Geometric optimization of thermal systems
NASA Astrophysics Data System (ADS)
Alebrahim, Asad Mansour
2000-10-01
The work in chapter 1 extends to three dimensions and to convective heat transfer the constructal method of minimizing the thermal resistance between a volume and one point. In the first part, the heat flow mechanism is conduction, and the heat generating volume is occupied by low conductivity material (k 0) and high conductivity inserts (kp) that are shaped as constant-thickness disks mounted on a common stem of kp material. In the second part the interstitial spaces once occupied by k0 material are bathed by forced convection. The internal and external geometric aspect ratios of the elemental volume and the first assembly are optimized numerically subject to volume constraints. Chapter 2 presents the constrained thermodynamic optimization of a cross-flow heat exchanger with ram air on the cold side, which is used in the environmental control systems of aircraft. Optimized geometric features such as the ratio of channel spacings and flow lengths are reported. It is found that the optimized features are relatively insensitive to changes in other physical parameters of the installation and relatively insensitive to the additional irreversibility due to discharging the ram-air stream into the atmosphere, emphasizing the robustness of the thermodynamic optimum. In chapter 3 the problem of maximizing exergy extraction from a hot stream by distributing streams over a heat transfer surface is studied. In the first part, the cold stream is compressed in an isothermal compressor, expanded in an adiabatic turbine, and discharged into the ambient. In the second part, the cold stream is compressed in an adiabatic compressor. Both designs are optimized with respect to the capacity-rate imbalance of the counter-flow and the pressure ratio maintained by the compressor. This study shows the tradeoff between simplicity and increased performance, and outlines the path for further conceptual work on the extraction of exergy from a hot stream that is being cooled gradually. The aim of chapter 4 was to optimize the performance of a boot-strap air cycle of an environmental control system (ECS) for aircraft. New in the present study was that the optimization refers to the performance of the entire ECS system, not to the performance of an individual component. Also, there were two heat exchangers, not one, and their relative positions and sizes were not specified in advance. This study showed that geometric optimization can be identified when the optimization procedure refers to the performance of the entire ECS system, not to the performance of an individual component. This optimized features were robust relative to some physical parameters. This robustness may be used to simplify future optimization of similar systems.
Optimizing the geometrical accuracy of curvilinear meshes
NASA Astrophysics Data System (ADS)
Toulorge, Thomas; Lambrechts, Jonathan; Remacle, Jean-François
2016-04-01
This paper presents a method to generate valid high order meshes with optimized geometrical accuracy. The high order meshing procedure starts with a linear mesh, that is subsequently curved without taking care of the validity of the high order elements. An optimization procedure is then used to both untangle invalid elements and optimize the geometrical accuracy of the mesh. Standard measures of the distance between curves are considered to evaluate the geometrical accuracy in planar two-dimensional meshes, but they prove computationally too costly for optimization purposes. A fast estimate of the geometrical accuracy, based on Taylor expansions of the curves, is introduced. An unconstrained optimization procedure based on this estimate is shown to yield significant improvements in the geometrical accuracy of high order meshes, as measured by the standard Hausdorff distance between the geometrical model and the mesh. Several examples illustrate the beneficial impact of this method on CFD solutions, with a particular role of the enhanced mesh boundary smoothness.
Evolutionary Optimization of a Geometrically Refined Truss
NASA Technical Reports Server (NTRS)
Hull, P. V.; Tinker, M. L.; Dozier, G. V.
2007-01-01
Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection, and stress on a benchmark cantilever truss problem. Predominantly traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This Technical Publication (TP) presents a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation: genetic algorithms and differential evolution to successfully optimize a benchmark structural optimization problem. A nontraditional solution to the benchmark problem is presented in this TP, specifically a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization toolset.
Geometrically nonlinear analysis of adhesively bonded joints
NASA Technical Reports Server (NTRS)
Dattaguru, B.; Everett, R. A., Jr.; Whitcomb, J. D.; Johnson, W. S.
1982-01-01
A geometrically nonlinear finite element analysis of cohesive failure in typical joints is presented. Cracked-lap-shear joints were chosen for analysis. Results obtained from linear and nonlinear analysis show that nonlinear effects, due to large rotations, significantly affect the calculated mode 1, crack opening, and mode 2, inplane shear, strain-energy-release rates. The ratio of the mode 1 to mode 2 strain-energy-relase rates (G1/G2) was found to be strongly affected by he adhesive modulus and the adherend thickness. The ratios between 0.2 and 0.8 can be obtained by varying adherend thickness and using either a single or double cracked-lap-shear specimen configuration. Debond growth rate data, together with the analysis, indicate that mode 1 strain-energy-release rate governs debond growth. Results from the present analysis agree well with experimentally measured joint opening displacements.
Optimization of biotechnological systems through geometric programming
Marin-Sanguino, Alberto; Voit, Eberhard O; Gonzalez-Alcon, Carlos; Torres, Nestor V
2007-01-01
Background In the past, tasks of model based yield optimization in metabolic engineering were either approached with stoichiometric models or with structured nonlinear models such as S-systems or linear-logarithmic representations. These models stand out among most others, because they allow the optimization task to be converted into a linear program, for which efficient solution methods are widely available. For pathway models not in one of these formats, an Indirect Optimization Method (IOM) was developed where the original model is sequentially represented as an S-system model, optimized in this format with linear programming methods, reinterpreted in the initial model form, and further optimized as necessary. Results A new method is proposed for this task. We show here that the model format of a Generalized Mass Action (GMA) system may be optimized very efficiently with techniques of geometric programming. We briefly review the basics of GMA systems and of geometric programming, demonstrate how the latter may be applied to the former, and illustrate the combined method with a didactic problem and two examples based on models of real systems. The first is a relatively small yet representative model of the anaerobic fermentation pathway in S. cerevisiae, while the second describes the dynamics of the tryptophan operon in E. coli. Both models have previously been used for benchmarking purposes, thus facilitating comparisons with the proposed new method. In these comparisons, the geometric programming method was found to be equal or better than the earlier methods in terms of successful identification of optima and efficiency. Conclusion GMA systems are of importance, because they contain stoichiometric, mass action and S-systems as special cases, along with many other models. Furthermore, it was previously shown that algebraic equivalence transformations of variables are sufficient to convert virtually any types of dynamical models into the GMA form. Thus, efficient methods for optimizing GMA systems have multifold appeal. PMID:17897440
Interplay between Peptide Bond Geometrical Parameters in Nonglobular Structural Contexts
Esposito, Luciana; De Simone, Alfonso; Vitagliano, Luigi
2013-01-01
Several investigations performed in the last two decades have unveiled that geometrical parameters of protein backbone show a remarkable variability. Although these studies have provided interesting insights into one of the basic aspects of protein structure, they have been conducted on globular and water-soluble proteins. We report here a detailed analysis of backbone geometrical parameters in nonglobular proteins/peptides. We considered membrane proteins and two distinct fibrous systems (amyloid-forming and collagen-like peptides). Present data show that in these systems the local conformation plays a major role in dictating the amplitude of the bond angle N-Cα-C and the propensity of the peptide bond to adopt planar/nonplanar states. Since the trends detected here are in line with the concept of the mutual influence of local geometry and conformation previously established for globular and water-soluble proteins, our analysis demonstrates that the interplay of backbone geometrical parameters is an intrinsic and general property of protein/peptide structures that is preserved also in nonglobular contexts. For amyloid-forming peptides significant distortions of the N-Cα-C bond angle, indicative of sterical hidden strain, may occur in correspondence with side chain interdigitation. The correlation between the dihedral angles Δω/ψ in collagen-like models may have interesting implications for triple helix stability. PMID:24455689
Minimizing stellarator turbulent transport by geometric optimization
NASA Astrophysics Data System (ADS)
Mynick, H. E.
2010-11-01
Up to now, a transport optimized stellarator has meant one optimized to minimize neoclassical transport,ootnotetextH.E. Mynick, Phys. Plasmas 13, 058102 (2006). while the task of also mitigating turbulent transport, usually the dominant transport channel in such designs, has not been addressed, due to the complexity of plasma turbulence in stellarators. However, with the advent of gyrokinetic codes valid for 3D geometries such as GENE,ootnotetextF. Jenko, W. Dorland, M. Kotschenreuther, B.N. Rogers, Phys. Plasmas 7, 1904 (2000). and stellarator optimization codes such as STELLOPT,ootnotetextA. Reiman, G. Fu, S. Hirshman, L. Ku, et al, Plasma Phys. Control. Fusion 41 B273 (1999). designing stellarators to also reduce turbulent transport has become a realistic possibility. We have been using GENE to characterize the dependence of turbulent transport on stellarator geometry,ootnotetextH.E Mynick, P.A. Xanthopoulos, A.H. Boozer, Phys.Plasmas 16 110702 (2009). and to identify key geometric quantities which control the transport level. From the information obtained from these GENE studies, we are developing proxy functions which approximate the level of turbulent transport one may expect in a machine of a given geometry, and have extended STELLOPT to use these in its cost function, obtaining stellarator configurations with turbulent transport levels substantially lower than those in the original designs.
Introduction to geometric processing through optimization.
Taubin, Gabriel
2012-01-01
As an introduction to the field, this article shows how to formulate several geometry-processing operations to solve systems of equations in the "least-squares" sense. The equations are derived from local geometric relations using elementary concepts from analytic geometry, such as points, lines, planes, vectors, and polygons. Simple and useful tools for interactive polygon mesh editing result from the most basic descent strategies to solve these optimization problems. Throughout the article, the author develops the mathematical formulations incrementally, keeping in mind that the objective is to implement simple software for interactive editing applications that works well in practice. Readers can implement higher-performance versions of these algorithms by replacing the simple solvers proposed here with more advanced ones. PMID:24806636
Optimized probabilistic quantum processors: A unified geometric approach 1
NASA Astrophysics Data System (ADS)
Bergou, Janos; Bagan, Emilio; Feldman, Edgar
Using probabilistic and deterministic quantum cloning, and quantum state separation as illustrative examples we develop a complete geometric solution for finding their optimal success probabilities. The method is related to the approach that we introduced earlier for the unambiguous discrimination of more than two states. In some cases the method delivers analytical results, in others it leads to intuitive and straightforward numerical solutions. We also present implementations of the schemes based on linear optics employing few-photon interferometry
Geometric Mechanics Reveals Optimal Complex Terrestrial Undulation Patterns
NASA Astrophysics Data System (ADS)
Gong, Chaohui; Astley, Henry; Schiebel, Perrin; Dai, Jin; Travers, Matthew; Goldman, Daniel; Choset, Howie; CMU Team; GT Team
Geometric mechanics offers useful tools for intuitively analyzing biological and robotic locomotion. However, utility of these tools were previously restricted to systems that have only two internal degrees of freedom and in uniform media. We show kinematics of complex locomotors that make intermittent contacts with substrates can be approximated as a linear combination of two shape bases, and can be represented using two variables. Therefore, the tools of geometric mechanics can be used to analyze motions of locomotors with many degrees of freedom. To demonstrate the proposed technique, we present studies on two different types of snake gaits which utilize combinations of waves in the horizontal and vertical planes: sidewinding (in the sidewinder rattlesnake C. cerastes) and lateral undulation (in the desert specialist snake C. occipitalis). C. cerastes moves by generating posteriorly traveling body waves in the horizontal and vertical directions, with a relative phase offset equal to +/-π/2 while C. occipitalismaintains a π/2 offset of a frequency doubled vertical wave. Geometric analysis reveals these coordination patterns enable optimal movement in the two different styles of undulatory terrestrial locomotion. More broadly, these examples demonstrate the utility of geometric mechanics in analyzing realistic biological and robotic locomotion.
Comparison between first geometric-arithmetic index and atom-bond connectivity index
NASA Astrophysics Data System (ADS)
Das, Kinkar Ch.; Trinajstić, N.
2010-09-01
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.
Technology Transfer Automated Retrieval System (TEKTRAN)
Dietary fatty acid type alters atherosclerotic lesion progression and macrophage lipid accumulation. Incompletely elucidated are the mechanisms by which fatty acids differing in double-bond geometric or positional configuration alter arterial lipid accumulation. The objective of this study was to ev...
Geometrical parameters optimization for tube hydroforming using response surface method
NASA Astrophysics Data System (ADS)
Chebbah, M. S.; Azaouzi, M.
2014-10-01
In tube hydroforming (THF) the optimal thickness variation of a product is influenced by the geometrical, material and process parameters. In this study different values of initial tube length combined with various fillet and entry radii of the die are taken into account to predict an acceptable T-shaped tube of which the minimum wall thickness fulfills the industrial demand. To reach this goal, an integrated optimization approach, using the classical explicit dynamic (ED) incremental approach using ABAQUS® commercial code together with an optimization algorithm was developed. This latter consists in constructing an explicit form of the objective function by response surface methodology (RSM) based on diffuse approximation (DA) according to the design variables. To search the global optimum of the objective function, the sequential quadratic programming (SQP) algorithm has been used.
Optimization of the geometrical stability in square ring laser gyroscopes
NASA Astrophysics Data System (ADS)
Santagata, R.; Beghi, A.; Belfi, J.; Beverini, N.; Cuccato, D.; Di Virgilio, A.; Ortolan, A.; Porzio, A.; Solimeno, S.
2015-03-01
Ultra-sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth. Our project for this goal is called GINGER (gyroscopes in general relativity), and consists of a ground-based triaxial array of ring lasers aimed at measuring the rotation rate of the Earth with an accuracy of {{10}-14} rad {{s}-1}. Such an ambitious goal is now within reach, as large-area ring lasers are very close to the required sensitivity and stability. However, demanding constraints on the geometrical stability of the optical path of the laser inside the ring cavity are required. Thus, we have begun a detailed study of the geometry of an optical cavity in order to find a control strategy for its geometry that could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions that allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.
Wikfeldt, K. T.; Michaelides, A.
2014-01-28
Ab initio simulations that account for nuclear quantum effects have been used to examine the order-disorder transition in squaric acid, a prototypical H-bonded antiferroelectric crystal. Our simulations reproduce the >100 K difference in transition temperature observed upon deuteration as well as the strong geometrical isotope effect observed on intermolecular separations within the crystal. We find that collective transfer of protons along the H-bonding chains – facilitated by quantum mechanical tunneling – is critical to the order-disorder transition and the geometrical isotope effect. This sheds light on the origin of isotope effects and the importance of tunneling in squaric acid which likely extends to other H-bonded ferroelectrics.
Optimization of absorption placement using geometrical acoustic models and least squares.
Saksela, Kai; Botts, Jonathan; Savioja, Lauri
2015-04-01
Given a geometrical model of a space, the problem of optimally placing absorption in a space to match a desired impulse response is in general nonlinear. This has led some to use costly optimization procedures. This letter reformulates absorption assignment as a constrained linear least-squares problem. Regularized solutions result in direct distribution of absorption in the room and can accommodate multiple frequency bands, multiple sources and receivers, and constraints on geometrical placement of absorption. The method is demonstrated using a beam tracing model, resulting in the optimal absorption placement on the walls and ceiling of a classroom. PMID:25920877
Geometrical optimization of a local ballistic magnetic sensor
Kanda, Yuhsuke; Hara, Masahiro; Nomura, Tatsuya; Kimura, Takashi
2014-04-07
We have developed a highly sensitive local magnetic sensor by using a ballistic transport property in a two-dimensional conductor. A semiclassical simulation reveals that the sensitivity increases when the geometry of the sensor and the spatial distribution of the local field are optimized. We have also experimentally demonstrated a clear observation of a magnetization process in a permalloy dot whose size is much smaller than the size of an optimized ballistic magnetic sensor fabricated from a GaAs/AlGaAs two-dimensional electron gas.
Geometric Optimization of Thermo-electric Coolers Using Simulated Annealing
NASA Astrophysics Data System (ADS)
Khanh, D. V. K.; Vasant, P. M.; Elamvazuthi, I.; Dieu, V. N.
2015-09-01
The field of thermo-electric coolers (TECs) has grown drastically in recent years. In an extreme environment as thermal energy and gas drilling operations, TEC is an effective cooling mechanism for instrument. However, limitations such as the relatively low energy conversion efficiency and ability to dissipate only a limited amount of heat flux may seriously damage the lifetime and performance of the instrument. Until now, many researches were conducted to expand the efficiency of TECs. The material parameters are the most significant, but they are restricted by currently available materials and module fabricating technologies. Therefore, the main objective of finding the optimal TECs design is to define a set of design parameters. In this paper, a new method of optimizing the dimension of TECs using simulated annealing (SA), to maximize the rate of refrigeration (ROR) was proposed. Equality constraint and inequality constraint were taken into consideration. This work reveals that SA shows better performance than Cheng's work.
Liu, Zhiguo; Wang, Guitao; Li, Zhanting; Wang, Renxiao
2008-11-11
We have conducted potential of mean force (PMF) analyses to derive the geometrical parameters of various types of hydrogen bonds on protein-ligand binding interface. Our PMF analyses are based on a set of 4535 high-quality protein-ligand complex structures, which are compiled through a systematic mining of the entire Protein Data Bank. Hydrogen bond donor and acceptor atoms are classified into several basic types. Both distance- and angle-dependent statistical potentials are derived for each donor-acceptor pair, from which distance and angle cutoffs are obtained in an objective, unambiguous manner. These donor-acceptor pairs are also studied by quantum mechanics (QM) calculations at the MP2/6-311++G** level on model molecules. Comparison of the outcomes of PMF analyses and QM calculations suggests that QM calculation may serve as an alternative approach for characterizing hydrogen bond geometry. Both of our PMF analyses and QM calculations indicate that C-H···O hydrogen bonds are relatively weak as compared to common hydrogen bonds formed between nitrogen and oxygen atoms. A survey on the protein-ligand complex structures in our data set has revealed that Cα-H···O hydrogen bonds observed in protein-ligand binding are frequently accompanied by bifurcate N-H···O hydrogen bonds. Thus, the Cα-H···O hydrogen bonds in such cases would better be interpreted as secondary interactions. PMID:26620338
Multi-response Optimization of Geometrical Factors in Bi-layered Tube Hydroforming
NASA Astrophysics Data System (ADS)
Alaswad, A.; Olabi, A. G.; Benyounis, K. Y.
2011-01-01
In the last years many researchers were concentrating to develop and design new unconventional metal forming processes. Among such new technologies, tube hydroforming was proved as one of the most promising. Geometries of the tube and die were found to have significant effects on the hydroformed part. Based on the mathematical models, which describe the effect of the geometrical factors on bi-layered tube hydroforming, a multi-response optimization study was proposed in this paper with the aim to achieve different quality objectives for two different criteria. The optimal geometrical factors of bi-layered tube hydroforming combinations were tabulated and discussed.
NASA Astrophysics Data System (ADS)
Nguyen, Q. H.; Choi, S. B.
2010-11-01
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.
Geometric optimization of a neutron detector based on a lithium glass-polymer composite
NASA Astrophysics Data System (ADS)
Mayer, M.; Nattress, J.; Trivelpiece, C.; Jovanovic, I.
2015-06-01
We report on the simulation and optimization of a neutron detector based on a glass-polymer composite that achieves high gamma rejection. Lithium glass is embedded in polyvinyltoluene in three geometric forms: disks, rods, and spheres. Optimal shape, geometric configuration, and size of the lithium glass fragments are determined using Geant4 simulations. All geometrical configurations maintain an approximate 7% glass to polymer mass ratio. Results indicate a 125-mm diameter as the optimal detector size for initial prototype design achieving a 10% efficiency for the thermalization of incident fission neutrons from 252Cf. The geometrical features of a composite detector are shown to have little effect on the intrinsic neutron efficiency, but a significant effect on the gamma rejection is observed. The sphere geometry showed the best overall performance with an intrinsic neutron efficiency of approximately 6% with a gamma rejection better than 10-7 for 280-?m diameter spheres. These promising results provide a motivation for prototype composite detector development based on the simulated designs.
Geometric versus numerical optimal control of a dissipative spin-(1/2) particle
Lapert, M.; Sugny, D.; Zhang, Y.; Braun, M.; Glaser, S. J.
2010-12-15
We analyze the saturation of a nuclear magnetic resonance (NMR) signal using optimal magnetic fields. We consider both the problems of minimizing the duration of the control and its energy for a fixed duration. We solve the optimal control problems by using geometric methods and a purely numerical approach, the grape algorithm, the two methods being based on the application of the Pontryagin maximum principle. A very good agreement is obtained between the two results. The optimal solutions for the energy-minimization problem are finally implemented experimentally with available NMR techniques.
Optimization of bond transducer vibrations using active and semiactive control
NASA Astrophysics Data System (ADS)
Neubauer, Marcus; Brökelmann, Michael; Schwarzendahl, Sebastian M.; Hesse, Hans-J.; Wallaschek, Jörg
2012-04-01
In ultrasonic wire bonding the required vibrations are generated by an ultrasonic transducer driven in its longitudinal mode. Asymmetries lead to additional orthogonal motions, which result in unwanted fluctuating normal forces in the friction contact. In this publication, a novel design of an ultrasonic transducer with control actuators is presented. The parasitic vibrations are damped in an active control and by the semi-active piezoelectric shunt damping with inductance-resistance networks. A Finite-Element model is developed to optimize the dimensions and the placement of the piezoceramics and to tune the electrical networks. Measurements are conducted on a prototype transducer which validate the simulation results.
NASA Technical Reports Server (NTRS)
Horowitz, Stephen; Chen, Tai-An; Chandrasekaran, Venkataraman; Tedjojuwono, Ken; Cattafesta, Louis; Nishida, Toshikazu; Sheplak, Mark
2004-01-01
This paper presents a geometric Moir optical-based floating-element shear stress sensor for wind tunnel turbulence measurements. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Measured results indicate a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.
Optimization of the blade trailing edge geometric parameters for a small scale ORC turbine
NASA Astrophysics Data System (ADS)
Zhang, L.; Zhuge, W. L.; Peng, J.; Liu, S. J.; Zhang, Y. J.
2013-12-01
In general, the method proposed by Whitfield and Baines is adopted for the turbine preliminary design. In this design procedure for the turbine blade trailing edge geometry, two assumptions (ideal gas and zero discharge swirl) and two experience values (WR and γ) are used to get the three blade trailing edge geometric parameters: relative exit flow angle β6, the exit tip radius R6t and hub radius R6h for the purpose of maximizing the rotor total-to-static isentropic efficiency. The method above is established based on the experience and results of testing using air as working fluid, so it does not provide a mathematical optimal solution to instruct the optimization of geometry parameters and consider the real gas effects of the organic, working fluid which must be taken into consideration for the ORC turbine design procedure. In this paper, a new preliminary design and optimization method is established for the purpose of reducing the exit kinetic energy loss to improve the turbine efficiency ηts, and the blade trailing edge geometric parameters for a small scale ORC turbine with working fluid R123 are optimized based on this method. The mathematical optimal solution to minimize the exit kinetic energy is deduced, which can be used to design and optimize the exit shroud/hub radius and exit blade angle. And then, the influence of blade trailing edge geometric parameters on turbine efficiency ηts are analysed and the optimal working ranges of these parameters for the equations are recommended in consideration of working fluid R123. This method is used to modify an existing ORC turbine exit kinetic energy loss from 11.7% to 7%, which indicates the effectiveness of the method. However, the internal passage loss increases from 7.9% to 9.4%, so the only way to consider the influence of geometric parameters on internal passage loss is to give the empirical ranges of these parameters, such as the recommended ranges that the value of γ is at 0.3 to 0.4, and the value of τ is at 0.5 to 0.6.
Optimization of the Geometric Phase Sensitivity of an Array of Atom Ring Interferometers
NASA Astrophysics Data System (ADS)
Sandoval-Sanchez, Karina; Campo, Christian; Rivera, Tabitha; Toland, John
2015-05-01
Sagnac, and Aharonov-Bohm phase shifts are important geometric phase shifts in atom interferometry. These phase shifts characterize rotational and magnetic field interference effects respectively. Theoretical explorations have shown that a series of ring interferometers can be connected in series to increase the sensitivity of the overall device while keeping the maximum path separation less than the coherence length of the atoms. It has also been shown that the application of an area chirp to the rings will further enhance the sensitivity of the array of rings to geometric phase shifts. Area chirp refers to characterizing all of the rings in the array to a fixed percentage of a reference ring, this allows for the phase shifts in each ring to be characterized by one ring. The goal of this project is to determine a set of parameters namely kL, the product of the ring circumference and the wave number and γ, the chirp factor for the area chirp, that optimize the geometric phase sensitivity for an array of N rings. We model the transmission coefficient of a quantum matter wave through an area chirped array of interferometers as a function of phase, using transfer matrices to represent the transmission and reflection of individual rings in the array. Isolated transmission resonances represent the domain of interest, these are regions of high phase sensitivity. After optimizing a ring array without loss we apply velocity broadening to the input matter waves to investigate a more realistic output.
Witte, Marnix G.; Geer, Joris van der; Schneider, Christoph; Lebesque, Joos V.; Alber, Markus; Herk, Marcel van
2007-09-15
The purpose of this work was the development of a probabilistic planning method with biological cost functions that does not require the definition of margins. Geometrical uncertainties were integrated in tumor control probability (TCP) and normal tissue complication probability (NTCP) objective functions for inverse planning. For efficiency reasons random errors were included by blurring the dose distribution and systematic errors by shifting structures with respect to the dose. Treatment plans were made for 19 prostate patients following four inverse strategies: Conformal with homogeneous dose to the planning target volume (PTV), a simultaneous integrated boost using a second PTV, optimization using TCP and NTCP functions together with a PTV, and probabilistic TCP and NTCP optimization for the clinical target volume without PTV. The resulting plans were evaluated by independent Monte Carlo simulation of many possible treatment histories including geometrical uncertainties. The results showed that the probabilistic optimization technique reduced the rectal wall volume receiving high dose, while at the same time increasing the dose to the clinical target volume. Without sacrificing the expected local control rate, the expected rectum toxicity could be reduced by 50% relative to the boost technique. The improvement over the conformal technique was larger yet. The margin based biological technique led to toxicity in between the boost and probabilistic techniques, but its control rates were very variable and relatively low. During evaluations, the sensitivity of the local control probability to variations in biological parameters appeared similar for all four strategies. The sensitivity to variations of the geometrical error distributions was strongest for the probabilistic technique. It is concluded that probabilistic optimization based on tumor control probability and normal tissue complication probability is feasible. It results in robust prostate treatment plans with an improved balance between local control and rectum toxicity, compared to conventional techniques.
Implementation and Optimization of miniGMG - a Compact Geometric Multigrid Benchmark
Williams, Samuel; Kalamkar, Dhiraj; Singh, Amik; Deshpande, Anand M.; Straalen, Brian Van; Smelyanskiy, Mikhail; Almgren, Ann; Dubey, Pradeep; Shalf, John; Oliker, Leonid
2012-12-01
Multigrid methods are widely used to accelerate the convergence of iterative solvers for linear systems used in a number of different application areas. In this report, we describe miniGMG, our compact geometric multigrid benchmark designed to proxy the multigrid solves found in AMR applications. We explore optimization techniques for geometric multigrid on existing and emerging multicore systems including the Opteron-based Cray XE6, Intel Sandy Bridge and Nehalem-based Infiniband clusters, as well as manycore-based architectures including NVIDIA's Fermi and Kepler GPUs and Intel's Knights Corner (KNC) co-processor. This report examines a variety of novel techniques including communication-aggregation, threaded wavefront-based DRAM communication-avoiding, dynamic threading decisions, SIMDization, and fusion of operators. We quantify performance through each phase of the V-cycle for both single-node and distributed-memory experiments and provide detailed analysis for each class of optimization. Results show our optimizations yield significant speedups across a variety of subdomain sizes while simultaneously demonstrating the potential of multi- and manycore processors to dramatically accelerate single-node performance. However, our analysis also indicates that improvements in networks and communication will be essential to reap the potential of manycore processors in large-scale multigrid calculations.
NASA Astrophysics Data System (ADS)
Mignani, A. G.; Ciaccheri, L.; Giannelli, L.; Mencaglia, A. A.
2012-03-01
An experimental study was carried out, aimed at optimizing the optical/geometrical configuration for measuring the concentration of biological cells by means of static light scattering measurements. A LED-based optoelectronic setup making use of optical fibers was experimented, as the precursor of a low-cost device to be integrated in instrumentation for cytometry. Two biological sample types were considered as test samples of the most popular analyses - cervical cells and urine, respectively. The most suitable wavelengths and detecting angles were identified, and calibration curves were calculated.
Geometrical optimization of sensors for eddy currents nondestructive testing and evaluation
Thollon, F.; Burais, N.
1995-05-01
Design of Non Destructive Testing (NDT) and Non Destructive Evaluation (NDE) sensors is possible by solving Maxwell`s relations with FEM or BIM. But the large number of geometrical and electrical parameters of sensor and tested material implies many results that don`t give necessarily a well adapted sensor. The authors have used a genetic algorithm for automatic optimization. After having tested this algorithm with analytical solution of Maxwell`s relations for cladding thickness measurement, the method has been implemented in finite element package.
Dinkla, Anna M. Laarse, Rob van der; Koedooder, Kees; Petra Kok, H.; Wieringen, Niek van; Pieters, Bradley R.; Bel, Arjan
2015-01-15
Purpose: Dose optimization for stepping source brachytherapy can nowadays be performed using automated inverse algorithms. Although much quicker than graphical optimization, an experienced treatment planner is required for both methods. With automated inverse algorithms, the procedure to achieve the desired dose distribution is often based on trial-and-error. Methods: A new approach for stepping source prostate brachytherapy treatment planning was developed as a quick and user-friendly alternative. This approach consists of the combined use of two novel tools: Enhanced geometrical optimization (EGO) and interactive inverse planning (IIP). EGO is an extended version of the common geometrical optimization method and is applied to create a dose distribution as homogeneous as possible. With the second tool, IIP, this dose distribution is tailored to a specific patient anatomy by interactively changing the highest and lowest dose on the contours. Results: The combined use of EGO–IIP was evaluated on 24 prostate cancer patients, by having an inexperienced user create treatment plans, compliant to clinical dose objectives. This user was able to create dose plans of 24 patients in an average time of 4.4 min/patient. An experienced treatment planner without extensive training in EGO–IIP also created 24 plans. The resulting dose-volume histogram parameters were comparable to the clinical plans and showed high conformance to clinical standards. Conclusions: Even for an inexperienced user, treatment planning with EGO–IIP for stepping source prostate brachytherapy is feasible as an alternative to current optimization algorithms, offering speed, simplicity for the user, and local control of the dose levels.
Parametric geometric model and shape optimization of an underwater glider with blended-wing-body
NASA Astrophysics Data System (ADS)
Sun, Chunya; Song, Baowei; Wang, Peng
2015-11-01
Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.
Geometric-attributes-based segmentation of cortical bone slides using optimized neural networks.
Hage, Ilige S; Hamade, Ramsey F
2016-05-01
In cortical bone, solid (lamellar and interstitial) matrix occupies space left over by porous microfeatures such as Haversian canals, lacunae, and canaliculi-containing clusters. In this work, pulse-coupled neural networks (PCNN) were used to automatically distinguish the microfeatures present in histology slides of cortical bone. The networks' parameters were optimized using particle swarm optimization (PSO). When forming the fitness functions for the PSO, we considered the microfeatures' geometric attributes-namely, their size (based on measures of elliptical perimeter or area), shape (based on measures of compactness or the ratio of minor axis length to major axis length), and a two-way combination of these two geometric attributes. This hybrid PCNN-PSO method was further enhanced for pulse evaluation by combination with yet another method, adaptive threshold (AT), where the PCNN algorithm is repeated until the best threshold is found corresponding to the maximum variance between two segmented regions. Together, this framework of using PCNN-PSO-AT constitutes, we believe, a novel framework in biomedical imaging. Using this framework and extracting microfeatures from only one training image, we successfully extracted microfeatures from other test images. The high fidelity of all resultant segments was established using quantitative metrics such as precision, specificity, and Dice indices. PMID:26104115
An optimal hydrogen-bond surrogate for α-helices.
Joy, Stephen T; Arora, Paramjit S
2016-04-14
Substitution of a main chain i → i + 4 hydrogen bond with a covalent bond can nucleate and stabilize the α-helical conformation in peptides. Herein we describe the potential of different alkene isosteres to mimic intramolecular hydrogen bonds and stabilize α-helices in diverse peptide sequences. PMID:27046675
Coogan, Sean C P; Raubenheimer, David; Stenhouse, Gordon B; Nielsen, Scott E
2014-01-01
Nutrient balance is a strong determinant of animal fitness and demography. It is therefore important to understand how the compositions of available foods relate to required balance of nutrients and habitat suitability for animals in the wild. These relationships are, however, complex, particularly for omnivores that often need to compose balanced diets by combining their intake from diverse nutritionally complementary foods. Here we apply geometric models to understand how the nutritional compositions of foods available to an omnivorous member of the order Carnivora, the grizzly bear (Ursus arctos L.), relate to optimal macronutrient intake, and assess the seasonal nutritional constraints on the study population in west-central Alberta, Canada. The models examined the proportion of macronutrients that bears could consume by mixing their diet from food available in each season, and assessed the extent to which bears could consume the ratio of protein to non-protein energy previously demonstrated using captive bears to optimize mass gain. We found that non-selective feeding on ungulate carcasses provided a non-optimal macronutrient balance with surplus protein relative to fat and carbohydrate, reflecting adaptation to an omnivorous lifestyle, and that optimization through feeding selectively on different tissues of ungulate carcasses is unlikely. Bears were, however, able to dilute protein intake to an optimal ratio by mixing their otherwise high-protein diet with carbohydrate-rich fruit. Some individual food items were close to optimally balanced in protein to non-protein energy (e.g. Hedysarum alpinum roots), which may help explain their dietary prevalence. Ants may be consumed particularly as a source of lipids. Overall, our analysis showed that most food available to bears in the study area were high in protein relative to lipid or carbohydrate, suggesting the lack of non-protein energy limits the fitness (e.g. body size and reproduction) and population density of grizzly bears in this ecosystem. PMID:24841821
Coogan, Sean C. P.; Raubenheimer, David; Stenhouse, Gordon B.; Nielsen, Scott E.
2014-01-01
Nutrient balance is a strong determinant of animal fitness and demography. It is therefore important to understand how the compositions of available foods relate to required balance of nutrients and habitat suitability for animals in the wild. These relationships are, however, complex, particularly for omnivores that often need to compose balanced diets by combining their intake from diverse nutritionally complementary foods. Here we apply geometric models to understand how the nutritional compositions of foods available to an omnivorous member of the order Carnivora, the grizzly bear (Ursus arctos L.), relate to optimal macronutrient intake, and assess the seasonal nutritional constraints on the study population in west-central Alberta, Canada. The models examined the proportion of macronutrients that bears could consume by mixing their diet from food available in each season, and assessed the extent to which bears could consume the ratio of protein to non-protein energy previously demonstrated using captive bears to optimize mass gain. We found that non-selective feeding on ungulate carcasses provided a non-optimal macronutrient balance with surplus protein relative to fat and carbohydrate, reflecting adaptation to an omnivorous lifestyle, and that optimization through feeding selectively on different tissues of ungulate carcasses is unlikely. Bears were, however, able to dilute protein intake to an optimal ratio by mixing their otherwise high-protein diet with carbohydrate-rich fruit. Some individual food items were close to optimally balanced in protein to non-protein energy (e.g. Hedysarum alpinum roots), which may help explain their dietary prevalence. Ants may be consumed particularly as a source of lipids. Overall, our analysis showed that most food available to bears in the study area were high in protein relative to lipid or carbohydrate, suggesting the lack of non-protein energy limits the fitness (e.g. body size and reproduction) and population density of grizzly bears in this ecosystem. PMID:24841821
Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization
NASA Technical Reports Server (NTRS)
Halbig, Michael C.; Singh, Mrityunjay
2008-01-01
Joining and integration methods are critically needed as enabling technologies for the full utilization of advanced ceramic components in aerospace and aeronautics applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. In the application, several SiC substrates with different hole patterns to form fuel and combustion air channels are bonded to form the injector. Diffusion bonding is a joining approach that offers uniform bonds with high temperature capability, chemical stability, and high strength. Diffusion bonding was investigated with the aid of titanium foils and coatings as the interlayer between SiC substrates to aid bonding. The influence of such variables as interlayer type, interlayer thickness, substrate finish, and processing time were investigated. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.
Geometric optimization of helical tail designs to calibrate swimming velocities of microswimmers
NASA Astrophysics Data System (ADS)
Demir, Ebru; Yesilyurt, Serhat
2014-11-01
Artificial microswimmers present both a solution and a challenge as alternative tools to be used in medical applications, namely, drug delivery and minimally invasive surgeries. Achieving desired amount of controlled displacement of microswimmers at desired velocities plays an important role in determining the success of such applications. In this study, a non-dimensionalised CFD model is utilised to investigate the effects of various geometrical parameters on swimming velocities of microswimmers with helical tails in cylindrical confinements, such as helix wavelength, helical body thickness, and diameter. To this end, a ``one wavelength long'' helical tail is placed inside a cylindrical channel of the same length with periodic boundary conditions applied to both ends, constituting an infinite helix model. As the channel diameter is kept constant, a parametric study of abovementioned geometric identities is conducted to observe the change in the swimming velocities. Furthermore, effects of helix-channel eccentricity and helix rotation about the longitudinal axis on swimming velocity of a dimensionally optimized helix are investigated to reveal near wall effects. The results are found to be in good agreement with the theoretical models existing in the literature.
Riemannian geometric approach to human arm dynamics, movement optimization, and invariance
NASA Astrophysics Data System (ADS)
Biess, Armin; Flash, Tamar; Liebermann, Dario G.
2011-03-01
We present a generally covariant formulation of human arm dynamics and optimization principles in Riemannian configuration space. We extend the one-parameter family of mean-squared-derivative (MSD) cost functionals from Euclidean to Riemannian space, and we show that they are mathematically identical to the corresponding dynamic costs when formulated in a Riemannian space equipped with the kinetic energy metric. In particular, we derive the equivalence of the minimum-jerk and minimum-torque change models in this metric space. Solutions of the one-parameter family of MSD variational problems in Riemannian space are given by (reparametrized) geodesic paths, which correspond to movements with least muscular effort. Finally, movement invariants are derived from symmetries of the Riemannian manifold. We argue that the geometrical structure imposed on the arm’s configuration space may provide insights into the emerging properties of the movements generated by the motor system.
Stereoelectronic requirements for optimal hydrogen-bond-catalyzed enolization.
Pápai, Imre; Hamza, Andrea; Pihko, Petri M; Wierenga, Rik K
2011-03-01
Protein crystallographic analysis of the active sites of enolizing enzymes and structural analysis of hydrogen-bonded carbonyl compounds in small molecule crystal structures, complemented by quantum chemical calculations on related model enolization reactions, suggest a new stereoelectronic model that accounts for the observed out-of-plane orientation of hydrogen-bond donors (HBDs) in the oxyanion holes of enolizing enzymes. The computational results reveal that the lone-pair directionality of HBDs characteristic for hydrogen-bonded carbonyls is reduced upon enolization, and the enolate displays almost no directional preference for hydrogen bonding. Positioning the HBDs perpendicular to the carbonyl plane induces strain in the catalyst-substrate complex, which is released upon enolization, resulting in more favorable kinetics and thermodynamics than the in-plane arrangement of HBDs. PMID:21308811
On the geometrical and mechanical multi-aspect optimization of PPy/MWCNT actuators
NASA Astrophysics Data System (ADS)
Khalili, Nazanin; Naguib, Hani E.; Kwon, Roy H.
2014-03-01
Polypyrrole (PPy) conducting polymers as one of the most well-known actuation materials have shown numerous applications in a variety of fields such as biomedical devices as well as biomimetic robotics. This study investigates the multiobjective optimization of a PPy/MWCNTs actuator through an electrochemomechanical model. The multilayer actuator is composed of a PVDF layer, as the core membrane and an electrolyte reservoir, as well as two one layer of a conjugated polymer and one layer of multiwalled carbon nanotubes deposited on each side of the PVDF layer. In order to obtain the optimum values for each decision variable (i.e., geometrical and electrochemical), the two main outputs of the bending actuator, the tip displacement and blocking force, have been mathematically modeled and formulated as the objective functions. A multiobjective optimization algorithm is applied to simultaneously maximize the blocking force and tip displacement generated by the actuator. Furthermore, a range for each design variable is defined within which none of the objective functions of the film-type actuator dominates the other one while they are both kept within an acceptable range. The results obtained from the mathematical model are experimentally verified. Moreover, in order to determine the performance of the fabricated actuator, its outputs are compared with their counterparts of a neat PPy actuator.
Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method
Oudjene, M.; Ben-Ayed, L.; Batoz, J.-L.
2007-05-17
The determination of optimum tool shapes in clinch forming process is needed to achieve the required high quality of clinch joints. The design of the tools (punch and die) is crucial since the strength of the clinch joints is closely correlated to the tools geometry. To increase the strength of clinch joints, an automatic optimization procedure is developed. The objective function is defined in terms of the maximum value of the tensile force, obtained by separation of the sheets. Feasibility constraints on the geometrical parameters are also taken into account. First, a Python Script is used to generate the ABAQUS finite element model, to run the computations and post-process results, which are exported in an ASCII file. Then, this ASCII file is read by a FORTRAN program, in which the response surface approximation and SQP algorithm are implemented. The results show the potential interest of the developed optimization procedure towards the improvement of the strength of the clinch forming joints to tensile loading.
Geometrical Optimization Of Clinch Forming Process Using The Response Surface Method
NASA Astrophysics Data System (ADS)
Oudjene, M.; Ben-Ayed, L.; Batoz, J.-L.
2007-05-01
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.
Optimization of the Geometric Beta for the SSR2 Cavities of the Project X
Solyak, N.; Vostrikov, A.; Yakovlev, V.P.; Awida, M.H.; Berrutti, P.; Gonin, I.V.; /Fermilab
2012-05-01
Project X based on the 3 GeV CW superconducting Linac and is currently in the R&D phase. The CW SC Linac starts from a low-energy SCRF section (2.1 - 165 MeV) containing three different types of resonators. HWR f = 162.5 MHz (2.1 - 11 MeV) having beta= 0.11, SSR1 f = 325 MHz (11 - 35 MeV) having beta = 0.21. In this paper we present the analysis that lead to the final design of SSR2 f = 325 MHz cavity (35 - 165 MeV). We present the results of optimization of the geometric beta and the comparison between single, double and triple spoke resonators used in Project X frontend. A {beta} optimization has been carried out for the last spoke cavity section of Project X front end. The optimization process of {beta}{sub opt} for a single spoke resonator family SSR2 shown that {beta}{sub opt} = 0.47 looks better than the previous choice, which is {beta}{sub opt} = 0.4. This change can save some cavities and provide the same final energy for this section, 160 MeV. Single double and triple spoke resonator performances have been compared. The best option is the single spoke resonator SSR2 because the NTTF of a multi-spoke resonator is much narrower than a single one. In the energy range considered (40-160 MeV) the most efficient resonator is the single spoke one.
NASA Astrophysics Data System (ADS)
Newman, James Charles, III
1997-10-01
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.
Galbraith; Schreiner; Harris; Wei; Wittkopp; Shaik
2000-04-14
The Bergman cyclization of (Z)-hex-3-ene-1,5-diynes (1, enediynes), which produces pharmacologically important DNA-cleaving biradicals (1,4-benzyne, 2), was studied by using Hartree-Fock (HF) and density-functional theory (DFT) based valence bond (VB) methods (VB-HF and VB-DFT, respectively). We found that only three VB configurations are needed to arrive at results not too far from complete active space [CASSCF(6 x 6)] computations, while the quality of VB-DTF utilizing the same three configurations improves upon CASSCF(6 x 6) analogous to CASPT2. The dominant VB configuration in 1 contributes little to 2, while the most important biradical configuration in 2 plays a negligible role in 1. The avoided crossing of the energy curves of these two configurations along the reaction coordinate leads to the transition state (TS). As a consequence of the shape and position of the crossing section, the changes in geometry and in the electronic wavefunction along the reaction coordinate are non-synchronous; the TS is geometrically approximately 80% product-like and electronically approximately 70% reactant-like. While the pi resonance in the TS is very small, it is large (64.4 kcal mol(-1)) for 2 (cf. benzene=61.5 kcal mol(-1)). As a consequence, substituents operating on the sigma electrons should be much more effective in changing the Bergman reaction cyclization barrier. Furthermore, additional sigma resonance in 2 results in unusually high values for the nucleus-independent chemical shift (NICS, a direct measure for aromaticity). Similarly, the high NICS value of the TS is due mostly to sigma resonance to which the NICS procedure is relatively sensitive. PMID:10840967
NASA Astrophysics Data System (ADS)
Moroni, Giovanni; Syam, Wahyudin P.; Petrò, Stefano
2014-08-01
Product quality is a main concern today in manufacturing; it drives competition between companies. To ensure high quality, a dimensional inspection to verify the geometric properties of a product must be carried out. High-speed non-contact scanners help with this task, by both speeding up acquisition speed and increasing accuracy through a more complete description of the surface. The algorithms for the management of the measurement data play a critical role in ensuring both the measurement accuracy and speed of the device. One of the most fundamental parts of the algorithm is the procedure for fitting the substitute geometry to a cloud of points. This article addresses this challenge. Three relevant geometries are selected as case studies: a non-linear least-squares fitting of a circle, sphere and cylinder. These geometries are chosen in consideration of their common use in practice; for example the sphere is often adopted as a reference artifact for performance verification of a coordinate measuring machine (CMM) and a cylinder is the most relevant geometry for a pin-hole relation as an assembly feature to construct a complete functioning product. In this article, an improvement of the initial point guess for the Levenberg-Marquardt (LM) algorithm by employing a chaos optimization (CO) method is proposed. This causes a performance improvement in the optimization of a non-linear function fitting the three geometries. The results show that, with this combination, a higher quality of fitting results a smaller norm of the residuals can be obtained while preserving the computational cost. Fitting an ‘incomplete-point-cloud’, which is a situation where the point cloud does not cover a complete feature e.g. from half of the total part surface, is also investigated. Finally, a case study of fitting a hemisphere is presented.
NASA Astrophysics Data System (ADS)
Seo, Hee; Lee, Se Hyung; Kim, Chan Hyeong; An, So Hyun; Lee, Ju Hahn; Lee, Chun Sik
2008-06-01
A novel type of Compton camera, called a double-scattering Compton imager (DOCI), is under development for nuclear medicine and molecular imaging applications. Two plane-type position-sensitive semiconductor detectors are employed as the scatterer detectors, and a 3″×3″ cylindrical NaI(Tl) scintillation detector is employed as the absorber detector. This study determined the optimal geometrical configuration of these component detectors to maximize the performance of the Compton camera in imaging resolution and sensitivity. To that end, the Compton camera was simulated very realistically, with the GEANT4 detector simulation toolkit, including various detector characteristics such as energy resolution, spatial resolution, energy discrimination, and Doppler energy broadening. According to our simulation results, the Compton camera is expected to show its maximum performance when the two scatterer detectors are positioned in parallel, with ˜8 cm of separation. The Compton camera will show the maximum performance also when the gamma-ray energy is about 500 keV, which suggests that the Compton camera is a suitable device to image the distribution of the positron emission tomography (PET) isotopes in the human body.
Process optimization for diffusion bonding of tungsten with EUROFER97 using a vanadium interlayer
NASA Astrophysics Data System (ADS)
Basuki, Widodo Widjaja; Aktaa, Jarir
2015-04-01
Solid-state diffusion bonding is a selected joining technology to bond divertor components consisting of tungsten and EUROFER97 for application in fusion power plants. Due to the large mismatch in their coefficient of thermal expansions, which leads to serious thermally induced residual stresses after bonding, a thin vanadium plate is introduced as an interlayer. However, the diffusion of carbon originated from EUROFER97 in the vanadium interlayer during the bonding process can form a vanadium carbide layer, which has detrimental influences on the mechanical properties of the joint. For optimal bonding results, the thickness of this layer and the residual stresses has to be decreased sufficiently without a significant reduction of material transport especially at the vanadium/tungsten interface, which can be achieved by varying the diffusion bonding temperature and duration. The investigation results show that at a sufficiently low bonding temperature of 700 °C and a bonding duration of 4 h, the joint reaches a reasonable high ductility and toughness especially at elevated test temperature of 550 °C with elongation to fracture of 20% and mean absorbed Charpy impact energy of 2 J (using miniaturized Charpy impact specimens). The strength of the bonded materials is about 332 MPa at RT and 291 MPa at 550 °C. Furthermore, a low bonding temperature of 700 °C can also help to avoid the grain coarsening and the alteration of the grain structure especially of the EUROFER97 close to the bond interface.
NASA Astrophysics Data System (ADS)
Paul, Bijan Kumar; Guchhait, Nikhil
2013-02-01
Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ?(r) and Laplacian ?2?(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ?(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems.
Optimization of laser-assisted glass frit bonding process by response surface methodology
NASA Astrophysics Data System (ADS)
Wang, Wen; Xiao, Yanyi; Wu, Xingyang; Zhang, Jianhua
2016-03-01
In this work, a systematic study on laser-assisted glass frit bonding process was carried out by response surface methodology (RSM). Laser power, sealing speed and spot diameter were considered as key bonding parameters. Combined with a central rotatable experimental design, RSM was employed to establish mathematical model to predict the relationship between the shear force after bonding and the bonding process parameters. The model was validated experimentally. Based on the model, the interaction effects of the process parameters on the shear force were analyzed and the optimum bonding parameters were achieved. The results indicate that the model can be used to illustrate the relationship between the shear force and the bonding parameters. The predicted results obtained under the optimized parameters by the models are consistent with the experimental results.
Inter- and intra-chain disulfide bond prediction based on optimal feature selection.
Niu, Shen; Huang, Tao; Feng, Kai-Yan; He, Zhisong; Cui, Weiren; Gu, Lei; Li, Haipeng; Cai, Yu-Dong; Li, Yixue
2013-03-01
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
Cooperative Effects and Optimal Halogen Bonding Motifs for Self-Assembling Systems
2015-01-01
Halogen bonding, due to its directionality and tunable strength, is being increasingly utilized in self-assembling materials and crystal engineering. Using density functional theory (DFT) and molecular mechanics (OPLS/CM1Ax) calculations, multiply halogen bonded complexes of brominated imidazole and pyridine are investigated along with their potential in construction of self-assembling architectures. Dimers with 1–10 halogen bonds are considered and reveal maximal binding energies of 3–36 kcal/mol. Cooperative (nonadditive) effects are found in complexes that extend both along and perpendicular to the halogen bonding axes, with interaction energies depending on polarization, secondary interactions, and ring spacers. Four structural motifs were identified to yield optimal halogen bonding. For the largest systems, the excellent agreement found between the DFT and OPLS/CM1Ax results supports the utility of the latter approach for analysis and design of self-assembling supramolecular structures. PMID:24678636
Mohammadipour, Amir H; Alavi, Seyed Hafez
2009-03-01
This study attempts to optimize the geometric cross-section dimensions of raised pedestrian crosswalks (RPC), employing safety and comfort measures which reflect environmental conditions and drivers behavioral patterns in Qazvin, Iran. Geometric characteristics including street width, ramp lengths, top flat crown length and height, and 4672 spot speed observations of 23 implemented RPCs were considered. The authors established geometric and analytical equations to satisfactorily express the discomfort that vehicle occupants experience while traversing an RPC and the crossing risk to pedestrians. Artificial neural networks (ANN) are reputed for their capability to learn and generalize complex engineering phenomena and were therefore adopted to cope with the highly nonlinear relationship between the before-RPC spot speeds, the geometric characteristics, and spot speeds on the RPC. This on-RPC spot speed has been utilized for computing the above-mentioned criteria. Combining these criteria, a new judgment index was created to identify the optimum RPC which fulfills the highest comfort and safety levels. It was observed that the variable with the highest impact is the second ramp length, followed by the first ramp length, top flat crown length, before-RPC spot speed, height, and street width, in order of magnitude. PMID:19245891
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...
NASA Technical Reports Server (NTRS)
Hrinda, Glenn A.; Nguyen, Duc T.
2008-01-01
A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.
E–H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound
Robinson, Thomas P; De Rosa, Daniel M; Aldridge, Simon; Goicoechea, Jose M
2015-01-01
The synthesis of a phosphorus(III) compound bearing a N,N-bis(3,5-di-tert-butyl-2-phenoxy)amide ligand is reported. This species has been found to react with ammonia and water, activating the E–H bonds in both substrates by formal oxidative addition to afford the corresponding phosphorus(V) compounds. In the case of water, both O–H bonds can be activated, splitting the molecule into its constituent elements. To our knowledge, this is the first example of a compound based on main group elements that sequentially activates water in this manner. PMID:26404498
NASA Astrophysics Data System (ADS)
Hasbullah Mohd Isa, Wan; Fikri Muhammad, Khairul; Mohd Khairuddin, Ismail; Ishak, Ismayuzri; Razlan Yusoff, Ahmad
2016-02-01
This paper presents the new form of coils for electromagnetic energy harvesting system based on topology optimization method which look-liked a cap to maximize the power output. It could increase the number of magnetic flux linkage interception of a cylindrical permanent magnet which in this case is of 10mm diameter. Several coils with different geometrical properties have been build and tested on a vibration generator with frequency of 100Hz. The results showed that the coil with lowest number of winding transduced highest power output of 680μW while the highest number of windings generated highest voltage output of 0.16V.
NASA Astrophysics Data System (ADS)
Archer, Cristina; Ghaisas, Niranjan
2015-04-01
The energy generation at a wind farm is controlled primarily by the average wind speed at hub height. However, two other factors impact wind farm performance: 1) the layout of the wind turbines, in terms of spacing between turbines along and across the prevailing wind direction; staggering or aligning consecutive rows; angles between rows, columns, and prevailing wind direction); and 2) atmospheric stability, which is a measure of whether vertical motion is enhanced (unstable), suppressed (stable), or neither (neutral). Studying both factors and their complex interplay with Large-Eddy Simulation (LES) is a valid approach because it produces high-resolution, 3D, turbulent fields, such as wind velocity, temperature, and momentum and heat fluxes, and it properly accounts for the interactions between wind turbine blades and the surrounding atmospheric and near-surface properties. However, LES are computationally expensive and simulating all the possible combinations of wind directions, atmospheric stabilities, and turbine layouts to identify the optimal wind farm configuration is practically unfeasible today. A new, geometry-based method is proposed that is computationally inexpensive and that combines simple geometric quantities with a minimal number of LES simulations to identify the optimal wind turbine layout, taking into account not only the actual frequency distribution of wind directions (i.e., wind rose) at the site of interest, but also atmospheric stability. The geometry-based method is calibrated with LES of the Lillgrund wind farm conducted with the Software for Offshore/onshore Wind Farm Applications (SOWFA), based on the open-access OpenFOAM libraries. The geometric quantities that offer the best correlations (>0.93) with the LES results are the blockage ratio, defined as the fraction of the swept area of a wind turbine that is blocked by an upstream turbine, and the blockage distance, the weighted distance from a given turbine to all upstream turbines that can potentially block it. Based on blockage ratio and distance, an optimization procedure is proposed that explores many different layout variables and identifies, given actual wind direction and stability distributions, the optimal wind farm layout, i.e., the one with the highest wind energy production. The optimization procedure is applied to both the calibration wind farm (Lillgrund) and a test wind farm (Horns Rev) and a number of layouts more efficient than the existing ones are identified. The optimization procedure based on geometric models proposed here can be applied very quickly (within a few hours) to any proposed wind farm, once enough information on wind direction frequency and, if available, atmospheric stability frequency has been gathered and once the number of turbines and/or the areal extent of the wind farm have been identified.
Rakhmilevitch, David; Sarkar, Soumyajit; Bitton, Ora; Kronik, Leeor; Tal, Oren
2016-03-01
Molecular junctions based on ferromagnetic electrodes allow the study of electronic spin transport near the limit of spintronics miniaturization. However, these junctions reveal moderate magnetoresistance that is sensitive to the orbital structure at their ferromagnet-molecule interfaces. The key structural parameters that should be controlled in order to gain high magnetoresistance have not been established, despite their importance for efficient manipulation of spin transport at the nanoscale. Here, we show that single-molecule junctions based on nickel electrodes and benzene molecules can yield a significant anisotropic magnetoresistance of up to ∼200% near the conductance quantum G0. The measured magnetoresistance is mechanically tuned by changing the distance between the electrodes, revealing a nonmonotonic response to junction elongation. These findings are ascribed with the aid of first-principles calculations to variations in the metal-molecule orientation that can be adjusted to obtain highly spin-selective orbital hybridization. Our results demonstrate the important role of geometrical considerations in determining the spin transport properties of metal-molecule interfaces. PMID:26926769
A Single-Lap Joint Adhesive Bonding Optimization Method Using Gradient and Genetic Algorithms
NASA Technical Reports Server (NTRS)
Smeltzer, Stanley S., III; Finckenor, Jeffrey L.
1999-01-01
A natural process for any engineer, scientist, educator, etc. is to seek the most efficient method for accomplishing a given task. In the case of structural design, an area that has a significant impact on the structural efficiency is joint design. Unless the structure is machined from a solid block of material, the individual components which compose the overall structure must be joined together. The method for joining a structure varies depending on the applied loads, material, assembly and disassembly requirements, service life, environment, etc. Using both metallic and fiber reinforced plastic materials limits the user to two methods or a combination of these methods for joining the components into one structure. The first is mechanical fastening and the second is adhesive bonding. Mechanical fastening is by far the most popular joining technique; however, in terms of structural efficiency, adhesive bonding provides a superior joint since the load is distributed uniformly across the joint. The purpose of this paper is to develop a method for optimizing single-lap joint adhesive bonded structures using both gradient and genetic algorithms and comparing the solution process for each method. The goal of the single-lap joint optimization is to find the most efficient structure that meets the imposed requirements while still remaining as lightweight, economical, and reliable as possible. For the single-lap joint, an optimum joint is determined by minimizing the weight of the overall joint based on constraints from adhesive strengths as well as empirically derived rules. The analytical solution of the sin-le-lap joint is determined using the classical Goland-Reissner technique for case 2 type adhesive joints. Joint weight minimization is achieved using a commercially available routine, Design Optimization Tool (DOT), for the gradient solution while an author developed method is used for the genetic algorithm solution. Results illustrate the critical design variables as a function of adhesive properties and convergences of different joints based on the two optimization methods.
ERIC Educational Resources Information Center
Magnasco, Valerio
2008-01-01
Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and…
Geometrical optimization of an annulus Compton suppression system using Monte Carlo simulation.
Han, Jubong; Lee, K B; Park, T S; Lee, J M; Lee, S H
2013-11-01
We are planning to construct a Compton-suppression system permitting accurate and precise determinations of radioactivity of low-level environmental samples. An annulus guard detector (NaI) and a plug-in detector (NaI) are being used as suppression detectors with an HPGe primary detector. The geometry of the Compton suppression spectrometer was optimized by simulation with PENELOPE for obtaining the highest suppression factor (SF) for a point source. The results of the simulations show that the ultimate value of the suppression factor is 7.87 0.18, obtained when the source is located at 57% of an annuls guard detector. PMID:23583087
Optimal image alignment with random projections of manifolds: algorithm and geometric analysis.
Kokiopoulou, Effrosyni; Kressner, Daniel; Frossard, Pascal
2011-06-01
This paper addresses the problem of image alignment based on random measurements. Image alignment consists of estimating the relative transformation between a query image and a reference image. We consider the specific problem where the query image is provided in compressed form in terms of linear measurements captured by a vision sensor. We cast the alignment problem as a manifold distance minimization problem in the linear subspace defined by the measurements. The transformation manifold that represents synthesis of shift, rotation, and isotropic scaling of the reference image can be given in closed form when the reference pattern is sparsely represented over a parametric dictionary. We show that the objective function can then be decomposed as the difference of two convex functions (DC) in the particular case where the dictionary is built on Gaussian functions. Thus, the optimization problem becomes a DC program, which in turn can be solved globally by a cutting plane method. The quality of the solution is typically affected by the number of random measurements and the condition number of the manifold that describes the transformations of the reference image. We show that the curvature, which is closely related to the condition number, remains bounded in our image alignment problem, which means that the relative transformation between two images can be determined optimally in a reduced subspace. PMID:21189239
Geometric modeling of space-optimal unit-cell-based tissue engineering scaffolds
NASA Astrophysics Data System (ADS)
Rajagopalan, Srinivasan; Lu, Lichun; Yaszemski, Michael J.; Robb, Richard A.
2005-04-01
Tissue engineering involves regenerating damaged or malfunctioning organs using cells, biomolecules, and synthetic or natural scaffolds. Based on their intended roles, scaffolds can be injected as space-fillers or be preformed and implanted to provide mechanical support. Preformed scaffolds are biomimetic "trellis-like" structures which, on implantation and integration, act as tissue/organ surrogates. Customized, computer controlled, and reproducible preformed scaffolds can be fabricated using Computer Aided Design (CAD) techniques and rapid prototyping devices. A curved, monolithic construct with minimal surface area constitutes an efficient substrate geometry that promotes cell attachment, migration and proliferation. However, current CAD approaches do not provide such a biomorphic construct. We address this critical issue by presenting one of the very first physical realizations of minimal surfaces towards the construction of efficient unit-cell based tissue engineering scaffolds. Mask programmability, and optimal packing density of triply periodic minimal surfaces are used to construct the optimal pore geometry. Budgeted polygonization, and progressive minimal surface refinement facilitate the machinability of these surfaces. The efficient stress distributions, as deduced from the Finite Element simulations, favor the use of these scaffolds for orthopedic applications.
Optimizing galvanic pulse plating parameters to improve indium bump to bump bonding
NASA Astrophysics Data System (ADS)
Coleman, Jonathan J.; Rowen, Adam; Mani, Seethambal S.; Yelton, W. Graham; Arrington, Christian; Gillen, Rusty; Hollowell, Andrew E.; Okerlund, Daniel; Ionescu, Adrian
2010-02-01
The plating characteristics of a commercially available indium plating solution are examined and optimized to help meet the increasing performance demands of integrated circuits requiring substantial numbers of electrical interconnections over large areas. Current fabrication techniques rely on evaporation of soft metals, such as indium, into lift-off resist profiles. This becomes increasingly difficult to accomplish as pitches decrease and aspect ratios increase. To minimize pixel dimensions and maximize the number of pixels per unit area, lithography and electrochemical deposition (ECD) of indium has been investigated. Pulse ECD offers the capability of improving large area uniformity ideal for large area device hybridization. Electrochemical experimentation into lithographically patterned molds allow for large areas of bumps to be fabricated for low temperature indium to indium bonds. The galvanic pulse profile, in conjunction with the bath configuration, determines the uniformity of the plated array. This pulse is manipulated to produce optimal properties for hybridizing arrays of aligned and bonded indium bumps. The physical properties of the indium bump arrays are examined using a white light interferometer, a SEM and tensile pull testing. This paper provides details from the electroplating processes as well as conclusions leading to optimized plating conditions.
Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids
Lewis, Nathan S.; Freund, Michael S.; Briglin, Shawn M.; Tokumaru, Phil; Martin, Charles R.; Mitchell, David T.
2006-10-17
Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.
Spatiotemporal and geometric optimization of sensor arrays for detecting analytes in fluids
Lewis, Nathan S.; Freund, Michael S.; Briglin, Shawn S.; Tokumaru, Phillip; Martin, Charles R.; Mitchell, David
2009-09-29
Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.
Kosaka, Ryo; Yada, Toru; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi
2013-09-01
A hydrodynamically levitated centrifugal blood pump with a semi-open impeller has been developed for mechanical circulatory assistance. However, a narrow bearing gap has the potential to cause hemolysis. The purpose of the present study is to optimize the geometric configuration of the hydrodynamic step bearing in order to reduce hemolysis by expansion of the bearing gap. First, a numerical analysis of the step bearing, based on lubrication theory, was performed to determine the optimal design. Second, in order to assess the accuracy of the numerical analysis, the hydrodynamic forces calculated in the numerical analysis were compared with those obtained in an actual measurement test using impellers having step lengths of 0%, 33%, and 67% of the vane length. Finally, a bearing gap measurement test and a hemolysis test were performed. As a result, the numerical analysis revealed that the hydrodynamic force was the largest when the step length was approximately 70%. The hydrodynamic force calculated in the numerical analysis was approximately equivalent to that obtained in the measurement test. In the measurement test and the hemolysis test, the blood pump having a step length of 67% achieved the maximum bearing gap and reduced hemolysis, as compared with the pumps having step lengths of 0% and 33%. It was confirmed that the numerical analysis of the step bearing was effective, and the developed blood pump having a step length of approximately 70% was found to be a suitable configuration for the reduction of hemolysis. PMID:23834855
Vanderbei, Robert J.; P Latin-Small-Letter-Dotless-I nar, Mustafa C.; Bozkaya, Efe B.
2013-02-15
An American option (or, warrant) is the right, but not the obligation, to purchase or sell an underlying equity at any time up to a predetermined expiration date for a predetermined amount. A perpetual American option differs from a plain American option in that it does not expire. In this study, we solve the optimal stopping problem of a perpetual American option (both call and put) in discrete time using linear programming duality. Under the assumption that the underlying stock price follows a discrete time and discrete state Markov process, namely a geometric random walk, we formulate the pricing problem as an infinite dimensional linear programming (LP) problem using the excessive-majorant property of the value function. This formulation allows us to solve complementary slackness conditions in closed-form, revealing an optimal stopping strategy which highlights the set of stock-prices where the option should be exercised. The analysis for the call option reveals that such a critical value exists only in some cases, depending on a combination of state-transition probabilities and the economic discount factor (i.e., the prevailing interest rate) whereas it ceases to be an issue for the put.
Optimal tubular adhesive-bonded lap joint of the carbon fiber epoxy composite shaft
NASA Astrophysics Data System (ADS)
Kim, Ki S.; Kim, Won T.; Lee, Dai G.; Jun, Eui J.
The effects of the adhesive thickness and the adherend surface roughness on the fatigue strength of a tubular adhesive-bonded single lap joint were investigated using fatigue test specimens whose adherends were made of S45C carbon steel. Results of fatigue tests showed that the optimal arithmetic surface roughness of the adherends is about 2 microns and the optimal adhesive thickness is about 0.15 mm. Using these values, the prototype torsional adhesive joints were manufactured for power transmission shafts of an automotive vehicle or a small helicopter, and static tests under torque were performed on a single-lap joint, a single-lap joint with scarf, a double-lap joint, and a double-lap joint with scarf. It was found that the double-lap joint was superior among the joints, in terms of torque capacity and manufacturing cost.
NASA Astrophysics Data System (ADS)
Zhang, Yue; Sun, Xian; Thiele, Antje; Hinz, Stefan
2015-10-01
Synthetic aperture radar (SAR) systems, such as TanDEM-X, TerraSAR-X and Cosmo-SkyMed, acquire imagery with high spatial resolution (HR), making it possible to observe objects in urban areas with high detail. In this paper, we propose a new top-down framework for three-dimensional (3D) building reconstruction from HR interferometric SAR (InSAR) data. Unlike most methods proposed before, we adopt a generative model and utilize the reconstruction process by maximizing a posteriori estimation (MAP) through Monte Carlo methods. The reason for this strategy refers to the fact that the noisiness of SAR images calls for a thorough prior model to better cope with the inherent amplitude and phase fluctuations. In the reconstruction process, according to the radar configuration and the building geometry, a 3D building hypothesis is mapped to the SAR image plane and decomposed to feature regions such as layover, corner line, and shadow. Then, the statistical properties of intensity, interferometric phase and coherence of each region are explored respectively, and are included as region terms. Roofs are not directly considered as they are mixed with wall into layover area in most cases. When estimating the similarity between the building hypothesis and the real data, the prior, the region term, together with the edge term related to the contours of layover and corner line, are taken into consideration. In the optimization step, in order to achieve convergent reconstruction outputs and get rid of local extrema, special transition kernels are designed. The proposed framework is evaluated on the TanDEM-X dataset and performs well for buildings reconstruction.
Processing parameter optimization for the laser dressing of bronze-bonded diamond wheels
NASA Astrophysics Data System (ADS)
Deng, H.; Chen, G. Y.; Zhou, C.; Li, S. C.; Zhang, M. J.
2014-01-01
In this paper, a pulsed fiber-laser dressing method for bronze-bonded diamond wheels was studied systematically and comprehensively. The mechanisms for the laser dressing of bronze-bonded diamond wheels were theoretically analyzed, and the key processing parameters that determine the results of laser dressing, including the laser power density, pulse overlap ratio, ablation track line overlap ratio, and number of scanning cycles, were proposed for the first time. Further, the effects of these four key parameters on the oxidation-damaged layer of the material surface, the material removal efficiency, the material surface roughness, and the average protrusion height of the diamond grains were explored and summarized through pulsed laser ablation experiments. Under the current experimental conditions, the ideal values of the laser power density, pulse overlap ratio, ablation track line overlap ratio, and number of scanning cycles were determined to be 4.2 × 107 W/cm2, 30%, 30%, and 16, respectively. Pulsed laser dressing experiments were conducted on bronze-bonded diamond wheels using the optimized processing parameters; next, both the normal and tangential grinding forces produced by the dressed grinding wheel were measured while grinding alumina ceramic materials. The results revealed that the normal and tangential grinding forces produced by the laser-dressed grinding wheel during grinding were smaller than those of grinding wheels dressed using the conventional mechanical method, indicating that the pulsed laser dressing technology provides irreplaceable advantages relative to the conventional mechanical dressing method.
NASA Astrophysics Data System (ADS)
Asfahani, J.; Tlas, M.
2015-10-01
An easy and practical method for interpreting residual gravity anomalies due to simple geometrically shaped models such as cylinders and spheres has been proposed in this paper. This proposed method is based on both the deconvolution technique and the simplex algorithm for linear optimization to most effectively estimate the model parameters, e.g., the depth from the surface to the center of a buried structure (sphere or horizontal cylinder) or the depth from the surface to the top of a buried object (vertical cylinder), and the amplitude coefficient from the residual gravity anomaly profile. The method was tested on synthetic data sets corrupted by different white Gaussian random noise levels to demonstrate the capability and reliability of the method. The results acquired show that the estimated parameter values derived by this proposed method are close to the assumed true parameter values. The validity of this method is also demonstrated using real field residual gravity anomalies from Cuba and Sweden. Comparable and acceptable agreement is shown between the results derived by this method and those derived from real field data.
Methodology for optimal configuration in structural health monitoring of composite bonded joints
NASA Astrophysics Data System (ADS)
Quaegebeur, N.; Micheau, P.; Masson, P.; Castaings, M.
2012-10-01
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.
NASA Astrophysics Data System (ADS)
Kanatani, Kenichi
The “geometric AIC” and the “geometric MDL” have been proposed as model selection criteria for geometric fitting problems. These correspond to Akaike's “AIC” and Rissanen's “BIC” well known in the statistical estimation framework. Another well known criterion is Schwarz' “BIC”, but its counterpart for geometric fitting has not been known. This paper introduces the corresponding criterion, which we call the “geometric BIC”, and shows that it is of the same form as the geometric MDL. Our result gives a justification to the geometric MDL from the Bayesian principle.
Akimoto, Tetsuo . E-mail: takimoto@showa.gunma-u.ac.jp; Katoh, Hiroyuki; Kitamoto, Yoshizumi; Shirai, Katsuyuki; Shioya, Mariko; Nakano, Takashi
2006-04-01
Purpose: To evaluate the advantages of anatomy-based inverse optimization (IO) in planning high-dose-rate (HDR) brachytherapy. Methods and Materials: A total of 114 patients who received HDR brachytherapy (9 Gy in two fractions) combined with hypofractionated external beam radiotherapy (EBRT) were analyzed. The dose distributions of HDR brachytherapy were optimized using geometric optimization (GO) in 70 patients and by anatomy-based IO in the remaining 44 patients. The correlation between the dose-volume histogram parameters, including the urethral dose and the incidence of acute genitourinary (GU) toxicity, was evaluated. Results: The averaged values of the percentage of volume receiving 80-150% of the prescribed minimal peripheral dose (V{sub 8}-V{sub 15}) of the urethra generated by anatomy-based IO were significantly lower than the corresponding values generated by GO. Similarly, the averaged values of the minimal dose received by 5-50% of the target volume (D{sub 5}-D{sub 5}) obtained using anatomy-based IO were significantly lower than those obtained using GO. Regarding acute toxicity, Grade 2 or worse acute GU toxicity developed in 23% of all patients, but was significantly lower in patients for whom anatomy-based IO (16%) was used than in those for whom GO was used (37%), consistent with the reduced urethral dose (p <0.01). Conclusion: The results of this study suggest that anatomy-based IO is superior to GO for dose optimization in HDR brachytherapy for prostate cancer.
Dias, Francilena Maria Campos Santos; Pinzan-Vercelino, Célia Regina Maio; Tavares, Rudys Rodolfo de Jesus; Gurgel, Júlio de Araújo; Bramante, Fausto Silva; Fialho, Melissa Nogueira Proença
2015-01-01
OBJECTIVE: To compare shear bond strength of different direct bonding techniques of orthodontic brackets to acrylic resin surfaces. METHODS: The sample comprised 64 discs of chemically activated acrylic resin (CAAR) randomly divided into four groups: discs in group 1 were bonded by means of light-cured composite resin (conventional adhesive); discs in group 2 had surfaces roughened with a diamond bur followed by conventional direct bonding by means of light-cured composite resin; discs in group 3 were bonded by means of CAAR (alternative adhesive); and discs in group 4 had surfaces roughened with a diamond bur followed by direct bonding by means of CAAR. Shear bond strength values were determined after 24 hours by means of a universal testing machine at a speed of 0.5 mm/min, and compared by analysis of variance followed by post-hoc Tukey test. Adhesive remnant index (ARI) was measured and compared among groups by means of Kruskal-Wallis and Dunn tests. RESULTS: Groups 3 and 4 had significantly greater shear bond strength values in comparison to groups 1 and 2. Groups 3 and 4 yielded similar results. Group 2 showed better results when compared to group 1. In ARI analyses, groups 1 and 2 predominantly exhibited a score equal to 0, whereas groups 3 and 4 predominantly exhibited a score equal to 3. CONCLUSIONS: Direct bonding of brackets to acrylic resin surfaces using CAAR yielded better results than light-cured composite resin. Surface preparation with diamond bur only increased shear bond strength in group 2. PMID:26352846
Potrebko, Peter S; McCurdy, Boyd M C; Butler, James B; El-Gubtan, Adel S; Nugent, Zoann
2007-10-01
A fast, geometric beam angle optimization (BAO) algorithm for clinical intensity-modulated radiation therapy (IMRT) was implemented on ten localized prostate cancer patients on the Radiation Therapy Oncology Group (RTOG) 0126 protocol. The BAO algorithm computed the beam intersection volume (BIV) within the rectum and bladder using five and seven equiangular-spaced beams as a function of starting gantry angle for comparison to the V 75 Gy and V 70 Gy. A mathematical theory was presented to explain the correlation of BIV with dose and dose-volume metrics. The class solution 'W' pattern in the rectal V 75 Gy and V 70 Gy as a function of starting gantry angle using five equiangular-spaced beams (with two separate minima centered near 20 degrees and 50 degrees) was reproduced by the 5 BIV within the rectum. A strong correlation was found between the rectal 5 BIV and the rectal V 75 Gy and V 70 Gy as a function of starting gantry angle. The BAO algorithm predicted the location of the two dosimetric minima in rectal V 75 Gy and V 70 Gy (optimal starting gantry angles) to within 5 degrees. It was demonstrated that the BIV geometric variations for seven equiangular-spaced beams were too small to translate into a strong dosimetric effect in the rectal V 75 Gy and V 70 Gy. The relatively flat distribution with starting gantry angle of the bladder V 75 Gy and V 70 Gy was reproduced by the bladder five and seven BIV for each patient. A geometric BAO method based on BIV has the advantage over dosimetric BAO methods of simplicity and rapid computation time. This algorithm can be used as a standalone optimization method or act as a rapid calculation filter to reduce the search space for a dosimetric BAO method. Given the clinically infeasible computation times of many dosimetric beam orientation optimization algorithms, this robust geometric BIV algorithm has the potential to facilitate beam angle selection for prostate IMRT in clinical practice. PMID:17985640
NASA Astrophysics Data System (ADS)
Shestakov, A. F.; Denisov, E. T.; Emel'Yanova, N. S.; Denisova, T. G.
2009-03-01
The energy and geometry of the transition state in reactions of the ethyl peroxyl radical with ethane, ethanol (its ? and ? C-H bonds), acetone, butanone-2, and acetaldehyde were calculated by the density functional theory method. In all these reactions (except EtO2/ + ethanol ? C-H bond), the CHO reaction center has an almost linear configuration (? = 176 2); polar interaction only influences the r ? (CO) interatomic bond. In the reaction of EtO2/ with the ethanol ? C-H bond, it is the O-HO H-bond formed in the transition state that determines the configuration of the reaction center with the angle ?(CHO) = 160. The results were used to estimate the r ? (CH) and r ? (OH) interatomic bonds in the transition state by the method of intersecting parabolas and the contribution of polar interaction to the activation energy of reactions between peroxyl radicals and aldehydes and ketones.
Bayro-Corrochano, E J
2001-01-01
This paper shows the analysis and design of feedforward neural networks using the coordinate-free system of Clifford or geometric algebra. It is shown that real-, complex-, and quaternion-valued neural networks are simply particular cases of the geometric algebra multidimensional neural networks and that some of them can also be generated using support multivector machines (SMVMs). Particularly, the generation of radial basis function for neurocomputing in geometric algebra is easier using the SMVM, which allows one to find automatically the optimal parameters. The use of support vector machines in the geometric algebra framework expands its sphere of applicability for multidimensional learning. Interesting examples of nonlinear problems show the effect of the use of an adequate Clifford geometric algebra which alleviate the training of neural networks and that of SMVMs. PMID:18249926
Tjäderhane, Leo; Nascimento, Fabio D.; Breschi, Lorenzo; Mazzoni, Annalisa; Tersariol, Ivarne L.S.; Geraldeli, Saulo; Tezvergil-Mutluay, Arzu; Carrilho, Marcela R.; Carvalho, Ricardo M.; Tay, Franklin R.; Pashley, David H.
2012-01-01
Objectives Contemporary adhesives lose their bond strength to dentin regardless of the bonding system used. This loss relates to the hydrolysis of collagen matrix of the hybrid layers. The preservation of the collagen matrix integrity is a key issue in the attempts to improve the dentin bonding durability. Methods Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface. Results The identities, roles and function of collagenolytic enzymes in mineralized dentin has been gathered only within last 15 years, but they have already been demonstrated to have an important role in dental hard tissue pathologies, including the degradation of the hybrid layer. Identifying responsible enzymes facilitates the development of new, more efficient methods to improve the stability of dentin-adhesive bond and durability of bond strength. Significance Understanding the nature and role of proteolytic degradation of dentin-adhesive interfaces has improved immensely and has practically grown to a scientific field of its own within only 10 years, holding excellent promise that stable resin-dentin bonds will be routinely available in a daily clinical setting already in a near future. PMID:22901826
NASA Astrophysics Data System (ADS)
Luo, Wen; Feng, Yiyu; Qin, Chengqun; Li, Man; Li, Shipei; Cao, Chen; Long, Peng; Liu, Enzuo; Hu, Wenping; Yoshino, Katsumi; Feng, Wei
2015-10-01
An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg-1 by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template.An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg-1 by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03558a
Jungbauer, Stefan H; Huber, Stefan M
2015-09-23
In contrast to hydrogen bonding, which is firmly established in organocatalysis, there are still very few applications of halogen bonding in this field. Herein, we present the first catalytic application of cationic halogen-bond donors in a halide abstraction reaction. First, halopyridinium-, haloimidazolium-, and halo-1,2,3-triazolium-based catalysts were systematically tested. In contrast to the pyridinium compounds, both the imidazolium and the triazolium salts showed promising potency. For the haloimidazolium-based organocatalysts, we could show that the catalytic activity is based on halogen bonding using, e.g., the chlorinated derivatives as reference compounds. On the basis of these studies, halobenzimidazolium organocatalysts were then investigated. Monodentate compounds featured the same trends as the corresponding imidazolium analogues but showed a stronger catalytic activity. In order to prepare bidentate versions which are preorganized for anion binding, a new class of rigid bis(halobenzimidazolium) compounds was synthesized and structurally characterized. The corresponding syn isomer showed unprecedented catalytic potency and could be used in as low as 0.5 mol % in the benchmark reaction of 1-chloroisochroman with a silyl enol ether. Calculations confirmed that the syn isomer may bind in a bidentate fashion to chloride. The respective anti isomer is less active and binds halides in a monodentate fashion. Kinetic investigations confirmed that the syn isomer led to a 20-fold rate acceleration compared to a neutral tridentate halogen-bond donor. The strength of the preorganized halogen-bond donor seems to approach the limit under the reaction conditions, as decomposition is observed in the presence of chloride in the same solvent at higher temperatures. Calorimetric titrations of the syn isomer with bromide confirmed the strong halogen-bond donor strength of the former (K ≈ 4 × 10(6) M(-1), ΔG ≈ 38 kJ/mol). PMID:26329271
NASA Astrophysics Data System (ADS)
Yoon, Yoonjin
There has been growing interest in air transportation community to develop a routing decision model based on probabilistic characterization of severe weather. In the probabilistic air traffic management (PATM), decisions are made based on the stochastic weather information in the expected total cost sense. Probabilistic approach aims to enhance routing flexibility and reduce the risks associated with uncertainty of the future weather. In this research, a geometric model is adopted to generate optimal route choice when the future weather is stochastic. The geometric recourse model (GRM) is a strategic PATM model that incorporates route hedging and en-route recourse options to respond to weather change. Hedged routes are routes other than the nominal or detour route, and aircraft is re-routed to fly direct to the destination, which is called recourse, when the weather restricted airspace become flyable. Aircraft takes either the first recourse or the second recourse: The first recourse occurs when weather clears before aircraft reaches it flying on the initial route. The second recourse occurs when the aircraft is at the weather region. There are two variations of GRM: Single Recourse Model (SRM) with first recourse only and Dual Recourse Model (DRM) with both the first and second recourse options. When the weather clearance time follows a uniform distribution, SRM becomes convex with optimal route being either the detour or a hedged route. The DRM has a special property when the maximum storm duration time is less than the flight time to the tip of the storm on the detour route: it is always optimal to take the nominal route. The performance study is conducted by measuring the cost saving from either SRM or DRM. The result shows that there are cases with substantial cost saving, reaching nearly 30% with DRM. The ground-airborne hybrid model is an extension of the GRM, where both ground holding as well as route hedging are considered. The optimal combination of ground delay and route choice is determined by weather characteristics as well as the ground-airborne cost ratio. The numerical analysis reveals that whenever ground delay is required, the optimal route choice is the nominal one, while a non-nominal route is optimal when the ground delay is zero. There exists a unique critical cost ratio associated with given weather condition, which determines whether ground holding is optimal or not.
Luo, Wen; Feng, Yiyu; Qin, Chengqun; Li, Man; Li, Shipei; Cao, Chen; Long, Peng; Liu, Enzuo; Hu, Wenping; Yoshino, Katsumi; Feng, Wei
2015-10-21
An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg(-1) by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template. PMID:26289389
Laser Surface Preparation of Epoxy Composites for Secondary Bonding: Optimization of Ablation Depth
NASA Technical Reports Server (NTRS)
Palmieri, Frank L.; Hopkins, John; Wohl, Christopher J.; Lin, Yi; Connell, John W.; Belcher, Marcus A.; Blohowiak, Kay Y.
2015-01-01
Surface preparation has been identified as one of the most critical aspects of attaining predictable and reliable adhesive bonds. Energetic processes such as laser ablation or plasma treatment are amenable to automation and are easily monitored and adjusted for controlled surface preparation. A laser ablation process was developed to accurately remove a targeted depth of resin, approximately 0.1 to 20 micrometers, from a carbon fiber reinforced epoxy composite surface while simultaneously changing surface chemistry and creating micro-roughness. This work demonstrates the application of this process to prepare composite surfaces for bonding without exposing or damaging fibers on the surface. Composite panels were prepared in an autoclave and had a resin layer approximately 10 micrometers thick above the fiber reinforcement. These composite panels were laser surface treated using several conditions, fabricated into bonded panels and hygrothermally aged. Bond performance of aged, experimental specimens was compared with grit blast surface treated specimens using a modified double cantilever beam test that enabled accelerated saturation of the specimen with water. Comparison of bonded specimens will be used to determine how ablation depth may affect average fracture energies and failure modes.
Optimizing dentin bond durability: strategies to prevent hydrolytic degradation of the hybrid layer
Tjäderhane, Leo; Nascimento, Fabio D.; Breschi, Lorenzo; Mazzoni, Annalisa; Tersariol, Ivarne L.S.; Geraldeli, Saulo; Tezvergil-Mutluay, Arzu; Carrilho, Marcela; Carvalho, Ricardo M.; Tay, Franklin R.; Pashley, David H.
2014-01-01
Objectives Endogenous dentin collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, are responsible for the time-related hydrolysis of collagen matrix of the hybrid layers. As the integrity of the collagen matrix is essential for the preservation of long-term dentin bond strength, inhibition or inactivation of endogenous dentin proteases is necessary for durable resin-bonded composite resin restorations. Methods Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface. Several tentative approaches to prevent enzyme function either directly or indirectly have been proposed in the literature. Results Chlorhexidine, a general inhibitor of both MMPs and cysteine cathepsins, applied before primer/adhesive application is the most tested method. In general, these experiments have shown that enzyme inhibition is a promising scheme to improve hybrid layer preservation and bond strength durability. Other enzyme inhibitors, e.g. enzyme-inhibiting monomers and antimicrobial compounds, may be considered promising alternatives that would allow more simple clinical application than chlorhexidine. Cross-linking collagen and/or dentin organic matrix-bound enzymes could render hybrid layer organic matrix resistant to degradation, and complete removal of water from the hybrid layer with ethanol wet bonding or biomimetic remineralization should eliminate hydrolysis of both collagen and resin components. Significance Identification of the enzymes responsible for the hydrolysis of hybrid layer collagen and understanding their function has prompted several innovative approaches to retain the hybrid layer integrity and strong dentin bonding. The ultimate goal, prevention of collagen matrix degradation with techniques and commercially available materials that are simple and effective in clinical settings may be achievable in several ways, and will likely become reality in the near future. PMID:23953737
Insect kinin analogs with cis-peptide bond motif 4-aminopyroglutamate: Optimal stereochemistry
Technology Transfer Automated Retrieval System (TEKTRAN)
The insect kinins are present in a wide variety of insects and function as potent diuretic peptides, though they are subject to rapid degradation by internal peptidases. Insect kinin analogs incorporating stereochemical variants of (2S,4S)-4-aminopyroglutamate (APy), a cis-peptide bond motif, demon...
Ning, Bende; Qu, Xiaobo; Guo, Di; Hu, Changwei; Chen, Zhong
2013-11-01
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
Extremal Optimization for Ground States of the Sherrington-Kirkpatrick Spin Glass with Levy Bonds
NASA Astrophysics Data System (ADS)
Boettcher, Stefan
Ground states of Ising spin glasses on fully connected graphs are studied for a broadly distributed bond family. In particular, bonds J distributed according to a Levy distribution P(J) / 1/|J|1+α; |J| > 1; are investigated for a range of powers α. We determine ground state energy density variation with α and their finite-size corrections. We find that the energies attain universally the Parisi-energy of the SK as long as the second moment of P (J) exists (α > 2). They compare favorably with recent one-step replica symmetry breaking predictions well below α = 2. At and just below α = 2, the simulations deviate significantly from theoretical expectations. The finite-size investigation reveals that the corrections exponent ω decays from the putative SK value ωSK = = 2/3 already well above α = 2, at which point it reaches a minimum.
NASA Astrophysics Data System (ADS)
Muñoz, P.; Pastor, D.; Capmany, J.; Martínez, A.
2003-09-01
In this paper, the procedure to optimize flat-top Arrayed Waveguide Grating (AWG) devices in terms of transmission and dispersion properties is presented. The systematic procedure consists on the stigmatization and minimization of the Light Path Function (LPF) used in classic planar spectrograph theory. The resulting geometry arrangement for the Arrayed Waveguides (AW) and the Output Waveguides (OW) is not the classical Rowland mounting, but an arbitrary geometry arrangement. Simulation using previous published enhanced modeling show how this geometry reduces the passband ripple, asymmetry and dispersion, in a design example.
Belogolova, Elena F; Sidorkin, Valery F
2013-06-27
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, δN, 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
Kossiakoff, A.A.; Ultsch, M. ); White, S. ); Eigenbrot, C. )
1991-02-05
The neutron structure of subtilisin BPN{prime} has been refined and analyzed at 2.0-{angstrom} resolution. The structure studied was a mutant variant of subtilisin, Met222 {yields} Gln, and was used because large, uninhibited crystals could be grown, which was not the case for the native molecule. Comparison of the structure with that of the native molecule indicated that the two structures are essentially the same. Using the capability of the neutron method to locate hydrogen and deuterium atoms, the protonation states of the six histidine residues were assigned. The active site histidine, His64, was found to be neutral at the pH of the analysis (pH 6.1). This group has an unexpectedly low pK{sub a} compared to assignments made by other techniques. The altered pK{sub a} of the group could result from electrostatic effects of other molecules in the crystal lattice. The dihedral conformations of a majority of the hydroxyl rotors were assigned. The hydrogen exchange pattern of subtilisin identified the {beta}-sheet and {alpha}-helix secondary structure elements to be the most resistant to exchange. Fifty-five percent of the peptide amide hydrogens were fully exchanged, 15% unexchanged, and 30% partially exchanged. The largest concentration of unexchanged sites was in the seven-stranded parallel {beta}-sheet, in which there were 11 fully protected groups. Little correlation was found between H-bound length and angle and a peptide group's susceptibility toward exchange. Of the five {alpha}-helices the most protected from exchange is the one defined by residues 224-236. The pattern of exchange identifies regions in this helix where the H-bonding regularity is disrupted.
Bhattacharya, Debswapna; Cheng, Jianlin
2013-01-01
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). PMID:22927229
NASA Technical Reports Server (NTRS)
Coe, P. L., Jr.; Huffman, J. K.
1979-01-01
An investigation conducted in the Langley 7 by 10 foot tunnel to determine the influence of an optimized leading-edge deflection on the low speed aerodynamic performance of a configuration with a low aspect ratio, highly swept wing. The sensitivity of the lateral stability derivative to geometric anhedral was also studied. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to spanwise variation of unwash, the resulting optimized leading edge was a smooth, continuously warped surface for which the deflection varied from 16 deg at the side of body to 50 deg at the wing tip. For the particular configuration studied, levels of leading-edge suction on the order of 90 percent were achieved. The results of tests conducted to determine the sensitivity of the lateral stability derivative to geometric anhedral indicate values which are in reasonable agreement with estimates provided by simple vortex-lattice theories.
Wang, Feng; Graetz, Jason; Moreno, M Sergio; Ma, Chao; Wu, Lijun; Volkov, Vyacheslav; Zhu, Yimei
2011-02-22
Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer. PMID:21218844
Lin, Qisheng; Vetter, Jordan; Corbett, John D
2013-06-01
Sr3Au8Sn3 was synthesized through fusion of a stoichiometric amount of pure metals at 800 °C and annealing treatments at lower temperatures. Single-crystal X-ray diffraction analyses revealed that Sr3Au8Sn3 has a La3Al11-type Immm structure (a = 4.6767(8) 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 ΔE 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
NASA Technical Reports Server (NTRS)
Ojalvo, I. U.
1983-01-01
A procedure for minimizing the elastic shear stress concentration in adhesive lap joints is presented. The proposed method is based upon tapering the adherends to achieve smooth stiffness transitions and uniform shear stresses. Both single and double lap splices are considered, but numerical examples are restricted to the case of double lap joints. Nonisotropic materials and nonoptimum design limitations, such as minimum and maximum thickness adherends, load-line eccentricity, and peel stresses are treated, and typical results are presented.
Ghani, Muhammad. U.; Yan, Aimin; Wong, Molly. D.; Li, Yuhua; Ren, Liqiang; Wu, Xizeng; Liu, Hong
2016-01-01
The objective of this study was to investigate the optimization of a high energy in-line phase sensitive x-ray imaging prototype under different geometric and operating conditions for mammography application. A phase retrieval algorithm based on phase attenuation duality (PAD) was applied to the phase contrast images acquired by the prototype. Imaging performance was investigated at four magnification values of 1.67, 2, 2.5 and 3 using an acrylic edge, an American College of Radiology (ACR) mammography phantom and contrast detail (CD) phantom with tube potentials of 100, 120 and 140 kVp. The ACR and CD images were acquired at the same mean glandular dose (MGD) of 1.29 mGy with a computed radiography (CR) detector of 43.75 µm pixel pitch at a fixed source to image distance (SID) of 170 cm. The x-ray tube focal spot size was kept constant as 7 µm while a 2.5 mm thick aluminum (Al) filter was used for beam hardening. The performance of phase contrast and phase retrieved images were compared with computer simulations based on the relative phase contrast factor (RPF) at high x-ray energies. The imaging results showed that the x-ray tube operated at 100 kVp under the magnification of 2.5 exhibits superior imaging performance which is in accordance to the computer simulations. As compared to the phase contrast images, the phase retrieved images of the ACR and CD phantoms demonstrated improved imaging contrast and target discrimination. We compared the CD phantom images acquired in conventional contact mode with and without the anti-scatter grid using the same prototype at 1.295 mGy and 2.59 mGy using 40 kVp, a 25 µm rhodium (Rh) filter. At the same radiation dose, the phase sensitive images provided improved detection capabilities for both the large and small discs, while compared to the double dose image acquired in conventional mode, the observer study also indicated that the phase sensitive images provided improved detection capabilities for the large discs. This study therefore validates the potential of using high energy phase contrast x-ray imaging to improve lesion detection and reduce radiation dose for clinical applications such as mammography. PMID:26756405
NASA Astrophysics Data System (ADS)
Lu, Haw-Minn
1998-11-01
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.
Technology Transfer Automated Retrieval System (TEKTRAN)
The insect kinins are present in a wide variety of insects and function as potent diuretic peptides, though they are subject to rapid degradation by internal peptidases. Insect kinin analogs incorporating stereochemical variants of (2S,4S)-4-aminopyroglutamate (APy), a cis-peptide bond motif, demon...
NASA Astrophysics Data System (ADS)
Joseph, R. I.; Fry, R. L.; Dogra, V. K.
2003-03-01
This paper proposes a framework for quantifying logical and geometric inquiry through specific interpretations of Bayes' Theorem and Information Theory. In logical inquiry there are a countable number of possible discrete answers that define the inquiry, and Bayes' Theorem serves to move the observer posing the question along a trajectory in a hyberbolic figure in a manner suggested by Rodriguez. For N=3, this plane is a hyperbolic triangle whose angles sum to zero — the smallest possible value in the hyperbolic plane where the sum of the angles of a triangle must sum to a positive number less than pi. In euclidean space, the hyberbolic figure becomes a multi-dimensional simplex or polyhedron described by Shannon in his paper on a geometrical perspective of channel capacity. A theory of geometric inquiry requires that one consider an observer who conjointly possesses an objective reality space Θ and a physical or measurable space X. It is discussed how the matching of these spaces characterizes the ability of an observer to distinguish its posited objective reality. A simple functional form I is suggested as a measure of the degree of distinguishability for an observer. This form corresponds to the trace of the Fisher information matrix of p(x|θ) over θ∈ Θ. The origin and precise specification of the requirements that give rise to the specified functional form are unknown and represents an important area of future study with clues suggested in the work of Balasubramanian. At the same time, the question is asked regarding the nature of the metrics and probability distributions arising when an observer balances prior ignorance and prior knowledge through the extremizing of a functional J (p,∇p) = I + λH over probability densities p. The functional I is the a priori ability of the observer to distinguish pure space, H is the prior ignorance of the same observer over the same space, and λ is a scalar Lagrange multiplier ostensibly needed to balance units, but having additional interesting properties. Explicit solutions are derived for optimal p in both one and in general in N dimensions for λ = 0 and λ ≠ 0. In particular, the distributions that result when λ ≠ 0 include gaussian densities satisfying the functional form of distributions defining the elements of the Fisher Information matrix of pure-space as discussed by Rodriguez which possesses negative curvature when spatial uncertainty exists. Although only inquiry is discussed, a formalized conjoint theory of inquiry and control has significant implications regarding the engineering and design of intelligent systems that operate cybernetically.
Deforming geometric transitions
NASA Astrophysics Data System (ADS)
Rossi, Michele
2015-04-01
After a quick review of the wild structure of the complex moduli space of Calabi-Yau 3-folds and the role of geometric transitions in this context (the Calabi-Yau web) the concept of deformation equivalence for geometric transitions is introduced to understand the arrows of the Gross-Reid Calabi-Yau web as deformation-equivalence classes of geometric transitions. Then the focus will be on some results and suitable examples to understand under which conditions it is possible to get simple geometric transitions, which are almost the only well-understood geometric transitions both in mathematics and in physics.
Xiao, Ruijuan; Li, Hong; Chen, Liquan
2015-01-01
Looking for solid state electrolytes with fast lithium ion conduction is an important prerequisite for developing all-solid-state lithium secondary batteries. By combining the simulation techniques in different levels of accuracy, e.g. the bond-valence (BV) method and the density functional theory (DFT), a high-throughput design and optimization scheme is proposed for searching fast lithium ion conductors as candidate solid state electrolytes for lithium rechargeable batteries. The screening from more than 1000 compounds is performed through BV-based method, and the ability to predict reliable tendency of the Li+ migration energy barriers is confirmed by comparing with the results from DFT calculations. β-Li3PS4 is taken as a model system to demonstrate the application of this combination method in optimizing properties of solid electrolytes. By employing the high-throughput DFT simulations to more than 200 structures of the doping derivatives of β-Li3PS4, the effects of doping on the ionic conductivities in this material are predicted by the BV calculations. The O-doping scheme is proposed as a promising way to improve the kinetic properties of this materials, and the validity of the optimization is proved by the first-principles molecular dynamics (FPMD) simulations. PMID:26387639
Xiao, Ruijuan; Li, Hong; Chen, Liquan
2015-01-01
Looking for solid state electrolytes with fast lithium ion conduction is an important prerequisite for developing all-solid-state lithium secondary batteries. By combining the simulation techniques in different levels of accuracy, e.g. the bond-valence (BV) method and the density functional theory (DFT), a high-throughput design and optimization scheme is proposed for searching fast lithium ion conductors as candidate solid state electrolytes for lithium rechargeable batteries. The screening from more than 1000 compounds is performed through BV-based method, and the ability to predict reliable tendency of the Li(+) migration energy barriers is confirmed by comparing with the results from DFT calculations. ?-Li3PS4 is taken as a model system to demonstrate the application of this combination method in optimizing properties of solid electrolytes. By employing the high-throughput DFT simulations to more than 200 structures of the doping derivatives of ?-Li3PS4, the effects of doping on the ionic conductivities in this material are predicted by the BV calculations. The O-doping scheme is proposed as a promising way to improve the kinetic properties of this materials, and the validity of the optimization is proved by the first-principles molecular dynamics (FPMD) simulations. PMID:26387639
NASA Astrophysics Data System (ADS)
Xiao, Ruijuan; Li, Hong; Chen, Liquan
2015-09-01
Looking for solid state electrolytes with fast lithium ion conduction is an important prerequisite for developing all-solid-state lithium secondary batteries. By combining the simulation techniques in different levels of accuracy, e.g. the bond-valence (BV) method and the density functional theory (DFT), a high-throughput design and optimization scheme is proposed for searching fast lithium ion conductors as candidate solid state electrolytes for lithium rechargeable batteries. The screening from more than 1000 compounds is performed through BV-based method, and the ability to predict reliable tendency of the Li+ migration energy barriers is confirmed by comparing with the results from DFT calculations. β-Li3PS4 is taken as a model system to demonstrate the application of this combination method in optimizing properties of solid electrolytes. By employing the high-throughput DFT simulations to more than 200 structures of the doping derivatives of β-Li3PS4, the effects of doping on the ionic conductivities in this material are predicted by the BV calculations. The O-doping scheme is proposed as a promising way to improve the kinetic properties of this materials, and the validity of the optimization is proved by the first-principles molecular dynamics (FPMD) simulations.
Bent Bonds and Multiple Bonds.
ERIC Educational Resources Information Center
Robinson, Edward A.; Gillespie, Ronald J.
1980-01-01
Considers carbon-carbon multiple bonds in terms of Pauling's bent bond model, which allows direct calculation of double and triple bonds from the length of a CC single bond. Lengths of these multiple bonds are estimated from direct measurements on "bent-bond" models constructed of plastic tubing and standard kits. (CS)
NASA Astrophysics Data System (ADS)
Pariona, Moisés Meza; de Oliveira, Fabiane; Teleginski, Viviane; Machado, Siliane; Pinto, Marcio Augusto Villela
2015-07-01
Al-1.5 wt% Fe alloy was irradiate by Yb-fiber laser beam using the laser surface remelting (LSR) technique, generating weld fillets that covered the whole surface of the sample. The laser-treatment showed to be an efficient technology for corrosion resistance improvements. In this study, the finite element method was used to simulate the solidification processes by LSR technique. The method Multigrid was employed in order to reduce the CPU time, which is important to the viability for industrial applications. Multigrid method is a technique very promising of optimization that reduced drastically the CPU time. The result was highly satisfactory, because the CPU time has fallen dramatically in comparison when it was not used Multigrid method. To validate the result of numerical simulation with the experimental result was done the microstructural characterization of laser-treated layer by the optical microscopy and SEM techniques and however, that both results showing be consistent.
NASA Astrophysics Data System (ADS)
Pariona, Moisés Meza; de Oliveira, Fabiane; Teleginski, Viviane; Machado, Siliane; Pinto, Marcio Augusto Villela
2016-05-01
Al-1.5 wt% Fe alloy was irradiate by Yb-fiber laser beam using the laser surface remelting (LSR) technique, generating weld fillets that covered the whole surface of the sample. The laser-treatment showed to be an efficient technology for corrosion resistance improvements. In this study, the finite element method was used to simulate the solidification processes by LSR technique. The method Multigrid was employed in order to reduce the CPU time, which is important to the viability for industrial applications. Multigrid method is a technique very promising of optimization that reduced drastically the CPU time. The result was highly satisfactory, because the CPU time has fallen dramatically in comparison when it was not used Multigrid method. To validate the result of numerical simulation with the experimental result was done the microstructural characterization of laser-treated layer by the optical microscopy and SEM techniques and however, that both results showing be consistent.
Irvine, D M; Cole, A J; Hanna, G G; McGarry, C K
2015-01-01
Objective: The aim of this study was to identify sources of anatomical misrepresentation owing to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimize the four-dimensional CT (4DCT) scan protocol and improve geometrical–temporal accuracy. Methods: A phantom with an imaging insert was driven with a sinusoidal superior–inferior motion of varying amplitude and period for 4DCT scanning. The length of a high-density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied, including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested. Results: No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall- or couch-mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5 s rather than 1.0 s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose. Conclusion: The 4DCT accuracy may be increased by optimizing scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace may lead to spatial artefacts, and this risk can be reduced by using a couch-mounted infrared camera. Advances in knowledge: This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed. PMID:25470359
Exploring New Geometric Worlds
ERIC Educational Resources Information Center
Nirode, Wayne
2015-01-01
When students work with a non-Euclidean distance formula, geometric objects such as circles and segment bisectors can look very different from their Euclidean counterparts. Students and even teachers can experience the thrill of creative discovery when investigating these differences among geometric worlds. In this article, the author describes a…
Geometric Reasoning for Automated Planning
NASA Technical Reports Server (NTRS)
Clement, Bradley J.; Knight, Russell L.; Broderick, Daniel
2012-01-01
An important aspect of mission planning for NASA s operation of the International Space Station is the allocation and management of space for supplies and equipment. The Stowage, Configuration Analysis, and Operations Planning teams collaborate to perform the bulk of that planning. A Geometric Reasoning Engine is developed in a way that can be shared by the teams to optimize item placement in the context of crew planning. The ISS crew spends (at the time of this writing) a third or more of their time moving supplies and equipment around. Better logistical support and optimized packing could make a significant impact on operational efficiency of the ISS. Currently, computational geometry and motion planning do not focus specifically on the optimized orientation and placement of 3D objects based on multiple distance and containment preferences and constraints. The software performs reasoning about the manipulation of 3D solid models in order to maximize an objective function based on distance. It optimizes for 3D orientation and placement. Spatial placement optimization is a general problem and can be applied to object packing or asset relocation.
Geometric methods in quantum computation
NASA Astrophysics Data System (ADS)
Zhang, Jun
Recent advances in the physical sciences and engineering have created great hopes for new computational paradigms and substrates. One such new approach is the quantum computer, which holds the promise of enhanced computational power. Analogous to the way a classical computer is built from electrical circuits containing wires and logic gates, a quantum computer is built from quantum circuits containing quantum wires and elementary quantum gates to transport and manipulate quantum information. Therefore, design of quantum gates and quantum circuits is a prerequisite for any real application of quantum computation. In this dissertation we apply geometric control methods from differential geometry and Lie group representation theory to analyze the properties of quantum gates and to design optimal quantum circuits. Using the Cartan decomposition and the Weyl group, we show that the geometric structure of nonlocal two-qubit gates is a 3-Torus. After further reducing the symmetry, the geometric representation of nonlocal gates is seen to be conveniently visualized as a tetrahedron. Each point in this tetrahedron except on the base corresponds to a different equivalent class of nonlocal gates. This geometric representation is one of the cornerstones for the discussion on quantum computation in this dissertation. We investigate the properties of those two-qubit operations that can generate maximal entanglement. It is an astonishing finding that if we randomly choose a two-qubit operation, the probability that we obtain a perfect entangler is exactly one half. We prove that given a two-body interaction Hamiltonian, it is always possible to explicitly construct a quantum circuit for exact simulation of any arbitrary nonlocal two-qubit gate by turning on the two-body interaction for at most three times, together with at most four local gates. We also provide an analytic approach to construct a universal quantum circuit from any entangling gate supplemented with local gates. Closed form solutions have been derived for each step in this explicit construction procedure. Moreover, the minimum upper bound is found to construct a universal quantum circuit from any Controlled-Unitary gate. A near optimal explicit construction of universal quantum circuits from a given Controlled-Unitary is provided. For the Controlled-NOT and Double-CNOT gate, we then develop simple analytic ways to construct universal quantum circuits with exactly three applications, which is the least possible for these gates. We further discover a new quantum gate (named B gate) that achieves the desired universality with minimal number of gates. Optimal implementation of single-qubit quantum gates is also investigated. Finally, as a real physical application, a constructive way to implement any arbitrary two-qubit operation on a spin electronics system is discussed.
Geometric intrinsic symmetries
Gozdz, A. Szulerecka, A.; Pedrak, A.
2013-08-15
The problem of geometric symmetries in the intrinsic frame of a many-body system (nucleus) is considered. An importance of symmetrization group notion is discussed. Ageneral structure of the intrinsic symmetry group structure is determined.
A Babylonian Geometrical Algebra.
ERIC Educational Resources Information Center
Bidwell, James K.
1986-01-01
A possible method of derivation of prescriptions for solving problems, found in Babylonian cuneiform texts, is presented. It is a kind of "geometric algebra" based mainly on one figure and the manipulation of or within various areas and segments. (MNS)
Geometric Algebra for Physicists
NASA Astrophysics Data System (ADS)
Doran, Chris; Lasenby, Anthony
2003-07-01
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.
Geometrical Uncertainties in Radiotherapy
NASA Astrophysics Data System (ADS)
Remeijer, Peter
Geometrical uncertainties are a fact in any radiotherapy practice. Lasers can be misaligned, patients are mobile and the definition of the target volume is not always very easy. To deal with these uncertainties a safety margin is applied, i.e. a larger volume than the target itself is treated. In this chapter we will discuss common sources of geometrical uncertainties and how to compute these safety margins.
Dealing with Multiple Requirements in Geometric Arrangements.
Gomez-Nieto, Erick; Casaca, Wallace; Motta, Danilo; Hartmann, Ivar; Taubin, Gabriel; Nonato, Luis Gustavo
2016-03-01
Existing algorithms for building layouts from geometric primitives are typically designed to cope with requirements such as orthogonal alignment, overlap removal, optimal area usage, hierarchical organization, among others. However, most techniques are able to tackle just a few of those requirements simultaneously, impairing their use and flexibility. In this work we propose a novel methodology for building layouts from geometric primitives that concurrently addresses a wider range of requirements. Relying on multidimensional projection and mixed integer optimization, our approach arranges geometric objects in the visual space so as to generate well structured layouts that preserve the semantic relation among objects while still making an efficient use of display area. Moreover, scalability is handled through a hierarchical representation scheme combined with navigation tools. A comprehensive set of quantitative comparisons against existing geometry-based layouts and applications on text, image, and video data set visualization prove the effectiveness of our approach. PMID:26469283
NASA Astrophysics Data System (ADS)
Thiruvikraman, C.; Balasubramanian, V.; Sridhar, K.
2014-06-01
High velocity oxygen fuel (HVOF)-sprayed cermet coatings are extensively used to combat erosion-corrosion in naval applications and in slurry environments. HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance have significant influence on coating characteristics like adhesion bond strength and shear strength. This paper presents the use of statistical techniques in particular response surface methodology (RSM), analysis of variance, and regression analysis to develop empirical relationships to predict adhesion bond strength and lap shear bond strength of HVOF-sprayed WC-CrC-Ni coatings. The developed empirical relationships can be effectively used to predict adhesion bond strength and lap shear bond strength of HVOF-sprayed WC-CrC-Ni coatings at 95% confidence level. Response graphs and contour plots were constructed to identify the optimum HVOF spray parameters to attain maximum bond strength in WC-CrC-Ni coatings.
ERIC Educational Resources Information Center
Pollack, Rachel H.
2000-01-01
Notes trends toward increased borrowing by colleges and universities and offers guidelines for institutions that are considering issuing bonds to raise money for capital projects. Discussion covers advantages of using bond financing, how use of bonds impacts on traditional fund raising, other cautions and concerns, and some troubling aspects of…
ERIC Educational Resources Information Center
Frazier, Laura Corbin
2000-01-01
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)
Ponou, Simeon; Lidin, Sven; Zhang, Yuemei; Miller, Gordon J.
2014-04-18
The quaternary phase Ca5Mg0.95Ag1.05(1)Ge5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma – Wyckoff sequence c12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å3, Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R2+nT2X2+n, previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm – Wyckoff sequence f5c2. The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed.
Inflation from geometrical tachyons
Thomas, Steven; Ward, John
2005-10-15
We propose an alternative formulation of tachyon inflation using the geometrical tachyon arising from the time dependent motion of a BPS D3-brane in the background geometry due to k parallel NS5-branes arranged around a ring of radius R. Because of the fact that the mass of this geometrical tachyon field is {radical}(2/k) times smaller than the corresponding open-string tachyon mass, we find that the slow-roll conditions for inflation and the number of e-foldings can be satisfied in a manner that is consistent with an effective 4-dimensional model and with a perturbative string coupling. We also show that the metric perturbations produced at the end of inflation can be sufficiently small and do not lead to the inconsistencies that plague the open-string tachyon models. Finally we argue for the existence of a minimum of the geometrical tachyon potential which could give rise to a traditional reheating mechanism.
PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism
NASA Astrophysics Data System (ADS)
Gardner, Jason S.
2011-04-01
Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry based on triangles and tetrahedra. Most studies have centred around the kagomé and pyrochlore based magnets but recent work has looked at other structures including the delafossite, langasites, hyper-kagomé, garnets and Laves phase materials to name a few. Personally, I hope this issue serves as a great reference to scientist both new and old to this field, and that we all continue to have fun in this very frustrated playground. Finally, I want to thank the HFM 2010 organizers and all the sponsors whose contributions were an essential part of the success of the meeting in Baltimore. Geometrically frustrated magnetism contents Spangolite: an s = 1/2 maple leaf lattice antiferromagnet? T Fennell, J O Piatek, R A Stephenson, G J Nilsen and H M Rønnow Two-dimensional magnetism and spin-size effect in the S = 1 triangular antiferromagnet NiGa2S4 Yusuke Nambu and Satoru Nakatsuji Short range ordering in the modified honeycomb lattice compound SrHo2O4 S Ghosh, H D Zhou, L Balicas, S Hill, J S Gardner, Y Qi and C R Wiebe Heavy fermion compounds on the geometrically frustrated Shastry-Sutherland lattice M S Kim and M C Aronson A neutron polarization analysis study of moment correlations in (Dy0.4Y0.6)T2 (T = Mn, Al) J R Stewart, J M Hillier, P Manuel and R Cywinski Elemental analysis and magnetism of hydronium jarosites—model kagome antiferromagnets and topological spin glasses A S Wills and W G Bisson The Herbertsmithite Hamiltonian: μSR measurements on single crystals Oren Ofer, Amit Keren, Jess H Brewer, Tianheng H Han and Young S Lee Classical topological order in kagome ice Andrew J Macdonald, Peter C W Holdsworth and Roger G Melko Magnetic phase diagrams of classical triangular and kagome antiferromagnets M V Gvozdikova, P-E Melchy and M E Zhitomirsky The ordering of XY spin glasses Hikaru Kawamura Dynamic and thermodynamic properties of the generalized diamond chain model for azurite Andreas Honecker, Shijie Hu, Robert Peters and Johannes Richter Classical height models with topological order Christopher L Henley A search for disorder in the spin glass double perovskites Sr2CaReO6 and Sr2MgReO6 using neutron diffraction and neutron pair distribution function analysis J E Greedan, Shahab Derakhshan, F Ramezanipour, J Siewenie and Th Proffen Order and disorder in the local and long-range structure of the spin-glass pyrochlore, Tb2Mo2O7 Yu Jiang, Ashfia Huq, Corwin H Booth, Georg Ehlers, John E Greedan and Jason S Gardner The magnetic phase diagram of Gd2Sn2O7 R S Freitas and J S Gardner Calculation of the expected zero-field muon relaxation rate in the geometrically frustrated rare earth pyrochlore Gd2Sn2O7 antiferromagnet P A McClarty, J N Cosman, A G Del Maestro and M J P Gingras Magnetic frustration in the disordered pyrochlore Yb2GaSbO7 J A Hodges, P Dalmas de Réotier, A Yaouanc, P C M Gubbens, P J C King and C Baines Titanium pyrochlore magnets: how much can be learned from magnetization measurements? O A Petrenko, M R Lees and G Balakrishnan Local susceptibility of the Yb2Ti2O7 rare earth pyrochlore computed from a Hamiltonian with anisotropic exchange J D Thompson, P A McClarty and M J P Gingras Slow and static spin correlations in Dy2 + xTi2 - xO7 - δ J S Gardner, G Ehlers, P Fouquet, B Farago and J R Stewart The spin ice Ho2Ti2O7 versus the spin liquid Tb2Ti2O7: field-induced magnetic structures A P Sazonov, A Gukasov and I Mirebeau Magnetic monopole dynamics in spin ice L D C Jaubert and P C W Holdsworth
ERIC Educational Resources Information Center
Burgess, Claudia R.
2014-01-01
Designed for a broad audience, including educators, camp directors, afterschool coordinators, and preservice teachers, this investigation aims to help individuals experience mathematics in unconventional and exciting ways by engaging them in the physical activity of building geometric shapes using ropes. Through this engagement, the author…
Geometric Series via Probability
ERIC Educational Resources Information Center
Tesman, Barry
2012-01-01
Infinite series is a challenging topic in the undergraduate mathematics curriculum for many students. In fact, there is a vast literature in mathematics education research on convergence issues. One of the most important types of infinite series is the geometric series. Their beauty lies in the fact that they can be evaluated explicitly and that…
NASA Technical Reports Server (NTRS)
Ives, David
1995-01-01
This paper presents a highly automated hexahedral grid generator based on extensive geometrical and solid modeling operations developed in response to a vision of a designer-driven one day turnaround CFD process which implies a designer-driven one hour grid generation process.
1500 System Geometric Dictionary.
ERIC Educational Resources Information Center
Peloquin, Paul V.
A general description is provided of the "geometric dictionary," a graphic display aid, used by the Computer-Assisted Instruction Laboratory at the Pennsylvania State University. The purpose of the description is to enable the reader to duplicate and use the dictionary on any cathode ray tube terminal of the IBM 1500 system. The major advantages…
ERIC Educational Resources Information Center
Smart, Julie; Marshall, Jeff
2007-01-01
Children possess a genuine curiosity for exploring the natural world around them. One third grade teacher capitalized on this inherent trait by leading her students on "A Geometric Scavenger Hunt." The four-lesson inquiry investigation described in this article integrates mathematics and science. Among the students' discoveries was the fact that…
Pragmatic geometric model evaluation
NASA Astrophysics Data System (ADS)
Pamer, Robert
2015-04-01
Quantification of subsurface model reliability is mathematically and technically demanding as there are many different sources of uncertainty and some of the factors can be assessed merely in a subjective way. For many practical applications in industry or risk assessment (e. g. geothermal drilling) a quantitative estimation of possible geometric variations in depth unit is preferred over relative numbers because of cost calculations for different scenarios. The talk gives an overview of several factors that affect the geometry of structural subsurface models that are based upon typical geological survey organization (GSO) data like geological maps, borehole data and conceptually driven construction of subsurface elements (e. g. fault network). Within the context of the trans-European project "GeoMol" uncertainty analysis has to be very pragmatic also because of different data rights, data policies and modelling software between the project partners. In a case study a two-step evaluation methodology for geometric subsurface model uncertainty is being developed. In a first step several models of the same volume of interest have been calculated by omitting successively more and more input data types (seismic constraints, fault network, outcrop data). The positions of the various horizon surfaces are then compared. The procedure is equivalent to comparing data of various levels of detail and therefore structural complexity. This gives a measure of the structural significance of each data set in space and as a consequence areas of geometric complexity are identified. These areas are usually very data sensitive hence geometric variability in between individual data points in these areas is higher than in areas of low structural complexity. Instead of calculating a multitude of different models by varying some input data or parameters as it is done by Monte-Carlo-simulations, the aim of the second step of the evaluation procedure (which is part of the ongoing work) is to calculate basically two model variations that can be seen as geometric extremes of all available input data. This does not lead to a probability distribution for the spatial position of geometric elements but it defines zones of major (or minor resp.) geometric variations due to data uncertainty. Both model evaluations are then analyzed together to give ranges of possible model outcomes in metric units.
Geometric direct search algorithms for image registration.
Lee, Seok; Choi, Minseok; Kim, Hyungmin; Park, Frank Chongwoo
2007-09-01
A widely used approach to image registration involves finding the general linear transformation that maximizes the mutual information between two images, with the transformation being rigid-body [i.e., belonging to SE(3)] or volume-preserving [i.e., belonging to SL(3)]. In this paper, we present coordinate-invariant, geometric versions of the Nelder-Mead optimization algorithm on the groups SL(3), SE(3), and their various subgroups, that are applicable to a wide class of image registration problems. Because the algorithms respect the geometric structure of the underlying groups, they are numerically more stable, and exhibit better convergence properties than existing local coordinate-based algorithms. Experimental results demonstrate the improved convergence properties of our geometric algorithms. PMID:17784595
Algebraic and geometric spread in finite frames
NASA Astrophysics Data System (ADS)
King, Emily J.
2015-08-01
When searching for finite unit norm tight frames (FUNTFs) of M vectors in FN which yield robust representations, one is concerned with finding frames consisting of frame vectors which are in some sense as spread apart as possible. Algebraic spread and geometric spread are the two most commonly used measures of spread. A frame with optimal algebraic spread is called full spark and is such that any subcollection of N frame vectors is a basis for FN. A Grassmannian frame is a FUNTF which satisfies the Grassmannian packing problem; that is, the frame vectors are optimally geometrically spread given fixed M and N. A particular example of a Grassmannian frame is an equiangular frame, which is such that the absolute value of all inner products of distinct vectors is equal. The relationship between these two types of optimal spread is complicated. The folk knowledge for many years was that equiangular frames were full spark; however, this is now known not to hold for an infinite class of equiangular frames. The exact relationship between these types of spread will be further explored in this talk, as well as Plücker coordinates and coherence, which are measures of how much a frame misses being optimally algebraically or geometrically spread.
Geometric simulation of flexible motion in proteins.
Wells, Stephen A
2014-01-01
This chapter describes the use of physically simplified analysis and simulation methods-pebble-game rigidity analysis, coarse-grained elastic network modeling, and template-based geometric simulation-to explore flexible motion in protein structures. Substantial amplitudes of flexible motion can be explored rapidly in an all-atom model, retaining realistic covalent bonding, steric exclusion, and a user-defined network of noncovalent polar and hydrophobic interactions, using desktop computing resources. Detailed instructions are given for simulations using FIRST/FRODA software installed on a UNIX/Linux workstation. Other implementations of similar methods exist, particularly NMSim and FRODAN, and are available online. Topics covered include rigidity analysis and constraints, geometric simulation of flexible motion, targeting between known structures, and exploration of motion along normal mode eigenvectors. PMID:24061922
Effect of bonding on the performance of a piezoactuator-based active control system
NASA Technical Reports Server (NTRS)
Baz, A.; Poh, S.
1987-01-01
The utilization of piezoelectric actuators in controlling the structural vibrations of flexible beams is studied. A Modified Independent Modal Space Control (MIMSC) method is devised to select the optimal location, control gains and excitation voltage of the piezoelectric actuators in a way that would minimize the amplitudes of vibrations of beams to which these actuators are bonded, as well as the input control energy necessary to suppress these vibrations. The presented method accounts for the effects that the piezoelectric actuators and the bonding layers have on changing the elastic and inertial properties of the flexible beams. Numerical examples are presented to illustrate the application of the MIMSC method and to demonstrate the effect of the physical and geometrical properties of the bonding layer on the dynamic performance of the actively controlled beams. The obtained results emphasize the importance of the devised method in designing more realistic active control systems for flexible beams, in particular, and large flexible structures in general.
ERIC Educational Resources Information Center
Allard, M. June
Institutional bonding was examined at a public, urban commuter college with exceptionally high attrition and visibly low morale. Changes in bonding and attrition were measured 6 years after a 2-year effort to develop school identity and student feelings of membership. It was found that a simple index of campus morale is provided by level of
Geometric measures of entanglement
Uyanik, K.; Turgut, S.
2010-03-15
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.
Geometrical deuteron stripping revisited
Neoh, Y. S.; Yap, S. L.
2014-03-05
We investigate the reality of the idea of geometrical deuteron stripping originally envisioned by Serber. By taking into account of realistic deuteron wavefunction, nuclear density, and nucleon stopping mean free path, we are able to estimate inclusive deuteron stripping cross section for deuteron energy up to before pion production. Our semiclassical model contains only one global parameter constant for all nuclei which can be approximated by Woods-Saxon or any other spherically symmetric density distribution.
Theoretical study of the S bond H···O blue-shifted hydrogen bond
NASA Astrophysics Data System (ADS)
Yang, Yong
Theoretical calculations were performed to study the nature of the hydrogen bonds in the complexes HCHO···HSO, HCOOH···HSO, HCHO···HOO, and HCOOH···HOO. The geometric structures and vibrational frequencies of these four complexes at the MP2/6-31G(d,p) and MP2/6-311+G(d,p) levels are calculated by standard and counterpoise-corrected methods, respectively. The results indicate that in the complexes HCHO···HSO and HCOOH···HSO the S bond H bond is strongly contracted. In the S bond H···O hydrogen bonds, the calculated blue shifts for the S bond H stretching frequencies are in the vicinity of 50 cm-1. While in the complexes HCHO···HOO and HCOOH···HOO, the O bond H bond is elongated and O bond H···O red-shifted hydrogen bonds are found. From the natural bond orbital analysis it can be seen that the X bond H bond length in the X bond H···Y hydrogen bond is controlled by a balance of four main factors in the opposite directions: hyperconjugation, electron density redistribution, rehybridization, and structural reorganization. Among them hyperconjugation has the effect of elongating the X bond H bond. Electron density redistribution and rehybridization belong to the bond shortening effects, while structural reorganization has an uncertain influence on the X bond H bond length. In the complexes HCHO···HSO and HCOOH···HSO, the shortening effects dominate which lead to the blue shift of the S bond H stretching frequencies. In the complexes HCHO···HOO and HCOOH···HOO where elongating effects are dominant, the O bond H···O hydrogen bonds are red-shifted.
Foundations of Geometric Algebra computing
NASA Astrophysics Data System (ADS)
Hildenbrand, Dietmar
2012-09-01
Geometric Algebra has the power to lead easily from the geometric intuition of solving an engineering application to its efficient implementation on current and future computing platforms. It is easy to develop new algorithms in areas such as computer graphics, robotics, computer animation and computer simulation. Owing to its geometric intuitiveness, compactness and simplicity, algorithms based on Geometric Algebra can lead to enhanced quality, a reduction in development time and solutions that are more easily understandable and maintainable. Often, a clear structure and greater elegance result in lower runtime performance. However, based on our computing technology, Geometric Algebra implementations can even be faster and more robust than conventional ones. We present an example on how easy it is to describe algorithms in Geometric Algebra and introduce our technology for the integration of Geometric Algebra into standard programming languages. We really do hope that this technology can support the widespread use of Geometric Algebra Computing technology in many engineering fields.
Geometric diffusion of quantum trajectories
Yang, Fan; Liu, Ren-Bao
2015-01-01
A quantum object can acquire a geometric phase (such as Berry phases and Aharonov–Bohm phases) when evolving along a path in a parameter space with non-trivial gauge structures. Inherent to quantum evolutions of wavepackets, quantum diffusion occurs along quantum trajectories. Here we show that quantum diffusion can also be geometric as characterized by the imaginary part of a geometric phase. The geometric quantum diffusion results from interference between different instantaneous eigenstate pathways which have different geometric phases during the adiabatic evolution. As a specific example, we study the quantum trajectories of optically excited electron-hole pairs in time-reversal symmetric insulators, driven by an elliptically polarized terahertz field. The imaginary geometric phase manifests itself as elliptical polarization in the terahertz sideband generation. The geometric quantum diffusion adds a new dimension to geometric phases and may have applications in many fields of physics, e.g., transport in topological insulators and novel electro-optical effects. PMID:26178745
NASA Astrophysics Data System (ADS)
Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih
2013-09-01
In the present work, the experimental and theoretical vibrational spectra of 4-chlorobenzothioamide were investigated. The FT-IR (400-4000 cm-1) and μ-Raman spectra (100-4000 cm-1) of 4-chlorobenzothioamide in the solid phase were recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared and Raman intensities of the title molecule in the ground state were calculated using ab initio Hartree-Fock and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 4-chlorobenzothioamide was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯S hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.
NASA Astrophysics Data System (ADS)
Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih
2014-06-01
In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.
Characteristics of hydrogen bond revealed from water clusters
NASA Astrophysics Data System (ADS)
Song, Yan; Chen, Hongshan; Zhang, Cairong; Zhang, Yan; Yin, Yuehong
2014-09-01
The hydrogen bond network is responsible for the exceptional physical and chemical properties of water, however, the description of hydrogen bond remains a challenge for the studies of condensed water. The investigation of structural and binding properties of water clusters provides a key for understanding the H-bonds in bulk water. In this paper, a new set of geometric parameters are defined to describe the extent of the overlap between the bonding orbital of the donor OH and the nonbonding orbital of the lone-pair of the acceptor molecule. This orbital overlap plays a dominant role for the strength of H-bonds. The dependences of the binding energy of the water dimer on these parameters are studied. The results show that these parameters properly describe the H-bond strength. The ring, book, cage and prism isomers of water hexamer form 6, 7, 8 and 9 H-bonds, and the strength of the bonding in these isomers changes markedly. The internally-solvated and the all-surface structures of (H2O) n for n = 17, 19 and 21 are nearly isoenergetic. The internally-solvated isomers form fewer but stronger H-bonds. The hydrogen bonding in the above clusters are investigated in detail. The geometric parameters can well describe the characters of the H-bonds, and they correlate well with the H-bond strength. For the structures forming stronger H-bonds, the H-bond lengths are shorter, the angle parameters are closer to the optimum values, and their rms deviations are smaller. The H-bonds emanating from DDAA and DDA molecules as H-donor are relatively weak. The vibrational spectra of (H2O) n ( n = 17, 19 and 21) are studied as well. The stretching vibration of the intramolecular OH bond is sensitive to its bonding environment. The H-bond strength judged from the geometric parameters is in good agreement with the bonding strength judged from the stretching frequencies.
Geometric phase in Bohmian mechanics
Chou, Chia-Chun; Wyatt, Robert E.
2010-10-15
Using the quantum kinematic approach of Mukunda and Simon, we propose a geometric phase in Bohmian mechanics. A reparametrization and gauge invariant geometric phase is derived along an arbitrary path in configuration space. The single valuedness of the wave function implies that the geometric phase along a path must be equal to an integer multiple of 2{pi}. The nonzero geometric phase indicates that we go through the branch cut of the action function from one Riemann sheet to another when we locally travel along the path. For stationary states, quantum vortices exhibiting the quantized circulation integral can be regarded as a manifestation of the geometric phase. The bound-state Aharonov-Bohm effect demonstrates that the geometric phase along a closed path contains not only the circulation integral term but also an additional term associated with the magnetic flux. In addition, it is shown that the geometric phase proposed previously from the ensemble theory is not gauge invariant.
Methods and apparatuses for signaling with geometric constellations
NASA Technical Reports Server (NTRS)
Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)
2012-01-01
Communication systems are described that use signal constellations, which have unequally spaced (i.e. geometrically shaped) points. In many embodiments, the communication systems use specific geometric constellations that are capacity optimized at a specific SNR. In addition, ranges within which the constellation points of a capacity optimized constellation can be perturbed and are still likely to achieve a given percentage of the optimal capacity increase compared to a constellation that maximizes d.sub.min, are also described. Capacity measures that are used in the selection of the location of constellation points include, but are not limited to, parallel decode (PD) capacity and joint capacity.
NASA Astrophysics Data System (ADS)
Moosavi-Tekyeh, Zainab; Taherian, Fatemeh; Tayyari, Sayyed Faramarz
2016-05-01
The structural parameters, and vibrational frequencies of 5-nitrosalicylaldehyde (5NSA) were studied by the FT-IR and Raman spectra and the quantum chemical calculations carried out at the B3LYP/6-311++G(d,p) level of theory in order to investigate the intramolecular hydrogen bonding (IHB) present in its structure. The strength and nature of IHB in the optimized structure of 5NSA were studied in detail by means of the atoms in molecules (AIM) and the natural bond orbital (NBO) approaches. The results obtained were then compared with the corresponding data for its parent molecule, salicylaldehyde (SA). Comparisons made between the geometrical structures for 5NSA and SA, their OH/OD stretching and out-of-plane bending modes, their enthalpies for the hydrogen bond, and their AIM parameters demonstrated a stronger H-bonding in 5NSA compared with that in SA. The calculated binding enthalpy (ΔHbind) for 5NSA was -10.92 kcal mol-1. The observed νOH and γOH appeared at about 3120 cm-1 and 786 cm-1 respectively. The stretching frequency shift of H-bond formation was 426 cm-1 which is consistent with ΔHbind and the strength of H-bond in 5NSA. The delocalization energies and electron delocalization indices derived by the NBO and AIM approaches indicate that the resonance effects were responsible for the stronger IHB in 5NSA than in SA.
Rahm, Martin; Hoffmann, Roald
2016-03-23
The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496
Wood, Peter A; Pidcock, Elna; Allen, Frank H
2008-08-01
The occurrence, geometries and energies of hydrogen bonds from N-H and O-H donors to the S acceptors of thiourea derivatives, thioamides and thiones are compared with data for their O analogues - ureas, amides and ketones. Geometrical data derived from the Cambridge Structural Database indicate that hydrogen bonds to the C[double bond]S acceptors are much weaker than those to their C[double bond]O counterparts: van der Waals normalized hydrogen bonds to O are shorter than those to S by approximately 0.25 A. Further, the directionality of the approach of the hydrogen bond with respect to S, defined by the C[double bond]S...H angle, is in the range 102-109 degrees , much lower than the analogous C[double bond]O...H angle which lies in the range 127-140 degrees . Ab initio calculations using intermolecular perturbation theory show good agreement with the experimental results: the differences in hydrogen-bond directionality are closely reproduced, and the interaction energies of hydrogen bonds to S are consistently weaker than those to O, by approximately 12 kJ mol(-1), for each of the three compound classes. There are no CSD examples of hydrogen bonds to aliphatic thiones, (Csp(3))(2)C=S, consistent with the near-equality of the electronegativities of C and S. Thioureas and thioamides have electron-rich N substituents replacing the Csp(3) atoms. Electron delocalization involving C[double bond]S and the N lone pairs then induces a significant >C(delta+)[double bond]S(delta-) dipole, which enables the formation of the medium-strength C[double bond]S...H bonds observed in thioureas and thioamides. PMID:18641451
Geometrical aspects of entanglement
Leinaas, Jon Magne; Myrheim, Jan; Ovrum, Eirik
2006-07-15
We study geometrical aspects of entanglement, with the Hilbert-Schmidt norm defining the metric on the set of density matrices. We focus first on the simplest case of two two-level systems and show that a 'relativistic' formulation leads to a complete analysis of the question of separability. Our approach is based on Schmidt decomposition of density matrices for a composite system and nonunitary transformations to a standard form. The positivity of the density matrices is crucial for the method to work. A similar approach works to some extent in higher dimensions, but is a less powerful tool. We further present a numerical method for examining separability and illustrate the method by a numerical study of bound entanglement in a composite system of two three-level systems.
Goldberg, P.W.
1993-04-01
In this paper we consider the problem of learning the positions of spheres in metric spaces, given as data randomly drawn points classified according to whether they are internal or external to an unknown sphere. The particular metrics under consideration are geometrical shape metrics, and the results are intended to be applicable to the problem of learning to identify a shape from related shapes classified according to whether they resemble it visually. While it is typically NP-hard to locate a central point for a hypothesis sphere, we find that it is however often possible to obtain a non-spherical hypothesis which can accurately predict whether further random points lie within the unknown sphere. We exhibit algorithms which achieve this, and in the process indicate useful general techniques for computational learning. Finally we exhibit a natural shape metric and show that it defines a class of spheres not predictable in this sense, subject to standard cryptographic assumptions.
Noga, M.T.
1984-01-01
This thesis addresses a number of important problems that fall within the framework of the new discipline of Computational Geometry. The list of topics covered includes sorting and selection, convex hull algorithms, the L/sub 1/ hull, determination of the minimum encasing rectangle of a set of points, the Euclidean and L/sub 1/ diameter of a set of points, the metric traveling salesman problem, and finding the superrange of star-shaped and monotype polygons. The main theme of all the work was to develop a set of very fast state-of-the-art algorithms that supersede any rivals in terms of speed and ease of implementation. In some cases existing algorithms were refined; for others new techniques were developed that add to the present database of fast adaptive geometric algorithms. What emerges is a collection of techniques that is successful at merging modern tools developed in analysis of algorithms with those of classical geometry.
Geometric Frustration with Disorder
NASA Astrophysics Data System (ADS)
Woo, Nayoon; Silevitch, Daniel M.; Rosenbaum, Thomas F.
2014-03-01
We study the effects of Nd doping on the geometrically-frustrated Heisenberg antiferromagnet Gadolinium Gallium Garnet (GGG), using linear and nonlinear ac magnetic susceptibility. Doping levels from 0.1 to 1 percent Nd alleviate the intrinsic frustration of pure GGG and elevate the ordering temperature compared to the pure material. We use nonlinear pump-probe magnetic susceptometry to examine cluster dynamics for both the pure and the doped series. At low frequency (~10 Hz), spectral hole burning is possible, indicating the presence of spin clusters with discrete energy levels largely decoupled from the overall spin bath. At kHz, we find a Fano resonance, revealing scattering pathways between spin cluster excitations and the bath. We trace the evolution of this resonance behavior as a function of dopant concentration.
Imperfect Geometric Control and Overdamping for The Damped Wave Equation
NASA Astrophysics Data System (ADS)
Burq, Nicolas; Christianson, Hans
2015-05-01
We consider the damped wave equation on a manifold with imperfect geometric control. We show the sub-exponential energy decay estimate in (Christianson, J Funct Anal 258(3):1060-1065, 2010) is optimal in the case of one hyperbolic periodic geodesic. We show if the equation is overdamped, then the energy decays exponentially. Finally we show if the equation is overdamped but geometric control fails for one hyperbolic periodic geodesic, then nevertheless the energy decays exponentially.
Sajan, D; Joseph, Lynnette; Vijayan, N; Karabacak, M
2011-10-15
The spectroscopic properties of the crystallized nonlinear optical molecule L-histidinium bromide monohydrate (abbreviated as L-HBr-mh) have been recorded and analyzed by FT-IR, FT-Raman and UV techniques. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the crystal were calculated with the help of density functional theory computations. The optimized geometric bond lengths and bond angles obtained by using DFT (B3LYP/6-311++G(d,p)) show good agreement with the experimental data. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The natural bond orbital (NBO) analysis confirms the occurrence of strong intra and intermolecular N-H⋯O hydrogen bonding. PMID:21775197
Geometric mechanics of periodic pleated origami.
Wei, Z Y; Guo, Z V; Dudte, L; Liang, H Y; Mahadevan, L
2013-05-24
Origami structures are mechanical metamaterials with properties that arise almost exclusively from the geometry of the constituent folds and the constraint of piecewise isometric deformations. Here we characterize the geometry and planar and nonplanar effective elastic response of a simple periodically folded Miura-ori structure, which is composed of identical unit cells of mountain and valley folds with four-coordinated ridges, defined completely by two angles and two lengths. We show that the in-plane and out-of-plane Poisson's ratios are equal in magnitude, but opposite in sign, independent of material properties. Furthermore, we show that effective bending stiffness of the unit cell is singular, allowing us to characterize the two-dimensional deformation of a plate in terms of a one-dimensional theory. Finally, we solve the inverse design problem of determining the geometric parameters for the optimal geometric and mechanical response of these extreme structures. PMID:23745895
Delaney, P. )
1993-10-01
Yankee and Euromarket bonds may soon find their way into the financing of power projects in Latin America. For developers seeking long-term commitments under build, own, operate, and transfer (BOOT) power projects in Latin America, the benefits are substantial.
ERIC Educational Resources Information Center
Reynolds, Cathryn
1989-01-01
The combined effect of the "Serrano" decision and Proposition 13 left California school districts with aging, overcrowded facilities. Chico schools won a $18.5 million general obligation bond election for facilities construction. With $11 billion needed for new school construction, California will need to tap local sources. A sidebar outlines…
Non-hydrogen bond interactions involving the methionine sulfur atom.
Pal, D; Chakrabarti, P
2001-08-01
Of all the nonbonded interactions, hydrogen bond, because of its geometry involving polar atoms, is the most easily recognizable. Here we characterize two interactions involving the divalent sulfur of methionine (Met) residues that do not need any participation of proton. In one an oxygen atom of the main-chain carbonyl group or a carboxylate side chain is used. In another an aromatic atom interacting along the face of the ring is utilized. In these, the divalent sulfur behaves as an electrophile and the other electron-rich atom, a nucleophile. The stereochemistry of the interaction is such that the nucleophile tends to approach approximately along the extension of one of the covalent bonds to S. The nitrogen atom of histidine side chain is extensively used in these nonbonded contacts. There is no particular geometric pattern in the interaction of S with the edge of an aromatic ring, except when an N-H group in involved, which is found within 40 degrees from the perpendicular to the sulfide plane, thus defining the geometry of hydrogen bond interaction involving the sulfur atom. As most of the Met residues which partake in such stereospecific interactions are buried, these would be important for the stability of the protein core, and their incorporation in the binding site would be useful for molecular recognition and optimization of the site's affinity for partners (especially containing aromatic and heteroaromatic groups). Mutational studies aimed at replacing Met by other residues would benefit from the delineation of these interactions. PMID:11565843
Roumeli, Eleftheria; Papageorgiou, Dimitrios G; Tsanaktsis, Vasilios; Terzopoulou, Zoe; Chrissafis, Konstantinos; Avgeropoulos, Apostolos; Bikiaris, Dimitrios N
2015-06-01
In this work, the synthesis, structural characteristics, interfacial bonding, and mechanical properties of poly(ε-caprolactone) (PCL) nanocomposites with small amounts (0.5, 1.0, and 2.5 wt %) of amino-functionalized multiwalled carbon nanotubes (f-MWCNTs) prepared by ring-opening polymerization (ROP) are reported. This method allows the creation of a covalent-bonding zone on the surface of nanotubes, which leads to efficient debundling and therefore satisfactory dispersion and effective load transfer in the nanocomposites. The high covalent grafting extent combined with the higher crystallinity provide the basis for a significant enhancement of the mechanical properties, which was detected in the composites with up to 1 wt % f-MWCNTs. Increasing filler concentration encourages intrinsic aggregation forces, which allow only minor grafting efficiency and poorer dispersion and hence inferior mechanical performance. f-MWCNTs also cause a significant improvement on the polymerization reaction of PCL. Indeed, the in situ polymerization kinetics studies reveal a significant decrease in the reaction temperature, by a factor of 30-40 °C, combined with accelerated the reaction kinetics during initiation and propagation and a drastically reduced effective activation energy. PMID:25950403
Anderson, Robert C.
1976-06-22
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.
Technology Transfer Automated Retrieval System (TEKTRAN)
The disaccharide alpha-maltose is a molecular template for amylose. Our previous DFT work on maltose is expanded to a set of 63 fully optimized (B3LYP/6-311++G**) conformations. All clockwise, and counter clockwise hydroxyl groups, as well as 'kink' and band-slip conformers, are studied. Adiabati...
Geometrical method of decoupling
NASA Astrophysics Data System (ADS)
Baumgarten, C.
2012-12-01
The computation of tunes and matched beam distributions are essential steps in the analysis of circular accelerators. If certain symmetries—like midplane symmetry—are present, then it is possible to treat the betatron motion in the horizontal, the vertical plane, and (under certain circumstances) the longitudinal motion separately using the well-known Courant-Snyder theory, or to apply transformations that have been described previously as, for instance, the method of Teng and Edwards. In a preceding paper, it has been shown that this method requires a modification for the treatment of isochronous cyclotrons with non-negligible space charge forces. Unfortunately, the modification was numerically not as stable as desired and it was still unclear, if the extension would work for all conceivable cases. Hence, a systematic derivation of a more general treatment seemed advisable. In a second paper, the author suggested the use of real Dirac matrices as basic tools for coupled linear optics and gave a straightforward recipe to decouple positive definite Hamiltonians with imaginary eigenvalues. In this article this method is generalized and simplified in order to formulate a straightforward method to decouple Hamiltonian matrices with eigenvalues on the real and the imaginary axis. The decoupling of symplectic matrices which are exponentials of such Hamiltonian matrices can be deduced from this in a few steps. It is shown that this algebraic decoupling is closely related to a geometric “decoupling” by the orthogonalization of the vectors E→, B→, and P→, which were introduced with the so-called “electromechanical equivalence.” A mathematical analysis of the problem can be traced down to the task of finding a structure-preserving block diagonalization of symplectic or Hamiltonian matrices. Structure preservation means in this context that the (sequence of) transformations must be symplectic and hence canonical. When used iteratively, the decoupling algorithm can also be applied to n-dimensional systems and requires O(n2) iterations to converge to a given precision.
A geometric framework for nonlinear visual coding
NASA Astrophysics Data System (ADS)
Barth, Erhardt; Watson, Andrew B.
2000-08-01
It is argued that important aspects of early and middle level visual coding may be understood as resulting from basic geometric processing of the visual input. The input is treated as a hypersurface defined by image intensity as a function of two spatial coordinates and time. Analytical results show how the Riemann curvature tensor R of this hypersurface represents speed and direction of motion. Moreover, the results can predict the selectivity of MT neurons for multiple motions and for motion in a direction along the optimal spatial orientation. Finally, a model based on integrated R components predicts global-motion percepts related to the barber-pole illusion.
Aerospace plane guidance using geometric control theory
NASA Technical Reports Server (NTRS)
Van Buren, Mark A.; Mease, Kenneth D.
1990-01-01
A reduced-order method employing decomposition, based on time-scale separation, of the 4-D state space in a 2-D slow manifold and a family of 2-D fast manifolds is shown to provide an excellent approximation to the full-order minimum-fuel ascent trajectory. Near-optimal guidance is obtained by tracking the reduced-order trajectory. The tracking problem is solved as regulation problems on the family of fast manifolds, using the exact linearization methodology from nonlinear geometric control theory. The validity of the overall guidance approach is indicated by simulation.
Soydaş, Emine; Bozkaya, Uğur
2015-04-14
An assessment of orbital-optimized MP2.5 (OMP2.5) [ Bozkaya, U.; Sherrill, C. D. J. Chem. Phys. 2014, 141, 204105 ] for thermochemistry and kinetics is presented. The OMP2.5 method is applied to closed- and open-shell reaction energies, barrier heights, and aromatic bond dissociation energies. The performance of OMP2.5 is compared with that of the MP2, OMP2, MP2.5, MP3, OMP3, CCSD, and CCSD(T) methods. For most of the test sets, the OMP2.5 method performs better than MP2.5 and CCSD, and provides accurate results. For barrier heights of radical reactions and aromatic bond dissociation energies OMP2.5-MP2.5, OMP2-MP2, and OMP3-MP3 differences become obvious. Especially, for aromatic bond dissociation energies, standard perturbation theory (MP) approaches dramatically fail, providing mean absolute errors (MAEs) of 22.5 (MP2), 17.7 (MP2.5), and 12.8 (MP3) kcal mol(-1), while the MAE values of the orbital-optimized counterparts are 2.7, 2.4, and 2.4 kcal mol(-1), respectively. Hence, there are 5-8-folds reductions in errors when optimized orbitals are employed. Our results demonstrate that standard MP approaches dramatically fail when the reference wave function suffers from the spin-contamination problem. On the other hand, the OMP2.5 method can reduce spin-contamination in the unrestricted Hartree-Fock (UHF) initial guess orbitals. For overall evaluation, we conclude that the OMP2.5 method is very helpful not only for challenging open-shell systems and transition-states but also for closed-shell molecules. Hence, one may prefer OMP2.5 over MP2.5 and CCSD as an O(N(6)) method, where N is the number of basis functions, for thermochemistry and kinetics. The cost of the OMP2.5 method is comparable with that of CCSD for energy computations. However, for analytic gradient computations, the OMP2.5 method is only half as expensive as CCSD. PMID:26574366
The rotational spectrum and geometrical structure of thiozone, S3.
McCarthy, Michael C; Thorwirth, Sven; Gottlieb, Carl A; Thaddeus, Patrick
2004-04-01
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
Correlated algebraic-geometric codes
NASA Astrophysics Data System (ADS)
Guruswami, Venkatesan; Patthak, Anindya C.
2008-03-01
We define a new family of error-correcting codes based on algebraic curves over finite fields, and develop efficient list decoding algorithms for them. Our codes extend the class of algebraic-geometric (AG) codes via a (nonobvious) generalization of the approach in the recent breakthrough work of Parvaresh and Vardy (2005). Our work shows that the PV framework applies to fairly general settings by elucidating the key algebraic concepts underlying it. Also, more importantly, AG codes of arbitrary block length exist over fixed alphabets Sigma , thus enabling us to establish new trade-offs between the list decoding radius and rate over a bounded alphabet size. The work of Parvaresh and Vardy (2005) was extended in Guruswami and Rudra (2006) to give explicit codes that achieve the list decoding capacity (optimal trade-off between rate and fraction of errors corrected) over large alphabets. A similar extension of this work along the lines of Guruswami and Rudra could have substantial impact. Indeed, it could give better trade-offs than currently known over a fixed alphabet (say, GF(2^{12}) ), which in turn, upon concatenation with a fixed, well-understood binary code, could take us closer to the list decoding capacity for binary codes. This may also be a promising way to address the significant complexity drawback of the result of Guruswami and Rudra, and to enable approaching capacity with bounded list size independent of the block length (the list size and decoding complexity in their work are both n^{Omega(1/\\varepsilon)} where \\varepsilon is the distance to capacity). Similar to algorithms for AG codes from Guruswami and Sudan (1999) and (2001), our encoding/decoding algorithms run in polynomial time assuming a natural polynomial-size representation of the code. For codes based on a specific ``optimal'' algebraic curve, we also present an expected polynomial time algorithm to construct the requisite representation. This in turn fills an important void in the literature by presenting an efficient construction of the representation often assumed in the list decoding algorithms for AG codes.
The geometric resistivity correction factor for several geometrical samples
NASA Astrophysics Data System (ADS)
Yilmaz, Serdar
2015-08-01
This paper reviews the geometric resistivity correction factor of the 4-point probe DC electrical conductivity measurement method using several geometrical samples. During the review of the literature, only the articles that include the effect of geometry on resistivity calculation were considered. Combinations of equations used for various geometries were also given. Mathematical equations were given in the text without details. Expressions for the most commonly used geometries were presented in a table for easy reference.
Geometric Effects on Electron Cloud
Wang, L
2007-07-06
The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit the machine performances by inducing beam instabilities, beam emittance increase, beam loss, vacuum pressure increases and increased heat load on the vacuum chamber wall. The electron multipacting is a kind of geometric resonance phenomenon and thus is sensitive to the geometric parameters such as the aperture of the beam pipe, beam shape and beam bunch fill pattern, etc. This paper discusses the geometric effects on the electron cloud build-up in a beam chamber and examples are given for different beams and accelerators.
Pi Bond Orders and Bond Lengths
ERIC Educational Resources Information Center
Herndon, William C.; Parkanyi, Cyril
1976-01-01
Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)
Current Concept of Geometrical Accuracy
NASA Astrophysics Data System (ADS)
Görög, Augustín; Görögová, Ingrid
2014-06-01
Within the solving VEGA 1/0615/12 research project "Influence of 5-axis grinding parameters on the shank cutteŕs geometric accuracy", the research team will measure and evaluate geometrical accuracy of the produced parts. They will use the contemporary measurement technology (for example the optical 3D scanners). During the past few years, significant changes have occurred in the field of geometrical accuracy. The objective of this contribution is to analyse the current standards in the field of geometric tolerance. It is necessary to bring an overview of the basic concepts and definitions in the field. It will prevent the use of outdated and invalidated terms and definitions in the field. The knowledge presented in the contribution will provide the new perspective of the measurement that will be evaluated according to the current standards.
NASA Technical Reports Server (NTRS)
1977-01-01
Another spinoff to the food processing industry involves a dry lubricant developed by General Magnaplate Corp. of Linden, N.J. Used in such spacecraft as Apollo, Skylab and Viking, the lubricant is a coating bonded to metal surfaces providing permanent lubrication and corrosion resistance. The coating lengthens equipment life and permits machinery to be operated at greater speed, thus increasing productivity and reducing costs. Bonded lubricants are used in scores of commercia1 applications. They have proved particularly valuable to food processing firms because, while increasing production efficiency, they also help meet the stringent USDA sanitation codes for food-handling equipment. For example, a cookie manufacturer plagued production interruptions because sticky batter was clogging the cookie molds had the brass molds coated to solve the problem. Similarly, a pasta producer faced USDA action on a sanitation violation because dough was clinging to an automatic ravioli-forming machine; use of the anti-stick coating on the steel forming plates solved the dual problem of sanitation deficiency and production line downtime.
Solving Geometric Problems by Using Unit Blocks.
ERIC Educational Resources Information Center
Andrews, Angela Giglio
1999-01-01
Discusses the importance of using children's previous experiences with geometric figures to build foundations for developing geometric thinking. Describes how children's play with unit blocks can be structured to give them experiences with geometric concepts. Contains 12 references. (ASK)
ERIC Educational Resources Information Center
Kahn, Steven P.
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…
Antenna with Dielectric Having Geometric Patterns
NASA Technical Reports Server (NTRS)
Dudley, Kenneth L. (Inventor); Elliott, Holly A. (Inventor); Cravey, Robin L. (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Watson, Kent A. (Inventor); Smith, Jr., Joseph G. (Inventor)
2013-01-01
An antenna includes a ground plane, a dielectric disposed on the ground plane, and an electrically-conductive radiator disposed on the dielectric. The dielectric includes at least one layer of a first dielectric material and a second dielectric material that collectively define a dielectric geometric pattern, which may comprise a fractal geometry. The radiator defines a radiator geometric pattern, and the dielectric geometric pattern is geometrically identical, or substantially geometrically identical, to the radiator geometric pattern.
Algebraic, geometric, and stochastic aspects of genetic operators
NASA Technical Reports Server (NTRS)
Foo, N. Y.; Bosworth, J. L.
1972-01-01
Genetic algorithms for function optimization employ genetic operators patterned after those observed in search strategies employed in natural adaptation. Two of these operators, crossover and inversion, are interpreted in terms of their algebraic and geometric properties. Stochastic models of the operators are developed which are employed in Monte Carlo simulations of their behavior.
Computational geometric mechanics and control of rigid bodies
NASA Astrophysics Data System (ADS)
Lee, Taeyoung
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.
Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach.
Arrieta, Jorge; Cartwright, Julyan H E; Gouillart, Emmanuelle; Piro, Nicolas; Piro, Oreste; Tuval, Idan
2015-01-01
Mixing fluid in a container at low Reynolds number--in an inertialess environment--is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase. We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the "belly phase," peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing. PMID:26154384
Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach
Arrieta, Jorge; Cartwright, Julyan H. E.; Gouillart, Emmanuelle; Piro, Nicolas; Piro, Oreste; Tuval, Idan
2015-01-01
Mixing fluid in a container at low Reynolds number— in an inertialess environment—is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase. We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the “belly phase,” peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing. PMID:26154384
Simulation on Measurement Method of Geometric Distortion of Telescopes
NASA Astrophysics Data System (ADS)
Li, F.; Ren, S. L.
2015-11-01
Measuring the geometric distortion is conducive to improve the astrometric accuracy of telescopes, which is meaningful for many disciplines of astronomy, such as stellar clusters, natural satellites, asteroids, comets, and the other celestial bodies in the solar system. For this reason, researchers have developed an iterative self-calibration method to measure the geometric distortion of telescopes by observing a dense star field in the dithering mode, and have achieved many good results. However, the previous work did not constrain the density of star field or the dithering number in the observing mode, but chose relative good conditions to observe, which took up much observing time. In order to explore the validity of self-calibration method, and optimize its observing conditions, it is necessary to carry out the corresponding simulation. Firstly, we introduce the self-calibration method in detail in the present work. By the simulation method, the effectiveness of self-calibration method to give the geometric distortion is proved, and the observing conditions, such as the density of star field and dithering number, are optimized to give the geometric distortion with a high accuracy. Considering the practical application for correcting the geometric distortion, we also analyze the relation between the number of reference stars in the field of view and the astrometric accuracy by virtue of the simulation method.
NASA Astrophysics Data System (ADS)
Rathi, Somilkumar; Ray, Asok
2008-03-01
Ab initio calculations within the framework of hybrid density functional theory and finite cluster approximation have been performed for the electronic and geometric structures of three different types of armchair germanium carbide nanotubes from (3, 3) to (11, 11). Full geometry and spin optimizations with unrestricted symmetry have been performed. A detailed comparison of the structures and stabilities of the three types of nanotubes will be presented. The dependence of the electronic band gaps on the respective tube diameters, energy density of states, dipole moments as well as Mulliken charge distributions have been investigated. Radial buckling of tube along with bond length variations is also studied. All armchair GeC nanotubes investigated so far are semiconducting in nature. Applications in the field of nano-optoelectronic devices, molecular electronics and band gap engineering are envisioned for GeC nanotubes.
Pauling bond strength, bond length and electron density distribution
Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.
2014-01-18
A power law regression equation, /r)-0.21, determined for a large number of oxide crystals at ambient conditions and /r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ρ(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, σ, power law expression σ = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, <ρ(rc)> = r[(1.41)/
NASA Astrophysics Data System (ADS)
Hirn, Ulrich; Schennach, Robert
2015-05-01
The process of papermaking requires substantial amounts of energy and wood consumption, which contributes to larger environmental costs. In order to optimize the production of papermaking to suit its many applications in material science and engineering, a quantitative understanding of bonding forces between the individual pulp fibers is of importance. Here we show the first approach to quantify the bonding energies contributed by the individual bonding mechanisms. We calculated the impact of the following mechanisms necessary for paper formation: mechanical interlocking, interdiffusion, capillary bridges, hydrogen bonding, Van der Waals forces, and Coulomb forces on the bonding energy. Experimental results quantify the area in molecular contact necessary for bonding. Atomic force microscopy experiments derive the impact of mechanical interlocking. Capillary bridges also contribute to the bond. A model based on the crystal structure of cellulose leads to values for the chemical bonds. In contrast to general believe which favors hydrogen bonding Van der Waals bonds play the most important role according to our model. Comparison with experimentally derived bond energies support the presented model. This study characterizes bond formation between pulp fibers leading to insight that could be potentially used to optimize the papermaking process, while reducing energy and wood consumption.
Hirn, Ulrich; Schennach, Robert
2015-01-01
The process of papermaking requires substantial amounts of energy and wood consumption, which contributes to larger environmental costs. In order to optimize the production of papermaking to suit its many applications in material science and engineering, a quantitative understanding of bonding forces between the individual pulp fibers is of importance. Here we show the first approach to quantify the bonding energies contributed by the individual bonding mechanisms. We calculated the impact of the following mechanisms necessary for paper formation: mechanical interlocking, interdiffusion, capillary bridges, hydrogen bonding, Van der Waals forces, and Coulomb forces on the bonding energy. Experimental results quantify the area in molecular contact necessary for bonding. Atomic force microscopy experiments derive the impact of mechanical interlocking. Capillary bridges also contribute to the bond. A model based on the crystal structure of cellulose leads to values for the chemical bonds. In contrast to general believe which favors hydrogen bonding Van der Waals bonds play the most important role according to our model. Comparison with experimentally derived bond energies support the presented model. This study characterizes bond formation between pulp fibers leading to insight that could be potentially used to optimize the papermaking process, while reducing energy and wood consumption. PMID:26000898
Geometric scalar theory of gravity
Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D.; Moschella, U. E-mail: eduhsb@cbpf.br E-mail: egoulart@cbpf.br E-mail: toniato@cbpf.br
2013-06-01
We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor — which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models — does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.
Geometrical modelling of textile reinforcements
NASA Technical Reports Server (NTRS)
Pastore, Christopher M.; Birger, Alexander B.; Clyburn, Eugene
1995-01-01
The mechanical properties of textile composites are dictated by the arrangement of yarns contained with the material. Thus to develop a comprehensive understanding of the performance of these materials, it is necessary to develop a geometrical model of the fabric structure. This task is quite complex, as the fabric is made form highly flexible yarn systems which experience a certain degree of compressability. Furthermore there are tremendous forces acting on the fabric during densification typically resulting in yarn displacement and misorientation. The objective of this work is to develop a methodology for characterizing the geometry of yarns within a fabric structure including experimental techniques for evaluating these models. Furthermore, some applications of these geometric results to mechanical prediction models are demonstrated. Although more costly than its predecessors, the present analysis is based on the detailed architecture developed by one of the authors and his colleagues and accounts for many of the geometric complexities that other analyses ignore.
Geometric pumping in autophoretic channels.
Michelin, Sébastien; Montenegro-Johnson, Thomas D; De Canio, Gabriele; Lobato-Dauzier, Nicolas; Lauga, Eric
2015-08-01
Many microfluidic devices use macroscopic pressure differentials to overcome viscous friction and generate flows in microchannels. In this work, we investigate how the chemical and geometric properties of the channel walls can drive a net flow by exploiting the autophoretic slip flows induced along active walls by local concentration gradients of a solute species. We show that chemical patterning of the wall is not required to generate and control a net flux within the channel, rather channel geometry alone is sufficient. Using numerical simulations, we determine how geometric characteristics of the wall influence channel flow rate, and confirm our results analytically in the asymptotic limit of lubrication theory. PMID:26000567
Geometrical Optics of Dense Aerosols
Hay, Michael J.; Valeo, Ernest J.; Fisch, Nathaniel J.
2013-04-24
Assembling a free-standing, sharp-edged slab of homogeneous material that is much denser than gas, but much more rare ed than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed fi eld, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the nite particle density reduces the eff ective Stokes number of the flow, a critical result for controlled focusing. __________________________________________________
Geometric integration for particle accelerators
NASA Astrophysics Data System (ADS)
Forest, Étienne
2006-05-01
This paper is a very personal view of the field of geometric integration in accelerator physics—a field where often work of the highest quality is buried in lost technical notes or even not published; one has only to think of Simon van der Meer Nobel prize work on stochastic cooling—unpublished in any refereed journal. So I reconstructed the relevant history of geometrical integration in accelerator physics as much as I could by talking to collaborators and using my own understanding of the field. The reader should not be too surprised if this account is somewhere between history, science and perhaps even fiction.
Geometrical spin symmetry and spin
Pestov, I. B.
2011-07-15
Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.
Designing molecular devices by altering bond lengths.
Lamba, Vijay; Wilkinson, Suman J; Arora, Charu
2011-12-01
The work focuses on a theoretical approach to investigating the electric field (EF) dependence of bond-length alternation, the geometric and electronic structures of molecular wires used in the design of molecular electronic devices, the EF dependence of SCF energy, and the spatial distribution of the frontier orbitals of the molecular wires. Just as the bond length is an important influence on the conductance of the molecular wire, the dependence of the conductance on the chain length was also studied. We have also investigated how the current-voltage (I-V) characteristics change with bond length, as the bond length plays an important role in determining the conductance of molecular wires. PMID:21369931
Geometric registration and rectification of spaceborne SAR imagery
NASA Technical Reports Server (NTRS)
Curlander, J. C.; Pang, S. N.
1982-01-01
This paper describes the development of automated location and geometric rectification techniques for digitally processed synthetic aperture radar (SAR) imagery. A software package has been developed that is capable of determining the absolute location of an image pixel to within 60 m using only the spacecraft ephemeris data and the characteristics of the SAR data collection and processing system. Based on this location capability algorithms have been developed that geometrically rectify the imagery, register it to a common coordinate system and mosaic multiple frames to form extended digital SAR maps. These algorithms have been optimized using parallel processing techniques to minimize the operating time. Test results are given using Seasat SAR data.
NASA Astrophysics Data System (ADS)
Yin, Zhifu; Qi, Liping; Zou, Helin; Sun, Lei; Xu, Shenbo
2015-08-01
Plastic planar nanofluidic chips are becoming increasingly important for biological and chemical applications. However, the majority of the present bonding methods for planar nanofluidic chips suffer from high dimension loss and low bonding strength. In this work, a novel thermal bonding technique based on O2 plasma and ethanol treatment was proposed. With the assistance of O2 plasma and ethanol, the PET (polyethylene terephthalate) planar nanofluidic chip can be bonded at a low bonding temperature of 50 °C. To increase the bonding rate and bonding strength, the O2 plasma parameters and thermal bonding parameters were optimized during the bonding process. The tensile test indicates that the bonding strength of the PET planar nanofluidic chip can reach 0.954 MPa, while the auto-fluorescence test demonstrates that there is no leakage or blockage in any of the bonded micro- or nanochannels.
A geometric approach to direct minimization
NASA Astrophysics Data System (ADS)
van Voorhis, Troy; Head-Gordon, Martin
The approach presented, geometric direct minimization (GDM), is derived from purely geometrical arguments, and is designed to minimize a function of a set of orthonormal orbitals. The optimization steps consist of sequential unitary transformations of the orbitals, and convergence is accelerated using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) approach in the iterative subspace, together with a diagonal approximation to the Hessian for the remaining degrees of freedom. The approach is tested by implementing the solution of the self-consistent field (SCF) equations and comparing results with the standard direct inversion in the iterative subspace (DIIS) method. It is found that GDM is very robust and converges in every system studied, including several cases in which DIIS fails to find a solution. For main group compounds, GDM convergence is nearly as rapid as DIIS, whereas for transition metalcontaining systems we find that GDM is significantly slower than DIIS. A hybrid procedure where DIIS is used for the first several iterations and GDM is used thereafter is found to provide a robust solution for transition metal-containing systems.
Celestial mechanics with geometric algebra
NASA Technical Reports Server (NTRS)
Hestenes, D.
1983-01-01
Geometric algebra is introduced as a general tool for Celestial Mechanics. A general method for handling finite rotations and rotational kinematics is presented. The constants of Kepler motion are derived and manipulated in a new way. A new spinor formulation of perturbation theory is developed.
Geometric quantum noise of spin.
Shnirman, Alexander; Gefen, Yuval; Saha, Arijit; Burmistrov, Igor S; Kiselev, Mikhail N; Altland, Alexander
2015-05-01
The presence of geometric phases is known to affect the dynamics of the systems involved. Here, we consider a quantum degree of freedom, moving in a dissipative environment, whose dynamics is described by a Langevin equation with quantum noise. We show that geometric phases enter the stochastic noise terms. Specifically, we consider small ferromagnetic particles (nanomagnets) or quantum dots close to Stoner instability, and investigate the dynamics of the total magnetization in the presence of tunneling coupling to the metallic leads. We generalize the Ambegaokar-Eckern-Schön effective action and the corresponding semiclassical equations of motion from the U(1) case of the charge degree of freedom to the SU(2) case of the magnetization. The Langevin forces (torques) in these equations are strongly influenced by the geometric phase. As a first but nontrivial application, we predict low temperature quantum diffusion of the magnetization on the Bloch sphere, which is governed by the geometric phase. We propose a protocol for experimental observation of this phenomenon. PMID:25978252
Vergence, Vision, and Geometric Optics
ERIC Educational Resources Information Center
Keating, Michael P.
1975-01-01
Provides a definition of vergence in terms of the curvature of the wave fronts, and gives examples to illustrate the advantages of this approach. The vergence treatment of geometrical optics provides both conceptual and algebraic advantages, particularly for the life science student, over the traditional object distance-image distance-focal length…
What Determines Bond Costs. Municipal Bonds Series.
ERIC Educational Resources Information Center
Young, Douglas; And Others
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
A geometrical perspective for the bargaining problem.
Wong, Kelvin Kian Loong
2010-01-01
A new treatment to determine the Pareto-optimal outcome for a non-zero-sum game is presented. An equilibrium point for any game is defined here as a set of strategy choices for the players, such that no change in the choice of any single player will increase the overall payoff of all the players. Determining equilibrium for multi-player games is a complex problem. An intuitive conceptual tool for reducing the complexity, via the idea of spatially representing strategy options in the bargaining problem is proposed. Based on this geometry, an equilibrium condition is established such that the product of their gains over what each receives is maximal. The geometrical analysis of a cooperative bargaining game provides an example for solving multi-player and non-zero-sum games efficiently. PMID:20436675
A geometric approach to quantum state separation
NASA Astrophysics Data System (ADS)
Bagan, E.; Yerokhin, V.; Shehu, A.; Feldman, E.; Bergou, J. A.
2015-12-01
Probabilistic quantum state transformations can be characterized by the degree of state separation they provide. This, in turn, sets limits on the success rate of these transformations. We consider optimum state separation of two known pure states in the general case where the known states have arbitrary a priori probabilities. The problem is formulated from a geometric perspective and shown to be equivalent to the problem of finding tangent curves within two families of conics that represent the unitarity constraints and the objective functions to be optimized, respectively. We present the corresponding analytical solutions in various forms. In the limit of perfect state separation, which is equivalent to unambiguous state discrimination, the solution exhibits a phenomenon analogous to a second order symmetry breaking phase transition. We also propose a linear optics implementation of separation which is based on the dual rail representation of qubits and single-photon multiport interferometry.
Random broadcast on random geometric graphs
Bradonjic, Milan; Elsasser, Robert; Friedrich, Tobias
2009-01-01
In this work, we consider the random broadcast time on random geometric graphs (RGGs). The classic random broadcast model, also known as push algorithm, is defined as: starting with one informed node, in each succeeding round every informed node chooses one of its neighbors uniformly at random and informs it. We consider the random broadcast time on RGGs, when with high probability: (i) RGG is connected, (ii) when there exists the giant component in RGG. We show that the random broadcast time is bounded by {Omicron}({radical} n + diam(component)), where diam(component) is a diameter of the entire graph, or the giant component, for the regimes (i), or (ii), respectively. In other words, for both regimes, we derive the broadcast time to be {Theta}(diam(G)), which is asymptotically optimal.
ERIC Educational Resources Information Center
Sanderson, R. T.
1972-01-01
The continuation of a paper discussing chemical bonding from a bond energy viewpoint, with a number of examples of single and multiple bonds. (Part I appeared in volume 1 number 3, pages 16-23, February 1972.) (AL)
Students' Perceptions of Parental Bonding Styles and Their Academic Burnout
ERIC Educational Resources Information Center
Shin, Hyojung; Lee, Jayoung; Kim, Boyoung; Lee, Sang Min
2012-01-01
This study investigated how parental bonding style affects academic burnout in Korean adolescents. Participants were 447 middle school students, who completed the Parental Bonding Instrument and the Maslach Burnout Inventory-Student Survey. MANCOVA results confirmed that adolescents reporting the optimal bonding parental style, for both mother and…
Geometrical Phases in Quantum Mechanics
NASA Astrophysics Data System (ADS)
Christian, Joy Julius
In quantum mechanics, the path-dependent geometrical phase associated with a physical system, over and above the familiar dynamical phase, was initially discovered in the context of adiabatically changing environments. Subsequently, Aharonov and Anandan liberated this phase from the original formulation of Berry, which used Hamiltonians, dependent on curves in a classical parameter space, to represent the cyclic variations of the environments. Their purely quantum mechanical treatment, independent of Hamiltonians, instead used the non-trivial topological structure of the projective space of one-dimensional subspaces of an appropriate Hilbert space. The geometrical phase, in their treatment, results from a parallel transport of the time-dependent pure quantum states along a curve in this space, which is endowed with an abelian connection. Unlike Berry, they were able to achieve this without resort to an adiabatic approximation or to a time-independent eigenvalue equation. Prima facie, these two approaches are conceptually quite different. After a review of both approaches, an exposition bridging this apparent conceptual gap is given; by rigorously analyzing a model composite system, it is shown that, in an appropriate correspondence limit, the Berry phase can be recovered as a special case from the Aharonov-Anandan phase. Moreover, the model composite system is used to show that Berry's correction to the traditional Born-Oppenheimer energy spectra indeed brings the spectra closer to the exact results. Then, an experimental arrangement to measure geometrical phases associated with cyclic and non-cyclic variations of quantum states of an entangled composite system is proposed, utilizing the fundamental ideas of the recently opened field of two-particle interferometry. This arrangement not only resolves the controversy regarding the true nature of the phases associated with photon states, but also unequivocally predicts experimentally accessible geometrical phases in a truly quantum regime, and allows, for the first time, the measurements of such phases associated with arbitrary non-cyclic evolutions of entangled linear-momentum photon -states. This non-classical manifestation of the geometrical phases is due to the entangled character of linear-momentum photon-states of two correlated photons produced by parametric down-conversion in non-linear crystals. Finally, the non-local aspect of the geometrical phase is contrasted with the fundamental non-locality of quantum mechanics due to the entangled character of quantum states.
Mittra, Kaustuv; Sengupta, Kushal; Singha, Asmita; Bandyopadhyay, Sabyasachi; Chatterjee, Sudipta; Rana, Atanu; Samanta, Subhra; Dey, Abhishek
2016-02-01
An iron porphyrin with a pre-organized hydrogen bonding (H-Bonding) distal architecture is utilized to avoid the inherent loss of entropy associated with H-Bonding from solvent (water) and mimic the behavior of metallo-enzyme active sites attributed to H-Bonding interactions of active site with the 2nd sphere residues. Resonance Raman (rR) data on these iron porphyrin complexes indicate that H-Bonding to an axial ligand like hydroxide can result in both stronger or weaker Fe(III)-OH bond relative to iron porphyrin complexes. The 6-coordinate (6C) complexes bearing water derived axial ligands, trans to imidazole or thiolate axial ligand with H-Bonding stabilize a low spin (LS) ground state (GS) when a complex without H-Bonding stabilizes a high spin (HS) ground state. DFT calculations reproduce the trend in the experimental data and provide a mechanism of how H-Bonding can indeed lead to stronger metal ligand bonds when the axial ligand donates an H-Bond and lead to weaker metal ligand bonds when the axial ligand accepts an H-Bond. The experimental and computational results explain how a weak Fe(III)-OH bond (due to H-Bonding) can lead to the stabilization of low spin ground state in synthetic mimics and in enzymes containing iron porphyrin active sites. H-Bonding to a water ligand bound to a reduced ferrous active site can only strengthen the Fe(II)-OH2 bond and thus exclusion of water and hydrophilic residues from distal sites of O2 binding/activating heme proteins is necessary to avoid inhibition of O2 binding by water. These results help demonstrate the predominant role played by H-Bonding and subtle changes in its orientation in determining the geometric and electronic structure of iron porphyrin based active sites in nature. PMID:26638009
Geometrical modelling of textile reinforcements
NASA Technical Reports Server (NTRS)
Pastore, Christopher M.; Birger, Alexander B.; Clyburn, Eugene
1995-01-01
The mechanical properties of textile composites are dictated by the arrangement of yarns contained within the material. Thus, to develop a comprehensive understanding of the performance of these materials, it is necessary to develop a geometrical model of the fabric structure. This task is quite complex, as the fabric is made from highly flexible yarn systems which experience a certain degree of compressibility. Furthermore there are tremendous forces acting on the fabric during densification typically resulting in yarn displacement and misorientation. The objective of this work is to develop a methodology for characterizing the geometry of yarns within a fabric structure including experimental techniques for evaluating these models. Furthermore, some applications of these geometric results to mechanical property predictions models are demonstrated.
The verdict geometric quality library.
Knupp, Patrick Michael; Ernst, C.D. (Elemental Technologies, Inc., American Fork, UT); Thompson, David C.; Stimpson, C.J.; Pebay, Philippe Pierre
2006-03-01
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.
Geometrical interpretation of optical absorption
Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L.; Montesinos-Amilibia, J. M.
2011-08-15
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.
Geometrical scaling for identified particles
NASA Astrophysics Data System (ADS)
Praszalowicz, Michal
2013-12-01
We show that recently measured transverse momentum spectra of identified particles exhibit geometrical scaling (GS) in scaling variable τ=(( where m=√{m2+pT2}-m. We explore consequences of GS and show that both mid rapidity multiplicity and mean transverse momenta grow as powers of scattering energy. Furthermore, assuming Tsallis-like parametrization of the spectra we calculate the coefficients of this growth. We also show that Tsallis temperature is related to the average saturation scale.
Geometrical and FEA study on Millipede Forming
NASA Astrophysics Data System (ADS)
Kong, Lingran; Tang, Di; Ding, Shichao; Zhang, Yuankun
2013-12-01
Millipede Forming is an innovative sheet metal forming approach that has been proposed and developed in Australia. U-channels, Z-channels or tubular products can be made by Millipede Forming. While a strip moves through an optimal transitional surface between the entry to exit of a forming stand, the redundant longitudinal membrane strain can be significantly reduced compared to the conventional roll forming, which is the essential principle to obtaining high quality products. The incremental forming process studied has demonstrated major advantages on space efficiency, power consumption and materials sensitivities. The purpose of this study is to investigate the effects of main geometrical parameters and their optimization, in order to minimize the redundant longitudinal strains into elastic to avoid the redundant plastic deformations at flange during forming. In this study, a mild-steel U-channel sample with 10 mm flange width, fabricated by Millipede Forming in a forming length of 200 mm has been studied. Theoretical longitudinal membrane strains at profile's edge of different transitional surfaces and downhill pass are also analyzed. The results showed that obtaining an optimal transitional surface is essential and necessary in controlling the peak longitudinal strain to an acceptable amount and that by increasing downhill pass, longitudinal strain can be significantly reduced. The optimized transitional surface and downhill pass flow were simulated by Abaqus, and the peak longitudinal strain was finally less than 0.2% through a very short forming length of 200 mm. The results prove that Millipede Forming can achieve a better product quality in a much shorter forming distance than conventional roll forming.
Geometric Tachyon and Warm Inflation
NASA Astrophysics Data System (ADS)
Bhattacharjee, Anindita; Deshamukhya, Atri
2013-03-01
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.
Geometric mean for subspace selection.
Tao, Dacheng; Li, Xuelong; Wu, Xindong; Maybank, Stephen J
2009-02-01
Subspace selection approaches are powerful tools in pattern classification and data visualization. One of the most important subspace approaches is the linear dimensionality reduction step in the Fisher's linear discriminant analysis (FLDA), which has been successfully employed in many fields such as biometrics, bioinformatics, and multimedia information management. However, the linear dimensionality reduction step in FLDA has a critical drawback: for a classification task with c classes, if the dimension of the projected subspace is strictly lower than c - 1, the projection to a subspace tends to merge those classes, which are close together in the original feature space. If separate classes are sampled from Gaussian distributions, all with identical covariance matrices, then the linear dimensionality reduction step in FLDA maximizes the mean value of the Kullback-Leibler (KL) divergences between different classes. Based on this viewpoint, the geometric mean for subspace selection is studied in this paper. Three criteria are analyzed: 1) maximization of the geometric mean of the KL divergences, 2) maximization of the geometric mean of the normalized KL divergences, and 3) the combination of 1 and 2. Preliminary experimental results based on synthetic data, UCI Machine Learning Repository, and handwriting digits show that the third criterion is a potential discriminative subspace selection method, which significantly reduces the class separation problem in comparing with the linear dimensionality reduction step in FLDA and its several representative extensions. PMID:19110492
Polar metals by geometric design.
Kim, T H; Puggioni, D; Yuan, Y; Xie, L; Zhou, H; Campbell, N; Ryan, P J; Choi, Y; Kim, J-W; Patzner, J R; Ryu, S; Podkaminer, J P; Irwin, J; Ma, Y; Fennie, C J; Rzchowski, M S; Pan, X Q; Gopalan, V; Rondinelli, J M; Eom, C B
2016-05-01
Gauss's law dictates that the net electric field inside a conductor in electrostatic equilibrium is zero by effective charge screening; free carriers within a metal eliminate internal dipoles that may arise owing to asymmetric charge distributions. Quantum physics supports this view, demonstrating that delocalized electrons make a static macroscopic polarization, an ill-defined quantity in metals--it is exceedingly unusual to find a polar metal that exhibits long-range ordered dipoles owing to cooperative atomic displacements aligned from dipolar interactions as in insulating phases. Here we describe the quantum mechanical design and experimental realization of room-temperature polar metals in thin-film ANiO3 perovskite nickelates using a strategy based on atomic-scale control of inversion-preserving (centric) displacements. We predict with ab initio calculations that cooperative polar A cation displacements are geometrically stabilized with a non-equilibrium amplitude and tilt pattern of the corner-connected NiO6 octahedral--the structural signatures of perovskites--owing to geometric constraints imposed by the underlying substrate. Heteroepitaxial thin-films grown on LaAlO3 (111) substrates fulfil the design principles. We achieve both a conducting polar monoclinic oxide that is inaccessible in compositionally identical films grown on (001) substrates, and observe a hidden, previously unreported, non-equilibrium structure in thin-film geometries. We expect that the geometric stabilization approach will provide novel avenues for realizing new multifunctional materials with unusual coexisting properties. PMID:27096369
Optimized actuators for ultrathin deformable primary mirrors.
Laslandes, Marie; Patterson, Keith; Pellegrino, Sergio
2015-05-20
A novel design and selection scheme for surface-parallel actuators for ultrathin, lightweight mirrors is presented. The actuation system consists of electrodes printed on a continuous layer of piezoelectric material bonded to an optical-quality substrate. The electrodes provide almost full coverage of the piezoelectric layer, in order to maximize the amount of active material that is available for actuation, and their shape is optimized to maximize the correctability and stroke of the mirror for a chosen number of independent actuators and for a dominant imperfection mode. The starting point for the design of the electrodes is the observation that the correction of a figure error that has at least two planes of mirror symmetry is optimally done with twin actuators that have the same optimized shape but are rotated through a suitable angle. Additional sets of optimized twin actuators are defined by considering the intersection between the twin actuators, and hence an arbitrarily fine actuation pattern can be generated. It is shown that this approach leads to actuator systems with better performance than simple, geometrically based actuators. Several actuator patterns to correct third-order astigmatism aberrations are presented, and an experimental demonstration of a 41-actuator mirror is also presented. PMID:26192533
Geometric and Electronic Properties of Edge-decorated Graphene Nanoribbons
Chang, Shen-Lin; Lin, Shih-Yang; Lin, Shih-Kang; Lee, Chi-Hsuan; Lin, Ming-Fa
2014-01-01
Edge-decorated graphene nanoribbons are investigated with the density functional theory; they reveal three stable geometric structures. The first type is a tubular structure formed by the covalent bonds of decorating boron or nitrogen atoms. The second one consists of curved nanoribbons created by the dipole-dipole interactions between two edges when decorated with Be, Mg, or Al atoms. The final structure is a flat nanoribbon produced due to the repulsive force between two edges; most decorated structures belong to this type. Various decorating atoms, different curvature angles, and the zigzag edge structure are reflected in the electronic properties, magnetic properties, and bonding configurations. Most of the resulting structures are conductors with relatively high free carrier densities, whereas a few are semiconductors due to the zigzag-edge-induced anti-ferromagnetism. PMID:25123103
Geometrical Visualisation--Epistemic and Emotional
ERIC Educational Resources Information Center
Rodd, Melissa
2010-01-01
A well-documented experience of students of elementary Euclidean geometry is "seeing" a geometric result and being sure about its truth; this sort of experience gives rise to the notion of geometrical visualisation that is developed here. In this essay a philosophical argument for the epistemic potential of geometrical visualisation is reviewed,…
Development of a Geometric Spatial Visualization Tool
ERIC Educational Resources Information Center
Ganesh, Bibi; Wilhelm, Jennifer; Sherrod, Sonya
2009-01-01
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 patterns)…
Bond angles around a tetravalent atom.
Bohn, Robert K; Allen, Wesley D
2015-03-01
Relationships among the six bond angles about a central tetravalent atom depend on symmetry, ranging from the most symmetrical Td point group to the least symmetrical C1 point group having only the identity element. Exact relationships are derived here in two ways: (1) a purely algebraic treatment of the general mathematical conditions among the bond angles, followed by factorizations that arise from various symmetry constraints and (2) a reverse approach based on geometric analysis, starting with the most symmetrical Td case and relaxing constraints stepwise to lower point groups. The mathematical formulas show systematically how the degrees of freedom among the bond angles increase from zero to a maximum of five as the symmetry is relaxed from the Td symmetry. PMID:25291015
Fractal geometrical properties of nuclei
NASA Astrophysics Data System (ADS)
Ma, Wei-Hu; Wang, Jian-Song; Wang, Qi; Mukherjee, S.; Yang, Lei; Yang, Yan-Yun; Huang, Mei-Rong
2015-10-01
We present a new idea to understand the structure of nuclei and compare it to the liquid drop model. After discussing the probability that the nuclear system may be a fractal object with the characteristic of self-similarity, the irregular nuclear structure properties and the self-similarity characteristic are considered to be an intrinsic aspect of the nuclear structure properties. For the description of nuclear geometric properties, the nuclear fractal dimension is an irreplaceable variable similar to the nuclear radius. In order to determine these two variables, a new nuclear potential energy formula which is related to the fractal dimension is put forward and the phenomenological semiempirical Bethe-Weizscker binding energy formula is modified using the fractal geometric theory. One important equation set with two equations is obtained, which is related to the concept that the fractal dimension should be a dynamic parameter in the process of nuclear synthesis. The fractal dimensions of the light nuclei are calculated and their physical meanings are discussed. We compare the nuclear fractal mean density radii with the radii calculated by the liquid drop model for the light stable and unstable nuclei using rational nuclear fractal structure types. In the present model of fractal nuclear structure there is an obvious additional feature compared to the liquid drop model, since the present model can reflect the geometric information of the nuclear structure, especially for nuclei with clusters, such as the ?-cluster nuclei and halo nuclei. Supported by National Basic Research Program of China (973 Program) (2014CB845405, 2013CB8344x), National Natural Science Foundation of China (U1432247, 11205209, 11205221)
Science, art and geometrical imagination
NASA Astrophysics Data System (ADS)
Luminet, Jean-Pierre
2011-06-01
From the geocentric, closed world model of Antiquity to the wraparound universe models of relativistic cosmology, the parallel history of space representations in science and art illustrates the fundamental 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.
SQCD Vacua and Geometrical Engineering
Tatar, Radu; Wetenhall, Ben
2008-11-23
We consider the geometrical engineering constructions for the N = 1 SQCD vacua. After one T-duality, these geometries with wrapped D5 branes become N = 1 brane configurations with NS-branes and D4-branes. After performing a flop, the geometries contain branes, antibranes and branes wrapped on non-holomorphic cycles. The various tachyon condensations between pairs of wrapped D5 branes and anti-D5 branes together with deformations of the cycles give rise to a variety of supersymmetric and metastable non-supersymmetric vacua.
Geometric reasoning and spatial understanding
Binford, T.O.
1982-01-01
Progress has been made on extensions to ACRONYM which include: representation and reasoning with time, events, and sequences; collaboration with MIT to develop geometric learning: representation of function, and reasoning between structure and function. A new ribbon finder for ACRONYM is under construction. Work in figure/ground separation is underway as a basis for the ribbon finder. Preliminary results are shown in grouping operations to determine regularities in images. A stereo system has been completed which combines edge-based stereo matching with surface interpolation utilizing correspondence of gray levels. Design of a new stereo vision system is underway.
Oxidative addition of the C-I bond on aluminum nanoclusters
NASA Astrophysics Data System (ADS)
Sengupta, Turbasu; Das, Susanta; Pal, Sourav
2015-07-01
Energetics and the in-depth reaction mechanism of the oxidative addition step of the cross-coupling reaction are studied in the framework of density functional theory (DFT) on aluminum nanoclusters. Aluminum metal in its bulk state is totally inactive towards carbon-halogen bond dissociation but selected Al nanoclusters (size ranging from 3 to 20 atoms) have shown a significantly lower activation barrier towards the oxidative addition reaction. The calculated energy barriers are lower than the gold clusters and within a comparable range with the conventional and most versatile Pd catalyst. Further investigations reveal that the activation energies and other reaction parameters are highly sensitive to the geometrical shapes and electronic structures of the clusters rather than their size, imposing the fact that comprehensive studies on aluminum clusters can be beneficial for nanoscience and nanotechnology. To understand the possible reaction mechanism in detail, the reaction pathway is investigated with the ab initio Born Oppenheimer Molecular Dynamics (BOMD) simulation and the Natural Bond Orbital (NBO) analysis. In short, our theoretical study highlights the thermodynamic and kinetic details of C-I bond dissociation on aluminum clusters for future endeavors in cluster chemistry.Energetics and the in-depth reaction mechanism of the oxidative addition step of the cross-coupling reaction are studied in the framework of density functional theory (DFT) on aluminum nanoclusters. Aluminum metal in its bulk state is totally inactive towards carbon-halogen bond dissociation but selected Al nanoclusters (size ranging from 3 to 20 atoms) have shown a significantly lower activation barrier towards the oxidative addition reaction. The calculated energy barriers are lower than the gold clusters and within a comparable range with the conventional and most versatile Pd catalyst. Further investigations reveal that the activation energies and other reaction parameters are highly sensitive to the geometrical shapes and electronic structures of the clusters rather than their size, imposing the fact that comprehensive studies on aluminum clusters can be beneficial for nanoscience and nanotechnology. To understand the possible reaction mechanism in detail, the reaction pathway is investigated with the ab initio Born Oppenheimer Molecular Dynamics (BOMD) simulation and the Natural Bond Orbital (NBO) analysis. In short, our theoretical study highlights the thermodynamic and kinetic details of C-I bond dissociation on aluminum clusters for future endeavors in cluster chemistry. Electronic supplementary information (ESI) available: Cartesian coordinates for the optimized structures and harmonic frequencies, sample IRC data and plot, grid data for three dimensional potential energy surface and contour plot and data for BOMD simulation. See DOI: 10.1039/c5nr02278a
NASA Technical Reports Server (NTRS)
Gwo, Dz-Hung (Inventor)
2003-01-01
A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.
Five-dimensional geometric electrovacuum problem with a geometric scalar field
NASA Astrophysics Data System (ADS)
Kiselev, A. S.; Krechet, V. G.
2012-03-01
A generalized geometric Reissner-Nordstrom problem taking into account a geometric scalar field G 44 ( x) is treated in the context of the five-dimensional geometric theory of gravitation and electromagnetism. A general solution is obtained for the corresponding five-dimensional Einstein vacuum equations. The essential contribution of the geometric scalar field, which can give rise to wormholes, is shown.
Chemically-bonded brick production based on burned clay by means of semidry pressing
NASA Astrophysics Data System (ADS)
Voroshilov, Ivan; Endzhievskaya, Irina; Vasilovskaya, Nina
2016-01-01
We presented a study on the possibility of using the burnt rocks of the Krasnoyarsk Territory for production of chemically-bonded materials in the form of bricks which are so widely used in multistory housing and private house construction. The radiographic analysis of the composition of burnt rock was conducted and a modifier to adjust the composition uniformity was identified. The mixing moisture content was identified and optimal amount at 13-15% was determined. The method of semidry pressing has been chosen. The process of obtaining moldings has been theoretically proved; the advantages of chemically-bonded wall materials compared to ceramic brick were shown. The production of efficient artificial stone based on material burnt rocks, which is comparable with conventionally effective ceramic materials or effective with cell tile was proved, the density of the burned clay-based cell tile makes up to 1630-1785 kg m3, with compressive strength of 13.6-20.0 MPa depending on the compression ratio and cement consumption, frost resistance index is F50, and the thermal conductivity in the masonry is λ = 0,459-0,546 W m * °C. The clear geometric dimensions of pressed products allow the use of the chemically-bonded brick based on burnt clay as a facing brick.
Geometric pumping in autophoretic channels
NASA Astrophysics Data System (ADS)
Michelin, Sebastien; Montenegro Johnson, Thomas; de Canio, Gabriele; Lobatto-Dauzier, Nicolas; Lauga, Eric
2015-11-01
Pumping at the microscale has important applications from biological fluid handling to lab-on-a-chip systems. It can be achieved either from a global (e.g. imposed pressure gradient) or local forcing (e.g. ciliary pumping). Phoretic slip flows generated from concentration or temperature gradients are examples of such local flow forcing. Autophoresis is currently receiving much attention for the design of self-propelled particles achieving force- and torque-free locomotion by combining two essential surface properties: (i) an activity that modifies the solute content of the particle's environment (e.g. catalytic reaction or solute release), and (ii) a mobility that generates a slip flow from the resulting local concentration gradients. Recent work showed that geometric asymmetry is sufficient for a chemically-homogeneous particle to self-propel. Here we extend this idea to micro-pumping in active channels whose walls possess both chemical activity and phoretic mobility. Using a combination of theoretical analysis and numerical simulations, we show that geometrically-asymmetric but chemically-homogeneous channels can generate pumping and analyze the resulting flow patterns.
Geometrical deployment for braided stent.
Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Yilmaz, Hasan; Farhat, Mohamed; Erceg, Gorislav; Lovblad, Karl-Olof; Vargas, Maria Isabel; Kulcsar, Zsolt; Pereira, Vitor Mendes
2016-05-01
The prediction of flow diverter stent (FDS) implantation for the treatment of intracranial aneurysms (IAs) is being increasingly required for hemodynamic simulations and procedural planning. In this paper, a deployment model was developed based on geometrical properties of braided stents. The proposed mathematical description is first applied on idealized toroidal vessels demonstrating the stent shortening in curved vessels. It is subsequently generalized to patient specific vasculature predicting the position of the filaments along with the length and local porosity of the stent. In parallel, in-vitro and in-vivo FDS deployments were measured by contrast-enhanced cone beam CT (CBCT) in idealized and patient-specific geometries. These measurements showed a very good qualitative and quantitative agreement with the virtual deployments and provided experimental validations of the underlying geometrical assumptions. In particular, they highlighted the importance of the stent radius assessment in the accuracy of the deployment prediction. Thanks to its low computational cost, the proposed model is potentially implementable in clinical practice providing critical information for patient safety and treatment outcome assessment. PMID:26891065
NPP VIIRS Geometric Performance Status
NASA Technical Reports Server (NTRS)
Lin, Guoqing; Wolfe, Robert E.; Nishihama, Masahiro
2011-01-01
Visible Infrared Imager Radiometer Suite (VIIRS) instrument on-board the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite is scheduled for launch in October, 2011. It is to provide satellite measured radiance/reflectance data for both weather and climate applications. Along with radiometric calibration, geometric characterization and calibration of Sensor Data Records (SDRs) are crucial to the VIIRS Environmental Data Record (EDR) algorithms and products which are used in numerical weather prediction (NWP). The instrument geometric performance includes: 1) sensor (detector) spatial response, parameterized by the dynamic field of view (DFOV) in the scan direction and instantaneous FOV (IFOV) in the track direction, modulation transfer function (MTF) for the 17 moderate resolution bands (M-bands), and horizontal spatial resolution (HSR) for the five imagery bands (I-bands); 2) matrices of band-to-band co-registration (BBR) from the corresponding detectors in all band pairs; and 3) pointing knowledge and stability characteristics that includes scan plane tilt, scan rate and scan start position variations, and thermally induced variations in pointing with respect to orbital position. They have been calibrated and characterized through ground testing under ambient and thermal vacuum conditions, numerical modeling and analysis. This paper summarizes the results, which are in general compliance with specifications, along with anomaly investigations, and describes paths forward for characterizing on-orbit BBR and spatial response, and for improving instrument on-orbit performance in pointing and geolocation.
NPP VIIRS geometric performance status
NASA Astrophysics Data System (ADS)
Lin, Guoqing; Wolfe, Robert E.; Nishihama, Masahiro
2011-10-01
Visible Infrared Imager Radiometer Suite (VIIRS) instrument on-board the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite is scheduled for launch in October, 2011. It is to provide satellite measured radiance/reflectance data for both weather and climate applications. Along with radiometric calibration, geometric characterization and calibration of Sensor Data Records (SDRs) are crucial to the VIIRS Environmental Data Record (EDR) algorithms and products which are used in numerical weather prediction (NWP). The instrument geometric performance includes: 1) sensor (detector) spatial response, parameterized by the dynamic field of view (DFOV) in the scan direction and instantaneous FOV (IFOV) in the track direction, modulation transfer function (MTF) for the 17 moderate resolution bands (M-bands), and horizontal spatial resolution (HSR) for the five imagery bands (I-bands); 2) matrices of band-to-band co-registration (BBR) from the corresponding detectors in all band pairs; and 3) pointing knowledge and stability characteristics that includes scan plane tilt, scan rate and scan start position variations, and thermally induced variations in pointing with respect to orbital position. They have been calibrated and characterized through ground testing under ambient and thermal vacuum conditions, numerical modeling and analysis. This paper summarizes the results, which are in general compliance with specifications, along with anomaly investigations, and describes paths forward for characterizing on-orbit BBR and spatial response, and for improving instrument on-orbit performance in pointing and geolocation.
Optimal Biofilm Featues: metabolic and geometric response to multiple oxidants
NASA Astrophysics Data System (ADS)
Kempes, C.; Okegbe, C.; Mears-Clarke, Z.; Follows, M. J.; Dietrich, L.
2014-12-01
An important challenge in understanding complex microbial mat communities is determining how groups of a single species balance metabolic requirements with the dynamics of resource supply. We have investigated this problem in the context of redox resources within a single-species bacterial biofilm. We developed a mathematical model of oxidant availability and metabolic response within biofilm features and we show that observed biofilm geometries maximize cellular reproduction and growth efficiency. Our model accurately predicts the measured distribution of two types of electron acceptors: oxygen, which is available from the environment, and phenazines, redox-active small molecules produced by the bacterium. Because our model is based on resource dynamics, we are also able to predict observed shifts in feature geometry based on changes in the availability of redox resources such as variations in the external availability of oxygen or the removal of phenazines. This analysis suggests various avenues for understanding microstructure and the evolution of spatial metabolism in microbial mats.
Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations
NASA Technical Reports Server (NTRS)
Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin
2000-01-01
A methodology is presented for determining the fatigue life of bonded composite skin/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange/skin specimens to verify the approach.
The geometric structure of single-walled nanotubes.
Lee, Richard K F; Cox, Barry J; Hill, James M
2010-06-01
In this paper, we survey a number of existing geometric structures which have been proposed by the authors as possible models for various nanotubes. Atoms assemble into molecules following the laws of quantum mechanics, and in general computational approaches to predicting the molecular structure can be arduous and involve considerable computing time. Fortunately, nature favours minimum energy structures which tend to be either very symmetric or very unsymmetric, and which therefore can be analyzed from a geometrical perspective. The conventional rolled-up model of nanotubes completely ignores any effects due to curvature and the present authors have proposed a number of exact geometric models. Here we review a number of these recent developments relating to the geometry of nanotubes, including both the traditional rolled-up models and some exact polyhedral constructions. We review a number of formulae for four materials, carbon, silicon, boron and boron nitride, and we also include results for the case when the bond lengths may take on distinct values. PMID:20648281
Geometric methods for wavelet-based image compression
NASA Astrophysics Data System (ADS)
Wakin, Michael B.; Romberg, Justin K.; Choi, Hyeokho; Baraniuk, Richard G.
2003-11-01
Natural images can be viewed as combinations of smooth regions, textures, and geometry. Wavelet-based image coders, such as the space-frequency quantization (SFQ) algorithm, provide reasonably efficient representations for smooth regions (using zerotrees, for example) and textures (using scalar quantization) but do not properly exploit the geometric regularity imposed on wavelet coefficients by features such as edges. In this paper, we develop a representation for wavelet coefficients in geometric regions based on the wedgelet dictionary, a collection of geometric atoms that construct piecewise-linear approximations to contours. Our wedgeprint representation implicitly models the coherency among geometric wavelet coefficients. We demonstrate that a simple compression algorithm combining wedgeprints with zerotrees and scalar quantization can achieve near-optimal rate-distortion performance D(R) ~ (log R)2/R2 for the class of piecewise-smooth images containing smooth C2 regions separated by smooth C2 discontinuities. Finally, we extend this simple algorithm and propose a complete compression framework for natural images using a rate-distortion criterion to balance the three representations. Our Wedgelet-SFQ (WSFQ) coder outperforms SFQ in terms of visual quality and mean-square error.
Flat plate heat pipe collectors made by roll bonding
NASA Astrophysics Data System (ADS)
Tanner, W.; Molt, W.; Flesch, T.
1983-10-01
Roll bonded heat pipes for solar collector applications are discussed. Thermodynamics of roll bonded plates with integrated heat exchanger were examined for different geometrical configurations. Prototypes were laboratory checked and modified. A strength problem occurred with increasing heat pipe pressure in the temperature range 130 to 200 C. Deformation of plates can be avoided by a pressure relief system. A version with three interrelated rolled sheets and an auxiliary stiffening channel structure at the rear side improves results without a pressure relief system. It is concluded that application of roll bonded heat pipes for solar collectors is not economical.
Diffusion bonding aeroengine components
NASA Astrophysics Data System (ADS)
Fitzpatrick, G. A.; Broughton, T.
1988-10-01
The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.
Bonding silicones with epoxies
Tira, J.S.
1980-01-01
It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.
Spinner, Miriam R.
1978-01-01
Maternal-infant bonding is a vital process which begins in early infancy and continues over the next few years. The bonding process has tremendous implications for both mother and child and is affected by many factors. Bonding problems occur and the family practitioner can identify these potential problems before pregnancy, during pregnancy, and in the postpartum period, and arrange assistance so the bonding process can unfold normally. PMID:21301556
Su, Neil Qiang; Adamo, Carlo; Xu, Xin
2013-11-01
We present a systematic investigation on the optimized geometric parameters for covalently bonded molecules, nonbonded intermolecular complexes, and transition state structures from three PBE (Perdew-Burke-Ernzerhof)-based doubly hybrid (DH) density functionals, namely PBE0-DH, PBE0-2, and xDH-PBE0. While the former two are the B2PLYP-type of DH functionals with no fit parameters, the latter is the XYG3-type of DH functional (xDH for short) with three fit parameters, whose energy expression is constructed by using density and orbital information from another standard (general) Kohn-Sham functional (i.e., PBE0) for doing the self-consistent field calculations. Generally good performances have been obtained with all three DH functionals, in particular, with xDH-PBE0. PMID:24206286
An algorithm for converting a virtual-bond chain into a complete polypeptide backbone chain
NASA Technical Reports Server (NTRS)
Luo, N.; Shibata, M.; Rein, R.
1991-01-01
A systematic analysis is presented of the algorithm for converting a virtual-bond chain, defined by the coordinates of the alpha-carbons of a given protein, into a complete polypeptide backbone. An alternative algorithm, based upon the same set of geometric parameters used in the Purisima-Scheraga algorithm but with a different "linkage map" of the algorithmic procedures, is proposed. The global virtual-bond chain geometric constraints are more easily separable from the loal peptide geometric and energetic constraints derived from, for example, the Ramachandran criterion, within the framework of this approach.
NASA Technical Reports Server (NTRS)
Burkett, F. S.
1978-01-01
Report makes it relatively easy for hybrid-circuit manufacturers to convert integrated circuit chips with aluminum bead leads. Report covers: techniques for handling tiny chips; proper geometries for ultrasonic bonding tips; best combinations of pressure, pulse time, and ultrasonic energy for bonding; and best thickness for metal films to which beam leads are bonded.
Phenomenological modeling of geometric metasurfaces
NASA Astrophysics Data System (ADS)
Ye, Weimin; Guo, Qinghua; Xiang, Yuanjiang; Fan, Dianyuan; Zhang, Shuang
2016-04-01
Metasurfaces, with their superior capability in manipulating the optical wavefront at the subwavelength scale and low manufacturing complexity, have shown great potential for planar photonics and novel optical devices. However, vector field simulation of metasurfaces is so far limited to periodic-structured metasurfaces containing a small number of meta-atoms in the unit cell by using full-wave numerical methods. Here, we propose a general phenomenological method to analytically model metasurfaces made up of arbitrarily distributed meta-atoms based on the assumption that the meta-atoms possess localized resonances with Lorentz-Drude forms, whose exact form can be retrieved from the full wave simulation of a single element. Applied to phase modulated geometric metasurfaces, our analytical results show good agreement with full-wave numerical simulations. The proposed theory provides an efficient method to model and design optical devices based on metasurfaces.
Geometrical characteristics of uniportal VATS.
Bertolaccini, Luca; Rocco, Gaetano; Viti, Andrea; Terzi, Alberto
2013-08-01
In terms of accuracy and efficacy Uniportal Video-Assisted Thoracic Surgery (VATS) resections are comparable to standard VATS. In standard three-ports VATS, the geometric configuration of a parallelogram generates interference with the optical source, creating a plane with a torsion angle not favorable on the flat two-dimensional vision of currently available monitors. The potential advantages of single-port VATS approach include not only the one intercostal space incision (reduction of postoperative pain) but also a translational approach of VATS instruments along a sagittal plane. Accordingly, the Uniportal approach enables VATS instruments to draw two parallel lines on the plane, bringing them to approach the target lesion from a caudo-cranial perspective thus achieving a projective plane. As a consequence, taking advantage of the unique spatial features specific to uniportal VATS, the surgeon is enabled to bring the operative fulcrum inside the chest to address the target lesion in a fashion similar to open surgery. PMID:24040527
NASA Technical Reports Server (NTRS)
Vanderplaats, G. N.; Chen, Xiang; Zhang, Ning-Tian
1988-01-01
The use of formal numerical optimization methods for the design of gears is investigated. To achieve this, computer codes were developed for the analysis of spur gears and spiral bevel gears. These codes calculate the life, dynamic load, bending strength, surface durability, gear weight and size, and various geometric parameters. It is necessary to calculate all such important responses because they all represent competing requirements in the design process. The codes developed here were written in subroutine form and coupled to the COPES/ADS general purpose optimization program. This code allows the user to define the optimization problem at the time of program execution. Typical design variables include face width, number of teeth and diametral pitch. The user is free to choose any calculated response as the design objective to minimize or maximize and may impose lower and upper bounds on any calculated responses. Typical examples include life maximization with limits on dynamic load, stress, weight, etc. or minimization of weight subject to limits on life, dynamic load, etc. The research codes were written in modular form for easy expansion and so that they could be combined to create a multiple reduction optimization capability in future.
Geometric parameter inverse model for drawbeads based on grey relational analysis and GA-BP
NASA Astrophysics Data System (ADS)
Xie, Yanmin
2013-12-01
In sheet metal forming, the wrinkling and fracture can be eliminated via an appropriate drawbead design. Proper drawbead design method to reduce time and cost is highly required. In the paper, the geometric parameters influencing semi-circular drawbead force are firstly analyzed making use of grey relational analysis, and the main parameters are obtained. The main parameters are sampled making use of Latin hypercube. The box forming is simulated with DYNAFORM, and the sample data are obtained. In the back propagation (BP) neural network, the thinning, thickening and major strains are selected as input parameters, and drawbead geometric parameters are selected as output objective. The inverse model of drawbead geometric parameters is established. The BP neural network weights are optimized with genetic algorithm (GA). Compared with the predictive values by BP, the parameters values by GA-BP are more accurate. Based on the GA-BP, the nonlinear relationship of the forming quality and drawbead geometric parameters is obtained making use of the optimized BP weights. Finally the optimum geometric parameters of drawbeads are obtained based on GA. The numerical simulations of box forming are compared before optimization and after optimization. The results show the optimized drawbeads can greatly improve the formability of sheet metal forming.
Theoretical study of the red- and blue-shifted hydrogen bonds of nitroxyl and acetylene dimers
NASA Astrophysics Data System (ADS)
Liu, Ying; Liu, Wenqing; Yang, Yong; Liu, Jianguo
Ab initio molecular orbital and density functional theory (DFT) in conjunction with different basis sets calculations were performed to study the C bond H?O red-shifted and N bond H?? blue-shifted hydrogen bonds in HNO bond C2H2 dimers. The geometric structures, vibrational frequencies and interaction energies were calculated by both standard and counterpoise (CP)-corrected methods. In addition, the G3B3 method was employed to calculate the interaction energies. The topological and natural bond orbital (NBO) analysis were investigated the origin of N bond H?? blue-shifted hydrogen bond. From the NBO analysis, the electron density decrease in the ?* (N bond H) is due to the significant electron density redistribution effect. The blue shifts of the N bond H stretching frequency are attributed to a cooperative effect between the rehybridization and electron density redistribution.
Hansen, D Flemming; Westler, William M; Kunze, Micha B A; Markley, John L; Weinhold, Frank; Led, Jens J
2012-03-14
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 (15)N 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 (15)N 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 (15)N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site. PMID:22329704
Geometric view of adaptive optics control.
Wiberg, Donald M; Max, Claire E; Gavel, Donald T
2005-05-01
The objective of an astronomical adaptive optics control system is to minimize the residual wave-front error remaining on the science-object wave fronts after being compensated for atmospheric turbulence and telescope aberrations. Minimizing the mean square wave-front residual maximizes the Strehl ratio and the encircled energy in pointlike images and maximizes the contrast and resolution of extended images. We prove the separation principle of optimal control for application to adaptive optics so as to minimize the mean square wave-front residual. This shows that the residual wave-front error attributable to the control system can be decomposed into three independent terms that can be treated separately in design. The first term depends on the geometry of the wave-front sensor(s), the second term depends on the geometry of the deformable mirror(s), and the third term is a stochastic term that depends on the signal-to-noise ratio. The geometric view comes from understanding that the underlying quantity of interest, the wave-front phase surface, is really an infinite-dimensional vector within a Hilbert space and that this vector space is projected into subspaces we can control and measure by the deformable mirrors and wave-front sensors, respectively. When the control and estimation algorithms are optimal, the residual wave front is in a subspace that is the union of subspaces orthogonal to both of these projections. The method is general in that it applies both to conventional (on-axis, ground-layer conjugate) adaptive optics architectures and to more complicated multi-guide-star- and multiconjugate-layer architectures envisaged for future giant telescopes. We illustrate the approach by using a simple example that has been worked out previously [J. Opt. Soc. Am. A 73, 1171 (1983)] for a single-conjugate, static atmosphere case and follow up with a discussion of how it is extendable to general adaptive optics architectures. PMID:15898546
Geometric solitons of Hamiltonian flows on manifolds
Song, Chong; Sun, Xiaowei; Wang, Youde
2013-12-15
It is well-known that the LIE (Locally Induction Equation) admit soliton-type solutions and same soliton solutions arise from different and apparently irrelevant physical models. By comparing the solitons of LIE and Killing magnetic geodesics, we observe that these solitons are essentially decided by two families of isometries of the domain and the target space, respectively. With this insight, we propose the new concept of geometric solitons of Hamiltonian flows on manifolds, such as geometric Schrödinger flows and KdV flows for maps. Moreover, we give several examples of geometric solitons of the Schrödinger flow and geometric KdV flow, including magnetic curves as geometric Schrödinger solitons and explicit geometric KdV solitons on surfaces of revolution.
On the nature of blueshifting hydrogen bonds.
Mo, Yirong; Wang, Changwei; Guan, Liangyu; Braïda, Benoît; Hiberty, Philippe C; Wu, Wei
2014-07-01
The block-localized wave function (BLW) method can derive the energetic, geometrical, and spectral changes with the deactivation of electron delocalization, and thus provide a unique way to elucidate the origin of improper, blueshifting hydrogen bonds versus proper, redshifting hydrogen bonds. A detailed analysis of the interactions of F(3)CH with NH(3) and OH(2) shows that blueshifting is a long-range phenomenon. Since among the various energy components contributing to hydrogen bonds, only the electrostatic interaction has long-range characteristics, we conclude that the contraction and blueshifting of a hydrogen bond is largely caused by electrostatic interactions. On the other hand, lengthening and redshifting is primarily due to the short-range n(Y)→σ*(X-H) hyperconjugation. The competition between these two opposing factors determines the final frequency change direction, for example, redshifting in F(3)CH⋅⋅⋅NH(3) and blueshifting in F(3)CH⋅⋅⋅OH(2). This mechanism works well in the series F(n)Cl(3)-n CH⋅⋅⋅Y (n=0-3, Y=NH(3), OH(2), SH(2)) and other systems. One exception is the complex of water and benzene. We observe the lengthening and redshifting of the O-H bond of water even with the electron transfer between benzene and water completely quenched. A distance-dependent analysis for this system reveals that the long-range electrostatic interaction is again responsible for the initial lengthening and redshifting. PMID:24862363
Bonding thermoplastic polymers
Wallow, Thomas I.; Hunter, Marion C.; Krafcik, Karen Lee; Morales, Alfredo M.; Simmons, Blake A.; Domeier, Linda A.
2008-06-24
We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.
Prospective bonding applications
NASA Astrophysics Data System (ADS)
Ancenay, H.; Benazet, D.
1981-07-01
Adhesive bonding in industry and in the laboratory is surveyed and prospects for its wider utilization are assessed. The economic impact of bonding technology on industry is discussed. Research is reviewed, centering on the development of nondestructive testing and inspection techniques. Traditional (wood) as well as new materials susceptible to bonding are considered. Applications in construction and civil engineering, in aeronautics, and in the automobile industry are covered. The use of glues in mechanical constructions, in assembling cylindrical parts, and in metal-metal bonding are examined. Hybrid assembling and bonding of composite materials are included.
Unifying geometric entanglement and geometric phase in a quantum phase transition
NASA Astrophysics Data System (ADS)
Azimi Mousolou, Vahid; Canali, Carlo M.; Sjöqvist, Erik
2013-07-01
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.
Gary S. Groenewold
2005-08-01
Simple bond cleavage is a class of fragmentation reactions in which a single bond is broken, without formation of new bonds between previously unconnected atoms. Because no bond making is involved, simple bond cleavages are endothermic, and activation energies are generally higher than for rearrangement eliminations. The rate of simple bond cleavage reactions is a strong function of the internal energy of the molecular ion, which reflects a loose transition state that resembles reaction products, and has a high density of accessible states. For this reason, simple bond cleavages tend to dominate fragmentation reactions for highly energized molecular ions. Simple bond cleavages have negligible reverse activation energy, and hence they are used as valuable probes of ion thermochemistry, since the energy dependence of the reactions can be related to the bond energy. In organic mass spectrometry, simple bond cleavages of odd electron ions can be either homolytic or heterolytic, depending on whether the fragmentation is driven by the radical site or the charge site. Simple bond cleavages of even electron ions tend to be heterolytic, producing even electron product ions and neutrals.
Unexpected hydrogen bond dynamics in imidazolium-based ionic liquids.
Thar, Jens; Brehm, Martin; Seitsonen, Ari P; Kirchner, Barbara
2009-11-19
Employing first-principles molecular dynamics simulations, we characterize the structural and dynamical hydrogen bonding in the ionic liquid [C(2)C(1)im][SCN]. The geometric picture indicates a superior role for the most acidic hydrogen bond (at H2) as compared to the two other hydrogen atoms at the rear. Despite the structural picture, the hydrogen bond dynamics at H2 is found to decay faster than the according dynamics at the H4 and H5 proton. Neglecting the directionality provides a dynamics which reflects the geometrical analysis. Two movements are identified. First, a fast (<0.3 ps) hopping of the anion above and below the imidazolium ring and second translational motion of the anion away from the cation in-plane of the imidazolium ring (5-10 ps). PMID:19852454
Triangular spin tubes with bond randomness
NASA Astrophysics Data System (ADS)
Miura, Yoko; Manaka, Hirotaka
2013-06-01
We performed X-ray diffraction, magnetic susceptibility, and magnetization experiments on nonequilateral triangular spin tubes composed of α-KCr1- x Fe x F4 ( x = 0˜0.13), which consisted of one-dimensional Heisenberg antiferromagnets coexisting with geometrically-frustrated spin systems with bond randomness. The variation of lattice parameters with x may indicate that the Fe3+ ions constitute the low-spin state ( S = 1/2). As a result of analyses of the frustration factor and the spin-flop transition field, we found that the effect of geometrical spin frustration was enhanced and that the magnetic anisotropy was weakened as x was increased. Because these results are remarkably similar to the previous results for α-KCr1- x Al x F4, the effect of the chemical impurity substitutions, whether they are magnetic or nonmagnetic ions, on α-KCrF4 is clearly understood.
A wire scanning based method for geometric calibration of high resolution CT system
NASA Astrophysics Data System (ADS)
Jiang, Ruijie; Li, Guang; Gu, Ning; Chen, Gong; Luo, Shouhua
2015-03-01
This paper is about geometric calibration of the high resolution CT (Computed Tomography) system. Geometric calibration refers to the estimation of a set of parameters that describe the geometry of the CT system. Such parameters are so important that a little error of them will degrade the reconstruction images seriously, so more accurate geometric parameters are needed in the higher-resolution CT systems. But conventional calibration methods are not accurate enough for the current high resolution CT system whose resolution can reach sub-micrometer or even tens of nanometers. In this paper, we propose a new calibration method which has higher accuracy and it is based on the optimization theory. The superiority of this method is that we build a new cost function which sets up a relationship between the geometrical parameters and the binary reconstruction image of a thin wire. When the geometrical parameters are accurate, the cost function reaches its maximum value. In the experiment, we scanned a thin wire as the calibration data and a thin bamboo stick as the validation data to verify the correctness of the proposed method. Comparing with the image reconstructed with the geometric parameters calculated by using the conventional calibration method, the image reconstructed with the parameters calculated by our method has less geometric artifacts, so it can verify that our method can get more accurate geometric calibration parameters. Although we calculated only one geometric parameter in this paper, the geometric artifacts are still eliminated significantly. And this method can be easily generalized to all the geometrical parameters calibration in fan-beam or cone-beam CT systems.
Bond dissociation energies from the topology of the charge density using gradient bundle analysis
NASA Astrophysics Data System (ADS)
Morgenstern, Amanda; Eberhart, Mark
2016-02-01
New and more robust models of chemical bonding are necessary to further our understanding of chemical phenomena. Among these are bond bundle and gradient bundle methods, which analyze bonding interactions in terms of property distributions over geometrically defined volumes. These methods have been shown to provide a systematic framework from which to search for structure-property relationships. In addition to providing a brief review of some of the relationships found using this framework, we present new findings that relate the lowering of kinetic energy in bonding regions to bond dissociation energy.
Control of tree water networks: A geometric programming approach
NASA Astrophysics Data System (ADS)
Sela Perelman, L.; Amin, S.
2015-10-01
This paper presents a modeling and operation approach for tree water supply systems. The network control problem is approximated as a geometric programming (GP) problem. The original nonlinear nonconvex network control problem is transformed into a convex optimization problem. The optimization model can be efficiently solved to optimality using state-of-the-art solvers. Two control schemes are presented: (1) operation of network actuators (pumps and valves) and (2) controlled demand shedding allocation between network consumers with limited resources. The dual of the network control problem is formulated and is used to perform sensitivity analysis with respect to hydraulic constraints. The approach is demonstrated on a small branched-topology network and later extended to a medium-size irrigation network. The results demonstrate an intrinsic trade-off between energy costs and demand shedding policy, providing an efficient decision support tool for active management of water systems.
Geometric programming prediction of design trends for OMV protective structures
NASA Technical Reports Server (NTRS)
Mog, R. A.; Horn, J. R.
1990-01-01
The global optimization trends of protective honeycomb structural designs for spacecraft subject to hypervelocity meteroid and space debris are presented. This nonlinear problem is first formulated for weight minimization of the orbital maneuvering vehicle (OMV) using a generic monomial predictor. Five problem formulations are considered, each dependent on the selection of independent design variables. Each case is optimized by considering the dual geometric programming problem. The dual variables are solved for in terms of the generic estimated exponents of the monomial predictor. The primal variables are then solved for by conversion. Finally, parametric design trends are developed for ranges of the estimated regression parameters. Results specify nonmonotonic relationships for the optimal first and second sheet mass per unit areas in terms of the estimated exponents.
Geometric asymmetry driven Janus micromotors
NASA Astrophysics Data System (ADS)
Zhao, Guanjia; Pumera, Martin
2014-09-01
The production and application of nano-/micromotors is of great importance. In order for the motors to work, asymmetry in their chemical composition or physical geometry must be present if no external asymmetric field is applied. In this paper, we present a ``coconut'' micromotor made of platinum through the partial or complete etching of the silica templates. It was shown that although both the inner and outer surfaces are made of the same material (Pt), motion of the structure can be observed as the convex surface is capable of generating oxygen bubbles. This finding shows that not only the chemical asymmetry of the micromotor, but also its geometric asymmetry can lead to fast propulsion of the motor. Moreover, a considerably higher velocity can be seen for partially etched coconut structures than the velocities of Janus or fully etched, shell-like motors. These findings will have great importance on the design of future micromotors.The production and application of nano-/micromotors is of great importance. In order for the motors to work, asymmetry in their chemical composition or physical geometry must be present if no external asymmetric field is applied. In this paper, we present a ``coconut'' micromotor made of platinum through the partial or complete etching of the silica templates. It was shown that although both the inner and outer surfaces are made of the same material (Pt), motion of the structure can be observed as the convex surface is capable of generating oxygen bubbles. This finding shows that not only the chemical asymmetry of the micromotor, but also its geometric asymmetry can lead to fast propulsion of the motor. Moreover, a considerably higher velocity can be seen for partially etched coconut structures than the velocities of Janus or fully etched, shell-like motors. These findings will have great importance on the design of future micromotors. Electronic supplementary information (ESI) available: Additional SEM images, data analysis, Videos S-1 and S-2. See DOI: 10.1039/c4nr02393e
Geometric Quantization and Foliation Reduction
NASA Astrophysics Data System (ADS)
Skerritt, Paul
A standard question in the study of geometric quantization is whether symplectic reduction interacts nicely with the quantized theory, and in particular whether "quantization commutes with reduction." Guillemin and Sternberg first proposed this question, and answered it in the affirmative for the case of a free action of a compact Lie group on a compact Kahler manifold. Subsequent work has focused mainly on extending their proof to non-free actions and non-Kahler manifolds. For realistic physical examples, however, it is desirable to have a proof which also applies to non-compact symplectic manifolds. In this thesis we give a proof of the quantization-reduction problem for general symplectic manifolds. This is accomplished by working in a particular wavefunction representation, associated with a polarization that is in some sense compatible with reduction. While the polarized sections described by Guillemin and Sternberg are nonzero on a dense subset of the Kahler manifold, the ones considered here are distributional, having support only on regions of the phase space associated with certain quantized, or "admissible", values of momentum. We first propose a reduction procedure for the prequantum geometric structures that "covers" symplectic reduction, and demonstrate how both symplectic and prequantum reduction can be viewed as examples of foliation reduction. Consistency of prequantum reduction imposes the above-mentioned admissibility conditions on the quantized momenta, which can be seen as analogues of the Bohr-Wilson-Sommerfeld conditions for completely integrable systems. We then describe our reduction-compatible polarization, and demonstrate a one-to-one correspondence between polarized sections on the unreduced and reduced spaces. Finally, we describe a factorization of the reduced prequantum bundle, suggested by the structure of the underlying reduced symplectic manifold. This in turn induces a factorization of the space of polarized sections that agrees with its usual decomposition by irreducible representations, and so proves that quantization and reduction do indeed commute in this context. A significant omission from the proof is the construction of an inner product on the space of polarized sections, and a discussion of its behavior under reduction. In the concluding chapter of the thesis, we suggest some ideas for future work in this direction.
Coherent Control of Bond Making
NASA Astrophysics Data System (ADS)
Levin, Liat; Skomorowski, Wojciech; Rybak, Leonid; Kosloff, Ronnie; Koch, Christiane P.; Amitay, Zohar
2015-06-01
We demonstrate coherent control of bond making, a milestone on the way to coherent control of photoinduced bimolecular chemical reactions. In strong-field multiphoton femtosecond photoassociation experiments, we find the yield of detected magnesium dimer molecules to be enhanced for positively chirped pulses and suppressed for negatively chirped pulses. Our ab initio model shows that control is achieved by purification combined with chirp-dependent Raman transitions. Experimental closed-loop phase optimization using a learning algorithm yields an improved pulse that utilizes vibrational coherent dynamics in addition to chirp-dependent Raman transitions. Our results show that coherent control of binary photoreactions is feasible even under thermal conditions.
NASA Astrophysics Data System (ADS)
Chuang, S. Y.; Chang, F. H.; Bell, J. R.
Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.
Geometric reasoning about assembly tools
Wilson, R.H.
1997-01-01
Planning for assembly requires reasoning about various tools used by humans, robots, or other automation to manipulate, attach, and test parts and subassemblies. This paper presents a general framework to represent and reason about geometric accessibility issues for a wide variety of such assembly tools. Central to the framework is a use volume encoding a minimum space that must be free in an assembly state to apply a given tool, and placement constraints on where that volume must be placed relative to the parts on which the tool acts. Determining whether a tool can be applied in a given assembly state is then reduced to an instance of the FINDPLACE problem. In addition, the author presents more efficient methods to integrate the framework into assembly planning. For tools that are applied either before or after their target parts are mated, one method pre-processes a single tool application for all possible states of assembly of a product in polynomial time, reducing all later state-tool queries to evaluations of a simple expression. For tools applied after their target parts are mated, a complementary method guarantees polynomial-time assembly planning. The author presents a wide variety of tools that can be described adequately using the approach, and surveys tool catalogs to determine coverage of standard tools. Finally, the author describes an implementation of the approach in an assembly planning system and experiments with a library of over one hundred manual and robotic tools and several complex assemblies.
Mobility in geometrically confined membranes
Domanov, Yegor A.; Aimon, Sophie; Toombes, Gilman E. S.; Renner, Marianne; Quemeneur, Franois; Triller, Antoine; Turner, Matthew S.; Bassereau, Patricia
2011-01-01
Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrck, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the membrane size for membranes of finite size [Saffman P, Delbrck M (1975) Proc Natl Acad Sci USA 72:31113113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrck to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous SaffmanDelbrck theory and elucidates the role of membrane geometry and size in regulating lateral diffusion. PMID:21768336
Geometrical aspects of quantum spaces
Ho, P.M.
1996-05-11
Various geometrical aspects of quantum spaces are presented showing the possibility of building physics on quantum spaces. In the first chapter the authors give the motivations for studying noncommutative geometry and also review the definition of a Hopf algebra and some general features of the differential geometry on quantum groups and quantum planes. In Chapter 2 and Chapter 3 the noncommutative version of differential calculus, integration and complex structure are established for the quantum sphere S{sub 1}{sup 2} and the quantum complex projective space CP{sub q}(N), on which there are quantum group symmetries that are represented nonlinearly, and are respected by all the aforementioned structures. The braiding of S{sub q}{sup 2} and CP{sub q}(N) is also described. In Chapter 4 the quantum projective geometry over the quantum projective space CP{sub q}(N) is developed. Collinearity conditions, coplanarity conditions, intersections and anharmonic ratios is described. In Chapter 5 an algebraic formulation of Reimannian geometry on quantum spaces is presented where Riemannian metric, distance, Laplacian, connection, and curvature have their quantum counterparts. This attempt is also extended to complex manifolds. Examples include the quantum sphere, the complex quantum projective space and the two-sheeted space. The quantum group of general coordinate transformations on some quantum spaces is also given.
NASA Astrophysics Data System (ADS)
Ozkanlar, Abdullah; Zhou, Tiecheng; Clark, Aurora E.
2014-12-01
The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the use of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed.
Ozkanlar, Abdullah Zhou, Tiecheng; Clark, Aurora E.
2014-12-07
The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the use of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed.
The geometric semantics of algebraic quantum mechanics.
Cruz Morales, John Alexander; Zilber, Boris
2015-08-01
In this paper, we will present an ongoing project that aims to use model theory as a suitable mathematical setting for studying the formalism of quantum mechanics. We argue that this approach provides a geometric semantics for such a formalism by means of establishing a (non-commutative) duality between certain algebraic and geometric objects. PMID:26124252
Geometric Growing Patterns: What's the Rule?
ERIC Educational Resources Information Center
Hourigan, Mairéad; Leavy, Aisling
2015-01-01
While within a geometric repeating pattern, there is an identifiable core which is made up of objects that repeat in a predictable manner, a geometric growing pattern (also called visual or pictorial growing patterns in other curricula) "is a pattern that is made from a sequence of figures [or objects] that change from one term to the next in…
Early Sex Differences in Weighting Geometric Cues
ERIC Educational Resources Information Center
Lourenco, Stella F.; Addy, Dede; Huttenlocher, Janellen; Fabian, Lydia
2011-01-01
When geometric and non-geometric information are both available for specifying location, men have been shown to rely more heavily on geometry compared to women. To shed insight on the nature and developmental origins of this sex difference, we examined how 18- to 24-month-olds represented the geometry of a surrounding (rectangular) space when…
Parabolas: Connection between Algebraic and Geometrical Representations
ERIC Educational Resources Information Center
Shriki, Atara
2011-01-01
A parabola is an interesting curve. What makes it interesting at the secondary school level is the fact that this curve is presented in both its contexts: algebraic and geometric. Being one of Apollonius' conic sections, the parabola is basically a geometric entity. It is, however, typically known for its algebraic characteristics, in particular…
Early Sex Differences in Weighting Geometric Cues
ERIC Educational Resources Information Center
Lourenco, Stella F.; Addy, Dede; Huttenlocher, Janellen; Fabian, Lydia
2011-01-01
When geometric and non-geometric information are both available for specifying location, men have been shown to rely more heavily on geometry compared to women. To shed insight on the nature and developmental origins of this sex difference, we examined how 18- to 24-month-olds represented the geometry of a surrounding (rectangular) space when
Bonded semiconductor substrate
Atwater, Jr.; Harry A. , Zahler; James M.
2010-07-13
Ge/Si and other nonsilicon film heterostructures are formed by hydrogen-induced exfoliation of the Ge film which is wafer bonded to a cheaper substrate, such as Si. A thin, single-crystal layer of Ge is transferred to Si substrate. The bond at the interface of the Ge/Si heterostructures is covalent to ensure good thermal contact, mechanical strength, and to enable the formation of an ohmic contact between the Si substrate and Ge layers. To accomplish this type of bond, hydrophobic wafer bonding is used, because as the invention demonstrates the hydrogen-surface-terminating species that facilitate van der Waals bonding evolves at temperatures above 600.degree. C. into covalent bonding in hydrophobically bound Ge/Si layer transferred systems.
The Random Cluster Model for Robust Geometric Fitting.
Pham, Trung T; Chin, Tat-Jun; Yu, Jin; Suter, David
2014-08-01
Random hypothesis generation is central to robust geometric model fitting in computer vision. The predominant technique is to randomly sample minimal subsets of the data, and hypothesize the geometric models from the selected subsets. While taking minimal subsets increases the chance of successively "hitting" inliers in a sample, hypotheses fitted on minimal subsets may be severely biased due to the influence of measurement noise, even if the minimal subsets contain purely inliers. In this paper we propose Random Cluster Models, a technique used to simulate coupled spin systems, to conduct hypothesis generation using subsets larger than minimal. We show how large clusters of data from genuine instances of the model can be efficiently harvested to produce accurate hypotheses that are less affected by the vagaries of fitting on minimal subsets. A second aspect of the problem is the optimization of the set of structures that best fit the data. We show how our novel hypothesis sampler can be integrated seamlessly with graph cuts under a simple annealing framework to optimize the fitting efficiently. Unlike previous methods that conduct hypothesis sampling and fitting optimization in two disjoint stages, our algorithm performs the two subtasks alternatingly and in a mutually reinforcing manner. Experimental results show clear improvements in overall efficiency. PMID:26353345
Geometric calibration of a hyperspectral imaging system.
Spiclin, Ziga; Katrasnik, Jaka; Bürmen, Miran; Pernus, Franjo; Likar, Bostjan
2010-05-20
Every imaging system requires a geometric calibration to yield accurate optical measurements. Geometric calibration typically involves imaging of a known calibration object and finding the parameters of a camera model and a model of optical aberrations. Optical aberrations can vary significantly across the wide spectral ranges of hyperspectral imaging systems, which can lead to inaccurate geometric calibrations if conventional methods were used. We propose a method based on a B-spline transformation field to align the spectral images of the calibration object to the model image of the calibration object. The degree of spatial alignment between the ideal and the spectral images is measured by normalized cross correlation. Geometric calibration was performed on a hyperspectral imaging system based on an acousto-optic tunable filter designed for the near-infrared spectral range (1.0-1.7microm). The proposed method can accurately characterize wavelength dependent optical aberrations and produce transformations for efficient subpixel geometric calibration. PMID:20490242
Rapid bonding of Pyrex glass microchips.
Akiyama, Yoshitake; Morishima, Keisuke; Kogi, Atsuna; Kikutani, Yoshikuni; Tokeshi, Manabu; Kitamori, Takehiko
2007-03-01
A newly developed vacuum hot press system has been specially designed for the thermal bonding of glass substrates in the fabrication process of Pyrex glass microchemical chips. This system includes a vacuum chamber equipped with a high-pressure piston cylinder and carbon plate heaters. A temperature of up to 900 degrees C and a force of as much as 9800 N could be applied to the substrates in a vacuum atmosphere. The Pyrex substrates bonded with this system under different temperatures, pressures, and heating times were evaluated by tensile strength tests, by measurements of thickness, and by observations of the cross-sectional shapes of the microchannels. The optimal bonding conditions of the Pyrex glass substrates were 570 degrees C for 10 min under 4.7 N/mm(2) of applied pressure. Whereas more than 16 h is required for thermal bonding with a conventional furnace, the new system could complete the whole bonding processes within just 79 min, including heating and cooling periods. Such improvements should considerably enhance the production rate of Pyrex glass microchemical chips. Whereas flat and dust-free surfaces are required for conventional thermal bonding, especially without long and repeated heating periods, our hot press system could press a fine dust into glass substrates so that even the areas around the dust were bonded. Using this capability, we were able to successfully integrate Pt/Ti thin film electrodes into a Pyrex glass microchip. PMID:17370301
Bond strength of repaired amalgam restorations.
Rey, Rosalia; Mondragon, Eduardo; Shen, Chiayi
2015-01-01
This in vitro study investigated the interfacial flexural strength (FS) of amalgam repairs and the optimal combination of repair materials and mechanical retention required for a consistent and durable repair bond. Amalgam bricks were created, each with 1 end roughened to expose a fresh surface before repair. Four groups followed separate repair protocols: group 1, bonding agent with amalgam; group 2, bonding agent with composite resin; group 3, mechanical retention (slot) with amalgam; and group 4, slot with bonding agent and amalgam. Repaired specimens were stored in artificial saliva for 1, 10, 30, 120, or 360 days before being loaded to failure in a 3-point bending test. Statistical analysis showed significant changes in median FS over time in groups 2 and 4. The effect of the repair method on the FS values after each storage period was significant for most groups except the 30-day storage groups. Amalgam-amalgam repair with adequate condensation yielded the most consistent and durable bond. An amalgam bonding agent could be beneficial when firm condensation on the repair surface cannot be achieved or when tooth structure is involved. Composite resin can be a viable option for amalgam repair in an esthetically demanding region, but proper mechanical modification of the amalgam surface and selection of the proper bonding system are essential. PMID:26325656
Noland, R.A.; Walker, D.E.
1961-06-13
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.
NASA Technical Reports Server (NTRS)
Plueddemann, E.
1986-01-01
Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.
GaalopHigh Performance Parallel Computing Based on Conformal Geometric Algebra
NASA Astrophysics Data System (ADS)
Hildenbrand, Dietmar; Pitt, Joachim; Koch, Andreas
We present Gaalop (Geometric algebra algorithms optimizer), our tool for high-performance computing based on conformal geometric algebra. The main goal of Gaalop is to realize implementations that are most likely faster than conventional solutions. In order to achieve this goal, our focus is on parallel target platforms like FPGA (field-programmable gate arrays) or the CUDA technology from NVIDIA. We describe the concepts, current status, and future perspectives of Gaalop dealing with optimized software implementations, hardware implementations, and mixed solutions. An inverse kinematics algorithm of a humanoid robot is described as an example.
NASA Astrophysics Data System (ADS)
Mercier, Patrick H. J.
Seventy-five synthetic powder trioctahedral mica samples (between Mg, Co, Ni, and Fe end members, with different degrees of oxidation, vacancy and Al/Si contents, and including an OH/F substitution series) were studied by room-temperature powder X-ray diffraction. The iron-bearing samples were studied by 57Fe Mossbauer spectroscopy. Subsets of the samples were also characterized by scanning electron microscopy combined with energy dispersive spectroscopy, optical microscopy, X-ray fluorescence spectroscopy, and gas chromatography. Lattice parameters (refined under the 1M stacking polytype, space group C2/m) were determined for all powder samples and iron site populations ([4]Fe 3+, [6]Fe2+, and [6]Fe 2+) were obtained from Mossbauer spectroscopy. The relation (c/a)cosbeta* = 113 was found to hold exactly (within experimental error) for all synthetic powders whereas it does not hold in general for synthetic and natural 1M single-crystals. The above relation is predicted to hold for geometric home-octahedral sheets (having equal M1 and M2 site bond lengths) and not to hold for geometric meso-octahedral sheets (having unequal M1 and M2 site bond lengths). The counter-rotation of the M2 site of 1M single-crystals exactly (within experimental error) follows the geometric meso-octahedral sheet model, which, assuming a uniform octahedral sheet height and site-specific M1 and M2 bond lengths, predicts site-specific flattening angles and a counter-rotation angle for the M2 site which is uniquely determined by the bond length difference between the M1 and M2 sites. A geometric meso-octahedral 2:1 layer silicate was shown to require corrugated tetrahedral sheets composed of bond-distorted tetrahedra. Key geometric meso-octahedral distortions in 1M single-crystals were identified and elucidated: (i) intra-layer top-bottom displacements within a TOT layer; and (ii) a tetrahedral bending angle between the apical bond and the pyramidal base formed by the three basal bonds. Plots of lattice parameter b versus average-octahedral-bond-length allowed the following distinction to be made: Unoxidized divalent synthetic solid solution series tend to evolve along constant flattening-angle lines whereas trivalent octahedral cation and vacancy bearing natural single-crystals and synthetic powders follow trends with varying flattening angles. We found that the bond length of a given interlayer cationic species monotonously increases as the tetrahedral rotation angle alpha decreases in trioctahedral-1 M single-crystals. An upper limit of tetrahedral rotation of alpha = 9.5° was demonstrated to occur in trioctahedral-1M K-rich micas having an
Characterizing the geometrical edges of nonlocal two-qubit gates
Balakrishnan, S.; Sankaranarayanan, R.
2009-05-15
Nonlocal two-qubit gates are geometrically represented by tetrahedron known as Weyl chamber within which perfect entanglers form a polyhedron. We identify that all edges of the Weyl chamber and polyhedron are formed by single parametric gates. Nonlocal attributes of these edges are characterized using entangling power and local invariants. In particular, SWAP{sup -{alpha}} family of gates with 0{<=}{alpha}{<=}1 constitutes one edge of the Weyl chamber with SWAP{sup -1/2} being the only perfect entangler. Finally, optimal constructions of controlled-NOT using SWAP{sup -1/2} gate and gates belong to three edges of the polyhedron are presented.
Optimal domain decomposition strategies
NASA Technical Reports Server (NTRS)
Yoon, Yonghyun; Soni, Bharat K.
1995-01-01
The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.
Nondestructive determination of cohesive strength of adhesive-bonded composites
NASA Technical Reports Server (NTRS)
Thompson, D. O.
1969-01-01
Systematic plan determines vibration responses and modes of honeycomb composites, correlates vibrational responses of composite specimens varying in strength of cohesive bond, determines effects of thickness variation of the face sheet over the frequency range, optimizes the characteristics of the excitation transducer, and measures bond strength.
The role of bond tangency and bond gap in hard sphere crystallization of chains.
Karayiannis, Nikos Ch; Foteinopoulou, Katerina; Laso, Manuel
2015-03-01
We report results from Monte Carlo simulations on dense packings of linear, freely-jointed chains of hard spheres of uniform size. In contrast to our past studies where bonded spheres along the chain backbone were tangent, in the present work a finite tolerance in the bond is allowed. Bond lengths are allowed to fluctuate in the interval [σ, σ + dl], where σ is the sphere diameter. We find that bond tolerance affects the phase behaviour of hard-sphere chains, especially in the close vicinity of the melting transition. First, a critical dl(crit) exists marking the threshold for crystallization, whose value decreases with increasing volume fraction. Second, bond gaps enhance the onset of phase transition by accelerating crystal nucleation and growth. Finally, bond tolerance has an effect on crystal morphologies: in the tangent limit the majority of structures correspond to stack-faulted random hexagonal close packing (rhcp). However, as bond tolerance increases a wealth of diverse structures can be observed: from single fcc (or hcp) crystallites to random hcp/fcc stackings with multiple directions. By extending the simulations over trillions of MC steps (10(12)) we are able to observe crystal-crystal transitions and perfection even for entangled polymer chains in accordance to the Ostwald's rule of stages in crystal polymorphism. Through simple geometric arguments we explain how the presence of rigid or flexible constraints affects crystallization in general atomic and particulate systems. Based on the present results, it can be concluded that proper tuning of bond gaps and of the connectivity network can be a controlling factor for the phase behaviour of model, polymer-based colloidal and granular systems. PMID:25594158
Geometric problem in medical imaging
NASA Astrophysics Data System (ADS)
Robinson, Stephen B.; Hemler, Paul F.; Webber, Richard L.
2000-10-01
In this paper we provide a rigorous mathematical foundation for Tuned- Aperture Computed Tomography, a generalization of standard tomosynthesis that provides a significantly more flexible diagnostic tool. We also describe how the general TACT algorithm simplifies in important special cases, and we investigate the possibility of optimizing the algorithm by reducing the number of fiducial reference points. The key theoretical problem is how to sue information within an x-ray image to discover, after the fact, what the relative positions of the x-ray source, the patient, and the x-ray detector were when the x-ray image was created.
Bio-inspired interfacial strengthening strategy through geometrically interlocking designs.
Zhang, Yuming; Yao, Haimin; Ortiz, Christine; Xu, Jinquan; Dao, Ming
2012-11-01
Many biological materials, such as nacre and bone, are hybrid materials composed of stiff brittle ceramics and compliant organic materials. These natural organic/inorganic composites exhibit much enhanced strength and toughness in comparison to their constituents and inspires enormous biomimetic endeavors aiming to synthesize materials with superior mechanical properties. However, most current synthetic composites have not exhibited their full potential of property enhancement compared to the natural prototypes they are mimicking. One of the key issues is the weak junctions between stiff and compliant phases, which need to be optimized according to the intended functions of the composite material. Motivated by the geometrically interlocking designs of natural biomaterials, here we propose an interfacial strengthening strategy by introducing geometrical interlockers on the interfaces between compliant and stiff phases. Finite element analysis (FEA) shows that the strength of the composite depends strongly on the geometrical features of interlockers including shape, size, and structural hierarchy. Even for the most unfavorable scenario when neither adhesion nor friction is present between stiff and compliant phases, the tensile strength of the composites with proper interlocker design can reach up to 70% of the ideal value. The findings in this paper would provide guidelines to the improvement of the mechanical properties of current biomimetic composites. PMID:23032427
Tangram solved? Prefrontal cortex activation analysis during geometric problem solving.
Ayaz, Hasan; Shewokis, Patricia A; Izzetoğlu, Meltem; Çakır, Murat P; Onaral, Banu
2012-01-01
Recent neuroimaging studies have implicated prefrontal and parietal cortices for mathematical problem solving. Mental arithmetic tasks have been used extensively to study neural correlates of mathematical reasoning. In the present study we used geometric problem sets (tangram tasks) that require executive planning and visuospatial reasoning without any linguistic representation interference. We used portable optical brain imaging (functional near infrared spectroscopy--fNIR) to monitor hemodynamic changes within anterior prefrontal cortex during tangram tasks. Twelve healthy subjects were asked to solve a series of computerized tangram puzzles and control tasks that required same geometric shape manipulation without problem solving. Total hemoglobin (HbT) concentration changes indicated a significant increase during tangram problem solving in the right hemisphere. Moreover, HbT changes during failed trials (when no solution found) were significantly higher compared to successful trials. These preliminary results suggest that fNIR can be used to assess cortical activation changes induced by geometric problem solving. Since fNIR is safe, wearable and can be used in ecologically valid environments such as classrooms, this neuroimaging tool may help to improve and optimize learning in educational settings. PMID:23366983
Mirror profile optimization for nano-focusing KB mirror
Zhang Lin; Baker, Robert; Barrett, Ray; Cloetens, Peter; Dabin, Yves
2010-06-23
A KB focusing mirror width profile has been optimized to achieve nano-focusing for the nano-imaging end-station ID22NI at the ESRF. The complete mirror and flexure bender assembly has been modeled in 3D with finite element analysis using ANSYS. Bender stiffness, anticlastic effects and geometrical non-linear effects have been considered. Various points have been studied: anisotropy and crystal orientation, stress in the mirror and bender, actuator resolution and the mirror-bender adhesive bonding... Extremely high performance of the mirror is expected with residual slope error smaller than 0.6 {mu}rad, peak-to-valley, compared to the bent slope of 3000 {mu}rad.
On geometric factors for neutral particle analyzers
Stagner, L.; Heidbrink, W. W.
2014-11-15
Neutral particle analyzers (NPA) detect neutralized energetic particles that escape from plasmas. Geometric factors relate the counting rate of the detectors to the intensity of the particle source. Accurate geometric factors enable quick simulation of geometric effects without the need to resort to slower Monte Carlo methods. Previously derived expressions [G. R. Thomas and D. M. Willis, “Analytical derivation of the geometric factor of a particle detector having circular or rectangular geometry,” J. Phys. E: Sci. Instrum. 5(3), 260 (1972); J. D. Sullivan, “Geometric factor and directional response of single and multi-element particle telescopes,” Nucl. Instrum. Methods 95(1), 5–11 (1971)] for the geometric factor implicitly assume that the particle source is very far away from the detector (far-field); this excludes applications close to the detector (near-field). The far-field assumption does not hold in most fusion applications of NPA detectors. We derive, from probability theory, a generalized framework for deriving geometric factors that are valid for both near and far-field applications as well as for non-isotropic sources and nonlinear particle trajectories.
Geometric quantum discord under noisy environment
NASA Astrophysics Data System (ADS)
Huang, Zhiming; Qiu, Daowen
2016-02-01
In this work, we mainly analyze the dynamics of geometric quantum discord under a common dissipating environment. Our results indicate that geometric quantum discord is generated when the initial state is a product state. The geometric quantum discord increases from zero to a stable value with the increasing time, and the variations of stable values depend on the system size. For different initial product states, geometric quantum discord has some different behaviors in contrast with entanglement. For initial maximally entangled state, it is shown that geometric quantum discord decays with the increasing dissipated time. It is found that for EPR state, entanglement is more robust than geometric quantum discord, which is a sharp contrast to the existing result that quantum discord is more robust than entanglement in noisy environments. However, for GHZ state and W state, geometric quantum discord is more stable than entanglement. By the comparison of quantum discord and entanglement, we find that a common dissipating environment brings complicated effects on quantum correlation, which may deepen our understanding of physical impacts of decohering environment on quantum correlation. In the end, we analyze the effects of collective dephasing noise and rotating noise to a class of two-qubit X states, and we find that quantum correlation is not altered by the collective noises.
On geometric factors for neutral particle analyzers.
Stagner, L; Heidbrink, W W
2014-11-01
Neutral particle analyzers (NPA) detect neutralized energetic particles that escape from plasmas. Geometric factors relate the counting rate of the detectors to the intensity of the particle source. Accurate geometric factors enable quick simulation of geometric effects without the need to resort to slower Monte Carlo methods. Previously derived expressions [G. R. Thomas and D. M. Willis, "Analytical derivation of the geometric factor of a particle detector having circular or rectangular geometry," J. Phys. E: Sci. Instrum. 5(3), 260 (1972); J. D. Sullivan, "Geometric factor and directional response of single and multi-element particle telescopes," Nucl. Instrum. Methods 95(1), 5-11 (1971)] for the geometric factor implicitly assume that the particle source is very far away from the detector (far-field); this excludes applications close to the detector (near-field). The far-field assumption does not hold in most fusion applications of NPA detectors. We derive, from probability theory, a generalized framework for deriving geometric factors that are valid for both near and far-field applications as well as for non-isotropic sources and nonlinear particle trajectories. PMID:25430216
Geometric quantum discord under noisy environment
NASA Astrophysics Data System (ADS)
Huang, Zhiming; Qiu, Daowen
2016-05-01
In this work, we mainly analyze the dynamics of geometric quantum discord under a common dissipating environment. Our results indicate that geometric quantum discord is generated when the initial state is a product state. The geometric quantum discord increases from zero to a stable value with the increasing time, and the variations of stable values depend on the system size. For different initial product states, geometric quantum discord has some different behaviors in contrast with entanglement. For initial maximally entangled state, it is shown that geometric quantum discord decays with the increasing dissipated time. It is found that for EPR state, entanglement is more robust than geometric quantum discord, which is a sharp contrast to the existing result that quantum discord is more robust than entanglement in noisy environments. However, for GHZ state and W state, geometric quantum discord is more stable than entanglement. By the comparison of quantum discord and entanglement, we find that a common dissipating environment brings complicated effects on quantum correlation, which may deepen our understanding of physical impacts of decohering environment on quantum correlation. In the end, we analyze the effects of collective dephasing noise and rotating noise to a class of two-qubit X states, and we find that quantum correlation is not altered by the collective noises.
Geometric gyrokinetic theory for edge plasmas
Qin, H.; Cohen, R. H.; Nevins, W. M.; Xu, X. Q.
2007-05-15
It turns out that gyrokinetic theory can be geometrically formulated as a special case of a geometrically generalized Vlasov-Maxwell system. It is proposed that the phase space of the space-time is a seven-dimensional fiber bundle P over the four-dimensional space-time M, and that a Poincare-Cartan-Einstein 1-form {gamma} on the seven-dimensional phase space determines a particle's worldline 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 gyrosymmetry, for magnetized plasmas, and the 1-form {gamma} again uniquely defines the gyrosymmetry. The objective is to decouple the gyrophase dynamics from the rest of the particle dynamics by finding the gyrosymmetry in {gamma}. Compared to 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 space-time 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 cannot be achieved using classical methods. What the geometric method offers is a systematic treatment and simplified calculations.
Geometric Gyrokinetic Theory for Edge Plasma
Qin, H; Cohen, R H; Nevins, W M; Xu, X Q
2007-01-18
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.
Planning Successful Bond Campaigns.
ERIC Educational Resources Information Center
North Carolina State Dept. of Public Instruction, Raleigh. Div. of School Support.
This document contains specific recommendations for conducting bond campaigns. It outlines the three major considerations of any bond campaign: (1) committee organization and appointment; (2) time lines; and (3) getting out the vote. The publication focuses on the need for total community involvement and outlines some of the components for…
ERIC Educational Resources Information Center
Bank, Stephen P.; Kahn, Michael D.
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…
NASA Technical Reports Server (NTRS)
Boerio, J.
1984-01-01
Interfacial bonding stability by in situ ellipsometry was investigated. It is found that: (1) gamma MPS is an effective primer for bonding ethylene vinyl acetate (EVA) to aluminum; (2) ellipsometry is an effective in situ technique for monitoring the stability of polymer/metal interfaces; (3) the aluminized back surface of silicon wafers contain significant amounts of silicon and may have glass like properties.
ERIC Educational Resources Information Center
Sanderson, R. T.
1972-01-01
Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)
ERIC Educational Resources Information Center
Pearce, Joseph Chilton
1994-01-01
Examines the nature of mother-child bonding from the prenatal stage through early infancy, discussing how the mother's actions, even before birth, stimulate her child's senses. Explains the crucial role that physical contact, breastfeeding, and visual stimuli have on mother-child bonding in human and animal newborns. (MDM)
Bauzá, Antonio; Mooibroek, Tiddo J; Frontera, Antonio
2016-02-01
Tetrel (Tr) bonding is first placed into perspective as a σ-hole bonding interaction with atoms of the Tr family. An sp(3) R4 Tr unit has four σ-holes with which a Lewis base can form a complex. We then highlight some inspiring crystal structures where Tr bonding is obvious, followed by an account of our own work. We have shown that Tr bonding is ubiquitous in the solid state and we have highlighted that Tr bonding with carbon is possible when C is placed in the appropriate chemical context. We hope that this account serves as an initial guide and source of inspiration for others wishing to exploit this vastly underexplored interaction. PMID:26814022
Ultrasonically bonded value assembly
NASA Technical Reports Server (NTRS)
Salvinski, R. J. (Inventor)
1975-01-01
A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.
NASA Technical Reports Server (NTRS)
Pontius, James T. (Inventor)
2010-01-01
The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.
NASA Technical Reports Server (NTRS)
1989-01-01
A joint development program between Hartford Steam Boiler Inspection Technologies and The Weyerhaeuser Company resulted in an internal bond analyzer (IBA), a device which combines ultrasonics with acoustic emission testing techniques. It is actually a spinoff from a spinoff, stemming from a NASA Lewis invented acousto-ultrasonic technique that became a system for testing bond strength of composite materials. Hartford's parent company, Acoustic Emission Technology Corporation (AET) refined and commercialized the technology. The IBA builds on the original system and incorporates on-line process control systems. The IBA determines bond strength by measuring changes in pulsar ultrasonic waves injected into a board. Analysis of the wave determines the average internal bond strength for the panel. Results are displayed immediately. Using the system, a mill operator can adjust resin/wood proportion, reduce setup time and waste, produce internal bonds of a consistent quality and automatically mark deficient products.
Yusupov, Marat; Yusupova, Gulnara
2014-01-01
The natural bases of nucleic acids have a strong preference for one tautomer form, guaranteeing fidelity in their hydrogen bonding potential. However, base pairs observed in recent crystal structures of polymerases and ribosomes are best explained by an alternative base tautomer, leading to the formation of base pairs with Watson-Crick-like geometries. These observations set limits to geometric selection in molecular recognition of complementary Watson-Crick pairs for fidelity in replication and translation processes. PMID:24765524
Thermodynamics of water structural reorganization due to geometric confinement
NASA Astrophysics Data System (ADS)
Stroberg, Wylie; Lichter, Seth
2015-03-01
Models of aqueous solvation have successfully quantified the behavior of water near convex bodies. However, many important processes occurring in aqueous solution involve interactions between solutes and surfaces with complicated non-convex geometries. Examples include the folding of proteins, hydrophobic association of solutes, ligand-receptor binding, and water confined within nanotubes and pores. For these geometries, models for solvation of convex bodies fail to account for the added interactions associated with structural confinement. Due to water's propensity to form networks of hydrogen bonds, small alterations to the confining geometry can induce large structural rearrangement within the water. We perform systematic Monte Carlo simulations of water confined to cylindrical cavities of varying aspect ratio to investigate how small geometric changes to the confining geometry may cause large changes to the structure and thermodynamic state of water. Using the Wang-Landau algorithm, we obtain free energies, enthalpies, entropies, and heat capacities across a broad range of temperatures, and show how these quantities are influenced by the structural rearrangement of water molecules due to geometric perturbations.
Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.
Zins, Emilie-Laure; Silvi, Bernard; Alikhani, M Esmaïl
2015-04-14
Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a σ X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A σ X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the νX-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes. PMID:25760795
Aakeröy, Christer B.; Spartz, Christine L.; Dembowski, Sean; Dwyre, Savannah; Desper, John
2015-01-01
As halogen bonds gain prevalence in supramolecular synthesis and materials chemistry, it has become necessary to examine more closely how such interactions compete with or complement hydrogen bonds whenever both are present within the same system. As hydrogen and halogen bonds have several fundamental features in common, it is often difficult to predict which will be the primary interaction in a supramolecular system, especially as they have comparable strength and geometric requirements. To address this challenge, a series of molecules containing both hydrogen- and halogen-bond donors were co-crystallized with various monotopic, ditopic symmetric and ditopic asymmetric acceptor molecules. The outcome of each reaction was examined using IR spectroscopy and, whenever possible, single-crystal X-ray diffraction. 24 crystal structures were obtained and subsequently analyzed, and the synthon preferences of the competing hydrogen- and halogen-bond donors were rationalized against a background of calculated molecular electrostatic potential values. It has been shown that readily accessible electrostatic potentials can offer useful practical guidelines for predicting the most likely primary synthons in these co-crystals as long as the potential differences are weighted appropriately. PMID:26306192
NASA Astrophysics Data System (ADS)
Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.
2013-01-01
In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the σ* and π* 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.
Void-free wafer-level adhesive bonding utilizing modified poly (diallyl phthalate)
NASA Astrophysics Data System (ADS)
Zhong, Fang; Dong, Tao; Yong, He; Yan, Su; Wang, Kaiying
2013-12-01
A new thermosetting polymer, modified poly (diallyl phthalate) (PDAP), is used as intermediate layer to realize a void-free wafer-level transfer bonding, in which the bonding interface contains patterned metal. Through glass-silicon bonding experiments, bonding defects are easily recognized with light microscopy. Three typical defect types are identified as: uneven flow defect, particle defect and bubble defect. The processing parameters, such as bonding pressure, pre-baking temperature, polymer thickness and coating conditions, have been optimized based on analysis of the defect formation. The optimized conditions have yielded a void-free wafer-level adhesive bonding. Then, the die shearing test indicates a good bonding strength. Additionally, the transfer bonding process is applied in SOI-silicon bonding as a practical example of MEMS fabrication.
Geometric symmetries in superfluid vortex dynamics
Kozik, Evgeny; Svistunov, Boris
2010-10-01
Dynamics of quantized vortex lines in a superfluid feature symmetries associated with the geometric character of the complex-valued field, w(z)=x(z)+iy(z), describing the instant shape of the line. Along with a natural set of Noether's constants of motion, which - apart from their rather specific expressions in terms of w(z) - are nothing but components of the total linear and angular momenta of the fluid, the geometric symmetry brings about crucial consequences for kinetics of distortion waves on the vortex lines, the Kelvin waves. It is the geometric symmetry that renders Kelvin-wave cascade local in the wave-number space. Similar considerations apply to other systems with purely geometric degrees of freedom.
Using Proportional Reasoning to Solve Geometric Problems
ERIC Educational Resources Information Center
Pandiscio, Eric A
2004-01-01
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.
The perception of geometrical structure from congruence
NASA Technical Reports Server (NTRS)
Lappin, Joseph S.; Wason, Thomas D.
1989-01-01
The principle function of vision is to measure the environment. As demonstrated by the coordination of motor actions with the positions and trajectories of moving objects in cluttered environments and by rapid recognition of solid objects in varying contexts from changing perspectives, vision provides real-time information about the geometrical structure and location of environmental objects and events. The geometric information provided by 2-D spatial displays is examined. It is proposed that the geometry of this information is best understood not within the traditional framework of perspective trigonometry, but in terms of the structure of qualitative relations defined by congruences among intrinsic geometric relations in images of surfaces. The basic concepts of this geometrical theory are outlined.
The geometric phase in nonlinear dissipative systems
Ning, C.Z.; Haken, H. )
1992-10-30
In this paper, the authors review the recent progress made in generalizing the concept of the geometric phase to nonlinear dissipative systems. The authors first illustrate the usual form of the parallel transport law with an elementary example of the parallel shift of a line on the complex plane. Important results about the non-adiabatical geometric (Aharonov and Anandan or AA) phase [sup 18] for the Schrodinger equations are reviewed in order to make a comparison with results for dissipative systems. The authors show that a geometric phase can be defined for dissipative systems with the cyclic attractors. Systems undergoing the Hopf bifurcation with a continuous symmetry are shown to possess such cyclic attractors. Examples from laser physics are discussed to exhibit the applicability of our formalism and the widespread existence of the geometric phase in dissipative systems.
Heat transfer in geometrically similar cylinders
NASA Technical Reports Server (NTRS)
Riekert, P; Held, A
1941-01-01
The power and heat-stress conditions of geometrically similar engines are discussed. The advantages accruing from smaller cylinder dimensions are higher specific horsepower, lower weight per horsepower, lower piston temperature, and less frontal area, with reduced detonation tendency.
Surgical correction of gynecomastia: a geometric approach.
Martin, Antony E; Olinger, Thomas A; Yu, Jack C
2015-05-01
Many techniques are available for surgical correction of gynecomastia. In this article, we describe a technique based on geometrical principles that is simple to execute, effective, highly reproducible, and relies less on intuition of the surgeon. PMID:25919255
The variational subspace valence bond method
Fletcher, Graham D.
2015-04-07
The variational subspace valence bond (VSVB) method based on overlapping orbitals is introduced. VSVB provides variational support against collapse for the optimization of overlapping linear combinations of atomic orbitals (OLCAOs) using modified orbital expansions, without recourse to orthogonalization. OLCAO have the advantage of being naturally localized, chemically intuitive (to individually model bonds and lone pairs, for example), and transferrable between different molecular systems. Such features are exploited to avoid key computational bottlenecks. Since the OLCAO can be doubly occupied, VSVB can access very large problems, and calculations on systems with several hundred atoms are presented.
Machine Learning and Geometric Technique for SLAM
NASA Astrophysics Data System (ADS)
Bernal-Marin, Miguel; Bayro-Corrochano, Eduardo
This paper describes a new approach for building 3D geometric maps using a laser rangefinder, a stereo camera system and a mathematical system the Conformal Geometric Algebra. The use of a known visual landmarks in the map helps to carry out a good localization of the robot. A machine learning technique is used for recognition of objects in the environment. These landmarks are found using the Viola and Jones algorithm and are represented with their position in the 3D virtual map.
The Geometric Grids of the Hieratic Numeral.
NASA Astrophysics Data System (ADS)
Aboulfotouh, Hossam M. K.
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.
Dilemmas in zirconia bonding: A review.
Dbradović-Djuricić, Kosovka; Medić, Vesna; Dodić, Slobodan; Gavrilov, Dragan; Antonijević, Djordje; Zrilić, Milorad
2013-01-01
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
Graphene geometric diodes for terahertz rectennas
NASA Astrophysics Data System (ADS)
Zhu, Zixu; Joshi, Saumil; Grover, Sachit; Moddel, Garret
2013-05-01
We demonstrate a new thin-film graphene diode called a geometric diode that relies on geometric asymmetry to provide rectification at 28 THz. The geometric diode is coupled to an optical antenna to form a rectenna that rectifies incoming radiation. This is the first reported graphene-based antenna-coupled diode working at 28 THz, and potentially at optical frequencies. The planar structure of the geometric diode provides a low RC time constant, on the order of 10-15 s, required for operation at optical frequencies, and a low impedance for efficient power transfer from the antenna. Fabricated geometric diodes show asymmetric current-voltage characteristics consistent with Monte Carlo simulations for the devices. Rectennas employing the geometric diode coupled to metal and graphene antennas rectify 10.6 µm radiation, corresponding to an operating frequency of 28 THz. The graphene bowtie antenna is the first demonstrated functional antenna made using graphene. Its response indicates that graphene is a suitable terahertz resonator material. Applications for this terahertz diode include terahertz-wave and optical detection, ultra-high-speed electronics and optical power conversion.
Geometrically invariant watermarking using feature points.
Bas, Patrick; Chassery, Jean-Marc; Macq, Benot
2002-01-01
This paper presents a new approach for watermarking of digital images providing robustness to geometrical distortions. The weaknesses of classical watermarking methods to geometrical distortions are outlined first. Geometrical distortions can be decomposed into two classes: global transformations such as rotations and translations and local transformations such as the StirMark attack. An overview of existing self-synchronizing schemes is then presented. Theses schemes can use periodical properties of the mark, invariant properties of transforms, template insertion, or information provided by the original image to counter geometrical distortions. Thereafter, a new class of watermarking schemes using the image content is presented. We propose an embedding and detection scheme where the mark is bound with a content descriptor defined by salient points. Three different types of feature points are studied and their robustness to geometrical transformations is evaluated to develop an enhanced detector. The embedding of the signature is done by extracting feature points of the image and performing a Delaunay tessellation on the set of points. The mark is embedded using a classical additive scheme inside each triangle of the tessellation. The detection is done using correlation properties on the different triangles. The performance of the presented scheme is evaluated after JPEG compression, geometrical attack and transformations. Results show that the fact that the scheme is robust to these different manipulations. Finally, in our concluding remarks, we analyze the different perspectives of such content-based watermarking scheme. PMID:18249723
Investigation of geometrical and scoring grid resolution for Monte Carlo dose calculations for IMRT
NASA Astrophysics Data System (ADS)
DeSmedt, B.; Vanderstraeten, B.; Reynaert, N.; DeNeve, W.; Thierens, H.
2005-09-01
Monte Carlo based treatment planning of two different patient groups treated with step-and-shoot IMRT (head-and-neck and lung treatments) with different CT resolutions and scoring methods is performed to determine the effect of geometrical and scoring voxel sizes on DVHs and calculation times. Dose scoring is performed in two different ways: directly into geometrical voxels (or in a number of grouped geometrical voxels) or into scoring voxels defined by a separate scoring grid superimposed on the geometrical grid. For the head-and-neck cancer patients, more than 2% difference is noted in the right optical nerve when using voxel dimensions of 4 × 4 × 4 mm3 compared to the reference calculation with 1 × 1 × 2 mm3 voxel dimensions. For the lung cancer patients, 2% difference is noted in the spinal cord when using voxel dimensions of 4 × 4 × 10 mm3 compared to the 1 × 1 × 5 mm3 calculation. An independent scoring grid introduces several advantages. In cases where a relatively high geometrical resolution is required and where the scoring resolution is less important, the number of scoring voxels can be limited while maintaining a high geometrical resolution. This can be achieved either by grouping several geometrical voxels together into scoring voxels or by superimposing a separate scoring grid of spherical voxels with a user-defined radius on the geometrical grid. For the studied lung cancer cases, both methods produce accurate results and introduce a speed increase by a factor of 10-36. In cases where a low geometrical resolution is allowed, but where a high scoring resolution is required, superimposing a separate scoring grid on the geometrical grid allows a reduction in geometrical voxels while maintaining a high scoring resolution. For the studied head-and-neck cancer cases, calculations performed with a geometrical resolution of 2 × 2 × 2 mm3 and a separate scoring grid containing spherical scoring voxels with a radius of 2 mm produce accurate results and introduce a speed increase by a factor of 13. The scoring grid provides an additional degree of freedom for limiting calculation time and memory requirements by selecting optimized scoring and geometrical voxel dimensions in an independent way.
Cavallo, Gabriella; Metrangolo, Pierangelo; Milani, Roberto; Pilati, Tullio; Priimagi, Arri; Resnati, Giuseppe; Terraneo, Giancarlo
2016-02-24
The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185
2016-01-01
The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185
Application of geometric algebra for the description of polymer conformations.
Chys, Pieter
2008-03-14
In this paper a Clifford algebra-based method is applied to calculate polymer chain conformations. The approach enables the calculation of the position of an atom in space with the knowledge of the bond length (l), valence angle (theta), and rotation angle (phi) of each of the preceding bonds in the chain. Hence, the set of geometrical parameters {l(i),theta(i),phi(i)} yields all the position coordinates p(i) of the main chain atoms. Moreover, the method allows the calculation of side chain conformations and the computation of rotations of chain segments. With these features it is, in principle, possible to generate conformations of any type of chemical structure. This method is proposed as an alternative for the classical approach by matrix algebra. It is more straightforward and its final symbolic representation considerably simpler than that of matrix algebra. Approaches for realistic modeling by means of incorporation of energetic considerations can be combined with it. This article, however, is entirely focused at showing the suitable mathematical framework on which further developments and applications can be built. PMID:18345877
A new decomposition strategy for parallel bonded molecular dynamics
Plimpton, S.; Hendrickson, B.; Heffelfinger, G.
1992-12-31
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.
Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications
NASA Technical Reports Server (NTRS)
Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, J. Douglas
2007-01-01
A robust joining approach is critically needed for a Micro-Electro-Mechanical Systems-Lean Direct Injector (MEMS-LDI) application which requires leak free joints with high temperature mechanical capability. Diffusion bonding is well suited for the MEMS-LDI application. Diffusion bonds were fabricated using titanium interlayers between silicon carbide substrates during hot pressing. The interlayers consisted of either alloyed titanium foil or physically vapor deposited (PVD) titanium coatings. Microscopy shows that well adhered, crack free diffusion bonds are formed under optimal conditions. Under less than optimal conditions, microcracks are present in the bond layer due to the formation of intermetallic phases. Electron microprobe analysis was used to identify the reaction formed phases in the diffusion bond. Various compatibility issues among the phases in the interlayer and substrate are discussed. Also, the effects of temperature, pressure, time, silicon carbide substrate type, and type of titanium interlayer and thickness on the microstructure and composition of joints are discussed.
ERIC Educational Resources Information Center
Van Der Werf, Martin
2003-01-01
Describes how a long-predicted decline in the fortunes of small private colleges is beginning to show up in the bond market, as the number of colleges now rated in the junk category has nearly doubled. (EV)
Bonding aerogels with polyurethanes
Matthews, F.M.; Hoffman, D.M.
1989-11-01
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.
Esrafili, Mehdi D; Mohammadian-Sabet, Fariba; Solimannejad, Mohammad
2015-04-01
In this work, the interplay between anion-π and pnicogen bond interactions is investigated by ab initio calculations. Cooperative effects are observed in the studied complexes in which anion-π and pnicogen bond interactions coexist. These effects are analyzed in detail in terms of the energetic, geometric, charge-transfer and electron density properties of the complexes. The cooperative energy ranges from -1.8 to -4.1kcalmol(-1). The effect of an anion-π bond on a pnicogen bond is more pronounced than that of a pnicogen bond on an anion-π bond. The enhancing mechanism is analyzed in views with the charge-transfer, electrostatic potential and electron density analysis. PMID:25698102
Diffusion Bonding of Silicon Carbide Ceramics using Titanium Interlayers
NASA Technical Reports Server (NTRS)
Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, James D.
2006-01-01
Robust joining approaches for silicon carbide ceramics are critically needed to fabricate leak free joints with high temperature mechanical capability. In this study, titanium foils and physical vapor deposited (PVD) titanium coatings were used to form diffusion bonds between SiC ceramics using hot pressing. Silicon carbide substrate materials used for bonding include sintered SiC and two types of CVD SiC. Microscopy results show the formation of well adhered diffusion bonds. The bond strengths as determined from pull tests are on the order of several ksi, which is much higher than required for a proposed application. Microprobe results show the distribution of silicon, carbon, titanium, and other minor elements across the diffusion bond. Compositions of several phases formed in the joint region were identified. Potential issues of material compatibility and optimal bond formation will also be discussed.
Cryogenic evaluation of epoxy bond strength
NASA Astrophysics Data System (ADS)
Albritton, N.; Young, W.
The purpose of the work presented here was to determine methods of optimizing the adhesion of a particular epoxy (CTD-101K, Composite Technology Development Inc.) to a particular nickel-based alloy substrate (Incoloy ® 908, Inco Alloys International) for cryogenic applications. Initial efforts were focused on surface preparation of the substrate material via various mechanical and chemical cleaning techniques. Test samples, fabricated to simulate the conduit-to-insulation interface, were put through a mock heat treat and vacuum/pressure impregnation process. Samples were compression/shear load tested to compare the bond strengths at room temperature and liquid nitrogen temperature. The resulting data indicate that acid etching creates a higher bond strength than the other tested techniques and that the bond formed is stronger at cryogenic temperatures than at room temperature. A description of the experiment along with the resulting data is presented here.
Geometrical criteria for characterizing open and closed states of WPD-loop in PTP1B
NASA Astrophysics Data System (ADS)
Shinde, Ranajit Nivrutti; Elizabeth Sobhia, M.
2012-06-01
Distinctive movement of WPD-loop occurs during the catalysis of phosphotyrosine by protein tyrosine phosphatase 1B (PTP1B). This loop is in the "open" state in apo-form whereas it is catalytically competent in the "closed" state. During the closure of this loop, unique hydrogen bond interactions are formed between different residues of the PTP1B. Present study examines such interactions from the available 118 crystal structures of PTP1B. It gives insights into the five novel hydrogen bonds essentially formed in the "closed" loop structures. Additionally, the study provides distance ranges between the atoms involved in the hydrogen bonds. This information can be used as a geometrical criterion in the characterization of conformational state of the WPD-loop especially in the molecular dynamics simulations.
NASA Astrophysics Data System (ADS)
Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir
2015-10-01
A modeling based optimization process of the solid state diffusion bonding is presented for joining ferritic oxide dispersion strengthened steels PM2000. An optimization study employing varying bonding temperatures and pressures results in almost the same strength and toughness of the bonded compared to the as received material. TEM investigations of diffusion bonded samples show a homogeneous distribution of oxide particles at the bonding seam similar to that in the bulk. Hence, no loss in strength or creep resistance due to oxide particle agglomeration is found, as verified by the mechanical properties observed for the joint.
Introduction to Dynamical Systems and Geometric Mechanics
NASA Astrophysics Data System (ADS)
Maruskin, Jared M.
2012-01-01
Introduction to Dynamical Systems and Geometric Mechanics provides a comprehensive tour of two fields that are intimately entwined: dynamical systems is the study of the behavior of physical systems that may be described by a set of nonlinear first-order ordinary differential equations in Euclidean space, whereas geometric mechanics explores similar systems that instead evolve on differentiable manifolds. In the study of geometric mechanics, however, additional geometric structures are often present, since such systems arise from the laws of nature that govern the motions of particles, bodies, and even galaxies. In the first part of the text, we discuss linearization and stability of trajectories and fixed points, invariant manifold theory, periodic orbits, PoincarÃ© maps, Floquet theory, the PoincarÃ©-Bendixson theorem, bifurcations, and chaos. The second part of the text begins with a self-contained chapter on differential geometry that introduces notions of manifolds, mappings, vector fields, the Jacobi-Lie bracket, and differential forms. The final chapters cover Lagrangian and Hamiltonian mechanics from a modern geometric perspective, mechanics on Lie groups, and nonholonomic mechanics via both moving frames and fiber bundle decompositions. The text can be reasonably digested in a single-semester introductory graduate-level course. Each chapter concludes with an application that can serve as a springboard project for further investigation or in-class discussion.
27 CFR 24.147 - Operations bond or unit bond.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Operations bond or unit bond. 24.147 Section 24.147 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Establishment and Operations Bonds and Consents of Surety § 24.147 Operations bond or unit...
30 CFR 281.33 - Bonds and bonding requirements.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF... SHELF Financial Considerations § 281.33 Bonds and bonding requirements. (a) When the leasing...
30 CFR 281.33 - Bonds and bonding requirements.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF... Bonds and bonding requirements. (a) When the leasing notice specifies that payment of a portion of...
Analysis and design of structural bonded joints
Tong, L.; Steven, G.P.
1999-04-01
This is the first book to focus on failure prediction, damage tolerance, optimum design and stitched joining technology for composite materials. Not only is it the first book to discuss failure mechanisms and predictions of metal and composite bonded joints using both strength of materials and fracture mechanics methods, but also examined are the analysis, design and manufacturing of stitched joints using Resin Transfer Moulding and Resin Film Infusion. These techniques have great potential in the manufacturing of lightweight composite structures. The damage tolerance of structural bonded joints is comprehensively covered and when dealing with optimum design the latest Evolutionary Structural Optimization technology is used to develop optimal joint design with improved strength. The contents include: stress analysis techniques; failure criteria and strength prediction; damage tolerance; optimum design; effect of transverse stitching; and selected applications.
Overview on METEOSAT geometrical image data processing
NASA Technical Reports Server (NTRS)
Diekmann, Frank J.
1994-01-01
Digital Images acquired from the geostationary METEOSAT satellites are processed and disseminated at ESA's European Space Operations Centre in Darmstadt, Germany. Their scientific value is mainly dependent on their radiometric quality and geometric stability. This paper will give an overview on the image processing activities performed at ESOC, concentrating on the geometrical restoration and quality evaluation. The performance of the rectification process for the various satellites over the past years will be presented and the impacts of external events as for instance the Pinatubo eruption in 1991 will be explained. Special developments both in hard and software, necessary to cope with demanding tasks as new image resampling or to correct for spacecraft anomalies, are presented as well. The rotating lens of MET-5 causing severe geometrical image distortions is an example for the latter.
Gender recognition based on face geometric features
NASA Astrophysics Data System (ADS)
Xiao, Jie; Guo, Zhaoli; Cai, Chao
2013-10-01
Automatic gender recognition based on face images plays an important role in computer vision and machine vision. In this paper, a novel and simple gender recognition method based on face geometric features is proposed. The method is divided in three steps. Firstly, Pre-processing step provides standard face images for feature extraction. Secondly, Active Shape Model (ASM) is used to extract geometric features in frontal face images. Thirdly, Adaboost classifier is chosen to separate the two classes (male and female). We tested it on 2570 pictures (1420 males and 1150 females) downloaded from the internet, and encouraging results were acquired. The comparison of the proposed geometric feature based method and the full facial image based method demonstrats its superiority.
The geometric phase controls ultracold chemistry.
Kendrick, B K; Hazra, Jisha; Balakrishnan, N
2015-01-01
The geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two Born-Oppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O+OH?H+O2 reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity. PMID:26224326
The geometric phase controls ultracold chemistry
Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.
2015-01-01
The geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two BornOppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O+OH?H+O2 reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity. PMID:26224326
New developments on the geometric nonholonomic integrator
NASA Astrophysics Data System (ADS)
Ferraro, Sebastián; Jiménez, Fernando; Martín de Diego, David
2015-04-01
In this paper, we will discuss new developments regarding the geometric nonholonomic integrator (GNI) (Ferraro et al 2008 Nonlinearity 21 1911-28 Ferraro et al 2009 Discrete Contin. Dyn. Syst. (Suppl.) 220-9). GNI is a discretization scheme adapted to nonholonomic mechanical systems through a discrete geometric approach. This method was designed to account for some of the special geometric structures associated to a nonholonomic motion, like preservation of energy, preservation of constraints or the nonholonomic momentum equation. First, we study the GNI versions of the symplectic-Euler methods, paying special attention to their convergence behaviour. Then, we construct an extension of the GNI in the case of affine constraints. Finally, we generalize the proposed method to nonholonomic reduced systems, an important subclass of examples in nonholonomic dynamics. We illustrate the behaviour of the proposed method with the example of the inhomogeneous sphere rolling without slipping on a table.
The geometric phase controls ultracold chemistry
NASA Astrophysics Data System (ADS)
Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.
2015-07-01
The geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two Born-Oppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O+OH-->H+O2 reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity.
Geometric spin echo under zero field.
Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo
2016-01-01
Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936
The geometric phase controls ultracold chemistry
Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.
2015-07-30
In this study, the geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two Born–Oppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O + OH → H + O_{2} reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity.
NASA Technical Reports Server (NTRS)
Christian, Jerry D.
1973-01-01
Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.
Physical understanding through variational reasoning: electron sharing and covalent bonding.
Ruedenberg, Klaus; Schmidt, Michael W
2009-03-12
Energy changes of stationary states resulting from geometric parameter changes in the Hamiltonian can be understood by variational reasoning in terms of the physical attributes of the kinetic and the potential energy functionals. In atoms as well as molecules, the energy minimization determines the ground state as the optimal compromise between the potential pull of the nuclear attractions and the localization-resisting kinetic pressure of the electron cloud. This variational competition is analyzed for the exact ab initio ground-state wave function of the hydrogen molecule ion to elucidate the formation of the bond. Its electronic wave function is shown to differ from the ground-state wave function of the hydrogen atom by polarization, sharing, and contraction, and the corresponding contributions to the binding energy are examined in detail. All told, the critical feature is that a molecular orbital, contracting (in the variational context) toward two nuclei simultaneously, can lower its potential energy while maintaining a certain degree of delocalization. As a consequence, its kinetic energy functional has a lower value than that of an orbital contracting toward a single nucleus equally closely. By contrast, the potential energy functional is lowered equally effectively whether the orbital contracts toward one nucleus or simultaneously toward two nuclei. Because of this weaker kinetic energy pressure, the electrostatic potential pull of the nuclei in the molecule is able to attach the orbital more tightly to each of the nuclei than the pull of the single nucleus in the atom is able to do. The role of the virial theorem is clarified. Generalizations to other molecules are discussed. PMID:19228050
Code of Federal Regulations, 2011 CFR
2011-10-01
... quotation in excess of $2,000, shall be accompanied by a guaranty or a bid bond in a sum equal to twenty...-LUMPSUMREP Contract. The stand- ard Government form of bid bond (Standard Form 24 Revised November 1950) shall be used. (b) In compliance with the perform- ance bond and payment bond requirements of Article...
Model-based vision using geometric hashing
NASA Astrophysics Data System (ADS)
Akerman, Alexander, III; Patton, Ronald
1991-04-01
The Geometric Hashing technique developed by the NYU Courant Institute has been applied to various automatic target recognition applications. In particular, I-MATH has extended the hashing algorithm to perform automatic target recognition ofsynthetic aperture radar (SAR) imagery. For this application, the hashing is performed upon the geometric locations of dominant scatterers. In addition to being a robust model-based matching algorithm -- invariant under translation, scale, and 3D rotations of the target -- hashing is of particular utility because it can still perform effective matching when the target is partially obscured. Moreover, hashing is very amenable to a SIMD parallel processing architecture, and thus potentially realtime implementable.
The geometric phase in quantum physics
Bohm, A.
1993-03-01
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.
A geometric approach to quantum vortices
NASA Astrophysics Data System (ADS)
Penna, Vittorio; Spera, Mauro
1989-12-01
In this paper a geometrical description is given of the theory of quantum vortices first developed by Rasetti and Regge [Physica A 80, 217 (1975)] relying on the symplectic techniques of Marsden and Weinstein [J. Phys. D 7, 305 (1983)], and Kirillov-Kostant-Souriau geometric quantization. The RR-current algebra is interpreted as the natural Hamiltonian algebra associated to a certain coadjoint orbit of the group G=SDiff(R3), the KKS prequantization condition of which is related to the Feynman-Onsager relation. This orbit is also shown to possess a G-invariant Kaehler structure, whence, in principle, it is possible to quantize it in a natural way.
Geometrically controlled tensile response of braided sutures.
Rawal, Amit; Sibal, Apurv; Saraswat, Harshvardhan; Kumar, Vijay
2015-03-01
Sutures are the materials used for wound closure that are caused by surgery or trauma. The main pre-requisite to the success of the suture is to obtain ultimate level of tensile properties with defined geometrical constraints. In this communication, the model for tensile properties of braided sutures has been proposed by elucidating the most important geometrical and material parameters. The model has accounted for the kinematical changes occurring in the braid and constituent strand geometries under defined level of strain. A comparison has been made between the theoretical and experimental results of stress-strain characteristics of braided sutures. PMID:25579946
Local Geometrical Machinery for Complexity and Control
NASA Astrophysics Data System (ADS)
Ivancevic, Vladimir G.; Reid, Darryn J.
2015-11-01
In this Chapter, we present local geometrical machinery for studying complexity and control, consisting of dynamics on Kähler manifolds, which combine three geometrical structures-Riemannian, symplectic and complex (Hermitian)-in a mutually compatible way. In other words, every Kähler manifold is simultaneously Riemannian, symplectic and complex (Hermitian). It is well known that Riemannian manifolds represent the stage on which Lagrangian dynamics is set, symplectic manifolds represent the stage for Hamiltonian dynamics, and complex (Hermitian) varieties comprise the stage for quantum dynamics. Therefore, Kähler manifolds represent the richest dynamical stage available where Lagrangian, Hamiltonian, and quantum dynamics all dance together.
Scale-invariant geometric random graphs
NASA Astrophysics Data System (ADS)
Xie, Zheng; Rogers, Tim
2016-03-01
We introduce and analyze a class of growing geometric random graphs that are invariant under rescaling of space and time. Directed connections between nodes are drawn according to influence zones that depend on node position in space and time, mimicking the heterogeneity and increased specialization found in growing networks. Through calculations and numerical simulations we explore the consequences of scale invariance for geometric random graphs generated this way. Our analysis reveals a dichotomy between scale-free and Poisson distributions of in- and out-degree, the existence of a random number of hub nodes, high clustering, and unusual percolation behavior. These properties are similar to those of empirically observed web graphs.
Geometric-phase atom optics and interferometry
NASA Astrophysics Data System (ADS)
Zygelman, B.
2015-10-01
We illustrate how geometric gauge forces and topological phase effects emerge in atomic and molecular systems without employing assumptions that rely on adiabaticity. We show how geometric magnetism may be harnessed to engineer novel quantum devices including a velocity sieve, a component in mass spectrometers, for neutral atoms. We introduce and outline a possible experimental setup that demonstrates topological interferometry for neutral spin-1/2 systems. For that two-level system, we study the transition from Abelian to non-Abelian behavior and explore its relation to the molecular Aharonov-Bohm effect.
Geometric accuracy in airborne SAR images
NASA Technical Reports Server (NTRS)
Blacknell, D.; Quegan, S.; Ward, I. A.; Freeman, A.; Finley, I. P.
1989-01-01
Uncorrected across-track motions of a synthetic aperture radar (SAR) platform can cause both a severe loss of azimuthal positioning accuracy in, and defocusing of, the resultant SAR image. It is shown how the results of an autofocus procedure can be incorporated in the azimuth processing to produce a fully focused image that is geometrically accurate in azimuth. Range positioning accuracy is also discussed, leading to a comprehensive treatment of all aspects of geometric accuracy. The system considered is an X-band SAR.
Double-bond defect modelling in As-S glasses
NASA Astrophysics Data System (ADS)
Boyko, V.; Shpotyuk, O.; Hyla, M.
2010-11-01
Ab initio calculations with the RHF/6-311G* basis set are used for geometrical optimization of regular pyramidal and defect quasi-tetrahedral clusters in binary As-S glasses. It is shown that quasi-tetrahedral S=AsS3/2 structural units are impossible as main network-building blocks in these glasses.
Primary School Teacher Candidates' Geometric Habits of Mind
ERIC Educational Resources Information Center
Köse, Nilu¨fer Y.; Tanisli, Dilek
2014-01-01
Geometric habits of mind are productive ways of thinking that support learning and using geometric concepts. Identifying primary school teacher candidates' geometric habits of mind is important as they affect the development of their future students' geometric thinking. Therefore, this study attempts to determine primary school…
Methods and Apparatuses for Signaling with Geometric Constellations in a Raleigh Fading Channel
NASA Technical Reports Server (NTRS)
Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)
2015-01-01
Communication systems are described that use signal constellations, which have unequally spaced (i.e., `geometrically` shaped) points. In many embodiments, the communication systems use specific geometric constellations that are capacity optimized at a specific SNR (signal to noise ratio). In addition, ranges within which the constellation points of a capacity optimized constellation can be perturbed and are still likely to achieve a given percentage of the optimal capacity increase compared to a constellation that maximizes d (sub min) (i.e. minimum distance between constellations) are also described. Capacity measures that are used in the selection of the location of constellation points include, but are not limited to, parallel decode (PD) capacity and joint capacity.
Insulation bonding test system
NASA Technical Reports Server (NTRS)
Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)
1984-01-01
A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.
Surface activation enhanced low temperature silicon wafer bonding
NASA Astrophysics Data System (ADS)
Gan, Qing
Direct wafer bonding technology has received great attention since 1985. It enables to realize the novel combinations of different materials for expanded functionality and provides a versatile device technology for transferring device layers to another wafer for further processing or device integration onto one wafer. Silicon direct wafer bonding has found a wide range of applications including Silicon-on-Insulator (SOI) wafers, micromechanical devices, and sensors and actuators. One of the challenges facing this technology is to achieve strong bonding at low temperatures that can survive post-wafer bonding processing. This dissertation presents the results of developing new wafer bonding processes for achieving high bonding energy at low temperatures. For thermal oxide covered silicon wafer bonding, dilute HF solution has been used to etch the wafers prior to room temperature bonding. The bonding energy has been significantly enhanced which reached silicon fracture energy after annealed at 100°C for 45 hours. For native oxide covered silicon wafers, the pre-treatment in dilute HNO3 and dilute HF mixtures has been found to be able to enhance the bonding energy at low temperatures. This is attributed to the incorporation of fluorine in native oxide during the pre-treatment. Various approaches have also been explored for hydrophobic silicon wafer bonding. Both boron doped surface layers and the amorphous surface layers have demonstrated an ability to significantly enhance the bonding energy at low temperatures, with silicon fracture energy achieved at 300--400°C for hydrophobically bonded pairs. The thermal management of heterojunction bipolar transistor (HBT) circuits fabricated by Symmetric Intrinsic HBT (SIHBT) processing was also studied in this research project using simulation method. Design criteria of selecting the surrogate substrates, interconnection dimension, and dielectric materials for the optimization of thermal management have been obtained.
Mechanics of tunable helices and geometric frustration in biomimetic seashells
NASA Astrophysics Data System (ADS)
Guo, Qiaohang; Chen, Zi; Li, Wei; Dai, Pinqiang; Ren, Kun; Lin, Junjie; Taber, Larry A.; Chen, Wenzhe
2014-03-01
Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, add to the variety of this family of aesthetic beauty. Here we develop a comprehensive theoretical framework for tunable helical morphologies, and report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves equilibrium. In this work, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessarily be locally optimized. This novel approach can be applied to develop materials and devices of tunable geometries with a range of applications in nano/biotechnology.
29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.
Code of Federal Regulations, 2010 CFR
2010-07-01
... bonding. 2580.412-20 Section 2580.412-20 Labor Regulations Relating to Labor (Continued) EMPLOYEE BENEFITS SECURITY ADMINISTRATION, DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580.412-20 Use of existing...
29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.
Code of Federal Regulations, 2011 CFR
2011-07-01
... bonding. 2580.412-20 Section 2580.412-20 Labor Regulations Relating to Labor (Continued) EMPLOYEE BENEFITS SECURITY ADMINISTRATION, DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580.412-20 Use of existing...
Structure, nonstoichiometry, and geometrical frustration of α -tetragonal boron
NASA Astrophysics Data System (ADS)
Uemura, Naoki; Shirai, Koun; Eckert, Hagen; Kunstmann, Jens
2016-03-01
Recent discoveries of supposedly pure α -tetragonal boron require to revisit its structure. The system is also interesting with respect to a new type of geometrical frustration in elemental crystals, which was found in β -rhombohedral boron. Based on density functional theory calculations, the present study has resolved the structural and thermodynamic characteristics of pure α -tetragonal boron. Different from β -rhombohedral boron, the conditions for stable covalent bonding (a band gap and completely filled valence bands) are almost fulfilled at a composition B52 with two 4 c interstitial sites occupied. This indicates that the ground state of pure α -tetragonal boron is stoichiometric. However, the covalent condition is not perfectly fulfilled because nonbonding in-gap states exist that cannot be eliminated. The half occupation of the 4 c sites yields a macroscopic amount of residual entropy, which is as large as that of β -rhombohedral boron. Therefore α -tetragonal boron can be classified as an elemental crystal with geometrical frustration. Deviations from stoichiometry can occur only at finite temperatures. Thermodynamic considerations show that deviations δ from the stoichiometric composition (B52 +δ) are small and positive. For the reported high-pressure syntheses conditions δ is predicted to be about 0.1 to 0.2. An important difference between pure and C- or N-containing α -tetragonal boron is found in the occupation of interstitial sites: the pure form prefers to occupy the 4 c sites, whereas in C- or N-containing forms, a mixture of 2 a , 8 h , and 8 i sites are occupied. The present article provides relations of site occupation, δ values, and lattice parameters, which enable us to identify pure α -tetragonal boron and distinguish the pure form from other ones.
Geometric Models for Collaborative Search and Filtering
ERIC Educational Resources Information Center
Bitton, Ephrat
2011-01-01
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 both…
If Only Clairaut Had Dynamic Geometric Tools
ERIC Educational Resources Information Center
Chang, Hyewon; Reys, Barbara J.
2013-01-01
Geometry is a major area of study in middle school mathematics, yet middle school and secondary students have difficulty learning important geometric concepts. This article considers Alexis-Claude Clairaut's approach that emphasizes engaging student curiosity about key ideas and theorems instead of directly teaching theorems before their…
A Geometric Approach to Fair Division
ERIC Educational Resources Information Center
Barbanel, Julius
2010-01-01
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 existence…
Geometrical tile design for complex neighborhoods.
Czeizler, Eugen; Kari, Lila
2009-01-01
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
Using geometric algebra to study optical aberrations
Hanlon, J.; Ziock, H.
1997-05-01
This paper uses Geometric Algebra (GA) to study vector aberrations in optical systems with square and round pupils. GA is a new way to produce the classical optical aberration spot diagrams on the Gaussian image plane and surfaces near the Gaussian image plane. Spot diagrams of the third, fifth and seventh order aberrations for square and round pupils are developed to illustrate the theory.
The geometrical significance of the Laplacian
NASA Astrophysics Data System (ADS)
Styer, Daniel F.
2015-12-01
The Laplacian operator can be defined, not only as a differential operator, but also through its averaging properties. Such a definition lends geometric significance to the operator: a large Laplacian at a point reflects a "nonconformist" (i.e., different from average) character for the function there. This point of view is used to motivate the wave equation for a drumhead.
Global Geometric Properties of Martian Impact Craters
NASA Technical Reports Server (NTRS)
Garvin, J. B.; Sakimoto, S. E. H.; Frawley, J. J.; Schnetzler, C.
2002-01-01
We present impact crater geometric properties for more than 5000 fresh martian features using high resolution Mars Orbiter Laser Altimeter digital elevation models and topographic profiles. We discuss global results and significant regional variations. Additional information is contained in the original extended abstract.
Gibbs Delaunay Tessellations with Geometric Hardcore Conditions
NASA Astrophysics Data System (ADS)
Dereudre, David
2008-04-01
In this paper, we prove the existence of infinite Gibbs Delaunay tessellations on ℝ2. The interaction depends on the local geometry of the tessellation. We introduce a geometric hardcore condition on small and large cells, consequently we can construct more regular infinite random Delaunay tessellations.
Geometric Transformations in Middle School Mathematics Textbooks
ERIC Educational Resources Information Center
Zorin, Barbara
2011-01-01
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 curriculum…
Impossible Geometric Constructions: A Calculus Writing Project
ERIC Educational Resources Information Center
Awtrey, Chad
2013-01-01
This article discusses a writing project that offers students the opportunity to solve one of the most famous geometric problems of Greek antiquity; namely, the impossibility of trisecting the angle [pi]/3. Along the way, students study the history of Greek geometry problems as well as the life and achievements of Carl Friedrich Gauss. Included is…
Geometric Determinants of Human Spatial Memory
ERIC Educational Resources Information Center
Hartley, Tom; Trinkler, Iris; Burgess, Neil
2004-01-01
Geometric alterations to the boundaries of a virtual environment were used to investigate the representations underlying human spatial memory. Subjects encountered a cue object in a simple rectangular enclosure, with distant landmarks for orientation. After a brief delay, during which they were removed from the arena, subjects were returned to it…
Geometric interpretations for resonances of plasmonic nanoparticles
Liu, Wei; Oulton, Rupert F.; Kivshar, Yuri S.
2015-01-01
The field of plasmonics can be roughly categorized into two branches: surface plasmon polaritons (SPPs) propagating in waveguides and localized surface plasmons (LSPs) supported by scattering particles. Investigations along these two directions usually employ different approaches, resulting in more or less a dogma that the two branches progress almost independently of each other, with few interactions. Here in this work we interpret LSPs from a Bohr model based geometric perspective relying on SPPs, thus establishing a connection between these two sub-fields. Besides the clear explanations of conventional scattering features of plasmonic nanoparticles, based on this geometric model we further demonstrate other anomalous scattering features (higher order modes supported at lower frequencies, and blueshift of the resonance with increasing particle sizes) and multiple electric resonances of the same order supported at different frequencies, which have been revealed to originate from backward SPP modes and multiple dispersion bands supported in the corresponding plasmonic waveguides, respectively. Inspired by this geometric model, it is also shown that, through solely geometric tuning, the absorption of each LSP resonance can be maximized to reach the single channel absorption limit, provided that the scattering and absorption rates are tuned to be equal. PMID:26173797
Modern Geometric Algebra: A (Very Incomplete!) Survey
ERIC Educational Resources Information Center
Suzuki, Jeff
2009-01-01
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…
Geometrizing the Quantum - A Toy Model
Koch, Benjamin
2009-12-15
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.
Geometric Interpretations of Some Psychophysical Results.
ERIC Educational Resources Information Center
Levine, Michael V.
A theory of psychophysics is discussed that enlarges the classical theory in three general ways: (1) the multidimensional nature of perception is made explicit; (2) the transformations of the theory are interpreted geometrically; and (3) attributes are distinguished from sensations and only partially ordered. It is shown that, with the enlarged…
Reinforcing Geometric Properties with Shapedoku Puzzles
ERIC Educational Resources Information Center
Wanko, Jeffrey J.; Nickell, Jennifer V.
2013-01-01
Shapedoku is a new type of puzzle that combines logic and spatial reasoning with understanding of basic geometric concepts such as slope, parallelism, perpendicularity, and properties of shapes. Shapedoku can be solved by individuals and, as demonstrated here, can form the basis of a review for geometry students as they create their own. In this…
Reinforcing Geometric Properties with Shapedoku Puzzles
ERIC Educational Resources Information Center
Wanko, Jeffrey J.; Nickell, Jennifer V.
2013-01-01
Shapedoku is a new type of puzzle that combines logic and spatial reasoning with understanding of basic geometric concepts such as slope, parallelism, perpendicularity, and properties of shapes. Shapedoku can be solved by individuals and, as demonstrated here, can form the basis of a review for geometry students as they create their own. In this
More Meaning from the Geometric Mean.
ERIC Educational Resources Information Center
Dorner, Bryan C.
2003-01-01
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)
Generic scalar potentials in geometric scalar gravity
NASA Astrophysics Data System (ADS)
Kan, Nahomi; Shiraishi, Kiyoshi
2016-01-01
We discuss a generic form of the scalar potential appearing in the geometric scalar theory of gravity. We find the conditions on the potential by considering weak and strong gravity. The modified black hole solutions are obtained for generic potentials and the inverse problems on a black hole and on a spherical body (`pseudo-gravastar') are investigated.
Shabanpoor, Fazel; Hossain, Mohammed Akhter; Lin, Feng; Wade, John D
2013-01-01
Numerous methods have been developed for the formation of disulfide bonds in recombinant DNA-derived and chemically synthesized peptides and proteins, but only a few have found widespread acceptance. The choice of method(s) for formation of disulfide in synthetic peptides and proteins needs to be tailored for each individual polypeptide in such a way so that the reaction conditions are selective, efficient, and safe and give the maximum yield. Here we describe the sequential formation of three disulfide bonds regioselectively which has been optimized for the synthesis of two-chained, heterodimeric polypeptide members of the insulin-relaxin superfamily. PMID:23943479
Bonding to porcelain and gold.
Wood, D P; Jordan, R E; Way, D C; Galil, K A
1986-03-01
To test the effectiveness of bonding orthodontic attachments to porcelain, edgewise brackets were bonded to 160 lower incisor, porcelain denture teeth by means of two different resin systems and three different porcelain bonding agents. Bonding to porcelain was found to be not only effective, but the use of a porcelain primer before bonding resulted in shear strengths comparable to those achieved with conventional acid-etch enamel bonding when the same resin was used. Roughening the porcelain surface and bonding with a heavily filled resin without a porcelain primer provided shear strengths (30.6 lbs) comparable to conventional acid-etch enamel bonding with a lightly filled resin (28.8 lbs). Roughening the porcelain surface before bonding, adding porcelain primers, and using highly filled resins all added significantly to bond strength, but caused a progressively greater risk of porcelain fracture during debonding. One of three methods to polish porcelain completely restored a roughened porcelain surface to its former appearance. The porcelain bonding primers failed to provide a significant increase in bond strength when bonding to gold. However, a roughened gold surface bonded with a heavily filled resin provided shear strengths (27.3 lbs). comparable to conventional acid-etch enamel bonding by means of a lightly filled resin (28.8 lbs). The use of a highly filled resin on an intact, glazed porcelain surface without using a porcelain primer may provide sufficient bond strength clinically. If more bond strength is needed, the use of Reliance porcelain primer on an intact glaze is preferable to Ormco porcelain primer or Fusion. Still greater bond strength can be developed by roughening the porcelain surface before application of a primer and use of a highly filled resin. The potential for porcelain fracture in debonding, however, is much increased and it is questionable whether bond strengths of this magnitude are required clinically. PMID:2937306
Correlation applied to the recognition of regular geometric figures
NASA Astrophysics Data System (ADS)
Lasso, William; Morales, Yaileth; Vega, Fabio; Díaz, Leonardo; Flórez, Daniel; Torres, Cesar
2013-11-01
It developed a system capable of recognizing of regular geometric figures, the images are taken by the software automatically through a process of validating the presence of figure to the camera lens, the digitized image is compared with a database that contains previously images captured, to subsequently be recognized and finally identified using sonorous words referring to the name of the figure identified. The contribution of system set out is the fact that the acquisition of data is done in real time and using a spy smart glasses with usb interface offering an system equally optimal but much more economical. This tool may be useful as a possible application for visually impaired people can get information of surrounding environment.
Large mode area photonic crystal fibers with high geometrical birefringence
NASA Astrophysics Data System (ADS)
Golojuch, Grzegorz; Urbańczyk, Waclaw
2008-12-01
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 Λ = 8.8 μm, the phase birefringence reaches B = 1.0×10-4 at wavelength λ = 1.3 μm and B = 1.5×10-4 at λ = 1.5 μm. 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 μm.
X-ray CT geometrical calibration via locally linear embedding.
Chen, Mianyi; Xi, Yan; Cong, Wenxiang; Liu, Baodong; Wei, Biao; Wang, Ge
2016-03-14
For X-ray computed tomography (CT), geometric calibration and rigid patient motion compensation are inter-related issues for optimization of image reconstruction quality. Non-calibrated system geometry and patient movement during a CT scan will result in streak-like, blurring and other artifacts in reconstructed images. In this paper, we propose a locally linear embedding based calibration approach to address this challenge under a rigid 2D object assumption and a more general way than what has been reported before. In this method, projections are linearly represented by up-sampled neighbors via locally linear embedding, and CT system parameters are iteratively estimated from projection data themselves. Numerical and experimental studies show that images reconstructed with calibrated parameters are in excellent agreement with the counterparts reconstructed with the true parameters. PMID:27002904
A GEOMETRICAL HEIGHT SCALE FOR SUNSPOT PENUMBRAE
Puschmann, K. G.; Ruiz Cobo, B.; MartInez Pillet, V. E-mail: brc@iac.e
2010-09-10
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.
Redmond, Robert W.; Kochevar, Irene E.
2012-01-10
Photochemical tissue bonding methods include the application of a photosensitizer to a tissue and/or tissue graft, followed by irradiation with electromagnetic energy to produce a tissue seal. The methods are useful for tissue adhesion, such as in wound closure, tissue grafting, skin grafting, musculoskeletal tissue repair, ligament or tendon repair and corneal repair.
ERIC Educational Resources Information Center
Common Ground: Archeology and Ethnography in the Public Interest, 1998
1998-01-01
An interview with Linda Mayro, archaeologist and cultural resources manager for Pima County, Arizona, discusses efforts of local groups to preserve local Native-American and Mexican cultural-heritage sites in oppositon to commercial land developers. A public information campaign led to passage of a $6.4 million historic preservation bond. (SAS)
Flax Fiber - Interfacial Bonding
Technology Transfer Automated Retrieval System (TEKTRAN)
Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...
ERIC Educational Resources Information Center
Holden, Alan
The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry
ERIC Educational Resources Information Center
Akeroyd, F. Michael
1982-01-01
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)
King, L.D.P.
1964-02-25
A process for bonding or joining graphite members together in which a thin platinum foil is placed between the members, heated in an inert atmosphere to a temperature of 1800 deg C, and then cooled to room temperature is described. (AEC)
ERIC Educational Resources Information Center
Ford, Kim, Ed.
2001-01-01
Offers brief descriptions of 12 recently and not-so-recently published books for young adults, that speak to a wide range of interests at a variety of reading levels, and that could be "just the ticket" to help a reluctant reader bond with books. (SR)
Lenz, Stefan A P; Kellie, Jennifer L; Wetmore, Stacey D
2012-12-13
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
An integrated approach to the synthesis of geometrically non-linear structures
NASA Technical Reports Server (NTRS)
Smaoui, H.; Schmit, L. A.
1988-01-01
An integrated approach to the minimum weight design of geometrically nonlinear three-dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The nonlinear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the constraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically nonlinear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.
An improved image compression algorithm using binary space partition scheme and geometric wavelets.
Chopra, Garima; Pal, A K
2011-01-01
Geometric wavelet is a recent development in the field of multivariate nonlinear piecewise polynomials approximation. The present study improves the geometric wavelet (GW) image coding method by using the slope intercept representation of the straight line in the binary space partition scheme. The performance of the proposed algorithm is compared with the wavelet transform-based compression methods such as the embedded zerotree wavelet (EZW), the set partitioning in hierarchical trees (SPIHT) and the embedded block coding with optimized truncation (EBCOT), and other recently developed "sparse geometric representation" based compression algorithms. The proposed image compression algorithm outperforms the EZW, the Bandelets and the GW algorithm. The presented algorithm reports a gain of 0.22 dB over the GW method at the compression ratio of 64 for the Cameraman test image. PMID:20615810
Geometric frustration on a 1/9th site depleted triangular lattice
NASA Astrophysics Data System (ADS)
Hopkinson, John; Beck, Jarrett
2013-03-01
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 1/9th site depleted and 1/7th bond depleted triangular lattice. The AFI model on this corner-shared triangle net is found to have a large residual entropy per spin S/N = 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 1/9th depleted cobalt hydroxide oxalate. This work was supported by NSERC (JMH) and NSERC USRA (JJB)
ERIC Educational Resources Information Center
Richards, Lynn V.; Coventry, Kenny R.; Clibbens, John
2004-01-01
The effect of both geometric and extra-geometric factors on children's production of "in" is reported (free-response paradigm). Eighty children across four age groups (means 4;1, 5;5, 6;1, and 7;1) were shown video scenes of puppets placing real objects in various positions with reference to a bowl and a plate. Located objects were placed at three…
The Calculation of Accurate Metal-Ligand Bond Energies
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W.; Partridge, Harry, III; Ricca, Alessandra; Arnold, James O. (Technical Monitor)
1997-01-01
The optimization of the geometry and calculation of zero-point energies are carried out at the B3LYP level of theory. The bond energies are determined at this level, as well as at the CCSD(T) level using very large basis sets. The successive OH bond energies to the first row transition metal cations are reported. For most systems there has been an experimental determination of the first OH. In general, the CCSD(T) values are in good agreement with experiment. The bonding changes from mostly covalent for the early metals to mostly electrostatic for the late transition metal systems.
NASA Astrophysics Data System (ADS)
Liu, Xiao-Dong; Meng, Dong-Dong; Hagihala, Masato; Zheng, Xu-Guang; Guo, Qi-Xin
2011-07-01
Mid-infrared absorption and Raman spectra of the geometrically frustrated material series, hydroxyl cobalt halides ß-Co2(OH)3Cl and ß-Co2(OH)3Br, are first, to the best of our knowledge, measured at room temperature, to study the corresponding relationship between their vibrational spectral properties and crystal microstructures. Through the comparative analysis of the four spectra we have categorically assigned the OH-related vibration modes of hydroxyl groups in the trimeric hydrogen bond environment (Co3 ≡OH)3 ... Cl/Br, and tentatively suggested vibration modes of O-Co-O, Co-O and Cl/Br-Co-Cl/Br units. These results can also become the basis for analysing their low-temperature spectral properties, which can help to understand the underlying physics of their exotic geometric frustration phenomena around phase transition temperatures.
Spectral weighted geometric phase for mixed quantum states
NASA Astrophysics Data System (ADS)
Andersson, Ole; Heydari, Hoshang
2014-12-01
Geometric phase has found a broad spectrum of applications in both classical and quantum physics. In this work we discuss a geometric phase for mixed quantum states based on traces of spectral weighted holonomies. Our approach applies to general unitary evolutions of both nondegenerate and degenerate mixed states, and it generalizes the standard definition of geometric phase for mixed states, which is based on quantum interferometry. We provide an explicit formula for the geometric phase that can be easily implemented for computations in quantum physics, and we discuss higher order analogs of the geometric phase that might be defined at points where the ordinary geometric phase is undefined.
27 CFR 24.147 - Operations bond or unit bond.
Code of Federal Regulations, 2012 CFR
2012-04-01
... or contiguous distilled spirits plant qualified under 27 CFR part 19 for the production of distilled... amended, give an operations bond or unit bond in accordance with the applicable provisions of 27 CFR part... BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Establishment and Operations Bonds and Consents of...
27 CFR 24.147 - Operations bond or unit bond.
Code of Federal Regulations, 2011 CFR
2011-04-01
... amended, give an operations bond or unit bond in accordance with the applicable provisions of 27 CFR part... or contiguous distilled spirits plant qualified under 27 CFR part 19 for the production of distilled... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Operations bond or...
Geometric modeling for computer aided design
NASA Technical Reports Server (NTRS)
Schwing, James L.
1993-01-01
Over the past several years, it has been the primary goal of this grant to design and implement software to be used in the conceptual design of aerospace vehicles. The work carried out under this grant was performed jointly with members of the Vehicle Analysis Branch (VAB) of NASA LaRC, Computer Sciences Corp., and Vigyan Corp. This has resulted in the development of several packages and design studies. Primary among these are the interactive geometric modeling tool, the Solid Modeling Aerospace Research Tool (smart), and the integration and execution tools provided by the Environment for Application Software Integration and Execution (EASIE). In addition, it is the purpose of the personnel of this grant to provide consultation in the areas of structural design, algorithm development, and software development and implementation, particularly in the areas of computer aided design, geometric surface representation, and parallel algorithms.
a Modular Geometric Model for Underwater Photogrammetry
NASA Astrophysics Data System (ADS)
Maas, H.-G.
2015-04-01
Underwater applications of photogrammetric measurement techniques usually need to deal with multimedia photogrammetry aspects, which are characterized by the necessity of handling optical rays that are broken at interfaces between optical media with different refrative indices according to Snell's Law. This so-called multimedia geometry has to be incorporated into geometric models in order to achieve correct measurement results. The paper shows a flexible yet strict geometric model for the handling of refraction effects on the optical path, which can be implemented as a module into photogrammetric standard tools such as spatial resection, spatial intersection, bundle adjustment or epipolar line computation. The module is especially well suited for applications, where an object in water is observed by cameras in air through one or more plane parallel glass interfaces, as it allows for some simplifications here.
Geometric distortions of opticommercial panoramic television systems
NASA Technical Reports Server (NTRS)
Govorov, V. M.
1974-01-01
One of the problems solvable by the spaceborne television system, topographical surveying, makes high demands on image quality, particularly on the geometric distortions introduced by the television camera. It is the geometric distortions which determine measurement accuracy and, consequently, the possibility of creating reliable planetary surface maps. Comparative analysis of the different television systems capable of solving the problem showed that the requirements on quality of the transmitted images are best satisfied by television cameras with opticomechanical scanning. The design of panoramic television systems and the process of image construction by the opticomechanical camera are discussed. Results indicate that panoramic television cameras have the necessary instrumental accuracy and permit determination of the direction to objects with an error practically equal to the resolution.
Differential geometric approach to atmospheric refraction.
NASA Astrophysics Data System (ADS)
Kropla, W. C.; Lehn, W. H.
1992-04-01
Differential geometric techniques are presented and used to model the optical properties of the atmosphere under conditions that produce superior mirages. Optical path length replaces the usual Euclidean metric as a distance-measuring function and is used to construct a surface on which the paths of light rays are geodesics. The geodesic equations are shown to be equivalent to the ray equation in the plane. A differential equation that relates the Gaussian curvature of the surface and the refractive index of the atmosphere is derived. This equation is solved for the cases in which the curvature vanishes or is constant. Illustrative examples based on observation demonstrate the use of geometric techniques in the analysis of mirage images.
The bouncing ball through a geometrical series
NASA Astrophysics Data System (ADS)
Flores, Sergio; Alfaro, Luis L.; Chavez, Juan E.; Bastarrachea, Aztlan; Hurtado, Jazmin
2008-10-01
The mathematical representation of the physical situation related to a bouncing ball on the floor is an important understanding difficulty for most of the students during the introductory mechanics and mathematics courses. The research group named Physics and mathematics in context from the University of Ciudad Juarez is concerned about the versatility in the change from a mathematical representation to the own physical context of any problem under a traditional instruction. In this case, the main idea is the association of the physical properties of the bouncing ball situation to the nearest mathematical model based on a geometrical series. The proposal of the cognitive development is based on a geometrical series that shows the time the ball takes to stop. In addition, we show the behavior of the ratio of the consecutive heights during the motion.
Geometric stability of topological lattice phases
Jackson, T. S.; Möller, Gunnar; Roy, Rahul
2015-01-01
The fractional quantum Hall (FQH) effect illustrates the range of novel phenomena which can arise in a topologically ordered state in the presence of strong interactions. The possibility of realizing FQH-like phases in models with strong lattice effects has attracted intense interest as a more experimentally accessible venue for FQH phenomena which calls for more theoretical attention. Here we investigate the physical relevance of previously derived geometric conditions which quantify deviations from the Landau level physics of the FQHE. We conduct extensive numerical many-body simulations on several lattice models, obtaining new theoretical results in the process, and find remarkable correlation between these conditions and the many-body gap. These results indicate which physical factors are most relevant for the stability of FQH-like phases, a paradigm we refer to as the geometric stability hypothesis, and provide easily implementable guidelines for obtaining robust FQH-like phases in numerical or real-world experiments. PMID:26530311
Geometric phase in inhomogeneous optical nutation
NASA Astrophysics Data System (ADS)
Yu, Yanxia; Pan, Hui; Xue, Liyuan; Guo, Liping; Wang, Zisheng
2015-11-01
Optical nutation and its geometric phase are investigated in terms of an inhomogeneous Bloch equation with a constant term. The analytic solution of optical nutation is obtained by mapping it onto a Bloch sphere structure. We find that a constant, from the equilibrium value of the population inversion in the absence of the laser beam, trends to keep the quantum coherence and is helpful to preserve quantum message. We show that the Berry phase of optical nutation is related to the inner evolution in processing of the optical nutation under a quasicyclic evolution. Furthermore, we find that the Berry phases of two-state mixture change very slowly with its environment variable so as to be robust against the decoherent effect. Our results provide a guidance to implement fault-tolerant geometric quantum computation in the echo approach with an inhomogeneous Bloch equation.
Geometric stiffening in multibody system simulation
NASA Astrophysics Data System (ADS)
Wallrapp, O.; Schwertassek, R.
Modeling of general flexible bodies in multibody systems based on geometric stiffening is described, and an efficient method for evaluating the geometric stiffening terms is presented. It is demonstrated that general flexible bodies can be easily incorporated into multibody system models and the corresponding computer codes yield the same results as a much more time-consuming finite element analysis of the system dynamics. The approach uses preprocessed flexible body data based on a finite element code. The proposed method makes it possible to reduce simulation time in a flexible multibody system without sacrificing the accuracy of the results. The approach is being implemented into the SIMPACK code based on an O(N)-formalism for the generation of the system equations.
Geometric stability of topological lattice phases.
Jackson, T S; Möller, Gunnar; Roy, Rahul
2015-01-01
The fractional quantum Hall (FQH) effect illustrates the range of novel phenomena which can arise in a topologically ordered state in the presence of strong interactions. The possibility of realizing FQH-like phases in models with strong lattice effects has attracted intense interest as a more experimentally accessible venue for FQH phenomena which calls for more theoretical attention. Here we investigate the physical relevance of previously derived geometric conditions which quantify deviations from the Landau level physics of the FQHE. We conduct extensive numerical many-body simulations on several lattice models, obtaining new theoretical results in the process, and find remarkable correlation between these conditions and the many-body gap. These results indicate which physical factors are most relevant for the stability of FQH-like phases, a paradigm we refer to as the geometric stability hypothesis, and provide easily implementable guidelines for obtaining robust FQH-like phases in numerical or real-world experiments. PMID:26530311
Geometric stability of topological lattice phases
NASA Astrophysics Data System (ADS)
Jackson, T. S.; Möller, Gunnar; Roy, Rahul
2015-11-01
The fractional quantum Hall (FQH) effect illustrates the range of novel phenomena which can arise in a topologically ordered state in the presence of strong interactions. The possibility of realizing FQH-like phases in models with strong lattice effects has attracted intense interest as a more experimentally accessible venue for FQH phenomena which calls for more theoretical attention. Here we investigate the physical relevance of previously derived geometric conditions which quantify deviations from the Landau level physics of the FQHE. We conduct extensive numerical many-body simulations on several lattice models, obtaining new theoretical results in the process, and find remarkable correlation between these conditions and the many-body gap. These results indicate which physical factors are most relevant for the stability of FQH-like phases, a paradigm we refer to as the geometric stability hypothesis, and provide easily implementable guidelines for obtaining robust FQH-like phases in numerical or real-world experiments.
Geometrical geodesy techniques in Goddard earth models
NASA Technical Reports Server (NTRS)
Lerch, F. J.
1974-01-01
The method for combining geometrical data with satellite dynamical and gravimetry data for the solution of geopotential and station location parameters is discussed. Geometrical tracking data (simultaneous events) from the global network of BC-4 stations are currently being processed in a solution that will greatly enhance of geodetic world system of stations. Previously the stations in Goddard earth models have been derived only from dynamical tracking data. A linear regression model is formulated from combining the data, based upon the statistical technique of weighted least squares. Reduced normal equations, independent of satellite and instrumental parameters, are derived for the solution of the geodetic parameters. Exterior standards for the evaluation of the solution and for the scale of the earth's figure are discussed.
Fast decoding algorithms for geometric coded apertures
NASA Astrophysics Data System (ADS)
Byard, Kevin
2015-12-01
Fast decoding algorithms are described for the class of coded aperture designs known as geometric coded apertures which were introduced by Gourlay and Stephen. When compared to the direct decoding method, the algorithms significantly reduce the number of calculations required when performing the decoding for these apertures and hence speed up the decoding process. Experimental tests confirm the efficacy of these fast algorithms, demonstrating a speed up of approximately two to three orders of magnitude over direct decoding.
Geometric Transitions and Dynamical SUSY Breaking
Aganagic, Mina; Beem, Christopher; Kachru, Shamit; /UC, Berkeley /SLAC
2007-10-01
We show that the physics of D-brane theories that exhibit dynamical SUSY breaking due to stringy instanton effects is well captured by geometric transitions, which recast the non-perturbative superpotential as a classical flux superpotential. This allows for simple engineering of Fayet, Polonyi, O'Raifeartaigh, and other canonical models of supersymmetry breaking in which an exponentially small scale of breaking can be understood either as coming from stringy instantons or as arising from the classical dynamics of fluxes.
Geometric continuum regularization of quantum field theory
Halpern, M.B. . Dept. of Physics)
1989-11-08
An overview of the continuum regularization program is given. The program is traced from its roots in stochastic quantization, with emphasis on the examples of regularized gauge theory, the regularized general nonlinear sigma model and regularized quantum gravity. In its coordinate-invariant form, the regularization is seen as entirely geometric: only the supermetric on field deformations is regularized, and the prescription provides universal nonperturbative invariant continuum regularization across all quantum field theory. 54 refs.
Generalized Chaplygin gas as geometrical dark energy
Heydari-Fard, M.; Sepangi, H. R.
2007-11-15
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.
Broadband Hybrid Holographic Multiplexing with Geometric Metasurfaces.
Huang, Lingling; Mühlenbernd, Holger; Li, Xiaowei; Song, Xu; Bai, Benfeng; Wang, Yongtian; Zentgraf, Thomas
2015-11-01
An effective way for broadband holographic multiplexing based on geometric metasurfaces is demonstrated by the integration of several recording channels into a single device. Each image can be individually addressed with a unique set of parameters, such as circular polarization, position, and angle. Such a technique paves the way for a wide range of applications related to optical patterning, encryption, and information processing. PMID:26398589
Multiphase flow in geometrically simple fracture intersections
Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.
2006-01-01
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.
Low temperature reactive bonding
Makowiecki, Daniel M.; Bionta, Richard M.
1995-01-01
The joining technique requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process.
Advanced Stress, Strain And Geometrical Analysis In Semiconductor Devices
Neels, Antonia; Dommann, Alex; Niedermann, Philippe; Farub, Claudiu; Kaenel, Hans von
2010-11-24
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.
The geometric and electronic structure of Be(10bar10)
NASA Astrophysics Data System (ADS)
Hofmann, Ph.; Plummer, E. W.; Pohl, K.; Stumpf, R.
1996-03-01
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.
Global-Local Finite Element Analysis for Thermo-Mechanical Stresses in Bonded Joints
NASA Technical Reports Server (NTRS)
Shkarayev, S.; Madenci, Erdogan; Camarda, C. J.
1997-01-01
An analysis of adhesively bonded joints using conventional finite elements does not capture the singular behavior of the stress field in regions where two or three dissimilar materials form a junction with or without free edges. However, these regions are characteristic of the bonded joints and are prone to failure initiation. This study presents a method to capture the singular stress field arising from the geometric and material discontinuities in bonded composites. It is achieved by coupling the local (conventional) elements with global (special) elements whose interpolation functions are constructed from the asymptotic solution.
Padgett, E.V. Jr.; Warf, D.H.
1964-04-28
An improved process of bonding aluminum to aluminum without fusion by ultrasonic vibrations plus pressure is described. The surfaces to be bonded are coated with an aqueous solution of alkali metal stearate prior to assembling for bonding. (AEC) O H19504 Present information is reviewed on steady state proliferation, differentiation, and maturation of blood cells in mammals. Data are cited from metabolic tracer studies, autoradiographic studies, cytologic studies, studies of hematopoietic response to radiation injuries, and computer analyses of blood cell production. A 3-step model for erythropoiesis and a model for granulocyte kinetics are presented. New approaches to the study of lymphocytopoiesis described include extracorporeal blood irradiation to deplete lymphocytic tissue without direct injury to the formative tissues as a means to study the stressed system, function control, and rates of proliferation. It is pointed out that present knowledge indicates that lymphocytes comprise a mixed family, with diverse life spans, functions, and migration patterns with apparent aimless recycling from modes to lymph to blood to nodes that has not yet been quantitated. Areas of future research are postulated. (70 references.) (C.H.)
Cooperativity in Tetrel Bonds.
Marín-Luna, Marta; Alkorta, Ibon; Elguero, José
2016-02-01
A theoretical study of the cooperativity in linear chains of (H3SiCN)n and (H3SiNC)n complexes connected by tetrel bonds has been carried out by means of MP2 and CCSD(T) computational methods. In all cases, a favorable cooperativity is observed, especially in some of the largest linear chains of (H3SiNC)n, where the effect is so large that the SiH3 group is almost equidistant to the two surrounding CN groups and it becomes planar. In addition, the combination of tetrel bonds with other weak interactions (halogen, chalcogen, pnicogen, triel, beryllium, lithium, and hydrogen bond) has been explored using ternary complexes, (H3SiCN)2:XY and (H3SiNC)2:XY. In all cases, positive cooperativity is obtained, especially in the (H3SiNC)2:ClF and (H3SiNC)2:SHF ternary complexes, where, respectively, halogen and chalcogen shared complexes are formed. PMID:26756083
Syntactic Approach To Geometric Surface Shell Determination
NASA Astrophysics Data System (ADS)
DeGryse, Donald G.; Panton, Dale J.
1980-12-01
Autonomous terminal homing of a smart missile requires a stored reference scene of the target for which the missle is destined. The reference scene is produced from stereo source imagery by deriving a three-dimensional model containing cultural structures such as buildings, towers, bridges, and tanks. This model is obtained by the precise matching of cultural features from one image of the stereo pair to the other. In the past, this stereo matching process has relied heavily on local edge operators and a gray scale matching metric. The processing is performed line by line over the imagery and the amount of geometric control is minimal. As a result, the gross structure of the scene is determined but the derived three-dimensional data is noisy, oscillatory, and at times significantly inaccurate. This paper discusses new concepts that are currently being developed to stabilize this geometric reference preparation process. The new concepts involve the use of a structural syntax which will be used as a geometric constraint on automatic stereo matching. The syntax arises from the stereo configuration of the imaging platforms at the time of exposure and the knowledge of how various cultural structures are constructed. The syntax is used to parse a scene in terms of its cultural surfaces and to dictate to the matching process the allowable relative positions and orientations of surface edges in the image planes. Using the syntax, extensive searches using a gray scale matching metric are reduced.
Landsat-5 bumper-mode geometric correction
Storey, J.C.; Choate, Michael J.
2004-01-01
The Landsat-5 Thematic Mapper (TM) scan mirror was switched from its primary operating mode to a backup mode in early 2002 in order to overcome internal synchronization problems arising from long-term wear of the scan mirror mechanism. The backup bumper mode of operation removes the constraints on scan start and stop angles enforced in the primary scan angle monitor operating mode, requiring additional geometric calibration effort to monitor the active scan angles. It also eliminates scan timing telemetry used to correct the TM scan geometry. These differences require changes to the geometric correction algorithms used to process TM data. A mathematical model of the scan mirror's behavior when operating in bumper mode was developed. This model includes a set of key timing parameters that characterize the time-varying behavior of the scan mirror bumpers. To simplify the implementation of the bumper-mode model, the bumper timing parameters were recast in terms of the calibration and telemetry data items used to process normal TM imagery. The resulting geometric performance, evaluated over 18 months of bumper-mode operations, though slightly reduced from that achievable in the primary operating mode, is still within the Landsat specifications when the data are processed with the most up-to-date calibration parameters.
Fibril-based, geometrical microtubule - kinetochore attachments
NASA Astrophysics Data System (ADS)
Bertalan, Zsolt; La Porta, Caterina; Maiato, Helder; Zapperi, Stefano
2014-03-01
Mechanical factors involved in regulating the stability of microtubule-kinetochore attachments during cell division are poorly understood. Various aspects of these attachments are essential for proper chromosome segregation. We introduce and simulate a mechanical model of microtubule-kinetochore interactions in which the stability of the attachment is due to the geometrical conformations of curling protofilaments entangled in kinethochore fibrils. The main load of the simulations are done in two dimensions due to the geometric shape of the protofilament curl. However, since the microtubule-kinetochore fibril entanglement is inherently a three dimensional problem, we also model and test the attachment in 3D. The model allows us to reproduce with good accuracy in vitro experimental measurements of the detachment times of yeast kinetochores from MTs under external pulling forces. Numerical simulations also suggest a purely geometrical mechanism that does not require changes in chemical affinities to control the switch between stable and unstable attachments. Supported by the European Research Council through the Advanced Grant 2011 SIZEFFECTS.
Geometric Morphometrics of Rodent Sperm Head Shape
Varea Sánchez, María; Bastir, Markus; Roldan, Eduardo R. S.
2013-01-01
Mammalian spermatozoa, particularly those of rodent species, are extremely complex cells and differ greatly in form and dimensions. Thus, characterization of sperm size and, particularly, sperm shape represents a major challenge. No consensus exists on a method to objectively assess size and shape of spermatozoa. In this study we apply the principles of geometric morphometrics to analyze rodent sperm head morphology and compare them with two traditional morphometry methods, that is, measurements of linear dimensions and dimensions-derived parameters calculated using formulae employed in sperm morphometry assessments. Our results show that geometric morphometrics clearly identifies shape differences among rodent spermatozoa. It is also capable of discriminating between size and shape and to analyze these two variables separately. Thus, it provides an accurate method to assess sperm head shape. Furthermore, it can identify which sperm morphology traits differ between species, such as the protrusion or retraction of the base of the head, the orientation and relative position of the site of flagellum insertion, the degree of curvature of the hook, and other distinct anatomical features and appendices. We envisage that the use of geometric morphometrics may have a major impact on future studies focused on the characterization of sperm head formation, diversity of sperm head shape among species (and underlying evolutionary forces), the effects of reprotoxicants on changes in cell shape, and phenotyping of genetically-modified individuals. PMID:24312234
The geometric phase controls ultracold chemistry
Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.
2015-07-30
In this study, the geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two Born–Oppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O + OH → H + O2more » reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity.« less
Geometrical branching model: Correlations and jets
NASA Astrophysics Data System (ADS)
Hwa, Rudolph C.
1988-04-01
A geometrical model for multiparticle production at low as well as high pT is discussed. Below the threshold of substantial production of jets, the model has geometrical scaling and Koba-Nielsen-Olesen scaling, the latter being a result of Furry branching in multiplicity distribution at each impact parameter. Above the threshold the production of jets is explicitly taken into account by use of perturbative QCD. The separation into soft and hard components is done in the eikonal formalism consistent with unitarity. Geometrical scaling defines the soft component of the eikonal function. The hard component is related to the jet-production cross section; the pT cutoff is not chosen arbitrarily, but is to be determined by ?el and ?tot. Forward-backward multiplicity correlation can be calculated separately for the cases of no jets and with jets. The emphasis in this paper is on the formalism of the model. The procedure to determine the multiplicity distribution at all s is discussed.
Evolutionary optimization of a Genetically Refined Truss
NASA Technical Reports Server (NTRS)
Hull, Patrick V.; Tinker, Michael L.; Dozier, Gerry
2005-01-01
Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection and stress on a benchmark cantilever truss problem. Predominantly traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This paper will present a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation: Genetic Algorithms and Differential Evolution to successfully optimize a benchmark structural optimization problem. An non-traditional solution to the benchmark problem is presented in this paper, specifically a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization toolset.
Mukhopadhyay, Anamika; Pandey, Prasenjit; Chakraborty, Tapas
2010-04-15
In 1:1 CH...O hydrogen bonded complexes between haloforms and ethers, a correlation of the spectral shifts of nu(C-H) bands (Deltanu(C-H)) of the donors (haloforms) with C-O-C angular strain of the acceptors (ethers) is investigated by the electronic structure theory method at the MP2/6-311++G** level. The calculation predicts that the three-member cyclic ether (oxirane) that has the smallest C-O-C angle induces a much larger blue shifting effect on nu(C-H) transition of fluoroform compared with that by the open chain analogue, dimethyl ether. The natural bond orbital (NBO) analysis reveals that the effect originates because of higher "s" character in the hybrid lone electron pair orbital of the oxygen atom of the former, which is responsible for a smaller contribution to n(O) --> sigma*(C-H) hyperconjugation interaction energy between the donor-acceptor molecules. The optimized structures of the two complexes are largely different with respect to the intermolecular orientational parameters at the hydrogen bonding sites, and similar behavior is also predicted for the two chloroform complexes. Partial optimizations on a series of structures show that the total binding energy of the complexes are insensitive with respect to those geometric parameters. However, the Deltanu(C-H), hyperconjugation interaction energies and hybridization of the carbon-centric bonding orbital of the C-H bond are sensitive with respect to those parameters. The predicted Deltanu(C-H) of each complex is analyzed with respect to the IR spectral shift measured by van der Veken and coworkers in cryosolutions of inert gases. The disagreement found between the measured and calculated IR shifts is interpreted to be the outcome of deformation of the complex geometries along shallow binding potential energy surfaces owing to solvation in the liquefied inert gases. PMID:20334425
19 CFR 113.12 - Bond application.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 19 Customs Duties 1 2010-04-01 2010-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond... merchandise to file a written bond application which may be in the form of a letter. The application...
19 CFR 113.12 - Bond application.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 19 Customs Duties 1 2014-04-01 2014-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond... merchandise to file a written bond application which may be in the form of a letter. The application...
19 CFR 113.12 - Bond application.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 19 Customs Duties 1 2011-04-01 2011-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond... merchandise to file a written bond application which may be in the form of a letter. The application...
19 CFR 113.12 - Bond application.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 19 Customs Duties 1 2012-04-01 2012-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond... merchandise to file a written bond application which may be in the form of a letter. The application...
19 CFR 113.12 - Bond application.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 19 Customs Duties 1 2013-04-01 2013-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond... merchandise to file a written bond application which may be in the form of a letter. The application...
Code of Federal Regulations, 2013 CFR
2013-10-01
... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...
Code of Federal Regulations, 2012 CFR
2012-10-01
... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...
Code of Federal Regulations, 2014 CFR
2014-10-01
... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...
Rapid Adhesive Bonding of Composites
NASA Technical Reports Server (NTRS)
Stein, B. A.; Tyeryar, J. R.; Fox, R. L.; Sterling, S. Elmo, Jr.; Buckley, J. D.; Inge, Spencer V., Jr.; Burcher, L. G.; Wright, Robert E., Jr.
1986-01-01
Strong bonds created in less time and with less power than use of conventional bonding methods. Rapid adhesive bonding (RAB) technique for composites uses high-frequency induction heating toroids to quickly heat metallic susceptor impregnated with thermoplastic adhesive or sandwiched between thermoset or thermoplastic adhesive cloths or films. Susceptor steel screen or perforated steel foil.
Annual Bond Referenda Survey: 1998.
ERIC Educational Resources Information Center
New Jersey School Boards Association, Trenton.
An annual school bond survey for New Jersey reveals that while the state's voters had approved 60 percent of the school bond issues in 1998, the communities clearly could not meet the state's multi- billion dollar construction needs on their own. Further, communities with high property taxes had fewer bond elections and approved less of them than…
Coulombic Models in Chemical Bonding.
ERIC Educational Resources Information Center
Sacks, Lawrence J.
1986-01-01
Compares the coulumbic point charge model for hydrogen chloride with the valence bond model. It is not possible to assign either a nonpolar or ionic canonical form of the valence bond model, while the covalent-ionic bond distribution does conform to the point charge model. (JM)
Monte Carlo based geometrical model for efficiency calculation of an n-type HPGe detector.
Cabal, Fatima Padilla; Lopez-Pino, Neivy; Bernal-Castillo, Jose Luis; Martinez-Palenzuela, Yisel; Aguilar-Mena, Jimmy; D'Alessandro, Katia; Arbelo, Yuniesky; Corrales, Yasser; Diaz, Oscar
2010-12-01
A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ((241)Am, (133)Ba, (22)Na, (60)Co, (57)Co, (137)Cs and (152)Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized. PMID:20643556
A Micromachined Geometric Moire Interferometric Floating-Element Shear Stress Sensor
NASA Technical Reports Server (NTRS)
Horowitz, S.; Chen, T.; Chandrasekaran, V.; Tedjojuwono, K.; Nishida, T.; Cattafesta, L.; Sheplak, M.
2004-01-01
This paper presents the development of a floating-element shear stress sensor that permits the direct measurement of skin friction based on geometric Moir interferometry. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Experimental characterization indicates a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.
NASA Astrophysics Data System (ADS)
Narita, Kohei; Okada, Susumu
2016-04-01
We used density functional theory to study the geometric and electronic structure of dimerized and one-dimensionally polymerized corannulene as ultra-narrow graphene ribbons with corrugation and topological defects. Our computations reveal that the relative stability and electronic structure of dimerized and polymerized corannulene are sensitive to the intermolecular covalent networks. The energy gap between the highest occupied and lowest unoccupied states of corannulene dimers is narrower than that of isolated corannulene. The corannulene polymers are semiconductors with a direct energy gap of about 1 eV depending on intermolecular bonds. The polymers possess moderate mechanical stiffness having Young's moduli of 200 GPa.
NASA Technical Reports Server (NTRS)
Altshuller, Aubrey P
1955-01-01
The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.
Geometric Approaches to Quadratic Equations from Other Times and Places.
ERIC Educational Resources Information Center
Allaire, Patricia R.; Bradley, Robert E.
2001-01-01
Focuses on geometric solutions of quadratic problems. Presents a collection of geometric techniques from ancient Babylonia, classical Greece, medieval Arabia, and early modern Europe to enhance the quadratic equation portion of an algebra course. (KHR)
Understanding the hydrogen bonds in ionic liquids and their roles in properties and reactions.
Dong, Kun; Zhang, Suojiang; Wang, Jianji
2016-05-21
Ionic liquids (ILs) have many potential applications in the chemical industry. In order to understand ILs, their molecular details have been extensively investigated. Intuitively, electrostatic forces are solely important in ILs. However, experiments and calculations have provided strong evidence for the existence of H-bonds in ILs and their roles in the properties and applications of ILs. As a structure-directing force, H-bonds are responsible for ionic pairing, stacking and self-assembling. Their geometric structure, interaction energy and electronic configuration in the ion-pairs of imidazolium-based ILs and protic ionic liquids (PILs) show a great number of differences compared to conventional H-bonds. In particular, their cooperation with electrostatic, dispersion and π interactions embodies the physical nature of H-bonds in ILs, which anomalously influences their properties, leading to a decrease in their melting points and viscosities and thus fluidizing them. Using ILs as catalysts and solvents, many reactions can be activated by the presence of H-bonds, which reduce the reaction barriers and stabilize the transition states. In the dissolution of lignocellulosic biomass by ILs, H-bonds exhibit a most important role in disrupting the H-bonding network of cellulose and controlling microscopic ordering into domains. In this article, a critical review is presented regarding the structural features of H-bonds in ILs and PILs, the correlation between H-bonds and the properties of ILs, and the roles of H-bonds in typical reactions. PMID:27042709
Vector-based model of elastic bonds for simulation of granular solids.
Kuzkin, Vitaly A; Asonov, Igor E
2012-11-01
A model (further referred to as the V model) for the simulation of granular solids, such as rocks, ceramics, concrete, nanocomposites, and agglomerates, composed of bonded particles (rigid bodies), is proposed. It is assumed that the bonds, usually representing some additional gluelike material connecting particles, cause both forces and torques acting on the particles. Vectors rigidly connected with the particles are used to describe the deformation of a single bond. The expression for potential energy of the bond and corresponding expressions for forces and torques are derived. Formulas connecting parameters of the model with longitudinal, shear, bending, and torsional stiffnesses of the bond are obtained. It is shown that the model makes it possible to describe any values of the bond stiffnesses exactly; that is, the model is applicable for the bonds with arbitrary length/thickness ratio. Two different calibration procedures depending on bond length/thickness ratio are proposed. It is shown that parameters of the model can be chosen so that under small deformations the bond is equivalent to either a Bernoulli-Euler beam or a Timoshenko beam or short cylinder connecting particles. Simple analytical expressions, relating parameters of the V model with geometrical and mechanical characteristics of the bond, are derived. Two simple examples of computer simulation of thin granular structures using the V model are given. PMID:23214773
Vector-based model of elastic bonds for simulation of granular solids
NASA Astrophysics Data System (ADS)
Kuzkin, Vitaly A.; Asonov, Igor E.
2012-11-01
A model (further referred to as the V model) for the simulation of granular solids, such as rocks, ceramics, concrete, nanocomposites, and agglomerates, composed of bonded particles (rigid bodies), is proposed. It is assumed that the bonds, usually representing some additional gluelike material connecting particles, cause both forces and torques acting on the particles. Vectors rigidly connected with the particles are used to describe the deformation of a single bond. The expression for potential energy of the bond and corresponding expressions for forces and torques are derived. Formulas connecting parameters of the model with longitudinal, shear, bending, and torsional stiffnesses of the bond are obtained. It is shown that the model makes it possible to describe any values of the bond stiffnesses exactly; that is, the model is applicable for the bonds with arbitrary length/thickness ratio. Two different calibration procedures depending on bond length/thickness ratio are proposed. It is shown that parameters of the model can be chosen so that under small deformations the bond is equivalent to either a Bernoulli-Euler beam or a Timoshenko beam or short cylinder connecting particles. Simple analytical expressions, relating parameters of the V model with geometrical and mechanical characteristics of the bond, are derived. Two simple examples of computer simulation of thin granular structures using the V model are given.
Neural network solutions to logic programs with geometric constraints
NASA Astrophysics Data System (ADS)
Parikh, Jo Ann; Werkheiser, Anne; Subrahmanian, V. S.
1993-09-01
Hybrid knowledge bases (HKBs), proposed by Nerode and Subrahmanian, provide a uniform theoretical framework for dealing with the mixed data types and multiple reasoning modes required for solving logical deployment problems. Algorithms based on mixed integer linear programming techniques have been developed for the syntactic subset of HKBs corresponding to function-free Prolog-like logic programs. In this study, we examine the ability of neural networks to solve a more comprehensive set of problems expressed within the hybrid knowledge base framework. The objective of this research is to design and implement a nonlinear optimization procedure for solving extended logic programs with neural networks. We focus upon two types of extensions which are typically required in the formulation of logical deployment problems. The first type of extension, which we shall refer to as a Type I extension, consists of embedding numerical and geometric constraints into logic programs. The second type of extension, which we shall call a Type II extension, consists of incorporating optimization problems into logic clauses.
Femtosecond quantum control of molecular bond formation
Nuernberger, Patrick; Wolpert, Daniel; Weiss, Horst; Gerber, Gustav
2010-01-01
Ultrafast lasers are versatile tools used in many scientific areas, from welding to eye surgery. They are also used to coherently manipulate light–matter interactions such as chemical reactions, but so far control experiments have concentrated on cleavage or rearrangement of existing molecular bonds. Here we demonstrate the synthesis of several molecular species starting from small reactant molecules in laser-induced catalytic surface reactions, and even the increase of the relative reaction efficiency by feedback-optimized laser pulses. We show that the control mechanism is nontrivial and sensitive to the relative proportion of the reactants. The control experiments open up a pathway towards photocatalysis and are relevant for research in physics, chemistry, and biology where light-induced bond formation is important. PMID:20505117
Water lubricates hydrogen-bonded molecular machines.
Panman, Matthijs R; Bakker, Bert H; den Uyl, David; Kay, Euan R; Leigh, David A; Buma, Wybren Jan; Brouwer, Albert M; Geenevasen, Jan A J; Woutersen, Sander
2013-11-01
The mechanical behaviour of molecular machines differs greatly from that of their macroscopic counterparts. This applies particularly when considering concepts such as friction and lubrication, which are key to optimizing the operation of macroscopic machinery. Here, using time-resolved vibrational spectroscopy and NMR-lineshape analysis, we show that for molecular machinery consisting of hydrogen-bonded components the relative motion of the components is accelerated strongly by adding small amounts of water. The translation of a macrocycle along a thread and the rotation of a molecular wheel around an axle both accelerate significantly on the addition of water, whereas other protic liquids have much weaker or opposite effects. We tentatively assign the superior accelerating effect of water to its ability to form a three-dimensional hydrogen-bond network between the moving parts of the molecular machine. These results may indicate a more general phenomenon that helps explain the function of water as the 'lubricant of life'. PMID:24153370
Water lubricates hydrogen-bonded molecular machines
NASA Astrophysics Data System (ADS)
Panman, Matthijs R.; Bakker, Bert H.; den Uyl, David; Kay, Euan R.; Leigh, David A.; Buma, Wybren Jan; Brouwer, Albert M.; Geenevasen, Jan A. J.; Woutersen, Sander
2013-11-01
The mechanical behaviour of molecular machines differs greatly from that of their macroscopic counterparts. This applies particularly when considering concepts such as friction and lubrication, which are key to optimizing the operation of macroscopic machinery. Here, using time-resolved vibrational spectroscopy and NMR-lineshape analysis, we show that for molecular machinery consisting of hydrogen-bonded components the relative motion of the components is accelerated strongly by adding small amounts of water. The translation of a macrocycle along a thread and the rotation of a molecular wheel around an axle both accelerate significantly on the addition of water, whereas other protic liquids have much weaker or opposite effects. We tentatively assign the superior accelerating effect of water to its ability to form a three-dimensional hydrogen-bond network between the moving parts of the molecular machine. These results may indicate a more general phenomenon that helps explain the function of water as the ‘lubricant of life’.
On the bond distance in methane
NASA Technical Reports Server (NTRS)
Bowen-Jenkins, Philippa; Pettersson, Lars G. M.; Siegbahn, Per; Almloef, Jan; Taylor, Peter R.
1987-01-01
The equilibrium bond distance in methane was optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valence correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers.
On the bond distance in methane
NASA Technical Reports Server (NTRS)
Bowen-Jenkins, Philippa; Pettersson, Lars G. M.; Siegbahn, Per; Almlof, Jan; Taylor, Peter R.
1988-01-01
The equilibrium bond distance in methane has been optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valance correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers.
Geometric phase for neutrino propagation in magnetic field
NASA Astrophysics Data System (ADS)
Joshi, Sandeep; Jain, Sudhir R.
2016-03-01
The geometric phase for neutrinos propagating in an adiabatically varying magnetic field in matter is calculated. It is shown that for neutrino propagation in sufficiently large magnetic field the neutrino eigenstates develop a significant geometric phase. The geometric phase varies from 2π for magnetic fields ∼ fraction of a micro gauss to π for fields ∼107 gauss or more. The variation of geometric phase with magnetic field parameters is shown and its phenomenological implications are discussed.
Scar revision techniques: z-plasty, w-plasty, and geometric broken line closure.
Shockley, William W
2011-08-01
This article addresses the use of scar revision surgery as it relates to the use of Z-plasty, W-plasty, and geometric broken line closure. Each of these techniques is discussed in detail and the author provides perspectives regarding the indications, advantages, and limitations of each procedure. The surgeon should be experienced with each of these and apply these methods as appropriate. As with any technique, careful preoperative planning along with meticulous execution will lead to optimal results. PMID:21856534
Methodology and method and appartus for signaling with capacity optimized constellations
NASA Technical Reports Server (NTRS)
Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)
2012-01-01
Communication systems are described that use geometrically shaped constellations that have increased capacity compared to conventional constellations operating within a similar SNR band. In several embodiments, the geometrically shaped is optimized based upon a capacity measure such as parallel decoding capacity or joint capacity. In many embodiments, a capacity optimized geometrically shaped constellation can be used to replace a conventional constellation as part of a firmware upgrade to transmitters and receivers within a communication system. In a number of embodiments, the geometrically shaped constellation is optimized for an Additive White Gaussian Noise channel or a fading channel.
Zhang, Zongbo; Wang, Xiaodong; Luo, Yi; He, Shengqiang; Wang, Liding
2010-06-15
A thermal assisted ultrasonic bonding method for poly(methyl methacrylate) (PMMA) microfluidic devices has been presented. The substrates were preheated to 20-30 degrees C lower than glass transition temperature (T(g)) of the polymer. Then low amplitude ultrasonic vibration was employed to generate facial heat at the interface of PMMA substrates. PMMA microfluidic chips were successfully bonded with bulk temperature well below T(g) of the material and with pressure two orders lower than conventional thermal bonding, which was of great benefit to reduce the deformation of microstructures. The bonding process was optimized by Taguchi method. This bonding technique showed numerous superiorities including high bonding strength (0.95MPa), low dimension loss (0.3-0.8%) and short bonding time. Finally, a micromixer was successfully bonded by this method and its performance was demonstrated. PMID:20441903
Effect of quantum nuclear motion on hydrogen bonding
McKenzie, Ross H. Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.
2014-05-07
This work considers how the properties of hydrogen bonded complexes, X–H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O–H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X–H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.
Identifying and Fostering Higher Levels of Geometric Thinking
ERIC Educational Resources Information Center
Škrbec, Maja; Cadež, Tatjana Hodnik
2015-01-01
Pierre M. Van Hiele created five levels of geometric thinking. We decided to identify the level of geometric thinking in the students in Slovenia, aged 9 to 11 years. The majority of students (60.7%) are at the transition between the zero (visual) level and the first (descriptive) level of geometric thinking. Nearly a third (31.7%) of students is…
Fournier, Véronique; Juanéda, Pierre; Destaillats, Frédéric; Dionisi, Fabiola; Lambelet, Pierre; Sébédio, Jean-Louis; Berdeaux, Olivier
2006-09-29
Addition of long-chain polyunsaturated fatty acids (LC-PUFAs) from marine oil into food products implies preliminary refining procedures of the oil which thermal process affects the integrity of LC-PUFAs. Deodorization, the major step involving high temperatures, is a common process used for the refining of edible fats and oils. The present study evaluates the effect of deodorization temperature on the formation of LC-PUFA geometrical isomers. Chemically isomerized eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were used as reference samples. Fish oil samples have been deodorized at 180, 220 and 250 degrees C for 3 h and pure EPA and DHA fatty acid methyl esters (FAMEs) were chemically isomerized using p-toluenesulfinic acid as catalyst. FAMEs prepared from fish oil were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). Geometrical isomers produced by both processes were fractionated by silver-ion thin-layer chromatography (Ag-TLC) and silver-ion high-performance liquid chromatography (Ag-HPLC). The FAME fractions were subsequently analyzed by gas chromatography (GC) on a 100 m highly polar cyanopropylpolysiloxane coated capillary column, CP-Sil 88. Our results show that thermally induced geometrical isomerization appears to be a directed reaction and some ethylenic double bond positions on the hydrocarbon chain are more prone to stereomutation. Only minor changes were observed in the EPA and DHA trans isomers content and distribution after deodorization at 180 degrees C. The analyses of EPA and DHA isomer fractions revealed that it is possible to quantify EPA geometrical isomers by GC using the described conditions. However, we notice that a mono-trans isomer of DHA, formed during both chemical and thermal treatments, co-elute with all-cis DHA. This feature should be taken into consideration for the quantification of DHA geometrical isomers. PMID:16893549
Bond Inspection by Impact Test
NASA Astrophysics Data System (ADS)
Yang, Y.; Xiang, D.; Qin, Y.; Li, F.; Coulter, R. V.
2010-02-01
Kissing bond detection has been a challenging issue for NDE of bonded structures in aeronautical industry. A novel impact test technique for bond inspection has been developed, which shows great potential for kissing bond detection. The impact test employs a solenoid to produce impact forces in a bonded structure, and the induced elastic wave in the structure was picked up by an EMAT sensor, which located side by side with the solenoid. Both solenoid and EMAT sensor are integrated into a tap header that is mounted onto an automatic 2-D scanner to realize an automatic 2-D scanning. Multiple samples with artificial defects including kissing bonds and disbonds were used to test the impact test technique. The results show that those bond defects in the samples can be detected by the developed impact test technique. For comparison purpose, those samples were also tested with traditional ultrasonic C-scan.
Bond strength of direct and indirect bonded brackets after thermocycling.
Daub, Jacob; Berzins, David W; Linn, Brandon James; Bradley, Thomas Gerard
2006-03-01
Thermocycling simulates the temperature dynamics in the oral environment. With direct bonding, thermocycling reduces the bond strength of orthodontic adhesives to tooth structure. The purpose of this study was to evaluate the shear bond strengths (SBS) of one direct and two indirect bonding methods/adhesives after thermocycling. Sixty human premolars were divided into three groups. Teeth in group 1 were bonded directly with Transbond XT. Teeth in group 2 were indirect bonded with Transbond XT/Sondhi Rapid Set, which is chemically cured. Teeth in group 3 were indirect bonded with Enlight LV/Orthosolo and light cured. Each sample was thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Mean SBS in groups 1, 2, and 3 were not statistically significantly different (13.6 +/- 2.9, 12.3 +/- 3.0, and 11.6 +/- 3.2 MPa, respectively; P > .05). However, when these values were compared with the results of a previous study using the same protocol, but without thermocycling, the SBS was reduced significantly (P = .001). Weibull analysis further showed that group 3 had the lowest bonding survival rate at the minimum clinically acceptable bond-strength range. The Adhesive Remnant Index was also determined, and group 2 had a significantly (P < .05) higher percentage of bond failures at the resin/enamel interface. PMID:16539557
Low temperature reactive bonding
Makowiecki, D.M.; Bionta, R.M.
1995-06-23
Disclosed is a joining technique that requires no external heat source and generates very little heat. It involves the reaction of thin multilayered films deposited on faying (closely fit or joining) surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process. It can be used for joining silicon wafers and integrated circuits.
Low temperature reactive bonding
Makowiecki, D.M.; Bionta, R.M.
1995-01-17
The joining technique is disclosed that requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process. 5 figures.
Minimizing dose during fluoroscopic tracking through geometric performance feedback
Siddique, S.; Fiume, E.; Jaffray, D. A.
2011-01-01
Purpose: There is a growing concern regarding the dose delivered during x-ray fluoroscopy guided procedures, particularly in interventional cardiology and neuroradiology, and in real-time tumor tracking radiotherapy and radiosurgery. Many of these procedures involve long treatment times, and as such, there is cause for concern regarding the dose delivered and the associated radiation related risks. An insufficient dose, however, may convey less geometric information, which may lead to inaccuracy and imprecision in intervention placement. The purpose of this study is to investigate a method for achieving the required tracking uncertainty for a given interventional procedure using minimal dose.Methods: A simple model is used to demonstrate that a relationship exists between imaging dose and tracking uncertainty. A feedback framework is introduced that exploits this relationship to modulate the tube current (and hence the dose) in order to maintain the required uncertainty for a given interventional procedure. This framework is evaluated in the context of a fiducial tracking problem associated with image-guided radiotherapy in the lung. A particle filter algorithm is used to robustly track the fiducial as it traverses through regions of high and low quantum noise. Published motion models are incorporated in a tracking test suite to evaluate the dose-localization performance trade-offs.Results: It is shown that using this framework, the entrance surface exposure can be reduced by up to 28.6% when feedback is employed to operate at a geometric tracking uncertainty of 0.3 mm.Conclusions: The analysis reveals a potentially powerful technique for dynamic optimization of fluoroscopic imaging parameters to control the applied dose by exploiting the trade-off between tracking uncertainty and x-ray exposure per frame. PMID:21776784
Quantum optimization and maximum clique problems
NASA Astrophysics Data System (ADS)
Yatsenko, Vitaliy A.; Pardalos, Panos M.; Chiarini, Bruno H.
2004-08-01
This paper describes a new approach to global optimization and control uses geometric methods and modern quantum mathematics. Polynomial extremal problems (PEP) are considered. PEP constitute one of the most important subclasses of nonlinear programming models. Their distinctive feature is that an objective function and constraints can be expressed by polynomial functions in one or several variables. A general approach to optimization based on quantum holonomic computing algorithms and instanton mechanism. An optimization method based on geometric Lie - algebraic structures on Grassmann manifolds and related with Lax type flows is proposed. Making use of the differential geometric techniques it is shown that associated holonomy groups properly realizing quantum computation can be effectively found concerning polynomial problems. Two examples demonstrating calculation aspects of holonomic quantum computer and maximum clique problems in very large graphs, are considered in detail.
A geometric hidden Markov tree wavelet model
NASA Astrophysics Data System (ADS)
Romberg, Justin K.; Wakin, Michael B.; Choi, Hyeokho; Baraniuk, Richard G.
2003-11-01
In the last few years, it has become apparent that traditional wavelet-based image processing algorithms and models have significant shortcomings in their treatment of edge contours. The standard modeling paradigm exploits the fact that wavelet coefficients representing smooth regions in images tend to have small magnitude, and that the multiscale nature of the wavelet transform implies that these small coefficients will persist across scale (the canonical example is the venerable zero-tree coder). The edge contours in the image, however, cause more and more large magnitude wavelet coefficients as we move down through scale to finer resolutions. But if the contours are smooth, they become simple as we zoom in on them, and are well approximated by straight lines at fine scales. Standard wavelet models exploit the grayscale regularity of the smooth regions of the image, but not the geometric regularity of the contours. In this paper, we build a model that accounts for this geometric regularity by capturing the dependencies between complex wavelet coefficients along a contour. The Geometric Hidden Markov Tree (GHMT) assigns each wavelet coefficient (or spatial cluster of wavelet coefficients) a hidden state corresponding to a linear approximation of the local contour structure. The shift and rotational-invariance properties of the complex wavelet transform allow the GHMT to model the behavior of each coefficient given the presence of a linear edge at a specified orientation --- the behavior of the wavelet coefficient given the state. By connecting the states together in a quadtree, the GHMT ties together wavelet coefficients along a contour, and also models how the contour itself behaves across scale. We demonstrate the effectiveness of the model by applying it to feature extraction.
Geometric entanglement in topologically ordered states
NASA Astrophysics Data System (ADS)
Orús, Román; Wei, Tzu-Chieh; Buerschaper, Oliver; Van den Nest, Maarten
2014-01-01
Here we investigate the connection between topological order and the geometric entanglement, as measured by the logarithm of the overlap between a given state and its closest product state of blocks. We do this for a variety of topologically ordered systems such as the toric code, double semion, colour code and quantum double models. As happens for the entanglement entropy, we find that for sufficiently large block sizes the geometric entanglement is, up to possible sub-leading corrections, the sum of two contributions: a bulk contribution obeying a boundary law times the number of blocks and a contribution quantifying the underlying pattern of long-range entanglement of the topologically ordered state. This topological contribution is also present in the case of single-spin blocks in most cases, and constitutes an alternative characterization of topological order for these quantum states based on a multipartite entanglement measure. In particular, we see that the topological term for the two-dimensional colour code is twice as much as the one for the toric code, in accordance with recent renormalization group arguments (Bombin et al 2012 New J. Phys. 14 073048). Motivated by these results, we also derive a general formalism to obtain upper- and lower-bounds to the geometric entanglement of states with a non-Abelian group symmetry, and which we explicitly use to analyse quantum double models. Furthermore, we also provide an analysis of the robustness of the topological contribution in terms of renormalization and perturbation theory arguments, as well as a numerical estimation for small systems. Some of the results in this paper rely on the ability to disentangle single sites from the quantum state, which is always possible for the systems that we consider. Additionally we relate our results to the behaviour of the relative entropy of entanglement in topologically ordered systems, and discuss a number of numerical approaches based on tensor networks that could be employed to extract this topological contribution for large systems beyond exactly solvable models.
Kanagathara, N; Marchewka, M K; Drozd, M; Gunasekaran, S; Rajakumar, P R; Anbalagan, G
2015-06-15
Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400 nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by (1)H and (13)C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358K for heating and cooling, respectively. PMID:25796010
NASA Astrophysics Data System (ADS)
Kanagathara, N.; Marchewka, M. K.; Drozd, M.; Gunasekaran, S.; Rajakumar, P. R.; Anbalagan, G.
2015-06-01
Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400 nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by 1H and 13C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358 K for heating and cooling, respectively.
Geometric derivation of the quantum speed limit
Jones, Philip J.; Kok, Pieter
2010-08-15
The Mandelstam-Tamm and Margolus-Levitin inequalities play an important role in the study of quantum-mechanical processes in nature since they provide general limits on the speed of dynamical evolution. However, to date there has been only one derivation of the Margolus-Levitin inequality. In this paper, alternative geometric derivations for both inequalities are obtained from the statistical distance between quantum states. The inequalities are shown to hold for unitary evolution of pure and mixed states, and a counterexample to the inequalities is given for evolution described by completely positive trace-preserving maps. The counterexample shows that there is no quantum speed limit for nonunitary evolution.
Extended geometric scaling from generalized traveling waves
Peschanski, R.
2010-03-01
We define a mapping of the QCD Balitsky-Kovchegov equation in the diffusive approximation with noise and a generalized coupling allowing a common treatment of the fixed and running QCD couplings. It corresponds to the extension of the stochastic Fisher and Kolmogorov-Petrovskii-Piscounov equation to the radial wave propagation in a medium with negative-gradient absorption responsible for anomalous diffusion, noninteger dimension, and damped noise fluctuations. We obtain its analytic traveling-wave solutions with a new scaling curve and for running coupling a new scaling variable allowing to extend the range and validity of the geometric-scaling QCD prediction beyond the previously known domain.
Geometrical optics model of Mie resonances
Roll; Schweiger
2000-07-01
The geometrical optics model of Mie resonances is presented. The ray path geometry is given and the resonance condition is discussed with special emphasis on the phase shift that the rays undergo at the surface of the dielectric sphere. On the basis of this model, approximate expressions for the positions of first-order resonances are given. Formulas for the cavity mode spacing are rederived in a simple manner. It is shown that the resonance linewidth can be calculated regarding the cavity losses. Formulas for the mode density of Mie resonances are given that account for the different width of resonances and thus may be adapted to specific experimental situations. PMID:10883983
Unification Principle and a Geometric Field Theory
NASA Astrophysics Data System (ADS)
Wanas, Mamdouh I.; Osman, Samah N.; El-Kholy, Reham I.
2015-08-01
In the context of the geometrization philosophy, a covariant field theory is constructed. The theory satisfies the unification principle. The field equations of the theory are constructed depending on a general differential identity in the geometry used. The Lagrangian scalar used in the formalism is neither curvature scalar nor torsion scalar, but an alloy made of both, the W-scalar. The physical contents of the theory are explored depending on different methods. The analysis shows that the theory is capable of dealing with gravity, electromagnetism and material distribution with possible mutual interactions. The theory is shown to cover the domain of general relativity under certain conditions.
Supersymmetric QCD vacua and geometrical engineering
Tatar, Radu; Wetenhall, Ben
2008-02-15
We consider the geometrical engineering constructions for the N=1 supersymmetric QCD vacua recently proposed by Giveon and Kutasov. After 1 T-duality, the geometries with wrapped D5 branes become N=1 brane configurations with NS branes and D4 branes. The field theories encoded by the geometries contain extra massive adjoint fields for the flavor group. After performing a flop, the geometries contain branes, antibranes and branes wrapped on nonholomorphic 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 nonsupersymmetric vacua.
A Geometric Framework for Rectangular Shape Detection.
Li, Qi
2014-07-25
Rectangular shape detection has a wide range of applications, such as license plate detection, vehicle detection and building detection. In this paper, we propose a geometric framework for rectangular shape detection based on the channelscale space of RGB images. The framework consists of algorithms developed to address three issues of a candidate shape (i.e., a connected component of edge points), including: i) outliers, ii) open shape, and iii) fragmentation. Furthermore, we propose an interestness measure for rectangular shapes by integrating imbalanced points (one type of interest points). Our experimental study shows the promise of the proposed framework. PMID:25073169
Toroidal Precession as a Geometric Phase
J.W. Burby and H. Qin
2012-09-26
Toroidal precession is commonly understood as the orbit-averaged toroidal drift of guiding centers in axisymmetric and quasisymmetric configurations. We give a new, more natural description of precession as a geometric phase effect. In particular, we show that the precession angle arises as the holonomy of a guiding center's poloidal trajectory relative to a principal connection. The fact that this description is physically appropriate is borne out with new, manifestly coordinate-independent expressions for the precession angle that apply to all types of orbits in tokamaks and quasisymmetric stellarators alike. We then describe how these expressions may be fruitfully employed in numerical calculations of precession.
Geometric continuous dynamical decoupling with bounded controls
Chen Pochung
2006-02-15
We develop a framework to implement the dynamical decoupling of open quantum systems using continuous pulse sequences. By exploiting the geometric perspective of the continuous dynamical decoupling, we show that the decoupling pulses can be intuitively designed in the basis of the structure function of the SU(n) corresponding to the control Hamiltonian. Several examples are given to illustrate the basic idea. We argue that in practice the efficiency of the decoupling is determined by the minimum attainable decoupling cycle time T{sub c} instead of the order of the discrete decoupling group.
Minimal representations, geometric quantization, and unitarity.
Brylinski, R; Kostant, B
1994-01-01
In the framework of geometric quantization we explicitly construct, in a uniform fashion, a unitary minimal representation pio of every simply-connected real Lie group Go such that the maximal compact subgroup of Go has finite center and Go admits some minimal representation. We obtain algebraic and analytic results about pio. We give several results on the algebraic and symplectic geometry of the minimal nilpotent orbits and then "quantize" these results to obtain the corresponding representations. We assume (Lie Go)C is simple. PMID:11607478
Hidden geometric character of relativistic quantum mechanics
NASA Astrophysics Data System (ADS)
Almeida, José B.
2007-01-01
Geometry can be an unsuspected source of equations with physical relevance, as everybody is aware since Einstein formulated the general theory of relativity. However, efforts to extend a similar type of reasoning to other areas of physics, namely, electrodynamics, quantum mechanics, and particle physics, usually had very limited success; particularly in quantum mechanics the standard formalism is such that any possible relation to geometry is impossible to detect; other authors have previously trod the geometric path to quantum mechanics, some of that work being referred to in the text. In this presentation we will follow an alternate route to show that quantum mechanics has indeed a strong geometric character. The paper makes use of geometric algebra, also known as Clifford algebra, in five-dimensional space-time. The choice of this space is given the character of first principle, justified solely by the consequences that can be derived from such choice and their consistency with experimental results. Given a metric space of any dimension, one can define monogenic functions, the natural extension of analytic functions to higher dimensions; such functions have null vector derivative and have previously been shown by other authors to play a decisive role in lower dimensional spaces. All monogenic functions have null Laplacian by consequence; in a hyperbolic space this fact leads inevitably to a wave equation with planelike solutions. This is also true for five-dimensional space-time and we will explore those solutions, establishing a parallel with the solutions of the free particle Dirac equation. For this purpose we will invoke the isomorphism between the complex algebra of 4×4 matrices, also known as Dirac's matrices. There is one problem with this isomorphism, because the solutions to Dirac's equation are usually known as spinors (column matrices) that do not belong to the 4×4 matrix algebra and as such are excluded from the isomorphism. We will show that a solution in terms of Dirac spinors is equivalent to a plane wave solution. Just as one finds in the standard formulation, monogenic functions can be naturally split into positive/negative energy together with left/right ones. This split is provided by geometric projectors and we will show that there is a second set of projectors providing an alternate fourfold split. The possible implications of this alternate split are not yet fully understood and are presently the subject of profound research.
Geometrical Wake of a Smooth Flat Collimator
Stupakov, G.V.; /SLAC
2011-09-09
A transverse geometrical wake generated by a beam passing through a smooth flat collimator with a gradually varying gap between the upper and lower walls is considered. Based on generalization of the approach recently developed for a smooth circular taper we reduce the electromagnetic problem of the impedance calculation to the solution of two much simpler static problems - a magnetostatic and an electrostatic ones. The solution shows that in the limit of not very large frequencies, the impedance increases with the ratio h/d where h is the width and d is the distance between the collimating jaws. Numerical results are presented for the NLC Post Linac collimator.
Geometric optics and the "hairy ball theorem"
NASA Astrophysics Data System (ADS)
Bormashenko, Edward; Kazachkov, Alexander
Applications of the hairy ball theorem to the geometrical optics are discussed. When the ideal mirror, topologically equivalent to a sphere, is illuminated at every point, the "hairy ball theorem" prescribes the existence of at least one point at which the incident light will be normally reflected. For the more general case of the surface, topologically equivalent to a sphere, which is both reflecting and refracting the "hairy ball theorem" predicts the existence of at least one point, at which the incident light will be normally reflected and also normally refracted.
On the geometric formulation of Hamiltonian dynamics.
Calderon, Eran; Horwitz, Lawrence; Kupferman, Raz; Shnider, Steven
2013-03-01
Under a proper assignment of a metric and a connection, the (classical) dynamical trajectories can be identified as geodesics of the underlying manifold. We show how these geometric structures can be derived; specifically, we construct them explicitly for configuration and phase spaces of Hamiltonian systems. We demonstrate how the correspondence between geometry and dynamics can be applied to study the conserved quantities of a dynamical system. Lastly, we demonstrate how the mean-curvature of the energy level-sets in phase-space might be correlated with strongly chaotic behavior. PMID:23556957