Moon-based Earth Observation for Large Scale Geoscience Phenomena

NASA Astrophysics Data System (ADS)

Guo, Huadong; Liu, Guang; Ding, Yixing

2016-07-01

The capability of Earth observation for large-global-scale natural phenomena needs to be improved and new observing platform are expected. We have studied the concept of Moon as an Earth observation in these years. Comparing with manmade satellite platform, Moon-based Earth observation can obtain multi-spherical, full-band, active and passive information,which is of following advantages: large observation range, variable view angle, long-term continuous observation, extra-long life cycle, with the characteristics of longevity ,consistency, integrity, stability and uniqueness. Moon-based Earth observation is suitable for monitoring the large scale geoscience phenomena including large scale atmosphere change, large scale ocean change,large scale land surface dynamic change,solid earth dynamic change,etc. For the purpose of establishing a Moon-based Earth observation platform, we already have a plan to study the five aspects as follows: mechanism and models of moon-based observing earth sciences macroscopic phenomena; sensors' parameters optimization and methods of moon-based Earth observation; site selection and environment of moon-based Earth observation; Moon-based Earth observation platform; and Moon-based Earth observation fundamental scientific framework.

Experiments on Thermal Convection in Rotating Spherical Shells With Radial Gravity: The Geophysical Fluid Flow Cell

NASA Technical Reports Server (NTRS)

Hart, John E.

1996-01-01

Experiments designed to study the fluid dynamics of buoyancy driven circulations in rotating spherical shells were conducted on the United States Microgravity Laboratory 2 spacelab mission. These experiments address several aspects of prototypical global convection relevant to large scale motions on the Sun, Earth, and on the giant planets. The key feature is the consistent modeling of radially directed gravity in spherical geometry by using dielectric polarization forces. Imagery of the planforms of thermally driven flows for rapidly-rotating regimes shows an initial separation and eventual merger of equatorial and polar convection as the heating (i.e. the Rayleigh number) is increased. At low rotation rates, multiple-states of motion for the same external parameters were observed.

Non-Gaussianity and Excursion Set Theory: Halo Bias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adshead, Peter; Baxter, Eric J.; Dodelson, Scott

2012-09-01

We study the impact of primordial non-Gaussianity generated during inflation on the bias of halos using excursion set theory. We recapture the familiar result that the bias scales asmore » $$k^{-2}$$ on large scales for local type non-Gaussianity but explicitly identify the approximations that go into this conclusion and the corrections to it. We solve the more complicated problem of non-spherical halos, for which the collapse threshold is scale dependent.« less

Large-Scale periodic solar velocities: An observational study

NASA Technical Reports Server (NTRS)

Dittmer, P. H.

1977-01-01

Observations of large-scale solar velocities were made using the mean field telescope and Babcock magnetograph of the Stanford Solar Observatory. Observations were made in the magnetically insensitive ion line at 5124 A, with light from the center (limb) of the disk right (left) circularly polarized, so that the magnetograph measures the difference in wavelength between center and limb. Computer calculations are made of the wavelength difference produced by global pulsations for spherical harmonics up to second order and of the signal produced by displacing the solar image relative to polarizing optics or diffraction grating.

Thermodynamic properties and static structure factor for a Yukawa fluid in the mean spherical approximation.

PubMed

Montes-Perez, J; Cruz-Vera, A; Herrera, J N

2011-12-01

This work presents the full analytic expressions for the thermodynamic properties and the static structure factor for a hard sphere plus 1-Yukawa fluid within the mean spherical approximation. To obtain these properties of the fluid type Yukawa analytically it was necessary to solve an equation of fourth order for the scaling parameter on a large scale. The physical root of this equation was determined by imposing physical conditions. The results of this work are obtained from seminal papers of Blum and Høye. We show that is not necessary the use the series expansion to solve the equation for the scaling parameter. We applied our theoretical result to find the thermodynamic and the static structure factor for krypton. Our results are in good agreement with those obtained in an experimental form or by simulation using the Monte Carlo method.

Spherical Harmonics Reveal Standing EEG Waves and Long-Range Neural Synchronization during Non-REM Sleep.

PubMed

Sivakumar, Siddharth S; Namath, Amalia G; Galán, Roberto F

2016-01-01

Previous work from our lab has demonstrated how the connectivity of brain circuits constrains the repertoire of activity patterns that those circuits can display. Specifically, we have shown that the principal components of spontaneous neural activity are uniquely determined by the underlying circuit connections, and that although the principal components do not uniquely resolve the circuit structure, they do reveal important features about it. Expanding upon this framework on a larger scale of neural dynamics, we have analyzed EEG data recorded with the standard 10-20 electrode system from 41 neurologically normal children and adolescents during stage 2, non-REM sleep. We show that the principal components of EEG spindles, or sigma waves (10-16 Hz), reveal non-propagating, standing waves in the form of spherical harmonics. We mathematically demonstrate that standing EEG waves exist when the spatial covariance and the Laplacian operator on the head's surface commute. This in turn implies that the covariance between two EEG channels decreases as the inverse of their relative distance; a relationship that we corroborate with empirical data. Using volume conduction theory, we then demonstrate that superficial current sources are more synchronized at larger distances, and determine the characteristic length of large-scale neural synchronization as 1.31 times the head radius, on average. Moreover, consistent with the hypothesis that EEG spindles are driven by thalamo-cortical rather than cortico-cortical loops, we also show that 8 additional patients with hypoplasia or complete agenesis of the corpus callosum, i.e., with deficient or no connectivity between cortical hemispheres, similarly exhibit standing EEG waves in the form of spherical harmonics. We conclude that spherical harmonics are a hallmark of spontaneous, large-scale synchronization of neural activity in the brain, which are associated with unconscious, light sleep. The analogy with spherical harmonics in quantum mechanics suggests that the variances (eigenvalues) of the principal components follow a Boltzmann distribution, or equivalently, that standing waves are in a sort of "thermodynamic" equilibrium during non-REM sleep. By extension, we speculate that consciousness emerges as the brain dynamics deviate from such equilibrium.

Spherical Harmonics Reveal Standing EEG Waves and Long-Range Neural Synchronization during Non-REM Sleep

PubMed Central

Sivakumar, Siddharth S.; Namath, Amalia G.; Galán, Roberto F.

2016-01-01

Previous work from our lab has demonstrated how the connectivity of brain circuits constrains the repertoire of activity patterns that those circuits can display. Specifically, we have shown that the principal components of spontaneous neural activity are uniquely determined by the underlying circuit connections, and that although the principal components do not uniquely resolve the circuit structure, they do reveal important features about it. Expanding upon this framework on a larger scale of neural dynamics, we have analyzed EEG data recorded with the standard 10–20 electrode system from 41 neurologically normal children and adolescents during stage 2, non-REM sleep. We show that the principal components of EEG spindles, or sigma waves (10–16 Hz), reveal non-propagating, standing waves in the form of spherical harmonics. We mathematically demonstrate that standing EEG waves exist when the spatial covariance and the Laplacian operator on the head's surface commute. This in turn implies that the covariance between two EEG channels decreases as the inverse of their relative distance; a relationship that we corroborate with empirical data. Using volume conduction theory, we then demonstrate that superficial current sources are more synchronized at larger distances, and determine the characteristic length of large-scale neural synchronization as 1.31 times the head radius, on average. Moreover, consistent with the hypothesis that EEG spindles are driven by thalamo-cortical rather than cortico-cortical loops, we also show that 8 additional patients with hypoplasia or complete agenesis of the corpus callosum, i.e., with deficient or no connectivity between cortical hemispheres, similarly exhibit standing EEG waves in the form of spherical harmonics. We conclude that spherical harmonics are a hallmark of spontaneous, large-scale synchronization of neural activity in the brain, which are associated with unconscious, light sleep. The analogy with spherical harmonics in quantum mechanics suggests that the variances (eigenvalues) of the principal components follow a Boltzmann distribution, or equivalently, that standing waves are in a sort of “thermodynamic” equilibrium during non-REM sleep. By extension, we speculate that consciousness emerges as the brain dynamics deviate from such equilibrium. PMID:27445777

Spherical-shell boundaries for two-dimensional compressible convection in a star

NASA Astrophysics Data System (ADS)

Pratt, J.; Baraffe, I.; Goffrey, T.; Geroux, C.; Viallet, M.; Folini, D.; Constantino, T.; Popov, M.; Walder, R.

2016-10-01

Context. Studies of stellar convection typically use a spherical-shell geometry. The radial extent of the shell and the boundary conditions applied are based on the model of the star investigated. We study the impact of different two-dimensional spherical shells on compressible convection. Realistic profiles for density and temperature from an established one-dimensional stellar evolution code are used to produce a model of a large stellar convection zone representative of a young low-mass star, like our sun at 106 years of age. Aims: We analyze how the radial extent of the spherical shell changes the convective dynamics that result in the deep interior of the young sun model, far from the surface. In the near-surface layers, simple small-scale convection develops from the profiles of temperature and density. A central radiative zone below the convection zone provides a lower boundary on the convection zone. The inclusion of either of these physically distinct layers in the spherical shell can potentially affect the characteristics of deep convection. Methods: We perform hydrodynamic implicit large eddy simulations of compressible convection using the MUltidimensional Stellar Implicit Code (MUSIC). Because MUSIC has been designed to use realistic stellar models produced from one-dimensional stellar evolution calculations, MUSIC simulations are capable of seamlessly modeling a whole star. Simulations in two-dimensional spherical shells that have different radial extents are performed over tens or even hundreds of convective turnover times, permitting the collection of well-converged statistics. Results: To measure the impact of the spherical-shell geometry and our treatment of boundaries, we evaluate basic statistics of the convective turnover time, the convective velocity, and the overshooting layer. These quantities are selected for their relevance to one-dimensional stellar evolution calculations, so that our results are focused toward studies exploiting the so-called 321D link. We find that the inclusion in the spherical shell of the boundary between the radiative and convection zones decreases the amplitude of convective velocities in the convection zone. The inclusion of near-surface layers in the spherical shell can increase the amplitude of convective velocities, although the radial structure of the velocity profile established by deep convection is unchanged. The impact of including the near-surface layers depends on the speed and structure of small-scale convection in the near-surface layers. Larger convective velocities in the convection zone result in a commensurate increase in the overshooting layer width and a decrease in the convective turnover time. These results provide support for non-local aspects of convection.

The NASA/MSFC global reference atmospheric model: MOD 3 (with spherical harmonic wind model)

NASA Technical Reports Server (NTRS)

Justus, C. G.; Fletcher, G. R.; Gramling, F. E.; Pace, W. B.

1980-01-01

Improvements to the global reference atmospheric model are described. The basic model includes monthly mean values of pressure, density, temperature, and geostrophic winds, as well as quasi-biennial and small and large scale random perturbations. A spherical harmonic wind model for the 25 to 90 km height range is included. Below 25 km and above 90 km, the GRAM program uses the geostrophic wind equations and pressure data to compute the mean wind. In the altitudes where the geostrophic wind relations are used, an interpolation scheme is employed for estimating winds at low latitudes where the geostrophic wind relations being to mesh down. Several sample wind profiles are given, as computed by the spherical harmonic model. User and programmer manuals are presented.

The Geophysical Fluid Flow Cell Experiment

NASA Technical Reports Server (NTRS)

Hart, J. E.; Ohlsen, D.; Kittleman, S.; Borhani, N.; Leslie, F.; Miller, T.

1999-01-01

The Geophysical Fluid Flow Cell (GFFC) experiment performed visualizations of thermal convection in a rotating differentially heated spherical shell of fluid. In these experiments dielectric polarization forces are used to generate a radially directed buoyancy force. This enables the laboratory simulation of a number of geophysically and astrophysically important situations in which sphericity and rotation both impose strong constraints on global scale fluid motions. During USML-2 a large set of experiments with spherically symmetric heating were carried out. These enabled the determination of critical points for the transition to various forms of nonaxisymmetric convection and, for highly turbulent flows, the transition latitudes separating the different modes of motion. This paper presents a first analysis of these experiments as well as data on the general performance of the instrument during the USML-2 flight.

Self-similar dynamic converging shocks - I. An isothermal gas sphere with self-gravity

NASA Astrophysics Data System (ADS)

Lou, Yu-Qing; Shi, Chun-Hui

2014-07-01

We explore novel self-similar dynamic evolution of converging spherical shocks in a self-gravitating isothermal gas under conceivable astrophysical situations. The construction of such converging shocks involves a time-reversal operation on feasible flow profiles in self-similar expansion with a proper care for the increasing direction of the specific entropy. Pioneered by Guderley since 1942 but without self-gravity so far, self-similar converging shocks are important for implosion processes in aerodynamics, combustion, and inertial fusion. Self-gravity necessarily plays a key role for grossly spherical structures in very broad contexts of astrophysics and cosmology, such as planets, stars, molecular clouds (cores), compact objects, planetary nebulae, supernovae, gamma-ray bursts, supernova remnants, globular clusters, galactic bulges, elliptical galaxies, clusters of galaxies as well as relatively hollow cavity or bubble structures on diverse spatial and temporal scales. Large-scale dynamic flows associated with such quasi-spherical systems (including collapses, accretions, fall-backs, winds and outflows, explosions, etc.) in their initiation, formation, and evolution are likely encounter converging spherical shocks at times. Our formalism lays an important theoretical basis for pertinent astrophysical and cosmological applications of various converging shock solutions and for developing and calibrating numerical codes. As examples, we describe converging shock triggered star formation, supernova explosions, and void collapses.

Extended general relativity: Large-scale antigravity and short-scale gravity with ω=-1 from five-dimensional vacuum

NASA Astrophysics Data System (ADS)

Madriz Aguilar, José Edgar; Bellini, Mauricio

2009-08-01

Considering a five-dimensional (5D) Riemannian spacetime with a particular stationary Ricci-flat metric, we obtain in the framework of the induced matter theory an effective 4D static and spherically symmetric metric which give us ordinary gravitational solutions on small (planetary and astrophysical) scales, but repulsive (anti gravitational) forces on very large (cosmological) scales with ω=-1. Our approach is an unified manner to describe dark energy, dark matter and ordinary matter. We illustrate the theory with two examples, the solar system and the great attractor. From the geometrical point of view, these results follow from the assumption that exists a confining force that make possible that test particles move on a given 4D hypersurface.

Spherical collapse in chameleon models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brax, Ph.; Rosenfeld, R.; Steer, D.A., E-mail: brax@spht.saclay.cea.fr, E-mail: rosenfel@ift.unesp.br, E-mail: daniele.steer@apc.univ-paris7.fr

2010-08-01

We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in themore » presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity.« less

Colloidal core-seeded semiconductor nanorods as fluorescent labels for in-vitro diagnostics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chan, YinThai

2016-03-01

Colloidal semiconductor nanocrystals are ideal fluorophores for clinical diagnostics, therapeutics, and highly sensitive biochip applications due to their high photostability, size-tunable color of emission and flexible surface chemistry. The relatively recent development of core-seeded semiconductor nanorods showed that the presence of a rod-like shell can confer even more advantageous physicochemical properties than their spherical counterparts, such as large multi-photon absorption cross-sections and facet-specific chemistry that can be exploited to deposit secondary nanoparticles. It may be envisaged that these highly fluorescent nanorods can be integrated with large scale integrated (LSI) microfluidic systems that allow miniaturization and integration of multiple biochemical processes in a single device at the nanoliter scale, resulting in a highly sensitive and automated detection platform. In this talk, I will describe a LSI microfluidic device that integrates RNA extraction, reverse transcription to cDNA, amplification and target pull-down to detect histidine decarboxylase (HDC) gene directly from human white blood cells samples. When anisotropic colloidal semiconductor nanorods (NRs) were used as the fluorescent readout, the detection limit was found to be 0.4 ng of total RNA, which was much lower than that obtained using spherical quantum dots (QDs) or organic dyes. This was attributed to the large action cross-section of NRs and their high probability of target capture in a pull-down detection scheme. The combination of large scale integrated microfluidics with highly fluorescent semiconductor NRs may find widespread utility in point-of-care devices and multi-target diagnostics.

Self-similar perturbations of a Friedmann universe

NASA Technical Reports Server (NTRS)

Carr, Bernard J.; Yahil, Amos

1990-01-01

The present analysis of spherically symmetric self-similar solutions to the Einstein equations gives attention to those solutions that are asymptotically k = 0 Friedmann at large z values, and possess finite but perturbed density at the origin. Such solutions represent nonlinear density fluctuations which grow at the same rate as the universe's particle horizon. The overdense solutions span only a narrow range of parameters, and resemble static isothermal gas spheres just within the sonic point; the underdense solutions may have arbitrarily low density at the origin while exhibiting a unique relationship between amplitude and scale. Their relevance to large-scale void formation is considered.

Large-scale deformed QRPA calculations of the gamma-ray strength function based on a Gogny force

NASA Astrophysics Data System (ADS)

Martini, M.; Goriely, S.; Hilaire, S.; Péru, S.; Minato, F.

2016-01-01

The dipole excitations of nuclei play an important role in nuclear astrophysics processes in connection with the photoabsorption and the radiative neutron capture that take place in stellar environment. We present here the results of a large-scale axially-symmetric deformed QRPA calculation of the γ-ray strength function based on the finite-range Gogny force. The newly determined γ-ray strength is compared with experimental photoabsorption data for spherical as well as deformed nuclei. Predictions of γ-ray strength functions and Maxwellian-averaged neutron capture rates for Sn isotopes are also discussed.

Generation of dense granular deposits for porosity analysis: assessment and application of large-scale non-smooth granular dynamics

NASA Astrophysics Data System (ADS)

Schruff, T.; Liang, R.; Rüde, U.; Schüttrumpf, H.; Frings, R. M.

2018-01-01

The knowledge of structural properties of granular materials such as porosity is highly important in many application-oriented and scientific fields. In this paper we present new results of computer-based packing simulations where we use the non-smooth granular dynamics (NSGD) method to simulate gravitational random dense packing of spherical particles with various particle size distributions and two types of depositional conditions. A bin packing scenario was used to compare simulation results to laboratory porosity measurements and to quantify the sensitivity of the NSGD regarding critical simulation parameters such as time step size. The results of the bin packing simulations agree well with laboratory measurements across all particle size distributions with all absolute errors below 1%. A large-scale packing scenario with periodic side walls was used to simulate the packing of up to 855,600 spherical particles with various particle size distributions (PSD). Simulation outcomes are used to quantify the effect of particle-domain-size ratio on the packing compaction. A simple correction model, based on the coordination number, is employed to compensate for this effect on the porosity and to determine the relationship between PSD and porosity. Promising accuracy and stability results paired with excellent computational performance recommend the application of NSGD for large-scale packing simulations, e.g. to further enhance the generation of representative granular deposits.

Spherical harmonics analysis of surface density fluctuations of spherical ionic SDS and nonionic C12E8 micelles: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Yoshii, Noriyuki; Nimura, Yuki; Fujimoto, Kazushi; Okazaki, Susumu

2017-07-01

The surface structure and its fluctuation of spherical micelles were investigated using a series of density correlation functions newly defined by spherical harmonics and Legendre polynomials based on the molecular dynamics calculations. To investigate the influence of head-group charges on the micelle surface structure, ionic sodium dodecyl sulfate and nonionic octaethyleneglycol monododecylether (C12E8) micelles were investigated as model systems. Large-scale density fluctuations were observed for both micelles in the calculated surface static structure factor. The area compressibility of the micelle surface evaluated by the surface static structure factor was tens-of-times larger than a typical value of a lipid membrane surface. The structural relaxation time, which was evaluated from the surface intermediate scattering function, indicates that the relaxation mechanism of the long-range surface structure can be well described by the hydrostatic approximation. The density fluctuation on the two-dimensional micelle surface has similar characteristics to that of three-dimensional fluids near the critical point.

Spherical harmonics analysis of surface density fluctuations of spherical ionic SDS and nonionic C12E8 micelles: A molecular dynamics study.

PubMed

Yoshii, Noriyuki; Nimura, Yuki; Fujimoto, Kazushi; Okazaki, Susumu

2017-07-21

The surface structure and its fluctuation of spherical micelles were investigated using a series of density correlation functions newly defined by spherical harmonics and Legendre polynomials based on the molecular dynamics calculations. To investigate the influence of head-group charges on the micelle surface structure, ionic sodium dodecyl sulfate and nonionic octaethyleneglycol monododecylether (C 12 E 8 ) micelles were investigated as model systems. Large-scale density fluctuations were observed for both micelles in the calculated surface static structure factor. The area compressibility of the micelle surface evaluated by the surface static structure factor was tens-of-times larger than a typical value of a lipid membrane surface. The structural relaxation time, which was evaluated from the surface intermediate scattering function, indicates that the relaxation mechanism of the long-range surface structure can be well described by the hydrostatic approximation. The density fluctuation on the two-dimensional micelle surface has similar characteristics to that of three-dimensional fluids near the critical point.

Tests and applications of nonlinear force-free field extrapolations in spherical geometry

NASA Astrophysics Data System (ADS)

Guo, Y.; Ding, M. D.

2013-07-01

We test a nonlinear force-free field (NLFFF) optimization code in spherical geometry with an analytical solution from Low and Lou. The potential field source surface (PFSS) model is served as the initial and boundary conditions where observed data are not available. The analytical solution can be well recovered if the boundary and initial conditions are properly handled. Next, we discuss the preprocessing procedure for the noisy bottom boundary data, and find that preprocessing is necessary for NLFFF extrapolations when we use the observed photospheric magnetic field as bottom boundaries. Finally, we apply the NLFFF model to a solar area where four active regions interacting with each other. An M8.7 flare occurred in one active region. NLFFF modeling in spherical geometry simultaneously constructs the small and large scale magnetic field configurations better than the PFSS model does.

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.

Large Eddy Simulation of a Turbulent Jet

NASA Technical Reports Server (NTRS)

Webb, A. T.; Mansour, Nagi N.

2001-01-01

Here we present the results of a Large Eddy Simulation of a non-buoyant jet issuing from a circular orifice in a wall, and developing in neutral surroundings. The effects of the subgrid scales on the large eddies have been modeled with the dynamic large eddy simulation model applied to the fully 3D domain in spherical coordinates. The simulation captures the unsteady motions of the large-scales within the jet as well as the laminar motions in the entrainment region surrounding the jet. The computed time-averaged statistics (mean velocity, concentration, and turbulence parameters) compare well with laboratory data without invoking an empirical entrainment coefficient as employed by line integral models. The use of the large eddy simulation technique allows examination of unsteady and inhomogeneous features such as the evolution of eddies and the details of the entrainment process.

The Numerical Studies Program for the Atmospheric General Circulation Experiment (AGCE) for Spacelab Flights

NASA Technical Reports Server (NTRS)

Fowlis, W. W. (Editor); Davis, M. H. (Editor)

1981-01-01

The atmospheric general circulation experiment (AGCE) numerical design for Spacelab flights was studied. A spherical baroclinic flow experiment which models the large scale circulations of the Earth's atmosphere was proposed. Gravity is simulated by a radial dielectric body force. The major objective of the AGCE is to study nonlinear baroclinic wave flows in spherical geometry. Numerical models must be developed which accurately predict the basic axisymmetric states and the stability of nonlinear baroclinic wave flows. A three dimensional, fully nonlinear, numerical model and the AGCE based on the complete set of equations is required. Progress in the AGCE numerical design studies program is reported.

Tailoring the chirality of light emission with spherical Si-based antennas.

PubMed

Zambrana-Puyalto, Xavier; Bonod, Nicolas

2016-05-21

Chirality of light is of fundamental importance in several enabling technologies with growing applications in life sciences, chemistry and photodetection. Recently, some attention has been focused on chiral quantum emitters. Consequently, optical antennas which are able to tailor the chirality of light emission are needed. Spherical nanoresonators such as colloids are of particular interest to design optical antennas since they can be synthesized at a large scale and they exhibit good optical properties. Here, we show that these colloids can be used to tailor the chirality of a chiral emitter. To this purpose, we derive an analytic formalism to model the interaction between a chiral emitter and a spherical resonator. We then compare the performances of metallic and dielectric spherical antennas to tailor the chirality of light emission. It is seen that, due to their strong electric dipolar response, metallic spherical nanoparticles spoil the chirality of light emission by yielding achiral fields. In contrast, thanks to the combined excitation of electric and magnetic modes, dielectric Si-based particles feature the ability to inhibit or to boost the chirality of light emission. Finally, it is shown that dual modes in dielectric antennas preserve the chirality of light emission.

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

NASA Technical Reports Server (NTRS)

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Electromagnetic liquid pistons for capillarity-based pumping

NASA Astrophysics Data System (ADS)

Malouin, Bernard; Olles, Joseph; Cheng, Lili; Hirsa, Amir; Vogel, Michael

2011-11-01

Two adjoining ferrofluid droplets can behave as an electronically-controlled oscillator or switch by an appropriate balance of magnetic, capillary, and inertial forces. Their motion can be exploited to displace a surrounding liquid, forming electromagnetic liquid pistons. Such ferrofluid pistons can pump a precise volume of liquid via finely tunable amplitudes or resonant frequencies with no solid moving parts. Here we demonstrate the use of these liquid pistons in capillarity-dominated systems for variable focal distance liquid lenses with nearly perfect spherical interfaces. These liquid/liquid lenses feature many promising qualities not previously realized together in a liquid lens, including large apertures, immunity to evaporation, invariance to orientation relative to gravity, and low driving voltages. The dynamics of these liquid pistons is examined, with experimental measurements showing good agreement with a spherical cap model. A centimeter-scale lens was shown to respond in excess of 30 Hz, with resonant frequencies over 1 kHz predicted for scaled down systems.

The curious case of large-N expansions on a (pseudo)sphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polyakov, Alexander M.; Saleem, Zain H.; Stokes, James

We elucidate the large-N dynamics of one-dimensional sigma models with spherical and hyperbolic target spaces and find a duality between the Lagrange multiplier and the angular momentum. In the hyperbolic model we propose a new class of operators based on the irreducible representations of hyperbolic space. We also uncover unexpected zero modes which lead to the double scaling of the 1/N expansion and explore these modes using Gelfand-Dikiy equations.

The curious case of large-N expansions on a (pseudo)sphere

DOE PAGES

Polyakov, Alexander M.; Saleem, Zain H.; Stokes, James

2015-02-03

We elucidate the large-N dynamics of one-dimensional sigma models with spherical and hyperbolic target spaces and find a duality between the Lagrange multiplier and the angular momentum. In the hyperbolic model we propose a new class of operators based on the irreducible representations of hyperbolic space. We also uncover unexpected zero modes which lead to the double scaling of the 1/N expansion and explore these modes using Gelfand-Dikiy equations.

Three-Dimensional Spherical Models of Convection in the Earth's Mantle.

PubMed

Bercovici, D; Schubert, G; Glatzmaier, G A

1989-05-26

Three-dimensional, spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation. Thus, subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs, which are cooler than the surrounding mantle. Cylindrical mantle plumes that cause hotspots such as Hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large-scale mantle circulation. Active sheetlike upwellings that could be associated with mid-ocean ridges did not develop in the model simulations, a result that is in agreement with evidence suggesting that ridges are passive phenomena resulting from the tearing of surface plates by the pull of descending slabs.

Nonlinear generation of large-scale magnetic fields in forced spherical shell dynamos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Livermore, P. W.; Hughes, D. W.; Tobias, S. M.

2010-03-15

In an earlier paper [P. W. Livermore, D. W. Hughes, and S. M. Tobias, ''The role of helicity and stretching in forced kinematic dynamos in a spherical shell'', Phys. Fluids 19, 057101 (2007)], we considered the kinematic dynamo action resulting from a forced helical flow in a spherical shell. Although mean field electrodynamics suggests that the resulting magnetic field should have a significant mean (axisymmetric) component, we found no evidence for this; the dynamo action was distinctly small scale. Here we extend our investigation into the nonlinear regime in which the magnetic field reacts back on the velocity via themore » Lorentz force. Our main result is somewhat surprising, namely, that nonlinear effects lead to a considerable change in the structure of the magnetic field, its final state having a significant mean component. By investigating the dominant flow-field interactions, we isolate the dynamo mechanism and show schematically how the generation process differs between the kinematic and nonlinear regimes. In addition, we are able to calculate some components of the transport coefficient {alpha} and thus discuss our results within the context of mean field electrodynamics.« less

Non-spherical micro- and nanoparticles: fabrication, characterization and drug delivery applications.

PubMed

Mathaes, Roman; Winter, Gerhard; Besheer, Ahmed; Engert, Julia

2015-03-01

Micro- and nanoparticles in drug and vaccine delivery have opened up new possibilities in pharmaceutics. In the past, researchers focused mainly on particle size, surface chemistry and the use of various materials to control particle characteristics and functions. Lately, shape has been acknowledged as an important design parameter having an impact on the interaction with biological systems. In this review, we report on the latest developments in fabrication methods to tailor particle geometry, summarize analytical techniques for non-spherical particles and highlight the most important findings regarding their interaction with biological systems and their potential applications in drug delivery. The impact of shape on particle internalization into different cell types and particle biodistribution has been extensively studied in the past. Current research focuses on shape-dependent uptake mechanisms and applications for tumour therapy and vaccination. Different fabrication methods can be used to produce a variety of different particle types and shapes. Key challenges will be the transfer of new non-spherical particle fabrication methods from lab-scale to industrial large-scale production. Not all techniques may be scalable for the production of high quantities of particles. It will also be challenging to transfer the promising in vitro findings to suitable in vivo models.

The relation between degree-2160 spectral models of Earth's gravitational and topographic potential: a guide on global correlation measures and their dependency on approximation effects

NASA Astrophysics Data System (ADS)

Hirt, Christian; Rexer, Moritz; Claessens, Sten; Rummel, Reiner

2017-10-01

Comparisons between high-degree models of the Earth's topographic and gravitational potential may give insight into the quality and resolution of the source data sets, provide feedback on the modelling techniques and help to better understand the gravity field composition. Degree correlations (cross-correlation coefficients) or reduction rates (quantifying the amount of topographic signal contained in the gravitational potential) are indicators used in a number of contemporary studies. However, depending on the modelling techniques and underlying levels of approximation, the correlation at high degrees may vary significantly, as do the conclusions drawn. The present paper addresses this problem by attempting to provide a guide on global correlation measures with particular emphasis on approximation effects and variants of topographic potential modelling. We investigate and discuss the impact of different effects (e.g., truncation of series expansions of the topographic potential, mass compression, ellipsoidal versus spherical approximation, ellipsoidal harmonic coefficient versus spherical harmonic coefficient (SHC) representation) on correlation measures. Our study demonstrates that the correlation coefficients are realistic only when the model's harmonic coefficients of a given degree are largely independent of the coefficients of other degrees, permitting degree-wise evaluations. This is the case, e.g., when both models are represented in terms of SHCs and spherical approximation (i.e. spherical arrangement of field-generating masses). Alternatively, a representation in ellipsoidal harmonics can be combined with ellipsoidal approximation. The usual ellipsoidal approximation level (i.e. ellipsoidal mass arrangement) is shown to bias correlation coefficients when SHCs are used. Importantly, gravity models from the International Centre for Global Earth Models (ICGEM) are inherently based on this approximation level. A transformation is presented that enables a transformation of ICGEM geopotential models from ellipsoidal to spherical approximation. The transformation is applied to generate a spherical transform of EGM2008 (sphEGM2008) that can meaningfully be correlated degree-wise with the topographic potential. We exploit this new technique and compare a number of models of topographic potential constituents (e.g., potential implied by land topography, ocean water masses) based on the Earth2014 global relief model and a mass-layer forward modelling technique with sphEGM2008. Different to previous findings, our results show very significant short-scale correlation between Earth's gravitational potential and the potential generated by Earth's land topography (correlation +0.92, and 60% of EGM2008 signals are delivered through the forward modelling). Our tests reveal that the potential generated by Earth's oceans water masses is largely unrelated to the geopotential at short scales, suggesting that altimetry-derived gravity and/or bathymetric data sets are significantly underpowered at 5 arc-min scales. We further decompose the topographic potential into the Bouguer shell and terrain correction and show that they are responsible for about 20 and 25% of EGM2008 short-scale signals, respectively. As a general conclusion, the paper shows the importance of using compatible models in topographic/gravitational potential comparisons and recommends the use of SHCs together with spherical approximation or EHCs with ellipsoidal approximation in order to avoid biases in the correlation measures.

Inversion of very large matrices encountered in large scale problems of photogrammetry and photographic astrometry

NASA Technical Reports Server (NTRS)

Brown, D. C.

1971-01-01

The simultaneous adjustment of very large nets of overlapping plates covering the celestial sphere becomes computationally feasible by virtue of a twofold process that generates a system of normal equations having a bordered-banded coefficient matrix, and solves such a system in a highly efficient manner. Numerical results suggest that when a well constructed spherical net is subjected to a rigorous, simultaneous adjustment, the exercise of independently established control points is neither required for determinancy nor for production of accurate results.

Prevalence and associations of anisometropia with spherical ametropia, cylindrical power, age, and sex in refractive surgery candidates.

PubMed

Linke, Stephan J; Richard, Gisbert; Katz, Toam

2011-09-29

To analyze the prevalence and associations of anisometropia with spherical ametropia, astigmatism, age, and sex in a refractive surgery population. Medical records of 27,070 eyes of 13,535 refractive surgery candidates were reviewed. Anisometropia, defined as the absolute difference in mean spherical equivalent powers between right and left eyes, was analyzed for subjective (A(subj)) and cycloplegic refraction (A(cycl)). Correlations between anisometropia (>1 diopter) and spherical ametropia, cylindrical power, age, and sex, were analyzed using χ² and nonparametric Kruskal-Wallis or Mann-Whitney tests and binomial logistic regression analyses. Power vector analysis was applied for further analysis of cylindrical power. Prevalence of A(subj) was 18.5% and of A(cycl) was 19.3%. In hyperopes, logistic regression analysis revealed that only spherical refractive error (odds ratio [OR], 0.72) and age (OR, 0.97) were independently associated with anisometropia. A(subj) decreased with increasing spherical ametropia and advancing age. Cylindrical power and sex did not significantly affect A(subj). In myopes all explanatory variables (spherical power OR, 0.93; cylindrical power OR, 0.75; age OR, 1.02; sex OR, 0.8) were independently associated with anisometropia. Cylindrical power was most strongly associated with anisometropia. Advancing age and increasing spherical/cylindrical power correlated positively with increasing anisometropia in myopic subjects. Female sex was more closely associated with anisometropia. This large-scale retrospective analysis confirmed an independent association between anisometropia and both spherical ametropia and age in refractive surgery candidates. Notably, an inverse relationship between these parameters in hyperopes was observed. Cylindrical power and female sex were independently associated with anisometropia in myopes.

Embedded Spherical Localization for Micro Underwater Vehicles Based on Attenuation of Electro-Magnetic Carrier Signals

PubMed Central

Duecker, Daniel-André; Geist, A. René; Hengeler, Michael; Kreuzer, Edwin; Pick, Marc-André; Rausch, Viktor; Solowjow, Eugen

2017-01-01

Self-localization is one of the most challenging problems for deploying micro autonomous underwater vehicles (μAUV) in confined underwater environments. This paper extends a recently-developed self-localization method that is based on the attenuation of electro-magnetic waves, to the μAUV domain. We demonstrate a compact, low-cost architecture that is able to perform all signal processing steps present in the original method. The system is passive with one-way signal transmission and scales to possibly large μAUV fleets. It is based on the spherical localization concept. We present results from static and dynamic position estimation experiments and discuss the tradeoffs of the system. PMID:28445419

Observation of instability-induced current redistribution in a spherical-torus plasma.

PubMed

Menard, J E; Bell, R E; Gates, D A; Kaye, S M; LeBlanc, B P; Levinton, F M; Medley, S S; Sabbagh, S A; Stutman, D; Tritz, K; Yuh, H

2006-09-01

A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.

Embedded Spherical Localization for Micro Underwater Vehicles Based on Attenuation of Electro-Magnetic Carrier Signals.

PubMed

Duecker, Daniel-André; Geist, A René; Hengeler, Michael; Kreuzer, Edwin; Pick, Marc-André; Rausch, Viktor; Solowjow, Eugen

2017-04-26

Self-localization is one of the most challenging problems for deploying micro autonomous underwater vehicles ( μ AUV) in confined underwater environments. This paper extends a recently-developed self-localization method that is based on the attenuation of electro-magnetic waves, to the μ AUV domain. We demonstrate a compact, low-cost architecture that is able to perform all signal processing steps present in the original method. The system is passive with one-way signal transmission and scales to possibly large μ AUV fleets. It is based on the spherical localization concept. We present results from static and dynamic position estimation experiments and discuss the tradeoffs of the system.

Halo modelling in chameleon theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lombriser, Lucas; Koyama, Kazuya; Li, Baojiu, E-mail: lucas.lombriser@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: baojiu.li@durham.ac.uk

2014-03-01

We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on localmore » scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations.« less

Simulation and scaling analysis of a spherical particle-laden blast wave

NASA Astrophysics Data System (ADS)

Ling, Y.; Balachandar, S.

2018-02-01

A spherical particle-laden blast wave, generated by a sudden release of a sphere of compressed gas-particle mixture, is investigated by numerical simulation. The present problem is a multiphase extension of the classic finite-source spherical blast-wave problem. The gas-particle flow can be fully determined by the initial radius of the spherical mixture and the properties of gas and particles. In many applications, the key dimensionless parameters, such as the initial pressure and density ratios between the compressed gas and the ambient air, can vary over a wide range. Parametric studies are thus performed to investigate the effects of these parameters on the characteristic time and spatial scales of the particle-laden blast wave, such as the maximum radius the contact discontinuity can reach and the time when the particle front crosses the contact discontinuity. A scaling analysis is conducted to establish a scaling relation between the characteristic scales and the controlling parameters. A length scale that incorporates the initial pressure ratio is proposed, which is able to approximately collapse the simulation results for the gas flow for a wide range of initial pressure ratios. This indicates that an approximate similarity solution for a spherical blast wave exists, which is independent of the initial pressure ratio. The approximate scaling is also valid for the particle front if the particles are small and closely follow the surrounding gas.

Simulation and scaling analysis of a spherical particle-laden blast wave

NASA Astrophysics Data System (ADS)

Ling, Y.; Balachandar, S.

2018-05-01

A spherical particle-laden blast wave, generated by a sudden release of a sphere of compressed gas-particle mixture, is investigated by numerical simulation. The present problem is a multiphase extension of the classic finite-source spherical blast-wave problem. The gas-particle flow can be fully determined by the initial radius of the spherical mixture and the properties of gas and particles. In many applications, the key dimensionless parameters, such as the initial pressure and density ratios between the compressed gas and the ambient air, can vary over a wide range. Parametric studies are thus performed to investigate the effects of these parameters on the characteristic time and spatial scales of the particle-laden blast wave, such as the maximum radius the contact discontinuity can reach and the time when the particle front crosses the contact discontinuity. A scaling analysis is conducted to establish a scaling relation between the characteristic scales and the controlling parameters. A length scale that incorporates the initial pressure ratio is proposed, which is able to approximately collapse the simulation results for the gas flow for a wide range of initial pressure ratios. This indicates that an approximate similarity solution for a spherical blast wave exists, which is independent of the initial pressure ratio. The approximate scaling is also valid for the particle front if the particles are small and closely follow the surrounding gas.

Supercontinent Formation in 3-D Spherical Mantle Convection Models With Multiple Continental Blocks

NASA Astrophysics Data System (ADS)

Zhang, N.; Zhong, S.; McNamara, A.

2007-12-01

Much of the large-scale tectonics on the Earth in the last Ga is predominated by the assembly and breakup of supercontinents Rodinia and Pangea. However, the mechanism that is responsible for supercontinent formation remains poorly understood. Zhong et al [2007] recently showed that mantle convection with moderately strong lithosphere and lower mantle is characterized by a largely degree-1 planform in which one hemisphere is predominated by upwellings while the other by downwellings. They further suggested that the downwellings should attract all the continental blocks to merge in the downwelling hemisphere, thus leading to supercontinent formation there. However, Zhong et al. [2007] did not consider drifting and collision processes of continents. In this study, we explore the supercontinent formation mechanisms by including drifting and collision processes of multiple continental blocks in 3-D spherical mantle convection models. We use thermochemical CitcomS code to model 3-D spherical mantle convection with continental blocks. In our models, particles are used to represent continents and to track their motions. We found that for models with mantle viscosity (i.e., moderately strong lithosphere and lower mantle) that leads to degree-1 convection as reported in Zhong et al. [2007], initially evenly- distributed continental blocks always merge to form a supercontinent on a time-scale of about 6 transit times (i.e., corresponding to about 300 Ma). The hemisphere where a supercontinent is formed is predominated by downwellings as continents merge towards there, while the other hemisphere by upwellings. However, after the supercontinent formation, upwellings are generated beneath the supercontinent. This scenario is qualitatively consistent with what Zhong et al. [2007] proposed. We also found that while some convection models with intrinsically small-scale planforms may also lead to formation of a supercontinent, some other models may fail to produce a supercontinent. For these models with intrinsically small-scale planforms, the merged continental blocks promote long-wavelength mantle structure near the continents. However, in non-continental regions, convective wavelengths remain relatively small. We suggest that time-scales for supercontinent formation and convective wavelengths in non-continental area are important parameters that help constrain mechanisms for supercontinent formation.

Mercury's Crustal Magnetic Field from MESSENGER Data

NASA Astrophysics Data System (ADS)

Plattner, A.; Johnson, C.

2017-12-01

We present a regional spherical-harmonic based crustal magnetic field model for Mercury between latitudes 45° and 70° N, derived from MESSENGER magnetic field data. In addition to contributions from the core dynamo, the bow shock, and the magnetotail, Mercury's magnetic field is also influenced by interactions with the solar wind. The resulting field-aligned currents generate magnetic fields that are typically an order of magnitude stronger at spacecraft altitude than the field from sources within Mercury's crust. These current sources lie within the satellite path and so the resulting magnetic field can not be modeled using potential-field approaches. However, these fields are organized in the local-time frame and their spatial structure differs from that of the smaller-scale crustal field. We account for large-scale magnetic fields in the local-time reference frame by subtracting from the data a low-degree localized vector spherical-harmonic model including curl components fitted at satellite altitude. The residual data exhibit consistent signals across individual satellite tracks in the body fixed reference frame, similar to those obtained via more rudimentary along-track filtering approaches. We fit a regional internal-source spherical-harmonic model to the night-time radial component of the residual data, allowing a maximum spherical-harmonic degree of L = 150. Due to the cross-track spacing of the satellite tracks, spherical-harmonic degrees beyond L = 90 are damped. The strongest signals in the resulting model are in the region around the Caloris Basin and over Suisei Planitia, as observed previously. Regularization imposed in the modeling allows the field to be downward continued to the surface. The strongest surface fields are 30 nT. Furthermore, the regional power spectrum of the model shows a downward dipping slope between spherical-harmonic degrees 40 and 80, hinting that the main component of the crustal field lies deep within the crust.

A fast algorithm for forward-modeling of gravitational fields in spherical coordinates with 3D Gauss-Legendre quadrature

NASA Astrophysics Data System (ADS)

Zhao, G.; Liu, J.; Chen, B.; Guo, R.; Chen, L.

2017-12-01

Forward modeling of gravitational fields at large-scale requires to consider the curvature of the Earth and to evaluate the Newton's volume integral in spherical coordinates. To acquire fast and accurate gravitational effects for subsurface structures, subsurface mass distribution is usually discretized into small spherical prisms (called tesseroids). The gravity fields of tesseroids are generally calculated numerically. One of the commonly used numerical methods is the 3D Gauss-Legendre quadrature (GLQ). However, the traditional GLQ integration suffers from low computational efficiency and relatively poor accuracy when the observation surface is close to the source region. We developed a fast and high accuracy 3D GLQ integration based on the equivalence of kernel matrix, adaptive discretization and parallelization using OpenMP. The equivalence of kernel matrix strategy increases efficiency and reduces memory consumption by calculating and storing the same matrix elements in each kernel matrix just one time. In this method, the adaptive discretization strategy is used to improve the accuracy. The numerical investigations show that the executing time of the proposed method is reduced by two orders of magnitude compared with the traditional method that without these optimized strategies. High accuracy results can also be guaranteed no matter how close the computation points to the source region. In addition, the algorithm dramatically reduces the memory requirement by N times compared with the traditional method, where N is the number of discretization of the source region in the longitudinal direction. It makes the large-scale gravity forward modeling and inversion with a fine discretization possible.

Simulation of large scale motions and small scale structures in planetary atmospheres and oceans: From laboratory to space experiments on ISS

NASA Astrophysics Data System (ADS)

Egbers, Christoph; Futterer, Birgit; Zaussinger, Florian; Harlander, Uwe

2014-05-01

Baroclinic waves are responsible for the transport of heat and momentum in the oceans, in the Earth's atmosphere as well as in other planetary atmospheres. The talk will give an overview on possibilities to simulate such large scale as well as co-existing small scale structures with the help of well defined laboratory experiments like the baroclinic wave tank (annulus experiment). The analogy between the Earth's atmosphere and the rotating cylindrical annulus experiment only driven by rotation and differential heating between polar and equatorial regions is obvious. From the Gulf stream single vortices seperate from time to time. The same dynamics and the co-existence of small and large scale structures and their separation can be also observed in laboratory experiments as in the rotating cylindrical annulus experiment. This experiment represents the mid latitude dynamics quite well and is part as a central reference experiment in the German-wide DFG priority research programme ("METSTRÖM", SPP 1276) yielding as a benchmark for lot of different numerical methods. On the other hand, those laboratory experiments in cylindrical geometry are limited due to the fact, that the surface and real interaction between polar and equatorial region and their different dynamics can not be really studied. Therefore, I demonstrate how to use the very successful Geoflow I and Geoflow II space experiment hardware on ISS with future modifications for simulations of small and large scale planetary atmospheric motion in spherical geometry with differential heating between inner and outer spheres as well as between the polar and equatorial regions. References: Harlander, U., Wenzel, J., Wang, Y., Alexandrov, K. & Egbers, Ch., 2012, Simultaneous PIV- and thermography measurements of partially blocked flow in a heated rotating annulus, Exp. in Fluids, 52 (4), 1077-1087 Futterer, B., Krebs, A., Plesa, A.-C., Zaussinger, F., Hollerbach, R., Breuer, D. & Egbers, Ch., 2013, Sheet-like and plume-like thermal flow in a spherical convection experiment performed under microgravity, J. Fluid Mech., vol. 75, p 647-683

Theory of quasi-spherical accretion in X-ray pulsars

NASA Astrophysics Data System (ADS)

Shakura, N.; Postnov, K.; Kochetkova, A.; Hjalmarsdotter, L.

2012-02-01

A theoretical model for quasi-spherical subsonic accretion on to slowly rotating magnetized neutron stars is constructed. In this model, the accreting matter subsonically settles down on to the rotating magnetosphere forming an extended quasi-static shell. This shell mediates the angular momentum removal from the rotating neutron star magnetosphere during spin-down episodes by large-scale convective motions. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere. The settling regime of accretion can be realized for moderate accretion rates ? g s-1. At higher accretion rates, a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of the spin-up/spin-down rates (the angular rotation frequency derivative ?, and ? near the torque reversal) of X-ray pulsars with known orbital periods, it is possible to determine the main dimensionless parameters of the model, as well as to estimate the magnetic field of the neutron star. We illustrate the model by determining these parameters for three wind-fed X-ray pulsars GX 301-2, Vela X-1 and GX 1+4. The model explains both the spin-up/spin-down of the pulsar frequency on large time-scales and the irregular short-term frequency fluctuations, which can correlate or anticorrelate with the X-ray flux fluctuations in different systems. It is shown that in real pulsars an almost iso-angular-momentum rotation law with ω˜ 1/R2, due to strongly anisotropic radial turbulent motions sustained by large-scale convection, is preferred.

Prospects for gravitational wave astronomy with next generation large-scale pulsar timing arrays

NASA Astrophysics Data System (ADS)

Wang, Yan; Mohanty, Soumya D.

2018-02-01

Next generation radio telescopes, namely the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Square Kilometer Array (SKA), will revolutionize the pulsar timing arrays (PTAs) based gravitational wave (GW) searches. We review some of the characteristics of FAST and SKA, and the resulting PTAs, that are pertinent to the detection of gravitational wave signals from individual supermassive black hole binaries.

On the Propagation and Interaction of Spherical Blast Waves

NASA Technical Reports Server (NTRS)

Kandula, Max; Freeman, Robert

2007-01-01

The characteristics and the scaling laws of isolated spherical blast waves have been briefly reviewed. Both self-similar solutions and numerical solutions of isolated blast waves are discussed. Blast profiles in the near-field (strong shock region) and the far-field (weak shock region) are examined. Particular attention is directed at the blast overpressure and shock propagating speed. Consideration is also given to the interaction of spherical blast waves. Test data for the propagation and interaction of spherical blast waves emanating from explosives placed in the vicinity of a solid propellant stack are presented. These data are discussed with regard to the scaling laws concerning the decay of blast overpressure.

Large displacement spherical joint

DOEpatents

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.

Micro-scale blood particulate dynamics using a non-uniform rational B-spline-based isogeometric analysis.

PubMed

Chivukula, V; Mousel, J; Lu, J; Vigmostad, S

2014-12-01

The current research presents a novel method in which blood particulates - biconcave red blood cells (RBCs) and spherical cells are modeled using isogeometric analysis, specifically Non-Uniform Rational B-Splines (NURBS) in 3-D. The use of NURBS ensures that even with a coarse representation, the geometry of the blood particulates maintains an accurate description when subjected to large deformations. The fundamental advantage of this method is the coupling of the geometrical description and the stress analysis of the cell membrane into a single, unified framework. Details on the modeling approach, implementation of boundary conditions and the membrane mechanics analysis using isogeometric modeling are presented, along with validation cases for spherical and biconcave cells. Using NURBS - based isogeometric analysis, the behavior of individual cells in fluid flow is presented and analyzed in different flow regimes using as few as 176 elements for a spherical cell and 220 elements for a biconcave RBC. This work provides a framework for modeling a large number of 3-D deformable biological cells, each with its own geometric description and membrane properties. To the best knowledge of the authors, this is the first application of the NURBS - based isogeometric analysis to model and simulate blood particulates in flow in 3D. Copyright © 2014 John Wiley & Sons, Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Y.K.M.; Strickler, D.J.

The spherical torus is a very small aspect ratio (A < 2) confinement concept obtained by retaining only the indispensable components inboard to the plasma torus. MHD equilibrium calculations show that spherical torus plasmas with safety factor q > 2 are characterized by high toroidal beta (..beta../sub t/ > 0.2), low poloidal beta (..beta../sub p/ < 0.3), naturally large elongation (kappa greater than or equal to 2), large plasma current with I/sub p//(aB/sub t0/) up to about 7 MA/mT, strong paramagnetism (B/sub t//B/sub t0/ > 1.5), and strong plasma helicity (F comparable to THETA). A large near-omnigeneous region is seenmore » at the large-major-radius, bad-curvature region of the plasma in comparison with the conventional tokamaks. These features combine to engender the spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost. Because of its strong paramagnetism and helicity, the spherical torus plasma shares some of the desirable features of spheromak and reversed-field pinch (RFP) plasmas, but with tokamak-like confinement and safety factor q. The general class of spherical tori, which includes the spherical tokamak (q > 1), the spherical pinch (1 > q > O), and the spherical RFP (q < O), have magnetic field configurations unique in comparison with conventional tokamaks and RFPs. 22 refs., 12 figs.« less

Large-scale structure of randomly jammed spheres

NASA Astrophysics Data System (ADS)

Ikeda, Atsushi; Berthier, Ludovic; Parisi, Giorgio

2017-05-01

We numerically analyze the density field of three-dimensional randomly jammed packings of monodisperse soft frictionless spherical particles, paying special attention to fluctuations occurring at large length scales. We study in detail the two-point static structure factor at low wave vectors in Fourier space. We also analyze the nature of the density field in real space by studying the large-distance behavior of the two-point pair correlation function, of density fluctuations in subsystems of increasing sizes, and of the direct correlation function. We show that such real space analysis can be greatly improved by introducing a coarse-grained density field to disentangle genuine large-scale correlations from purely local effects. Our results confirm that both Fourier and real space signatures of vanishing density fluctuations at large scale are absent, indicating that randomly jammed packings are not hyperuniform. In addition, we establish that the pair correlation function displays a surprisingly complex structure at large distances, which is however not compatible with the long-range negative correlation of hyperuniform systems but fully compatible with an analytic form for the structure factor. This implies that the direct correlation function is short ranged, as we also demonstrate directly. Our results reveal that density fluctuations in jammed packings do not follow the behavior expected for random hyperuniform materials, but display instead a more complex behavior.

Large-scale flows, sheet plumes and strong magnetic fields in a rapidly rotating spherical dynamo

NASA Astrophysics Data System (ADS)

Takahashi, F.

2011-12-01

Mechanisms of magnetic field intensification by flows of an electrically conducting fluid in a rapidly rotating spherical shell is investigated. Bearing dynamos of the Eartn and planets in mind, the Ekman number is set at 10-5. A strong dipolar solution with magnetic energy 55 times larger than the kinetic energy of thermal convection is obtained. In a regime of small viscosity and inertia with the strong magnetic field, convection structure consists of a few large-scale retrograde flows in the azimuthal direction and sporadic thin sheet-like plumes. The magnetic field is amplified through stretching of magnetic lines, which occurs typically through three types of flow: the retrograde azimuthal flow near the outer boundary, the downwelling flow of the sheet plume, and the prograde azimuthal flow near the rim of the tangent cylinder induced by the downwelling flow. It is found that either structure of current loops or current sheets is accompanied in each flow structure. Current loops emerge as a result of stretching the magnetic lines along the magnetic field, wheres the current sheets are formed to counterbalance the Coriolis force. Convection structure and processes of magnetic field generation found in the present model are distinct from those in models at larger/smaller Ekman number.

Statistical properties of edge plasma turbulence in the Large Helical Device

NASA Astrophysics Data System (ADS)

Dewhurst, J. M.; Hnat, B.; Ohno, N.; Dendy, R. O.; Masuzaki, S.; Morisaki, T.; Komori, A.

2008-09-01

Ion saturation current (Isat) measurements made by three tips of a Langmuir probe array in the Large Helical Device are analysed for two plasma discharges. Absolute moment analysis is used to quantify properties on different temporal scales of the measured signals, which are bursty and intermittent. Strong coherent modes in some datasets are found to distort this analysis and are consequently removed from the time series by applying bandstop filters. Absolute moment analysis of the filtered data reveals two regions of power-law scaling, with the temporal scale τ ≈ 40 µs separating the two regimes. A comparison is made with similar results from the Mega-Amp Spherical Tokamak. The probability density function is studied and a monotonic relationship between connection length and skewness is found. Conditional averaging is used to characterize the average temporal shape of the largest intermittent bursts.

A multiball read-out for the spherical proportional counter

NASA Astrophysics Data System (ADS)

Giganon, A.; Giomataris, I.; Gros, M.; Katsioulas, I.; Navick, X. F.; Tsiledakis, G.; Savvidis, I.; Dastgheibi-Fard, A.; Brossard, A.

2017-12-01

We present a novel concept of proportional gas amplification for the read-out of the spherical proportional counter. The standard single-ball read-out presents limitations for large diameter spherical detectors and high-pressure operations. We have developed a multi-ball read-out system which consists of several balls placed at a fixed distance from the center of the spherical vessel. Such a module can tune the volume electric field at the desired value and can also provide detector segmentation with individual ball read-out. In the latter case, the large volume of the vessel becomes a spherical time projection chamber with 3D capabilities.

Theoretical and experimental studies in support of the geophysical fluid flow experiment

NASA Technical Reports Server (NTRS)

Hart, J.; Toomre, J.

1985-01-01

Meteorologists and astrophysicists interested in large scale planetary and solar circulations have come to recognize the importance of rotation and stratification in determining the character of these flows. In particular, the effect of latitude-dependent Coriolis force on nonlinear convection is thought to play a crucial role in such phenomena as differential rotation on the Sun, cloud band orientation on Jupiter, and the generation of magnetic fields in thermally driven dynamos. The continuous low-gravity environment of the orbiting space shuttle offers a unique opportunity to make laboratory studies of such large-scale thermally driven flows under the constraint imposed by rotation and sphericity. This is possible because polarization forces in a dielectric liquid, which are linearly dependent on fluid temperature, give rise to an effectively radial buoyancy force when a radial electrostatic field is imposed. The Geophysical Fluid Flow Cell (GFFC) is an implementation of this ideal in which fluid is contained between two rotating hemispheres that are differentially heated and stressed with a large a-c voltage. The experiment, to be flown on Spacelab III (currently set for launch April 29, 1985), will explore non-linear mode selection and high Rayleigh number turbulence in a rotating convecting spherical shell of liquid. Experiments will be carried out in a low driving parameter range where some limited numerical experimentation is currently feasible, as well as in a parameter range significantly beyond numerical computation for many years.

Solitary waves in shallow water hydrodynamics and magnetohydrodynamics in rotating spherical coordinates

NASA Astrophysics Data System (ADS)

London, Steven D.

2018-01-01

In a recent paper (London, Geophys. Astrophys. Fluid Dyn. 2017, vol. 111, pp. 115-130, referred to as L1), we considered a perfect electrically conducting rotating fluid in the presence of an ambient toroidal magnetic field, governed by the shallow water magnetohydrodynamic (MHD) equations in a modified equatorial ?-plane approximation. In conjunction with a WKB type approximation, we used a multiple scale asymptotic scheme, previously developed by Boyd (J. Phys. Oceanogr. 1980, vol. 10, pp. 1699-1717) for equatorial solitary hydrodynamic waves, and found solitary MHD waves. In this paper, as in L1, we apply a WKB type approximation in order to extend the results of L1 from the modified ?-plane to the full spherical geometry. We have included differential rotation in the analysis in order to make the results more relevant to the solar case. In addition, we consider the case of hydrodynamic waves on the rotating sphere in the presence of a differential rotation intended to roughly model the varying large scale currents in the oceans and atmosphere. In the hydrodynamic case, we find the usual equatorial solitary waves as found by Boyd, as well as waves in bands away from the equator for sufficiently strong currents. In the MHD case, we find basically the same equatorial waves found in L1. L1 also found non-equatorial modes; no such modes are found in the full spherical geometry.

Laboratory observation of electron phase-space holes during magnetic reconnection.

PubMed

Fox, W; Porkolab, M; Egedal, J; Katz, N; Le, A

2008-12-19

We report the observation of large-amplitude, nonlinear electrostatic structures, identified as electron phase-space holes, during magnetic reconnection experiments on the Versatile Toroidal Facility at MIT. The holes are positive electric potential spikes, observed on high-bandwidth ( approximately 2 GHz) Langmuir probes. Investigations with multiple probes establish that the holes travel at or above the electron thermal speed and have a three-dimensional, approximately spherical shape, with a scale size approximately 2 mm. This corresponds to a few electron gyroradii, or many tens of Debye lengths, which is large compared to holes considered in simulations and observed by satellites, whose length scale is typically only a few Debye lengths. Finally, a statistical study over many discharges confirms that the holes appear in conjunction with the large inductive electric fields and the creation of energetic electrons associated with the magnetic energy release.

Tidal interactions in the expanding universe - The formation of prolate systems

NASA Technical Reports Server (NTRS)

Binney, J.; Silk, J.

1979-01-01

The study estimates the magnitude of the anisotropy that can be tidally induced in neighboring initially spherical protostructures, be they protogalaxies, protoclusters, or even uncollapsed density enhancements in the large-scale structure of the universe. It is shown that the linear analysis of tidal interactions developed by Peebles (1969) predicts that the anisotropy energy of a perturbation grows to first order in a small dimensionless parameter, whereas the net angular momentum acquired is of second order. A simple model is presented for the growth of anisotropy by tidal interactions during the nonlinear stage of the development of perturbations. A possible observational test is described of the alignment predicted by the model between the orientations of large-scale perturbations and the positions of neighboring density enhancements.

Alternative experiments using the geophysical fluid flow cell

NASA Technical Reports Server (NTRS)

Hart, J. E.

1984-01-01

This study addresses the possibility of doing large scale dynamics experiments using the Geophysical Fluid Flow Cell. In particular, cases where the forcing generates a statically stable stratification almost everywhere in the spherical shell are evaluated. This situation is typical of the Earth's atmosphere and oceans. By calculating the strongest meridional circulation expected in the spacelab experiments, and testing its stability using quasi-geostrophic stability theory, it is shown that strongly nonlinear baroclinic waves on a zonally symmetric modified thermal wind will not occur. The Geophysical Fluid Flow Cell does not have a deep enough fluid layer to permit useful studies of large scale planetary wave processes arising from instability. It is argued, however, that by introducing suitable meridional barriers, a significant contribution to the understanding of the oceanic thermocline problem could be made.

Mantle plumes and continental tectonics.

PubMed

Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

1992-04-10

Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

Using Global Plate Velocity Boundary Conditions for Embedded Regional Geodynamic Models

NASA Astrophysics Data System (ADS)

Taramon Gomez, Jorge; Morgan, Jason; Perez-Gussinye, Marta

2015-04-01

The treatment of far-field boundary conditions is one of the most poorly resolved issues for regional modeling of geodynamic processes. In viscous flow, the choice of far-field boundary conditions often strongly shapes the large-scale structure of a geosimulation. The mantle velocity field along the sidewalls and base of a modeling region is typically much more poorly known than the geometry of past global motions of the surface plates as constrained by global plate motion reconstructions. For regional rifting models it has become routine to apply highly simplified 'plate spreading' or 'uniform rifting' boundary conditions to a 3-D model that limits its ability to simulate the geodynamic evolution of a specific rifted margin. One way researchers are exploring the sensitivity of regional models to uncertain boundary conditions is to use a nested modeling approach in which a global model is used to determine a large-scale flow pattern that is imposed as a constraint along the boundaries of the region to be modeled. Here we explore the utility of a different approach that takes advantage of the ability of finite element models to use unstructured meshes than can embed much higher resolution sub-regions within a spherical global mesh. In our initial project to validate this approach, we create a global spherical mesh in which a higher resolution sub-region is created around the nascent South Atlantic Rifting Margin. Global Plate motion BCs and plate boundaries are applied for the time of the onset of rifting, continuing through several 10s of Ma of rifting. Thermal, compositional, and melt-related buoyancy forces are only non-zero within the high-resolution subregion, elsewhere, motions are constrained by surface plate-motion constraints. The total number of unknowns needed to solve an embedded regional model with this approach is less than 1/3 larger than that needed for a structured-mesh solution on a Cartesian or spherical cap sub-regional mesh. Here we illustrate the initial steps within this workflow for creating time-varying surface boundary conditions (using GPlates), and a time-variable unstructured 3-D spherical mesh.

Galactic cosmic-ray mediation of a spherical solar wind flow. 1: The steady state cold gas hydrodynamical approximation

NASA Technical Reports Server (NTRS)

Le Roux, J. A.; Ptuskin, V. S.

1995-01-01

Realistic models of the outer heliosphere should consider that the interstellar cosmic-ray pressure becomes comparable to pressures in the solar wind at distances more than 100 AU from the Sun. The cosmic-ray pressure dynamically affects solar wind flow through deceleration. This effect, which occurs over a scale length of the order of the effective diffusion length at large radial distances, has important implications for cosmic-ray modulation and acceleration. As a first step toward solution of this nonlinear problem, a steady state numerical model was developed for a relatively cold spherical solar wind flow which encounters the confining isotropic pressure of the surrounding Galactic medium. This pressure is assumed to be dominated by energetic particles (Galactic cosmic rays). The system of equations, which are solved self-consistently, includes the relevant hydrodynamical equations for the solar wind flow and the spherical cosmic-ray transport equation. To avoid the closure parameter problem of the two-fluid model, the latter equation is solved for the energy-dependent cosmic-ray distribution function.

An analytical model for the evolution of the coldest component of the Boomerang Nebula

NASA Astrophysics Data System (ADS)

Bohigas, J.

2017-04-01

The most striking feature of the Boomerang Nebula is a large nearly spherical cloud where the temperature is close to 2 K. At its inner and outer boundaries, this cloud is expanding at velocities close to 35 and 180 km s-1. The cloud surrounds an asymptotic giant branch (AGB) star and a smaller bipolar molecular cloud, expanding much more slowly. The ultracold spherical cloud has been and still is expanding into a rarefied medium, since there is no trace of a shock wave. This ultracold cloud is modelled using the analytical solution for a power-driven expansion of a spherically symmetric cloud, followed by an adiabatic expansion phase, both into a vacuum. Assuming that the cloud is at a distance of 1500 pc, the present temperature and velocity profile are reproduced with a model where the cloud has an energy close to 8.5 × 1046 erg per solar mass and was ejected 1000 yr ago. In this model, the power-driven phase lasts for ˜10 yr and half of the energy is injected in less than a year. The general features of this model, are amenable with what is found in other spherical shells surrounding AGB stars, the small amount of mass lost by massive OH/IR stars and evolutionary models indicating that there may be extremely high and abrupt mass-loss phases in AGB stars. The energy and time-scale suggest that the ejection of the cold spherical cloud was an intermediate luminosity transient.

Searches for Large-scale Anisotropy in the Arrival Directions of Cosmic Rays Detected above Energy of 1019 eV at the Pierre Auger Observatory and the Telescope Array

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Cordier, A.; Coutu, S.; Covault, C. E.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fuji, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; González, N.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Hartmann, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Mallamaci, M.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J. A. J.; Matthews, J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pękala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Peters, C.; Petrera, S.; Petrolini, A.; Petrov, Y.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Cabo, I.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Pierre Auger Collaboration; Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Chae, M. J.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.; Telescope Array Collaboration

2014-10-01

Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.

Heat transfer rate within non-spherical thick grains

NASA Astrophysics Data System (ADS)

Huchet, Florian; Richard, Patrick; Joniot, Jules; Le Guen, Laurédan

2017-06-01

The prediction of the internal heat conduction into non-spherical thick grains constitutes a significant issue for physical modeling of a large variety of application involving convective exchanges between fluid and grains. In that context, the present paper deals with heat rate measurements of various sizes of particles, the thermal sensors being located at the interface fluid/grain and into the granular materials. Their shape is designed as cuboid in order to control the surface exchanges. In enclosed coneshaped apparatus, a sharp temperature gradient is ensured from a hot source releasing the air stream temperature equal to about 400°C. Two orientations of grain related to the air stream are considered: diagonally and straight arrangements. The thermal diffusivity of the grains and the Biot numbers are estimated from an analytical solution established for slab. The thermal kinetics evolution is correlated to the sample granular mass and its orientation dependency is demonstrated. Consequently, a generalized scaling law is proposed which is funded from the effective area of the heat transfer at the grain-scale, the dimensionless time being defined from the calculated diffusional coefficients.

Solution of Eshelby's inclusion problem with a bounded domain and Eshelby's tensor for a spherical inclusion in a finite spherical matrix based on a simplified strain gradient elasticity theory

NASA Astrophysics Data System (ADS)

Gao, X.-L.; Ma, H. M.

2010-05-01

A solution for Eshelby's inclusion problem of a finite homogeneous isotropic elastic body containing an inclusion prescribed with a uniform eigenstrain and a uniform eigenstrain gradient is derived in a general form using a simplified strain gradient elasticity theory (SSGET). An extended Betti's reciprocal theorem and an extended Somigliana's identity based on the SSGET are proposed and utilized to solve the finite-domain inclusion problem. The solution for the disturbed displacement field is expressed in terms of the Green's function for an infinite three-dimensional elastic body in the SSGET. It contains a volume integral term and a surface integral term. The former is the same as that for the infinite-domain inclusion problem based on the SSGET, while the latter represents the boundary effect. The solution reduces to that of the infinite-domain inclusion problem when the boundary effect is not considered. The problem of a spherical inclusion embedded concentrically in a finite spherical elastic body is analytically solved by applying the general solution, with the Eshelby tensor and its volume average obtained in closed forms. This Eshelby tensor depends on the position, inclusion size, matrix size, and material length scale parameter, and, as a result, can capture the inclusion size and boundary effects, unlike existing Eshelby tensors. It reduces to the classical Eshelby tensor for the spherical inclusion in an infinite matrix if both the strain gradient and boundary effects are suppressed. Numerical results quantitatively show that the inclusion size effect can be quite large when the inclusion is very small and that the boundary effect can dominate when the inclusion volume fraction is very high. However, the inclusion size effect is diminishing as the inclusion becomes large enough, and the boundary effect is vanishing as the inclusion volume fraction gets sufficiently low.

Fabrication of stainless steel spherical anodes for use with boat-mounted boom electroshocker

USGS Publications Warehouse

Martinez, Patrick J.; Tiffan, Kenneth F.

1992-01-01

A frugal method of fabricating spherical anodes from stainless steel mixing bowls is presented. We believe that the purported mechanical disadvantages of using spherical electrodes are largely unfounded.

Optimization and large scale computation of an entropy-based moment closure

NASA Astrophysics Data System (ADS)

Kristopher Garrett, C.; Hauck, Cory; Hill, Judith

2015-12-01

We present computational advances and results in the implementation of an entropy-based moment closure, MN, in the context of linear kinetic equations, with an emphasis on heterogeneous and large-scale computing platforms. Entropy-based closures are known in several cases to yield more accurate results than closures based on standard spectral approximations, such as PN, but the computational cost is generally much higher and often prohibitive. Several optimizations are introduced to improve the performance of entropy-based algorithms over previous implementations. These optimizations include the use of GPU acceleration and the exploitation of the mathematical properties of spherical harmonics, which are used as test functions in the moment formulation. To test the emerging high-performance computing paradigm of communication bound simulations, we present timing results at the largest computational scales currently available. These results show, in particular, load balancing issues in scaling the MN algorithm that do not appear for the PN algorithm. We also observe that in weak scaling tests, the ratio in time to solution of MN to PN decreases.

Optimization and large scale computation of an entropy-based moment closure

DOE PAGES

Hauck, Cory D.; Hill, Judith C.; Garrett, C. Kristopher

2015-09-10

We present computational advances and results in the implementation of an entropy-based moment closure, M N, in the context of linear kinetic equations, with an emphasis on heterogeneous and large-scale computing platforms. Entropy-based closures are known in several cases to yield more accurate results than closures based on standard spectral approximations, such as P N, but the computational cost is generally much higher and often prohibitive. Several optimizations are introduced to improve the performance of entropy-based algorithms over previous implementations. These optimizations include the use of GPU acceleration and the exploitation of the mathematical properties of spherical harmonics, which aremore » used as test functions in the moment formulation. To test the emerging high-performance computing paradigm of communication bound simulations, we present timing results at the largest computational scales currently available. Lastly, these results show, in particular, load balancing issues in scaling the M N algorithm that do not appear for the P N algorithm. We also observe that in weak scaling tests, the ratio in time to solution of M N to P N decreases.« less

Watermarking on 3D mesh based on spherical wavelet transform.

PubMed

Jin, Jian-Qiu; Dai, Min-Ya; Bao, Hu-Jun; Peng, Qun-Sheng

2004-03-01

In this paper we propose a robust watermarking algorithm for 3D mesh. The algorithm is based on spherical wavelet transform. Our basic idea is to decompose the original mesh into a series of details at different scales by using spherical wavelet transform; the watermark is then embedded into the different levels of details. The embedding process includes: global sphere parameterization, spherical uniform sampling, spherical wavelet forward transform, embedding watermark, spherical wavelet inverse transform, and at last resampling the mesh watermarked to recover the topological connectivity of the original model. Experiments showed that our algorithm can improve the capacity of the watermark and the robustness of watermarking against attacks.

On the Interaction and Coalescence if Spherical Blast Waves

NASA Technical Reports Server (NTRS)

Kandula, Max; Freeman, Robert J.

2005-01-01

The scaling and similarity laws concerning the propagation of isolated spherical blast waves are briefly reviewed. Both point source explosions and high pressure gas explosions are considered. Test data on blast overpressure from the interaction and coalescence of spherical blast waves emanating from explosives in the form of shaped charges of different strength placed in the vicinity of a solid propellant stack are presented. These data are discussed with regard to the scaling laws concerning the decay of blast overpressure. The results point out the possibility of detecting source explosions from far-field pressure measurements.

Spherical nanoindentation of proton irradiated 304 stainless steel: A comparison of small scale mechanical test techniques for measuring irradiation hardening

DOE PAGES

Weaver, Jordan S.; Pathak, Siddhartha; Reichardt, Ashley; ...

2017-06-27

Experimentally quantifying the mechanical effects of radiation damage in reactor materials is necessary for the development and qualification of new materials for improved performance and safety. This can be achieved in a high-throughput fashion through a combination of ion beam irradiation and small scale mechanical testing in contrast to the high cost and laborious nature of bulk testing of reactor irradiated samples. The current paper focuses on using spherical nanoindentation stress-strain curves on unirradiated and proton irradiated (10 dpa at 360 °C) 304 stainless steel to quantify the mechanical effects of radiation damage. Spherical nanoindentation stress-strain measurements show a radiation-inducedmore » increase in indentation yield strength from 1.36 GPa to 2.72 GPa and a radiation-induced increase in indentation work hardening rate of 10 GPa–30 GPa. These measurements are critically compared against Berkovich nanohardness, micropillar compression, and micro-tension measurements on the same material and similar grain orientations. The ratio of irradiated to unirradiated yield strength increases by a similar factor of 2 when measured via spherical nanoindentation or Berkovich nanohardness testing. A comparison of spherical indentation stress-strain curves to uniaxial (micropillar and micro-tension) stress-strain curves was achieved using a simple scaling relationship which shows good agreement for the unirradiated condition and poor agreement in post-yield behavior for the irradiated condition. Finally, the disagreement between spherical nanoindentation and uniaxial stress-strain curves is likely due to the plastic instability that occurs during uniaxial tests but is absent during spherical nanoindentation tests.« less

Spherical nanoindentation of proton irradiated 304 stainless steel: A comparison of small scale mechanical test techniques for measuring irradiation hardening

NASA Astrophysics Data System (ADS)

Weaver, Jordan S.; Pathak, Siddhartha; Reichardt, Ashley; Vo, Hi T.; Maloy, Stuart A.; Hosemann, Peter; Mara, Nathan A.

2017-09-01

Experimentally quantifying the mechanical effects of radiation damage in reactor materials is necessary for the development and qualification of new materials for improved performance and safety. This can be achieved in a high-throughput fashion through a combination of ion beam irradiation and small scale mechanical testing in contrast to the high cost and laborious nature of bulk testing of reactor irradiated samples. The current work focuses on using spherical nanoindentation stress-strain curves on unirradiated and proton irradiated (10 dpa at 360 °C) 304 stainless steel to quantify the mechanical effects of radiation damage. Spherical nanoindentation stress-strain measurements show a radiation-induced increase in indentation yield strength from 1.36 GPa to 2.72 GPa and a radiation-induced increase in indentation work hardening rate of 10 GPa-30 GPa. These measurements are critically compared against Berkovich nanohardness, micropillar compression, and micro-tension measurements on the same material and similar grain orientations. The ratio of irradiated to unirradiated yield strength increases by a similar factor of 2 when measured via spherical nanoindentation or Berkovich nanohardness testing. A comparison of spherical indentation stress-strain curves to uniaxial (micropillar and micro-tension) stress-strain curves was achieved using a simple scaling relationship which shows good agreement for the unirradiated condition and poor agreement in post-yield behavior for the irradiated condition. The disagreement between spherical nanoindentation and uniaxial stress-strain curves is likely due to the plastic instability that occurs during uniaxial tests but is absent during spherical nanoindentation tests.

Spherical nanoindentation of proton irradiated 304 stainless steel: A comparison of small scale mechanical test techniques for measuring irradiation hardening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Pathak, Siddhartha; Reichardt, Ashley

Experimentally quantifying the mechanical effects of radiation damage in reactor materials is necessary for the development and qualification of new materials for improved performance and safety. This can be achieved in a high-throughput fashion through a combination of ion beam irradiation and small scale mechanical testing in contrast to the high cost and laborious nature of bulk testing of reactor irradiated samples. The current paper focuses on using spherical nanoindentation stress-strain curves on unirradiated and proton irradiated (10 dpa at 360 °C) 304 stainless steel to quantify the mechanical effects of radiation damage. Spherical nanoindentation stress-strain measurements show a radiation-inducedmore » increase in indentation yield strength from 1.36 GPa to 2.72 GPa and a radiation-induced increase in indentation work hardening rate of 10 GPa–30 GPa. These measurements are critically compared against Berkovich nanohardness, micropillar compression, and micro-tension measurements on the same material and similar grain orientations. The ratio of irradiated to unirradiated yield strength increases by a similar factor of 2 when measured via spherical nanoindentation or Berkovich nanohardness testing. A comparison of spherical indentation stress-strain curves to uniaxial (micropillar and micro-tension) stress-strain curves was achieved using a simple scaling relationship which shows good agreement for the unirradiated condition and poor agreement in post-yield behavior for the irradiated condition. Finally, the disagreement between spherical nanoindentation and uniaxial stress-strain curves is likely due to the plastic instability that occurs during uniaxial tests but is absent during spherical nanoindentation tests.« less

Potential for protein surface shape analysis using spherical harmonics and 3D Zernike descriptors.

PubMed

Venkatraman, Vishwesh; Sael, Lee; Kihara, Daisuke

2009-01-01

With structure databases expanding at a rapid rate, the task at hand is to provide reliable clues to their molecular function and to be able to do so on a large scale. This, however, requires suitable encodings of the molecular structure which are amenable to fast screening. To this end, moment-based representations provide a compact and nonredundant description of molecular shape and other associated properties. In this article, we present an overview of some commonly used representations with specific focus on two schemes namely spherical harmonics and their extension, the 3D Zernike descriptors. Key features and differences of the two are reviewed and selected applications are highlighted. We further discuss recent advances covering aspects of shape and property-based comparison at both global and local levels and demonstrate their applicability through some of our studies.

Fast response of electron-scale turbulence to auxiliary heating cessation in National Spherical Torus Experiment

DOE PAGES

Ren, Y.; Wang, W. X.; LeBlanc, B. P.; ...

2015-11-03

In this letter, we report the first observation of the fast response of electron-scale turbulence to auxiliary heating cessation in National Spherical Torus eXperiment [Ono et al., Nucl. Fusion 40, 557 (2000)]. The observation was made in a set of RF-heated L-mode plasmas with toroidal magnetic field of 0.55 T and plasma current of 300 kA. It is observed that electron-scale turbulence spectral power (measured with a high-k collective microwave scattering system) decreases significantly following fast cessation of RF heating that occurs in less than 200 μs. The large drop in the turbulence spectral power has a short time delaymore » of about 1–2 ms relative to the RF cessation and happens on a time scale of 0.5–1 ms, much smaller than the energy confinement time of about 10 ms. Power balance analysis shows a factor of about 2 decrease in electron thermal diffusivity after the sudden drop of turbulence spectral power. Measured small changes in equilibrium profiles across the RF cessation are unlikely able to explain this sudden reduction in the measured turbulence and decrease in electron thermal transport, supported by local linear stability analysis and both local and global nonlinear gyrokinetic simulations. Furthermore, the observations imply that nonlocal flux-driven mechanism may be important for the observed turbulence and electron thermal transport.« less

Inertial effects on thermochemically driven convection and hydromagnetic dynamos in a spherical shell

NASA Astrophysics Data System (ADS)

Šimkanin, Ján; Kyselica, Juraj; Guba, Peter

2018-03-01

We investigate the thermochemical convection and hydromagnetic dynamos in a spherical shell using the so-called codensity formulation with different buoyancy sources: the secular cooling from the mantle, the buoyancy sources due to the solidification at the inner core boundary and the combination of the two sources. Numerical simulations of the fully non-linear problem are performed using the PARODY code. In the thermochemical regime, we find that when the Prandtl numbers are lower than Ekman numbers, inertial convection is preferred, while the large-scale columnar convection is preferred otherwise. Unlike the large-scale convection, the inertial convection is found to be almost independent of the nature of driving buoyancy source. Moreover, the codensity field evolves to a new, radially symmetric stationary state. At the Ekman numbers much smaller than the Prandtl numbers, we have obtained the westward equatorial zonal flow in the chemically driven regime, while for the other cases zonal flows are eastward near the equator. In the dynamo regime, inertial convection is preferred when the Prandtl numbers are lower than Ekman numbers and the generated dipolar magnetic fields oscillate from the polar region to the mid-latitudes and back. In this case, the generated magnetic fields are independent of the type of buoyancy source. At the Prandtl numbers greater than Ekman numbers, both dipolar and hemispherical dynamos are found.

Method to produce large, uniform hollow spherical shells

DOEpatents

Hendricks, C.D.

1983-09-26

The invention is a method to produce large uniform hollow spherical shells by (1) forming uniform size drops of heat decomposable or vaporizable material, (2) evaporating the drops to form dried particles, (3) coating the dried particles with a layer of shell forming material and (4) heating the composite particles to melt the outer layer and to decompose or vaporize the inner particle to form an expanding inner gas bubble. The expanding gas bubble forms the molten outer layer into a shell of relatively large diameter. By cycling the temperature and pressure on the molten shell, nonuniformities in wall thickness can be reduced. The method of the invention is utilized to produce large uniform spherical shells, in the millimeter to centimeter diameter size range, from a variety of materials and of high quality, including sphericity, concentricity and surface smoothness, for use as laser fusion or other inertial confinement fusion targets as well as other applications.

Regular and chaotic dynamics of non-spherical bodies. Zeldovich's pancakes and emission of very long gravitational waves

NASA Astrophysics Data System (ADS)

Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.

2015-10-01

> In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincaré diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as `Zeldovich's pancakes'. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. Violent relaxation, mass and angular momentum losses are taken into account phenomenologically. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves.

Liposome Technology for Industrial Purposes

PubMed Central

Wagner, Andreas; Vorauer-Uhl, Karola

2011-01-01

Liposomes, spherical vesicles consisting of one or more phospholipid bilayers, were first described in the mid 60s by Bangham and coworkers. Since then, liposomes have made their way to the market. Today, numerous lab scale but only a few large-scale techniques are available. However, a lot of these methods have serious limitations in terms of entrapment of sensitive molecules due to their exposure to mechanical and/or chemical stress. This paper summarizes exclusively scalable techniques and focuses on strengths, respectively, limitations in respect to industrial applicability. An additional point of view was taken to regulatory requirements concerning liposomal drug formulations based on FDA and EMEA documents. PMID:21490754

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Arka; Dalal, Neal, E-mail: abanerj6@illinois.edu, E-mail: dalaln@illinois.edu

We present a new method for simulating cosmologies that contain massive particles with thermal free streaming motion, such as massive neutrinos or warm/hot dark matter. This method combines particle and fluid descriptions of the thermal species to eliminate the shot noise known to plague conventional N-body simulations. We describe this method in detail, along with results for a number of test cases to validate our method, and check its range of applicability. Using this method, we demonstrate that massive neutrinos can produce a significant scale-dependence in the large-scale biasing of deep voids in the matter field. We show that thismore » scale-dependence may be quantitatively understood using an extremely simple spherical expansion model which reproduces the behavior of the void bias for different neutrino parameters.« less

Shock wave propagation in layered planetary embryos

NASA Astrophysics Data System (ADS)

Arkani-Hamed, Jafar; Ivanov, Boris A.

2014-05-01

The propagation of impact-induced shock wave inside a planetary embryo is investigated using the Hugoniot equations and a new scaling law, governing the particle velocity variations along a shock ray inside a spherical body. The scaling law is adopted to determine the impact heating of a growing embryo in its early stage when it is an undifferentiated and uniform body. The new scaling law, similar to other existing scaling laws, is not suitable for a large differentiated embryo consisting of a silicate mantle overlying an iron core. An algorithm is developed in this study on the basis of the ray theory in a spherically symmetric body which relates the shock parameters at the top of the core to those at the base of the mantle, thus enabling the adoption of scaling laws to estimate the impact heating of both the mantle and the core. The algorithm is applied to two embryo models: a simple two-layered model with a uniform mantle overlying a uniform core, and a model where the pre-shock density and acoustic velocity of the embryo are radially dependent. The former illustrates details of the particle velocity, shock pressure, and temperature increase behind the shock front in a 2D axisymmetric geometry. The latter provides a means to compare the results with those obtained by a hydrocode simulation. The agreement between the results of the two techniques in revealing the effects of the core-mantle boundary on the shock wave transmission across the boundary is encouraging.

A new method of presentation the large-scale magnetic field structure on the Sun and solar corona

NASA Technical Reports Server (NTRS)

Ponyavin, D. I.

1995-01-01

The large-scale photospheric magnetic field, measured at Stanford, has been analyzed in terms of surface harmonics. Changes of the photospheric field which occur within whole solar rotation period can be resolved by this analysis. For this reason we used daily magnetograms of the line-of-sight magnetic field component observed from Earth over solar disc. We have estimated the period during which day-to-day full disc magnetograms must be collected. An original algorithm was applied to resolve time variations of spherical harmonics that reflect time evolution of large-scale magnetic field within solar rotation period. This method of magnetic field presentation can be useful enough in lack of direct magnetograph observations due to sometimes bad weather conditions. We have used the calculated surface harmonics to reconstruct the large-scale magnetic field structure on the source surface near the sun - the origin of heliospheric current sheet and solar wind streams. The obtained results have been compared with spacecraft in situ observations and geomagnetic activity. We tried to show that proposed technique can trace shon-time variations of heliospheric current sheet and short-lived solar wind streams. We have compared also our results with those obtained traditionally from potential field approximation and extrapolation using synoptic charts as initial boundary conditions.

Flux amplification in helicity injected spherical tori

NASA Astrophysics Data System (ADS)

Tang, X. Z.; Boozer, A. H.

2005-04-01

An important measure of the effective current drive by helicity injection into spheromaks and spherical tori is provided by the flux amplification factor, defined as the ratio between the closed poloidal flux in the relaxed mean field and the initial injector vacuum poloidal flux. Flux amplification in magnetic helicity injection is governed by a resonant behavior for Taylor-relaxed plasmas satisfying j =kB. Under the finite net toroidal flux constraint in a spherical torus (ST), the constrained linear resonance k1c is upshifted substantially from the primary Jensen-Chu resonance k1 that was known to be responsible for flux amplification in spheromak formation. Standard coaxial helicity injection into a ST operates at large M, with M the characteristic dimensionless parameter defined as the ratio between the toroidal flux in the discharge chamber and the injector poloidal flux. Meaningful flux amplification for ST plasmas is limited by a critical kr at which edge toroidal field reverses its direction. The kr is downshifted from k1 by a small amount inversely proportional to M. The maximum flux amplification factor Ar≡A(k=kr) scales linearly with M. At the other end of k, substantial flux amplification A(k =ko)˜1 becomes available for ko that scales inversely proportional to M, a significant departure from that in spheromak formation. These important parameters follow the inequality ko

Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection.

PubMed

Yoshida, Masaki; Hamano, Yozo

2015-02-12

Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr(-1)) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean.

Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection

PubMed Central

Yoshida, Masaki; Hamano, Yozo

2015-01-01

Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr−1) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean. PMID:25673102

Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods.

PubMed

Rateb, Ashraf; Kuo, Chung-Yen; Imani, Moslem; Tseng, Kuo-Hsin; Lan, Wen-Hau; Ching, Kuo-En; Tseng, Tzu-Pang

2017-03-10

Spherical harmonics (SH) and mascon solutions are the two most common types of solutions for Gravity Recovery and Climate Experiment (GRACE) mass flux observations. However, SH signals are degraded by measurement and leakage errors. Mascon solutions (the Jet Propulsion Laboratory (JPL) release, herein) exhibit weakened signals at submascon resolutions. Both solutions require a scale factor examined by the CLM4.0 model to obtain the actual water storage signal. The Slepian localization method can avoid the SH leakage errors when applied to the basin scale. In this study, we estimate SH errors and scale factors for African hydrological regimes. Then, terrestrial water storage (TWS) in Africa is determined based on Slepian localization and compared with JPL-mascon and SH solutions. The three TWS estimates show good agreement for the TWS of large-sized and humid regimes but present discrepancies for the TWS of medium and small-sized regimes. Slepian localization is an effective method for deriving the TWS of arid zones. The TWS behavior in African regimes and its spatiotemporal variations are then examined. The negative TWS trends in the lower Nile and Sahara at -1.08 and -6.92 Gt/year, respectively, are higher than those previously reported.

Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods

PubMed Central

Rateb, Ashraf; Kuo, Chung-Yen; Imani, Moslem; Tseng, Kuo-Hsin; Lan, Wen-Hau; Ching, Kuo-En; Tseng, Tzu-Pang

2017-01-01

Spherical harmonics (SH) and mascon solutions are the two most common types of solutions for Gravity Recovery and Climate Experiment (GRACE) mass flux observations. However, SH signals are degraded by measurement and leakage errors. Mascon solutions (the Jet Propulsion Laboratory (JPL) release, herein) exhibit weakened signals at submascon resolutions. Both solutions require a scale factor examined by the CLM4.0 model to obtain the actual water storage signal. The Slepian localization method can avoid the SH leakage errors when applied to the basin scale. In this study, we estimate SH errors and scale factors for African hydrological regimes. Then, terrestrial water storage (TWS) in Africa is determined based on Slepian localization and compared with JPL-mascon and SH solutions. The three TWS estimates show good agreement for the TWS of large-sized and humid regimes but present discrepancies for the TWS of medium and small-sized regimes. Slepian localization is an effective method for deriving the TWS of arid zones. The TWS behavior in African regimes and its spatiotemporal variations are then examined. The negative TWS trends in the lower Nile and Sahara at −1.08 and −6.92 Gt/year, respectively, are higher than those previously reported. PMID:28287453

Back in the saddle: large-deviation statistics of the cosmic log-density field

NASA Astrophysics Data System (ADS)

Uhlemann, C.; Codis, S.; Pichon, C.; Bernardeau, F.; Reimberg, P.

2016-08-01

We present a first principle approach to obtain analytical predictions for spherically averaged cosmic densities in the mildly non-linear regime that go well beyond what is usually achieved by standard perturbation theory. A large deviation principle allows us to compute the leading order cumulants of average densities in concentric cells. In this symmetry, the spherical collapse model leads to cumulant generating functions that are robust for finite variances and free of critical points when logarithmic density transformations are implemented. They yield in turn accurate density probability distribution functions (PDFs) from a straightforward saddle-point approximation valid for all density values. Based on this easy-to-implement modification, explicit analytic formulas for the evaluation of the one- and two-cell PDF are provided. The theoretical predictions obtained for the PDFs are accurate to a few per cent compared to the numerical integration, regardless of the density under consideration and in excellent agreement with N-body simulations for a wide range of densities. This formalism should prove valuable for accurately probing the quasi-linear scales of low-redshift surveys for arbitrary primordial power spectra.

D-He-3 spherical torus fusion reactor system study

NASA Astrophysics Data System (ADS)

Macon, William A., Jr.

1992-04-01

This system study extrapolates present physics knowledge and technology to predict the anticipated characteristics of D-He3 spherical torus fusion reactors and their sensitivity to uncertainties in important parameters. Reference cases for steady-state 1000 MWe reactors operating in H-mode in both the 1st stability regime and the 2nd stability regime were developed and assessed quantitatively. These devices would a very small aspect ratio (A=1,2), a major radius of about 2.0 m, an on-axis magnetic field less than 2 T, a large plasma current (80-120 MA) dominated by the bootstrap effect, and high plasma beta (greater than O.6). The estimated cost of electricity is in the range of 60-90 mills/kW-hr, assuming the use of a direct energy conversion system. The inherent safety and environmental advantages of D-He3 fusion indicate that this reactor concept could be competitive with advanced fission breeder reactors and large-scale solar electric plants by the end of the 21st century if research and development can produce the anticipated physics and technology advances.

The Backscattering Phase Function for a Sphere with a Two-Scale Relief of Rough Surface

NASA Astrophysics Data System (ADS)

Klass, E. V.

2017-12-01

The backscattering of light from spherical surfaces characterized by one and two-scale roughness reliefs has been investigated. The analysis is performed using the three-dimensional Monte-Carlo program POKS-RG (geometrical-optics approximation), which makes it possible to take into account the roughness of objects under study by introducing local geometries of different levels. The geometric module of the program is aimed at describing objects by equations of second-order surfaces. One-scale roughness is set as an ensemble of geometric figures (convex or concave halves of ellipsoids or cones). The two-scale roughness is modeled by convex halves of ellipsoids, with surface containing ellipsoidal pores. It is shown that a spherical surface with one-scale convex inhomogeneities has a flatter backscattering phase function than a surface with concave inhomogeneities (pores). For a sphere with two-scale roughness, the dependence of the backscattering intensity is found to be determined mostly by the lower-level inhomogeneities. The influence of roughness on the dependence of the backscattering from different spatial regions of spherical surface is analyzed.

Error analysis and correction of lever-type stylus profilometer based on Nelder-Mead Simplex method

NASA Astrophysics Data System (ADS)

Hu, Chunbing; Chang, Suping; Li, Bo; Wang, Junwei; Zhang, Zhongyu

2017-10-01

Due to the high measurement accuracy and wide range of applications, lever-type stylus profilometry is commonly used in industrial research areas. However, the error caused by the lever structure has a great influence on the profile measurement, thus this paper analyzes the error of high-precision large-range lever-type stylus profilometry. The errors are corrected by the Nelder-Mead Simplex method, and the results are verified by the spherical surface calibration. It can be seen that this method can effectively reduce the measurement error and improve the accuracy of the stylus profilometry in large-scale measurement.

Using synchronization in multi-model ensembles to improve prediction

NASA Astrophysics Data System (ADS)

Hiemstra, P.; Selten, F.

2012-04-01

In recent decades, many climate models have been developed to understand and predict the behavior of the Earth's climate system. Although these models are all based on the same basic physical principles, they still show different behavior. This is for example caused by the choice of how to parametrize sub-grid scale processes. One method to combine these imperfect models, is to run a multi-model ensemble. The models are given identical initial conditions and are integrated forward in time. A multi-model estimate can for example be a weighted mean of the ensemble members. We propose to go a step further, and try to obtain synchronization between the imperfect models by connecting the multi-model ensemble, and exchanging information. The combined multi-model ensemble is also known as a supermodel. The supermodel has learned from observations how to optimally exchange information between the ensemble members. In this study we focused on the density and formulation of the onnections within the supermodel. The main question was whether we could obtain syn-chronization between two climate models when connecting only a subset of their state spaces. Limiting the connected subspace has two advantages: 1) it limits the transfer of data (bytes) between the ensemble, which can be a limiting factor in large scale climate models, and 2) learning the optimal connection strategy from observations is easier. To answer the research question, we connected two identical quasi-geostrohic (QG) atmospheric models to each other, where the model have different initial conditions. The QG model is a qualitatively realistic simulation of the winter flow on the Northern hemisphere, has three layers and uses a spectral imple-mentation. We connected the models in the original spherical harmonical state space, and in linear combinations of these spherical harmonics, i.e. Empirical Orthogonal Functions (EOFs). We show that when connecting through spherical harmonics, we only need to connect 28% of the state variables to obtain synchronization. In addition, when connecting through EOFs, we can reduce this percentage even more to 12%. This reduction is caused by the more efficient description of the model state variables when using EOFs. The connected state variables center around the medium scale structures in the model. Small and large scale structures need not be connected in order to obtain synchronization. This could be related to the baroclinic instabilities in the QG model which are located in the medium scale structures of the model. The baroclinic instabilities are the main source of divergence between the two connected models.

Spherical harmonic analysis of a model-generated climatology

NASA Technical Reports Server (NTRS)

Christidis, Z. D.; Spar, J.

1981-01-01

Monthly mean fields of 850 mb temperature (T850), 500 mb geopotential height (G500) and sea level pressure (SLP) were generated in the course of a five-year climate simulation run with a global general circulation model. Both the model-generated climatology and an observed climatology were subjected to spherical harmonic analysis, with separate analyses of the globe and the Northern Hemisphere. Comparison of the dominant harmonics of the two climatologies indicates that more than 95% of the area-weighted spatial variance of G500 and more than 90% of that of T850 are explained by fewer than three components, and that the model adequately simulates these large-scale characteristics. On the other hand, as many as 25 harmonics are needed to explain 95% of the observed variance of SLP, and the model simulation of this field is much less satisfactory. The model climatology is also evaluated in terms of the annual cycles of the dominant harmonics.

A NEW THREE-DIMENSIONAL SOLAR WIND MODEL IN SPHERICAL COORDINATES WITH A SIX-COMPONENT GRID

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Xueshang; Zhang, Man; Zhou, Yufen, E-mail: fengx@spaceweather.ac.cn

In this paper, we introduce a new three-dimensional magnetohydrodynamics numerical model to simulate the steady state ambient solar wind from the solar surface to 215 R {sub s} or beyond, and the model adopts a splitting finite-volume scheme based on a six-component grid system in spherical coordinates. By splitting the magnetohydrodynamics equations into a fluid part and a magnetic part, a finite volume method can be used for the fluid part and a constrained-transport method able to maintain the divergence-free constraint on the magnetic field can be used for the magnetic induction part. This new second-order model in space andmore » time is validated when modeling the large-scale structure of the solar wind. The numerical results for Carrington rotation 2064 show its ability to produce structured solar wind in agreement with observations.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boreyko, Jonathan B; Mruetusatorn, Prachya; Sarles, Stephen A

Droplet interface bilayers (DIBs) are a robust platform for studying synthetic cellular membranes; however, to date no DIBs have been produced at cellular length scales. Here, we create microscale droplet interface bilayers ( DIBs) at the interface between aqueous femtoliter-volume droplets within an oil-filled microfluidic channel. The uniquely large area-to-volume ratio of the droplets results in strong evaporation effects, causing the system to transition through three distinct regimes. First, the two adjacent droplets shrink into the shape of a single spherical droplet, where an augmented lipid bilayer partitions two hemi-spherical volumes. In the second regime, the combined effects of themore » shrinking monolayers and growing bilayer force the confined bilayer to buckle to conserve its mass. Finally, at a bending moment corresponding to a critical shear stress, the buckling bilayer fissions a vesicle to regulate its shape and stress. The DIBs produced here enable evaporation-induced bilayer dynamics reminiscent of endo- and exocytosis in cells.« less

Testing large flats with computer generated holograms

NASA Astrophysics Data System (ADS)

Pariani, Giorgio; Tresoldi, Daniela; Spanò, Paolo; Bianco, Andrea

2012-09-01

We describe the optical test of a large flat based on a spherical mirror and a dedicated CGH. The spherical mirror, which can be accurately manufactured and tested in absolute way, allows to obtain a quasi collimated light beam, and the hologram performs the residual wavefront correction. Alignment tools for the spherical mirror and the hologram itself are encoded in the CGH. Sensitivity to fabrication errors and alignment has been evaluated. Tests to verify the effectiveness of our approach are now under execution.

The 3D distribution of cordierite and biotite in hornfels from the Bugaboo contact aureole (British Columbia, Canada)

NASA Astrophysics Data System (ADS)

Gaidies, Fred; Petley-Ragan, Arianne; Pattison, David

2016-04-01

The size, abundance, shape and spatial distribution of metamorphic minerals bears important information on the rates and mechanisms of fundamental processes that take place during metamorphic crystallization. X-ray computed tomography (XR-CT) has become the method of choice to study the three-dimensional (3D) disposition of minerals in rocks as it allows investigation of relatively large sample volumes at sufficiently high resolution required for statistically meaningful analyses, and as its non-destructive fashion permits further studies such as mineral chemical, isotopic or crystallographic analyses of select grains identified through XR-CT. We present results obtained through the quantification of the 3D disposition of cordierite and biotite crystals in a hornfels from the contact aureole of the Bugaboo Batholith (British Columbia, Canada) using XR-CT and global as well as scale-dependent pattern statistics (Petley-Ragan et al., 2016). The results demonstrate a random distribution of cordierite and biotite crystal sizes for all scales across the entire rock volume studied indicative of interface-controlled prograde metamorphic reaction kinetics. We show that the common approach to approximate the shape of crystals as spherical underestimates the influence of the Strauss hard-core process on rock texture which may be misinterpreted to reflect ordering of crystal sizes by inhibition of nucleation and growth commonly associated with diffusion-controlled reaction kinetics. According to our findings, Strauss hard-core ordering develops at length scales equal to and less than the average major axis of the crystal population. This is significantly larger than what is obtained if a spherical crystal geometry would be assumed, and increases with deviation from sphericity. For the cordierite and biotite populations investigated in this research, Strauss hard-core ordering developed at length scales of up to ˜2.2 and 1.25 mm, respectively, which is almost 1 mm longer than the scales that would be obtained if a spherical geometry would have been assumed. Our results highlight the importance of a critical assessment of the geometrical model assumptions commonly applied in the 3D analysis of crystal size distributions, and underline the need for a quantitative understanding of interface processes in order to appreciate their role in the kinetics of contact metamorphic reactions and rock texture formation. References: Petley-Ragan A, Gaidies F, Pattison DRM (2016) A statistical analysis of the distribution of cordierite and biotite in hornfels from the Bugaboo contact aureole: implications for the kinetics of porphyroblast crystallization. Journal of Metamorphic Geology 34:85-101

Models for randomly distributed nanoscopic domains on spherical vesicles

NASA Astrophysics Data System (ADS)

Anghel, Vinicius N. P.; Bolmatov, Dima; Katsaras, John

2018-06-01

The existence of lipid domains in the plasma membrane of biological systems has proven controversial, primarily due to their nanoscopic size—a length scale difficult to interrogate with most commonly used experimental techniques. Scattering techniques have recently proven capable of studying nanoscopic lipid domains populating spherical vesicles. However, the development of analytical methods able of predicting and analyzing domain pair correlations from such experiments has not kept pace. Here, we developed models for the random distribution of monodisperse, circular nanoscopic domains averaged on the surface of a spherical vesicle. Specifically, the models take into account (i) intradomain correlations corresponding to form factors and interdomain correlations corresponding to pair distribution functions, and (ii) the analytical computation of interdomain correlations for cases of two and three domains on a spherical vesicle. In the case of more than three domains, these correlations are treated either by Monte Carlo simulations or by spherical analogs of the Ornstein-Zernike and Percus-Yevick (PY) equations. Importantly, the spherical analog of the PY equation works best in the case of nanoscopic size domains, a length scale that is mostly inaccessible by experimental approaches such as, for example, fluorescent techniques and optical microscopies. The analytical form factors and structure factors of nanoscopic domains populating a spherical vesicle provide a new and important framework for the quantitative analysis of experimental data from commonly studied phase-separated vesicles used in a wide range of biophysical studies.

Precision calculations of the cosmic shear power spectrum projection

NASA Astrophysics Data System (ADS)

Kilbinger, Martin; Heymans, Catherine; Asgari, Marika; Joudaki, Shahab; Schneider, Peter; Simon, Patrick; Van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Hildebrandt, Hendrik; Köhlinger, Fabian; Kuijken, Konrad; Viola, Massimo

2017-12-01

We compute the spherical-sky weak-lensing power spectrum of the shear and convergence. We discuss various approximations, such as flat-sky, and first- and second-order Limber equations for the projection. We find that the impact of adopting these approximations is negligible when constraining cosmological parameters from current weak-lensing surveys. This is demonstrated using data from the Canada-France-Hawaii Telescope Lensing Survey. We find that the reported tension with Planck cosmic microwave background temperature anisotropy results cannot be alleviated. For future large-scale surveys with unprecedented precision, we show that the spherical second-order Limber approximation will provide sufficient accuracy. In this case, the cosmic-shear power spectrum is shown to be in agreement with the full projection at the sub-percent level for ℓ > 3, with the corresponding errors an order of magnitude below cosmic variance for all ℓ. When computing the two-point shear correlation function, we show that the flat-sky fast Hankel transformation results in errors below two percent compared to the full spherical transformation. In the spirit of reproducible research, our numerical implementation of all approximations and the full projection are publicly available within the package NICAEA at http://www.cosmostat.org/software/nicaea.

Effect of boric acid on the properties of Li{sub 2}MnO{sub 3}·LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders prepared by large-scale spray pyrolysis with droplet classifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Young Jun; Choi, Seung Ho; Sim, Chul Min

2012-12-15

Graphical abstract: Display Omitted Highlights: ► Spherical shape Li{sub 2}MnO{sub 3}·LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders are prepared by large-scale spray pyrolysis with droplet classifier. ► Boric acid improves the morphological and electrochemical properties of the composite cathode powders. ► The discharge capacity of the composite cathode powders decreases from 217 to 196 mAh g{sup −1} by the 30th cycle. -- Abstract: Spherically shaped 0.3Li{sub 2}MnO{sub 3}·0.7LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders with filled morphology and narrow size distribution are prepared by large-scale spray pyrolysis. A droplet classification reduces the standard deviation of the size distribution of themore » composite cathode powders. Addition of boric acid improves the morphological properties of the product powders by forming a lithium borate glass material with low melting temperature. The optimum amount of boric acid dissolved in the spray solution is 0.8 wt% of the composite powders. The powders prepared from the spray solution with 0.8 wt% boric acid have a mixed layered crystal structure comprising Li{sub 2}MnO{sub 3} and LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} phases, thus forming a composite compound. The initial charge and discharge capacities of the composite cathode powders prepared from the 0.8 wt% boric acid spray solution are 297 and 217 mAh g{sup −1}, respectively. The discharge capacity of the powders decreases from 217 to 196 mAh g{sup −1} by the 30th cycle, in which the capacity retention is 90%.« less

Large Scale Brownian Dynamics of Confined Suspensions of Rigid Particles

NASA Astrophysics Data System (ADS)

Donev, Aleksandar; Sprinkle, Brennan; Balboa, Florencio; Patankar, Neelesh

2017-11-01

We introduce new numerical methods for simulating the dynamics of passive and active Brownian colloidal suspensions of particles of arbitrary shape sedimented near a bottom wall. The methods also apply for periodic (bulk) suspensions. Our methods scale linearly in the number of particles, and enable previously unprecedented simulations of tens to hundreds of thousands of particles. We demonstrate the accuracy and efficiency of our methods on a suspension of boomerang-shaped colloids. We also model recent experiments on active dynamics of uniform suspensions of spherical microrollers. This work was supported in part by the National Science Foundation under award DMS-1418706, and by the U.S. Department of Energy under award DE-SC0008271.

Fractal scaling laws of black carbon aerosol and their influence on spectral radiative properties

NASA Astrophysics Data System (ADS)

Tiwari, S.; Chakrabarty, R. K.; Heinson, W.

2016-12-01

Current estimates of the direct radiative forcing for Black Carbon (BC) aerosol span over a poorly constrained range between 0.2 and 1 W.m-2. To improve this large uncertainty, tighter constraints need to be placed on BC's key wavelength-dependent optical properties, namely, the absorption (MAC) and scattering (MSC) cross sections per unit mass and hemispherical upscatter fraction (β; a dimensionless scattering directionality parameter). These parameters are very sensitive to changes in particle morphology and complex refractive index nindex. Their interplay determines the magnitude of net positive or negative radiative forcing efficiencies. The current approach among climate modelers for estimating MAC and MSC values of BC is from their optical cross-sections calculated assuming spherical particle morphology with homogeneous, constant-valued refractive index in the visible solar spectrum. The β values are typically assumed to be a constant across this spectrum. This approach, while being computationally inexpensive and convenient, ignores the inherent fractal morphology of BC and its scaling behaviors, and resulting optical properties. In this talk, I will present recent results from my laboratory on determination of the fractal scaling laws of BC aggregate packing density and its complex refractive index for size spanning across three orders of magnitude, and their effects on spectral (Visible-infrared wavelength) scaling of MAC, MSC, and β values. Our experiments synergistically combined novel BC generation techniques, aggregation models, contact-free multi-wavelength optical measurements, and electron microscopy analysis. The scale dependence of nindex on aggregate size followed power-law exponents of -1.4 and -0.5 for sub- and super-micron size aggregates, respectively. The spherical Rayleigh-optics approximation limits, used by climate models for spectral extrapolation of BC optical cross-sections and deconvolution of multi-species mixing ratios, are redefined using the concept of phase shift parameter. I will highlight the importance of size-dependent β values and its role in offsetting the strong light absorbing nature of BC. Finally, the errors introduced in forcing efficiency calculations of BC by assuming spherical homogeneous morphology will be evaluated.

Laboratory and theoretical models of planetary-scale instabilities and waves

NASA Technical Reports Server (NTRS)

Hart, John E.; Toomre, Juri

1990-01-01

Meteorologists and planetary astronomers interested in large-scale planetary and solar circulations recognize the importance of rotation and stratification in determining the character of these flows. In the past it has been impossible to accurately model the effects of sphericity on these motions in the laboratory because of the invariant relationship between the uni-directional terrestrial gravity and the rotation axis of an experiment. Researchers studied motions of rotating convecting liquids in spherical shells using electrohydrodynamic polarization forces to generate radial gravity, and hence centrally directed buoyancy forces, in the laboratory. The Geophysical Fluid Flow Cell (GFFC) experiments performed on Spacelab 3 in 1985 were analyzed. Recent efforts at interpretation led to numerical models of rotating convection with an aim to understand the possible generation of zonal banding on Jupiter and the fate of banana cells in rapidly rotating convection as the heating is made strongly supercritical. In addition, efforts to pose baroclinic wave experiments for future space missions using a modified version of the 1985 instrument led to theoretical and numerical models of baroclinic instability. Rather surprising properties were discovered, which may be useful in generating rational (rather than artificially truncated) models for nonlinear baroclinic instability and baroclinic chaos.

Double slotted socket spherical joint

DOEpatents

Bieg, Lothar F.; Benavides, Gilbert L.

2001-05-22

A new class of spherical joints is disclosed. These spherical joints are capable of extremely large angular displacements (full cone angles in excess of 270.degree.), while exhibiting no singularities or dead spots in their range of motion. These joints can improve or simplify a wide range of mechanical devices.

Spherical cows in dark matter indirect detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernal, Nicolás; Necib, Lina; Slatyer, Tracy R., E-mail: nicolas.bernal@uan.edu.co, E-mail: lnecib@mit.edu, E-mail: tslatyer@mit.edu

2016-12-01

Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated wellmore » outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.« less

Spherical cows in dark matter indirect detection

NASA Astrophysics Data System (ADS)

Bernal, Nicolás; Necib, Lina; Slatyer, Tracy R.

2016-12-01

Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.

Non-Gaussian Multi-resolution Modeling of Magnetosphere-Ionosphere Coupling Processes

NASA Astrophysics Data System (ADS)

Fan, M.; Paul, D.; Lee, T. C. M.; Matsuo, T.

2016-12-01

The most dynamic coupling between the magnetosphere and ionosphere occurs in the Earth's polar atmosphere. Our objective is to model scale-dependent stochastic characteristics of high-latitude ionospheric electric fields that originate from solar wind magnetosphere-ionosphere interactions. The Earth's high-latitude ionospheric electric field exhibits considerable variability, with increasing non-Gaussian characteristics at decreasing spatio-temporal scales. Accurately representing the underlying stochastic physical process through random field modeling is crucial not only for scientific understanding of the energy, momentum and mass exchanges between the Earth's magnetosphere and ionosphere, but also for modern technological systems including telecommunication, navigation, positioning and satellite tracking. While a lot of efforts have been made to characterize the large-scale variability of the electric field in the context of Gaussian processes, no attempt has been made so far to model the small-scale non-Gaussian stochastic process observed in the high-latitude ionosphere. We construct a novel random field model using spherical needlets as building blocks. The double localization of spherical needlets in both spatial and frequency domains enables the model to capture the non-Gaussian and multi-resolutional characteristics of the small-scale variability. The estimation procedure is computationally feasible due to the utilization of an adaptive Gibbs sampler. We apply the proposed methodology to the computational simulation output from the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) magnetosphere model. Our non-Gaussian multi-resolution model results in characterizing significantly more energy associated with the small-scale ionospheric electric field variability in comparison to Gaussian models. By accurately representing unaccounted-for additional energy and momentum sources to the Earth's upper atmosphere, our novel random field modeling approach will provide a viable remedy to the current numerical models' systematic biases resulting from the underestimation of high-latitude energy and momentum sources.

Three-dimensional presentation of the earth and planets in classrooms and science centers with a spherical screen

NASA Astrophysics Data System (ADS)

Saito, A.; Tsugawa, T.; Odagi, Y.; Nishi, N.; Miyazaki, S.; Ichikawa, H.

2012-12-01

Educational programs have been developed for the earth and planetary science using a three-dimensional presentation system of the Earth and planets with a spherical screen. They have been used in classrooms of universities, high schools, elementary schools, and science centers. Two-dimensional map is a standard tool to present the data of the Earth and planets. However the distortion of the shape is inevitable especially for the map of wide areas. Three-dimensional presentation of the Earth, such as globes, is an only way to avoid this distortion. There are several projects to present the earth and planetary science results in three-dimension digitally, such as Science on a sphere (SOS) by NOAA, and Geo-cosmos by the National Museum of Emerging Science and Innovation (Miraikan), Japan. These projects are relatively large-scale in instruments and cost, and difficult to use in classrooms and small-scale science centers. Therefore we developed a portable, scalable and affordable system of the three-dimensional presentation of the Earth and planets, Dagik Earth. This system uses a spherical screen and a PC projector. Several educational programs have been developed using Dagik Earth under collaboration of the researchers of the earth and planetary science and science education, school teachers, and curators of science centers, and used in schools and museums in Japan, Taiwan and other countries. It helps learners to achieve the proper cognition of the shape and size of the phenomena on the Earth and planets. Current status and future development of the project will be introduced in the presentation.

Observations of reduced electron Gyroscale fluctuations in national spherical torus experiment H-mode plasmas with large ExB flow shear.

PubMed

Smith, D R; Kaye, S M; Lee, W; Mazzucato, E; Park, H K; Bell, R E; Domier, C W; Leblanc, B P; Levinton, F M; Luhmann, N C; Menard, J E; Yuh, H

2009-06-05

Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.

Viscous decay of nonlinear oscillations of a spherical bubble at large Reynolds number

NASA Astrophysics Data System (ADS)

Smith, W. R.; Wang, Q. X.

2017-08-01

The long-time viscous decay of large-amplitude bubble oscillations is considered in an incompressible Newtonian fluid, based on the Rayleigh-Plesset equation. At large Reynolds numbers, this is a multi-scaled problem with a short time scale associated with inertial oscillation and a long time scale associated with viscous damping. A multi-scaled perturbation method is thus employed to solve the problem. The leading-order analytical solution of the bubble radius history is obtained to the Rayleigh-Plesset equation in a closed form including both viscous and surface tension effects. Some important formulae are derived including the following: the average energy loss rate of the bubble system during each cycle of oscillation, an explicit formula for the dependence of the oscillation frequency on the energy, and an implicit formula for the amplitude envelope of the bubble radius as a function of the energy. Our theory shows that the energy of the bubble system and the frequency of oscillation do not change on the inertial time scale at leading order, the energy loss rate on the long viscous time scale being inversely proportional to the Reynolds number. These asymptotic predictions remain valid during each cycle of oscillation whether or not compressibility effects are significant. A systematic parametric analysis is carried out using the above formula for the energy of the bubble system, frequency of oscillation, and minimum/maximum bubble radii in terms of the Reynolds number, the dimensionless initial pressure of the bubble gases, and the Weber number. Our results show that the frequency and the decay rate have substantial variations over the lifetime of a decaying oscillation. The results also reveal that large-amplitude bubble oscillations are very sensitive to small changes in the initial conditions through large changes in the phase shift.

Electric double layer electrostatics of pH-responsive spherical polyelectrolyte brushes in the decoupled regime.

PubMed

Li, Hao; Chen, Guang; Das, Siddhartha

2016-11-01

Understanding the behavior and properties of spherical polyelectrolyte brushes (SPEBs), which are polyelectrolyte brushes grafted to a spherical core, is fundamental to many applications in biomedical, chemical and petroleum engineering as well as in pharmaceutics. In this paper, we study the pH-responsive electrostatics of such SPEBs in the decoupled regime. In the first part of the paper, we derive the scaling conditions in terms of the grafting density of the PEs on the spherical core that ensure that the analysis can be performed in the decoupled regime. In such a regime the elastic and the excluded volume effects of polyelectrolyte brushes (PEBs) can be decoupled from the electrostatic effects associated with the PE charge and the induced EDL. As a consequence the PE brush height, assumed to be dictated by the balance of the elastic and excluded volume effects, can be independent of the electrostatic effects. In the second part, we quantify the pH-responsive electrostatics of the SPEBs - we pinpoint that the radial monomer distribution for a given brush molecule exhibit a non-unique cubic distribution that decays away from the spherical core. Such a monomer distribution ensures that the hydrogen ion concentration is appropriately accounted for in the description of the SPEB thermodynamics. We anticipate that the present analysis, which provides possibly one of the first models for probing the electrostatics of pH-responsive SPEBs in a thermodynamically-consistent framework, will be vital for understanding the behavior of a large number of entities ranging from PE-coated NPs and stealth liposomes to biomolecules like bacteria and viruses. Copyright © 2016 Elsevier B.V. All rights reserved.

Aberration of a negative ion beam caused by space charge effect.

PubMed

Miyamoto, K; Wada, S; Hatayama, A

2010-02-01

Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.

Phytofabrication and characterization of monodisperse copper oxide nanoparticles using Albizia lebbeck leaf extract

NASA Astrophysics Data System (ADS)

Jayakumarai, G.; Gokulpriya, C.; Sudhapriya, R.; Sharmila, G.; Muthukumaran, C.

2015-12-01

Simple effective and rapid approach for the green synthesis of copper oxide nanoparticles (CONPs) using of Albizia lebbeck leaf extract was investigated in this study. Various instrumental techniques were adopted to characterize the synthesized CONPs, viz. UV-Vis spectroscopy, SEM, TEM, EDS and XRD. The synthesized CONPs were found to be spherical in shape and size less than 100 nm. It could be concluded that A. lebbeck leaf extract can be used as a cheap and effective reducing agent for CONPs production in large scale.

Seismic Constraints on Interior Solar Convection

NASA Technical Reports Server (NTRS)

Hanasoge, Shravan M.; Duvall, Thomas L.; DeRosa, Marc L.

2010-01-01

We constrain the velocity spectral distribution of global-scale solar convective cells at depth using techniques of local helioseismology. We calibrate the sensitivity of helioseismic waves to large-scale convective cells in the interior by analyzing simulations of waves propagating through a velocity snapshot of global solar convection via methods of time-distance helioseismology. Applying identical analysis techniques to observations of the Sun, we are able to bound from above the magnitudes of solar convective cells as a function of spatial convective scale. We find that convection at a depth of r/R(solar) = 0.95 with spatial extent l < 30, where l is the spherical harmonic degree, comprise weak flow systems, on the order of 15 m/s or less. Convective features deeper than r/R(solar) = 0.95 are more difficult to image due to the rapidly decreasing sensitivity of helioseismic waves.

Titanate and titania nanostructures and nanostructure assemblies, and methods of making same

DOEpatents

Wong, Stanislaus S.; Mao, Yuanbing

2016-06-14

The invention relates to nanomaterial's and assemblies including, a micrometer-scale spherical aggregate comprising: a plurality of one-dimensional nanostructures comprising titanium and oxygen, wherein the one-dimensional nanostructures radiate from a hollow central core thereby forming a spherical aggregate.

Titanate and titania nanostructures and nanostructure assemblies, and methods of making same

DOEpatents

Wong, Stanislaus S; Mao, Yuanbing

2013-05-14

The invention relates to nanomaterials and assemblies including, a micrometer-scale spherical aggregate comprising: a plurality of one-dimensional nanostructures comprising titanium and oxygen, wherein the one-dimensional nanostructures radiate from a hollow central core thereby forming a spherical aggregate.

Shape effects on time-scale divergence at athermal jamming transition of frictionless non-spherical particles

NASA Astrophysics Data System (ADS)

Yuan, Ye; Jin, Weiwei; Liu, Lufeng; Li, Shuixiang

2017-10-01

The critical behaviors of a granular system at the jamming transition have been extensively studied from both mechanical and thermodynamic perspectives. In this work, we numerically investigate the jamming behaviors of a variety of frictionless non-spherical particles, including spherocylinder, ellipsoid, spherotetrahedron and spherocube. In particular, for a given particle shape, a series of random configurations at different fixed densities are generated and relaxed to minimize interparticle overlaps using the relaxation algorithm. We find that as the jamming point (i.e., point J) is approached, the number of iteration steps (defined as the "time-scale" for our systems) required to completely relax the interparticle overlaps exhibits a clear power-law divergence. The dependence of the detailed mathematical form of the power-law divergence on particle shapes is systematically investigated and elucidated, which suggests that the shape effects can be generally categorized as elongation and roundness. Importantly, we show the jamming transition density can be accurately determined from the analysis of time-scale divergence for different non-spherical shapes, and the obtained values agree very well with corresponding ones reported in literature. Moreover, we study the plastic behaviors of over-jammed packings of different particles under a compression-expansion procedure and find that the jamming of ellipsoid is much more robust than other non-spherical particles. This work offers an alternative approximate procedure besides conventional packing algorithms for studying athermal jamming transition in granular system of frictionless non-spherical particles.

Scalable MWIR and LWIR optical system designs employing a large spherical primary mirror and small refractive aberration correctors

NASA Astrophysics Data System (ADS)

Beach, David A.

2001-12-01

Design variants of a recently developed optical imaging system have been computed for the thermal infrared spectral bands, which offer some advantages for long-range surveillance and astronomy. Only the spherical primary mirror has the full pupil diameter, all other components being sub-diameter, so scaling is possible up to relatively large pupils. Low-cost fabrication is enabled by the prevalence of spherical optical surfaces. Both MWIR and LWIR spectral transmissions are enabled by the choice of corrector materials, the examples given employing germanium and sapphire for 3.5 - 5.5 micrometers and germanium and zinc selenide for 3.5 - 5.5 micrometers and 8 - 12 micrometers passbands. Diffraction at these wavelengths is the main contributor to resolution constraints, so high numerical aperture values are preferred to enable a better match of blur spot diameter to generally available pixel dimensions. The systems described can routinely be designed to have speeds of f/0.8 or faster, while maintaining diffraction-limited performance over useful angular fields. Because the new design system employs a relayed catadioptric, it is possible to make the aperture stop of the system coincident with the window of the detector cryostat, enabling precise radiometric geometry. The central obscuration provides a convenient location for a calibration source, and both this and a mask for secondary spider supports can be included within the detector cold screen structure. Dual-band operation could be enabled by inclusion of a spectral beam splitter prior to a dual relay/imager system.

Scaling of Linking and Writhing Numbers for Spherically Confined and Topologically Equilibrated Flexible Polymers

PubMed Central

Marko, John F.

2011-01-01

Scaling laws for Gauss linking number Ca and writhing number Wr for spherically confined flexible polymers with thermally fluctuating topology are analyzed. For ideal (phantom) polymers each of N segments of length unity confined to a spherical pore of radius R there are two scaling regimes: for sufficiently weak confinement (R ⪢ N1/3) each chain has |Wr| ≈ N1/2, and each pair of chains has average |Ca| ≈ N/R3/2; alternately for sufficiently tight confinement (N1/3 ⪢ R), |Wr| ≈ |CA| ≈ N/R3/2. Adding segment-segment avoidance modifies this result: for n chains with excluded volume interactions |Ca| ≈ (N/n)1/2f(ϕ) where f is a scaling function that depends approximately linearly on the segment concentration ϕ = nN/R3. Scaling results for writhe are used to estimate the maximum writhe of a polymer; this is demonstrated to be realizable through a writhing instability that occurs for a polymer which is able to change knotting topology and which is subject to an applied torque. Finally, scaling results for linking are used to estimate bounds on the entanglement complexity of long chromosomal DNA molecules inside cells, and to show how “lengthwise” chromosome condensation can suppress DNA entanglement. PMID:21686050

Short-scale turbulent fluctuations driven by the electron-temperature gradient in the national spherical torus experiment.

PubMed

Mazzucato, E; Smith, D R; Bell, R E; Kaye, S M; Hosea, J C; LeBlanc, B P; Wilson, J R; Ryan, P M; Domier, C W; Luhmann, N C; Yuh, H; Lee, W; Park, H

2008-08-15

Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k perpendicular rho(e)=0.1-0.4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient.

Potential Field Modeling at Global to Prospect Scales - Adding Value to the Geological, Seismic, Gravity, Magnetic and Rock Property Datasets of Australia

NASA Astrophysics Data System (ADS)

Lane, R. J. L.

2015-12-01

At Geoscience Australia, we are upgrading our gravity and magnetic modeling tools to provide new insights into the composition, properties, and structure of the subsurface. The scale of the investigations varies from the size of tectonic plates to the size of a mineral prospect. To accurately model potential field data at all of these scales, we require modeling software that can operate in both spherical and Cartesian coordinate frameworks. The models are in the form of a mesh, with spherical prismatic (tesseroid) elements for spherical coordinate models of large volumes, and rectangular prisms for smaller volumes evaluated in a Cartesian coordinate framework. The software can compute the forward response of supplied rock property models and can perform inversions using constraints that vary from weak generic smoothness through to very specific reference models compiled from various types of "hard facts" (i.e., surface mapping, drilling information, crustal seismic interpretations). To operate efficiently, the software is being specifically developed to make use of the resources of the National Computational Infrastructure (NCI) at the Australian National University (ANU). The development of these tools is been carried out in collaboration with researchers from the Colorado School of Mines (CSM) and the China University of Geosciences (CUG) and is at the stage of advanced testing. The creation of individual 3D geological models will provide immediate insights. Users will also be able to combine models, either by stitching them together or by nesting smaller and more detailed models within a larger model. Comparison of the potential field response of a composite model with the observed fields will give users a sense of how comprehensively these models account for the observations. Users will also be able to model the residual fields (i.e., the observed minus calculated response) to discover features that are not represented in the input composite model.

Fabrication and characterization of millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} ceramic hollow spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Haoting; Liao, Qilong, E-mail: liaoqilong@swust.edu.cn; Dai, Yunya

2016-04-15

Highlights: • Millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} hollow spheres have been prepared. • The diameters of the prepared hollow spheres are 500–1300μm. • The degree of sphericity for the prepared hollow spheres is above 98%. • The mechanisms of transparency are discussed. - Abstract: Millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} ceramic hollow spheres have been successfully prepared using the oil-in-water (paraffin-in-alumina sol) droplets as precursors made by self-made T-shape micro-emulsion device. The main crystalline phase of the obtained hollow sphere is alpha alumina. The prepared translucent La{sub 2}O{sub 3}-containing Al{sub 2}O{sub 3} ceramic hollow spheresmore » have diameters of 500–1300 μm, wall thickness of about 23 μm and the degree of sphericity of above 98%. With the increase of the La{sub 2}O{sub 3} content, grains and grain-boundaries of the alumina spherical shell for the prepared millimeter-scale hollow spheres become regular and clear gradually. When the La{sub 2}O{sub 3} content is 0.1 wt.%, the crystal surface of the obtained Al{sub 2}O{sub 3} spherical shell shows optimal grains and few pores, and its transmittance reaches 42% at 532 nm laser light. This method provides a promising technique of preparing millimeter-scale translucent ceramic hollow spheres for laser inertial confined fusion.« less

Spherical Model Integrating Academic Competence with Social Adjustment and Psychopathology.

ERIC Educational Resources Information Center

Schaefer, Earl S.; And Others

This study replicates and elaborates a three-dimensional, spherical model that integrates research findings concerning social and emotional behavior, psychopathology, and academic competence. Kindergarten teachers completed an extensive set of rating scales on 100 children, including the Classroom Behavior Inventory and the Child Adaptive Behavior…

Large-deformation electrohydrodynamics of an elastic capsule in a DC electric field

NASA Astrophysics Data System (ADS)

Das, Sudip; Thaokar, Rochish M.

2018-04-01

The dynamics of a spherical elastic capsule, containing a Newtonian fluid bounded by an elastic membrane and immersed in another Newtonian fluid, in a uniform DC electric field is investigated. Discontinuity of electrical properties such as conductivities of the internal and external fluid media as well as capacitance and conductance of the membrane lead to a net interfacial Maxwell stress which can cause the deformation of such an elastic capsule. We investigate this problem considering well established membrane laws for a thin elastic membrane, with fully resolved hydrodynamics in the Stokes flow limit and describe the electrostatics using the capacitor model. In the limit of small deformation, the analytical theory predicts the dynamics fairly satisfactorily. Large deformations at high capillary number though necessitate a numerical approach (Boundary element method in the present case) to solve this highly non-linear problem. Akin to vesicles, at intermediate times, highly nonlinear biconcave shapes along with squaring and hexagon like shapes are observed when the outer medium is more conducting. The study identifies the essentiality of parameters such as high membrane capacitance, low membrane conductance, low hydrodynamic time scales and high capillary number for observation of these shape transitions. The transition is due to large compressive Maxwell stress at the poles at intermediate times. Thus such shape transition can be seen in spherical globules admitting electrical capacitance, possibly, irrespective of the nature of the interfacial restoring force.

Modeling mantle convection in the spherical annulus

NASA Astrophysics Data System (ADS)

Hernlund, John W.; Tackley, Paul J.

2008-12-01

Most methods for modeling mantle convection in a two-dimensional (2D) circular annular domain suffer from innate shortcomings in their ability to capture several characteristics of the spherical shell geometry of planetary mantles. While methods such as rescaling the inner and outer radius to reduce anomalous effects in a 2D polar cylindrical coordinate system have been introduced and widely implemented, such fixes may have other drawbacks that adversely affect the outcome of some kinds of mantle convection studies. Here we propose a new approach that we term the "spherical annulus," which is a 2D slice that bisects the spherical shell and is quantitatively formulated at the equator of a spherical polar coordinate system after neglecting terms in the governing equations related to variations in latitude. Spherical scaling is retained in this approximation since the Jacobian function remains proportional to the square of the radius. We present example calculations to show that the behavior of convection in the spherical annulus compares favorably against calculations performed in other 2D annular domains when measured relative to those in a fully three-dimensional (3D) spherical shell.

Supercontinental warming of the mantle at the origin of gigantic flood basalts

NASA Astrophysics Data System (ADS)

Coltice, N.; Phillips, B. R.; Bertrand, H.; Ricard, Y.; Rey, P.

2006-12-01

Continents episodically cluster together into a supercontinent, eventually breaking up with intense magmatic activity supposedly causedby mantle plumes. The break-up of Pangea, the last supercontinent, was accompanied by the emplacement of the largest known continental flood basalt, the Central Atlantic Magmatic Province, causing massive extinctions at the Triassic/Jurassic boundary. However, there is little support for a plume origin for this catastrophic event. On the basis of 2D and 3D spherical convection modelling in a internally heated mantle, we show that continental aggregation leads to large-scale melting without requiring the involvement of plumes. When only internal heat sources in the mantle are considered, the formationof a supercontinent causes the enlargement of the wavelength of the flow and a subcontinental warming as large as 100^{\\mboxo}C. This temperature increase may lead to large- scale melting without the involvment of plumes. Our results suggest the existence of two distinct types of continental flood basalts, caused by plume or by supercontinental warming. We review some potential candidates for our proposed model.

A Practical Computational Method for the Anisotropic Redshift-Space 3-Point Correlation Function

NASA Astrophysics Data System (ADS)

Slepian, Zachary; Eisenstein, Daniel J.

2018-04-01

We present an algorithm enabling computation of the anisotropic redshift-space galaxy 3-point correlation function (3PCF) scaling as N2, with N the number of galaxies. Our previous work showed how to compute the isotropic 3PCF with this scaling by expanding the radially-binned density field around each galaxy in the survey into spherical harmonics and combining these coefficients to form multipole moments. The N2 scaling occurred because this approach never explicitly required the relative angle between a galaxy pair about the primary galaxy. Here we generalize this work, demonstrating that in the presence of azimuthally-symmetric anisotropy produced by redshift-space distortions (RSD) the 3PCF can be described by two triangle side lengths, two independent total angular momenta, and a spin. This basis for the anisotropic 3PCF allows its computation with negligible additional work over the isotropic 3PCF. We also present the covariance matrix of the anisotropic 3PCF measured in this basis. Our algorithm tracks the full 5-D redshift-space 3PCF, uses an accurate line of sight to each triplet, is exact in angle, and easily handles edge correction. It will enable use of the anisotropic large-scale 3PCF as a probe of RSD in current and upcoming large-scale redshift surveys.

Hunting high and low: disentangling primordial and late-time non-Gaussianity with cosmic densities in spheres

NASA Astrophysics Data System (ADS)

Uhlemann, C.; Pajer, E.; Pichon, C.; Nishimichi, T.; Codis, S.; Bernardeau, F.

2018-03-01

Non-Gaussianities of dynamical origin are disentangled from primordial ones using the formalism of large deviation statistics with spherical collapse dynamics. This is achieved by relying on accurate analytical predictions for the one-point probability distribution function and the two-point clustering of spherically averaged cosmic densities (sphere bias). Sphere bias extends the idea of halo bias to intermediate density environments and voids as underdense regions. In the presence of primordial non-Gaussianity, sphere bias displays a strong scale dependence relevant for both high- and low-density regions, which is predicted analytically. The statistics of densities in spheres are built to model primordial non-Gaussianity via an initial skewness with a scale dependence that depends on the bispectrum of the underlying model. The analytical formulas with the measured non-linear dark matter variance as input are successfully tested against numerical simulations. For local non-Gaussianity with a range from fNL = -100 to +100, they are found to agree within 2 per cent or better for densities ρ ∈ [0.5, 3] in spheres of radius 15 Mpc h-1 down to z = 0.35. The validity of the large deviation statistics formalism is thereby established for all observationally relevant local-type departures from perfectly Gaussian initial conditions. The corresponding estimators for the amplitude of the non-linear variance σ8 and primordial skewness fNL are validated using a fiducial joint maximum likelihood experiment. The influence of observational effects and the prospects for a future detection of primordial non-Gaussianity from joint one- and two-point densities-in-spheres statistics are discussed.

Acoustic wavefield and Mach wave radiation of flashing arcs in strombolian explosion measured by image luminance

NASA Astrophysics Data System (ADS)

Genco, Riccardo; Ripepe, Maurizio; Marchetti, Emanuele; Bonadonna, Costanza; Biass, Sebastien

2014-10-01

Explosive activity often generates visible flashing arcs in the volcanic plume considered as the evidence of the shock-front propagation induced by supersonic dynamics. High-speed image processing is used to visualize the pressure wavefield associated with flashing arcs observed in strombolian explosions. Image luminance is converted in virtual acoustic signal compatible with the signal recorded by pressure transducer. Luminance variations are moving with a spherical front at a 344.7 m/s velocity. Flashing arcs travel at the sound speed already 14 m above the vent and are not necessarily the evidence of a supersonic explosive dynamics. However, seconds later, the velocity of small fragments increases, and the spherical acousto-luminance wavefront becomes planar recalling the Mach wave radiation generated by large scale turbulence in high-speed jet. This planar wavefront forms a Mach angle of 55° with the explosive jet axis, suggesting an explosive dynamics moving at Mo = 1.22 Mach number.

Three-dimensional computer model for the atmospheric general circulation experiment

NASA Technical Reports Server (NTRS)

Roberts, G. O.

1984-01-01

An efficient, flexible, three-dimensional, hydrodynamic, computer code has been developed for a spherical cap geometry. The code will be used to simulate NASA's Atmospheric General Circulation Experiment (AGCE). The AGCE is a spherical, baroclinic experiment which will model the large-scale dynamics of our atmosphere; it has been proposed to NASA for future Spacelab flights. In the AGCE a radial dielectric body force will simulate gravity, with hot fluid tending to move outwards. In order that this force be dominant, the AGCE must be operated in a low gravity environment such as Spacelab. The full potential of the AGCE will only be realized by working in conjunction with an accurate computer model. Proposed experimental parameter settings will be checked first using model runs. Then actual experimental results will be compared with the model predictions. This interaction between experiment and theory will be very valuable in determining the nature of the AGCE flows and hence their relationship to analytical theories and actual atmospheric dynamics.

Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.

Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearlymore » establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. As a result, this nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.« less

Exact solution of mean-field plus an extended T = 1 nuclear pairing Hamiltonian in the seniority-zero symmetric subspace

NASA Astrophysics Data System (ADS)

Pan, Feng; Ding, Xiaoxue; Launey, Kristina D.; Dai, Lianrong; Draayer, Jerry P.

2018-05-01

An extended pairing Hamiltonian that describes multi-pair interactions among isospin T = 1 and angular momentum J = 0 neutron-neutron, proton-proton, and neutron-proton pairs in a spherical mean field, such as the spherical shell model, is proposed based on the standard T = 1 pairing formalism. The advantage of the model lies in the fact that numerical solutions within the seniority-zero symmetric subspace can be obtained more easily and with less computational time than those calculated from the mean-field plus standard T = 1 pairing model. Thus, large-scale calculations within the seniority-zero symmetric subspace of the model is feasible. As an example of the application, the average neutron-proton interaction in even-even N ∼ Z nuclei that can be suitably described in the f5 pg9 shell is estimated in the present model, with a focus on the role of np-pairing correlations.

Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

DOE PAGES

Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; ...

2017-03-16

Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearlymore » establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. As a result, this nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.« less

Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

NASA Astrophysics Data System (ADS)

Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

2017-03-01

Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.

Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power.

PubMed

Li, Binsong; Bian, Kaifu; Lane, J Matthew D; Salerno, K Michael; Grest, Gary S; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

2017-03-16

Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.

Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

PubMed Central

Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

2017-01-01

Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales. PMID:28300067

Motion of a Spherical Domain Wall and the Large-Scale Structure Formation

NASA Astrophysics Data System (ADS)

Yamamoto, K.; Tomita, K.

1991-11-01

The evolution of a wall-like structure in the universe is investigated by assuming a simplified model of a domain wall. The domain wall is approximated as a thin spherical shell with domain wall-like matter, which is assumed to interact with dust-like dark matter in an entirely inelastic manner, and its motion in an expanding universe is numerically studied in the general-relativistic treatment. We evaluate the lifetime of the wall, which is defined as the characteristic time for the wall to shrink due to its own tension. It is necessary that this time is not smaller than the cosmic age, in order that the walls avoid the collapse to the present time and play an important role in the structure formation of the universe. It is shown that, in spite of the above interaction, the strong restriction is imposed on the surface density of the domain walls and the allowed values are too small to have any influences on the background model.

Synthesis of water dispersible boron core silica shell (B@SiO2) nanoparticles

NASA Astrophysics Data System (ADS)

Walton, Nathan I.; Gao, Zhe; Eygeris, Yulia; Ghandehari, Hamidreza; Zharov, Ilya

2018-04-01

Water dispersible boron nanoparticles have great potential as materials for boron neutron capture therapy of cancer and magnetic resonance imaging, if they are prepared on a large scale with uniform size and shape and hydrophilic modifiable surface. We report the first method to prepare spherical, monodisperse, water dispersible boron core silica shell nanoparticles (B@SiO2 NPs) suitable for aforementioned biomedical applications. In this method, 40 nm elemental boron nanoparticles, easily prepared by mechanical milling and carrying 10-undecenoic acid surface ligands, are hydrosilylated using triethoxysilane, followed by base-catalyzed hydrolysis of tetraethoxysilane, which forms a 10-nm silica shell around the boron core. This simple two-step process converts irregularly shaped hydrophobic boron particles into the spherically shaped uniform nanoparticles. The B@SiO2 NPs are dispersible in water and the silica shell surface can be modified with primary amines that allow for the attachment of a fluorophore and, potentially, of targeting moieties. [Figure not available: see fulltext.

Simulation of current-filament dynamics and relaxation in the Pegasus Spherical Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Bryan, J. B.; Sovinec, C. R.; Bird, T. M.

Nonlinear numerical computation is used to investigate the relaxation of non-axisymmetric current-channels from washer-gun plasma sources into 'tokamak-like' plasmas in the Pegasus toroidal experiment [Eidietis et al. J. Fusion Energy 26, 43 (2007)]. Resistive MHD simulations with the NIMROD code [Sovinec et al. Phys. Plasmas 10(5), 1727-1732 (2003)] utilize ohmic heating, temperature-dependent resistivity, and anisotropic, temperature-dependent thermal conduction corrected for regions of low magnetization to reproduce critical transport effects. Adjacent passes of the simulated current-channel attract and generate strong reversed current sheets that suggest magnetic reconnection. With sufficient injected current, adjacent passes merge periodically, releasing axisymmetric current rings from themore » driven channel. The current rings have not been previously observed in helicity injection for spherical tokamaks, and as such, provide a new phenomenological understanding for filament relaxation in Pegasus. After large-scale poloidal-field reversal, a hollow current profile and significant poloidal flux amplification accumulate over many reconnection cycles.« less

Controlling Particle Morphologies at Fluid Interfaces: Macro- and Micro- approaches

NASA Astrophysics Data System (ADS)

Beesabathuni, Shilpa Naidu

The controlled generation of varying shaped particles is important for many applications: consumer goods, biomedical diagnostics, food processing, adsorbents and pharmaceuticals which can benefit from the availability of geometrically complex and chemically inhomogeneous particles. This thesis presents two approaches to spherical and non-spherical particle synthesis using macro and microfluidics. In the first approach, a droplet microfluidic technique is explored to fabricate spherical conducting polymer, polyaniline, particles with precise control over morphology and functionality. Microfluidics has recently emerged as an important alternate to the synthesis of complex particles. The conducting polymer, polyaniline, is widely used and known for its stability, high conductivity, and favorable redox properties. In this approach, monodisperse micron-sized polyaniline spherical particles were synthesized using two-phase droplet microfluidics from Aniline and Ammonium persulfate oxidative polymerization in an oil-based continuous phase. The morphology of the polymerized particles is porous in nature which can be used for encapsulation as well as controlled release applications. Encapsulation of an enzyme, glucose oxidase, was also performed using the technique to synthesize microspheres for glucose sensing. The polymer microspheres were characterized using SEM, UV-Vis and EDX to understand the relationship between their microstructure and stability. In the second approach, molten drop impact in a cooling aqueous medium to generate non-spherical particles was explored. Viscoelastic wax based materials are widely used in many applications and their performance and application depends on the particle morphology and size. The deformation of millimeter size molten wax drops as they impacted an immiscible liquid interface was investigated. Spherical molten wax drops impinged on a cooling water bath, then deformed and as a result of solidification were arrested into various shapes such as ellipsoids, mushrooms, spherulites and discs. The final morphology of the wax particles is governed by the interfacial, inertial, viscous and thermal effects, which can be studied over a range of Weber, Capillary, Reynolds and Stefan numbers. A simplified Stefan problem for a spherical drop was solved. The time required to initiate a phase transition at the interface of the molten wax and water after impact was estimated and correlated with the drop deformation history and final wax particle shape to develop a capability to predict the shape. While the microfluidic synthesis approach offers precise control over morphology and functionality, large particle throughput is a limitation. The drop impact in a liquid medium emulsion approach is limited to crosslinking or heat sensitive materials but can be extended to large scale production for industrial applications. Both approaches are simple, robust and cost effective making them viable and attractive solutions for complex particle synthesis. The choice of the approach is dependent on considerations such as particle material, size, shape, throughput and end application.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazarus, E; Peng, Yueng Kay Martin

Oak Ridge National Laboratory (ORNL) proposes to build the Spherical Torus Experiment (STX), a very low aspect ratio toroidal confinement device. This proposal concentrates on tokamak operation of the experiment; however, it can in principle be operated as a pinch or reversed-field pinch as well. As a tokamak, the spherical torus confines a plasma that is characterized by high toroidal beta, low poloidal beta, large natural elongation, high plasma current for a given edge q, and strong paramagnetism. These features combine to offer the possibility of a compact, low-field fusion device. The figure below shows that when compared to amore » conventional tokamak the spherical torus represents a major change in geometry. The primary goals of the experiment will be to demonstrate a capability for high beta (20%) in the first stability regime, to extend our knowledge of tokamak confinement scaling, and to test oscillating-field current drive. The experiment will operate in the high-beta, collisionless regime, which is achieved in STX at low temperatures because of the geometry. At a minimum, operation of STX will help to resolve fundamental questions regarding the scaling of beta and confinement in tokamaks. Complete success in this program would have a significant impact on toroidal fusion research in that it would demonstrate solutions to the problems of beta and steady-state operation in the tokamak. The proposed device has a major radius of 0.45 m, a toroidai field of 0.5 T, a plasma current of 900 kA, and heating by neutral beam injection. We estimate 30 months for design, construction, and assembly. The budget estimate, including contingency and escalation, is $6.8 million.« less

Cosmological Perturbation Theory and the Spherical Collapse model - I. Gaussian initial conditions

NASA Astrophysics Data System (ADS)

Fosalba, Pablo; Gaztanaga, Enrique

1998-12-01

We present a simple and intuitive approximation for solving the perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear evolution in Lagrangian space is then given by a simple local transformation over the initial conditions, although it is not local in Euler space. This transformation is found to be described by the spherical collapse (SC) dynamics, as it is the exact solution in the shearless (and therefore local) approximation in Lagrangian space. Taking advantage of this property, it is straightforward to derive the one-point cumulants, xi_J, for both the unsmoothed and smoothed density fields to arbitrary order in the perturbative regime. To leading-order this reproduces, and provides us with a simple explanation for, the exact results obtained by Bernardeau. We then show that the SC model leads to accurate estimates for the next corrective terms when compared with the results derived in the exact perturbation theory making use of the loop calculations. The agreement is within a few per cent for the hierarchical ratios S_J=xi_J/xi^J-1_2. We compare our analytic results with N-body simulations, which turn out to be in very good agreement up to scales where sigma~1. A similar treatment is presented to estimate higher order corrections in the Zel'dovich approximation. These results represent a powerful and readily usable tool to produce analytical predictions that describe the gravitational clustering of large-scale structure in the weakly non-linear regime.

Simultaneous stochastic inversion for geomagnetic main field and secular variation. I - A large-scale inverse problem

NASA Technical Reports Server (NTRS)

Bloxham, Jeremy

1987-01-01

The method of stochastic inversion is extended to the simultaneous inversion of both main field and secular variation. In the present method, the time dependency is represented by an expansion in Legendre polynomials, resulting in a simple diagonal form for the a priori covariance matrix. The efficient preconditioned Broyden-Fletcher-Goldfarb-Shanno algorithm is used to solve the large system of equations resulting from expansion of the field spatially to spherical harmonic degree 14 and temporally to degree 8. Application of the method to observatory data spanning the 1900-1980 period results in a data fit of better than 30 nT, while providing temporally and spatially smoothly varying models of the magnetic field at the core-mantle boundary.

ISS-based Development of Elements and Operations for Robotic Assembly of A Space Solar Power Collector

NASA Technical Reports Server (NTRS)

Valinia, Azita; Moe, Rud; Seery, Bernard D.; Mankins, John C.

2013-01-01

We present a concept for an ISS-based optical system assembly demonstration designed to advance technologies related to future large in-space optical facilities deployment, including space solar power collectors and large-aperture astronomy telescopes. The large solar power collector problem is not unlike the large astronomical telescope problem, but at least conceptually it should be easier in principle, given the tolerances involved. We strive in this application to leverage heavily the work done on the NASA Optical Testbed Integration on ISS Experiment (OpTIIX) effort to erect a 1.5 m imaging telescope on the International Space Station (ISS). Specifically, we examine a robotic assembly sequence for constructing a large (meter diameter) slightly aspheric or spherical primary reflector, comprised of hexagonal mirror segments affixed to a lightweight rigidizing backplane structure. This approach, together with a structured robot assembler, will be shown to be scalable to the area and areal densities required for large-scale solar concentrator arrays.

Effects of compressibility on the temperature jump at the interface of layered, spherical-shell convection

NASA Technical Reports Server (NTRS)

Yen, David A.; Zhang, Shuxia; Langenberger, Sherri E.

1988-01-01

Large temperature jumps at the interface of layered convection are important to the argument used against the likelihood of separate circulations in the upper and lower mantles. This problem was studied within the framework of a compressible, constant viscosity spherical-shell model. Both mechanical and thermal coupling configurations are considered. Although the temperature jumps are reduced by compressibility, their magnitudes remain quite large, in the case of mechanical coupling. For thermal coupling, the temperature jumps become smaller but still are substantial, between 500 to 1000 C. In layered spherical-shell convection, flows in the lower mantle are several times greater than the surface velocities.

Modified circular velocity law

NASA Astrophysics Data System (ADS)

Djeghloul, Nazim

2018-05-01

A modified circular velocity law is presented for a test body orbiting around a spherically symmetric mass. This law exhibits a distance scale parameter and allows to recover both usual Newtonian behaviour for lower distances and a constant velocity limit at large scale. Application to the Galaxy predicts the known behaviour and also leads to a galactic mass in accordance with the measured visible stellar mass so that additional dark matter inside the Galaxy can be avoided. It is also shown that this circular velocity law can be embedded in a geometrical description of spacetime within the standard general relativity framework upon relaxing the usual asymptotic flatness condition. This formulation allows to redefine the introduced Newtonian scale limit in term of the central mass exclusively. Moreover, a satisfactory answer to the galactic escape speed problem can be provided indicating the possibility that one can also get rid of dark matter halo outside the Galaxy.

Plasma surface figuring of large optical components

NASA Astrophysics Data System (ADS)

Jourdain, R.; Castelli, M.; Morantz, P.; Shore, P.

2012-04-01

Fast figuring of large optical components is well known as a highly challenging manufacturing issue. Different manufacturing technologies including: magnetorheological finishing, loose abrasive polishing, ion beam figuring are presently employed. Yet, these technologies are slow and lead to expensive optics. This explains why plasma-based processes operating at atmospheric pressure have been researched as a cost effective means for figure correction of metre scale optical surfaces. In this paper, fast figure correction of a large optical surface is reported using the Reactive Atom Plasma (RAP) process. Achievements are shown following the scaling-up of the RAP figuring process to a 400 mm diameter area of a substrate made of Corning ULE®. The pre-processing spherical surface is characterized by a 3 metres radius of curvature, 2.3 μm PVr (373nm RMS), and 1.2 nm Sq nanometre roughness. The nanometre scale correction figuring system used for this research work is named the HELIOS 1200, and it is equipped with a unique plasma torch which is driven by a dedicated tool path algorithm. Topography map measurements were carried out using a vertical work station instrumented by a Zygo DynaFiz interferometer. Figuring results, together with the processing times, convergence levels and number of iterations, are reported. The results illustrate the significant potential and advantage of plasma processing for figuring correction of large silicon based optical components.

Fifth dimension of life and the 4/5 allometric scaling law for human brain.

PubMed

He, Ji-Huan; Zhang, Juan

2004-01-01

Brain cells are not spherical. The basal metabolic rate (B) of a spherical cell scales as B approximately r2, where r is the radius of the cell; that of a brain cell scales as B approximately r(d), where r is the characteristic radius of the cell and d is the fractal dimensionality of its contour. The fractal geometry of the cell leads to a 4/5 allometric scaling law for human brain, uniquely endowing humans with a 5th dimension and successfully explains why the scaling exponent varies during rest and exercise. A striking analogy between Kleiber's 3/4 law and Newton's second law is heuristically illustrated. A physical explanation is given for the 4th dimension of life for three-dimensional organisms and the 5th dimension for human brain.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shang Yazhuo; Hu Jun; Liu Honglai, E-mail: yazhuoshang@ecust.edu.c

Novel large-scale hollow ZnO spherical shells were synthesized by ionic liquids assisted hydrothermal oxidization of pure zinc powder without any catalyst at a relatively low temperature of 160 deg. C. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) patterns show that the shells are composed of ZnO and the structure of the shells is very unique. Textured flower-like ZnO consisting of ZnO rods is grown on the outer surfaces of shells forming a triple assembly. Room-temperature photoluminescence spectra of the oxidized material show a sharp peak at 379 nm and a wider broad peak centeredmore » at 498 nm. The possible growth mechanism of the triple assembly of ZnO is discussed in detail. - Graphical abstract: A proposed growth mechanism of large scale hollow ZnO. Bubbles provide the aggregation center for ionic liquids that leads to the formation of hollow Zn particle-dotted shells, buoyancy promotes shells to go upward, the breach occurs when shells are subjected to overpressure.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Pathak, Siddhartha; Reichardt, Ashley

Experimentally quantifying the mechanical effects of radiation damage in reactor materials is necessary for the development and qualification of new materials for improved performance and safety. This can be achieved in a high-throughput fashion through a combination of ion beam irradiation and small scale mechanical testing in contrast to the high cost and laborious nature of bulk testing of reactor irradiated samples. The current paper focuses on using spherical nanoindentation stress-strain curves on unirradiated and proton irradiated (10 dpa at 360 °C) 304 stainless steel to quantify the mechanical effects of radiation damage. Spherical nanoindentation stress-strain measurements show a radiation-inducedmore » increase in indentation yield strength from 1.36 GPa to 2.72 GPa and a radiation-induced increase in indentation work hardening rate of 10 GPa–30 GPa. These measurements are critically compared against Berkovich nanohardness, micropillar compression, and micro-tension measurements on the same material and similar grain orientations. The ratio of irradiated to unirradiated yield strength increases by a similar factor of 2 when measured via spherical nanoindentation or Berkovich nanohardness testing. A comparison of spherical indentation stress-strain curves to uniaxial (micropillar and micro-tension) stress-strain curves was achieved using a simple scaling relationship which shows good agreement for the unirradiated condition and poor agreement in post-yield behavior for the irradiated condition. Finally, the disagreement between spherical nanoindentation and uniaxial stress-strain curves is likely due to the plastic instability that occurs during uniaxial tests but is absent during spherical nanoindentation tests.« less

A k-space method for acoustic propagation using coupled first-order equations in three dimensions.

PubMed

Tillett, Jason C; Daoud, Mohammad I; Lacefield, James C; Waag, Robert C

2009-09-01

A previously described two-dimensional k-space method for large-scale calculation of acoustic wave propagation in tissues is extended to three dimensions. The three-dimensional method contains all of the two-dimensional method features that allow accurate and stable calculation of propagation. These features are spectral calculation of spatial derivatives, temporal correction that produces exact propagation in a homogeneous medium, staggered spatial and temporal grids, and a perfectly matched boundary layer. Spectral evaluation of spatial derivatives is accomplished using a fast Fourier transform in three dimensions. This computational bottleneck requires all-to-all communication; execution time in a parallel implementation is therefore sensitive to node interconnect latency and bandwidth. Accuracy of the three-dimensional method is evaluated through comparisons with exact solutions for media having spherical inhomogeneities. Large-scale calculations in three dimensions were performed by distributing the nearly 50 variables per voxel that are used to implement the method over a cluster of computers. Two computer clusters used to evaluate method accuracy are compared. Comparisons of k-space calculations with exact methods including absorption highlight the need to model accurately the medium dispersion relationships, especially in large-scale media. Accurately modeled media allow the k-space method to calculate acoustic propagation in tissues over hundreds of wavelengths.

Spherical roller bearing analysis. SKF computer program SPHERBEAN. Volume 3: Program correlation with full scale hardware tests

NASA Technical Reports Server (NTRS)

Kleckner, R. J.; Rosenlieb, J. W.; Dyba, G.

1980-01-01

The results of a series of full scale hardware tests comparing predictions of the SPHERBEAN computer program with measured data are presented. The SPHERBEAN program predicts the thermomechanical performance characteristics of high speed lubricated double row spherical roller bearings. The degree of correlation between performance predicted by SPHERBEAN and measured data is demonstrated. Experimental and calculated performance data is compared over a range in speed up to 19,400 rpm (0.8 MDN) under pure radial, pure axial, and combined loads.

Four-mirror extreme ultraviolet (EUV) lithography projection system

DOEpatents

Cohen, Simon J; Jeong, Hwan J; Shafer, David R

2000-01-01

The invention is directed to a four-mirror catoptric projection system for extreme ultraviolet (EUV) lithography to transfer a pattern from a reflective reticle to a wafer substrate. In order along the light path followed by light from the reticle to the wafer substrate, the system includes a dominantly hyperbolic convex mirror, a dominantly elliptical concave mirror, spherical convex mirror, and spherical concave mirror. The reticle and wafer substrate are positioned along the system's optical axis on opposite sides of the mirrors. The hyperbolic and elliptical mirrors are positioned on the same side of the system's optical axis as the reticle, and are relatively large in diameter as they are positioned on the high magnification side of the system. The hyperbolic and elliptical mirrors are relatively far off the optical axis and hence they have significant aspherical components in their curvatures. The convex spherical mirror is positioned on the optical axis, and has a substantially or perfectly spherical shape. The spherical concave mirror is positioned substantially on the opposite side of the optical axis from the hyperbolic and elliptical mirrors. Because it is positioned off-axis to a degree, the spherical concave mirror has some asphericity to counter aberrations. The spherical concave mirror forms a relatively large, uniform field on the wafer substrate. The mirrors can be tilted or decentered slightly to achieve further increase in the field size.

Electronic and molecular structure of carbon grains

NASA Technical Reports Server (NTRS)

Almloef, Jan; Luethi, Hans-Peter

1990-01-01

Clusters of carbon atoms have been studied with large-scale ab initio calculations. Planar, single-sheet graphite fragments with 6 to 54 atoms were investigated, as well as the spherical C(sub 60) Buckminsterfullerene molecule. Polycyclic aromatic hydrocarbons (PAHs) have also been considered. Thermodynamic differences between diamond- and graphite-like grains have been studied in particular. Saturation of the peripheral bonds with hydrogen is found to provide a smooth and uniform convergence of the properties with increasing cluster size. For the graphite-like clusters the convergence to bulk values is much slower than for the three-dimensional complexes.

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

NASA Technical Reports Server (NTRS)

Klumpar, D. M. (Principal Investigator)

1982-01-01

Efforts in support of the development of a model of the magnetic fields due to ionospheric and magnetospheric electrical currents are discussed. Specifically, progress made in reading MAGSAT tapes and plotting the deviation of the measured magnetic field components with respect to a spherical harmonic model of the main geomagnetic field is reported. Initial tests of the modeling procedure developed to compute the ionosphere/magnetosphere-induced fields at satellite orbit are also described. The modeling technique utilizes a liner current element representation of the large scale current system.

Can we understand the turbulent solar wind via turbulent simulations?

NASA Technical Reports Server (NTRS)

Grappin, R.; Mangeney, A.

1995-01-01

We attempt to assess the present understanding of the turbulent solar wind using numerical simulations. The solar wind may be considered as a kind of wind tunnel with peculiar properties: the tunnel is spherical; the source of the wind is rotating; and the medium is a plasma containing a large-scale magnetic field. These constraints lead to anisotropic dynamics of the fluctuations on the one hand, and to non-standard (turbulent?) transport properties of the global plasma on the other hand. How much of this rich physics can we approach today via numerical simulations?

Superconducting transition detectors for low-energy gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Kurfess, J. D.; Johnson, W. N.; Fritz, G. G.; Strickman, M. S.; Kinzer, R. L.; Jung, G.; Drukier, A. K.; Chmielowski, M.

1990-08-01

A program to investigate superconducting devices such as STDs for use in high-resolution Compton telescopes and coded-aperture detectors is presented. For higher energy applications, techniques are investigated with potential for scaling to large detectors, while also providing excellent energy and positional resolution. STDs are discussed, utilizing a uniform array of spherical granules tens of microns in diameter. The typical temperature-magnetic field phase for a low-temperature superconductor, the signal produced by the superconducting-normal transition in the 32-m diameter Sn granule, and the temperature history of an STD granule following heating by an ionizing particle are illustrated.

Characteristics of laser beam focusing with single spherical mirrors during laser treatment

NASA Astrophysics Data System (ADS)

Borkin, A. G.; Drobyazko, S. V.; Kosheleva, G. A.; Pavlovich, Yu. V.; Senatorov, Yu. M.; Fromm, V. A.; Kurchatov, I. V.

1988-04-01

Focusing of a laser beam with a single spherical mirror is analyzed, such a mirror being combined with a rotatable annular plane mirror in a coaxial configuration. Its focal length must be sufficiently large to ensure adequately high power density and to avoid shielding. When the distance from mirror to laser cavity is too large, then the laser beam may degenerate into a nonannular one and its focusing without loss may become unattainable. Tilting the spherical mirror will make this possible, even when the laser beam is not annular, if astigmatism as well as spherical aberration are minimized. Such a focusing mirror made of metal is theoretically shown to be much more effective than a focusing lens made of KC1 crystal; this has been confirmed experimentally in a CO sub 2 laser facility for perforation of tubular seperator meshes.

Aperture averaging in strong oceanic turbulence

NASA Astrophysics Data System (ADS)

Gökçe, Muhsin Caner; Baykal, Yahya

2018-04-01

Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.

Simulations of Turbulent Flows with Strong Shocks and Density Variations: Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanjiva Lele

2012-10-01

The target of this SciDAC Science Application was to develop a new capability based on high-order and high-resolution schemes to simulate shock-turbulence interactions and multi-material mixing in planar and spherical geometries, and to study Rayleigh-Taylor and Richtmyer-Meshkov turbulent mixing. These fundamental problems have direct application in high-speed engineering flows, such as inertial confinement fusion (ICF) capsule implosions and scramjet combustion, and also in the natural occurrence of supernovae explosions. Another component of this project was the development of subgrid-scale (SGS) models for large-eddy simulations of flows involving shock-turbulence interaction and multi-material mixing, that were to be validated with the DNSmore » databases generated during the program. The numerical codes developed are designed for massively-parallel computer architectures, ensuring good scaling performance. Their algorithms were validated by means of a sequence of benchmark problems. The original multi-stage plan for this five-year project included the following milestones: 1) refinement of numerical algorithms for application to the shock-turbulence interaction problem and multi-material mixing (years 1-2); 2) direct numerical simulations (DNS) of canonical shock-turbulence interaction (years 2-3), targeted at improving our understanding of the physics behind the combined two phenomena and also at guiding the development of SGS models; 3) large-eddy simulations (LES) of shock-turbulence interaction (years 3-5), improving SGS models based on the DNS obtained in the previous phase; 4) DNS of planar/spherical RM multi-material mixing (years 3-5), also with the two-fold objective of gaining insight into the relevant physics of this instability and aiding in devising new modeling strategies for multi-material mixing; 5) LES of planar/spherical RM mixing (years 4-5), integrating the improved SGS and multi-material models developed in stages 3 and 5. This final report is outlined as follows. Section 2 shows an assessment of numerical algorithms that are best suited for the numerical simulation of compressible flows involving turbulence and shock phenomena. Sections 3 and 4 deal with the canonical shock-turbulence interaction problem, from the DNS and LES perspectives, respectively. Section 5 considers the shock-turbulence inter-action in spherical geometry, in particular, the interaction of a converging shock with isotropic turbulence as well as the problem of the blast wave. Section 6 describes the study of shock-accelerated mixing through planar and spherical Richtmyer-Meshkov mixing as well as the shock-curtain interaction problem In section 7 we acknowledge the different interactions between Stanford and other institutions participating in this SciDAC project, as well as several external collaborations made possible through it. Section 8 presents a list of publications and presentations that have been generated during the course of this SciDAC project. Finally, section 9 concludes this report with the list of personnel at Stanford University funded by this SciDAC project.« less

A hybrid-drive nonisobaric-ignition scheme for inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, X. T., E-mail: xthe@iapcm.ac.cn; Center for Applied Physics and Technology, HEDPS, Peking University, Beijing 100871; IFSA Collaborative Innovation Center of MoE, Shanghai Jiao-Tong University, Shanghai 200240

A new hybrid-drive (HD) nonisobaric ignition scheme of inertial confinement fusion (ICF) is proposed, in which a HD pressure to drive implosion dynamics increases via increasing density rather than temperature in the conventional indirect drive (ID) and direct drive (DD) approaches. In this HD (combination of ID and DD) scheme, an assembled target of a spherical hohlraum and a layered deuterium-tritium capsule inside is used. The ID lasers first drive the shock to perform a spherical symmetry implosion and produce a large-scale corona plasma. Then, the DD lasers, whose critical surface in ID corona plasma is far from the radiationmore » ablation front, drive a supersonic electron thermal wave, which slows down to a high-pressure electron compression wave, like a snowplow, piling up the corona plasma into high density and forming a HD pressurized plateau with a large width. The HD pressure is several times the conventional ID and DD ablation pressure and launches an enhanced precursor shock and a continuous compression wave, which give rise to the HD capsule implosion dynamics in a large implosion velocity. The hydrodynamic instabilities at imploding capsule interfaces are suppressed, and the continuous HD compression wave provides main pdV work large enough to hotspot, resulting in the HD nonisobaric ignition. The ignition condition and target design based on this scheme are given theoretically and by numerical simulations. It shows that the novel scheme can significantly suppress implosion asymmetry and hydrodynamic instabilities of current isobaric hotspot ignition design, and a high-gain ICF is promising.« less

Nonlinear spherical perturbations in quintessence models of dark energy

NASA Astrophysics Data System (ADS)

Pratap Rajvanshi, Manvendra; Bagla, J. S.

2018-06-01

Observations have confirmed the accelerated expansion of the universe. The accelerated expansion can be modelled by invoking a cosmological constant or a dynamical model of dark energy. A key difference between these models is that the equation of state parameter w for dark energy differs from ‑1 in dynamical dark energy (DDE) models. Further, the equation of state parameter is not constant for a general DDE model. Such differences can be probed using the variation of scale factor with time by measuring distances. Another significant difference between the cosmological constant and DDE models is that the latter must cluster. Linear perturbation analysis indicates that perturbations in quintessence models of dark energy do not grow to have a significant amplitude at small length scales. In this paper we study the response of quintessence dark energy to non-linear perturbations in dark matter. We use a fully relativistic model for spherically symmetric perturbations. In this study we focus on thawing models. We find that in response to non-linear perturbations in dark matter, dark energy perturbations grow at a faster rate than expected in linear perturbation theory. We find that dark energy perturbation remains localised and does not diffuse out to larger scales. The dominant drivers of the evolution of dark energy perturbations are the local Hubble flow and a supression of gradients of the scalar field. We also find that the equation of state parameter w changes in response to perturbations in dark matter such that it also becomes a function of position. The variation of w in space is correlated with density contrast for matter. Variation of w and perturbations in dark energy are more pronounced in response to large scale perturbations in matter while the dependence on the amplitude of matter perturbations is much weaker.

Model Scaling of Hydrokinetic Ocean Renewable Energy Systems

NASA Astrophysics Data System (ADS)

von Ellenrieder, Karl; Valentine, William

2013-11-01

Numerical simulations are performed to validate a non-dimensional dynamic scaling procedure that can be applied to subsurface and deeply moored systems, such as hydrokinetic ocean renewable energy devices. The prototype systems are moored in water 400 m deep and include: subsurface spherical buoys moored in a shear current and excited by waves; an ocean current turbine excited by waves; and a deeply submerged spherical buoy in a shear current excited by strong current fluctuations. The corresponding model systems, which are scaled based on relative water depths of 10 m and 40 m, are also studied. For each case examined, the response of the model system closely matches the scaled response of the corresponding full-sized prototype system. The results suggest that laboratory-scale testing of complete ocean current renewable energy systems moored in a current is possible. This work was supported by the U.S. Southeast National Marine Renewable Energy Center (SNMREC).

Impact of Primary Spherical Aberration, Spatial Frequency and Stiles Crawford Apodization on Wavefront determined Refractive Error: A Computational Study

PubMed Central

Xu, Renfeng; Bradley, Arthur; Thibos, Larry N.

2013-01-01

Purpose We tested the hypothesis that pupil apodization is the basis for central pupil bias of spherical refractions in eyes with spherical aberration. Methods We employed Fourier computational optics in which we vary spherical aberration levels, pupil size, and pupil apodization (Stiles Crawford Effect) within the pupil function, from which point spread functions and optical transfer functions were computed. Through-focus analysis determined the refractive correction that optimized retinal image quality. Results For a large pupil (7 mm), as spherical aberration levels increase, refractions that optimize the visual Strehl ratio mirror refractions that maximize high spatial frequency modulation in the image and both focus a near paraxial region of the pupil. These refractions are not affected by Stiles Crawford Effect apodization. Refractions that optimize low spatial frequency modulation come close to minimizing wavefront RMS, and vary with level of spherical aberration and Stiles Crawford Effect. In the presence of significant levels of spherical aberration (e.g. C40 = 0.4 µm, 7mm pupil), low spatial frequency refractions can induce −0.7D myopic shift compared to high SF refraction, and refractions that maximize image contrast of a 3 cycle per degree square-wave grating can cause −0.75D myopic drift relative to refractions that maximize image sharpness. Discussion Because of small depth of focus associated with high spatial frequency stimuli, the large change in dioptric power across the pupil caused by spherical aberration limits the effective aperture contributing to the image of high spatial frequencies. Thus, when imaging high spatial frequencies, spherical aberration effectively induces an annular aperture defining that portion of the pupil contributing to a well-focused image. As spherical focus is manipulated during the refraction procedure, the dimensions of the annular aperture change. Image quality is maximized when the inner radius of the induced annulus falls to zero, thus defining a circular near paraxial region of the pupil that determines refraction outcome. PMID:23683093

A new family of distribution functions for spherical galaxies

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin E.

1991-06-01

The present study describes a new family of anisotropic distribution functions for stellar systems designed to keep control of the orbit distribution at fixed energy. These are quasi-separable functions of energy and angular momentum, and they are specified in terms of a circularity function h(x) which fixes the distribution of orbits on the potential's energy surfaces outside some anisotropy radius. Detailed results are presented for a particular set of radially anisotropic circularity functions h-alpha(x). In the scale-free logarithmic potential, exact analytic solutions are shown to exist for all scale-free circularity functions. Intrinsic and projected velocity dispersions are calculated and the expected properties are presented in extensive tables and graphs. Several applications of the quasi-separable distribution functions are discussed. They include the effects of anisotropy or a dark halo on line-broadening functions, the radial orbit instability in anisotropic spherical systems, and violent relaxation in spherical collapse.

Large-Angle Magnetic Suspension (LAMS)

NASA Technical Reports Server (NTRS)

Oglevie, Ronald E.; Eisenhaure, David B.; Downer, James R.

1988-01-01

Spherical LAMS is magnetic syspension that provides dual functions of magnetic bearing and rotorgimbal system. Provides two degrees of angular freedom within single magnetic suspension system. Approach employs spherically-shaped magnetic-gap surfaces to achieve much-larger angular freedom than available from previous suspensions.

Buckling vs. particle desorption in a particle-covered drop subject to compressive surface stresses: a simulation study.

PubMed

Gu, Chuan; Botto, Lorenzo

2018-01-31

Predicting the behaviour of particle-covered fluid interfaces under compression has implications in several fields. The surface-tension driven adhesion of particles to drops and bubbles is exploited for example to enhance the stability of foams and emulsion and develop new generation materials. When a particle-covered fluid interface is compressed, one can observe either smooth buckling or particle desorption from the interface. The microscopic mechanisms leading to the buckling-to-desorption transition are not fully understood. In this paper we simulate a spherical drop covered by a monolayer of spherical particles. The particle-covered interface is subject to time-dependent compressive surface stresses that mimic the slow deflation of the drop. The buckling-to-desorption transition depends in a non-trivial way on three non-dimensional parameters: the ratio Π s /γ of particle-induced surface pressure and bare surface tension, the ratio a/R of particle and drop radii, and the parameter f characterising the strength of adhesion of each particle to the interface. Based on the insights from the simulations, we propose a configuration diagram describing the effect of these controlling parameters. We find that particle desorption is highly correlated with a mechanical instability that produces small-scale undulations of the monolayer of the order of the particle size that grow when the surface pressure is sufficiently large. We argue that the large local curvature associated with these small undulations can produce large normal forces, enhancing the probability of desorption.

First-principles study of the binding energy between nanostructures and its scaling with system size

NASA Astrophysics Data System (ADS)

Tao, Jianmin; Jiao, Yang; Mo, Yuxiang; Yang, Zeng-Hui; Zhu, Jian-Xin; Hyldgaard, Per; Perdew, John P.

2018-04-01

The equilibrium van der Waals binding energy is an important factor in the design of materials and devices. However, it presents great computational challenges for materials built up from nanostructures. Here we investigate the binding-energy scaling behavior from first-principles calculations. We show that the equilibrium binding energy per atom between identical nanostructures can scale up or down with nanostructure size, but can be parametrized for large N with an analytical formula (in meV/atom), Eb/N =a +b /N +c /N2+d /N3 , where N is the number of atoms in a nanostructure and a , b , c , and d are fitting parameters, depending on the properties of a nanostructure. The formula is consistent with a finite large-size limit of binding energy per atom. We find that there are two competing factors in the determination of the binding energy: Nonadditivities of van der Waals coefficients and center-to-center distance between nanostructures. To decode the detail, the nonadditivity of the static multipole polarizability is investigated from an accurate spherical-shell model. We find that the higher-order multipole polarizability displays ultrastrong intrinsic nonadditivity, no matter if the dipole polarizability is additive or not.

Space filling minimal surfaces and sphere packings

NASA Astrophysics Data System (ADS)

Elser, Veit

1994-05-01

A space filling minimal surface is defined to be any embedded minimal surface without boundary with the property that the area and genus enclosed by any large spherical region scales in proportion to the volume of the region. The triply periodic minimal surfaces are one realization, but not necessarily the only one. By using the genus per unit volume of the surface, a meaningful comparison of surface areas can be made even in cases where there is no unit cell. Of the known periodic minimal surfaces this measure of the surface area is smallest for Schoen's FRD surface. This surface is one of several that is closely related to packings of spheres. Its low area is largely due to the fact that the corresponding sphere packing (fcc) has the maximal kissing number.

Local Helicity Injection Systems for Non-solenoidal Startup in the PEGASUS Toroidal Experiment

NASA Astrophysics Data System (ADS)

Perry, J. M.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Lewicki, B. T.; Redd, A. J.

2013-10-01

Local helicity injection is being developed in the PEGASUS Toroidal Experiment for non-solenoidal startup in spherical tokamaks. The effective loop voltage due to helicity injection scales with the area of the injectors, requiring the development of electron current injectors with areas much larger than the 2 cm2 plasma arc injectors used to date. Solid and gas-effused metallic electrodes were found to be unusable due to reduced injector area utilization from localized cathode spots and narrow operational regimes. An integrated array of 8 compact plasma arc sources is thus being developed for high current startup. It employs two monolithic power systems, for the plasma arc sources and the bias current extraction system. The array effectively eliminates impurity fueling from plasma-material interaction by incorporating a local scraper-limiter and conical-frustum bias electrodes to mitigate the effects of cathode spots. An energy balance model of helicity injection indicates that the resulting 20 cm2 of total injection area should provide sufficient current drive to reach 0.3 MA. At that level, helicity injection drive exceeds that from poloidal induction, which is the relevant operational regime for large-scale spherical tokamaks. Future placement of the injector array near an expanded boundary divertor region will test simultaneous optimization of helicity drive and the Taylor relaxation current limit. Work supported by US DOE Grant DE-FG02-96ER54375.

Numerically modelling the large scale coronal magnetic field

NASA Astrophysics Data System (ADS)

Panja, Mayukh; Nandi, Dibyendu

2016-07-01

The solar corona spews out vast amounts of magnetized plasma into the heliosphere which has a direct impact on the Earth's magnetosphere. Thus it is important that we develop an understanding of the dynamics of the solar corona. With our present technology it has not been possible to generate 3D magnetic maps of the solar corona; this warrants the use of numerical simulations to study the coronal magnetic field. A very popular method of doing this, is to extrapolate the photospheric magnetic field using NLFF or PFSS codes. However the extrapolations at different time intervals are completely independent of each other and do not capture the temporal evolution of magnetic fields. On the other hand full MHD simulations of the global coronal field, apart from being computationally very expensive would be physically less transparent, owing to the large number of free parameters that are typically used in such codes. This brings us to the Magneto-frictional model which is relatively simpler and computationally more economic. We have developed a Magnetofrictional Model, in 3D spherical polar co-ordinates to study the large scale global coronal field. Here we present studies of changing connectivities between active regions, in response to photospheric motions.

Spherical harmonics coefficients for ligand-based virtual screening of cyclooxygenase inhibitors.

PubMed

Wang, Quan; Birod, Kerstin; Angioni, Carlo; Grösch, Sabine; Geppert, Tim; Schneider, Petra; Rupp, Matthias; Schneider, Gisbert

2011-01-01

Molecular descriptors are essential for many applications in computational chemistry, such as ligand-based similarity searching. Spherical harmonics have previously been suggested as comprehensive descriptors of molecular structure and properties. We investigate a spherical harmonics descriptor for shape-based virtual screening. We introduce and validate a partially rotation-invariant three-dimensional molecular shape descriptor based on the norm of spherical harmonics expansion coefficients. Using this molecular representation, we parameterize molecular surfaces, i.e., isosurfaces of spatial molecular property distributions. We validate the shape descriptor in a comprehensive retrospective virtual screening experiment. In a prospective study, we virtually screen a large compound library for cyclooxygenase inhibitors, using a self-organizing map as a pre-filter and the shape descriptor for candidate prioritization. 12 compounds were tested in vitro for direct enzyme inhibition and in a whole blood assay. Active compounds containing a triazole scaffold were identified as direct cyclooxygenase-1 inhibitors. This outcome corroborates the usefulness of spherical harmonics for representation of molecular shape in virtual screening of large compound collections. The combination of pharmacophore and shape-based filtering of screening candidates proved to be a straightforward approach to finding novel bioactive chemotypes with minimal experimental effort.

Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications

NASA Technical Reports Server (NTRS)

Sanandres, Luis

1994-01-01

Hydrostatic Journal Bearings (HJB's) are reliable and resilient fluid film rotor support elements ideal to replace roller bearings in cryogenic turbomachinery. HJB' will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, large direct stiffness, and damping force coefficients. An analysis for the performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings (HJB's) is presented. Spherical bearings allow tolerance for shaft misalignment without force performance degradation and have also the ability to support axial loads. The spherical HJB combines these advantages to provide a bearing design which could be used efficiently on high performance turbomachinery. The motion of a barotropic liquid on the thin film bearing lands is described by bulk-flow mass and momentum equations. These equations are solved numerically using an efficient CFD method. Numerical predictions of load capacity and force coefficients for a 6 recess, spherical HJB in a LO2 environment are presented. Fluid film axial forces and force coefficients of a magnitude about 20% of the radial load capacity are predicted for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to affect greatly the static and dynamic force performance of the bearing studied.

Multidimensional Multiphysics Simulation of TRISO Particle Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. D. Hales; R. L. Williamson; S. R. Novascone

2013-11-01

Multidimensional multiphysics analysis of TRISO-coated particle fuel using the BISON finite-element based nuclear fuels code is described. The governing equations and material models applicable to particle fuel and implemented in BISON are outlined. Code verification based on a recent IAEA benchmarking exercise is described, and excellant comparisons are reported. Multiple TRISO-coated particles of increasing geometric complexity are considered. It is shown that the code's ability to perform large-scale parallel computations permits application to complex 3D phenomena while very efficient solutions for either 1D spherically symmetric or 2D axisymmetric geometries are straightforward. Additionally, the flexibility to easily include new physical andmore » material models and uncomplicated ability to couple to lower length scale simulations makes BISON a powerful tool for simulation of coated-particle fuel. Future code development activities and potential applications are identified.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Kai; Zheng Yuhua; Jia Guang

Nano/micro-sized coordination polymer La(1,3,5-BTC)(H{sub 2}O){sub 6} with controllable morphologies have been successfully prepared on a large scale via a simple solution phase method at room temperature. By rationally adjusting the synthetic parameters such as concentration, molar ratio of reactants, surfactant, and solvent, the La(1,3,5-BTC)(H{sub 2}O){sub 6} with 3D flowerlike, wheatearlike, spherical, sheaflike, taillike, bundlelike hierarchical architectures, and 1D nanorods can be selectively prepared. More interestingly, the photoluminescence color of codoped Eu{sup 3+} and Tb{sup 3+} lanthanum 1,3,5-benzenetricarboxylate phosphors can be easily tuned from red, orange, yellow, green-yellow to green by changing co-doping concentration of activator ions, making the material hasmore » potential applications in building minioptoelectronic devices, biomedicine, and color display fields. - Graphical abstract: La(1,3,5-BTC)(H{sub 2}O){sub 6} with 3D flowerlike, wheatearlike, spherical, sheaflike, taillike, bundlelike architectures, and 1D nanorods were selectively prepared; color-tunable photoluminescence from red to green was also realized by co-doping Eu{sup 3+} and Tb{sup 3+}.« less

Spherical collapse and virialization in f ( T ) gravities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Rui-Hui; Zhai, Xiang-Hua; Li, Xin-Zhou, E-mail: 1000379711@smail.shnu.edu.cn, E-mail: zhaixh@shnu.edu.cn, E-mail: kychz@shnu.edu.cn

2017-03-01

Using the classical top-hat profile, we study the non-linear growth of spherically symmetric density perturbation and structure formation in f ( T ) gravities. In particular, three concrete models, which have been tested against the observation of large-scale evolution and linear perturbation of the universe in the cosmological scenario, are investigated in this framework, covering both minimal and nonminimal coupling cases of f ( T ) gravities. Moreover, we consider the virialization of the overdense region in the models after they detach from the background expanding universe and turn around to collapse. We find that there are constraints in themore » magnitude and occurring epoch of the initial perturbation. The existence of these constraints indicates that a perturbation that is too weak or occurs too late will not be able to stop the expanding of the overdense region. The illustration of the evolution of the perturbation shows that in f ( T ) gravities, the initial perturbation within the constraints can eventually lead to clustering and form structure. The evolution also shows that nonminimal coupling models collapse slower than the minimal coupling one.« less

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes

NASA Astrophysics Data System (ADS)

O'Brien, S. A.; Harvey, A.; Griffin, A.; Donnelly, T.; Mulcahy, D.; Coleman, J. N.; Donegan, J. F.; McCloskey, D.

2017-11-01

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter—the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

PubMed

O'Brien, S A; Harvey, A; Griffin, A; Donnelly, T; Mulcahy, D; Coleman, J N; Donegan, J F; McCloskey, D

2017-11-24

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Some anticipated contributions to core fluid dynamics from the GRM

NASA Technical Reports Server (NTRS)

Vanvorhies, C.

1985-01-01

It is broadly maintained that the secular variation (SV) of the large scale geomagnetic field contains information on the fluid dynamics of Earth's electrically conducting outer core. The electromagnetic theory appropriate to a simple Earth model has recently been combined with reduced geomagnetic data in order to extract some of this information and ascertain its significance. The simple Earth model consists of a rigid, electrically insulating mantle surrounding a spherical, inviscid, and perfectly conducting liquid outer core. This model was tested against seismology by using truncated spherical harmonic models of the observed geomagnetic field to locate Earth's core-mantle boundary, CMB. Further electromagnetic theory has been developed and applied to the problem of estimating the horizontal fluid motion just beneath CMB. Of particular geophysical interest are the hypotheses that these motions: (1) include appreciable surface divergence indicative of vertical motion at depth, and (2) are steady for time intervals of a decade or more. In addition to the extended testing of the basic Earth model, the proposed GRM provides a unique opportunity to test these dynamical hypotheses.

Collective motion of squirmers in a quasi-2D geometry

NASA Astrophysics Data System (ADS)

Zöttl, Andreas; Stark, Holger

2013-03-01

Microorganisms like bacteria, algae or spermatozoa typically move in an aqueous environment where they interact via hydrodynamic flow fields. Recent experiments studied the collective motion of dense suspensions of bacteria where swarming and large-scale turbulence emerged. Moreover, spherical artificial microswimmers, so-called squirmers, have been constructed and studied in a quasi-2D geometry. Here we present a numerical study of the collective dynamics of squirmers confined in quasi-2D between two parallel walls. Because of their spherical shape the reorientation of squirmers is solely due to noise and hydrodynamic interactions via induced flow fields. This is in contrast to elongated swimmers like bacteria which locally align due to steric interactions. We study the collective motion of pushers, pullers and potential swimmers at different densities. At small densities the squirmers are oriented parallel to the walls and pairwise collisions determine the reorientation rate. In dense suspensions rotational diffusion is greatly enhanced and pushers, in particular, tend to orient perpendicular to the walls. This effects the dynamics of the emerging clusters. In very dense suspensions we observe active jamming and long-lived crystalline structures.

Analysis of the nonlinearity of Asian summer monsoon intraseasonal variability using spherical PDFs

NASA Astrophysics Data System (ADS)

Jajcay, Nikola; Hannachi, Abdel

2013-04-01

The Asian summer monsoon (ASM) is a high-dimensional and highly complex phenomenon affecting more than one fifth of the world population. The intraseasonal component of the ASM undergoes periods of active and break phases associated respectively with enhanced and reduced rainfall over the Indian subcontinent and surroundings. In this paper the nonlinear nature of the intraseasonal monsoon variability is investigated using the leading EOFs of ERA-40 sea level pressure reanalyses field over the ASM region. The probability density function is then computed in spherical coordinates using a Epaneshnikov kernel method. Three significant modes are identified. They represent respectively (i) East - West mode with above normal sea level pressure over East China sea and below normal pressure over Himalayas, (ii) mode with above normal sea level pressure over East China sea (without compensating centre of opposite sign as in (i)) and (iii) mode with below normal sea level pressure over East China sea (same as (ii) but with opposite sign). Relationship to large scale flow are also investigated and discussed.

On the frequency spectra of the core magnetic field Gauss coefficients

NASA Astrophysics Data System (ADS)

Lesur, Vincent; Wardinski, Ingo; Baerenzung, Julien; Holschneider, Matthias

2018-03-01

From monthly mean observatory data spanning 1957-2014, geomagnetic field secular variation values were calculated by annual differences. Estimates of the spherical harmonic Gauss coefficients of the core field secular variation were then derived by applying a correlation based modelling. Finally, a Fourier transform was applied to the time series of the Gauss coefficients. This process led to reliable temporal spectra of the Gauss coefficients up to spherical harmonic degree 5 or 6, and down to periods as short as 1 or 2 years depending on the coefficient. We observed that a k-2 slope, where k is the frequency, is an acceptable approximation for these spectra, with possibly an exception for the dipole field. The monthly estimates of the core field secular variation at the observatory sites also show that large and rapid variations of the latter happen. This is an indication that geomagnetic jerks are frequent phenomena and that significant secular variation signals at short time scales - i.e. less than 2 years, could still be extracted from data to reveal an unexplored part of the core dynamics.

Effects of Group Size and Lack of Sphericity on the Recovery of Clusters in K-means Cluster Analysis.

PubMed

Craen, Saskia de; Commandeur, Jacques J F; Frank, Laurence E; Heiser, Willem J

2006-06-01

K-means cluster analysis is known for its tendency to produce spherical and equally sized clusters. To assess the magnitude of these effects, a simulation study was conducted, in which populations were created with varying departures from sphericity and group sizes. An analysis of the recovery of clusters in the samples taken from these populations showed a significant effect of lack of sphericity and group size. This effect was, however, not as large as expected, with still a recovery index of more than 0.5 in the "worst case scenario." An interaction effect between the two data aspects was also found. The decreasing trend in the recovery of clusters for increasing departures from sphericity is different for equal and unequal group sizes.

The sagitta and lens thickness: the exact solution and a matrix approximation for lenses with toric, spherical, and cylindrical surfaces.

PubMed

Harris, W F

1989-03-01

The exact equation for sagitta of spherical surfaces is generalized to toric surfaces which include spherical and cylindrical surfaces as special cases. Lens thickness, therefore, can be calculated accurately anywhere on a lens even in cases of extreme spherical and cylindrical powers and large diameters. The sagittae of tire- and barrel-form toric surfaces differ off the principal meridians, as is shown by a numerical example. The same holds for pulley- and capstan-form toric surfaces. A general expression is given for thickness at an arbitrary point on a toric lens. Approximate expressions are derived and re-expressed in terms of matrices. The matrix provides an elegant means of generalizing equations for spherical surfaces and lenses to toric surfaces and lenses.

Variation in ejecta size with ejection velocity

NASA Technical Reports Server (NTRS)

Vickery, Ann M.

1987-01-01

The sizes and ranges of over 25,000 secondary craters around twelve large primaries on three different planets were measured and used to infer the size-velocity distribution of that portion of the primary crater ejecta that produced the secondaries. The ballistic equation for spherical bodies was used to convert the ranges to velocities, and the velocities and crater sizes were used in the appropriate Schmidt-Holsapple scaling relation of estimate ejecta sizes, and the velocity exponent was determined. The latter are generally between -1 and -13, with an average value of about -1.9. Problems with data collection made it impossible to determine a simple, unique relation between size and velocity.

A decision support system for map projections of small scale data

USGS Publications Warehouse

Finn, Michael P.; Usery, E. Lynn; Posch, Stephan T.; Seong, Jeong Chang

2004-01-01

The use of commercial geographic information system software to process large raster datasets of terrain elevation, population, land cover, vegetation, soils, temperature, and rainfall requires both projection from spherical coordinates to plane coordinate systems and transformation from one plane system to another. Decision support systems deliver information resulting in knowledge that assists in policies, priorities, or processes. This paper presents an approach to handling the problems of raster dataset projection and transformation through the development of a Web-enabled decision support system to aid users of transformation processes with the selection of appropriate map projections based on data type, areal extent, location, and preservation properties.

VHF electromagnetic wave propagation

NASA Astrophysics Data System (ADS)

Gole, P.

Theoretical and experimental study of large-scale VHF propagation characteristics is presented. Certain phenomena that are difficult to model, such as the effects of ground near the antenna, are examined from a purely experimental point of view. The characteristics of electromagnetic waves over a spherical surface and through a medium having a certain refractive index, such as is the case for waves propagated over the earth's surface, are analytically described. Two mathematical models are used, one for the case of the receiver being within the radioelectric horizon of the transmitter and the other for when it is not. Propagation phenomena likely to increase the false alarm probability of an air surveillance radar are briefly considered.

Solution of the Eshelby problem in gradient elasticity for multilayer spherical inclusions

NASA Astrophysics Data System (ADS)

Volkov-Bogorodskii, D. B.; Lurie, S. A.

2016-03-01

We consider gradient models of elasticity which permit taking into account the characteristic scale parameters of the material. We prove the Papkovich-Neuber theorems, which determine the general form of the gradient solution and the structure of scale effects. We derive the Eshelby integral formula for the gradient moduli of elasticity, which plays the role of the closing equation in the self-consistent three-phase method. In the gradient theory of deformations, we consider the fundamental Eshelby-Christensen problem of determining the effective elastic properties of dispersed composites with spherical inclusions; the exact solution of this problem for classical models was obtained in 1976. This paper is the first to present the exact analytical solution of the Eshelby-Christensen problem for the gradient theory, which permits estimating the influence of scale effects on the stress state and the effective properties of the dispersed composites under study.We also analyze the influence of scale factors.

On capturing the grain-scale elastic and plastic anisotropy of alpha-Ti with spherical nanoindentation and electron back-scattered diffraction

DOE PAGES

Weaver, Jordan S.; Priddy, Matthew W.; McDowell, David L.; ...

2016-09-01

Here, spherical nanoindentation combined with electron back-scattered diffraction has been employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti of two different compositions (in two different titanium alloys). Data analyses protocols needed to reliably extract the desired properties of interest are extended and demonstrated in this paper. Specifically, the grain-scale mechanical response is extracted in the form of indentation stress-strain curves for commercially pure (CP-Ti) alpha-Ti and alloyed (Ti-64) titanium from measurements on polycrystalline samples. The results are compared with responses of single crystals and nanoindentation tests (hardness and modulus) from the literature, and the measuredmore » indentation moduli are validated using crystal-elastic finite element simulations. The results obtained in this study show that (i) it is possible to characterize reliably the elastic and plastic anisotropy of alpha-Ti (hcp) of varying alloying contents with spherical nanoindentation stress-strain curves, (ii) the indentation modulus of alpha-Ti-64 is 5–10% less than CP-Ti, and (iii) the indentation yield strength of alpha-Ti-64 is 50–80% higher than CP-Ti.« less

3D Visible-Light Invisibility Cloak.

PubMed

Zheng, Bin; Zhu, Rongrong; Jing, Liqiao; Yang, Yihao; Shen, Lian; Wang, Huaping; Wang, Zuojia; Zhang, Xianmin; Liu, Xu; Li, Erping; Chen, Hongsheng

2018-06-01

The concept of an invisibility cloak is a fixture of science fiction, fantasy, and the collective imagination. However, a real device that can hide an object from sight in visible light from absolutely any viewpoint would be extremely challenging to build. The main obstacle to creating such a cloak is the coupling of the electromagnetic components of light, which would necessitate the use of complex materials with specific permittivity and permeability tensors. Previous cloaking solutions have involved circumventing this obstacle by functioning either in static (or quasistatic) fields where these electromagnetic components are uncoupled or in diffusive light scattering media where complex materials are not required. In this paper, concealing a large-scale spherical object from human sight from three orthogonal directions is reported. This result is achieved by developing a 3D homogeneous polyhedral transformation and a spatially invariant refractive index discretization that considerably reduce the coupling of the electromagnetic components of visible light. This approach allows for a major simplification in the design of 3D invisibility cloaks, which can now be created at a large scale using homogeneous and isotropic materials.

Interrogating heterogeneous compaction of meteoritic material at the mesoscale using analog experiments and numerical models

NASA Astrophysics Data System (ADS)

Derrick, James; Rutherford, Michael; Davison, Thomas; Chapman, David; Eakins, Daniel; Collins, Gareth

2017-06-01

Chondritic meteorites were lithified during solar system formation by compaction of bimodal mixtures of mm-scale, spherical, solidified melt droplets (chondrules) surrounded by a porous matrix of much finer grained dust. A possible compaction mechanism is low-velocity planetesimal collisions, which were common in the early solar system. Mesoscale numerical simulations of such impacts indicate heterogeneous compaction, with large porosity and temperature variations over sub-mm scales in the matrix and chondrules largely unaffected. In particular, compaction and heating are enhanced in front of the chondrule and suppressed in its wake. Such observations may provide a new tool for interpreting evidence for impact in meteorites. Here we present impact experiments that replicate compaction surrounding an individual chondrule using analog materials: Soda Lime glass beads/rods and 70% porous silica powder matrix (Sipernat). Real-time, X-ray imaging of the experiments, combined with mesoscale modelling, provides experimental confirmation of anisotropic matrix compaction surrounding individual chondrules, aligned with the shock direction. JGD is supported by EPSRC studentship funding; GSC are supported by STFC Grant ST/N000803/1.

The Earth is flat when personally significant experiences with the sphericity of the Earth are absent.

PubMed

Carbon, Claus-Christian

2010-07-01

Participants with personal and without personal experiences with the Earth as a sphere estimated large-scale distances between six cities located on different continents. Cognitive distances were submitted to a specific multidimensional scaling algorithm in the 3D Euclidean space with the constraint that all cities had to lie on the same sphere. A simulation was run that calculated respective 3D configurations of the city positions for a wide range of radii of the proposed sphere. People who had personally experienced the Earth as a sphere, at least once in their lifetime, showed a clear optimal solution of the multidimensional scaling (MDS) routine with a mean radius deviating only 8% from the actual radius of the Earth. In contrast, the calculated configurations for people without any personal experience with the Earth as a sphere were compatible with a cognitive concept of a flat Earth. 2010 Elsevier B.V. All rights reserved.

Sensitivity of the orbiting JEM-EUSO mission to large-scale anisotropies

NASA Astrophysics Data System (ADS)

Weiler, Thomas; Anchordoqui, Luis; Denton, Peter

2013-04-01

Uniform sky coverage and very large apertures are advantages of future extreme-energy, space-based cosmic-ray observatories. In this talk we will quantify the advantage of an all-sky/4pi observatory such as JEM-EUSO over the one to two steradian coverage of a ground-based observatory such as Auger. We exploit the availability of spherical harmonics in the case of 4pi coverage. The resulting Y(lm) coefficients will likely become a standard analysis tool for near-future, space-based, cosmic-ray astronomy. We demonstrate the use of Y(lm)'s with extractions of simulated dipole and quadrupole anisotropies. (A dipole anisotropy is expected if a single source-region such as Cen A dominates the sky, while a quadrupole moment is expected if a 2D source region such as the Supergalactic Plane dominates the sky.)

Early Onset of Ground State Deformation in Neutron Deficient Polonium Isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cocolios, T. E.; Van de Walle, J.; ISOLDE, CERN, CH-1211 Geneva 23

2011-02-04

In-source resonant ionization laser spectroscopy of the even-A polonium isotopes {sup 192-210,216,218}Po has been performed using the 6p{sup 3}7s {sup 5}S{sub 2} to 6p{sup 3}7p {sup 5}P{sub 2} ({lambda}=843.38 nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in {sup 200-210}Po with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, whichmore » is only partly reproduced by beyond mean field calculations.« less

Critical scaling near the yielding transition in granular media

NASA Astrophysics Data System (ADS)

Clark, Abram H.; Thompson, Jacob D.; Shattuck, Mark D.; Ouellette, Nicholas T.; O'Hern, Corey S.

2018-06-01

We show that the yielding transition in granular media displays second-order critical-point scaling behavior. We carry out discrete element simulations in the low-inertial-number limit for frictionless, purely repulsive spherical grains undergoing simple shear at fixed nondimensional shear stress Σ in two and three spatial dimensions. To find a mechanically stable (MS) packing that can support the applied Σ , isotropically prepared states with size L must undergo a total strain γms(Σ ,L ) . The number density of MS packings (∝γms-1 ) vanishes for Σ >Σc≈0.11 according to a critical scaling form with a length scale ξ ∝|Σ - Σc|-ν , where ν ≈1.7 -1.8 . Above the yield stress (Σ >Σc ), no MS packings that can support Σ exist in the large-system limit L /ξ ≫1 . MS packings generated via shear possess anisotropic force and contact networks, suggesting that Σc is associated with an upper limit in the degree to which these networks can be deformed away from those for isotropic packings.

The large-scale structure of the halo of the Andromeda galaxy. I. Global stellar density, morphology and metallicity properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibata, Rodrigo A.; Martin, Nicolas F.; Lewis, Geraint F.

We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite the presence of copious substructures, the global halo populations follow closely power-law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component (defined as the population that cannot be resolved into spatially distinct substructures with PAndAS). Fitting a three-dimensional halo model reveals that the most metal-poor populations ([Fe/H]<−1.7) are distributed approximately spherically (slightly prolate withmore » ellipticity c/a = 1.09 ± 0.03), with only a relatively small fraction residing in discernible stream-like structures (f {sub stream} = 42%). The sphericity of the ancient smooth component strongly hints that the dark matter halo is also approximately spherical. More metal-rich populations contain higher fractions of stars in streams, with f {sub stream} becoming as high as 86% for [Fe/H]>−0.6. The space density of the smooth metal-poor component has a global power-law slope of γ = –3.08 ± 0.07, and a non-parametric fit shows that the slope remains nearly constant from 30 kpc to ∼300 kpc. The total stellar mass in the halo at distances beyond 2° is ∼1.1 × 10{sup 10} M {sub ☉}, while that of the smooth component is ∼3 × 10{sup 9} M {sub ☉}. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly ∼8 × 10{sup 9} M {sub ☉}. We detect a substantial metallicity gradient, which declines from ([Fe/H]) = –0.7 at R = 30 kpc to ([Fe/H]) = –1.5 at R = 150 kpc for the full sample, with the smooth halo being ∼0.2 dex more metal poor than the full sample at each radius. While qualitatively in line with expectations from cosmological simulations, these observations are of great importance as they provide a prototype template that such simulations must now be able to reproduce in quantitative detail.« less

Coma of modified Gregorian and Cassegrainian mirror systems

NASA Technical Reports Server (NTRS)

Jones, R. T.

1976-01-01

The equivalence of the classical Newtonian, Cassegrainian, and Gregorian mirror systems with respect to the first two Seidel aberrations is rederived by means of a simple congruence. The effects of arbitrary small modifications of the two mirror systems are then studied and general formulas are derived for the effects of such modifications on the spherical aberration and coma. Spherical aberration is corrected to the third order if the amount of glass removed from one surface is replaced at the corresponding zone of the other surface. Modifications in which one surface is made spherical while the other is adjusted to eliminate spherical aberration result in large increases of coma for systems having the usual amplifying ratios.

Large radius of curvature measurement based on the evaluation of interferogram-quality metric in non-null interferometry

NASA Astrophysics Data System (ADS)

Yang, Zhongming; Dou, Jiantai; Du, Jinyu; Gao, Zhishan

2018-03-01

Non-null interferometry could use to measure the radius of curvature (ROC), we have presented a virtual quadratic Newton rings phase-shifting moiré-fringes measurement method for large ROC measurement (Yang et al., 2016). In this paper, we propose a large ROC measurement method based on the evaluation of the interferogram-quality metric by the non-null interferometer. With the multi-configuration model of the non-null interferometric system in ZEMAX, the retrace errors and the phase introduced by the test surface are reconstructed. The interferogram-quality metric is obtained by the normalized phase-shifted testing Newton rings with the spherical surface model in the non-null interferometric system. The radius curvature of the test spherical surface can be obtained until the minimum of the interferogram-quality metric is found. Simulations and experimental results are verified the feasibility of our proposed method. For a spherical mirror with a ROC of 41,400 mm, the measurement accuracy is better than 0.13%.

Energy gain calculations in Penning fusion systems using a bounce-averaged Fokker-Planck model

NASA Astrophysics Data System (ADS)

Chacón, L.; Miley, G. H.; Barnes, D. C.; Knoll, D. A.

2000-11-01

In spherical Penning fusion devices, a spherical cloud of electrons, confined in a Penning-like trap, creates the ion-confining electrostatic well. Fusion energy gains for these systems have been calculated in optimistic conditions (i.e., spherically uniform electrostatic well, no collisional ion-electron interactions, single ion species) using a bounce-averaged Fokker-Planck (BAFP) model. Results show that steady-state distributions in which the Maxwellian ion population is dominant correspond to lowest ion recirculation powers (and hence highest fusion energy gains). It is also shown that realistic parabolic-like wells result in better energy gains than square wells, particularly at large well depths (>100 kV). Operating regimes with fusion power to ion input power ratios (Q-value) >100 have been identified. The effect of electron losses on the Q-value has been addressed heuristically using a semianalytic model, indicating that large Q-values are still possible provided that electron particle losses are kept small and well depths are large.

Surface Structure Spread Single Crystals (S4C): Preparation and characterization

NASA Astrophysics Data System (ADS)

de Alwis, A.; Holsclaw, B.; Pushkarev, V. V.; Reinicker, A.; Lawton, T. J.; Blecher, M. E.; Sykes, E. C. H.; Gellman, A. J.

2013-02-01

A set of six spherically curved Cu single crystals referred to as Surface Structure Spread Single Crystals (S4Cs) has been prepared in such a way that their exposed surfaces collectively span all possible crystallographic surface orientations that can be cleaved from the face centered cubic Cu lattice. The method for preparing these S4Cs and for finding the high symmetry pole point is described. Optical profilometry has been used to determine the true shapes of the S4Cs and show that over the majority of the surface, the shape is extremely close to that of a perfect sphere. The local orientations of the surfaces lie within ± 1° of the orientation expected on the basis of the spherical shape; their orientation is as good as that of many commercially prepared single crystals. STM imaging has been used to characterize the atomic level structure of the Cu(111) ± 11°-S4C. This has shown that the average step densities and the average step orientations match those expected based on the spherical shape. In other words, although there is some distribution of step-step spacing and step orientations, there is no evidence of large scale reconstruction or faceting. The Cu S4Cs have local structures based on the ideal termination of the face centered cubic Cu lattice in the direction of termination. The set of Cu S4Cs will serve as the basis for high throughput investigations of structure sensitive surface chemistry on Cu.

Petrology of Mississippian carbonate eolianites and associated facies: Ste. Genevieve Limestone of Indiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dodd, J.R.; Brown, T.W.; Harris, C.D.

1990-05-01

Descriptions of carbonate eolianites of pre-Pleistocene age are rare. Based largely on sedimentary structures and facies associations, Hunter has recently identified eolian deposits in the middle Mississippian Ste. Genevieve Limestone near Corydon, Indiana. Eolianite grainstones contain a diverse assemblage of allochems, including a variety of skeletal grains, ooids (some broken and abraded), peloids, intraclasts, and abundant quartz silt. Carbonate grains, which rarely exceed 0.5 mm are usually more spherical than grains from associated marine unit. Eolian units contain cross-laminations that sometimes coarsen upward. No evidence for vadose cement was found in the eolianite units; the extensive solution packing suggest thatmore » cementation did not occur until burial to considerable depth. Marine grainstones, which probably formed on shallow shoals or an open platform, are common in the section. They contain a diverse assemblage of skeletal grain types as well as ooids, peloids, and intraclasts; however, one grain type (such as ooids) frequently dominates an individual unit. Detrital quartz grains are rare. Rounding of grains is usually good, but sphericity of skeletal grains which were not originally spherical is low. Fine laminations are uncommon, and no systematic grading is found on a thin-section scale. Grains and fossils in excess of 10 mm are common in the marine unit. Carbonate mud-rich rocks that probably formed in a shallow lagoonal setting also occur in the Ste. Genevieve section as do poorly developed exposure surfaces with pedogenic features.« less

Riemannian Metric Optimization on Surfaces (RMOS) for Intrinsic Brain Mapping in the Laplace-Beltrami Embedding Space

PubMed Central

Gahm, Jin Kyu; Shi, Yonggang

2018-01-01

Surface mapping methods play an important role in various brain imaging studies from tracking the maturation of adolescent brains to mapping gray matter atrophy patterns in Alzheimer’s disease. Popular surface mapping approaches based on spherical registration, however, have inherent numerical limitations when severe metric distortions are present during the spherical parameterization step. In this paper, we propose a novel computational framework for intrinsic surface mapping in the Laplace-Beltrami (LB) embedding space based on Riemannian metric optimization on surfaces (RMOS). Given a diffeomorphism between two surfaces, an isometry can be defined using the pullback metric, which in turn results in identical LB embeddings from the two surfaces. The proposed RMOS approach builds upon this mathematical foundation and achieves general feature-driven surface mapping in the LB embedding space by iteratively optimizing the Riemannian metric defined on the edges of triangular meshes. At the core of our framework is an optimization engine that converts an energy function for surface mapping into a distance measure in the LB embedding space, which can be effectively optimized using gradients of the LB eigen-system with respect to the Riemannian metrics. In the experimental results, we compare the RMOS algorithm with spherical registration using large-scale brain imaging data, and show that RMOS achieves superior performance in the prediction of hippocampal subfields and cortical gyral labels, and the holistic mapping of striatal surfaces for the construction of a striatal connectivity atlas from substantia nigra. PMID:29574399

Non-astigmatic imaging with matched pairs of spherically bent reflectors

DOEpatents

Bitter, Manfred Ludwig [Princeton, NJ; Hill, Kenneth Wayne [Plainsboro, NJ; Scott, Steven Douglas [Wellesley, MA; Feder, Russell [Newton, PA; Ko, Jinseok [Cambridge, MA; Rice, John E [N. Billerica, MA; Ince-Cushman, Alexander Charles [New York, NY; Jones, Frank [Manalapan, NJ

2012-07-10

Arrangements for the point-to-point imaging of a broad spectrum of electromagnetic radiation and ultrasound at large angles of incidence employ matched pairs of spherically bent reflectors to eliminate astigmatic imaging errors. Matched pairs of spherically bent crystals or spherically bent multi-layers are used for X-rays and EUV radiation; and matched pairs of spherically bent mirrors that are appropriate for the type of radiation are used with microwaves, infrared and visible light, or ultrasound. The arrangements encompass the two cases, where the Bragg angle--the complement to the angle of incidence in optics--is between 45.degree. and 90.degree. on both crystals/mirrors or between 0.degree. and 45.degree. on the first crystal/mirror and between 45.degree. and 90.degree. on the second crystal/mirror, where the angles of convergence and divergence are equal. For x-rays and EUV radiation, also the Bragg condition is satisfied on both spherically bent crystals/multi-layers.

Allometric scaling in-vitro

NASA Astrophysics Data System (ADS)

Ahluwalia, Arti

2017-02-01

About two decades ago, West and coworkers established a model which predicts that metabolic rate follows a three quarter power relationship with the mass of an organism, based on the premise that tissues are supplied nutrients through a fractal distribution network. Quarter power scaling is widely considered a universal law of biology and it is generally accepted that were in-vitro cultures to obey allometric metabolic scaling, they would have more predictive potential and could, for instance, provide a viable substitute for animals in research. This paper outlines a theoretical and computational framework for establishing quarter power scaling in three-dimensional spherical constructs in-vitro, starting where fractal distribution ends. Allometric scaling in non-vascular spherical tissue constructs was assessed using models of Michaelis Menten oxygen consumption and diffusion. The models demonstrate that physiological scaling is maintained when about 5 to 60% of the construct is exposed to oxygen concentrations less than the Michaelis Menten constant, with a significant concentration gradient in the sphere. The results have important implications for the design of downscaled in-vitro systems with physiological relevance.

Halo assembly bias and the tidal anisotropy of the local halo environment

NASA Astrophysics Data System (ADS)

Paranjape, Aseem; Hahn, Oliver; Sheth, Ravi K.

2018-05-01

We study the role of the local tidal environment in determining the assembly bias of dark matter haloes. Previous results suggest that the anisotropy of a halo's environment (i.e. whether it lies in a filament or in a more isotropic region) can play a significant role in determining the eventual mass and age of the halo. We statistically isolate this effect, using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 1011.6 ≲ (m/h-1 M⊙) ≲ 1014.9. We probe the large-scale environment, using a novel halo-by-halo estimator of linear bias. For the small-scale environment, we identify a variable αR that captures the tidal anisotropy in a region of radius R = 4R200b around the halo and correlates strongly with halo bias at fixed mass. Segregating haloes by αR reveals two distinct populations. Haloes in highly isotropic local environments (αR ≲ 0.2) behave as expected from the simplest, spherically averaged analytical models of structure formation, showing a negative correlation between their concentration and large-scale bias at all masses. In contrast, haloes in anisotropic, filament-like environments (αR ≳ 0.5) tend to show a positive correlation between bias and concentration at any mass. Our multiscale analysis cleanly demonstrates how the overall assembly bias trend across halo mass emerges as an average over these different halo populations, and provides valuable insights towards building analytical models that correctly incorporate assembly bias. We also discuss potential implications for the nature and detectability of galaxy assembly bias.

Non-contact XUV metrology of Ru/B4C multilayer optics by means of Hartmann wavefront analysis.

PubMed

Ruiz-Lopez, Mabel; Dacasa, Hugo; Mahieu, Benoit; Lozano, Magali; Li, Lu; Zeitoun, Philippe; Bleiner, Davide

2018-02-20

Short-wavelength imaging, spectroscopy, and lithography scale down the characteristic length-scale to nanometers. This poses tight constraints on the optics finishing tolerances, which is often difficult to characterize. Indeed, even a tiny surface defect degrades the reflectivity and spatial projection of such optics. In this study, we demonstrate experimentally that a Hartmann wavefront sensor for extreme ultraviolet (XUV) wavelengths is an effective non-contact analytical method for inspecting the surface of multilayer optics. The experiment was carried out in a tabletop laboratory using a high-order harmonic generation as an XUV source. The wavefront sensor was used to measure the wavefront errors after the reflection of the XUV beam on a spherical Ru/B 4 C multilayer mirror, scanning a large surface of approximately 40 mm in diameter. The results showed that the technique detects the aberrations in the nanometer range.

The Rapidly Rotating Sun

NASA Technical Reports Server (NTRS)

Hanasoge, Shravan M.; Duvall, Thomas L., Jr.; Sreenivasan, Katepalli R.

2012-01-01

Convection in the solar interior is thought to comprise structures at a continuum of scales, from large to small. This conclusion emerges from phenomenological studies and numerical simulations though neither covers the proper range of dynamical parameters of solar convection. In the present work, imaging techniques of time-distance helioseismology applied to observational data reveal no long-range order in the convective motion. We conservatively bound the associated velocity magnitudes, as a function of depth and the spherical-harmonic degree l to be 20-100 times weaker than prevailing estimates within the wavenumber band l < 60. The observationally constrained kinetic energy is approximately a thousandth of the theoretical prediction, suggesting the prevalence of an intrinsically different paradigm of turbulence. A fundamental question arises: what mechanism of turbulence transports the heat ux of a solar luminosity outwards? The Sun is seemingly a much faster rotator than previously thought, with advection dominated by Coriolis forces at scales l < 60.

Correlations among the parameters of the spherical model for eclipsing binaries

NASA Technical Reports Server (NTRS)

Sobieski, S.; White, J. E.

1971-01-01

Correlation coefficients were computed to investigate the parameters for describing the spherical model of an eclipsing binary system. Regions in parameter hyperspace were identified where strong correlations exist and, by implication, the solution determinacy is low. The results are presented in tabular form for a large number of system configurations.

Large-Angular-Scale Anisotropy in the Cosmic Background Radiation

DOE R&D Accomplishments Database

Gorenstein, M. V.; Smoot, G. F.

1980-05-01

We report the results of an extended series of airborne measurements of large-angular-scale anisotropy in the 3 K cosmic background radiation. Observations were carried out with a dual-antenna microwave radiometer operating at 33 GHz (.089 cm wavelength) flown on board a U-2 aircraft to 20 km altitude. In eleven flights, between December 1976 and May 1978, the radiometer measured differential intensity between pairs of directions distributed over most of the northern hemisphere with an rms sensitivity of 47 mK Hz{sup 1?}. The measurements how clear evidence of anisotropy that is readily interpreted as due to the solar motion relative to the sources of the radiation. The anisotropy is well fit by a first order spherical harmonic of amplitude 360{+ or -}50km sec{sup -1} toward the direction 11.2{+ or -}0.5 hours of right ascension and 19 {+ or -}8 degrees declination. A simultaneous fit to a combined hypotheses of dipole and quadrupole angular distributions places a 1 mK limit on the amplitude of most components of quadrupole anisotropy with 90% confidence. Additional analysis places a 0.5 mK limit on uncorrelated fluctuations (sky-roughness) in the 3 K background on an angular scale of the antenna beam width, about 7 degrees.

Neocortical dynamics at multiple scales: EEG standing waves, statistical mechanics, and physical analogs.

PubMed

Ingber, Lester; Nunez, Paul L

2011-02-01

The dynamic behavior of scalp potentials (EEG) is apparently due to some combination of global and local processes with important top-down and bottom-up interactions across spatial scales. In treating global mechanisms, we stress the importance of myelinated axon propagation delays and periodic boundary conditions in the cortical-white matter system, which is topologically close to a spherical shell. By contrast, the proposed local mechanisms are multiscale interactions between cortical columns via short-ranged non-myelinated fibers. A mechanical model consisting of a stretched string with attached nonlinear springs demonstrates the general idea. The string produces standing waves analogous to large-scale coherent EEG observed in some brain states. The attached springs are analogous to the smaller (mesoscopic) scale columnar dynamics. Generally, we expect string displacement and EEG at all scales to result from both global and local phenomena. A statistical mechanics of neocortical interactions (SMNI) calculates oscillatory behavior consistent with typical EEG, within columns, between neighboring columns via short-ranged non-myelinated fibers, across cortical regions via myelinated fibers, and also derives a string equation consistent with the global EEG model. Copyright © 2010 Elsevier Inc. All rights reserved.

Voids in Gravitational Instability Scenarios - Part One - Global Density and Velocity Fields in an Einstein - De-Sitter Universe

NASA Astrophysics Data System (ADS)

van de Weygaert, R.; van Kampen, E.

1993-07-01

The first results of an extensive study of the structure and dynamics of underdense regions in gravitational instability scenarios are presented. Instead of adopting spherically symmetric voids with some idealized initial density and velocity profile, underdense regions of a given size and depth, embedded in an initial density fluctuation field, are generated. In order to accomplish this in a consistent way, these initial conditions are set up by means of Bertschinger's constrained random field code. The generated particle samples of 64^3^ particles in a box of side 100 Mpc are followed into the non-linear regime by Bertschinger's PM N- body code. In this way we address the dependence of the structure and kinematics of the void both on the initial depth of the void and on the fluctuation field in which it is embedded. In particular, this study provides some understanding of how far fluctuations on small scales modify the dynamics of the large-scale void, and especially of how far the properties of small structures inside the void are affected by the global properties of the void. One of the conspicuous features of the initial density fields inside protovoids appears to be the existence of a `void hierarchy', with small voids embedded in larger voids. The survival of this hierarchy during the riot evolution of the void depends critically on the initial depth as well as on the clustering scenario involved. As well as presenting a qualitative discussion of the structure of underdense regions in initial density fields in different scenarios, and the results of simulations of the ensuing non-linear evolution, we concentrate in particular on a comparison of the global density and velocity fields in voids with predictions from linear theory as well as from the spherical outflow model. The relation between the initial linear depth, the resulting non-linear depth and the excess expansion velocities in voids is addressed. In addition, we find that, while near its centre a void becomes more and more spherical, the shape of its boundary is influenced to a large extent by the structures surrounding the void and therefore is generally more irregular. In this first study we concentrate on single voids in Einstein-de Sitter universes. The underdense regions considered are linear 1 σ_0_, 2 σ_0_ and 3 σ_0_ dips in fields that are Gaussian-smoothed on a scale of R_G_ = 10 h^-1^ Mpc, approximately half the size of the Bootes void. These regions are studied in terms of the Cold Dark Matter and Hot Dark Matter scenarios as well as in terms of the scale-free scenarios P(k) is proportional to k^0^, k^-1^ and k^-2^. The Hubble constant is taken to be H_0_ = 100 h km s^-1^ Mpc^-1^.

Spherical Particle in Nematic Liquid Crystal Under an External Field: The Saturn Ring Regime

NASA Astrophysics Data System (ADS)

Alama, Stan; Bronsard, Lia; Lamy, Xavier

2018-03-01

We consider a nematic liquid crystal occupying the exterior region in R^3 outside of a spherical particle, with radial strong anchoring. Within the context of the Landau-de Gennes theory, we study minimizers subject to an external field, modeled by an additional term which favors nematic alignment parallel to the field. When the external field is high enough, we obtain a scaling law for the energy. The energy scale corresponds to minimizers concentrating their energy in a boundary layer around the particle, with quadrupolar symmetry. This suggests the presence of a Saturn ring defect around the particle, rather than a dipolar director field typical of a point defect.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ata, Metin; Baumgarten, Falk; Bautista, Julian

We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshiftsmore » $0.8 < z < 2.2$ and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.5$$\\sigma$$. We determine the spherically averaged BAO distance to $z = 1.52$ to 4.4 per cent precision: $$D_V(z=1.52)=3855\\pm170 \\left(r_{\\rm d}/r_{\\rm d, fid}\\right)\\ $$Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat $$\\Lambda$$CDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Using these BAO data alone and marginalizing over the length of the standard ruler, we find $$\\Omega_{\\Lambda} > 0$$ at 6.5$$\\sigma$$ significance when testing a $$\\Lambda$$CDM model with free curvature.« less

Comparison of approximate solutions to the phonon Boltzmann transport equation with the relaxation time approximation: Spherical harmonics expansions and the discrete ordinates method

NASA Astrophysics Data System (ADS)

Christenson, J. G.; Austin, R. A.; Phillips, R. J.

2018-05-01

The phonon Boltzmann transport equation is used to analyze model problems in one and two spatial dimensions, under transient and steady-state conditions. New, explicit solutions are obtained by using the P1 and P3 approximations, based on expansions in spherical harmonics, and are compared with solutions from the discrete ordinates method. For steady-state energy transfer, it is shown that analytic expressions derived using the P1 and P3 approximations agree quantitatively with the discrete ordinates method, in some cases for large Knudsen numbers, and always for Knudsen numbers less than unity. However, for time-dependent energy transfer, the PN solutions differ qualitatively from converged solutions obtained by the discrete ordinates method. Although they correctly capture the wave-like behavior of energy transfer at short times, the P1 and P3 approximations rely on one or two wave velocities, respectively, yielding abrupt, step-changes in temperature profiles that are absent when the angular dependence of the phonon velocities is captured more completely. It is shown that, with the gray approximation, the P1 approximation is formally equivalent to the so-called "hyperbolic heat equation." Overall, these results support the use of the PN approximation to find solutions to the phonon Boltzmann transport equation for steady-state conditions. Such solutions can be useful in the design and analysis of devices that involve heat transfer at nanometer length scales, where continuum-scale approaches become inaccurate.

A Compact Magnetic Field-Based Obstacle Detection and Avoidance System for Miniature Spherical Robots.

PubMed

Wu, Fang; Vibhute, Akash; Soh, Gim Song; Wood, Kristin L; Foong, Shaohui

2017-05-28

Due to their efficient locomotion and natural tolerance to hazardous environments, spherical robots have wide applications in security surveillance, exploration of unknown territory and emergency response. Numerous studies have been conducted on the driving mechanism, motion planning and trajectory tracking methods of spherical robots, yet very limited studies have been conducted regarding the obstacle avoidance capability of spherical robots. Most of the existing spherical robots rely on the "hit and run" technique, which has been argued to be a reasonable strategy because spherical robots have an inherent ability to recover from collisions. Without protruding components, they will not become stuck and can simply roll back after running into bstacles. However, for small scale spherical robots that contain sensitive surveillance sensors and cannot afford to utilize heavy protective shells, the absence of obstacle avoidance solutions would leave the robot at the mercy of potentially dangerous obstacles. In this paper, a compact magnetic field-based obstacle detection and avoidance system has been developed for miniature spherical robots. It utilizes a passive magnetic field so that the system is both compact and power efficient. The proposed system can detect not only the presence, but also the approaching direction of a ferromagnetic obstacle, therefore, an intelligent avoidance behavior can be generated by adapting the trajectory tracking method with the detection information. Design optimization is conducted to enhance the obstacle detection performance and detailed avoidance strategies are devised. Experimental results are also presented for validation purposes.

Topography- and topology-driven spreading of non-Newtonian power-law liquids on a flat and a spherical substrate

NASA Astrophysics Data System (ADS)

Iwamatsu, Masao

2017-10-01

The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids on a flat and a spherical rough and textured substrate is theoretically studied in the capillary-controlled spreading regime. A droplet whose scale is much larger than that of the roughness of substrate is considered. The equilibrium contact angle on a rough substrate is modeled by the Wenzel and the Cassie-Baxter model. Only the viscous energy dissipation within the droplet volume is considered, and that within the texture of substrate by imbibition is neglected. Then, the energy balance approach is adopted to derive the evolution equation of the contact angle. When the equilibrium contact angle vanishes, the relaxation of dynamic contact angle θ of a droplet obeys a power-law decay θ ˜t-α except for the Newtonian and the non-Newtonian shear-thinning liquid of the Wenzel model on a spherical substrate. The spreading exponent α of the non-Newtonian shear-thickening liquid of the Wenzel model on a spherical substrate is larger than others. The relaxation of the Newtonian liquid of the Wenzel model on a spherical substrate is even faster showing the exponential relaxation. The relaxation of the non-Newtonian shear-thinning liquid of Wenzel model on a spherical substrate is fastest and finishes within a finite time. Thus, the topography (roughness) and the topology (flat to spherical) of substrate accelerate the spreading of droplet.

Special issue on current research in astrophysical magnetism

NASA Astrophysics Data System (ADS)

Kosovichev, Alexander; Lundstedt, Henrik; Brandenburg, Axel

2012-06-01

Much of what Hannes Alfvén envisaged some 70 years ago has now penetrated virtually all branches of astrophysical research. Indeed, magnetic fields can display similar properties over a large range of scales. We have therefore been able to take advantage of the transparency of galaxies and the interstellar medium to obtain measurements inside them. On the other hand, the Sun is much closer, allowing us to obtain a detailed picture of the interaction of flows and magnetic fields at the surface, and more recently in the interior by helioseismology. Moreover, the solar timescales are generally much shorter, making studies of dynamical processes more direct. This special issue on current research in astrophysical magnetism is based on work discussed during a one month Nordita program Dynamo, Dynamical Systems and Topology and comprises papers that fall into four different categories (A)-(D). (A) Papers on small-scale magnetic fields and flows in astrophysics 1. E M de Gouveia Dal Pino, M R M Leão, R Santos-Lima, G Guerrero, G Kowal and A Lazarian Magnetic flux transport by turbulent reconnection in astrophysical flows 2. Philip R Goode, Valentyna Abramenko and Vasyl Yurchyshyn New solar telescope in Big Bear: evidence for super-diffusivity and small-scale solar dynamos? 3. I N Kitiashvili, A G Kosovichev, N N Mansour, S K Lele and A A Wray Vortex tubes of turbulent solar convection The above collection of papers begins with a review of astrophysical reconnection and introduces the concept of dynamos necessary to explain the existence of contemporary magnetic fields both on galactic and solar scales (paper 1). This is complemented by observations with the new Big Bear Solar Observatory telescope, allowing us to see magnetic field amplification on small scales (paper 2). This in turn is complemented by realistic simulations of subsurface and surface flow patterns (paper 3). (B) Papers on theoretical approaches to turbulent fluctuations 4. Nathan Kleeorin and Igor Rogachevskii Growth rate of small-scale dynamo at low magnetic Prandtl numbers 5. Erico L Rempel, Abraham C-L Chian and Axel Brandenburg Lagrangian chaos in an ABC-forced nonlinear dynamo 6. J E Snellman, M Rheinhardt, P J Käpylä, M J Mantere and A Brandenburg Mean-field closure parameters for passive scalar turbulence Research in dynamo theory has been actively pursued for over half a century. It started by trying to understand the large-scale magnetic fields of the Sun and the Earth, and subsequently also in galaxies. Such large-scale fields can nowadays be understood in terms of mean-field dynamo theory that explains the possibility of large-scale field generation under anisotropic conditions lacking mirror symmetry. However, even when none of this is the case, dynamos can still work, and they are called small-scale dynamos that were referred to in paper 2. This was studied originally under the assumption that the flow is smooth compared with the magnetic field, but in the Sun the opposite is the case. This is because viscosity is much smaller than magnetic diffusivity, i.e., their ratio, which is the magnetic Prandtl number, is small. In that case the physics of small-scale dynamos changes, but dynamos still exist even then (paper 4). Tracing the flow lines in nonlinear small-scale dynamos is important for understanding their mixing properties (paper 5). Turbulent mixing is a generic concept that applies not only to magnetic field, but also to passive scalars which are often used as a prototype for studying this. Turbulence simulations have helped tremendously in quantifying the ability of turbulent flows to mix, but the more we know, the more complicated it becomes. It turns out that spatial and temporal coupling is an important consideration for allowing accurate comparison between numerical simulations and mean-field theory (paper 6). (C) The large-scale solar cycle 7. V V Pipin and D D Sokoloff The fluctuating α-effect and Waldmeier relations in the nonlinear dynamo models1 8. Radostin D Simitev and Friedrich H Busse Solar cycle properties described by simple convection-driven dynamos The mean-field concept has helped us constructing detailed models of the solar cycle and to make comparison with observed features of the solar 11-year cycle. One such feature is the Waldmeier relation between growth time and amplitude of the cycle, and there is another relation for the declining part of the cycle. These relations reflect nonlinear aspects of the model and therefore constitute an important test of the model (paper 7). While mean-field theory is a useful concept for modeling solar activity, it must eventually be tested against fully three-dimensional simulations. At present, such simulations are often quite idealized, because only the large scales of the turbulent convection of stars can be resolved. Nevertheless, numerical simulations begin to show many properties that are also seen in the Sun (paper 8). (D) Flow and dynamo properties in spherical shells 9. Maxim Reshetnyak and Pavel Hejda Kinetic energy cascades in quasi-geostrophic convection in a spherical shell 10. Radostin D Simitev and Friedrich H Busse Bistable attractors in a model of convection-driven spherical dynamos As the rotation speed is increased, the flow becomes more strongly constrained by the Coriolis force. In a spherical shell, such a flow is additionally constrained by gravity, or at least by the geometry of the domain. Such flows are called geostrophic. Only now are we beginning to learn about the subtle properties of the kinetic energy cascade in such flows (paper 9). Turbulent systems are highly nonlinear and it is in principle possible to find multiple solutions of the equations even for the same boundary and initial conditions. For turbulent systems, we can only ask about the statistical properties of the solutions, and the question of multiple solutions is then less obvious. However, in turbulent dynamos in convective shells, a nice example has been found where this is possible. A detailed account of this is given in paper 10. Most of the participants of the Nordita program were able to stay for the full month of the program, allowing them to think about new ideas that will be reflected not only in papers on the short term, but also in new projects and collaborations on a larger scale in the years to come. We therefore thank Nordita for providing a stimulating atmosphere and acknowledge the generous support. 1This paper has been published as V V Pipin and D D Sokoloff 2011 Phys. Scr. 84 065903.

Spherical Demons: Fast Surface Registration

PubMed Central

Yeo, B.T. Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

2009-01-01

We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast – registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:18979813

Spherical demons: fast surface registration.

PubMed

Yeo, B T Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

2008-01-01

We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast - registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces.

Experiment to Form and Characterize a Section of a Spherically Imploding Plasma Liner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, S. C.; Langendorf, S. J.; Yates, K. C.

Here, we describe an experiment to form and characterize a section of a spherically imploding plasma liner by merging six supersonic plasma jets that are launched by newly designed contoured-gap coaxial plasma guns. This experiment is a prelude to forming a fully spherical imploding plasma liner using many dozens of plasma guns, as a standoff driver for plasma-jet-driven magneto-inertial fusion. The objectives of the six-jet experiments are to assess the evolution and scalings of liner Mach number and uniformity, which are important metrics for spherically imploding plasma liners to compress magnetized target plasmas to fusion conditions. Lastly, this article describesmore » the design of the coaxial plasma guns, experimental characterization of the plasma jets, six-jet experimental setup and diagnostics, initial diagnostic data from three- and six-jet experiments, and the high-level objectives of associated numerical modeling.« less

Experiment to Form and Characterize a Section of a Spherically Imploding Plasma Liner

DOE PAGES

Hsu, S. C.; Langendorf, S. J.; Yates, K. C.; ...

2017-12-18

Here, we describe an experiment to form and characterize a section of a spherically imploding plasma liner by merging six supersonic plasma jets that are launched by newly designed contoured-gap coaxial plasma guns. This experiment is a prelude to forming a fully spherical imploding plasma liner using many dozens of plasma guns, as a standoff driver for plasma-jet-driven magneto-inertial fusion. The objectives of the six-jet experiments are to assess the evolution and scalings of liner Mach number and uniformity, which are important metrics for spherically imploding plasma liners to compress magnetized target plasmas to fusion conditions. Lastly, this article describesmore » the design of the coaxial plasma guns, experimental characterization of the plasma jets, six-jet experimental setup and diagnostics, initial diagnostic data from three- and six-jet experiments, and the high-level objectives of associated numerical modeling.« less

Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

2015-05-01

Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

Thermal stability tests of CFRP sandwich panels for far infrared astronomy

NASA Technical Reports Server (NTRS)

Hoffmann, W. F.; Helwig, G.; Scheulen, D.

1986-01-01

An account is given of fabrication methods and low temperature figure tests for CFRP sandwich panels, in order to ascertain their applicability to ultralightweight 3-m aperture primary mirrors for balloon-borne sub-mm and far-IF telescopes that must maintain a 1-2 micron rms surface figure accuracy at -40 to -50 C. Optical figure measurements on the first two of a series of four 0.5-m test panels, replicated to a spherical surface, show a radius-of-curvature change and astigmatism down to -60 C; this approximately follows the composite's theoretical predictions and implies that material and process control is excellent, so that the large scale changes observed can be compensated for.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schollmeier, Marius S.; Geissel, Matthias; Shores, Jonathon E.

We present calculations for the field of view (FOV), image fluence, image monochromaticity, spectral acceptance, and image aberrations for spherical crystal microscopes, which are used as self-emission imaging or backlighter systems at large-scale high energy density physics facilities. Our analytic results are benchmarked with ray-tracing calculations as well as with experimental measurements from the 6.151 keV backlighter system at Sandia National Laboratories. Furthermore, the analytic expressions can be used for x-ray source positions anywhere between the Rowland circle and object plane. We discovered that this enables quick optimization of the performance of proposed but untested, bent-crystal microscope systems to findmore » the best compromise between FOV, image fluence, and spatial resolution for a particular application.« less

Dark field differential dynamic microscopy enables accurate characterization of the roto-translational dynamics of bacteria and colloidal clusters

NASA Astrophysics Data System (ADS)

Cerbino, Roberto; Piotti, Davide; Buscaglia, Marco; Giavazzi, Fabio

2018-01-01

Micro- and nanoscale objects with anisotropic shape are key components of a variety of biological systems and inert complex materials, and represent fundamental building blocks of novel self-assembly strategies. The time scale of their thermal motion is set by their translational and rotational diffusion coefficients, whose measurement may become difficult for relatively large particles with small optical contrast. Here we show that dark field differential dynamic microscopy is the ideal tool for probing the roto-translational Brownian motion of anisotropic shaped particles. We demonstrate our approach by successful application to aqueous dispersions of non-motile bacteria and of colloidal aggregates of spherical particles.

A numerical study of bifurcations in a barotropic shear flow

NASA Technical Reports Server (NTRS)

Huerre, P.; Keefe, L. R.; Meunier, G.; Redekopp, L. G.; Spalart, P. R.; Rogers, M. M.

1988-01-01

In the last few years, more and more evidence has emerged suggesting that transition to turbulence may be viewed as a succession of bifurcations to deterministic chaos. Most experimental and numerical observations have been restricted to Rayleigh-Benard convection and Taylor-Couette flow between concentric cylinders. An attempt is made to accurately describe the bifurcation sequence leading to chaos in a 2-D temporal free shear layer on the beta-plane. The beta-plane is a locally Cartesian reduction of the equations describing the dynamicss of a shallow layer of fluid on a rotating spherical planet. It is a valid model for large scale flows of interest in meteorology and oceanography.

Adsorption energy as a metric for wettability at the nanoscale

PubMed Central

Giro, Ronaldo; Bryant, Peter W.; Engel, Michael; Neumann, Rodrigo F.; Steiner, Mathias B.

2017-01-01

Wettability is the affinity of a liquid for a solid surface. For energetic reasons, macroscopic drops of liquid form nearly spherical caps. The degree of wettability is then captured by the contact angle where the liquid-vapor interface meets the solid-liquid interface. As droplet volumes shrink to the scale of attoliters, however, surface interactions become significant, and droplets assume distorted shapes. In this regime, the contact angle becomes ambiguous, and a scalable metric for quantifying wettability is needed, especially given the emergence of technologies exploiting liquid-solid interactions at the nanoscale. Here we combine nanoscale experiments with molecular-level simulation to study the breakdown of spherical droplet shapes at small length scales. We demonstrate how measured droplet topographies increasingly reveal non-spherical features as volumes shrink. Ultimately, the nanoscale droplets flatten out to form layer-like molecular assemblies at the solid surface. For the lack of an identifiable contact angle at small scales, we introduce a droplet’s adsorption energy density as a new metric for a liquid’s affinity for a surface. We discover that extrapolating the macroscopic idealization of a drop to the nanoscale, though it does not geometrically resemble a realistic droplet, can nonetheless recover its adsorption energy if line tension is included. PMID:28397869

Large-scale fluctuations in the cosmic ionizing background: the impact of beamed source emission

NASA Astrophysics Data System (ADS)

Suarez, Teresita; Pontzen, Andrew

2017-12-01

When modelling the ionization of gas in the intergalactic medium after reionization, it is standard practice to assume a uniform radiation background. This assumption is not always appropriate; models with radiative transfer show that large-scale ionization rate fluctuations can have an observable impact on statistics of the Lyman α forest. We extend such calculations to include beaming of sources, which has previously been neglected but which is expected to be important if quasars dominate the ionizing photon budget. Beaming has two effects: first, the physical number density of ionizing sources is enhanced relative to that directly observed; and secondly, the radiative transfer itself is altered. We calculate both effects in a hard-edged beaming model where each source has a random orientation, using an equilibrium Boltzmann hierarchy in terms of spherical harmonics. By studying the statistical properties of the resulting ionization rate and H I density fields at redshift z ∼ 2.3, we find that the two effects partially cancel each other; combined, they constitute a maximum 5 per cent correction to the power spectrum P_{H I}(k) at k = 0.04 h Mpc-1. On very large scales (k < 0.01 h Mpc-1) the source density renormalization dominates; it can reduce, by an order of magnitude, the contribution of ionizing shot noise to the intergalactic H I power spectrum. The effects of beaming should be considered when interpreting future observational data sets.

Production of primary mirror segments for the Giant Magellan Telescope

NASA Astrophysics Data System (ADS)

Martin, H. M.; Allen, R. G.; Burge, J. H.; Davis, J. M.; Davison, W. B.; Johns, M.; Kim, D. W.; Kingsley, J. S.; Law, K.; Lutz, R. D.; Strittmatter, P. A.; Su, P.; Tuell, M. T.; West, S. C.; Zhou, P.

2014-07-01

Segment production for the Giant Magellan Telescope is well underway, with the off-axis Segment 1 completed, off-axis Segments 2 and 3 already cast, and mold construction in progress for the casting of Segment 4, the center segment. All equipment and techniques required for segment fabrication and testing have been demonstrated in the manufacture of Segment 1. The equipment includes a 28 m test tower that incorporates four independent measurements of the segment's figure and geometry. The interferometric test uses a large asymmetric null corrector with three elements including a 3.75 m spherical mirror and a computer-generated hologram. For independent verification of the large-scale segment shape, we use a scanning pentaprism test that exploits the natural geometry of the telescope to focus collimated light to a point. The Software Configurable Optical Test System, loosely based on the Hartmann test, measures slope errors to submicroradian accuracy at high resolution over the full aperture. An enhanced laser tracker system guides the figuring through grinding and initial polishing. All measurements agree within the expected uncertainties, including three independent measurements of radius of curvature that agree within 0.3 mm. Segment 1 was polished using a 1.2 m stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital polisher for deterministic small-scale figuring. For the remaining segments, the Mirror Lab is building a smaller, orbital stressed lap to combine the smoothing capability with deterministic figuring.

MODELING OF ION-EXCHANGE FOR CESIUM REMOVAL FROM DISSOLVED SALTCAKE IN SRS TANKS 1-3, 37 AND 41

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, F

2007-08-15

This report presents an evaluation of the expected performance of engineered Crystalline Silicotitanate (CST) and spherical Resorcinol-Formaldehyde (RF) ion exchange resin for the removal of cesium from dissolved saltcake in SRS Tanks 1-3, 37 and 41. The application presented in this report reflects the expected behavior of engineered CST IE-911 and spherical RF resin manufactured at the intermediate-scale (approximately 100 gallon batch size; batch 5E-370/641). It is generally believed that scale-up to production-scale in RF resin manufacturing will result in similarly behaving resin batches whose chemical selectivity is unaffected while total capacity per gram of resin may vary. As such,more » the predictions provided within this report should provide reasonable estimates of production-scale column performance. Two versions of the RF cesium isotherm were used. The older version provides a conservative estimate of the resin capacity while the newer version more accurately fits the most recent experimental data.« less

Correlations among the parameters of the spherical model for eclipsing binaries.

NASA Technical Reports Server (NTRS)

Sobieski, S.; White, J.

1973-01-01

Correlation coefficients have been computed to investigate the parameters used to describe the spherical model of an eclipsing binary system. Regions in parameter hyperspace have been identified where strong correlations exist and, by implication, the solution determinacy is low. The results are presented in tabular form for a large number of system configurations.

Impact of subgrid fluid turbulence on inertial particles subject to gravity

NASA Astrophysics Data System (ADS)

Rosa, Bogdan; Pozorski, Jacek

2017-07-01

Two-phase turbulent flows with the dispersed phase in the form of small, spherical particles are increasingly often computed with the large-eddy simulation (LES) of the carrier fluid phase, coupled to the Lagrangian tracking of particles. To enable further model development for LES with inertial particles subject to gravity, we consider direct numerical simulations of homogeneous isotropic turbulence with a large-scale forcing. Simulation results, both without filtering and in the a priori LES setting, are reported and discussed. A full (i.e. a posteriori) LES is also performed with the spectral eddy viscosity. Effects of gravity on the dispersed phase include changes in the average settling velocity due to preferential sweeping, impact on the radial distribution function and radial relative velocity, as well as direction-dependent modification of the particle velocity variance. The filtering of the fluid velocity, performed in spectral space, is shown to have a non-trivial impact on these quantities.

Disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars

NASA Astrophysics Data System (ADS)

Horowitz, C. J.; Berry, D. K.; Briggs, C. M.; Caplan, M. E.; Cumming, A.; Schneider, A. S.

2015-04-01

Nuclear pasta, with non-spherical shapes, is expected near the base of the crust in neutron stars. Large scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low conductivity pasta layer by increasing an impurity parameter Qimp. Predictions of light curves for the low mass X-ray binary MXB 1659-29, assuming a large Qimp, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust). This research was supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

Spherical nanoindentation stress-strain analysis, Version 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Turner, David; Miller, Calvin

Nanoindentation is a tool that allows the mechanical response of a variety of materials at the nano to micron length scale to be measured. Recent advances in spherical nanoindentation techniques have allowed for a more reliable and meaningful characterization of the mechanical response from nanoindentation experiments in the form on an indentation stress-strain curve. This code base, Spin, is written in MATLAB (The Mathworks, Inc.) and based on the analysis protocols developed by S.R. Kalidindi and S. Pathak [1, 2]. The inputs include the displacement, load, harmonic contact stiffness, harmonic displacement, and harmonic load from spherical nanoindentation tests in themore » form of an Excel (Microsoft) spreadsheet. The outputs include indentation stress-strain curves and indentation properties as well their variance due to the uncertainty of the zero-point correction in the form of MATLAB data (.mat) and figures (.png). [1] S. Pathak, S.R. Kalidindi. Spherical nanoindentation stress–strain curves, Mater. Sci. Eng R-Rep 91 (2015). [2] S.R. Kalidindi, S. Pathak. Determination of the effective zero-point and the extraction of spherical nanoindentation stress-strain curves, Acta Materialia 56 (2008) 3523-3532.« less

Scaling laws for impact fragmentation of spherical solids.

PubMed

Timár, G; Kun, F; Carmona, H A; Herrmann, H J

2012-07-01

We investigate the impact fragmentation of spherical solid bodies made of heterogeneous brittle materials by means of a discrete element model. Computer simulations are carried out for four different system sizes varying the impact velocity in a broad range. We perform a finite size scaling analysis to determine the critical exponents of the damage-fragmentation phase transition and deduce scaling relations in terms of radius R and impact velocity v(0). The scaling analysis demonstrates that the exponent of the power law distributed fragment mass does not depend on the impact velocity; the apparent change of the exponent predicted by recent simulations can be attributed to the shifting cutoff and to the existence of unbreakable discrete units. Our calculations reveal that the characteristic time scale of the breakup process has a power law dependence on the impact speed and on the distance from the critical speed in the damaged and fragmented states, respectively. The total amount of damage is found to have a similar behavior, which is substantially different from the logarithmic dependence on the impact velocity observed in two dimensions.

Self-assembly of Spherical Macroions in Solution: A Coarse-grained Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Liu, Zhuonan; Liu, Tianbo; Tsige, Mesfin

2015-03-01

Macroions (such as polyoxometalates) in solution can form a stable hollow spherical super-molecular structure called blackberry when they have moderate surface charge density and size (1-10 nm). Depending on the surface charge density of macroions, the size of the blackberry can be from 20 to more than 100 nm. Other macroions such as dendrimers can also self-assemble into similar super-molecular structure in solution. Existing theories such as Debye-Hückel and DLVO theories cannot explain this phenomenon and we are not aware of any other theory that can explain this. Previous studies using all-atom Molecular Dynamics simulations have shown identical macroions forming oligomers mediated by counterions. Due to the limitations in all-atom simulation and available computational capabilities, these studies handled only small systems with simple macroions, leading to less conclusive but still relevant results on the self-assembly behavior. To overcome these limitations, in this work large-scale coarse-grained modeling of macroions in solution is used. In order to understand the origin of the attractive force that is responsible for the self-assembly of macroions, different types of macroions in different solution conditions are studied. This work was supported by NSF Grant DMR0847580.

How the morphology of dusts influences packing density in small solar system bodies

NASA Astrophysics Data System (ADS)

Zangmeister, C.; Radney, J. G.; Zachariah, M. R.

2014-12-01

Large planetary seedlings, comets, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (Φf) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction, a regime that includes small solar system bodies. The Φf of rigid aggregated structures across 6 orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ≈ 17 nm monomeric subunits and aggregates made from uniform monomeric 6 mm spherical subunits at the macroscale. We find Φf = 0.36 ± 0.02 at both the nano- and macroscale. These values are remarkably similar to qf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that Φf is independent of both monomer and aggregate size. These observations suggest thatqf of rigid aggregates is independent of spatial dimension across varied formative conditions ranging from interstellar space to pharmaceutical manufacturing.

Identification of vortexes obstructing the dynamo mechanism in laboratory experiments

NASA Astrophysics Data System (ADS)

Limone, A.; Hatch, D. R.; Forest, C. B.; Jenko, F.

2013-06-01

The magnetohydrodynamic dynamo effect explains the generation of self-sustained magnetic fields in electrically conducting flows, especially in geo- and astrophysical environments. Yet the details of this mechanism are still unknown, e.g., how and to which extent the geometry, the fluid topology, the forcing mechanism, and the turbulence can have a negative effect on this process. We report on numerical simulations carried out in spherical geometry, analyzing the predicted velocity flow with the so-called singular value decomposition, a powerful technique that allows us to precisely identify vortexes in the flow which would be difficult to characterize with conventional spectral methods. We then quantify the contribution of these vortexes to the growth rate of the magnetic energy in the system. We identify an axisymmetric vortex, whose rotational direction changes periodically in time, and whose dynamics are decoupled from those of the large scale background flow, that is detrimental for the dynamo effect. A comparison with experiments is carried out, showing that similar dynamics were observed in cylindrical geometry. These previously unexpected eddies, which impede the dynamo effect, offer an explanation for the experimental difficulties in attaining a dynamo in spherical geometry.

On the Inversion for Mass (Re)Distribution from Global (Time-Variable) Gravity Field

NASA Technical Reports Server (NTRS)

Chao, Benjamin F.

2004-01-01

The well-known non-uniqueness of the gravitational inverse problem states the following: The external gravity field, even if completely and exactly known, cannot Uniquely determine the density distribution of the body that produces the gravity field. This is an intrinsic property of a field that obeys the Laplace equation, as already treated in mathematical as well as geophysical literature. In this paper we provide conceptual insight by examining the problem in terms of spherical harmonic expansion of the global gravity field. By comparing the multipoles and the moments of the density function, we show that in 3-S the degree of knowledge deficiency in trying to inversely recover the density distribution from external gravity field is (n+l)(n+2)/2 - (2n+l) = n(n-1)/2 for each harmonic degree n. On the other hand, on a 2-D spherical shell we show via a simple relationship that the inverse solution of the surface density distribution is unique. The latter applies quite readily in the inversion of time-variable gravity signals (such as those observed by the GRACE space mission) where the sources over a wide range of the scales largely come from the Earth's Surface.

Modelling realistic TiO2 nanospheres: A benchmark study of SCC-DFTB against hybrid DFT

NASA Astrophysics Data System (ADS)

Selli, Daniele; Fazio, Gianluca; Di Valentin, Cristiana

2017-10-01

TiO2 nanoparticles (NPs) are nowadays considered fundamental building blocks for many technological applications. Morphology is found to play a key role with spherical NPs presenting higher binding properties and chemical activity. From the experimental point of view, the characterization of these nano-objects is extremely complex, opening a large room for computational investigations. In this work, TiO2 spherical NPs of different sizes (from 300 to 4000 atoms) have been studied with a two-scale computational approach. Global optimization to obtain stable and equilibrated nanospheres was performed with a self-consistent charge density functional tight-binding (SCC-DFTB) simulated annealing process, causing a considerable atomic rearrangement within the nanospheres. Those SCC-DFTB relaxed structures have been then optimized at the DFT(B3LYP) level of theory. We present a systematic and comparative SCC-DFTB vs DFT(B3LYP) study of the structural properties, with particular emphasis on the surface-to-bulk sites ratio, coordination distribution of surface sites, and surface energy. From the electronic point of view, we compare HOMO-LUMO and Kohn-Sham gaps, total and projected density of states. Overall, the comparisons between DFTB and hybrid density functional theory show that DFTB provides a rather accurate geometrical and electronic description of these nanospheres of realistic size (up to a diameter of 4.4 nm) at an extremely reduced computational cost. This opens for new challenges in simulations of very large systems and more extended molecular dynamics.

On- and off-eye spherical aberration of soft contact lenses and consequent changes of effective lens power.

PubMed

Dietze, Holger H; Cox, Michael J

2003-02-01

Soft contact lenses produce a significant level of spherical aberration affecting their power on-eye. A simple model assuming that a thin soft contact lens aligns to the cornea predicts that these effects are similar on-eye and off-eye. The wavefront aberration for 17 eyes and 33 soft contact lenses on-eye was measured with a Shack-Hartmann wavefront sensor. The Zernike coefficients describing the on-eye spherical aberration of the soft contact lens were compared with off-eye ray-tracing results. Paraxial and effective lens power changes were determined. The model predicts the on-eye spherical aberration of soft contact lenses closely. The resulting power change for a +/- 7.00 D spherical soft contact lens is +/- 0.5 D for a 6-mm pupil diameter and +/- 0.1 D for a 3-mm pupil diameter. Power change is negligible for soft contact lenses corrected for off-eye spherical aberration. For thin soft contact lenses, the level of spherical aberration and the consequent power change is similar on-eye and off-eye. Soft contact lenses corrected for spherical aberration in air will be expected to be aberration-free on-eye and produce only negligibly small power changes. For soft contact lenses without aberration correction, for higher levels of ametropia and large pupils, the soft contact lens power should be determined with trial lenses with their power and p value similar to the prescribed lens. The benefit of soft contact lenses corrected for spherical aberration depends on the level of ocular spherical aberration.

Cortical surface registration using spherical thin-plate spline with sulcal lines and mean curvature as features.

PubMed

Park, Hyunjin; Park, Jun-Sung; Seong, Joon-Kyung; Na, Duk L; Lee, Jong-Min

2012-04-30

Analysis of cortical patterns requires accurate cortical surface registration. Many researchers map the cortical surface onto a unit sphere and perform registration of two images defined on the unit sphere. Here we have developed a novel registration framework for the cortical surface based on spherical thin-plate splines. Small-scale composition of spherical thin-plate splines was used as the geometric interpolant to avoid folding in the geometric transform. Using an automatic algorithm based on anisotropic skeletons, we extracted seven sulcal lines, which we then incorporated as landmark information. Mean curvature was chosen as an additional feature for matching between spherical maps. We employed a two-term cost function to encourage matching of both sulcal lines and the mean curvature between the spherical maps. Application of our registration framework to fifty pairwise registrations of T1-weighted MRI scans resulted in improved registration accuracy, which was computed from sulcal lines. Our registration approach was tested as an additional procedure to improve an existing surface registration algorithm. Our registration framework maintained an accurate registration over the sulcal lines while significantly increasing the cross-correlation of mean curvature between the spherical maps being registered. Copyright © 2012 Elsevier B.V. All rights reserved.

Large-scale outflows in luminous QSOs revisited. The impact of beam smearing on AGN feedback efficiencies

NASA Astrophysics Data System (ADS)

Husemann, B.; Scharwächter, J.; Bennert, V. N.; Mainieri, V.; Woo, J.-H.; Kakkad, D.

2016-10-01

Context. Feedback from active galactic nuclei (AGN) is thought to play an important role in quenching star formation in galaxies. However, the efficiency with which AGN dissipate their radiative energy into the ambient medium remains strongly debated. Aims: Enormous observational efforts have been made to constrain the energetics of AGN feedback by mapping the kinematics of the ionized gas on kpc scale. We study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (NLR) due to seeing. Methods: We re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar objects (QSOs) (0.4

Schmidt Telescope

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

A type of telescope, invented by the Estonian optician Bernhard Schmidt (1879-1935), that is used to photograph large areas of the sky. Because, in its original design, it was useable only for photography, the instrument is also known as the Schmidt camera. The Schmidt uses a concave spherical mirror as its light collector and corrects for the optical defect, known as spherical aberration, that i...

An intersecting chord method for minimum circumscribed sphere and maximum inscribed sphere evaluations of sphericity error

NASA Astrophysics Data System (ADS)

Liu, Fei; Xu, Guanghua; Zhang, Qing; Liang, Lin; Liu, Dan

2015-11-01

As one of the Geometrical Product Specifications that are widely applied in industrial manufacturing and measurement, sphericity error can synthetically scale a 3D structure and reflects the machining quality of a spherical workpiece. Following increasing demands in the high motion performance of spherical parts, sphericity error is becoming an indispensable component in the evaluation of form error. However, the evaluation of sphericity error is still considered to be a complex mathematical issue, and the related research studies on the development of available models are lacking. In this paper, an intersecting chord method is first proposed to solve the minimum circumscribed sphere and maximum inscribed sphere evaluations of sphericity error. This new modelling method leverages chord relationships to replace the characteristic points, thereby significantly reducing the computational complexity and improving the computational efficiency. Using the intersecting chords to generate a virtual centre, the reference sphere in two concentric spheres is simplified as a space intersecting structure. The position of the virtual centre on the space intersecting structure is determined by characteristic chords, which may reduce the deviation between the virtual centre and the centre of the reference sphere. In addition,two experiments are used to verify the effectiveness of the proposed method with real datasets from the Cartesian coordinates. The results indicate that the estimated errors are in perfect agreement with those of the published methods. Meanwhile, the computational efficiency is improved. For the evaluation of the sphericity error, the use of high performance computing is a remarkable change.

Comparing Time-Dependent Geomagnetic and Atmospheric Effects on Cosmogenic Nuclide Production Rate Scaling

NASA Astrophysics Data System (ADS)

Lifton, N. A.

2014-12-01

A recently published cosmogenic nuclide production rate scaling model based on analytical fits to Monte Carlo simulations of atmospheric cosmic ray flux spectra (both of which agree well with measured spectra) (Lifton et al., 2014, Earth Planet. Sci. Lett. 386, 149-160: termed the LSD model) provides two main advantages over previous scaling models: identification and quantification of potential sources of bias in the earlier models, and the ability to generate nuclide-specific scaling factors easily for a wide range of input parameters. The new model also provides a flexible framework for exploring the implications of advances in model inputs. In this work, the scaling implications of two recent time-dependent spherical harmonic geomagnetic models spanning the Holocene will be explored. Korte and Constable (2011, Phys. Earth Planet. Int. 188, 247-259) and Korte et al. (2011, Earth Planet. Sci. Lett. 312, 497-505) recently updated earlier spherical harmonic paleomagnetic models used by Lifton et al. (2014) with paleomagnetic measurements from sediment cores in addition to archeomagnetic and volcanic data. These updated models offer improved accuracy over the previous versions, in part to due to increased temporal and spatial data coverage. With the new models as input, trajectory-traced estimates of effective vertical cutoff rigidity (RC- the standard method for ordering cosmic ray data) yield significantly different time-integrated scaling predictions when compared to the earlier models. These results will be compared to scaling predictions using another recent time-dependent spherical harmonic model of the Holocene geomagnetic field by Pavón-Carrasco et al. (2014, Earth Planet. Sci. Lett. 388, 98-109), based solely on archeomagnetic and volcanic paleomagnetic data, but extending to 14 ka. In addition, the potential effects of time-dependent atmospheric models on LSD scaling predictions will be presented. Given the typical dominance of altitudinal over latitudinal scaling effects on cosmogenic nuclide production, incorporating transient global simulations of atmospheric structure (e.g., Liu et al., 2009, Science 325, 310-314) into scaling frameworks may contribute to improved understanding of long-term production rate variations.

Distinct contributions of the fornix and inferior longitudinal fasciculus to episodic and semantic autobiographical memory.

PubMed

Hodgetts, Carl J; Postans, Mark; Warne, Naomi; Varnava, Alice; Lawrence, Andrew D; Graham, Kim S

2017-09-01

Autobiographical memory (AM) is multifaceted, incorporating the vivid retrieval of contextual detail (episodic AM), together with semantic knowledge that infuses meaning and coherence into past events (semantic AM). While neuropsychological evidence highlights a role for the hippocampus and anterior temporal lobe (ATL) in episodic and semantic AM, respectively, it is unclear whether these constitute dissociable large-scale AM networks. We used high angular resolution diffusion-weighted imaging and constrained spherical deconvolution-based tractography to assess white matter microstructure in 27 healthy young adult participants who were asked to recall past experiences using word cues. Inter-individual variation in the microstructure of the fornix (the main hippocampal input/output pathway) related to the amount of episodic, but not semantic, detail in AMs - independent of memory age. Conversely, microstructure of the inferior longitudinal fasciculus, linking occipitotemporal regions with ATL, correlated with semantic, but not episodic, AMs. Further, these significant correlations remained when controlling for hippocampal and ATL grey matter volume, respectively. This striking correlational double dissociation supports the view that distinct, large-scale distributed brain circuits underpin context and concepts in AM. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

A large-scale test of free-energy simulation estimates of protein-ligand binding affinities.

PubMed

Mikulskis, Paulius; Genheden, Samuel; Ryde, Ulf

2014-10-27

We have performed a large-scale test of alchemical perturbation calculations with the Bennett acceptance-ratio (BAR) approach to estimate relative affinities for the binding of 107 ligands to 10 different proteins. Employing 20-Å truncated spherical systems and only one intermediate state in the perturbations, we obtain an error of less than 4 kJ/mol for 54% of the studied relative affinities and a precision of 0.5 kJ/mol on average. However, only four of the proteins gave acceptable errors, correlations, and rankings. The results could be improved by using nine intermediate states in the simulations or including the entire protein in the simulations using periodic boundary conditions. However, 27 of the calculated affinities still gave errors of more than 4 kJ/mol, and for three of the proteins the results were not satisfactory. This shows that the performance of BAR calculations depends on the target protein and that several transformations gave poor results owing to limitations in the molecular-mechanics force field or the restricted sampling possible within a reasonable simulation time. Still, the BAR results are better than docking calculations for most of the proteins.

Controlled crystallization and granulation of nano-scale β-Ni(OH) 2 cathode materials for high power Ni-MH batteries

NASA Astrophysics Data System (ADS)

He, Xiangming; Li, Jianjun; Cheng, Hongwei; Jiang, Changyin; Wan, Chunrong

A novel synthesis of controlled crystallization and granulation was attempted to prepare nano-scale β-Ni(OH) 2 cathode materials for high power Ni-MH batteries. Nano-scale β-Ni(OH) 2 and Co(OH) 2 with a diameter of 20 nm were prepared by controlled crystallization, mixed by ball milling, and granulated to form about 5 μm spherical grains by spray drying granulation. Both the addition of nano-scale Co(OH) 2 and granulation significantly enhanced electrochemical performance of nano-scale Ni(OH) 2. The XRD and TEM analysis shown that there were a large amount of defects among the crystal lattice of as-prepared nano-scale Ni(OH) 2, and the DTA-TG analysis shown that it had both lower decomposition temperature and higher decomposition reaction rate, indicating less thermal stability, as compared with conventional micro-scale Ni(OH) 2, and indicating that it had higher electrochemical performance. The granulated grains of nano-scale Ni(OH) 2 mixed with nano-scale Co(OH) 2 at Co/Ni = 1/20 presented the highest specific capacity reaching its theoretical value of 289 mAh g -1 at 1 C, and also exhibited much improved electrochemical performance at high discharge capacity rate up to 10 C. The granulated grains of nano-scale β-Ni(OH) 2 mixed with nano-scale Co(OH) 2 is a promising cathode active material for high power Ni-MH batteries.

Note: Attenuation motion of acoustically levitated spherical rotor

NASA Astrophysics Data System (ADS)

Lü, P.; Hong, Z. Y.; Yin, J. F.; Yan, N.; Zhai, W.; Wang, H. P.

2016-11-01

Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

Note: Attenuation motion of acoustically levitated spherical rotor.

PubMed

Lü, P; Hong, Z Y; Yin, J F; Yan, N; Zhai, W; Wang, H P

2016-11-01

Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

Riemannian metric optimization on surfaces (RMOS) for intrinsic brain mapping in the Laplace-Beltrami embedding space.

PubMed

Gahm, Jin Kyu; Shi, Yonggang

2018-05-01

Surface mapping methods play an important role in various brain imaging studies from tracking the maturation of adolescent brains to mapping gray matter atrophy patterns in Alzheimer's disease. Popular surface mapping approaches based on spherical registration, however, have inherent numerical limitations when severe metric distortions are present during the spherical parameterization step. In this paper, we propose a novel computational framework for intrinsic surface mapping in the Laplace-Beltrami (LB) embedding space based on Riemannian metric optimization on surfaces (RMOS). Given a diffeomorphism between two surfaces, an isometry can be defined using the pullback metric, which in turn results in identical LB embeddings from the two surfaces. The proposed RMOS approach builds upon this mathematical foundation and achieves general feature-driven surface mapping in the LB embedding space by iteratively optimizing the Riemannian metric defined on the edges of triangular meshes. At the core of our framework is an optimization engine that converts an energy function for surface mapping into a distance measure in the LB embedding space, which can be effectively optimized using gradients of the LB eigen-system with respect to the Riemannian metrics. In the experimental results, we compare the RMOS algorithm with spherical registration using large-scale brain imaging data, and show that RMOS achieves superior performance in the prediction of hippocampal subfields and cortical gyral labels, and the holistic mapping of striatal surfaces for the construction of a striatal connectivity atlas from substantia nigra. Copyright © 2018 Elsevier B.V. All rights reserved.

Helioseismic Constraints on the Depth Dependence of Large-Scale Solar Convection

NASA Astrophysics Data System (ADS)

Woodard, Martin F.

2017-08-01

A recent helioseismic statistical waveform analysis of subsurface flow based on a 720-day time series of SOHO/MDI Medium-l spherical-harmonic coefficients has been extended to cover a greater range of subphotospheric depths. The latest analysis provides estimates of flow-dependent oscillation-mode coupling-strength coefficients b(s,t;n,l) over the range l = 30 to 150 of mode degree (angular wavenumber) for solar p-modes in the approximate frequency range 2 to 4 mHz. The range of penetration depths of this mode set covers most of the solar convection zone. The most recent analysis measures spherical harmonic (s,t) components of the flow velocity for odd s in the angular wavenumber range 1 to 19 for t not much smaller than s at a given s. The odd-s b(s,t;n,l) coefficients are interpreted as averages over depth of the depth-dependent amplitude of one spherical-harmonic (s,t) component of the toroidal part of the flow velocity field. The depth-dependent weighting function defining the average velocity is the fractional kinetic energy density in radius of modes of the (n,l) multiplet. The b coefficients have been converted to estimates of root velocity power as a function of l0 = nu0*l/nu(n,l), which is a measure of mode penetration depth. (nu(n,l) is mode frequency and nu0 is a reference frequency equal to 3 mHz.) A comparison of the observational results with simple convection models will be presented.

Theory based scaling of edge turbulence and implications for the scrape-off layer width

NASA Astrophysics Data System (ADS)

Myra, J. R.; Russell, D. A.; Zweben, S. J.

2016-11-01

Turbulence and plasma parameter data from the National Spherical Torus Experiment (NSTX) [Ono et al., Nucl. Fusion 40, 557 (2000)] is examined and interpreted based on various theoretical estimates. In particular, quantities of interest for assessing the role of turbulent transport on the midplane scrape-off layer heat flux width are assessed. Because most turbulence quantities exhibit large scatter and little scaling within a given operation mode, this paper focuses on length and time scales and dimensionless parameters between operational modes including Ohmic, low (L), and high (H) modes using a large NSTX edge turbulence database [Zweben et al., Nucl. Fusion 55, 093035 (2015)]. These are compared with theoretical estimates for drift and interchange rates, profile modification saturation levels, a resistive ballooning condition, and dimensionless parameters characterizing L and H mode conditions. It is argued that the underlying instability physics governing edge turbulence in different operational modes is, in fact, similar, and is consistent with curvature-driven drift ballooning. Saturation physics, however, is dependent on the operational mode. Five dimensionless parameters for drift-interchange turbulence are obtained and employed to assess the importance of turbulence in setting the scrape-off layer heat flux width λq and its scaling. An explicit proportionality of the width λq to the safety factor and major radius (qR) is obtained under these conditions. Quantitative estimates and reduced model numerical simulations suggest that the turbulence mechanism is not negligible in determining λq in NSTX, at least for high plasma current discharges.

Theory based scaling of edge turbulence and implications for the scrape-off layer width

DOE PAGES

Myra, J. R.; Russell, D. A.; Zweben, S. J.

2016-11-01

Turbulence and plasma parameter data from the National Spherical Torus Experiment (NSTX) is examined and interpreted based on various theoretical estimates. In particular, quantities of interest for assessing the role of turbulent transport on the midplane scrape-off layer heat flux width are assessed. Because most turbulence quantities exhibit large scatter and little scaling within a given operation mode, this paper focuses on length and time scales and dimensionless parameters between operational modes including Ohmic, low (L), and high (H) modes using a large NSTX edge turbulence database. These are compared with theoretical estimates for drift and interchange rates, profile modificationmore » saturation levels, a resistive ballooning condition, and dimensionless parameters characterizing L and H mode conditions. It is argued that the underlying instability physics governing edge turbulence in different operational modes is, in fact, similar, and is consistent with curvature-driven drift ballooning. Saturation physics, however, is dependent on the operational mode. Five dimensionless parameters for drift-interchange turbulence are obtained and employed to assess the importance of turbulence in setting the scrape-off layer heat flux width λ q and its scaling. An explicit proportionality of the width λ q to the safety factor and major radius (qR) is obtained under these conditions. Lastly, quantitative estimates and reduced model numerical simulations suggest that the turbulence mechanism is not negligible in determining λ q in NSTX, at least for high plasma current discharges.« less

Grand Minima and Equatorward Propagation in a Cycling Stellar Convective Dynamo

NASA Astrophysics Data System (ADS)

Augustson, Kyle C.; Brun, Allan Sacha; Miesch, Mark; Toomre, Juri

2015-08-01

The 3-D magnetohydrodynamic (MHD) Anelastic Spherical Harmonic (ASH) code, using slope-limited diffusion, is employed to capture convective and dynamo processes achieved in a global-scale stellar convection simulation for a model solar-mass star rotating at three times the solar rate. The dynamo generated magnetic fields possesses many time scales, with a prominent polarity cycle occurring roughly every 6.2 years. The magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation. The polarity reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. An equatorial migration of the magnetic field is seen, which is due to the strong modulation of the differential rotation rather than a dynamo wave. A poleward migration of magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This simulation also enters an interval with reduced magnetic energy at low latitudes lasting roughly 16 years (about 2.5 polarity cycles), during which the polarity cycles are disrupted and after which the dynamo recovers its regular polarity cycles. An analysis of this grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families. This intermittent dynamo state potentially results from the simulations relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The time scales that appear to be relevant to the magnetic polarity reversal are also identified.

Laboratory Study of Homogeneous and Isotropic Turbulence at High Reynolds Number

NASA Astrophysics Data System (ADS)

Pecenak, Zachary; Dou, Zhongwang; Yang, Fan; Cao, Lujie; Liang, Zach; Meng, Hui

2013-11-01

To study particle dynamics modified by isotropic turbulence at high Reynolds numbers and provide experimental data for DNS validation, we have developed a soccer-ball-shaped truncated icosahedron turbulence chamber with 20 adjoining hexagon surfaces, 12 pentagon surfaces and twenty symettrically displaced fans, which form an enclosed chamber of 1m diameter. We use Particle Image Velocimetry (PIV) technique to characterize the base turbulent flow, using different PIV set ups to capture various characteristic scales of turbulence. Results show that the stationary isotropic turbulence field is a spherical domain with diameter of 40 mm with quasi-zero mean velocities. The maximum rms velocity is ~1.5 m/s, corresponding to a Taylor microscale Re of 450. We extract from the PIV velocity field the whole set of turbulent flow parameters including: turbulent kinetic energy, turbulent intensity, kinetic energy dissipation rate, large eddy length and time scales, the Kolmogorov length, time and velocity scales, Taylor microscale and Re, which are critical to the study of inter-particle statistics modified by turbulence. This research is funded by an NSF grant CBET-0967407.

HORIZON RUN 3: TOPOLOGY AS A STANDARD RULER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Speare, Robert; Gott, J. Richard; Kim, Juhan

2015-02-01

We study the physically self-bound cold dark matter halo distribution, which we associate with the massive galaxies within Horizon Run 3, to estimate the accuracy of the determination of the cosmological distance scale measured by the topology analysis. We apply the routine '''Contour 3D''' to the 108 Mock Survey of π steradians out to redshift z = 0.6, which effectively corresponds to the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) survey, and compare the topology with that of a Gaussian random phase field. We find that given three separate smoothing lengths λ = 15, 21, and 34 h {sup –1} Mpc,more » the least χ{sup 2} fit genus per unit volume (g) yields a 1.7% fractional uncertainty in smoothing length and angular diameter distance to z = 0.6. This is an improvement on former calibrations and presents an error estimate competitive with baryon acoustic oscillation scale techniques. We also present three-dimensional graphics of the Horizon Run 3 spherical mock survey to show a wealth of large-scale structures of the universe that are expected for surveys like BOSS.« less

Application of identifying transmission spheres for spherical surface testing

NASA Astrophysics Data System (ADS)

Han, Christopher B.; Ye, Xin; Li, Xueyuan; Wang, Quanzhao; Tang, Shouhong; Han, Sen

2017-06-01

We developed a new application on Microsoft Foundation Classes (MFC) to identify correct transmission spheres (TS) for Spherical Surface Testing (SST). Spherical surfaces are important optical surfaces, and the wide application and high production rate of spherical surfaces necessitates an accurate and highly reliable measuring device. A Fizeau Interferometer is an appropriate tool for SST due to its subnanometer accuracy. It measures the contour of a spherical surface using a common path, which is insensitive to the surrounding circumstances. The Fizeau Interferometer transmits a wide laser beam, creating interference fringes from re-converging light from the transmission sphere and the test surface. To make a successful measurement, the application calculates and determines the appropriate transmission sphere for the test surface. There are 3 main inputs from the test surfaces that are utilized to determine the optimal sizes and F-numbers of the transmission spheres: (1) the curvatures (concave or convex), (2) the Radii of Curvature (ROC), and (3) the aperture sizes. The application will firstly calculate the F-numbers (i.e. ROC divided by aperture) of the test surface, secondly determine the correct aperture size of a convex surface, thirdly verify that the ROC of the test surface must be shorter than the reference surface's ROC of the transmission sphere, and lastly calculate the percentage of area that the test surface will be measured. However, the amount of interferometers and transmission spheres should be optimized when measuring large spherical surfaces to avoid requiring a large amount of interferometers and transmission spheres for each test surface. Current measuring practices involve tedious and potentially inaccurate calculations. This smart application eliminates human calculation errors, optimizes the selection of transmission spheres (including the least number required) and interferometer sizes, and increases efficiency.

Spherical crystals of Pb 1 - xSn xTe grown in microgravity

NASA Astrophysics Data System (ADS)

Kinoshita, Kyoichi; Yamada, Tomoaki

1996-07-01

Pb 1- xSn xTe spherical crystals were unintentionally obtained along with a cylindrical Pb 1 - xSn xTe crystal grown during the {SL-J}/{FMPT} mission on board the space shuttle "Endeavor". About 25 spherical crystals ranged from 0.5 to 11 mm in diameter. Melt leaked from the melt reservoir into the spring that plays the role of pushing the melt toward a seed crystal and eliminating free surface areas of the melt. Because of the surface tension of the melt, spherical melt drops formed in the hollow of the spring, then solidified into spherical crystals during the cooling process. Some of the crystals had lower dislocation densities, in the order of 10 4 cm -2, two orders smaller than those of terrestrially grown crystals from a melt. The experiment showed a way of stably positioning a large volume of liquid in microgravity without touching the crucible wall and a way of reducing crystalline defects by such growth.

Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials

NASA Technical Reports Server (NTRS)

Shukla, R. P.; Dokhanian, Mostafa; Venkateswarlu, Putcha; George, M. C.

1990-01-01

The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.

Baroclinic instability with variable static stability - A design study for a spherical atmospheric model experiment. [for Spacelab flight

NASA Technical Reports Server (NTRS)

Giere, A. C.; Fowlis, W. W.

1980-01-01

The effect of a radially-variable, dielectric body force, analogous to gravity on baroclinic instability for the design of a spherical, synoptic-scale, atmospheric model experiment in a Spacelab flight is investigated. Exact solutions are examined for quasi-geostrophic baroclinic instability in which the rotational Froude number is a linear function of the height. Flow in a rotating rectilinear channel with a vertically variable body force without horizontal shear of the basic state is also discussed.

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects.

PubMed

Kobashi, Hidenaga; Kamiya, Kazutaka; Handa, Tomoya; Ando, Wakako; Kawamorita, Takushi; Igarashi, Akihito; Shimizu, Kimiya

2015-07-28

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R(2) = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions.

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects

PubMed Central

Kobashi, Hidenaga; Kamiya, Kazutaka; Handa, Tomoya; Ando, Wakako; Kawamorita, Takushi; Igarashi, Akihito; Shimizu, Kimiya

2015-01-01

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R2 = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions. PMID:26218972

Revisiting the use of hyperdiffusivities in numerical dynamo models

NASA Astrophysics Data System (ADS)

Fournier, A.; Aubert, J.

2012-04-01

The groundbreaking numerical dynamo models of Glatzmaier & Roberts (1995) and Kuang & Bloxham (1997) received some criticism due to their use of hyperdiffusivities, whereby small scale processes artificially experience much stronger dissipation than large scale processes. This stronger dissipation they chose was anisotropic, in that it was only effective in the horizontal direction, and parameterized in spectral space using the following generic formula for any diffusive parameter ν ν(l) = ν0 ifl ≤ l0, ν(l) = ν0[1 + a(l- l0)n] ifl > l0, in which l is the spherical harmonic degree, ν0 is a reference value, l0 is the degree above which hyperdiffusivities start operating, and a and n are real numbers. Following the same choice as the studies mentioned above (which had most notably l0 = 0), Grote & Busse (2000) showed in a fully nonlinear context that the usage of hyperdiffusivities could lead to substantially different dynamics and magnetic field generation mechanisms. Without questioning the physical relevance of this parameterization of subgrid scale processes, we wish here to revisit the use of hyperdiffusivities (as defined mathematically above), on the account of the observation that today's models are run with a truncation at much larger spherical harmonic degree than early models. Consequently, they do not require hyperdiffusivities to kick in at the largest scales (l0 can be set to several tens). An exploration of those regions of parameter space less accessible to numerical models could therefore benefit from their use, provided they do not alter noticeably the largest scales of the dynamo (which are the ones expressing themselves in the record of the geomagnetic secular variation). We compare the statistics of a direct numerical simulation with the statistics of several hyperdiffusive simulations. In the prospect of exploring the parameter space and constructing statistics for their subsequent use for geomagnetic data assimilation practice, we conclude that a sensible use of hyperdiffusivities can lead to a much wanted decrease in computational cost, while not altering the nature of the solution.

Mechanical characterization of Ti-6Al-4V titanium alloy at multiple length scales using spherical indentation stress-strain measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Kalidindi, Surya R.

Recent advances in spherical indentation stress-strain protocols and analyses have demonstrated the capability for measuring reliably the local mechanical responses in polycrystalline metal samples at different length scales, ranging from sub-micron (regions within individual grains) to several hundreds of microns (regions covering several grains). These recent advances have now made it possible to study systematically the mechanical behavior of a single material system at different length scales, with tremendous potential to obtain new insights into the role of individual phases, interfaces, and other microscale constituents on the macroscale mechanical response of the material. In this paper, we report spherical indentationmore » stress-strain measurements with different indenter sizes (microns to millimeters) on Ti-6Al-4V (Ti-64) which capture the mechanical response of single phase alpha-Ti-64, single colony (alpha-beta), few colonies, and many colonies of Ti-64. The results show that the average mechanical response (indentation modulus and yield strength) from multiple indentations remains relatively unchanged from single phase alpha to many colonies of Ti-64, while the variance in the response decreases with indenter size. In conclusion, the work-hardening response in indentation tests follows a similar behavior up to indentation zones of many colonies, which shows significantly higher work hardening rates.« less

Mechanical characterization of Ti-6Al-4V titanium alloy at multiple length scales using spherical indentation stress-strain measurements

DOE PAGES

Weaver, Jordan S.; Kalidindi, Surya R.

2016-12-01

Recent advances in spherical indentation stress-strain protocols and analyses have demonstrated the capability for measuring reliably the local mechanical responses in polycrystalline metal samples at different length scales, ranging from sub-micron (regions within individual grains) to several hundreds of microns (regions covering several grains). These recent advances have now made it possible to study systematically the mechanical behavior of a single material system at different length scales, with tremendous potential to obtain new insights into the role of individual phases, interfaces, and other microscale constituents on the macroscale mechanical response of the material. In this paper, we report spherical indentationmore » stress-strain measurements with different indenter sizes (microns to millimeters) on Ti-6Al-4V (Ti-64) which capture the mechanical response of single phase alpha-Ti-64, single colony (alpha-beta), few colonies, and many colonies of Ti-64. The results show that the average mechanical response (indentation modulus and yield strength) from multiple indentations remains relatively unchanged from single phase alpha to many colonies of Ti-64, while the variance in the response decreases with indenter size. In conclusion, the work-hardening response in indentation tests follows a similar behavior up to indentation zones of many colonies, which shows significantly higher work hardening rates.« less

Laboratory and theoretical models of planetary-scale instabilities and waves

NASA Technical Reports Server (NTRS)

Hart, John E.; Toomre, Juri

1991-01-01

Meteorologists and planetary astronomers interested in large-scale planetary and solar circulations recognize the importance of rotation and stratification in determining the character of these flows. The two outstanding problems of interest are: (1) the origins and nature of chaos in baroclinically unstable flows; and (2) the physical mechanisms responsible for high speed zonal winds and banding on the giant planets. The methods used to study these problems, and the insights gained, are useful in more general atmospheric and climate dynamic settings. Because the planetary curvature or beta-effect is crucial in the large scale nonlinear dynamics, the motions of rotating convecting liquids in spherical shells were studied using electrohydrodynamic polarization forces to generate radial gravity and centrally directed buoyancy forces in the laboratory. The Geophysical Fluid Flow Cell (GFFC) experiments performed on Spacelab 3 in 1985 were analyzed. The interpretation and extension of these results have led to the construction of efficient numerical models of rotating convection with an aim to understand the possible generation of zonal banding on Jupiter and the fate of banana cells in rapidly rotating convection as the heating is made strongly supercritical. Efforts to pose baroclinic wave experiments for future space missions using a modified version of the 1985 instrument have led us to develop theoretical and numerical models of baroclinic instability. Some surprising properties of both these models were discovered.

Facile room-temperature solution-phase synthesis of a spherical covalent organic framework for high-resolution chromatographic separation.

PubMed

Yang, Cheng-Xiong; Liu, Chang; Cao, Yi-Meng; Yan, Xiu-Ping

2015-08-07

A simple and facile room-temperature solution-phase synthesis was developed to fabricate a spherical covalent organic framework with large surface area, good solvent stability and high thermostability for high-resolution chromatographic separation of diverse important industrial analytes including alkanes, cyclohexane and benzene, α-pinene and β-pinene, and alcohols with high column efficiency and good precision.

The role of zonally asymmetric heating in the vertical and temporal structure of the global scale flow fields during FGGE SOP-1

NASA Technical Reports Server (NTRS)

Paegle, J.; Kalnay, E.; Baker, W. E.

1981-01-01

The global scale structure of atmospheric flow is best documented on time scales longer than a few days. Theoretical and observational studies of ultralong waves have emphasized forcing due to global scale variations of topography and surface heat flux, possibly interacting with baroclinically unstable or vertically refracting basic flows. Analyses of SOP-1 data in terms of global scale spherical harmonics is documented with emphasis upon weekly transitions.

Background reduction of a spherical gaseous detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fard, Ali Dastgheibi; Loaiza, Pia; Piquemal, Fabrice

The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of detector. It consists of a large spherical volume filled with gas, using a single detection readout channel. The detector allows 100 % detection efficiency. SEDINE is a low background version of SPC installed at the Laboratoire Souterrain de Modane (LSM) underground laboratory (4800 m.w.e) looking for rare events at very low energy threshold, below 100 eV. This work presents the details on the chemical cleaning to reduce internal {sup 210}Pb surface contamination on the copper vessel and the external radon reduction achieved via circulation of pure airmore » inside anti-radon tent. It will be also show the radon measurement of pure gases (Ar, N, Ne, etc) which are used in the underground laboratory for the low background experiments.« less

Correcting spherical aberrations induced by an unknown medium through determination of its refractive index and thickness.

PubMed

Iwaniuk, Daniel; Rastogi, Pramod; Hack, Erwin

2011-09-26

In imaging and focusing applications, spherical aberration induces axial broadening of the point spread function (PSF). A transparent medium between lens and object of interest induces spherical aberration. We propose a method that first obtains both the physical thickness and the refractive index of the aberration inducing medium in situ by measuring the induced focal shifts for paraxial and large angle rays. Then, the fourth order angle dependence of the optical path difference inside the medium is used to correct the spherical aberration using a phase-only spatial light modulator. The obtained measurement accuracy of 3% is sufficient for a complete compensation as demonstrated in a model microscope with NA 0.3 with glass plate induced axial broadening of the PSF by a factor of 5. © 2011 Optical Society of America

Synthesis and characterization of nanostructured titanium carbide for fuel cell applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Paviter; Singh, Harwinder; Singh, Bikramjeet

2016-04-13

Titanium carbide (TiC) nanoparticles have been successfully synthesized by carbo-thermic reaction of titanium and acetone at 800 °C. This method is relatively low temperature synthesis route. It can be used for large scale production of TiC. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA) techniques. XRD analysis confirmed the formation of single phase TiC. XRD analysis confirmed that the particles are spherical in shape with an average particle size of 13 nm. DTA analysis shows that the phase is stable upto 900 °C and the material can be used formore » high temperature applications.« less

Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay, E-mail: akshaykumar.tiet@gmail.com

2015-05-15

Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H{sub 3}BO{sub 3}). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications asmore » well boron neutron capture therapy (BNCT)« less

Motion of a Drop on a Solid Surface Due to a Wettability Gradient

NASA Technical Reports Server (NTRS)

Subramanian, R.; Moumen, Nadjoua; McLaughlin, John B.

2005-01-01

The hydrodynamic force experienced by a spherical-cap drop moving on a solid surface is obtained from two approximate analytical solutions and used to predict the quasi-steady speed of the drop in a wettability gradient. One solution is based on approximation of the shape of the drop as a collection of wedges, and the other is based on lubrication theory. Also, asymptotic results from both approximations for small contact angles, as well as an asymptotic result from lubrication theory that is good when the length scale of the drop is large compared with the slip length, are given. The results for the hydrodynamic force also can be used to predict the quasi-steady speed of a drop sliding down an incline.

Dynamics of an elastic sphere containing a thin creeping region and immersed in an acoustic region for similar viscous-elastic and acoustic time- and length-scales

NASA Astrophysics Data System (ADS)

Gat, Amir; Friedman, Yonathan

2017-11-01

The characteristic time of low-Reynolds number fluid-structure interaction scales linearly with the ratio of fluid viscosity to solid Young's modulus. For sufficiently large values of Young's modulus, both time- and length-scales of the viscous-elastic dynamics may be similar to acoustic time- and length-scales. However, the requirement of dominant viscous effects limits the validity of such regimes to micro-configurations. We here study the dynamics of an acoustic plane wave impinging on the surface of a layered sphere, immersed within an inviscid fluid, and composed of an inner elastic sphere, a creeping fluid layer and an external elastic shell. We focus on configurations with similar viscous-elastic and acoustic time- and length-scales, where the viscous-elastic speed of interaction between the creeping layer and the elastic regions is similar to the speed of sound. By expanding the linearized spherical Reynolds equation into the relevant spectral series solution for the hyperbolic elastic regions, a global stiffness matrix of the layered elastic sphere was obtained. This work relates viscous-elastic dynamics to acoustic scattering and may pave the way to the design of novel meta-materials with unique acoustic properties. ISF 818/13.

Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank

NASA Technical Reports Server (NTRS)

Majumdar, A. K.; Steadman, T. E.; Maroney, J. L.; Sass, J. P.; Fesmire, J. E.

2007-01-01

A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaboration effort. The Generalized Fluid System Simulation Program, integrating flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC- 39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: First measurement of Baryon Acoustic Oscillations between redshift 0.8 and 2.2

DOE PAGES

Ata, Metin

2017-06-20

Here, we present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshifts 0.8 < z < 2.2 and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.5σ . We determine the spherically averaged BAO distance to z = 1.52 to 4.4 per cent precision: D V (zmore » = 1:52) = 3855 170 (r d/r d,fid) Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat CDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Bu using these BAO data alone and marginalizing over the length of the standard ruler, we find Ω Λ > 0 at 6.5σ significance when testing a CDM model with free curvature.« less

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: First measurement of Baryon Acoustic Oscillations between redshift 0.8 and 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ata, Metin

Here, we present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshifts 0.8 < z < 2.2 and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.5σ . We determine the spherically averaged BAO distance to z = 1.52 to 4.4 per cent precision: D V (zmore » = 1:52) = 3855 170 (r d/r d,fid) Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat CDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Bu using these BAO data alone and marginalizing over the length of the standard ruler, we find Ω Λ > 0 at 6.5σ significance when testing a CDM model with free curvature.« less

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: first measurement of baryon acoustic oscillations between redshift 0.8 and 2.2

NASA Astrophysics Data System (ADS)

Ata, Metin; Baumgarten, Falk; Bautista, Julian; Beutler, Florian; Bizyaev, Dmitry; Blanton, Michael R.; Blazek, Jonathan A.; Bolton, Adam S.; Brinkmann, Jonathan; Brownstein, Joel R.; Burtin, Etienne; Chuang, Chia-Hsun; Comparat, Johan; Dawson, Kyle S.; de la Macorra, Axel; Du, Wei; du Mas des Bourboux, Hélion; Eisenstein, Daniel J.; Gil-Marín, Héctor; Grabowski, Katie; Guy, Julien; Hand, Nick; Ho, Shirley; Hutchinson, Timothy A.; Ivanov, Mikhail M.; Kitaura, Francisco-Shu; Kneib, Jean-Paul; Laurent, Pierre; Le Goff, Jean-Marc; McEwen, Joseph E.; Mueller, Eva-Maria; Myers, Adam D.; Newman, Jeffrey A.; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pâris, Isabelle; Pellejero-Ibanez, Marcos; Percival, Will J.; Petitjean, Patrick; Prada, Francisco; Prakash, Abhishek; Rodríguez-Torres, Sergio A.; Ross, Ashley J.; Rossi, Graziano; Ruggeri, Rossana; Sánchez, Ariel G.; Satpathy, Siddharth; Schlegel, David J.; Schneider, Donald P.; Seo, Hee-Jong; Slosar, Anže; Streblyanska, Alina; Tinker, Jeremy L.; Tojeiro, Rita; Vargas Magaña, Mariana; Vivek, M.; Wang, Yuting; Yèche, Christophe; Yu, Liang; Zarrouk, Pauline; Zhao, Cheng; Zhao, Gong-Bo; Zhu, Fangzhou

2018-02-01

We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147 000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshifts 0.8 < z < 2.2 and measure their spherically averaged clustering in both configuration and Fourier space. Our observational data set and the 1400 simulated realizations of the data set allow us to detect a preference for BAO that is greater than 2.8σ. We determine the spherically averaged BAO distance to z = 1.52 to 3.8 per cent precision: DV(z = 1.52) = 3843 ± 147(rd/rd, fid)Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat ΛCDM best-fitting cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Using these BAO data alone and marginalizing over the length of the standard ruler, we find ΩΛ > 0 at 6.6σ significance when testing a ΛCDM model with free curvature.

The Large-scale Structure of the Halo of the Andromeda Galaxy. I. Global Stellar Density, Morphology and Metallicity Properties

NASA Astrophysics Data System (ADS)

Ibata, Rodrigo A.; Lewis, Geraint F.; McConnachie, Alan W.; Martin, Nicolas F.; Irwin, Michael J.; Ferguson, Annette M. N.; Babul, Arif; Bernard, Edouard J.; Chapman, Scott C.; Collins, Michelle; Fardal, Mark; Mackey, A. D.; Navarro, Julio; Peñarrubia, Jorge; Rich, R. Michael; Tanvir, Nial; Widrow, Lawrence

2014-01-01

We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite the presence of copious substructures, the global halo populations follow closely power-law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component (defined as the population that cannot be resolved into spatially distinct substructures with PAndAS). Fitting a three-dimensional halo model reveals that the most metal-poor populations ([{{Fe/H}] \\lt -1.7}) are distributed approximately spherically (slightly prolate with ellipticity c/a = 1.09 ± 0.03), with only a relatively small fraction residing in discernible stream-like structures (f stream = 42%). The sphericity of the ancient smooth component strongly hints that the dark matter halo is also approximately spherical. More metal-rich populations contain higher fractions of stars in streams, with f stream becoming as high as 86% for [{Fe/H] \\gt -0.6}. The space density of the smooth metal-poor component has a global power-law slope of γ = -3.08 ± 0.07, and a non-parametric fit shows that the slope remains nearly constant from 30 kpc to ~300 kpc. The total stellar mass in the halo at distances beyond 2° is ~1.1 × 1010 M ⊙, while that of the smooth component is ~3 × 109 M ⊙. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly ~8 × 109 M ⊙. We detect a substantial metallicity gradient, which declines from lang[Fe/H]rang = -0.7 at R = 30 kpc to lang[Fe/H]rang = -1.5 at R = 150 kpc for the full sample, with the smooth halo being ~0.2 dex more metal poor than the full sample at each radius. While qualitatively in line with expectations from cosmological simulations, these observations are of great importance as they provide a prototype template that such simulations must now be able to reproduce in quantitative detail. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Noncommutative spherically symmetric spacetimes at semiclassical order

NASA Astrophysics Data System (ADS)

Fritz, Christopher; Majid, Shahn

2017-07-01

Working within the recent formalism of Poisson-Riemannian geometry, we completely solve the case of generic spherically symmetric metric and spherically symmetric Poisson-bracket to find a unique answer for the quantum differential calculus, quantum metric and quantum Levi-Civita connection at semiclassical order O(λ) . Here λ is the deformation parameter, plausibly the Planck scale. We find that r, t, d r, d t are all forced to be central, i.e. undeformed at order λ, while for each value of r, t we are forced to have a fuzzy sphere of radius r with a unique differential calculus which is necessarily nonassociative at order λ2 . We give the spherically symmetric quantisation of the FLRW cosmology in detail and also recover a previous analysis for the Schwarzschild black hole, now showing that the quantum Ricci tensor for the latter vanishes at order λ. The quantum Laplace-Beltrami operator for spherically symmetric models turns out to be undeformed at order λ while more generally in Poisson-Riemannian geometry we show that it deforms to □f+λ2ωαβ(Ricγα-Sγα)(∇^βdf)γ+O(λ2) in terms of the classical Levi-Civita connection \\widehat\

Spherical demons: fast diffeomorphic landmark-free surface registration.

PubMed

Yeo, B T Thomas; Sabuncu, Mert R; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

2010-03-01

We present the Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizors for the modified Demons objective function can be efficiently approximated on the sphere using iterative smoothing. Based on one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast. The Spherical Demons algorithm can also be modified to register a given spherical image to a probabilistic atlas. We demonstrate two variants of the algorithm corresponding to warping the atlas or warping the subject. Registration of a cortical surface mesh to an atlas mesh, both with more than 160 k nodes requires less than 5 min when warping the atlas and less than 3 min when warping the subject on a Xeon 3.2 GHz single processor machine. This is comparable to the fastest nondiffeomorphic landmark-free surface registration algorithms. Furthermore, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different applications that use registration to transfer segmentation labels onto a new image 1) parcellation of in vivo cortical surfaces and 2) Brodmann area localization in ex vivo cortical surfaces.

Spherical Demons: Fast Diffeomorphic Landmark-Free Surface Registration

PubMed Central

Yeo, B.T. Thomas; Sabuncu, Mert R.; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

2010-01-01

We present the Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizors for the modified Demons objective function can be efficiently approximated on the sphere using iterative smoothing. Based on one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast. The Spherical Demons algorithm can also be modified to register a given spherical image to a probabilistic atlas. We demonstrate two variants of the algorithm corresponding to warping the atlas or warping the subject. Registration of a cortical surface mesh to an atlas mesh, both with more than 160k nodes requires less than 5 minutes when warping the atlas and less than 3 minutes when warping the subject on a Xeon 3.2GHz single processor machine. This is comparable to the fastest non-diffeomorphic landmark-free surface registration algorithms. Furthermore, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different applications that use registration to transfer segmentation labels onto a new image: (1) parcellation of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:19709963

Atlas of wide-field-of-view outgoing longwave radiation derived from Nimbus 6 Earth radiation budget data set, July 1975 to June 1978

NASA Technical Reports Server (NTRS)

Bess, T. Dale; Smith, G. Louis

1987-01-01

An atlas of monthly mean outgoing longwave radiation global contour maps and associated spherical harmonic coefficients is presented. The atlas contains 36 months of continuous data from July 1975 to June 1978. The data were derived from the first Earth radiation budget experiment, which was flown on the Nimbus-6 Sun-synchronous satellite in 1975. Only the wide-field-of-view longwave measurements are cataloged in this atlas. The contour maps along with the associated sets of spherical harmonic coefficients form a valuable data set for studying different aspects of our changing climate over monthly, annual, and interannual scales in the time domain, and over regional, zonal, and global scales in the spatial domain.

Glass Bubbles Insulation for Liquid Hydrogen Storage Tanks

NASA Astrophysics Data System (ADS)

Sass, J. P.; Cyr, W. W. St.; Barrett, T. M.; Baumgartner, R. G.; Lott, J. W.; Fesmire, J. E.

2010-04-01

A full-scale field application of glass bubbles insulation has been demonstrated in a 218,000 L liquid hydrogen storage tank. This work is the evolution of extensive materials testing, laboratory scale testing, and system studies leading to the use of glass bubbles insulation as a cost efficient and high performance alternative in cryogenic storage tanks of any size. The tank utilized is part of a rocket propulsion test complex at the NASA Stennis Space Center and is a 1960's vintage spherical double wall tank with an evacuated annulus. The original perlite that was removed from the annulus was in pristine condition and showed no signs of deterioration or compaction. Test results show a significant reduction in liquid hydrogen boiloff when compared to recent baseline data prior to removal of the perlite insulation. The data also validates the previous laboratory scale testing (1000 L) and full-scale numerical modeling (3,200,000 L) of boiloff in spherical cryogenic storage tanks. The performance of the tank will continue to be monitored during operation of the tank over the coming years.

CONSISTENT SCALING LAWS IN ANELASTIC SPHERICAL SHELL DYNAMOS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Rakesh K.; Gastine, Thomas; Christensen, Ulrich R.

2013-09-01

Numerical dynamo models always employ parameter values that differ by orders of magnitude from the values expected in natural objects. However, such models have been successful in qualitatively reproducing properties of planetary and stellar dynamos. This qualitative agreement fuels the idea that both numerical models and astrophysical objects may operate in the same asymptotic regime of dynamics. This can be tested by exploring the scaling behavior of the models. For convection-driven incompressible spherical shell dynamos with constant material properties, scaling laws had been established previously that relate flow velocity and magnetic field strength to the available power. Here we analyzemore » 273 direct numerical simulations using the anelastic approximation, involving also cases with radius-dependent magnetic, thermal, and viscous diffusivities. These better represent conditions in gas giant planets and low-mass stars compared to Boussinesq models. Our study provides strong support for the hypothesis that both mean velocity and mean magnetic field strength scale as a function of the power generated by buoyancy forces in the same way for a wide range of conditions.« less

Glass Bubbles Insulation for Liquid Hydrogen Storage Tanks

NASA Technical Reports Server (NTRS)

Sass, J. P.; SaintCyr, W. W.; Barrett, T. M.; Baumgartner, R. G.; Lott, J. W.; Fesmire, J. E.

2009-01-01

A full-scale field application of glass bubbles insulation has been demonstrated in a 218,000 L liquid hydrogen storage tank. This work is the evolution of extensive materials testing, laboratory scale testing, and system studies leading to the use of glass bubbles insulation as a cost efficient and high performance alternative in cryogenic storage tanks of any size. The tank utilized is part of a rocket propulsion test complex at the NASA Stennis Space Center and is a 1960's vintage spherical double wall tank with an evacuated annulus. The original perlite that was removed from the annulus was in pristine condition and showed no signs of deterioration or compaction. Test results show a significant reduction in liquid hydrogen boiloff when compared to recent baseline data prior to removal of the perlite insulation. The data also validates the previous laboratory scale testing (1000 L) and full-scale numerical modeling (3,200,000 L) of boiloff in spherical cryogenic storage tanks. The performance of the tank will continue to be monitored during operation of the tank over the coming years. KEYWORDS: Glass bubble, perlite, insulation, liquid hydrogen, storage tank.

Stratiform clouds and their interaction with atmospheric motion

NASA Technical Reports Server (NTRS)

Clark, John H. E.; Shirer, Hampton N.

1990-01-01

During 1989 and 1990, the researchers saw the publication of two papers and the submission of a third for review on work supported primarily by the previous contract, NAS8-36150; the delivery of an invited talk at the SIAM Conference on Dynamical Systems in Orlando, Florida; and the start of two new projects on the radiative effects of stratocumulus on the large-scale flow. The published papers discuss aspects of stratocumulus circulations (Laufersweiler and Shirer, 1989) and the Hadley to Rossby regime transition in rotating spherical systems (Higgins and Shirer, 1990). The submitted paper (Haack and Shirer, 1990) discusses a new nonlinear model of roll circulations that are forced both dynamically and thermally. The invited paper by H. N. Shirer and R. Wells presented an objective means for determining appropriate truncation levels for low-order models of flows involving two incommensurate periods; this work has application to the Hadley to Rossby transition problem in quasi-geostrophic flows (Moroz and Holmes, 1984). The new projects involve the development of a multi-layered quasi-geostrophic channel model for study of the modulation of the large-scale flow by stratocumulus clouds that typically develop off the coasts of continents. In this model the diabatic forcing in the lowest layer will change in response to the (parameterized) development of extensive fields of stratocumulus clouds. To guide creation of this parameterization scheme, researchers are producing climatologies of stratocumulus frequency and the authors correlate these frequencies with the phasing and amplitude of the large-scale flow pattern. Researchers discuss the above topics in greater detail.

Electron density and plasma dynamics of a spherical theta pinch

NASA Astrophysics Data System (ADS)

Teske, C.; Liu, Y.; Blaes, S.; Jacoby, J.

2012-03-01

A spherical theta pinch for plasma stripper applications has been developed and investigated regarding the electron density and the plasma confinement during the pinching sequence. The setup consists of a 6 μH induction coil surrounding a 4000 ml spherical discharge vessel and a capacitor bank with interchangeable capacitors leading to an overall capacitance of 34 μF and 50 μF, respectively. A thyristor switch is used for driving the resonant circuit. Pulsed coil currents reached values of up to 26 kA with maximum induction of 500 mT. Typical gas pressures were 0.7 Pa up to 120 Pa with ArH2 (2.8% H2)-gas as a discharge medium. Stark broadening measurements of the Hβ emission line were carried out in order to evaluate the electron density of the discharge. In accordance with the density measurements, the transfer efficiency was estimated and a scaling law between electron density and discharge energy was established for the current setup. The densities reached values of up to 8 × 1022 m-3 for an energy of 1.6 kJ transferred into the plasma. Further, the pinching of the discharge plasma was documented and the different stages of the pinching process were analyzed. The experimental evidence suggests that concerning the recent setup of the spherical theta pinch, a linear scaling law between the transferred energy and the achievable plasma density can be applied for various applications like plasma strippers and pulsed ion sources.

Accuracy of methods for calculating volumetric wear from coordinate measuring machine data of retrieved metal-on-metal hip joint implants.

PubMed

Lu, Zhen; McKellop, Harry A

2014-03-01

This study compared the accuracy and sensitivity of several numerical methods employing spherical or plane triangles for calculating the volumetric wear of retrieved metal-on-metal hip joint implants from coordinate measuring machine measurements. Five methods, one using spherical triangles and four using plane triangles to represent the bearing and the best-fit surfaces, were assessed and compared on a perfect hemisphere model and a hemi-ellipsoid model (i.e. unworn models), computer-generated wear models and wear-tested femoral balls, with point spacings of 0.5, 1, 2 and 3 mm. The results showed that the algorithm (Method 1) employing spherical triangles to represent the bearing surface and to scale the mesh to the best-fit surfaces produced adequate accuracy for the wear volume with point spacings of 0.5, 1, 2 and 3 mm. The algorithms (Methods 2-4) using plane triangles to represent the bearing surface and to scale the mesh to the best-fit surface also produced accuracies that were comparable to that with spherical triangles. In contrast, if the bearing surface was represented with a mesh of plane triangles and the best-fit surface was taken as a smooth surface without discretization (Method 5), the algorithm produced much lower accuracy with a point spacing of 0.5 mm than Methods 1-4 with a point spacing of 3 mm.

Axisymmetric inertial modes in a spherical shell at low Ekman numbers

NASA Astrophysics Data System (ADS)

Rieutord, M.; Valdettaro, L.

2018-06-01

We investigate the asymptotic properties of axisymmetric inertial modes propagating in a spherical shell when viscosity tends to zero. We identify three kinds of eigenmodes whose eigenvalues follow very different laws as the Ekman number $E$ becomes very small. First are modes associated with attractors of characteristics that are made of thin shear layers closely following the periodic orbit traced by the characteristic attractor. Second are modes made of shear layers that connect the critical latitude singularities of the two hemispheres of the inner boundary of the spherical shell. Third are quasi-regular modes associated with the frequency of neutral periodic orbits of characteristics. We thoroughly analyse a subset of attractor modes for which numerical solutions point to an asymptotic law governing the eigenvalues. We show that three length scales proportional to $E^{1/6}$, $E^{1/4}$ and $E^{1/3}$ control the shape of the shear layers that are associated with these modes. These scales point out the key role of the small parameter $E^{1/12}$ in these oscillatory flows. With a simplified model of the viscous Poincar\\'e equation, we can give an approximate analytical formula that reproduces the velocity field in such shear layers. Finally, we also present an analysis of the quasi-regular modes whose frequencies are close to $\\sin(\\pi/4)$ and explain why a fluid inside a spherical shell cannot respond to any periodic forcing at this frequency when viscosity vanishes.

The correlation function for density perturbations in an expanding universe. I - Linear theory

NASA Technical Reports Server (NTRS)

Mcclelland, J.; Silk, J.

1977-01-01

The evolution of the two-point correlation function for adiabatic density perturbations in the early universe is studied. Analytical solutions are obtained for the evolution of linearized spherically symmetric adiabatic density perturbations and the two-point correlation function for these perturbations in the radiation-dominated portion of the early universe. The results are then extended to the regime after decoupling. It is found that: (1) adiabatic spherically symmetric perturbations comparable in scale with the maximum Jeans length would survive the radiation-dominated regime; (2) irregular fluctuations are smoothed out up to the scale of the maximum Jeans length in the radiation era, but regular fluctuations might survive on smaller scales; (3) in general, the only surviving structures for irregularly shaped adiabatic density perturbations of arbitrary but finite scale in the radiation regime are the size of or larger than the maximum Jeans length in that regime; (4) infinite plane waves with a wavelength smaller than the maximum Jeans length but larger than the critical dissipative damping scale could survive the radiation regime; and (5) black holes would also survive the radiation regime and might accrete sufficient mass after decoupling to nucleate the formation of galaxies.

Comparative structural and electrochemical study of high density spherical and non-spherical Ni(OH) 2 as cathode materials for Ni-metal hydride batteries

NASA Astrophysics Data System (ADS)

Shangguan, Enbo; Chang, Zhaorong; Tang, Hongwei; Yuan, Xiao-Zi; Wang, Haijiang

In this paper we compare the behavior of non-spherical and spherical β-Ni(OH) 2 as cathode materials for Ni-MH batteries in an attempt to explore the effect of microstructure and surface properties of β-Ni(OH) 2 on their electrochemical performances. Non-spherical β-Ni(OH) 2 powders with a high-density are synthesized using a simple polyacrylamide (PAM) assisted two-step drying method. X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric/differential thermal analysis (TG-DTA), Brunauer-Emmett-Teller (BET) testing, laser particle size analysis, and tap-density testing are used to characterize the physical properties of the synthesized products. Electrochemical characterization, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and a charge/discharge test, is also performed. The results show that the non-spherical β-Ni(OH) 2 materials exhibit an irregular tabular shape and a dense solid structure, which contains many overlapped sheet nano crystalline grains, and have a high density of structural disorder and a large specific surface area. Compared with the spherical β-Ni(OH) 2, the non-spherical β-Ni(OH) 2 materials have an enhanced discharge capacity, higher discharge potential plateau and superior cycle stability. This performance improvement can be attributable to a higher proton diffusion coefficient (4.26 × 10 -9 cm 2 s -1), better reaction reversibility, and lower electrochemical impedance of the synthesized material.

National Laboratory for Advanced Scientific Visualization at UNAM - Mexico

NASA Astrophysics Data System (ADS)

Manea, Marina; Constantin Manea, Vlad; Varela, Alfredo

2016-04-01

In 2015, the National Autonomous University of Mexico (UNAM) joined the family of Universities and Research Centers where advanced visualization and computing plays a key role to promote and advance missions in research, education, community outreach, as well as business-oriented consulting. This initiative provides access to a great variety of advanced hardware and software resources and offers a range of consulting services that spans a variety of areas related to scientific visualization, among which are: neuroanatomy, embryonic development, genome related studies, geosciences, geography, physics and mathematics related disciplines. The National Laboratory for Advanced Scientific Visualization delivers services through three main infrastructure environments: the 3D fully immersive display system Cave, the high resolution parallel visualization system Powerwall, the high resolution spherical displays Earth Simulator. The entire visualization infrastructure is interconnected to a high-performance-computing-cluster (HPCC) called ADA in honor to Ada Lovelace, considered to be the first computer programmer. The Cave is an extra large 3.6m wide room with projected images on the front, left and right, as well as floor walls. Specialized crystal eyes LCD-shutter glasses provide a strong stereo depth perception, and a variety of tracking devices allow software to track the position of a user's hand, head and wand. The Powerwall is designed to bring large amounts of complex data together through parallel computing for team interaction and collaboration. This system is composed by 24 (6x4) high-resolution ultra-thin (2 mm) bezel monitors connected to a high-performance GPU cluster. The Earth Simulator is a large (60") high-resolution spherical display used for global-scale data visualization like geophysical, meteorological, climate and ecology data. The HPCC-ADA, is a 1000+ computing core system, which offers parallel computing resources to applications that requires large quantity of memory as well as large and fast parallel storage systems. The entire system temperature is controlled by an energy and space efficient cooling solution, based on large rear door liquid cooled heat exchangers. This state-of-the-art infrastructure will boost research activities in the region, offer a powerful scientific tool for teaching at undergraduate and graduate levels, and enhance association and cooperation with business-oriented organizations.

Electrons on a spherical surface: Physical properties and hollow spherical clusters

NASA Astrophysics Data System (ADS)

Cricchio, Dario; Fiordilino, Emilio; Persico, Franco

2012-07-01

We discuss the physical properties of a noninteracting electron gas constrained to a spherical surface. In particular we consider its chemical potentials, its ionization potential, and its electric static polarizability. All these properties are discussed analytically as functions of the number N of electrons. The trends obtained with increasing N are compared with those of the corresponding properties experimentally measured or theoretically evaluated for quasispherical hollow atomic and molecular clusters. Most of the properties investigated display similar trends, characterized by a prominence of shell effects. This leads to the definition of a scale-invariant distribution of magic numbers which follows a power law with critical exponent -0.5. We conclude that our completely mechanistic and analytically tractable model can be useful for the analysis of self-assembling complex systems.

Vertical interferometer workstation for testing large spherical optics

NASA Astrophysics Data System (ADS)

Truax, B.

2013-09-01

The design of an interferometer workstation for the testing of large concave and convex spherical optics is presented. The workstation handles optical components and mounts up to 425 mm in diameter with mass of up to 40 kg with 6 axes of adjustment. A unique method for the implementation of focus, roll and pitch was used allowing for extremely precise adjustment. The completed system includes transmission spheres with f-numbers from f/1.6 to f/0.82 incorporating reference surface diameters of up to 306 mm and surface accuracies of better than 63 nm PVr. The design challenges and resulting solutions are discussed. System performance results are presented.

Saving SALT: repairs to the spherical aberration corrector of the Southern African Large Telescope (SALT)

NASA Astrophysics Data System (ADS)

O'Donoghue, Darragh E.; O'Connor, James; Crause, Lisa A.; Strumpfer, Francois; Strydom, Ockert J.; Brink, Janus D.; Sass, Craig; Wiid, Eben; Atad-Ettedgui, Eli

2010-07-01

The construction of the Southern African Large Telescope (SALT) was largely completed by the end of 2005. At the beginning of 2006, it was realized that the telescope's image quality suffered from optical aberrations, chiefly a focus gradient across the focal plane, but also accompanied by astigmatism and higher order aberrations. In the previous conference in this series, a paper was presented describing the optical system engineering investigation which had been conducted to diagnose the problem. This investigation exonerated the primary mirror as the cause, as well as the science instruments, and was isolated to the interface between the telescope and a major optical sub-system, the spherical aberration corrector (SAC). This is a complex sub-system of four aspheric mirrors which corrects the spherical aberration of the 11-m primary mirror. In the last two years, a solution to this problem was developed which involved removing the SAC from the telescope, installing a modification of the SAC/telescope interface, re-aligning and testing the four SAC mirrors and re-installation on the telescope. This paper describes the plan, discusses the details and shows progress to date and the current status.

Area law microstate entropy from criticality and spherical symmetry

NASA Astrophysics Data System (ADS)

Dvali, Gia

2018-05-01

It is often assumed that the area law of microstate entropy and the holography are intrinsic properties exclusively of the gravitational systems, such as black holes. We construct a nongravitational model that exhibits an entropy that scales as area of a sphere of one dimension less. It is represented by a nonrelativistic bosonic field living on a d -dimensional sphere of radius R and experiencing an angular-momentum-dependent attractive interaction. We show that the system possesses a quantum critical point with the emergent gapless modes. Their number is equal to the area of a d -1 -dimensional sphere of the same radius R . These gapless modes create an exponentially large number of degenerate microstates with the corresponding microstate entropy given by the area of the same d -1 -dimensional sphere. Thanks to a double-scaling limit, the counting of the entropy and of the number of the gapless modes is made exact. The phenomenon takes place for arbitrary number of dimensions and can be viewed as a version of holography.

Elastocapillarity: When Surface Tension Deforms Elastic Solids

NASA Astrophysics Data System (ADS)

Bico, José; Reyssat, Étienne; Roman, Benoît

2018-01-01

Although negligible at large scales, capillary forces may become dominant for submillimetric objects. Surface tension is usually associated with the spherical shape of small droplets and bubbles, wetting phenomena, imbibition, or the motion of insects at the surface of water. However, beyond liquid interfaces, capillary forces can also deform solid bodies in their bulk, as observed in recent experiments with very soft gels. Capillary interactions, which are responsible for the cohesion of sandcastles, can also bend slender structures and induce the bundling of arrays of fibers. Thin sheets can spontaneously wrap liquid droplets within the limit of the constraints dictated by differential geometry. This review aims to describe the different scaling parameters and characteristic lengths involved in elastocapillarity. We focus on three main configurations, each characterized by a specific dimension: three-dimensional (3D), deformations induced in bulk solids; 1D, bending and bundling of rod-like structures; and 2D, bending and stretching of thin sheets. Although each configuration deserves a detailed review, we hope our broad description provides a general view of elastocapillarity.

Maps of the Southern Millimeter-wave Sky from Combined 2500 deg$^2$ SPT-SZ and Planck Temperature Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chown, R.; et al.

We present three maps of the millimeter-wave sky created by combining data from the South Pole Telescope (SPT) and the Planck satellite. We use data from the SPT-SZ survey, a survey of 2540 deg$^2$ of the the sky with arcminute resolution in three bands centered at 95, 150, and 220 GHz, and the full-mission Planck temperature data in the 100, 143, and 217 GHz bands. A linear combination of the SPT-SZ and Planck data is computed in spherical harmonic space, with weights derived from the noise of both instruments. This weighting scheme results in Planck data providing most of themore » large-angular-scale information in the combined maps, with the smaller-scale information coming from SPT-SZ data. A number of tests have been done on the maps. We find their angular power spectra to agree very well with theoretically predicted spectra and previously published results.« less

Ram-pressure scaling and non-uniformity characterization of a spherically imploding liner formed by hypervelocity plasma jets

NASA Astrophysics Data System (ADS)

Cassibry, Jason; Dougherty, Jesse; Thompson, Seth; Hsu, Scott; Witherspoon, F. D.; University of AL in Huntsville Team; Los Alamos National Laboratory Team; HyperV Technologies Corp. Team

2014-10-01

Three-dimensional modeling of plasma liner formation and implosion is performed using the Smoothed Particle Hydrodynamics Code (SPHC) with radiation, thermal transport, and tabular equations of state (EOS), accounting for ionization, in support of a proposed 60-gun plasma liner formation experiment for plasma-jet driven magneto-inertial fusion (PJMIF). Previous SPHC modeling showed that ideal gas law scaling of peak stagnation pressure increased linearly with density and number of jets, quadratically with jet radius and velocity, and inversely with the initial jet length, while results with tabular EOS, thermal transport, and radiation have greater sensitivity to the initial jet distribution. A series of simulations are conducted to study the effects of initial jet conditions on peak ram pressure and liner non-uniformity during plasma liner implosion. The growth rate of large-amplitude density perturbations introduced by the discrete jets are computed and compared with predictions by the Bell-Plesset equation.

Two-point correlation function in systems with van der Waals type interaction

NASA Astrophysics Data System (ADS)

Dantchev, D.

2001-09-01

The behavior of the bulk two-point correlation function G( r; T| d ) in d-dimensional system with van der Waals type interactions is investigated and its consequences on the finite-size scaling properties of the susceptibility in such finite systems with periodic boundary conditions is discussed within mean-spherical model which is an example of Ornstein and Zernike type theory. The interaction is supposed to decay at large distances r as r - (d + σ), with 2 < d < 4, 2 < σ < 4 and d + σ≤6. It is shown that G( r; T| d ) decays as r - (d - 2) for 1 ≪ r≪ξ, exponentially for ξ≪ r≪ r *, where r * = (σ - 2)ξlnξ, and again in a power law as r - (d + σ) for r≫ r *. The analytical form of the leading-order scaling function of G( r; T| d ) in any of these regimes is derived.

Hemocytes of the cochineal insect: ultrastructure.

PubMed

Caselín-Castro, Sandra; Llanderal-Cázares, Celina; Méndez-Gallegos, Santiago de Jesús; Ramírez-Cruz, Arturo; Hernández-Hernández, Fidel de la Cruz

2010-03-01

Using transmission electron microscopy, light microscopy (Giemsa May-Grumwald), and the Periodic Acid-Schif (PAS) and Sudan Black B staining techniques, hemocytes in the hemolymph of adult female Dactylopius coccus were characterized. The following, in order of abundance, were found: granulocytes, plasmatocytes, prohemocytes, and oenocytoids. Granulocytes varied in size with granulations in the cytoplasm, a large quantity of mitochondria, rugose endoplasmatic reticulum, ribosomes and vesicles, central or exocentric, spherical and occasionally lobulate nucleus. Plasmatocytes were polymorphic with irregularities in the plasma membrane; cytoplasm contained mitochondria, rugose endoplasmatic reticulum and vesicles, and exocentric, spherical, or irregular nucleus. In both types of hemocytes, scant polysaccharides and lipids were found. Prohemocytes were small and spherical with homogeneous cytoplasm and large exocentric nuclei. Oenocytoids were oval or irregular with dense homogeneous cytoplasm and elongated exocentric nuclei. The percentages of granulocytes on different days (d 1 and 10) during the life of the adult female were significantly different, as were those of plasmatocytes on d 30 and 50 and prohemocytes on d 1 and 50. (c) 2010 Wiley Periodicals, Inc.

Large radius of curvature measurement based on virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer.

PubMed

Yang, Zhongming; Wang, Kailiang; Cheng, Jinlong; Gao, Zhishan; Yuan, Qun

2016-06-10

We have proposed a virtual quadratic Newton rings phase-shifting moiré-fringes measurement method in a nonnull interferometer to measure the large radius of curvature for a spherical surface. In a quadratic polar coordinate system, linear carrier testing Newton rings interferogram and virtual Newton rings interferogram form the moiré fringes. It is possible to retrieve the wavefront difference data between the testing and standard spherical surface from the moiré fringes after low-pass filtering. Based on the wavefront difference data, we deduced a precise formula to calculate the radius of curvature in the quadratic polar coordinate system. We calculated the retrace error in the nonnull interferometer using the multi-configuration model of the nonnull interferometric system in ZEMAX. Our experimental results indicate that the measurement accuracy is better than 0.18% for a spherical mirror with a radius of curvature of 41,400 mm.

Potential scattering on a spherical surface

NASA Astrophysics Data System (ADS)

Zhang, Jian; Ho, Tin-Lun

2018-06-01

The advances in cold atom experiments have allowed construction of confining traps in the form of curved surfaces. This opens up the possibility of studying quantum gases in curved manifolds. On closed surfaces, many fundamental processes are affected by the local and global properties, i.e. the curvature and the topology of the surface. In this paper, we study the problem of potential scattering on a spherical surface and discuss its difference with that on a 2D plane. For bound states with angular momentum m, their energies (E m ) on a sphere are related to those on a 2D plane (-| {E}m,o| ) as {E}m=-| {E}m,o| +{E}R≤ft[\\tfrac{{m}2-1}{3}+O≤ft(\\tfrac{{r}o2}{{R}2}\\right)\\right], where {E}R={{{\\hslash }}}2/(2{{MR}}2), and R is the radius of the sphere. Due to the finite extent of the manifold, the phase shifts on a sphere at energies E∼ {E}R differ significantly from those on a 2D plane. As energy E approaches zero, the phase shift in the planar case approaches 0, whereas in the spherical case it reaches a constant that connects the microscopic length scale to the largest length scale R.

The PLX- α project: demonstrating the viability of spherically imploding plasma liners as an MIF driver

NASA Astrophysics Data System (ADS)

Hsu, S. C.; Witherspoon, F. D.; Cassibry, J. T.; Gilmore, M.; Samulyak, R.; Stoltz, P.; the PLX-α Team

2015-11-01

Under ARPA-E's ALPHA program, the Plasma Liner Experiment-ALPHA (PLX- α) project aims to demonstrate the viability and scalability of spherically imploding plasma liners as a standoff, high-implosion-velocity magneto-inertial-fusion (MIF) driver that is potentially compatible with both low- and high- β targets. The project has three major objectives: (a) advancing existing contoured-gap coaxial-gun technology to achieve higher operational reliability/precision and better control/reproducibility of plasma-jet properties and profiles; (2) conducting ~ π / 2 -solid-angle plasma-liner experiments with 9 guns to demonstrate (along with extrapolations from modeling) that the jet-merging process leads to Mach-number degradation and liner uniformity that are acceptable for MIF; and (3) conducting 4 π experiments with up to 60 guns to demonstrate the formation of an imploding spherical plasma liner for the first time, and to provide empirical ram-pressure and uniformity scaling data for benchmarking our codes and informing us whether the scalings justify further development beyond ALPHA. This talk will provide an overview of the PLX- α project as well as key research results to date. Supported by ARPA-E's ALPHA program; original PLX construction supported by DOE Fusion Energy Sciences.

Independent and collective roles of surface structures at different length scales on pool boiling heat transfer

PubMed Central

Li, Calvin H.; Rioux, Russell P.

2016-01-01

Spherical Cu nanocavity surfaces are synthesized to examine the individual role of contact angles in connecting lateral Rayleigh-Taylor wavelength to vertical Kevin-Helmholtz wavelength on hydrodynamic instability for the onset of pool boiling Critical Heat Flux (CHF). Solid and porous Cu pillar surfaces are sintered to investigate the individual role of pillar structure pitch at millimeter scale, named as module wavelength, on hydrodynamic instability at CHF. Last, spherical Cu nanocavities are coated on the porous Cu pillars to create a multiscale Cu structure, which is studied to examine the collective role and relative significance of contact angles and module wavelength on hydrodynamic instability at CHF, and the results indicate that module wavelength plays the dominant role on hydrodynamic instability at CHF when the height of surface structures is equal or above ¼ Kelvin-Helmholtz wavelength. Pool boiling Heat Transfer Coefficient (HTC) enhancements on spherical Cu nanocavity surfaces, solid and porous Cu pillar surfaces, and the integrated multiscale structure have been investigated, too. The experimental results reveal that the nanostructures and porous pillar structures can be combined together to achieve even higher enhancement of HTC than that of individual structures. PMID:27841322

Fluidization of spherocylindrical particles

NASA Astrophysics Data System (ADS)

Mahajan, Vinay V.; Nijssen, Tim M. J.; Fitzgerald, Barry W.; Hofman, Jeroen; Kuipers, Hans; Padding, Johan T.

2017-06-01

Multiphase (gas-solid) flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like) particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.

Deformation induced dynamic recrystallization and precipitation strengthening in an Mg−Zn−Mn alloy processed by high strain rate rolling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Jimiao; Song, Min

2016-11-15

The microstructure of a high strain-rate rolled Mg−Zn−Mn alloy was investigated by transmission electron microscopy to understand the relationship between the microstructure and mechanical properties. The results indicate that: (1) a bimodal microstructure consisting of the fine dynamic recrystallized grains and the largely deformed grains was formed; (2) a large number of dynamic precipitates including plate-like MgZn{sub 2} phase, spherical MgZn{sub 2} phase and spherical Mn particles distribute uniformly in the grains; (3) the major facets of many plate-like MgZn{sub 2} precipitates deviated several to tens of degrees (3°–30°) from the matrix basal plane. It has been shown that themore » high strength of the alloy is attributed to the formation of the bimodal microstructure, dynamic precipitation, and the interaction between the dislocations and the dynamic precipitates. - Highlights: •A bimodal microstructure was formed in a high strain-rate rolled Mg−Zn−Mn alloy. •Plate-like MgZn{sub 2}, spherical MgZn{sub 2} and spherical Mn phases were observed. •The major facet of the plate-like MgZn{sub 2} deviated from the matrix basal plane.« less

High throughput exploration of process-property linkages in Al-6061 using instrumented spherical microindentation and microstructurally graded samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Khosravani, Ali; Castillo, Andrew

Recent spherical nanoindentation protocols have proven robust at capturing the local elastic-plastic response of polycrystalline metal samples at length scales much smaller than the grain size. In this work, we extend these protocols to length scales that include multiple grains to recover microindentation stress-strain curves. These new protocols are first established in this paper and then demonstrated for Al-6061 by comparing the measured indentation stress-strain curves with the corresponding measurements from uniaxial tension tests. More specifically, the scaling factors between the uniaxial yield strength and the indentation yield strength was determined to be about 1.9, which is significantly lower thanmore » the value of 2.8 used commonly in literature. Furthermore, the reasons for this difference are discussed. Second, the benefits of these new protocols in facilitating high throughput exploration of process-property relationships are demonstrated through a simple case study.« less

High throughput exploration of process-property linkages in Al-6061 using instrumented spherical microindentation and microstructurally graded samples

DOE PAGES

Weaver, Jordan S.; Khosravani, Ali; Castillo, Andrew; ...

2016-06-14

Recent spherical nanoindentation protocols have proven robust at capturing the local elastic-plastic response of polycrystalline metal samples at length scales much smaller than the grain size. In this work, we extend these protocols to length scales that include multiple grains to recover microindentation stress-strain curves. These new protocols are first established in this paper and then demonstrated for Al-6061 by comparing the measured indentation stress-strain curves with the corresponding measurements from uniaxial tension tests. More specifically, the scaling factors between the uniaxial yield strength and the indentation yield strength was determined to be about 1.9, which is significantly lower thanmore » the value of 2.8 used commonly in literature. Furthermore, the reasons for this difference are discussed. Second, the benefits of these new protocols in facilitating high throughput exploration of process-property relationships are demonstrated through a simple case study.« less

a Smaller Scale

ERIC Educational Resources Information Center

Takemae, Seiji; Kirwin, Peter; McIntosh, Gordon

2013-01-01

In this paper, we describe a lab activity for measuring a spherical balloon's circumference. The procedure we discuss is based on the method used by Eratosthenes to measure the Earth's circumference.

Target categorization of aerosol and clouds by continuous multiwavelength-polarization lidar measurements

NASA Astrophysics Data System (ADS)

Baars, Holger; Seifert, Patric; Engelmann, Ronny; Wandinger, Ulla

2017-09-01

Absolute calibrated signals at 532 and 1064 nm and the depolarization ratio from a multiwavelength lidar are used to categorize primary aerosol but also clouds in high temporal and spatial resolution. Automatically derived particle backscatter coefficient profiles in low temporal resolution (30 min) are applied to calibrate the lidar signals. From these calibrated lidar signals, new atmospheric parameters in temporally high resolution (quasi-particle-backscatter coefficients) are derived. By using thresholds obtained from multiyear, multisite EARLINET (European Aerosol Research Lidar Network) measurements, four aerosol classes (small; large, spherical; large, non-spherical; mixed, partly non-spherical) and several cloud classes (liquid, ice) are defined. Thus, particles are classified by their physical features (shape and size) instead of by source. The methodology is applied to 2 months of continuous observations (24 h a day, 7 days a week) with the multiwavelength-Raman-polarization lidar PollyXT during the High-Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE) in spring 2013. Cloudnet equipment was operated continuously directly next to the lidar and is used for comparison. By discussing three 24 h case studies, it is shown that the aerosol discrimination is very feasible and informative and gives a good complement to the Cloudnet target categorization. Performing the categorization for the 2-month data set of the entire HOPE campaign, almost 1 million pixel (5 min × 30 m) could be analysed with the newly developed tool. We find that the majority of the aerosol trapped in the planetary boundary layer (PBL) was composed of small particles as expected for a heavily populated and industrialized area. Large, spherical aerosol was observed mostly at the top of the PBL and close to the identified cloud bases, indicating the importance of hygroscopic growth of the particles at high relative humidity. Interestingly, it is found that on several days non-spherical particles were dispersed from the ground into the atmosphere.

Averaged ratio between complementary profiles for evaluating shape distortions of map projections and spherical hierarchical tessellations

NASA Astrophysics Data System (ADS)

Yan, Jin; Song, Xiao; Gong, Guanghong

2016-02-01

We describe a metric named averaged ratio between complementary profiles to represent the distortion of map projections, and the shape regularity of spherical cells derived from map projections or non-map-projection methods. The properties and statistical characteristics of our metric are investigated. Our metric (1) is a variable of numerical equivalence to both scale component and angular deformation component of Tissot indicatrix, and avoids the invalidation when using Tissot indicatrix and derived differential calculus for evaluating non-map-projection based tessellations where mathematical formulae do not exist (e.g., direct spherical subdivisions), (2) exhibits simplicity (neither differential nor integral calculus) and uniformity in the form of calculations, (3) requires low computational cost, while maintaining high correlation with the results of differential calculus, (4) is a quasi-invariant under rotations, and (5) reflects the distortions of map projections, distortion of spherical cells, and the associated distortions of texels. As an indicator of quantitative evaluation, we investigated typical spherical tessellation methods, some variants of tessellation methods, and map projections. The tessellation methods we evaluated are based on map projections or direct spherical subdivisions. The evaluation involves commonly used Platonic polyhedrons, Catalan polyhedrons, etc. Quantitative analyses based on our metric of shape regularity and an essential metric of area uniformity implied that (1) Uniform Spherical Grids and its variant show good qualities in both area uniformity and shape regularity, and (2) Crusta, Unicube map, and a variant of Unicube map exhibit fairly acceptable degrees of area uniformity and shape regularity.

Probing spherical tokamak plasmas using charged fusion products

NASA Astrophysics Data System (ADS)

Boeglin, Werner U.; Perez, Ramona V.; Darrow, Douglass S.; Cecconello, Marco; Klimek, Iwona; Allan, Scott Y.; Akers, Rob J.; Jones, Owen M.; Keeling, David L.; McClements, Ken G.; Scannell, Rory

2015-11-01

The detection of charged fusion products, such as protons and tritons resulting from D(d,p)t reactions, can be used to determine the fusion reaction rate profile in large spherical tokamak plasmas with neutral beam heating. The time resolution of a diagnostic of this type makes it possible to study the slowly-varying beam density profile, as well as rapid changes resulting from MHD instabilities. A 4-channel prototype proton detector (PD) was installed and operated on the MAST spherical tokamak in August/September 2013, and a new 6-channel system for the NSTX-U spherical tokamak is under construction. PD and neutron camera measurements obtained on MAST will be compared with TRANSP calculations, and the design of the new NSTX-U system will be presented, together with the first results from this diagnostic, if available. Supported in part by DOE DE-SC0001157.

Spherical gearing with intermediate ball elements: parameter ranges with a high contact ratio

NASA Astrophysics Data System (ADS)

Gorbenko, M. V.; Gorbenko, T. I.

2017-02-01

The paper presents analytical research of the geometry and kinematical parameters of spherical gearing with ball intermediate elements. The main attention is paid to the influence of the offset coefficient on the tooth geometry generation, the contact ratio and the motion transmission angle. Intermediate ball element racetracks on the gear are trochoidal curves on a spherical surface. Two areas for the offset coefficient values providing a high value of the contact ratio - basic trochoid (without offset) and prolate trochoid with abutting racetracks of adjacent ball elements ― were revealed. Analysis of the investigated parameters showed that for power transmission, it is preferable to use spherical gearing without an offset, and for kinematic transmission, it is possible to use profiles with a large offset. The present study allows making a rational choice of geometrical parameters depending on the transmission predestination.

Role of membrane stresses in the support of planetary topography

NASA Technical Reports Server (NTRS)

Turcotte, D. L.; Willemann, R. J.; Haxby, W. F.; Norberry, J.

1981-01-01

The role of membrane stresses and bending stresses in supporting topographic loads on planetary elastic lithospheres is examined. A dimensionless parameter is introduced in order to determine the ability of a spherical shell to support loads through membrane stresses. It is determined that when this parameter is large, membrane stresses can fully support topographic loads with flexure, and when it is small the influence of the membrane stresses can be neglected. Equations governing the behavior of a spherical shell are solved for a topographic load expressed in terms of spherical harmonics, and spherical harmonic expansions of the measured gravity and topography for Mars and the moon are compared with the theory. It is concluded that membrane stresses play an important role in the support of topographic loads on the moon and Mars. The correlation of observed gravitational potential anomalies with the topography on Mars is explained by membrane stresses in the elastic lithosphere.

Lattice Boltzmann Simulation of Water Isotope Fractionation During Growth of Ice Crystals in Clouds

NASA Astrophysics Data System (ADS)

Lu, G.; Depaolo, D.; Kang, Q.; Zhang, D.

2006-12-01

The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically- symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over-saturation, determines crystal morphology, there are no existing quantitative models that directly relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be a direct relationship between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D Lattice-Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. The input parameters needed are the isotope-dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the sticking coefficient (or accommodation coefficient) for ice is uncertain. The ratio D/k is a length that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions using a dimensionless Damkohler number: Da = kh/D, where h is the width of the 2D calculation domain. Varying the nondimensional Da in the model is equivalent to varying the scale (h) in the model. Our calculations confirm that the crystal/vapor isotopic fractionation approaches the equilibrium value, and the crystals are compact (circular in 2D) as the saturation factor approaches unity (S= 1.0). At higher oversaturation (e.g. S = 1.2), dendritic crystals of millimeter size develop on timescales appropriate to cloud processes, the isotopic fractionations are dominated by kinetic effects, and similar to those predicted by the spherical diffusion model. Dendritic crystals are constrained to be relatively large, with dimension much greater than D/k. The most difficult aspect of the modeling is to account for the large density difference between air and ice, which requires us to use a fictitious higher density for the vapor-oversaturated air and scale the crystal growth time accordingly. A different approach, using a larger scale simulation to derive boundary conditions for a nested smaller scale calculation is in progress. The results to date clarify the controls on dendritic crystal growth, the relationships between saturation state, growth rate, crystal morphology and isotopic fractionation, and provide limits on the value of the accommodation coefficient.

SIRTF primary mirror design, analysis, and testing

NASA Technical Reports Server (NTRS)

Sarver, George L., III; Maa, Scott; Chang, LI

1990-01-01

The primary mirror assembly (PMA) requirements and concepts for the Space Infrared Telescope Facility (SIRTF) program are discussed. The PMA studies at NASA/ARC resulted in the design of two engineering test articles, the development of a mirror mount cryogenic static load testing system, and the procurement and partial testing of a full scale spherical mirror mounting system. Preliminary analysis and testing of the single arch mirror with conical mount design and the structured mirror with the spherical mount design indicate that the designs will meet all figure and environmental requirements of the SIRTF program.

Evolution of density and velocity profiles of dark matter and dark energy in spherical voids

NASA Astrophysics Data System (ADS)

Novosyadlyj, Bohdan; Tsizh, Maksym; Kulinich, Yurij

2017-02-01

We analyse the evolution of cosmological perturbations which leads to the formation of large isolated voids in the Universe. We assume that initial perturbations are spherical and all components of the Universe (radiation, matter and dark energy) are continuous media with ideal fluid energy-momentum tensors, which interact only gravitationally. Equations of the evolution of perturbations for every component in the comoving to cosmological background reference frame are obtained from equations of energy and momentum conservation and Einstein's ones and are integrated numerically. Initial conditions are set at the early stage of evolution in the radiation-dominated epoch, when the scale of perturbation is much larger than the particle horizon. Results show how the profiles of density and velocity of matter and dark energy are formed and how they depend on parameters of dark energy and initial conditions. In particular, it is shown that final matter density and velocity amplitudes change within range ˜4-7 per cent when the value of equation-of-state parameter of dark energy w vary in the range from -0.8 to -1.2, and change within ˜1 per cent only when the value of effective sound speed of dark energy vary over all allowable range of its values.

Ejection of Metal Particles into Superfluid 4He by Laser Ablation.

PubMed

Buelna, Xavier; Freund, Adam; Gonzalez, Daniel; Popov, Evgeny; Eloranta, Jussi

2016-10-05

The dynamics following laser ablation of a metal target immersed in superfluid $^4$He is studied by time-resolved shadowgraph photography. The delayed ejection of hot micrometer-sized particles from the target surface into the liquid was indirectly observed by monitoring the formation and growth of gaseous bubbles around the particles. The experimentally determined particle average velocity distribution appears similar as previously measured in vacuum but exhibits a sharp cutoff at the speed of sound of the liquid. The propagation of the subsonic particles terminates in slightly elongated non-spherical gas bubbles residing near the target whereas faster particles reveal an unusual hydrodynamic response of the liquid. Based on the previously established semi-empirical model developed for macroscopic objects, the ejected transonic particles exhibit supercavitating flow to reduce their hydrodynamic drag. Supersonic particles appear to follow a completely different propagation mechanism as they leave discrete and semi-continuous bubble trails in the liquid. The relatively low number density of the observed non-spherical gas bubbles indicates that only large micron-sized particles are visualized in the experiments. Although the unique properties of superfluid helium allow a detailed characterization of these processes, the developed technique can be used to study the hydrodynamic response of any liquid to fast propagating objects on the micrometer-scale.

Regional inversion of GRACE data for continental water mass time-variations. Comparison with global hydrology models, classical spherical harmonics and "mascons" solutions

NASA Astrophysics Data System (ADS)

Seoane, L.; Ramillien, G.; Frappart, F.; Biancale, R.; Gratton, S.; Bourgogne, S.

2010-12-01

Time series of 2°-by-2° constrained/unconstrained GRACE geoid solutions have been computed with a 10-day resolution by using a new regional method recently implemented at GRGS (Toulouse, France). This approach uses the dynamical orbit analysis of GRACE Level-1 measurements, and specially accurate along-track KBRR residuals to estimate the continental water mass changes over large geographical regions. For validation, our GRACE-derived regional maps are compared to: (1) the global hydrological model outputs (WGHM, LaD, NOAH), (2) the NASA "mascons" solutions based on spherical harmonics and (3) the global solutions produced by GRGS and CSR, GFZ, JPL filtered with different methodologies (Gaussian, destriped and smoothed, ICA). In this study, we focus on the annual time scale of water mass redistributions occuring in drainage basins like Amazon or Congo. Each 2°-averaged surface element is characterized by its seasonal amplitude and phase. Even if the all sources are expected to provide quite comparable results for the continental water cycle, we suspect the residual differences are from smoothing effects of the spatial constraints included in the "mascons" solutions and the underestimating the seasonal amplitudes by global hydrological models.

Micro-Mechanical Modeling of Ductile Fracture in Welded Aluminum-Lithium Alloys

NASA Technical Reports Server (NTRS)

Ibrahim, Ahmed

2002-01-01

This computation model for microscopic crack growth in welded aluminum-lithium alloys consists of a cavity with initial volume specified by the fraction f(sub 0), i.e. the void volume relative to the cell volume. Thus, cell size D and initial porosity f(sub 0) defines the key parameters in this model. The choice of cell size requires: 1) D must be representative of the large inclusion spacing. 2) Predicted R-curves scale almost proportionally with D for fixed f(sub 0). 3) mapping of one finite element per cell must provide adequate resolution of the stress-strain fields in the active layer and the adjacent material. For the ferritic steels studied thus far with this model, calibrated cell sizes range from 50-200 microns with f(sub 0) in the 0.0001 to 0.004 micron range. This range of values for D and f (sub 0) satisfies issues 1) and 3). This computational model employs the Gurson and Tvergaard constitutive model for porous plastic materials to describe the progressive damage of cells due to the growth of pre-existing voids. The model derives from a rigid-plastic limit analysis of a solid having a volume fraction (f) of voids approximated by a homogenous spherical body containing a spherical void.

Quantized vortices and superflow in arbitrary dimensions: structure, energetics and dynamics

NASA Astrophysics Data System (ADS)

Goldbart, Paul M.; Bora, Florin

2009-05-01

The structure and energetics of superflow around quantized vortices, and the motion inherited by these vortices from this superflow, are explored in the general setting of a superfluid in arbitrary dimensions. The vortices may be idealized as objects of codimension 2, such as one-dimensional loops and two-dimensional closed surfaces, respectively, in the cases of three- and four-dimensional superfluidity. By using the analogy between the vortical superflow and Ampère-Maxwell magnetostatics, the equilibrium superflow containing any specified collection of vortices is constructed. The energy of the superflow is found to take on a simple form for vortices that are smooth and asymptotically large, compared with the vortex core size. The motion of vortices is analyzed in general, as well as for the special cases of hyper-spherical and weakly distorted hyper-planar vortices. In all dimensions, vortex motion reflects vortex geometry. In dimension 4 and higher, this includes not only extrinsic but also intrinsic aspects of the vortex shape, which enter via the first and second fundamental forms of classical geometry. For hyper-spherical vortices, which generalize the vortex rings of three-dimensional superfluidity, the energy-momentum relation is determined. Simple scaling arguments recover the essential features of these results, up to numerical and logarithmic factors.

Importance of Variable Density and Non-Boussinesq Effects on the Drag of Spherical Particles

NASA Astrophysics Data System (ADS)

Ganguli, Swetava; Lele, Sanjiva

2017-11-01

What are the forces that act on a particle as it moves in a fluid? How do they change in the presence of significant heat transfer from the particle, a variable density fluid or gravity? Last year, using particle-resolved simulations we quantified these effects on a single spherical particle and on particles in periodic lattices when O(10-3) 50%) in the absolute drag are observed as λ approaches unity. Oppenheimer, et al. (2016) [1] have proposed a theoretical formula for the drag of a heated sphere at extremely low Re. We show that when Re >O(10), inertial effects completely dominate the drag while when Re

Practical statistics in pain research.

PubMed

Kim, Tae Kyun

2017-10-01

Pain is subjective, while statistics related to pain research are objective. This review was written to help researchers involved in pain research make statistical decisions. The main issues are related with the level of scales that are often used in pain research, the choice of statistical methods between parametric or nonparametric statistics, and problems which arise from repeated measurements. In the field of pain research, parametric statistics used to be applied in an erroneous way. This is closely related with the scales of data and repeated measurements. The level of scales includes nominal, ordinal, interval, and ratio scales. The level of scales affects the choice of statistics between parametric or non-parametric methods. In the field of pain research, the most frequently used pain assessment scale is the ordinal scale, which would include the visual analogue scale (VAS). There used to be another view, however, which considered the VAS to be an interval or ratio scale, so that the usage of parametric statistics would be accepted practically in some cases. Repeated measurements of the same subjects always complicates statistics. It means that measurements inevitably have correlations between each other, and would preclude the application of one-way ANOVA in which independence between the measurements is necessary. Repeated measures of ANOVA (RMANOVA), however, would permit the comparison between the correlated measurements as long as the condition of sphericity assumption is satisfied. Conclusively, parametric statistical methods should be used only when the assumptions of parametric statistics, such as normality and sphericity, are established.

Ellipsoidal geometry in asteroid thermal models - The standard radiometric model

NASA Technical Reports Server (NTRS)

Brown, R. H.

1985-01-01

The major consequences of ellipsoidal geometry in an othewise standard radiometric model for asteroids are explored. It is shown that for small deviations from spherical shape a spherical model of the same projected area gives a reasonable aproximation to the thermal flux from an ellipsoidal body. It is suggested that large departures from spherical shape require that some correction be made for geometry. Systematic differences in the radii of asteroids derived radiometrically at 10 and 20 microns may result partly from nonspherical geometry. It is also suggested that extrapolations of the rotational variation of thermal flux from a nonspherical body based solely on the change in cross-sectional area are in error.

Low degree Earth's gravity coefficients determined from different space geodetic observations and climate models

NASA Astrophysics Data System (ADS)

Wińska, Małgorzata; Nastula, Jolanta

2017-04-01

Large scale mass redistribution and its transport within the Earth system causes changes in the Earth's rotation in space, gravity field and Earth's ellipsoid shape. These changes are observed in the ΔC21, ΔS21, and ΔC20 spherical harmonics gravity coefficients, which are proportional to the mass load-induced Earth rotational excitations. In this study, linear trend, decadal, inter-annual, and seasonal variations of low degree spherical harmonics coefficients of Earth's gravity field, determined from different space geodetic techniques, Gravity Recovery and Climate Experiment (GRACE), satellite laser ranging (SLR), Global Navigation Satellite System (GNSS), Earth rotation, and climate models, are examined. In this way, the contribution of each measurement technique to interpreting the low degree surface mass density of the Earth is shown. Especially, we evaluate an usefulness of several climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) to determine the low degree Earth's gravity coefficients using GRACE satellite observations. To do that, Terrestrial Water Storage (TWS) changes from several CMIP5 climate models are determined and then these simulated data are compared with the GRACE observations. Spherical harmonics ΔC21, ΔS21, and ΔC20 changes are calculated as the sum of atmosphere and ocean mass effect (GAC values) taken from GRACE and a land surface hydrological estimate from the selected CMIP5 climate models. Low degree Stokes coefficients of the surface mass density determined from GRACE, SLR, GNSS, Earth rotation measurements and climate models are compared to each other in order to assess their consistency. The comparison is done by using different types of statistical and signal processing methods.

TURBULENCE AND STEADY FLOWS IN THREE-DIMENSIONAL GLOBAL STRATIFIED MAGNETOHYDRODYNAMIC SIMULATIONS OF ACCRETION DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flock, M.; Dzyurkevich, N.; Klahr, H.

2011-07-10

We present full 2{pi} global three-dimensional stratified magnetohydrodynamic (MHD) simulations of accretion disks. We interpret our results in the context of protoplanetary disks. We investigate the turbulence driven by the magnetorotational instability (MRI) using the PLUTO Godunov code in spherical coordinates with the accurate and robust HLLD Riemann solver. We follow the turbulence for more than 1500 orbits at the innermost radius of the domain to measure the overall strength of turbulent motions and the detailed accretion flow pattern. We find that regions within two scale heights of the midplane have a turbulent Mach number of about 0.1 and amore » magnetic pressure two to three orders of magnitude less than the gas pressure, while in those outside three scale heights the magnetic pressure equals or exceeds the gas pressure and the turbulence is transonic, leading to large density fluctuations. The strongest large-scale density disturbances are spiral density waves, and the strongest of these waves has m = 5. No clear meridional circulation appears in the calculations because fluctuating radial pressure gradients lead to changes in the orbital frequency, comparable in importance to the stress gradients that drive the meridional flows in viscous models. The net mass flow rate is well reproduced by a viscous model using the mean stress distribution taken from the MHD calculation. The strength of the mean turbulent magnetic field is inversely proportional to the radius, so the fields are approximately force-free on the largest scales. Consequently, the accretion stress falls off as the inverse square of the radius.« less

Fractional Brownian motion run with a multi-scaling clock mimics diffusion of spherical colloids in microstructural fluids.

PubMed

Park, Moongyu; Cushman, John Howard; O'Malley, Dan

2014-09-30

The collective molecular reorientations within a nematic liquid crystal fluid bathing a spherical colloid cause the colloid to diffuse anomalously on a short time scale (i.e., as a non-Brownian particle). The deformations and fluctuations of long-range orientational order in the liquid crystal profoundly influence the transient diffusive regimes. Here we show that an anisotropic fractional Brownian process run with a nonlinear multiscaling clock effectively mimics this collective and transient phenomenon. This novel process has memory, Gaussian increments, and a multiscale mean square displacement that can be chosen independently from the fractal dimension of a particle trajectory. The process is capable of modeling multiscale sub-, super-, or classical diffusion. The finite-size Lyapunov exponents for this multiscaling process are defined for future analysis of related mixing processes.

Penetration of spherical projectiles into wet granular media.

PubMed

Birch, S P D; Manga, M; Delbridge, B; Chamberlain, M

2014-09-01

We measure experimentally the penetration depth d of spherical particles into a water-saturated granular medium made of much smaller sand-sized grains. We vary the density, size R, and velocity U of the impacting spheres, and the size δ of the grains in the granular medium. We consider velocities between 7 and 107 m/s, a range not previously addressed, but relevant for impacts produced by volcanic eruptions. We find that d∝R(1/3)δ(1/3)U(2/3). The scaling with velocity is similar to that identified in previous, low-velocity collisions, but it also depends on the size of the grains in the granular medium. We develop a model, consistent with the observed scaling, in which the energy dissipation is dominated by the work required to rearrange grains along a network of force chains in the granular medium.

The Design and Analysis of Electrically Large Custom-Shaped Reflector Antennas

DTIC Science & Technology

2013-06-01

GEO) satellite data are imported into STK and plotted to visualize the regions of the sky that the spherical reflector must have line of sight for...Magnetic Conductor PO Physical Optics STK Systems Tool Kit TE Transverse Electric xvii Acronym Definition TLE Two Line Element TM Transverse Magnetic...study for the spherical reflector, Systems Tool Kit ( STK ) software from Analytical Graphics Inc. (AGI) is used. In completing the cross-shaped

Contrast Density and mass function for spherical collapse of Lemaitre-Tolman-Bondi metric from fractal point of view

NASA Astrophysics Data System (ADS)

Chacón-Cardona, C. A.; Casas-Miranda, R. A.

2014-10-01

Recent works about large structure in the universe put in doubt the homogeneity transition almost universally accepted, (Joyce et al.2005), (Gaite 2007), (Chacón-Cardona & Casas-Miranda 2012). In the present work we develop theoretically the density contrast for the spherical collapse of an over-density of dark matter which evolve in a inhomogeneous universe inside a fractal cosmology presented by (Bondi 1947).

Tailoring of Nano- and Microstructure in Biomimetically Synthesized Ceramic Films

DTIC Science & Technology

2006-11-01

Eq. 5 where the Hamaker constant (A) for a flat and infinitely large substrate (subscript 1) and a spherical particle...is determined as (Israelachvili 1985): 232 12a A RV x = − Eq. 7 where the Hamaker constant for two like spherical particle (2) in a medium...close enough to be attracted to the equilibrium separation (0.3 nm). The Hamaker constants and the minimal interaction energies for substrate-solution

Earth Structure, Ice Mass Changes, and the Local Dynamic Geoid

NASA Astrophysics Data System (ADS)

Harig, C.; Simons, F. J.

2014-12-01

Spherical Slepian localization functions are a useful method for studying regional mass changes observed by satellite gravimetry. By projecting data onto a sparse basis set, the local field can be estimated more easily than with the full spherical harmonic basis. We have used this method previously to estimate the ice mass change in Greenland from GRACE data, and it can also be applied to other planetary problems such as global magnetic fields. Earth's static geoid, in contrast to the time-variable field, is in large part related to the internal density and rheological structure of the Earth. Past studies have used dynamic geoid kernels to relate this density structure and the internal deformation it induces to the surface geopotential at large scales. These now classical studies of the eighties and nineties were able to estimate the mantle's radial rheological profile, placing constraints on the ratio between upper and lower mantle viscosity. By combining these two methods, spherical Slepian localization and dynamic geoid kernels, we have created local dynamic geoid kernels which are sensitive only to density variations within an area of interest. With these kernels we can estimate the approximate local radial rheological structure that best explains the locally observed geoid on a regional basis. First-order differences of the regional mantle viscosity structure are accessible to this technique. In this contribution we present our latest, as yet unpublished results on the geographical and temporal pattern of ice mass changes in Antarctica over the past decade, and we introduce a new approach to extract regional information about the internal structure of the Earth from the static global gravity field. Both sets of results are linked in terms of the relevant physics, but also in being developed from the marriage of Slepian functions and geoid kernels. We make predictions on the utility of our approach to derive fully three-dimensional rheological Earth models, to be used for corrections for glacio-isostatic adjustment, as necessary for the interpretation of time-variable gravity observations in terms of ice sheet mass-balance studies.

Experimental approach to the fundamental limit of the extinction coefficients of ultra-smooth and highly spherical gold nanoparticles.

PubMed

Kim, Dong-Kwan; Hwang, Yoon Jo; Yoon, Cheolho; Yoon, Hye-On; Chang, Ki Soo; Lee, Gaehang; Lee, Seungwoo; Yi, Gi-Ra

2015-08-28

The theoretical extinction coefficients of gold nanoparticles (AuNPs) have been mainly verified by the analytical solving of the Maxwell equation for an ideal sphere, which was firstly founded by Mie (generally referred to as Mie theory). However, in principle, it has not been directly feasible with experimental verification especially for relatively large AuNPs (i.e., >40 nm), as conventionally proposed synthetic methods have inevitably resulted in a polygonal shaped, non-ideal Au nanosphere. Here, mono-crystalline, ultra-smooth, and highly spherical AuNPs of 40-100 nm were prepared by the procedure reported in our recent work (ACS Nano, 2013, 7, 11064). The extinction coefficients of the ideally spherical AuNPs of 40-100 nm were empirically extracted using the Beer-Lambert law, and were then compared with the theoretical limits obtained by the analytical and numerical methods. The obtained extinction coefficients of the ideally spherical AuNPs herein agree much more closely with the theoretical limits, compared with those of the faceted or polygonal shaped AuNPs. In addition, in order to further elucidate the importance of being spherical, we systematically compared our ideally spherical AuNPs with the polygonal counterparts; effectively addressing the role of the surface morphology on the spectral responses in both theoretical and experimental manners.

Electrokinetic and hydrodynamic properties of charged-particles systems. From small electrolyte ions to large colloids

NASA Astrophysics Data System (ADS)

Nägele, G.; Heinen, M.; Banchio, A. J.; Contreras-Aburto, C.

2013-11-01

Dynamic processes in dispersions of charged spherical particles are of importance both in fundamental science, and in technical and bio-medical applications. There exists a large variety of charged-particles systems, ranging from nanometer-sized electrolyte ions to micron-sized charge-stabilized colloids. We review recent advances in theoretical methods for the calculation of linear transport coefficients in concentrated particulate systems, with the focus on hydrodynamic interactions and electrokinetic effects. Considered transport properties are the dispersion viscosity, self- and collective diffusion coefficients, sedimentation coefficients, and electrophoretic mobilities and conductivities of ionic particle species in an external electric field. Advances by our group are also discussed, including a novel mode-coupling-theory method for conduction-diffusion and viscoelastic properties of strong electrolyte solutions. Furthermore, results are presented for dispersions of solvent-permeable particles, and particles with non-zero hydrodynamic surface slip. The concentration-dependent swelling of ionic microgels is discussed, as well as a far-reaching dynamic scaling behavior relating colloidal long- to short-time dynamics.

Nature of peptide wrapping onto metal nanoparticle catalysts and driving forces for size control.

PubMed

Ramezani-Dakhel, Hadi; Bedford, Nicholas M; Woehl, Taylor J; Knecht, Marc R; Naik, Rajesh R; Heinz, Hendrik

2017-06-22

Colloidal metal nanocrystals find many applications in catalysis, energy conversion devices, and therapeutics. However, the nature of ligand interactions and implications on shape control have remained uncertain at the atomic scale. Large differences in peptide adsorption strength and facet specificity were found on flat palladium surfaces versus surfaces of nanoparticles of 2 to 3 nm size using accurate atomistic simulations with the Interface force field. Folding of longer peptides across many facets explains the formation of near-spherical particles with local surface disorder, in contrast to the possibility of nanostructures of higher symmetry with shorter ligands. The average particle size in TEM correlates inversely with the surface coverage with a given ligand and with the strength of ligand adsorption. The role of specific amino acids and sequence mutations on the nanoparticle size and facet composition is discussed, as well as the origin of local surface disorder that leads to large differences in catalytic reactivity.

Self-assembly of large-scale crack-free gold nanoparticle films using a ‘drain-to-deposit’ strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Guang; Hallinan, Daniel T.

2016-04-26

Gold nanoparticles are widely studied due to the ease of controlled synthesis, facile surface modification, and interesting physical properties. However, a technique for depositing large-area, crack-free monolayers on solid substrates is lacking. Herein is presented a method for accomplishing this. Spherical gold nanoparticles were synthesized as an aqueous dispersion. Assembly into monolayers and ligand exchange occurred simultaneously at an organic/aqueous interface. Then the monolayer film was deposited onto arbitrary solid substrates by slowly pumping out the lower, aqueous phase. This allowed the monolayer film (and liquid–liquid interface) to descend without significant disturbance, eventually reaching substrates contained in the aqueous phase.more » The resulting macroscopic quality of the films was found to be superior to films transferred by Langmuir techniques. The surface plasmon resonance and Raman enhancement of the films were evaluated and found to be uniform across the surface of each film.« less

Stratification and energy fluxes in the anelastic convection model

NASA Astrophysics Data System (ADS)

Hejda, Pavel; Reshetnyak, Maxim

2013-04-01

Convection in the planetary cores is usually connected with the geostrophic state. At the onset of convection, the ratio of horizontal scale to the scale along the axis of rotation is proportional to the cube root of the Ekman number, which characterises the ratio of the viscous forces to the Coriolis force. The Ekman number is extremely small in the liquid cores, which is a source of strong anisotropy. Even if further increase of the heat sources leads to decrease of anisotropy, the final state is still highly anisotropic. The influence of the rapid rotation on the structure of the flows in the physical space is also manifested by a substantial change of the spectral properties of the turbulence in the core (Reshetnyak and Hejda, 2008; Hejda and Reshetnyak, 2009). If for the non-rotating flow the kinetic energy in the wave space propagates from the large scales to the small dissipative scales (the so-called direct Richardson-Kolmogorov cascade), then in presence of rotation the turbulence degenerates to the quasi two-dimensional state and the inverse cascade of the kinetic energy is observed. Having in mind that Cartesian and spherical geometries exhibit similar results and reproduce the inverse cascades of the kinetic energy (Reshetnyak and Hejda, 2012), there is an open question how this cascade contributes to the more general energy balance, which includes the heat flux equation. As the heat energy definition in the Boussinesq model is quite questionable, we consider the anelastic model, where the heat fluxes can be compared with the kinetic energy fluxes in the adequate way. Here we consider the spherical geometry model in the shell that limits our study to the cascades in the azimuthal wave-number. As the self-consistent anelastic model includes new term, the adiabatic cooling, which produces "stratification" in the outer part of the core, we consider its influence on convection in the physical and wave spaces. We show that even small cooling can change the convection substantially, shifting maximum of convection to the inner part of the liquid core. Similar to the Boussinesq model the both direct and inverse cascades of the kinetic energy as well as the direct cascade of the specific entropy in the wave space occur. Reshetnyak, M. and Hejda, P., 2008. Direct and inverse cascades in the geodynamo. Nonlin. Proc. Geophys. 15, 873-880. Hejda, P. and Reshetnyak, M., 2009. Effect of anisotropy in the geostrophic turbulence. Phys. Earth Planet. Inter. 177, 152-160, doi: 10.1016/j.pepi.2009.08.006. Reshetnyak, M. and Hejda, P., 2012. Kinetic energy cascades in quasi-geostrophic convection in a spherical shell. Physica Scripta 86, article No. 018408, doi: 10.1088/0031-8949/86/01/018408.

Monostatic lidar/radar invisibility using coated spheres.

PubMed

Zhai, Peng-Wang; You, Yu; Kattawar, George W; Yang, Ping

2008-02-04

The Lorenz-Mie theory is revisited to explicitly include materials whose permeability is different from unity. The expansion coefficients of the scattered field are given for light scattering by both homogeneous and coated spheres. It is shown that the backscatter is exactly zero if the impedance of the spherical particles is equal to the intrinsic impedance of the surrounding medium. If spherical particles are sufficiently large, the zero backscatter can be explained as impedance matching using the asymptotic expression for the radar backscattering cross section. In the case of a coated sphere, the shell can be regarded as a cloak if the product of the thickness and the imaginary part of the refractive index of the outer shell is large.

Cortical geometry as a determinant of brain activity eigenmodes: Neural field analysis

NASA Astrophysics Data System (ADS)

Gabay, Natasha C.; Robinson, P. A.

2017-09-01

Perturbation analysis of neural field theory is used to derive eigenmodes of neural activity on a cortical hemisphere, which have previously been calculated numerically and found to be close analogs of spherical harmonics, despite heavy cortical folding. The present perturbation method treats cortical folding as a first-order perturbation from a spherical geometry. The first nine spatial eigenmodes on a population-averaged cortical hemisphere are derived and compared with previous numerical solutions. These eigenmodes contribute most to brain activity patterns such as those seen in electroencephalography and functional magnetic resonance imaging. The eigenvalues of these eigenmodes are found to agree with the previous numerical solutions to within their uncertainties. Also in agreement with the previous numerics, all eigenmodes are found to closely resemble spherical harmonics. The first seven eigenmodes exhibit a one-to-one correspondence with their numerical counterparts, with overlaps that are close to unity. The next two eigenmodes overlap the corresponding pair of numerical eigenmodes, having been rotated within the subspace spanned by that pair, likely due to second-order effects. The spatial orientations of the eigenmodes are found to be fixed by gross cortical shape rather than finer-scale cortical properties, which is consistent with the observed intersubject consistency of functional connectivity patterns. However, the eigenvalues depend more sensitively on finer-scale cortical structure, implying that the eigenfrequencies and consequent dynamical properties of functional connectivity depend more strongly on details of individual cortical folding. Overall, these results imply that well-established tools from perturbation theory and spherical harmonic analysis can be used to calculate the main properties and dynamics of low-order brain eigenmodes.

Turning Around along the Cosmic Web

NASA Astrophysics Data System (ADS)

Lee, Jounghun; Yepes, Gustavo

2016-12-01

A bound violation designates a case in which the turnaround radius of a bound object exceeds the upper limit imposed by the spherical collapse model based on the standard ΛCDM paradigm. Given that the turnaround radius of a bound object is a stochastic quantity and that the spherical model overly simplifies the true gravitational collapse, which actually proceeds anisotropically along the cosmic web, the rarity of the occurrence of a bound violation may depend on the web environment. Assuming a Planck cosmology, we numerically construct the bound-zone peculiar velocity profiles along the cosmic web (filaments and sheets) around the isolated groups with virial mass {M}{{v}}≥slant 3× {10}13 {h}-1 {M}⊙ identified in the Small MultiDark Planck simulations and determine the radial distances at which their peculiar velocities equal the Hubble expansion speed as the turnaround radii of the groups. It is found that although the average turnaround radii of the isolated groups are well below the spherical bound limit on all mass scales, the bound violations are not forbidden for individual groups, and the cosmic web has an effect of reducing the rarity of the occurrence of a bound violation. Explaining that the spherical bound limit on the turnaround radius in fact represents the threshold distance up to which the intervention of the external gravitational field in the bound-zone peculiar velocity profiles around the nonisolated groups stays negligible, we discuss the possibility of using the threshold distance scale to constrain locally the equation of state of dark energy.

A Research Program of Spherical Tokamak in China

NASA Astrophysics Data System (ADS)

He, Ye-xi

2002-08-01

The mission of this program is to explore the spherical torus plasma with a SUNIST spherical tokamak. Main experiments in the start phase will be involved with breakdown and plasma current set-up with a mode of saving volt-second and without ohmic heating system, equilibrium and instability, current driving, heating and profile modification. The SUNIST is a university-scale conceptual spherical tokamak, with R = 0.3 m, A 1.3, Ip ~ 50 kA, BT < 0.15 T, and PRF = 100 kW. The only peculiarity of SUNIST is that there is a toroidal insulating break along the outer wall of vacuum vessel. The expected that advantages of this arrangement are helpful not only for saving flux swing, but also for having a deep understanding of what will influence the discharge startup and globe performances of plasma under different conditions of strong vessel eddy and ECR power assistance. Of course, the vessel structure of cross seal will be at a great risk of controlling vacuum quality, although we have achieved positive results on simulation test and vacuum vessel test.

Confinement dynamics of a semiflexible chain inside nano-spheres

NASA Astrophysics Data System (ADS)

Fathizadeh, A.; Heidari, Maziar; Eslami-Mossallam, B.; Ejtehadi, M. R.

2013-07-01

We study the conformations of a semiflexible chain, confined in nano-scaled spherical cavities, under two distinct processes of confinement. Radial contraction and packaging are employed as two confining procedures. The former method is performed by gradually decreasing the diameter of a spherical shell which envelopes a confined chain. The latter procedure is carried out by injecting the chain inside a spherical shell through a hole on the shell surface. The chain is modeled with a rigid body molecular dynamics simulation and its parameters are adjusted to DNA base-pair elasticity. Directional order parameter is employed to analyze and compare the confined chain and the conformations of the chain for two different sizes of the spheres are studied in both procedures. It is shown that for the confined chains in the sphere sizes of our study, they appear in spiral or tennis-ball structures, and the tennis-ball structure is more likely to be observed in more compact confinements. Our results also show that the dynamical procedure of confinement and the rate of the confinement are influential parameters of the structure of the chain inside spherical cavities.

Distributed Adaptive Binary Quantization for Fast Nearest Neighbor Search.

PubMed

Xianglong Liu; Zhujin Li; Cheng Deng; Dacheng Tao

2017-11-01

Hashing has been proved an attractive technique for fast nearest neighbor search over big data. Compared with the projection based hashing methods, prototype-based ones own stronger power to generate discriminative binary codes for the data with complex intrinsic structure. However, existing prototype-based methods, such as spherical hashing and K-means hashing, still suffer from the ineffective coding that utilizes the complete binary codes in a hypercube. To address this problem, we propose an adaptive binary quantization (ABQ) method that learns a discriminative hash function with prototypes associated with small unique binary codes. Our alternating optimization adaptively discovers the prototype set and the code set of a varying size in an efficient way, which together robustly approximate the data relations. Our method can be naturally generalized to the product space for long hash codes, and enjoys the fast training linear to the number of the training data. We further devise a distributed framework for the large-scale learning, which can significantly speed up the training of ABQ in the distributed environment that has been widely deployed in many areas nowadays. The extensive experiments on four large-scale (up to 80 million) data sets demonstrate that our method significantly outperforms state-of-the-art hashing methods, with up to 58.84% performance gains relatively.

Riding on irrelevant operators

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Rham, Claudia; Ribeiro, Raquel H., E-mail: Claudia.deRham@case.edu, E-mail: RaquelHRibeiro@case.edu

2014-11-01

We investigate the stability of a class of derivative theories known as P(X) and Galileons against corrections generated by quantum effects. We use an exact renormalisation group approach to argue that these theories are stable under quantum corrections at all loops in regions where the kinetic term is large compared to the strong coupling scale. This is the regime of interest for screening or Vainshtein mechanisms, and in inflationary models that rely on large kinetic terms. Next, we clarify the role played by the symmetries. While symmetries protect the form of the quantum corrections, theories equipped with more symmetries domore » not necessarily have a broader range of scales for which they are valid. We show this by deriving explicitly the regime of validity of the classical solutions for P(X) theories including Dirac-Born-Infeld (DBI) models, both in generic and for specific background field configurations. Indeed, we find that despite the existence of an additional symmetry, the DBI effective field theory has a regime of validity similar to an arbitrary P(X) theory. We explore the implications of our results for both early and late universe contexts. Conversely, when applied to static and spherical screening mechanisms, we deduce that the regime of validity of typical power-law P(X) theories is much larger than that of DBI.« less

The shape of galaxy dark matter haloes in massive galaxy clusters: insights from strong gravitational lensing

NASA Astrophysics Data System (ADS)

Jauzac, Mathilde; Harvey, David; Massey, Richard

2018-07-01

We assess how much unused strong lensing information is available in the deep Hubble Space Telescope imaging and Very Large Telescope/Multi Unit Spectroscopic Explorer spectroscopy of the Frontier Field clusters. As a pilot study, we analyse galaxy cluster MACS J0416.1-2403 (z = 0.397, M(R < 200 kpc) = 1.6 × 1014 M⊙), which has 141 multiple images with spectroscopic redshifts. We find that many additional parameters in a cluster mass model can be constrained, and that adding even small amounts of extra freedom to a model can dramatically improve its figures of merit. We use this information to constrain the distribution of dark matter around cluster member galaxies, simultaneously with the cluster's large-scale mass distribution. We find tentative evidence that some galaxies' dark matter has surprisingly similar ellipticity to their stars (unlike in the field, where it is more spherical), but that its orientation is often misaligned. When non-coincident dark matter and stellar haloes are allowed, the model improves by 35 per cent. This technique may provide a new way to investigate the processes and time-scales on which dark matter is stripped from galaxies as they fall into a massive cluster. Our preliminary conclusions will be made more robust by analysing the remaining five Frontier Field clusters.

Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry.

PubMed

Barry, T L; Davies, J H; Wolstencroft, M; Millar, I L; Zhao, Z; Jian, P; Safonova, I; Price, M

2017-05-12

The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e.g. under Indian Ocean) circulates down to the core-mantle boundary (CMB), but returns within ≥100 Myrs via large-scale convection to its approximate starting location. Modelled tracers pool at the CMB but do not disperse ubiquitously around it. Similarly, mantle beneath the Pacific does not spread to surrounding regions of the planet. The models fit global patterns of isotope data and may explain features such as the DUPAL anomaly and long-standing differences between Indian and Pacific Ocean crust. Indeed, the geochemical data suggests this mode of convection could have influenced the evolution of mantle composition since 550 Ma and potentially since the onset of plate tectonics.

Large-scale, near-Earth, magnetic fields from external sources and the corresponding induced internal field

NASA Technical Reports Server (NTRS)

Langel, R. A.; Estes, R. H.

1983-01-01

Data from MAGSAT analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-Earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk. The MAGSAT data was compared with POGO data. A local time variation of the external field persists even during very quiet magnetic conditions; both a diurnal and 8-hour period are present. A crude estimate of Sq current in the 45 deg geomagnetic latitude range is obtained for 1966 to 1970. The current strength, located in the ionosphere and induced in the Earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.

Large-scale, near-field magnetic fields from external sources and the corresponding induced internal field

NASA Technical Reports Server (NTRS)

Langel, R. A.; Estes, R. H.

1985-01-01

Data from Magsat analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk. The Magsat data was compared with POGO data. A local time variation of the external field persists even during very quiet magnetic conditions; both a diurnal and 8-hour period are present. A crude estimate of Sq current in the 45 deg geomagnetic latitude range is obtained for 1966 to 1970. The current strength, located in the ionosphere and induced in the earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.

Acoustic levitation of a large solid sphere

NASA Astrophysics Data System (ADS)

Andrade, Marco A. B.; Bernassau, Anne L.; Adamowski, Julio C.

2016-07-01

We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

Consider a non-spherical elephant: computational fluid dynamics simulations of heat transfer coefficients and drag verified using wind tunnel experiments.

PubMed

Dudley, Peter N; Bonazza, Riccardo; Porter, Warren P

2013-07-01

Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry. Copyright © 2013 Wiley Periodicals, Inc.

Stability of anti-de sitter space in Einstein-Gauss-Bonnet gravity.

PubMed

Deppe, Nils; Kolly, Allison; Frey, Andrew; Kunstatter, Gabor

2015-02-20

Recently it has been argued that in Einstein gravity anti-de Sitter spacetime is unstable against the formation of black holes for a large class of arbitrarily small perturbations. We examine the effects of including a Gauss-Bonnet term. In five dimensions, spherically symmetric Einstein-Gauss-Bonnet gravity has two key features: Choptuik scaling exhibits a radius gap, and the mass function goes to a finite value as the horizon radius vanishes. These suggest that black holes will not form dynamically if the total mass-energy content of the spacetime is too small, thereby restoring the stability of anti-de Sitter spacetime in this context. We support this claim with numerical simulations and uncover a rich structure in horizon radii and formation times as a function of perturbation amplitude.

Finite upper bound for the Hawking decay time of an arbitrarily large black hole in anti-de Sitter spacetime

NASA Astrophysics Data System (ADS)

Page, Don N.

2018-01-01

In an asymptotically flat spacetime of dimension d >3 and with the Newtonian gravitational constant G , a spherical black hole of initial horizon radius rh and mass M ˜rhd -3/G has a total decay time to Hawking emission of td˜rhd -1/G ˜G2 /(d -3 )M(d -1 )/(d -3 ) which grows without bound as the radius rh and mass M are taken to infinity. However, in asymptotically anti-de Sitter spacetime with a length scale ℓ and with absorbing boundary conditions at infinity, the total Hawking decay time does not diverge as the mass and radius go to infinity but instead remains bounded by a time of the order of ℓd-1/G .

Performance of bent-crystal x-ray microscopes for high energy density physics research

DOE PAGES

Schollmeier, Marius S.; Geissel, Matthias; Shores, Jonathon E.; ...

2015-05-29

We present calculations for the field of view (FOV), image fluence, image monochromaticity, spectral acceptance, and image aberrations for spherical crystal microscopes, which are used as self-emission imaging or backlighter systems at large-scale high energy density physics facilities. Our analytic results are benchmarked with ray-tracing calculations as well as with experimental measurements from the 6.151 keV backlighter system at Sandia National Laboratories. Furthermore, the analytic expressions can be used for x-ray source positions anywhere between the Rowland circle and object plane. We discovered that this enables quick optimization of the performance of proposed but untested, bent-crystal microscope systems to findmore » the best compromise between FOV, image fluence, and spatial resolution for a particular application.« less

Binding Energy of 79Cu: Probing the Structure of the Doubly Magic 78Ni from Only One Proton Away

NASA Astrophysics Data System (ADS)

Welker, A.; Althubiti, N. A. S.; Atanasov, D.; Blaum, K.; Cocolios, T. E.; Herfurth, F.; Kreim, S.; Lunney, D.; Manea, V.; Mougeot, M.; Neidherr, D.; Nowacki, F.; Poves, A.; Rosenbusch, M.; Schweikhard, L.; Wienholtz, F.; Wolf, R. N.; Zuber, K.

2017-11-01

The masses of the neutron-rich copper isotopes 75-79Cu are determined using the precision mass spectrometer ISOLTRAP at the CERN-ISOLDE facility. The trend from the new data differs significantly from that of previous results, offering a first accurate view of the mass surface adjacent to the Z =28 , N =50 nuclide 78Ni and supporting a doubly magic character. The new masses compare very well with large-scale shell-model calculations that predict shape coexistence in a doubly magic 78Ni and a new island of inversion for Z <28 . A coherent picture of this important exotic region begins to emerge where excitations across Z =28 and N =50 form a delicate equilibrium with a spherical mean field.

One-dimensional turbulence modeling for cylindrical and spherical flows: model formulation and application

NASA Astrophysics Data System (ADS)

Lignell, David O.; Lansinger, Victoria B.; Medina, Juan; Klein, Marten; Kerstein, Alan R.; Schmidt, Heiko; Fistler, Marco; Oevermann, Michael

2018-06-01

The one-dimensional turbulence (ODT) model resolves a full range of time and length scales and is computationally efficient. ODT has been applied to a wide range of complex multi-scale flows, such as turbulent combustion. Previous ODT comparisons to experimental data have focused mainly on planar flows. Applications to cylindrical flows, such as round jets, have been based on rough analogies, e.g., by exploiting the fortuitous consistency of the similarity scalings of temporally developing planar jets and spatially developing round jets. To obtain a more systematic treatment, a new formulation of the ODT model in cylindrical and spherical coordinates is presented here. The model is written in terms of a geometric factor so that planar, cylindrical, and spherical configurations are represented in the same way. Temporal and spatial versions of the model are presented. A Lagrangian finite-volume implementation is used with a dynamically adaptive mesh. The adaptive mesh facilitates the implementation of cylindrical and spherical versions of the triplet map, which is used to model turbulent advection (eddy events) in the one-dimensional flow coordinate. In cylindrical and spherical coordinates, geometric stretching of the three triplet map images occurs due to the radial dependence of volume, with the stretching being strongest near the centerline. Two triplet map variants, TMA and TMB, are presented. In TMA, the three map images have the same volume, but different radial segment lengths. In TMB, the three map images have the same radial segment lengths, but different segment volumes. Cylindrical results are presented for temporal pipe flow, a spatial nonreacting jet, and a spatial nonreacting jet flame. These results compare very well to direct numerical simulation for the pipe flow, and to experimental data for the jets. The nonreacting jet treatment overpredicts velocity fluctuations near the centerline, due to the geometric stretching of the triplet maps and its effect on the eddy event rate distribution. TMB performs better than TMA. A hybrid planar-TMB (PTMB) approach is also presented, which further improves the results. TMA, TMB, and PTMB are nearly identical in the pipe flow where the key dynamics occur near the wall away from the centerline. The jet flame illustrates effects of variable density and viscosity, including dilatational effects.

Modeling and Testing Dark Energy and Gravity with Galaxy Cluster Data

NASA Astrophysics Data System (ADS)

Rapetti, David; Cataneo, Matteo; Heneka, Caroline; Mantz, Adam; Allen, Steven W.; Von Der Linden, Anja; Schmidt, Fabian; Lombriser, Lucas; Li, Baojiu; Applegate, Douglas; Kelly, Patrick; Morris, Glenn

2018-06-01

The abundance of galaxy clusters is a powerful probe to constrain the properties of dark energy and gravity at large scales. We employed a self-consistent analysis that includes survey, observable-mass scaling relations and weak gravitational lensing data to obtain constraints on f(R) gravity, which are an order of magnitude tighter than the best previously achieved, as well as on cold dark energy of negligible sound speed. The latter implies clustering of the dark energy fluid at all scales, allowing us to measure the effects of dark energy perturbations at cluster scales. For this study, we recalibrated the halo mass function using the following non-linear characteristic quantities: the spherical collapse threshold, the virial overdensity and an additional mass contribution for cold dark energy. We also presented a new modeling of the f(R) gravity halo mass function that incorporates novel corrections to capture key non-linear effects of the Chameleon screening mechanism, as found in high resolution N-body simulations. All these results permit us to predict, as I will also exemplify, and eventually obtain the next generation of cluster constraints on such models, and provide us with frameworks that can also be applied to other proposed dark energy and modified gravity models using cluster abundance observations.

Violation of the Sphericity Assumption and Its Effect on Type-I Error Rates in Repeated Measures ANOVA and Multi-Level Linear Models (MLM).

PubMed

Haverkamp, Nicolas; Beauducel, André

2017-01-01

We investigated the effects of violations of the sphericity assumption on Type I error rates for different methodical approaches of repeated measures analysis using a simulation approach. In contrast to previous simulation studies on this topic, up to nine measurement occasions were considered. Effects of the level of inter-correlations between measurement occasions on Type I error rates were considered for the first time. Two populations with non-violation of the sphericity assumption, one with uncorrelated measurement occasions and one with moderately correlated measurement occasions, were generated. One population with violation of the sphericity assumption combines uncorrelated with highly correlated measurement occasions. A second population with violation of the sphericity assumption combines moderately correlated and highly correlated measurement occasions. From these four populations without any between-group effect or within-subject effect 5,000 random samples were drawn. Finally, the mean Type I error rates for Multilevel linear models (MLM) with an unstructured covariance matrix (MLM-UN), MLM with compound-symmetry (MLM-CS) and for repeated measures analysis of variance (rANOVA) models (without correction, with Greenhouse-Geisser-correction, and Huynh-Feldt-correction) were computed. To examine the effect of both the sample size and the number of measurement occasions, sample sizes of n = 20, 40, 60, 80, and 100 were considered as well as measurement occasions of m = 3, 6, and 9. With respect to rANOVA, the results plead for a use of rANOVA with Huynh-Feldt-correction, especially when the sphericity assumption is violated, the sample size is rather small and the number of measurement occasions is large. For MLM-UN, the results illustrate a massive progressive bias for small sample sizes ( n = 20) and m = 6 or more measurement occasions. This effect could not be found in previous simulation studies with a smaller number of measurement occasions. The proportionality of bias and number of measurement occasions should be considered when MLM-UN is used. The good news is that this proportionality can be compensated by means of large sample sizes. Accordingly, MLM-UN can be recommended even for small sample sizes for about three measurement occasions and for large sample sizes for about nine measurement occasions.

Spherical: an iterative workflow for assembling metagenomic datasets.

PubMed

Hitch, Thomas C A; Creevey, Christopher J

2018-01-24

The consensus emerging from the study of microbiomes is that they are far more complex than previously thought, requiring better assemblies and increasingly deeper sequencing. However, current metagenomic assembly techniques regularly fail to incorporate all, or even the majority in some cases, of the sequence information generated for many microbiomes, negating this effort. This can especially bias the information gathered and the perceived importance of the minor taxa in a microbiome. We propose a simple but effective approach, implemented in Python, to address this problem. Based on an iterative methodology, our workflow (called Spherical) carries out successive rounds of assemblies with the sequencing reads not yet utilised. This approach also allows the user to reduce the resources required for very large datasets, by assembling random subsets of the whole in a "divide and conquer" manner. We demonstrate the accuracy of Spherical using simulated data based on completely sequenced genomes and the effectiveness of the workflow at retrieving lost information for taxa in three published metagenomics studies of varying sizes. Our results show that Spherical increased the amount of reads utilized in the assembly by up to 109% compared to the base assembly. The additional contigs assembled by the Spherical workflow resulted in a significant (P < 0.05) changes in the predicted taxonomic profile of all datasets analysed. Spherical is implemented in Python 2.7 and freely available for use under the MIT license. Source code and documentation is hosted publically at: https://github.com/thh32/Spherical .

Imperfection sensitivity of pressured buckling of biopolymer spherical shells

NASA Astrophysics Data System (ADS)

Zhang, Lei; Ru, C. Q.

2016-06-01

Imperfection sensitivity is essential for mechanical behavior of biopolymer shells [such as ultrasound contrast agents (UCAs) and spherical viruses] characterized by high geometric heterogeneity. In this work, an imperfection sensitivity analysis is conducted based on a refined shell model recently developed for spherical biopolymer shells of high structural heterogeneity and thickness nonuniformity. The influence of related parameters (including the ratio of radius to average shell thickness, the ratio of transverse shear modulus to in-plane shear modulus, and the ratio of effective bending thickness to average shell thickness) on imperfection sensitivity is examined for pressured buckling. Our results show that the ratio of effective bending thickness to average shell thickness has a major effect on the imperfection sensitivity, while the effect of the ratio of transverse shear modulus to in-plane shear modulus is usually negligible. For example, with physically realistic parameters for typical imperfect spherical biopolymer shells, the present model predicts that actual maximum external pressure could be reduced to as low as 60% of that of a perfect UCA spherical shell or 55%-65% of that of a perfect spherical virus shell, respectively. The moderate imperfection sensitivity of spherical biopolymer shells with physically realistic imperfection is largely attributed to the fact that biopolymer shells are relatively thicker (defined by smaller radius-to-thickness ratio) and therefore practically realistic imperfection amplitude normalized by thickness is very small as compared to that of classical elastic thin shells which have much larger radius-to-thickness ratio.

Highly Luminescent Zn(x)Cd(1-x)Se/C Core/Shell Nanocrystals: Large Scale Synthesis, Structural and Cathodoluminescence Studies.

PubMed

Bhattacharyya, Sayan; Estrin, Yevgeni; Moshe, Ofer; Rich, Daniel H; Solovyov, Leonid A; Gedanken, A

2009-07-28

Zn(x)Cd(1-x)Se/C core/shell nanocrystals with 31-39 nm semiconducting core and 11-25 nm carbon shell were synthesized from solid state precursors in large scale amounts. A mixture of spherical and tripod nanostructures were obtained only in the one-step reaction (ZC3), where the Zn- and Cd-precursors were reacted simultaneously, rather than in the two step reactions (ZC1 and ZC2), where largely spherical nanostructures were observed. Rietveld analysis of the X-ray diffraction patterns of the samples prepared in three different ways, all under their autogenic pressure, reveal varying compositions of the Zn(x)Cd(1-x)Se nanocrystal core, where the cubic phases with higher Zn content were dominant compared to the hexagonal phases. Carbon encapsulation offers excellent protection to the nanocrystal core and is an added advantage for biological applications. Cathodoluminescence (CL) measurements with spatially integrated and highly localized excitations show distinct peaks and sharp lines at various wavelengths, representing emissions from single nanostructures possessing different compositions, phases, and sizes. Transmission electron microscopy (TEM) showed striations in the nanocrystals that are indicative of a composition modulation, and possibly reveal a phase separation and spinodal decomposition within the nanocrystals. Thermal quenching of the luminescence for both the near band-edge and defect related emissions were observed in the range 60-300 K. The measured activation energies of ∼50-70 meV were related to the presence of shallow donors or acceptors, deep level emissions, and thermal activation and quenching of the luminescence due to the thermal release of electrons from shallow donors to the conduction band or a thermal release of holes from shallow acceptors to the valence band. Spatially integrated CL spectra revealed the existence of broadening and additional components that are consistent with the presence of a composition modulation in the nanocrystals. Spatial localization of the emission in isolated single nanocrystals was studied using monochromatic CL imaging and local CL spectroscopy. CL spectra acquired by a highly localized excitation of individual nanocrystals showed energy shifts in the excitonic luminescence that are consistent with a phase separation into Zn- and Cd-rich regions. The simultaneous appearance of both structural and compositional phase separation for the synthesis of Zn(x)Cd(1-x)Se nanocrystals reveals the complexity and uniqueness of these results.

Free-Energy Barrier of Filling a Spherical Cavity in the Presence of Line Tension: Implication to the Energy Barrier between the Cassie and Wenzel States on a Superhydrophobic Surface with Spherical Cavities.

PubMed

Iwamatsu, Masao

2016-09-20

The free-energy barrier of filling a spherical cavity having an inner wall of various wettabilities is studied. The morphology and free energy of a lens-shaped droplet are determined from the minimum of the free energy. The effect of line tension on the free energy is also studied. Then, the equilibrium contact angle of the droplet is determined from the generalized Young's equation. By increasing the droplet volume within the spherical cavity, the droplet morphology changes from spherical with an equilibrium contact angle of 180° to a lens with a convex meniscus, where the morphological complete drying transition occurs. By further increasing the droplet volume, the meniscus changes from convex to concave. Then, the lens-shaped droplet with concave meniscus spreads over the whole inner wall, resulting in an equilibrium contact angle of 0° to leave a spherical bubble, where the morphological complete wetting transition occurs. Finally, the whole cavity is filled with liquid. The free energy shows a barrier from complete drying to complete wetting as a function of droplet volume, which corresponds to the energy barrier between the Cassie and Wenzel states of the superhydrophobic surface with spherical cavities. The free-energy maximum occurs when the meniscus of the droplet becomes flat, and it is given by an analytic formula. The effect of line tension is expressed by the scaled line tension, and this effect is largest at the free-energy maximum. The positive line tension increases the free-energy maximum, which thus increases the stability of the Cassie superhydrophobic state, whereas the negative line tension destabilizes the superhydrophobic state.

Spectral analysis of the Earth's topographic potential via 2D-DFT: a new data-based degree variance model to degree 90,000

NASA Astrophysics Data System (ADS)

Rexer, Moritz; Hirt, Christian

2015-09-01

Classical degree variance models (such as Kaula's rule or the Tscherning-Rapp model) often rely on low-resolution gravity data and so are subject to extrapolation when used to describe the decay of the gravity field at short spatial scales. This paper presents a new degree variance model based on the recently published GGMplus near-global land areas 220 m resolution gravity maps (Geophys Res Lett 40(16):4279-4283, 2013). We investigate and use a 2D-DFT (discrete Fourier transform) approach to transform GGMplus gravity grids into degree variances. The method is described in detail and its approximation errors are studied using closed-loop experiments. Focus is placed on tiling, azimuth averaging, and windowing effects in the 2D-DFT method and on analytical fitting of degree variances. Approximation errors of the 2D-DFT procedure on the (spherical harmonic) degree variance are found to be at the 10-20 % level. The importance of the reference surface (sphere, ellipsoid or topography) of the gravity data for correct interpretation of degree variance spectra is highlighted. The effect of the underlying mass arrangement (spherical or ellipsoidal approximation) on the degree variances is found to be crucial at short spatial scales. A rule-of-thumb for transformation of spectra between spherical and ellipsoidal approximation is derived. Application of the 2D-DFT on GGMplus gravity maps yields a new degree variance model to degree 90,000. The model is supported by GRACE, GOCE, EGM2008 and forward-modelled gravity at 3 billion land points over all land areas within the SRTM data coverage and provides gravity signal variances at the surface of the topography. The model yields omission errors of 9 mGal for gravity (1.5 cm for geoid effects) at scales of 10 km, 4 mGal (1 mm) at 2-km scales, and 2 mGal (0.2 mm) at 1-km scales.

Plasmoids in relativistic reconnection, from birth to adulthood: first they grow, then they go

NASA Astrophysics Data System (ADS)

Sironi, Lorenzo; Giannios, Dimitrios; Petropoulou, Maria

2016-10-01

Blobs, or quasi-spherical emission regions containing relativistic particles and magnetic fields, are often assumed ad hoc in emission models of relativistic astrophysical jets, yet their physical origin is still not well understood. Here, we employ a suite of large-scale 2D particle-in-cell simulations in electron-positron plasmas to demonstrate that relativistic magnetic reconnection can naturally account for the formation of quasi-spherical plasmoids filled with high-energy particles and magnetic fields. Our simulations extend to unprecedentedly long temporal and spatial scales, so we can capture the asymptotic physics independently of the initial setup. We characterize the properties of the plasmoids, continuously generated as a self-consistent by-product of the reconnection process: they are in rough energy equipartition between particles and magnetic fields; the upper energy cutoff of the plasmoid particle spectrum is proportional to the plasmoid width w, corresponding to a Larmor radius ˜0.2 w; the plasmoids grow in size at ˜0.1 of the speed of light, with most of the growth happening while they are still non-relativistic (`first they grow'); their growth is suppressed once they get accelerated to relativistic speeds by the field line tension, up to the Alfvén speed (`then they go'). The largest plasmoids reach a width wmax ˜ 0.2 L independently of the system length L, they have nearly isotropic particle distributions and contain the highest energy particles, whose Larmor radius is ˜0.03 L. The latter can be regarded as the Hillas criterion for relativistic reconnection. We briefly discuss the implications of our results for the high-energy emission from relativistic jets and pulsar winds.

THE OBSERVED M-{sigma} RELATIONS IMPLY THAT SUPER-MASSIVE BLACK HOLES GROW BY COLD CHAOTIC ACCRETION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nayakshin, Sergei; King, Andrew R.; Power, Chris

We argue that current observations of M-{sigma} relations for galaxies can be used to constrain theories of super-massive black holes (SMBHs) feeding. In particular, assuming that SMBH mass is limited only by the feedback on the gas that feeds it, we show that SMBHs fed via a planar galaxy-scale gas flow, such as a disk or a bar, should be much more massive than their counterparts fed by quasi-spherical inflows. This follows from the relative inefficiency of active galactic nucleus feedback on a flattened inflow. We find that even under the most optimistic conditions for SMBH feedback on flattened inflows,more » the mass at which the SMBH expels the gas disk and terminates its own growth is a factor of several higher than the one established for quasi-spherical inflows. Any beaming of feedback away from the disk and any disk self-shadowing strengthen this result further. Contrary to this theoretical expectation, recent observations have shown that SMBHs in pseudobulge galaxies (which are associated with barred galaxies) are typically under- rather than overmassive when compared with their classical bulge counterparts at a fixed value of {sigma}. We conclude from this that SMBHs are not fed by large (100 pc to many kpc) scale gas disks or bars, most likely because such planar flows are turned into stars too efficiently to allow any SMBH growth. Based on this and other related observational evidence, we argue that most SMBHs grow by chaotic accretion of gas clouds with a small and nearly randomly distributed direction of angular momentum.« less

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: First measurement of Baryon Acoustic Oscillations between redshift 0.8 and 2.2

DOE PAGES

Ata, Metin; Baumgarten, Falk; Bautista, Julian; ...

2017-10-11

We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshiftsmore » $0.8 < z < 2.2$ and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.5$$\\sigma$$. We determine the spherically averaged BAO distance to $z = 1.52$ to 4.4 per cent precision: $$D_V(z=1.52)=3855\\pm170 \\left(r_{\\rm d}/r_{\\rm d, fid}\\right)\\ $$Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat $$\\Lambda$$CDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Using these BAO data alone and marginalizing over the length of the standard ruler, we find $$\\Omega_{\\Lambda} > 0$$ at 6.5$$\\sigma$$ significance when testing a $$\\Lambda$$CDM model with free curvature.« less

Supernovae as seen by off-center observers in a local void

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blomqvist, Michael; Mörtsell, Edvard, E-mail: michaelb@astro.su.se, E-mail: edvard@fysik.su.se

2010-05-01

Inhomogeneous universe models have been proposed as an alternative explanation for the apparent acceleration of the cosmic expansion that does not require dark energy. In the simplest class of inhomogeneous models, we live within a large, spherically symmetric void. Several studies have shown that such a model can be made consistent with many observations, in particular the redshift-luminosity distance relation for type Ia supernovae, provided that the void is of Gpc size and that we live close to the center. Such a scenario challenges the Copernican principle that we do not occupy a special place in the universe. We usemore » the first-year Sloan Digital Sky Survey-II supernova search data set as well as the Constitution supernova data set to put constraints on the observer position in void models, using the fact that off-center observers will observe an anisotropic universe. We first show that a spherically symmetric void can give good fits to the supernova data for an on-center observer, but that the two data sets prefer very different voids. We then continue to show that the observer can be displaced at least fifteen percent of the void scale radius from the center and still give an acceptable fit to the supernova data. When combined with the observed dipole anisotropy of the cosmic microwave background however, we find that the data compells the observer to be located within about one percent of the void scale radius. Based on these results, we conclude that considerable fine-tuning of our position within the void is needed to fit the supernova data, strongly disfavouring the model from a Copernican principle point of view.« less

Shear Wave Generation by Explosions in Anisotropic Crystalline Rock

NASA Astrophysics Data System (ADS)

Rogers-Martinez, M. A.; Sammis, C. G.; Stroujkova, A. F.

2015-12-01

The use of seismic waves to discriminate between earthquakes and underground explosions is complicated by the observation that explosions routinely radiate strong S waves. Whether these S waves are primarily generated by non-linear processes at the source, or by mode conversions and scattering along the path remains an open question. It has been demonstrated that S waves are generated at the source by any mechanism that breaks the spherical symmetry of the explosion. Examples of such mechanisms include tectonic shear stress, spall, and anisotropy in the emplacement medium. Many crystalline rock massifs are transversely isotropic because they contain aligned fractures over a range of scales from microfractures at the grain scale (called the rift) to regional sets of joints. In this study we use a micromechanical damage mechanics to model the fracture damage patterns and seismic radiation generated by explosions in a material in which the initial distribution of fractures has a preferred direction. Our simulations are compared with a set of field experiments in a granite quarry in Barre, VT conducted by New England Research and Weston Geophysical. Barre granite has a strong rift plane of aligned microfractures. Our model captures two important results of these field studies: 1) the spatial extent of rock fracture and generation of S waves depends on the burn-rate of the explosion and 2) the resultant damage is anisotropic with most damage occurring in the preferred direction of the microfractures (the rift plane in the granite). The physical reason damage is enhanced in the rift direction is that the mode I stress intensity factor is large for each fracture in the array of parallel fractures in the rift plane. Tensile opening on the rift plane plus sliding on the preexisting fractures make strong non-spherical contributions to the moment tensor in the far-field.

Characterization of the crystal structure, kinematics, stresses and rotations in angular granular quartz during compaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurley, Ryan C.; Herbold, Eric B.; Pagan, Darren C.

Three-dimensional X-ray diffraction (3DXRD), a method for quantifying the position, orientation and elastic strain of large ensembles of single crystals, has recently emerged as an important tool for studying the mechanical response of granular materials during compaction. Applications have demonstrated the utility of 3DXRD and X-ray computed tomography (XRCT) for assessing strains, particle stresses and orientations, inter-particle contacts and forces, particle fracture mechanics, and porosity evolution in situ . Although past studies employing 3DXRD and XRCT have elucidated the mechanics of spherical particle packings and angular particle packings with a small number of particles, there has been limited effort tomore » date in studying angular particle packings with a large number of particles and in comparing the mechanics of these packings with those composed of a large number of spherical particles. Therefore, the focus of the present paper is on the mechanics of several hundred angular particles during compaction using in situ 3DXRD to study the crystal structure, kinematics, stresses and rotations of angular quartz grains. Comparisons are also made between the compaction response of angular grains and that of spherical grains, and stress-induced twinning within individual grains is discussed.« less

Characterization of the crystal structure, kinematics, stresses and rotations in angular granular quartz during compaction

DOE PAGES

Hurley, Ryan C.; Herbold, Eric B.; Pagan, Darren C.

2018-06-28

Three-dimensional X-ray diffraction (3DXRD), a method for quantifying the position, orientation and elastic strain of large ensembles of single crystals, has recently emerged as an important tool for studying the mechanical response of granular materials during compaction. Applications have demonstrated the utility of 3DXRD and X-ray computed tomography (XRCT) for assessing strains, particle stresses and orientations, inter-particle contacts and forces, particle fracture mechanics, and porosity evolution in situ . Although past studies employing 3DXRD and XRCT have elucidated the mechanics of spherical particle packings and angular particle packings with a small number of particles, there has been limited effort tomore » date in studying angular particle packings with a large number of particles and in comparing the mechanics of these packings with those composed of a large number of spherical particles. Therefore, the focus of the present paper is on the mechanics of several hundred angular particles during compaction using in situ 3DXRD to study the crystal structure, kinematics, stresses and rotations of angular quartz grains. Comparisons are also made between the compaction response of angular grains and that of spherical grains, and stress-induced twinning within individual grains is discussed.« less

Gravitationally neutral dark matter-dark antimatter universe crystal with epochs of decelerated and accelerated expansion

NASA Astrophysics Data System (ADS)

Gribov, I. A.; Trigger, S. A.

2016-11-01

A large-scale self-similar crystallized phase of finite gravitationally neutral universe (GNU)—huge GNU-ball—with spherical 2D-boundary immersed into an endless empty 3D- space is considered. The main principal assumptions of this universe model are: (1) existence of stable elementary particles-antiparticles with the opposite gravitational “charges” (M+gr and M -gr), which have the same positive inertial mass M in = |M ±gr | ≥ 0 and are equally presented in the universe during all universe evolution epochs; (2) the gravitational interaction between the masses of the opposite charges” is repulsive; (3) the unbroken baryon-antibaryon symmetry; (4) M+gr-M-gr “charges” symmetry, valid for two equally presented matter-antimatter GNU-components: (a) ordinary matter (OM)-ordinary antimatter (OAM), (b) dark matter (DM)-dark antimatter (DAM). The GNU-ball is weightless crystallized dust of equally presented, mutually repulsive (OM+DM) clusters and (OAM+DAM) anticlusters. Newtonian GNU-hydrodynamics gives the observable spatial flatness and ideal Hubble flow. The GNU in the obtained large-scale self-similar crystallized phase preserves absence of the cluster-anticluster collisions and simultaneously explains the observable large-scale universe phenomena: (1) the absence of the matter-antimatter clusters annihilation, (2) the self-similar Hubble flow stability and homogeneity, (3) flatness, (4) bubble and cosmic-net structures as 3D-2D-1D decrystallization phases with decelerative (a ≤ 0) and accelerative (a ≥ 0) expansion epochs, (5) the dark energy (DE) phenomena with Λ VACUUM = 0, (6) the DE and DM fine-tuning nature and predicts (7) evaporation into isolated huge M±gr superclusters without Big Rip.

Effects of Turbulence on Settling Velocities of Synthetic and Natural Particles

NASA Astrophysics Data System (ADS)

Jacobs, C.; Jendrassak, M.; Gurka, R.; Hackett, E. E.

2014-12-01

For large-scale sediment transport predictions, an important parameter is the settling or terminal velocity of particles because it plays a key role in determining the concentration of sediment particles within the water column as well as the deposition rate of particles onto the seabed. The settling velocity of particles is influenced by the fluid dynamic environment as well as attributes of the particle, such as its size, shape, and density. This laboratory study examines the effects of turbulence, generated by an oscillating grid, on both synthetic and natural particles for a range of flow conditions. Because synthetic particles are spherical, they serve as a reference for the natural particles that are irregular in shape. Particle image velocimetry (PIV) and high-speed imaging systems were used simultaneously to study the interaction between the fluid mechanics and sediment particles' dynamics in a tank. The particles' dynamics were analyzed using a custom two-dimensional tracking algorithm used to obtain distributions of the particle's velocity and acceleration. Turbulence properties, such as root-mean-square turbulent velocity and vorticity, were calculated from the PIV data. Results are classified by Stokes number, which was based-on the integral scale deduced from the auto-correlation function of velocity. We find particles with large Stokes numbers are unaffected by the turbulence, while particles with small Stokes numbers primarily show an increase in settling velocity in comparison to stagnant flow. The results also show an inverse relationship between Stokes number and standard deviation of the settling velocity. This research enables a better understanding of the interdependence between particles and turbulent flow, which can be used to improve parameterizations in large-scale sediment transport models.

Evaluation of Optimal Formulas for Gravitational Tensors up to Gravitational Curvatures of a Tesseroid

NASA Astrophysics Data System (ADS)

Deng, Xiao-Le; Shen, Wen-Bin

2018-01-01

The forward modeling of the topographic effects of the gravitational parameters in the gravity field is a fundamental topic in geodesy and geophysics. Since the gravitational effects, including for instance the gravitational potential (GP), the gravity vector (GV) and the gravity gradient tensor (GGT), of the topographic (or isostatic) mass reduction have been expanded by adding the gravitational curvatures (GC) in geoscience, it is crucial to find efficient numerical approaches to evaluate these effects. In this paper, the GC formulas of a tesseroid in Cartesian integral kernels are derived in 3D/2D forms. Three generally used numerical approaches for computing the topographic effects (e.g., GP, GV, GGT, GC) of a tesseroid are studied, including the Taylor Series Expansion (TSE), Gauss-Legendre Quadrature (GLQ) and Newton-Cotes Quadrature (NCQ) approaches. Numerical investigations show that the GC formulas in Cartesian integral kernels are more efficient if compared to the previously given GC formulas in spherical integral kernels: by exploiting the 3D TSE second-order formulas, the computational burden associated with the former is 46%, as an average, of that associated with the latter. The GLQ behaves better than the 3D/2D TSE and NCQ in terms of accuracy and computational time. In addition, the effects of a spherical shell's thickness and large-scale geocentric distance on the GP, GV, GGT and GC functionals have been studied with the 3D TSE second-order formulas as well. The relative approximation errors of the GC functionals are larger with the thicker spherical shell, which are the same as those of the GP, GV and GGT. Finally, the very-near-area problem and polar singularity problem have been considered by the numerical methods of the 3D TSE, GLQ and NCQ. The relative approximation errors of the GC components are larger than those of the GP, GV and GGT, especially at the very near area. Compared to the GC formulas in spherical integral kernels, these new GC formulas can avoid the polar singularity problem.

A global estimate of the Earth's magnetic crustal thickness

NASA Astrophysics Data System (ADS)

Vervelidou, Foteini; Thébault, Erwan

2014-05-01

The Earth's lithosphere is considered to be magnetic only down to the Curie isotherm. Therefore the Curie isotherm can, in principle, be estimated by analysis of magnetic data. Here, we propose such an analysis in the spectral domain by means of a newly introduced regional spatial power spectrum. This spectrum is based on the Revised Spherical Cap Harmonic Analysis (R-SCHA) formalism (Thébault et al., 2006). We briefly discuss its properties and its relationship with the Spherical Harmonic spatial power spectrum. This relationship allows us to adapt any theoretical expression of the lithospheric field power spectrum expressed in Spherical Harmonic degrees to the regional formulation. We compared previously published statistical expressions (Jackson, 1994 ; Voorhies et al., 2002) to the recent lithospheric field models derived from the CHAMP and airborne measurements and we finally developed a new statistical form for the power spectrum of the Earth's magnetic lithosphere that we think provides more consistent results. This expression depends on the mean magnetization, the mean crustal thickness and a power law value that describes the amount of spatial correlation of the sources. In this study, we make a combine use of the R-SCHA surface power spectrum and this statistical form. We conduct a series of regional spectral analyses for the entire Earth. For each region, we estimate the R-SCHA surface power spectrum of the NGDC-720 Spherical Harmonic model (Maus, 2010). We then fit each of these observational spectra to the statistical expression of the power spectrum of the Earth's lithosphere. By doing so, we estimate the large wavelengths of the magnetic crustal thickness on a global scale that are not accessible directly from the magnetic measurements due to the masking core field. We then discuss these results and compare them to the results we obtained by conducting a similar spectral analysis, but this time in the cartesian coordinates, by means of a published statistical expression (Maus et al., 1997). We also compare our results to crustal thickness global maps derived by means of additional geophysical data (Purucker et al., 2002).

Design and analysis of multilayer x ray/XUV microscope

NASA Technical Reports Server (NTRS)

Shealy, David L.

1990-01-01

The design and analysis of a large number of normal incidence multilayer x ray microscopes based on the spherical mirror Schwarzschild configuration is examined. Design equations for the spherical mirror Schwarzschild microscopes are summarized and used to evaluate mirror parameters for microscopes with magnifications ranging from 2 to 50x. Ray tracing and diffraction analyses are carried out for many microscope configurations to determine image resolution as a function of system parameters. The results are summarized in three publication included herein. A preliminary study of advanced reflecting microscope configurations, where aspherics are used in place of the spherical microscope mirror elements, has indicated that the aspherical elements will improve off-axis image resolution and increase the effective field of view.

The bottom of the universe: Flat earth science in the Age of Encounter.

PubMed

Allegro, James J

2017-03-01

This essay challenges the dominance of the spherical earth model in fifteenth- and early-sixteenth-century Western European thought. It examines parallel strains of Latin and vernacular writing that cast doubt on the existence of the southern hemisphere. Three factors shaped the alternate accounts of the earth as a plane and disk put forward by these sources: (1) the unsettling effects of maritime expansion on scientific thought; (2) the revival of interest in early Christian criticism of the spherical earth; and (3) a rigid empirical stance toward entities too large to observe in their entirety, including the earth. Criticism of the spherical earth model faded in the decades after Magellan's crew returned from circuiting the earth in 1522.

Dielectric Covered Planar Antennas

NASA Technical Reports Server (NTRS)

Llombart Juan, Nuria (Inventor); Lee, Choonsup (Inventor); Chattopadhyay, Goutam (Inventor); Gill, John J. (Inventor); Skalare, Anders J. (Inventor); Siegel, Peter H. (Inventor)

2014-01-01

An antenna element suitable for integrated arrays at terahertz frequencies is disclosed. The antenna element comprises an extended spherical (e.g. hemispherical) semiconductor lens, e.g. silicon, antenna fed by a leaky wave waveguide feed. The extended spherical lens comprises a substantially spherical lens adjacent a substantially planar lens extension. A couple of TE/TM leaky wave modes are excited in a resonant cavity formed between a ground plane and the substantially planar lens extension by a waveguide block coupled to the ground plane. Due to these modes, the primary feed radiates inside the lens with a directive pattern that illuminates a small sector of the lens. The antenna structure is compatible with known semiconductor fabrication technology and enables production of large format imaging arrays.

Evolution and statistics of non-sphericity of dark matter halos from cosmological N-body simulation

NASA Astrophysics Data System (ADS)

Suto, Daichi; Kitayama, Tetsu; Nishimichi, Takahiro; Sasaki, Shin; Suto, Yasushi

2016-12-01

We revisit the non-sphericity of cluster-mass-scale halos from cosmological N-body simulation on the basis of triaxial modeling. In order to understand the difference between the simulation results and the conventional ellipsoidal collapse model (EC), we first consider the evolution of individual simulated halos. The major difference between EC and the simulation becomes appreciable after the turnaround epoch. Moreover, it is sensitive to the individual evolution history of each halo. Despite such strong dependence on individual halos, the resulting non-sphericity of halos exhibits weak but robust mass dependence in a statistical fashion; massive halos are more spherical up to the turnaround, but gradually become less spherical by z = 0. This is clearly inconsistent with the EC prediction: massive halos are usually more spherical. In addition, at z = 0, inner regions of the simulated halos are less spherical than outer regions; that is, the density distribution inside the halos is highly inhomogeneous and therefore not self-similar (concentric ellipsoids with the same axis ratio and orientation). This is also inconsistent with the homogeneous density distribution that is commonly assumed in EC. Since most of previous fitting formulae for the probability distribution function (PDF) of the axis ratio of triaxial ellipsoids have been constructed under the self-similarity assumption, they are not accurate. Indeed, we compute the PDF of the projected axis ratio a1/a2 directly from the simulation data without the self-similarity assumption, and find that it is very sensitive to the assumption. The latter needs to be carefully taken into account in direct comparison with observations, and therefore we provide an empirical fitting formula for the PDF of a1/a2. Our preliminary analysis suggests that the derived PDF of a1/a2 roughly agrees with the current weak-lensing observations. More importantly, the present results will be useful for future exploration of the non-sphericity of clusters in X-ray and optical observations.

Wave Amplitude Dependent Engineering Model of Propellant Slosh in Spherical Tanks

NASA Technical Reports Server (NTRS)

Brodnick, Jacob; Westra, Douglas G.; Eberhart, Chad J.; Yang, Hong Q.; West, Jeffrey S.

2016-01-01

Liquid propellant slosh is often a concern for the controllability of flight vehicles. Anti-slosh devices are traditionally included in propellant tank designs to limit the amount of sloshing allowed during flight. These devices and any necessary supports can be quite heavy to meet various structural requirements. Some of the burden on anti-slosh devices can be relieved by exploiting the nonlinear behavior of slosh waves in bare smooth wall tanks. A nonlinear regime slosh model for bare spherical tanks was developed through a joint analytical and experimental effort by NASA/MSFC. The developed slosh model accounts for the large damping inherent in nonlinear slosh waves which is more accurate and drives conservatism from vehicle stability analyses that use traditional bare tank slosh models. A more accurate slosh model will result in more realistic predicted slosh forces during flight reducing or removing the need for active controls during a maneuver or baffles in the tank design. Lower control gains and smaller or fewer tank baffles can reduce cost and system complexity while increasing vehicle performance. Both Computational Fluid Dynamics (CFD) simulation and slosh testing of three different spherical tank geometries were performed to develop the proposed slosh model. Several important findings were made during this effort in addition to determining the parameters to the nonlinear regime slosh model. The linear regime slosh damping trend for spherical tanks reported in NASA SP-106 was shown to be inaccurate for certain regions of a tank. Additionally, transition to the nonlinear regime for spherical tanks was only found to occur at very large wave amplitudes in the lower hemisphere and was a strong function of the propellant fill level in the upper hemisphere. The nonlinear regime damping trend was also found to be a function of the propellant fill level.

Objective for EUV microscopy, EUV lithography, and x-ray imaging

DOEpatents

Bitter, Manfred; Hill, Kenneth W.; Efthimion, Philip

2016-05-03

Disclosed is an imaging apparatus for EUV spectroscopy, EUV microscopy, EUV lithography, and x-ray imaging. This new imaging apparatus could, in particular, make significant contributions to EUV lithography at wavelengths in the range from 10 to 15 nm, which is presently being developed for the manufacturing of the next-generation integrated circuits. The disclosure provides a novel adjustable imaging apparatus that allows for the production of stigmatic images in x-ray imaging, EUV imaging, and EUVL. The imaging apparatus of the present invention incorporates additional properties compared to previously described objectives. The use of a pair of spherical reflectors containing a concave and convex arrangement has been applied to a EUV imaging system to allow for the image and optics to all be placed on the same side of a vacuum chamber. Additionally, the two spherical reflector segments previously described have been replaced by two full spheres or, more precisely, two spherical annuli, so that the total photon throughput is largely increased. Finally, the range of permissible Bragg angles and possible magnifications of the objective has been largely increased.

Jetting from impact of a spherical drop with a deep layer

NASA Astrophysics Data System (ADS)

Zhang, Li; Toole, Jameson; Fazzaa, Kamel; Deegan, Robert; Deegan Group Team; X-Ray Science Division, Advanced Photon Source Collaboration

2011-11-01

We performed an experimental study of jets during the impact of a spherical drop with a deep layer of same liquid. Using high speed optical and X-ray imaging, we observe two types of jets: the so-called ejecta sheet which emerges almost immediately after impact and the lamella which emerges later. For high Reynolds number the two jets are distinct, while for low Reynolds number the two jets combine into a single continuous jet. We also measured the emergence time, speed, and position of the ejecta sheet and found simple scaling relations for these quantities.

Spherical nanoindentation stress-strain curves of commercially pure titanium and Ti-6Al-4V

DOE Data Explorer

Weaver, Jordan S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Priddy, Matthew W. [Georgia Inst. of Technology, Atlanta, GA (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidindi, Surya R. [Georgia Inst. of Technology, Atlanta, GA (United States)

2016-07-27

Spherical nanoindentation combined with electron back-scattered diffraction was employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti for commercially pure (CP-Ti) and alloyed (Ti-64) titanium. In addition, alpha-beta Ti (single colony) grains were characterized. The data set includes the nanoindentation force, displacement, and contact stiffness, the nanoindentation stress-strain analysis, and the alpha-Ti crystal orientations. Details of the samples and experimental protocols can be found in Weaver et al. (2016) Acta Materialia doi:10.1016/j.actamat.2016.06.053.

Dynamics and universal scaling law in geometrically-controlled sessile drop evaporation

PubMed Central

Sáenz, P. J.; Wray, A. W.; Che, Z.; Matar, O. K.; Valluri, P.; Kim, J.; Sefiane, K.

2017-01-01

The evaporation of a liquid drop on a solid substrate is a remarkably common phenomenon. Yet, the complexity of the underlying mechanisms has constrained previous studies to spherically symmetric configurations. Here we investigate well-defined, non-spherical evaporating drops of pure liquids and binary mixtures. We deduce a universal scaling law for the evaporation rate valid for any shape and demonstrate that more curved regions lead to preferential localized depositions in particle-laden drops. Furthermore, geometry induces well-defined flow structures within the drop that change according to the driving mechanism. In the case of binary mixtures, geometry dictates the spatial segregation of the more volatile component as it is depleted. Our results suggest that the drop geometry can be exploited to prescribe the particle deposition and evaporative dynamics of pure drops and the mixing characteristics of multicomponent drops, which may be of interest to a wide range of industrial and scientific applications. PMID:28294114

Dynamics and universal scaling law in geometrically-controlled sessile drop evaporation.

PubMed

Sáenz, P J; Wray, A W; Che, Z; Matar, O K; Valluri, P; Kim, J; Sefiane, K

2017-03-15

The evaporation of a liquid drop on a solid substrate is a remarkably common phenomenon. Yet, the complexity of the underlying mechanisms has constrained previous studies to spherically symmetric configurations. Here we investigate well-defined, non-spherical evaporating drops of pure liquids and binary mixtures. We deduce a universal scaling law for the evaporation rate valid for any shape and demonstrate that more curved regions lead to preferential localized depositions in particle-laden drops. Furthermore, geometry induces well-defined flow structures within the drop that change according to the driving mechanism. In the case of binary mixtures, geometry dictates the spatial segregation of the more volatile component as it is depleted. Our results suggest that the drop geometry can be exploited to prescribe the particle deposition and evaporative dynamics of pure drops and the mixing characteristics of multicomponent drops, which may be of interest to a wide range of industrial and scientific applications.

Probing Seismically Melting Induced Mantle Heterogeneities in Thermal-chemical Convection Models

NASA Astrophysics Data System (ADS)

Heck, H. V.; Davies, H.; Nowacki, A.; Wookey, J. M.

2015-12-01

Two regions at the base of the Earth's mantle (the Large Low-Shear Velocity Provinces) pose a fundamental problem in understanding large-scale mantle dynamics and history. Are they dense piles of (possibly primordial) material separated from mantle circulation, or large-scale thermal features which are part of global mantle convection? Or some combination of the two? We use our numerical 3D spherical mantle convection code to perform simulations of the Earths mantle dynamical evolution. We drive the surface velocity of the model according to 200 Ma plate motion reconstructions, to arrive at Earth-like structures in the mantle at present day. Variations in bulk chemistry will be tracked in two ways: 1) by starting the calculations with a (primordial) dense layer at the base of the mantle, and 2) by tracking basalt fraction which is fractionated upon melting close to the surface. The resulting distribution of chemical heterogeneity and temperature will be converted to seismic velocities. This will be done with a thermodynamical database (Stixrude & Lithgow-Bertelloni, GJI, 2005, 2011), allowing us to compare the model with previous observations of triplications and waveform complexity near the margins of the LLSVPs. These observations have been taken as proof that strong chemical variations are present; our simulations can be used to show whether this is true, or if purely thermal convection can also cause these features. We simulate finite-frequency, 3D seismograms at ~5 s period and compare these with previous studies.

Diagnostics for PLX-alpha

NASA Astrophysics Data System (ADS)

Gilmore, Mark; Hsu, Scott

2015-11-01

The goal of the Plasma Liner eXperiment PLX-alpha at Los Alamos National Laboratory is to establish the viability of creating a spherically imploding plasma liner for MIF and HED applications, using a spherical array of supersonic plasma jets launched by innovative contoured-gap coaxial plasma guns. PLX- α experiments will focus in particular on establishing the ram pressure and uniformity scalings of partial and fully spherical plasma liners. In order to characterize these parameters experimentally, a suite of diagnostics is planned, including multi-camera fast imaging, a 16-channel visible interferometer (upgraded from 8 channels) with reconfigurable, fiber-coupled front end, and visible and VUV high-resolution and survey spectroscopy. Tomographic reconstruction and data fusion techniques will be used in conjunction with interferometry, imaging, and synthetic diagnostics from modeling to characterize liner uniformity in 3D. Diagnostic and data analysis design, implementation, and status will be presented. Supported by the Advanced Research Projects Agency - Energy - U.S. Department of Energy.

A New Innovative Spherical Cermet Nuclear Fuel Element to Achieve an Ultra-Long Core Life for use in Grid-Appropriate LWRs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senor, David J.; Painter, Chad L.; Geelhood, Ken J.

2007-12-01

Spherical cermet fuel elements are proposed for use in the Atoms For Peace Reactor (AFPR-100) concept. AFPR-100 is a small-scale, inherently safe, proliferation-resistant reactor that would be ideal for deployment to nations with emerging economies that decide to select nuclear power for the generation of carbon-free electricity. The basic concept of the AFPR core is a water-cooled fixed particle bed, randomly packed with spherical fuel elements. The flow of coolant within the particle bed is at such a low rate that the bed does not fluidize. This report summarizes an approach to fuel fabrication, results associated with fuel performance modeling,more » core neutronics and thermal hydraulics analyses demonstrating a ~20 year core life, and a conclusion that the proliferation resistance of the AFPR reactor concept is high.« less

The numerical design of a spherical baroclinic experiment for Spacelab flights

NASA Technical Reports Server (NTRS)

Fowlis, W. W.; Roberts, G. O.

1982-01-01

The near-zero G environment of Spacelab is the basis of a true spherical experimental model of synoptic scale baroclinic atmospheric processes, using a radial dielectric body force analogous to gravity over a volume of liquid within two concentric spheres. The baroclinic motions are generated by corotating the spheres and imposing thermal boundary conditions, such that the liquid is subjected to a stable radial gradient and a latitudinal gradient. Owing to mathematical difficulties associated with the spherical geometry, quantitative design criteria can be acquired only by means of numerical models. The procedure adopted required the development of two computer codes based on the Navier-Stokes equations. The codes, of which the first calculates axisymmetric steady flow solutions and the second determines the growth or decay rates of linear wave perturbations with different wave numbers, are combined to generate marginal stability curves.

Field-Induced and Thermal Electron Currents from Earthed Spherical Emitters

NASA Astrophysics Data System (ADS)

Holgate, J. T.; Coppins, M.

2017-04-01

The theories of electron emission from planar surfaces are well understood, but they are not suitable for describing emission from spherical surfaces; their incorrect application to highly curved, nanometer-scale surfaces can overestimate the emitted current by several orders of magnitude. This inaccuracy is of particular concern for describing modern nanoscale electron sources, which continue to be modeled using the planar equations. In this paper, the field-induced and thermal currents are treated in a unified way to produce Fowler-Nordheim-type and Richardson-Schottky-type equations for the emitted current density from earthed nanoscale spherical surfaces. The limits of applicability of these derived expressions are considered along with the energy spectra of the emitted electrons. Within the relevant limits of validity, these equations are shown to reproduce the results of precise numerical calculations of the emitted current densities. The methods used here are adaptable to other one-dimensional emission problems.

Time-dependent corona models - Scaling laws

NASA Technical Reports Server (NTRS)

Korevaar, P.; Martens, P. C. H.

1989-01-01

Scaling laws are derived for the one-dimensional time-dependent Euler equations that describe the evolution of a spherically symmetric stellar atmosphere. With these scaling laws the results of the time-dependent calculations by Korevaar (1989) obtained for one star are applicable over the whole Hertzsprung-Russell diagram and even to elliptic galaxies. The scaling is exact for stars with the same M/R-ratio and a good approximation for stars with a different M/R-ratio. The global relaxation oscillation found by Korevaar (1989) is scaled to main sequence stars, a solar coronal hole, cool giants and elliptic galaxies.

Spreading law of non-Newtonian power-law liquids on a spherical substrate by an energy-balance approach.

PubMed

Iwamatsu, Masao

2017-07-01

The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids, both shear-thickening and shear-thinning liquids, that completely wet a spherical substrate is theoretically investigated in the capillary-controlled spreading regime. The crater-shaped droplet model with the wedge-shaped meniscus near the three-phase contact line is used to calculate the viscous dissipation near the contact line. Then the energy balance approach is adopted to derive the equation that governs the evolution of the contact line. The time evolution of the dynamic contact angle θ of a droplet obeys a power law θ∼t^{-α} with the spreading exponent α, which is different from Tanner's law for Newtonian liquids and those for non-Newtonian liquids on a flat substrate. Furthermore, the line-tension dominated spreading, which could be realized on a spherical substrate for late-stage of spreading when the contact angle becomes low and the curvature of the contact line becomes large, is also investigated.

Inertial migrations of cylindrical particles in rectangular microchannels: Variations of equilibrium positions and equivalent diameters

NASA Astrophysics Data System (ADS)

Su, Jinghong; Chen, Xiaodong; Hu, Guoqing

2018-03-01

Inertial migration has emerged as an efficient tool for manipulating both biological and engineered particles that commonly exist with non-spherical shapes in microfluidic devices. There have been numerous studies on the inertial migration of spherical particles, whereas the non-spherical particles are still largely unexplored. Here, we conduct three-dimensional direct numerical simulations to study the inertial migration of rigid cylindrical particles in rectangular microchannels with different width/height ratios under the channel Reynolds numbers (Re) varying from 50 to 400. Cylindrical particles with different length/diameter ratios and blockage ratios are also concerned. Distributions of surface force with the change of rotation angle show that surface stresses acting on the particle end near the wall are the major contributors to the particle rotation. We obtain lift forces experienced by cylindrical particles at different lateral positions on cross sections of two types of microchannels at various Re. It is found that there are always four stable equilibrium positions on the cross section of a square channel, while the stable positions are two or four in a rectangular channel, depending on Re. By comparing the equilibrium positions of cylindrical particles and spherical particles, we demonstrate that the equivalent diameter of cylindrical particles monotonously increases with Re. Our work indicates the influence of a non-spherical shape on the inertial migration and can be useful for the precise manipulation of non-spherical particles.

Lattice Boltzmann Simulation of Kinetic Isotope Effect During Snow Crystal Formation

NASA Astrophysics Data System (ADS)

Lu, G.; Depaolo, D. J.; Kang, Q.; Zhang, D.

2007-12-01

The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically-symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over- saturation, determines crystal morphology, there are no quantitative models that relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be direct relationships between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D lattice Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. Crystal growth patterns can be varied between random growth and deterministic growth (along the maximum concentration gradient for example). The input parameters needed are the isotope- dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the condensation coefficient for ice is uncertain. The ratio D/k is a length (order 1 micron) that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions. Our calculations confirm that the crystal/vapor isotopic fractionation approaches the equilibrium value, and the crystals are compact (circular in 2D) as the saturation factor approaches unity (S= 1.0). However, few natural crystals form under such conditions. At higher oversaturation (e.g. S = 1.2), dendritic crystals of millimeter size develop on timescales appropriate to cloud processes, and kinetic effects control isotopic fractionation. Fractionation factors for dendritic crystals are similar to those predicted by the spherical diffusion model, but the model also gives estimates of crystal heterogeneity. Dendritic crystals are constrained to be relatively large, with dimension much greater than about 20D/k. The most difficult aspect of the modeling is to account for the large density difference between air and ice, which requires us to use a fictitious higher density for the vapor-oversaturated air and scale the crystal growth time accordingly. An approach using a larger scale simulation and the domain decomposition method can provide a vapor flux for a nested smaller scale calculation. The results clarify the controls on crystal growth, and the relationships between saturation state, growth rate, crystal morphology and isotopic fractionation.

Characteristic microwave-background distortions from collapsing spherical domain walls

NASA Technical Reports Server (NTRS)

Goetz, Guenter; Notzold, Dirk

1990-01-01

The redshift distortion induced by collapsing spherical domain walls is calculated. The most frequent microwave background distortions are found to occur at large angles in the form of blue disks. This is the angular region currently measured by the COBE satellite. COBE could therefore detect signals predicted here for domain walls with surface energy density of the order of MeV. Such values for sigma are proposed in the late-time phase-transition scenario of Hill et al. (1989).

Single-axis four-mirror system: large spherical primary and small fields

NASA Astrophysics Data System (ADS)

Baranne, Andre

1998-08-01

A catoptric corrector of modest size can be used for large spherical primaries, easily integrated at the prime focus, this corrector gives back to the system, aspect and properties of 2-mirrors classical telescopes. In the last few years, progress in active and adaptative optics makes possible a lot of things, progress in measuring distances, new ideas on optical coatings, new materials and so on in a near future, all that makes the instrumentalist dreamy It is said that nobody knows today if the size of 3rd millennium telescopes will be limited or not by a theoretical, physical or technical phenomenon, thus let us imagine but with thoughtfulness because our projects will be surely restricted by financial considerations

From the Scale Model of the Sky to the Armillary Sphere

ERIC Educational Resources Information Center

Gangui, Alejandro; Casazza, Roberto; Paex, Carlos

2014-01-01

It is customary to employ a semi-spherical scale model to describe the apparent path of the Sun across the sky, whether it be its diurnal motion or its variation throughout the year. A flat surface and three bent semi-rigid wires (representing the three solar arcs during solstices and equinoxes) will do the job. On the other hand, since very early…

Planning for Coupling Effects in Bitoric Mixed Astigmatism Ablative Treatments.

PubMed

Alpins, Noel; Ong, James K Y; Stamatelatos, George

2017-08-01

To demonstrate how to determine the historical coupling adjustments of bitoric mixed astigmatism ablative treatments and how to use these historical coupling adjustments to adjust future bitoric treatments. The individual coupling adjustments of the myopic and hyperopic cylindrical components of a bitoric treatment were derived empirically from a retrospective study where the theoretical combined treatment effect on spherical equivalent was compared to the actual change in refractive spherical equivalent. The coupling adjustments that provided the best fit in both mean and standard deviation were determined to be the historical coupling adjustments. Theoretical treatments that incorporated the historical coupling adjustments were then calculated. The actual distribution of postoperative spherical equivalent errors was compared to the theoretically adjusted distribution. The study group comprised 242 eyes and included 118 virgin right eyes and 124 virgin left eyes of 155 individuals. For the laser used, the myopic coupling adjustment was -0.02 and the hyperopic coupling adjustment was 0.30, as derived by global nonlinear optimization. This implies that almost no adjustment of the myopic component of the bitoric treatment is necessary, but that the hyperopic component of the bitoric treatment generates a large amount of unintended spherical shift. The theoretically adjusted treatments targeted zero mean spherical equivalent error, as intended, and the distribution of the theoretical spherical equivalent errors had the same spread as the distribution of actual postoperative spherical equivalent errors. Bitoric mixed astigmatism ablative treatments may display non-trivial coupling effects. Historical coupling adjustments should be taken into consideration when planning mixed astigmatism treatments to improve surgical outcomes. [J Refract Surg. 2017;33(8):545-551.]. Copyright 2017, SLACK Incorporated.

Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms.

PubMed

Lefevre, Sjannie; McKenzie, David J; Nilsson, Göran E

2017-09-01

Some recent modelling papers projecting smaller fish sizes and catches in a warmer future are based on erroneous assumptions regarding (i) the scaling of gills with body mass and (ii) the energetic cost of 'maintenance'. Assumption (i) posits that insurmountable geometric constraints prevent respiratory surface areas from growing as fast as body volume. It is argued that these constraints explain allometric scaling of energy metabolism, whereby larger fishes have relatively lower mass-specific metabolic rates. Assumption (ii) concludes that when fishes reach a certain size, basal oxygen demands will not be met, because of assumption (i). We here demonstrate unequivocally, by applying accepted physiological principles with reference to the existing literature, that these assumptions are not valid. Gills are folded surfaces, where the scaling of surface area to volume is not constrained by spherical geometry. The gill surface area can, in fact, increase linearly in proportion to gill volume and body mass. We cite the large body of evidence demonstrating that respiratory surface areas in fishes reflect metabolic needs, not vice versa, which explains the large interspecific variation in scaling of gill surface areas. Finally, we point out that future studies basing their predictions on models should incorporate factors for scaling of metabolic rate and for temperature effects on metabolism, which agree with measured values, and should account for interspecific variation in scaling and temperature effects. It is possible that some fishes will become smaller in the future, but to make reliable predictions the underlying mechanisms need to be identified and sought elsewhere than in geometric constraints on gill surface area. Furthermore, to ensure that useful information is conveyed to the public and policymakers about the possible effects of climate change, it is necessary to improve communication and congruity between fish physiologists and fisheries scientists. © 2017 John Wiley & Sons Ltd.

Critical gravitational collapse with angular momentum. II. Soft equations of state

NASA Astrophysics Data System (ADS)

Gundlach, Carsten; Baumgarte, Thomas W.

2018-03-01

We study critical phenomena in the collapse of rotating ultrarelativistic perfect fluids, in which the pressure P is related to the total energy density ρ by P =κ ρ , where κ is a constant. We generalize earlier results for radiation fluids with κ =1 /3 to other values of κ , focusing on κ <1 /9 . For 1 /9 <κ ≲0.49 , the critical solution has only one unstable, growing mode, which is spherically symmetric. For supercritical data it controls the black-hole mass, while for subcritical data it controls the maximum density. For κ <1 /9 , an additional axial l =1 mode becomes unstable. This controls either the black-hole angular momentum, or the maximum angular velocity. In theory, the additional unstable l =1 mode changes the nature of the black-hole threshold completely: at sufficiently large initial rotation rates Ω and sufficient fine-tuning of the initial data to the black-hole threshold we expect to observe nontrivial universal scaling functions (familiar from critical phase transitions in thermodynamics) governing the black-hole mass and angular momentum, and, with further fine-tuning, eventually a finite black-hole mass almost everywhere on the threshold. In practice, however, the second unstable mode grows so slowly that we do not observe this breakdown of scaling at the level of fine-tuning we can achieve, nor systematic deviations from the leading-order power-law scalings of the black-hole mass. We do see systematic effects in the black-hole angular momentum, but it is not clear yet if these are due to the predicted nontrivial scaling functions, or to nonlinear effects at sufficiently large initial angular momentum (which we do not account for in our theoretical model).

Magnetic potential, vector and gradient tensor fields of a tesseroid in a geocentric spherical coordinate system

NASA Astrophysics Data System (ADS)

Du, Jinsong; Chen, Chao; Lesur, Vincent; Lane, Richard; Wang, Huilin

2015-06-01

We examined the mathematical and computational aspects of the magnetic potential, vector and gradient tensor fields of a tesseroid in a geocentric spherical coordinate system (SCS). This work is relevant for 3-D modelling that is performed with lithospheric vertical scales and global, continent or large regional horizontal scales. The curvature of the Earth is significant at these scales and hence, a SCS is more appropriate than the usual Cartesian coordinate system (CCS). The 3-D arrays of spherical prisms (SP; `tesseroids') can be used to model the response of volumes with variable magnetic properties. Analytical solutions do not exist for these model elements and numerical or mixed numerical and analytical solutions must be employed. We compared various methods for calculating the response in terms of accuracy and computational efficiency. The methods were (1) the spherical coordinate magnetic dipole method (MD), (2) variants of the 3-D Gauss-Legendre quadrature integration method (3-D GLQI) with (i) different numbers of nodes in each of the three directions, and (ii) models where we subdivided each SP into a number of smaller tesseroid volume elements, (3) a procedure that we term revised Gauss-Legendre quadrature integration (3-D RGLQI) where the magnetization direction which is constant in a SCS is assumed to be constant in a CCS and equal to the direction at the geometric centre of each tesseroid, (4) the Taylor's series expansion method (TSE) and (5) the rectangular prism method (RP). In any realistic application, both the accuracy and the computational efficiency factors must be considered to determine the optimum approach to employ. In all instances, accuracy improves with increasing distance from the source. It is higher in the percentage terms for potential than the vector or tensor response. The tensor errors are the largest, but they decrease more quickly with distance from the source. In our comparisons of relative computational efficiency, we found that the magnetic potential takes less time to compute than the vector response, which in turn takes less time to compute than the tensor gradient response. The MD method takes less time to compute than either the TSE or RP methods. The efficiency of the (GLQI and) RGLQI methods depends on the polynomial order, but the response typically takes longer to compute than it does for the other methods. The optimum method is a complex function of the desired accuracy, the size of the volume elements, the element latitude and the distance between the source and the observation. For a model of global extent with typical model element size (e.g. 1 degree horizontally and 10 km radially) and observations at altitudes of 10s to 100s of km, a mixture of methods based on the horizontal separation of the source and observation separation would be the optimum approach. To demonstrate the RGLQI method described within this paper, we applied it to the computation of the response for a global magnetization model for observations at 300 and 30 km altitude.

Pseudo-magnetic fields of strongly-curved graphene nanobubbles

NASA Astrophysics Data System (ADS)

Liu, Li-Chi

2018-04-01

We use the π-orbital axis vector (POAV) analysis to deal with large curvature effect of graphene in the tight-binding model. To test the validities of pseudo-magnetic fields (PMFs) derived from the tight-binding model and the model with Dirac equation coupled to a curved surface, we propose two types of spatially constant-field topographies for strongly-curved graphene nanobubbles, which correspond to these two models, respectively. It is shown from the latter model that the PMF induced by any spherical graphene nanobubble is always equivalent to the magnetic field caused by one magnetic monopole charge distributed on a complete spherical surface with the same radius. Such a PMF might be attributed to the isometry breaking of a graphene layer attached conformably to a spherical substrate with adhesion.

Local order and crystallization of dense polydisperse hard spheres

NASA Astrophysics Data System (ADS)

Coslovich, Daniele; Ozawa, Misaki; Berthier, Ludovic

2018-04-01

Computer simulations give precious insight into the microscopic behavior of supercooled liquids and glasses, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. We recently closed this gap for a class of models of size polydisperse fluids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. In this contribution, we study the interplay between compositional and geometric local orders in a model of polydisperse hard spheres equilibrated with this algorithm. Local compositional order has a weak state dependence, while local geometric order associated to icosahedral arrangements grows more markedly but only at very high density. We quantify the correlation lengths and the degree of sphericity associated to icosahedral structures and compare these results to those for the Wahnström Lennard-Jones mixture. Finally, we analyze the structure of very dense samples that partially crystallized following a pattern incompatible with conventional fractionation scenarios. The crystal structure has the symmetry of aluminum diboride and involves a subset of small and large particles with size ratio approximately equal to 0.5.

Two-dimensional simulations of thermonuclear burn in ignition-scale inertial confinement fusion targets under compressed axial magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, L. J.; Logan, B. G.; Zimmerman, G. B.

2013-07-15

We report for the first time on full 2-D radiation-hydrodynamic implosion simulations that explore the impact of highly compressed imposed magnetic fields on the ignition and burn of perturbed spherical implosions of ignition-scale cryogenic capsules. Using perturbations that highly convolute the cold fuel boundary of the hotspot and prevent ignition without applied fields, we impose initial axial seed fields of 20–100 T (potentially attainable using present experimental methods) that compress to greater than 4 × 10{sup 4} T (400 MG) under implosion, thereby relaxing hotspot areal densities and pressures required for ignition and propagating burn by ∼50%. The compressed fieldmore » is high enough to suppress transverse electron heat conduction, and to allow alphas to couple energy into the hotspot even when highly deformed by large low-mode amplitudes. This might permit the recovery of ignition, or at least significant alpha particle heating, in submarginal capsules that would otherwise fail because of adverse hydrodynamic instabilities.« less

Anomalous waterlike behavior in spherically-symmetric water models optimized with the relative entropy.

PubMed

Chaimovich, Aviel; Shell, M Scott

2009-03-28

Recent efforts have attempted to understand many of liquid water's anomalous properties in terms of effective spherically-symmetric pairwise molecular interactions entailing two characteristic length scales (so-called "core-softened" potentials). In this work, we examine the extent to which such simple descriptions of water are representative of the true underlying interactions by extracting coarse-grained potential functions that are optimized to reproduce the behavior of an all-atom model. To perform this optimization, we use a novel procedure based upon minimizing the relative entropy, a quantity that measures the extent to which a coarse-grained configurational ensemble overlaps with a reference all-atom one. We show that the optimized spherically-symmetric water models exhibit notable variations with the state conditions at which they were optimized, reflecting in particular the shifting accessibility of networked hydrogen bonding interactions. Moreover, we find that water's density and diffusivity anomalies are only reproduced when the effective coarse-grained potentials are allowed to vary with state. Our results therefore suggest that no state-independent spherically-symmetric potential can fully capture the interactions responsible for water's unique behavior; rather, the particular way in which the effective interactions vary with temperature and density contributes significantly to anomalous properties.

Visual Detection and Tracking System for a Spherical Amphibious Robot

PubMed Central

Guo, Shuxiang; Pan, Shaowu; Shi, Liwei; Guo, Ping; He, Yanlin; Tang, Kun

2017-01-01

With the goal of supporting close-range observation tasks of a spherical amphibious robot, such as ecological observations and intelligent surveillance, a moving target detection and tracking system was designed and implemented in this study. Given the restrictions presented by the amphibious environment and the small-sized spherical amphibious robot, an industrial camera and vision algorithms using adaptive appearance models were adopted to construct the proposed system. To handle the problem of light scattering and absorption in the underwater environment, the multi-scale retinex with color restoration algorithm was used for image enhancement. Given the environmental disturbances in practical amphibious scenarios, the Gaussian mixture model was used to detect moving targets entering the field of view of the robot. A fast compressive tracker with a Kalman prediction mechanism was used to track the specified target. Considering the limited load space and the unique mechanical structure of the robot, the proposed vision system was fabricated with a low power system-on-chip using an asymmetric and heterogeneous computing architecture. Experimental results confirmed the validity and high efficiency of the proposed system. The design presented in this paper is able to meet future demands of spherical amphibious robots in biological monitoring and multi-robot cooperation. PMID:28420134

Visual Detection and Tracking System for a Spherical Amphibious Robot.

PubMed

Guo, Shuxiang; Pan, Shaowu; Shi, Liwei; Guo, Ping; He, Yanlin; Tang, Kun

2017-04-15

With the goal of supporting close-range observation tasks of a spherical amphibious robot, such as ecological observations and intelligent surveillance, a moving target detection and tracking system was designed and implemented in this study. Given the restrictions presented by the amphibious environment and the small-sized spherical amphibious robot, an industrial camera and vision algorithms using adaptive appearance models were adopted to construct the proposed system. To handle the problem of light scattering and absorption in the underwater environment, the multi-scale retinex with color restoration algorithm was used for image enhancement. Given the environmental disturbances in practical amphibious scenarios, the Gaussian mixture model was used to detect moving targets entering the field of view of the robot. A fast compressive tracker with a Kalman prediction mechanism was used to track the specified target. Considering the limited load space and the unique mechanical structure of the robot, the proposed vision system was fabricated with a low power system-on-chip using an asymmetric and heterogeneous computing architecture. Experimental results confirmed the validity and high efficiency of the proposed system. The design presented in this paper is able to meet future demands of spherical amphibious robots in biological monitoring and multi-robot cooperation.

Pulsar Observations with Radio Telescope FAST

NASA Astrophysics Data System (ADS)

Nan, Ren-Dong; Wang, Qi-Ming; Zhu, Li-Chun; Zhu, Wen-Bai; Jin, Cheng-Jin; Gan, Heng-Qian

2006-12-01

FAST, Five hundred meter Aperture Spherical Telescope, is the Chinese effort for the international project SKA, Square Kilometer Array. An innovative engineering concept and design pave a new road to realizing huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Besides a general coverage of those critical technologies involved in FAST concept, the progresses in demonstrating model being constructed at the Miyun Radio Observatory of the NAOC is introduced. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of science goals, for example, the natural hydrogen line surveying in distant galaxies, looking for the first generation of shining objects, hearing the possible signal from other civilizations, etc. Among these subjects, the most striking one could be pulsar study. Large scale survey by FAST will not only improve the statistics of the pulsar population, but also may offer us a good fortune to pick up more of the most exotic, even unknown types like a sub-millisecond pulsar or a neutron star -- black hole binary as the telescope is put into operation.

Dynamics of Compressible Convection and Thermochemical Mantle Convection

NASA Astrophysics Data System (ADS)

Liu, Xi

The Earth's long-wavelength geoid anomalies have long been used to constrain the dynamics and viscosity structure of the mantle in an isochemical, whole-mantle convection model. However, there is strong evidence that the seismically observed large low shear velocity provinces (LLSVPs) in the lowermost mantle are chemically distinct and denser than the ambient mantle. In this thesis, I investigated how chemically distinct and dense piles influence the geoid. I formulated dynamically self-consistent 3D spherical convection models with realistic mantle viscosity structure which reproduce Earth's dominantly spherical harmonic degree-2 convection. The models revealed a compensation effect of the chemically dense LLSVPs. Next, I formulated instantaneous flow models based on seismic tomography to compute the geoid and constrain mantle viscosity assuming thermochemical convection with the compensation effect. Thermochemical models reconcile the geoid observations. The viscosity structure inverted for thermochemical models is nearly identical to that of whole-mantle models, and both prefer weak transition zone. Our results have implications for mineral physics, seismic tomographic studies, and mantle convection modelling. Another part of this thesis describes analyses of the influence of mantle compressibility on thermal convection in an isoviscous and compressible fluid with infinite Prandtl number. A new formulation of the propagator matrix method is implemented to compute the critical Rayleigh number and the corresponding eigenfunctions for compressible convection. Heat flux and thermal boundary layer properties are quantified in numerical models and scaling laws are developed.

Rheology Gradients at the Base of the Lithosphere and the Stabilization of Deep Mantle Plumes in Stagnant-Lid Planets

NASA Astrophysics Data System (ADS)

King, S. D.

2017-12-01

In high-Rayleigh-number, spherical-shell convection, such as one expects to find in the interiors of large silicate planetary bodies, plumes will migrate unless they are anchored to fixed structures. Within the Earth LLSVPs or core-mantle boundary topography have been proposed to anchor deep mantle plumes, fixing the location of hotspots. The relative stability of volcanic features on Mars and Venus, which are thought to be related to mantle plumes, have not be satisfactorily explained. Thus, it is surprising to see high-Rayleigh-number, stagnant-lid, spherical-shell convection calculations where plumes seeded by the structure of the initial condition persist in a stable configuration for more than 1 Gyr. By comparing calculations with a fixed lithospheric rheology structure with a lithosphere rheology determined by temperature and pressure, I show that in these calculations, topography on the base of the stagnant lid (i.e., the lithosphere-asthenosphere boundary) is responsible for the spatial stability of the plumes. If there is symmetry in the plume distribution, this symmetry can prevent the lithosphere becoming unstable and overturning, leading to a significantly over-thickened lithosphere relative to predictions based on scaling laws. This is confirmed by considering an identical calculation where the symmetry in the plume distribution is broken. I discuss geological and geophysical implications for planetary bodies resulting of long-lived, stable, mantle structures.

Faces of Pluto

NASA Image and Video Library

2015-06-11

These images, taken by NASA's New Horizons' Long Range Reconnaissance Imager (LORRI), show four different "faces" of Pluto as it rotates about its axis with a period of 6.4 days. All the images have been rotated to align Pluto's rotational axis with the vertical direction (up-down) on the figure, as depicted schematically in the upper left. From left to right, the images were taken when Pluto's central longitude was 17, 63, 130, and 243 degrees, respectively. The date of each image, the distance of the New Horizons spacecraft from Pluto, and the number of days until Pluto closest approach are all indicated in the figure.These images show dramatic variations in Pluto's surface features as it rotates. When a very large, dark region near Pluto's equator appears near the limb, it gives Pluto a distinctly, but false, non-spherical appearance. Pluto is known to be almost perfectly spherical from previous data. These images are displayed at four times the native LORRI image size, and have been processed using a method called deconvolution, which sharpens the original images to enhance features on Pluto. Deconvolution can occasionally introduce "false" details, so the finest details in these pictures will need to be confirmed by images taken from closer range in the next few weeks. All of the images are displayed using the same brightness scale. http://photojournal.jpl.nasa.gov/catalog/PIA19686

Spherical Harmonic Analyses of Intensity Mapping Power Spectra

NASA Astrophysics Data System (ADS)

Liu, Adrian; Zhang, Yunfan; Parsons, Aaron R.

2016-12-01

Intensity mapping is a promising technique for surveying the large-scale structure of our universe from z = 0 to z ˜ 150, using the brightness temperature field of spectral lines to directly observe previously unexplored portions of our cosmic timeline. Examples of targeted lines include the 21 cm hyperfine transition of neutral hydrogen, rotational lines of carbon monoxide, and fine-structure lines of singly ionized carbon. Recent efforts have focused on detections of the power spectrum of spatial fluctuations, but have been hindered by systematics such as foreground contamination. This has motivated the decomposition of data into Fourier modes perpendicular and parallel to the line of sight, which has been shown to be a particularly powerful way to diagnose systematics. However, such a method is well-defined only in the limit of a narrow-field, flat-sky approximation. This limits the sensitivity of intensity mapping experiments, as it means that wide surveys must be separately analyzed as a patchwork of smaller fields. In this paper, we develop a framework for analyzing intensity mapping data in a spherical Fourier-Bessel basis, which incorporates curved sky effects without difficulty. We use our framework to generalize a number of techniques in intensity mapping data analysis from the flat sky to the curved sky. These include visibility-based estimators for the power spectrum, treatments of interloper lines, and the “foreground wedge” signature of spectrally smooth foregrounds.

Quasinormal acoustic oscillations in the Michel flow

NASA Astrophysics Data System (ADS)

Chaverra, Eliana; Morales, Manuel D.; Sarbach, Olivier

2015-05-01

We study spherical and nonspherical linear acoustic perturbations of the Michel flow, which describes the steady radial accretion of a perfect fluid into a nonrotating black hole. The dynamics of such perturbations are governed by a scalar wave equation on an effective curved background geometry determined by the acoustic metric, which is constructed from the spacetime metric and the particle density and four-velocity of the fluid. For the problem under consideration in this paper the acoustic metric has the same qualitative features as an asymptotically flat, static and spherically symmetric black hole, and thus it represents a natural astrophysical analogue black hole. As for the case of a scalar field propagating on a Schwarzschild background, we show that acoustic perturbations of the Michel flow exhibit quasinormal oscillations. Based on a new numerical method for determining the solutions of the radial mode equation, we compute the associated frequencies and analyze their dependency on the mass of the black hole, the radius of the sonic horizon and the angular momentum number. Our results for the fundamental frequencies are compared to those obtained from an independent numerical Cauchy evolution, finding good agreement between the two approaches. When the radius of the sonic horizon is large compared to the event horizon radius, we find that the quasinormal frequencies scale approximately like the surface gravity associated with the sonic horizon.

Generating Bulk-Scale Ordered Optical Materials Using Shear-Assembly in Viscoelastic Media.

PubMed

Finlayson, Chris E; Baumberg, Jeremy J

2017-06-22

We review recent advances in the generation of photonics materials over large areas and volumes, using the paradigm of shear-induced ordering of composite polymer nanoparticles. The hard-core/soft-shell design of these particles produces quasi-solid "gum-like" media, with a viscoelastic ensemble response to applied shear, in marked contrast to the behavior seen in colloidal and granular systems. Applying an oscillatory shearing method to sub-micron spherical nanoparticles gives elastomeric photonic crystals (or "polymer opals") with intense tunable structural color. The further engineering of this shear-ordering using a controllable "roll-to-roll" process known as Bending Induced Oscillatory Shear (BIOS), together with the interchangeable nature of the base composite particles, opens potentially transformative possibilities for mass manufacture of nano-ordered materials, including advances in optical materials, photonics, and metamaterials/plasmonics.

Large scale ZnTe nanostructures on polymer micro patterns via capillary force photolithography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florence, S. Sasi, E-mail: sshanmugaraj@jazanu.edu.sa; Can, N.; Adam, H.

2016-06-10

A novel approach to prepare micro patterns ZnTe nanostructures on Si (100) substrate using thermal evaporation is proposed by capillary Force Lithography (CFL) technique on a self-assembled sacrificial Polystyrene mask. Polystyrene thin films on Si substrates are used to fabricate surface micro-relief patterns. ZnTe nanoparticles have been deposited by thermal evaporation method. The deposited ZnTe nanoparticles properties were assessed by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM). SEM studies indicated that the particles are uniform in size and shape, well dispersed and spherical in shape. This study reports the micro-arrays of ZnTe nanoparticles on a self-assembled sacrificial PS maskmore » using a capillary flow photolithography process which showed excellent, morphological properties which can be used in photovoltaic devices for anti-reflection applications.« less

Atmospheric scavenging of solid rocket exhaust effluents

NASA Technical Reports Server (NTRS)

Fenton, D. L.; Purcell, R. Y.

1978-01-01

Solid propellant rocket exhaust was directly utilized to ascertain raindrop scavenging rates for hydrogen chloride. Two chambers were used to conduct the experiments; a large, rigid walled, spherical chamber stored the exhaust constituents, while the smaller chamber housing all the experiments was charged as required with rocket exhaust HCl. Surface uptake experiments demonstrated an HCl concentration dependence for distilled water. Sea water and brackish water HCl uptake was below the detection limit of the chlorine-ion analysis technique used. Plant life HCl uptake experiments were limited to corn and soybeans. Plant age effectively correlated the HCl uptake data. Metallic corrosion was not significant for single 20 minute exposures to the exhaust HCl under varying relative humidity. Characterization of the aluminum oxide particles substantiated the similarity between the constituents of the small scale rocket and the full size vehicles.

Generating Bulk-Scale Ordered Optical Materials Using Shear-Assembly in Viscoelastic Media

PubMed Central

Finlayson, Chris E.; Baumberg, Jeremy J.

2017-01-01

We review recent advances in the generation of photonics materials over large areas and volumes, using the paradigm of shear-induced ordering of composite polymer nanoparticles. The hard-core/soft-shell design of these particles produces quasi-solid “gum-like” media, with a viscoelastic ensemble response to applied shear, in marked contrast to the behavior seen in colloidal and granular systems. Applying an oscillatory shearing method to sub-micron spherical nanoparticles gives elastomeric photonic crystals (or “polymer opals”) with intense tunable structural color. The further engineering of this shear-ordering using a controllable “roll-to-roll” process known as Bending Induced Oscillatory Shear (BIOS), together with the interchangeable nature of the base composite particles, opens potentially transformative possibilities for mass manufacture of nano-ordered materials, including advances in optical materials, photonics, and metamaterials/plasmonics. PMID:28773044

Acoustic levitation of a large solid sphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrade, Marco A. B., E-mail: marcobrizzotti@gmail.com; Bernassau, Anne L.; Adamowski, Julio C.

2016-07-25

We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setupmore » consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.« less

The correlation function of galaxy ellipticities produced by gravitational lensing

NASA Technical Reports Server (NTRS)

Miralda-Escude, Jordi

1991-01-01

The correlation of galaxy ellipticities produced by gravitational lensing is calculated as a function of the power spectrum of density fluctuations in the universe by generalizing an analytical method developed by Gunn (1967). The method is applied to a model where identical objects with spherically symmetric density profiles are randomly laid down in space, and to the cold dark matter model. The possibility of detecting this correlation is discussed. Although an ellipticity correlation can also be caused by an intrinsic alignment of the axes of galaxies belonging to a cluster or a supercluster, a method is suggested by which one type of correlation can be distinguished from another. The advantage of this ellipticity correlation is that it is one of the few astronomical observations that can directly probe large-scale mass fluctuations in the universe.

The evolution of void-filled cosmological structures

NASA Technical Reports Server (NTRS)

Regos, Eniko; Geller, Margaret J.

1991-01-01

1D, 2D, and 3D simulations are used here to investigate the salient features in the evolution of void-filled cosmological structures in universes with arbitrary values of Omega. It is found that the growth of a void as a function of time decreases significantly at the time corresponding to Omega = 0.5. In models constructed in 2D and 3D, suitable initial conditions lead to cellular structure with faceted voids similar to those observed in redshift surveys. Matter compressed to planes flows more rapidly toward condensations at the intersections than would be expected for spherical infall. The peculiar streaming velocities for void diameters of 5000 km/s should be observable. The simulations provide a more physical basis and dynamics for the bubbly and Voronois tesselation models used to derive statistical properties of cellular large-scale structure.

Oceanic tide maps and spherical harmonic coefficients from Geosat altimetry

NASA Technical Reports Server (NTRS)

Cartwright, D. E.; Ray, R. D.; Sanchez, B. V.

1991-01-01

Maps and tables for the global ocean tides, 69 degree N to 68 degree S, derived from two years of Geosat altimetry are presented. Global maps of local and Greenwich admittance of the (altimetric) ocean tide, and maps of amplitude and Greenwich phase lag of the ocean tide are shown for M(sub 2), S(sub 2), N(sub 2), O(sub 1), and K(sub 1). Larger scale maps of amplitude and phases are also shown for regional areas of special interest. Spherical harmonic coefficients of the ocean tide through degree and order 8 are tabulated for the six major constituents.

Nekrasov and Argyres-Douglas theories in spherical Hecke algebra representation

NASA Astrophysics Data System (ADS)

Rim, Chaiho; Zhang, Hong

2017-06-01

AGT conjecture connects Nekrasov instanton partition function of 4D quiver gauge theory with 2D Liouville conformal blocks. We re-investigate this connection using the central extension of spherical Hecke algebra in q-coordinate representation, q being the instanton expansion parameter. Based on AFLT basis together with intertwiners we construct gauge conformal state and demonstrate its equivalence to the Liouville conformal state, with careful attention to the proper scaling behavior of the state. Using the colliding limit of regular states, we obtain the formal expression of irregular conformal states corresponding to Argyres-Douglas theory, which involves summation of functions over Young diagrams.

Multiscale 3D Shape Analysis using Spherical Wavelets

PubMed Central

Nain, Delphine; Haker, Steven; Bobick, Aaron; Tannenbaum, Allen

2013-01-01

Shape priors attempt to represent biological variations within a population. When variations are global, Principal Component Analysis (PCA) can be used to learn major modes of variation, even from a limited training set. However, when significant local variations exist, PCA typically cannot represent such variations from a small training set. To address this issue, we present a novel algorithm that learns shape variations from data at multiple scales and locations using spherical wavelets and spectral graph partitioning. Our results show that when the training set is small, our algorithm significantly improves the approximation of shapes in a testing set over PCA, which tends to oversmooth data. PMID:16685992

Multiscale 3D shape analysis using spherical wavelets.

PubMed

Nain, Delphine; Haker, Steven; Bobick, Aaron; Tannenbaum, Allen R

2005-01-01

Shape priors attempt to represent biological variations within a population. When variations are global, Principal Component Analysis (PCA) can be used to learn major modes of variation, even from a limited training set. However, when significant local variations exist, PCA typically cannot represent such variations from a small training set. To address this issue, we present a novel algorithm that learns shape variations from data at multiple scales and locations using spherical wavelets and spectral graph partitioning. Our results show that when the training set is small, our algorithm significantly improves the approximation of shapes in a testing set over PCA, which tends to oversmooth data.

GRMHD formulation of highly super-Chandrasekhar magnetized white dwarfs: stable configurations of non-spherical white dwarfs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Upasana; Mukhopadhyay, Banibrata, E-mail: upasana@physics.iisc.ernet.in, E-mail: bm@physics.iisc.ernet.in

The topic of magnetized super-Chandrasekhar white dwarfs is in the limelight, particularly in the last few years, since our proposal of their existence. By full-scale general relativistic magnetohydrodynamic (GRMHD) numerical analysis, we confirm in this work the existence of stable, highly magnetized, significantly super-Chandrasekhar white dwarfs with mass more than 3 solar mass. While a poloidal field geometry renders the white dwarfs oblate, a toroidal field makes them prolate retaining an overall quasi-spherical shape, as speculated in our earlier work. These white dwarfs are expected to serve as the progenitors of over-luminous type Ia supernovae.

Origin of Noncubic Scaling Law in Disordered Granular Packing.

PubMed

Xia, Chengjie; Li, Jindong; Kou, Binquan; Cao, Yixin; Li, Zhifeng; Xiao, Xianghui; Fu, Yanan; Xiao, Tiqiao; Hong, Liang; Zhang, Jie; Kob, Walter; Wang, Yujie

2017-06-09

Recent diffraction experiments on metallic glasses have unveiled an unexpected noncubic scaling law between density and average interatomic distance, which led to the speculation of the presence of fractal glass order. Using x-ray tomography we identify here a similar noncubic scaling law in disordered granular packing of spherical particles. We find that the scaling law is directly related to the contact neighbors within the first nearest neighbor shell, and, therefore, is closely connected to the phenomenon of jamming. The seemingly universal scaling exponent around 2.5 arises due to the isostatic condition with a contact number around 6, and we argue that the exponent should not be universal.

Drag force scaling for penetration into granular media.

PubMed

Katsuragi, Hiroaki; Durian, Douglas J

2013-05-01

Impact dynamics is measured for spherical and cylindrical projectiles of many different densities dropped onto a variety non-cohesive granular media. The results are analyzed in terms of the material-dependent scaling of the inertial and frictional drag contributions to the total stopping force. The inertial drag force scales similar to that in fluids, except that it depends on the internal friction coefficient. The frictional drag force scales as the square-root of the density of granular medium and projectile, and hence cannot be explained by the combination of granular hydrostatic pressure and Coulomb friction law. The combined results provide an explanation for the previously observed penetration depth scaling.

The effect of latent heat release on synoptic-to-planetary wave interactions and its implication for satellite observations: Theoretical modeling

NASA Technical Reports Server (NTRS)

Branscome, Lee E.; Bleck, Rainer; Obrien, Enda

1990-01-01

The project objectives are to develop process models to investigate the interaction of planetary and synoptic-scale waves including the effects of latent heat release (precipitation), nonlinear dynamics, physical and boundary-layer processes, and large-scale topography; to determine the importance of latent heat release for temporal variability and time-mean behavior of planetary and synoptic-scale waves; to compare the model results with available observations of planetary and synoptic wave variability; and to assess the implications of the results for monitoring precipitation in oceanic-storm tracks by satellite observing systems. Researchers have utilized two different models for this project: a two-level quasi-geostrophic model to study intraseasonal variability, anomalous circulations and the seasonal cycle, and a 10-level, multi-wave primitive equation model to validate the two-level Q-G model and examine effects of convection, surface processes, and spherical geometry. It explicitly resolves several planetary and synoptic waves and includes specific humidity (as a predicted variable), moist convection, and large-scale precipitation. In the past year researchers have concentrated on experiments with the multi-level primitive equation model. The dynamical part of that model is similar to the spectral model used by the National Meteorological Center for medium-range forecasts. The model includes parameterizations of large-scale condensation and moist convection. To test the validity of results regarding the influence of convective precipitation, researchers can use either one of two different convective schemes in the model, a Kuo convective scheme or a modified Arakawa-Schubert scheme which includes downdrafts. By choosing one or the other scheme, they can evaluate the impact of the convective parameterization on the circulation. In the past year researchers performed a variety of initial-value experiments with the primitive-equation model. Using initial conditions typical of climatological winter conditions, they examined the behavior of synoptic and planetary waves growing in moist and dry environments. Surface conditions were representative of a zonally averaged ocean. They found that moist convection associated with baroclinic wave development was confined to the subtropics.

Application of close-packed structures in dental resin composites.

PubMed

Wang, Ruili; Habib, Eric; Zhu, X X

2017-03-01

The inorganic filler particles in dental resin composites serve to improve their mechanical properties and reduce polymerization shrinkage during their use. Efforts have been made in academia and industry to increase the filler particle content, but, few studies examine the theoretical basis for the maximum particle loading. This work evaluates the packing of spherical particles in a close-packed state for highly loaded composites. Calculations show that for low dispersity particles, the maximum amount of particles is 74.05vol%, regardless of the particle size. This can be further improved by using a mix of large and small particles or by the use of non-spherical particles. For representative spherical particles with a diameter of 1000nm, two types of secondary particles with respective sizes of 414nm (d I ) and 225nm (d II ) are selected. The results show that after embedding secondary particles I & II into primary spherical particles, the packing factor is increased to 81.19% for the close-packed structures, which shows an improvement of 9.64%, compared to the 74.05% obtained only with primary spherical particles. This packing factor is also higher than either structure with the embedded secondary particles I or II. Examples of these mixtures with different spherical particle sizes are shown as a theoretical estimation, serving as a guideline for the design and formulation of new dental resin composites with better properties and improved performance. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Saltation movement of large spherical particles

NASA Astrophysics Data System (ADS)

Chara, Z.; Dolansky, J.; Kysela, B.

2017-07-01

The paper presents experimental and numerical investigations of the saltation motion of a large spherical particle in an open channel. The channel bottom was roughed by one layer of glass rods of diameter 6 mm. The plastic spheres of diameter 25.7 mm and density 1160 kgm-3 were fed into the water channel and theirs positions were viewed by a digital camera. Two light sheets were placed above and under the channel, so the flow was simultaneously lighted from the top and the bottom. Only particles centers of which moved through the light sheets were recorded. Using a 2D PIV method the trajectories of the spheres and the velocity maps of the channel flow were analyzed. The Lattice-Boldzmann Method (LBM) was used to simulate the particle motion.

Polymer brushes in explicit poor solvents studied using a new variant of the bond fluctuation model

NASA Astrophysics Data System (ADS)

Jentzsch, Christoph; Sommer, Jens-Uwe

2014-09-01

Using a variant of the Bond Fluctuation Model which improves its parallel efficiency in particular running on graphic cards we perform large scale simulations of polymer brushes in poor explicit solvent. Grafting density, solvent quality, and chain length are varied. Different morphological structures in particular octopus micelles are observed for low grafting densities. We reconsider the theoretical model for octopus micelles proposed by Williams using scaling arguments with the relevant scaling variable being σ/σc, and with the characteristic grafting density given by σc ˜ N-4/3. We find that octopus micelles only grow laterally, but not in height and we propose an extension of the model by assuming a cylindrical shape instead of a spherical geometry for the micelle-core. We show that the scaling variable σ/σc can be applied to master plots for the averaged height of the brush, the size of the micelles, and the number of chains per micelle. The exponents in the corresponding power law relations for the grafting density and chain length are in agreement with the model for flat cylindrical micelles. We also investigate the surface roughness and find that polymer brushes in explicit poor solvent at grafting densities higher than the stretching transition are flat and surface rippling can only be observed close to the stretching transition.

Multiscale Molecular Dynamics Model for Heterogeneous Charged Systems

NASA Astrophysics Data System (ADS)

Stanton, L. G.; Glosli, J. N.; Murillo, M. S.

2018-04-01

Modeling matter across large length scales and timescales using molecular dynamics simulations poses significant challenges. These challenges are typically addressed through the use of precomputed pair potentials that depend on thermodynamic properties like temperature and density; however, many scenarios of interest involve spatiotemporal variations in these properties, and such variations can violate assumptions made in constructing these potentials, thus precluding their use. In particular, when a system is strongly heterogeneous, most of the usual simplifying assumptions (e.g., spherical potentials) do not apply. Here, we present a multiscale approach to orbital-free density functional theory molecular dynamics (OFDFT-MD) simulations that bridges atomic, interionic, and continuum length scales to allow for variations in hydrodynamic quantities in a consistent way. Our multiscale approach enables simulations on the order of micron length scales and 10's of picosecond timescales, which exceeds current OFDFT-MD simulations by many orders of magnitude. This new capability is then used to study the heterogeneous, nonequilibrium dynamics of a heated interface characteristic of an inertial-confinement-fusion capsule containing a plastic ablator near a fuel layer composed of deuterium-tritium ice. At these scales, fundamental assumptions of continuum models are explored; features such as the separation of the momentum fields among the species and strong hydrogen jetting from the plastic into the fuel region are observed, which had previously not been seen in hydrodynamic simulations.

Multiscale Experimental and Numerical Approach to the Powder Particle Shape Effect on Al-Al2O3 Coating Build-Up

NASA Astrophysics Data System (ADS)

Leger, P. E.; Sennour, M.; Delloro, F.; Borit, F.; Debray, A.; Gaslain, F.; Jeandin, M.; Ducos, M.

2017-10-01

Aluminum (Al) powders with spherical and irregular particle shapes were mixed with two alumina (Al2O3) powders with either a spherical or an angular particle shape to achieve high-performance cold-sprayed coatings onto steel. Two effects of the aluminum particle shape were observed. First, coating microstructure observation showed impinging heterogeneity depending on particle shape. Second, particle jet differences depending on particle morphology were shown by velocity maps. From the latter, SEM and XRD, three effects of the alumina particle shape were also shown, i.e., higher in-flight velocity of angular particles, fragmentation of spherical hollow particles and embedding of alumina particles with aluminum. Numerical simulation of particle impacts was developed to study the densification of Al coating due to Al2O3 addition through elucidation of Al-Al2O3 interaction behavior at the scale of the coating. Al/Al and Al/Al2O3 interfaces were investigated using TEM to understand coating strengthening effects due to alumina addition at the scale of the particle. As a whole, Al and Al2O3 particle shape effects were claimed to explain coating mechanical properties, e.g., microhardness and coating-substrate bond strength. This study resulted in specifying criteria to help cold spray users in selecting powders for their applications, to meet economic and technical requirements.

Grand Minima and Equatorward Propagation in a Cycling Stellar Convective Dynamo

NASA Astrophysics Data System (ADS)

Augustson, Kyle; Brun, Allan Sacha; Miesch, Mark; Toomre, Juri

2015-08-01

The 3D MHD Anelastic Spherical Harmonic code, using slope-limited diffusion, is employed to capture convective and dynamo processes achieved in a global-scale stellar convection simulation for a model solar-mass star rotating at three times the solar rate. The dynamo-generated magnetic fields possesses many timescales, with a prominent polarity cycle occurring roughly every 6.2 years. The magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation. The polarity reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. An equatorial migration of the magnetic field is seen, which is due to the strong modulation of the differential rotation rather than a dynamo wave. A poleward migration of magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This simulation also enters an interval with reduced magnetic energy at low latitudes lasting roughly 16 years (about 2.5 polarity cycles), during which the polarity cycles are disrupted and after which the dynamo recovers its regular polarity cycles. An analysis of this grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families. This intermittent dynamo state potentially results from the simulation’s relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The timescales that appear to be relevant to the magnetic polarity reversal are also identified.

GRAND MINIMA AND EQUATORWARD PROPAGATION IN A CYCLING STELLAR CONVECTIVE DYNAMO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Augustson, Kyle; Miesch, Mark; Brun, Allan Sacha

2015-08-20

The 3D MHD Anelastic Spherical Harmonic code, using slope-limited diffusion, is employed to capture convective and dynamo processes achieved in a global-scale stellar convection simulation for a model solar-mass star rotating at three times the solar rate. The dynamo-generated magnetic fields possesses many timescales, with a prominent polarity cycle occurring roughly every 6.2 years. The magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation. The polarity reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. An equatorial migration of themore » magnetic field is seen, which is due to the strong modulation of the differential rotation rather than a dynamo wave. A poleward migration of magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This simulation also enters an interval with reduced magnetic energy at low latitudes lasting roughly 16 years (about 2.5 polarity cycles), during which the polarity cycles are disrupted and after which the dynamo recovers its regular polarity cycles. An analysis of this grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families. This intermittent dynamo state potentially results from the simulation’s relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The timescales that appear to be relevant to the magnetic polarity reversal are also identified.« less

Galaxy clusters in the context of superfluid dark matter

NASA Astrophysics Data System (ADS)

Hodson, Alistair O.; Zhao, Hongsheng; Khoury, Justin; Famaey, Benoit

2017-11-01

Context. The mass discrepancy in the Universe has not been solved by the cold dark matter (CDM) or the modified Newtonian dynamics (MOND) paradigms so far. The problems and solutions of either scenario are mutually exclusive on large and small scales. It has recently been proposed, by assuming that dark matter is a superfluid, that MOND-like effects can be achieved on small scales whilst preserving the success of ΛCDM on large scales. Detailed models within this "superfluid dark matter" (SfDM) paradigm are yet to be constructed. Aims: Here, we aim to provide the first set of spherical models of galaxy clusters in the context of SfDM. We aim to determine whether the superfluid formulation is indeed sufficient to explain the mass discrepancy in galaxy clusters. Methods: The SfDM model is defined by two parameters. Λ can be thought of as a mass scale in the Lagrangian of the scalar field that effectively describes the phonons, and it acts as a coupling constant between the phonons and baryons. m is the mass of the DM particles. Based on these parameters, we outline the theoretical structure of the superfluid core and the surrounding "normal-phase" dark halo of quasi-particles. The latter are thought to encompass the largest part of galaxy clusters. Here, we set the SfDM transition at the radius where the density and pressure of the superfluid and normal phase coincide, neglecting the effect of phonons in the superfluid core. We then apply the formalism to a sample of galaxy clusters, and directly compare the SfDM predicted mass profiles to data. Results: We find that the superfluid formulation can reproduce the X-ray dynamical mass profile of clusters reasonably well, but with a slight under-prediction of the gravity in the central regions. This might be partly related to our neglecting of the effect of phonons in these regions. Two normal-phase halo profiles are tested, and it is found that clusters are better defined by a normal-phase halo resembling an Navarro-Frenk-White-like structure than an isothermal profile. Conclusions: In this first exploratory work on the topic, we conclude that depending on the amount of baryons present in the central galaxy and on the actual effect of phonons in the inner regions, this superfluid formulation could be successful in describing galaxy clusters. In the future, our model could be made more realistic by exploring non-sphericity and a more realistic SfDM to normal phase transition. The main result of this study is an estimate of the order of magnitude of the theory parameters for the superfluid formalism to be reasonably consistent with clusters. These values will have to be compared to the true values needed in galaxies.

Large Scale, High Resolution, Mantle Dynamics Modeling

NASA Astrophysics Data System (ADS)

Geenen, T.; Berg, A. V.; Spakman, W.

2007-12-01

To model the geodynamic evolution of plate convergence, subduction and collision and to allow for a connection to various types of observational data, geophysical, geodetical and geological, we developed a 4D (space-time) numerical mantle convection code. The model is based on a spherical 3D Eulerian fem model, with quadratic elements, on top of which we constructed a 3D Lagrangian particle in cell(PIC) method. We use the PIC method to transport material properties and to incorporate a viscoelastic rheology. Since capturing small scale processes associated with localization phenomena require a high resolution, we spend a considerable effort on implementing solvers suitable to solve for models with over 100 million degrees of freedom. We implemented Additive Schwartz type ILU based methods in combination with a Krylov solver, GMRES. However we found that for problems with over 500 thousend degrees of freedom the convergence of the solver degraded severely. This observation is known from the literature [Saad, 2003] and results from the local character of the ILU preconditioner resulting in a poor approximation of the inverse of A for large A. The size of A for which ILU is no longer usable depends on the condition of A and on the amount of fill in allowed for the ILU preconditioner. We found that for our problems with over 5×105 degrees of freedom convergence became to slow to solve the system within an acceptable amount of walltime, one minute, even when allowing for considerable amount of fill in. We also implemented MUMPS and found good scaling results for problems up to 107 degrees of freedom for up to 32 CPU¡¯s. For problems with over 100 million degrees of freedom we implemented Algebraic Multigrid type methods (AMG) from the ML library [Sala, 2006]. Since multigrid methods are most effective for single parameter problems, we rebuild our model to use the SIMPLE method in the Stokes solver [Patankar, 1980]. We present scaling results from these solvers for 3D spherical models. We also applied the above mentioned method to a high resolution (~ 1 km) 2D mantle convection model with temperature, pressure and phase dependent rheology including several phase transitions. We focus on a model of a subducting lithospheric slab which is subject to strong folding at the bottom of the mantle's D" region which includes the postperovskite phase boundary. For a detailed description of this model we refer to poster [Mantel convection models of the D" region, U17] [Saad, 2003] Saad, Y. (2003). Iterative methods for sparse linear systems. [Sala, 2006] Sala. M (2006) An Object-Oriented Framework for the Development of Scalable Parallel Multilevel Preconditioners. ACM Transactions on Mathematical Software, 32 (3), 2006 [Patankar, 1980] Patankar, S. V.(1980) Numerical Heat Transfer and Fluid Flow, Hemisphere, Washington.

Large scale structures in the kinetic gravity braiding model that can be unbraided

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimura, Rampei; Yamamoto, Kazuhiro, E-mail: rampei@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp

2011-04-01

We study cosmological consequences of a kinetic gravity braiding model, which is proposed as an alternative to the dark energy model. The kinetic braiding model we study is characterized by a parameter n, which corresponds to the original galileon cosmological model for n = 1. We find that the background expansion of the universe of the kinetic braiding model is the same as the Dvali-Turner's model, which reduces to that of the standard cold dark matter model with a cosmological constant (ΛCDM model) for n equal to infinity. We also find that the evolution of the linear cosmological perturbation inmore » the kinetic braiding model reduces to that of the ΛCDM model for n = ∞. Then, we focus our study on the growth history of the linear density perturbation as well as the spherical collapse in the nonlinear regime of the density perturbations, which might be important in order to distinguish between the kinetic braiding model and the ΛCDM model when n is finite. The theoretical prediction for the large scale structure is confronted with the multipole power spectrum of the luminous red galaxy sample of the Sloan Digital Sky survey. We also discuss future prospects of constraining the kinetic braiding model using a future redshift survey like the WFMOS/SuMIRe PFS survey as well as the cluster redshift distribution in the South Pole Telescope survey.« less

Wave Propagation in Non-Stationary Statistical Mantle Models at the Global Scale

NASA Astrophysics Data System (ADS)

Meschede, M.; Romanowicz, B. A.

2014-12-01

We study the effect of statistically distributed heterogeneities that are smaller than the resolution of current tomographic models on seismic waves that propagate through the Earth's mantle at teleseismic distances. Current global tomographic models are missing small-scale structure as evidenced by the failure of even accurate numerical synthetics to explain enhanced coda in observed body and surface waveforms. One way to characterize small scale heterogeneity is to construct random models and confront observed coda waveforms with predictions from these models. Statistical studies of the coda typically rely on models with simplified isotropic and stationary correlation functions in Cartesian geometries. We show how to construct more complex random models for the mantle that can account for arbitrary non-stationary and anisotropic correlation functions as well as for complex geometries. Although this method is computationally heavy, model characteristics such as translational, cylindrical or spherical symmetries can be used to greatly reduce the complexity such that this method becomes practical. With this approach, we can create 3D models of the full spherical Earth that can be radially anisotropic, i.e. with different horizontal and radial correlation functions, and radially non-stationary, i.e. with radially varying model power and correlation functions. Both of these features are crucial for a statistical description of the mantle in which structure depends to first order on the spherical geometry of the Earth. We combine different random model realizations of S velocity with current global tomographic models that are robust at long wavelengths (e.g. Meschede and Romanowicz, 2014, GJI submitted), and compute the effects of these hybrid models on the wavefield with a spectral element code (SPECFEM3D_GLOBE). We finally analyze the resulting coda waves for our model selection and compare our computations with observations. Based on these observations, we make predictions about the strength of unresolved small-scale structure and extrinsic attenuation.

Topology Trivialization and Large Deviations for the Minimum in the Simplest Random Optimization

NASA Astrophysics Data System (ADS)

Fyodorov, Yan V.; Le Doussal, Pierre

2014-01-01

Finding the global minimum of a cost function given by the sum of a quadratic and a linear form in N real variables over (N-1)-dimensional sphere is one of the simplest, yet paradigmatic problems in Optimization Theory known as the "trust region subproblem" or "constraint least square problem". When both terms in the cost function are random this amounts to studying the ground state energy of the simplest spherical spin glass in a random magnetic field. We first identify and study two distinct large-N scaling regimes in which the linear term (magnetic field) leads to a gradual topology trivialization, i.e. reduction in the total number {N}_{tot} of critical (stationary) points in the cost function landscape. In the first regime {N}_{tot} remains of the order N and the cost function (energy) has generically two almost degenerate minima with the Tracy-Widom (TW) statistics. In the second regime the number of critical points is of the order of unity with a finite probability for a single minimum. In that case the mean total number of extrema (minima and maxima) of the cost function is given by the Laplace transform of the TW density, and the distribution of the global minimum energy is expected to take a universal scaling form generalizing the TW law. Though the full form of that distribution is not yet known to us, one of its far tails can be inferred from the large deviation theory for the global minimum. In the rest of the paper we show how to use the replica method to obtain the probability density of the minimum energy in the large-deviation approximation by finding both the rate function and the leading pre-exponential factor.

Radiative transfer in spherical shell atmospheres. 2: Asymmetric phase functions

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Adams, C. N.

1977-01-01

The effects are investigated of sphericity on the radiation reflected from a planet with a homogeneous, conservative scattering atmosphere of optical thicknesses of 0.25 and 1.0. A Henyey-Greenstein phase function with asymmetry factors of 0.5 and 0.7 is considered. Significant differences were found when these results were compared with the plane-parallel calculations. Also large violations of the reciprocity theorem, which is only true for plane-parallel calculations, were noted. Results are presented for the radiance versus height distributions as a function of planetary phase angle.

Extended Applicability of the Spherical-Harmonic and Point-Mass Modeling of the Gravity Field,

DTIC Science & Technology

1980-02-01

the metric in spherical coordinates {X,F, rl reads ds2 = r2cos 2j dX2 + r 2d 2 + dr2 yielding the metric tensor and the associated metric tensor: {grs...leading to (3.52) would have required considerably more space if the tensor approach to this problem had been avoided, whether for pedagogical or other...useful, especially from the pedagogical point of view, since it addresses itself to large audiences and exposes the treated subject in great depth. On

Electrostatic similarity of proteins: Application of three dimensional spherical harmonic decomposition

PubMed Central

Długosz, Maciej; Trylska, Joanna

2008-01-01

We present a method for describing and comparing global electrostatic properties of biomolecules based on the spherical harmonic decomposition of electrostatic potential data. Unlike other approaches our method does not require any prior three dimensional structural alignment. The electrostatic potential, given as a volumetric data set from a numerical solution of the Poisson or Poisson–Boltzmann equation, is represented with descriptors that are rotation invariant. The method can be applied to large and structurally diverse sets of biomolecules enabling to cluster them according to their electrostatic features. PMID:18624502

Effect of Particle Morphology on the Reactivity of Explosively Dispersed Titanium Particles

NASA Astrophysics Data System (ADS)

Frost, David L.; Cairns, Malcolm; Goroshin, Samuel; Zhang, Fan

2009-12-01

The effect of particle morphology on the reaction of titanium (Ti) particles explosively dispersed during the detonation of either cylindrical or spherical charges has been investigated experimentally. The explosive charges consisted of packed beds of Ti particles saturated with nitromethane. The reaction behaviour of irregularly-shaped Ti particles in three size ranges is compared with tests with spherical Ti particles. The particle reaction is strongly dependent on particle morphology, e.g., 95 μm spherical Ti particles failed to ignite (in cylinders up to 49 mm in dia), whereas similarly sized irregular Ti particles readily ignited. For irregular particles, the uniformity of ignition on the particle cloud surface was almost independent of particle size, but depended on charge diameter. As the charge diameter was reduced, ignition in the conically expanding particle cloud occurred only at isolated spots or bands. For spherical charges, whereas large irregular Ti particles ignited promptly and uniformly throughout the particle cloud, the smallest particles dispersed nonuniformly and ignition occurred at isolated locations after a delay. Hence the charge geometry, as well as particle morphology, influences the reaction behaviour of the particles.

Characterization of the non axial thrust generated by large solid propellant rocket motors in three axis stabilized ascent

NASA Technical Reports Server (NTRS)

Kosmann, W. J.; Dionne, E. R.; Klemetson, R. W.

1978-01-01

Nonaxial thrusts produced by solid rocket motors during three-axis stabilized attitude control have been determined from ascent experience on twenty three Burner II, Burner IIA and Block 5D-1 upper stage vehicles. A data base representing four different rocket motor designs (three spherical and one extended spherical) totaling twenty five three-axis stabilized firings is generated. Solid rocket motor time-varying resultant and lateral side force vector magnitudes, directions and total impulses, and roll torque couple magnitudes, directions, and total impulses are tabulated in the appendix. Population means and three sigma deviations are plotted. Existing applicable ground test side force and roll torque magnitudes and total impulses are evaluated and compared to the above experience data base. Within the spherical motor population, the selected AEDC ground test data consistently underestimated experienced motor side forces, roll torques and total impulses. Within the extended spherical motor population, the selected AEDC test data predicted experienced motor side forces, roll torques, and total impulses, with surprising accuracy considering the very small size of the test and experience populations.

Morphological statistics of the cosmic web

NASA Astrophysics Data System (ADS)

Shandarin, Sergei F.

2004-07-01

We report the first systematic study of the supercluster-void network in the ΛCDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter density field in real space smoothed with the Ls = 5 h[minus sign]1Mpc Gaussian window. Superclusters and voids are defined as individual members of over-dense and under-dense excursion sets respectively. We determine the morphological properties of the cosmic web at a large number of dark matter density levels by computing Minkowski functionals for every supercluster and void. At the adopted smoothing scale individual superclusters totally occupy no more than about 5% of the total volume and contain no more than 20% of mass if the largest supercluster is excluded. Likewise, individual voids totally occupy no more than 14% of volume and contain no more than 4% of mass if the largest void is excluded. The genus of individual superclusters can be ˜ 5 while the genus of individual voids reaches ˜ 55, implying significant amount of substructure in superclusters and especially in voids. Large voids are typically distinctly non-spherical.

A Very Large Array search for emission from HI associated with nearby Lyman alpha absorbers

NASA Technical Reports Server (NTRS)

Van Gorkom, J. H.; Bahcall, J. N.; Jannuzi, B. T.; Schneider, D. P.

1993-01-01

We present a sensitive Very Large Array (VLA) search for H I emission from the vicinity of the Lyman alpha clouds in the Virgo Cluster, which were recently discovered with Hubble Space Telescope (HST) in absorption toward the nearest quasar 3C273. We searched an area of 40 by 40 arcmin centered on 3C273, covering a velocity range from 840 to 1840 km/s. The bandpass was self-calibrated on 3C273 leading to a spectral dynamic range of better than 10(exp 5) to 1. No H I was detected. The rms noise in the final images corresponds to a 3 sigma column density sensitivity of 2.8 x 10(exp 19) sq cm on scales of a few kpc. Small H I clouds could have been detected down to a few times 10(exp 6) solar mass. Our failure to detect H I emission at the higher column densities sets a lower limit to the radius of the Lyman alpha clouds of 3.9 kpc, assuming a spherical geometry.

Stopped-flow kinetic studies of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt.

PubMed

Zhang, Jingyan; Ge, Zhishen; Jiang, Xiaoze; Hassan, P A; Liu, Shiyong

2007-12-15

The kinetics and mechanism of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt, p-toluidine hydrochloride (PTHC), were investigated by stopped-flow with light scattering detection. Spherical sodium dodecyl sulfate (SDS) micelles transform into short ellipsoidal shapes at low salt concentrations ([PTHC]/[SDS], chi(PTHC)=0.3 and 0.4). Upon stopped-flow mixing aqueous solutions of spherical SDS micelles with PTHC, the scattered light intensity gradually increases with time. Single exponential fitting of the dynamic traces leads to characteristic relaxation time, tau(g), for the growth process from spherical to ellipsoidal micelles, and it increases with increasing SDS concentrations. This suggests that ellipsoidal micelles might be produced by successive insertion of unimers into spherical micelles, similar to the case of formation of spherical micelles as suggested by Aniansson-Wall (A-W) theory. At chi(PTHC) > or = 0.5, rod-like micelles with much higher axial ratio form. The scattered light intensity exhibits an initially abrupt increase and then levels off. The dynamic curves can be well fitted with single exponential functions, and the obtained tau(g) decreases with increasing SDS concentration. Thus, the growth from spherical to rod-like micelles might proceed via fusion of spherical micelles, in agreement with mechanism proposed by Ikeda et al. At chi(PTHC)=0.3 and 0.6, the apparent activation energies obtained from temperature dependent kinetic studies for the micellar growth are 40.4 and 3.6 kJ/mol, respectively. The large differences between activation energies for the growth from spherical to ellipsoidal micelles at low chi(PTHC) and the sphere-to-rod transition at high chi(PTHC) further indicate that they should follow different mechanisms. Moreover, the sphere-to-rod transition kinetics of sodium alkyl sulfate with varying hydrophobic chain lengths (n=10, 12, 14, and 16) are also studied. The longer the carbon chain lengths, the slower the sphere-to-rod transition.

The theory of nonstationary thermophoresis of a solid spherical particle

NASA Astrophysics Data System (ADS)

Kuzmin, M. K.; Yalamov, Yu. I.

2007-06-01

The theory of nonstationary thermophoresis of a solid spherical particle in a viscous gaseous medium is presented. The theory is constructed on the solutions of fluid-dynamics and thermal problems, each of which is split into stationary and strictly nonstationary parts. The solution of the stationary parts of the problems gives the final formula for determining the stationary component of the thermophoretic velocity of this particle. To determine the nonstationary component of the thermophoretic velocity of the particle, the corresponding formula in the space of Laplace transforms is derived. The limiting value theorems from operational calculus are used for obtaining the dependence of the nonstationary component of the thermophoretic velocity of the spherical particle on the strictly nonstationary temperature gradient for large and small values of time. The factors determining the thermophoretic velocity of the particle under investigation are determined.

Towards anti-causal Green's function for three-dimensional sub-diffraction focusing

NASA Astrophysics Data System (ADS)

Ma, Guancong; Fan, Xiying; Ma, Fuyin; de Rosny, Julien; Sheng, Ping; Fink, Mathias

2018-06-01

In causal physics, the causal Green's function describes the radiation of a point source. Its counterpart, the anti-causal Green's function, depicts a spherically converging wave. However, in free space, any converging wave must be followed by a diverging one. Their interference gives rise to the diffraction limit that constrains the smallest possible dimension of a wave's focal spot in free space, which is half the wavelength. Here, we show with three-dimensional acoustic experiments that we can realize a stand-alone anti-causal Green's function in a large portion of space up to a subwavelength distance from the focus point by introducing a near-perfect absorber for spherical waves at the focus. We build this subwavelength absorber based on membrane-type acoustic metamaterial, and experimentally demonstrate focusing of spherical waves beyond the diffraction limit.

Planar blast scaling with condensed-phase explosives in a shock tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Scott L

2011-01-25

Blast waves are strong shock waves that result from large power density deposition into a fluid. The rapid energy release of high-explosive (HE) detonation provides sufficiently high power density for blast wave generation. Often it is desirable to quantify the energy released by such an event and to determine that energy relative to other reference explosives to derive an explosive-equivalence value. In this study, we use condensed-phase explosives to drive a blast wave in a shock tube. The explosive material and quantity were varied to produce blast waves of differing strengths. Pressure transducers at varying lengths measured the post-shock pressure,more » shock-wave arrival time and sidewall impulse associated with each test. Blast-scaling concepts in a one-dimensional geometry were then used to both determine the energy release associated with each test and to verify the scaling of the shock position versus time, overpressure versus distance, and impulse. Most blast scaling measurements to-date have been performed in a three-dimensional geometry such as a blast arena. Testing in a three-dimensional geometry can be challenging, however, as spherical shock-wave symmetry is required for good measurements. Additionally, the spherical wave strength decays rapidly with distance and it can be necessary to utilize larger (several kg) quantities of explosive to prevent significant decay from occurring before an idealized blast wave has formed. Such a mode of testing can be expensive, require large quantities of explosive, and be limited by both atmospheric conditions (such as rain) and by noise complaints from the population density near the test arena. Testing is possible in more compact geometries, however. Non-planar blast waves can be formed into a quasi-planar shape by confining the shock diffraction with the walls of a shock tube. Regardless of the initial form, the wave shape will begin to approximate a planar front after successive wave reflections from the tube walls. Such a technique has previously been used to obtain blast scaling measurements in the planar geometry with gaseous explosives and the condensed-phase explosive nitroguanidine. Recently, there has been much interest in the blast characterization of various non-ideal high explosive (NIHE) materials. With non-ideals, the detonation reaction zone is significantly larger (up to several cm for ANFO) than more ideal explosives. Wave curvature, induced by charge-geometry, can significantly affect the energy release associated with NIHEs. To measure maximum NIHE energy release accurately, it is desirable to minimize any such curvature and, if possible, to overdrive the detonation shock to ensure completion of chemical reactions ahead of the sonic locus associated with the reaction zone. This is achieved in the current study through use of a powerful booster HE and a charge geometry consisting of short cylindrical lengths of NIHE initiated along the charge centerline.« less

The spectral element method (SEM) on variable-resolution grids: evaluating grid sensitivity and resolution-aware numerical viscosity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guba, O.; Taylor, M. A.; Ullrich, P. A.

2014-11-27

We evaluate the performance of the Community Atmosphere Model's (CAM) spectral element method on variable-resolution grids using the shallow-water equations in spherical geometry. We configure the method as it is used in CAM, with dissipation of grid scale variance, implemented using hyperviscosity. Hyperviscosity is highly scale selective and grid independent, but does require a resolution-dependent coefficient. For the spectral element method with variable-resolution grids and highly distorted elements, we obtain the best results if we introduce a tensor-based hyperviscosity with tensor coefficients tied to the eigenvalues of the local element metric tensor. The tensor hyperviscosity is constructed so that, formore » regions of uniform resolution, it matches the traditional constant-coefficient hyperviscosity. With the tensor hyperviscosity, the large-scale solution is almost completely unaffected by the presence of grid refinement. This later point is important for climate applications in which long term climatological averages can be imprinted by stationary inhomogeneities in the truncation error. We also evaluate the robustness of the approach with respect to grid quality by considering unstructured conforming quadrilateral grids generated with a well-known grid-generating toolkit and grids generated by SQuadGen, a new open source alternative which produces lower valence nodes.« less

A conserved pattern of differential expansion of cortical areas in simian primates.

PubMed

Chaplin, Tristan A; Yu, Hsin-Hao; Soares, Juliana G M; Gattass, Ricardo; Rosa, Marcello G P

2013-09-18

The layout of areas in the cerebral cortex of different primates is quite similar, despite significant variations in brain size. However, it is clear that larger brains are not simply scaled up versions of smaller brains: some regions of the cortex are disproportionately large in larger species. It is currently debated whether these expanded areas arise through natural selection pressures for increased cognitive capacity or as a result of the application of a common developmental sequence on different scales. Here, we used computational methods to map and quantify the expansion of the cortex in simian primates of different sizes to investigate whether there is any common pattern of cortical expansion. Surface models of the marmoset, capuchin, and macaque monkey cortex were registered using the software package CARET and the spherical landmark vector difference algorithm. The registration was constrained by the location of identified homologous cortical areas. When comparing marmosets with both capuchins and macaques, we found a high degree of expansion in the temporal parietal junction, the ventrolateral prefrontal cortex, and the dorsal anterior cingulate cortex, all of which are high-level association areas typically involved in complex cognitive and behavioral functions. These expanded maps correlated well with previously published macaque to human registrations, suggesting that there is a general pattern of primate cortical scaling.

Bubble Size Distribution in a Vibrating Bubble Column

NASA Astrophysics Data System (ADS)

Mohagheghian, Shahrouz; Wilson, Trevor; Valenzuela, Bret; Hinds, Tyler; Moseni, Kevin; Elbing, Brian

2016-11-01

While vibrating bubble columns have increased the mass transfer between phases, a universal scaling law remains elusive. Attempts to predict mass transfer rates in large industrial scale applications by extrapolating laboratory scale models have failed. In a stationary bubble column, mass transfer is a function of phase interfacial area (PIA), while PIA is determined based on the bubble size distribution (BSD). On the other hand, BSD is influenced by the injection characteristics and liquid phase dynamics and properties. Vibration modifies the BSD by impacting the gas and gas-liquid dynamics. This work uses a vibrating cylindrical bubble column to investigate the effect of gas injection and vibration characteristics on the BSD. The bubble column has a 10 cm diameter and was filled with water to a depth of 90 cm above the tip of the orifice tube injector. BSD was measured using high-speed imaging to determine the projected area of individual bubbles, which the nominal bubble diameter was then calculated assuming spherical bubbles. The BSD dependence on the distance from the injector, injector design (1.6 and 0.8 mm ID), air flow rates (0.5 to 5 lit/min), and vibration conditions (stationary and vibration conditions varying amplitude and frequency) will be presented. In addition to mean data, higher order statistics will also be provided.

The spectral element method on variable resolution grids: evaluating grid sensitivity and resolution-aware numerical viscosity

DOE PAGES

Guba, O.; Taylor, M. A.; Ullrich, P. A.; ...

2014-06-25

We evaluate the performance of the Community Atmosphere Model's (CAM) spectral element method on variable resolution grids using the shallow water equations in spherical geometry. We configure the method as it is used in CAM, with dissipation of grid scale variance implemented using hyperviscosity. Hyperviscosity is highly scale selective and grid independent, but does require a resolution dependent coefficient. For the spectral element method with variable resolution grids and highly distorted elements, we obtain the best results if we introduce a tensor-based hyperviscosity with tensor coefficients tied to the eigenvalues of the local element metric tensor. The tensor hyperviscosity ismore » constructed so that for regions of uniform resolution it matches the traditional constant coefficient hyperviscsosity. With the tensor hyperviscosity the large scale solution is almost completely unaffected by the presence of grid refinement. This later point is important for climate applications where long term climatological averages can be imprinted by stationary inhomogeneities in the truncation error. We also evaluate the robustness of the approach with respect to grid quality by considering unstructured conforming quadrilateral grids generated with a well-known grid-generating toolkit and grids generated by SQuadGen, a new open source alternative which produces lower valence nodes.« less

A parametrisation of modified gravity on nonlinear cosmological scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lombriser, Lucas, E-mail: llo@roe.ac.uk

2016-11-01

Viable modifications of gravity on cosmological scales predominantly rely on screening mechanisms to recover Einstein's Theory of General Relativity in the Solar System, where it has been well tested. A parametrisation of the effects of such modifications in the spherical collapse model is presented here for the use of modelling the modified nonlinear cosmological structure. The formalism allows an embedding of the different screening mechanisms operating in scalar-tensor theories through large values of the gravitational potential or its first or second derivatives as well as of linear suppression effects or more general transitions between modified and Einstein gravity limits. Eachmore » screening or suppression mechanism is parametrised by a time, mass, and environment dependent screening scale, an effective modified gravitational coupling in the fully unscreened limit that can be matched to linear theory, the exponent of a power-law radial profile of the screened coupling, determined by derivatives, symmetries, and potentials in the scalar field equation, and an interpolation rate between the screened and unscreened limits. Along with generalised perturbative methods, the parametrisation may be used to formulate a nonlinear extension to the linear parametrised post-Friedmannian framework to enable generalised tests of gravity with the wealth of observations from the nonlinear cosmological regime.« less

Concordance cosmology without dark energy

NASA Astrophysics Data System (ADS)

Rácz, Gábor; Dobos, László; Beck, Róbert; Szapudi, István; Csabai, István

2017-07-01

According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general relativistic theories. We estimate local expansion rates for a large number of such regions, and use a scale parameter calculated from the volume-averaged increments of local scale parameters at each time step in an otherwise standard cosmological N-body simulation. The particle mass, corresponding to a coarse graining scale, is an adjustable parameter. This mean field approximation neglects tidal forces and boundary effects, but it is the first step towards a non-perturbative statistical estimation of the effect of non-linear evolution of structure on the expansion rate. Using our algorithm, a simulation with an initial Ωm = 1 Einstein-de Sitter setting closely tracks the expansion and structure growth history of the Λ cold dark matter (ΛCDM) cosmology. Due to small but characteristic differences, our model can be distinguished from the ΛCDM model by future precision observations. Moreover, our model can resolve the emerging tension between local Hubble constant measurements and the Planck best-fitting cosmology. Further improvements to the simulation are necessary to investigate light propagation and confirm full consistency with cosmic microwave background observations.

Spherical crystallization: A technique use to reform solubility and flow property of active pharmaceutical ingredients.

PubMed

Chatterjee, Arindam; Gupta, Madan Mohan; Srivastava, Birendra

2017-01-01

Tablets have been choice of manufacturers over the years due to their comparatively low cost of manufacturing, packaging, shipping, and ease of administration; also have better stability and can be considered virtually tamper proof. A major challenge in formulation development of the tablets extends from lower solubility of the active agent to the elaborated manufacturing procedures for obtaining a compressible granular material. Moreover, the validation and documentation increases, as the numbers of steps increases for an industrially acceptable granulation process. Spherical crystallization (SC) is a promising technique, which encompass the crystallization, agglomeration, and spheronization phenomenon in a single step. Initially, two methods, spherical agglomeration, and emulsion solvent diffusion, were suggested to get a desired result. Later on, the introduction of modified methods such as crystallo-co-agglomeration, ammonia diffusion system, and neutralization techniques overcame the limitations of the older techniques. Under controlled conditions such as solvent composition, mixing rate and temperature, spherical dense agglomerates cluster from particles. Application of the SC technique includes production of compacted spherical particles of drug having improved uniformity in shape and size of particles, good bulk density, better flow properties as well as better solubility so SC when used on commercial scale will bring down the production costs of pharmaceutical tablet and will increase revenue for the pharmaceutical industries in the competitive market. This review summarizes the technologies available for SC and also suggests the parameters for evaluation of a viable product.

Cutoff size need not strongly influence molecular dynamics results for solvated polypeptides.

PubMed

Beck, David A C; Armen, Roger S; Daggett, Valerie

2005-01-18

The correct treatment of van der Waals and electrostatic nonbonded interactions in molecular force fields is essential for performing realistic molecular dynamics (MD) simulations of solvated polypeptides. The most computationally tractable treatment of nonbonded interactions in MD utilizes a spherical distance cutoff (typically, 8-12 A) to reduce the number of pairwise interactions. In this work, we assess three spherical atom-based cutoff approaches for use with all-atom explicit solvent MD: abrupt truncation, a CHARMM-style electrostatic shift truncation, and our own force-shifted truncation. The chosen system for this study is an end-capped 17-residue alanine-based alpha-helical peptide, selected because of its use in previous computational and experimental studies. We compare the time-averaged helical content calculated from these MD trajectories with experiment. We also examine the effect of varying the cutoff treatment and distance on energy conservation. We find that the abrupt truncation approach is pathological in its inability to conserve energy. The CHARMM-style shift truncation performs quite well but suffers from energetic instability. On the other hand, the force-shifted spherical cutoff method conserves energy, correctly predicts the experimental helical content, and shows convergence in simulation statistics as the cutoff is increased. This work demonstrates that by using proper and rigorous techniques, it is possible to correctly model polypeptide dynamics in solution with a spherical cutoff. The inherent computational advantage of spherical cutoffs over Ewald summation (and related) techniques is essential in accessing longer MD time scales.

Why the Pre-Copernican Cosmological Revolution Was Not a Revolution?

NASA Astrophysics Data System (ADS)

Pacholczyk, A. G.

The 'scientific component' of the Copernican cosmological revolution followed a seemingly minor local structural change (consisting of the transposition of the Earth and the Sun), initially not affecting the global Platonic-Aristotelian spherical symmetry of the Universe and the general arrangement of astronomical bodies at sufficiently large distances from its center. Yet this change resulted in a rich 'ideological component' of the Copernican revolution in the Popperian sense; the importance of this ideological component is generally regarded as a consequence of the tensions arising from apparent contradictions between the new cosmos and several Scriptural passages (as if the previous Platonic-Aristotelian cosmos were in perfect agreement with the Scriptures, which certainly was not the case). The scientific component of the pre-Copernican cosmological revolution (replacing the plane-parallel scriptural cosmos with the spherically symmetric non-scriptural Universe of Plato and Aristotle), was a major global change in the large-scale structure of the Universe. This change took place at different times in different places in Christendom, and was by no means ideologically revolutionary: the pre-Copernican revolution had a very insignificant 'ideological component'. In this paper, after examining this transition in more detail, we shall ask the pertinent question: why did the pre-Copernican cosmological revolution not have any significant 'ideological component'? If the God-created Universe could be depicted in the opinion of the majority of Church Fathers and Schoolmen by the (non-scriptural) spherically symmetric Platonic or Aristotelian model as well as by the (scriptural) tabernacular Babylonian model, then why couldn't it be described just as well in the opinion of 17th century churchmen by the (also non-scriptural) Copernican model? The paper suggests that the tentative answers to these questions are provided by different anthropocentric ramifications of respective cosmologies which determine the difference between the ideological components of the two cosmological revolutions. At the time of the Copernican revolution, there was no conceivable alternative to a geometric conceptualization of mankind's centrality in the Universe. That is why geometric decentralization was fought against with such intensity. It took three centuries and a radically different cosmological paradigm to find another (anthropic) form of understanding this centrality, after it was seemingly lost for such a long time.

Temperature effect on the small-to-large crossover lengthscale of hydrophobic hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Djikaev, Y. S., E-mail: idjikaev@buffalo.edu; Ruckenstein, E.

2013-11-14

The thermodynamics of hydration is expected to change gradually from entropic for small solutes to enthalpic for large ones. The small-to-large crossover lengthscale of hydrophobic hydration depends on the thermodynamic conditions of the solvent such as temperature, pressure, presence of additives, etc. We attempt to shed some light on the temperature dependence of the crossover lengthscale by using a probabilistic approach to water hydrogen bonding that allows one to obtain an analytic expression for the number of bonds per water molecule as a function of both its distance to a solute and solute radius. Incorporating that approach into the densitymore » functional theory, one can examine the solute size effects on its hydration over the entire small-to-large lengthscale range at a series of different temperatures. Knowing the dependence of the hydration free energy on the temperature and solute size, one can also obtain its enthalpic and entropic contributions as functions of both temperature and solute size. These functions can provide some interesting insight into the temperature dependence of the crossover lengthscale of hydrophobic hydration. The model was applied to the hydration of spherical particles of various radii in water in the temperature range from T = 293.15 K to T = 333.15 K. The model predictions for the temperature dependence of the hydration free energy of small hydrophobes are consistent with the experimental and simulational data on the hydration of simple molecular solutes. Three alternative definitions for the small-to-large crossover length-scale of hydrophobic hydration are proposed, and their temperature dependence is obtained. Depending on the definition and temperature, the small-to-large crossover in the hydration mechanism is predicted to occur for hydrophobes of radii from one to several nanometers. Independent of its definition, the crossover length-scale is predicted to decrease with increasing temperature.« less

Large aspheric optics for high-power, high-energy laser

NASA Astrophysics Data System (ADS)

Geyl, Roland; Houbre, Francois

2001-12-01

SAGEM, within its REOSC high performance optics product line, has developed through the years a specific knowledge in large plano, spherical and aspherical optics for high energy or high power laser. This paper is aimed to illustrate the application of aspheric optics for such laser application with several examples of increasing optical surface complexity.

Novel Approach to Conducting Blast Load Analyses Using Abaqus/Explicit-CEL

DTIC Science & Technology

2010-05-01

versus uncased, effects of afterburning , angle of incidence with respect to incoming shock, nearby geometry/barriers interacting with the shock...2. Blast parameters as a function of scaled distance – from TNT air blast data (DOE/TIC-11268, 1981). Due to inertial effects, the volume of air...positive phase duration) can be determined for a particular scaled distance. Figure 2 was generated from TNT air blast data for bare, spherical charges

Buckling Instability Causes Inertial Thrust for Spherical Swimmers at All Scales

NASA Astrophysics Data System (ADS)

Djellouli, Adel; Marmottant, Philippe; Djeridi, Henda; Quilliet, Catherine; Coupier, Gwennou

2017-12-01

Microswimmers, and among them aspirant microrobots, generally have to cope with flows where viscous forces are dominant, characterized by a low Reynolds number (Re). This implies constraints on the possible sequences of body motion, which have to be nonreciprocal. Furthermore, the presence of a strong drag limits the range of resulting velocities. Here, we propose a swimming mechanism which uses the buckling instability triggered by pressure waves to propel a spherical, hollow shell. With a macroscopic experimental model, we show that a net displacement is produced at all Re regimes. An optimal displacement caused by nontrivial history effects is reached at intermediate Re. We show that, due to the fast activation induced by the instability, this regime is reachable by microscopic shells. The rapid dynamics would also allow high-frequency excitation with standard traveling ultrasonic waves. Scale considerations predict a swimming velocity of order 1 cm /s for a remote-controlled microrobot, a suitable value for biological applications such as drug delivery.

Co-Seismic Mass Dislocation and its Effect on Earth's Rotation and Gravity

NASA Technical Reports Server (NTRS)

Chao, B. F.; Gross, R. S.

2002-01-01

Mantle processes often involve large-scale mass transport, ranging from mantle convection, tectonic motions, glacial isostatic adjustment, to tides, atmospheric and oceanic loadings, volcanism and seismicity. On very short time scale of less than an hour, co-seismic event, apart from the shaking that is the earthquake, leaves behind permanent (step-function-like) dislocations in the crust and mantle. This redistribution of mass changes the Earth's inertia tensor (and hence Earth's rotation in both length-of-day and polar motion), and the gravity field (in terms of spherical harmonic Stokes coefficients). The question is whether these effects are large enough to be of any significance. In this paper we report updated calculation results based on Chao & Gross (1987). The calculation uses the normal mode summation scheme, applied to nearly twenty thousand major earthquakes that occurred during 1976-2002, according to source mechanism solutions given by the Harvard Central Moment Tensor catalog. Compared to the truly large ones earlier in the century, the earthquakes we study are individually all too small to have left any discernible signature in geodetic records of Earth rotation or global gravity field. However, their collective effects continue to exhibit an extremely strong statistical tendencies. For example, earthquakes conspire to decrease J2 and J22 while shortening LOD, resulting in a rounder and more compact Earth. Strong tendency is also seen in the earthquakes trying to nudge the Earth rotation pole towards approximately 140 degrees E, roughly opposite to the observed polar drift direction. The geophysical significance and implications will be further studied.

Co-Seismic Mass Dislocation and Its Effect on Earth's Rotation and Gravity

NASA Technical Reports Server (NTRS)

Chao, Benjamin F.

1999-01-01

Mantle processes often involve large-scale mass transport, ranging from mantle convection, tectonic motions, glacial isostatic adjustment, to tides, atmospheric and oceanic loadings, volcanism and seismicity. On very short time scale of less than an hour, co-seismic event, apart from the "shaking" that is the earthquake, leaves behind permanent (step-function-like) dislocations in the crust and mantle. This redistribution of mass changes the Earth's inertia tensor (and hence Earth's rotation in both length-of-day and polar motion), and the gravity field (in terms of spherical harmonic Stokes coefficients). The question is whether these effects are large enough to be of any significance. In this paper we report updated calculation results. The calculation uses the normal mode summation scheme, applied to 15,814 major earthquakes that occurred during 1976-1998, according to source mechanism solutions given by the Harvard Central Moment Tensor catalog. Compared to the truly large ones earlier in the century, the earthquakes we study are individually all too small to have left any discernible signature in geodetic records of Earth rotation or global gravity field. However, their collective effects continue to exhibit an extremely strong statistical tendencies. For example, earthquakes conspire to decrease J(sub 2) and J(sub 22) while shortening LOD, resulting in a rounder and more compact Earth. Strong tendency is also seen in the earthquakes trying to "nudge" the Earth rotation pole towards about 140 degree E, roughly opposite to the observed polar drift direction. The geophysical significance and implications will be further studied.

Meridional flow in the solar convection zone. I. Measurements from gong data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kholikov, S.; Serebryanskiy, A.; Jackiewicz, J., E-mail: kholikov@noao.edu

2014-04-01

Large-scale plasma flows in the Sun's convection zone likely play a major role in solar dynamics on decadal timescales. In particular, quantifying meridional motions is a critical ingredient for understanding the solar cycle and the transport of magnetic flux. Because the signal of such features can be quite small in deep solar layers and be buried in systematics or noise, the true meridional velocity profile has remained elusive. We perform time-distance helioseismology measurements on several years worth of Global Oscillation Network Group Doppler data. A spherical harmonic decomposition technique is applied to a subset of acoustic modes to measure travel-timemore » differences to try to obtain signatures of meridional flows throughout the solar convection zone. Center-to-limb systematics are taken into account in an intuitive yet ad hoc manner. Travel-time differences near the surface that are consistent with a poleward flow in each hemisphere and are similar to previous work are measured. Additionally, measurements in deep layers near the base of the convection zone suggest a possible equatorward flow, as well as partial evidence of a sign change in the travel-time differences at mid-convection zone depths. This analysis on an independent data set using different measurement techniques strengthens recent conclusions that the convection zone may have multiple 'cells' of meridional flow. The results may challenge the common understanding of one large conveyor belt operating in the solar convection zone. Further work with helioseismic inversions and a careful study of systematic effects are needed before firm conclusions of these large-scale flow structures can be made.« less

Use of Spherical Instrumented Indentation to Evaluate the Tensile Properties of 3D Combined Structures

NASA Astrophysics Data System (ADS)

Song, Won-Seok; Kim, Seung-Gyu; Kim, Young-Cheon; Kwon, Dongil

2015-03-01

In this paper we propose a novel method, spherical indentation, for evaluation of the plastic properties of combined structures. Three-dimensional (3D) printed products, for example gradient metal alloys consisting of different kinds of material, contain interfaces that can act as weak points and threaten the mechanical reliability of products. Combined structures containing an interface between Cu alloy and Ag were prepared for testing. Samples were heat-treated at 100°C and 200°C for 3 h to optimize processing conditions. The indentation tensile properties of the samples were estimated by analyzing multiple loading-unloading curves obtained by use of the representative stress and strain method. A continuous increase in both yield strength and tensile strength was observed for the Cu alloy and the Cu/Ag interface after heat treatment at up to 200°C, because of precipitation hardening. These experimental results show that mechanical characterization of combined structures by spherical indentation is highly useful on the nano and micro scales.

iSAP: Interactive Sparse Astronomical Data Analysis Packages

NASA Astrophysics Data System (ADS)

Fourt, O.; Starck, J.-L.; Sureau, F.; Bobin, J.; Moudden, Y.; Abrial, P.; Schmitt, J.

2013-03-01

iSAP consists of three programs, written in IDL, which together are useful for spherical data analysis. MR/S (MultiResolution on the Sphere) contains routines for wavelet, ridgelet and curvelet transform on the sphere, and applications such denoising on the sphere using wavelets and/or curvelets, Gaussianity tests and Independent Component Analysis on the Sphere. MR/S has been designed for the PLANCK project, but can be used for many other applications. SparsePol (Polarized Spherical Wavelets and Curvelets) has routines for polarized wavelet, polarized ridgelet and polarized curvelet transform on the sphere, and applications such denoising on the sphere using wavelets and/or curvelets, Gaussianity tests and blind source separation on the Sphere. SparsePol has been designed for the PLANCK project. MS-VSTS (Multi-Scale Variance Stabilizing Transform on the Sphere), designed initially for the FERMI project, is useful for spherical mono-channel and multi-channel data analysis when the data are contaminated by a Poisson noise. It contains routines for wavelet/curvelet denoising, wavelet deconvolution, multichannel wavelet denoising and deconvolution.

Warm dark matter effects in a spherical collapse model with shear and angular momentum

NASA Astrophysics Data System (ADS)

Marciu, Mihai

2016-03-01

This paper investigates the nonlinear structure formation in a spherical top-hat collapse model based on the pseudo-Newtonian approximation. The system is composed of warm dark matter and dark energy and the dynamical properties of the collapsing region are analyzed for various parametrizations of the dark matter equation of state which are in agreement with current observations. Concerning dark energy, observational constraints of the Chevallier-Polarski-Linder model and the Jassal-Bagla-Padmanabhan equation of state have been considered. During the collapse, the positive dark matter pressure leads to an increase of growth for dark matter and dark energy perturbations and an accelerated expansion for the spherical region. Hence, in the warm dark matter hypothesis, the structure formation is accelerated and the inconsistencies of the Λ CDM model at the galactic scales could be solved. The results obtained are applicable only to adiabatic warm dark matter physical models which are compatible with the pseudo-Newtonian approach.

Neutron Generation by Laser-Driven Spherically Convergent Plasma Fusion.

PubMed

Ren, G; Yan, J; Liu, J; Lan, K; Chen, Y H; Huo, W Y; Fan, Z; Zhang, X; Zheng, J; Chen, Z; Jiang, W; Chen, L; Tang, Q; Yuan, Z; Wang, F; Jiang, S; Ding, Y; Zhang, W; He, X T

2017-04-21

We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 10^{14}-10^{15}  W/cm^{2} intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Y_{n} to be related to the laser energy E_{L}, the hohlraum radius R_{h}, and the pulse duration τ through a scaling law of Y_{n}∝(E_{L}/R_{h}^{1.2}τ^{0.2})^{2.5}. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.

Neutron Generation by Laser-Driven Spherically Convergent Plasma Fusion

NASA Astrophysics Data System (ADS)

Ren, G.; Yan, J.; Liu, J.; Lan, K.; Chen, Y. H.; Huo, W. Y.; Fan, Z.; Zhang, X.; Zheng, J.; Chen, Z.; Jiang, W.; Chen, L.; Tang, Q.; Yuan, Z.; Wang, F.; Jiang, S.; Ding, Y.; Zhang, W.; He, X. T.

2017-04-01

We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 1 014- 1 015 W /cm2 intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Yn to be related to the laser energy EL, the hohlraum radius Rh, and the pulse duration τ through a scaling law of Yn∝(EL/Rh1.2τ0.2 )2.5. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.

Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

DOE PAGES

Wang, W. X.; Ethier, S.; Ren, Y.; ...

2015-10-30

New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offeringmore » one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.« less

Bio-inspired in situ growth of monolayer silver nanoparticles on graphene oxide paper as multifunctional substrate

NASA Astrophysics Data System (ADS)

Li, Shi-Kuo; Yan, You-Xian; Wang, Jin-Long; Yu, Shu-Hong

2013-11-01

In this study, we report a facile bio-inspired method for large-scale preparation of highly dispersed Ag nanoparticles (NPs) on the surface of flexible reduced graphene oxide (rGO) paper with using dopamine (DA) both as a reductant and a surface modifier. Through the self-polymerization of dopamine, free-standing GO paper can be simultaneously reduced and modified with following in situ growth of monolayer Ag NPs on such a substrate. The spherical Ag NPs with an average diameter of 80 nm have a narrow size distribution and tunable cover density. Such a flexible rGO/Ag hybrid paper presents enhanced antibacterial activity against E. coli and a high active and sensitive SERS response toward Rhodamine 6G (R6G) molecules. The detection signals can be obtained while the R6G concentration is as low as to 10-8 M. This work provides a simple strategy for large-scale fabrication of monolayer Ag NPs on flexible rGO paper as a portable antibacterial substrate and a potential SERS substrate for molecular detection applications.In this study, we report a facile bio-inspired method for large-scale preparation of highly dispersed Ag nanoparticles (NPs) on the surface of flexible reduced graphene oxide (rGO) paper with using dopamine (DA) both as a reductant and a surface modifier. Through the self-polymerization of dopamine, free-standing GO paper can be simultaneously reduced and modified with following in situ growth of monolayer Ag NPs on such a substrate. The spherical Ag NPs with an average diameter of 80 nm have a narrow size distribution and tunable cover density. Such a flexible rGO/Ag hybrid paper presents enhanced antibacterial activity against E. coli and a high active and sensitive SERS response toward Rhodamine 6G (R6G) molecules. The detection signals can be obtained while the R6G concentration is as low as to 10-8 M. This work provides a simple strategy for large-scale fabrication of monolayer Ag NPs on flexible rGO paper as a portable antibacterial substrate and a potential SERS substrate for molecular detection applications. Electronic supplementary information (ESI) available: Preparation of GO aqueous colloid solution; XPS spectra of GO paper and PDA modified rGO paper; SEM images of rGO/Ag hybrid paper after immersed in mercaptoethanol solution or in high alkaline solution; photograph and SEM image of pure rGO paper after reaction with AgNO3 solution. SEM image and TEM graph of the pre-synthesized Ag NPs and their SEM images incubated with PDA modified rGO paper; SERS spectra of R6G (1.0 × 10-4 M) molecules before and after cleaning with concentrated hydrochloric acid liquid taken on rGO/Ag hybrid paper obtained by a reaction with 1.0 M AgNO3 solution; SERS spectra of R6G (1.0 × 10-4 M) molecules with different reusable cycles taken on rGO/Ag hybrid paper obtained by a reaction with 1.0 M AgNO3 solution; comparison between different kinds of substrates with the detection limit toward R6G. See DOI: 10.1039/c3nr03857b

Spherical Magnetic Vortex in an External Potential Field: A Dissipative Contraction

NASA Astrophysics Data System (ADS)

Solov'ev, A. A.

2013-09-01

We consider the dissipative evolution of a spherical magnetic vortex with a force-free internal structure, located in a resistive medium and held in equilibrium by the potential external field. The magnetic field inside the sphere is force-free (the model of Chandrasekhar in Proc. Natl. Acad. Sci. 42, 1, 1956). Topologically, it is a set of magnetic toroids enclosed in spherical layers. A new exact MHD solution has been derived, describing a slow, uniform, radial compression of a magnetic spheroid under the pressure of an ambient field, when the plasma density and pressure are growing inside it. There is no dissipation in the potential field outside the sphere, but inside the sphere, where the current density can be high enough, the magnetic energy is continuously converted into heat. Joule dissipation lowers the magnetic pressure inside the sphere, which balances the pressure of the ambient field. This results in radial contraction of the magnetic sphere with a speed defined by the conductivity of the plasma and the characteristic spatial scale of the magnetic field inside the sphere. Formally, the sphere shrinks to zero within a finite time interval (magnetic collapse). The time of compression can be relatively small, within a day, even for a sphere with a radius of about 1 Mm, if the magnetic helicity trapped initially in the sphere (which is proportional to the number of magnetic toroids in the sphere) is quite large. The magnetic system is open along its axis of symmetry. On this axis, the magnetic and electric fields are strictly radial and sign-variable along the radius, so the plasma will be ejected along the axis of magnetic sphere outwards in both directions (as jets) at a rate much higher than the diffusive one, and the charged particles will be accelerated unevenly, in spurts, creating quasi-regular X-ray spikes. The applications of the solution to solar flares are discussed.

Effects of snow grain shape on climate simulations: sensitivity tests with the Norwegian Earth System Model

NASA Astrophysics Data System (ADS)

Räisänen, Petri; Makkonen, Risto; Kirkevåg, Alf; Debernard, Jens B.

2017-12-01

Snow consists of non-spherical grains of various shapes and sizes. Still, in radiative transfer calculations, snow grains are often treated as spherical. This also applies to the computation of snow albedo in the Snow, Ice, and Aerosol Radiation (SNICAR) model and in the Los Alamos sea ice model, version 4 (CICE4), both of which are employed in the Community Earth System Model and in the Norwegian Earth System Model (NorESM). In this study, we evaluate the effect of snow grain shape on climate simulated by NorESM in a slab ocean configuration of the model. An experiment with spherical snow grains (SPH) is compared with another (NONSPH) in which the snow shortwave single-scattering properties are based on a combination of three non-spherical snow grain shapes optimized using measurements of angular scattering by blowing snow. The key difference between these treatments is that the asymmetry parameter is smaller in the non-spherical case (0.77-0.78 in the visible region) than in the spherical case ( ≈ 0.89). Therefore, for the same effective snow grain size (or equivalently, the same specific projected area), the snow broadband albedo is higher when assuming non-spherical rather than spherical snow grains, typically by 0.02-0.03. Considering the spherical case as the baseline, this results in an instantaneous negative change in net shortwave radiation with a global-mean top-of-the-model value of ca. -0.22 W m-2. Although this global-mean radiative effect is rather modest, the impacts on the climate simulated by NorESM are substantial. The global annual-mean 2 m air temperature in NONSPH is 1.17 K lower than in SPH, with substantially larger differences at high latitudes. The climatic response is amplified by strong snow and sea ice feedbacks. It is further demonstrated that the effect of snow grain shape could be largely offset by adjusting the snow grain size. When assuming non-spherical snow grains with the parameterized grain size increased by ca. 70 %, the climatic differences to the SPH experiment become very small. Finally, the impact of assumed snow grain shape on the radiative effects of absorbing aerosols in snow is discussed.

A regional analysis of cloudy mean spherical albedo over the marine stratocumulus region and the tropical Atlantic Ocean. M.S. Thesis

NASA Technical Reports Server (NTRS)

Ginger, Kathryn M.

1993-01-01

Since clouds are the largest variable in Earth's radiation budget, it is critical to determine both the spatial and temporal characteristics of their radiative properties. The relationships between cloud properties and cloud fraction are studied in order to supplement grid scale parameterizations. The satellite data used is from three hourly ISCCP (International Satellite Cloud Climatology Project) and monthly ERBE (Earth Radiation Budget Experiment) data on a 2.5 deg x 2.5 deg latitude-longitude grid. Mean cloud spherical albedo, the mean optical depth distribution, and cloud fraction are examined and compared off the coast of California and the mid-tropical Atlantic for July 1987 and 1988. Individual grid boxes and spatial averages over several grid boxes are correlated to Coakley's theory of reflection for uniform and broken layered cloud and to Kedem, et al.'s findings that rainfall volume and fractional area of rain in convective systems is linear. Kedem's hypothesis can be expressed in terms of cloud properties. That is, the total volume of liquid in a box is a linear function of cloud fraction. Results for the marine stratocumulus regime indicate that albedo is often invariant for cloud fractions of 20% to 80%. Coakley's satellite model of small and large clouds with cores (1 km) and edges (100 m) is consistent with this observation. The cores maintain high liquid water concentrations and large droplets while the edges contain low liquid water concentrations and small droplets. Large clouds are just a collection of cores. The mean optical depth (TAU) distributions support the above observation with TAU values of 3.55 to 9.38 favored across all cloud fractions. From these results, a method based upon Kedem, et al's theory is proposed to separate the cloud fraction and liquid water path (LWP) calculations in a general circulation model (GCM). In terms of spatial averaging, a linear relationship between albedo and cloud fraction is observed. For tropical locations outside the Intertropical Convergence Zone (ITCZ), results of cloud fraction and albedo spatial averaging followed that of the stratus boxes containing few overcast scenes. Both the ideas of Coakley and Kedem, et al. apply. Within the ITCZ, the grid boxes tended to have the same statistical properties as stratus boxes containing many overcast scenes. Because different dynamical forcing mechanisms are present, it is difficult to devise a method for determining subgrid scale variations. Neither of the theories proposed by Kedem, et al. or Coakley works well for the boxes with numerous overcast scenes.