses, tending toward cancellation. Quantitatively, the geometric hysteresis found experimentally by Miki et al. (J. Appl. Physiol. 75(4): 1630–1636, 1993) is consistent with little or no smooth muscle tone in anesthetized rabbits in control conditions, and with substantial smooth muscle activation following methacholine challenge. The observed local hysteretic boundary motion of the acinar duct would result in irreversible acinar flow fields, which might be important mechanistic contributors to aerosol mixing and deposition deep in the lung.

Kojic, M.; Butler, J. P.; Vlastelica, I.; Stojanovic, B.; Rankovic, V.; Tsuda, A.

2013-01-01

442

Multiphase flow in geometrically simple fracture intersections  

USGS Publications Warehouse

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

Basagaoglu, H.; Meakin, P.; Green, C. T.; Mathew, M.

2006-01-01

443

Ergodicity Breaking in Geometric Brownian Motion  

NASA Astrophysics Data System (ADS)

Geometric Brownian motion (GBM) is a model for systems as varied as financial instruments and populations. The statistical properties of GBM are complicated by nonergodicity, which can lead to ensemble averages exhibiting exponential growth while any individual trajectory collapses according to its time average. A common tactic for bringing time averages closer to ensemble averages is diversification. In this Letter, we study the effects of diversification using the concept of ergodicity breaking.

Peters, O.; Klein, W.

2013-03-01

444

A geometric approach to tree shape statistics  

Microsoft Academic Search

This article presents a new way to understand the descriptive ability of tree\\u000ashape statistics. Where before tree shape statistics were chosen by their\\u000aability to distinguish between macroevolutionary models, the ``resolution''\\u000apresented in this paper quantifies the ability of a statistic to differentiate\\u000abetween similar and different trees. We term this a ``geometric'' approach to\\u000adifferentiate it from the

Frederick A. Matsen

2005-01-01

445

Multiphase Flow in Geometrically Simple Fracture Intersections  

SciTech Connect

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to Study gravity-driven flow in geometrically simple fracture intersections. simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-filin flow oil smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

Hakan Basagaoglu; Paul Meakin; Sauro Succi; Timothy R. Ginn

2006-03-01

446

Validation of geometric models for fisheye lenses  

Microsoft Academic Search

The paper focuses on the photogrammetric investigation of geometric models for different types of optical fisheye constructions (equidistant, equisolid-angle, sterographic and orthographic projection). These models were implemented and thoroughly tested in a spatial resection and a self-calibrating bundle adjustment. For this purpose, fisheye images were taken with a Nikkor 8 mm fisheye lens on a Kodak DSC 14n Pro digital camera

D. Schneider; E. Schwalbe; H.-G. Maas

2009-01-01

447

Algebras and non-geometric flux vacua  

Microsoft Academic Search

In this work we classify the subalgebras satisfied by non-geometric Q-fluxes in type IIB orientifolds on T6\\/(Bbb Z2 × Bbb Z2) with three moduli (S, T, U). We find that there are five subalgebras compatible with the symmetries, each one leading to a characteristic flux-induced superpotential. Working in the 4-dimensional effective supergravity we obtain families of supersymmetric AdS4 vacua with

Adolfo Guarino; Jesús M. Moreno

2008-01-01

448

Generalized Chaplygin gas as geometrical dark energy  

NASA Astrophysics Data System (ADS)

The generalized Chaplygin gas provides an interesting candidate for the present accelerated expansion of the universe. We explore a geometrical explanation for the generalized Chaplygin gas within the context of brane world theories where matter fields are confined to the brane by means of the action of a confining potential. We obtain the modified Friedmann equations, deceleration parameter, and age of the universe in this scenario and show that they are consistent with the present observational data.

Heydari-Fard, M.; Sepangi, H. R.

2007-11-01

449

Geometric engineering of quantum field theories  

Microsoft Academic Search

Using the recent advances in our understanding of non-perturbative aspects of type 11 strings we show how non-trivial exact results for N = 2 quantum field theories can be reduced to T-dualities of string theory. This is done by constructing a local geometric realization of quantum field theories together with a local application of mirror symmetry. This construction is not

Sheldon Katz; Albrecht Klemm; Cumrun Vafa

1997-01-01

450

Improved Geometrical Scaling at the LHC  

SciTech Connect

We show that geometrical scaling exhibited by the p{sub T} spectra measured by the CMS Collaboration at the LHC is substantially improved if the exponent {lambda} of the saturation scale depends on p{sub T}. This dependence is shown to be the same as the dependence of small x exponent of F{sub 2} structure function in deep inelastic scattering taken at the scale p{sub T{approx_equal}}Q/2.

Praszalowicz, Michal [Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow (Poland)

2011-04-08

451

The van Hiele Levels of Geometric Understanding  

Microsoft Academic Search

A husband-and-wife team of Dutch educators, Pierre van Hiele and Dina van Hiele-Geldof, noticed the difficulties that their students had in learning geometry. These observations led them to develop a theory involving levels of thinking in geometry that students pass through as they pr ogress from merely recognizing a figure to being a ble to write a formal geometric proof

Marguerite Mason

452

Generalized Chaplygin gas as geometrical dark energy  

SciTech Connect

The generalized Chaplygin gas provides an interesting candidate for the present accelerated expansion of the universe. We explore a geometrical explanation for the generalized Chaplygin gas within the context of brane world theories where matter fields are confined to the brane by means of the action of a confining potential. We obtain the modified Friedmann equations, deceleration parameter, and age of the universe in this scenario and show that they are consistent with the present observational data.

Heydari-Fard, M.; Sepangi, H. R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839 (Iran, Islamic Republic of)

2007-11-15

453

Ergodicity breaking in geometric Brownian motion.  

PubMed

Geometric Brownian motion (GBM) is a model for systems as varied as financial instruments and populations. The statistical properties of GBM are complicated by nonergodicity, which can lead to ensemble averages exhibiting exponential growth while any individual trajectory collapses according to its time average. A common tactic for bringing time averages closer to ensemble averages is diversification. In this Letter, we study the effects of diversification using the concept of ergodicity breaking. PMID:23521245

Peters, O; Klein, W

2013-03-08

454

A Benchmark for Geometric Facial Beauty Study  

Microsoft Academic Search

\\u000a This paper presents statistical analyses for facial beauty study. A large-scale database was built, containing 23412 frontal\\u000a face images, 875 of them are marked as beautiful. We focus on the geometric feature defined by a set of landmarks on faces.\\u000a A normalization approach is proposed to filter out the non-shape variations – translation, rotation, and scale. The normalized\\u000a features are

Fangmei Chen; David Zhang

2010-01-01

455

Expander flows, geometric embeddings and graph partitioning  

Microsoft Academic Search

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

Sanjeev Arora; Satish Rao; Umesh V. Vazirani

2004-01-01

456

Geometric Scaling in Deep Inelastic Scattering  

SciTech Connect

The analysis of the scaling properties in deep-inelastic processes using the 'Quality Factor' (QF) method is summarised. Data from HERA and fixed target experiments with x<0.01 are considered. GRV, MRST and CTEQ parametrisations of F{sub 2} and F{sub 2}{sup c} are analysed in the same way to see whether these reproduce the geometric scaling properties seen in data.

Royon, Christophe [CEA/IRFU/Service de physique des particules, 91191 Gif-sur-Yvette cedex (France); Beuf, Guillaume; Peschanski, Robi [CEA/Service de physique theorique, 91191 Gif-sur-Yvette cedex (France); Salek, David [Institute of Particle and Nuclear Physics, Charles University, Prague (Czech Republic)

2009-03-23

457

Strapdown attitude algorithms from a geometric viewpoint  

Microsoft Academic Search

This paper derives various well-known strapdown inertial system attitude algorithms using a geometric viewpoint based on the Goodman-Robinson theorem. This theorem describes three-dimensional rotation kinematics of a rigid body. The attitude algorithms derived are the third-order quaternion and direction cosine matrix, the third-order quaternion modified to compute the cross-product term at twice the update rate and the computationally partitioned algorithm

Richard Mckern; Howard Musoff

1981-01-01

458

Geometric interpretation of vertex operator algebras.  

PubMed Central

In this paper, Vafa's approach to the formulation of conformal field theories is combined with the formal calculus developed in Frenkel, Lepowsky, and Meurman's work on the vertex operator construction of the Monster to give a geometric definition of vertex operator algebras. The main result announced is the equivalence between this definition and the algebraic one in the sense that the categories determined by these definitions are isomorphic.

Huang, Y Z

1991-01-01

459

Geometric stochastic resonance in a double cavity  

NASA Astrophysics Data System (ADS)

Geometric stochastic resonance of particles diffusing across a porous membrane subject to oscillating forces is characterized as a synchronization process. Noninteracting particle currents through a symmetric membrane pore are driven either perpendicular or parallel to the membrane, whereas, harmonic-mixing spectral current components are generated by the combined action of perpendicular and parallel drives. In view of potential applications to the transport of colloids and biological molecules through narrow pores, we also consider the role of particle repulsion as a controlling factor.

Ghosh, Pulak K.; Glavey, Russell; Marchesoni, Fabio; Savel'Ev, Sergey E.; Nori, Franco

2011-07-01

460

Optimal Design of Pitched Tapered Laminated Wood Beams.  

National Technical Information Service (NTIS)

The optimal design of a pitched tapered laminated woood beam is considered. An engineering formulation is given in which the volume of the beam is minimized. The problem is then reformulated and solved as a generalized geometric (signomial) program. Sampl...

J. D. Barrett M. Avriel

1976-01-01

461

Geometric attributes of retaining glycosyltransferase enzymes favor an orthogonal mechanism.  

PubMed

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

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

2013-08-01

462

Advanced Stress, Strain And Geometrical Analysis In Semiconductor Devices  

SciTech Connect

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

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

2010-11-24

463

Geometric Attributes of Retaining Glycosyltransferase Enzymes Favor an Orthogonal Mechanism  

PubMed Central

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

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

2013-01-01

464

The geometric and electronic structure of Be(10bar10)  

NASA Astrophysics Data System (ADS)

Beryllium is a simple metal with most unusual electronic and elastic properties. The bulk electronic density of states has a minimum at the Fermi-level indicating large deviations from free-electron like bonding(E.W. Plummer and J.B. Hannon, Prog. Surf. Sci. 46, 149 (1994).) . Cleaved perpendicular to the [10bar10] direction the bulk crystal can be terminated in two different ways whose first interlayer spacings differ by a factor of two. A recent calculations indicates that the local electronic density of states at the Fermi-level shows a maximum at this surface independent of the termination type(V.M. Silkin and E.V. Chulkov, to be published.) . We have determined the electronic and geometric structure of Be(10bar10) by ARUPS and LEED and compared to first-principles calculations. The bulk is uniquely terminated by a short interlayer spacing and the distance between first and second layer is contracted by 25% with respect to the bulk. The high electronic density of states at the Fermi-level is caused by a surface state at the barA point of the surface Brillouin zone. The experimental findings are in good agreement with the calculations.

Hofmann, Ph.; Plummer, E. W.; Pohl, K.; Stumpf, R.

1996-03-01

465

The geometric and the atomic world views  

PubMed Central

The atomic world view is based on the notion that matter is built of elementary constituents called atoms, and quantum mechanics was created in the pursuit of this view with probabilistic events caused by atomic particles. This conception involves unresolved ambiguities linked to the notion of an elementary quantum of action. The resolution of these problems in quantum mechanics requires a new, geometric, world view, which recognizes the occurrence of events, clicks in counters, coming without a cause, referred to as fortuitous. The possibility of a rational theory of probabilities for such events is based on the assignment to the individual click of a proper value of an element of (flat) space–time symmetry. Thereby, the distributions of uncaused clicks can be endowed with a geometric content in terms of the irreducible representations of space–time symmetry. Through fortuity, space–time invariance itself thus acquires a hitherto unrecognized role. Departing from the norms of physical theory, the uncaused click is not a measurement of something, and the reality mirrored in the distributions is the geometry of space time itself, and not a property of an imagined object. The geometric world view involves only the dimensions of space and time, and the absence of an irreducible dimension of mass is seen as the result of the discovery of new physical phenomena. Accordingly Planck's constant has no place in fundamental theory and is seen as a relic of dimensions that have become superfluous.

Bohr, Aage; Mottelson, Ben R.; Ulfbeck, Ole

2008-01-01

466

Geometric quantum computation using nuclear magnetic resonance  

PubMed

A significant development in computing has been the discovery that the computational power of quantum computers exceeds that of Turing machines. Central to the experimental realization of quantum information processing is the construction of fault-tolerant quantum logic gates. Their operation requires conditional quantum dynamics, in which one sub-system undergoes a coherent evolution that depends on the quantum state of another sub-system; in particular, the evolving sub-system may acquire a conditional phase shift. Although conventionally dynamic in origin, phase shifts can also be geometric. Conditional geometric (or 'Berry') phases depend only on the geometry of the path executed, and are therefore resilient to certain types of errors; this suggests the possibility of an intrinsically fault-tolerant way of performing quantum gate operations. Nuclear magnetic resonance techniques have already been used to demonstrate both simple quantum information processing and geometric phase shifts. Here we combine these ideas by performing a nuclear magnetic resonance experiment in which a conditional Berry phase is implemented, demonstrating a controlled phase shift gate. PMID:10706278

Jones; Vedral; Ekert; Castagnoli

2000-02-24

467

Closed geometric models in medical applications  

NASA Astrophysics Data System (ADS)

Conventional surface fitting methods give twisted surfaces and complicates capping closures. This is a typical character of surfaces that lack rectangular topology. We suggest an algorithm which overcomes these limitations. The analysis of the algorithm is presented with experimental results. This algorithm assumes the mass center lying inside the object. Both capping closure and twisting are results of inadequate information on the geometric proximity of the points and surfaces which are proximal in the parametric space. Geometric proximity at the contour level is handled by mapping the points along the contour onto a hyper-spherical space. The resulting angular gradation with respect to the centroid is monotonic and hence avoids the twisting problem. Inter-contour geometric proximity is achieved by partitioning the point set based on the angle it makes with the respective centroids. Avoidance of capping complications is achieved by generating closed cross curves connecting curves which are reflections about the abscissa. The method is of immense use for the generation of the deep cerebral structures and is applied to the deep structures generated from the Schaltenbrand- Wahren brain atlas.

Jagannathan, Lakshmipathy; Nowinski, Wieslaw L.; Raphel, Jose K.; Nguyen, Bonnie T.

1996-04-01

468

Salt Bridges: Geometrically Specific, Designable Interactions  

PubMed Central

Salt bridges occur frequently in proteins, providing conformational specificity and contributing to molecular recognition and catalysis. We present a comprehensive analysis of these interactions in protein structures by surveying a large database of protein structures. Salt bridges between Asp or Glu and His, Arg, or Lys display extremely well-defined geometric preferences. Several previously observed preferences are confirmed and others that were previously unrecognized are discovered. Salt bridges are explored for their preferences for different separations in sequence and in space, geometric preferences within proteins and at protein-protein interfaces, cooperativity in networked salt bridges, inclusion within metal-binding sites, preference for acidic electrons, apparent conformational side chain entropy reduction upon formation, and degree of burial. Salt bridges occur far more frequently between residues at close than distant sequence separations, but at close distances there remain strong preferences for salt bridges at specific separations. Specific types of complex salt bridges, involving three or more members, are also discovered. As we observe a strong relationship between the propensity to form a salt bridge and the placement of salt-bridging residues in protein sequences, we discuss the role that salt bridges might play in kinetically influencing protein folding and thermodynamically stabilizing the native conformation. We also develop a quantitative method to select appropriate crystal structure resolution and B-factor cutoffs. Detailed knowledge of these geometric and sequence dependences should aid de novo design and prediction algorithms.

Donald, Jason E.; Kulp, Daniel W.; DeGrado, William F.

2010-01-01

469

Geometric prediction structure for multiview video coding  

NASA Astrophysics Data System (ADS)

One of the critical issues to successful service of 3D video is how to compress huge amount of multi-view video data efficiently. In this paper, we described about geometric prediction structure for multi-view video coding. By exploiting the geometric relations between each camera pose, we can make prediction pair which maximizes the spatial correlation of each view. To analyze the relationship of each camera pose, we defined the mathematical view center and view distance in 3D space. We calculated virtual center pose by getting mean rotation matrix and mean translation vector. We proposed an algorithm for establishing the geometric prediction structure based on view center and view distance. Using this prediction structure, inter-view prediction is performed to camera pair of maximum spatial correlation. In our prediction structure, we also considered the scalability in coding and transmitting the multi-view videos. Experiments are done using JMVC (Joint Multiview Video Coding) software on MPEG-FTV test sequences. Overall performance of proposed prediction structure is measured in the PSNR and subjective image quality measure such as PSPNR.

Lee, Seok; Wey, Ho-Cheon; Park, Du-Sik

2010-02-01

470

Geometrical Theory of Spherical Harmonics for Geosciences  

NASA Astrophysics Data System (ADS)

Spherical harmonics play a central role in the modelling of spatial and temporal processes in the system Earth. The gravity field of the Earth and its temporal variations, sea surface topography, geomagnetic field, ionosphere etc., are just a few examples where spherical harmonics are used to represent processes in the system Earth. We introduce a novel method for the computation and rotation of spherical harmonics, Legendre polynomials and associated Legendre functions without making use of recursive relations. This novel geometrical approach allows calculation of spherical harmonics without any numerical instability up to an arbitrary degree and order, e.g. up to degree and order 106 and beyond. The algorithm is based on the trigonometric reduction of Legendre polynomials and the geometric rotation in hyperspace. It is shown that Legendre polynomials can be computed using trigonometric series by pre-computing amplitudes and translation terms for all angular arguments. It is shown that they can be treated as vectors in the Hilbert hyperspace leading to unitary hermitian rotation matrices with geometric properties. Thus, rotation of spherical harmonics about e.g. a polar or an equatorial axis can be represented in the similar way. This novel method allows stable calculation of spherical harmonics up to an arbitrary degree and order, i.e. up to degree and order 106 and beyond.

Svehla, Drazen

2010-05-01

471

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

PubMed

We present a theoretical polygon construction analysis of two-dimensional melting and freezing transitions in many-particle Yukawa systems. Two-dimensional melting transitions can be characterized as proliferation of geometrical defects--nontriangular polygons, obtained by removing unusually long bonds in the triangulation of particle positions. A liquid state is characterized by the temperature-independent number of quadrilaterals and linearly increasing number of pentagons. We analyze specific types of vertices, classified by the type and distribution of polygons surrounding them, and determine temperature dependencies of their concentrations. Solid-liquid phase transitions are followed by the peaks in the abundances of certain types of vertices. PMID:23214742

Radzvilavi?ius, Ar?nas

2012-11-09

472

A fast ellipse\\/circle detector using geometric symmetry  

Microsoft Academic Search

Through the use of a global geometric symmetry, a fast ellipse\\/circle detector is proposed in this paper. Based on the geometric symmetry, the proposed method first locates candidates of ellipse and circle centers. In the meantime, according to these candidate centers, all feature points in an input image are grouped into several subimages. Then, for each subimage, by using geometric

Chun-ta Ho; Ling-hwei Chen

1995-01-01

473

A Novel Watermarking Algorithm Resist to Geometrical Attacks  

Microsoft Academic Search

In this paper we present a novel watermarking algorithm based on feature points and integer discrete wavelet transform (IDWT) against geometric rotation and scaling. Geometric distortions are critical factors which hamper the application of the image digital watermarking in that most of the watermarking technique would fail after the image has been experienced geometric transform. The proposed scheme enhances the

Xiaoli Zhang; Lv Xin

2009-01-01

474

New Perspectives on Geometric Reflection Theory From Rough Surfaces  

Microsoft Academic Search

Exact wave theories of specular reflectance from rough surfaces are computationally intractable thus motivating the practical need for geometric reflectance models which treat only the geometric ray nature of light reflection. The cornerstone of geometric reflectance modeling from rough surfaces in computer vision and computer graphics over the past two decades has been the Torrance-Sparrow model. This model has worked

Andrew J. Lundberg; Lawrence B. Wolff; Diego A. Socolinsky

2001-01-01

475

Geometric reasoning for manufacturability evaluation--application to powder metallurgy  

Microsoft Academic Search

A new approach to perform geometric reasoning for manufacturability evaluation is developed using three-dimensional objects that are based on a process-dependent geometric model. It is demonstrated that by incorporating the limitations of the process directly in the geometric representation scheme, the task of manufacturability evaluation becomes straightforward and can be performed without either feature extraction or designing with features. The

Thomas E. Dissinger; Edward B. Magrab

1996-01-01

476

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

SciTech Connect

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

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

1986-03-01

477

A novel bonding technique to bond CTE mismatched devices  

Microsoft Academic Search

Thermal expansion mismatch between electronic devices and their substrates induces stresses in the assembly during bonding and operation. These stresses in extreme cases cause cracking of the electronic device during bonding. For GaAs devices back-side bonded to a high conductivity artificial diamond substrate using Au-Sn solder, analytical and numerical analyses were conducted to determine the bonding stresses in the GaAs

B. Chandran; W. F. Schmidt; M. H. Gordon

1996-01-01

478

How geometric details can affect the strength of adhesive lap joints  

SciTech Connect

The durability of adhesively bonded joints--when utilized as blade attachments--has a significant impact on the performance of wind turbines. Accordingly, there is interest in determining how geometric details affect the strength of these joints. Finite element analyses were performed to aid in the selection of three composite-to-metal joint geometries for compressive axial testing. Both monotonic and low-cycle fatigue tests were conducted. Analysis and testing of these joints provide insight into the effects of adding extra adhesive to the end of the bond or tapering the metal adherend. The issue of whether the relative performance of different joints in monotonic tests can be used to predict the relative fatigue strength of these joints is also addressed.

Metzinger, K.E.; Guess, T.R.

1996-12-31

479

Improving humidity bond reliability of copper bonding wires  

Microsoft Academic Search

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

480

CRIMINAL PROCEDURE Bonds and Recognizes: Regulate Bail Bond Recovery Agents  

Microsoft Academic Search

The Act establishes that the surety limit on criminal bonds can be no higher than twelve percent on bonds in the amount of $ 10,000 or less and no higher than fifteen percent on bonds in amounts greater than $ 10,000. Additionally, the Act defines bail recovery agent, establishes prerequisites for those people serving as bail recovery agents, and provides

Kevin Thomas McMurry

1999-01-01

481

Image quality assessment based on multiscale geometric analysis.  

PubMed

Reduced-reference (RR) image quality assessment (IQA) has been recognized as an effective and efficient way to predict the visual quality of distorted images. The current standard is the wavelet-domain natural image statistics model (WNISM), which applies the Kullback-Leibler divergence between the marginal distributions of wavelet coefficients of the reference and distorted images to measure the image distortion. However, WNISM fails to consider the statistical correlations of wavelet coefficients in different subbands and the visual response characteristics of the mammalian cortical simple cells. In addition, wavelet transforms are optimal greedy approximations to extract singularity structures, so they fail to explicitly extract the image geometric information, e.g., lines and curves. Finally, wavelet coefficients are dense for smooth image edge contours. In this paper, to target the aforementioned problems in IQA, we develop a novel framework for IQA to mimic the human visual system (HVS) by incorporating the merits from multiscale geometric analysis (MGA), contrast sensitivity function (CSF), and the Weber's law of just noticeable difference (JND). In the proposed framework, MGA is utilized to decompose images and then extract features to mimic the multichannel structure of HVS. Additionally, MGA offers a series of transforms including wavelet, curvelet, bandelet, contourlet, wavelet-based contourlet transform (WBCT), and hybrid wavelets and directional filter banks (HWD), and different transforms capture different types of image geometric information. CSF is applied to weight coefficients obtained by MGA to simulate the appearance of images to observers by taking into account many of the nonlinearities inherent in HVS. JND is finally introduced to produce a noticeable variation in sensory experience. Thorough empirical studies are carried out upon the LIVE database against subjective mean opinion score (MOS) and demonstrate that 1) the proposed framework has good consistency with subjective perception values and the objective assessment results can well reflect the visual quality of images, 2) different transforms in MGA under the new framework perform better than the standard WNISM and some of them even perform better than the standard full-reference IQA model, i.e., the mean structural similarity index, and 3) HWD performs best among all transforms in MGA under the framework. PMID:19447715

Gao, Xinbo; Lu, Wen; Tao, Dacheng; Li, Xuelong

2009-05-12

482

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

PubMed

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

483

Impact of geometric uncertainties on dose calculations for intensity modulated radiation therapy of prostate cancer  

NASA Astrophysics Data System (ADS)

Intensity-modulated radiation therapy (IMRT) uses non-uniform beam intensities within a radiation field to provide patient-specific dose shaping, resulting in a dose distribution that conforms tightly to the planning target volume (PTV). Unavoidable geometric uncertainty arising from patient repositioning and internal organ motion can lead to lower conformality index (CI) during treatment delivery, a decrease in tumor control probability (TCP) and an increase in normal tissue complication probability (NTCP). The CI of the IMRT plan depends heavily on steep dose gradients between the PTV and organ at risk (OAR). Geometric uncertainties reduce the planned dose gradients and result in a less steep or "blurred" dose gradient. The blurred dose gradients can be maximized by constraining the dose objective function in the static IMRT plan or by reducing geometric uncertainty during treatment with corrective verification imaging. Internal organ motion and setup error were evaluated simultaneously for 118 individual patients with implanted fiducials and MV electronic portal imaging (EPI). A Gaussian probability density function (PDF) is reasonable for modeling geometric uncertainties as indicated by the 118 patients group. The Gaussian PDF is patient specific and group standard deviation (SD) should not be used for accurate treatment planning for individual patients. In addition, individual SD should not be determined or predicted from small imaging samples because of random nature of the fluctuations. Frequent verification imaging should be employed in situations where geometric uncertainties are expected. Cumu