CYCLIC MAGNETIC ACTIVITY DUE TO TURBULENT CONVECTION IN SPHERICAL WEDGE GEOMETRY
Kaepylae, Petri J.; Mantere, Maarit J.; Brandenburg, Axel
2012-08-10
We report on simulations of turbulent, rotating, stratified, magnetohydrodynamic convection in spherical wedge geometry. An initially small-scale, random, weak-amplitude magnetic field is amplified by several orders of magnitude in the course of the simulation to form oscillatory large-scale fields in the saturated state of the dynamo. The differential rotation is solar-like (fast equator), but neither coherent meridional poleward circulation nor near-surface shear layer develop in these runs. In addition to a poleward branch of magnetic activity beyond 50 Degree-Sign latitude, we find for the first time a pronounced equatorward branch at around 20 Degree-Sign latitude, reminiscent of the solar cycle.
Information geometry of the spherical model.
Janke, W; Johnston, D A; Kenna, R
2003-04-01
Motivated by the observation that geometrizing statistical mechanics offers an interesting alternative to more standard approaches, we calculate the scaling behavior of the curvature R of the information geometry metric for the spherical model. We find that R approximately epsilon(-2), where epsilon=beta(c)-beta is the distance from criticality. The discrepancy from the naively expected scaling R approximately epsilon(-3) is explained and compared with that for the Ising model on planar random graphs, which shares the same critical exponents. PMID:12786435
Characterizing student mathematics teachers' levels of understanding in spherical geometry
NASA Astrophysics Data System (ADS)
Guven, Bulent; Baki, Adnan
2010-12-01
This article presents an exploratory study aimed at the identification of students' levels of understanding in spherical geometry as van Hiele did for Euclidean geometry. To do this, we developed and implemented a spherical geometry course for student mathematics teachers. Six structured, task-based interviews were held with eight student mathematics teachers at particular times through the course to determine the spherical geometry learning levels. After identifying the properties of spherical geometry levels, we developed Understandings in Spherical Geometry Test to test whether or not the levels form hierarchy, and 58 student mathematics teachers took the test. The outcomes seemed to support our theoretical perspective that there are some understanding levels in spherical geometry that progress through a hierarchical order as van Hiele levels in Euclidean geometry.
Characterizing Student Mathematics Teachers' Levels of Understanding in Spherical Geometry
ERIC Educational Resources Information Center
Guven, Bulent; Baki, Adnan
2010-01-01
This article presents an exploratory study aimed at the identification of students' levels of understanding in spherical geometry as van Hiele did for Euclidean geometry. To do this, we developed and implemented a spherical geometry course for student mathematics teachers. Six structured, "task-based interviews" were held with eight student…
Students Discovering Spherical Geometry Using Dynamic Geometry Software
ERIC Educational Resources Information Center
Guven, Bulent; Karatas, Ilhan
2009-01-01
Dynamic geometry software (DGS) such as Cabri and Geometers' Sketchpad has been regularly used worldwide for teaching and learning Euclidean geometry for a long time. The DGS with its inductive nature allows students to learn Euclidean geometry via explorations. However, with respect to non-Euclidean geometries, do we need to introduce them to…
NASA Astrophysics Data System (ADS)
Maksymowicz, Andrei
2015-09-01
Based on high-resolution bathymetry and geophysical observations, the precise continental wedge geometry along the Chilean margin is analyzed. The data show complex patterns in continental wedge geometry that challenge the most frequently used classification methodology for the convergent margin tectonics. A detailed modeling of the parameters involved in the Non-Cohesive Coulomb Wedge theory reveals a tectonic latitudinal segmentation of the Chilean offshore subduction zone. This segmentation is characterized by a sequence of broad segments with different basal effective friction coefficient and/or internal fluid pressure conditions, which are limited by the presence of bathymetric oceanic highs, fracture zones and Peninsulas. The results suggest a general increase of the fluid pressure inside the continental wedge north of 33°S, which is interpreted as a result of a more pervasive fracturing due to tectonic erosion at the base and within the continental wedge. The tectonic segmentation proposed here shows a close spatial relation with the short-term deformation process associated to the coseismic ruptures of large earthquakes in the Chilean margin.
Space Radiation Detector with Spherical Geometry
NASA Technical Reports Server (NTRS)
Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)
2012-01-01
A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.
Space Radiation Detector with Spherical Geometry
NASA Technical Reports Server (NTRS)
Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)
2011-01-01
A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.
Explosive fragmentation of liquids in spherical geometry
NASA Astrophysics Data System (ADS)
Milne, A.; Longbottom, A.; Frost, D. L.; Loiseau, J.; Goroshin, S.; Petel, O.
2016-07-01
Rapid acceleration of a spherical shell of liquid following central detonation of a high explosive causes the liquid to form fine jets that are similar in appearance to the particle jets that are formed during explosive dispersal of a packed layer of solid particles. Of particular interest is determining the dependence of the scale of the jet-like structures on the physical parameters of the system, including the fluid properties (e.g., density, viscosity, and surface tension) and the ratio of the mass of the liquid to that of the explosive. The present paper presents computational results from a multi-material hydrocode describing the dynamics of the explosive dispersal process. The computations are used to track the overall features of the early stages of dispersal of the liquid layer, including the wave dynamics, and motion of the spall and accretion layers. The results are compared with new experimental results of spherical charges surrounded by a variety of different fluids, including water, glycerol, ethanol, and vegetable oil, which together encompass a significant range of fluid properties. The results show that the number of jet structures is not sensitive to the fluid properties, but primarily dependent on the mass ratio. Above a certain mass ratio of liquid fill-to-explosive burster (F / B), the number of jets is approximately constant and consistent with an empirical model based on the maximum thickness of the accretion layer. For small values of F / B, the number of liquid jets is reduced, in contrast with explosive powder dispersal, where small F / B yields a larger number of particle jets. A hypothetical explanation of these features based on the nucleation of cavitation is explored numerically.
NASA Technical Reports Server (NTRS)
Maiden, D. L.
1975-01-01
A wind-tunnel investigation was conducted to determine the aeropropulsion performance (thrust-minus-drag) of a single-engine, variable-geometry, two-dimensional (2-D) wedge nozzle with simulated translating-shroud and collapsing-wedge mechanisms. The investigation was conducted statically and at Mach numbers from 0.60 to 2.01 at an angle of attack of 0 deg and at varied jet total-pressure ratios up to 21, depending on the Mach number. The results indicate that the isolated aeropropulsion performance of a variable-geometry two-dimensional wedge nozzle is competitive with axisymmetric nozzles at transonic and supersonic speeds, but the isolated performance is slightly inferior for static take-off and low subsonic speeds. With the use of a simple tertiary-air ejector, the static take-off performance was increased.
Shock Wave Boundary Layer Interaction Mechanism on a Double Wedge Geometry
NASA Astrophysics Data System (ADS)
Celik, Bayram; Barada, Mohammad Adel El Hajj Ali; Durna, Ahmet Selim
2015-11-01
A hypersonic test series by Swantek & Austin report complex shock wave boundary layer interaction mechanisms and unsteady surface heat flux from a double wedge geometry in a low enthalpy Mach 7 flow. In order to understand the physics of the flow and the heat transfer, we study the flow computationally and compare the results for the double wedge geometries, whose second angle is higher and lower than the maximum deflection angle at Mach 7. Apart from the numbers of comprehensive computational studies on the subject available in open literature, our study aims to describe the flow physics by taking the influence of both boundary layers that are formed on the two walls of the wedge into account. In addition to describing the flow and heat transfer mechanisms, we investigate the time for the flows to reach steady state. We evaluate the interaction mechanisms in term of instant and time average surface heat flux distributions. We perform all computations using a finite volume based compressible Navier-Stokes solver, rhoCentralFoam, which is one of the several compressible flow solvers of an open source software, openFOAM.
Hexatic order and surface ripples in spherical geometries.
Lenz, P; Nelson, D R
2001-09-17
In flat geometries, two-dimensional hexatic order has only a minor effect on capillary waves on a liquid substrate and on undulation modes in lipid bilayers. However, extended bond-orientational order alters the long-wavelength spectrum of these ripples in spherical geometries. We calculate this frequency shift and suggest that it might be detectable in lipid bilayer vesicles, at the surface of liquid metals, and in multielectron bubbles in liquid helium at low temperatures. Hexatic order also leads to a shift in the threshold for the fission instability induced in the later two systems by an excess of electric charge. PMID:11580526
Viscous Rayleigh-Taylor instability in spherical geometry
Mikaelian, Karnig O.
2016-02-08
We consider viscous fluids in spherical geometry, a lighter fluid supporting a heavier one. Chandrasekhar [Q. J. Mech. Appl. Math. 8, 1 (1955)] analyzed this unstable configuration providing the equations needed to find, numerically, the exact growth rates for the ensuing Rayleigh-Taylor instability. He also derived an analytic but approximate solution. We point out a weakness in his approximate dispersion relation (DR) and offer one that is to some extent improved.
Viscous Rayleigh-Taylor instability in spherical geometry
NASA Astrophysics Data System (ADS)
Mikaelian, Karnig O.
2016-02-01
We consider viscous fluids in spherical geometry, a lighter fluid supporting a heavier one. Chandrasekhar [Q. J. Mech. Appl. Math. 8, 1 (1955), 10.1093/qjmam/8.1.1] analyzed this unstable configuration providing the equations needed to find, numerically, the exact growth rates for the ensuing Rayleigh-Taylor instability. He also derived an analytic but approximate solution. We point out a weakness in his approximate dispersion relation (DR) and offer a somewhat improved one. A third DR, based on transforming a planar DR into a spherical one, suffers no unphysical predictions and compares reasonably well with the exact work of Chandrasekhar and a more recent numerical analysis of the problem [Terrones and Carrara, Phys. Fluids 27, 054105 (2015), 10.1063/1.4921648].
NASA Astrophysics Data System (ADS)
Wada, Ikuko; He, Jiangheng; Hasegawa, Akira; Nakajima, Junichi
2015-09-01
We develop a 3-D thermal model for the Northeast Japan subduction margin, using a realistic slab geometry for the subducting Pacific plate, and investigate the effects of oblique subduction and 3-D slab geometry on the mantle wedge flow pattern and the thermal structure. In the Tohoku region, the mantle wedge flow pattern is nearly two-dimensional resulting in a thermal structure similar to those obtained by a 2-D model, owing to the simple slab geometry and subduction nearly perpendicular to the margin. However, in Hokkaido, oblique subduction leads to 3-D mantle wedge flow with northerly inflow and west-northwestward outflow and also results in lower temperatures in the shallow part of the mantle wedge than in Tohoku due to lower sinking rate of the slab. Between Hokkaido and Tohoku, the slab has a hinge-like shape due to a relatively sharp change in the dip direction. In this hinge zone, northerly mantle inflow from Hokkaido and westerly mantle inflow from Tohoku converge, discouraging inflow from northwest and resulting in a cooler mantle wedge. The model-predicted mantle wedge flow patterns are consistent with observed seismic anisotropy and may explain the orientations of volcanic cross-chains. The predicted 3-D thermal structure correlates well with the along-arc variations in the location of the frontal arc volcanoes and help to provide new insights into the surface heat flow pattern and the down-dip extent of interplate earthquakes.
The AGCE related studies of baroclinic flows in spherical geometry
NASA Technical Reports Server (NTRS)
Hyun, J. M.
1983-01-01
Steady state, axisymmetric motions of a Boussineaq fluid continued in rotating spherical anmulus are considered. The motions are driven by latitudinally varying temperature gradient at the shells. Linearized formulations for a narrow gap are derived and the flow field is divided into the Ekman layers and the geostrophic interior. The Ekman layer flows are consistent with the known results for cylindrical geometries. Within the framework of rather restrictive assumptions, the interior flows are solved by a series of associated Legendre polynomials. The solutions show qualitative features valid at midlatitudes.
Acoustic perturbations on steady spherical accretion in Schwarzschild geometry
Naskar, Tapan; Chakravarty, Nabajit; Bhattacharjee, Jayanta K.; Ray, Arnab K.
2007-12-15
The stationary background flow in the spherically symmetric infall of a compressible fluid, coupled to the space-time defined by the static Schwarzschild metric, has been subjected to linearized acoustic perturbations. The perturbative procedure is based on the continuity condition and it shows that the coupling of the flow with the geometry of space-time brings about greater stability for the flow, to the extent that the amplitude of the perturbation, treated as a standing wave, decays in time, as opposed to the amplitude remaining constant in the Newtonian limit. In qualitative terms this situation simulates the effect of a dissipative mechanism in the classical Bondi accretion flow, defined in the Newtonian construct of space and time. As a result of this approach it becomes impossible to define an acoustic metric for a conserved spherically symmetric flow, described within the framework of Schwarzschild geometry. In keeping with this view, the perturbation, considered separately as a high-frequency traveling wave, also has its amplitude reduced.
Room geometry inference based on spherical microphone array eigenbeam processing.
Mabande, Edwin; Kowalczyk, Konrad; Sun, Haohai; Kellermann, Walter
2013-10-01
The knowledge of parameters characterizing an acoustic environment, such as the geometric information about a room, can be used to enhance the performance of several audio applications. In this paper, a novel method for three-dimensional room geometry inference based on robust and high-resolution beamforming techniques for spherical microphone arrays is presented. Unlike other approaches that are based on the measurement and processing of multiple room impulse responses, here, microphone array signal processing techniques for uncontrolled broadband acoustic signals are applied. First, the directions of arrival (DOAs) and time differences of arrival (TDOAs) of the direct signal and room reflections are estimated using high-resolution robust broadband beamforming techniques and cross-correlation analysis. In this context, the main challenges include the low reflected-signal to background-noise power ratio, the low energy of reflected signals relative to the direct signal, and their strong correlation with the direct signal and among each other. Second, the DOA and TDOA information is combined to infer the room geometry using geometric relations. The high accuracy of the proposed room geometry inference technique is confirmed by experimental evaluations based on both simulated and measured data for moderately reverberant rooms. PMID:24116416
Born Sensitivity Kernels in Spherical Geometry for Meridional Flows
NASA Astrophysics Data System (ADS)
Jackiewicz, Jason; Boening, Vincent; Roth, Markus; Kholikov, Shukur
2016-05-01
Measuring meridional flows deep in the solar convection zone is challenging because of their small amplitudes compared to other background signals. Typically such inferences are made using a ray theory that is best suited for slowly-varying flows. The implementation of finite-frequency Born theory has been shown to be more accurate for modeling flows of complex spatial structure in the near-surface region. Only until recently were such functions available in spherical geometry, which is necessary for applications to meridional flows. Here we compare these sensitivity kernels with corresponding ray kernels in a forward and inverse problem using numerical simulations. We show that they are suitable for inverting travel-time measurements and are more sensitive to small-scale variations of deep circulations.
Technology in Spherical Geometry Investigations: Reflections on Spontaneous Use and Motivation
ERIC Educational Resources Information Center
Sinclair, Margaret
2010-01-01
Students in a graduate geometry class used items such as paper, ribbon, plastic spheres, cardboard tubes, and markers to carry out investigations in spherical geometry. The hands-on activities helped students develop a new appreciation of geometry as a study of shape and space; however, the difficulty of subduing wayward elastics and drawing lines…
The solid angle (geometry factor) for a spherical surface source and an arbitrary detector aperture
Favorite, Jeffrey A.
2016-01-13
It is proven that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture.
NASA Astrophysics Data System (ADS)
Kincaid, C. R.; MacDougall, J. G.; Druken, K. A.; Fischer, K. M.
2010-12-01
Understanding patterns in plate scale mantle flow in subduction zones is key to models of thermal structure, dehydration reactions, volatile distributions and magma generation and transport in convergent margins. Different patterns of flow in the mantle wedge can generate distinct signatures in seismological observables. Observed shear wave fast polarization directions in several subduction zones are inconsistent with predictions of simple 2-D wedge corner flow. Geochemical signatures in a number of subduction zones also indicate 3-D flow and entrainment patterns in the wedge. We report on a series of laboratory experiments on subduction driven flow to characterize spatial and temporal variability in 3-D patterns in flow and shear-induced finite strain. Cases focus on how rollback subduction, along-strike dip changes in subducting plates and evolving gaps or tears in subduction zones control temporal-spatial patterns in 3-D wedge flow. Models utilize a glucose working fluid with a temperature dependent viscosity to represent the upper 2000 km of the mantle. Subducting lithosphere is modeled with two rubber-reinforced continuous belts. Belts pass around trench and upper/lower mantle rollers. The deeper rollers can move laterally to allow for time varying dip angle. Each belt has independent speed control and dip adjustment, allowing for along-strike changes in convergence rate and the evolution of slab gaps. Rollback is modeled using a translation system to produce either uniform and asymmetric lateral trench motion. Neutral density finite strain markers are distributed throughout the fluid and used as proxies for tracking the evolution of anisotropy through space and time in the evolving flow fields. Particle image velocimetry methods are also used to track time varying 3-D velocity fields for directly calculating anisotropy patterns. Results show that complex plate motions (rollback, steepening) and morphologies (gaps) in convergent margins produce flows with
Estimating basal friction in accretionary wedges from the geometry and spacing of frontal faults
NASA Astrophysics Data System (ADS)
Schott, Bertram; Koyi, Hemin A.
2001-12-01
Elastic theory applied to the deformation in accretionary wedges is used to calculate the condition for slip along an active frontal fault and the basal décollement. The equations for calculating the stresses can be solved for the coefficient of basal friction in the situation of the formation of a new frontal thrust fault. This allows us to calculate the efficient coefficient of basal friction, which includes the weakening effect of pore-fluid pressure, from geometric parameters and material properties only. The geometric parameters, like fault dip and layer thickness, can be derived from high-resolution seismic cross-sections. Application of our analysis to the Makran and the Nankai accretionary wedge allows us to estimate the upper limit of the effective coefficient of basal friction, μb≈0.16 and μb≈0.2, in these two areas respectively.
Active plasma resonance spectroscopy: eigenfunction solutions in spherical geometry
NASA Astrophysics Data System (ADS)
Oberrath, J.; Brinkmann, R. P.
2014-12-01
The term active plasma resonance spectroscopy denotes a class of related techniques which utilize, for diagnostic purposes, the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe: a radio frequent signal (in the GHz range) is coupled into the plasma via an antenna or probe, the spectral response is recorded, and a mathematical model is used to determine plasma parameters like the electron density. The mathematical model of an arbitrarily shaped probe-plasma system can be written in an abstract but very compact equation. It contains an appropriate operator, which describes the dynamical behavior and can be split into a conservative and a dissipative part. Based on the cold plasma model, this manuscript provides a solution strategy to determine the electrical admittance of a specific probe-plasma system derived from the abstract dynamical equation. Focusing on probes with a spherical-shaped probe tip the general admittance can be derived analytically. Therefore, the matrix representation of the resolvent of the dynamical operator is determined. This matrix representation is derived by means of the eigenfunctions and eigenvalues of the conservative operator. It can be shown that these eigenvalues represent the resonance frequencies of the probe-plasma system which are simply connected to the electron density. As an example, the result is applied to established probe designs: the spherical impedance probe and the multipole resonance probe.
Stationary premixed flames in spherical and cylindrical geometries
NASA Technical Reports Server (NTRS)
Ronney, P. D.; Whaling, K. N.; Abbud-Madrid, A.; Gatto, J. L.; Pisowiscz, V. L.
1994-01-01
Stationary source-free spherical flames ('flame balls') in premixed combustible gases were studied by employing low-gravity (micro-g) environments in a drop tower and an aircraft flying parabolic trajectories to diminish the impact of buoyancy-induced convective flow. Flame balls were found in all mixture families tested when: (1) the Lewis number Le of the deficient reactant was sufficiently low; and (2) the compositions were sufficiently close to the flammability limits. Probably as a consequence of the reduction in buoyant convection, the flammability limits at micro-g were significantly more dilute than those at Earth gravity; for example, 3.35% H2 vs 4.0% H2 in lean H2-air mixtures. By comparison with analytical and computational models, it is inferred that the phenomenon is probably related to diffusive-thermal effects in low-Le mixtures in conjunction with flame-front curvature and radiative heat losses from the combustion products. The chemical reaction mechanism appears to play no qualitative role. In the aircraft experiments, the gravity levels (approximately equal 10(exp -2)g(sub 0)) were found to cause noticeable motion of flame balls due to buoyancy, which in turn influenced the behavior of flame balls. At these g levels, a new type of transient, nearly cylindrical flame structure, termed 'flame strings,' was observed.
Simulations of plasma dynamo in cylindrical and spherical geometries
NASA Astrophysics Data System (ADS)
Khalzov, Ivan; Forest, Cary; Schnack, Dalton; Ebrahimi, Fatima
2010-11-01
We have performed the numerical investigation of plasma flow and possibility of dynamo effect in Madison Plasma Couette Experiment (MPCX) and Madison Plasma Dynamo Experiment (MPDX), which are being installed at the University of Wisconsin- Madison. Using the extended MHD code, NIMROD, we have studied several types of plasma flows appropriate for dynamo excitation. Calculations are done for isothermal compressible plasma model including two-fluid effects (Hall term), which is beyond the standard incompressible MHD picture. It is found that for magnetic Reynolds numbers exceeding the critical one the counter-rotating Von Karman flow (in cylinder) and Dudley- James flow (in sphere) result in self-generation of magnetic field. Depending on geometry and plasma parameters this field can either saturate at certain amplitude corresponding to a new stable equilibrium (laminar dynamo) or lead to turbulent dynamo. It is shown that plasma compressibility results in increase of the critical magnetic Reynolds number while two- fluid effects change the level of saturated dynamo field. The work is supported by NSF.
Nematic liquid crystal in the wedge and edge geometry in the case of homeotropic alignment.
Poniewierski, A
2010-02-01
Nematic liquid crystal confined to a wedge or edge is studied on the assumption that the confining surfaces provide strong and weak homeotropic anchorings, respectively. Both infinite and finite systems are considered. The model based on the Frank-Oseen and Rapini-Papoular formalisms predicts two textures of opposite rotations of the director as in the case of strong anchoring on both surfaces. However, the presence of weak anchoring results in a length scale lambda which characterizes the crossover between the regions close to the apex and far from it. The ratio lambda/b , where b is the extrapolation length, is a function of the opening angle alpha. Both stable and metastable textures are considered and the mechanism by which a texture loses its stability is found. It is related to the formation of a defect-like structure at the surface of weak anchoring whose distance from the apex is lambda(alpha) and the loss of stability is signalled by the divergence of lambda. Only in the limit alpha --> 2tau, the defect-like structure transforms into a defect of strength -1/2 located at a finite distance from the apex. PMID:20195687
Multigroup Time-Independent Neutron Transport Code System for Plane or Spherical Geometry.
Energy Science and Technology Software Center (ESTSC)
1986-12-01
Version 00 PALLAS-PL/SP solves multigroup time-independent one-dimensional neutron transport problems in plane or spherical geometry. The problems solved are subject to a variety of boundary conditions or a distributed source. General anisotropic scattering problems are treated for solving deep-penetration problems in which angle-dependent neutron spectra are calculated in detail.
Ablation Front Rayleigh-Taylor Growth Experiments in Spherically Convergent Geometry
Glendinning, S.G.; Cherfils, C.; Colvin, J.; Divol, L.; Galmiche, D.; Haan, S.; Marinak, M.M.; Remington, B.A.; Richard, A.L.; Wallace, R.
1999-11-03
Experiments were performed on the Nova laser, using indirectly driven capsules mounted in cylindrical gold hohlraums, to measure the Rayleigh-Taylor growth at the ablation front by time-resolved radiography. Modulations were preformed on the surface of Ge-doped plastic capsules. With initial modulations of 4 {micro}m, growth factors of about 6 in optical depth were seen, in agreement with simulations using the radiation hydrocode FCI2. With initial modulations of 1 {micro}m, growth factors of about 100-150 in optical depth were seen. The Rayleigh-Taylor (RT) instability at the ablation front in an inertial confinement fusion capsule has been the subject of considerable investigation. Much of this research has been concentrated on planar experiments, in which RT growth is inferred from radiography. The evolution is somewhat different in a converging geometry; the spatial wavelength decreases (affecting the onset of nonlinear saturation), and the shell thickens and compresses rather than decompressing as in a planar geometry. In a cylindrically convergent geometry, the latter effect is proportional to the radius, while in spherically convergent geometry, the latter effect is proportional to the radius squared. Experiments were performed on the Nova and Omega lasers in cylindrical geometry (using both direct and indirect drive) and have been performed in spherical geometry using direct drive.
TOA Lightning Location Retrieval on Spherical and Oblate Spheroidal Earth Geometries
NASA Technical Reports Server (NTRS)
Koshak, W. J.; Solakiewicz, R. J.; Arnold, James E. (Technical Monitor)
2000-01-01
A simple linear algebraic solution is introduced for retrieving the location and time-of-occurrence of lightning ground strikes on a spherical Earth from a network of four or more time-of-arrival (TOA) sensors. Since the solution accounts for Earth curvature, it represents an extension to earlier planar model results described by Koshak et al. A test of the retrieval method is provided using computer-simulated data sets. The method is easy to comprehend and completely avoids reference to the mathematics of spherical hyperbolas such as discussed by Lewis. A quasi-analytic extension to the spherical Earth solution is provided for an oblate spheroidal Earth geometry, and the importance/relevance of oblate effects are discussed. Future application of these methods in support of the North American National Lightning Detection Network (NALDN) described by Cummins et al. is desirable, but additional theoretical investigations are required to incorporate magnetic bearing information into the present solution process.
Sum frequency generation image reconstruction: aliphatic membrane under spherical cap geometry.
Volkov, Victor
2014-10-01
The article explores an opportunity to approach structural properties of phospholipid membranes using Sum Frequency Generation microscopy. To establish the principles of sum frequency generation image reconstruction in such systems, at first approach, we may adopt an idealistic spherical cap uniform assembly of hydrocarbon molecules. Quantum mechanical studies for decanoic acid (used here as a representative molecular system) provide necessary information on transition dipole moments and Raman tensors of the normal modes specific to methyl terminal - a typical moiety in aliphatic (and phospholipid) membranes. Relative degree of localization and frequencies of the normal modes of methyl terminals make nonlinearities of this moiety to be promising in structural analysis using Sum Frequency Generation imaging. Accordingly, the article describes derivations of relevant macroscopic nonlinearities and suggests a mapping procedure to translate amplitudes of the nonlinearities onto microscopy image plane according to geometry of spherical assembly, local molecular orientation, and optical geometry. Reconstructed images indicate a possibility to extract local curvature of bilayer envelopes of spherical character. This may have practical implications for structural extractions in membrane systems of practical relevance. PMID:25296798
Sum frequency generation image reconstruction: Aliphatic membrane under spherical cap geometry
Volkov, Victor
2014-10-07
The article explores an opportunity to approach structural properties of phospholipid membranes using Sum Frequency Generation microscopy. To establish the principles of sum frequency generation image reconstruction in such systems, at first approach, we may adopt an idealistic spherical cap uniform assembly of hydrocarbon molecules. Quantum mechanical studies for decanoic acid (used here as a representative molecular system) provide necessary information on transition dipole moments and Raman tensors of the normal modes specific to methyl terminal – a typical moiety in aliphatic (and phospholipid) membranes. Relative degree of localization and frequencies of the normal modes of methyl terminals make nonlinearities of this moiety to be promising in structural analysis using Sum Frequency Generation imaging. Accordingly, the article describes derivations of relevant macroscopic nonlinearities and suggests a mapping procedure to translate amplitudes of the nonlinearities onto microscopy image plane according to geometry of spherical assembly, local molecular orientation, and optical geometry. Reconstructed images indicate a possibility to extract local curvature of bilayer envelopes of spherical character. This may have practical implications for structural extractions in membrane systems of practical relevance.
NASA Astrophysics Data System (ADS)
Olsson, Peter
2016-03-01
A new directional decomposition of the acoustic 3D wave equation is derived for spherically symmetric geometries, where the wave fields do not need to possess such a symmetry. This provides an alternative basis for various applications of techniques like invariant embedding and time domain Green functions in spherically symmetric geometries. Contrary to previous results on spherical wave splittings, the new decomposition is given in a very explicit form. The wave equation considered incorporates effects from radially varying compressibility and density, but also from anisotropic density, a property of certain so called metafluids. By applying the new spherical wave splitting, we show that all spherically symmetric acoustic metafluid cloaks are diffeomorphic images of a homogeneous and isotropic spherical ball of perfect fluid.
NASA Technical Reports Server (NTRS)
Bizon, P. T.; Hill, R. J.; Guilliams, B. P.; Drake, S. K.; Kladden, J. L.
1979-01-01
An elastic stress analysis was performed on a wedge specimen (prismatic bar with single-wedge cross section) subjected to thermal cycles in fluidized beds. Seven different combinations consisting of three alloys (NASA TAZ-8A, 316 stainless steel, and A-286) and four thermal cycling conditions were analyzed. The analyses were performed as a joint effort of two laboratories using different models and computer programs (NASTRAN and ISO3DQ). Stress, strain, and temperature results are presented.
NASA Astrophysics Data System (ADS)
Das, Siddhartha; Mitra, Sushanta K.
2013-09-01
In this paper, we provide a theory to pinpoint the role of electric double layer (EDL) interactions in governing the contact angle of an electrolyte drop on a charged solid in air or a bubble on a charged surface within an electrolyte solution. The EDL interactions are analytically solved by representing the three phase contact line as a wedge edge, with the wedge being formed by the solid-liquid and the air-liquid interfaces, and calculating the corresponding Maxwell stresses. We demonstrate that the EDL effects induce an “electrowetting-like” behavior, resulting in a lowering of the contact angle. As a specific example, we use this model to analyze the effect of added salt on preformed surface nanobubbles, and find, in contrast to what has been reported earlier, that even for most moderate conditions, added salt may have remarkable effect in altering the contact angle in preformed surface nanobubbles.
Williamson, D.L.; Hack, J.J.; Jakob, R.; Swarztrauber, P.N. ); Drake, J.B. )
1991-08-01
A suite of seven test cases is proposed for the evaluation of numerical methods intended for the solution of the shallow water equations in spherical geometry. The shallow water equations exhibit the major difficulties associated with the horizontal dynamical aspects of atmospheric modeling on the spherical earth. These cases are designed for use in the evaluation of numerical methods proposed for climate modeling and to identify the potential trade-offs which must always be made in numerical modeling. Before a proposed scheme is applied to a full baroclinic atmospheric model it must perform well on these problems in comparison with other currently accepted numerical methods. The cases are presented in order of complexity. They consist of advection across the poles, steady state geostrophically balanced flow of both global and local scales, forced nonlinear advection of an isolated low, zonal flow impinging on an isolated mountain, Rossby-Haurwitz waves and observed atmospheric states. One of the cases is also identified as a computer performance/algorithm efficiency benchmark for assessing the performance of algorithms adapted to massively parallel computers. 31 refs.
Sensitivity Kernels for Flows in Time–Distance Helioseismology: Extension to Spherical Geometry
NASA Astrophysics Data System (ADS)
Böning, Vincent G. A.; Roth, Markus; Zima, Wolfgang; Birch, Aaron C.; Gizon, Laurent
2016-06-01
We extend an existing Born approximation method for calculating the linear sensitivity of helioseismic travel times to flows from Cartesian to spherical geometry. This development is necessary for using the Born approximation for inferring large-scale flows in the deep solar interior. As first sanity check, we compare two f-mode kernels from our spherical method and from an existing Cartesian method. The horizontal and total integrals agree to within 0.3%. As a second consistency test, we consider a uniformly rotating Sun and a travel distance of 42°. The analytical travel-time difference agrees with the forward-modeled travel-time difference to within 2%. In addition, we evaluate the impact of different choices of filter functions on the kernels for a meridional travel distance of 42°. For all filters, the sensitivity is found to be distributed over a large fraction of the convection zone. We show that the kernels depend on the filter function employed in the data analysis process. If modes of higher harmonic degree (90 ≲ l ≲ 170) are permitted, a noisy pattern of a spatial scale corresponding to l ≈ 260 appears near the surface. When mainly low-degree modes are used (l ≲ 70), the sensitivity is concentrated in the deepest regions and it visually resembles a ray-path-like structure. Among the different low-degree filters used, we find the kernel for phase-speed-filtered measurements to be best localized in depth.
A quantification of the non-spherical geometry and accretion of collapsing cores
NASA Astrophysics Data System (ADS)
Smith, Rowan J.; Glover, Simon C. O.; Bonnell, Ian A.; Clark, Paul C.; Klessen, Ralf S.
2011-02-01
We present the first detailed classification of the structures of Class 0 cores in a high-resolution simulation of a giant molecular cloud. The simulated cloud contains 104 M⊙ and produces over 350 cores which allows for meaningful statistics. Cores are classified into three types according to how much they depart from spherical symmetry. We find that three-quarters of the cores are better described as irregular filaments than as spheres. Recent Herschel results have shown that cores are formed within a network of filaments, which we find has had a significant impact on the resulting core geometries. We show that the column densities and ram pressure seen by the protostar are not uniform and generally peak along the axes of the filament. The angular momentum vector of the material in the cores varies both in magnitude and direction, which will cause the rotation vector of the central source to fluctuate during the collapse of the core. In the case of the more massive stars, accretion from the environment outside the original core volume is even more important than that from the core itself. This additional gas is primarily accreted on to the cores along the dense filaments in which the cores are embedded, and the sections of the surfaces of the cores which do not coincide with a filament have very little additional material passing through them. The assumption of spherical symmetry cannot be applied to the majority of collapsing cores, and is never a good description of how stars accrete gas from outside the original core radius. This has ramifications for our understanding of collapsing cores, in particular their line profiles, the effect of radiation upon them and their ability to fragment.
Ziegler, Andy; Koehler, Thomas; Nielsen, Tim; Proksa, Roland
2006-12-15
In cone-beam transmission tomography the measurements are performed with a divergent beam of x-rays. The reconstruction with iterative methods is an approach that offers the possibility to reconstruct the corresponding images directly from these measurements. Another approach based on spherically symmetric basis functions (blobs) has been reported with results demonstrating a better image quality for iterative reconstruction algorithms. When combining the two approaches (i.e., using blobs in iterative cone-beam reconstruction of divergent rays) the problem of blob sampling without introducing aliasing must be addressed. One solution to this problem is to select a blob size large enough to ensure a sufficient sampling, but this prevents a high resolution reconstruction, which is not desired. Another solution is a heuristic low-pass filtering, which removes this aliasing, but neglects the different contributions of blobs to the absorption depending on the spatial position in the volume and, therefore, cannot achieve the best image quality. This article presents a model of sampling the blobs which is motivated by the beam geometry. It can be used for high resolution reconstruction and can be implemented efficiently.
Critical experiments on single-unit spherical plutonium geometries reflected and moderated by oil
Rothe, R.E.
1997-05-01
Experimental critical configurations are reported for several dozen spherical and hemispherical single-unit assemblies of plutonium metal. Most were solid but many were hollow-centered, thick, shell-like geometries. All were constructed of nested plutonium (mostly {sup 2139}Pu) metal hemispherical shells. Three kinds of critical configurations are reported. Two required interpolation and/or extrapolation of data to obtain the critical mass because reflector conditions were essentially infinite. The first finds the plutonium essentially fully reflected by a hydrogen-rich oil; the second is essentially unreflected. The third kind reports the critical oil reflector height above a large plutonium metal assembly of accurately known mass (no interpolation required) when that mass was too great to permit full oil reflection. Some configurations had thicknesses of mild steel just outside the plutonium metal, separating it from the oil. These experiments were performed at the Rocky Flats Critical Mass Laboratory in the late 1960s. They have not been published in a form suitable for benchmark-quality comparisons against state-of-the-art computational techniques until this paper. The age of the data and other factors lead to some difficulty in reconstructing aspects of the program and may, in turn, decrease confidence in certain details. Whenever this is true, the point is acknowledged. The plutonium metal was alpha-phase {sup 239}Pu containing 5.9 wt-% {sup 240}Pu. All assemblies were formed by nesting 1.667-mm-thick (nominal) bare plutonium metal hemispherical shells, also called hemishells, until the desired configuration was achieved. Very small tolerance gaps machined into radial dimensions reduced the effective density a small amount in all cases. Steel components were also nested hemispherical shells; but these were nominally 3.333-mm thick. Oil was used as the reflector because of its chemical compatibility with plutonium metal.
NASA Astrophysics Data System (ADS)
Raskin, Cody; Owen, J. Michael
2016-04-01
Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such as planets with core-mantle boundaries.
ERIC Educational Resources Information Center
Piva, M.
2009-01-01
In introductory-level physics courses, the concept of surface tension is often illustrated using the example of capillary rise in thin tubes. In this paper the author describes experiments conducted using a planar geometry created with two small plates forming a thin wedge. The distribution of the fluid entering the wedge can be studied as a…
Low-complexity digital filter geometry for spherical coded imaging systems
NASA Astrophysics Data System (ADS)
Feng, Guotong; Shoaib, Mohammed; Robinson, M. D.
2009-08-01
Recent research in the area of electro-optical system design identified the benefits of spherical aberration for extending the depth-of-field of electro-optical imaging systems. In such imaging systems, spherical aberration is deliberately introduced by the optical system lowering system modulation transfer function (MTF) and then subsequently corrected using digital processing. Previous research, however, requires complex digital postprocessing algorithms severely limiting its applicability to only expensive systems. In this paper, we examine the ability of low-cost spatially invariant finite impulse response (FIR) digital filters to restore system MTF degraded by spherical aberration. We introduce an analytical model for choosing the minimum, and hence cheapest, FIR filter size capable of providing the critical level sharpening to render artifact-free images. We identify a robust quality criterion based on the post-processed MTF for developing this model. We demonstrate the reliability of the estimated model by showing simulated spherical coded imaging results. We also evaluate the hardware complexity of the FIR filters implemented for various spherical aberrations on a low-end Field-Programmable Gate Array (FPGA) platform.
NASA Astrophysics Data System (ADS)
Dewitt-Morette, Cécile; Low, Stephen G.; Schulman, Lawrence S.; Shiekh, Anwar Y.
1986-04-01
The wedge problem, that is, the propagation of radiation or particles in the presence of a wedge, is examined in different contexts. Generally, the paper follows the historical order from Sommerfeld's early work to recent stochastic results—hindsights and new results being woven in as appropriate. In each context, identifying the relevant mathematical problem has been the key to the solution. Thus each section can be given both a physics and a mathematics title: Section 2: diffraction by reflecting wedge; boundary value problem of differential equations; solutions defined on mutiply connected spaces. Section 3: geometrical theory of diffraction; identificiation of function spaces. Section 4: path integral solutions; path integration on multiply connected spaces; asymptotics on the boundaries of function spaces. Section 5: probing the shape of the wedge and the roughness of its surface; stochastic calculus. Several propagators and Green functions are given explicitly, some old ones and some new ones. They include the knife-edge propagator for Dirichlet and Neumann boundary conditions, the absorbing knife edge propagator, the wedge propagators, the propagator for a free particle on a μ-sheeted Riemann surface, the Dirichlet and the Neumann wedge Green function.
DeWitt-Morette, C.; Low, S.G.; Schulman, L.S.; Shiekh, A.Y.
1986-04-01
The wedge problem, that is, the propagation of radiation or particles in the presence of a wedge, is examined in different contexts. Generally, the paper follows the historical order from Sommerfeld's early work to recent stochastic results - hindsights and new results being woven in as appropriate. In each context, identifying the relevant mathematical problem has been the key to the solution. Thus each section can be given both a physics and a mathematics title: Section 2: diffraction by reflecting wedge; boundary value problem of differential equations; solutions defined on multiply connected spaces. Section 3: geometrical theory of diffraction; identification of function spaces. Section 4: path integral solutions; path integration on multiply connected spaces; asymptotics on the boundaries of function spaces. Section 5: probing the shape of the wedge and the roughness of its surface; stochastic calculus. Several propagators and Green functions are given explicitly, some old ones and some new ones. They include the knife-edge propagator for Dirichlet and Neumann boundary conditions, the absorbing knife edge propagator, the wedge propagators, the propagator for a free particle on a /sigma phi/-sheeted Riemann surface, the Dirichlet and the Neumann wedge Green function.
NASA Technical Reports Server (NTRS)
Egan, Michael P.; Leung, Chun Ming; Spagna, George F., Jr.
1988-01-01
The program solves the radiation transport problem in a dusty medium with one-dimensional planar, spherical or cylindrical geometry. It determines self-consistently the effects of multiple scattering, absorption, and re-emission of photons on the temperature of dust grains and the characteristics of the internal radiation field. The program can treat radiation field anisotropy, linear anisotropic scattering, and multi-grain components. The program output consists of the dust-temperature distribution, flux spectrum, surface brightness at each frequency and the observed intensities (involving a convolution with a telescope beam pattern).
NASA Astrophysics Data System (ADS)
Arciniaga, Michael; Peterson, Michael R.
2016-07-01
We derive the single-particle eigenenergies and eigenfunctions for massless Dirac fermions confined to the surface of a sphere in the presence of a magnetic monopole, i.e., we solve the Landau level problem for electrons in graphene on the Haldane sphere. With the single-particle eigenfunctions and eigenenergies we calculate the Haldane pseudopotentials for the Coulomb interaction in the second Landau level and calculate the effective pseudopotentials characterizing an effective Landau level mixing Hamiltonian entirely in the spherical geometry to be used in theoretical studies of the fractional quantum Hall effect in graphene. Our treatment is analogous to the formalism in the planar geometry and reduces to the planar results in the thermodynamic limit.
Guo, Y.; Ding, M. D.; Liu, Y.; Sun, X. D.; DeRosa, M. L.; Wiegelmann, T.
2012-11-20
We test a nonlinear force-free field (NLFFF) optimization code in spherical geometry using an analytical solution from Low and Lou. Several tests are run, ranging from idealized cases where exact vector field data are provided on all boundaries, to cases where noisy vector data are provided on only the lower boundary (approximating the solar problem). Analytical tests also show that the NLFFF code in the spherical geometry performs better than that in the Cartesian one when the field of view of the bottom boundary is large, say, 20 Degree-Sign Multiplication-Sign 20 Degree-Sign . Additionally, we apply the NLFFF model to an active region observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory (SDO) both before and after an M8.7 flare. For each observation time, we initialize the models using potential field source surface (PFSS) extrapolations based on either a synoptic chart or a flux-dispersal model, and compare the resulting NLFFF models. The results show that NLFFF extrapolations using the flux-dispersal model as the boundary condition have slightly lower, therefore better, force-free, and divergence-free metrics, and contain larger free magnetic energy. By comparing the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the Atmospheric Imaging Assembly on board SDO, we find that the NLFFF performs better than the PFSS not only for the core field of the flare productive region, but also for large EUV loops higher than 50 Mm.
NASA Technical Reports Server (NTRS)
Band, D. L.; Grindlay, J. E.
1986-01-01
Observational implications and constraints on spherical nonthermal synchrotron self-Compton models with applications to AGNs are discussed. The Compton optical depth of the source and the synchrotron optical depth are considered, and plausible electron distributions are discussed. The alpha(0x), alpha(rx), and alpha(0r) system of comparing the fluxes in different energy bands is related to the nonthermal models, and sample spectra are presented that show the spectral features the models can produce. The models are applied to radio-quiet AGNs. It is shown that the infrared and X-ray continua of the AGNs can be produced by nonthermal processes.
Numerical study of laminar plasma dynamo in cylindrical and spherical geometries
NASA Astrophysics Data System (ADS)
Khalzov, Ivan; Bayliss, Adam; Ebrahimi, Fatima; Forest, Cary; Schnack, Dalton
2009-05-01
We have performed the numerical investigation of possibility of laminar dynamo in two new experiments, Plasma Couette and Plasma Dynamo, which have been designed at the University of Wisconsin-Madison. The plasma is confined by a strong multipole magnetic field localized at the boundary of cylindrical (Plasma Couette) or spherical (Plasma Dynamo) chamber. Electrodes positioned between the magnet rings can be biased with arbitrary potentials so that Lorenz force ExB drives any given toroidal velocity profile at the surface. Using the extended MHD code, NIMROD, we have modeled several types of plasma flows appropriate for dynamo excitation. It is found that for high magnetic Reynolds numbers the counter-rotating von Karman flow (in cylinder) and Dudley-James flow (in sphere) can lead to self-generation of non-axisymmetric magnetic field. This field saturates at certain amplitude corresponding to a new stable equilibrium. The structure of this equilibrium is considered.
Gravity, Topography, Magnetics: Geoscience Data Analysis in Spherical and Planar Geometry
NASA Astrophysics Data System (ADS)
Simons, F. J.; Harig, C.; Lewis, K. W.; Plattner, A.
2015-12-01
Data in the Earth and planetary sciences (as well as in astronomy and cosmology, medical imaging, auditory signal processing, and computer vision) often inherently have a sphere (or an ellipsoid) as their domain. However, frequently our goal is to study phenomena in a specific region of the globe. We might either have data that only cover parts of the sphere (e.g. ocean altimetry, Shuttle radar topography), or we may seek to extract a local signal from a global data set (e.g. the continental fraction of the lithospheric magnetic field, or the portion of the time-varying geopotential that is due to ice mass changes). Spectral content is always finite: all sampled data are band-limited. When the region under study is not the whole sphere, but not small enough to justify two-dimensional projection either, the question arises how to best represent the data to perform our analysis, whatever our field of interest. We present SLEPIAN, a software suite with a multitude of numerical and computational tools, and several plotting routines, to accomplish ``spatiospectral'' spherical analysis in the geosciences and beyond.
NASA Astrophysics Data System (ADS)
Davis, Steven J.; Cao, Long; Caldeira, Ken; Hoffert, Martin I.
2013-03-01
Abstract Stabilizing CO2 emissions at current levels for fifty years is not consistent with either an atmospheric CO2 concentration below 500 ppm or global temperature increases below 2 °C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 'wedges', each of which ramps up linearly over a period of 50 years to ultimately avoid 1 GtC y-1 of CO2 emissions. But this level of mitigation will require affordable carbon-free energy systems to be deployed at the scale of tens of terawatts. Any hope for such fundamental and disruptive transformation of the global energy system depends upon coordinated efforts to innovate, plan, and deploy new transportation and energy systems that can provide affordable energy at this scale without emitting CO2 to the atmosphere. 1. Introduction In 2004, Pacala and Socolow published a study in Science arguing that '[h]umanity can solve the carbon and climate problem in the first half of this century simply by scaling up what we already know how to do' [1]. Specifically, they presented 15 options for 'stabilization wedges' that would grow linearly from zero to 1 Gt of carbon emissions avoided per year (GtC y-1 1 Gt = 1012 kg) over 50 years. The solution to the carbon and climate problem, they asserted, was 'to deploy the technologies and/or lifestyle changes necessary to fill all seven wedges of the stabilization triangle'. They claimed this would offset the growth of emissions and put us on a trajectory to stabilize atmospheric CO2 concentration at 500 ppm if emissions decreased sharply in the second half of the 21st century. The wedge concept has proven popular as an analytical tool for considering the potential of different technologies to reduce CO2 emissions. In the years since the paper was published, it has been cited more than 400 times, and
Davidsen, Jörn; Glass, Leon; Kapral, Raymond
2004-11-01
We analyze the way topological constraints and inhomogeneity in the excitability influence the dynamics of spiral waves on spheres and punctured spheres of excitable media. We generalize the definition of an index such that it characterizes not only each spiral but also each hole in punctured, oriented, compact, two-dimensional differentiable manifolds and show that the sum of the indices is conserved and zero. We also show that heterogeneity and geometry are responsible for the formation of various spiral-wave attractors, in particular pairs of spirals in which one spiral acts as a source and a second as a sink--the latter similar to an antispiral. The results provide a basis for the analysis of the propagation of waves in heterogeneous excitable media in physical and biological systems. PMID:15600724
NASA Astrophysics Data System (ADS)
Davis, Steven J.; Cao, Long; Caldeira, Ken; Hoffert, Martin I.
2013-03-01
Abstract Stabilizing CO2 emissions at current levels for fifty years is not consistent with either an atmospheric CO2 concentration below 500 ppm or global temperature increases below 2 °C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 'wedges', each of which ramps up linearly over a period of 50 years to ultimately avoid 1 GtC y-1 of CO2 emissions. But this level of mitigation will require affordable carbon-free energy systems to be deployed at the scale of tens of terawatts. Any hope for such fundamental and disruptive transformation of the global energy system depends upon coordinated efforts to innovate, plan, and deploy new transportation and energy systems that can provide affordable energy at this scale without emitting CO2 to the atmosphere. 1. Introduction In 2004, Pacala and Socolow published a study in Science arguing that '[h]umanity can solve the carbon and climate problem in the first half of this century simply by scaling up what we already know how to do' [1]. Specifically, they presented 15 options for 'stabilization wedges' that would grow linearly from zero to 1 Gt of carbon emissions avoided per year (GtC y-1 1 Gt = 1012 kg) over 50 years. The solution to the carbon and climate problem, they asserted, was 'to deploy the technologies and/or lifestyle changes necessary to fill all seven wedges of the stabilization triangle'. They claimed this would offset the growth of emissions and put us on a trajectory to stabilize atmospheric CO2 concentration at 500 ppm if emissions decreased sharply in the second half of the 21st century. The wedge concept has proven popular as an analytical tool for considering the potential of different technologies to reduce CO2 emissions. In the years since the paper was published, it has been cited more than 400 times, and
Smith, Karl H.
2002-01-01
A radial wedge flange clamp comprising a pair of flanges each comprising a plurality of peripheral flat wedge facets having flat wedge surfaces and opposed and mating flat surfaces attached to or otherwise engaged with two elements to be joined and including a series of generally U-shaped wedge clamps each having flat wedge interior surfaces and engaging one pair of said peripheral flat wedge facets. Each of said generally U-shaped wedge clamps has in its opposing extremities apertures for the tangential insertion of bolts to apply uniform radial force to said wedge clamps when assembled about said wedge segments.
NASA Astrophysics Data System (ADS)
Vaudelle, F.; Askoura, M.; L'Huillier, J. P.
2015-07-01
The non-invasive research of information inside biological tissues can be made by means of setups using continuous, time-dependent or frequency modulated light sources, which emit in the visible or near-infrared range. Moreover, the biological structures such as brain, breast or fruits, can be regarded as closer to a spherical shape than a slab. This paper focus on the retrieval of tissue optical parameters in a spherical geometry using fittings with analytical solutions adapted for semi-infinite geometry. The data were generated using three different optical spectroscopy methods: frequency-resolved, spatially-resolved, and time-resolved modes. Simulations based on a Monte Carlo code were performed on homogeneous spheres, with 18 spaced detectors located on their boundary. First, data are examined in the frequency domain. Second, they are treated with optimization algorithms to assess the optical coefficients. The computations show that the spatially-resolved measurements are often more robust than those related to the frequency-resolved mode. In the temporal domain, errors on the estimates are also exhibited with the fitting by the Fourier transform of a solution based on the semi-infinite geometry. Furthermore, when the analytical solution is modified by taking into account the spherical shape, the retrieval of the coefficients is improved.
A comparison of angular difference schemes for one-dimensional spherical geometry S{sub N} equations
Lathrop, K.D.
2000-03-01
To investigate errors caused by angular differencing in approximating the streaming terms of the transport equation, five different approximations are evaluated for three test problems in one-dimensional spherical geometry. The following schemes are compared: diamond, special truncation error minimizing weighted diamond, linear continuous (the original S{sub N} scheme), linear discontinuous, and new quadratic continuous. To isolate errors caused by angular differencing, the approximations are derived from the transport equation without spatial differencing, and the resulting coupled ordinary differential equations (ODEs) are solved with an ODE solver. Results from the approximations are compared with analytic solutions derived for two-region purely absorbing spheres. Most of the approximations are derived by taking moments of the conservation form of the transport equation. The quadratic continuous approximation is derived taking the zeroth moment of both the transport equation and the first angular derivative of the transport equation. The advantages of this approach are described, In all of the approximations, the desirability is shown of using an initializing computation of the {mu} = {minus}1 angular flux to correctly compute the central flux and of having a difference approximation that ensures this central flux is the same for all directions. The behavior of the standard discrete ordinates equations in the diffusion limit is reviewed, and the linear and quadratic continuous approximations are shown to have the correct diffusion limit if an equal interval discrete quadrature is used. In all three test problems, the weighted diamond difference approximation has smaller maximum and average relative flux errors than the diamond or the linear continuous difference approximations. The quadratic continuous approximation and the linear discontinuous approximation are both more accurate than the other approximations, and the quadratic continuous approximation has a
Modeling decenter, wedge, and tilt errors in optical tolerance analysis and simulation
NASA Astrophysics Data System (ADS)
Youngworth, Richard N.; Herman, Eric
2014-09-01
Many optical designs have lenses with circular outer profiles that are mounted in cylindrical barrels. This geometry leads to errors on mounting parameters such as decenter and tilt, and component error like wedge which are best modeled with a cylindrical or spherical coordinate system. In the absence of clocking registration, this class of errors is effectively reduced to an error magnitude with a random clocking azimuth. Optical engineers consequently must fully understand how cylindrical or spherical basis geometry relates to Cartesian representation. Understanding these factors as well as how optical design codes can differ in error application for Monte Carlo simulations produces the most effective statistical simulations for tolerance assignment, analysis, and verification. This paper covers these topics to aid practicing optical engineers and designers.
Thermally actuated wedge block
Queen, Jr., Charles C.
1980-01-01
This invention relates to an automatically-operating wedge block for maintaining intimate structural contact over wide temperature ranges, including cryogenic use. The wedging action depends on the relative thermal expansion of two materials having very different coefficients of thermal expansion. The wedge block expands in thickness when cooled to cryogenic temperatures and contracts in thickness when returned to room temperature.
NASA Technical Reports Server (NTRS)
Wood, Kenneth E.
1987-01-01
Structure assembled rapidly with simple hand tools. Proposed locking wedge joints enable rapid assembly of lightweight beams, towers, scaffolds, and other truss-type structures. Lightweight structure assembled from tubular struts joined at nodes by wedge pins fitting into mating slots. Joint assembled rapidly by seating wedge pin in V-shaped slots and deforming end of strut until primary pawl engages it.
High-energy rate forgings of wedges :
Reynolds, Thomas Bither; Everhart, Wesley; Switzner, Nathan T; Balch, Dorian K.; San Marchi, Christopher W.
2014-05-01
The wedge geometry is a simple geometry for establishing a relatively constant gradient of strain in a forged part. The geometry is used to establish gradients in microstructure and strength as a function of strain, forging temperature, and quenching time after forging. This geometry has previously been used to benchmark predictions of strength and recrystallization using Sandias materials model for type 304L austenitic stainless steel. In this report, the processing conditions, in particular the times to forge and quench the forged parts, are summarized based on information recorded during forging on June 18, 2013 of the so-called wedge geometry from type 316L and 21Cr-6Ni-9Mn austenitic stainless steels.
Long-range hybrid wedge plasmonic waveguide.
Zhang, Zhonglai; Wang, Jian
2014-01-01
We design a novel long-range hybrid wedge plasmonic (LRHWP) waveguide composed of two identical dielectric nanowires symmetrically placed on two opposed wedges of a diamond shaped metal wire. With strong coupling between the dielectric nanowire mode and long-range surface plasmon polariton (SPP) mode, both deep subwavelength mode confinement and low propagation loss are achieved. On one hand, when compared to the previous long-range hybrid SPP waveguide, LRHWP waveguide can achieve smaller mode size with similar propagation length; on the other hand, when compared to the previous hybrid wedge SPP waveguide, LRHWP waveguide can provide an order of magnitude longer propagation length with similar level of mode confinement. The designed LRHWP waveguide also features an overall advantage of one-order improvement of Figure of Merit. We further evaluate in detail the impacts of possible practical fabrication imperfections on the mode properties. The obtained results of mode properties show that the proposed LRHWP waveguide with an optimized wedge tip angle of 140 degree is fairly tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, asymmetry in the vertical direction, variation of wedge tip angle, tilt or rotation of metal wire, and variation of wedge tip curvature radius. PMID:25362900
Long-range hybrid wedge plasmonic waveguide
Zhang, Zhonglai; Wang, Jian
2014-01-01
We design a novel long-range hybrid wedge plasmonic (LRHWP) waveguide composed of two identical dielectric nanowires symmetrically placed on two opposed wedges of a diamond shaped metal wire. With strong coupling between the dielectric nanowire mode and long-range surface plasmon polariton (SPP) mode, both deep subwavelength mode confinement and low propagation loss are achieved. On one hand, when compared to the previous long-range hybrid SPP waveguide, LRHWP waveguide can achieve smaller mode size with similar propagation length; on the other hand, when compared to the previous hybrid wedge SPP waveguide, LRHWP waveguide can provide an order of magnitude longer propagation length with similar level of mode confinement. The designed LRHWP waveguide also features an overall advantage of one-order improvement of Figure of Merit. We further evaluate in detail the impacts of possible practical fabrication imperfections on the mode properties. The obtained results of mode properties show that the proposed LRHWP waveguide with an optimized wedge tip angle of 140 degree is fairly tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, asymmetry in the vertical direction, variation of wedge tip angle, tilt or rotation of metal wire, and variation of wedge tip curvature radius. PMID:25362900
Long polymers near wedges and cones
NASA Astrophysics Data System (ADS)
Hammer, Yosi; Kantor, Yacov
2015-12-01
We perform a Monte Carlo study of N -step self-avoiding walks, attached to the corner of an impenetrable wedge in two dimensions (d =2 ), or the tip of an impenetrable cone in d =3 , of sizes ranging up to N =106 steps. We find that the critical exponent γα, which determines the dependence of the number of available conformations on N for a cone or wedge with opening angle α , is in good agreement with the theory for d =2 . We study the end-point distribution of the walks in the allowed space and find similarities to the known behavior of random walks (ideal polymers) in the same geometry. For example, the ratio between the mean square end-to-end distances of a polymer near the cone or wedge and a polymer in free space depends linearly on γα, as is known for ideal polymers. We show that the end-point distribution of polymers attached to a wedge does not separate into a product of angular and radial functions, as it does for ideal polymers in the same geometry. The angular dependence of the end position of polymers near the wedge differs from theoretical predictions.
Long polymers near wedges and cones.
Hammer, Yosi; Kantor, Yacov
2015-12-01
We perform a Monte Carlo study of N-step self-avoiding walks, attached to the corner of an impenetrable wedge in two dimensions (d=2), or the tip of an impenetrable cone in d=3, of sizes ranging up to N=10(6) steps. We find that the critical exponent γ(α), which determines the dependence of the number of available conformations on N for a cone or wedge with opening angle α, is in good agreement with the theory for d=2. We study the end-point distribution of the walks in the allowed space and find similarities to the known behavior of random walks (ideal polymers) in the same geometry. For example, the ratio between the mean square end-to-end distances of a polymer near the cone or wedge and a polymer in free space depends linearly on γ(α), as is known for ideal polymers. We show that the end-point distribution of polymers attached to a wedge does not separate into a product of angular and radial functions, as it does for ideal polymers in the same geometry. The angular dependence of the end position of polymers near the wedge differs from theoretical predictions. PMID:26764719
Micromachine Wedge Stepping Motor
Allen, J.J.; Schriner, H.K.
1998-11-04
A wedge stepping motor, which will index a mechanism, has been designed and fabricated in the surface rnicromachine SUMMiT process. This device has demonstrated the ability to index one gear tooth at a time with speeds up to 205 teeth/see. The wedge stepper motor has the following features, whi:h will be useful in a number of applications. o The ability to precisely position mechanical components. . Simple pulse signals can be used for operation. o Only 2 drive signals are requixed for operation. o Torque and precision capabilities increase with device size . The device to be indexed is restrained at all times by the wedge shaped tooth that is used for actuation. This paper will discuss the theory of operation and desi=m of the wedge stepping motor. The fabrication and testing of I he device will also be presented.
Wedges for ultrasonic inspection
Gavin, Donald A.
1982-01-01
An ultrasonic transducer device is provided which is used in ultrasonic inspection of the material surrounding a threaded hole and which comprises a wedge of plastic or the like including a curved threaded surface adapted to be screwed into the threaded hole and a generally planar surface on which a conventional ultrasonic transducer is mounted. The plastic wedge can be rotated within the threaded hole to inspect for flaws in the material surrounding the threaded hole.
Taper Angle Evolution in Taiwan Accretionary Wedge
NASA Astrophysics Data System (ADS)
Chen, L.; Chi, W.; Liu, C.
2011-12-01
Liwen Chena,b, Wu-Cheng Chia, Char-Shine Liuc aInstitute of Earth Sciences, Academia Sinica, Taipei, Taiwan bInstitute of Geosciences, National Taiwan University, Taipei, Taiwan cInstitute of Oceanography, National Taiwan University, Taipei, Taiwan The critical taper model, originally developed using onland Taiwan as an example, is governed by force balance of a horizontal compressional wedge. This model has been successfully applied to many mountainous regions around the world. Among them, Taiwan is located in an oblique collision between the Luzon Arc and the Chinese Passive margin. Previous critical taper angle studies of Taiwan are mainly focusing on utilizing land data. In this study we want to extend these studies to offshore region from the subduction zone to collision zone. Here we study the varying taper angles of the double-vergent wedge derived from 1,000 km of reflection seismic profiles in both the pro-wedge and retro-wedge locations. These profiles were collected in the last two decades. For the retro-wedge, the topography slope angle changes from 2 to 8.8 degrees; some of the steep slope suggests that some part of the retrowedge is currently in a super-critical angle state. Such dramatic changes in taper angle probably strongly affect regional sedimentary processes, including slumping, in addition to structural deformation. These complex processes might even help develop a mélange or re-open a closed basin. We are currently working on studying the taper angle evolution of the pro-wedge from subduction to arc-continent collision zone in the offshore region. Though further works are needed, our preliminary results show that the evolution of wedge angles and the geometry of the wedge are closely linked and inseparable. The structures of the subducting plate might have strong influence on the deformation style of the over-riding plate. It would be interesting to combine the angle variation with the structure interpretation of the accretionary wedge
Mechanics of injection wedges in collision orogens
NASA Astrophysics Data System (ADS)
Thompson, A. B.; Schulmann, K.
2003-04-01
Instantaneously juxtaposed lithospheric sections, marked by different geothermal gradient and lithological make-up, are examined to identify zones of highly contrasting strength in adjacent transposed crust and lithospheric mantle. Three types of geotherms and four reference lithospheric segments: thin crust/hot geotherm (rift), thin crust/mean geotherm (relaxed rift), standard crust/hot geotherm (arc), standard crust/mean geotherm (normal crust), are compared with variable permutations of cratonic, standard and rifted lithosphere thicknesses. This permits identification of strong brittle-elastic or plastic mantle, lower and upper crust juxtaposed against plastic rocks of a weak adjacent lithosphere. Vertical positions of shallow dipping detachment zones thus delineate possible areas of hot or cold injection wedges which include: (i) Single shallow wedge (or Flake), (ii) Double shallow and deep wedge, (iii) Deep lithospheric crocodile, (iv) Crustal thickening due to shallow strength differences, (v) Mantle Lithosphere thickening, or wedging, due to deep mantle strength differences and (vii) Exchange tectonics as an extreme wedging process, in which horizontal mass exchange is approximately equal. Rheological calculations are compared to a database of seismic profiles in which the geometry of detachment zones and proposed thermal conditions and lithological make-ups have been presented.
NASA Technical Reports Server (NTRS)
1998-01-01
This image shows an area of crustal separation on Jupiter's moon, Europa. Lower resolution pictures taken earlier in the tour of NASA's Galileo spacecraft revealed that dark wedge-shaped bands in this region are areas where the icy crust has completely pulled apart. Dark material has filled up from below and filled the void created by this separation.
In the lower left corner of this image, taken by Galileo's onboard camera on December 16, 1997, a portion of one dark wedge area is visible, revealing a linear texture along the trend of the wedge. The lines of the texture change orientation slightly and reflect the fact that we are looking at a bend in the wedge. The older, bright background, visible on the right half of the image, is criss-crossed with ridges. A large, bright ridge runs east-west through the upper part of the image, cutting across both the older background plains and the wedge. This ridge is rough in texture, with numerous small terraces and troughs containing dark material.
North is to the top of the picture and the sun illuminates the surface from the northwest. This image, centered at approximately 16.5 degrees south latitude and 196.5 degrees west longitude, covers an area approximately 10 kilometers square (about 6.5 miles square). The resolution of this image is about 26 meters per picture element. This image was taken by the solid state imaging system from a distance of 1250 kilometers (750 miles).
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.
Wedge Waveguides and Resonators for Quantum Plasmonics
2015-01-01
Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light–matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited. We combine state-of-the-art metallic wedges with integrated reflectors and precisely placed colloidal quantum dots (down to the single-emitter level) and demonstrate quantum-plasmonic waveguides and resonators with performance approaching theoretical limits. By exploiting a nearly 10-fold improvement in wedge-plasmon propagation (19 μm at a vacuum wavelength, λvac, of 630 nm), efficient reflectors (93%), and effective coupling (estimated to be >70%) to highly emissive (∼90%) quantum dots, we obtain Ag plasmonic resonators at visible wavelengths with quality factors approaching 200 (3.3 nm line widths). As our structures offer modal volumes down to ∼0.004λvac3 in an exposed single-mode waveguide–resonator geometry, they provide advantages over both traditional photonic microcavities and localized-plasmonic resonators for enhancing light–matter interactions. Our results confirm the promise of wedges for creating plasmonic devices and for studying coherent quantum-plasmonic effects such as long-distance plasmon-mediated entanglement and strong plasmon–matter coupling. PMID:26284499
NASA Astrophysics Data System (ADS)
Scharstein, Robert W.; Davis, Anthony M.
1994-07-01
Two complementary analyses of the time-harmonic scattering by a penetrable wedge are presented. The distance from the apex (appropriately scaled by the wavenumber in the exterior region) of the exciting line source is the single length scale in this infinite-domain boundary value problem. The work summarized herein represents two mathematical approaches (among a series of candidates) to solve this important scattering problem and to visualize the wave physics.
Wedged AFM-cantilevers for parallel plate cell mechanics.
Stewart, Martin P; Hodel, Adrian W; Spielhofer, Andreas; Cattin, Cedric J; Müller, Daniel J; Helenius, Jonne
2013-04-01
The combination of atomic force microscopy (AFM) and optical microscopy has gained popularity for mechanical analysis of living cells. In particular, recent AFM-based assays featuring tipless cantilevers and whole-cell deformation have yielded insights into cellular function, structure, and dynamics. However, in these assays the standard ≈10° tilt of the cantilever prevents uniaxial loading, which complicates assessment of cellular geometry and can cause cell sliding or loss of loosely adherent cells. Here, we describe an approach to modify tipless cantilevers with wedges and, thereby, achieve proper parallel plate mechanics. We provide guidance on material selection, the wedge production process, property and geometry assessment, and the calibration of wedged cantilevers. Furthermore, we demonstrate their ability to simplify the assessment of cell shape, prevent lateral displacement of round cells during compression, and improve the assessment of cell mechanical properties. PMID:23473778
Bouncing and bursting in a wedge
NASA Astrophysics Data System (ADS)
Reyssat, Etienne; Cohen, Caroline; Quere, David
2015-11-01
Placed into an inhomogeneous confined medium, non-wetting drops tend to be expelled from the tightest regions, where their contact with the walls would be maximized. They preferentially explore more open areas which are favorable from the point of view of capillary energy. Following this principle, one may thus use the geometry of confined environments to control fluid droplets in various ways : displacing, filtering, fragmenting... In this communication, we present experimental results on the dynamics of Leidenfrost drops launched into a wedge formed by two quasi-horizontal glass plates. Influenced by the gradient of confinement, these non-wetting liquid pucks approach the apex of the wedge to a minimal distance where they bounce back. At higher impact velocity, we observe that drops tend to penetrate deeper into the wedge but often burst into a large number of small fragments. We also discuss ways to control the deviation of droplets from their initial trajectory. We propose scaling law analyses to explain the characteristics of the observed bouncing and bursting phenomena.
NASA Technical Reports Server (NTRS)
1997-01-01
This Imager for Mars Pathfinder (IMP) image taken near the end of daytime operations on Sol 50 shows the Sojourner rover between the rocks 'Wedge' (foreground) and 'Shark' (behind rover). The rover successfully deployed its Alpha Proton X-Ray Spectrometer on Shark on Sol 52.
Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.
Euclidean, Spherical, and Hyperbolic Shadows
ERIC Educational Resources Information Center
Hoban, Ryan
2013-01-01
Many classical problems in elementary calculus use Euclidean geometry. This article takes such a problem and solves it in hyperbolic and in spherical geometry instead. The solution requires only the ability to compute distances and intersections of points in these geometries. The dramatically different results we obtain illustrate the effect…
NASA Technical Reports Server (NTRS)
1997-01-01
Flat Top, the rectangular rock at right, is part of a stretch of rocky terrain in this image, taken by the deployed Imager for Mars Pathfinder (IMP) on Sol 3. Dust has accumulated on the top of Flat Top, but is not present on the sides due to the steep angles of the rock. This dust may have been placed by dust storms moving across the Martian surface. The rock dubbed 'Wedge' is at left. The objects have been studied using several different color filters on the IMP camera.
Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.
A Potential Field Model for Spherical Sub-domains
NASA Astrophysics Data System (ADS)
Fisher, George H.; Bercik, David; Welsch, Brian; Kazachenko, Maria D.; CGEM Team
2016-05-01
Potential field models are used widely in Solar Physics to estimate coronal magnetic field geometry and connectivity, to provide lower limits on magnetic energies, and to provide initial configurations for time-dependent models of magnetic fields in the solar atmosphere. Potential field models in a spherical geometry can be global, covering the entire Sun, or confined to localized sub-volumes of the sphere. Here, we focus on the latter case.We describe an efficient potential field model for localized spherical sub-volumes (wedges consisting of upper and lower limits of radius, co-latitude, and longitude), employing a finite-difference approach for the solution. The solution is derived in terms of a "poloidal" potential, which can then be used to find either the scalar potential or the vector potential for the magnetic field (if desired), as well as all three magnetic field components. The magnetic field components are computed on the faces of spherical voxels, and the finite difference grid is consistent with the well-known "Yee" grid. The inner spherical boundary is defined by radial magnetic field measurements, and at the outer radius a source-surface boundary condition is imposed.Potential field solutions on active region scales, at full HMI resolution, and with the source surface located a solar radius above the photosphere, can be obtained on a laptop computer in just a few minutes. The three-dimensional finite difference equations are solved using NCAR's FISHPACK elliptic equation solver.The potential field model was developed by the Coronal Global Evolutionary Model (CGEM) project, funded by the NASA and NSF Strategic Capabilities program. The potential field model described here was motivated by CGEM's need for such a model. The model will be released as open-source code when the model details are published.
Wedge Absorber Design for the Muon Ionisation Cooling Experiment
Rogers, C.; Snopok, P.; Coney, L.; Jansson, A.; /Fermilab
2010-05-01
In the Muon Ionisation Cooling Experiment (MICE), muons are cooled by ionisation cooling. Muons are passed through material, reducing the total momentum of the beam. This results in a decrease in transverse emittance and a slight increase in longitudinal emittance, but overall reduction of 6d beam emittance. In emittance exchange, a dispersive beam is passed through wedge-shaped absorbers. Muons with higher energy pass through more material, resulting in a reduction in longitudinal emittance as well as transverse emittance. We consider the cooling performance of different wedge materials and geometries and propose a set of measurements that would be made in MICE.We outline the resources these measurements would require and detail some constraints that guide the choice of wedge parameters.
Muhammad, Wazir; Maqbool, Muhammad; Shahid, Muhammad; Hussain, Amjad; Tahir, Sajjad; Matiullah; Rooh, Gul; Ahmad, Tanveer; Lee, Sang Hoon
2011-07-01
Wedge filters are commonly used in external beam radiotherapy to achieve a uniform dose distribution within the target volume. The main objective of this study was to investigate the accuracy of the beam modifier algorithm of Theraplan plus (TPP version 3.8) treatment planning system and to confirm that either the beam hardening, beam softening and attenuation coefficients along with wedge geometry and measured wedge factor at single depth and multiple fields sizes can be the replacement of wedged profile and wedged cross-sectional data or not. In this regard the effect of beam hardening and beam softening was studied with physical wedges for 6 MV photons. The Normalized Wedge Factors (NWFs) were measured experimentally as well as calculated with the Theraplan plus, as a function of depth and field size in a water phantom for 15°, 30°, 45°, and 60° wedge filters. The beam hardening and softening was determined experimentally by deriving the required coefficients for all wedge angles. The TPP version 3.8 requires wedge transmission factor at single depth and multiple field sizes. Without incorporating the hardening and softening coefficients the percent difference between measured and calculated NFWs was as high as 7%. After the introduction of these parameters into the algorithm, the agreement between measured and TPP (V 3.8) calculated NWFs were improved to within 2 percent for various depths. Similar improvement was observed in TPP version 3.8 while calculating NWFs for various field sizes when the required coefficients were adjusted. In conclusion, the dose calculation algorithm of TPP version 3.8 showed good accuracy for a 6 MV photon beam provided beam hardening and softening parameters are taken into account. From the results, it is also concluded that, the beam hardening, beam softening and attenuation coefficients along with wedge geometry and measured wedge factor at single depth and multiple fields sizes can be the replacement of wedged profile and
Kugland, Nathan; Doeppner, Tilo; Glenzer, Siegfried; Constantin, Carmen; Niemann, Chris; Neumayer, Paul
2015-04-07
A method is provided for characterizing spectrometric properties (e.g., peak reflectivity, reflection curve width, and Bragg angle offset) of the K.alpha. emission line reflected narrowly off angle of the direct reflection of a bent crystal and in particular of a spherically bent quartz 200 crystal by analyzing the off-angle x-ray emission from a stronger emission line reflected at angles far from normal incidence. The bent quartz crystal can therefore accurately image argon K.alpha. x-rays at near-normal incidence (Bragg angle of approximately 81 degrees). The method is useful for in-situ calibration of instruments employing the crystal as a grating by first operating the crystal as a high throughput focusing monochromator on the Rowland circle at angles far from normal incidence (Bragg angle approximately 68 degrees) to make a reflection curve with the He-like x-rays such as the He-.alpha. emission line observed from a laser-excited plasma.
Ultrasonic fluid densitometer having liquid/wedge and gas/wedge interfaces
Greenwood, Margaret S.
2000-01-01
The present invention is an ultrasonic liquid densitometer that uses a material wedge having two sections, one with a liquid/wedge interface and another with a gas/wedge interface. It is preferred that the wedge have an acoustic impedance that is near the acoustic impedance of the liquid, specifically less than a factor of 11 greater than the acoustic impedance of the liquid. Ultrasonic signals are internally reflected within the material wedge. Density of a liquid is determined by immersing the wedge into the liquid and measuring reflections of ultrasound at the liquid/wedge interface and at the gas/wedge interface.
Mechanics of fold-and-thrust belts and accretionary wedges Cohesive Coulomb theory
NASA Technical Reports Server (NTRS)
Dahlen, F. A.; Suppe, J.; Davis, D.
1984-01-01
A self-consistent theory for the mechanics of thin-skinned accretionary Coulomb wedges is developed and applied to the active fold-and-thrust belt of western Taiwan. The state of stress everywhere within a critical wedge is determined by solving the static equilibrium equations subject to the appropriate boundary conditions. The influence of wedge cohesion, which gives rise to a concave curvature of the critical topographic surface and affects the orientation of the principal stresses and Coulomb fracture within the wedge, is considered. The shape of the topographic surface and the angles at which thrust faults step up from the basal decollement in the Taiwanese belt is analyzed taking into account the extensive structural and fluid-pressure data available there. It is concluded that the gross geometry and structure of the Taiwan wedge are consistent with normal laboratory frictional and fracture strengths of sedimentary rocks.
Thermal-wave fields in solid wedges using the Green function method: Theory and experiment
NASA Astrophysics Data System (ADS)
Tai, Rui; Zhang, Jie; Wang, Chinhua; Mandelis, Andreas
2013-04-01
In this work, we establish a theoretical model for a cylindrical rod of radius R with opening angle θ illuminated by a modulated incident beam. The model uses the Green function method in cylindrical coordinates. An analytical expression for the Green function and thermal-wave field in such a solid is presented. The theory is validated in the limit of reducing the arbitrary wedge geometrical structure to simpler geometries. For acute angle wedges, it is shown that the thermal-wave field near the edge exhibits confinement behavior and increased amplitude compared to a flat (reference) solid with θ = π. For obtuse angle wedges, it is shown that the opposite is true and relaxation of confinement occurs leading to lower amplitude thermal-wave fields. The theory provides a basis for quantitative thermophysical characterization of wedge-shaped objects and it is tested using an AISI 304 steel wedge and photothermal radiometry detection.
Wavelength meter having elliptical wedge
Hackel, R.P.; Feldman, M.
1992-12-01
A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10[sup 8]. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing. 7 figs.
Wavelength meter having elliptical wedge
Hackel, Richard P.; Feldman, Mark
1992-01-01
A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10.sup.8. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing.
Spherical electrostatic electron spectrometer
NASA Astrophysics Data System (ADS)
Yang, T.-S.; Kolk, B.; Kachnowski, T.; Trooster, J.; Benczer-Koller, N.
1982-06-01
A high transmission, low energy spherical electrostatic electron spectrometer particularly suited to the geometry required for Mössbauer-conversion electron spectroscopy was built. A transmission of 13% at an energy resolution of 2% was obtained with an 0.5 cm diameter source of 13.6 keV electrons. Applications to the study of hyperfine interactions of surfaces and interfaces are discussed.
Electrodynamic Casimir effect in a medium-filled wedge.
Brevik, Iver; Ellingsen, Simen A; Milton, Kimball A
2009-04-01
We re-examine the electrodynamic Casimir effect in a wedge defined by two perfect conductors making dihedral angle alpha=pi/p. This system is analogous to the system defined by a cosmic string. We consider the wedge region as filled with an azimuthally symmetric material, with permittivity and permeability epsilon1, micro1 for distance from the axis ra. The results are closely related to those for a circular-cylindrical geometry, but with noninteger azimuthal quantum number mp. Apart from a zero-mode divergence, which may be removed by choosing periodic boundary conditions on the wedge, and may be made finite if dispersion is included, we obtain finite results for the free energy corresponding to changes in a for the case when the speed of light is the same inside and outside the radius a , and for weak coupling, |epsilon1-epsilon2|<1, for purely dielectric media. We also consider the radiation produced by the sudden appearance of an infinite cosmic string, situated along the cusp line of the pre-existing wedge. PMID:19518186
Minimum work analysis on the critical taper accretionary wedges- insights from analogue modeling
NASA Astrophysics Data System (ADS)
Santimano, Tasca; Rosenau, Matthias; Oncken, Onno
2014-05-01
The Critical taper theory (CTT) is a fundamental concept for the understanding of mountain building processes. Based on force balance it predicts the preferred steady state geometry of an accretionary wedge system and its tectonic regime (extensive, compressive, stable). However, it does not specify which structures are formed and reactivated to reach the preferred state. The latter can be predicted by the minimum work concept. Here we test both concepts and their interplay by analysing two simple sand wedge models which differ only in the thickness of the basal detachment (a layer of glass beads). While the steady state critical taper is controlled by internal and basal friction coefficients and therefore the same in all experiments, different processes can minimise work by 1. reducing gravitational work e.g. by lowering the amount of uplift or volume uplifted, or 2. reducing frictional work e.g. by lowering the load or due to low friction coefficient along thrusts. Since a thick detachment allows entrainment of low friction material and therefore lowering of the friction along active thrusts, we speculate that the style of wedge growth will differ between the two models. We observe that the wedge with a thin basal detachment localizes strain at the toe of the wedge periodically and reactivate older faults to reach the critical topography. On the contrary, in the wedge with the thicker detachment layer, friction along thrusts is lowered due to the entrainment of low friction material from the detachment zone, subsequently increasing the lifetime of a thrust. Long thrust episodes are always followed by a fault of shorter lifetime, with the aim of reaching the critical taper. From the two experiments, we analyze the time-series evolution of the wedge to infer the work done by the two styles of deformation and predict the trend over time to differ but the maximum work to be similar Our observations show that the critical taper theory determines the geometry of the
Wide FOV wedge prism endoscope.
Kim, Keri; Kim, Daeyoung; Matsumiya, Kiyoshi; Kobayashi, Etsuko; Dohi, Takeyoshi
2005-01-01
We.. have developed a novel robotic endoscope system. It can be used to observe a wide field of view without moving or bending the whole endoscope system. .. It consists of a rigid endoscope and two wedge prisms at the distal tip. Rotating each wedge prism respectively, we can change the direction of view. Accordingly it becomes possible to observe a wide field of view even in a small space, and suited to clinical uses because it does not damage body tissues or internal organs. .. Wedge prisms are designed to avoid vignetting which is caused by the refraction or the reflection at prisms. The endoscope has 10mm in diameter, and the drive unit is simply separable for the sterilization. In addition, since it has a simple and small drive unit, it does not obstruct surgeon or other surgery robots. The maximum movement of local field of view is 19degrees, and global field of view is 93degrees. In the evaluation experiment, we conformed that both of the image quality and the performance are acceptable. PMID:17281566
Dual Double-Wedge Pseudo-Depolarizer with Anamorphic PSF
NASA Technical Reports Server (NTRS)
Hill, Peter; Thompson, Patrick
2012-01-01
A polarized scene, which may occur at oblique illumination angles, creates a radiometric signal that varies as a function of viewing angle. One common optical component that is used to minimize such an effect is a polarization scrambler or depolarizer. As part of the CLARREO mission, the SOLARIS instrument project at Goddard Space Flight Center has developed a new class of polarization scramblers using a dual double-wedge pseudo-depolarizer that produces an anamorphic point spread function (PSF). The SOLARIS instrument uses two Wollaston type scramblers in series, each with a distinct wedge angle, to image a pseudo-depolarized scene that is free of eigenstates. Since each wedge is distinct, the scrambler is able to produce an anamorphic PSF that maintains high spatial resolution in one dimension by sacrificing the spatial resolution in the other dimension. This scrambler geometry is ideal for 1-D imagers, such as pushbroom slit spectrometers, which require high spectral resolution, high spatial resolution, and low sensitivity to polarized light. Moreover, the geometry is applicable to a wide range of scientific instruments that require both high SNR (signal-to-noise ratio) and low sensitivity to polarized scenes
Self-similar flows in spherical geometry
NASA Astrophysics Data System (ADS)
Gerin-Roze, Jean
2007-06-01
If we are looking at the implosion of a sphere starting with a strong shock, the study of self-similar flows is a classical problem. We will assume that: - The sphere contains a perfect gas with a polytropic coefficient γ=5/3. - The shock follows the equation: rc=A(-t)^α with t0
NASA Astrophysics Data System (ADS)
Wirth, E. A.; Long, M. D.; Mccormack, K. A.
2012-12-01
Many fundamental aspects of the mantle wedge above subducting slabs, such as the dynamics of mantle flow and the transport of water and melt, have yet to be fully understood. A complete characterization of seismic anisotropy can yield powerful constraints on mantle flow and the degree of mantle wedge hydration. In this study, we characterize the geometry and strength of anisotropy in the mantle wedges beneath northeast Japan and the Ryukyu arc, which overlie the subducting Pacific and Philippine Sea plates, respectively. We compute radial and transverse component P-to-S receiver functions from 15 stations of the F-net array using the multitaper correlation receiver function estimator (Park and Levin, 2000). In both regions, we observe P-to-SV converted energy on radial component receiver functions that are consistent with conversions originating at the subducting oceanic Moho and the top of the subducting oceanic crust. We also observe P-to-SH conversions on the transverse component receiver functions that are consistent with the presence of multiple anisotropic and/or dipping layers. We compute synthetic receiver functions using a forward modeling scheme to create models for the depths, thicknesses, and strengths of the anisotropic layers beneath both northeast Japan and Ryukyu. Beneath Ryukyu, we detect evidence for a layer of strong anisotropy and high Vp/Vs ratio directly above the slab, consistent with the presence of serpentinite. We see no evidence of this signature in receiver functions from northeast Japan; instead, we see evidence for relatively modest anisotropy due to olivine fabric. We also detect a low-velocity region in the mantle wedge beneath northeast Japan, which may be consistent with the presence of partial melt. Since the presence of serpentinite indicates significant hydration of the wedge, the contrast in anisotropic structure between Ryukyu and northeast Japan has important implications for our understanding of slab hydration and how water
The wedge bias in reionization 21-cm power spectrum measurements
NASA Astrophysics Data System (ADS)
Jensen, Hannes; Majumdar, Suman; Mellema, Garrelt; Lidz, Adam; Iliev, Ilian T.; Dixon, Keri L.
2016-02-01
A proposed method for dealing with foreground emission in upcoming 21-cm observations from the epoch of reionization is to limit observations to an uncontaminated window in Fourier space. Foreground emission can be avoided in this way, since it is limited to a wedge-shaped region in k∥, k⊥ space. However, the power spectrum is anisotropic owing to redshift-space distortions from peculiar velocities. Consequently, the 21-cm power spectrum measured in the foreground avoidance window - which samples only a limited range of angles close to the line-of-sight direction - differs from the full redshift-space spherically averaged power spectrum which requires an average over all angles. In this paper, we calculate the magnitude of this `wedge bias' for the first time. We find that the bias amplifies the difference between the real-space and redshift-space power spectra. The bias is strongest at high redshifts, where measurements using foreground avoidance will overestimate the redshift-space power spectrum by around 100 per cent, possibly obscuring the distinctive rise and fall signature that is anticipated for the spherically averaged 21-cm power spectrum. In the later stages of reionization, the bias becomes negative, and smaller in magnitude (≲20 per cent).
Mobile wedges in an active turbulent bath
NASA Astrophysics Data System (ADS)
Kaiser, Andreas; Sokolov, Andrey; Lowen, Hartmut; Aronson, Igor S.
The motion of micro-wedges in a turbulent bacterial bath is explored using computer simulations with explicit modeling of the bacteria and experiments. We demonstrate that collective turbulentlike motion in a bacterial bath can power and steer the directed transport of mesoscopic carriers through the suspension. We will show that both polar ordering and swirl shielding inside the wedge yield an optimal transport velocity. Finally, we show the behavior of several wedges exposed to a bacterial bath.
Hollow spherical shell manufacture
O'Holleran, T.P.
1991-11-26
A process is disclosed for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry. 3 figures.
Hollow spherical shell manufacture
O'Holleran, Thomas P.
1991-01-01
A process for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry.
On the Superradiance of Spin-1 Waves in an Equatorial Wedge around a Kerr Hole.
Aguirre
2000-01-20
Recently Van Putten has suggested that superradiance of magnetosonic waves in a toroidal magnetosphere around a Kerr black hole may play a role in the central engine of gamma-ray bursts. In this context, he computed (in the WKB approximation) the superradiant amplification of scalar waves confined to a thin equatorial wedge around a Kerr hole and found that the superradiance is higher than for radiation incident over all angles. This Letter presents calculations of both spin-0 (scalar) superradiance (integrating the radial equation rather than using the WKB method) and spin-1 (electromagnetic/magnetosonic) superradiance in Van Putten's wedge geometry. In contrast to the scalar case, spin-1 superradiance decreases in the wedge geometry, decreasing the likelihood of its astrophysical importance. PMID:10615024
Application of slip-line analysis to the mechanical model of active accretionary wedge
NASA Astrophysics Data System (ADS)
Song, I.; Lee, H.; Kim, J.
2012-04-01
shows that the solution for the simple geometry of accretionary wedge is equivalent to the critical taper solution given by Davis et al. (1983). If a sedimentary formation covers the critical wedge, the stress underneath the formation is reduced to maintain the equilibrium with the basal friction strength. Thus the formation of sediment basin on top of the active accretionary wedge leads to the stress relaxation in the region below the basin. The topography of seafloor plays a crucial role in changing the basal friction along the base fault so that the geometry of the fault might be changed. Our numerical analysis also reveals that the pore pressure within the wedge and the décollement fault has no effect on the accretionary wedge angle.
NASA Astrophysics Data System (ADS)
Ge, Wenjun; Modest, Michael F.; Marquez, Ricardo
2015-05-01
The spherical harmonics (PN) method is a radiative transfer equation solver, which approximates the radiative intensity as a truncated series of spherical harmonics. For general 3-D configurations, N(N + 1) / 2 intensity coefficients must be solved from a system of coupled second-order elliptic PDEs. In 2-D axisymmetric applications, the number of equations and intensity coefficients reduces to (N + 1) 2 / 4 if the geometric relations of the intensity coefficients are taken into account. This paper presents the mathematical details for the transformation and its implementation on the OpenFOAM finite volume based CFD software platform. The transformation and implementation are applicable to any arbitrary axisymmetric geometry, but the examples to test the new formulation are based on a wedge grid, which is the most common axisymmetric geometry in CFD simulations, because OpenFOAM and most other platforms do not have true axisymmetric solvers. Two example problems for the new axisymmetric PN formulation are presented, and the results are verified with that of the general 3-D PN solver, a Photon Monte Carlo solver and exact solutions.
Ice Particle Impacts on a Moving Wedge
NASA Technical Reports Server (NTRS)
Vargas, Mario; Struk, Peter M.; Kreeger, Richard E.; Palacios, Jose; Lyer, Kaushik A.; Gold, Robert E.
2014-01-01
This work presents the results of an experimental study of ice particle impacts on a moving wedge. The experiment was conducted in the Adverse Environment Rotor Test Stand (AERTS) facility located at Penn State University. The wedge was placed at the tip of a rotating blade. Ice particles shot from a pressure gun intercepted the moving wedge and impacted it at a location along its circular path. The upward velocity of the ice particles varied from 7 to 12 meters per second. Wedge velocities were varied from 0 to 120 meters per second. Wedge angles tested were 0, 30, 45, and 60. High speed imaging combined with backlighting captured the impact allowing observation of the effect of velocity and wedge angle on the impact and the post-impact fragment behavior. It was found that the pressure gun and the rotating wedge could be synchronized to consistently obtain ice particle impacts on the target wedge. It was observed that the number of fragments increase with the normal component of the impact velocity. Particle fragments ejected immediately after impact showed velocities higher than the impact velocity. The results followed the major qualitative features observed by other researchers for hailstone impacts, even though the reduced scale size of the particles used in the present experiment as compared to hailstones was 4:1.
Ice Particle Impacts on a Moving Wedge
NASA Technical Reports Server (NTRS)
Vargas, Mario; Struk, Peter M.; Kreeger, Richard E.; Palacios, Jose; Iyer, Kaushik A.; Gold, Robert E.
2014-01-01
This work presents the results of an experimental study of ice particle impacts on a moving wedge. The experiment was conducted in the Adverse Environment Rotor Test Stand (AERTS) facility located at Penn State University. The wedge was placed at the tip of a rotating blade. Ice particles shot from a pressure gun intercepted the moving wedge and impacted it at a location along its circular path. The upward velocity of the ice particles varied from 7 to 12 meters per second. Wedge velocities were varied from 0 to 120 meters per second. Wedge angles tested were 0 deg, 30 deg, 45 deg, and 60 deg. High speed imaging combined with backlighting captured the impact allowing observation of the effect of velocity and wedge angle on the impact and the post-impact fragment behavior. It was found that the pressure gun and the rotating wedge could be synchronized to consistently obtain ice particle impacts on the target wedge. It was observed that the number of fragments increase with the normal component of the impact velocity. Particle fragments ejected immediately after impact showed velocities higher than the impact velocity. The results followed the major qualitative features observed by other researchers for hailstone impacts, even though the reduced scale size of the particles used in the present experiment as compared to hailstones was 4:1.
Wedged Fibers Suppress Feedback of Laser Beam
NASA Technical Reports Server (NTRS)
Ladany, I.
1986-01-01
When injected laser is coupled into optical fiber, emission instabilities arise because of optical feedback losses from fiber into laser. Coupling efficiencies as high as 80 percent, however, obtained by shaping end of multimode fiber into obtuse-angled wedge. Because slanted sides eliminate back reflection, such wedged fiber achieves high coupling efficiency.
Tumor Targeting, Trifunctional Dendritic Wedge
2015-01-01
We report in vitro and in vivo evaluation of a newly designed trifunctional theranostic agent for targeting solid tumors. This agent combines a dendritic wedge with high boron content for boron neutron capture therapy or boron MRI, a monomethine cyanine dye for visible-light fluorescent imaging, and an integrin ligand for efficient tumor targeting. We report photophysical properties of the new agent, its cellular uptake and in vitro targeting properties. Using live animal imaging and intravital microscopy (IVM) techniques, we observed a rapid accumulation of the agent and its retention for a prolonged period of time (up to 7 days) in fully established animal models of human melanoma and murine mammary adenocarcinoma. This macromolecular theranostic agent can be used for targeted delivery of high boron load into solid tumors for future applications in boron neutron capture therapy. PMID:25350602
Application of the critical Coulomb wedge theory to hyper-extended, magma-poor rifted margins
NASA Astrophysics Data System (ADS)
Nirrengarten, M.; Manatschal, G.; Yuan, X. P.; Kusznir, N. J.; Maillot, B.
2016-05-01
The Critical Coulomb Wedge Theory (CCWT) has been extensively used in compressional tectonics to resolve the shape of orogenic or accretionary prisms, while it is less applied to extensional and gravitational wedges despite the fact that it can be described by the same equation. In particular, the hyper-extended domain at magma-poor rifted margins, forming the oceanward termination of extended continental crust, satisfies the three main requirements of the CCWT: 1) it presents a wedge shape, 2) the rocks forming the wedge are completely brittle (frictional), and 3) the base of the wedge corresponds to a low friction décollement. However hyper-extended margins present a fully frictional behaviour only for a very thin crust; therefore this study is limited to the termination of hyper-extended continental crust which deforms in the latest stage of continental rifting. In this paper we define a method to measure the surface slope and the basal deep of this wedge that we apply to 17 hyper-extended, magma-poor rifted margins in order to compare the results to the values predicted by the CCWT. Because conjugate pairs of hyper-extended, magma-poor rifted margins are commonly asymmetric, due to detachment faulting, the wedges in the upper and lower plate margins corresponding respectively to the hanging wall and footwall of the detachment system are different. While the stress field in the upper plate wedge corresponds to a tectonic extensional wedge, the one in the lower plate matches that of a gravity extensional wedge. Using typical frictional properties of phyllosilicates (e.g. clays and serpentine), the shape of the hyper-extended wedges can be resolved by the CCWT using consistent fluid overpressures. Our results show that all lower plate margins are gravitationally stable and therefore have a close to critical shape whereas the tectonic extensional wedges at upper plate margins are critical, sub or sup critical due to the detachment initial angle and the duration of
Spherical colloidal photonic crystals.
Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze
2014-12-16
generated by evaporation-induced nanoparticle crystallization or polymerization of ordered nanoparticle crystallization arrays. In particular, because microfluidics was used for the generation of the droplet templates, the development of spherical colloidal PhCs has progressed significantly. These new strategies not only ensure monodispersity, but also increase the structural and functional diversity of the PhC beads, paving the way for the development of advanced optoelectronic devices. In this Account, we present the research progress on spherical colloidal PhCs, including their design, preparation, and potential applications. We outline various types of spherical colloidal PhCs, such as close-packed, non-close-packed, inverse opal, biphasic or multiphasic Janus structured, and core-shell structured geometries. Based on their unique optical properties, applications of the spherical colloidal PhCs for displays, sensors, barcodes, and cell culture microcarriers are presented. Future developments of the spherical colloidal PhC materials are also envisioned. PMID:25393430
The effect of a dynamic wedge in the medial tangential field upon the contralateral breast dose
McParland, B.J. )
1990-12-01
The elevated incidence of breast cancer following irradiation of breast tissue has led to concern over the magnitude of the scattered radiation received by the uninvolved contralateral breast during radiation therapy for a primary breast lesion and the risk of an induced contralateral breast cancer. Some linear accelerators use a single dynamic (or universal) wedge that is mounted within the treatment head at an extended distance from the patient. Because of the combined effects of distance and shielding, the contralateral breast dose due to a medial tangent containing a dynamic wedge is expected to be less than that containing a conventional wedge. This paper presents contralateral breast dose (CBD) measurements performed on an anthropomorphic phantom with breast prostheses irradiated with 6 MV X rays from a linear accelerator equipped with a dynamic wedge. Doses were measured at 15 points within the contralateral breast prosthesis with thermoluminescent dosimeters. It was found that the contralateral breast dose per unit target breast dose decreases with the perpendicular distance from the posterior edge of the medial tangent to the dose measurement point and increases with effective wedge angle by factors ranging up to 2.8, in agreement with data presented earlier for a water phantom geometry. This dose elevation showed no statistically significant dependence (p less than 0.05) upon the perpendicular distance from the beam edge. Comparisons with data in the literature show that the contralateral breast dose increase by a dynamic wedge is typically only about half of that reported for a conventional wedge for the same wedge angle and distance from the beam.
Capillarity driven motion of solid film wedges
Wong, H.; Miksis, M.J.; Voorhees, P.W.; Davis, S.H.
1997-06-01
A solid film freshly deposited on a substrate may form a non-equilibrium contact angle with the substrate, and will evolve. This morphological evolution near the contact line is investigated by studying the motion of a solid wedge on a substrate. The contact angle of the wedge changes at time t = 0 from the wedge angle {alpha} to the equilibrium contact angle {beta}, and its effects spread into the wedge via capillarity-driven surface diffusion. The film profiles at different times are found to be self-similar, with the length scale increasing as t{sup 1 4}. The self-similar film profile is determined numerically by a shooting method for {alpha} and {beta} between 0 and 180. In general, the authors find that the film remains a wedge when {alpha} = {beta}. For {alpha} < {beta}, the film retracts, whereas for {alpha} > {beta}, the film extends. For {alpha} = 90{degree}, the results describe the growth of grain-boundary grooves for arbitrary dihedral angles. For {beta} = 90{degree}, the solution also applies to a free-standing wedge, and the thin-wedge profiles agree qualitatively with those observed in transmission electron microscope specimens.
Ultrasonic transducer with laminated coupling wedge
Karplus, Henry H. B.
1976-08-03
An ultrasonic transducer capable of use in a high-temperature environment incorporates a laminated metal coupling wedge including a reflecting edge shaped as a double sloping roof and a transducer crystal backed by a laminated metal sound absorber disposed so as to direct sound waves through the coupling wedge and into a work piece, reflections from the interface between the coupling wedge and the work piece passing to the reflecting edge. Preferably the angle of inclination of the two halves of the reflecting edge are different.
NASA Technical Reports Server (NTRS)
1997-01-01
Developed largely through a Small Business Innovation Research contract through Langley Research Center, Interactive Picture Corporation's IPIX technology provides spherical photography, a panoramic 360-degrees. NASA found the technology appropriate for use in guiding space robots, in the space shuttle and space station programs, as well as research in cryogenic wind tunnels and for remote docking of spacecraft. Images of any location are captured in their entirety in a 360-degree immersive digital representation. The viewer can navigate to any desired direction within the image. Several car manufacturers already use IPIX to give viewers a look at their latest line-up of automobiles. Another application is for non-invasive surgeries. By using OmniScope, surgeons can look more closely at various parts of an organ with medical viewing instruments now in use. Potential applications of IPIX technology include viewing of homes for sale, hotel accommodations, museum sites, news events, and sports stadiums.
Pressure Distributions About Finite Wedges in Bounded and Unbounded Subsonic Streams
NASA Technical Reports Server (NTRS)
Donoughe, Patrick L; Prasse, Ernst I
1953-01-01
An analytical investigation of incompressible flow about wedges was made to determine effects of tunnel-wedge ratio and wedge angle on the wedge pressure distributions. The region of applicability of infinite wedge-type velocity distribution was examined for finite wedges. Theoretical and experimental pressure coefficients for various tunnel-wedge ratios, wedge angles, and subsonic Mach numbers were compared.
NASA Astrophysics Data System (ADS)
Santra, M.; Goff, J. A.; Steel, R. J.
2011-12-01
several prograding and offlapping deltaic clinothems. The geometry of these clinothems indicates that they are truncated at the top, particularly in the proximal part of the wedge. The clinoform height systematically increases seaward as they gradually approach the Pleistocene shelf edge. These observations lead to the interpretation that the offlapping sediment wedge represents the strike-elongate lobes of a falling-stage, wave-influenced delta system fed by pre-LGM paleo-Hudson River Channel(s) that probably reached the late Pleistocene shelf-edge off New Jersey.
NASA Astrophysics Data System (ADS)
Strayer, L.; Suppe, J.
2012-12-01
It is increasingly clear that many major faults are weak relative to quasistatic friction because of dynamical effects involving the microprocesses of high-velocity friction and the energetics of large-scale fault rupture. Even at the toes of accretionary wedges where velocity strengthening is expected, large displacements can occur dynamically. We seek to better understand the relationship between the large-scale strength of such faults and of the crust containing them over a timescale much greater than seismic cycles. Critical-taper theory provides straightforward quantitative relationships between accretionary wedge geometry and absolute basal fault and wedge strengths with minimal assumptions. Wedge tapers constrain the far-field stresses under which detachments slip and wedges grow during wedge-growing events, whether they are dynamical or quasistatic. To date most applications of wedge mechanics to accretionary wedges involve analog and numerical modeling with largely conceptual insight, for example illuminating the role of geological heterogeneity. Here we demonstrate that recent theoretical advances that are successful in extracting absolute wedge and detachment strengths from the geometry of active wedges can also be applied to extract large-scale strengths in distinct element numerical models in both mechanically homogeneous and heterogeneous wedges. The distinct element method (DEM) is an ideal tool for the study and modeling of critical taper wedges: model wedges can be initially cohesive (bonded) or cohesionless. Faults and folds form naturally as the result of progressive bond breakage during shortening and wedge growth. Heterogeneity can be introduced by creating layered groups of particles of differing mechanical properties. The DEM suffers to some extent in that macro material properties cannot be directly prescribed but rather must be defined by a modest number of micro-properties and the process in necessarily iterative and developing a wide
Gui, Chengcheng; Wang, Jian
2015-01-01
We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff/A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10 μm) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60 μm) is favorable to obtain smaller Aeff/A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius. PMID:26155782
Gui, Chengcheng; Wang, Jian
2015-01-01
We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff /A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10 μm) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60 μm) is favorable to obtain smaller Aeff /A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius. PMID:26155782
A numerical study of the interaction between the mantle wedge, subducting slab, and overriding plate
NASA Astrophysics Data System (ADS)
Eberle, Michael A.; Grasset, Olivier; Sotin, Christophe
2002-12-01
We have formulated a numerical model with strongly temperature-dependent viscosity to calculate thermal structure and flow-field in subduction zones. One important particularity of the model is that the overriding plate is not fixed over its whole thickness in order to allow material exchange between the wedge and the upper lithosphere. Numerical problems due to very high-viscosity contrasts are avoided by coupling a finite difference method and a finite element method for solving the energy conservation equation and the Stockes equation, respectively. In this model, a temperature decrease from 1400 to 1300 °C increases the viscosity by an order of magnitude. We study the temperature structure and the velocity field of the subducting slab and mantle wedge. Surface heat flow, velocity anomalies, and geometry of the partial melting zone are also calculated. To study the effect that boundary conditions play on the interaction between the mantle wedge, overriding plate and subducting plate, we examine models with both fixed and free-slip conditions applied to the overriding plate. When the overriding plate is allowed to move laterally (free-slip), the subducting slab is thick, and both the temperature field and the convective motions in the mantle wedge are similar to those observed when using constant viscosity numerical models or analytical corner flow models. If the surface of the overriding plate is fixed, the subducting slab is thin and the mantle wedge impinges upon the overriding plate forming a high-temperature nose between the overriding plate and subducting lithosphere. Furthermore, viscous decoupling occurs implicitly at shallow depth between the slab and the wedge because hot material from the wedge is entrained close to the trench. In that case, the subducting slab tectonically erodes the lower lithosphere of the overriding plate leading to high-temperatures, low seismic velocities, high attenuation and high heat flow beneath volcanic arc, in agreement
A numerical model of deformation and fluid-flow in an evolving thrust wedge
NASA Astrophysics Data System (ADS)
Strayer, Luther M.; Hudleston, Peter J.; Lorig, Loren J.
2001-06-01
To investigate deformation and fluid-flow in an actively deforming tectonic wedge, we model the evolution of a large, two-dimensional (100 km long, 5 km thick), mechanically and hydrologically homogeneous and isotropic pile of sedimentary strata that is deformed to become a thrust wedge. We compare both 'dry' and 'wet' cases, in order to illustrate: (1) the relative importance of fluids on wedge evolution, and (2) the effect of brittle deformation on fluid-flow. We use an elastic-plastic constitutive relation, including a Mohr-Coulomb failure criterion and a non-associated flow rule, and coupled fluid flow, with bulk rock properties that approximate typical foreland sedimentary strata. Simulations are made both with and without dilation. The model is fully dynamic, but inertial forces remain small. Results show that deformation within the wedge is accommodated by reverse-slip movement on shear bands, which migrate in both directions through the wedge as both fore- and back-thrusts. The model has features predicted by the critical-taper theory: (1) overall wedge geometry; (2) crudely self-similar growth during evolution; (3) more intense deformation toward the rear of the wedge. The models show strong overall in-sequence faulting behavior with major thrusts isolating relatively undeformed packages, which are moved in a piggyback manner upon the active thrusts. Intermittent out-of-sequence faulting does however occur, in order to maintain the wedge taper. Fluid-flow in the deforming wedge is dominated by topography, but is also strongly affected by dilational plastic deformation. In all simulations, there is focused fluid flow within fault zones. When mechanical time-stepping is shut off (uncoupled), flow systems evolve to steady-state where inflow equals outflow. By subtracting the two 'states' we isolate the mechanical fluid response from the total coupled system response. The mechanical fluid response is manifest as contours of head and pressure difference and
Evaluating the dose to the contralateral breast when using a dynamic wedge versus a regular wedge.
Weides, C D; Mok, E C; Chang, W C; Findley, D O; Shostak, C A
1995-01-01
The incidence of secondary cancers in the contralateral breast after primary breast irradiation is several times higher than the incidence of first time breast cancer. Studies have shown that the scatter radiation to the contralateral breast may play a large part in the induction of secondary breast cancers. Factors that may contribute to the contralateral breast dose may include the use of blocks, the orientation of the field, and wedges. Reports have shown that the use of regular wedges, particularly for the medial tangential field, gives a significantly higher dose to the contralateral breast compared to an open field. This paper compares the peripheral dose outside the field using a regular wedge, a dynamic wedge, and an open field technique. The data collected consisted of measurements taken with patients, solid water and a Rando phantom using a Varian 2300CD linear accelerator. Ion chambers, thermoluminescent dosimeters (TLD), diodes, and films were the primary means for collecting the data. The measurements show that the peripheral dose outside the field using a dynamic wedge is close to that of open fields, and significantly lower than that of regular wedges. This information indicates that when using a medial wedge, a dynamic wedge should be used. PMID:8703326
Structure of turbulent wedges created by isolated surface roughness
NASA Astrophysics Data System (ADS)
Kuester, Matthew S.; White, Edward B.
2016-04-01
Isolated surface roughness in a laminar boundary layer can create a wedge of turbulence that spreads laterally into the surrounding laminar flow. Some recent studies have identified high- and low-speed streaks along the exterior of turbulent wedges. In this experiment, developing turbulent wedges are measured to observe the creation of these streaks. Naphthalene shear stress surface visualization and hotwire measurements are utilized to investigate the details of turbulent wedges created by cylinders in a laminar flat-plate boundary layer. Both the surface visualization and the hotwire measurements show high- and low-speed streaks in the wake of the cylinder that devolve into a turbulent wedge. The turbulent wedge spreading is associated with the emergence of these high- and low-speed streaks along the outside of the wedge. As the wedge evolves in the streamwise direction, these streaks persist inside of the core of the wedge, while new, lower amplitude streaks form along the outside of the wedge. Adding asymmetry to the cylinder moved the virtual origin closer to the roughness and increased the vortex shedding frequency, while adding small-scale roughness features did not strongly affect turbulent wedge development. Intermittency calculations additionally show the origin of the turbulent core inside of the wedge. The structure and spacing of the high-speed streaks along the extremities of the turbulent wedge give insight into the spreading angle of the turbulent wedge.
Two-dimensional electronic spectroscopy with birefringent wedges.
Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio
2014-12-01
We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria. PMID:25554272
Two-dimensional electronic spectroscopy with birefringent wedges
NASA Astrophysics Data System (ADS)
Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio
2014-12-01
We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria.
Two-dimensional electronic spectroscopy with birefringent wedges
Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio
2014-12-15
We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria.
Two-dimensional meniscus in a wedge
Kagan, M.; Pinczewski, W.V.; Oren, P.E.
1995-03-15
This paper presents a closed-form analytical solution of the augmented Young-Laplace equation for the meniscus profile in a two-dimensional wedge-shaped capillary. The solution is valid for monotonic forms of disjoining pressure which are repulsive in nature. In the limit of negligible disjoining pressure, it is shown to reduce to the classical solution of constant curvature. The character of the solution is examined and examples of practical interest which demonstrate the application of the solution to the computation of the meniscus profile in a wedge-shaped capillary are discussed.
A review of dynamics modelling of friction wedge suspensions
NASA Astrophysics Data System (ADS)
Wu, Qing; Cole, Colin; Spiryagin, Maksym; Sun, Yan Quan
2014-11-01
Three-piece bogies with friction wedge suspensions are the most widely used bogies in heavy haul trains. Fiction wedge suspensions play a key role in these wagon systems. This article reviews current techniques in dynamic modelling of friction wedge suspension with various motivations: to improve dynamic models of friction wedge suspensions so as to improve general wagon dynamics simulations; to seek better friction wedge suspension models for wagon stability assessments in complex train systems; to improve the modelling of other friction devices, such as friction draft gear. Relevant theories and friction wedge suspension models developed by using commercial simulation packages and in-house simulation packages are reviewed.
Growth of the South Pyrenean orogenic wedge
NASA Astrophysics Data System (ADS)
Meigs, Andrew J.; Burbank, Douglas W.
1997-04-01
A six-step reconstruction of the South Pyrenean foreland fold-and-thrust belt in Spain delineates the topographic slope, basal décollement angle, internal deformation, and thrust-front advance from the Early Eocene until the end of contractional deformation in the Late Oligocene. Style of thrust-front advance, dip of the basal décollement, slope of the upper surface, and internal deformation are decoupled and not simply related. Internal deformation increased, decreased, and maintained surface slope angle at different stages. From the onset to the cessation of deformation, the basal décollement angle decreased overall suggesting translation of the thrust belt onto stronger crust with time. Taper angle of the Pyrenean thrust wedge was fundamentally controlled by the flexural rigidity of the lower plate, the relative rate of creation of structural relief in the rear versus the front of the wedge, the extent of deposition of eroded material within the deforming wedge, and the taper of the pretectonic stratigraphic wedge.
38. INTERIOR VIEW, DENISON MULTIPRESS FOR INSERTION OF WEDGES ONTO ...
38. INTERIOR VIEW, DENISON MULTI-PRESS FOR INSERTION OF WEDGES ONTO HANDLES AND CUTTING OFF SCRAP END OF HANDLE FOLLOWING WEDGE INSERTION, BRIAN KIMBLE, OPERATOR - Warwood Tool Company, Foot of Nineteenth Street, Wheeling, Ohio County, WV
21 CFR 884.5200 - Hemorrhoid prevention pressure wedge.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Hemorrhoid prevention pressure wedge. 884.5200... Devices § 884.5200 Hemorrhoid prevention pressure wedge. (a) Identification. A hemorrhoid prevention pressure wedge provides mechanical support to the perianal region during the labor and delivery...
21 CFR 884.5200 - Hemorrhoid prevention pressure wedge.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Hemorrhoid prevention pressure wedge. 884.5200... Devices § 884.5200 Hemorrhoid prevention pressure wedge. (a) Identification. A hemorrhoid prevention pressure wedge provides mechanical support to the perianal region during the labor and delivery...
NASA Astrophysics Data System (ADS)
Ellahi, R.; Hassan, M.; Zeeshan, A.; Khan, Ambreen A.
2015-07-01
The flow of mixed convection nanofluid over wedge under the effects of porous medium is investigated. The HFE-7100 Engineered Fluid having Nimonic 80a metal nanoparticles of spherical and non-spherical shapes with different sizes is used. The particle shape effects on Bejan number and entropy generation are taken into account. The system of partial differential equations is first written in terms of ordinary differential equations using adequate similarity transformations and then solved analytically. Analytical solutions of the resulting equations are obtained for the velocity and temperature profiles. Simultaneous effects of porous medium, particle volume friction, mixed convection parameter, and angle of wedge in the presence of different shapes nanoparticles are demonstrated graphically. Effects of particle concentrations, sizes on wall stress, heat transfer coefficient of Skin friction, and Nusselt are discussed in the form of tables.
NASA Astrophysics Data System (ADS)
Ellahi, R.; Hassan, M.; Zeeshan, A.; Khan, Ambreen A.
2016-06-01
The flow of mixed convection nanofluid over wedge under the effects of porous medium is investigated. The HFE-7100 Engineered Fluid having Nimonic 80a metal nanoparticles of spherical and non-spherical shapes with different sizes is used. The particle shape effects on Bejan number and entropy generation are taken into account. The system of partial differential equations is first written in terms of ordinary differential equations using adequate similarity transformations and then solved analytically. Analytical solutions of the resulting equations are obtained for the velocity and temperature profiles. Simultaneous effects of porous medium, particle volume friction, mixed convection parameter, and angle of wedge in the presence of different shapes nanoparticles are demonstrated graphically. Effects of particle concentrations, sizes on wall stress, heat transfer coefficient of Skin friction, and Nusselt are discussed in the form of tables.
NASA Astrophysics Data System (ADS)
Morales Crespo, R.
2015-08-01
This paper solves and analyses the complete characterization of the plasma-sheath transition and the characteristic I-V curves of an active and collisional plasma close to a cylindrical or spherical wall considering a wide range of the parameter which describe the model to be useful for experimental measures. Despite the difficulty of including the three possible pre-sheath mechanisms, this characterization is obtained from a self-consistent model using three easily measurable parameters, namely the electric potential of the wall, the positive ion current collected by the wall, and the radius of the wall. These parameters are easy to measure and facilitate the diagnosis of plasmas from an experimental point of view.
NASA Astrophysics Data System (ADS)
Buddensiek, M.-L.; Sheng, J.; Crosby, T.; Schuster, G. T.; Bruhn, R. L.; He, R.
2008-02-01
Four high-resolution seismic surveys were conducted across the Wasatch Fault Zone near Mapleton, Utah. The objective was twofold: (1) To use velocity tomograms and reflection images to delineate fault structures and colluvial wedges to more than twice the depth of the Mapleton Megatrench excavated by URS personnel, (2) to assess the strengths and limitations of traveltime and waveform tomography by synthetic studies and comparison of the tomogram to the ground truth seen in the Megatrench log. Four out of the five faults within the trench area are accurately identified in the migrated image and in the tomograms, and the main fault's dip angle is estimated to be between 71 and 80°. Two additional faults are interpreted outside the trench. The faults can be delineated down to 30 m below the surface, which is 20 m deeper than the excavated trench. Five out of six colluvial wedges found in the trench log were seen as low-velocity zones (LVZs) in the tomogram, however the biggest colluvial wedge could not be identified by either tomography method. Waveform tomography prevailed over ray-based traveltime tomography by more clearly recovering the faults and LVZs. A newly discovered LVZ at a depth of 18-21 m below the surface possibly represents a colluvial wedge and is estimated to be less than 21000 years old. If this LVZ is a colluvial wedge, the earthquake history obtained by trenching can be extended from 13500 to 21000 yr with seismic tomography. Our results further demonstrate the capability of tomography in identifying faults, and show that waveform tomography more accurately resolves colluvial wedges compared to traveltime tomography. However, despite the successful recovery of most faults and some, but not all, colluvial wedges, both tomography methods show many more LVZs besides the wedges, so that an unambiguous interpretation cannot be made. A major part of the ambiguity in the tomograms is due to the many major faults, which result in an uneven raypath
Arc-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua.
Hoernle, Kaj; Abt, David L; Fischer, Karen M; Nichols, Holly; Hauff, Folkmar; Abers, Geoffrey A; van den Bogaard, Paul; Heydolph, Ken; Alvarado, Guillermo; Protti, Marino; Strauch, Wilfried
2008-02-28
Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge or eroded fore-arc complexes but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (63-190 mm yr(-1)) and are comparable to the magnitude of subducting Cocos plate motion (approximately 85 mm yr(-1)). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones. PMID:18223639
Radiative transfer in spherical atmospheres
NASA Technical Reports Server (NTRS)
Kalkofen, W.; Wehrse, R.
1984-01-01
A method for defining spherical model atmospheres in radiative/convective and hydrostatic equilibrium is presented. A finite difference form is found for the transfer equation and a matrix operator is developed as the discrete space analog (in curvilinear coordinates) of a formal integral in plane geometry. Pressure is treated as a function of temperature. Flux conservation is maintained within the energy equation, although the correct luminosity transport must be assigned for any given level of the atmosphere. A perturbed integral operator is used in a complete linearization of the transfer and constraint equations. Finally, techniques for generating stable solutions in economical computer time are discussed.
Hexatic undulations in curved geometries.
Lenz, Peter; Nelson, David R
2003-03-01
We discuss the influence of two-dimensional hexatic order on capillary waves and undulation modes in spherical and cylindrical geometries. In planar geometries, extended bond-orientational order has only a minor effect on the fluctuations of liquid surfaces or lipid bilayers. However, in curved geometries, the long-wavelength spectrum of these ripples is altered. We calculate this frequency shift and discuss applications to spherical vesicles, liquid metal droplets, bubbles and cylindrical jets coated with surface-active molecules, and to multielectron bubbles in liquid helium at low temperatures. Hexatic order also leads to a shift in the threshold for the fission instability of charged droplets and bubbles, and for the Plateau-Rayleigh instability of liquid jets. PMID:12689068
Laser-generated ultrasonic pulse shapes at solid wedges.
Pupyrev, Pavel D; Lomonosov, Alexey M; Mayer, Andreas P
2016-08-01
Laser pulses focused near the tip of an elastic wedge generate acoustic waves guided at its apex. The shapes of the acoustic wedge wave pulses depend on the energy and the profile of the exciting laser pulse and on the anisotropy of the elastic medium the wedge is made of. Expressions for the acoustic pulse shapes have been derived in terms of the modal displacement fields of wedge waves for laser excitation in the thermo-elastic regime and for excitation via a pressure pulse exerted on the surface. The physical quantity considered is the local inclination of a surface of the wedge, which is measured optically by laser-probe-beam deflection. Experimental results on pulse shapes in the thermo-elastic regime are presented and confirmed by numerical calculations. They pertain to an isotropic sharp-angle wedge with two wedge-wave branches and to a non-reciprocity phenomenon at rectangular silicon edges. PMID:27135188
Wedge assembly for electrical transformer component spacing
Baggett, Franklin E.; Cage, W. Franklin
1991-01-01
A wedge assembly that is easily inserted between two surfaces to be supported thereby, and thereafter expanded to produce a selected spacing between those surfaces. This wedge assembly has two outer members that are substantially identical except that they are mirror images of each other. Oppositely directed faces of these of these outer members are substantially parallel for the purpose of contacting the surfaces to be separated. The outer faces of these outer members that are directed toward each other are tapered so as to contact a center member having complementary tapers on both faces. A washer member is provided to contact a common end of the outer members, and a bolt member penetrates this washer and is threadably received in a receptor of the center member. As the bolt member is threaded into the center member, the center member is drawn further into the gap between the outer members and thereby separates these outer members to contact the surfaces to be separated. In the preferred embodiment, the contacting surfaces of the outer member and the center member are provided with guide elements. The wedge assembly is described for use in separating the secondary windings from the laminations of an electrical power transformer.
Complex interactions between diapirs and 4-D subduction driven mantle wedge circulation.
NASA Astrophysics Data System (ADS)
Sylvia, R. T.; Kincaid, C. R.
2015-12-01
Analogue laboratory experiments generate 4-D flow of mantle wedge fluid and capture the evolution of buoyant mesoscale diapirs. The mantle is modeled with viscous glucose syrup with an Arrhenius type temperature dependent viscosity. To characterize diapir evolution we experiment with a variety of fluids injected from multiple point sources. Diapirs interact with kinematically induced flow fields forced by subducting plate motions replicating a range of styles observed in dynamic subduction models (e.g., rollback, steepening, gaps). Data is collected using high definition timelapse photography and quantified using image velocimetry techniques. While many studies assume direct vertical connections between the volcanic arc and the deeper mantle source region, our experiments demonstrate the difficulty of creating near vertical conduits. Results highlight extreme curvature of diapir rise paths. Trench-normal deflection occurs as diapirs are advected downward away from the trench before ascending into wedge apex directed return flow. Trench parallel deflections up to 75% of trench length are seen in all cases, exacerbated by complex geometry and rollback motion. Interdiapir interaction is also important; upwellings with similar trajectory coalesce and rapidly accelerate. Moreover, we observe a new mode of interaction whereby recycled diapir material is drawn down along the slab surface and then initiates rapid fluid migration updip along the slab-wedge interface. Variability in trajectory and residence time leads to complex petrologic inferences. Material from disparate source regions can surface at the same location, mix in the wedge, or become fully entrained in creeping flow adding heterogeneity to the mantle. Active diapirism or any other vertical fluid flux mechanism employing rheological weakening lowers viscosity in the recycling mantle wedge affecting both solid and fluid flow characteristics. Many interesting and insightful results have been presented based
Characterization of the Thermal-Wave Field in a Wedge-Shaped Solid Using the Green's Function Method
NASA Astrophysics Data System (ADS)
Zhang, Jie; Tai, Rui; Wang, Chinhua; Mandelis, Andreas
2013-09-01
In this study, a theoretical model is established for a wedge-like solid with an open sector surrounded by walls of radius of a cylindrical rod illuminated by a modulated circular Gaussian incident beam by means of the Green’s function method in cylindrical coordinates. An analytical expression for the thermal-wave field in such a sample is presented. The theory is validated by reducing the arbitrary geometrical structure of the wedge to simpler geometries. It is shown that the frequency dependence of the thermal-wave field near the edge exhibits a large phase lag compared with that at a location far from the edge. The theory provides a foundation for quantitatively characterizing wedge-shaped industrial samples, such as metals with sintered edges, using photothermal methods in a non-contact and non-destructive manner.
Wightman function and scalar Casimir densities for a wedge with two cylindrical boundaries
Saharian, A.A. Tarloyan, A.S.
2008-07-15
Wightman function, the vacuum expectation values of the field square and the energy-momentum tensor are investigated for a massive scalar field with general curvature coupling parameter inside a wedge with two coaxial cylindrical boundaries. It is assumed that the field obeys Dirichlet boundary condition on bounding surfaces. The application of a variant of the generalized Abel-Plana formula enables to extract from the expectation values the contribution corresponding to the geometry of a wedge with a single shell and to present the interference part in terms of exponentially convergent integrals. The local properties of the vacuum are investigated in various asymptotic regions of the parameters. The vacuum forces acting on the boundaries are presented as the sum of self-action and interaction terms. It is shown that the interaction forces between the separate parts of the boundary are always attractive. The generalization to the case of a scalar field with Neumann boundary condition is discussed.
Stress intensity factors in a cracked infinite elastic wedge loaded by a rigid punch
NASA Technical Reports Server (NTRS)
Erdogan, F.; Civelek, M. B.
1978-01-01
A plane elastic wedge-shaped solid was split through the application of a rigid punch. It was assumed that the coefficient of friction on the the contact area was constant, and the problem had a plane of symmetry with respect to loading and geometry, with the crack in the plane of symmetry. The problem was formulated in terms of a system of integral equations with the contact stress and the derivative of the crack surface displacement as the unknown functions. The solution was obtained for an internal crack and for an edge crack. The results include primarily the stress intensity factors at the crack tips, and the measure of the stress singularity at the wedge apex, and at the end points of the contact area.
On the shape of a droplet in a wedge: new insight from electrowetting.
Baratian, D; Cavalli, A; van den Ende, D; Mugele, F
2015-10-21
The equilibrium morphology of liquid drops exposed to geometric constraints can be rather complex. Even for simple geometries, analytical solutions are scarce. Here, we investigate the equilibrium shape and position of liquid drops confined in the wedge between two solid surfaces at an angle α. Using electrowetting, we control the contact angle and thereby manipulate the shape and the equilibrium position of aqueous drops in ambient oil. In the absence of contact angle hysteresis and buoyancy, we find that the equilibrium shape is given by a truncated sphere, at a position that is determined by the drop volume and the contact angle. At this position, the net normal force between drop and the surfaces vanishes. The effect of buoyancy gives rise to substantial deviations from this equilibrium configuration which we discuss here as well. We eventually show how the geometric constraint and electrowetting can be used to position droplets inside a wedge in a controlled way, without mechanical actuation. PMID:26186493
NASA Astrophysics Data System (ADS)
Hoth, Silvan; Kukowski, Nina; Oncken, Onno
2008-08-01
Timeseries derived from two-dimensional sandbox simulations involving surface erosion are taken for the first time to be implemented into flexure calculations of foreland basins. Based on our results we highlight that orogenic systems are a four component system, consisting of a pro-foreland basin, a pro-wedge, a retro-wedge, and a retro-foreland basin. These four components are mechanically coupled via the load dependence of tectonic faulting [Mandl, G., 1988. Mechanics of tectonic faulting, 1st Edition. Elsevier, Amsterdam.] and the finite flexural rigidity of lithospheric plates [Beaumont, C., 1981. Foreland basins. Geophys. J. R. Astron. Soc. 5 (2), 291-329.]. We further demonstrate that the impact of pro-wedge erosion is most pronounced within the pro-wedge but also modifies the shape and size of the retro-wedge, which in turn changes the geometry and propagation velocity of the retro-foreland basin and vice versa. This suggests that one out of the four components of an orogenic system cannot be fully understood without recognition of the other three components. Thus, spatial separation between processes or observations does not necessarily imply their physical independence. This conceptual model is applied in a case study to the Pyrenean orogenic wedge and its Ebro and Aquitaine foreland basins. Our analysis suggests that the Pyrenean pro- and retro-wedge are mechanically coupled and that this coupling manifests itself in the migration of depocentres in both foreland basins. We finally explore implications for the formation of Mississippi Valley Type deposits.
Spatial symmetry breaking in rapidly rotating convective spherical shells
NASA Technical Reports Server (NTRS)
Zhang, Keke; Schubert, Gerald
1995-01-01
Many problems in geophysical and astrophysical convection systems are characterized by fast rotation and spherical shell geometry. The combined effects of Coriolis forces and spherical shell geometry produce a unique spatial symmetry for the convection pattern in a rapidly rotating spherical shell. In this paper, we first discuss the general spatial symmetries for rotating spherical shell convection. A special model, a spherical shell heated from below, is then used to illustrate how and when the spatial symmetries are broken. Symmetry breaking occurs via a sequence of spatial transitions from the primary conducting state to the complex multiple-layered columnar structure. It is argued that, because of the dominant effects of rotation, the sequence of spatial transitions identified from this particular model is likely to be generally valid. Applications of the spatial symmetry breaking to planetary convection problems are also discussed.
Spherical quartz crystals investigated with synchrotron radiation
NASA Astrophysics Data System (ADS)
Pereira, N. R.; Macrander, A. T.; Hill, K. W.; Baronova, E. O.; George, K. M.; Kotick, J.
2015-10-01
The quality of x-ray spectra and images obtained from plasmas with spherically bent crystals depends in part on the crystal's x-ray diffraction across the entire crystal surface. We employ the energy selectivity and high intensity of synchrotron radiation to examine typical spherical crystals from alpha-quartz for their diffraction quality, in a perpendicular geometry that is particularly convenient to examine sagittal focusing. The crystal's local diffraction is not ideal: the most noticeable problems come from isolated regions that so far have failed to correlate with visible imperfections. Excluding diffraction from such problem spots has little effect on the focus beyond a decrease in background.
Spherical quartz crystals investigated with synchrotron radiation.
Pereira, N R; Macrander, A T; Hill, K W; Baronova, E O; George, K M; Kotick, J
2015-10-01
The quality of x-ray spectra and images obtained from plasmas with spherically bent crystals depends in part on the crystal's x-ray diffraction across the entire crystal surface. We employ the energy selectivity and high intensity of synchrotron radiation to examine typical spherical crystals from alpha-quartz for their diffraction quality, in a perpendicular geometry that is particularly convenient to examine sagittal focusing. The crystal's local diffraction is not ideal: the most noticeable problems come from isolated regions that so far have failed to correlate with visible imperfections. Excluding diffraction from such problem spots has little effect on the focus beyond a decrease in background. PMID:26520963
Spherical quartz crystals investigated with synchrotron radiation
Pereira, N. R.; Macrander, A. T.; Hill, K. W.; Baronova, E. O.; George, K. M.; Kotick, J.
2015-10-15
The quality of x-ray spectra and images obtained from plasmas with spherically bent crystals depends in part on the crystal’s x-ray diffraction across the entire crystal surface. We employ the energy selectivity and high intensity of synchrotron radiation to examine typical spherical crystals from alpha-quartz for their diffraction quality, in a perpendicular geometry that is particularly convenient to examine sagittal focusing. The crystal’s local diffraction is not ideal: the most noticeable problems come from isolated regions that so far have failed to correlate with visible imperfections. Excluding diffraction from such problem spots has little effect on the focus beyond a decrease in background.
Optimal clinical implementation of the Siemens virtual wedge
Walker, C.P.; Richmond, N.D.; Lambert, G.D
2003-09-30
Installation of a modern high-energy Siemens Primus linear accelerator at the Northern Centre for Cancer Treatment (NCCT) provided the opportunity to investigate the optimal clinical implementation of the Siemens virtual wedge filter. Previously published work has concentrated on the production of virtual wedge angles at 15 deg., 30 deg., 45 deg., and 60 deg. as replacements for the Siemens hard wedges of the same nominal angles. However, treatment plan optimization of the dose distribution can be achieved with the Primus, as its control software permits the selection of any virtual wedge angle from 15 degree sign to 60 degree sign in increments of 1 deg. The same result can also be produced from a combination of open and 60 deg. wedged fields. Helax-TMS models both of these modes of virtual wedge delivery by the wedge angle and the wedge fraction methods respectively. This paper describes results of timing studies in the planning of optimized patient dose distributions by both methods and in the subsequent treatment delivery procedures. Employment of the wedge fraction method results in the delivery of small numbers of monitor units to the beam's central axis; therefore, wedge profile stability and delivered dose with low numbers of monitor units were also investigated. The wedge fraction was proven to be the most efficient method when the time taken for both planning and treatment delivery were taken into consideration, and is now used exclusively for virtual wedge treatment delivery in Newcastle. It has also been shown that there are no unfavorable dosimetric consequences from its practical implementation.
Impingement of water droplets on wedges and double-wedge airfoils at supersonic speeds
NASA Technical Reports Server (NTRS)
Serafini, John S
1954-01-01
An analytical solution has been obtained for the equations of motion of water droplets impinging on a wedge in a two-dimensional supersonic flow field with a shock wave attached to the wedge. The closed-form solution yields analytical expressions for the equation of the droplet trajectory, the local rate of impingement and the impingement velocity at any point on the wedge surface, and the total rate of impingement. The analytical expressions are utilized to determine the impingement on the forward surfaces of diamond airfoils in supersonic flow fields with attached shock waves. The results presented include the following conditions: droplet diameters from 2 to 100 microns, pressure altitudes from sea level to 30,000 feet, free-stream static temperatures from 420 degrees r, free stream Mach numbers from 1.1 to 2.0, semiapex angles for the wedge from 1.14 degrees to 7.97 degrees, thickness-to-chord ratios for the diamond airfoil from 0.02 to 0.14, chord lengths from 1 to 20 feet, and angles of attack from zero to the inverse tangent of the airfoil thickness-to-chord ratio.
Opening wedge osteotomies for correction of hallux valgus: a review of wedge plate fixation.
Smith, W Bret; Hyer, Christopher F; DeCarbo, William T; Berlet, Gregory C; Lee, Thomas H
2009-12-01
Osteotomy of the proximal metatarsal for the correction of moderate to severe hallux valgus deformity is commonly performed. The purpose of this study is to review the early results of a technique for the correction of hallux valgus, an opening wedge osteotomy of the proximal first metatarsal with opening wedge plate fixation. A review was performed of the results of 47 patients (49 feet) who underwent correction of hallux valgus with proximal metatarsal opening wedge osteotomy. All osteotomies were secured with plate fixation on the medial side. Evaluation consisted of preoperative and postoperative radiographic as well as clinical evaluations. Mean corrections of 7 degrees were achieved for the 1-2 intermetatarsal angles. Fourteen complications occurred, 6 of which involved mild hardware irritation and did not affect outcome. Four nonunions or delayed unions were identified. The authors find the opening wedge osteotomy of the proximal first metatarsal to be a technically straightforward procedure for correcting moderate to severe hallux valgus. The correction obtained is comparable to other described techniques. PMID:20400425
Ogawa, Hiroyasu; Matsumoto, Kazu; Ogawa, Takahiro; Takeuchi, Kentaro; Akiyama, Haruhiko
2016-01-01
Background: Medial opening wedge high tibial osteotomy (HTO) is a well-established surgery for medial compartment knee osteoarthritis (OA) wherein the lower extremity is realigned to shift the load distribution from the medial compartment of the knee to the lateral compartment. However, this surgery is known to affect the posterior tibial slope angle (PTSA), which could lead to abnormal knee kinematics and instability, and eventually to knee OA. Although PTSA control is as important as coronal realignment, few appropriate measurements for this parameter have been reported. The placement of a wedge spacer might have an effect on PTSA. Purpose: To elucidate the relationship between the PTSA and the direction of insertion of a wedge spacer. Study Design: Case series; Level of evidence, 4. Methods: This study assessed 43 knees from 34 patients who underwent medial opening wedge HTO for knee OA. Pre- and postoperative lateral radiographs of the knee as well as postoperative computed tomography scans were performed to evaluate the relationship among PTSA, wedge insertion angle (WIA), and opening gap ratio (distance of the anterior opening gap/distance of the posterior opening gap at the osteotomy site). Results: The PTSA significantly increased from 9.0° ± 2.8° preoperatively to 13.2° ± 4.1° postoperatively (P < .001), resulting in a mean ΔPTSA of 4.7° ± 4.5°. The mean opening gap ratio was 0.86 ± 0.11, and the mean WIA was 25.9° ± 8.4°. The WIA and opening gap ratio were both highly correlated with ΔPTSA (r = 0.71 and 0.72, respectively), implying that a smaller WIA or smaller gap ratio leads to less increase in posterior slope. Conclusion: The direction of wedge insertion is highly correlated with PTSA increase, which suggests that the PTSA can be controlled for by adjusting the direction of wedge insertion during surgery. Clinical Relevance: Study results suggest that it is possible to adjust the PTSA by controlling the WIA during surgery. Proper
MANUAL DEGATING OPERATIONS PERFORMED BY SLEDGEHAMMERS AND PNEUMATIC WEDGE SEPARATORS. ...
MANUAL DEGATING OPERATIONS PERFORMED BY SLEDGE-HAMMERS AND PNEUMATIC WEDGE SEPARATORS. - Southern Ductile Casting Company, Shaking, Degating & Sand Systems, 2217 Carolina Avenue, Bessemer, Jefferson County, AL
Molecular Depth Profiling by Wedged Crater Beveling
Mao, Dan; Lu, Caiyan; Winograd, Nicholas; Wucher, Andreas
2011-01-01
Time-of-flight secondary ion mass spectrometry and atomic force microscopy are employed to characterize a wedge-shaped crater eroded by a 40keV C60+ cluster ion beam on an organic film of Irganox 1010 doped with Irganox 3114 delta layers. From an examination of the resulting surface, the information about depth resolution, topography and erosion rate can be obtained as a function of crater depth for every depth in a single experiment. It is shown that when measurements are performed at liquid nitrogen temperature, a constant erosion rate and reduced bombardment induced surface roughness is observed. At room temperature, however, the erosion rate drops by ~1/3 during the removal of the 400 nm Irganox film and the roughness gradually increased to from 1 nm ~4 nm. From SIMS lateral images of the beveled crater and AFM topography results, depth resolution was further improved by employing glancing angles of incidence and lower primary ion beam energy. Sub-10 nm depth resolution was observed under the optimized conditions on a routine basis. In general, we show that the wedge-crater beveling is an important tool for elucidating the factors that are important for molecular depth profiling experiments. PMID:21744861
Protzman, Nicole M; Wobst, Garrett M; Storts, Eric C; Mulhern, Jennifer L; McCarroll, Raymond E; Brigido, Stephen A
2015-01-01
Evans calcaneal osteotomy remains a cornerstone in the correction of the flexible flatfoot. Although multiple techniques have been used to maintain the length of the lateral column, a low profile wedge locking plate was recently introduced as an alternative to the traditional tricortical allograft wedge. We hypothesized that the wedge locking plate would better maintain the mid-calcaneal length compared with the tricortical allograft wedge. To test this hypothesis, after Evans osteotomy, the mid-calcaneal length was measured in the immediate postoperative period and again at 3 and 6 months. A total of 24 patients met the inclusion criteria. The mean patient age was 48.1 years (range 11 to 66). Of the 24 patients, 9 (37.5%) were treated with a tricortical allograft wedge and 15 (62.5%) with a wedge locking plate. At 3 months postoperatively, the mean decrease in mid-calcaneal length was similar for the tricortical allograft wedge group (1.3 ± 1.9 mm) and the wedge locking plate group (0.5 ± 0.9 mm, p = .275). At 6 months postoperatively, however, the mean decrease in mid-calcaneal length was greater for the tricortical allograft wedge group (2.8 ± 1.7 mm) than for the wedge locking plate group (0.6 ± 0.7 mm, p = .004). The 2 groups demonstrated a similar incidence of dorsally displaced distal calcaneal fragments throughout the study endpoint (p ≥ .052). These results suggest that the wedge locking plate better maintains the mid-calcaneal length over time compared with the tricortical allograft wedge. PMID:25998470
Leung, Ka-Ngo
2006-11-21
A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.
ERIC Educational Resources Information Center
Desseyn, H. O.; And Others
1985-01-01
Compares linear-nonlinear and planar-nonplanar geometry through the valence-shell electron pairs repulsion (V.S.E.P.R.), Mulliken-Walsh, and electrostatic force theories. Indicates that although the V.S.E.P.R. theory has more advantages for elementary courses, an explanation of the best features of the different theories offers students a better…
Transition induced by fixed and freely convecting spherical particles in laminar boundary layers
NASA Astrophysics Data System (ADS)
Petrie, H. L.; Morris, P. J.; Bajwa, A. R.; Vincent, D. C.
1993-08-01
An experimental and analytical study of aspects of transition induced by disturbances from spherical particles in laminar boundary layers is discussed. The generation of turbulent wedges by fixed spherical particles in a laminar boundary layer on or near the surface of a flat plate is considered experimentally using flow visualization with fluorescent dye and laser Doppler velocimetry. Turbulent spots generated by freely convecting spherical particles that are released in the freestream to fall into a flat plate laminar boundary layer and impact the plate are also discussed. A combination of dye flow visualization and a video based particle tracking technique was used to study the convecting particle problem. Although the Reynolds number at the critical condition for turbulent wedge generation by fixed particles and turbulent spot generation by convecting particles are similar, transition in these two situations appears to be fundamentally different. The development of a turbulent wedge near the critical condition is a relatively gradual process. In contrast, turbulent spots form relatively quickly after the convecting particles enter the boundary layer and impact the plate. Turbulent wedge formation downstream of a fixed particle results from the destabilization of the near wall flow by the vortical structures shed into particle wake. This shedding process is dominated by periodically shed loop shaped hairpin vortices. Observation of subharmonic oscillations at 1/2 and 1/4 of this shedding frequency suggest that a chaotic route to turbulence by a series of period doubling bifurcations is possible.
Trench-parallel anisotropy produced by serpentine deformation in the hydrated mantle wedge.
Katayama, Ikuo; Hirauchi, Ken-ichi; Michibayashi, Katsuyoshi; Ando, Jun-ichi
2009-10-22
Seismic anisotropy is a powerful tool for detecting the geometry and style of deformation in the Earth's interior, as it primarily reflects the deformation-induced preferred orientation of anisotropic crystals. Although seismic anisotropy in the upper mantle is generally attributed to the crystal-preferred orientation of olivine, the strong trench-parallel anisotropy (delay time of one to two seconds) observed in several subduction systems is difficult to explain in terms of olivine anisotropy, even if the entire mantle wedge were to act as an anisotropic source. Here we show that the crystal-preferred orientation of serpentine, the main hydrous mineral in the upper mantle, can produce the strong trench-parallel seismic anisotropy observed in subduction systems. High-pressure deformation experiments reveal that the serpentine c-axis tends to rotate to an orientation normal to the shear plane during deformation; consequently, seismic velocity propagating normal to the shear plane (plate interface) is much slower than that in other directions. The seismic anisotropy estimated for deformed serpentine aggregates is an order of magnitude greater than that for olivine, and therefore the alignment of serpentine in the hydrated mantle wedge results in a strong trench-parallel seismic anisotropy in the case of a steeply subducting slab. This hypothesis is also consistent with the presence of a hydrous phase in the mantle wedge, as inferred from anomalously low seismic-wave velocities. PMID:19847262
Viscid-inviscid interaction associated with incompressible flow past wedges at high Reynolds number
NASA Technical Reports Server (NTRS)
Warpinski, N. R.; Chow, W. L.
1977-01-01
An analytical method is suggested for the study of the viscid inviscid interaction associated with incompressible flow past wedges with arbitrary angles. It is shown that the determination of the nearly constant pressure (base pressure) prevailing within the near wake is really the heart of the problem, and the pressure can only be established from these interactive considerations. The basic free streamline flow field is established through two discrete parameters which adequately describe the inviscid flow around the body and the wake. The viscous flow processes such as the boundary layer buildup, turbulent jet mixing, and recompression are individually analyzed and attached to the inviscid flow in the sense of the boundary layer concept. The interaction between the viscous and inviscid streams is properly displayed by the fact that the aforementioned discrete parameters needed for the inviscid flow are determined by the viscous flow condition at the point of reattachment. It is found that the reattachment point behaves as a saddle point singularity for the system of equations describing the recompressive viscous flow processes, and this behavior is exploited for the establishment of the overall flow field. Detailed results such as the base pressure, pressure distributions on the wedge, and the geometry of the wake are determined as functions of the wedge angle.
Stability of spherical converging shock wave
Murakami, M.; Sanz, J.; Iwamoto, Y.
2015-07-15
Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓ{sub c}, such that all the eigenmode perturbations for ℓ > ℓ{sub c} are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.
Stability of spherical converging shock wave
NASA Astrophysics Data System (ADS)
Murakami, M.; Sanz, J.; Iwamoto, Y.
2015-07-01
Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓc, such that all the eigenmode perturbations for ℓ > ℓc are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.
Simulation on the aggregation process of spherical particle confined in a spherical shell
NASA Astrophysics Data System (ADS)
Wang, J.; Xu, J. J.; Zhang, L.
2016-04-01
The aggregation process of spherical particles confined in a spherical shell was studied by using a diffusion-limited cluster-cluster aggregation (DLCA) model. The influence of geometrical confinement and wetting-like properties of the spherical shell walls on the particle concentration profile, aggregate structure and aggregation kinetics had been explored. The results show that there will be either depletion or absorption particles near the shell walls depending on the wall properties. It is observed that there are four different types of density distribution which can be realized by modifying the property of the inner or outer spherical shell wall. In addition, the aggregate structure will become more compact in the confined spherical shell comparing to bulk system with the same particle volume fraction. The analysis on the aggregation kinetics indicates that geometrical confinement will promote the aggregation process by reducing the invalid movement of the small aggregates and by constraining the movement of those large aggregates. Due to the concave geometrical characteristic of the outer wall of the spherical shell, its effects on the aggregating kinetics and the structure of the formed aggregates are more evident than those of the inner wall. This study will provide some instructive information of controlling the density distribution of low-density porous polymer hollow spherical shells and helps to predict gel structures developed in confined geometries.
Magneto-optical and photoemission studies of ultrathin wedges
Bader, S.D.; Li, Dongqi
1995-12-01
Magnetic phase transitions of Fe wedges grown epitaxially on Cu(100) are detected via the surface magneto-optical Kerr effect and used to construct a phase diagram for face centered Fe. Also, the confinement of Cu sp- and d-quantum-well states is studied for Cu/Co(wedge)/Cu(100) utilizing undulator-based photoemission experiments.
28. REPRESENTATIVE CENTER WEDGE. BALANCE WHEELS ON TRACK, WITH RACK ...
28. REPRESENTATIVE CENTER WEDGE. BALANCE WHEELS ON TRACK, WITH RACK TO OUTSIDE, SHOWN TO RIGHT OF THE WEDGE. PHOTO TAKEN AT SOUTH SWING SPAN. - George P. Coleman Memorial Bridge, Spanning York River at U.S. Route 17, Yorktown, York County, VA
Programmable shape transformation of elastic spherical domes.
Abdullah, Arif M; Braun, Paul V; Hsia, K Jimmy
2016-07-20
We investigate mismatch strain driven programmable shape transformation of spherical domes and report the effects of different geometric and structural characteristics on dome behavior in response to applied mismatch strain. We envision a bilayer dome design where the differential swelling of the inner layer with respect to the passive outer layer in response to changes in dome surroundings (such as the introduction of an organic solvent) introduces mismatch strain within the bilayer system and causes dome shape transformation. Finite element analysis reveals that, in addition to snap-through, spherical domes undergo bifurcation buckling and eventually gradual bending to morph into cylinders with increasing mismatch strain. Besides demonstrating how the snap-through energy barrier depends on the spherical dome shape, our analysis identifies three distinct groups of dome geometries based on their mismatch strain-transformed configuration relationships. Our experiments with polymer-based elastic bilayer domes that exhibit differential swelling in organic solvents qualitatively confirm the finite element predictions. We establish that, in addition to externally applied stimuli (mismatch strain), bilayer spherical dome morphing can be tuned and hence programmed through its geometry and structural characteristics. Incorporation of an elastic instability mechanism such as snap-through within the framework of stimuli-responsive functional devices can improve their response time which is otherwise controlled by diffusion. Hence, our proposed design guidelines can be used to realize deployable, multi-functional, reconfigurable, and therefore, adaptive structures responsive to a diverse set of stimuli across multiple length scales. PMID:27435451
Characterization of CNRS Fizeau wedge laser tuner
NASA Astrophysics Data System (ADS)
A fringe detection and measurement system was constructed for use with the CNRS Fizeau wedge laser tuner, consisting of three circuit boards. The first board is a standard Reticon RC-100 B motherboard which is used to provide the timing, video processing, and housekeeping functions required by the Reticon RL-512 G photodiode array used in the system. The sampled and held video signal from the motherboard is processed by a second, custom fabricated circuit board which contains a high speed fringe detection and locating circuit. This board includes a dc level discriminator type fringe detector, a counter circuit to determine fringe center, a pulsed laser triggering circuit, and a control circuit to operate the shutter for the He-Ne reference laser beam. The fringe center information is supplied to the third board, a commercial single board computer, which governs the data collection process and interprets the results.
Characterization of CNRS Fizeau wedge laser tuner
NASA Technical Reports Server (NTRS)
1984-01-01
A fringe detection and measurement system was constructed for use with the CNRS Fizeau wedge laser tuner, consisting of three circuit boards. The first board is a standard Reticon RC-100 B motherboard which is used to provide the timing, video processing, and housekeeping functions required by the Reticon RL-512 G photodiode array used in the system. The sampled and held video signal from the motherboard is processed by a second, custom fabricated circuit board which contains a high speed fringe detection and locating circuit. This board includes a dc level discriminator type fringe detector, a counter circuit to determine fringe center, a pulsed laser triggering circuit, and a control circuit to operate the shutter for the He-Ne reference laser beam. The fringe center information is supplied to the third board, a commercial single board computer, which governs the data collection process and interprets the results.
Configuration and Generation of Substorm Current Wedge
NASA Astrophysics Data System (ADS)
Chu, Xiangning
The substorm current wedge (SCW), a core element of substorm dynamics coupling the magnetotail to the ionosphere, is crucial in understanding substorms. It has been suggested that the field-aligned currents (FACs) in the SCW are caused by either pressure gradients or flow vortices, or both. Our understanding of FAC generations is based predominately on numerical simulations, because it has not been possible to organize spacecraft observations in a coordinate system determined by the SCW. This dissertation develops an empirical inversion model of the current wedge and inverts midlatitude magnetometer data to obtain the parameters of the current wedge for three solar cycles. This database enables statistical data analysis of spacecraft plasma and magnetic field observations relative to the SCW coordinate. In chapter 2, a new midlatitude positive bay (MPB) index is developed and calculated for three solar cycles of data. The MPB index is processed to determine the substorm onset time, which is shown to correspond to the auroral breakup onset with at most 1-2 minutes difference. Substorm occurrence rate is found to depend on solar wind speed while substorm duration is rather constant, suggesting that substorm process has an intrinsic pattern independent of external driving. In chapter 3, an SCW inversion technique is developed to determine the strength and locations of the FACs in an SCW. The inversion parameters for FAC strength and location, and ring current strength are validated by comparison with other measurements. In chapter 4, the connection between earthward flows and auroral poleward expansion is examined using improved mapping, obtained from a newly-developed dynamic magnetospheric model by superimposing a standard magnetospheric field model with substorm current wedge obtained from the inversion technique. It is shown that the ionospheric projection of flows observed at a fixed point in the equatorial plane map to the bright aurora as it expands poleward
Fabrication of wedged multilayer Laue lenses
Prasciolu, M.; Leontowich, A. F. G.; Krzywinski, J.; Andrejczuk, A.; Chapman, H. N.; Bajt, S.
2015-01-01
We present a new method to fabricate wedged multilayer Laue lenses, in which the angle of diffracting layers smoothly varies in the lens to achieve optimum diffracting efficiency across the entire pupil of the lens. This was achieved by depositing a multilayer onto a flat substrate placed in the penumbra of a straight-edge mask. The distance between the mask and the substrate was calibrated and the multilayer Laue lens was cut in a position where the varying layer thickness and the varying layer tilt simultaneously satisfy the Fresnel zone plate condition and Bragg’s law for all layers in the stack. This method can be used to extend the achievable numerical aperture of multilayer Laue lenses to reach considerably smaller focal spot sizes than achievable with lenses composed of parallel layers.
Fabrication of wedged multilayer Laue lenses
Prasciolu, M.; Leontowich, A. F. G.; Krzywinski, J.; Andrejczuk, A.; Chapman, H. N.; Bajt, S.
2015-01-01
We present a new method to fabricate wedged multilayer Laue lenses, in which the angle of diffracting layers smoothly varies in the lens to achieve optimum diffracting efficiency across the entire pupil of the lens. This was achieved by depositing a multilayer onto a flat substrate placed in the penumbra of a straight-edge mask. The distance between the mask and the substrate was calibrated and the multilayer Laue lens was cut in a position where the varying layer thickness and the varying layer tilt simultaneously satisfy the Fresnel zone plate condition and Bragg’s law for all layers in the stack.more » This method can be used to extend the achievable numerical aperture of multilayer Laue lenses to reach considerably smaller focal spot sizes than achievable with lenses composed of parallel layers.« less
Wide scanning spherical antenna
NASA Technical Reports Server (NTRS)
Shen, Bing (Inventor); Stutzman, Warren L. (Inventor)
1995-01-01
A novel method for calculating the surface shapes for subreflectors in a suboptic assembly of a tri-reflector spherical antenna system is introduced, modeled from a generalization of Galindo-Israel's method of solving partial differential equations to correct for spherical aberration and provide uniform feed to aperture mapping. In a first embodiment, the suboptic assembly moves as a single unit to achieve scan while the main reflector remains stationary. A feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan thereby eliminating the need to oversize the main spherical reflector. In an alternate embodiment, both the main spherical reflector and the suboptic assembly are fixed. A flat mirror is used to create a virtual image of the suboptic assembly. Scan is achieved by rotating the mirror about the spherical center of the main reflector. The feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan.
Ground penetrating radar estimates of permafrost ice wedge depth
NASA Astrophysics Data System (ADS)
Parsekian, A.; Slater, L. D.; Nolan, J. T.; Grosse, G.; Walter Anthony, K. M.
2013-12-01
Vertical ground ice wedges associated with polygonal patterning in permafrost environments form due to frost cracking of soils under harsh winter conditions and subsequent infilling of cracks with snow melt water. Ice wedge polygon patterns have implications for lowland geomorphology, hydrology, and vulnerability of permafrost to thaw. Ice wedge dimensions may exceed two meters width at the surface and several meters depth, however few studies have addressed the question of ice wedge depth due to challenges related to measuring the vertical dimension below the ground. Vertical exposures where ice wedges maybe observed are limited to rapidly retreating lake, river, and coastal bluffs. Coring though the ice wedges to determine vertical extent is possible, however that approach is time consuming and labor intensive. Many geophysical investigations have noted signal anomalies related to the presence of ice wedges, but no reliable method for extracting wedge dimensions from geophysical data has been yet proposed. Here we present new evidence that ground penetrating radar (GPR) may be a viable method for estimating ice wedge depth. We present three new perspectives on processing GPR data collected over ice wedges that show considerable promise for use as a fast, cost effective method for evaluating ice wedge depth. Our novel approaches include 1) a simple frequency-domain analysis, 2) an S-transform frequency domain analysis and 3) an analysis of the returned signal power as a radar cross section (RCS) treating subsurface ice wedges as dihedral corner retro-reflectors. Our methods are demonstrated and validated using finite-difference time domain FDTD) GPR forward models of synthetic idealized ice wedges and field data from permafrost sites in Alaska. Our results indicate that frequency domain and signal power data provide information that is easier to extract from raw GPR data than similar information in the time domain. We also show that we can simplify the problem by
Transmission of a Gaussian beam by a Fizeau interferential wedge.
Stoykova, Elena
2005-12-01
Analysis of transmission of a finite-diameter Gaussian beam by a Fizeau interferential wedge is presented. The fringe calculation is based on angular spectrum expansion of the complex amplitude of the incident wave field. The developed approach is applicable to any beam diameter and wedge thickness at any distance from the wedge and yields as a boundary case the fringes at plane-wave illumination. The spatial region of resonant transmission on the wedge surface is given by the width of the transmitted peak for plane-wave illumination. At higher coating reflectivity, the direction of the transmitted beam is deviated with respect to that of the incident beam. Evaluation of the spectral response based on the spectral width of the transmitted power curve is introduced as more realistic for a correct description of the application of a Fizeau wedge as an interferential selector in laser resonators. PMID:16396037
Evolution of Strain in Obliquely Convergent Analog Doubly-Vergent Wedges
NASA Astrophysics Data System (ADS)
Davis, D. M.; Haq, S. S.
2012-12-01
We have conducted a range of analog experiments across the parameter space from 0° to 70°, in which we have tracked the evolution of the model geometries and strain fields. Surface deformation is monitored by photographic analysis of the experiment and a plane laser is used to obtain precise topography of the developing pro and retro-wedges normal to strike At both high and low obliquities, our results are broadly consistent with theoretical expectations. At obliquities ranging from 0° to close to 60°, doubly-vergent wedges with the same combination of a broad, minimum taper pro-wedge and a narrower, maximum-taper double retro-wedge found in normal convergence at obliquities up to close to 60°. Above about 60° obliquity, though, the orogen continues to grow with a much greater degree of symmetry; it never develops the broad prowedge that characterizes the orogens at low to moderately high obliquities. This result is entirely consistent with the rotation of stresses and reversal in principal stress order associated with the transition from an essentially convergent orogen with some margin-parallel shear to transpression with dominant strike-slip, as described by various authors. This marked change in tectonic style and orogen shape at about 60° obliquity is accompanied by a change in the distribution of shear within the model. In normal convergence, there is no margin-parallel shear to be accommodated, so it is everywhere equal to zero. Margin-normal shortening is accommodated across the orogen, but, as taper is maintained, it occurs most rapidly near the deformation front (at left). In no case is there extension in these purely frictional models, unlike the case with a ductile layer at depth. At non-zero obliquities, there is also margin-parallel shear to be distributed across the margin. In addition to a broad zone centered on the topographic high (over the tip of the backstop), that shear is distributed across the prowedge, where it is accommodated in the
The role of aerothermochemistry in double cone and double wedge flows
NASA Astrophysics Data System (ADS)
Swantek, Andrew
In this work, hypervelocity flows over double cone and double wedge geometries are studied. The flow configurations established over the double cone/double wedge models are extremely sensitive to thermochemistry, and thus serve as ideal benchmarks for validating chemical models. The goals of this research are: i) to investigate the coupling between the fluid mechanics and thermochemistry in these flow fields by varying freestream flow composition and enthalpy, ii) to implement a diagnostic suite for time-resolved surface and freestream measurements, iii) to investigate the nature of flow field unsteadiness across various test conditions, and lastly iv) to extend the experimental database for shock wave boundary/layer interactions. An expansion tube is used to generate flows with enthalpies ranging from 2.2-8.0 MJ/kg (2-4 km/s) and Mach numbers from 4-7. The expansion tube is a novel impulse facility for accelerating a test gas to these velocities, while maintaining a minimally dissociated freestream. Additionally, the facility allows variation of the freestream composition (between nitrogen and air), while maintaining freestream test parameters (Mach number, density, enthalpy) to within 0.5%. Two models are used: a 25-55 degree double cone model and a 30-55 degree double wedge. There are four diagnostic components to this research which aim to enable a better understanding of these canonical flow fields. Single frame, high resolution schlieren photography is used to visualize various flow features including: the separation zone formed in the corner, the triple point interaction, and a supersonic shear layer. From these images, a separation zone length scaling parameter is determined. This parameter, derived for wedge geometries, is successfully applied to conical geometries by using a judicious choice of flow properties for scaling. In the wedge image series, nitrogen test conditions exhibit a distinct increase in bow shock standoff distance. Additionally, aft
NASA Astrophysics Data System (ADS)
Cembranos, J. A. R.; Dobado, A.; Maroto, A. L.
Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space-time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.
The matching of wedge transmission factors across six multi-energy linear accelerators.
Weston, S J; Thompson, R C A; Morgan, A M
2007-01-01
Elekta Precise linear accelerators create a wedged isodose distribution using a single, fixed, motorized wedge with a nominal wedge angle of 60 degrees. Wedge angles of less than 60 degrees can be produced by varying the proportion of open and wedge monitor units for a given exposure. The fixed wedge can be replaced with a mobile wedge, the position of which can be moved in order to adjust the wedge transmission factor (WTF). Using the original fixed wedges installed in our fleet of six Elekta accelerators, we found a range of 4% in measured wedge transmission factor for 6 MV beams. Results are presented which demonstrate that by using the mobile wedge it is possible to match the wedge transmission factors to within 1% for the six linear accelerators over three energies. PMID:17267473
Large displacement spherical joint
Bieg, Lothar F.; Benavides, Gilbert L.
2002-01-01
A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.
Recent Progress on Spherical Torus Research
Ono, Masayuki; Kaita, Robert
2014-01-01
The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ~ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ~ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of attractive fusion energy power source. Since the start of the two megaampere class ST facilities in 2000, National Spherical Torus Experiment (NSTX) in the US and Mega Ampere Spherical Tokamak (MAST) in UK, active ST research has been conducted worldwide. More than sixteen ST research facilities operating during this period have achieved remarkable advances in all of fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.
Scalar and vector spherical harmonic spectral equations of rotating magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Ivers, D. J.; Phillips, C. G.
2008-12-01
Vector spherical harmonic analyses have been used effectively to solve laminar and mean-field magnetohydrodynamic dynamo problems with product interactions, such as magnetic induction, anisotropic alpha-effect and anisotropic magnetic diffusion, that are difficult to analyse spectrally in spherical geometries. Spectral forms of the non-linear rotating, Boussinesq and anelastic, momentum, magnetic induction and heat equations are derived for spherical geometries from vector spherical harmonic expansions of the velocity, magnetic induction, vorticity, electrical current and gravitational acceleration and from scalar spherical harmonic expansions of the pressure and temperature. By combining the vector spherical harmonic spectral forms of the momentum equation and the magnetic induction equation with poloidal-toroidal representations of the velocity and the magnetic field, non-linear spherical harmonic spectral equations are also derived for the poloidal-toroidal potentials of the velocity or the momentum density in the anelastic approximation and the magnetic field. Both compact and spectral interaction expansion forms are given. Vector spherical harmonic spectral forms of the linearized rotating magnetic induction, momentum and heat equations for a general basic state can be obtained by linearizing the corresponding non-linear spectral equations. Similarly, the spherical harmonic spectral equations for the poloidal-toroidal potentials of the velocity and the magnetic field may be linearized. However, for computational applications, new alternative hybrid linearized spectral equations are derived. The algorithmically simpler hybrid equations depend on vector spherical harmonic expansions of the velocity, magnetic field, vorticity, electrical current and gravitational acceleration of the basic state and scalar spherical harmonic expansions of the poloidal-toroidal potentials of the perturbation velocity, magnetic field and temperature. The spectral equations derived
The effect of a compliant accretionary wedge on earthquake rupture and tsunamigenesis
NASA Astrophysics Data System (ADS)
Lotto, Gabriel; Jeppson, Tamara; Dunham, Eric; Tobin, Harold
2016-04-01
The 11 March 2011 Tohoku megathrust earthquake ruptured through the shallowest part of the subduction zone boundary, resulting in tens of meters of displacement at the seafloor. This extreme shallow slip generated a devastating tsunami. The elastic properties of off-fault materials have an important role in determining slip along a fault. Laboratory ultrasonic velocity measurements performed on samples of rock obtained from the area surrounding the Tohoku earthquake principal fault zone during the Japan Trench Fast Drilling Project (JFAST) have shown that shallow off-fault materials are extremely compliant - P-wave velocities of 2.0-2.4 km/s, S-wave velocities of 0.7-1.0 km/s, and shear moduli ranging from 1.0-2.2 GPa. Seismic imaging around the JFAST drill site corroborates the presence of a compliant, low-velocity frontal prism at the toe of the hanging wall. This compliant wedge is likely a fairly robust feature across the horizontal extent of the Japan Trench and may have contributed to the large amount of displacement recorded. In order to investigate the impact of compliant off fault materials on earthquake rupture and tsunamigenesis, we employ a 2-D finite difference method that models the full seismic and tsunami wavefield associated with dynamic rupture on a dipping fault in a heterogeneous medium. Our numerical method rigorously couples the elastodynamic response of the solid Earth to that of a compressible ocean in the presence of gravity. Idealized models of subduction zone earthquakes show that the presence of a compliant wedge leads to increased slip, greater seafloor displacement, and a larger tsunami. However, preliminary results for a representative Tohoku geometry were not so simple; the compliant wedge enhanced slip and seafloor deformation but only in a localized zone, and tsunami height was not significantly affected. This surprising result indicates that the details of geometry and material structure we observe in real subduction zones are
Random walks, diffusion limited aggregation in a wedge, and average conformal maps.
Sander, Leonard M; Somfai, Ellák
2005-06-01
We investigate diffusion-limited aggregation (DLA) in a wedge geometry. Arneodo and collaborators have suggested that the ensemble average of DLA cluster density should be close to the noise-free selected Saffman-Taylor finger. We show that a different, but related, ensemble average, that of the conformal maps associated with random clusters, yields a nontrivial shape which is also not far from the Saffman-Taylor finger. However, we have previously demonstrated that the same average of DLA in a channel geometry is not the Saffman-Taylor finger. This casts doubt on the idea that the average of noisy diffusion-limited growth is governed by a simple transcription of noise-free results. PMID:16035911
Characterizing human retinotopic mapping with conformal geometry: a preliminary study
NASA Astrophysics Data System (ADS)
Ta, Duyan; Shi, Jie; Barton, Brian; Brewer, Alyssa; Lu, Zhong-Lin; Wang, Yalin
2014-03-01
Functional magnetic resonance imaging (fMRI) has been widely used to measure the retinotopic organization of early visual cortex in the human brain. Previous studies have identified multiple visual field maps (VFMs) based on statistical analysis of fMRI signals, but the resulting geometry has not been fully characterized with mathematical models. Here we test whether VFMs V1 and V2 obey the least restrictive of all geometric mappings; that is, whether they are anglepreserving and therefore maintain conformal mapping. We measured retinotopic organization in individual subjects using standard traveling-wave fMRI methods. Visual stimuli consisted of black and white, drifting checkerboards comprising rotating wedges and expanding rings to measure the cortical representations of polar angle and eccentricity, respectively. These representations were then projected onto a 3D cortical mesh of each hemisphere. By generating a mapped unit disk that is conformal of the VFMs using spherical stereographic projection and computing the parameterized coordinates of the eccentricity and polar angle gradients, we computed Beltrami coefficients to check whether the mapping from the visual field to the V1 and V2 cortical representations is conformal. We find that V1 and V2 exhibit local conformality. Our analysis of the Beltrami coefficient shows that selected regions of V1 and V2 that contain reasonably smooth eccentricity and polar angle gradients do show significant local conformality, warranting further investigation of this approach for analysis of early and higher visual cortex. These results suggest that such a mathematical model can be used to characterize the early VFMs in human visual cortex.
An experimental investigation of supersonic flow past a wedge-cylinder configuration
NASA Technical Reports Server (NTRS)
Barnette, D. W.
1976-01-01
An experimental investigation of supersonic flow past double-wedge configurations was conducted. Over the range of geometries tested, it was found that, while theoretical solutions both for a Type V pattern and for a Type VI pattern could be generated for a particular flow condition (as defined by the geometry and the free-stream conditions), the weaker, Type VI pattern was observed experimentally. More rigorous flow-field solutions were developed for the flow along the wing leading-edge. Solutions were developed for the three-dimensional flow in the plane of symmetry of a swept cylinder (which represented the wing leading-edge) which was mounted on a wedge (which generated the "bow" shock wave). A numerical code was developed using integral techniques to calculate the flow in the shock layer upstream of the interaction region (i.e., near the wing root). Heat transfer rates were calculated for various free stream conditions. The present investigation was undertaken to examine the effects of crossflow on the resultant flow-field and to verify the flow model used in theoretical calculations.
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Nadler, Walter; Grassberger, Peter
2005-06-01
Lattice animals are one of the few critical models in statistical mechanics violating conformal invariance. We present here simulations of two-dimensional site animals on square and triangular lattices in nontrivial geometries. The simulations are done with the pruned-enriched Rosenbluth method (PERM) algorithm, which gives very precise estimates of the partition sum, yielding precise values for the entropic exponent θ (ZN˜μNN-θ) . In particular, we studied animals grafted to the tips of wedges with a wide range of angles α , to the tips of cones (wedges with the sides glued together), and to branching points of Riemann surfaces. The latter can either have k sheets and no boundary, generalizing in this way cones to angles α>360° , or can have boundaries, generalizing wedges. We find conformal invariance behavior, θ˜1/α , only for small angles (α≪2π) , while θ≈const-α/2π for α≫2π . These scalings hold both for wedges and cones. A heuristic (nonconformal) argument for the behavior at large α is given, and comparison is made with critical percolation.
NASA Astrophysics Data System (ADS)
Morgan, Julia K.
2015-05-01
Particle-based numerical simulations of cohesive contractional wedges can yield important perspectives on the formation and evolution of fold and thrust belts, offering particular insights into the mechanical evolution of the systems. Results of several discrete element method simulations are presented here, demonstrating the stress and strain evolution of systems with different initial cohesive strengths. Particle assemblages consolidated under gravity, and bonded to impart cohesion, are pushed from the left at a constant velocity above a weak, unbonded décollement surface. Internal thrusting causes horizontal shortening and vertical thickening, forming wedge geometries. The mean wedge taper is similar for all simulations, consistent with their similar residual and basal sliding friction values. In all examples presented here, both forethrusts and back thrusts occur, but forethrusts accommodate most of the shortening. Fault spacing and offset increase with increasing cohesion. Significant tectonic volume strain also occurs, with the greatest incremental volume strain occurring just outboard of the deformation front. This diffuse shortening serves to strengthen the unfaulted domain in front of the deformed wedge, preconditioning these materials for brittle (dilative) failure. The reach of this volumetric strain and extent of décollement slip increase with cohesive strength, defining the extent of stress transmission. Stress paths for elements tracked through the simulations demonstrate systematic variations in shear stress in response to episodes of both décollement slip and thrust fault activity, providing a direct explanation for stress fluctuations during convergence.
Refined numerical solution of the transonic flow past a wedge
NASA Technical Reports Server (NTRS)
Liang, S.-M.; Fung, K.-Y.
1985-01-01
A numerical procedure combining the ideas of solving a modified difference equation and of adaptive mesh refinement is introduced. The numerical solution on a fixed grid is improved by using better approximations of the truncation error computed from local subdomain grid refinements. This technique is used to obtain refined solutions of steady, inviscid, transonic flow past a wedge. The effects of truncation error on the pressure distribution, wave drag, sonic line, and shock position are investigated. By comparing the pressure drag on the wedge and wave drag due to the shocks, a supersonic-to-supersonic shock originating from the wedge shoulder is confirmed.
Recirculating wedges for metal-vapor plasma tubes
Hall, Jerome P.; Sawvel, Robert M.; Draggoo, Vaughn G.
1994-01-01
A metal vapor laser is disclosed that recycles condensed metal located at the terminal ends of a plasma tube back toward the center of the tube. A pair of arcuate wedges are incorporated on the bottom of the plasma tube near the terminal ends. The wedges slope downward toward the center so that condensed metal may be transported under the force of gravity away from the terminal ends. The wedges are curved to fit the plasma tube to thereby avoid forming any gaps within the tube interior.
Recirculating wedges for metal-vapor plasma tubes
Hall, J.P.; Sawvel, R.M.; Draggoo, V.G.
1994-06-28
A metal vapor laser is disclosed that recycles condensed metal located at the terminal ends of a plasma tube back toward the center of the tube. A pair of arcuate wedges are incorporated on the bottom of the plasma tube near the terminal ends. The wedges slope downward toward the center so that condensed metal may be transported under the force of gravity away from the terminal ends. The wedges are curved to fit the plasma tube to thereby avoid forming any gaps within the tube interior. 8 figures.
Octave spanning wedge dispersive mirrors with low dispersion oscillations.
Habel, Florian; Shirvanyan, Vage; Trubetskov, Michael; Burger, Christian; Sommer, Annkatrin; Kling, Matthias F; Schultze, Martin; Pervak, Vladimir
2016-05-01
A novel concept for octave spanning dispersive mirrors with low spectral dispersion oscillations is presented. The key element of the so-called wedge dispersive mirror is a slightly wedged layer which is coated on a specially optimized dispersive multilayer stack by a common sputter coating process. The group delay dispersion (GDD) of a pulse reflected on a wedge dispersive mirror is nearly free of oscillations. Fabricated mirrors with negative GDD demonstrate the compression of a pulse down to 3.8 fs as good as double angled mirrors optimized for the same bandwidth. PMID:27137538
NASA Astrophysics Data System (ADS)
Stover, E.; Berger, G.; Wendel, M.; Petter, J.
2015-10-01
A method for non-contact 3D form testing of aspheric surfaces including determination of decenter and wedge errors and lens thickness is presented. The principle is based on the absolute measurement capability of multi-wavelength interferometry (MWLI). The approach produces high density 3D shape information and geometric parameters at high accuracy in short measurement times. The system allows inspection of aspheres without restrictions in terms of spherical departures, of segmented and discontinuous optics. The optics can be polished or ground and made of opaque or transparent materials.
NASA Astrophysics Data System (ADS)
Ge, Wenjun; Modest, Michael F.; Roy, Somesh P.
2016-03-01
The high-order spherical harmonics (PN) method for 2-D Cartesian domains is extracted from the 3-D formulation. The number of equations and intensity coefficients reduces to (N + 1)2 / 4 in the 2-D Cartesian formulation compared with N(N + 1) / 2 for the general 3-D PN formulation. The Marshak boundary conditions are extended to solve problems with nonblack and mixed diffuse-specular surfaces. Additional boundary conditions for specified radiative wall flux, for symmetry/specular reflection boundaries have also been developed. The mathematical details of the formulations and their implementation in the OpenFOAM finite volume based CFD software platform are presented. The accuracy and computational cost of the 2-D Cartesian PN are compared with that of the 3-D PN solver and a Photon Monte Carlo solver for a square enclosure, as well as a 45° wedge geometry with variable radiative properties. The new boundary conditions have been applied for both test cases, and the boundary condition for mixed diffuse-specular surfaces is further illustrated by numerical examples of a rectangular geometry enclosed by walls with different surface characteristics.
Substorm current wedge composition by wedgelets
NASA Astrophysics Data System (ADS)
Liu, Jiang; Angelopoulos, V.; Chu, Xiangning; Zhou, Xu-Zhi; Yue, Chao
2015-03-01
Understanding how a substorm current wedge (SCW) is formed is crucial to comprehending the substorm phenomenon. One SCW formation scenario suggests that the substorm time magnetosphere is coupled to the ionosphere via "wedgelets," small building blocks of an SCW. Wedgelets are field-aligned currents (FACs) carried by elemental flux transport units known as dipolarizing flux bundles (DFBs). A DFB is a magnetotail flux tube with magnetic field stronger than that of the ambient plasma. Its leading edge, known as a "dipolarization front" or "reconnection front," is a product of near-Earth reconnection. Dipolarizing flux bundles, and thus wedgelets, are localized—each is only <3 RE wide. How these localized wedgelets combine to become large-scale (several hours of magnetic local time) region-1-sense SCW FACs is unclear. To determine how this occurs, we investigated wedgelets statistically using Time History of Events and Macroscale Interactions during Substorms (THEMIS) data. The results show wedgelet asymmetries: in the dawn (dusk) sector of the magnetotail, a wedgelet has more FAC toward (away from) the Earth than away from (toward) the Earth, so the net FAC is toward (away from) the Earth. The combined effect of many wedgelets is therefore the same as that of large-scale region-1-sense SCW, supporting the idea that they comprise the SCW.
Applications of Differential Geometry to Cartography
ERIC Educational Resources Information Center
Benitez, Julio; Thome, Nestor
2004-01-01
This work introduces an application of differential geometry to cartography. The mathematical aspects of some geographical projections of Earth surface are revealed together with some of its more important properties. An important problem since the discovery of the 'spherical' form of the Earth is how to compose a reliable map of the surface of…
Quantifying the effects of material properties on analog models of critical taper wedges
NASA Astrophysics Data System (ADS)
Hofmann, F.; Rosenau, M.; Schreurs, G.; Friedrich, A. M.
2012-04-01
Analogue models are inherently handmade and reflect their creator's shaping character. For example, sieving style in combination with grain geometry and distribution have been claimed to influence bulk material properties and the outcome of analogue experiments. Few studies exist that quantify these effects and here we aim at investigating the impact of bulk properties of granular materials on the structural development of convergent brittle wedges in analogue experiments. In a systematic fashion, natural sands as well as glass beads of different grain size and size distribution were sieved by different persons from different heights and the resulting bulk density was measured. A series of analogue experiments in both the push and pull setup were performed. The differences in the outcome of experiments were analyzed based on sidewall pictures and 3D laserscanning of the surface. A new high-resolution approach to measuring surface slope automatically is introduced and applied to the evaluation of images and profiles. This procedure is compared to manual methods of determining surface slope. The effect of sidewall friction was quantified by measuring lateral changes in surface slope. The resulting dataset is used to identify the main differences between pushed and pulled wedge experiments in the light of critical taper theory. The bulk density of granular material was found to be highly dependent on sieve height. Sieve heights of less than 50 cm produced a bulk density that was up to 10% less than the maximum bulk density; an effect equally shown for different people sieving the material. Glass beads were found to produce a more regular structure of in-sequence-thrusts in both, space and time, than sands while displaying less variability. Surface slope was found to be highly transient for pushed wedge experiments, whereas it reached and attained a stable value in pulled experiments. Pushed wedges are inferred to develop into a supercritical state because they exceed
Spherical geodesic mesh generation
Fung, Jimmy; Kenamond, Mark Andrew; Burton, Donald E.; Shashkov, Mikhail Jurievich
2015-02-27
In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.
VIEW OF LINE OF DRILL HOLES WITH METAL WEDGES, IN ...
VIEW OF LINE OF DRILL HOLES WITH METAL WEDGES, IN NORTHERN QUARRY AREA, FACING NORTH - Granite Hill Plantation, Quarry No. 2, South side of State Route 16, 1.3 miles northeast east of Sparta, Sparta, Hancock County, GA
VIEW OF LINE OF DRILL HOLES WITH METAL WEDGES, IN ...
VIEW OF LINE OF DRILL HOLES WITH METAL WEDGES, IN NORTHERN QUARRY AREA, FACING SOUTHEAST - Granite Hill Plantation, Quarry No. 2, South side of State Route 16, 1.3 miles northeast east of Sparta, Sparta, Hancock County, GA
DETAIL VIEW OF THREEPART METAL WEDGE EMBEDDED IN EDGE OF ...
DETAIL VIEW OF THREE-PART METAL WEDGE EMBEDDED IN EDGE OF QUARRY WALL, FACING EAST - Granite Hill Plantation, Quarry No. 3, South side of State Route 16, 1.3 miles northeast east of Sparta, Sparta, Hancock County, GA
DETAIL VIEW OF THREEPART METAL WEDGE EMBEDDED IN EDGE OF ...
DETAIL VIEW OF THREE-PART METAL WEDGE EMBEDDED IN EDGE OF QUARRY WALL, FACING NORTHWEST - Granite Hill Plantation, Quarry No. 3, South side of State Route 16, 1.3 miles northeast east of Sparta, Sparta, Hancock County, GA
49 CFR 215.113 - Defective plain bearing wedge.
Code of Federal Regulations, 2011 CFR
2011-10-01
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Freight Car Components... car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not...
49 CFR 215.113 - Defective plain bearing wedge.
Code of Federal Regulations, 2014 CFR
2014-10-01
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Freight Car Components... car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not...
49 CFR 215.113 - Defective plain bearing wedge.
Code of Federal Regulations, 2010 CFR
2010-10-01
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Freight Car Components... car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not...
49 CFR 215.113 - Defective plain bearing wedge.
Code of Federal Regulations, 2013 CFR
2013-10-01
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Freight Car Components... car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not...
49 CFR 215.113 - Defective plain bearing wedge.
Code of Federal Regulations, 2012 CFR
2012-10-01
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Freight Car Components... car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not...
Propagation in an elastic wedge using the virtual source technique.
Abawi, Ahmad T; Porter, Michael B
2007-03-01
The virtual source technique, which is based on the boundary integral method, provides the means to impose boundary conditions on arbitrarily shaped boundaries by replacing them by a collection of sources whose amplitudes are determined from the boundary conditions. In this paper the virtual source technique is used to model propagation of waves in a range-dependent ocean overlying an elastic bottom with arbitrarily shaped ocean-bottom interface. The method is applied to propagation in an elastic Pekeris waveguide, an acoustic wedge, and an elastic wedge. In the case of propagation in an elastic Pekeris waveguide, the results agree very well with those obtained from the wavenumber integral technique, as they do with the solution of the parabolic equation (PE) technique in the case of propagation in an acoustic wedge. The results for propagation in an elastic wedge qualitatively agree with those obtained from an elastic PE solution. PMID:17407873
Wedge Heat-Flux Indicators for Flash Thermography
NASA Technical Reports Server (NTRS)
Koshti, Ajay M.
2003-01-01
Wedge indicators have been proposed for measuring thermal radiation that impinges on specimens illuminated by flash lamps for thermographic inspection. Heat fluxes measured by use of these indicators would be used, along with known thermal, radiative, and geometric properties of the specimens, to estimate peak flash temperatures on the specimen surfaces. These indicators would be inexpensive alternatives to high-speed infrared pyrometers, which would otherwise be needed for measuring peak flash surface temperatures. The wedge is made from any suitable homogenous material such as plastic. The choice of material is governed by the equation given. One side of the wedge is covered by a temperature sensitive compound that decomposes irreversibly when its temperature exceeds a rated temperature (T-rated). The uncoated side would be positioned alongside or in place of the specimen and exposed to the flash, then the wedge thickness at the boundary between the white and blackened portions measured.
The crack and wedging problem for an orthotropic strip
NASA Technical Reports Server (NTRS)
Cinar, A.; Erdogan, F.
1982-01-01
The plane elasticity problem for an orthotropic strip containing a crack parallel to its boundaries is considered. The problem is formulated under general mixed mode loading conditions. The stress intensity factors depend on two dimensionless orthotropic constants only. For the crack problem the results are given for a single crack and two collinear cracks. The calculated results show that of the two orthotropic constants the influence of the stiffness ratio on the stress intensity factors is much more significant than that of the shear parameter. The problem of loading the strip by a rigid rectangular lengths continuous contact is maintained along the wedge strip interface; at a certain critical wedge length the separation starts at the midsection of the wedge, and the length of the separation zone increases rapidly with increasing wedge length.
The crack and wedging problem for an orthotropic strip
NASA Technical Reports Server (NTRS)
Cinar, A.; Erdogan, F.
1983-01-01
The plane elasticity problem for an orthotropic strip containing a crack parallel to its boundaries is considered. The problem is formulated under general mixed mode loading conditions. The stress intensity factors depend on two dimensionless orthotropic constants only. For the crack problem the results are given for a single crack and two collinear cracks. The calculated results show that of the two orthotropic constants the influence of the stiffness ratio on the stress intensity factors is much more significant than that of the shear parameter. The problem of loading the strip by a rigid rectangular lengths continuous contact is maintained along the wedge strip interface; at a certain critical wedge length the separation starts at the midsection of the wedge, and the length of the separation zone increases rapidly with increasing wedge length. Previously announced in STAR as N82-26707
Stress singularities at the vertex of a cylindrically anisotropic wedge
NASA Technical Reports Server (NTRS)
Delale, F.; Erdogan, F.; Boduroglu, H.
1980-01-01
The plane elasticity problem for a cylindrically anisotropic solid is formulated. The form of the solution for an infinite wedge shaped domain with various homogeneous boundary conditions is derived and the nature of the stress singularity at the vertex of the wedge is studied. The characteristic equations giving the stress singularity and the angular distribution of the stresses around the vertex of the wedge are obtained for three standard homogeneous boundary conditions. The numerical examples show that the singular behavior of the stresses around the vertex of an anisotropic wedge may be significantly different from that of the isotropic material. Some of the results which may be of practical importance are that for a half plane the stress state at r = 0 may be singular and for a crack the power of stress singularity may be greater or less than 1/2.
Single-photon cooling in a wedge billiard
Choi, S.; Sundaram, B.; Raizen, M. G.
2010-09-15
Single-photon cooling (SPC), noted for its potential as a versatile method for cooling a variety of atomic species, has recently been demonstrated experimentally. In this paper, we study possible ways to improve the performance of SPC by applying it to atoms trapped inside a wedge billiard. The main feature of the wedge billiard for atoms, also experimentally realized recently, is that the nature of atomic trajectories within it changes from stable periodic orbit to random chaotic motion with the change in wedge angle. We find that a high cooling efficiency is possible in this system with a relatively weak dependence on the wedge angle and that chaotic dynamics, rather than a regular orbit, is more desirable for enhancing the performance of SPC.
Geophysical Surveys for Detecting Distribution and Shape of Ice Wedges
NASA Astrophysics Data System (ADS)
Watanabe, T.; Matsuoka, N.; Ikeda, A.
2006-12-01
Recent development of applied geophysical methods has shown detailed structure in various periglacial features. However, these methods have been rarely applied to studies in ice wedges. Thus, we attempted to display distribution and shape of ice wedges using a ground penetrating radar (GPR) and a direct current (DC) resistivity meter. The surveys were performed at a comprehensive monitoring site of ice-wedging in Adventdalen, Svalbard, where troughs and small cracks form polygonal patterns on the ground. Unknown structure below such new cracks is also focused in this study. We obtained 37 GPR profiles using 250 MHz signal. 2-D resistivity surveys were also performed along 14 GPR profiles. The electrodes were placed at 1 m intervals and their combination followed the Wenner array. In addition, shallow boreholes were dug across 5 troughs/cracks to estimate the width of ice wedge. The analyzed results show parabolic patterns formed by the multiple radar waveforms and largely increasing gradients of DC resistivity below the troughs and small cracks. The strong reflections of the radar signals and the starting zones of the increasing resistivity lay about 1 m deep, which corresponded to the top of ice wedges (0.7-0.9 m deep) revealed by the drilling. In the GPR profiles, a relatively flat pattern of the reflection was sandwiched by a pair of parabolic patterns below each well-developed trough, whereas a sharp parabolic pattern was detected below each small crack. These results mean that the presence of narrow ice wedges is detectable by the GPR method and the top of a parabolic pattern roughly corresponds to one edge of an ice wedge table. In the DC resistivity profiles, a high resistivity core exists below each trough and crack. The high resistivity probably resulted from ice having lower unfrozen water content than the surrounding silt materials. The heights of the cores indicate that the ice wedges were formed at least between 1 m and 3 m deep. The cores are, however
Seismicity of the forearc marginal wedge (accrertionary prism)
Chen, A.T.; Frohlich, C.; Latham, G.V.
1982-05-10
Three different types of seismic data have been examined for seismic events occurring within the zone called the accreted wedge or forearc marginal wedge that underlies the inner trench wall of some arcs. These types of data are (1) teleseismically recorded earthquakes that have been reported in the literature as occurring in major arc-trench regions; these events fail to demonstrate that earthquakes occur within the accreted wedge because the uncertainty of focal depth usually exceeds the depth dimension of the accreted wedge; these data include many tsunamigenic earthquakes, (2) local earthquakes located by combined ocean bottom seismograph and land networks in the arc-trench region in the New Hebrides and the central and eastern Aleutian Trench; none of the more reliable of these hypocenters lies within the accreted wedge; (3) S-P intervals measured at stations on islands located on the outer ridge or at ocean bottom seismograph stations on the forearc marginal wedge; these data do not show the existence of events occurring within the accreted wedge; e.g., from 18 ocean bottom seismograph stations with a cumulative operation time of about 1 year, the smallest S-P time is about 2.5 s for events in the New Hebrides and about 4 s for events in the Adak and Kodiak regions. We found no S-P time smaller than 2 s from 6 years of seismograms recorded at Middleton Island, Alaska, and no S-P time smaller than 4 s from 25 years of seismograms recorded on Barbados. All of the events could have occured outside the forearc marginal wedge.
Optical refractometry based on Fresnel diffraction from a phase wedge.
Tavassoly, M Taghi; Saber, Ahad
2010-11-01
A method that utilizes the Fresnel diffraction of light from the phase step formed by a transparent wedge is introduced for measuring the refractive indices of transparent solids, liquids, and solutions. It is shown that, as a transparent wedge of small apex angle is illuminated perpendicular to its surface by a monochromatic parallel beam of light, the Fresnel fringes, caused by abrupt change in refractive index at the wedge lateral boundary, are formed on a screen held perpendicular to the beam propagation direction. The visibility of the fringes varies periodically between zero and 1 in the direction normal to the wedge apex. For a known or measured apex angle, the wedge refractive index is obtained by measuring the period length by a CCD. To measure the refractive index of a transparent liquid or solution, the wedge is installed in a transparent rectangle cell containing the sample. Then, the cell is illuminated perpendicularly and the visibility period is measured. By using modest optics, one can measure the refractive index at a relative uncertainty level of 10(-5). There is no limitation on the refractive index range. The method can be applied easily with no mechanical manipulation. The measuring apparatus can be very compact with low mechanical and optical noises. PMID:21042389
Kumar, Rajesh; Kar, D C; Sharma, S D; Mayya, Y S
2012-01-01
A universal wedge filter of 15W × 20 cm(2) and 60° nominal wedge angle is designed and placed between the collimating jaws and penumbra trimmers inside the treatment head. A pneumatically driven actuating mechanism toggles the wedge between the wedge IN position and wedge OUT position. The effective wedge angles were determined using an analytical formula. An accumulated wedge profile at a depth of 10 cm which was measured using a 2D profiler and dose values at depths of 10 cm and 20 cm for the same experimental setup were used as input parameters in the formula used for determining effective wedge angles. The relationship between the wedge beam weight and effective wedge angle was established. The planned wedge angles were compared with the measured wedge angles and the differences are found to be less than 2° throughout the range of field sizes. Planned doses for various field sizes and wedge angles were measured for verification and the differences were found to be less than 1.8%. This study established that the relationship between the beam weights and effective wedge angles implemented for the motorized wedge filter of medical linacs is not directly applicable for the motorized wedge filter of Telecobalt. PMID:21486704
NASA Astrophysics Data System (ADS)
Santimano, Tasca; Rosenau, Matthias; Oncken, Onno
2015-06-01
Analogue models are not perfectly reproducible even under controlled boundary conditions which make their interpretation and application not always straight forward. As any scientific experiment they include some random component which can be influenced both by intrinsic (inherent processes) and extrinsic (boundary conditions, material properties) sources. In order to help in the assessment of analogue model results, we discriminate and quantify the intrinsic versus extrinsic variability of results from "sandbox" models of accretionary wedges that were repeated in a controlled environment. The extrinsic source of variability, i.e. the parameter varied is the nature of the décollement (material, friction and thickness). Experiment observables include geometric properties of the faults (lifetime, spacing, dip) as well as wedge geometry (height, slope, length). For each variable we calculated the coefficient of variance (CV) and quantified the variability as a symmetric distribution (Normal, Laplacian) or asymmetric distribution (Gamma) using a Chi squared test (χ2). Observables like fault dip/back thrust dip (CV = 0.6-0.7/0.2-0.6) are less variable and decrease in magnitude with decreasing basal friction. Variables that are time dependent like fault lifetime (CV = 0.19-0.56) and fault spacing (CV = 0.12 - 0.36) have a higher CV consequently affecting the variability of wedge slope (CV = 0.12-0.33). These observables also increase in magnitude with increasing basal friction. As the mechanical complexity of the evolving wedge increases over time so does the CV and asymmetry of the distribution. In addition, we confirm the repeatability of experiments using an ANOVA test. Through the statistical analysis of results from repeated experiments we present a tool to quantify variability and an alternative method to gaining better insights into the dynamic mechanics of deformation in analogue sand wedges.
Retroreflector spherical satellite
NASA Astrophysics Data System (ADS)
Akentyev, A. S.; Vasiliev, V. P.; Sadovnikov, M. A.; Sokolov, A. L.; Shargorodskiy, V. D.
2015-10-01
Specific features of spherical retroreflector arrays for high-precision laser ranging are considered, and errors in distance measurements are analyzed. A version of a glass retroreflector satellite with a submillimeter "target error" is proposed. Its corner cube reflectors are located in depressions to reduce the working angular aperture, and their faces have a dielectric interference coating.
Hollow spherical supramolecular dendrimers.
Percec, Virgil; Peterca, Mihai; Dulcey, Andrés E; Imam, Mohammad R; Hudson, Steven D; Nummelin, Sami; Adelman, Peter; Heiney, Paul A
2008-10-01
The synthesis of a library containing 12 conical dendrons that self-assemble into hollow spherical supramolecular dendrimers is reported. The design principles for this library were accessed by development of a method that allows the identification of hollow spheres, followed by structural and retrostructural analysis of their Pm3n cubic lattice. The first hollow spherical supramolecular dendrimer was made by replacing the tapered dendron, from the previously reported tapered dendritic dipeptide that self-assembled into helical pores, with its constitutional isomeric conical dendron. This strategy generated a conical dendritic dipeptide that self-assembled into a hollow spherical supramolecular dendrimer that self-organizes in a Pm3n cubic lattice. Other examples of hollow spheres were assembled from conical dendrons without a dipeptide at their apex. These are conical dendrons originated from tapered dendrons containing additional benzyl ether groups at their apex. The inner part of the hollow sphere assembled from the dipeptide resembles the path of a spherical helix or loxodrome and, therefore, is chiral. The spheres assembled from other conical dendrons are nonhelical, even when they contain stereocenters on the alkyl groups from their periphery. Functionalization of the apex of the conical dendrons with diethylene glycol allowed the encapsulation of LiOTf and RbOTf in the center of the hollow sphere. These experiments showed that hollow spheres function as supramolecular dendritic capsules and therefore are expected to display functions complementary to those of other related molecular and supramolecular structures. PMID:18771261
NASA Technical Reports Server (NTRS)
Hall, L. G.
1969-01-01
Radial focusing of electrons in ion source produces greater ion densities, resulting in higher resolution and focus capability for a given source volume. Electron beam is focused near exit aperture by spherical fields. High density ions allow focusing ion beam to high density at echo, allowing high current through small aperture.
NASA Technical Reports Server (NTRS)
Meyer, Jay L. (Inventor); Messick, Glenn C. (Inventor); Nardell, Carl A. (Inventor); Hendlin, Martin J. (Inventor)
2011-01-01
A spherical mounting assembly for mounting an optical element allows for rotational motion of an optical surface of the optical element only. In that regard, an optical surface of the optical element does not translate in any of the three perpendicular translational axes. More importantly, the assembly provides adjustment that may be independently controlled for each of the three mutually perpendicular rotational axes.
Rotating convection in elliptical geometries
NASA Astrophysics Data System (ADS)
Evonuk, M.
2014-12-01
Tidal interactions between hot jupiter planets and their host stars are likely to result in non-spherical geometries. These elliptical instabilities may have interesting effects on interior fluid convective patterns, which in turn influence the nature of the magnetic dynamo within these planets. Simulations of thermal convection in the 2D rotating equatorial plane are conducted to determine to first order the effect of ellipticity on convection for varying density contrasts with differing convective vigor and rotation rate. This survey is conducted in two dimensions in order to simulate a broad range of ellipticities and to maximize the parameter space explored.
Close packing of rods on spherical surfaces
NASA Astrophysics Data System (ADS)
Smallenburg, Frank; Löwen, Hartmut
2016-04-01
We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find a rich variety of cluster structures. For larger clusters, we find that the best-packed configurations up to around 100 particles are highly dependent on the exact number of particles and aspect ratio. For even larger clusters, we find largely disordered clusters for very short rods (L/D = 0.25), while slightly longer rods (L/D = 0.5 or 1) prefer a global baseball-like geometry of smectic-like domains, similar to the behavior of large-scale nematic shells. Intriguingly, we observe that when compared to their optimal flat-plane packing, short rods adapt to the spherical geometry more efficiently than both spheres and longer rods. Our results provide predictions for experimentally realizable systems of colloidal rods trapped at the interface of emulsion droplets.
Close packing of rods on spherical surfaces.
Smallenburg, Frank; Löwen, Hartmut
2016-04-28
We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find a rich variety of cluster structures. For larger clusters, we find that the best-packed configurations up to around 100 particles are highly dependent on the exact number of particles and aspect ratio. For even larger clusters, we find largely disordered clusters for very short rods (L/D = 0.25), while slightly longer rods (L/D = 0.5 or 1) prefer a global baseball-like geometry of smectic-like domains, similar to the behavior of large-scale nematic shells. Intriguingly, we observe that when compared to their optimal flat-plane packing, short rods adapt to the spherical geometry more efficiently than both spheres and longer rods. Our results provide predictions for experimentally realizable systems of colloidal rods trapped at the interface of emulsion droplets. PMID:27131565
Colloidal cholesteric liquid crystal in spherical confinement.
Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S; Lavrentovich, Oleg D; Kumacheva, Eugenia
2016-01-01
The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545
Colloidal cholesteric liquid crystal in spherical confinement
Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia
2016-01-01
The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545
Crack problems in cylindrical and spherical shells
NASA Technical Reports Server (NTRS)
Erdogan, F.
1976-01-01
Standard plate or shell theories were used as a starting point to study the fracture problems in thin-walled cylindrical and spherical shells, assuming that the plane of the crack is perpendicular to the surface of the sheet. Since recent studies have shown that local shell curvatures may have a rather considerable effect on the stress intensity factor, the crack problem was considered in conjunction with a shell rather than a plate theory. The material was assumed to be isotropic and homogeneous, so that approximate solutions may be obtained by approximating the local shell crack geometry with an ideal shell which has a solution, namely a spherical shell with a meridional crack, a cylindrical shell with a circumferential crack, or a cylindrical shell with an axial crack. A method of solution for the specially orthotropic shells containing a crack was described; symmetric and skew-symmetric problems are considered in cylindrical shells with an axial crack.
Frequency domain photothermal radiometry with spherical solids
Wang, Chinhua; Liu, Yue; Mandelis, Andreas; Shen, Jun
2007-04-15
Motivated by increasing practical and industrial applications of photothermal techniques in the measurement of materials of various shapes with curvature, we extend the applications of photothermal diagnostics to solid spheres, in which both theoretical and experimental photothermal radiometry studies on spherical geometries and thermal diffusivity of the sample are discussed. Based on the Green function method, a full thermal-wave field distribution of a spherical solid is obtained. The characteristics of the thermal-wave field with respect to thermophysical properties of the material, the diameter of the solid, the size of the incident laser beam, and the measurement angle are discussed. Experimental results with steel spheres of different diameters exhibit good agreement between the theory and the experiments.
Predicting orogenic wedge styles as a function of analogue erosion law and material softening
NASA Astrophysics Data System (ADS)
Mary, Baptiste C. L.; Maillot, Bertrand; Leroy, Yves M.
2013-10-01
The evolution of a compressive frictional wedge on a weak, frictional and planar décollement, subjected to frontal accretion, is predicted with a two step method called sequential limit analysis. The first step consists in finding, with the kinematic approach of limit analysis, the length of the active décollement and the dips of the emerging ramp and of the conjugate shear plane composing the emerging thrust fold. The second step leads to a modification of the geometry, first, because of the thrust fold development due to compression and, second, because of erosion. Erosion consists in removing periodically any material above a fictitious line at a selected slope, as done in analogue experiments. This application of sequential limit analysis generalizes the critical Coulomb wedge theory since it follows the internal deformation development. With constant frictional properties, the deformation is mostly diffuse, a succession of thrust folds being activated so that the topographic slope reaches exactly the theoretical, critical value. Frictional weakening on the ramps results in a deformation style composed of thrust sheets and horses. Applying an erosion slope at the critical topographic value leads to exhumation in the frontal, central, or rear region of the wedge depending on the erosion period and the weakening. Erosion at slopes slightly above or below the critical value results in exhumation toward the foreland or the hinterland, respectively, regardless of the erosion period. Exhumation is associated with duplexes, imbricate fans, antiformal stacks, and major backthrusting. Comparisons with sandbox experiments confirm that the thickness, dips, vergence, and exhumation of thrust sheets can be reproduced with friction and erosion parameters within realistic ranges of values.
NASA Astrophysics Data System (ADS)
Pollyea, R.; Van Dusen, E.; Fischer, M. P.
2014-12-01
In recent years, investigators have revisited the problem of basin-scale fluid flow with an emphasis on depth-dependent permeability, which is a frequently observed geological phenomenon that is seldom accounted for in basin-scale flow models. These recent investigations have shown that depth-dependent permeability at the basin scale strongly influences the relationship between sub-basin and regional-scale flow paths. Here, we revisit topography driven fluid flow within a foreland basin using a numerical modeling experiment designed to assess first-order fluid system behavior when permeability decreases systematically with depth. Critical taper theory is invoked to define two-dimensional basin geometry, and three sub-aerially exposed orogenic wedge models are presented with critical taper angles of 2°, 4°, and 10°. To assess the combined influence of topographic slope and depth-dependent permeability, a constant rate infiltration is applied at the wedge surface and a transient simulation is performed within each model for 500,000 years. Our results suggest that fluid system structure within the narrowly tapering orogenic wedge (2°) is explained by recent investigations applying depth-decaying permeability to the classic Tóth basin; however, increasing topographic slope beyond 3° results in a fundamentally different fluid system architecture. As topographic slope increases, fluid system structure is characterized by (1) dominant regional flow paths and little, if any, sub-basin scale fluid circulation, (2) shallow meteoric water penetration, (3) a stratified distribution of groundwater residence time without pronounced stagnation points. Moreover, for a given detachment slope, these effects become more pronounced as topographic gradient increases.
Using cyclic steps on drift wedges to amend established models of carbonate platform slopes
NASA Astrophysics Data System (ADS)
Betzler, Christian; Lindhorst, Sebastian; Eberli, Gregor; Reijmer, John; Lüdmann, Thomas
2015-04-01
Hydroacoustic and sedimentological data of the western flank of Great Bahama Bank and Cay Sal Bank document how the interplay of offbank sediment export, along-slope transport, and erosion together shape facies and thickness distribution of slope deposits. The integrated data set depicts the combined product of these processes and allows formulating a comprehensive model of a periplatform drift that significantly amends established models of carbonate platform slope facies distribution and geometry. The basinward thinning wedge of the periplatform drift at the foot of the escarpment of Great Bahama Bank displays along- and down-slope variations in sedimentary architecture. Sediments consist of periplatform ooze, i.e. carbonate mud and muddy carbonate sand, coarsening basinward. In zones of lower contour current speed, depth related facies belts develop. In the upper part of the periplatform drift wedge in a water depth of 180 to 300 m and slope angles of 6° - 9° the seafloor displays a smooth surface. Parasound data indicate that this facies is characterized by a parallel layering. Basinward, the slope shows a distinct break at which the seafloor inclination diminishes to 1° to 2°. Downslope of this break, the drift wedge has a 3 - 4 km wide pervasive cover of bedforms down to a water depth of around 500 m. The steep flanks and internal stratification of the wavy bedforms face upslope, indicating upstream migration; the bedforms therefore share all the characteristics of cyclic step sedimentation. This is the first description of cyclic step sedimentation patterns in carbonate slope depositional systems. This new slope sedimentation model aids in understanding the complexity of carbonate slope sedimentation models with facies belts perpendicular and parallel to the platform margin. The new model sharply contrasts with existing slope facies models in which facies belts are solely positioned parallel to the platform margin.
Seismic reflection images of the accretionary wedge of Costa Rica
Shipley, T.H.; Stoffa, P.L. ); McIntosh, K.; Silver, E.A. )
1990-05-01
The large-scale structure of modern accretionary wedges is known almost entirely from seismic reflection investigations using single or grids of two-dimensional profiles. The authors will report on the first three-dimensional seismic reflection data volume collected of a wedge. This data set covers a 9-km-wide {times} 22-km-long {times} 6-km-thick volume of the accretionary wedge just arcward of the Middle America Trench off Costa Rica. The three-dimensional processing has improved the imaging ability of the multichannel data, and the data volume allows mapping of structures from a few hundred meters to kilometers in size. These data illustrate the relationships between the basement, the wedge shape, and overlying slope sedimentary deposits. Reflections from within the wedge define the gross structural features and tectonic processes active along this particular convergent margin. So far, the analysis shows that the subdued basement relief (horst and graben structures seldom have relief of more than a few hundred meters off Costa Rica) does affect the larger scale through going structural features within the wedge. The distribution of mud volcanoes and amplitude anomalies associated with the large-scale wedge structures suggests that efficient fluid migration paths may extend from the top of the downgoing slab at the shelf edge out into the lower and middle slope region at a distance of 50-100 km. Offscraping of the uppermost (about 45 m) sediment occurs within 4 km of the trench, creating a small pile of sediments near the trench lower slope. Underplating of parts of the 400-m-thick subducted sedimentary section begins at a very shallow structural level, 4-10 km arcward of the trench. Volumetrically, the most important accretionary process is underplating.
Aligning Optical Fibers by Means of Actuated MEMS Wedges
NASA Technical Reports Server (NTRS)
Morgan, Brian; Ghodssi, Reza
2007-01-01
Microelectromechanical systems (MEMS) of a proposed type would be designed and fabricated to effect lateral and vertical alignment of optical fibers with respect to optical, electro-optical, optoelectronic, and/or photonic devices on integrated circuit chips and similar monolithic device structures. A MEMS device of this type would consist of a pair of oppositely sloped alignment wedges attached to linear actuators that would translate the wedges in the plane of a substrate, causing an optical fiber in contact with the sloping wedge surfaces to undergo various displacements parallel and perpendicular to the plane. In making it possible to accurately align optical fibers individually during the packaging stages of fabrication of the affected devices, this MEMS device would also make it possible to relax tolerances in other stages of fabrication, thereby potentially reducing costs and increasing yields. In a typical system according to the proposal (see Figure 1), one or more pair(s) of alignment wedges would be positioned to create a V groove in which an optical fiber would rest. The fiber would be clamped at a suitable distance from the wedges to create a cantilever with a slight bend to push the free end of the fiber gently to the bottom of the V groove. The wedges would be translated in the substrate plane by amounts Dx1 and Dx2, respectively, which would be chosen to move the fiber parallel to the plane by a desired amount Dx and perpendicular to the plane by a desired amount Dy. The actuators used to translate the wedges could be variants of electrostatic or thermal actuators that are common in MEMS.
Geometry of area without length
NASA Astrophysics Data System (ADS)
Ho, Pei-Ming; Inami, Takeo
2016-01-01
To define a free string by the Nambu-Goto action, all we need is the notion of area, and mathematically the area can be defined directly in the absence of a metric. Motivated by the possibility that string theory admits backgrounds where the notion of length is not well defined but a definition of area is given, we study space-time geometries based on the generalization of a metric to an area metric. In analogy with Riemannian geometry, we define the analogues of connections, curvatures, and Einstein tensor. We propose a formulation generalizing Einstein's theory that will be useful if at a certain stage or a certain scale the metric is ill defined and the space-time is better characterized by the notion of area. Static spherical solutions are found for the generalized Einstein equation in vacuum, including the Schwarzschild solution as a special case.
Du, Jun; Zheng, Guang-Ying; Wen, Cheng-Lin; Zhang, Xiao-Fang; Zhu, Yu
2016-01-01
AIM To evaluate the clinical value of wedge resection at corneal limbus in patients with traumatic corneal scarring and high irregular astigmatism. METHODS Patients with traumatic corneal astigmatism received wedge resection at least 6mo after suture removal from corneal wound. The uncorrected distance visual acuities (UCVA) and best corrected distance visual acuities (BCVA), pre- and post-operation astigmatism, spherical equivalent (SE), safety and complications were evaluated. RESULTS Ten eyes (10 patients) were enrolled in this study. Mean follow-up time after wedge resection was 37.8±15.4mo (range, 20-61mo). The mean UCVA improved from +1.07±0.55 logMAR to +0.43±0.22 logMAR (P=0.000) and the mean BCVA from +0.50±0.30 logMAR to +0.15±0.17 logMAR (P=0.000). The mean astigmatism power measured by retinoscopy was -2.03±2.27 D postoperatively and -2.83±4.52 D preoperatively (P=0.310). The mean SE was -0.74±1.61 D postoperatively and -0.64±1.89 D preoperatively (P=0.601). Two cases developed mild pannus near the sutures. No corneal perforation, infectious keratitis or wound gape occurred. CONCLUSION Corneal-scleral limbal wedge resection with compression suture is a safe, effective treatment for poor patients with high irregular corneal astigmatism after corneal-scleral penetrating injury. Retinoscopy can prove particularly useful for high irregular corneal astigmatism when other measurements are not amenable. PMID:27366685
ul Haq, Muhammad Noaman; Saeed, R.; Shah, Asif
2010-08-15
The propagation of ion acoustic shock waves in cylindrical and spherical geometries has been investigated. The plasma system consists of cold ions, Boltzmannian electrons and positrons. Spherical, cylindrical Korteweg-de Vries-Burger equations have been derived by reductive perturbation technique and their shock behavior is studied by employing finite difference method. Our main emphasis is on the behavior of shock as it moves toward and away from center of spherical and cylindrical geometries. It is noticed, that the shock wave strength and steepness accrues with time as it moves toward the center and shock enervates as it moves away from center. The strength of shock in spherical geometry is found to dominate over shock strength in cylindrical geometry. Positron concentration, kinematic viscosity are also found to have significant effect on the shock structure and propagation. The results may have relevance in the inertial confinement fusion plasmas.
Five questions to consider before conducting a stepped wedge trial.
Hargreaves, James R; Copas, Andrew J; Beard, Emma; Osrin, David; Lewis, James J; Davey, Calum; Thompson, Jennifer A; Baio, Gianluca; Fielding, Katherine L; Prost, Audrey
2015-01-01
Researchers should consider five questions before starting a stepped wedge trial. Why are you planning one? Researchers sometimes think that stepped wedge trials are useful when there is little doubt about the benefit of the intervention being tested. However, if the primary reason for an intervention is to measure its effect, without equipoise there is no ethical justification for delaying implementation in some clusters. By contrast, if you are undertaking pragmatic research, where the primary reason for rolling out the intervention is for it to exert its benefits, and if phased implementation is inevitable, a stepped wedge trial is a valid option and provides better evidence than most non-randomized evaluations. What design will you use? Two common stepped wedge designs are based on the recruitment of a closed or open cohort. In both, individuals may experience both control and intervention conditions and you should be concerned about carry-over effects. In a third, continuous-recruitment, short-exposure design, individuals are recruited as they become eligible and experience either control or intervention condition, but not both. How will you conduct the primary analysis? In stepped wedge trials, control of confounding factors through secular variation is essential. 'Vertical' approaches preserve randomization and compare outcomes between randomized groups within periods. 'Horizontal' approaches compare outcomes before and after crossover to the intervention condition. Most analysis models used in practice combine both types of comparison. The appropriate analytic strategy should be considered on a case-by-case basis. How large will your trial be? Standard sample size calculations for cluster randomized trials do not accommodate the specific features of stepped wedge trials. Methods exist for many stepped wedge designs, but simulation-based calculations provide the greatest flexibility. In some scenarios, such as when the intracluster correlation coefficient is
Spherical torus fusion reactor
Peng, Yueng-Kay M.
1989-04-04
A fusion reactor is provided having a near spherical-shaped plasma with a modest central opening through which straight segments of toroidal field coils extend that carry electrical current for generating a toroidal magnet plasma confinement fields. By retaining only the indispensable components inboard of the plasma torus, principally the cooled toroidal field conductors and in some cases a vacuum containment vessel wall, the fusion reactor features an exceptionally small aspect ratio (typically about 1.5), a naturally elongated plasma cross section without extensive field shaping, requires low strength magnetic containment fields, small size and high beta. These features combine to produce a spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost.
Spherical torus fusion reactor
Peng, Yueng-Kay M.
1989-01-01
A fusion reactor is provided having a near spherical-shaped plasma with a modest central opening through which straight segments of toroidal field coils extend that carry electrical current for generating a toroidal magnet plasma confinement fields. By retaining only the indispensable components inboard of the plasma torus, principally the cooled toroidal field conductors and in some cases a vacuum containment vessel wall, the fusion reactor features an exceptionally small aspect ratio (typically about 1.5), a naturally elongated plasma cross section without extensive field shaping, requires low strength magnetic containment fields, small size and high beta. These features combine to produce a spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost.
Recent progress on spherical torus research
NASA Astrophysics Data System (ADS)
Ono, Masayuki; Kaita, Robert
2015-04-01
The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ˜ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ˜ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.
Recent progress on spherical torus research
Ono, Masayuki; Kaita, Robert
2015-04-15
The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R{sub 0}/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.
Thrust wedges and fluid overpressures: Sandbox models involving pore fluids
NASA Astrophysics Data System (ADS)
Mourgues, R.; Cobbold, P. R.
2006-05-01
The well-known model for the critical taper of an accretionary wedge includes overpressure as a first-order parameter. Fluid overpressures reduce frictional resistance at the base of a wedge but they also act as body forces on all material particles of the wedge, in addition to that of gravity. By means of sandbox modeling, many workers have tried to verify the predictions of the critical taper model, but few of them have so far incorporated true fluid pressures. We have used scaled experiments, in which compressed air flows through sand packs, so as to model the deformation of overpressured wedges. A new apparatus provides for a horizontally varying fluid pressure, for example, a linear variation, as in the critical taper model. We have done three series of experiments, involving horizontal shortening of homogeneous or multilayered sand models for various gradients of fluid pressure. As predicted by the critical taper model, the apical angle of the resulting wedge depends on the overpressure gradient. In homogeneous sand at a high overpressure gradient, deformation becomes diffuse and looks ductile. In multilayered models, detachments form beneath layers of low permeability, so that thrusts propagate rapidly toward the undeformed foreland. The efficiency of a detachment and its ability to propagate depend not only on the fluid pressure but also on the permeability ratios between the various layers.
Polymer wedge for perfectly vertical light coupling to silicon
NASA Astrophysics Data System (ADS)
Schrauwen, J.; Scheerlinck, S.; Van Thourhout, D.; Baets, R.
2009-02-01
We present the design and fabrication of a refractive polymer wedge that allows perfectly vertical coupling of light into a silicon waveguide, which is of interest for flip-chip bonding of vertical cavity emitting light sources on a silicon integrated circuit. The structure includes a conventional diffractive grating coupler that requires off-normal incidence to avoid second order Bragg reflections. The polymer wedge is thus used to refract vertically impinging light into an off-normal wave that couples into the underlying grating. The fabrication involves two steps: mold fabrication and imprint replication. Firstly negative wedge-shaped craters are etched into a quartz mold by Focused-ion-beam milling. Secondly the mold is used to imprint a UV-curable polymer onto a silicon chip containing waveguides and grating couplers, and so replicating the wedges. The characterization setup consisted of a fiber-to-fiber transmission measurement of a silicon waveguide equipped with a pair of grating couplers and polymer wedges. The obtained fiber coupling efficiency was equal to the efficiency of regular grating couplers and fiber positioned at an off-normal angle. The proposed fabrication method enables low cost integration of vertical cavity emitting light sources on silicon integrated photonic circuits.
Diffusion induced flow on a wedge-shaped obstacle
NASA Astrophysics Data System (ADS)
Zagumennyi, Ia V.; Dimitrieva, N. F.
2016-08-01
In this paper the problem of evolution of diffusion induced flow on a wedge-shaped obstacle is analyzed numerically. The governing set of fundamental equations is solved using original solvers from the open source OpenFOAM package on supercomputer facilities. Due to breaking of naturally existing diffusion flux of a stratifying agent by the impermeable surface of the wedge a complex multi-level vortex system of compensatory fluid motions is formed around the obstacle. Sharp edges of the obstacle generate extended high-gradient horizontal interfaces which are clearly observed in laboratory experiments by high-resolution Schlieren visualization. Formation of an intensive pressure depression zone in front of the leading vertex of the wedge is responsible for generation of propulsive force resulting in a self-displacement of the obstacle along the neutral buoyancy horizon in a stably stratified environment. The size of the pressure deficiency area near the sharp vertex of a concave wedge is about twice that for a convex one. This demonstrates a more intensive propulsion mechanism in case of the concave wedge and, accordingly, a higher velocity of its self-movement in a continuously stratified medium.
Density functional study of complete, first-order and critical wedge filling transitions.
Malijevský, Alexandr; Parry, Andrew O
2013-07-31
We present numerical studies of complete, first-order and critical wedge filling transitions, at a right angle corner, using a microscopic fundamental measure density functional theory. We consider systems with short-ranged, cut-off Lennard-Jones, fluid-fluid forces and two types of wall-fluid potential: a purely repulsive hard wall and also a long-ranged potential with three different strengths. For each of these systems we first determine the wetting properties occurring at a planar wall, including any wetting transition and the dependence of the contact angle on temperature. The hard wall corner is completely filled by vapour on approaching bulk coexistence and the numerical results for the growth of the meniscus thickness are in excellent agreement with effective Hamiltonian predictions for the critical exponents and amplitudes, at leading and next-to-leading order. In the presence of the attractive wall-fluid interaction, the corresponding planar wall-fluid interface exhibits a first-order wetting transition for each of the interaction strengths considered. In the right angle wedge geometry the two strongest interactions produce first-order filling transitions while for the weakest interaction strength, for which wetting and filling occur closest to the bulk critical point, the filling transition is second-order. For this continuous transition the critical exponent describing the divergence of the meniscus thickness is found to be in good agreement with effective Hamiltonian predictions. PMID:23836779
Spherical nitroguandine process
Sanchez, J.A.; Roemer, E.L.; Stretz, L.A.
1990-10-30
A process of preparing spherical high bulk density nitroguanidine by dissolving low bulk density nitroguanidine in N-methyl pyrrolidone at elevated temperatures and then cooling the solution to lower temperatures as a liquid characterized as a nonsolvent for the nitroguanidine is presented. The process is enhanced by inclusion in the solution of from about 1 ppm up to about 250 ppm of a metal salt such as nickel nitrate, zinc nitrate or chromium nitrate, preferably from about 20 to about 50 ppm.
Spherical nitroguanidine process
Sanchez, John A.; Roemer, Edward L.; Stretz, Lawrence A.
1990-01-01
A process of preparing spherical high bulk density nitroguanidine by dissing low bulk density nitroguanidine in N-methyl pyrrolidone at elevated temperatures and then cooling the solution to lower temperatures as a liquid characterized as a nonsolvent for the nitroguanidine is provided. The process is enhanced by inclusion in the solution of from about 1 ppm up to about 250 ppm of a metal salt such as nickel nitrate, zinc nitrate or chromium nitrate, preferably from about 20 to about 50 ppm.
2D and 3D numerical models on compositionally buoyant diapirs in the mantle wedge
NASA Astrophysics Data System (ADS)
Hasenclever, Jörg; Morgan, Jason Phipps; Hort, Matthias; Rüpke, Lars H.
2011-11-01
We present 2D and 3D numerical model calculations that focus on the physics of compositionally buoyant diapirs rising within a mantle wedge corner flow. Compositional buoyancy is assumed to arise from slab dehydration during which water-rich volatiles enter the mantle wedge and form a wet, less dense boundary layer on top of the slab. Slab dehydration is prescribed to occur in the 80-180 km deep slab interval, and the water transport is treated as a diffusion-like process. In this study, the mantle's rheology is modeled as being isoviscous for the benefit of easier-to-interpret feedbacks between water migration and buoyant viscous flow of the mantle. We use a simple subduction geometry that does not change during the numerical calculation. In a large set of 2D calculations we have identified that five different flow regimes can form, in which the position, number, and formation time of the diapirs vary as a function of four parameters: subduction angle, subduction rate, water diffusivity (mobility), and mantle viscosity. Using the same numerical method and numerical resolution we also conducted a suite of 3D calculations for 16 selected parameter combinations. Comparing the 2D and 3D results for the same model parameters reveals that the 2D models can only give limited insights into the inherently 3D problem of mantle wedge diapirism. While often correctly predicting the position and onset time of the first diapir(s), the 2D models fail to capture the dynamics of diapir ascent as well as the formation of secondary diapirs that result from boundary layer perturbations caused by previous diapirs. Of greatest importance for physically correct results is the numerical resolution in the region where diapirs nucleate, which must be high enough to accurately capture the growth of the thin wet boundary layer on top of the slab and, subsequently, the formation, morphology, and ascent of diapirs. Here 2D models can be very useful to quantify the required resolution, which we
Single crystal metal wedges for surface acoustic wave propagation
Fisher, Edward S.
1982-01-01
An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.
Reverse wedge osteotomy of the distal radius in Madelung's deformity.
Mallard, F; Jeudy, J; Rabarin, F; Raimbeau, G; Fouque, P-A; Cesari, B; Bizot, P; Saint-Cast, Y
2013-06-01
Madelung's deformity results from a growth defect in the palmar and ulnar region of the distal radius. It presents as an excessively inclined radial joint surface, inducing "spontaneous progressive palmar subluxation of the wrist". The principle of reverse wedge osteotomy (RWO) consists in the reorientation of the radial joint surface by taking a circumferential bone wedge, the base of which is harvested from the excess of the radial and dorsal cortical bone of the distal radius, then turning it over and putting back this reverse wedge into the osteotomy so as to obtain closure on the excess and opening on the deficient cortical bone. RWO corrects the palmar subluxation of the carpus and improves distal radio-ulnar alignment. All five bilaterally operated patients were satisfied, esthetically and functionally. Its corrective power gives RWO a place apart among the surgical techniques currently available in Madelung's deformity. PMID:23622863
Single crystal metal wedges for surface acoustic wave propagation
Fisher, E.S.
1980-05-09
An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.