Institute of Scientific and Technical Information of China (English)
曹黎; 成秋明
2012-01-01
由不同尺度过程或作用叠加而形成的混合场在地学领域很常见,研究如何量化这些场的尺度不变性以及如何刻画其各项异性特征具有重要意义.介绍了近期研发的图像各向异性尺度不变性模拟和分解方法,并将其应用于遥感图像处理中.该方法是将各向异性尺度不变性模拟(SIG)和分形滤波(S-A)方法融合的,对于任意二维场,先用S-A模型判断其是否为混合场.如果是混合场,用S-A模型对其进行模式分解,然后再运用SIG模型量化分解后的各组分的各向异性尺度不变性,并描述其具体变换特征.基于一幅混合遥感影像的应用实例表明,该方法能够有效地量化二维混合场的各向异性尺度不变性.此外,混合场只有在正确分解成不同尺度的组分之后才能得到合理的利用.%Mixing fields caused by processes and effects with different scales are very common in geosciences researches. It is important to work out methods to quantify anisotropic scale invariance for these fields. This paper puts forward a newly developed anisotropic scale invariance quantification and mixing data decomposition method for images and applies it to remote sensing image processing, which is an integrated model of the SIG (scale invariant generator) model and S-A (spectrum-area) model. For any 2D fields, S-A model is used to identify if it is a mixing field. If it is, decompose it into different components also by S-A. Then use SIG model to quantify the decomposed components' anisotropic scale invariance and describe their transformation characteristics. An application of processing a mixing remote sensing image demonstrates that this method is able to quantify anisotropic scale invariance for 2D mixing fields and mixing fields must be decomposed properly before application.
Holography for chiral scale-invariant models
R.N. Caldeira Costa; M. Taylor
2010-01-01
Deformation of any d-dimensional conformal field theory by a constant null source for a vector operator of dimension (d + z -1) is exactly marginal with respect to anisotropic scale invariance, of dynamical exponent z. The holographic duals to such deformations are AdS plane waves, with z=2 being th
Semi-implicit anisotropic cosmic ray transport on an unstructured moving mesh
Pakmor, Ruediger; Simpson, Christine M; Kannan, Rahul; Springel, Volker
2016-01-01
In the interstellar medium of galaxies and the intracluster gas of galaxy clusters, the charged particles making up cosmic rays are moving almost exclusively along (but not across) magnetic field lines. The resulting anisotropic transport of cosmic rays in the form of diffusion or streaming not only affects the gas dynamics but also rearranges the magnetic fields themselves. The coupled dynamics of magnetic fields and cosmic rays can thus impact the formation and evolution of galaxies and the thermal evolution of galaxy clusters in critical ways. Numerically studying these effects requires solvers for anisotropic diffusion that are accurate, efficient, and robust, requirements that have proven difficult to satisfy in practice. Here, we present an anisotropic diffusion solver on an unstructured moving mesh that is conservative, does not violate the entropy condition, allows for semi-implicit time integration with individual timesteps, and only requires solving a single linear system of equations per timestep. ...
Local Scale Invariance and Inflation
Singh, Naveen K
2016-01-01
We study the inflation and the cosmological perturbations generated during the inflation in a local scale invariant model. The local scale invariant model introduces a vector field $S_{\\mu}$ in this theory. In this paper, for simplicity, we consider the temporal part of the vector field $S_t$. We show that the temporal part is associated with the slow roll parameter of scalar field. Due to local scale invariance, we have a gauge degree of freedom. In a particular gauge, we show that the local scale invariance provides sufficient number of e-foldings for the inflation. Finally, we estimate the power spectrum of scalar perturbation in terms of the parameters of the theory.
Hidden scale invariance of metals
DEFF Research Database (Denmark)
Hummel, Felix; Kresse, Georg; Dyre, Jeppe C.;
2015-01-01
of metals making the condensed part of the thermodynamic phase diagram effectively one dimensional with respect to structure and dynamics. DFT computed density scaling exponents, related to the Grüneisen parameter, are in good agreement with experimental values for the 16 elements where reliable data were......Density functional theory (DFT) calculations of 58 liquid elements at their triple point show that most metals exhibit near proportionality between the thermal fluctuations of the virial and the potential energy in the isochoric ensemble. This demonstrates a general “hidden” scale invariance...... available. Hidden scale invariance is demonstrated in detail for magnesium by showing invariance of structure and dynamics. Computed melting curves of period three metals follow curves with invariance (isomorphs). The experimental structure factor of magnesium is predicted by assuming scale invariant...
Exact cosmological solutions of scale-invariant gravity theories
Barrow, J D; Barrow, John D.
2006-01-01
We have found new anisotropic vacuum solutions for the scale-invariant gravity theories which generalise Einstein's general relativity to a theory derived from the Lagrangian $R^{1+\\delta}$. These solutions are expanding universes of Kasner form with an initial spacetime singularity at $t=0 $ and exist for $-1/20$.
Hidden scale invariance of metals
Hummel, Felix; Kresse, Georg; Dyre, Jeppe C.; Pedersen, Ulf R.
2015-11-01
Density functional theory (DFT) calculations of 58 liquid elements at their triple point show that most metals exhibit near proportionality between the thermal fluctuations of the virial and the potential energy in the isochoric ensemble. This demonstrates a general "hidden" scale invariance of metals making the condensed part of the thermodynamic phase diagram effectively one dimensional with respect to structure and dynamics. DFT computed density scaling exponents, related to the Grüneisen parameter, are in good agreement with experimental values for the 16 elements where reliable data were available. Hidden scale invariance is demonstrated in detail for magnesium by showing invariance of structure and dynamics. Computed melting curves of period three metals follow curves with invariance (isomorphs). The experimental structure factor of magnesium is predicted by assuming scale invariant inverse power-law (IPL) pair interactions. However, crystal packings of several transition metals (V, Cr, Mn, Fe, Nb, Mo, Ta, W, and Hg), most post-transition metals (Ga, In, Sn, and Tl), and the metalloids Si and Ge cannot be explained by the IPL assumption. The virial-energy correlation coefficients of iron and phosphorous are shown to increase at elevated pressures. Finally, we discuss how scale invariance explains the Grüneisen equation of state and a number of well-known empirical melting and freezing rules.
Hidden scale invariance of metals
DEFF Research Database (Denmark)
Hummel, Felix; Kresse, Georg; Dyre, Jeppe C.;
2015-01-01
Density functional theory (DFT) calculations of 58 liquid elements at their triple point show that most metals exhibit near proportionality between the thermal fluctuations of the virial and the potential energy in the isochoric ensemble. This demonstrates a general “hidden” scale invariance of m...
Scale invariance and renormalization group
International Nuclear Information System (INIS)
Scale invariance enabled the understanding of cooperative phenomena and the study of elementary interactions, such as phase transition phenomena, the Curie critical temperature and spin rearrangement in crystals. The renormalization group method, due to K. Wilson in 1971, allowed for the study of collective phenomena, using an iterative process from smaller scales to larger scales, leading to universal properties and the description of matter state transitions or long polymer behaviour; it also enabled to reconsider the quantum electrodynamic theory and its relations to time and distance scales
Inflation and classical scale invariance
Racioppi, Antonio
2014-01-01
BICEP2 measurement of primordial tensor modes in CMB suggests that cosmological inflation is due to a slowly rolling inflaton taking trans-Planckian values and provides further experimental evidence for the absence of large $M_{\\rm P}$ induced operators. We show that classical scale invariance solves the problem and allows for a remarkably simple scale-free inflaton model without any gauge group. Due to trans-Planckian inflaton values and VEVs, a dynamically induced Coleman-Weinberg-type inflaton potential of the model can predict tensor-to-scalar ratio $r$ in a large range. Precise determination of $r$ in future experiments will allow to test the proposed field-theoretic framework.
Scale invariant Volkov–Akulov supergravity
Directory of Open Access Journals (Sweden)
S. Ferrara
2015-10-01
Full Text Available A scale invariant goldstino theory coupled to supergravity is obtained as a standard supergravity dual of a rigidly scale-invariant higher-curvature supergravity with a nilpotent chiral scalar curvature. The bosonic part of this theory describes a massless scalaron and a massive axion in a de Sitter Universe.
A scale invariance criterion for LES parametrizations
Directory of Open Access Journals (Sweden)
Urs Schaefer-Rolffs
2015-01-01
Full Text Available Turbulent kinetic energy cascades in fluid dynamical systems are usually characterized by scale invariance. However, representations of subgrid scales in large eddy simulations do not necessarily fulfill this constraint. So far, scale invariance has been considered in the context of isotropic, incompressible, and three-dimensional turbulence. In the present paper, the theory is extended to compressible flows that obey the hydrostatic approximation, as well as to corresponding subgrid-scale parametrizations. A criterion is presented to check if the symmetries of the governing equations are correctly translated into the equations used in numerical models. By applying scaling transformations to the model equations, relations between the scaling factors are obtained by demanding that the mathematical structure of the equations does not change.The criterion is validated by recovering the breakdown of scale invariance in the classical Smagorinsky model and confirming scale invariance for the Dynamic Smagorinsky Model. The criterion also shows that the compressible continuity equation is intrinsically scale-invariant. The criterion also proves that a scale-invariant turbulent kinetic energy equation or a scale-invariant equation of motion for a passive tracer is obtained only with a dynamic mixing length. For large-scale atmospheric flows governed by the hydrostatic balance the energy cascade is due to horizontal advection and the vertical length scale exhibits a scaling behaviour that is different from that derived for horizontal length scales.
Gansen, A.; Hachemi, M. El; Belouettar, S.; Hassan, O.; Morgan, K.
2016-09-01
The standard Yee algorithm is widely used in computational electromagnetics because of its simplicity and divergence free nature. A generalization of the classical Yee scheme to 3D unstructured meshes is adopted, based on the use of a Delaunay primal mesh and its high quality Voronoi dual. This allows the problem of accuracy losses, which are normally associated with the use of the standard Yee scheme and a staircased representation of curved material interfaces, to be circumvented. The 3D dual mesh leapfrog-scheme which is presented has the ability to model both electric and magnetic anisotropic lossy materials. This approach enables the modelling of problems, of current practical interest, involving structured composites and metamaterials.
Rainbow gravity and scale-invariant fluctuations
Amelino-Camelia, Giovanni; Gubitosi, Giulia; Magueijo, Joao
2013-01-01
We re-examine a recently proposed scenario where the deformed dispersion relations associated with a flow of the spectral dimension to a UV value of 2 leads to a scale-invariant spectrum of cosmological fluctuations, without the need for inflation. In that scenario Einstein gravity was assumed. The theory displays a wavelength-dependent speed of light but by transforming to a suitable "rainbow frame" this feature can be removed, at the expense of modifying gravity. We find that the ensuing rainbow gravity theory is such that gravity switches off at high energy (or at least leads to a universal conformal coupling). This explains why the fluctuations are scale-invariant on all scales: there is no horizon scale as such. For dispersion relations that do not lead to exact scale invariance we find instead esoteric inflation in the rainbow frame. We argue that these results shed light on the behaviour of gravity under the phenomenon of dimensional reduction.
Universality Classes of Scale Invariant Inflation
Ozkan, Mehmet; Roest, Diederik
2015-01-01
We investigate the inflationary implications of extensions of Poincare symmetry. The simplest constructions with local scale invariance lead to universal predictions: the spectral index is $n_s = 1-2/N$, in excellent agreement with Planck data, while the tensor-to-scalar ratio is determined by a fre
Physics Fun with Discrete Scale Invariance
Georgi, Howard
2016-01-01
I construct a quantum field theory model with discrete scale invariance at tree level. The model has some unusual mathematical properties (such as the appearance of $q$-hypergeometric series) and may possibly have some interesting physical properties as well. In this note, I explore some possible physics that could be regarded as a violation of standard effective field theory ideas.
Scale invariant density perturbations from cyclic cosmology
Frampton, Paul Howard
2016-04-01
It is shown how quantum fluctuations of the radiation during the contraction era of a comes back empty (CBE) cyclic cosmology can provide density fluctuations which re-enter the horizon during the subsequent expansion era and at lowest order are scale invariant, in a Harrison-Zel’dovich-Peebles sense. It is necessary to be consistent with observations of large scale structure.
Broken Scale Invariance and Anomalous Dimensions
Wilson, K. G.
1970-05-01
Mack and Kastrup have proposed that broken scale invariance is a symmetry of strong interactions. There is evidence from the Thirring model and perturbation theory that the dimensions of fields defined by scale transformations will be changed by the interaction from their canonical values. We review these ideas and their consequences for strong interactions.
Scale invariant features extraction for stereo vision
Institute of Scientific and Technical Information of China (English)
Liu Li; Peng Fuyuan; Tian Yan; Wan Yaping
2009-01-01
Stable local feature detection is a fundamental component of many stereo vision problems such as 3-D reconstruction, object localization, and object tracking. A robust method for extracting scale-invariant feature points is presented. First, the Harris corners in three-level pyramid are extracted. Then, the points detected at the highest level of the pyramid are correctly propagated to the lower level by pyramid based scale invariant (PBSI) method. The corners detected repeatedly in different levels are chosen as final feature points. Finally, the characteristic scale is obtained based on maximum entropy method. The experimental results show that the algorithm has low computation cost, strong antinoise capability, and excellent performance in the presence of significant scale changes.
The relativistic virial theorem and scale invariance
Gaite, Jose
2013-01-01
The virial theorem is related to the dilatation properties of bound states. This is realized, in particular, by the Landau-Lifshitz formulation of the relativistic virial theorem, in terms of the trace of the energy-momentum tensor. We construct a Hamiltonian formulation of dilatations in which the relativistic virial theorem naturally arises as the condition of stability against dilatations. A bound state becomes scale invariant in the ultrarelativistic limit, in which its energy vanishes. However, for very relativistic bound states, scale invariance is broken by quantum effects and the virial theorem must include the energy-momentum tensor trace anomaly. This quantum field theory virial theorem is directly related to the Callan-Symanzik equations. The virial theorem is applied to QED and then to QCD, focusing on the bag model of hadrons. In massless QCD, according to the virial theorem, 3/4 of a hadron mass corresponds to quarks and gluons and 1/4 to the trace anomaly.
Scale-Invariant Random Spatial Networks
Aldous, David J
2012-01-01
Real-world road networks have an approximate scale-invariance property; can one devise mathematical models of random networks whose distributions are {\\em exactly} invariant under Euclidean scaling? This requires working in the continuum plane. We introduce an axiomatization of a class of processes we call {\\em scale-invariant random spatial networks}, whose primitives are routes between each pair of points in the plane. We prove that one concrete model, based on minimum-time routes in a binary hierarchy of roads with different speed limits, satisfies the axioms, and note informally that two other constructions (based on Poisson line processes and on dynamic proximity graphs) are expected also to satisfy the axioms. We initiate study of structure theory and summary statistics for general processes in this class.
Scale invariance, unimodular gravity and dark energy
Shaposhnikov, Mikhail; Zenhausern, Daniel
2008-01-01
We demonstrate that the combination of the ideas of unimodular gravity, scale invariance, and the existence of an exactly massless dilaton leads to the evolution of the universe supported by present observations: inflation in the past, followed by the radiation and matter dominated stages and accelerated expansion at present. All mass scales in this type of theories come from one and the same source. © 2008 Elsevier B.V. All rights reserved.
The relativistic virial theorem and scale invariance
Gaite, Jose
2013-01-01
The virial theorem is related to the dilatation properties of bound states. This is realized, in particular, by the Landau-Lifshitz formulation of the relativistic virial theorem, in terms of the trace of the energy-momentum tensor. We construct a Hamiltonian formulation of dilatations in which the relativistic virial theorem naturally arises as the condition of stability against dilatations. A bound state becomes scale invariant in the ultrarelativistic limit, in which its energy vanishes. H...
Generalized scale invariance, clouds and radiative transfer on multifractal clouds
Energy Technology Data Exchange (ETDEWEB)
Lovejoy, S.; Schertzer, D. [Univ. Pierre et Marie Curie, Paris (France)
1995-09-01
Recent systematic satellite studies (LANDSAT, AVHRR, METEOSAT) of cloud radiances using (isotropic) energy spectra have displayed excellent scaling from at least about 300m to about 4000km, even for individual cloud pictures. At first sight, this contradicts the observed diversity of cloud morphology, texture and type. The authors argue that the explanation of this apparent paradox is that the differences are due to anisotropy, e.g. differential stratification and rotation. A general framework for anisotropic scaling expressed in terms of isotropic self-similar scaling and fractals and multifractals is needed. Schertzer and Lovejoy have proposed Generalized Scale Invariance (GSI) in response to this need. In GSI, the statistics of the large and small scales of system can be related to each other by a scale changing operator T{sub {lambda}} which depends only on the scale ratio {lambda}{sub i} there is no characteristic size. 3 refs., 1 fig.
A scale invariant covariance structure on jet space
DEFF Research Database (Denmark)
Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo
2005-01-01
This paper considers scale invariance of statistical image models. We study statistical scale invariance of the covariance structure of jet space under scale space blurring and derive the necessary structure and conditions of the jet covariance matrix in order for it to be scale invariant. As part...... results where we estimate the scale invariant jet covariance of natural images and show that it resembles that of Brownian images....
Natural Inflation with Hidden Scale Invariance
Barrie, Neil D; Liang, Shelley
2016-01-01
We propose a new class of natural inflation models based on a hidden scale invariance. In a very generic Wilsonian effective field theory with an arbitrary number of scalar fields, which exhibits scale invariance via the dilaton, the potential necessarily contains a flat direction in the classical limit. This flat direction is lifted by small quantum corrections and inflation is realised without need for an unnatural fine-tuning. In the conformal limit, the effective potential becomes linear in the inflaton field, yielding to specific predictions for the spectral index and the tensor-to-scalar ratio, being respectively: $n_s-1\\approx 0.025\\left(\\frac{N_{\\star}}{60}\\right)^{-1}$ and $r\\approx 0.0667\\left(\\frac{N_{\\star}}{60}\\right)^{-1}$, where $N_{\\star}\\approx 30-65$ is a number of efolds during observable inflation. This predictions are in reasonable agreement with cosmological measurements. Further improvement of the accuracy of these measurements may turn out to be critical in falsifying our scenario.
Natural inflation with hidden scale invariance
Directory of Open Access Journals (Sweden)
Neil D. Barrie
2016-05-01
Full Text Available We propose a new class of natural inflation models based on a hidden scale invariance. In a very generic Wilsonian effective field theory with an arbitrary number of scalar fields, which exhibits scale invariance via the dilaton, the potential necessarily contains a flat direction in the classical limit. This flat direction is lifted by small quantum corrections and inflation is realised without need for an unnatural fine-tuning. In the conformal limit, the effective potential becomes linear in the inflaton field, yielding to specific predictions for the spectral index and the tensor-to-scalar ratio, being respectively: ns−1≈−0.025(N⋆60−1 and r≈0.0667(N⋆60−1, where N⋆≈30–65 is a number of efolds during observable inflation. This predictions are in reasonable agreement with cosmological measurements. Further improvement of the accuracy of these measurements may turn out to be critical in falsifying our scenario.
Unimodular Gravity with Pseudo-scale Invariance
Jain, Pankaj; Singh, Naveen K
2011-01-01
We consider a model of gravity and matter fields which is invariant only under unimodular general coordinate transformations (GCT). The determinant of the metric is treated as a separate field which transforms as a scalar under unimodular GCT. Furthermore we also demand that the theory obeys pseudo-scale invariance. We study the implications of the resulting theory. We solve the resulting field equations for a sperically symmetric system in vacuum. We find that the resulting solution contains an additional term in comparison to the standard Schwarzchild solution. We also study the cosmological implications of the model. We find that both in case of radiation and matter dominated universe it predicts an accelerated expansion. Furthermore the model does not admit a cosmological constant, thereby solving its fine tuning problem.
Scale-invariant nonlinear optics in gases
Heyl, C M; Miranda, M; Louisy, M; Kovacs, K; Tosa, V; Balogh, E; Varjú, K; L'Huillier, A; Couairon, A; Arnold, C L
2015-01-01
Nonlinear optical methods are becoming ubiquitous in many areas of modern photonics. They are, however, often limited to a certain range of input parameters, such as pulse energy and average power, since restrictions arise from, for example, parasitic nonlinear effects, damage problems and geometrical considerations. Here, we show that many nonlinear optics phenomena in gaseous media are scale-invariant if spatial coordinates, gas density and laser pulse energy are scaled appropriately. We develop a general scaling model for (3+1)-dimensional wave equations, demonstrating the invariant scaling of nonlinear pulse propagation in gases. Our model is numerically applied to high-order harmonic generation and filamentation as well as experimentally verified using the example of pulse post-compression via filamentation. Our results provide a simple recipe for up-or downscaling of nonlinear processes in gases with numerous applications in many areas of science.
Scale-invariant geometric random graphs
Xie, Zheng
2015-01-01
We introduce and analyze a class of growing geometric random graphs that are invariant under rescaling of space and time. Directed connections between nodes are drawn according to an influence zone that depends on node position in space and time, capturing the heterogeneity and increased specialization found in growing networks. Through calculations and numerical simulations we explore the consequences of scale-invariance for geometric graphs generated this way. Our analysis reveals a dichotomy between scale-free and Poisson distributions of in- and out-degree, the existence of a random number of hub nodes, high clustering, and unusual percolation behaviour. Moreover, we show how these properties provide a good fit to those of empirically observed web graphs.
Scale invariance and universality of economic fluctuations
Stanley, H. E.; Amaral, L. A. N.; Gopikrishnan, P.; Plerou, V.
2000-08-01
In recent years, physicists have begun to apply concepts and methods of statistical physics to study economic problems, and the neologism “econophysics” is increasingly used to refer to this work. Much recent work is focused on understanding the statistical properties of time series. One reason for this interest is that economic systems are examples of complex interacting systems for which a huge amount of data exist, and it is possible that economic time series viewed from a different perspective might yield new results. This manuscript is a brief summary of a talk that was designed to address the question of whether two of the pillars of the field of phase transitions and critical phenomena - scale invariance and universality - can be useful in guiding research on economics. We shall see that while scale invariance has been tested for many years, universality is relatively less frequently discussed. This article reviews the results of two recent studies - (i) The probability distribution of stock price fluctuations: Stock price fluctuations occur in all magnitudes, in analogy to earthquakes - from tiny fluctuations to drastic events, such as market crashes. The distribution of price fluctuations decays with a power-law tail well outside the Lévy stable regime and describes fluctuations that differ in size by as much as eight orders of magnitude. (ii) Quantifying business firm fluctuations: We analyze the Computstat database comprising all publicly traded United States manufacturing companies within the years 1974-1993. We find that the distributions of growth rates is different for different bins of firm size, with a width that varies inversely with a power of firm size. Similar variation is found for other complex organizations, including country size, university research budget size, and size of species of bird populations.
Scale-invariant correlations and the distribution of prime numbers
International Nuclear Information System (INIS)
Negative correlations in the distribution of prime numbers are found to display a scale invariance. This occurs in conjunction with a nonstationary behavior. We compare the prime number series to a type of fractional Brownian motion which incorporates both the scale invariance and the nonstationary behavior. Interesting discrepancies remain. The scale invariance also appears to imply the Riemann hypothesis and we study the use of the former as a test of the latter.
Scale invariance, conformality, and generalized free fields
Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; Luty, Markus A.; Prilepina, Valentina
2016-02-01
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum field theories with scale invariance but not conformal invariance. An important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen is that trace of the energy-momentum tensor T could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if T is a generalized free field unless the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functions cannot be understood from the leading terms of the coordinate space OPE. This invalidates a recent argument by Farnsworth-Luty-Prilepina (FLP). Despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.
Computing with scale-invariant neural representations
Howard, Marc; Shankar, Karthik
The Weber-Fechner law is perhaps the oldest quantitative relationship in psychology. Consider the problem of the brain representing a function f (x) . Different neurons have receptive fields that support different parts of the range, such that the ith neuron has a receptive field at xi. Weber-Fechner scaling refers to the finding that the width of the receptive field scales with xi as does the difference between the centers of adjacent receptive fields. Weber-Fechner scaling is exponentially resource-conserving. Neurophysiological evidence suggests that neural representations obey Weber-Fechner scaling in the visual system and perhaps other systems as well. We describe an optimality constraint that is solved by Weber-Fechner scaling, providing an information-theoretic rationale for this principle of neural coding. Weber-Fechner scaling can be generated within a mathematical framework using the Laplace transform. Within this framework, simple computations such as translation, correlation and cross-correlation can be accomplished. This framework can in principle be extended to provide a general computational language for brain-inspired cognitive computation on scale-invariant representations. Supported by NSF PHY 1444389 and the BU Initiative for the Physics and Mathematics of Neural Systems,.
Scale Invariance, Conformality, and Generalized Free Fields
Dymarsky, Anatoly; Komargodski, Zohar; Luty, Markus A; Prilepina, Valentina
2014-01-01
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum field theories with scale invariance but not conformal invariance. An important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen is that trace of the energy-momentum tensor $T$ could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if $T$ is a generalized free field unless the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functio...
THE MOND LIMIT FROM SPACETIME SCALE INVARIANCE
International Nuclear Information System (INIS)
The modified Newtonian dynamics (MOND) limit is shown to follow from a requirement of spacetime scale invariance of the equations of motion for nonrelativistic, purely gravitational systems, i.e., invariance of the equations of motion under (t, r) → (λt, λr) in the limit a 0 → ∞. It is suggested that this should replace the definition of the MOND limit based on the low-acceleration behavior of a Newtonian-MOND interpolating function. In this way, the salient, deep-MOND results-asymptotically flat rotation curves, the mass-rotational-speed relation (baryonic Tully-Fisher relation), the Faber-Jackson relation, etc.,-follow from a symmetry principle. For example, asymptotic flatness of rotation curves reflects the fact that radii change under scaling, while velocities do not. I then comment on the interpretation of the deep-MOND limit as one of 'zero mass': rest masses, whose presence obstructs scaling symmetry, become negligible compared to the 'phantom', dynamical masses-those that some would attribute to dark matter. Unlike the former masses, the latter transform in a way that is consistent with the symmetry. Finally, I discuss the putative MOND-cosmology connection in light of another, previously known symmetry of the deep-MOND limit. In particular, it is suggested that MOND is related to the asymptotic de Sitter geometry of our universe. It is conjectured, for example that in an exact de Sitter cosmos, deep-MOND physics would exactly apply to local systems. I also point out, in this connection, the possible relevance of a de Sitter-conformal-field-theory (dS/CFT) duality.
The Scale Invariant Synchrotron Jet of Flat Spectrum Radio Quasars
Indian Academy of Sciences (India)
L. M. Du; J. M. Bai; Z. H. Xie; T. F. Yi; Y. B. Xu; R. Xue; X. H. Wang
2015-06-01
In this paper, the scale invariance of the synchrotron jet of Flat Spectrum Radio Quasars has been studied using a sample of combined sources from FKM04 and from SDSS DR3 catalogue. Since the research of scale invariance has been focused on sub-Eddington cases that can be fitted onto the fundamental plane, while near-Eddington sources such as FSRQs have not been explicitly studied. The extracted physical properties of synchrotron jet of FSRQs have been shown to be scale invariant using our sample. The results are in good agreement with theoretical expectations of Heinz & Sunyaev (2003). Therefore, the jet synchrotron is shown to be scale independent, regardless of the accretion modes. Results in this article thus lend support to the scale invariant model of the jet synchrotron throughout the mass scale of black hole systems.
Modified dispersion relations, inflation and scale-invariance
Bianco, Stefano; Wilson-Ewing, Edward
2016-01-01
For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to red-shift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This can be done by inflation with a sufficiently large Hubble rate, without any requirement for slow roll. We also show that in the case of slow-roll inflation, modes that start in their vacuum quantum state will become nearly scale-invariant when they exit the Hubble radius for any power law modified dispersion relation.
Manifestly scale-invariant regularization and quantum effective operators
Ghilencea, D M
2016-01-01
Scale invariant theories are often used to address the hierarchy problem, however the regularization of their quantum corrections introduces a dimensionful coupling (dimensional regularization) or scale (Pauli-Villars, etc) which break this symmetry explicitly. We show how to avoid this problem and study the implications of a manifestly scale invariant regularization in (classical) scale invariant theories. We use a dilaton-dependent subtraction function $\\mu(\\sigma)$ which after spontaneous breaking of scale symmetry generates the usual DR subtraction scale $\\mu(\\langle\\sigma\\rangle)$. One consequence is that "evanescent" interactions generated by scale invariance of the action in $d=4-2\\epsilon$ (but vanishing in $d=4$), give rise to new, finite quantum corrections. We find a (finite) correction $\\Delta U(\\phi,\\sigma)$ to the one-loop scalar potential for $\\phi$ and $\\sigma$, beyond the Coleman-Weinberg term. $\\Delta U$ is due to an evanescent correction ($\\propto\\epsilon$) to the field-dependent masses (of...
A DISCUSSION ABOUT SCALE INVARIANTS FOR TENSOR FUNCTIONS
Institute of Scientific and Technical Information of China (English)
Huang Yongnian; Luo Xiongping; Emily S.C.Ching
2000-01-01
It is found that in some cases the complete and irreducible scale invariants given by Ref.[1]are not independent.There are some implicit functional relations among them.The scale invariants for two different cases are calculated.The first case is an arbitrary second order tensor.The second case includes a symmetric tensor,an antisymmetric tensor and a vector.By using the eigentensor notation it is proved that in the first case there are only six independent scale invariants rather than seven as reported in Ref.[1]and in the second case there are only nine independent scale invariants which are leas than that obtained in Ref.[1].
Incorporating scale invariance into the cellular associative neural network
Burles, Nathan; O'Keefe, Simon; Austin, James
2014-01-01
This paper describes an improvement to the Cellular Associative Neural Network, an architecture based on the distributed model of a cellular automaton, allowing it to perform scale invariant pattern matching. The use of tensor products and superposition of patterns allows the system to recall patterns at multiple resolutions simultaneously. Our experimental results show that the architecture is capable of scale invariant pattern matching, but that further investigation is needed to reduce the...
Scale-Invariant Rotating Black Holes in Quadratic Gravity
Directory of Open Access Journals (Sweden)
Guido Cognola
2015-07-01
Full Text Available Black hole solutions in pure quadratic theories of gravity are interesting since they allow the formulation of a set of scale-invariant thermodynamics laws. Recently, we have proven that static scale-invariant black holes have a well-defined entropy, which characterizes equivalent classes of solutions. In this paper, we generalize these results and explore the thermodynamics of rotating black holes in pure quadratic gravity.
Scale invariant cosmology II: model equations and properties
Maeder, Andre
2016-01-01
We want to establish the basic properties of a scale invariant cosmology, that also accounts for the hypothesis of scale invariance of the empty space at large scales. We write the basic analytical properties of the scale invariant cosmological models. The hypothesis of scale invariance of the empty space at large scale brings interesting simplifications in the scale invariant equations for cosmology. There is one new term, depending on the scale factor of the scale invariant cosmology, that opposes to gravity and favours an accelerated expansion. We first consider a zero-density model and find an accelerated expansion, going like t square. In models with matter present, the displacements due to the new term make a significant contribution Omega_l to the energy-density of the Universe, satisfying an equation of the form Omega_m + Omega_k + Omega_l = 1. Unlike the Friedman's models, there is a whole family of flat models (k=0) with different density parameters Omega_m smaller than 1. We examine the basic relat...
Evolving Planck Mass in Classically Scale-Invariant Theories
Kannike, K; Spethmann, C; Veermäe, H
2016-01-01
We consider classically scale-invariant theories with non-minimally coupled scalar fields, where the Planck mass and the hierarchy of physical scales are dynamically generated. The classical theories possess a fixed point, where scale invariance is spontaneously broken. In these theories, however, the Planck mass becomes unstable in the presence of explicit sources of scale invariance breaking, such as non-relativistic matter and cosmological constant terms. We quantify the constraints on such classical models from Big Bang Nucleosynthesis that lead to an upper bound on the non-minimal coupling and require trans-Planckian field values. We show that quantum corrections to the scalar potential can stabilise the fixed point close to the minimum of the Coleman-Weinberg po- tential. The time-averaged motion of the evolving fixed point is strongly suppressed, thus the limits on the evolving gravitational constant from Big Bang Nucleosynthesis and other measurements do not presently constrain this class of theories....
Scale invariant alternatives to General Relativity II: Dilaton properties
Karananas, Georgios K
2016-01-01
In the present paper we revisit gravitational theories which are invariant under TDiffs - transverse (volume preserving) diffeomorphisms and global scale transformations. It is known that these theories can be rewritten in an equivalent diffeomorphism-invariant form with an action including an integration constant (cosmological constant for the particular case of non scale-invariant unimodular gravity). The presence of this integration constant, in general, breaks explicitly scale invariance and induces a run-away potential for (otherwise massless) dilaton, associated with the determinant of the metric tensor. We show, however, that if the metric carries mass dimension $\\left[\\text{GeV}\\right]^{-2}$, the scale invariance of the system is preserved, unlike the situation in theories in which the metric has mass dimension different from $-2$. The dilaton remains massless and couples to other fields only through derivatives, without any conflict with observations. We observe that one can define a specific limit f...
Binary optical filters for scale invariant pattern recognition
Reid, Max B.; Downie, John D.; Hine, Butler P.
1992-01-01
Binary synthetic discriminant function (BSDF) optical filters which are invariant to scale changes in the target object of more than 50 percent are demonstrated in simulation and experiment. Efficient databases of scale invariant BSDF filters can be designed which discriminate between two very similar objects at any view scaled over a factor of 2 or more. The BSDF technique has considerable advantages over other methods for achieving scale invariant object recognition, as it also allows determination of the object's scale. In addition to scale, the technique can be used to design recognition systems invariant to other geometric distortions.
Signatures of discrete scale invariance in Dst time series
Balasis, Georgios; Papadimitriou, Constantinos; Daglis, Ioannis A.; Anastasiadis, Anastasios; Athanasopoulou, Labrini; Eftaxias, Konstantinos
2011-07-01
Self-similar systems are characterized by continuous scale invariance and, in response, the existence of power laws. However, a significant number of systems exhibits discrete scale invariance (DSI) which in turn leads to log-periodic corrections to scaling that decorate the pure power law. Here, we present the results of a search of log-periodic corrections to scaling in the squares of Dst index increments which are taken as proxies of the energy dissipation rate in the magnetosphere. We show that Dst time series exhibit DSI and discuss the consequence of this feature, as well as the possible implications of Dst DSI on space weather forecasting efforts.
Scale invariant Strichartz estimates on tori and applications
Killip, Rowan; Visan, Monica
2014-01-01
We prove scale-invariant Strichartz inequalities for the Schrodinger equation on rectangular tori (rational or irrational) in all dimensions. We use these estimates to give a unified and simpler treatment of local well-posedness of the energy-critical nonlinear Schrodinger equation in dimensions three and four.
Pérez-Nadal, Guillem
2016-01-01
We consider a non-relativistic free scalar field theory with a type of anisotropic scale invariance in which the number of coordinates "scaling like time" is generically greater than one. We propose the Cartesian product of two curved spaces, with the metric of each space parameterized by the other space, as a notion of curved background to which the theory can be extended. We study this type of geometries, and find a family of extensions of the theory to curved backgrounds in which the anisotropic scale invariance is promoted to a local, Weyl-type symmetry.
From dynamical scaling to local scale-invariance: a tutorial
Henkel, Malte
2016-01-01
Dynamical scaling arises naturally in various many-body systems far from equilibrium. After a short historical overview, the elements of possible extensions of dynamical scaling to a local scale-invariance will be introduced. Schr\\"odinger-invariance, the most simple example of local scale-invariance, will be introduced as a dynamical symmetry in the Edwards-Wilkinson universality class of interface growth. The Lie algebra construction, its representations and the Bargman superselection rules will be combined with non-equilibrium Janssen-de Dominicis field-theory to produce explicit predictions for responses and correlators, which can be compared to the results of explicit model studies. At the next level, the study of non-stationary states requires to go over, from Schr\\"odinger-invariance, to ageing-invariance. The ageing algebra admits new representations, which acts as dynamical symmetries on more general equations, and imply that each non-equilibrium scaling operator is characterised by two distinct, ind...
Gauge coupling unification in a classically scale invariant model
Haba, Naoyuki; Ishida, Hiroyuki; Takahashi, Ryo; Yamaguchi, Yuya
2016-02-01
There are a lot of works within a class of classically scale invariant model, which is motivated by solving the gauge hierarchy problem. In this context, the Higgs mass vanishes at the UV scale due to the classically scale invariance, and is generated via the Coleman-Weinberg mechanism. Since the mass generation should occur not so far from the electroweak scale, we extend the standard model only around the TeV scale. We construct a model which can achieve the gauge coupling unification at the UV scale. In the same way, the model can realize the vacuum stability, smallness of active neutrino masses, baryon asymmetry of the universe, and dark matter relic abundance. The model predicts the existence vector-like fermions charged under SU(3) C with masses lower than 1 TeV, and the SM singlet Majorana dark matter with mass lower than 2.6 TeV.
Scale Invariance via a Phase of Slow Expansion
Joyce, Austin
2011-01-01
We consider a cosmological scenario in which a scale-invariant spectrum of curvature perturbations is generated by a rapidly-evolving equation of state on a slowly expanding background. This scenario generalizes the "adiabatic ekpyrotic" mechanism proposed recently in arXiv:0910.2230. Whereas the original proposal assumed a slowly contracting background, the present work shows that the mechanism works equally well on an expanding background. This greatly expands the realm of broader cosmological scenarios in which this mechanism can be embedded. We present a phase space analysis and show that both the expanding and contracting versions of the scenario are dynamical attractors, with the expanding branch having a broader basin of attraction. In both cases, a finite range of scale invariant modes can be generated within the regime of validity of perturbation theory.
Scale invariance via a phase of slow expansion
Joyce, Austin; Khoury, Justin
2011-07-01
We consider a cosmological scenario in which a scale-invariant spectrum of curvature perturbations is generated by a rapidly evolving equation of state on a slowly expanding background. This scenario generalizes the “adiabatic ekpyrotic” mechanism proposed recently by Khoury and Steinhardt [Phys. Rev. Lett.PRLTAO0031-9007 104, 091301 (2010)10.1103/PhysRevLett.104.091301]. Whereas the original proposal assumed a slowly contracting background, the present work shows that the mechanism works equally well on an expanding background. This greatly expands the realm of broader cosmological scenarios in which this mechanism can be embedded. We present a phase space analysis and show that both the expanding and contracting versions of the scenario are dynamical attractors, with the expanding branch having a broader basin of attraction. In both cases, a finite range of scale-invariant modes can be generated within the regime of validity of perturbation theory.
Scale-invariance as the origin of dark radiation?
Directory of Open Access Journals (Sweden)
Dmitry Gorbunov
2014-12-01
Full Text Available Recent cosmological data favor R2-inflation and some amount of non-standard dark radiation in the Universe. We show that a framework of high energy scale invariance can explain these data. The spontaneous breaking of this symmetry provides gravity with the Planck mass and particle physics with the electroweak scale. We found that the corresponding massless Nambu–Goldstone bosons – dilatons – are produced at reheating by the inflaton decay right at the amount needed to explain primordial abundances of light chemical elements and anisotropy of the cosmic microwave background. Then we extended the discussion on the interplay with Higgs-inflation and on general class of inflationary models where dilatons are allowed and may form the dark radiation. As a result we put a lower limit on the reheating temperature in a general scale invariant model of inflation.
Curvaton reheating in a Scale Invariant Two Measures Theory
Guendelman, Eduardo I
2015-01-01
The curvaton reheating mechanism in a Scale Invariant Two Measures Theory defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space-time manifold which are metric independent is studied. The model involves two scalar matter fields, a dilaton, that transforms under scale transformations and it will be used also as the inflaton of the model and another scalar, which does not transform under scale transformations and which will play the role of a curvaton field. Potentials of appropriate form so that the pertinent action is invariant under global Weyl-scale symmetry are introduced. Scale invariance is spontaneously broken upon integration of the equations of motion. After performing transition to the physical Einstein frame we obtain: (i) For given value of the curvaton field an effective potential for the scalar field with two flat regions for the dilaton which allows for a unified description of both early universe inflation as ...
Scale-invariance as the origin of dark radiation?
Energy Technology Data Exchange (ETDEWEB)
Gorbunov, Dmitry, E-mail: gorby@ms2.inr.ac.ru [Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow (Russian Federation); Moscow Institute of Physics and Technology, 141700 Dolgoprudny (Russian Federation); Tokareva, Anna [Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow (Russian Federation); Faculty of Physics of Moscow State University, 119991 Moscow (Russian Federation)
2014-12-12
Recent cosmological data favor R{sup 2}-inflation and some amount of non-standard dark radiation in the Universe. We show that a framework of high energy scale invariance can explain these data. The spontaneous breaking of this symmetry provides gravity with the Planck mass and particle physics with the electroweak scale. We found that the corresponding massless Nambu–Goldstone bosons – dilatons – are produced at reheating by the inflaton decay right at the amount needed to explain primordial abundances of light chemical elements and anisotropy of the cosmic microwave background. Then we extended the discussion on the interplay with Higgs-inflation and on general class of inflationary models where dilatons are allowed and may form the dark radiation. As a result we put a lower limit on the reheating temperature in a general scale invariant model of inflation.
Gauge coupling unification in a classically scale invariant model
Haba, Naoyuki; Takahashi, Ryo; Yamaguchi, Yuya
2015-01-01
There are a lot of works within a class of classically scale invariant model, which is motivated by solving the gauge hierarchy problem. In this context, the Higgs mass vanishes at the UV scale due to the classically scale invariance, and is generated via the Coleman-Weinberg mechanism. Since the mass generation should occur not so far from the electroweak scale, we extend the standard model only around the TeV scale. We construct a model which can achieve the gauge coupling unification at the UV scale. In the same way, the model can realize the vacuum stability, smallness of active neutrino masses, baryon asymmetry of the universe, and dark matter relic abundance. The model predicts the existence vector-like fermions charged under $SU(3)_C$ with masses lower than $1\\,{\\rm TeV}$, and the SM singlet Majorana dark matter with mass lower than $2.6\\,{\\rm TeV}$.
Scale-invariance of human EEG signals in sleep
Cai, S M; Wang, B H; Yang, H J; Zhou, P L; Zhou, T; Cai, Shi-Min; Jiang, Zhao-Hui; Wang, Bing-Hong; Yang, Hui-Jie; Zhou, Pei-Ling; Zhou, Tao
2007-01-01
We investigate the dynamical properties of electroencephalogram (EEG) signals of human in sleep. By using a modified random walk method, We demonstrate that the scale-invariance is embedded in EEG signals after a detrending procedure. Further more, we study the dynamical evolution of probability density function (PDF) of the detrended EEG signals by nonextensive statistical modeling. It displays scale-independent property, which is markedly different from the turbulent-like scale-dependent PDF evolution.
Kernel based visual tracking with scale invariant features
Institute of Scientific and Technical Information of China (English)
Risheng Han; Zhongliang Jing; Yuanxiang Li
2008-01-01
The kernel based tracking has two disadvantages:the tracking window size cannot be adjusted efficiently,and the kernel based color distribution may not have enough ability to discriminate object from clutter background.FDr boosting up the feature's discriminating ability,both scale invariant features and kernel based color distribution features are used as descriptors of tracked object.The proposed algorithm can keep tracking object of varying scales even when the surrounding background is similar to the object's appearance.
Scale-invariant properties of the APM-Stromlo survey
Labini, F. Sylos; Montuori, M.
1997-01-01
We investigate the statistical properties of the APM-Stromlo redshift survey by using the concepts and methods of modern Statistical Physics. We find that galaxy distribution in this survey exhibits scale invariant properties with fractal dimension $D = 2.1 \\pm 0.1$, up to $\\sim 40 \\hmp$, i.e. the limit of its statistical validity, without any tendency towards homogenization. No intrinsic characteristic scales are definitely found in this galaxy sample. We present several tests to study the s...
Directory of Open Access Journals (Sweden)
Xiaoming Xi
2013-07-01
Full Text Available Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in retina identification. As digital retina images always suffer from deformations, the Scale Invariant Feature Transform (SIFT, which is known for its distinctiveness and invariance for scale and rotation, has been introduced to retinal based identification. However, some shortcomings like the difficulty of feature extraction and mismatching exist in SIFT-based identification. To solve these problems, a novel preprocessing method based on the Improved Circular Gabor Transform (ICGF is proposed. After further processing by the iterated spatial anisotropic smooth method, the number of uninformative SIFT keypoints is decreased dramatically. Tested on the VARIA and eight simulated retina databases combining rotation and scaling, the developed method presents promising results and shows robustness to rotations and scale changes.
Scale invariant cosmology III: dynamical models and comparisons with observations
Maeder, Andre
2016-01-01
We examine the properties of the scale invariant cosmological models, also making the specific hypothesis of the scale invariance of the empty space at large scales. Numerical integrations of the cosmological equations for different values of the curvature parameter k and of the density parameter Omega_m are performed. We compare the dynamical properties of the models to the observations at different epochs. The main numerical data and graphical representations are given for models computed with different curvatures and density parameters. The models with non-zero density start explosively with first a braking phase followed by a continuously accelerating expansion. The comparison of the models with the recent observations from supernovae SN Ia, BAO and CMB data from Planck 2015 shows that the scale invariant model with k=0 and Omega_m=0.30 very well fits the observations in the usual Omega_m vs. Omega_Lambda plane and consistently accounts for the accelerating expansion or dark energy. The expansion history ...
One-loop potential with scale invariance and effective operators
Ghilencea, D M
2016-01-01
We study quantum corrections to the scalar potential in classically scale invariant theories, using a manifestly scale invariant regularization. To this purpose, the subtraction scale $\\mu$ of the dimensional regularization is generated after spontaneous scale symmetry breaking, from a subtraction function of the fields, $\\mu(\\phi,\\sigma)$. This function is then uniquely determined from general principles showing that it depends on the dilaton only, with $\\mu(\\sigma)\\sim \\sigma$. The result is a scale invariant one-loop potential $U$ for a higgs field $\\phi$ and dilaton $\\sigma$ that contains an additional {\\it finite} quantum correction $\\Delta U(\\phi,\\sigma)$, beyond the Coleman Weinberg term. $\\Delta U$ contains new, non-polynomial effective operators like $\\phi^6/\\sigma^2$ whose quantum origin is explained. A flat direction is maintained at the quantum level, the model has vanishing vacuum energy and the one-loop correction to the mass of $\\phi$ remains small without tuning (of its self-coupling, etc) bey...
Self-organization in a model of economic system with scale invariant interactions
Pis`mak, Yu. M.
2001-10-01
The method of constructing the local scale invariant stochastic models is proposed. The possible extension of minimal scale-invariant interaction principle for stochastic systems is formulated. A simple scale invariant model that possesses an economical interpretation is considered. Essential characteristics of its self-organization mechanisms are discussed.
Non-linear quantum noise effects in scale invariant junctions
International Nuclear Information System (INIS)
We study non-equilibrium steady state transport in scale invariant quantum junctions with focus on the particle and heat fluctuations captured by the two-point current correlation functions. We show that the nonlinear behavior of the particle current affects both the particle and heat noise. The existence of domains of enhancement and reduction of the noise power with respect to the linear regime are observed. The impact of the statistics is explored. We demonstrate that the bosonic particle noise exceeds the fermionic one in the common domain of heat bath parameters. Multi-lead configurations are also investigated and the effect of probe terminals on the noise is discussed. (paper)
Scale invariant behavior in a large N matrix model
Narayanan, Rajamani; Neuberger, Herbert
2016-01-01
Eigenvalue distributions of properly regularized Wilson-loop operators are used to study the transition from UV behavior to IR behavior in gauge theories coupled to matter that potentially have an IR fixed point. We numerically demonstrate the emergence of scale invariance in a matrix model that describes S U (N ) gauge theory coupled to two flavors of massless adjoint fermions in the large N limit. The eigenvalue distribution of Wilson loops of varying sizes cannot be described by a universal lattice beta function connecting the UV to the IR.
Scale invariance of human electroencephalogram signals in sleep
Cai, Shi-Min; Jiang, Zhao-Hui; Zhou, Tao; Zhou, Pei-Ling; Yang, Hui-Jie; Wang, Bing-Hong
2007-12-01
In this paper, we investigate the dynamical properties of electroencephalogram (EEG) signals of humans in sleep. By using a modified random walk method, we demonstrate that scale-invariance is embedded in EEG signals after a detrending procedure is applied. Furthermore, we study the dynamical evolution of the probability density function (PDF) of the detrended EEG signals by nonextensive statistical modeling. It displays a scale-independent property, which is markedly different from the usual scale-dependent PDF evolution and cannot be described by the Fokker-Planck equation.
Active Shape Models Using Scale Invariant Feature Transform
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A new active shape models (ASMs) was presented, which is driven by scale invariant feature transform (SIFT) local descriptor instead of normalizing first order derivative profiles in the original formulation, to segment lung fields from chest radiographs. The modified SIFT local descriptor, more distinctive than the general intensity and gradient features, is used to characterize the image features in the vicinity of each pixel at each resolution level during the segmentation optimization procedure. Experimental results show that the proposed method is more robust and accurate than the original ASMs in terms of an average overlap percentage and average contour distance in segmenting the lung fields from an available public database.
Higgs naturalness and dark matter stability by scale invariance
Jun Guo; Zhaofeng Kang
2015-01-01
Extending the spacetime symmetries of standard model (SM) by scale invariance (SI) may address the Higgs naturalness problem. In this article we attempt to embed accidental dark matter (DM) into SISM, requiring that the symmetry protecting DM stability is accidental due to the model structure rather than imposed by hand. In this framework, if the light SM-like Higgs boson is the pseudo Goldstone boson of SI spontaneously breaking, we can even pine down the model, two-Higgs-doublets plus a rea...
The MOND limit from space-time scale invariance
Milgrom, Mordehai
2008-01-01
The MOND limit is shown to follow from a requirement of space-time scale invariance of the equations of motion for nonrelativistic, purely gravitational systems; i.e., invariance of the equations of motion under (t,r) goes to (qt,qr), in the limit a0 goes to infinity. It is suggested that this should replace the definition of the MOND limit based on the low-acceleration behavior of a Newtonian-MOND interpolating function. In this way, the salient, deep-MOND results--asymptotically flat rotati...
Scale-Invariant Correlations in Dynamic Bacterial Clusters
Chen, Xiao; Dong, Xu; Be'er, Avraham; Swinney, Harry L.; Zhang, H. P.
2012-04-01
In Bacillus subtilis colonies, motile bacteria move collectively, spontaneously forming dynamic clusters. These bacterial clusters share similarities with other systems exhibiting polarized collective motion, such as bird flocks or fish schools. Here we study experimentally how velocity and orientation fluctuations within clusters are spatially correlated. For a range of cell density and cluster size, the correlation length is shown to be 30% of the spatial size of clusters, and the correlation functions collapse onto a master curve after rescaling the separation with correlation length. Our results demonstrate that correlations of velocity and orientation fluctuations are scale invariant in dynamic bacterial clusters.
Scale invariant behavior in a large N matrix model
Narayanan, Rajamani
2016-01-01
Eigenvalue distributions of properly regularized Wilson loop operators are used to study the transition from ultra-violet (UV) behavior to infra-red (IR) behavior in gauge theories coupled to matter that potentially have an IR fixed point (FP). We numerically demonstrate emergence of scale invariance in a matrix model that describes $SU(N)$ gauge theory coupled to two flavors of massless adjoint fermions in the large $N$ limit. The eigenvalue distribution of Wilson loops of varying sizes cannot be described by a universal lattice beta-function connecting the UV to the IR.
QCD Analysis of the Scale-Invariance of Jets
Larkoski, Andrew J
2012-01-01
Studying the substructure of jets has become a powerful tool for event discrimination and for studying QCD. Typically, jet substructure studies rely on Monte Carlo simulation for vetting their usefulness; however, when possible, it is also important to compute observables with analytic methods. Here, we present a global next-to-leading-log resummation of the angular correlation function which measures the contribution to the mass of a jet from constituents that are within an angle R with respect to one another. For a scale-invariant jet, the angular correlation function should scale as a power of R. Deviations from this behavior can be traced to the breaking of scale invariance in QCD. To do the resummation, we use soft-collinear effective theory relying on the recent proof of factorization of jet observables at e+ e- colliders. Non-trivial requirements of factorization of the angular correlation function are discussed. The calculation is compared to Monte Carlo parton shower and next-to-leading order results...
AN ADVANCED SCALE INVARIANT FEATURE TRANSFORM ALGORITHM FOR FACE RECOGNITION
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Mohammad Mohsen Ahmadinejad
2016-06-01
Full Text Available In computer vision, Scale-invariant feature transform (SIFT algorithm is widely used to describe and detect local features in images due to its excellent performance. But for face recognition, the implementation of SIFT was complicated because of detecting false key-points in the face image due to irrelevant portions like hair style and other background details. This paper proposes an algorithm for face recognition to improve recognition accuracy by selecting relevant SIFT key-points only that by rejecting false key points. In the new proposed Haar-Cascade SIFT algorithm (HC-SIFT, the accuracy in face recognition has been increased from 52.6% to 75.1% from SIFT to HC- SIFT algorithm.
Duality and scale invariant magnetic fields from bouncing universes
Chowdhury, Debika; Jain, Rajeev Kumar
2016-01-01
Recently, we had numerically shown that, for a non-minimal coupling that is a simple power of the scale factor, scale invariant magnetic fields arise in a class of bouncing universes. In this work, we {\\it analytically}\\/ evaluate the spectrum of magnetic and electric fields generated in a sub-class of such models. We illustrate that, for cosmological scales which have wavenumbers much smaller than the wavenumber associated with the bounce, the shape of the spectrum is preserved across the bounce. Using the analytic solutions obtained, we also illustrate that the problem of backreaction is severe at the bounce. Finally, we show that the power spectrum of the magnetic field remains invariant under a two parameter family of transformations of the non-minimal coupling function.
Generation of scale invariant magnetic fields in bouncing universes
Sriramkumar, L.; Atmjeet, Kumar; Jain, Rajeev Kumar
2015-09-01
We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic field can arise before the bounce for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape after the bounce. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the e-Script N-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and evaluate the spectra of the electric and magnetic fields at a suitable time after the bounce. As one could have intuitively expected, though the complete spectra depend on the details of the bounce, we find that, under the original conditions, scale invariant spectra of the magnetic fields do arise for wavenumbers much smaller than the scale associated with the bounce. We also show that magnetic fields which correspond to observed strengths today can be generated for specific values of the parameters. But, we find that, at the bounce, the backreaction due to the electromagnetic modes that have been generated can be significantly large calling into question the viability of the model. We briefly discuss the implications of our results.
Levels of complexity in scale-invariant neural signals
Ivanov, Plamen Ch.; Ma, Qianli D. Y.; Bartsch, Ronny P.; Hausdorff, Jeffrey M.; Nunes Amaral, Luís A.; Schulte-Frohlinde, Verena; Stanley, H. Eugene; Yoneyama, Mitsuru
2009-04-01
Many physical and physiological signals exhibit complex scale-invariant features characterized by 1/f scaling and long-range power-law correlations, indicating a possibly common control mechanism. Specifically, it has been suggested that dynamical processes, influenced by inputs and feedback on multiple time scales, may be sufficient to give rise to 1/f scaling and scale invariance. Two examples of physiologic signals that are the output of hierarchical multiscale physiologic systems under neural control are the human heartbeat and human gait. Here we show that while both cardiac interbeat interval and gait interstride interval time series under healthy conditions have comparable 1/f scaling, they still may belong to different complexity classes. Our analysis of the multifractal scaling exponents of the fluctuations in these two signals demonstrates that in contrast to the multifractal behavior found in healthy heartbeat dynamics, gait time series exhibit less complex, close to monofractal behavior. Further, we find strong anticorrelations in the sign and close to random behavior for the magnitude of gait fluctuations at short and intermediate time scales, in contrast to weak anticorrelations in the sign and strong positive correlation for the magnitude of heartbeat interval fluctuations—suggesting that the neural mechanisms of cardiac and gait control exhibit different linear and nonlinear features. These findings are of interest because they underscore the limitations of traditional two-point correlation methods in fully characterizing physiological and physical dynamics. In addition, these results suggest that different mechanisms of control may be responsible for varying levels of complexity observed in physiological systems under neural regulation and in physical systems that possess similar 1/f scaling.
Scale-invariant power spectra from a Weyl-invariant scalar-tensor theory
Energy Technology Data Exchange (ETDEWEB)
Myung, Yun Soo [Inje University, Institute of Basic Sciences and Department of Computer Simulation, Gimhae (Korea, Republic of); Park, Young-Jai [Sogang University, Department of Physics, Seoul (Korea, Republic of)
2016-02-15
We obtain scale-invariant scalar and tensor power spectra from a Weyl-invariant scalar-tensor theory in de Sitter spacetime. This implies that the Weyl invariance guarantees the implementation of the scale invariance of the power spectrum in de Sitter spacetime. We establish a deep connection between the Weyl invariance of the action and the scale invariance of the power spectrum in de Sitter spacetime. (orig.)
Classical scale invariance in the inert doublet model
Plascencia, Alexis D
2015-01-01
The inert doublet model (IDM) is a minimal extension of the Standard Model (SM) that can account for the dark matter in the universe. Naturalness arguments motivate us to study whether the model can be embedded into a theory with dynamically generated scales. In this work we study a classically scale invariant version of the IDM with a minimal hidden sector, which has a $U(1)_{\\text{CW}}$ gauge symmetry and a complex scalar $\\Phi$. The mass scale is generated in the hidden sector via the Coleman-Weinberg (CW) mechanism and communicated to the two Higgs doublets via portal couplings. Since the CW scalar remains light, acquires a vacuum expectation value and mixes with the SM Higgs boson, the phenomenology of this construction can be modified with respect to the traditional IDM. We analyze the impact of adding this CW scalar and the $Z'$ gauge boson on the calculation of the dark matter relic density and on the spin-independent nucleon cross section for direct detection experiments. Finally, by studying the RG ...
Scale invariance of a diode-like tunnel junction
Cabrera, Hugo; Zanin, Danilo Andrea; de Pietro, Lorenzo Giuseppe; Michaels, Thomas; Thalmann, Peter; Ramsperger, Urs; Vindigni, Alessandro; Pescia, Danilo
2013-03-01
In Near Field-Emission SEM (NFESEM), electrostatic considerations favor a diode-like tunnel junction consisting of an atomic-sized source mounted at the apex of a thin wire placed at nanometric distances from a collector. The quantum mechanical tunnel process, instead, can provide a barrier toward miniaturization. In the first place, it deteriorates the generation of electrons by introducing non-linearities within the classically forbidden zone that exponentially increase with decreasing sizes. In addition, in the direct tunnelling regime, i.e. when the distance between emitter and collector d approaches the subnanometer range, a characteristic length appears, making the cross-over from the (almost) scale-invariant electric-field assisted regime to the essentially different STM-regime. We have observed that the experimental data relating the current I to the two experimental variables V (bias voltage between tip and collector) and d can be made (almost) collapse onto a ``scaling curve'' relating I to the single variable V .d-λ , λ being some exponent that depends solely on the geometry of the junction. This scaling property can be used to highlight non-linear aspects of the quantum mechanical tunnelling process.
Naturalness and Dimensional Transmutation in Classically Scale-Invariant Gravity
Einhorn, Martin B
2014-01-01
We discuss the nature of quantum field theories involving gravity that are classically scale-invariant. We show that gravitational radiative corrections are crucial in the determination of the nature of the vacuum state in such theories, which are renormalisable, technically natural, and can be asymptotically free in all dimensionless couplings. In the pure gravity case, we discuss the role of the Gauss-Bonnet term, and we find that Dimensional Transmutation (DT) \\`a la Coleman-Weinberg leads to extrema of the effective action corresponding to nonzero values of the curvature, but such that these extrema are local maxima. In even the simplest extension of the theory to include scalar fields, we show that the same phenomenon can lead to extrema that are local minima of the effective action, with both non-zero curvature and non-zero scalar vacuum expectation values, leading to spontaneous generation of the Planck mass. Although we find an asymptotically free (AF) fixed point exists, unfortunately, no running of ...
Weyl Current, Scale-Invariant Inflation and Planck Scale Generation
Ferreira, Pedro G; Ross, Graham G
2016-01-01
Scalar fields, $\\phi_i$ can be coupled non-minimally to curvature and satisfy the general criteria: (i) the theory has no mass input parameters, including the Planck mass; (ii) the $\\phi_i$ have arbitrary values and gradients, but undergo a general expansion and relaxation to constant values that satisfy a nontrivial constraint, $K(\\phi_i) =$ constant; (iii) this constraint breaks scale symmetry spontaneously, and the Planck mass is dynamically generated; (iv) there can be adequate inflation associated with slow roll in a scale invariant potential subject to the constraint; (v) the final vacuum can have a small to vanishing cosmological constant (vi) large hierarchies in vacuum expectation values can naturally form; (vii) there is a harmless dilaton which naturally eludes the usual constraints on massless scalars. These models are governed by a global Weyl scale symmetry and its conserved current, $K_\\mu$ . At the quantum level the Weyl scale symmetry can be maintained by an invariant specification of renorma...
Efficient rotation- and scale-invariant texture analysis
Fung, Kam-Keung; Lam, Kin-Man
2010-10-01
Texture analysis plays an important role in content-based image retrieval and other areas of image processing. It is often desirable for the texture classifier to be rotation and scale invariant. Furthermore, to enable real-time usage, it is desirable to perform the classification efficiently. Toward these goals, we propose several enhancements to the multiresolution Gabor analysis. The first is a new set of kernels called Slit, which can replace Gabor wavelets in applications where high computational speed is desired. Compared to Gabor, feature extraction using Slit requires only 11 to 17% of the numeric operations. The second is to make the features more rotation invariant. We propose a circular sum of the feature elements from the same scale of the feature vector. This has the effect of averaging the feature vector from all orientations. The third is a slide-matching scheme for the final stage of the classifier, which can be applied to different types of distance measures. Distances are calculated at slightly different scales, and the smallest value is used as the actual distance measures. Experimental results using different image databases and distance measures show distinct improvements over existing schemes.
Dark Matter and Leptogenesis Linked by Classical Scale Invariance
Khoze, Valentin V
2016-01-01
In this work we study a classically scale invariant extension of the Standard Model that can explain simultaneously dark matter and the baryon asymmetry in the universe. In our set-up we introduce a dark sector, namely a non-Abelian SU(2) hidden sector coupled to the SM via the Higgs portal, and a singlet sector responsible for generating Majorana masses for three right-handed sterile neutrinos. The gauge bosons of the dark sector are mass-degenerate and stable, and this makes them suitable as dark matter candidates. Our model also accounts for the matter-anti-matter asymmetry. The lepton flavour asymmetry is produced during CP-violating oscillations of the GeV-scale right-handed neutrinos, and converted to the baryon asymmetry by the electroweak sphalerons. All the characteristic scales in the model: the electro-weak, dark matter and the leptogenesis/neutrino mass scales, are generated radiatively, have a common origin and related to each other via scalar field couplings in perturbation theory.
Scale Invariant Gabor Descriptor-based Noncooperative Iris Recognition
Directory of Open Access Journals (Sweden)
Zhi Zhou
2010-01-01
Full Text Available A new noncooperative iris recognition method is proposed. In this method, the iris features are extracted using a Gabor descriptor. The feature extraction and comparison are scale, deformation, rotation, and contrast-invariant. It works with off-angle and low-resolution iris images. The Gabor wavelet is incorporated with scale-invariant feature transformation (SIFT for feature extraction to better extract the iris features. Both the phase and magnitude of the Gabor wavelet outputs were used in a novel way for local feature point description. Two feature region maps were designed to locally and globally register the feature points and each subregion in the map is locally adjusted to the dilation/contraction/deformation. We also developed a video-based non-cooperative iris recognition system by integrating video-based non-cooperative segmentation, segmentation evaluation, and score fusion units. The proposed method shows good performance for frontal and off-angle iris matching. Video-based recognition methods can improve non-cooperative iris recognition accuracy.
Scale Invariant Gabor Descriptor-Based Noncooperative Iris Recognition
Directory of Open Access Journals (Sweden)
Du Yingzi
2010-01-01
Full Text Available Abstract A new noncooperative iris recognition method is proposed. In this method, the iris features are extracted using a Gabor descriptor. The feature extraction and comparison are scale, deformation, rotation, and contrast-invariant. It works with off-angle and low-resolution iris images. The Gabor wavelet is incorporated with scale-invariant feature transformation (SIFT for feature extraction to better extract the iris features. Both the phase and magnitude of the Gabor wavelet outputs were used in a novel way for local feature point description. Two feature region maps were designed to locally and globally register the feature points and each subregion in the map is locally adjusted to the dilation/contraction/deformation. We also developed a video-based non-cooperative iris recognition system by integrating video-based non-cooperative segmentation, segmentation evaluation, and score fusion units. The proposed method shows good performance for frontal and off-angle iris matching. Video-based recognition methods can improve non-cooperative iris recognition accuracy.
Generation of scale invariant magnetic fields in bouncing universes
Sriramkumar, L; Jain, Rajeev Kumar
2015-01-01
We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic fields can arise {\\it before the bounce} for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape {\\it after the bounce}. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the ${\\rm e}$-${\\cal N}$-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and eva...
Scale-Invariance of Support Vector Machines based on the Triangular Kernel
Sahbi, Hichem; Fleuret, François
2002-01-01
This report focuses on the scale-invariance and the good performances of Support Vector Machines based on the triangular kernel. After a mathematica- l analysis of the scale-invariance of learning with that kernel, we illustrate its behavior with a simple 2D classification problem and compare its performances to those of a Gaussian kernel on face detection and handwritten character recognition
Rotation and Scale Invariant Wavelet Feature for Content-Based Texture Image Retrieval.
Lee, Moon-Chuen; Pun, Chi-Man
2003-01-01
Introduces a rotation and scale invariant log-polar wavelet texture feature for image retrieval. The underlying feature extraction process involves a log-polar transform followed by an adaptive row shift invariant wavelet packet transform. Experimental results show that this rotation and scale invariant wavelet feature is quite effective for image…
Saremi, Saeed; Sejnowski, Terrence J.
2016-01-01
Natural images are scale invariant with structures at all length scales. We formulated a geometric view of scale invariance in natural images using percolation theory, which describes the behavior of connected clusters on graphs. We map images to the percolation model by defining clusters on a binary representation for images. We show that critical percolating structures emerge in natural images and study their scaling properties by identifying fractal dimensions and exponents for the scale-invariant distributions of clusters. This formulation leads to a method for identifying clusters in images from underlying structures as a starting point for image segmentation. PMID:26415153
International Nuclear Information System (INIS)
Los Alamos National Laboratory has developed an efficient unstructured version of KIVA-3V, which will be called KIVA-4. KIVA-4 like its predecessor KIVA-3V solves the three-dimensional compressible Navier-Stokes equations in complex geometries with moving boundaries (e.g. pistons and valves). KIVA-4 also inherits the spray and combustion capabilities of KIVA-3V in that it models vaporizing fuel droplets and combusting fuel vapor. KIVA-4 improves the capabilities of KIVA-3V by allowing computations to be performed on unstructured grids, which are generally better and more easily generated grids. KIVA-4 also can use multiple fuel species in vaporizing fuel particles, in contrast to KIVA-3V, which only can use one fuel species. Most importantly, KIVA-4 is no more than 10% slower than KIVA-3V.
Directory of Open Access Journals (Sweden)
Y. Kawada
2007-10-01
Full Text Available We investigate the time-scale invariant changes in electromagnetic and mechanical energy releases prior to a rock failure or a large earthquake. The energy release processes are caused by damage evolutions such as crack propagation, motion of charged dislocation, area-enlargement of sheared asperities and repetitive creep-rate changes. Damage mechanics can be used to represent the time-scale invariant evolutions of both brittle and plastic damages. Irreversible thermodynamics applied to the damage mechanics reveals that the damage evolution produces the variations in charge, dipole and electromagnetic signals in addition to mechanical energy release, and yields the time-scale invariant patterns of Benioff electromagnetic radiation and cumulative Benioff strain-release. The irreversible thermodynamic framework of damage mechanics is also applicable to the seismo-magnetic effect, and the time-scale invariance is recognized in the remanent magnetization change associated with damage evolution prior to a rock failure.
The Harris Corner Detection Method Based on Three Scale Invariance Spaces
Yutan Wang; Huixin Wang; Jing Li; Biming Li
2012-01-01
In order to solve the problem that the traditional Harris comer operator hasnt the property of variable scales and is sensitive to noises, an improved three scale Harris corner detection algorithm was proposed. First, three scale spaces with the characteristic of scale invariance were constructed using discrete Gaussian convolution. Then, Harris scale invariant detector was used to extract comers in each scale image. Finally, supportable and unsupportable set of points were classified accordi...
Synthetic circular-harmonic phase-only filter for shift, rotation and scaling-invariant correlation
DEFF Research Database (Denmark)
Zi-Liang, ping; Dalsgaard, Erik
1995-01-01
A syntetic circuler-harmonic phase-only filter is described. With this filter and a Fourier-transform correlator it is possible to obtain shift, rotation and scaling-invariant correlations......A syntetic circuler-harmonic phase-only filter is described. With this filter and a Fourier-transform correlator it is possible to obtain shift, rotation and scaling-invariant correlations...
The neural correlates of processing scale-invariant environmental sounds at birth.
Gervain, Judit; Werker, Janet F; Black, Alexis; Geffen, Maria N
2016-06-01
Sensory systems are thought to have evolved to efficiently represent the full range of sensory stimuli encountered in the natural world. The statistics of natural environmental sounds are characterized by scale-invariance: the property of exhibiting similar patterns at different levels of observation. The statistical structure of scale-invariant sounds remains constant at different spectro-temporal scales. Scale-invariance plays a fundamental role in how efficiently animals and human adults perceive acoustic signals. However, the developmental origins and brain correlates of the neural encoding of scale-invariant environmental sounds remain unexplored. Here, we investigate whether the human brain extracts the statistical property of scale-invariance. Synthetic sounds generated by a mathematical model to respect scale-invariance or violate it were presented to newborns. In alternating blocks, the two sound types were presented together in an alternating fashion, whereas in non-alternating blocks, only one type of sound was presented. Newborns' brain responses were measured using near-infrared spectroscopy. We found that scale-invariant and variable-scale sounds were discriminated by the newborn brain, as suggested by differential activation in the left frontal and temporal areas to alternating vs. non-alternating blocks. These results indicate that newborns already detect and encode scale-invariance as a characteristic feature of acoustic stimuli. This suggests that the mathematical principle of efficient coding of information guides the auditory neural code from the beginning of human development, a finding that may help explain how evolution has prepared the brain for perceiving the natural world.
On the Hagedorn Behaviour of Singular Scale-Invariant Plane Waves
Blau, Matthias; Borunda, Monica; O'Loughlin, Martin
2004-01-01
As a step towards understanding the properties of string theory in time-dependent and singular spacetimes, we study the divergence of density operators for string ensembles in singular scale-invariant plane waves, i.e. those plane waves that arise as the Penrose limits of generic power-law spacetime singularities. We show that the scale invariance implies that the Hagedorn behaviour of bosonic and supersymmetric strings in these backgrounds, even with the inclusion of RR or NS fields, is the ...
Unstructured Mesh Movement and Viscous Mesh Generation for CFD-Based Design Optimization Project
National Aeronautics and Space Administration — The innovations proposed are twofold: 1) a robust unstructured mesh movement method able to handle isotropic (Euler), anisotropic (viscous), mixed element (hybrid)...
Note on the production of scale-invariant entropy perturbation in the Ekpyrotic universe
Li, Mingzhe
2013-01-01
In the standard entropic mechanism adopted in the simple Ekpyrotic models to generate the nearly scale-invariant and Gaussian primordial perturbation, the entropy direction is tachyonically unstable. In this paper, we consider the stable production of the scale-invariant entropy perturbation in the Ekpyrotic universe via non-minimal couplings. In this model the non-minimally coupled massless scalar field serves as a spectator and is stabilized by the non-minimal couplings. It always corresponds to the entropy field during the contraction and with appropriate couplings can obtain a scale-invariant spectrum. This scenario requires additional mechanisms such as curvaton or modulated preheating to convert the entropy perturbation to the curvature perturbation after the bounce.
Patil, Sandeep Baburao; Sinha, G. R.
2016-07-01
India, having less awareness towards the deaf and dumb peoples leads to increase the communication gap between deaf and hard hearing community. Sign language is commonly developed for deaf and hard hearing peoples to convey their message by generating the different sign pattern. The scale invariant feature transform was introduced by David Lowe to perform reliable matching between different images of the same object. This paper implements the various phases of scale invariant feature transform to extract the distinctive features from Indian sign language gestures. The experimental result shows the time constraint for each phase and the number of features extracted for 26 ISL gestures.
Local Scale-Invariance of the 2+1 dimensional Kardar-Parisi-Zhang model
Kelling, Jeffrey; Gemming, Sibylle
2016-01-01
Local Scale-Invariance theory is tested by extensive dynamical simulations of the driven dimer lattice gas model, describing the surface growth of the 2+1 dimensional Kardar-Parisi-Zhang surfaces. Very precise measurements of the universal autoresponse function enabled us to perform nonlinear fitting with the scaling forms, suggested by local scale-invariance (LSI). While the simple LSI ansatz does not seem to work, forms based on logarithmic extension of LSI provide satisfactory description of the full (measured) time evolution of the autoresponse function.
Inflation and reheating in theories with spontaneous scale invariance symmetry breaking
Rinaldi, Massimiliano; Vanzo, Luciano
2016-07-01
We study a scale-invariant model of quadratic gravity with a nonminimally coupled scalar field. We focus on cosmological solutions and find that scale invariance is spontaneously broken and a mass scale naturally emerges. Before the symmetry breaking, the Universe undergoes an inflationary expansion with nearly the same observational predictions of Starobinsky's model. At the end of inflation, the Hubble parameter and the scalar field converge to a stable fixed point through damped oscillations and the usual Einstein-Hilbert action is recovered. The oscillations around the fixed point can reheat the Universe in various ways, and we study in detail some of these possibilities.
Scale-invariant scalar spectrum from the nonminimal derivative coupling with fourth-order term
Myung, Yun Soo
2015-01-01
An exactly scale-invariant spectrum of scalar perturbation generated during de Sitter spacetime is found from the gravity model of the nonminimal derivative coupling with fourth-order term. The nonminimal derivative coupling term generates a healthy (ghost-free) fourth-order derivative term, while the fourth-order term provides an unhealthy (ghost) fourth-order derivative term. The Harrison-Zel'dovich spectrum obtained from Fourier transforming the fourth-order propagator in de Sitter space is recovered by computing the power spectrum in its momentum space directly. It shows that this model provides a truly scale-invariant spectrum, in addition to the Lee-Wick scalar theory.
Inflation and reheating in theories with spontaneous scale invariance symmetry breaking
Rinaldi, Massimiliano
2015-01-01
We study a scale-invariant model of quadratic gravity with a non-minimally coupled scalar field. We focus on cosmological solutions and find that scale invariance is spontaneously broken and a mass scale naturally emerges. Before the symmetry breaking, the Universe undergoes an inflationary expansion with the same characteristics of Starobinsky's model. At the end of inflation, the Hubble parameter and the scalar field converge to a stable fixed point through damped oscillations that are responsible for the reheating of the Universe via parametric amplification of other matter fields.
On the Hagedorn Behaviour of Singular Scale-Invariant Plane Waves
Blau, Matthias; O'Loughlin, M; Blau, Matthias; Borunda, Monica; Loughlin, Martin O'
2005-01-01
As a step towards understanding the properties of string theory in time-dependent and singular spacetimes, we study the divergence of density operators for string ensembles in singular scale-invariant plane waves, i.e. those plane waves that arise as the Penrose limits of generic spacetime singularities. We show that the scale invariance implies that the Hagedorn behaviour of bosonic and supersymmetric strings in these backgrounds, even with the inclusion of RR or NS fields, is the same as that of strings in flat space. This is in marked contrast to the behaviour of strings in the BFHP plane wave which exhibit quantitatively and qualitatively different thermodynamic properties.
Nakayama, Yu
2016-01-01
We show that eleven dimensional supergravity in Euclidean signature admits an exact classical solution with isometry corresponding to a three dimensional scale invariant field theory without conformal invariance. We also construct the holographic renormalization group flow that connects the known UV conformal fixed point and the new scale invariant but not conformal fixed point. In view of holography, the existence of such classical solutions suggests that the topologically twisted M2-brane gauge theory possesses a scale invariant but not conformal phase.
Scale-invariant helical magnetic fields and the duration of inflation
Kahniashvili, Tina; Durrer, Ruth; Tevzadze, Alexander G; Yin, Winston
2016-01-01
In this paper we study a (nearly) scale-invariant helical magnetic field generated during inflation. We show that, if the helicity of such fields is measured, it can be used to determine the beginning of inflation. Upper bounds can be used to derive constraints on the minimal duration of inflation if one assumes that the magnetic fields generated during inflation are helical.
Are galaxy distributions scale invariant? A perspective from dynamical systems theory
McCauley, J L
1997-01-01
Unless there is evidence for fractal scaling with a single exponent over distances .1 <= r <= 100 h^-1 Mpc then the widely accepted notion of scale invariance of the correlation integral for .1 <= r <= 10 h^-1 Mpc must be questioned. The attempt to extract a scaling exponent \
Space-time scaling invariant traveling wave solutions of some nonlinear fractional equations
HE, Tianlan; Fang, Hui
2012-01-01
In this paper, a homogeneous principle is proposed to seek the space-time scaling invariant traveling wave solutions expressed by power functions for some fractional differential equations. Applying this principle to generalized fractional Benjamin-Ono equations and generalized fractional ZakharovKuznetsov equations, the traveling wave solutions expressed by power functions have been obtained under some parameter conditions.
On the geometrical interpretation of scale-invariant models of inflation
Karananas, Georgios K
2016-01-01
We study the geometrical properties of scale-invariant two-field models of inflation. In particular, we show that when the field-derivative space in the Einstein frame is maximally symmetric during inflation, the inflationary predictions can be universal and independent of the details of the theory.
Discrete Scale Invariance in the Cascade Heart Rate Variability Of Healthy Humans
Lin, D C
2004-01-01
Evidence of discrete scale invariance (DSI) in daytime healthy heart rate variability (HRV) is presented based on the log-periodic power law scaling of the heart beat interval increment. Our analysis suggests multiple DSI groups and a dynamic cascading process. A cascade model is presented to simulate such a property.
Non-Static Plane Symmetric Zeldovich Fluid Model In Scale Invariant Theory
Institute of Scientific and Technical Information of China (English)
B. Mishra
2004-01-01
@@ The perfect fluid distribution in scale invariant theory of gravitation is studied, when the spacetime is described by non-static plane symmetric metric with a time-dependent gauge function. The Zeldovich model of the universe is constructed and some physical properties of the model are discussed.
Khoury, Justin
2009-01-01
The universe can be made flat and smooth by undergoing a phase of ultra-slow (ekpyrotic) contraction with equation of state w >> 1, a condition that is achievable with a single, canonical scalar field and conventional general relativity. It has been argued, though, that another goal, generating scale-invariant density perturbations, requires at least two scalar fields and a two-step process that first produces entropy fluctuations and then converts them to curvature perturbations. In this paper, we exploit a loophole in the argument and introduce an ekpyrotic model based on a single, canonical scalar field that utilizes a purely "adiabatic mechanism" to generate nearly scale-invariant curvature fluctuations. The curvature perturbation tends to a constant at long wavelengths, indicating that the background evolution is a dynamical attractor. The resulting spectrum is slightly red with distinctive non-gaussian fluctuations.
The Pseudo-Conformal Universe: Scale Invariance from Spontaneous Breaking of Conformal Symmetry
Hinterbichler, Kurt
2011-01-01
We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no exponential superluminal expansion of space-time. Instead, the early universe is described by a conformal field theory minimally coupled to gravity. The conformal fields develop a time-dependent expectation value which breaks the flat space so(4,2) conformal symmetry down to so(4,1), the symmetries of de Sitter, giving perturbations a scale invariant spectrum. The solution is an attractor, at least in the case of a single time-dependent field. Meanwhile, the metric background remains approximately flat but slowly contracts, which makes the universe increasingly flat, homogeneous and isotropic, akin to the smoothing mechanism of ekpyrotic cosmology. Our scenario is very general, requiring only a conformal field theory capable of developing the appropriate time-dependent expec...
Generating Scale-Invariant Perturbations from Rapidly-Evolving Equation of State
Khoury, Justin
2011-01-01
Recently, we introduced an ekpyrotic model based on a single, canonical scalar field that generates nearly scale invariant curvature fluctuations through a purely "adiabatic mechanism" in which the background evolution is a dynamical attractor. Despite the starkly different physical mechanism for generating fluctuations, the two-point function is identical to inflation. In this paper, we further explore this concept, focusing in particular on issues of non-gaussianity and quantum corrections. We find that the degeneracy with inflation is broken at three-point level: for the simplest case of an exponential potential, the three-point amplitude is strongly scale dependent, resulting in a breakdown of perturbation theory on small scales. However, we show that the perturbative breakdown can be circumvented -- and all issues raised in Linde et al. (arXiv:0912.0944) can be addressed -- by altering the potential such that power is suppressed on small scales. The resulting range of nearly scale invariant, gaussian mod...
The Scale-invariant Power Spectrum of Primordial Curvature Perturbation in CSTB Cosmos
Li, Changhong
2014-01-01
We investigate the spectrum of cosmological perturbations in a bounce cosmos modeled by a scalar field coupled to the string tachyon field (CSTB cosmos). By explicit computation of its primordial spectral index we show the power spectrum of curvature perturbations, generated during the tachyon matter dominated contraction phase, to be nearly scale invariant. We propose a unified space of parameters for a systematic study of inflationary/bouncing cosmologies. We find that CSTB cosmos is dual--in Wands's sense--to the slow-roll inflation model as can be easily seen from this unified parameter space. Guaranteed by the dynamical attractor behavior of CSTB Cosmos, this scale invariance is free of the fine-tuning problem, in contrast to the slow-roll inflation model.
Scale-Invariant Models with One-Loop Neutrino Mass and Dark Matter Candidates
Ahriche, Amine; McDonald, Kristian L; Nasri, Salah
2016-01-01
We construct a list of minimal scale-invariant models at the TeV scale that generate one-loop neutrino mass and give viable dark matter candidates. The models generically contain a singlet scalar and a $Z_2$-odd sector comprised of singlet, doublet and/or triplet SU(2) multiplets. The dark matter may reside in a single multiplet or arise as an admixture of several multiplets. We find fifteen independent models, for which the dark matter is a viable candidate and neutrino mass results from a diagram with just one of the irreducible scale-invariant one-loop topologies. A further eight "non-pure" cases give hybrid one-/two-loop masses. All models predict new TeV scale physics, including a singlet scalar that generically mixes with the Higgs boson.
Inflation and reheating in scale-invariant scalar-tensor gravity
Tambalo, Giovanni
2016-01-01
We consider the scale-invariant inflationary model studied in [1]. The Lagrangian includes all the scale-invariant operators that can be built with combinations of $R, R^{2}$ and one scalar field. The equations of motion show that the symmetry is spontaneously broken after an arbitrarily long inflationary period and a fundamental mass scale is generated. Upon symmetry breaking, and in the Jordan frame, both Hubble function and the scalar field undergo damped oscillations that can eventually amplify Standard Model fields and reheat the Universe. In the present work, we study in detail inflation and the reheating mechanism of this model in the Einstein frame and we compare some of the results with the latest observational data.
A new dynamics of electroweak symmetry breaking with classically scale invariance
Haba, Naoyuki; Kitazawa, Noriaki; Yamaguchi, Yuya
2015-01-01
We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu-Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu-Goldstone bosons, and show they can decay fast enough without cosmological problems. We further evaluate the energy dependences of the couplings between elementary fields perturbatively, and find that our model is the first one which realizes the flatland scenario with the dimensional transmutation by the strong coupling dynam...
A new dynamics of electroweak symmetry breaking with classically scale invariance
Directory of Open Access Journals (Sweden)
Naoyuki Haba
2016-04-01
Full Text Available We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu–Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu–Goldstone bosons, and show they can decay fast enough without cosmological problems. We further show that our model can make the electroweak vacuum stable.
On the Hagedorn behaviour of singular scale-invariant plane waves
International Nuclear Information System (INIS)
As a step towards understanding the properties of string theory in time-dependent and singular spacetimes, we study the divergence of density operators for string ensembles in singular scale-invariant plane waves, i.e. those plane waves that arise as the Penrose limits of generic power-law spacetime singularities. We show that the scale invariance implies that the Hagedorn behaviour of bosonic and supersymmetric strings in these backgrounds, even with the inclusion of RR or NS fields, is the same as that of strings in flat space. This is in marked contrast to the behaviour of strings in the BFHP plane wave which exhibit quantitatively and qualitatively different thermodynamic properties
Void probability as a function of the void's shape and scale-invariant models
Elizalde, E.; Gaztanaga, E.
1991-01-01
The dependence of counts in cells on the shape of the cell for the large scale galaxy distribution is studied. A very concrete prediction can be done concerning the void distribution for scale invariant models. The prediction is tested on a sample of the CfA catalog, and good agreement is found. It is observed that the probability of a cell to be occupied is bigger for some elongated cells. A phenomenological scale invariant model for the observed distribution of the counts in cells, an extension of the negative binomial distribution, is presented in order to illustrate how this dependence can be quantitatively determined. An original, intuitive derivation of this model is presented.
Direct detection of singlet dark matter in classically scale-invariant standard model
Directory of Open Access Journals (Sweden)
Kazuhiro Endo
2015-10-01
Full Text Available Classical scale invariance is one of the possible solutions to explain the origin of the electroweak scale. The simplest extension is the classically scale-invariant standard model augmented by a multiplet of gauge singlet real scalar. In the previous study it was shown that the properties of the Higgs potential deviate substantially, which can be observed in the International Linear Collider. On the other hand, since the multiplet does not acquire vacuum expectation value, the singlet components are stable and can be dark matter. In this letter we study the detectability of the real singlet scalar bosons in the experiment of the direct detection of dark matter. It is shown that a part of this model has already been excluded and the rest of the parameter space is within the reach of the future experiment.
Scale invariance of incident size distributions in response to sizes of their causes.
Englehardt, James D
2002-04-01
Incidents can be defined as low-probability, high-consequence events and lesser events of the same type. Lack of data on extremely large incidents makes it difficult to determine distributions of incident size that reflect such disasters, even though they represent the great majority of total losses. If the form of the incident size distribution can be determined, then predictive Bayesian methods can be used to assess incident risks from limited available information. Moreover, incident size distributions have generally been observed to have scale invariant, or power law, distributions over broad ranges. Scale invariance in the distributions of sizes of outcomes of complex dynamical systems has been explained based on mechanistic models of natural and built systems, such as models of self-organized criticality. In this article, scale invariance is shown to result also as the maximum Shannon entropy distribution of incident sizes arising as the product of arbitrary functions of cause sizes. Entropy is shown by simulation and derivation to be maximized as a result of dependence, diversity, abundance, and entropy of multiplicative cause sizes. The result represents an information-theoretic explanation of invariance, parallel to those of mechanistic models. For example, distributions of incident size resulting from 30 partially dependent causes are shown to be scale invariant over several orders of magnitude. Empirical validation of power law distributions of incident size is reviewed, and the Pareto (power law) distribution is validated against oil spill, hurricane, and insurance data. The applicability of the Pareto distribution, in particular, for assessment of total losses over a planning period is discussed. Results justify the use of an analytical, predictive Bayesian version of the Pareto distribution, derived previously, to assess incident risk from available data.
Diffusion Time-Scale Invariance, Markovization Processes and Memory Effects in Lennard-Jones Liquids
Yulmetyev, Renat M.; Mokshin, Anatolii V.; Hänggi, Peter
2004-01-01
We report the results of calculation of diffusion coefficients for Lennard-Jones liquids, based on the idea of time-scale invariance of relaxation processes in liquids. The results were compared with the molecular dynamics data for Lennard-Jones system and a good agreement of our theory with these data over a wide range of densities and temperatures was obtained. By calculations of the non-Markovity parameter we have estimated numerically statistical memory effects of diffusion in detail.
Bianchi type VI1 cosmological model with wet dark fluid in scale invariant theory of gravitation
Mishra, B
2014-01-01
In this paper, we have investigated Bianchi type VIh, II and III cosmological model with wet dark fluid in scale invariant theory of gravity, where the matter field is in the form of perfect fluid and with a time dependent gauge function (Dirac gauge). A non-singular model for the universe filled with disorder radiation is constructed and some physical behaviors of the model are studied for the feasible VIh (h = 1) space-time.
Electroweak Higgs as a pseudo-Goldstone boson of broken scale invariance
Foot, Robert; Kobakhidze, Archil(ARC Centre of Excellence for Particle Physics at the Terascale, School of Physics, The University of Sydney, NSW, 2006, Australia); Volkas, Raymond R.
2007-01-01
We point out that it is possible to associate the electroweak Higgs boson with the pseudo-Goldstone boson of broken scale invariance, thus resolving the hierarchy problem in a technically natural way. We illustrate this idea with two specific gauge models. Besides being consistent with all currently available experimental data, both models maintain the predictive power of the standard model, since the first model has only one additional parameter beyond the standard model, and the second has ...
Searching and fixating: scale-invariance vs. characteristic timescales in attentional processes
Shinde, D P; Mishra, R K
2011-01-01
In an experiment involving semantic search, the visual movements of sample populations subjected to visual and aural input were tracked in a taskless paradigm. The probability distributions of saccades and fixations were obtained and analyzed. Scale-invariance was observed in the saccadic distributions, while the fixation distributions revealed the presence of a characteristic (attentional) time scale for literate subjects. A detailed analysis of our results suggests that saccadic eye motions are an example of Levy, rather than Brownian, dynamics.
Dark Matter from a Classically Scale-Invariant $SU(3)_X$
Karam, Alexandros; Tamvakis, Kyriakos
2016-01-01
In this work we study a classically scale-invariant extension of the Standard Model in which the dark matter and electroweak scales are generated through the Coleman-Weinberg mechanism. The extra $SU(3)_X$ gauge factor gets completely broken by the vevs of two scalar triplets. Out of the eight resulting massive vector bosons the three lightest are stable due to an intrinsic $Z_2\\times Z_2'$ discrete symmetry and can constitute dark matter candidates. We analyze the phenomenological viability ...
Producing a scale-invariant spectrum of perturbations in a Hagedorn phase of string cosmology.
Nayeri, Ali; Brandenberger, Robert H; Vafa, Cumrun
2006-07-14
We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.
Dark Energy and Dark Matter in General Relativity with local scale invariance
Aluri, Pavan Kumar; Jain, Pankaj; Singh, Naveen K.
2008-01-01
We consider a generalization of Einstein's general theory of relativity such that it respects local scale invariance. This requires the introduction of a scalar and a vector field in the action. We show that the theory naturally displays both dark energy and dark matter. We solve the resulting equations of motion assuming an FRW metric. The solutions are found to be almost identical to those corresponding to the standard $\\Lambda$CDM model
The Scale-invariant Power Spectrum of Primordial Curvature Perturbation in CSTB Cosmos
Li, Changhong; Cheung, Yeuk-Kwan E.
2013-01-01
We investigate the spectrum of cosmological perturbations in a bounce cosmos modeled by a scalar field coupled to the string tachyon field (CSTB cosmos). By explicit computation of its primordial spectral index we show the power spectrum of curvature perturbations, generated during the tachyon matter dominated contraction phase, to be nearly scale invariant. We propose a unified space of parameters for a systematic study of inflationary/bouncing cosmologies. We find that CSTB cosmos is dual--...
The Harris Corner Detection Method Based on Three Scale Invariance Spaces
Directory of Open Access Journals (Sweden)
Yutan Wang
2012-11-01
Full Text Available In order to solve the problem that the traditional Harris comer operator hasnt the property of variable scales and is sensitive to noises, an improved three scale Harris corner detection algorithm was proposed. First, three scale spaces with the characteristic of scale invariance were constructed using discrete Gaussian convolution. Then, Harris scale invariant detector was used to extract comers in each scale image. Finally, supportable and unsupportable set of points were classified according to whether the corresponding corners in every scale image support that of the original images. After the operations to those unsupportable set of points, the noised corners and most of unstable corners could be got rid of. The corners extracted by the three and the original scale spaces also had scale invariant property. The experiments results proved that, compared with the scale space on the whole Gaussian pyramid, the utilization factor of the image was increased, the calculation time is decreased, and the image was high recurrence rate and stability.
A biologically plausible model of time-scale invariant interval timing.
Almeida, Rita; Ledberg, Anders
2010-02-01
The temporal durations between events often exert a strong influence over behavior. The details of this influence have been extensively characterized in behavioral experiments in different animal species. A remarkable feature of the data collected in these experiments is that they are often time-scale invariant. This means that response measurements obtained under intervals of different durations coincide when plotted as functions of relative time. Here we describe a biologically plausible model of an interval timing device and show that it is consistent with time-scale invariant behavior over a substantial range of interval durations. The model consists of a set of bistable units that switch from one state to the other at random times. We first use an abstract formulation of the model to derive exact expressions for some key quantities and to demonstrate time-scale invariance for any range of interval durations. We then show how the model could be implemented in the nervous system through a generic and biologically plausible mechanism. In particular, we show that any system that can display noise-driven transitions from one stable state to another can be used to implement the timing device. Our work demonstrates that a biologically plausible model can qualitatively account for a large body of data and thus provides a link between the biology and behavior of interval timing.
Probing the Scale Invariance of the Inflationary Power Spectrum in Expanding Dipolar Condensates
Chä, Seok-Yeong
2016-01-01
We consider an analogue de Sitter cosmos in an expanding quasi-two-dimensional Bose-Einstein condensate, with dominant dipole-dipole interactions between the atoms or molecules in the ultracold gas. It is demonstrated that a hallmark signature of inflationary cosmology, the scale invariance of the power spectrum of inflaton field correlations, experiences strong modifications when at the initial stage of expansion the excitation spectrum displays a roton minimum. Dipolar quantum gases thus furnish a viable laboratory tool to experimentally investigate, with well-defined and controllable initial conditions, whether primordial oscillation spectra deviating from Lorentz invariance at trans-Planckian momenta violate standard predictions of inflationary cosmology.
Shift-scale invariance based computer code for wiggler radiation simulation
Smolyakov, N V
2001-01-01
A new package of computer codes for calculating incoherent electromagnetic radiation from a relativistic electron beam moving in arbitrary three-dimensional magnetic field is developed at Hiroshima University. The codes are able to accept either an experimentally measured magnetic field or numerically simulated field map (with field errors, if necessary). The near-field effects as well as the electron beam emittance effects are also included into simulation. The codes are based on the shift-scale invariance property of radiation spectra that enables us to reduce considerably the bulk of individual calculations of single electron radiation.
Generating scale-invariant tensor perturbations in the non-inflationary universe
Directory of Open Access Journals (Sweden)
Mingzhe Li
2014-09-01
Full Text Available It is believed that the recent detection of large tensor perturbations strongly favors the inflation scenario in the early universe. This common sense depends on the assumption that Einstein's general relativity is valid at the early universe. In this paper we show that nearly scale-invariant primordial tensor perturbations can be generated during a contracting phase before the radiation dominated epoch if the theory of gravity is modified by the scalar–tensor theory at that time. The scale-invariance protects the tensor perturbations from suppressing at large scales and they may have significant amplitudes to fit BICEP2's result. We construct a model to achieve this purpose and show that the universe can bounce to the hot big bang after long time contraction, and at almost the same time the theory of gravity approaches to general relativity through stabilizing the scalar field. Theoretically, such models are dual to inflation models if we change to the frame in which the theory of gravity is general relativity. Dual models are related by the conformal transformations. With this study we reinforce the point that only the conformal invariant quantities such as the scalar and tensor perturbations are physical. How did the background evolve before the radiation time depends on the frame and has no physical meaning. It is impossible to distinguish different pictures by later time cosmological probes.
A regional GEV scale-invariant framework for Intensity-Duration-Frequency analysis
Blanchet, J.; Ceresetti, D.; Molinié, G.; Creutin, J.-D.
2016-09-01
We propose in this paper a regional formulation of Intensity-Duration-Frequency curves of point-rainfall maxima in a scale-invariant Generalized Extreme Value (GEV) framework. The two assumptions we make is that extreme daily rainfall is GEV-distributed - which is justified by Extreme Value Theory (EVT) - and that extremes of aggregated daily rainfall follow simple-scaling relationships. Following these assumptions, we develop in a unified way a GEV simple-scaling model for extremes of aggregated daily rainfall over the range of durations where scaling applies. Then we propose a way of correcting this model for measurement frequency, giving a new GEV-scaling model for extremes of aggregated hourly rainfall. This model deviates from the simple-scaling assumption. This framework is applied to the Mediterranean region of Cévennes-Vivarais, France. A network of about 300 daily raingage stations covering the last 50 years and accumulated to span the range 1 day-1 week is used to fit the scale invariant GEV-model locally. By means of spatial interpolation of the model parameters, and correction for measurement frequency, we are able to build a regional model with good performances down to 1 h duration, even though only one hourly station is used to build the model. Finally we produce mean and return level maps within the region in the range 1 h-1 week and comment on the potential rain storms leading to these maps.
Generating scale-invariant tensor perturbations in the non-inflationary universe
Li, Mingzhe
2014-01-01
It is believed that the recent detection of large tensor perturbations strongly favors the inflation scenario in the early universe and leaves very small room to the alternatives. This common sense depends on the assumption that Einstein's general relativity is valid at the early universe. In this paper we show that nearly scale-invariant primordial tensor perturbations can be generated during a non-inflationary period, such as the contracting phase, before the radiation dominated epoch if the theory of gravity is scalar-tensor at that time. The scale-invariance protect the tensor perturbations from suppressing at large scales and they may have significant amplitudes to fit BICEP2's result. These models are dual to inflation models in the context of general relativity. In terms of the frame or conformal invariant properties of the scalar and tensor perturbations we suggest that only the invariant perturbations are physical. How the background evolves before the radiation time depends on the frames and it is h...
Generating scale-invariant tensor perturbations in the non-inflationary universe
Li, Mingzhe
2014-09-01
It is believed that the recent detection of large tensor perturbations strongly favors the inflation scenario in the early universe. This common sense depends on the assumption that Einstein's general relativity is valid at the early universe. In this paper we show that nearly scale-invariant primordial tensor perturbations can be generated during a contracting phase before the radiation dominated epoch if the theory of gravity is modified by the scalar-tensor theory at that time. The scale-invariance protects the tensor perturbations from suppressing at large scales and they may have significant amplitudes to fit BICEP2's result. We construct a model to achieve this purpose and show that the universe can bounce to the hot big bang after long time contraction, and at almost the same time the theory of gravity approaches to general relativity through stabilizing the scalar field. Theoretically, such models are dual to inflation models if we change to the frame in which the theory of gravity is general relativity. Dual models are related by the conformal transformations. With this study we reinforce the point that only the conformal invariant quantities such as the scalar and tensor perturbations are physical. How did the background evolve before the radiation time depends on the frame and has no physical meaning. It is impossible to distinguish different pictures by later time cosmological probes.
The pseudo-conformal universe: scale invariance from spontaneous breaking of conformal symmetry
International Nuclear Information System (INIS)
We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no exponential accelerated expansion of space-time. Instead, the early universe is described by a conformal field theory minimally coupled to gravity. The conformal fields develop a time-dependent expectation value which breaks the flat space so(4,2) conformal symmetry down to so(4,1), the symmetries of de Sitter, giving perturbations a scale invariant spectrum. The solution is an attractor, at least in the case of a single time-dependent field. Meanwhile, the metric background remains approximately flat but slowly contracts, which makes the universe increasingly flat, homogeneous and isotropic, akin to the smoothing mechanism of ekpyrotic cosmology. Our scenario is very general, requiring only a conformal field theory capable of developing the appropriate time-dependent expectation values, and encompasses existing incarnations of this idea, specifically the U(1) model of Rubakov and the Galileon Genesis scenario. Its essential features depend only on the symmetry breaking pattern and not on the details of the underlying lagrangian. It makes generic observational predictions that make it potentially distinguishable from standard inflation, in particular significant non-gaussianities and the absence of primordial gravitational waves
Two-loop scale-invariant scalar potential and quantum effective operators
Ghilencea, D M; Olszewski, P
2016-01-01
Spontaneous breaking of quantum scale invariance may provide a solution to the hierarchy and cosmological constant problems. In a scale-invariant regularization, we compute the two-loop potential of a higgs-like scalar $\\phi$ in theories in which scale symmetry is broken only spontaneously by the dilaton ($\\sigma$). Its vev $\\langle\\sigma\\rangle$ generates the DR subtraction scale ($\\mu\\sim\\langle\\sigma\\rangle$), which avoids the explicit scale symmetry breaking by traditional regularizations (where $\\mu$=fixed scale). The two-loop potential contains effective operators of non-polynomial nature as well as new corrections, beyond those obtained with explicit breaking ($\\mu$=fixed scale). These operators have the form: $\\phi^6/\\sigma^2$, $\\phi^8/\\sigma^4$, etc, which generate an infinite series of higher dimensional polynomial operators upon expansion about $\\langle\\sigma\\rangle\\gg \\langle\\phi\\rangle$, where such hierarchy is arranged by {\\it one} initial, classical tuning. These operators emerge at the quantum...
Dark matter from a classically scale-invariant S U (3 )X
Karam, Alexandros; Tamvakis, Kyriakos
2016-09-01
In this work we study a classically scale-invariant extension of the Standard Model in which the dark matter and electroweak scales are generated through the Coleman-Weinberg mechanism. The extra S U (3 )X gauge factor gets completely broken by the vacuum expectation values of two scalar triplets. Out of the eight resulting massive vector bosons the three lightest are stable due to an intrinsic Z2×Z2' discrete symmetry and can constitute dark matter candidates. We analyze the phenomenological viability of the predicted multi-Higgs sector imposing theoretical and experimental constraints. We perform a comprehensive analysis of the dark matter predictions of the model solving numerically the set of coupled Boltzmann equations involving all relevant dark matter processes and explore the direct detection prospects of the dark matter candidates.
Dark matter and neutrino masses from a classically scale-invariant multi-Higgs portal
Karam, Alexandros
2016-01-01
We present a classically scale-invariant model where the dark matter, neutrino and electroweak mass scales are dynamically generated from dimensionless couplings. The Standard Model gauge sector is extended by a dark $SU(2)_X$ gauge symmetry that is completely broken through a complex scalar doublet via the Coleman-Weinberg mechanism. The three resulting dark vector bosons of equal mass are stable and can play the role of dark matter. We also incorporate right-handed neutrinos which are coupled to a real singlet scalar that communicates with the other scalars through portal interactions. The multi-Higgs sector is analyzed by imposing theoretical and experimental constraints. We compute the dark matter relic abundance and study the possibility of the direct detection of the dark matter candidate from XENON 1T.
Dark Matter from a Classically Scale-Invariant $SU(3)_X$
Karam, Alexandros
2016-01-01
In this work we study a classically scale-invariant extension of the Standard Model in which the dark matter and electroweak scales are generated through the Coleman-Weinberg mechanism. The extra $SU(3)_X$ gauge factor gets completely broken by the vevs of two scalar triplets. Out of the eight resulting massive vector bosons the three lightest are stable due to an intrinsic $Z_2\\times Z_2'$ discrete symmetry and can constitute dark matter candidates. We analyze the phenomenological viability of the predicted multi-Higgs sector imposing theoretical and experimental constraints. We perform a comprehensive analysis of the dark matter predictions of the model solving numerically the set of coupled Boltzmann equations involving all relevant dark matter processes and explore the direct detection prospects of the dark matter candidates.
Viswanathan, G M
2006-01-01
A challenging problem in physics concerns the possibility of forecasting rare but extreme phenomena such as large earthquakes, financial market crashes, and material rupture. A promising line of research involves the early detection of precursory log-periodic oscillations to help forecast extreme events in collective phenomena where discrete scale invariance plays an important role. Here I investigate two distinct approaches towards the general problem of how to detect log-periodic oscillations in arbitrary time series without prior knowledge of the location of the moveable singularity. I first show that the problem has a definite solution in Fourier space, however the technique involved requires an unrealistically large signal to noise ratio. I then show that the quadrature signal obtained via analytic continuation onto the imaginary axis, using the Hilbert transform, necessarily retains the log-periodicities found in the original signal. This finding allows the development of a new method of detecting log-p...
Scale Invariance at low accelerations (aka MOND) and the dynamical anomalies in the Universe
Milgrom, Mordehai
2016-01-01
Galactic systems, and the Universe at large, exhibit large dynamical anomalies: The observed matter in them falls very short of providing enough gravity to account for their dynamics. The mainstream response to this conundrum is to invoke large quantities of `dark matter' (DM) -- which purportedly supplies the needed extra gravity -- and also of `dark energy' (DE), to account for further anomalies in cosmology, such as the observed, accelerated expansion. The MOND paradigm offers a different solution: a breakdown of standard dynamics (gravity and/or inertia) in the limit of low accelerations -- below some acceleration $a_0$. In this limit, dynamics become space-time scale invariant, and is controlled by a gravitational constant $\\mathcal{A}_0\\equiv Ga_0$, which replaces Newton's $G$. With the new dynamics, the various detailed manifestations of the anomalies in galaxies disappear with no need for DM. The cosmological anomalies could, but need not have to do with small accelerations. For example, the need for ...
Directory of Open Access Journals (Sweden)
Reza Oji
2012-10-01
Full Text Available Object detection is a fundamental task in computer vision and has many applications in image processing.This paper proposes a new approach for object detection by applying scale invariant feature transform(SIFT in an automatic segmentation algorithm. SIFT is an invariant algorithm respect to scale, translationand rotation. The features are very distinct and provide stable keypoints that can be used for matching anobject in different images. At first, an object is trained with different aspects for finding best keypoints. Theobject can be recognized in the other images by using achieved keypoints. Then, a robust segmentationalgorithm is used to detect the object with full boundary based on SIFT keypoints. In segmentationalgorithm, a merging role is defined to merge the regions in image with the assistance of keypoints. Theresults show that the proposed approach is reliable for object detection and can extract object boundarywell.
Large Scale-Invariant Fluctuations in Normal Blood Cell Counts A sign of criticality?
Perazzo, C A; Chialvo, D R; Willshaw, P; Perazzo, Carlos A.; Fernandez, Elmer A.; Chialvo, Dante R.; Willshaw, Peter
2000-01-01
All types of blood cells are formed by differentiation from a small self-maintaining population of pluri-potential stem cells in the bone marrow. Despite abundant information on the molecular aspects of division, differentiation, commitment and maturation of these cells, comparatively little is known about the dynamics of the system as a whole, and how it works to maintain this complex ``ecology'' in the observed normal ranges throughout life. Here we report unexpected large, scale-free, fluctuations detected from the first long-term analysis of the day-to-day variability of a healthy animal's blood cell counts measured over one thousand days. This scale-invariance cannot be accounted for by current theoretical models, and resembles some of the scenarios described for self-organized criticality.
A position, rotation, and scale invariant image descriptor based on rays and circular paths
Solorza-Calderón, Selene
2015-09-01
In this paper a rotation, scale and translation (RST) invariant image descriptor based on 1D signatures is presented. The position invariant is obtained using the amplitude spectrum of the Fourier transform of the image. That spectrum is introduced in the analytical Fourier-Mellin transform (AFMT) to obtain the scale invariance. From the normalized AFMT amplitude spectrum two 1D signatures are constructed. To build a 1D circular signature, circular path binary masks are used to filter the spectrum image. On the other hand, ray path binary filters are utilized in the construction of the 1D ray signature. These 1D signatures are RST invariant image descriptors. The Latin alphabet letters in Arial font style were used to test the descriptor efficiency. According with the statistical analysis of bootstrap with a constant replacement B = 1000 and normal distribution, the descriptor has a confidence level at least of 95%.
On Supersymmetric Geometric Flows and $\\mathcal{R}^2$ Inflation From Scale Invariant Supergravity
Rajpoot, Subhash
2016-01-01
Models of geometric flows pertaining to $\\mathcal{R}^2$ scale invariant (super) gravity theories coupled to conformally invariant matter fields are investigated. Related to this work are supersymmetric scalar manifolds that are isomorphic to the K\\"{a}hlerian spaces $\\mathcal{M}_n=SU(1,1+k)/U(1)\\times SU(1+k)$ as generalizations of the non-supersymmetric analogs with $SO(1,1+k)/SO(1+k)$ manifolds. For curved superspaces with geometric evolution of physical objects, a complete supersymmetric theory has to be elaborated on nonholonomic (super) manifolds and bundles determined by non-integrable superdistributions with additional constraints on (super) field dynamics and geometric evolution equations. We also consider generalizations of Perelman's functionals using such nonholonomic variables which result in the decoupling of geometric flow equations and Ricci soliton equations with supergravity modifications of the $R^2$ gravity theory. As such, it is possible to construct exact non-homogeneous and locally aniso...
Automated Image Retrieval of Chest CT Images Based on Local Grey Scale Invariant Features.
Arrais Porto, Marcelo; Cordeiro d'Ornellas, Marcos
2015-01-01
Textual-based tools are regularly employed to retrieve medical images for reading and interpretation using current retrieval Picture Archiving and Communication Systems (PACS) but pose some drawbacks. All-purpose content-based image retrieval (CBIR) systems are limited when dealing with medical images and do not fit well into PACS workflow and clinical practice. This paper presents an automated image retrieval approach for chest CT images based local grey scale invariant features from a local database. Performance was measured in terms of precision and recall, average retrieval precision (ARP), and average retrieval rate (ARR). Preliminary results have shown the effectiveness of the proposed approach. The prototype is also a useful tool for radiology research and education, providing valuable information to the medical and broader healthcare community. PMID:26262345
Real-time object tracking based on scale-invariant features employing bio-inspired hardware.
Yasukawa, Shinsuke; Okuno, Hirotsugu; Ishii, Kazuo; Yagi, Tetsuya
2016-09-01
We developed a vision sensor system that performs a scale-invariant feature transform (SIFT) in real time. To apply the SIFT algorithm efficiently, we focus on a two-fold process performed by the visual system: whole-image parallel filtering and frequency-band parallel processing. The vision sensor system comprises an active pixel sensor, a metal-oxide semiconductor (MOS)-based resistive network, a field-programmable gate array (FPGA), and a digital computer. We employed the MOS-based resistive network for instantaneous spatial filtering and a configurable filter size. The FPGA is used to pipeline process the frequency-band signals. The proposed system was evaluated by tracking the feature points detected on an object in a video. PMID:27268260
Emergent Cosmology, Inflation and Dark Energy from Spontaneous Breaking of Scale Invariance
Guendelman, Eduardo; Nissimov, Emil; Pacheva, Svetlana
2014-01-01
A new class of gravity-matter models defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space-time manifold are studied in some detail. These models involve an additional R^2 (square of the scalar curvature) term as well as scalar matter field potentials of appropriate form so that the pertinent action is invariant under global Weyl-scale symmetry. Scale invariance is spontaneously broken upon integration of the equations of motion. After performing transition to the physical Einstein frame we obtain: (i) An effective potential for the scalar field with two flat regions which allows for a unified description of both early universe inflation as well as of present dark energy epoch; (ii) For a definite parameter range the model possesses a non-singular "emergent universe" solution which describes an initial phase of evolution that precedes the inflationary phase.
Discretization of Continuous Time Discrete Scale Invariant Processes: Estimation and Spectra
Rezakhah, Saeid; Maleki, Yasaman
2016-07-01
Imposing some flexible sampling scheme we provide some discretization of continuous time discrete scale invariant (DSI) processes which is a subsidiary discrete time DSI process. Then by introducing some simple random measure we provide a second continuous time DSI process which provides a proper approximation of the first one. This enables us to provide a bilateral relation between covariance functions of the subsidiary process and the new continuous time processes. The time varying spectral representation of such continuous time DSI process is characterized, and its spectrum is estimated. Also, a new method for estimation time dependent Hurst parameter of such processes is provided which gives a more accurate estimation. The performance of this estimation method is studied via simulation. Finally this method is applied to the real data of S & P500 and Dow Jones indices for some special periods.
Tavares, Gustavo Marques
The Standard Model of particle physics describes all known elementary particles and their interactions. Despite its great experimental success, we know that the Standard Model is not a complete description of Nature and therefore new phenomena should be observed at higher energies. In the coming years the Large Hadron Collider will test the Standard Model by colliding protons with center of mass energies of up to 14 TeV providing some of the most stringent tests on the Standard Model. Experimental searches for Dark Matter provide a complementary program to test physics at the weak scale. In the near future new experimental data coming from direct detection experiments, and from satellites and telescopes will drastically improve our sensitivity to weak scale dark matter. This could lead to the first direct observation of dark matter, and thus of physics beyond the Standard Model. In this thesis I propose different extensions of the Standard Model and discuss their experimental consequences. I first discuss models for Axigluons, which are spin one particles in the adjoint representation of the SU(3) color gauge group. These models were motivated by the measurement of higher than predicted forward-backward asymmetry in top quark pair production at the Tevatron. I study different scenarios for Axigluon models that can explain the Tevatron result and explore their signatures at the Large Hadron Collider. Second I discuss the implications of ultraviolet scale invariance for the Standard Model, which has been advocated as a solution to the hierarchy problem. I show that in order to solve the hierarchy problem with scale invariance, new physics is required not far from the weak scale. In the last part of this thesis I propose a new model for dark matter, in which dark matter is charged under a hidden non-Abelian gauge group. This leads to modifications in the sensitivity of the usual experimental searches for dark matter in addition to distinct signatures in the Cosmic
Mining unstructured software data
Bacchelli, Alberto; Lanza, Michele
2013-01-01
Our thesis is that the analysis of unstructured data supports software understanding and evolution analysis, and complements the data mined from structured sources. To this aim, we implemented the necessary toolset and investigated methods for exploring, exposing, and exploiting unstructured data.To validate our thesis, we focused on development email data. We found two main challenges in using it to support program comprehension and software development: The disconnection between emai...
Directory of Open Access Journals (Sweden)
Yuchou Chang
2008-02-01
Full Text Available Scale-invariant feature transform (SIFT transforms a grayscale image into scale-invariant coordinates of local features that are invariant to image scale, rotation, and changing viewpoints. Because of its scale-invariant properties, SIFT has been successfully used for object recognition and content-based image retrieval. The biggest drawback of SIFT is that it uses only grayscale information and misses important visual information regarding color. In this paper, we present the development of a novel color feature extraction algorithm that addresses this problem, and we also propose a new clustering strategy using clustering ensembles for video shot detection. Based on Fibonacci lattice-quantization, we develop a novel color global scale-invariant feature transform (CGSIFT for better description of color contents in video frames for video shot detection. CGSIFT first quantizes a color image, representing it with a small number of color indices, and then uses SIFT to extract features from the quantized color index image. We also develop a new space description method using small image regions to represent global color features as the second step of CGSIFT. Clustering ensembles focusing on knowledge reuse are then applied to obtain better clustering results than using single clustering methods for video shot detection. Evaluation of the proposed feature extraction algorithm and the new clustering strategy using clustering ensembles reveals very promising results for video shot detection.
Directory of Open Access Journals (Sweden)
Hong Yi
2008-01-01
Full Text Available Abstract Scale-invariant feature transform (SIFT transforms a grayscale image into scale-invariant coordinates of local features that are invariant to image scale, rotation, and changing viewpoints. Because of its scale-invariant properties, SIFT has been successfully used for object recognition and content-based image retrieval. The biggest drawback of SIFT is that it uses only grayscale information and misses important visual information regarding color. In this paper, we present the development of a novel color feature extraction algorithm that addresses this problem, and we also propose a new clustering strategy using clustering ensembles for video shot detection. Based on Fibonacci lattice-quantization, we develop a novel color global scale-invariant feature transform (CGSIFT for better description of color contents in video frames for video shot detection. CGSIFT first quantizes a color image, representing it with a small number of color indices, and then uses SIFT to extract features from the quantized color index image. We also develop a new space description method using small image regions to represent global color features as the second step of CGSIFT. Clustering ensembles focusing on knowledge reuse are then applied to obtain better clustering results than using single clustering methods for video shot detection. Evaluation of the proposed feature extraction algorithm and the new clustering strategy using clustering ensembles reveals very promising results for video shot detection.
View FImP miracle (by scale invariance) à la self-interaction
Kang, Zhaofeng
2015-12-01
Combining feebly interacting massive particle (FIMP) dark matter (DM) with scale invariance (SI) leads to extremely light FIMP (thus the FImP) with FImP miracle, i.e., the mass and relic generations of FImP DM share the same dynamics. In this paper we show that due to the lightness of FImP, it, especially for a scalar FImP, can easily accommodate large DM self-interaction. For a fermionic FImP, such as the sterile neutrino, self-interaction additionally requires a mediator which is another FImP, a scalar boson with mass either much lighter or heavier than the FImP DM. DM self-interaction opens a new window to observe FImP (miracle), which does not leave traces in the conventional DM searches. As an example, FImP can account for the offsets between the centroid of DM halo and stars of galaxies recently observed in the galaxy cluster Abel 3827.
Discriminative phenomenological features of scale invariant models for electroweak symmetry breaking
Directory of Open Access Journals (Sweden)
Katsuya Hashino
2016-01-01
Full Text Available Classical scale invariance (CSI may be one of the solutions for the hierarchy problem. Realistic models for electroweak symmetry breaking based on CSI require extended scalar sectors without mass terms, and the electroweak symmetry is broken dynamically at the quantum level by the Coleman–Weinberg mechanism. We discuss discriminative features of these models. First, using the experimental value of the mass of the discovered Higgs boson h(125, we obtain an upper bound on the mass of the lightest additional scalar boson (≃543 GeV, which does not depend on its isospin and hypercharge. Second, a discriminative prediction on the Higgs-photon–photon coupling is given as a function of the number of charged scalar bosons, by which we can narrow down possible models using current and future data for the di-photon decay of h(125. Finally, for the triple Higgs boson coupling a large deviation (∼+70% from the SM prediction is universally predicted, which is independent of masses, quantum numbers and even the number of additional scalars. These models based on CSI can be well tested at LHC Run II and at future lepton colliders.
A Scale Invariant Interest Point Detector in Gabor Based Energy Space
Institute of Scientific and Technical Information of China (English)
CAO Zheng-Cai; MA Feng-Le; FU Yi-Li; ZHANG Jian
2014-01-01
Interest point detection is a fundamental issue in many intermediate level vision problems and plays a significant role in vision systems. The previous interest point detectors are designed to detect some special image structures such as corners, junctions, line terminations and so on. These detectors based on some simplified 2D feature models will not work for image fea-tures that differ significantly from the models. In this paper, a scale invariant interest point detector, which is appropriate for most types of image features, is proposed based on an iterative method in the Gabor based energy space. It detects interest points by noting that there are some similarities in the phase domain for all types of image features, which are obtained by different detectors respectively. Firstly, this approach obtains the positions of candidate points by detecting the local maxima of a series of energy maps constructed by Gabor filter responses. Secondly, an iterative algorithm is adopted to select the corre-sponding characteristic scales and accurately locate the interest points simultaneously in the Gabor based energy space. Finally, in order to improve the real-time performance of the approach, a fast implementation of Gabor function is used to accelerate the process of energy space construction. Experiments show that this approach has a broader applicability than the other detec-tors and has a good performance under rotation and some other image changes.
Digital Library ImageRetrieval usingScale Invariant Feature and Relevance Vector Machine
Directory of Open Access Journals (Sweden)
Hongtao Zhang
2014-10-01
Full Text Available With the advance of digital library, the digital content develops with rich information connotation. Traditional information retrieval methods based on external characteristic and text description are unable to sufficientlyreveal and express the substance and semantic relation of multimedia information, and unable to fully reveal and describe the representative characteristics of information. Because of the abundant connotation of image content and the people’s abstract subjectivity in studying image content, the visual feature of the image is difficult to be described by key words. Therefore, this method not always can meet people’s needs, and the study of digital library image retrieval technique based on content is important to both academic research and application. At present, image retrieval methods are mainly based on the text and content, etc. But these existing algorithms have shortages, such as large errors and slow speeds. Motivated by the above fact, we in this paper propose a new approach based on relevance vector machine (RVM. The proposed approach first extracts the patch-level scale invariant image feature (SIFT, and then constructs the global features for images. The image feature is then delivered into RVM for retrieval. We evaluate the proposed approach on Corel dataset. The experimental result shows that the proposed method in this text has high accuracy when retrieves images.
A Scale-invariant Higgs Sector and Structure of the Vacuum
Endo, Kazuhiro
2015-01-01
In view of the current status of measured Higgs boson properties, we consider a question whether only the Higgs self-interactions can deviate significantly from the Standard-Model (SM) predictions. This may be possible if the Higgs effective potential is irregular at the origin. As an example we investigate an extended Higgs sector with singlet scalar(s) and classical scale invariance. We develop a perturbative formulation necessary to analyze this model in detail. The behavior of a phenomenologically valid potential in the perturbative regime is studied around the electroweak scale. We reproduce known results: The Higgs self-interactions are substantially stronger than the SM predictions, while the Higgs interactions with other SM particles are barely changed. We further predict that the interactions of singlet scalar(s), which is a few to several times heavier than the Higgs boson, tend to be fairly strong. If probed, these features will provide vivid clues to the structure of the vacuum. We also examine Ve...
FImP Miracle of Sterile Neutrino Dark Matter by Scale Invariance
Kang, Zhaofeng
2014-01-01
The standard model (SM) with sterile neutrinos provides the simplest idea to understand nonzero neutrino masses. As a bonus, the lightest sterile neutrino $N_1$, even in the absence of a protective symmetry, can be a dark matter (DM) candidate provided that it is as light as the keV scale. We observe that if this idea is realized in the scale invariant SM, which may address the hierarchy problem, extra singlet scalars $S$ with nonzero vacuum expected value (VEV) should be introduced to give Majorana masses for the sterile neutrinos. Such a fact yields an attractive picture: Given $\\langle S\\rangle\\sim $TeV via the Coleman-Weinberg mechanism, which is strongly favored by Higgs phenomenologies, the correct orders of DM mass (by dynamics instead of hand) and DM relic density (by freeze-in instead of oscillation) are surprisingly addressed by the same vertex $SN_1N_1$. This coincidence is an even stronger version of the WIMP miracle and dubbed as FImP miracle. Interestingly, a 7.1 keV $N_1$ with correct relic den...
Self-organization of developing embryo using scale-invariant approach
Directory of Open Access Journals (Sweden)
Tiraihi Taki
2011-06-01
Full Text Available Abstract Background Self-organization is a fundamental feature of living organisms at all hierarchical levels from molecule to organ. It has also been documented in developing embryos. Methods In this study, a scale-invariant power law (SIPL method has been used to study self-organization in developing embryos. The SIPL coefficient was calculated using a centro-axial skew symmetrical matrix (CSSM generated by entering the components of the Cartesian coordinates; for each component, one CSSM was generated. A basic square matrix (BSM was constructed and the determinant was calculated in order to estimate the SIPL coefficient. This was applied to developing C. elegans during early stages of embryogenesis. The power law property of the method was evaluated using the straight line and Koch curve and the results were consistent with fractal dimensions (fd. Diffusion-limited aggregation (DLA was used to validate the SIPL method. Results and conclusion The fractal dimensions of both the straight line and Koch curve showed consistency with the SIPL coefficients, which indicated the power law behavior of the SIPL method. The results showed that the ABp sublineage had a higher SIPL coefficient than EMS, indicating that ABp is more organized than EMS. The fd determined using DLA was higher in ABp than in EMS and its value was consistent with type 1 cluster formation, while that in EMS was consistent with type 2.
Directory of Open Access Journals (Sweden)
Hanlun Li
2016-01-01
Full Text Available In the past few years, many multispectral systems which consist of several identical monochrome cameras equipped with different bandpass filters have been developed. However, due to the significant difference in the intensity between different band images, image registration becomes very difficult. Considering the common structural characteristic of the multispectral systems, this paper proposes an effective method for registering different band images. First we use the phase correlation method to calculate the parameters of a coarse-offset relationship between different band images. Then we use the scale invariant feature transform (SIFT to detect the feature points. For every feature point in a reference image, we can use the coarse-offset parameters to predict the location of its matching point. We only need to compare the feature point in the reference image with the several near feature points from the predicted location instead of the feature points all over the input image. Our experiments show that this method does not only avoid false matches and increase correct matches, but also solve the matching problem between an infrared band image and a visible band image in cases lacking man-made objects.
Mosaic of the Curved Human Retinal Images Based on the Scale-Invariant Feature Transform
Institute of Scientific and Technical Information of China (English)
LI Ju-peng; CHEN Hou-jin; ZHANG Xin-yuan; YAO Chang
2008-01-01
.To meet the needs in the fundus examination, including outlook widening, pathology tracking, etc., this paper describes a robust feature-based method for fully-automatic mosaic of the curved human retinal images photographed by a fundus microscope. The kernel of this new algorithm is the scale-, rotation-and illumination-invariant interest point detector & feature descriptor-Scale-Invariant Feature Transform. When matched interest points according to second-nearest-neighbor strategy, the parameters of the model are estimated using the correct matches of the interest points,extracted by a new inlier identification scheme based on Sampson distance from putative sets. In order to preserve image features, bilinear warping and multi-band blending techniques are used to create panoramic retinal images. Experiments show that the proposed method works well with rejection error in 0.3 pixels, even for those cases where the retinal images without discernable vascular structure in contrast to the state-of-the-art algorithms.
Scale Invariant Kaluza-Klein Theory and the Fate of the Gravitational Collapse
Quirós, I
2002-01-01
Pushing forward the similitudes between the gravitational collapse and the expansion of the universe (in the reversed sense of time), it should be expected that, during the collapse, eventually, a spacetime domain would be reached where attained energy scales are very high. In consequence some of the compactified extra dimensions may be decompactified and some presently broken symmetries may be restored. A more fundamental theory (of which Einstein's theory is a symmetry broken phase) is then expected to take account of further description of the collapse. I propose a simple (classical) model for the description of the late stages of the gravitational collapse: A non-Riemannian, scale-invariant version of 5-dimensional Kaluza-Klein theory in which the standard Riemann structure of the higher-dimensional manifold is replaced by a Weyl-integrable one. A class of solutions, that generalize the "soliton" one by Gross and Perry and Davidson and Owen, is found. This class contains both naked singularities and wormh...
The B=2 system in the chiral quark-soliton model with broken scale invariance
Sarti, Valentina Mantovani; Vento, Vicente
2013-01-01
We study the interaction between two B=1 states in the Chiral-Dilaton Model with scale invariance where baryons are described as non-topological solitons arising from the interaction of chiral mesons and quarks. By using the hedgehog solution for the B=1 states we construct, via a product ansatz, three possible B=2 configurations to analyse the role of the relative orientation of the hedgehog quills in the dynamics. We investigate the behaviour of these solutions in the range of long and intermediate distances between the two solitons. Since the product ansatz breaks down as the two solitons get close, we explore the short range distances regime by building up a six quarks bag and by evaluating the interaction energy as a function of the inter-soliton separation. We calculate the interaction energy as a function of the inter-soliton distance for the B=2 system and we show that for small separations the six quarks bag, assuming a hedgehog structure, provides a stable bound state that at large separations conne...
Embedding inflation into the Standard Model - more evidence for classical scale invariance
Kannike, Kristjan; Raidal, Martti
2014-01-01
If cosmological inflation is due to a slowly rolling single inflation field taking trans-Planckian values as suggested by the BICEP2 measurement of primordial tensor modes in CMB, embedding inflation into the Standard Model challenges standard paradigm of effective field theories. Together with an apparent absence of Planck scale contributions to the Higgs mass and to the cosmological constant, BICEP2 provides further experimental evidence for the absence of large $M_{\\rm P}$ induced operators. We show that classical scale invariance, the paradigm that all fundamental scales in Nature are induced by quantum effects, solves the problem and allows for a remarkably simple scale-free Standard Model extension with inflaton without extending the gauge group. Due to trans-Planckian inflaton values and vevs, a dynamically induced Coleman-Weinberg-type inflaton potential of the model can predict tensor-to-scalar ratio $r$ in a large range, converging around the prediction of chaotic $m^2\\phi^2$ inflation for a large t...
A non-scale-invariant form for coarse-grained diffusion-reaction equations
Ostvar, Sassan; Wood, Brian D.
2016-09-01
The process of mixing and reaction is a challenging problem to understand mathematically. Although there have been successes in describing the effective properties of mixing and reaction under a number of regimes, process descriptions for early times have been challenging for cases where the structure of the initial conditions is highly segregated. In this paper, we use the method of volume averaging to develop a rigorous theory for diffusive mixing with reactions from initial to asymptotic times under highly segregated initial conditions in a bounded domain. One key feature that arises in this development is that the functional form of the averaged differential mass balance equations is not, in general, scale invariant. Upon upscaling, an additional source term arises that helps to account for the initial configuration of the reacting chemical species. In this development, we derive the macroscopic parameters (a macroscale source term and an effectiveness factor modifying the reaction rate) defined in the macroscale diffusion-reaction equation and provide example applications for several initial configurations.
From elasticity to inelasticity in cancer cell mechanics: A loss of scale-invariance
Laperrousaz, B.; Drillon, G.; Berguiga, L.; Nicolini, F.; Audit, B.; Satta, V. Maguer; Arneodo, A.; Argoul, F.
2016-08-01
Soft materials such as polymer gels, synthetic biomaterials and living biological tissues are generally classified as viscoelastic or viscoplastic materials, because they behave neither as pure elastic solids, nor as pure viscous fluids. When stressed beyond their linear viscoelastic regime, cross-linked biopolymer gels can behave nonlinearly (inelastically) up to failure. In living cells, this type of behavior is more frequent because their cytoskeleton is basically made of cross-linked biopolymer chains with very different structural and flexibility properties. These networks have high sensitivity to stress and great propensity to local failure. But in contrast to synthetic passive gels, they can "afford" these failures because they have ATP driven reparation mechanisms which often allow the recovery of the original texture. A cell pressed in between two plates for a long period of time may recover its original shape if the culture medium brings all the nutrients for keeping it alive. When the failure events are too frequent or too strong, the reparation mechanisms may abort, leading to an irreversible loss of mechanical homeostasis and paving the way for chronic diseases such as cancer. To illustrate this discussion, we consider a model of immature cell transformation during cancer progression, the chronic myelogenous leukemia (CML), where the formation of the BCR-ABL oncogene results from a single chromosomal translocation t(9; 22). Within the assumption that the cell response to stress is scale invariant, we show that the power-law exponent that characterizes their mechanosensitivity can be retrieved from AFM force indentation curves. Comparing control and BCR-ABL transduced cells, we observe that in the later case, one month after transduction, a small percentage the cancer cells no longer follows the control cell power law, as an indication of disruption of the initial cytoskeleton network structure.
Traffic sign recognition based on a context-aware scale-invariant feature transform approach
Yuan, Xue; Hao, Xiaoli; Chen, Houjin; Wei, Xueye
2013-10-01
A new context-aware scale-invariant feature transform (CASIFT) approach is proposed, which is designed for the use in traffic sign recognition (TSR) systems. The following issues remain in previous works in which SIFT is used for matching or recognition: (1) SIFT is unable to provide color information; (2) SIFT only focuses on local features while ignoring the distribution of global shapes; (3) the template with the maximum number of matching points selected as the final result is instable, especially for images with simple patterns; and (4) SIFT is liable to result in errors when different images share the same local features. In order to resolve these problems, a new CASIFT approach is proposed. The contributions of the work are as follows: (1) color angular patterns are used to provide the color distinguishing information; (2) a CASIFT which effectively combines local and global information is proposed; and (3) a method for computing the similarity between two images is proposed, which focuses on the distribution of the matching points, rather than using the traditional SIFT approach of selecting the template with maximum number of matching points as the final result. The proposed approach is particularly effective in dealing with traffic signs which have rich colors and varied global shape distribution. Experiments are performed to validate the effectiveness of the proposed approach in TSR systems, and the experimental results are satisfying even for images containing traffic signs that have been rotated, damaged, altered in color, have undergone affine transformations, or images which were photographed under different weather or illumination conditions.
The Unstructured Clinical Interview
Jones, Karyn Dayle
2010-01-01
In mental health, family, and community counseling settings, master's-level counselors engage in unstructured clinical interviewing to develop diagnoses based on the "Diagnostic and Statistical Manual of Mental Disorders" (4th ed., text rev.; "DSM-IV-TR"; American Psychiatric Association, 2000). Although counselors receive education about…
Elizalde, E.; Gaztanaga, E.
1992-01-01
The dependence of counts in cells on the shape of the cell for the large scale galaxy distribution is studied. A very concrete prediction can be done concerning the void distribution for scale invariant models. The prediction is tested on a sample of the CfA catalog, and good agreement is found. It is observed that the probability of a cell to be occupied is bigger for some elongated cells. A phenomenological scale invariant model for the observed distribution of the counts in cells, an extension of the negative binomial distribution, is presented in order to illustrate how this dependence can be quantitatively determined. An original, intuitive derivation of this model is presented.
Institute of Scientific and Technical Information of China (English)
ZHANG Yu; HOU ZhanFeng; LIU YuXin
2009-01-01
We study systematically the evolutive behaviors of some energy ratios,E2 transition rate ratios and Isomer shift in the nuclear shape phase transitions.We find that the quantities sensitive to the phase transition and independent of free parameter(s) are approximately particle number N scale invariant around the critical point of the first order phase transition,similar to that in the second order phase transition.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
We study systematically the evolutive behaviors of some energy ratios,E2 transition rate ratios and isomer shift in the nuclear shape phase transitions.We find that the quantities sensitive to the phase transition and independent of free parameter(s) are approximately particle number N scale invariant around the critical point of the first order phase transition,similar to that in the second order phase transition.
Brause, Rüdiger W.; Arlt, Björn; Tratar, Erwin
1999-01-01
For the efficient management of large image databases, the automated characterization of images and the usage of that characterization for searching and ordering tasks is highly desirable. The purpose of the project SEMACODE is to combine the still unsolved problem of content-oriented characterization of images with scale-invariant object recognition and modelbased compression methods. To achieve this goal, existing techniques as well as new concepts related to pattern matching, image encodin...
Strongly first-order electroweak phase transition and classical scale invariance
Farzinnia, Arsham; Ren, Jing
2014-10-01
In this work, we examine the possibility of realizing a strongly first-order electroweak phase transition within the minimal classically scale-invariant extension of the standard model (SM), previously proposed and analyzed as a potential solution to the hierarchy problem. By introducing one complex gauge-singlet scalar and three (weak scale) right-handed Majorana neutrinos, the scenario was successfully rendered capable of achieving a radiative breaking of the electroweak symmetry (by means of the Coleman-Weinberg mechanism), inducing nonzero masses for the SM neutrinos (via the seesaw mechanism), presenting a pseudoscalar dark matter candidate (protected by the CP symmetry of the potential), and predicting the existence of a second CP-even boson (with suppressed couplings to the SM content) in addition to the 125 GeV scalar. In the present treatment, we construct the full finite-temperature one-loop effective potential of the model, including the resummed thermal daisy loops, and demonstrate that finite-temperature effects induce a first-order electroweak phase transition. Requiring the thermally driven first-order phase transition to be sufficiently strong at the onset of the bubble nucleation (corresponding to nucleation temperatures TN˜100-200 GeV) further constrains the model's parameter space; in particular, an O(0.01) fraction of the dark matter in the Universe may be simultaneously accommodated with a strongly first-order electroweak phase transition. Moreover, such a phase transition disfavors right-handed Majorana neutrino masses above several hundreds of GeV, confines the pseudoscalar dark matter masses to ˜1-2 TeV, predicts the mass of the second CP-even scalar to be ˜100-300 GeV, and requires the mixing angle between the CP-even components of the SM doublet and the complex singlet to lie within the range 0.2≲sinω ≲0.4. The obtained results are displayed in comprehensive exclusion plots, identifying the viable regions of the parameter space
Murase, M.
1996-01-01
with self-organization, has been thought to underlie `creative' aspects of biological phenomena such as the origin of life, adaptive evolution of viruses, immune recognition and brain function. It therefore must be surprising to find that the same principles will also underlie `non-creative' aspects, for example, the development of cancer and the aging of complex organisms. Although self-organization has extensively been studied in nonliving things such as chemical reactions and laser physics, it is undoubtedly true that the similar sources of the order are available to living things at different levels and scales. Several paradigm shifts are, however, required to realize how the general principles of natural selection can be extensible to non-DNA molecules which do not possess the intrinsic nature of self-reproduction. One of them is, from the traditional, genetic inheritance view that DNA (or RNA) molecules are the ultimate unit of heritable variations and natural selection at any organization level, to the epigenetic (nongenetic) inheritance view that any non-DNA molecule can be the target of heritable variations and molecular selection to accumulate in certain biochemical environment. Because they are all enriched with a β-sheet content, ready to mostly interact with one another, different denatured proteins like β-amyloid, PHF and prions can individually undergo self-templating or self-aggregating processes out of gene control. Other paradigm shifts requisite for a break-through in the etiology of neurodegenerative disorders will be discussed. As it is based on the scale-invariant principles, the present theory also predicts plausible mechanisms underlying quite different classes of disorders such as amyotrophic lateral sclerosis (ALS), atherosclerosis, senile cataract and many other symptoms of aging. The present theory, thus, provides the consistent and comprehensive account to the origin of aging by means of natural selection and self-organization.
Hatanaka, Hisaki(School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Republic of Korea); Jung, Dong-Won; Ko, Pyungwon
2016-01-01
In this paper, we revisit a scale-invariant extension of the standard model (SM) with a strongly interacting hidden sector within AdS/QCD approach. Using the AdS/QCD, we reduce the number of input parameters to three, i.e. hidden pion decay constant, hidden pion mass and $\\tan\\beta$ that is defined as the ratio of the vacuum expectation values (VEV) of the singlet scalar field and the SM Higgs boson. As a result, our model has sharp predictability. We perform the phenomenological analysis of ...
Atick-Witten Hagedorn Conjecture, near scale-invariant matter and blue-tilted gravity power spectrum
Biswas, Tirthabir; Mazumdar, Anupam
2014-01-01
We will provide an interesting new mechanism to generate almost scale invariant seed density perturbations with a red spectrum, while keeping the gravitational wave spectrum blue-tilted in a stringy thermal contracting phase at temperatures beyond the Hagedorn temperature. This phase is often referred to as the Hagedorn phase where the free energy has been conjectured by Atick and Witten to grow more slowly than ordinary radiation. The primordial fluctuations are created by the statistical thermal fluctuations determined by the partition function, rather than quantum vacuum driven fluid dynamical fluctuations. In order for our mechanism to work we require a non-singular bouncing cosmology.
Yu, Yongtao; Guan, Haiyan; Zai, Dawei; Ji, Zheng
2016-02-01
This paper proposes a rotation-and-scale-invariant method for detecting airplanes from high-resolution satellite images. To improve feature representation capability, a multi-layer feature generation model is created to produce high-order feature representations for local image patches through deep learning techniques. To effectively estimate airplane centroids, a Hough forest model is trained to learn mappings from high-order patch features to the probabilities of an airplane being present at specific locations. To handle airplanes with varying orientations, patch orientation is defined and integrated into the Hough forest to augment Hough voting. The scale invariance is achieved by using a set of scale factors embedded in the Hough forest. Quantitative evaluations on the images collected from Google Earth service show that the proposed method achieves a completeness, correctness, quality, and F1-measure of 0.968, 0.972, 0.942, and 0.970, respectively, in detecting airplanes with arbitrary orientations and sizes. Comparative studies also demonstrate that the proposed method outperforms the other three existing methods in accurately and completely detecting airplanes in high-resolution remotely sensed images.
Unstructured Documents Categorization: A Study
Directory of Open Access Journals (Sweden)
Debnath Bhattacharyya
2008-12-01
Full Text Available The main purpose of communication is to transfer information from onecorner to another of the world. The information is basically stored in forms of documents or files created on the basis of requirements. So, the randomness of creation and storage makes them unstructured in nature. As a consequence, data retrieval and modification become hard nut to crack. The data, that is required frequently, should maintain certain pattern. Otherwise, problems like retrievingerroneous data or anomalies in modification or time consumption in retrieving process may hike. As every problem has its own solution, these unstructured documents have also given the solution named unstructured document categorization. That means, the collected unstructured documents will be categorized based on some given constraints. This paper is a review which deals with different techniques like text and data mining, genetic algorithm, lexicalchaining, binarization method to reach the fulfillment of desired unstructured document categorization appeared in the literature.
尺度不变特征变换算子综述%Summarization of the scale invariant feature transform
Institute of Scientific and Technical Information of China (English)
刘立; 詹茵茵; 罗扬; 刘朝晖; 彭复员
2013-01-01
With the development of software and hardware technique,computer vision has become a hot research fields in image processing.Scale invariant feature transform (SIFT) is one of the most successful vision algorithm nowadays and it is widely studied by the computer vision community because of its unique features.SIFT is scale invariant,rotation invariant and illumination invariant.However,it also has some problems such as it is only part affine has a rather the high computation complexity.Many extended or modified algorithms of the SIFT are developed unceasingly.In this paper,we summarize the history,the evolved processing,and the application of the SIFT and compares those algorithm effects.At last,the paper discusses the feature direction and provides reference for computer vision researchers.%随着计算机软件与硬件技术的发展,计算机视觉算法逐渐成为图像处理领域的研究热点.其中SIFT(scale invariant feature transform)算法是目前机器视觉领域应用最成功的算法之一.由于在尺度不变、旋转不变、光照不变等方面的独特优势,SIFT被广大视觉领域的研究者借鉴与学习.但是SIFT算法本身也存在一些问题,如仿射性能不太理想,计算复杂度过高等,因此针对它的多种改进算法不断出现.本文对SIFT的发展历史、SIFT算法的演变以及它不同领域的典型应用给出了一个比较全面的综述,比较了各类算法的优缺点.最后给出了该算法未来可能的发展方向,为视觉研究者提供参考.
Energy Technology Data Exchange (ETDEWEB)
Wang, Sai, E-mail: wangsai@itp.ac.cn [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100049, Beijing (China); Chang, Zhe [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100049, Beijing (China); Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing (China)
2015-06-11
We propose the gravity’s rainbow scenario as a possible alternative of the inflation paradigm to account for the flatness and horizon problems. We focus on studying the cosmological scalar perturbations which are seeded by the quantum fluctuations in the very early universe. The scalar power spectrum is expected to be nearly scale-invariant. We estimate the rainbow index λ and energy scale M in the gravity’s rainbow scenario by analyzing the Planck temperature and WMAP polarization datasets. The constraints on them are given by λ=2.933±0.012 and ln(10{sup 5}M/M{sub p})=-0.401{sub -0.451}{sup +0.457} at the 68 % confidence level.
Energy Technology Data Exchange (ETDEWEB)
Wang, Sai [Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Chang, Zhe [Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China)
2015-06-15
We propose the gravity's rainbow scenario as a possible alternative of the inflation paradigm to account for the flatness and horizon problems. We focus on studying the cosmological scalar perturbations which are seeded by the quantum fluctuations in the very early universe. The scalar power spectrum is expected to be nearly scale-invariant. We estimate the rainbow index λ and energy scale M in the gravity's rainbow scenario by analyzing the Planck temperature and WMAP polarization datasets. The constraints on them are given by λ = 2.933 ± 0.012 and ln(10{sup 5}M/M{sub p}) = -0.401{sub -0.451}{sup +0.457} at the 68% confidence level. (orig.)
Fu, Yi-Jia; Wan, Feng; Sang, Hai-Bo; Xie, Bai-Song
2016-01-01
The Thomson scattering spectra by an electron moving in the laser-magnetic resonance acceleration regime are computed numerically and analytically. The dependence of fundamental frequency on the laser intensity and magnetic resonance parameter is examined carefully. By calculating the emission of a single electron in a circularly polarized plane-wave laser field and constant external magnetic field, the scale invariance of the radiation spectra is evident in terms of harmonic orders. The scaling law of backscattered spectra are exhibited remarkably for the laser intensity as well for the initial axial momentum of the electron when the cyclotron frequency of the electron approaches the laser frequency. The results indicate that the magnetic resonance parameter plays an important role on the strength of emission. And the rich features of scattering spectra found may be applicable to the radiation source tunability.
Nishida, Yusuke
2014-10-01
We study massless Dirac fermions in a supercritical Coulomb potential with the emphasis on that its low-energy physics is universal and parametrized by a single quantity per supercritical angular momentum channel. This low-energy parameter with the dimension of length is defined only up to multiplicative factors and thus each supercritical channel exhibits the discrete scale invariance. In particular, we show that the induced vacuum polarization has a power-law tail whose coefficient is a sum of log-periodic functions with respect to the distance from the potential center. This coefficient can also be expressed in terms of the energy and width of so-called atomic collapse resonances. Our universal predictions on the vacuum polarization and its relationship to atomic collapse resonances shed light on the longstanding fundamental problem of quantum electrodynamics and can in principle be tested by graphene experiments with charged impurities.
Institute of Scientific and Technical Information of China (English)
Jian Zhao,Na Zhang,Jian Jia,; Huanwei Wang
2015-01-01
Contraposing the need of the robust digital watermark for the copyright protection field, a new digital watermarking algo-rithm in the non-subsampled contourlet transform (NSCT) domain is proposed. The largest energy sub-band after NSCT is selected to embed watermark. The watermark is embedded into scale-invariant feature transform (SIFT) regions. During embedding, the initial region is divided into some cirque sub-regions with the same area, and each watermark bit is embedded into one sub-region. Extensive simulation results and comparisons show that the algo-rithm gets a good trade-off of invisibility, robustness and capacity, thus obtaining good quality of the image while being able to effec-tively resist common image processing, and geometric and combo attacks, and normalized similarity is almost al reached.
View FImP Miracle (by Scale Invariance) $\\acute{\\rm a}$ $\\rm la$ Self-interaction
Kang, Zhaofeng
2015-01-01
Combining feebly interacting massive particle (FIMP) dark matter (DM) with scale invariance (SI) leads to extremely light FIMP (thus the FImP) with FImP miracle, i.e., the mass and relic generations of FImP DM share the same dynamics. In this paper we show that due to the lightness of FImP, it, especially for a scalar FImP, can easily accommodate large DM self-interaction. For a fermionic FImP, such as the sterile neutrino, self-interaction additionally requires a mediator which is another FImP, a scalar boson with mass either much lighter or heavier than the FImP DM. DM self-interaction opens a new window to observe FImP (miracle), which does not leave traces in the conventional DM searches. As an example, FImP can account for the offsets between the centroid of DM halo and stars of galaxies recently observed in the galaxy cluster Abel 3827.
Hatanaka, Hisaki; Ko, Pyungwon
2016-01-01
In this paper, we revisit a scale-invariant extension of the standard model (SM) with a strongly interacting hidden sector within AdS/QCD approach. Using the AdS/QCD, we reduce the number of input parameters to three, i.e. hidden pion decay constant, hidden pion mass and $\\tan\\beta$ that is defined as the ratio of the vacuum expectation values (VEV) of the singlet scalar field and the SM Higgs boson. As a result, our model has sharp predictability. We perform the phenomenological analysis of the hidden pions which is one of the dark matter (DM) candidates in this model. With various theoretical and experimental constraints we search for the allowed parameter space and find that both resonance and non-resonance solutions are possible. Some typical correlations among various observables such as thermal relic density of hidden pions, Higgs signal strengths and DM-nucleon cross section are investigated. We provide some benchmark points for experimental tests.
Sohrab, Siavash
2016-03-01
A scale-invariant model of statistical mechanics is applied to described modified forms of four laws of classical thermodynamics. Following de Broglie formula λrk = h /mkvrk , frequency of matter waves is defined as νrk = k /mkvrk leading to stochastic definitions of (Planck, Boltzmann) universal constants (h =mk c , k =mk c), λrkνrk = c , relating to spatiotemporal Casimir vacuum fluctuations. Invariant Mach number Maβ = v /vrβ is introduced leading to hierarchy of ``supersonic'' flow separated by shock front, viewed as ``event-horizon'' EHβ, from subsonic flow that terminates at surface of stagnant condensate of ``atoms'' defined as ``black-hole'' BHβ at scale β thus resulting in hierarchy of embedded ``black holes'' at molecular- atomic-, electron-, photon-, tachyon-. . . scales, ad infinitum. Classical black hole will correspond to solid phase photon or solid-light. It is argued that Bardeen-Carter-Hawking (1973) first law of black hole mechanics δM = (κ / 8 π) δA +ΩH δJ +ΦH δQ , instead of dE = TdS - PdV suggested by Bekenstein (1973), is analogous to first law of thermodynamics expressed as TdS = PdV + dE such that entropy of black hole, rather than to its horizon surface area, will be related to its total energy hence enthalpy H = TS leading to SBH = 4 kN in exact agreement with prediction of Major and Setter.
Sohrab, Siavash H.; Pitch, Nancy (Technical Monitor)
1999-01-01
A scale-invariant statistical theory of fields is presented that leads to invariant definition of density, velocity, temperature, and pressure, The definition of Boltzmann constant is introduced as k(sub k) = m(sub k)v(sub k)c = 1.381 x 10(exp -23) J x K(exp -1), suggesting that the Kelvin absolute temperature scale is equivalent to a length scale. Two new state variables called the reversible heat Q(sub rev) = TS and the reversible work W(sub rev) = PV are introduced. The modified forms of the first and second law of thermodynamics are presented. The microscopic definition of heat (work) is presented as the kinetic energy due to the random (peculiar) translational, rotational, and pulsational motions. The Gibbs free energy of an element at scale Beta is identified as the total system energy at scale (Beta-1), thus leading to an invariant form of the first law of thermodynamics U(sub Beta) = Q(sub Beta) - W(sub Beta) +N(e3)U(sub Beta-1).
Paganelli, Chiara; Peroni, Marta; Riboldi, Marco; Sharp, Gregory C.; Ciardo, Delia; Alterio, Daniela; Orecchia, Roberto; Baroni, Guido
2013-01-01
Adaptive radiation therapy (ART) aims at compensating for anatomic and pathological changes to improve delivery along a treatment fraction sequence. Current ART protocols require time-consuming manual updating of all volumes of interest on the images acquired during treatment. Deformable image registration (DIR) and contour propagation stand as a state of the ART method to automate the process, but the lack of DIR quality control methods hinder an introduction into clinical practice. We investigated the scale invariant feature transform (SIFT) method as a quantitative automated tool (1) for DIR evaluation and (2) for re-planning decision-making in the framework of ART treatments. As a preliminary test, SIFT invariance properties at shape-preserving and deformable transformations were studied on a computational phantom, granting residual matching errors below the voxel dimension. Then a clinical dataset composed of 19 head and neck ART patients was used to quantify the performance in ART treatments. For the goal (1) results demonstrated SIFT potential as an operator-independent DIR quality assessment metric. We measured DIR group systematic residual errors up to 0.66 mm against 1.35 mm provided by rigid registration. The group systematic errors of both bony and all other structures were also analyzed, attesting the presence of anatomical deformations. The correct automated identification of 18 patients who might benefit from ART out of the total 22 cases using SIFT demonstrated its capabilities toward goal (2) achievement.
POLYNOMIAL PRESERVING RECOVERY FOR ANISOTROPIC AND IRREGULAR GRIDS
Institute of Scientific and Technical Information of China (English)
Zhimin Zhang
2004-01-01
Some properties of a newly developed polynomial preserving gradient recovery technique are discussed. Both practical and theoretical issues are addressed. Bounded-ness property is considered especially under anisotropic grids. For even-order finite element space, an ultra-convergence property is established under translation invariant meshes; for linear element, a superconvergence result is proven for unstructured grids generated by the Delaunay triangulation.
Mandapaka, Pradeep V.; Qin, Xiaosheng
2015-11-01
Scaling behavior of rainfall time series is characterized using monofractal, spectral, and multifractal frameworks. The study analyzed temporal scale-invariance of rainfall in the tropical island of Singapore using a large dataset comprising 31 years of hourly and 3 years of 1-min rainfall measurements. First, the rainfall time series is transformed into an occurrence-non-occurrence binary series, and its scaling behavior is analyzed using box-counting analysis. The results indicated that the rainfall support displays fractal structure, but within a limited range of scales. The rainfall support has a fractal dimension ( D f ) of 0.56 for scales ranging from 1 min to 1.5 h and a D f of 0.37 from 1.5 h to 1.5 days. The results further showed that the fractal dimension decreases with the increase in the threshold used to define binary series. Spectral analysis carried out on the rainfall time series and the corresponding binary series showed three distinct scaling regimes of 4 min-2 h, 2-24 h, and 24 h-1 month. In all the scaling regimes, the spectral exponents for the rainfall series were smaller than those for the binary series. The study then investigated the presence of multiscaling behavior in rainfall time series using moment scaling analysis. The results confirmed that the rainfall fluctuations display a multiscaling structure, which was modeled in the framework of universal multifractals. The results from this study would not only improve our understanding of the temporal rainfall structure in Singapore and the surrounding Maritime Continent but also help us build and parameterize parsimonious models and statistical downscaling techniques for rainfall in this region.
Shape Analysis for Unstructured Sharing
Li, Huisong; Rival, Xavier; Chang, Bor-Yuh Evan
2015-01-01
Shape analysis aims to infer precise structural properties of imperative memory states and has been applied heavily to verify safety properties on imperative code over pointer-based data structures. Recent advances in shape analysis based on separation logic has leveraged sum-marization predicates that describe unbounded heap regions like lists or trees using inductive definitions. Unfortunately, data structures with un-structured sharing, such as graphs, are challenging to describe and reaso...
ADAPTIVE LAYERED CARTESIAN CUT CELL METHOD FOR THE UNSTRUCTURED HEXAHEDRAL GRIDS GENERATION
Institute of Scientific and Technical Information of China (English)
WU Peining; TAN Jianrong; LIU Zhenyu
2007-01-01
Adaptive layered Cartesian cut cell method is presented to solve the difficulty of the unstructured hexahedral anisotropic Cartesian grids generation from the complex CAD model. Vertex merging algorithm based on relaxed AVL tree is investigated to construct topological structure for stereo lithography (STL) files, and a topology-based self-adaptive layered slicing algorithm with special features control strategy is brought forward. With the help of convex hull, a new points-in-polygon method is employed to improve the Cartesian cut cell method. By integrating the self-adaptive layered slicing algorithm and the improved Cartesian cut cell method, the adaptive layered Cartesian cut cell method gains the volume data of the complex CAD model in STL file and generates the unstructured hexahedral anisotropic Cartesian grids.
Approaches for Managing and Analyzing Unstructured Data
Directory of Open Access Journals (Sweden)
N. Veeranjaneyulu
2014-01-01
Full Text Available Large volumes of data that will be stored and accessed in future is unstructured. The unstructured data is generated in a very fast pace and uses large storage areas. This increases the storage budget. Extracting value from this unstructured data which balances the budget is the most challenging task. Archives of interactive media, satellite and medical images, information from social network sites, legal documents, presentations and web pages from various data sources affects the data center's ability to maintain control over the unstructured data. Therefore, it is very essential to design systems to provide efficient storage, and access to these vast and continuously growing repositories of unstructured data. This can be achieved by retrieving structured information from the unstructured data. In this paper, we discuss approaches to process and manage such data. We also elaborate the architecture, technologies and applications to facilitate system design and evaluation.
Anisotropic universe with anisotropic sources
Energy Technology Data Exchange (ETDEWEB)
Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha, E-mail: aluri@iucaa.ernet.in, E-mail: sukanta@iiserb.ac.in, E-mail: manabendra@iiserb.ac.in, E-mail: snigdha@iiserb.ac.in [Department of Physics, IISER Bhopal, Bhopal - 462023 (India)
2013-12-01
We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.
Numerical experiments on unstructured PIC stability.
Energy Technology Data Exchange (ETDEWEB)
Day, David Minot
2011-04-01
Particle-In-Cell (PIC) is a method for plasmas simulation. Particles are pushed with Verlet time integration. Fields are modeled using finite differences on a tensor product mesh (cells). The Unstructured PIC methods studied here use instead finite element discretizations on unstructured (simplicial) meshes. PIC is constrained by stability limits (upper bounds) on mesh and time step sizes. Numerical evidence (2D) and analysis will be presented showing that similar bounds constrain unstructured PIC.
Approaches for Managing and Analyzing Unstructured Data
N. Veeranjaneyulu; M. Nirupama Bhat; A.Raghunath
2014-01-01
Large volumes of data that will be stored and accessed in future is unstructured. The unstructured data is generated in a very fast pace and uses large storage areas. This increases the storage budget. Extracting value from this unstructured data which balances the budget is the most challenging task. Archives of interactive media, satellite and medical images, information from social network sites, legal documents, presentations and web pages from various data sources affects the data cen...
Natively unstructured loops differ from other loops.
Directory of Open Access Journals (Sweden)
Avner Schlessinger
2007-07-01
Full Text Available Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%-70% of all worm proteins observed to have more than seven protein-protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested
Natively unstructured loops differ from other loops.
Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard
2007-07-01
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%-70% of all worm proteins observed to have more than seven protein-protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long
Material Induced Anisotropic Damage
Niazi, M.S.; Wisselink, H.H.; Meinders, V.T.; Boogaard, van den A.H.; Hora, P.
2012-01-01
The anisotropy in damage can be driven by two different phenomena; anisotropic defor-mation state named Load Induced Anisotropic Damage (LIAD) and anisotropic (shape and/or distribution) second phase particles named Material Induced Anisotropic Damage (MIAD). Most anisotropic damage models are based
Scale invariance of the η-deformed AdS5 × S5 superstring, T-duality and modified type II equations
Arutyunov, G.; Frolov, S.; Hoare, B.; Roiban, R.; Tseytlin, A. A.
2016-02-01
We consider the ABF background underlying the η-deformed AdS5 ×S5 sigma model. This background fails to satisfy the standard IIB supergravity equations which indicates that the corresponding sigma model is not Weyl invariant, i.e. does not define a critical string theory in the usual sense. We argue that the ABF background should still define a UV finite theory on a flat 2d world-sheet implying that the η-deformed model is scale invariant. This property follows from the formal relation via T-duality between the η-deformed model and the one defined by an exact type IIB supergravity solution that has 6 isometries albeit broken by a linear dilaton. We find that the ABF background satisfies candidate type IIB scale invariance conditions which for the R-R field strengths are of the second order in derivatives. Surprisingly, we also find that the ABF background obeys an interesting modification of the standard IIB supergravity equations that are first order in derivatives of R-R fields. These modified equations explicitly depend on Killing vectors of the ABF background and, although not universal, they imply the universal scale invariance conditions. Moreover, we show that it is precisely the non-isometric dilaton of the T-dual solution that leads, after T-duality, to modification of type II equations from their standard form. We conjecture that the modified equations should follow from κ-symmetry of the η-deformed model. All our observations apply also to η-deformations of AdS3 ×S3 ×T4and AdS2 ×S2 ×T6models.
Scale invariance of the η-deformed AdS5×S5 superstring, T-duality and modified type II equations
Directory of Open Access Journals (Sweden)
G. Arutyunov
2016-02-01
Full Text Available We consider the ABF background underlying the η-deformed AdS5×S5 sigma model. This background fails to satisfy the standard IIB supergravity equations which indicates that the corresponding sigma model is not Weyl invariant, i.e. does not define a critical string theory in the usual sense. We argue that the ABF background should still define a UV finite theory on a flat 2d world-sheet implying that the η-deformed model is scale invariant. This property follows from the formal relation via T-duality between the η-deformed model and the one defined by an exact type IIB supergravity solution that has 6 isometries albeit broken by a linear dilaton. We find that the ABF background satisfies candidate type IIB scale invariance conditions which for the R–R field strengths are of the second order in derivatives. Surprisingly, we also find that the ABF background obeys an interesting modification of the standard IIB supergravity equations that are first order in derivatives of R–R fields. These modified equations explicitly depend on Killing vectors of the ABF background and, although not universal, they imply the universal scale invariance conditions. Moreover, we show that it is precisely the non-isometric dilaton of the T-dual solution that leads, after T-duality, to modification of type II equations from their standard form. We conjecture that the modified equations should follow from κ-symmetry of the η-deformed model. All our observations apply also to η-deformations of AdS3×S3×T4and AdS2×S2×T6models.
Scale invariance of the eta-deformed AdS5 x S5 superstring, T-duality and modified type II equations
Arutyunov, G; Hoare, B; Roiban, R; Tseytlin, A A
2015-01-01
We consider the ABF background underlying the eta-deformed AdS5 x S5 sigma model. This background fails to satisfy the standard IIB supergravity equations which indicates that the corresponding sigma model is not Weyl invariant, i.e. does not define a critical string theory in the usual sense. We argue that the ABF background should still correspond to UV finite theory on a flat 2d world-sheet, implying that the eta-deformed model is scale invariant. This property follows from the formal relation via T-duality between the eta-deformed model and the one defined by an exact type IIB supergravity solution that has 6 isometries albeit broken by a linear dilaton. We find that the ABF background satisfies candidate type IIB scale invariance conditions which for the R-R field strengths are of the second order in derivatives. Surprisingly, we also find that the this background obeys an interesting modification of the standard IIB supergravity equations that are first order in derivatives of R-R fields. These modified...
Adaptive and Unstructured Mesh Cleaving
Bronson, Jonathan R.; Sastry, Shankar P.; Levine, Joshua A.; Whitaker, Ross T.
2015-01-01
We propose a new strategy for boundary conforming meshing that decouples the problem of building tetrahedra of proper size and shape from the problem of conforming to complex, non-manifold boundaries. This approach is motivated by the observation that while several methods exist for adaptive tetrahedral meshing, they typically have difficulty at geometric boundaries. The proposed strategy avoids this conflict by extracting the boundary conforming constraint into a secondary step. We first build a background mesh having a desired set of tetrahedral properties, and then use a generalized stenciling method to divide, or “cleave”, these elements to get a set of conforming tetrahedra, while limiting the impacts cleaving has on element quality. In developing this new framework, we make several technical contributions including a new method for building graded tetrahedral meshes as well as a generalization of the isosurface stuffing and lattice cleaving algorithms to unstructured background meshes. PMID:26137171
Best Practices for Unstructured Grid Shock Fitting
McCloud, Peter L.
2017-01-01
Unstructured grid solvers have well-known issues predicting surface heat fluxes when strong shocks are present. Various efforts have been made to address the underlying numerical issues that cause the erroneous predictions. The present work addresses some of the shortcomings of unstructured grid solvers, not by addressing the numerics, but by applying structured grid best practices to unstructured grids. A methodology for robust shock detection and shock fitting is outlined and applied to production relevant cases. Results achieved by using the Loci-CHEM Computational Fluid Dynamics solver are provided.
Quantum search of a real unstructured database
Broda, Bogusław
2016-02-01
A simple circuit implementation of the oracle for Grover's quantum search of a real unstructured classical database is proposed. The oracle contains a kind of quantumly accessible classical memory, which stores the database.
Energy Technology Data Exchange (ETDEWEB)
Sonnino, Giorgio, E-mail: gsonnino@ulb.ac.be [Université Libre de Bruxelles (U.L.B.), Department of Physics, Campus de la Plaine Code Postal 231 - Boulevard du Triomphe, 1050 Brussels (Belgium); Cardinali, Alessandro [EURATOM-ENEA Fusion Association, Via E. Fermi 45, C.P. 65-00044 Frascati, Rome (Italy); Steinbrecher, Gyorgy [EURATOM-MEdC Fusion Association, Physics Faculty, University of Craiova, Str. A.I. Cuza 13, 200585 Craiova (Romania); Peeters, Philippe [Université Libre de Bruxelles (U.L.B.), Department of Physics, Campus de la Plaine Code Postal 231 - Boulevard du Triomphe, 1050 Brussels (Belgium); Sonnino, Alberto [Université Catholique de Louvain (UCL), Ecole Polytechnique de Louvain (EPL), Rue Archimède, 1 bte L6.11.01, 1348 Louvain-la-Neuve (Belgium); Nardone, Pasquale [Université Libre de Bruxelles (U.L.B.), Department of Physics, Campus de la Plaine Code Postal 231 - Boulevard du Triomphe, 1050 Brussels (Belgium)
2013-12-09
We derive the expression of the reference distribution function for magnetically confined plasmas far from the thermodynamic equilibrium. The local equilibrium state is fixed by imposing the minimum entropy production theorem and the maximum entropy (MaxEnt) principle, subject to scale invariance restrictions. After a short time, the plasma reaches a state close to the local equilibrium. This state is referred to as the reference state. The aim of this Letter is to determine the reference distribution function (RDF) when the local equilibrium state is defined by the above mentioned principles. We prove that the RDF is the stationary solution of a generic family of stochastic processes corresponding to an universal Landau-type equation with white parametric noise. As an example of application, we consider a simple, fully ionized, magnetically confined plasmas, with auxiliary Ohmic heating. The free parameters are linked to the transport coefficients of the magnetically confined plasmas, by the kinetic theory.
Natively Unstructured Loops Differ from Other Loops
Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard
2007-01-01
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS r...
Natively unstructured loops differ from other loops.
Avner Schlessinger; Jinfeng Liu; Burkhard Rost
2007-01-01
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS r...
Exploring Sparse, Unstructured Video Collections of Places
Tompkin, J. H.
2013-01-01
The abundance of mobile devices and digital cameras with video capture makes it easy to obtain large collections of video clips that contain the same location, environment, or event. However, such an unstructured collection is difficult to comprehend and explore. We propose a system that analyses collections of unstructured but related video data to create a Videoscape: a data structure that enables interactive exploration of video collections by visually navigating — spatially and/or tempora...
Hatanaka, Hisaki; Jung, Dong-Won; Ko, Pyungwon
2016-08-01
In this paper, we revisit a scale-invariant extension of the standard model (SM) with a strongly interacting hidden sector within AdS/QCD approach. Using the AdS/QCD, we reduce the number of input parameters to three, i.e. hidden pion decay constant, hidden pion mass and tan β that is defined as the ratio of the vacuum expectation values (VEV) of the singlet scalar field and the SM Higgs boson. As a result, our model has sharp predictability. We perform the phenomenological analysis of the hidden pions which is one of the dark matter (DM) candidates in this model. With various theoretical and experimental constraints we search for the allowed parameter space and find that both resonance and non-resonance solutions are possible. Some typical correlations among various observables such as thermal relic density of hidden pions, Higgs boson signal strengths and DM-nucleon cross section are investigated. We provide some benchmark points for experimental tests.
MHD simulations on an unstructured mesh
International Nuclear Information System (INIS)
We describe work on a full MHD code using an unstructured mesh. MH3D++ is an extension of the PPPL MH3D resistive full MHD code. MH3D++ replaces the structured mesh and finite difference / fourier discretization of MH3D with an unstructured mesh and finite element / fourier discretization. Low level routines which perform differential operations, solution of PDEs such as Poisson's equation, and graphics, are encapsulated in C++ objects to isolate the finite element operations from the higher level code. The high level code is the same, whether it is run in structured or unstructured mesh versions. This allows the unstructured mesh version to be benchmarked against the structured mesh version. As a preliminary example, disruptions in DIIID reverse shear equilibria are studied numerically with the MH3D++ code. Numerical equilibria were first produced starting with an EQDSK file containing equilibrium data of a DIII-D L-mode negative central shear discharge. Using these equilibria, the linearized equations are time advanced to get the toroidal mode number n = 1 linear growth rate and eigenmode, which is resistively unstable. The equilibrium and linear mode are used to initialize 3D nonlinear runs. An example shows poloidal slices of 3D pressure surfaces: initially, on the left, and at an intermediate time, on the right
Scale invariance and superfluid turbulence
Energy Technology Data Exchange (ETDEWEB)
Sen, Siddhartha, E-mail: siddhartha.sen@tcd.ie [CRANN, Trinity College Dublin, Dublin 2 (Ireland); R.K. Mission Vivekananda University, Belur 711 202, West Bengal (India); Ray, Koushik, E-mail: koushik@iacs.res.in [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Calcutta 700 032 (India)
2013-11-11
We construct a Schroedinger field theory invariant under local spatial scaling. It is shown to provide an effective theory of superfluid turbulence by deriving, analytically, the observed Kolmogorov 5/3 law and to lead to a Biot–Savart interaction between the observed filament excitations of the system as well.
Supersymmetry, supercurrent, and scale invariance
Energy Technology Data Exchange (ETDEWEB)
Piguet, Olivier [Universidade Catolica de Petropolis, RJ (Brazil). Inst. de Fisica]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Del Cima, Oswaldo M. (colab.)
1996-11-01
The aim of the present lectures is to give an introduction to the renormalization of supersymmetric gauge theories in 4-dimensional space-time. This will include the analysis of the ultraviolet divergences, and much emphasis will be put on the so-called `ultraviolet finite` models. Examples of the latter might be relevant as realistic `grand unified theories` of the particle interactions. 67 refs.
Anisotropic magnetism in field-structured composites
International Nuclear Information System (INIS)
Magnetic field-structured composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g., rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chainlike particle structures, and a biaxial field produces sheetlike particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCs of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material. (c) 2000 The American Physical Society
Hypersonic Flow Computations on Unstructured Meshes
Bibb, K. L.; Riley, C. J.; Peraire, J.
1997-01-01
A method for computing inviscid hypersonic flow over complex configurations using unstructured meshes is presented. The unstructured grid solver uses an edge{based finite{volume formulation. Fluxes are computed using a flux vector splitting scheme that is capable of representing constant enthalpy solutions. Second{order accuracy in smooth flow regions is obtained by linearly reconstructing the solution, and stability near discontinuities is maintained by locally forcing the scheme to reduce to first-order accuracy. The implementation of the algorithm to parallel computers is described. Computations using the proposed method are presented for a sphere-cone configuration at Mach numbers of 5.25 and 10.6, and a complex hypersonic re-entry vehicle at Mach numbers of 4.5 and 9.8. Results are compared to experimental data and computations made with established structured grid methods. The use of the solver as a screening tool for rapid aerodynamic assessment of proposed vehicles is described.
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
Energy Technology Data Exchange (ETDEWEB)
Palmer, T.S.; Zika, M.R.; Madsen, N.K.
2000-07-27
Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module.
Unstructured Object Recognition using Morphological Learning
S. Kar; Chandran, S.
2002-01-01
A technique of object recognition which can detect absence or presence of objects of interest without making explicit use of their underlying geometric structure is deemed suitable for many practical applications. In this work, a method of recognising unstructured objects has been presented, wherein several gray patterns are input as examples to a morphological rule-based learning algorithm. The output of the algorithm are the corresponding gray structuring elements capable of recogni...
Unstructured Direct Elicitation of Decision Rules
Ding, Min; John R. Hauser; Dong, Songting; Dzyabura, Daria; Yang, Zhilin; Su, Chenting; Gaskin, Steven
2010-01-01
We investigate the feasibility of unstructured direct-elicitation (UDE) of decision rules consumers use to form consideration sets. With incentives to think hard and answer truthfully, tested formats ask respondents to state non-compensatory, compensatory, or mixed rules for agents who will select a product for the respondents. In a mobile-phone study two validation tasks (one delayed 3 weeks) ask respondents to indicate which of 32 mobile phones they would consider from a fractional 4[supers...
Unstructured grids for sonic-boom analysis
Fouladi, Kamran
1993-01-01
A fast and efficient unstructured grid scheme is evaluated for sonic-boom applications. The scheme is used to predict the near-field pressure signatures of a body of revolution at several body lengths below the configuration, and those results are compared with experimental data. The introduction of the 'sonic-boom grid topology' to this scheme make it well suited for sonic-boom applications, thus providing an alternative to conventional multiblock structured grid schemes.
Promoting mashup creation through unstructured data extraction
Laga, Nassim; Bertin, Emmanuel; Crespi, Noel
2012-01-01
Service composition tools are usually based on an input/output mapping pattern. Inputs and output are declared by the service developer when publishing his service. However, services might also generate unstructured data such as email and instant messages content. That data are hardly expectable by developers. Consequently, much data are unavoidably left out by current service composition tools. In this paper we firstly propose and implement an enhancement to current SOA in order to facilitat...
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
International Nuclear Information System (INIS)
Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module
Computing Flows Using Chimera and Unstructured Grids
Liou, Meng-Sing; Zheng, Yao
2006-01-01
DRAGONFLOW is a computer program that solves the Navier-Stokes equations of flows in complexly shaped three-dimensional regions discretized by use of a direct replacement of arbitrary grid overlapping by nonstructured (DRAGON) grid. A DRAGON grid (see figure) is a combination of a chimera grid (a composite of structured subgrids) and a collection of unstructured subgrids. DRAGONFLOW incorporates modified versions of two prior Navier-Stokes-equation-solving programs: OVERFLOW, which is designed to solve on chimera grids; and USM3D, which is used to solve on unstructured grids. A master module controls the invocation of individual modules in the libraries. At each time step of a simulated flow, DRAGONFLOW is invoked on the chimera portion of the DRAGON grid in alternation with USM3D, which is invoked on the unstructured subgrids of the DRAGON grid. The USM3D and OVERFLOW modules then immediately exchange their solutions and other data. As a result, USM3D and OVERFLOW are coupled seamlessly.
Directory of Open Access Journals (Sweden)
Pedro Pedrosa Rebouças Filho
2015-06-01
results and expediting the decision making process. Two different methods are proposed: One using the transformed Scale Invariant Feature Transform (SIFT, and the second using features extractor Speeded Up Robust Features (SURF. Although slower, the SIFT method is more stable and has a better performance than the SURF method and can be applied to real applications. The best results were obtained using SIFT with Peak Signal-to-Noise Ratio = 61.38, Mean squared error = 0.048 and mean-structural-similarity = 0.999, and processing time of 4.91 seconds for mosaic building. The methodology proposed shows be more promissory in aiding specialists during analysis of metallographic images.
Anisotropic Stars II Stability
Dev, K; Dev, Krsna; Gleiser, Marcelo
2003-01-01
We investigate the stability of self-gravitating spherically symmetric anisotropic spheres under radial perturbations. We consider both the Newtonian and the full general-relativistic perturbation treatment. In the general-relativistic case, we extend the variational formalism for spheres with isotropic pressure developed by Chandrasekhar. We find that, in general, when the tangential pressure is greater than the radial pressure, the stability of the anisotropic sphere is enhanced when compared to isotropic configurations. In particular, anisotropic spheres are found to be stable for smaller values of the adiabatic index $\\gamma$.
Reinterpreting aircraft measurements in anisotropic scaling turbulence
Directory of Open Access Journals (Sweden)
S. Lovejoy
2009-02-01
-scale and the critical transition scale. The latter varies quite widely from scales of kilometers to greater than several hundred kilometers. We theoretically explain this behaviour by considering the absolute slopes (|Δz/Δx| of the aircraft as a function of lag Δx and scale invariant lag Δx/Δz^{1/Hz}. Finally, we revisit four earlier aircraft campaigns including GASP and MOZAIC showing that they can be very easily explained by the proposed combination of altitude/wind and anisotropic but scaling turbulence.
Accurately simulating anisotropic thermal conduction on a moving mesh
Kannan, Rahul; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark
2015-01-01
We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretisation stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the co...
Numerical simulation of H2/air detonation using unstructured mesh
Togashi, Fumiya; Löhner, Rainald; Tsuboi, Nobuyuki
2009-06-01
To explore the capability of unstructured mesh to simulate detonation wave propagation phenomena, numerical simulation of H2/air detonation using unstructured mesh was conducted. The unstructured mesh has several adv- antages such as easy mesh adaptation and flexibility to the complicated configurations. To examine the resolution dependency of the unstructured mesh, several simulations varying the mesh size were conducted and compared with a computed result using a structured mesh. The results show that the unstructured mesh solution captures the detailed structure of detonation wave, as well as the structured mesh solution. To capture the detailed detonation cell structure, the unstructured mesh simulations required at least twice, ideally 5times the resolution of structured mesh solution.
Anisotropic Contrast Optical Microscope
Peev, D; Kananizadeh, N; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M
2016-01-01
An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. We demonstrate the anisotropic contrast optical microscope by mea...
Diagnostic tools for 3D unstructured oceanographic data
C. J. Cotter; G. J. Gorman
2007-01-01
Most ocean models in current use are built upon structured meshes. It follows that most existing tools for extracting diagnostic quantities (volume and surface integrals, for example) from ocean model output are constructed using techniques and software tools which assume structured meshes. The greater complexity inherent in unstructured meshes (especially fully unstructured grids which are unstructured in the vertical as well as the horizontal direction) has left some oceanographers, accusto...
Implicit schemes and parallel computing in unstructured grid CFD
Venkatakrishnam, V.
1995-01-01
The development of implicit schemes for obtaining steady state solutions to the Euler and Navier-Stokes equations on unstructured grids is outlined. Applications are presented that compare the convergence characteristics of various implicit methods. Next, the development of explicit and implicit schemes to compute unsteady flows on unstructured grids is discussed. Next, the issues involved in parallelizing finite volume schemes on unstructured meshes in an MIMD (multiple instruction/multiple data stream) fashion are outlined. Techniques for partitioning unstructured grids among processors and for extracting parallelism in explicit and implicit solvers are discussed. Finally, some dynamic load balancing ideas, which are useful in adaptive transient computations, are presented.
Predicting structured metadata from unstructured metadata
Posch, Lisa; Panahiazar, Maryam; Dumontier, Michel; Gevaert, Olivier
2016-01-01
Enormous amounts of biomedical data have been and are being produced by investigators all over the world. However, one crucial and limiting factor in data reuse is accurate, structured and complete description of the data or data about the data—defined as metadata. We propose a framework to predict structured metadata terms from unstructured metadata for improving quality and quantity of metadata, using the Gene Expression Omnibus (GEO) microarray database. Our framework consists of classifiers trained using term frequency-inverse document frequency (TF-IDF) features and a second approach based on topics modeled using a Latent Dirichlet Allocation model (LDA) to reduce the dimensionality of the unstructured data. Our results on the GEO database show that structured metadata terms can be the most accurately predicted using the TF-IDF approach followed by LDA both outperforming the majority vote baseline. While some accuracy is lost by the dimensionality reduction of LDA, the difference is small for elements with few possible values, and there is a large improvement over the majority classifier baseline. Overall this is a promising approach for metadata prediction that is likely to be applicable to other datasets and has implications for researchers interested in biomedical metadata curation and metadata prediction. Database URL: http://www.yeastgenome.org/
An unstructured-mesh atmospheric model for nonhydrostatic dynamics: Towards optimal mesh resolution
Szmelter, Joanna; Zhang, Zhao; Smolarkiewicz, Piotr K.
2015-08-01
The paper advances the limited-area anelastic model (Smolarkiewicz et al. (2013) [45]) for investigation of nonhydrostatic dynamics in mesoscale atmospheric flows. New developments include the extension to a tetrahedral-based median-dual option for unstructured meshes and a static mesh adaptivity technique using an error indicator based on inherent properties of the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA). The model employs semi-implicit nonoscillatory forward-in-time integrators for soundproof PDEs, built on MPDATA and a robust non-symmetric Krylov-subspace elliptic solver. Finite-volume spatial discretisation adopts an edge-based data structure. Simulations of stratified orographic flows and the associated gravity-wave phenomena in media with uniform and variable dispersive properties verify the advancement and demonstrate the potential of heterogeneous anisotropic discretisation with large variation in spatial resolution for study of complex stratified flows that can be computationally unattainable with regular grids.
A new procedure for dynamic adaption of three-dimensional unstructured grids
Biswas, Rupak; Strawn, Roger
1993-01-01
A new procedure is presented for the simultaneous coarsening and refinement of three-dimensional unstructured tetrahedral meshes. This algorithm allows for localized grid adaption that is used to capture aerodynamic flow features such as vortices and shock waves in helicopter flowfield simulations. The mesh-adaption algorithm is implemented in the C programming language and uses a data structure consisting of a series of dynamically-allocated linked lists. These lists allow the mesh connectivity to be rapidly reconstructed when individual mesh points are added and/or deleted. The algorithm allows the mesh to change in an anisotropic manner in order to efficiently resolve directional flow features. The procedure has been successfully implemented on a single processor of a Cray Y-MP computer. Two sample cases are presented involving three-dimensional transonic flow. Computed results show good agreement with conventional structured-grid solutions for the Euler equations.
PARTI primitives for unstructured and block structured problems
Sussman, Alan; Saltz, Joel; Das, Raja; Gupta, S.; Mavriplis, Dimitri; Ponnusamy, Ravi; Crowley, Kay
1992-01-01
Described here is a set of primitives (PARTI) developed to efficiently execute unstructured and block structured problems on distributed memory parallel machines. We present experimental data from a 3-D unstructured Euler solver run on the Intel Touchstone Delta to demonstrate the usefulness of our methods.
Quasiparticle anisotropic hydrodynamics
Alqahtani, Mubarak
2016-01-01
We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.
Averaging anisotropic cosmologies
International Nuclear Information System (INIS)
We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate 'average' spacetime behaviour in general relativity
Robust Unstructured Road Detection: The Importance of Contextual Information
Directory of Open Access Journals (Sweden)
Erke Shang
2013-03-01
Full Text Available Unstructured road detection is a key step in an unmanned guided vehicle (UGV system for road following. However, current vision‐based unstructured road detection algorithms are usually affected by continuously changing backgrounds, different road types (shape, colour, variable lighting conditions and weather conditions. Therefore, a confidence map of road distribution, one of contextual information cues, is theoretically analysed and experimentally generated to help detect unstructured roads. Two traditional algorithms, support vector machine (SVM and k‐nearest neighbour (KNN, are carried out to verify the helpfulness of the proposed confidence map. Following this, a novel algorithm, which combines SVM, KNN and the confidence map under a Bayesian framework, is proposed to improve the overall performance of the unstructured road detections. The proposed algorithm has been evaluated using different types of unstructured roads and the experimental results show its effectiveness.
Algebraic turbulence modeling for unstructured and adaptive meshes
Mavriplis, Dimitri J.
1990-01-01
An algebraic turbulence model based on the Baldwin-Lomax model, has been implemented for use on unstructured grids. The implementation is based on the use of local background structured turbulence meshes. At each time-step, flow variables are interpolated from the unstructured mesh onto the background structured meshes, the turbulence model is executed on these meshes, and the resulting eddy viscosity values are interpolated back to the unstructured mesh. Modifications to the algebraic model were required to enable the treatment of more complicated flows, such as confluent boundary layers and wakes. The model is used in conjuction with an efficient unstructured multigrid finite-element Navier-Stokes solver in order to compute compressible turbulent flows on fully unstructured meshes. Solutions about single and multiple element airfoils are obtained and compared with experimental data.
Molecular anisotropic magnetoresistance
Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy
2015-12-01
Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.
Hwu, Chyanbin
2010-01-01
As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a
Florkowski, W.; Maj, R.
The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.
Florkowski, Wojciech
2013-01-01
The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.
Anisotropic models for compact stars
Maurya, S K; Ray, Saibal; Dayanandan, Baiju
2015-01-01
In the present paper we obtain an anisotropic analogue of Durgapal-Fuloria (1985) perfect fluid solution. The methodology consists of contraction of anisotropic factor $\\Delta$ by the help of both metric potentials $e^{\
Partitioning of unstructured meshes for load balancing
International Nuclear Information System (INIS)
Many large-scale engineering and scientific calculations involve repeated updating of variables on an unstructured mesh. To do these types of computations on distributed memory parallel computers, it is necessary to partition the mesh among the processors so that the load balance is maximized and inter-processor communication time is minimized. This can be approximated by the problem, of partitioning a graph so as to obtain a minimum cut, a well-studied combinatorial optimization problem. Graph partitioning algorithms are discussed that give good but not necessarily optimum solutions. These algorithms include local search methods recursive spectral bisection, and more general purpose methods such as simulated annealing. It is shown that a general procedure enables to combine simulated annealing with Kernighan-Lin. The resulting algorithm is both very fast and extremely effective. (authors) 23 refs., 3 figs., 1 tab
Energy transfer in structured and unstructured environments
DEFF Research Database (Denmark)
Iles-Smith, Jake; Dijkstra, Arend G.; Lambert, Neill;
2016-01-01
We explore excitonic energy transfer dynamics in a molecular dimer system coupled to both structured and unstructured oscillator environments. By extending the reaction coordinate master equation technique developed by Iles-Smith et al. [Phys. Rev. A 90, 032114 (2014)], we go beyond the commonly...... correlations generated between the system and its environment when the Born-Markov approximations no longer hold. Finally, we apply the reaction coordinate formalism to the case of a structured environment comprising of both underdamped (i.e., sharply peaked) and overdamped (broad) components simultaneously...... of motion over a wide range of parameters. Furthermore, we show that the Zusman equations, which may be obtained in a semiclassical limit of the reaction coordinate model, are often incapable of describing the correct dynamical behaviour. This demonstrates the necessity of properly accounting for quantum...
Unstructured Object Recognition using Morphological Learning
Directory of Open Access Journals (Sweden)
S. Kar
2002-07-01
Full Text Available A technique of object recognition which can detect absence or presence of objects of interest without making explicit use of their underlying geometric structure is deemed suitable for many practical applications. In this work, a method of recognising unstructured objects has been presented, wherein several gray patterns are input as examples to a morphological rule-based learning algorithm. The output of the algorithm are the corresponding gray structuring elements capable of recognising patterns in query images. The learning is carried out offline before recognition of the queries. The technique has been tested to identify fuel pellet surface imperfections. Robustness wrt intensity, orientation, and shape variations of the query patterns is built into the method. Moreover, simplicity of the recognition process leading to reduced computational time makes the method attractive to solve many practical problems.
PRESSURE CORRECTION METHOD ON UNSTRUCTURED GRIDS
Institute of Scientific and Technical Information of China (English)
LAI Xi-jun; WANG De-guan; CHEN Yang
2004-01-01
In this paper, an unstructured, collocated finite volume method for solving the Navier-Stokes equations was developed by virtue of auxiliary points. The derivatives were determined by the Gauss theorem. The proposed method could provide control volumes with arbitrary geometry and preserve the second-order accuracy even if highly distorted grids are used. Although arbitrary number of cell faces can be used, the hybrid quadrilateral/triangular grids are more desirable for the simplicity of implementation and applications to engineering problems. The pressure-velocity coupling was treated using a SIMPLE-like algorithm. The Generalized Minimum Residual (GMRES) method with the Incomplete LU (ILU) preconditioner was used to solve linear equations. Four test cases were studied for validating the proposed method. In using this method, grid quality is not important. Thus, engineers can pay mostly attention to physical mechanism of problems. Turbulence models can be simply integrated and the method can be straightforwardly extended to treat three-dimensional problems.
Extraction of information from unstructured text
Energy Technology Data Exchange (ETDEWEB)
Irwin, N.H.; DeLand, S.M.; Crowder, S.V.
1995-11-01
Extracting information from unstructured text has become an emphasis in recent years due to the large amount of text now electronically available. This status report describes the findings and work done by the end of the first year of a two-year LDRD. Requirements of the approach included that it model the information in a domain independent way. This means that it would differ from current systems by not relying on previously built domain knowledge and that it would do more than keyword identification. Three areas that are discussed and expected to contribute to a solution include (1) identifying key entities through document level profiling and preprocessing, (2) identifying relationships between entities through sentence level syntax, and (3) combining the first two with semantic knowledge about the terms.
A new numerical method on unstructured grids
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using the expansion of basic function to approach the exact function,the central and upwind schemes of derivative are constructed. By using the polynomial as basic function,applying the technique of flux splitting method and the combination of central and upwind schemes,the non-physical fluctuation near the shock wave is suppressed. The first-order basic function scheme of polynomial type for solving inviscid compressible flow numerically is constructed in this paper. Several numerical results of many typical examples for one-,two-and three-dimensional inviscid compressible steady flow illustrate that it is a new scheme with high accuracy and high resolution for shock wave. Especially,combining with the adaptive remeshing technique,the satisfactory results can be obtained by these schemes.
Reinterpreting aircraft measurements in anisotropic scaling turbulence
Directory of Open Access Journals (Sweden)
S. J. Hovde
2009-07-01
.4, 0.73. The latter being very close to those estimated by drop sondes (2.4, 0.75 in the vertical direction. In addition, for each leg we estimate the energy flux, the sphero-scale and the critical transition scale. The latter varies quite widely from scales of kilometers to greater than several hundred kilometers. The overall conclusion is that up to the critical scale, the aircraft follows a fractal trajectory which may increase the intermittency of the measurements, but doesn't strongly affect the scaling exponents whereas for scales larger than the critical scale, the aircraft follows isobars whose exponents are different from those along isoheights (and equal to the vertical exponent perpendicular to the isoheights. We bolster this interpretation by considering the absolute slopes (|Δz/Δx| of the aircraft as a function of lag Δx and of scale invariant lag Δx/Δz^{1/Hz}.
We then revisit four earlier aircraft campaigns including GASP and MOZAIC showing that they all have nearly identical transitions and can thus be easily explained by the proposed combination of altitude/wind in an anisotropic but scaling turbulence. Finally, we argue that this reinterpretation in terms of wide range anisotropic scaling is compatible with atmospheric phenomenology including convection.
Recognition and characterization of unstructured environmental sounds
Chu, Selina
2011-12-01
Environmental sounds are what we hear everyday, or more generally sounds that surround us ambient or background audio. Humans utilize both vision and hearing to respond to their surroundings, a capability still quite limited in machine processing. The first step toward achieving multimodal input applications is the ability to process unstructured audio and recognize audio scenes (or environments). Such ability would have applications in content analysis and mining of multimedia data or improving robustness in context aware applications through multi-modality, such as in assistive robotics, surveillances, or mobile device-based services. The goal of this thesis is on the characterization of unstructured environmental sounds for understanding and predicting the context surrounding of an agent or device. Most research on audio recognition has focused primarily on speech and music. Less attention has been paid to the challenges and opportunities for using audio to characterize unstructured audio. My research focuses on investigating challenging issues in characterizing unstructured environmental audio and to develop novel algorithms for modeling the variations of the environment. The first step in building a recognition system for unstructured auditory environment was to investigate on techniques and audio features for working with such audio data. We begin by performing a study that explore suitable features and the feasibility of designing an automatic environment recognition system using audio information. In my initial investigation to explore the feasibility of designing an automatic environment recognition system using audio information, I have found that traditional recognition and feature extraction for audio were not suitable for environmental sound, as they lack any type of structures, unlike those of speech and music which contain formantic and harmonic structures, thus dispelling the notion that traditional speech and music recognition techniques can simply
On the Newtonian anisotropic configurations
Energy Technology Data Exchange (ETDEWEB)
Shojai, F. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of); Fazel, M.R.; Stepanian, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Kohandel, M. [Alzahra University, Department of Sciences, Tehran (Iran, Islamic Republic of)
2015-06-15
In this paper we are concerned with the effects of an anisotropic pressure on the boundary conditions of the anisotropic Lane-Emden equation and the homology theorem. Some new exact solutions of this equation are derived. Then some of the theorems governing the Newtonian perfect fluid star are extended, taking the anisotropic pressure into account. (orig.)
Indian Academy of Sciences (India)
B B Bhowmik; A Rajput
2004-06-01
Anisotropic Bianchi Type-I cosmological models have been studied on the basis of Lyra's geometry. Two types of models, one with constant deceleration parameter and the other with variable deceleration parameter have been derived by considering a time-dependent displacement field.
Dynamics of Anisotropic Universes
Pérez, J
2006-01-01
We present a general study of the dynamical properties of Anisotropic Bianchi Universes in the context of Einstein General Relativity. Integrability results using Kovalevskaya exponents are reported and connected to general knowledge about Bianchi dynamics. Finally, dynamics toward singularity in Bianchi type VIII and IX universes are showed to be equivalent in some precise sence.
BIG Data Analytics: A Framework for Unstructured Data Analysis
Directory of Open Access Journals (Sweden)
P.Mohan Kumar
2013-02-01
Full Text Available Nowadays, most of information saved in companies are unstructured models. Retrieval and extraction of the information is essential works and importance in semantic web areas. Many of these requirements will be depend on the unstructured data analysis. More than 80% of all potentially useful business information is unstructured data, in kind of sensor readings, console logs and so on. The large number and complexity of unstructured data opens up many new possibilities for the analyst. Text mining and natural language processing are two techniques with their methods for knowledge discovery from textual context in documents. This is an approach to organize a complex unstructured data and to retrieve necessary information. The paper is to find an efficient way of storing unstructured data and appropriate approach of fetching data. Unstructured data targeted in this work to organize, is the publictweets of Twitter. Building an Big Data application that gets stream of public tweets from twitter which is latter stored in the HBase using Hadoop cluster and followed by data analysis for data retrieved from HBase by REST calls is the pragmatic approach of this project.
Inhomogeneous Anisotropic Cosmology
Kleban, Matthew
2016-01-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that ${\\it arbitrarily}$ inhomogeneous and anisotropic cosmologies with "flat" (including toroidal) and "open" (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potenti...
Molecular anisotropic magnetoresistance
Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy
2015-01-01
Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by $3d$ transition-metal wires. We show that the gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symm...
Modeling Load Balancing in Heterogeneous Unstructured P2P Systems
Directory of Open Access Journals (Sweden)
Zhi J. Li
2005-01-01
Full Text Available Load balancing is a generally concerned problem in peer-to-peer (P2P systems. Many researches on load balancing in the structured P2P systems have been launched currently, such as Chord or other DHTs. Although the researches on load balancing in unstructured P2P systems are emerged nowadays, the simple mechanisms achieved can only perform effectively in uniform environment. In this study, the influence on load balancing of the heterogeneity existed universally in unstructured P2P systems are analyzed, the unstructured P2P systems and their load balancing and the heterogeneity are modeled. Based on the formal model, the load balancing is analyzed quantitatively under static and dynamic environment and the typical load balancing algorithms are also analyzed. Some important conclusions are drawn which can be used in new models of load balancing in unstructured P2P systems.
Mesh Adaptation and Shape Optimization on Unstructured Meshes Project
National Aeronautics and Space Administration — In this SBIR CRM proposes to implement the entropy adjoint method for solution adaptive mesh refinement into the Loci/CHEM unstructured flow solver. The scheme will...
Warehousing Structured and Unstructured Data for Data Mining.
Miller, L. L.; Honavar, Vasant; Barta, Tom
1997-01-01
Describes an extensible object-oriented view system that supports the integration of both structured and unstructured data sources in either the multidatabase or data warehouse environment. Discusses related work and data mining issues. (AEF)
An assessment of unstructured grid technology for timely CFD analysis
Kinard, Tom A.; Schabowski, Deanne M.
1995-01-01
An assessment of two unstructured methods is presented in this paper. A tetrahedral unstructured method USM3D, developed at NASA Langley Research Center is compared to a Cartesian unstructured method, SPLITFLOW, developed at Lockheed Fort Worth Company. USM3D is an upwind finite volume solver that accepts grids generated primarily from the Vgrid grid generator. SPLITFLOW combines an unstructured grid generator with an implicit flow solver in one package. Both methods are exercised on three test cases, a wing, and a wing body, and a fully expanded nozzle. The results for the first two runs are included here and compared to the structured grid method TEAM and to available test data. On each test case, the set up procedure are described, including any difficulties that were encountered. Detailed descriptions of the solvers are not included in this paper.
Seismic Wave Simulation for Complex Rheologies on Unstructured Meshes
de la Puente, Josep
2008-01-01
The possibility of using accurate numerical methods to simulate seismic wavefields on unstructured meshes for complex rheologies is explored. In particular, the Discontinuous Galerkin (DG) finite element method for seismic wave propagation is extended to the rheological types of viscoelasticity, anisotropy and poroelasticity. First is presented the DG method for the elastic isotropic case on tetrahedral unstructured meshes. Then an extension to viscoelastic wave propagation based upon a Gener...
GENERATION AND APPLICATION OF UNSTRUCTURED ADAPTIVE MESHES WITH MOVING BOUNDARIES
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper presents a method to generate unstructured adaptive meshes with moving boundaries and its application to CFD. Delaunay triangulation criterion in conjunction with the automatic point creation is used to generate 2-D and 3-D unstructured grids. A local grid regeneration method is proposed to cope with moving boundaries. Numerical examples include the interactions of shock waves with movable bodies and the movement of a projectile within a ram accelerator, illustrating an efficient and robust mesh generation method developed.``
Structured, unstructured, and semistructured search in semistructured databases
Balmin, Andrey
2006-01-01
A single framework for storing and querying XML data, using denormalized schema decompositions, can support both structured queries and unstructured searches, as well as serve as a foundation for combining the two forms of information access. XML data format becomes increasingly popular in applications that mix structured data and unstructured text. These applications require integration of structured query and text search mechanisms to access XML data. First, we introduce a framework for sto...
On unstructured distributed search over BitTorrent
Mayor, W.; Cox, I
2013-01-01
Current BitTorrent discovery methods rely on either centralised systems or structured peer-to-peer (P2P) networks. These methods present security weaknesses that can be exploited in order to censor or remove information from the network. To alleviate this threat, we propose incorporating an unstructured peer-to-peer information discovery mechanism that can be used in the event that the centralised or structured P2P mechanisms are compromised. Unstructured P2P information discovery has fewer s...
Multiphase flow of immiscible fluids on unstructured moving meshes
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam; Fursund, Jens; Christensen , Brian Bunch; Bærentzen, Jakob Andreas; Bridson, Robert
2012-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between ...
The Initial State of a Primordial Anisotropic Stage of Inflation
Energy Technology Data Exchange (ETDEWEB)
Blanco-Pillado, Jose J. [Department of Theoretical Physics, University of the Basque Country UPV/EHU,48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science,Maria Diaz de Haro 3, 48013 Bilbao (Spain); Minamitsuji, Masato [Yukawa Institute for Theoretical Physics, Kyoto University,Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502 (Japan); CENTRA, Instituto Superior Tecnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2015-06-12
We investigate the possibility that the inflationary period in the early universe was preceded by a primordial stage of strong anisotropy. In particular we focus on the simplest model of this kind, where the spacetime is described by a non-singular Kasner solution that quickly evolves into an isotropic de Sitter space, the so-called Kasner-de Sitter solution. The initial Big Bang singularity is replaced, in this case, by a horizon. We show that the extension of this metric to the region behind the horizon contains a timelike singularity which will be visible by cosmological observers. This makes it impossible to have a reliable prediction of the quantum state of the cosmological perturbations in the region of interest. In this paper we consider the possibility that this Kasner-de Sitter universe is obtained as a result of a quantum tunneling process effectively substituting the region behind the horizon by an anisotropic parent vacuum state, namely a 1+1 dimensional spacetime compactified over an internal flat torus, T{sub 2}, which we take it to be of the form de Sitter{sub 2}×T{sub 2} or Minkowski{sub 2}×T{sub 2}. As a first approximation to understand the effects of this anisotropic initial state, we compute the power spectrum of a massless scalar field in these backgrounds. In both cases, the spectrum converges at small scales to the isotropic scale invariant form and only present important deviations from it at the largest possible scales. We find that the decompactification scenario from M{sub 2}×T{sub 2} leads to a suppressed and slightly anisotropic power spectrum at large scales which could be related to some of the anomalies present in the current CMB data. On the other hand, the spectrum of the universe with a dS{sub 2}×T{sub 2} parent vacuum presents an enhancement in power at large scales not consistent with observations.
Model anisotropic quantum Hall states
Qiu, R. -Z.; Haldane, F.D.M.; Wan, Xin; Yang, Kun; Yi, Su
2012-01-01
Model quantum Hall states including Laughlin, Moore-Read and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multi-body Hamiltonians, and explicitly illustrate the existence of geometric degrees of in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeri...
Material Induced Anisotropic Damage in DP600
Niazi, M.S.; Wisselink, H.H.; Meinders, V.T.; Boogaard, van den A.H.
2013-01-01
Plasticity induced damage development in metals is anisotropic by nature. The anisotropy in damage is driven by two different phenomena; anisotropic deformation state i.e. Load Induced Anisotropic Damage (LIAD) and anisotropic microstructure i.e. Material Induced Anisotropic Damage (MIAD). The contr
On the Relativistic anisotropic configurations
Shojai, F; Stepanian, A
2016-01-01
In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov (TOV) equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behaviour of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed.
On the relativistic anisotropic configurations
Energy Technology Data Exchange (ETDEWEB)
Shojai, F. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of); Kohandel, M. [Alzahra University, Department of Physics and Chemistry, Tehran (Iran, Islamic Republic of); Stepanian, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of)
2016-06-15
In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behavior of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed. (orig.)
Anisotropically Inflating Universes
Barrow, J D; Barrow, John D.; Hervik, Sigbjorn
2008-01-01
We show that in theories of gravity that add quadratic curvature invariants to the Einstein-Hilbert action there exist expanding vacuum cosmologies with positive cosmological constant which do not approach the de Sitter universe. Exact solutions are found which inflate anisotropically. This behaviour is driven by the Ricci curvature invariant and has no counterpart in the general relativistic limit. These examples show that the cosmic no-hair theorem does not hold in these higher-order extensions of general relativity and raises new questions about the ubiquity of inflation in the very early universe and the thermodynamics of gravitational fields.
Anisotropic Stars Exact Solutions
Dev, K; Dev, Krsna; Gleiser, Marcelo
2000-01-01
We study the effects of anisotropic pressure on the properties of spherically symmetric, gravitationally bound objects. We consider the full general relativistic treatment of this problem and obtain exact solutions for various form of equations of state connecting the radial and tangential pressures. It is shown that pressure anisotropy can have significant effects on the structure and properties of stellar objects. In particular, the maximum value of 2M/R can approach unity (2M/R < 8/9 for isotropic objects) and the surface redshift can be arbitrarily large.
Gardiner, Thomas
2013-10-01
Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Anisotropic Intermittency of Magnetohydrodynamic Turbulence
Osman, K T; Chapman, S C; Hnat, B
2013-01-01
A higher-order multiscale analysis of spatial anisotropy in inertial range magnetohydrodynamic turbulence is presented using measurements from the STEREO spacecraft in fast ambient solar wind. We show for the first time that, when measuring parallel to the local magnetic field direction, the full statistical signature of the magnetic and Els\\"asser field fluctuations is that of a non-Gaussian globally scale-invariant process. This is distinct from the classic multi-exponent statistics observed when the local magnetic field is perpendicular to the flow direction. These observations are interpreted as evidence for the weakness, or absence, of a parallel magnetofluid turbulence energy cascade. As such, these results present strong observational constraints on the statistical nature of intermittency in turbulent plasmas.
The Prolog Interface to the Unstructured Information Management Architecture
Fodor, Paul; Ferrucci, David
2008-01-01
In this paper we describe the design and implementation of the Prolog interface to the Unstructured Information Management Architecture (UIMA) and some of its applications in natural language processing. The UIMA Prolog interface translates unstructured data and the UIMA Common Analysis Structure (CAS) into a Prolog knowledge base, over which, the developers write rules and use resolution theorem proving to search and generate new annotations over the unstructured data. These rules can explore all the previous UIMA annotations (such as, the syntactic structure, parsing statistics) and external Prolog knowledge bases (such as, Prolog WordNet and Extended WordNet) to implement a variety of tasks for the natural language analysis. We also describe applications of this logic programming interface in question analysis (such as, focus detection, answer-type and other constraints detection), shallow parsing (such as, relations in the syntactic structure), and answer selection.
Thermodynamics of anisotropic branes
Ávila, Daniel; Patiño, Leonardo; Trancanelli, Diego
2016-01-01
We study the thermodynamics of flavor D7-branes embedded in an anisotropic black brane solution of type IIB supergravity. The flavor branes undergo a phase transition between a `Minkowski embedding', in which they lie outside of the horizon, and a `black hole embedding', in which they fall into the horizon. This transition depends on two independent dimensionless ratios, which are formed out of the black hole temperature, its anisotropy parameter, and the mass of the flavor degrees of freedom. It happens either at a critical temperature or at a critical anisotropy. A general lesson we learn from this analysis is that the anisotropy, in this particular realization, induces similar effects as the temperature. In particular, increasing the anisotropy bends the branes more and more into the horizon. Moreover, we observe that the transition becomes smoother for higher anisotropies.
Averaging anisotropic cosmologies
Barrow, J D; Barrow, John D.; Tsagas, Christos G.
2006-01-01
We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of pressure-free Bianchi-type models. Adopting the Buchert averaging scheme, we identify the kinematic backreaction effects by focussing on spacetimes with zero or isotropic spatial curvature. This allows us to close the system of the standard scalar formulae with a propagation equation for the shear magnitude. We find no change in the already known conditions for accelerated expansion. The backreaction terms are expressed as algebraic relations between the mean-square fluctuations of the models' irreducible kinematical variables. Based on these we investigate the early evolution of averaged vacuum Bianchi type $I$ universes and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. We also discuss the possibility of accelerated expansion due to ...
van Kats, C. M.
2008-10-01
The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with
Extending the MODPATH algorithm to rectangular unstructured grids
Pollock, David W.
2016-01-01
The recent release of MODFLOW-USG, which allows model grids to have irregular, unstructured connections, requires a modification of the particle-tracking algorithm used by MODPATH. This paper describes a modification of the semi-analytical particle-tracking algorithm used by MODPATH that allows it to be extended to rectangular-based unstructured grids by dividing grid cells with multi-cell face connections into sub-cells. The new method will be incorporated in the next version of MODPATH which is currently under development.
Accurately simulating anisotropic thermal conduction on a moving mesh
Kannan, Rahul; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark
2016-05-01
We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretization stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the conductive heat transport in galaxy clusters, the evolution of supernova remnants, or the distribution of heat from black hole-driven jets into the intracluster medium.
Anisotropic Inflation with General Potentials
Shi, Jiaming; Qiu, Taotao
2015-01-01
Anomalies in recent observational data indicate that there might be some "anisotropic hair" generated in an inflation period. To obtain general information about the effects of this anisotropic hair to inflation models, we studied anisotropic inflation models that involve one vector and one scalar using several types of potentials. We determined the general relationship between the degree of anisotropy and the fraction of the vector and scalar fields, and concluded that the anisotropies behave independently of the potentials. We also generalized our study to the case of multi-directional anisotropies.
基于OpenStack云架构的尺度不变特征变换算法%Scale-invariant feature transform based on OpenStack cloud framework
Institute of Scientific and Technical Information of China (English)
曲进男; 唐政; 王帅群
2014-01-01
在OpenStack计算架构基础上，部署并解决了尺度不变特征变换( SIFT)特征提取在单一计算节点中计算效率的低下的问题。在保持计算结果精度的前提下，降低了系统计算资源负载，对大量SIFT计算请求进行实现，通过Nova以及Swift项目实现动态规划计算节点和面向对象存储，保证了原算法计算的精度，同时降低20%以上的系统负载，达到预期效果。%The computational efficiency of Scale-Invariant Feature Transform ( SIFT) algorithm for computing in a single node is low. For maintaining the accuracy of the premise, and the system calculating resource load was downgraded. A large number of SIFT calculation requests were implemented. Through Nova and Swift project, compute nodes dynamic programming and object-oriented storage were realized. The accuracy of the original algorithm was ensured, reducing the load on the system more than 20% as expected.
Application of the VOF method based on unstructured quadrilateral mesh
Institute of Scientific and Technical Information of China (English)
JI Chun-ning; SHI Ying
2008-01-01
To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface's line constant vs. the volume clipped by the interface was developed so as to improve the method's efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method's high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked.
Improving the efficiency of aerodynamic shape optimization on unstructured meshes
Carpentieri, G.; Tooren, M.J.L. van; Koren, B.
2006-01-01
In this paper the exact discrete adjoint of a finite volume formulation on unstructured meshes for the Euler equations in two dimensions is derived and implemented to support aerodynamic shape optimization. The accuracy of the discrete exact adjoint is demonstrated and compared with that of the appr
Unsupervised Ontology Generation from Unstructured Text. CRESST Report 827
Mousavi, Hamid; Kerr, Deirdre; Iseli, Markus R.
2013-01-01
Ontologies are a vital component of most knowledge acquisition systems, and recently there has been a huge demand for generating ontologies automatically since manual or supervised techniques are not scalable. In this paper, we introduce "OntoMiner", a rule-based, iterative method to extract and populate ontologies from unstructured or…
Unstructured CFD and Noise Prediction Methods for Propulsion Airframe Aeroacoustics
Pao, S. Paul; Abdol-Hamid, Khaled S.; Campbell, Richard L.; Hunter, Craig A.; Massey, Steven J.; Elmiligui, Alaa A.
2006-01-01
Using unstructured mesh CFD methods for Propulsion Airframe Aeroacoustics (PAA) analysis has the distinct advantage of precise and fast computational mesh generation for complex propulsion and airframe integration arrangements that include engine inlet, exhaust nozzles, pylon, wing, flaps, and flap deployment mechanical parts. However, accurate solution values of shear layer velocity, temperature and turbulence are extremely important for evaluating the usually small noise differentials of potential applications to commercial transport aircraft propulsion integration. This paper describes a set of calibration computations for an isolated separate flow bypass ratio five engine nozzle model and the same nozzle system with a pylon. These configurations have measured data along with prior CFD solutions and noise predictions using a proven structured mesh method, which can be used for comparison to the unstructured mesh solutions obtained in this investigation. This numerical investigation utilized the TetrUSS system that includes a Navier-Stokes solver, the associated unstructured mesh generation tools, post-processing utilities, plus some recently added enhancements to the system. New features necessary for this study include the addition of two equation turbulence models to the USM3D code, an h-refinement utility to enhance mesh density in the shear mixing region, and a flow adaptive mesh redistribution method. In addition, a computational procedure was developed to optimize both solution accuracy and mesh economy. Noise predictions were completed using an unstructured mesh version of the JeT3D code.
Multi-Dimensional Spectral Difference Method for Unstructured Grids
Liu, Yen; Vinokur, Marcel
2005-01-01
A new, high-order, conservative, and efficient method for conservation laws on unstructured grids is developed. It combines the best features of structured and unstructured grid methods to attain computational efficiency and geometric flexibility; it utilizes the concept of discontinuous and high-order local representations to achieve conservation and high accuracy; and it is based on the finite-difference formulation for simplicity. Universal reconstructions are obtained by distributing unknowns in a geometrically similar manner for all unstructured cells. Placements of the unknown and flux points with various order of accuracy are given for the line, triangular and tetrahedral elements. The data structure of the new method permits an optimum use of cache memory, resulting in further computational efficiency on modern computers. A new pointer system is developed that reduces memory requirements and simplifies programming for any order of accuracy. Numerical solutions are presented and compared with the exact solutions for wave propagation problems in both two and three dimensions to demonstrate the capability of the method. Excellent agreement has been found. The method is simpler and more efficient than previous discontinuous Galerkin and spectral volume methods for unstructured grids.
Raghavan, Preethi; Chen, James L; Fosler-Lussier, Eric; Lai, Albert M.
2014-01-01
Electronic health records capture patient information using structured controlled vocabularies and unstructured narrative text. While structured data typically encodes lab values, encounters and medication lists, unstructured data captures the physician's interpretation of the patient's condition, prognosis, and response to therapeutic intervention. In this paper, we demonstrate that information extraction from unstructured clinical narratives is essential to most clinical applications. We pe...
Intrinsically Unstructured Proteins: Potential Targets for Drug Discovery
Directory of Open Access Journals (Sweden)
Pathan Salma
2009-01-01
Full Text Available Problem statement: The function of a protein is dependent on its three-dimensional structure. However, numerous proteins lacking intrinsic globular 3D structure under physiological conditions had been recognized. These proteins are frequently involved in some of the most critical cellular control mechanisms and it appears that their rapid turnover, aided by their unstructured nature in the unbound state, provides a level of control that allows rapid and accurate responses of the cell to changing environmental conditions. Approach: A significant number of proteins known to be involved in protein deposition disorders were now considered to Be Intrinsically Unstructured Proteins (IUPs. For example, Aß peptide and tau protein in Alzheimers disease, PrP in Prions disease and a-Synuclein in Parkinsons disease. The disorder of intrinsically unstructured proteins (IUP's was crucial to their functions. They may adopt defined but extended structures when bound to cognate ligands. Their amino acid compositions were less hydrophobic than those of soluble proteins. They lack hydrophobic cores and hence did not become insoluble when heated. About 40% of eukaryotic proteins had at least one long (>50 residues disordered region. Roughly 10% of proteins in various genomes had been predicted to be fully disordered. Presently over 100 IUP's had been identified; none are enzymes. Obviously, IUP's were greatly underrepresented in the Protein Data Bank, although there were few cases of an IUP bound to a folded (intrinsically structured protein. Results: The five functional categories for intrinsically unstructured proteins and domains were entropic chains (bristles to ensure spacing, springs, flexible spacers/linkers, effectors (inhibitors and disassemblers, scavengers, assemblers and display sites. These IUPs could serve as potential targets for Structure Based Drug Design (SBDD which stress on the transition
Photon states in anisotropic media
Indian Academy of Sciences (India)
Deepak Kumar
2002-08-01
Quantum aspects of optical polarization are discussed for waves traveling in anisotropic dielectric media with a view to relate the dynamics of polarization with that of photon spin and its manipulation by classical polarizers.
Gradient expansion for anisotropic hydrodynamics
Florkowski, Wojciech; Spaliński, Michał
2016-01-01
We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.
Variational Principle underlying Scale Invariant Social Systems
Hernando, A.; A. Plastino
2012-01-01
MaxEnt's variational principle, in conjunction with Shannon's logarithmic information measure, yields only exponential functional forms in straightforward fashion. In this communication we show how to overcome this limitation via the incorporation, into the variational process, of suitable dynamical information. As a consequence, we are able to formulate a somewhat generalized Shannonian Maximum Entropy approach which provides a unifying "thermodynamic-like" explanation for the scale-invarian...
Scale invariance and universality in economic phenomena
Stanley, H. E.; Amaral, L. A. N.; Gopikrishnan, P.; Plerou, V.; Salinger, M. A.
2002-03-01
This paper discusses some of the similarities between work being done by economists and by computational physicists seeking to contribute to economics. We also mention some of the differences in the approaches taken and seek to justify these different approaches by developing the argument that by approaching the same problem from different points of view, new results might emerge. In particular, we review two such new results. Specifically, we discuss the two newly discovered scaling results that appear to be `universal', in the sense that they hold for widely different economies as well as for different time periods: (i) the fluctuation of price changes of any stock market is characterized by a probability density function, which is a simple power law with exponent -4 extending over 102 standard deviations (a factor of 108 on the y-axis); this result is analogous to the Gutenberg-Richter power law describing the histogram of earthquakes of a given strength; (ii) for a wide range of economic organizations, the histogram that shows how size of organization is inversely correlated to fluctuations in size with an exponent ≈0.2. Neither of these two new empirical laws has a firm theoretical foundation. We also discuss results that are reminiscent of phase transitions in spin systems, where the divergent behaviour of the response function at the critical point (zero magnetic field) leads to large fluctuations. We discuss a curious `symmetry breaking' for values of Σ above a certain threshold value Σc here Σ is defined to be the local first moment of the probability distribution of demand Ω - the difference between the number of shares traded in buyer-initiated and seller-initiated trades. This feature is qualitatively identical to the behaviour of the probability density of the magnetization for fixed values of the inverse temperature.
Snow Avalanche Release, Scale Invariance and Criticallity
Dendievel, R.; Faillettaz, J.; Daudon, D.; Louchet, F.
It is widely recognised that a number of geophysical phenomena as volcanic eruptions, landslides, etc, obey the so-called Gutenberg-Richter relation, first established for the frequency-magnitude statistics of earthquakes, where is the occurence frequency of earthquakes with a magnitude greater than m. This power law behaviour, character- istic of critical phenomena, is usually evidenced in the form of a linear distribution in a double logarithmic plot, in a way similar to the self organised criticality of a sand pile (2). We have shown very recently and for the first time that snow avalanche release exhibited such a behaviour (3). The only reliable parameter we had at that time was the amplitude of the acoustic emission associated with the avalanche release. Since it was not possible to record several events in the same gully, data were taken in sev- eral gullys of the same mountain range. Yet, the data aligned quite well on a unique straight line, with a critical exponent of about 1.6. This observation suggests that the very nature of the release mechanism is independent of the average slope and mor- phology of the gully. In order to understand the origin of this critical behaviour and to further investigate the mechanisms responsible for avalanche release, the avalanche release is studied in the present paper both by discrete elements simulations and cel- lular automata, and compared to further field data. The discrete elements simulations deal with a population of spheres on a slope, experiencing both a gravitational stress, interactions with the substrate, and mutual contact interactions. A gradual increase of the slope or a gradual change in contact forces (accounting for thermal snow mi- crostructure evolution) eventually result in avalanche release. The conditions are ad- justed until the frequency-magnitude of avalanches exhibit a critical behaviour. The cellular automaton is more or less similar to a game of life: a 2-d grid of boxes repre- sents the interface between the substrate and the snow slab, loaded in shear by the slab weight. Each box can be in one of two states labelled 0 and 1, according whether the slab/substrate interface is locally cracked or not. The state of a box can be changed ac- cording whether a given number of neighbours are in a 0 state or in a 1 state. A group of adjacent boxes in the 0 state represents a crack. The automaton is run from vari- ous randomly generated initial populations. Avalanches of various sizes are recorded. The local rules are adjusted until the avalanche frequency- size distribution aligns on a critical line. In both cases, the critical slopes are compared to field data. 1 (1) B. Gutenberg and C.F. Richter, seismicity of the earth and associated phenomenon, 2d edition, Princeton University Press, Princeton (1954) (2) P. Bak, How Nature Works, Springer Verlag (1996) (3) F. Louchet, J. Faillettaz, D. Daudon, N. Bédouin, E. Collet, J. Lhuissier and A-M. Portal XXVI General Assembly of the European Geophysical Society, Nice (F), 25-30 mars 2001 2
Institute of Scientific and Technical Information of China (English)
龚俊斌; 张大志; 杨雪梅; 田金文
2011-01-01
针对合成孔径雷达与可见光图像在大角度旋转和大比例缩放情况下的高精度自动配准问题,提出了一种尺度和旋转不变的SAR(Synthetie Aperture Radar)和可见光图像自动配准算法.算法以SIFT(Scale Invariant Feature Transform)算法为基础,首先通过增强Frost滤波和自适应直方图均衡增强SAR和可见光图像的共性,使其显著提高能够提取出足够多的特征点数目,然后再通过特征描述方法、相似性度量方法、点匹配方法、特征点聚类方法和误匹配点剔除方法等方面对原始SIFT方法进行改进,有效地提高其在多源图像、强噪声、复杂成像条件下的特征提取和匹配性能,最后通过最小二乘法和相似变换模型实现SAR和可见光图像的精确配准.试验表明该算法对图像尺度和角度变化具有良好的适用性,在正确匹配点的比率和定位精度方面都优于原始SIFT算法和Harris算法,具有良好的工程应用前景.%Focus on the image regiatration problems for SAR ( Synthetic Aperture Radar) and optical images on condition that existing big scale and angle change, a novel image registration algorithm based on improved SIFT( Scale Invariant Feature Transform) is proposed. First, the enhanced Frost Filter and adaptive local histogram equalization is adopted to improve the common property of SAR and optical images to get enough SIFT points and high represent rate. Then multi-main-direction assignment, normalized cross-correlation measure, clustering analysis, and full hypothesis-proof-test methods are introduced into the algorithm lo improve the key point detection, point-pair matching and out-point-pair eliminating performance. Finally, based on the reserved points, the images are registered automatically by using similarity transformation model and least squares method. The experiment results approve that the propoaed method is better than SIFT, Harris and other popular state-of-art algorithms both
A fast and reliable overset unstructured grids approach
Institute of Scientific and Technical Information of China (English)
Zhong-Liang Kang; Chao Yan; Jian Yu; Yuan-Yuan Fang
2013-01-01
A cell-centred overset unstructured grids approach is developed.In this approach,the intergrid boundary is initially established based on the wall distance from the cell centre,and is then optimized.To accelerate the intergrid-boundary definition much more,a neighbor-to-neighbor donor search algorithm based on advancing-front method is modified with the help of minimum cuboid boxes.To simplify the communications between different grid cell types and to obtain second-order spatial accuracy,a new interpolation method is constructed based on linear reconstruction,which employs only one layer of fringe cells along the intergrid boundary.For unsteady flows with relative motion,the intergrid boundary can be redefined fast and automatically.Several numerical results show that the present dynamic overset unstructured grids approach is accurate and reliable.
Optimal state discrimination and unstructured search in nonlinear quantum mechanics
Childs, Andrew M.; Young, Joshua
2016-02-01
Nonlinear variants of quantum mechanics can solve tasks that are impossible in standard quantum theory, such as perfectly distinguishing nonorthogonal states. Here we derive the optimal protocol for distinguishing two states of a qubit using the Gross-Pitaevskii equation, a model of nonlinear quantum mechanics that arises as an effective description of Bose-Einstein condensates. Using this protocol, we present an algorithm for unstructured search in the Gross-Pitaevskii model, obtaining an exponential improvement over a previous algorithm of Meyer and Wong. This result establishes a limitation on the effectiveness of the Gross-Pitaevskii approximation. More generally, we demonstrate similar behavior under a family of related nonlinearities, giving evidence that the ability to quickly discriminate nonorthogonal states and thereby solve unstructured search is a generic feature of nonlinear quantum mechanics.
The Case for a Structured Approach to Managing Unstructured Data
Doan, AnHai; Baid, Akanksha; Chai, Xiaoyong; Chen, Fei; Chen, Ting; Chu, Eric; DeRose, Pedro; Gao, Byron; Gokhale, Chaitanya; Huang, Jiansheng; Shen, Warren; Vuong, Ba-Quy
2009-01-01
The challenge of managing unstructured data represents perhaps the largest data management opportunity for our community since managing relational data. And yet we are risking letting this opportunity go by, ceding the playing field to other players, ranging from communities such as AI, KDD, IR, Web, and Semantic Web, to industrial players such as Google, Yahoo, and Microsoft. In this essay we explore what we can do to improve upon this situation. Drawing on the lessons learned while managing relational data, we outline a structured approach to managing unstructured data. We conclude by discussing the potential implications of this approach to managing other kinds of non-relational data, and to the identify of our field.
Diagnostic tools for 3D unstructured oceanographic data
Cotter, C J
2007-01-01
Most operational ocean models are built upon structured meshes. It follows that most existing tools for extracting diagnostic quantities (volume and surface integrals, for example) from ocean model output are established on techniques which assume structured meshes. The greater complexity inherent in unstructured meshes has left some oceanographers, accustomed to traditional methods, unclear on how to calculate diagnostics on these meshes. In this paper we show that this should not be cause for concern as diagnostic data are easily obtained by writing appropriate filters using, for example, the open source 3D visualisation packages VTK and MayaVi. We demonstrate this in the particular case of calculating flux of vector fields through isosurfaces, using flow data obtained from the unstructured mesh finite element ocean code ICOM.
Multiresolution Representation in Unstructured Meshes : I. Preliminary Report
Abgrall, Remi; Harten, Ami
1994-01-01
In this paper we describe techniques to represent data which originate from discretization of functions in unstructured meshes in terms of their local scale components. To do so we consider a nested sequence of discretization which corresponds to increasing level of resolution, and define the scales as the ''difference in information" between any two successive levels. We obtain data compression by eliminating scale-coefficients which are sufficiently small. This capability for data compressi...
Towards Unstructured Mesh Generation Using the Inverse Poisson Problem
Bunin, Guy
2008-01-01
A novel approach to unstructured quadrilateral mesh generation for planar domains is presented. Away from irregular vertices, the resulting meshes have the properties of nearly conformal grids. The technique is based on a theoretical relation between the present problem, and the inverse Poisson (IP) problem with point sources. An IP algorithm is described, which constructs a point-source distribution, whose sources correspond to the irregular vertices of the mesh. Both the background theory a...
Unstructured Social Networks Data for Business Context Analysis
Walter MAIER; Dumitru RĂDOIU
2012-01-01
Communications technology has enabled new approaches to business context understanding. The paper proposes and explores a new mechanism through which unstructured social networks data about companies is gathered, aggregated and presented. The authors assume that collected data, interpreted through an adequate metrics, may be used as a tool for better understanding the business model of a company, its health and/or its sustainability. The paper does not address the issue of adequacy of the too...
Island Modeling Using Unstructured Grid during a Tropical Storm
Mourani Sinha; Ravi Kumar Yadav; Paromita Chakraborty
2016-01-01
The coastal wave dynamics of Agatti island situated on a coral atoll in Lakshadweep, India, having a notable topographic feature of steeper eastern shore over the western shore, is analysed in this study. A multinested model setup is generated using the global third-generation models WAM (Wave Modeling) and SWAN (Simulating Waves Nearshore). A high resolution unstructured grid is generated for the domain containing the island using SMS (Surface-Water Modeling System) interpolated with merged ...
The Case for a Structured Approach to Managing Unstructured Data
Doan, AnHai; Naughton, Jeff; Baid, Akanksha; Chai, Xiaoyong; Chen, Fei; Chen, Ting; Chu, Eric; DeRose, Pedro; Gao, Byron; Gokhale, Chaitanya; Huang, Jiansheng; Shen, Warren; Vuong, Ba-Quy
2009-01-01
The challenge of managing unstructured data represents perhaps the largest data management opportunity for our community since managing relational data. And yet we are risking letting this opportunity go by, ceding the playing field to other players, ranging from communities such as AI, KDD, IR, Web, and Semantic Web, to industrial players such as Google, Yahoo, and Microsoft. In this essay we explore what we can do to improve upon this situation. Drawing on the lessons learned while managing...
Continuum mechanics of anisotropic materials
Cowin, Stephen C
2013-01-01
Continuum Mechanics of Anisotropic Materials(CMAM) presents an entirely new and unique development of material anisotropy in the context of an appropriate selection and organization of continuum mechanics topics. These features will distinguish this continuum mechanics book from other books on this subject. Textbooks on continuum mechanics are widely employed in engineering education, however, none of them deal specifically with anisotropy in materials. For the audience of Biomedical, Chemical and Civil Engineering students, these materials will be dealt with more frequently and greater accuracy in their analysis will be desired. Continuum Mechanics of Anisotropic Materials' author has been a leader in the field of developing new approaches for the understanding of anisotropic materials.
A robust implicit shallow water equations solver on unstructured grid
Energy Technology Data Exchange (ETDEWEB)
Komaei, S.
2004-07-01
Flows in open channels are often modelled by a set of hyperbolic partial differential equations, i.e. the well known shallow water equations (SWE). Algorithms for solving SWE on structured grids have become widespread in recent years (Delis, Skeels and Ryrie 2000; Fennema and Chaudhry 1989; Panagiotopoulos and Soulis 2000; Valiani, Caleffi and Zanni 1999). However, these algorithms have shown difficulties in predicting satisfactory results in complex geometries due to mesh irregularities. As a result, attention has turned to the development of solution algorithms on arbitrary unstructured grids. The target of the present research is to develop an implicit robust scheme for solving two-dimensional SWE on unstructured grids. The proposed scheme should have capabilities to model flows in channels and natural rivers, flood propagation problems and flow over irregular beds. To achieve this goal, the following steps are necessary: 1. Studying the channel and river flows and flood propagation phenomena. 2. Developing an implicit two-dimensional hydrodynamic model on unstructured grids. 3. Verifying and validating the present model by experimental measurements, field data and the other numerical models. (orig.)
Computing Axisymmetric Jet Screech Tones using Unstructured Grids
Jorgenson, Philip C. E.; Loh, Ching Y.
2003-01-01
The purpose of this paper is to show that computations with an aeroacoustic feedback loop, the jet screech noise, can be obtained using truly unstructured grid technology. Numerical results are presented for a nozzle with two different lip thicknesses which will be referred to in this paper as a thin and a thick lip nozzle respectively. The space-time conservation element and solution element (CE/SE) method is used to solve the conservation laws of the compressible axisymmetric Navier-Stokes equations. The equations are time marched to predict the unsteady flow and the near-field screech tone noise issuing from an underexpanded circular jet. The CE/SE method uses an unstructured grid based data structure. The unstructured grids for these calculations are generated based on the method of Delaunay triangulation. Comparisons of numerical results with available experimental data are shown for flows corresponding to several different jet Mach numbers. Generally good agreement is obtained in terms of flow physics, screech tone frequency, and sound pressure level.
Unstructured Grids and the Multigroup Neutron Diffusion Equation
Directory of Open Access Journals (Sweden)
German Theler
2013-01-01
Full Text Available The neutron diffusion equation is often used to perform core-level neutronic calculations. It consists of a set of second-order partial differential equations over the spatial coordinates that are, both in the academia and in the industry, usually solved by discretizing the neutron leakage term using a structured grid. This work introduces the alternatives that unstructured grids can provide to aid the engineers to solve the neutron diffusion problem and gives a brief overview of the variety of possibilities they offer. It is by understanding the basic mathematics that lie beneath the equations that model real physical systems; better technical decisions can be made. It is in this spirit that this paper is written, giving a first introduction to the basic concepts which can be incorporated into core-level neutron flux computations. A simple two-dimensional homogeneous circular reactor is solved using a coarse unstructured grid in order to illustrate some basic differences between the finite volumes and the finite elements method. Also, the classic 2D IAEA PWR benchmark problem is solved for eighty combinations of symmetries, meshing algorithms, basic geometric entities, discretization schemes, and characteristic grid lengths, giving even more insight into the peculiarities that arise when solving the neutron diffusion equation using unstructured grids.
Verification of radiation transport codes with unstructured meshes
International Nuclear Information System (INIS)
Confidence in the results of a radiation transport code requires that the code be verified against problems with known solutions. Such verification problems may be generated by means of the method of manufactured solutions. Previously we reported the application of this method to the verification of radiation transport codes for structured meshes, in particular the SCEPTRE code. We extend this work to verification with unstructured meshes and again apply it to SCEPTRE. We report on additional complexities for unstructured mesh verification of transport codes. Refinement of such meshes for error convergence studies is more involved, particularly for tetrahedral meshes. Furthermore, finite element integrations arising from the presence of the streaming operator exhibit different behavior for unstructured meshes than for structured meshes. We verify SCEPTRE with a combination of 'exact' and 'inexact' problems. Errors in the results are consistent with the discretizations, either being limited to roundoff error or displaying the expected rates of convergence with mesh refinement. We also observe behaviors in the results that were difficult to analyze and predict from a strictly theoretical basis, thereby yielding benefits from verification activities beyond demonstrating code correctness. (author)
Evaluating Interpersonal Synchrony: Wavelet Transform Toward an Unstructured Conversation.
Fujiwara, Ken; Daibo, Ikuo
2016-01-01
This study examined whether interpersonal synchrony could be extracted using spectrum analysis (i.e., wavelet transform) in an unstructured conversation. Sixty-two female undergraduates were randomly paired and they engaged in a 6-min unstructured conversation. Interpersonal synchrony was evaluated by calculating the cross-wavelet coherence of the time-series movement data, extracted using a video-image analysis software. The existence of synchrony was tested using a pseudo-synchrony paradigm. In addition, the frequency at which the synchrony occurred and the distribution of the relative phase was explored. The results showed that the value of cross-wavelet coherence was higher in the experimental participant pairs than in the pseudo pairs. Further, the coherence value was higher in the frequency band under 0.5 Hz. These results support the validity of evaluating interpersonal synchron Behavioral mimicry and interpersonal syyby using wavelet transform even in an unstructured conversation. However, the role of relative phase was not clear; there was no significant difference between each relative-phase region. The theoretical contribution of these findings to the area of interpersonal coordination is discussed.
Heterogeneous Computing on Mixed Unstructured Grids with PyFR
Witherden, F D; Vincent, P E
2014-01-01
PyFR is an open-source high-order accurate computational fluid dynamics solver for mixed unstructured grids that can target a range of hardware platforms from a single codebase. In this paper we demonstrate the ability of PyFR to perform high-order accurate unsteady simulations of flow on mixed unstructured grids using heterogeneous multi-node hardware. Specifically, after benchmarking single-node performance for various platforms, PyFR v0.2.2 is used to undertake simulations of unsteady flow over a circular cylinder at Reynolds number 3 900 using a mixed unstructured grid of prismatic and tetrahedral elements on a desktop workstation containing an Intel Xeon E5-2697 v2 CPU, an NVIDIA Tesla K40c GPU, and an AMD FirePro W9100 GPU. Both the performance and accuracy of PyFR are assessed. PyFR v0.2.2 is freely available under a 3-Clause New Style BSD license (see www.pyfr.org).
Anisotropically structured magnetic aerogel monoliths
Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus
2014-10-01
Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and
Latest developments in anisotropic hydrodynamics
Tinti, Leonardo
2015-01-01
We discuss the leading order of anisotropic hydrodynamics expansion. It has already been shown that in the (0+1) and (1+1)-dimensional cases it is consistent with the second order viscous hydrodynamics, and it provides a striking agreement with the exact solutions of the Boltzmann equation. Quite recently, a new set of equations has been proposed for the leading order of anisotropic hydrodynamics, which is consistent with the second order viscous hydrodynamics in the most general (3+1)-dimensional case, and does not require a next-to-leading treatment for describing pressure anisotropies in the transverse plane.
Dynamical analysis of anisotropic inflation
Karčiauskas, Mindaugas
2016-06-01
The inflaton coupling to a vector field via the f(φ)2F μνFμν term is used in several contexts in the literature, such as to generate primordial magnetic fields, to produce statistically anisotropic curvature perturbation, to support anisotropic inflation, and to circumvent the η-problem. In this work, I perform dynamical analysis of this system allowing for the most general Bianchi I initial conditions. I also confirm the stability of attractor fixed points along phase-space directions that had not been investigated before.
Anisotropic hydrodynamics: Motivation and methodology
International Nuclear Information System (INIS)
In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches
Magnetic relaxation in anisotropic magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1971-01-01
The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...
Anisotropic Poisson Processes of Cylinders
Spiess, Malte
2010-01-01
Main characteristics of stationary anisotropic Poisson processes of cylinders (dilated k-dimensional flats) in d-dimensional Euclidean space are studied. Explicit formulae for the capacity functional, the covariance function, the contact distribution function, the volume fraction, and the intensity of the surface area measure are given which can be used directly in applications.
Failure in imperfect anisotropic materials
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2005-01-01
The fundamental cause of crack growth, namely nucleation and growth of voids, is investigated numerically for a two phase imperfect anisotropic material. A unit cell approach is adopted from which the overall stress strain is evaluated. Failure is observed as a sudden stress drop and depending...
Parallel performance of a preconditioned CG solver for unstructured finite element applications
Energy Technology Data Exchange (ETDEWEB)
Shadid, J.N.; Hutchinson, S.A.; Moffat, H.K. [Sandia National Labs., Albuquerque, NM (United States)
1994-12-31
A parallel unstructured finite element (FE) implementation designed for message passing MIMD machines is described. This implementation employs automated problem partitioning algorithms for load balancing unstructured grids, a distributed sparse matrix representation of the global finite element equations and a parallel conjugate gradient (CG) solver. In this paper a number of issues related to the efficient implementation of parallel unstructured mesh applications are presented. These include the differences between structured and unstructured mesh parallel applications, major communication kernels for unstructured CG solvers, automatic mesh partitioning algorithms, and the influence of mesh partitioning metrics on parallel performance. Initial results are presented for example finite element (FE) heat transfer analysis applications on a 1024 processor nCUBE 2 hypercube. Results indicate over 95% scaled efficiencies are obtained for some large problems despite the required unstructured data communication.
V.Thavavel; S. Siva Kumar
2012-01-01
The management of unstructured data is recognized as one of the major unsolved problems in the information industry and data mining paradigm. Unstructured data in computerized information that either does not have a data model and there are not easily usable by data mining. This paper proposes a solution to this problem by managing unstructured data in to structured data using legacy system and distributed data partitioned method for gives distributed data for mining multi text documents. Thi...
AN APPROACH FOR HANDLING UNSTRUCTURED DATUM ON EVENT MINING WITH HEURISTICAL TECHNIQUES
Directory of Open Access Journals (Sweden)
Mrs.V.Narayani
2010-07-01
Full Text Available Events are essential factors in the world of data mining. Hybrid dynamic systems, stochastic systems and discrete event system are some of the entities that deal with unstructured datum in event mining systems. In this paper we deal with a discrete event system which produces unstructured datum during its functional approach. We handle the unstructured datum towards the layered structured system with its various levels of impacts and implications.
AN APPROACH FOR HANDLING UNSTRUCTURED DATUM ON EVENT MINING WITH HEURISTICAL TECHNIQUES
Mrs.V.Narayani; Dr.S.P.Victor,; S. Rajkumar
2010-01-01
Events are essential factors in the world of data mining. Hybrid dynamic systems, stochastic systems and discrete event system are some of the entities that deal with unstructured datum in event mining systems. In this paper we deal with a discrete event system which produces unstructured datum during its functional approach. We handle the unstructured datum towards the layered structured system with its various levels of impacts and implications.
Institute of Scientific and Technical Information of China (English)
姚立健; 周高峰; 倪忠进; 张培培; 朱世威
2015-01-01
水果全表面图像信息是否完整，直接影响水果表面颜色和缺陷检测的结果。该文提出了一种基于尺度不变特征转换（SIFT，scale invariant feature transform）算子的图像拼接方法，实现多视角水果图像的拼接以获取完整的水果表面信息。首先以15°固定间隔旋转水果以获取各视角下的连续图像，在图像2R-G-B通道下实现图像目标和背景分离，并对目标图像进行灰度直方图均衡化以增强其纹理信息，有利于特征点的提取。运用SIFT算法提取图像特征点，因为特征向量数量多、维数高，采用普通的K-D树算法搜索匹配点将消耗大量时间，因此将图像划分为16个区域，通过多次试验可知中间4个区域为特征点是最容易匹配的区域，这样就缩小匹配点可能存在的区域。采用极线几何约束法和改进型随机抽样一致（random sample consensus，RANSAC）算法以提高图像拼接精度，减少匹配时间。根据平移矩阵，对前后图像进行拼接，从而实现水果表面图像的完整拼接。试验结果表明：该算法平均匹配精度提高35.0%，平均拼接时间为2.5 s，较传统K-D树算法缩短67.8%时间，拼接效果还原率为93.9%。该文算法具有一定的尺度、旋转以及仿射变换不变性，适用于随机呈现的不同姿态球状水果图像拼接。该研究可为基于机器视觉的农产品品质检测和等级划分提供科学参考。%The completely fruit surface image information is an important factor which will directly influence the detection results of fruit's surface color and defect. This paper took the common red delicious apple as the research object. An image feature extraction and matching method based on SIFT algorithm was proposed, and the multi-view fruit image were stitched effectively in this paper. The algorithm was helpful to obtain the completely fruit surface image information. Firstly, the fruits were
Comparison of Two Mesh Smoothing Techniques for Unstructured Grids
International Nuclear Information System (INIS)
In this paper two mesh smoothing techniques are applied to unstructured grids. These are based on the solution of elliptic equations, Laplace and Winslow. In the first case, the equations are solved by a barycentric averaging procedure, and a finite volume scheme is used for the second operator. The comparison of these two techniques are based on two quality measures, shape factor and minimum angle which both are local criteria. Also, a global quality smoothness criterion is introduced and used to assess global smoothing characteristics of these methods
Aligning Structured and Unstructured Medical Problems Using UMLS
Carlo, Lorena; Chase, Herbert S.; Weng, Chunhua
2010-01-01
This paper reports a pilot study to align medical problems in structured and unstructured EHR data using UMLS. A total of 120 medical problems in discharge summaries were extracted using NLP software (MedLEE) and aligned with 87 ICD-9 diagnoses for 19 non-overlapping hospital visits of 4 patients. The alignment accuracy was evaluated by a medical doctor. The average overlap of medical problems between the two data sources obtained by our automatic alignment method was 23.8%, which was about h...
Random walk search in unstructured P2P
Institute of Scientific and Technical Information of China (English)
Jia Zhaoqing; You Jinyuan; Rao Ruonan; Li Minglu
2006-01-01
Unstructured P2P has power-law link distribution, and the random walk in power-law networks is analyzed. The analysis results show that the probability that a random walker walks through the high degree nodes is high in the power-law network, and the information on the high degree nodes can be easily found through random walk. Random walk spread and random walk search method (RWSS) is proposed based on the analysis result. Simulation results show that RWSS achieves high success rates at low cost and is robust to high degree node failure.
Multisensory autonomous robotic inspection and manipulation in an unstructured environment
International Nuclear Information System (INIS)
In this paper we demonstrate the feasibility of an autonomous robotics inspection and manipulation in an unstructured environment, using information coming from a multisensory integrated system. The task is to perform a real operation, such as adjusting a valve, on a testbed representing an hydraulic circuit. The robotics system, made up of a mobile crawling robot and of an anthropomorphous, six-degree-of-freedom industrial robot, can achieve the goal by the joint use of vision, range and force/torque sensors. (author)
Institute of Scientific and Technical Information of China (English)
LI Yuguo; LUO Ming; PEI Jianxin
2013-01-01
In this paper,we extend the scope of numerical simulations of marine controlled-source electromagnetic (CSEM) fields in a particular case of anisotropy (dipping anisotropy) to the general case of anisotropy by using an adaptive finite element approach.In comparison to a dipping anisotropy case,the first order spatial derivatives of the strike-parallel components arise in the partial differential equations for generally anisotropic media,which cause a non-symmetric linear system of equations for finite element modeling.The adaptive finite element method is employed to obtain numerical solutions on a sequence of refined unstructured triangular meshes,which allows for arbitrary model geometries including bathymetry and dipping layers.Numerical results of a 2D anisotropic model show both anisotropy strike and dipping angles have great influence on the marine CSEM responses.
A triangulation-invariant method for anisotropic geodesic map computation on surface meshes.
Yoo, Sang Wook; Seong, Joon-Kyung; Sung, Min-Hyuk; Shin, Sung Yo; Cohen, Elaine
2012-10-01
This paper addresses the problem of computing the geodesic distance map from a given set of source vertices to all other vertices on a surface mesh using an anisotropic distance metric. Formulating this problem as an equivalent control theoretic problem with Hamilton-Jacobi-Bellman partial differential equations, we present a framework for computing an anisotropic geodesic map using a curvature-based speed function. An ordered upwind method (OUM)-based solver for these equations is available for unstructured planar meshes. We adopt this OUM-based solver for surface meshes and present a triangulation-invariant method for the solver. Our basic idea is to explore proximity among the vertices on a surface while locally following the characteristic direction at each vertex. We also propose two speed functions based on classical curvature tensors and show that the resulting anisotropic geodesic maps reflect surface geometry well through several experiments, including isocontour generation, offset curve computation, medial axis extraction, and ridge/valley curve extraction. Our approach facilitates surface analysis and processing by defining speed functions in an application-dependent manner.
Anisotropic Inflation and Cosmological Observations
Emami, Razieh
2015-01-01
Recent observations opened up a new window on the inflationary model building. As it was firstly reported by the WMAP data, there may be some indications of statistical anisotropy on the CMB map, although the statistical significance of these findings are under debate. Motivated by these observations, people begun considering new inflationary models which may lead to statistical anisotropy. The simplest possible way to construct anisotropic inflation is to introduce vector fields. During the course of this thesis, we study models of anisotropic inflation and their observational implications such as power spectrum, bispectrum etc. Firstly we build a new model, which contains the gauge field which breaks the conformal invariance while preserving the gauge invariance. We show that in these kind of models, there can be an attractor phase in the evolution of the system when the back-reaction of the gauge field becomes important in the evolution of the inflaton field. We then study the cosmological perturbation the...
Stealths on Anisotropic Holographic Backgrounds
Ayón-Beato, Eloy; Juárez-Aubry, María Montserrat
2015-01-01
In this paper, we are interested in exploring the existence of stealth configurations on anisotropic backgrounds playing a prominent role in the non-relativistic version of the gauge/gravity correspondence. By stealth configuration, we mean a nontrivial scalar field nonminimally coupled to gravity whose energy-momentum tensor evaluated on the anisotropic background vanishes identically. In the case of a Lifshitz spacetime with a nontrivial dynamical exponent z, we spotlight the role played by the anisotropy to establish the holographic character of the stealth configurations, i.e. the scalar field is shown to only depend on the radial holographic direction. This configuration which turns out to be massless and without integration constants is possible for a unique value of the nonminimal coupling parameter. Then, using a simple conformal argument, we map this configuration into a stealth solution defined on the so-called hyperscaling violation metric which is conformally related to the Lifshitz spacetime. Thi...
Conductivities in an anisotropic medium
Khimphun, Sunly; Park, Chanyong
2016-01-01
In order to imitate anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in low frequency limit shows a Drude peak and that in the intermediate frequency regime it reveals the power law behavior. Especially, when the anisotropy increases the exponent of the power law becomes smaller. In addition, we find that there exist a critical value for the anisotropy at which the DC conductivity reaches to its maximum value.
Numerical simulation of plasmas on an unstructured grid
International Nuclear Information System (INIS)
The use of unstructured grids provides some inherent advantages in the accurate simulation of plasma problems which involve complex configurations and where the treatment of complicated boundaries is important. The use of a triangular grid in two dimensions, and of a tetrahedral grid with arbitrary connectivity in three dimensions, allows a straightforward representation of complex geometries and naturally allows the resolution of the mesh to vary according to the requirements of a problem. We have constructed a very simple and efficient data structure to represent unstructured grids for geometries with arbitrarily shaped boundaries. The data contains information about the location of vertices, edges, sides, and cells and permits with one degree of indirectness the implementation of algorithms for field solvers and for particle orbit integration. The numerical algorithms that have been constructed include a potential solver, an electromagnetic solver for both the time and frequency domain, and a particle-in-cell simulation. The efficiency and vectorization of the basic code functions are retained and yield timing results comparable with structured mesh codes. They describe the method of grid generation, the numerical algorithm's for a variety of applications, and present typical results. These include particle-in-cell plasma simulations as well as purely electromagnetic cases which illustrate powerful features of local grid refinement for cavity and scattering problems
A numerical scheme for coastal morphodynamic modelling on unstructured grids
Guerin, Thomas; Bertin, Xavier; Dodet, Guillaume
2016-08-01
Over the last decade, modelling systems based on unstructured grids have been appearing increasingly attractive to investigate the dynamics of coastal zones. However, the resolution of the sediment continuity equation to simulate bed evolution is a complex problem which often leads to the development of numerical oscillations. To overcome this problem, addition of artificial diffusion or bathymetric filters are commonly employed methods, although these techniques can potentially over-smooth the bathymetry. This study aims to present a numerical scheme based on the Weighted Essentially Non-Oscillatory (WENO) formalism to solve the bed continuity equation on unstructured grids in a finite volume formulation. The new solution is compared against a classical method, which combines a basic node-centered finite volume method with artificial diffusion, for three idealized test cases. This comparison reveals that a higher accuracy is obtained with our new method while the addition of diffusion appears inappropriate mainly due to the arbitrary choice of the diffusion coefficient. Moreover, the increased computation time associated with the WENO-based method to solve the bed continuity equation is negligible when considering a fully-coupled simulation with tides and waves. Finally, the application of the new method to the pluri-monthly evolution of an idealized inlet subjected to tides and waves shows the development of realistic bed features (e.g. secondary flood channels, ebb-delta sandbars, or oblique sandbars at the adjacent beaches), that are smoothed or nonexistent when using additional diffusion.
Island Modeling Using Unstructured Grid during a Tropical Storm
Directory of Open Access Journals (Sweden)
Mourani Sinha
2016-01-01
Full Text Available The coastal wave dynamics of Agatti island situated on a coral atoll in Lakshadweep, India, having a notable topographic feature of steeper eastern shore over the western shore, is analysed in this study. A multinested model setup is generated using the global third-generation models WAM (Wave Modeling and SWAN (Simulating Waves Nearshore. A high resolution unstructured grid is generated for the domain containing the island using SMS (Surface-Water Modeling System interpolated with merged GEBCO (General Bathymetric Chart of the Oceans and SRTM (Shuttle Radar Topography Mission bathymetry. The SWAN model is integrated with a fine resolution of one minute by one minute during the tropical storm 01A (05–10 June 2004 which passed near the island. Model simulated significant wave height data when validated against satellite observations exhibited high accuracy. SWH (significant wave height is observed to be greater for the west coast than that over the east coast of the island due to steeper eastern shore and there is widespread wave energy dissipation along the southwest direction of wave propagation during normal conditions. The one-dimensional energy density spectra generated during the storm period exhibit multimodality with structured and unstructured grids.
Coupling of unstructured TLM and BEM for accurate 2D electromagnetic simulation
Simmons, Daniel; Cools, Kristof; Sewell, Phillip
2015-01-01
In this paper the hybridisation of the 2D time-domain boundary element method (BEM) with the unstructured transmission line method (UTLM) will be introduced, which enables accurate modeling of radiating boundary conditions and plane wave excitations of uniform and non-uniform targets modelled by geometrically accurate unstructured meshes. The method is demonstrated by comparing numerical results against analytical results.
Gpu Implementation of a Viscous Flow Solver on Unstructured Grids
Xu, Tianhao; Chen, Long
2016-06-01
Graphics processing units have gained popularities in scientific computing over past several years due to their outstanding parallel computing capability. Computational fluid dynamics applications involve large amounts of calculations, therefore a latest GPU card is preferable of which the peak computing performance and memory bandwidth are much better than a contemporary high-end CPU. We herein focus on the detailed implementation of our GPU targeting Reynolds-averaged Navier-Stokes equations solver based on finite-volume method. The solver employs a vertex-centered scheme on unstructured grids for the sake of being capable of handling complex topologies. Multiple optimizations are carried out to improve the memory accessing performance and kernel utilization. Both steady and unsteady flow simulation cases are carried out using explicit Runge-Kutta scheme. The solver with GPU acceleration in this paper is demonstrated to have competitive advantages over the CPU targeting one.
Mining Unstructured Data from Web Using Soft Computing
Directory of Open Access Journals (Sweden)
Ms.Sonali A. Deshpande
2012-01-01
Full Text Available Copious material is available from the World Wide Web (WWW in response to any user-provided query. It becomes tedious for the user to manually extract real required information from this material. Large document collections, such as those delivered by Internet search engines, are difficult and time-consuming for users to read and analyse. The detection of common and distinctive topics within a document set, together with the generation of multi-document summaries, can greatly ease the burden of information management. In the paper, a technique is proposed called Mining Unstructured Data From Web Using Soft Computing that creates the clusters of web documents using fuzzy clustering which focuses on this problem of mining the useful information from the collected web documents
Qubiter Algorithm Modification, Expressing Unstructured Unitary Matrices with Fewer CNOTs
Tucci, R R
2004-01-01
A quantum compiler is a software program for decomposing ("compiling") an arbitrary unitary matrix into a sequence of elementary operations (SEO). The author of this paper is also the author of a quantum compiler called Qubiter. Qubiter uses a matrix decomposition called the Cosine-Sine Decomposition (CSD) that is well known in the field of Computational Linear Algebra. One way of measuring the efficiency of a quantum compiler is to measure the number of CNOTs it uses to express an unstructured unitary matrix (a unitary matrix with no special symmetries). We will henceforth refer to this number as $\\epsilon$. In this paper, we show how to improve $\\epsilon$ for Qubiter so that it matches the current world record for $\\epsilon$, which is held by another quantum compiling algorithm based on CSD.
Multigrid and multilevel domain decomposition for unstructured grids
Energy Technology Data Exchange (ETDEWEB)
Chan, T.; Smith, B.
1994-12-31
Multigrid has proven itself to be a very versatile method for the iterative solution of linear and nonlinear systems of equations arising from the discretization of PDES. In some applications, however, no natural multilevel structure of grids is available, and these must be generated as part of the solution procedure. In this presentation the authors will consider the problem of generating a multigrid algorithm when only a fine, unstructured grid is given. Their techniques generate a sequence of coarser grids by first forming an approximate maximal independent set of the vertices and then applying a Cavendish type algorithm to form the coarser triangulation. Numerical tests indicate that convergence using this approach can be as fast as standard multigrid on a structured mesh, at least in two dimensions.
Adaptive IMEX schemes for high-order unstructured methods
Vermeire, Brian C.; Nadarajah, Siva
2015-01-01
We present an adaptive implicit-explicit (IMEX) method for use with high-order unstructured schemes. The proposed method makes use of the Gerschgorin theorem to conservatively estimate the influence of each individual degree of freedom on the spectral radius of the discretization. This information is used to split the system into implicit and explicit regions, adapting to unsteady features in the flow. We dynamically repartition the domain to balance the number of implicit and explicit elements per core. As a consequence, we are able to achieve an even load balance for each implicit/explicit stage of the IMEX scheme. We investigate linear advection-diffusion, isentropic vortex advection, unsteady laminar flow over an SD7003 airfoil, and turbulent flow over a circular cylinder. Results show that the proposed method consistently yields a stable discretization, and maintains the theoretical order of accuracy of the high-order spatial schemes.
SOMBI: Bayesian identification of parameter relations in unstructured cosmological data
Frank, Philipp; Enßlin, Torsten A
2016-01-01
This work describes the implementation and application of a correlation determination method based on Self Organizing Maps and Bayesian Inference (SOMBI). SOMBI aims to automatically identify relations between different observed parameters in unstructured cosmological or astrophysical surveys by automatically identifying data clusters in high-dimensional datasets via the Self Organizing Map neural network algorithm. Parameter relations are then revealed by means of a Bayesian inference within respective identified data clusters. Specifically such relations are assumed to be parametrized as a polynomial of unknown order. The Bayesian approach results in a posterior probability distribution function for respective polynomial coefficients. To decide which polynomial order suffices to describe correlation structures in data, we include a method for model selection, the Bayesian Information Criterion, to the analysis. The performance of the SOMBI algorithm is tested with mock data. As illustration we also provide ...
Domain-independent information extraction in unstructured text
Energy Technology Data Exchange (ETDEWEB)
Irwin, N.H. [Sandia National Labs., Albuquerque, NM (United States). Software Surety Dept.
1996-09-01
Extracting information from unstructured text has become an important research area in recent years due to the large amount of text now electronically available. This status report describes the findings and work done during the second year of a two-year Laboratory Directed Research and Development Project. Building on the first-year`s work of identifying important entities, this report details techniques used to group words into semantic categories and to output templates containing selective document content. Using word profiles and category clustering derived during a training run, the time-consuming knowledge-building task can be avoided. Though the output still lacks in completeness when compared to systems with domain-specific knowledge bases, the results do look promising. The two approaches are compatible and could complement each other within the same system. Domain-independent approaches retain appeal as a system that adapts and learns will soon outpace a system with any amount of a priori knowledge.
Turbulent convection in the Sun: modeling in unstructured meshes
Olshevsky, Vyacheslav; Ham, Frank
2014-01-01
We adopted an unstructured hydrodynamical solver CharLES to the problem of global convection in the Sun. With the aim to investigate the properties of solar turbulent convection and reproduce differential rotation pattern. We performed simulations in two spherical shells, with 1.3 and 10 million cells. In the first, coarse mesh, the solution does not reproduce realistic convection, and is dominated by numerical effects. In the second mesh, thermal conduction leads to cooling of bottom layers, that could not be compensated by solar irradiance. More simulations in the 10M cells mesh should be performed to investigate the influence of transport coefficients and numerical effects. Our estimate of the code performance suggests, that realistic simulations in even finer grids could be performed for reasonable computational cost.
Node Discovery and Interpretation in Unstructured Resource-Constrained Environments
DEFF Research Database (Denmark)
Gechev, Miroslav; Kasabova, Slavyana; Mihovska, Albena D.;
2014-01-01
in the context of long-term relationships and identifies several key variables in the context of communications in resource-constrained environments. The general theoretical model is described and several algorithms are proposed as part of the node discovery, identification, and linking processes in relation......A main characteristic of the Internet of Things networks is the large number of resource-constrained nodes, which, however, are required to perform reliable and fast data exchange; often of critical nature; over highly unpredictable and dynamic connections and network topologies. Reducing...... for the discovery, linking and interpretation of nodes in unstructured and resource-constrained network environments and their interrelated and collective use for the delivery of smart services. The model is based on a basic mathematical approach, which describes and predicts the success of human interactions...
Development of unstructured mesh generator on parallel computers
International Nuclear Information System (INIS)
A general-purpose unstructured mesh generator, 'GRID3D/UNST', has been developed on parallel computers. High-speed operations and large-scale memory capacity of parallel computers enable the system to generate a large-scale mesh at high speed. As a matter of fact, the system generates large-scale mesh composed of 2,400,000 nodes and 14,000,000 elements about 1.5 hours on HITACHI SR2201, 64 PEs (Processing Elements) through 2.5 hours pre-process on SUN. Also the system is built on standard FORTRAN, C and Motif, and therefore has high portability. The system enables us to solve a large-scale problem that has been impossible to be solved, and to break new ground in the field of science and engineering. (author)
3D unstructured mesh discontinuous finite element hydro
Energy Technology Data Exchange (ETDEWEB)
Prasad, M.K.; Kershaw, D.S.; Shaw, M.J. [Lawrence Livermore National Lab., CA (United States)
1995-07-01
The authors present detailed features of the ICF3D hydrodynamics code used for inertial fusion simulations. This code is intended to be a state-of-the-art upgrade of the well-known fluid code, LASNEX. ICF3D employs discontinuous finite elements on a discrete unstructured mesh consisting of a variety of 3D polyhedra including tetrahedra, prisms, and hexahedra. The authors discussed details of how the ROE-averaged second-order convection was applied on the discrete elements, and how the C++ coding interface has helped to simplify implementing the many physics and numerics modules within the code package. The author emphasized the virtues of object-oriented design in large scale projects such as ICF3D.
Key frame extraction from unstructured consumer video clips
Papin, Christophe; Luo, Jiebo
2007-01-01
We present a key frame extraction method dedicated to summarize unstructured consumer video clips acquired from digital cameras. Analysis of spatio-temporal changes over time provides meaningful information about the scene and the cameraman's general intents. First, camera and object motion are estimated and used to derive motion descriptors. A video is segmented into homogeneous segments based on major types of camera motion (e.g., pan, zoom, pause, steady). Dedicated rules are used to extract candidate key frames from each segment. Confidence measures are computed for the candidates to enable ranking in semantic relevance. This method is scalable so that we can produce any desired number of key frames from the candidates. We demonstrated the effectiveness of our method by comparing results with the ground truth agreed by multiple judges.
Discrete unified gas kinetic scheme on unstructured meshes
Zhu, Lianhua; Xu, Kun
2015-01-01
The recently proposed discrete unified gas kinetic scheme (DUGKS) is a finite volume method for deterministic solution of the Boltzmann model equation with asymptotic preserving property. In DUGKS, the numerical flux of the distribution function is determined from a local numerical solution of the Boltzmann model equation using an unsplitting approach. The time step and mesh resolution are not restricted by the molecular collision time and mean free path. To demonstrate the capacity of DUGKS in practical problems, this paper extends the DUGKS to arbitrary unstructured meshes. Several tests of both internal and external flows are performed, which include the cavity flow ranging from continuum to free molecular regimes, a multiscale flow between two connected cavities with a pressure ratio of 10000, and a high speed flow over a cylinder in slip and transitional regimes. The numerical results demonstrate the effectiveness of the DUGKS in simulating multiscale flow problems.
3D unstructured mesh discontinuous finite element hydro
International Nuclear Information System (INIS)
The authors present detailed features of the ICF3D hydrodynamics code used for inertial fusion simulations. This code is intended to be a state-of-the-art upgrade of the well-known fluid code, LASNEX. ICF3D employs discontinuous finite elements on a discrete unstructured mesh consisting of a variety of 3D polyhedra including tetrahedra, prisms, and hexahedra. The authors discussed details of how the ROE-averaged second-order convection was applied on the discrete elements, and how the C++ coding interface has helped to simplify implementing the many physics and numerics modules within the code package. The author emphasized the virtues of object-oriented design in large scale projects such as ICF3D
Spin precession in anisotropic cosmologies
Energy Technology Data Exchange (ETDEWEB)
Kamenshchik, A.Yu. [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); L. D. Landau Institute for Theoretical Physics, Moscow (Russian Federation); INFN, Bologna (Italy); Teryaev, O.V. [Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); Lomonosov Moscow State University, Moscow (Russian Federation)
2016-05-15
We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter. (orig.)
Anisotropic and nonlinear optical waveguides
Someda, CG
1992-01-01
Dielectric optical waveguides have been investigated for more than two decades. In the last ten years they have had the unique position of being simultaneously the backbone of a very practical and fully developed technology, as well as an extremely exciting area of basic, forefront research. Existing waveguides can be divided into two sets: one consisting of waveguides which are already in practical use, and the second of those which are still at the laboratory stage of their evolution. This book is divided into two separate parts: the first dealing with anisotropic waveguides, an
New charged anisotropic compact models
Kileba Matondo, D.; Maharaj, S. D.
2016-07-01
We find new exact solutions to the Einstein-Maxwell field equations which are relevant in the description of highly compact stellar objects. The relativistic star is charged and anisotropic with a quark equation of state. Exact solutions of the field equations are found in terms of elementary functions. It is interesting to note that we regain earlier quark models with uncharged and charged matter distributions. A physical analysis indicates that the matter distributions are well behaved and regular throughout the stellar structure. A range of stellar masses are generated for particular parameter values in the electric field. In particular the observed mass for a binary pulsar is regained.
Remarks on inhomogeneous anisotropic cosmology
Kaya, Ali
2016-08-01
Recently a new no-global-recollapse argument was given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this paper we discuss important properties of the mean curvature flow of spacelike surfaces in Lorentzian manifolds. We show that singularities may form during cosmic evolution, and the theorems forbidding the global recollapse lose their validity. The time evolution of the spatial scalar curvature that may kinematically prevent the recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis indicates a caveat in numerical solutions that give rise to inflation.
3D unstructured-mesh radiation transport codes
Energy Technology Data Exchange (ETDEWEB)
Morel, J. [Los Alamos National Lab., NM (United States)
1997-12-31
Three unstructured-mesh radiation transport codes are currently being developed at Los Alamos National Laboratory. The first code is ATTILA, which uses an unstructured tetrahedral mesh in conjunction with standard Sn (discrete-ordinates) angular discretization, standard multigroup energy discretization, and linear-discontinuous spatial differencing. ATTILA solves the standard first-order form of the transport equation using source iteration in conjunction with diffusion-synthetic acceleration of the within-group source iterations. DANTE is designed to run primarily on workstations. The second code is DANTE, which uses a hybrid finite-element mesh consisting of arbitrary combinations of hexahedra, wedges, pyramids, and tetrahedra. DANTE solves several second-order self-adjoint forms of the transport equation including the even-parity equation, the odd-parity equation, and a new equation called the self-adjoint angular flux equation. DANTE also offers three angular discretization options: $S{_}n$ (discrete-ordinates), $P{_}n$ (spherical harmonics), and $SP{_}n$ (simplified spherical harmonics). DANTE is designed to run primarily on massively parallel message-passing machines, such as the ASCI-Blue machines at LANL and LLNL. The third code is PERICLES, which uses the same hybrid finite-element mesh as DANTE, but solves the standard first-order form of the transport equation rather than a second-order self-adjoint form. DANTE uses a standard $S{_}n$ discretization in angle in conjunction with trilinear-discontinuous spatial differencing, and diffusion-synthetic acceleration of the within-group source iterations. PERICLES was initially designed to run on workstations, but a version for massively parallel message-passing machines will be built. The three codes will be described in detail and computational results will be presented.
Electromagnetism on anisotropic fractal media
Ostoja-Starzewski, Martin
2013-04-01
Basic equations of electromagnetic fields in anisotropic fractal media are obtained using a dimensional regularization approach. First, a formulation based on product measures is shown to satisfy the four basic identities of the vector calculus. This allows a generalization of the Green-Gauss and Stokes theorems as well as the charge conservation equation on anisotropic fractals. Then, pursuing the conceptual approach, we derive the Faraday and Ampère laws for such fractal media, which, along with two auxiliary null-divergence conditions, effectively give the modified Maxwell equations. Proceeding on a separate track, we employ a variational principle for electromagnetic fields, appropriately adapted to fractal media, so as to independently derive the same forms of these two laws. It is next found that the parabolic (for a conducting medium) and the hyperbolic (for a dielectric medium) equations involve modified gradient operators, while the Poynting vector has the same form as in the non-fractal case. Finally, Maxwell's electromagnetic stress tensor is reformulated for fractal systems. In all the cases, the derived equations for fractal media depend explicitly on fractal dimensions in three different directions and reduce to conventional forms for continuous media with Euclidean geometries upon setting these each of dimensions equal to unity.
ANISOTROPIC POLARIZATION TENSORS FOR ELLIPSES AND ELLIPSOIDS
Institute of Scientific and Technical Information of China (English)
Hyeonbae Kang; Kyoungsun Kim
2007-01-01
In this paper we present a systematic way of computing the polarization tensors,anisotropic as well as isotropic, based on the boundary integral method. We then use this method to compute the anisotropic polarization tensor for ellipses and ellipsoids. The computation reveals the pair of anisotropy and ellipses which produce the same polarization tensors.
Anisotropic weak Hardy spaces and interpolation theorems
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper, the authors establish the anisotropic weak Hardy spaces associated with very general discrete groups of dilations. Moreover, the atomic decomposition theorem of the anisotropic weak Hardy spaces is also given. As some applications of the above results, the authors prove some interpolation theorems and obtain the boundedness of the singular integral operators on these Hardy spaces.
ANISOTROPIC BIQUADRATIC ELEMENT WITH SUPERCLOSE RESULT
Institute of Scientific and Technical Information of China (English)
Dongyang SHI; Shipeng MAO; Hui LIANG
2006-01-01
The main aim of this paper is to study the convergence of biquadratic finite element for the second order problem on anisotropic meshes. By using some novel approaches and techniques, the optimal error estimates are obtained. At the same time, the anisotropic superclose results are also achieved. Furthermore, the numerical results are given to demonstrate our theoretical analysis.
Efficient Wavefield Extrapolation In Anisotropic Media
Alkhalifah, Tariq
2014-07-03
Various examples are provided for wavefield extrapolation in anisotropic media. In one example, among others, a method includes determining an effective isotropic velocity model and extrapolating an equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield. The effective isotropic velocity model can be based upon a kinematic geometrical representation of an anisotropic, poroelastic or viscoelastic wavefield. Extrapolating the equivalent propagation can use isotopic, acoustic or elastic operators based upon the determined effective isotropic velocity model. In another example, non-transitory computer readable medium stores an application that, when executed by processing circuitry, causes the processing circuitry to determine the effective isotropic velocity model and extrapolate the equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield. In another example, a system includes processing circuitry and an application configured to cause the system to determine the effective isotropic velocity model and extrapolate the equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield.
Multidisciplinary approach to cylindrical anisotropic metamaterials
International Nuclear Information System (INIS)
Anisotropic characteristics of cylindrically corrugated microstructures are analyzed in terms of their acoustic and electromagnetic (EM) behavior paying special attention to their differences and similarities. A simple analytical model has been developed using effective medium theory to understand the anisotropic features of both types of waves in terms of radial and angular components of the wave propagation velocity. The anisotropic constituent parameters have been obtained by measuring the resonances of cylindrical cavities, as well as from numerical simulations. This permits one to characterize propagation of acoustic and EM waves and to compare the fundamental anisotropic features generated by the corrugated effective medium. Anisotropic coefficients match closely in both physics fields but other relevant parameters show significant differences in the behavior of both types of waves. (paper)
Designing Anisotropic Inflation with Form Fields
Ito, Asuka
2015-01-01
We study inflation with anisotropic hair induced by form fields. In four dimensions, the relevant form fields are gauge (one-form) fields and two-form fields. Assuming the exponential form of potential and gauge kinetic functions, we find new exact power-law solutions endowed with anisotropic hair. We also explore the phase space of anisotropic inflation and find fixed points corresponding to the exact power-law solutions. Moreover, we perform the stability analysis around the fixed points to reveal the structure of the phase space. It turns out that one of the fixed points becomes an attractor and others (if any) are saddle points. In particular, the one corresponding to anisotropic inflation becomes an attractor when it exists. We also argue that various anisotropic inflation models can be designed by choosing coupling constants.
Designing anisotropic inflation with form fields
Ito, Asuka; Soda, Jiro
2015-12-01
We study inflation with anisotropic hair induced by form fields. In four dimensions, the relevant form fields are gauge (one-form) fields and two-form fields. Assuming the exponential form of potential and gauge kinetic functions, we find new exact power-law solutions endowed with anisotropic hair. We also explore the phase space of anisotropic inflation and find fixed points corresponding to the exact power-law solutions. Moreover, we perform the stability analysis around the fixed points to reveal the structure of the phase space. It turns out that one of the fixed points becomes an attractor and others (if any) are saddle points. In particular, the one corresponding to anisotropic inflation becomes an attractor when it exists. We also argue that various anisotropic inflation models can be designed by choosing coupling constants.
Directory of Open Access Journals (Sweden)
V. Thavavel
2012-01-01
Full Text Available The management of unstructured data is recognized as one of the major unsolved problems in the information industry and data mining paradigm. Unstructured data in computerized information that either does not have a data model and there are not easily usable by data mining. This paper proposes a solution to this problem by managing unstructured data in to structured data using legacy system and distributed data partitioned method for gives distributed data for mining multi text documents. This frame work gives the testing of the similarities among text documents and privacy preserving meta data hiding technique, which are explored in text mining.
Survey of Search and Replication Schemes in Unstructured P2P Networks
Thampi, Sabu M
2010-01-01
P2P computing lifts taxing issues in various areas of computer science. The largely used decentralized unstructured P2P systems are ad hoc in nature and present a number of research challenges. In this paper, we provide a comprehensive theoretical survey of various state-of-the-art search and replication schemes in unstructured P2P networks for file-sharing applications. The classifications of search and replication techniques and their advantages and disadvantages are briefly explained. Finally, the various issues on searching and replication for unstructured P2P networks are discussed.
Finite volume methods for the incompressible Navier-Stokes equations on unstructured grids
Energy Technology Data Exchange (ETDEWEB)
Meese, Ernst Arne
1998-07-01
Most solution methods of computational fluid dynamics (CFD) use structured grids based on curvilinear coordinates for compliance with complex geometries. In a typical industry application, about 80% of the time used to produce the results is spent constructing computational grids. Recently the use of unstructured grids has been strongly advocated. For unstructured grids there are methods for generating them automatically on quite complex domains. This thesis focuses on the design of Navier-Stokes solvers that can cope with unstructured grids and ''low quality grids'', thus reducing the need for human intervention in the grid generation.
Warm anisotropic inflationary universe model
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2014-02-15
This paper is devoted to the study of warm inflation using vector fields in the background of a locally rotationally symmetric Bianchi type I model of the universe. We formulate the field equations, and slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) in the slow-roll approximation. We evaluate all these parameters in terms of the directional Hubble parameter during the intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of the scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., the tensor-scalar ratio in terms of the inflaton. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and the Planck observational data. (orig.)
Warm Anisotropic Inflationary Universe Model
Sharif, M
2014-01-01
This paper is devoted to study the warm inflation using vector fields in the background of locally rotationally symmetric Bianchi type I universe model. We formulate the field equations, slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) under slow-roll approximation. We evaluate all these parameters in terms of directional Hubble parameter during intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., tensor-scalar ratio in terms of inflation. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and Planck observational data.
Anisotropic scaling of magnetohydrodynamic turbulence
Horbury, T S; Oughton, S
2008-01-01
We present a quantitative estimate of the anisotropic power and scaling of magnetic field fluctuations in inertial range magnetohydrodynamic turbulence, using a novel wavelet technique applied to spacecraft measurements in the solar wind. We show for the first time that, when the local magnetic field direction is parallel to the flow, the spacecraft-frame spectrum has a spectral index near 2. This can be interpreted as the signature of a population of fluctuations in field-parallel wavenumbers with a $k_{\\parallel}^{-2}$ spectrum but is also consistent with the presence of a "critical balance" style turbulent cascade. We also find, in common with previous studies, that most of the power is contained in wavevectors at large angles to the local magnetic field and that this component of the turbulence has a spectral index of 5/3.
Gravitational baryogenesis after anisotropic inflation
Fukushima, Mitsuhiro; Mizuno, Shuntaro; Maeda, Kei-ichi
2016-05-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence, it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Yagi, Kent
2015-01-01
Certain physical quantities that characterize neutron stars and quark stars (e.g. their mass, spin angular momentum and quadrupole moment) are interrelated in a way that is approximately insensitive to their internal structure. Such approximately universal relations are useful to break degeneracies in data analysis for future radio, X-ray and gravitational wave observations. Although the pressure inside compact stars is most likely nearly isotropic, certain scenarios have been put forth that suggest otherwise, for example due to phase transitions. We here investigate whether pressure anisotropy affects the approximate universal relations and whether it prevents their use in future observations. We achieve this by numerically constructing slowly-rotating and tidally-deformed, anisotropic, compact stars in General Relativity to third order in spin. We find that anisotropy affects the universal relations only weakly; the relations become less universal by a factor of 1.5-3 relative to the isotropic case, but rem...
Gravitational Baryogenesis after Anisotropic Inflation
Fukushima, Mitsuhiro; Maeda, Kei-ichi
2016-01-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Unstructured Computational Aerodynamics on Many Integrated Core Architecture
Al Farhan, Mohammed A.
2016-06-08
Shared memory parallelization of the flux kernel of PETSc-FUN3D, an unstructured tetrahedral mesh Euler flow code previously studied for distributed memory and multi-core shared memory, is evaluated on up to 61 cores per node and up to 4 threads per core. We explore several thread-level optimizations to improve flux kernel performance on the state-of-the-art many integrated core (MIC) Intel processor Xeon Phi “Knights Corner,” with a focus on strong thread scaling. While the linear algebraic kernel is bottlenecked by memory bandwidth for even modest numbers of cores sharing a common memory, the flux kernel, which arises in the control volume discretization of the conservation law residuals and in the formation of the preconditioner for the Jacobian by finite-differencing the conservation law residuals, is compute-intensive and is known to exploit effectively contemporary multi-core hardware. We extend study of the performance of the flux kernel to the Xeon Phi in three thread affinity modes, namely scatter, compact, and balanced, in both offload and native mode, with and without various code optimizations to improve alignment and reduce cache coherency penalties. Relative to baseline “out-of-the-box” optimized compilation, code restructuring optimizations provide about 3.8x speedup using the offload mode and about 5x speedup using the native mode. Even with these gains for the flux kernel, with respect to execution time the MIC simply achieves par with optimized compilation on a contemporary multi-core Intel CPU, the 16-core Sandy Bridge E5 2670. Nevertheless, the optimizations employed to reduce the data motion and cache coherency protocol penalties of the MIC are expected to be of value for CFD and many other unstructured applications as many-core architecture evolves. We explore large-scale distributed-shared memory performance on the Cray XC40 supercomputer, to demonstrate that optimizations employed on Phi hybridize to this context, where each of
The Anisotropic Geometrodynamics For Cosmology
Siparov, Sergey V.
2009-05-01
The classical geometrodynamics (GRT) and its modern features based on the use of the Fridman-Robertson-Walker type metrics are still unable to explain several important issues of extragalactic observations like flat rotation curves of the spiral galaxies, Tully-Fisher law, globular clusters behavior in comparisson to that of the stars belonging to the galactic plane etc. The chalenging problem of the Universe expansion acceleration stemming from the supernovae observations demands the existence of the repulsion forces which brings one to the choice between the cosmological constant and some quintessence. The popular objects of discussion are now still dark (matter and energy), nevertheless, they are supposed to correspond to more than 95% of the Universe which seems to be far from satisfactory. According to the equivalence principle we can not experimentally distinguish between the inertial forces and the gravitational ones. Since there exist the inertial forces depending on velocity (Coriolis), it seems plausible to explore the velocity dependent gravitational forces. From the mathematical point of view it means that we should use the anisotropic metric. It immediately turns out that the expression for the Einstein-Hilbert action changes in a natural way - contrary to the cases of f(R)-theories, additional scalar fields, arbitrary MOND functions etc.. We use the linear approximation for the metric and derive the generalized geodesics and the equation for the gravity force that contains not only the Newton-Einstein term. The relation between the obtained results and those of Lense-Thirring approach are discussed. The resulting anisotropic geometrodynamics includes all the results of the GRT and is used to give the explanation to the problems mentioned above. One of the impressive consequences is the possibility to explain the observed Hubble red shift not by the Doppler effect as usually but by the gravitational red shift originating from the metric anisotropy.
Anisotropic microstructure near the sun
International Nuclear Information System (INIS)
Radio scattering observations provide a means of measuring a two-dimensional projection of the three-dimensional spatial spectrum of electron density, i.e., in the plane perpendicular to the line of sight. Earlier observations have shown that the microstructure at scales of the order of 10 km becomes highly field-aligned inside of 10 R· [Armstrong et al., 1990]. Earlier work has also shown that density fluctuations at scales larger than 1000 km have a Kolmogorov spectrum, whereas the smaller scale structure has a flatter spectrum and is considerably enhanced above the Kolmogorov ''background'' [Coles et al., 1991]. Here we present new observations made during 1990 and 1992. These confirm the earlier work, which was restricted to one source on a few days, but they suggest that the anisotropy changes abruptly near 6 R· which was not clear in the earlier data. The axial ratio measurements are shown on Figure 1 below. The new observations were made with a more uniform sampling of the spatial plane. They show that contours of constant correlation are elliptical. This is apparently inconsistent with the spatial correlation of the ISEE-3 magnetic field which shows a 'Maltese Cross' shape [Matthaeus et al., 1990]. However this inconsistency may be only apparent: the magnetic field and density correlations need not have the same shape; the scale of the magnetic field correlations is at least 4 orders of magnitude larger; they are much further from the sun; and they are point measurements whereas ours are path-integrated. We also made two simultaneous measurements, at 10 R·, of the anisotropy on scales of 200 to 4000 km. Significant anisotropy was seen on the smaller scales, but the larger scale structure was essentially isotropic. This suggests that the process responsible for the anisotropic microstructure is independent of the larger scale isotropic turbulence. It is then tempting to speculate that the damping of this anisotropic process inside of 6 R· contributes to
Parallel unstructured AMR and gigabit networking for Beowulf-class clusters
Norton, C. D.; Cwik, T. A.
2001-01-01
The impact of gigabit networking with Myrinet 2000 hardware and MPICH-GM software on a 2-way SMP Beowulf-class cluster for parallel unstructured adaptive mesh refinement using the PYRAMID library is described.
On the Vortical-Flow Prediction Capability of an Unstructured-Grid Euler Solver
Ghaffari, Farhad
1994-01-01
The results from a concentrated computational effort are presented with the primary objective being directed at evaluating the vortical-flow-prediction capability of an unstructured-grid Euler solver. Both viscous and inviscid solutions, obtained from an established structured-grid method, along with an experimental wind-tunnel data are used as bench-mark measures to assess the validity of the unstructured-grid Euler results. Viscous effects on vortical flows are first identified by comparing the viscous and inviscid solutions obtained form the structured-grid method. Computational data analysis are then presented which reveal excellent correlations between the inviscid structured and unstructured-grid results in terms of off-surface flow structures, surface pressure distribution and the predicted longitudinal aerodynamic characteristics. The sensitivity of the unstructured-grid inviscid solutions to grid refinement is also discussed along with an analysis of the convergence and performance characteristics for each method.
Multigrid on unstructured grids using an auxiliary set of structured grids
Energy Technology Data Exchange (ETDEWEB)
Douglas, C.C.; Malhotra, S.; Schultz, M.H. [Yale Univ., New Haven, CT (United States)
1996-12-31
Unstructured grids do not have a convenient and natural multigrid framework for actually computing and maintaining a high floating point rate on standard computers. In fact, just the coarsening process is expensive for many applications. Since unstructured grids play a vital role in many scientific computing applications, many modifications have been proposed to solve this problem. One suggested solution is to map the original unstructured grid onto a structured grid. This can be used as a fine grid in a standard multigrid algorithm to precondition the original problem on the unstructured grid. We show that unless extreme care is taken, this mapping can lead to a system with a high condition number which eliminates the usefulness of the multigrid method. Theorems with lower and upper bounds are provided. Simple examples show that the upper bounds are sharp.
Learning the Structure of Biomedical Relationships from Unstructured Text.
Directory of Open Access Journals (Sweden)
Bethany Percha
2015-07-01
Full Text Available The published biomedical research literature encompasses most of our understanding of how drugs interact with gene products to produce physiological responses (phenotypes. Unfortunately, this information is distributed throughout the unstructured text of over 23 million articles. The creation of structured resources that catalog the relationships between drugs and genes would accelerate the translation of basic molecular knowledge into discoveries of genomic biomarkers for drug response and prediction of unexpected drug-drug interactions. Extracting these relationships from natural language sentences on such a large scale, however, requires text mining algorithms that can recognize when different-looking statements are expressing similar ideas. Here we describe a novel algorithm, Ensemble Biclustering for Classification (EBC, that learns the structure of biomedical relationships automatically from text, overcoming differences in word choice and sentence structure. We validate EBC's performance against manually-curated sets of (1 pharmacogenomic relationships from PharmGKB and (2 drug-target relationships from DrugBank, and use it to discover new drug-gene relationships for both knowledge bases. We then apply EBC to map the complete universe of drug-gene relationships based on their descriptions in Medline, revealing unexpected structure that challenges current notions about how these relationships are expressed in text. For instance, we learn that newer experimental findings are described in consistently different ways than established knowledge, and that seemingly pure classes of relationships can exhibit interesting chimeric structure. The EBC algorithm is flexible and adaptable to a wide range of problems in biomedical text mining.
Learning the Structure of Biomedical Relationships from Unstructured Text.
Percha, Bethany; Altman, Russ B
2015-07-01
The published biomedical research literature encompasses most of our understanding of how drugs interact with gene products to produce physiological responses (phenotypes). Unfortunately, this information is distributed throughout the unstructured text of over 23 million articles. The creation of structured resources that catalog the relationships between drugs and genes would accelerate the translation of basic molecular knowledge into discoveries of genomic biomarkers for drug response and prediction of unexpected drug-drug interactions. Extracting these relationships from natural language sentences on such a large scale, however, requires text mining algorithms that can recognize when different-looking statements are expressing similar ideas. Here we describe a novel algorithm, Ensemble Biclustering for Classification (EBC), that learns the structure of biomedical relationships automatically from text, overcoming differences in word choice and sentence structure. We validate EBC's performance against manually-curated sets of (1) pharmacogenomic relationships from PharmGKB and (2) drug-target relationships from DrugBank, and use it to discover new drug-gene relationships for both knowledge bases. We then apply EBC to map the complete universe of drug-gene relationships based on their descriptions in Medline, revealing unexpected structure that challenges current notions about how these relationships are expressed in text. For instance, we learn that newer experimental findings are described in consistently different ways than established knowledge, and that seemingly pure classes of relationships can exhibit interesting chimeric structure. The EBC algorithm is flexible and adaptable to a wide range of problems in biomedical text mining. PMID:26219079
New unstructured discretizations for fluid flows with augmented incompressibility
International Nuclear Information System (INIS)
In this research thesis belonging to the field of numerical analysis, the author addresses the discretization of Stokes and Navier-Stokes equations which are used to model incompressible flows on two- and three-dimensional unstructured grids by using a finite volume element method. The author presents the physical and mathematical modelling (Stokes and Navier-Stokes equations, theoretical framework for mathematical analysis). He addresses the discretization of Stokes equations and presents the finite volume element method which uses the finite element used in the Priceles code. Some drawbacks of this element are outlined and improvements are then proposed, first within the finite element framework, and then within the finite volume element framework. The new element is theoretically analysed and convergence results are given. As some problems remained, the discretization is slightly modified and gives good results. Then, the author addresses the discretization of Navier Stokes equations. Attention is paid to diffusion terms and convection terms. Neumann boundary conditions are taken into account. The results of three different calculations are presented and analysed
Constructing Social Networks from Unstructured Group Dialog in Virtual Worlds
Shah, Fahad; Sukthankar, Gita
Virtual worlds and massively multi-player online games are rich sources of information about large-scale teams and groups, offering the tantalizing possibility of harvesting data about group formation, social networks, and network evolution. However these environments lack many of the cues that facilitate natural language processing in other conversational settings and different types of social media. Public chat data often features players who speak simultaneously, use jargon and emoticons, and only erratically adhere to conversational norms. In this paper, we present techniques for inferring the existence of social links from unstructured conversational data collected from groups of participants in the Second Life virtual world. We present an algorithm for addressing this problem, Shallow Semantic Temporal Overlap (SSTO), that combines temporal and language information to create directional links between participants, and a second approach that relies on temporal overlap alone to create undirected links between participants. Relying on temporal overlap is noisy, resulting in a low precision and networks with many extraneous links. In this paper, we demonstrate that we can ameliorate this problem by using network modularity optimization to perform community detection in the noisy networks and severing cross-community links. Although using the content of the communications still results in the best performance, community detection is effective as a noise reduction technique for eliminating the extra links created by temporal overlap alone.
An unstructured second-order Godunov method for transverse MHD
International Nuclear Information System (INIS)
The Godunov method and its higher-order extensions have been very successful in treating flows with shock waves in gas dynamics. These algorithms for the inviscid Euler equations are based on exact local solutions to the Riemann problem. They have the desirable properties of being able to describe shock waves and contact discontinuities with a width of only a few mesh points, while preserving monotonicity in the physical variables (i.e., they are non-oscillatory). The authors have extended the Godunov method to the MHD equations, in order to simulate plasmas with small viscosity and resistivity. In the case of the transverse MHD model (a 2D system in which all quantities vary in the x-y plane, with a magnetic field transverse to the flow, i.e., B = Bz(x,y)z, with flow velocity v = vx(x,y)x + vy(x,y)y), the Riemann problem can be solved exactly. They have developed a 2D code which uses unstructured adaptive triangular meshes, and which is based on a magnetic Riemann solver. This code is particularly suited to modeling realistic geometries. They describe applications of this code to implosive plasma phenomena, including plasma pinches. 4 refs
Information Extraction from Unstructured Text for the Biodefense Knowledge Center
Energy Technology Data Exchange (ETDEWEB)
Samatova, N F; Park, B; Krishnamurthy, R; Munavalli, R; Symons, C; Buttler, D J; Cottom, T; Critchlow, T J; Slezak, T
2005-04-29
The Bio-Encyclopedia at the Biodefense Knowledge Center (BKC) is being constructed to allow an early detection of emerging biological threats to homeland security. It requires highly structured information extracted from variety of data sources. However, the quantity of new and vital information available from every day sources cannot be assimilated by hand, and therefore reliable high-throughput information extraction techniques are much anticipated. In support of the BKC, Lawrence Livermore National Laboratory and Oak Ridge National Laboratory, together with the University of Utah, are developing an information extraction system built around the bioterrorism domain. This paper reports two important pieces of our effort integrated in the system: key phrase extraction and semantic tagging. Whereas two key phrase extraction technologies developed during the course of project help identify relevant texts, our state-of-the-art semantic tagging system can pinpoint phrases related to emerging biological threats. Also we are enhancing and tailoring the Bio-Encyclopedia by augmenting semantic dictionaries and extracting details of important events, such as suspected disease outbreaks. Some of these technologies have already been applied to large corpora of free text sources vital to the BKC mission, including ProMED-mail, PubMed abstracts, and the DHS's Information Analysis and Infrastructure Protection (IAIP) news clippings. In order to address the challenges involved in incorporating such large amounts of unstructured text, the overall system is focused on precise extraction of the most relevant information for inclusion in the BKC.
Wang, Longhao
2012-01-01
Starting from multiple frequency domain measurements, this paper presents a procedure to formulate a dynamic model of a servo actuator that consists of a nominal model and an allowable model perturbation in the form of a parametric and unstructured uncertainty. A separation between parametric and unstructured uncertainty is achieved by first estimating low order linear parameter models via frequency domain curve fitting followed by a linear Principle Component Analysis (PCA) to bound the para...
Yan, Bo; Li, Yuguo; Liu, Ying
2016-07-01
In this paper, we present an adaptive finite element (FE) algorithm for direct current (DC) resistivity modeling in 2-D generally anisotropic conductivity structures. Our algorithm is implemented on an unstructured triangular mesh that readily accommodates complex structures such as topography and dipping layers and so on. We implement a self-adaptive, goal-oriented grid refinement algorithm in which the finite element analysis is performed on a sequence of refined grids. The grid refinement process is guided by an a posteriori error estimator. The problem is formulated in terms of total potentials where mixed boundary conditions are incorporated. This type of boundary condition is superior to the Dirichlet type of conditions and improves numerical accuracy considerably according to model calculations. We have verified the adaptive finite element algorithm using a two-layered earth with azimuthal anisotropy. The FE algorithm with incorporation of mixed boundary conditions achieves high accuracy. The relative error between the numerical and analytical solutions is less than 1% except in the vicinity of the current source location, where the relative error is up to 2.4%. A 2-D anisotropic model is used to demonstrate the effects of anisotropy upon the apparent resistivity in DC soundings.
A new algorithm for anisotropic solutions
Indian Academy of Sciences (India)
M Chaisi; S D Maharaj
2006-02-01
We establish a new algorithm that generates a new solution to the Einstein field equations, with an anisotropic matter distribution, from a seed isotropic solution. The new solution is expressed in terms of integrals of an isotropic gravitational potential; and the integration can be completed exactly for particular isotropic seed metrics. A good feature of our approach is that the anisotropic solutions necessarily have an isotropic limit. We find two examples of anisotropic solutions which generalise the isothermal sphere and the Schwarzschild interior sphere. Both examples are expressed in closed form involving elementary functions only.
Anisotropic surface tension of buckled fluid membrane
Noguchi, Hiroshi
2011-01-01
Solid sheets and fluid membranes exhibit buckling under lateral compression. Here, it is revealed that fluid membranes have anisotropic buckling surface tension contrary to solid sheets. Surprisingly, the surface tension perpendicular to the buckling direction shows stronger dependence than that parallel to it. Our theoretical predictions are supported by numerical simulations of a meshless membrane model. This anisotropic tension can be used to measure the membrane bending rigidity. It is al...
Theory of Compton scattering by anisotropic electrons
Poutanen, Juri; Vurm, Indrek
2010-01-01
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, and relativistic jets, clusters of galaxies as well as the early Universe. In most of the calculations it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or anisotropic cooling by synchrotron radiation, or anisotropic source of seed so...
Anisotropic rectangular metric for polygonal surface remeshing
Pellenard, Bertrand
2013-06-18
We propose a new method for anisotropic polygonal surface remeshing. Our algorithm takes as input a surface triangle mesh. An anisotropic rectangular metric, defined at each triangle facet of the input mesh, is derived from both a user-specified normal-based tolerance error and the requirement to favor rectangle-shaped polygons. Our algorithm uses a greedy optimization procedure that adds, deletes and relocates generators so as to match two criteria related to partitioning and conformity.
Rainbow metric from quantum gravity: anisotropic cosmology
Assanioussi, Mehdi; Dapor, Andrea
2016-01-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformatio...
Anisotropic cosmological solutions in massive vector theories
Heisenberg, Lavinia; Kase, Ryotaro; Tsujikawa, Shinji
2016-01-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component $v$ of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between...
Anisotropic Transport Properties of Complex Metallic Alloys
Smontara, Ana; Dolinšek, Janez
2010-01-01
Anisotropic transport properties (electrical resistivity, ρ, and thermal conductivity, κ) of the Y-phase Al-Ni-Co, o-Al13Co4 and Al4(Cr,Fe) complex metallic alloys were investigated. They belong to the class of decagonal approximant phases with stacked-layer crystallographic structure and allowed us to study the evolution of anisotropic transport properties with increasing structural complexity and the unit cell size.
Anisotropic Stars: Exact Solutions and Stability
Dev, Krsna; Gleiser, Marcelo
2004-01-01
I report on recent work concerning the existence and stability of self-gravitating spheres with anisotropic pressure. After presenting new exact solutions, Chandrasekhar's variational formalism for radial perturbations is generalized to anisotropic objects and applied to investigate their stability. It is shown that anisotropy can not only support stars of mass M and radius R with 2M/R > 8/9 and arbitrarily large surface redshifts, but that stable configurations exist for values of the adiaba...
PDF modeling of turbulent flows on unstructured grids
Bakosi, Jozsef
In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. Because the technique solves a transport equation for the PDF of the velocity and scalars, a mathematically exact treatment of advection, viscous effects and arbitrarily complex chemical reactions is possible; these processes are treated without closure assumptions. A set of algorithms is proposed to provide an efficient solution of the PDF transport equation modeling the joint PDF of turbulent velocity, frequency and concentration of a passive scalar in geometrically complex configurations. An unstructured Eulerian grid is employed to extract Eulerian statistics, to solve for quantities represented at fixed locations of the domain and to track particles. All three aspects regarding the grid make use of the finite element method. Compared to hybrid methods, the current methodology is stand-alone, therefore it is consistent both numerically and at the level of turbulence closure without the use of consistency conditions. Since both the turbulent velocity and scalar concentration fields are represented in a stochastic way, the method allows for a direct and close interaction between these fields, which is beneficial in computing accurate scalar statistics. Boundary conditions implemented along solid bodies are of the free-slip and no-slip type without the need for ghost elements. Boundary layers at no-slip boundaries are either fully resolved down to the viscous sublayer, explicitly modeling the high anisotropy and inhomogeneity of the low-Reynolds-number wall region without damping or wall-functions or specified via logarithmic wall-functions. As in moment closures and large eddy simulation, these wall-treatments provide the usual trade-off between resolution and computational cost as required by the given application. Particular attention is focused on
Anisotropic diffusion-limited aggregation.
Popescu, M N; Hentschel, H G E; Family, F
2004-06-01
Using stochastic conformal mappings, we study the effects of anisotropic perturbations on diffusion-limited aggregation (DLA) in two dimensions. The harmonic measure of the growth probability for DLA can be conformally mapped onto a constant measure on a unit circle. Here we map m preferred directions for growth to a distribution on the unit circle, which is a periodic function with m peaks in [-pi,pi) such that the angular width sigma of the peak defines the "strength" of anisotropy kappa= sigma(-1) along any of the m chosen directions. The two parameters (m,kappa) map out a parameter space of perturbations that allows a continuous transition from DLA (for small enough kappa ) to m needlelike fingers as kappa--> infinity. We show that at fixed m the effective fractal dimension of the clusters D(m,kappa) obtained from mass-radius scaling decreases with increasing kappa from D(DLA) approximately 1.71 to a value bounded from below by D(min) = 3 / 2. Scaling arguments suggest a specific form for the dependence of the fractal dimension D(m,kappa) on kappa for large kappa which compares favorably with numerical results. PMID:15244564
Simulation of all-scale atmospheric dynamics on unstructured meshes
Smolarkiewicz, Piotr K.; Szmelter, Joanna; Xiao, Feng
2016-10-01
The advance of massively parallel computing in the nineteen nineties and beyond encouraged finer grid intervals in numerical weather-prediction models. This has improved resolution of weather systems and enhanced the accuracy of forecasts, while setting the trend for development of unified all-scale atmospheric models. This paper first outlines the historical background to a wide range of numerical methods advanced in the process. Next, the trend is illustrated with a technical review of a versatile nonoscillatory forward-in-time finite-volume (NFTFV) approach, proven effective in simulations of atmospheric flows from small-scale dynamics to global circulations and climate. The outlined approach exploits the synergy of two specific ingredients: the MPDATA methods for the simulation of fluid flows based on the sign-preserving properties of upstream differencing; and the flexible finite-volume median-dual unstructured-mesh discretisation of the spatial differential operators comprising PDEs of atmospheric dynamics. The paper consolidates the concepts leading to a family of generalised nonhydrostatic NFTFV flow solvers that include soundproof PDEs of incompressible Boussinesq, anelastic and pseudo-incompressible systems, common in large-eddy simulation of small- and meso-scale dynamics, as well as all-scale compressible Euler equations. Such a framework naturally extends predictive skills of large-eddy simulation to the global atmosphere, providing a bottom-up alternative to the reverse approach pursued in the weather-prediction models. Theoretical considerations are substantiated by calculations attesting to the versatility and efficacy of the NFTFV approach. Some prospective developments are also discussed.
Anisotropic pressure and hyperons in neutron stars
Sulaksono, A
2014-01-01
We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.
Verification of Unstructured Mesh Capabilities in MCNP6 for Reactor Physics Problems
Energy Technology Data Exchange (ETDEWEB)
Burke, Timothy P. [Los Alamos National Laboratory; Martz, Roger L. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory
2012-08-22
New unstructured mesh capabilities in MCNP6 (developmental version during summer 2012) show potential for conducting multi-physics analyses by coupling MCNP to a finite element solver such as Abaqus/CAE[2]. Before these new capabilities can be utilized, the ability of MCNP to accurately estimate eigenvalues and pin powers using an unstructured mesh must first be verified. Previous work to verify the unstructured mesh capabilities in MCNP was accomplished using the Godiva sphere [1], and this work attempts to build on that. To accomplish this, a criticality benchmark and a fuel assembly benchmark were used for calculations in MCNP using both the Constructive Solid Geometry (CSG) native to MCNP and the unstructured mesh geometry generated using Abaqus/CAE. The Big Ten criticality benchmark [3] was modeled due to its geometry being similar to that of a reactor fuel pin. The C5G7 3-D Mixed Oxide (MOX) Fuel Assembly Benchmark [4] was modeled to test the unstructured mesh capabilities on a reactor-type problem.
ETL Design of Unstructured Data%非结构化数据的ETL设计
Institute of Scientific and Technical Information of China (English)
曹金山; 张泽滨
2011-01-01
为了实现非结构化数据的ETL处理,分析了数据整合的发展现状和业务需求,描述了目前国际流行的公共仓库元模型(CWM)以及在ETL实现中的作用,详细分析了结构化数据和非结构化数据的不同特点.针对两种数据的差异,提出了解决非结构化数据的属性提取和数据打包的方法,为非结构化数据形成元数据奠定了基础,从而实现了非结构化数据的ETL设计,设计完全满足标准的数据整合要求.%In order to realize ETL processing of unstructured data, the current situation and demands of data integration are analyzed. The popular CWM model and its application in ETL are described. The different features between structured dato and unstructured data are analized to get the property of unstructured data. This work provides a foundation for meta-data of unstructured data, and meets the demands of unstructured data ETL and data integration.
Placidi, Luca; Seddik, Hakime; Faria, Sergio H
2009-01-01
A complete theoretical presentation of the CAFFE model (Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor) is given. The CAFFE model is an application of the theory of mixtures with continuous diversity for the case of large ice masses in which the induced anisotropy can not be neglected. The anisotropic response of the material is considered via a simple anisotropic generalization of Glen's flow law based on a scalar anisotropic enhancement factor. Such an enhancement factor depends upon the orientation mass density, that corresponds to the distribution of lattice orientations or simply to the orientation distribution function. The evolution of anisotropy is assumed to be modeled by the evolution of the orientation mass density, that is governed by the balance of mass of the present mixture with continuous diversity and explicitly depends upon four distinct effects interpreted, respectively, with grain rotation, local rigid body rotation, grain boundary migration (...
Extension of ALE methodology to unstructured conical meshes
Directory of Open Access Journals (Sweden)
Hoch Philippe
2011-11-01
Full Text Available We propose a bi-dimensional finite volume extension of a continuous ALE method on unstructured cells whose edges are parameterized by rational quadratic Bezier curves. For each edge, the control point possess a weight that permits to represent any conic (see for example [LIGACH] and thanks to [WAGUSEDE,WAGU], we are able to compute the exact area of our cells. We then give an extension of scheme for remapping step based on volume fluxing [MARSHA] and self-intersection flux [ALE2DHAL]. For the rezoning phase, we propose a three step process based on moving nodes, followed by control point and weight re-adjustment. Finally, for the hydrodynamic step, we present the GLACE scheme [GLACE] extension (at first-order on conic cell using the same formalism. We only propose some preliminary first-order simulations for each steps: Remap, Pure Lagrangian and finally ALE (rezoning and remapping. Nous proposons une extension volumes finis bi-dimensionnelle d’une méthode ALE continue sur des cellules non structurées dont les bords sont paramétrés par des courbes de Bézier quadratiques rationnelles. Pour chaque arête, le point de contrôle possède un poids qui permet de représenter n’importe quelle conique [LIGACH] et grâce à [WAGUSEDE,WAGU], nous pouvons calculer l’aire exacte de nos cellules. Pour la phase de remapping, on donne l’extension de deux schéma, l’un basé sur le calcul de flux de volumes [MARSHA] et l’autre par flux avec auto-intersection [ALE2DHAL]. Pour la phase de lissage de maillage, nous proposons un processus en trois étapes basées sur le déplacement des noeuds, suivi de celui des points de contrôle puis finalement du rajustement du poids. Enfin, pour la phase hydrodynamique, on présente l’extension du schéma GLACE [GLACE] (à l’ordre un sur les cellules coniques en utilisant le même formalisme. Nous montrons seulement des simulations préliminairesl’ordre 1 sur chaque tape : Remap, Lagrange pur et ALE
Document Exploration and Automatic Knowledge Extraction for Unstructured Biomedical Text
Chu, S.; Totaro, G.; Doshi, N.; Thapar, S.; Mattmann, C. A.; Ramirez, P.
2015-12-01
We describe our work on building a web-browser based document reader with built-in exploration tool and automatic concept extraction of medical entities for biomedical text. Vast amounts of biomedical information are offered in unstructured text form through scientific publications and R&D reports. Utilizing text mining can help us to mine information and extract relevant knowledge from a plethora of biomedical text. The ability to employ such technologies to aid researchers in coping with information overload is greatly desirable. In recent years, there has been an increased interest in automatic biomedical concept extraction [1, 2] and intelligent PDF reader tools with the ability to search on content and find related articles [3]. Such reader tools are typically desktop applications and are limited to specific platforms. Our goal is to provide researchers with a simple tool to aid them in finding, reading, and exploring documents. Thus, we propose a web-based document explorer, which we called Shangri-Docs, which combines a document reader with automatic concept extraction and highlighting of relevant terms. Shangri-Docsalso provides the ability to evaluate a wide variety of document formats (e.g. PDF, Words, PPT, text, etc.) and to exploit the linked nature of the Web and personal content by performing searches on content from public sites (e.g. Wikipedia, PubMed) and private cataloged databases simultaneously. Shangri-Docsutilizes Apache cTAKES (clinical Text Analysis and Knowledge Extraction System) [4] and Unified Medical Language System (UMLS) to automatically identify and highlight terms and concepts, such as specific symptoms, diseases, drugs, and anatomical sites, mentioned in the text. cTAKES was originally designed specially to extract information from clinical medical records. Our investigation leads us to extend the automatic knowledge extraction process of cTAKES for biomedical research domain by improving the ontology guided information extraction
Estimating abundance of mountain lions from unstructured spatial sampling
Russell, Robin E.; Royle, J. Andrew; Desimone, Richard; Schwartz, Michael K.; Edwards, Victoria L.; Pilgrim, Kristy P.; Mckelvey, Kevin S.
2012-01-01
distance x sex on detection probability). These numbers translate to a total estimate of 293 mountain lions (95% Cl 182–451) to 529 (95% Cl 245–870) within the Blackfoot drainage. Results from the distance model are similar to previous estimates of 3.6 mountain lions/100 km2 for the study area; however, results from all other models indicated greater numbers of mountain lions. Our results indicate that unstructured spatial sampling combined with spatial capture–recapture analysis can be an effective method for estimating large carnivore densities.
Institute of Scientific and Technical Information of China (English)
Jayantha Pasdunkorale A.; Ian W. Turner
2005-01-01
An unstructured mesh finite volume discretisation method for simulating diffusion in anisotropic media in two-dimensional space is discussed. This technique is considered as an extension of the fully implicit hybrid control-volume finite-element method and it retains the local continuity of the flux at the control volume faces. A least squares function reconstruction technique together with a new flux decomposition strategy is used to obtain an accurate flux approximation at the control volume face, ensuring that the overall accuracy of the spatial discretisation maintains second order. This paper highlights that the new technique coincides with the traditional shape function technique when the correction term is neglected and that it significantly increases the accuracy of the previous linear scheme on coarse meshes when applied to media that exhibit very strong to extreme anisotropy ratios. It is concluded that the method can be used on both regular and irregular meshes,and appears independent of the mesh quality.
Anisotropic thermal conductivity of magnetic fluids
Institute of Scientific and Technical Information of China (English)
Xiaopeng Fang; Yimin Xuan; Qiang Li
2009-01-01
Considering the forces acting on the particles and the motion of the particles, this study uses a numerical simulation to investigate the three-dimensional microstructure of the magnetic fluids in the presence of an external magnetic field. A method is proposed for predicting the anisotropic thermal conductivity of magnetic fluids. By introducing an anisotropic structure parameter which characterizes the non-uniform distribution of particles suspended in the magnetic fluids, the traditional Maxwell formula is modified and extended to calculate anisotropic thermal conductivity of the magnetic fluids. The results show that in the presence of an external magnetic field the magnetic nanoparticles form chainlike clusters along the direction of the external magnetic field, which leads to the fact that the thermal conduc-tivity of the magnetic fluid along the chain direction is bigger than that along other directions. The thermal conductivity of the magnetic fluids presents an anisotropic feature. With the increase of the magnetic field strength the chainlike clusters in the magnetic fluid appear to be more obvious, so that the anisotropic feature of heat conduction in the fluids becomes more evident.
Effective medium theory for anisotropic metamaterials
Zhang, Xiujuan
2015-01-20
Materials with anisotropic material parameters can be utilized to fabricate many fascinating devices, such as hyperlenses, metasolids, and one-way waveguides. In this study, we analyze the effects of geometric anisotropy on a two-dimensional metamaterial composed of a rectangular array of elliptic cylinders and derive an effective medium theory for such a metamaterial. We find that it is possible to obtain a closed-form analytical solution for the anisotropic effective medium parameters, provided the aspect ratio of the lattice and the eccentricity of the elliptic cylinder satisfy certain conditions. The derived effective medium theory not only recovers the well-known Maxwell-Garnett results in the quasi-static regime, but is also valid beyond the long-wavelength limit, where the wavelength in the host medium is comparable to the size of the lattice so that previous anisotropic effective medium theories fail. Such an advance greatly broadens the applicable realm of the effective medium theory and introduces many possibilities in the design of structures with desired anisotropic material characteristics. A real sample of a recently theoretically proposed anisotropic medium, with a near-zero index to control the flux, is achieved using the derived effective medium theory, and control of the electromagnetic waves in the sample is clearly demonstrated.
Anisotropic matching principle for the hydrodynamic expansion
Tinti, Leonardo
2016-10-01
Following the recent success of anisotropic hydrodynamics, I propose here a new, general prescription for the hydrodynamic expansion around an anisotropic background. The anisotropic distribution fixes exactly the complete energy-momentum tensor, just like the effective temperature fixes the proper energy density in the ordinary expansion around local equilibrium. This means that momentum anisotropies are already included at the leading order, allowing for large pressure anisotropies without the need of a next-to-leading-order treatment. The first moment of the Boltzmann equation (local four-momentum conservation) provides the time evolution of the proper energy density and the four-velocity. Differently from previous prescriptions, the dynamic equations for the pressure corrections are not derived from the zeroth or second moment of the Boltzmann equation, but they are taken directly from the exact evolution given by the Boltzmann equation. As known in the literature, the exact evolution of the pressure corrections involves higher moments of the Boltzmann distribution, which cannot be fixed by the anisotropic distribution alone. Neglecting the next-to-leading-order contributions corresponds to an approximation, which depends on the chosen form of the anisotropic distribution. I check the the effectiveness of the leading-order expansion around the generalized Romatschke-Stricklad distribution, comparing with the exact solution of the Boltzmann equation in the Bjorken limit with the collisional kernel treated in the relaxation-time approximation, finding an unprecedented agreement.
General Expression of Elastic Tensor for Anisotropic Materials
Institute of Scientific and Technical Information of China (English)
HUANG Bo
2005-01-01
In order to formulate a general expression of elastic tensor for anisotropic materials, a method of tensor derivative is used for determining relationship between fourth-order elastic tensor and second-order structure tensor that has satisfied material symmetrical conditions. From this general expression of elastic tensor, specific expressions of elastic tensor for different anisotropic materials, such as isotropic materials, transverse isotropic materials and orthogonal-anisotropic materials, can be deduced. This expression underlies the scalar description of anisotropic factors, which are used for classifying and analyzing anisotropic materials. Cubic crystals are analyzed macroscopically by means of the general expression and anisotropic factor.
Clustering Unstructured Data (Flat Files) - An Implementation in Text Mining Tool
Safeer, Yasir; Ali, Anis Noor
2010-01-01
With the advancement of technology and reduced storage costs, individuals and organizations are tending towards the usage of electronic media for storing textual information and documents. It is time consuming for readers to retrieve relevant information from unstructured document collection. It is easier and less time consuming to find documents from a large collection when the collection is ordered or classified by group or category. The problem of finding best such grouping is still there. This paper discusses the implementation of k-Means clustering algorithm for clustering unstructured text documents that we implemented, beginning with the representation of unstructured text and reaching the resulting set of clusters. Based on the analysis of resulting clusters for a sample set of documents, we have also proposed a technique to represent documents that can further improve the clustering result.
An unstructured grid, three-dimensional model based on the shallow water equations
Casulli, V.; Walters, R.A.
2000-01-01
A semi-implicit finite difference model based on the three-dimensional shallow water equations is modified to use unstructured grids. There are obvious advantages in using unstructured grids in problems with a complicated geometry. In this development, the concept of unstructured orthogonal grids is introduced and applied to this model. The governing differential equations are discretized by means of a semi-implicit algorithm that is robust, stable and very efficient. The resulting model is relatively simple, conserves mass, can fit complicated boundaries and yet is sufficiently flexible to permit local mesh refinements in areas of interest. Moreover, the simulation of the flooding and drying is included in a natural and straightforward manner. These features are illustrated by a test case for studies of convergence rates and by examples of flooding on a river plain and flow in a shallow estuary. Copyright ?? 2000 John Wiley & Sons, Ltd.
Institute of Scientific and Technical Information of China (English)
WU Hongchun; LIU Pingping; ZHOU Yongqiang; CAO Liangzhi
2007-01-01
The fuel assembly or core with unstructured geometry is frequently used in the advanced reactor. To calculate the fuel assembly, the transmission probability method (TPM) is widely used. However, the rectangular or hexagonal meshes are mainly used in the TPM codes for the normal core structure. The triangle meshes are most useful for expressing the complicated unstructured geometry. Even though the finite element method and Monte-Carlo methodare well suited for solving the unstructured geometry problem, they are very time-consuming. Therefore, a TPM code based on the triangle meshes is developed here. This code was applied to the hybrid fuel geometry, and compared with the results of the MCNP code and other codes. The results of the comparison were consistent with each other. The TPM with triangle meshes can thus be applied to the two-dimensional arbitrary fuel assembly.
Theory of Compton scattering by anisotropic electrons
Poutanen, Juri
2010-01-01
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, and relativistic jets, clusters of galaxies as well as the early Universe. In most of the calculations it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or anisotropic cooling by synchrotron radiation, or anisotropic source of seed soft photons. We develop here an analytical theory of Compton scattering by anisotropic distribution of electrons that can simplify significantly the calculations. Assuming that the electron angular distribution can be represented by a second order polynomial over cosine of some angle (dipole and quadrupole anisotropy), we integrate the exact Klein-Nishina cross-section over the angles. Exact analytical and approximate formulae valid for any photon and electron energies are derived for the redistribution functions describin...
Micromechanics and dislocation theory in anisotropic elasticity
Lazar, Markus
2016-01-01
In this work, dislocation master-equations valid for anisotropic materials are derived in terms of kernel functions using the framework of micromechanics. The second derivative of the anisotropic Green tensor is calculated in the sense of generalized functions and decomposed into a sum of a $1/R^3$-term plus a Dirac $\\delta$-term. The first term is the so-called "Barnett-term" and the latter is important for the definition of the Green tensor as fundamental solution of the Navier equation. In addition, all dislocation master-equations are specified for Somigliana dislocations with application to 3D crack modeling. Also the interior Eshelby tensor for a spherical inclusion in an anisotropic material is derived as line integral over the unit circle.
Anisotropic matching principle for the hydrodynamics expansion
Tinti, Leonardo
2015-01-01
Following the recent success of anisotropic hydrodynamics we propose a new, general prescription for the hydrodynamics expansion around an anisotropic background. The anisotropic distribution is fixing exactly the complete energy-momentum tensor, just like the effective temperature is fixing the proper energy density in the ordinary expansion around local equilibrium. This means that momen- tum anisotropies are already included at the leading order, allowing for large pressure anisotropies without the need of a next to leading order treatment. The first moment of the Boltzmann equation (local four-momentum conservation) provides the time evolution of the proper energy density and the four velocity. Differently from previous prescriptions, the dynamic equations for the pressure corrections are not derived from the zeroth or second moment of the Boltzmann equation, but they are taken directly from the exact evolution given by the Boltzmann equation. We check the effec- tiveness of this new approach by matching ...
Anisotropic pseudopotential for polarized dilute quantum gases
International Nuclear Information System (INIS)
An anisotropic pseudopotential arising in the context of collisions of two particles polarized by an external field is rigorously derived and its properties are investigated. Such a low-energy pseudopotential may be useful in describing collective properties of dilute quantum gases, such as molecules polarized by an electric field or metastable 3P2 atoms polarized by a magnetic field. The pseudopotential is expressed in terms of the reactance (K) matrix and derivatives of the Dirac δ function. In most applications, it may be represented as a sum of a traditional spherically symmetric contact term and an anisotropic part. The former contribution may be parametrized by a generalized scattering length. The anisotropic part of the pseudopotential may be characterized by the off-diagonal scattering length for dipolar interactions and off-diagonal scattering volume for quadrupolar interactions. The two-body matrix element of the pseudopotential in a basis of plane waves is also derived
Obtuse triangle suppression in anisotropic meshes
Sun, Feng
2011-12-01
Anisotropic triangle meshes are used for efficient approximation of surfaces and flow data in finite element analysis, and in these applications it is desirable to have as few obtuse triangles as possible to reduce the discretization error. We present a variational approach to suppressing obtuse triangles in anisotropic meshes. Specifically, we introduce a hexagonal Minkowski metric, which is sensitive to triangle orientation, to give a new formulation of the centroidal Voronoi tessellation (CVT) method. Furthermore, we prove several relevant properties of the CVT method with the newly introduced metric. Experiments show that our algorithm produces anisotropic meshes with much fewer obtuse triangles than using existing methods while maintaining mesh anisotropy. © 2011 Elsevier B.V. All rights reserved.
Quasiparticle anisotropic hydrodynamics for central collisions
Alqahtani, Mubarak; Strickland, Michael
2016-01-01
We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative...
Gravitational stresses in anisotropic rock masses
Amadei, B.; Savage, W.Z.; Swolfs, H.S.
1987-01-01
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.
Adaptive Routing Algorithms in Unstructured Peer-to-Peer (P2P) Systems
Achmad Nizar Hidayanto; Stephane Bressan
2011-01-01
There are a variety of peer-to-peer (P2P) systems for sharing documents currently available. According to their data organization, P2P systems are classified into two categories: structured andunstructured P2P systems. In structured P2P systems, peers are organized according to some mapping techniques, e.g. hashing function. Whereas in unstructured P2P system, peers are connected to each others randomly; resources are not moved to other peers but hosted on site. Unstructured P2P systems offer...
Vemaganti, Gururaja R.; Wieting, Allan R.
1990-01-01
A higher-order streamline upwinding Petrov-Galerkin finite element method is employed for high speed viscous flow analysis using structured and unstructured meshes. For a Mach 8.03 shock interference problem, successive mesh adaptation was performed using an adaptive remeshing method. Results from the finite element algorithm compare well with both experimental data and results from an upwind cell-centered method. Finite element results for a Mach 14.1 flow over a 24 degree compression corner compare well with experimental data and two other numerical algorithms for both structured and unstructured meshes.
Unstructured-grid methods development for unsteady aerodynamic and aeroelastic analyses
Batina, John T.; Lee, Elizabeth M.; Kleb, William L.; Rausch, Russ D.
1992-01-01
The current status of unstructured grid methods developed in the Unsteady Aerodynamics Branch at NASA Langley Research Center is described. These methods are being developed for unsteady aerodynamic and aeroelastic analyses. Flow solvers that have been developed for the solution of unsteady Euler equations are highlighted. The results demonstrate two and three dimensional applications for both steady and unsteady flows. Comparisons are also made with solutions obtained using a structured grid code and with experimental data to determine the accuracy of the unstructured grid methodology. These comparisons show good agreement which thus verifies the accuracy.
Relativistic Solutions of Anisotropic Compact Objects
Paul, Bikash Chandra
2016-01-01
We present a class of new relativistic solutions with anisotropic fluid for compact stars in hydrostatic equilibrium. The interior space-time geometry considered here for compact objects are described by parameters namely, $\\lambda$, $k$, $A$, $R$ and $n$. The values of the geometrical parameters are determined here for obtaining a class of physically viable stellar models. The energy-density, radial pressure and tangential pressure are finite and positive inside the anisotropic stars. Considering some stars of known mass we present stellar models which describe compact astrophysical objects with nuclear density.
Bouncing Anisotropic Universes with Varying Constants
Barrow, John D
2013-01-01
We examine the evolution of a closed, homogeneous and anisotropic cosmology subject to a variation of the fine structure 'constant', \\alpha, within the context of the theory introduced by Bekenstein, Sandvik, Barrow and Magueijo, which generalises Maxwell's equations and general relativity. The variation of \\alpha permits an effective ghost scalar field, whose negative energy density becomes dominant at small length scales, leading to a bouncing cosmology. A thermodynamically motivated coupling which describes energy exchange between the effective ghost field and the radiation field leads to an expanding, isotropizing sequence of bounces. In the absence of entropy production we also find solutions with stable anisotropic oscillations around a static universe.
One-Dimensional Anisotropic Band Gap Structure
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The band gap structure of one-dimensional anisotropic photonic crystal has been studied by means of the transfer matrix formalism. From the analytic expressions and numeric calculations we see some general characteristics of the band gap structure of anisotropic photonic crystals, each band separates into two branches and the two branches react to polarization sensitively. In the practical case of oblique incidence, gaps move towards high frequency when the angle of incidence increases. Under some special conditions, the two branches become degenerate again.
Anisotropic Gold Nanocrystals:. Synthesis and Characterization
Stiufiuc, R.; Toderas, F.; Iosin, M.; Stiufiuc, G.
In this letter we report on successful preparation and characterization of anisotropic gold nanocrystals bio-synthesized by reduction of aqueous chloroaurate ions in pelargonium plant extract. The nanocrystals have been characterized by means of Transmission Electron Microscopy (TEM), UV-VIS absorption spectroscopy and tapping mode atomic force microscopy (TM-AFM). Using these investigation techniques, the successful formation of anisotropic single nanocrystals with the preferential growth direction along the gold (111) plane has been confirmed. The high detail phase images could give us an explanation concerning the growth mechanism of the nanocrystals.
CAVITATION BIFURCATION FOR COMPRESSIBLE ANISOTROPIC HYPERELASTIC MATERIALS
Institute of Scientific and Technical Information of China (English)
ChengChangjun; RenJiusheng
2004-01-01
The effect of material anisotropy on the bifurcation for void tormation in anisotropic compressible hyperelastic materials is examined. Numerical solutions are obtained in an anisotropic sphere, whose material is transversely isotropic in the radial direction. It is shown that the bifurcation may occur either to the right or to the left, depending on the degree of material anisotropy. The deformation and stress contribution in the sphere before cavitation are different from those after cavitation. The stability of solutions is discussed through a comparison of energy.
Anisotropic Stars: Exact Solutions and Stability
Dev, K; Dev, Krsna; Gleiser, Marcelo
2004-01-01
I report on recent work concerning the existence and stability of self-gravitating spheres with anisotropic pressure. After presenting new exact solutions, Chandrasekhar's variational formalism for radial perturbations is generalized to anisotropic objects and applied to investigate their stability. It is shown that anisotropy can not only support stars of mass M and radius R with 2M/R > 8/9 and arbitrarily large surface redshifts, but that stable configurations exist for values of the adiabatic index smaller than the corresponding isotropic value.
Controllable underwater anisotropic oil-wetting
Energy Technology Data Exchange (ETDEWEB)
Yong, Jiale; Chen, Feng, E-mail: chenfeng@mail.xjtu.edu.cn; Yang, Qing; Farooq, Umar; Bian, Hao; Du, Guangqing; Hou, Xun [State Key Laboratory for Manufacturing System Engineering and Key Laboratory of Photonics Technology for Information of Shaanxi Province, School of Electronics and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)
2014-08-18
This Letter demonstrates a simple method to achieve underwater anisotropic oil-wetting using silicon surfaces with a microgroove array produced by femtosecond laser ablation. The oil contact angles along the direction perpendicular to the grooves are consistently larger than those parallel to the microgroove arrays in water because the oil droplet is restricted by the energy barrier that exists between the non-irradiated domain and the trapped water in the laser-ablated microgrooves. This underwater anisotropic oil-wetting is able to be controlled, and the anisotropy can be tuned from 0° to ∼20° by adjusting the period of the microgroove arrays.
Anisotropic nanomaterials preparation, properties, and applications
Li, Quan
2015-01-01
In this book anisotropic one-dimensional and two-dimensional nanoscale building blocks and their assembly into fascinating and qualitatively new functional structures embracing both hard and soft components are explained. Contributions from leading experts regarding important aspects like synthesis, assembly, properties and applications of the above materials are compiled into a reference book. The anisotropy, i.e. the direction-dependent physical properties, of materials is fascinating and elegant and has sparked the quest for anisotropic materials with useful properties. With such a curiosi
Directory of Open Access Journals (Sweden)
José Antonio Martínez García
2009-04-01
Full Text Available ResumenEsta investigación presenta un nuevo método para el estudio de la invarianza de escala que complementa otros métodos existentes, lo que contribuye a realizar un análisis ecléctico y multifocal de un problema importante en la investigación de marketing, y en particular en la investigación de servicios deportivos. Este método está basado en la utilización del cálculo integral y tiene una sencilla interpretación geométrica. Se describen y comparan varios procedimientos para testar la invarianza de escala, y se realiza un re-análisis de la investigación de Martínez y Martínez (2008b sobre la percepción de calidad del consumidor de servicios deportivos. Los resultados muestran cómo existen diferencias sobre las conclusiones originales de estos autores. De este modo, las escalas de siete opciones de respuesta sí son invariantes, mientras que la de cinco opciones no lo son. Finalmente, se discuten las bondades y las limitaciones del método integral, abogando por la triangulación estadística para dar robustez a los resultados empíricos.AbstractThis research introduces a new method to analyse scale invariance, which overcomes some shortcomings of other procedures. Under an eclectic perspective, this method must help to provide insights in the marketing research discipline, and specifically in the sports service management. The method is grounded on the use of definite integrals to compute the area between two functions. In addition, several procedures for testing scale invariance are depicted and compared. An empirical application is achieved by re-analysing the study of Martínez & Martínez (2008b on perceived quality in sports services. Results shows that misleading conclusions were derived from the original study of those authors. Finally, advantages and shortcomings of the new method are discussed.
Albedo and constant source problems for extremely anisotropic scattering
International Nuclear Information System (INIS)
The half-space albedo problem and the constant source problem have been solved for a combination of the linearly anisotropic scattering and Inoenue's scattering functions. The linear transport equation for extremely anisotropic scattering kernel can be converted into an equivalent equation with a linearly anisotropic scattering kernel and the modified FN method can be used for albedo calculations. (orig.)
Anisotropic Diffusion for Medical Image Enhancement
Directory of Open Access Journals (Sweden)
Nezamoddin N. Kachouie
2010-10-01
Full Text Available Advances in digital imaging techniques have made possible the acquisition of large volumes of Transrectal Ultrasound (TRUS prostate images so that there is considerable demand for automated segmentation. Prostate cancer diagnosis and treatment rely on segmentation of these Transrectal Ultrasound (TRUS prostate images, a challenging and difficult task due to weak prostate boundaries, speckle noise and the narrow range of gray levels, leading most image segmentation methods to perform poorly. The enhancement of ultrasound images is challenging, however prostate segmentation can be effectively improved in contrast enhanced images. Anisotropic diffusion has been used for image analysis based on selective smoothness or enhancement of local features such as region boundaries. In its formal form, anisotropic diffusion tends to encourage within-region smoothness and avoid diffusion across different regions. In this paper we extend the anisotropic diffusion to multiple directions such that segmentation methods can effectively be applied based on rich extracted features. A preliminary segmentation method based on extended diffusion is proposed. Finally an adaptive anisotropic diffusion is introduced based on image statistics.
Orphan-Free Anisotropic Voronoi Diagrams
Canas, Guillermo D
2011-01-01
We describe conditions under which an appropriately-defined anisotropic Voronoi diagram of a set of sites in Euclidean space is guaranteed to be composed of connected cells in any number of dimensions. These conditions are natural for problems in optimization and approximation, and algorithms already exist to produce sets of sites that satisfy them.
Anisotropic Power Law Inflation from Rolling Tachyons
Bhowmick, Samrat
2011-01-01
We provide an explicit solution representing an anisotropic power law inflation within the framework of rolling tachyon model. This is generated by allowing a non-minimal coupling between the tachyon and the world-volume gauge field on non-BPS D3 brane.
Nucleation in suspensions of anisotropic colloids
Schilling, T.; Frenkel, D.
2005-01-01
We report Monte Carlo studies of liquid crystal nucleation in two types of anisotropic colloidal systems: hard rods and hard ellipsoids. In both cases we find that nucleation pathways differ strongly from the pathways in systems of spherical particles. Short hard rods show an effect of self-poisonin
Surface instabilities during straining of anisotropic materials
DEFF Research Database (Denmark)
Legarth, Brian Nyvang; Richelsen, Ann Bettina
2006-01-01
The development of instabilities in traction-free surfaces is investigated numerically using a unit cell model. Full finite strain analyses are conducted using isotropic as well as anisotropic yield criteria and both plane strain tension and compression are considered. In the load range of tension...
ANISOTROPIC PARABOLIC EQUATIONS WITH MEASURE DATA
Institute of Scientific and Technical Information of China (English)
Li Fengquan; Zhao Huixiu
2001-01-01
In this paper, we prove the existence of solutions to anisotropic parabolic equations with right hand side term in the bounded Radon measure M(Q) and the initial condition in M(Ω) or in Lm space (with m "small").
A generalized anisotropic deformation formulation for geomaterials
Lei, Z.; Rougier, Esteban; Knight, E. E.; Munjiza, A.; Viswanathan, H.
2016-04-01
In this paper, the combined finite-discrete element method (FDEM) has been applied to analyze the deformation of anisotropic geomaterials. In the most general case geomaterials are both non-homogeneous and non-isotropic. With the aim of addressing anisotropic material problems, improved 2D FDEM formulations have been developed. These formulations feature the unified hypo-hyper elastic approach combined with a multiplicative decomposition-based selective integration for volumetric and shear deformation modes. This approach is significantly different from the co-rotational formulations typically encountered in finite element codes. Unlike the co-rotational formulation, the multiplicative decomposition-based formulation naturally decomposes deformation into translation, rotation, plastic stretches, elastic stretches, volumetric stretches, shear stretches, etc. This approach can be implemented for a whole family of finite elements from solids to shells and membranes. This novel 2D FDEM based material formulation was designed in such a way that the anisotropic properties of the solid can be specified in a cell by cell basis, therefore enabling the user to seed these anisotropic properties following any type of spatial variation, for example, following a curvilinear path. In addition, due to the selective integration, there are no problems with volumetric or shear locking with any type of finite element employed.
Spin Wave Theory of Strongly Anisotropic Magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1977-01-01
A strong anisotropy gives rise to a non-spherical precession of the spins with different amplitudes in the x and y directions. The highly anharmonic exchange interaction thereby becomes effectively anisotropic. The possibility of detecting a genuine two-ion anisotropy is discussed, and comments a...... are given on the interpretation of the spin wave data in Tb and Er....
A discrete anisotropic model for Scheibe aggregates
Directory of Open Access Journals (Sweden)
O. Bang
1991-05-01
Full Text Available A discrete anisotropic nonlinear model for the dynamics of Scheibe aggregates is investigated. The collapse of the collective excitations found by Möbius and Kuhn is described as a shrinking ring wave, which is eventually absorbed by an acceptor molecule. An optimal acceptor loss is found.
Cegarra, J.; van Wezel, Wouter
2012-01-01
In this article, the authors focus on scheduling situations. Because of their unstructured nature and hard combinatorial complexity, scheduling situations have always been a predominant application area for decision support systems (DSSes). After setting out the generic characteristics of a DSS, the
36 CFR 1236.24 - What are the additional requirements for managing unstructured electronic records?
2010-07-01
... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false What are the additional requirements for managing unstructured electronic records? 1236.24 Section 1236.24 Parks, Forests, and Public... Additional Requirements for Electronic Records § 1236.24 What are the additional requirements for...
Laird, Shelby Gull; McFarland-Piazza, Laura; Allen, Sydnye
2014-01-01
Outdoor environmental education and provision of unstructured exploration of nature are often forgotten aspects of the early childhood experience. The aim of this study was to understand how adults' early experiences in nature relate to their attitudes and practices in providing such experiences for young children. This study surveyed 33 parents…
Siennick, Sonja E.; Osgood, D. Wayne
2012-01-01
Companions are central to explanations of the risky nature of unstructured and unsupervised socializing, yet we know little about whom adolescents are with when hanging out. We examine predictors of how often friendship dyads hang out via multilevel analyses of longitudinal friendship-level data on over 5,000 middle schoolers. Adolescents hang out…
Diemer, Roberta A.; And Others
1996-01-01
Twenty-five distressed adult clients received 2 sessions each of dream and event interpretation using the Hill model during 12 sessions of successful therapy. No differences were found in depth, insight, and working alliance among dream interpretation, event interpretation, and unstructured sessions, suggesting that dream interpretation is as…
Modeling dam-break flows using finite volume method on unstructured grid
Two-dimensional shallow water models based on unstructured finite volume method and approximate Riemann solvers for computing the intercell fluxes have drawn growing attention because of their robustness, high adaptivity to complicated geometry and ability to simulate flows with mixed regimes and di...
On the performance of a 2D unstructured computational rheology code on a GPU
Pereira, S.P.; Vuik, K.; Pinho, F.T.; Nobrega, J.M.
2013-01-01
The present work explores the massively parallel capabilities of the most advanced architecture of graphics processing units (GPUs) code named “Fermi”, on a two-dimensional unstructured cell-centred finite volume code. We use the SIMPLE algorithm to solve the continuity and momentum equations that w
Denner, Fabian; van Wachem, Berend G. M.
2015-10-01
Total variation diminishing (TVD) schemes are a widely applied group of monotonicity-preserving advection differencing schemes for partial differential equations in numerical heat transfer and computational fluid dynamics. These schemes are typically designed for one-dimensional problems or multidimensional problems on structured equidistant quadrilateral meshes. Practical applications, however, often involve complex geometries that cannot be represented by Cartesian meshes and, therefore, necessitate the application of unstructured meshes, which require a more sophisticated discretisation to account for their additional topological complexity. In principle, TVD schemes are applicable to unstructured meshes, however, not all the data required for TVD differencing is readily available on unstructured meshes, and the solution suffers from considerable numerical diffusion as a result of mesh skewness. In this article we analyse TVD differencing on unstructured three-dimensional meshes, focusing on the non-linearity of TVD differencing and the extrapolation of the virtual upwind node. Furthermore, we propose a novel monotonicity-preserving correction method for TVD schemes that significantly reduces numerical diffusion caused by mesh skewness. The presented numerical experiments demonstrate the importance of accounting for the non-linearity introduced by TVD differencing and of imposing carefully chosen limits on the extrapolated virtual upwind node, as well as the efficacy of the proposed method to correct mesh skewness.
Institute of Scientific and Technical Information of China (English)
HUA Zu-lin; XING Ling-hang; GU Li
2008-01-01
The modified QUICK scheme on unstructured grid was used to improve the advection flux approximation, and the depth-averaged turbulence model with the scheme based on FVM by SIMPLE series algorithm was established and applied to spur-dike flow computation. In this model, the over-relaxed approach was adopted to estimate the diffusion flux in view of its advantages in reducing errors and sustaining numerical stability usually encountered in non-orthogonal meshes. Two spur-dike cases with different defection angles (90oand 135o) were analyzed to validate the model. Computed results show that the predicted velocities and recirculation lengths are in good agreement with the observed data. Moreover, the computations on structured and unstructured grids were compared in terms of the approximately equivalent grid numbers. It can be concluded that the precision with unstructured grids is higher than that with structured grids in spite that the CPU time required is slightly more with unstructured grids. Thus, it is significant to apply the method to numerical simulation of practical hydraulic engineering.
Biedron, Robert T.; Vatsa, Veer N.; Atkins, Harold L.
2005-01-01
We apply an unsteady Reynolds-averaged Navier-Stokes (URANS) solver for unstructured grids to unsteady flows on moving and stationary grids. Example problems considered are relevant to active flow control and stability and control. Computational results are presented using the Spalart-Allmaras turbulence model and are compared to experimental data. The effect of grid and time-step refinement are examined.
Children's Active Learning through Unstructured Play in Malaysia
Fatai O., Ismail Abdul; Faqih, Asrul; Bustan, Wafa K.
2014-01-01
Play is generally identified as a basic tool for effective learning and development in children. This study explores the ways in which amorphous or unstructured play contributes to children's overall development at the pre-primary level, helping to develop cognitive, social, and motor skills. The findings indicate that through unstructured…
Institute of Scientific and Technical Information of China (English)
Vagif S. GULIYEV; Rza Ch. MUSTAFAYEV
2011-01-01
In this paper we give the conditions on the pair (ω1,ω2) which ensures the boundedness of the anisotropic maximal operator and anisotropic singular integral operators from one generalized Morrey space Mp,ω1 to another Mp,ω2,1 ＜ p ＜ oo,and from the space M1,ω1 to the weak space W M1,ω2.
Vanzo, Davide; Siviglia, Annunziato; Toro, Eleuterio F.
2016-09-01
The purpose of this paper is twofold. First, using the Cattaneo's relaxation approach, we reformulate the system of governing equations for the pollutant transport by shallow water flows over non-flat topography and anisotropic diffusion as hyperbolic balance laws with stiff source terms. The proposed relaxation system circumvents the infinite wave speed paradox which is inherent in standard advection-diffusion models. This turns out to give a larger stability range for the choice of the time step. Second, following a flux splitting approach, we derive a novel numerical method to discretise the resulting problem. In particular, we propose a new flux splitting and study the associated two systems of differential equations, called the "hydrodynamic" and the "relaxed diffusive" system, respectively. For the presented splitting we analyse the resulting two systems of differential equations and propose two discretisation schemes of the Godunov-type. These schemes are simple to implement, robust, accurate and fast when compared with existing methods. The resulting method is implemented on unstructured meshes and is systematically assessed for accuracy, robustness and efficiency on a carefully selected suite of test problems including non-flat topography and wetting and drying problems. Formal second order accuracy is assessed through convergence rates studies.
Views on the Anisotropic Nature of Ilva Valley Region
Directory of Open Access Journals (Sweden)
GABRIELA-ALINA MUREŞAN
2012-01-01
Full Text Available There are two concepts important for the authors of this article: anisotropic region and anisotropic space. Anisotropic region is defined by A. Dauphiné, the geographer (-mathematician, as a territorial unit whose structure results from the organisation of space along one or more axes. From the point of view of a territorial system, this type of region has some characteristics which differentiate it both from the homogeneous region and from the polarised one. These specificities have been analysed for Ilva Valley. The region of Ilva Valley is formed along the morphological axis represented by the Ilva River. The aim is to identify these specificities or their absence within this region. In this way we can determine whether this region is an anisotropic one or just an anisotropic space, namely whether it can be considered as evolving towards an anisotropic region, not yet complying with all characteristics of anisotropic regions.
Silicon as an anisotropic mechanical material
DEFF Research Database (Denmark)
Thomsen, Erik Vilain; Reck, Kasper; Skands, Gustav Erik;
2014-01-01
While silicon is an anisotropic material it is often in literature treated as an isotropic material when it comes to plate calculations. This leads to considerable errors in the calculated deflection. To overcome this problem, we present an in-depth analysis of the bending behavior of thin...... both exact analytical expressions and approximate expressions calculated by the Galerkin method. The results are applied to plates made on silicon (0 0 1), (0 1 1) and (1 1 1) substrates, respectively, and analytical equations for the deflection, strain energy and resonance frequency of such plates...... are presented. These expressions are in excellent agreement with anisotropic finite element calculations. The calculated deflection differs less than 0.1%, for both circular and rectangular plates, compared to finite element calculations. The results are presented as ready-to-use facilitating accurate...
Anisotropic Long-Range Spin Systems
Defenu, Nicolò; Ruffo, Stefano
2016-01-01
We consider anisotropic long-range interacting spin systems in $d$ dimensions. The interaction between the spins decays with the distance as a power law with different exponents in different directions: we consider an exponent $d_{1}+\\sigma_1$ in $d_1$ directions and another exponent $d_{2}+\\sigma_2$ in the remaining $d_2\\equiv d-d_1$ ones. We introduce a low energy effective action with non analytic power of the momenta. As a function of the two exponents $\\sigma_1$ and $\\sigma_2$ we show the system to have three different regimes, two where it is actually anisotropic and one where the isotropy is finally restored. We determine the phase diagram and provide estimates of the critical exponents as a function of the parameters of the system, in particular considering the case of one of the two $\\sigma$'s fixed and the other varying. A discussion of the physical relevance of our results is also presented.
Rainbow metric from quantum gravity: anisotropic cosmology
Assanioussi, Mehdi
2016-01-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter $\\beta$ in the modified dispersion relation of the modes. Hence inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [arXiv:1412.6000], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
New formulation of leading order anisotropic hydrodynamics
Tinti, Leonardo
2014-01-01
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)--dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)--dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, {the new form of anisotropic hydrodynamics leads to better agree...
Anisotropic hydrodynamics for conformal Gubser flow
Strickland, Michael; Ryblewski, Radoslaw
2015-01-01
In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)_q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equa...
Anisotropic brane gravity with a confining potential
Heydari-Fard, M
2007-01-01
We consider an anisotropic brane world with Bianchi type I and V geometries where the mechanism of confining the matter on the brane is through the use of a confining potential. The resulting equations on the anisotropic brane are modified by an extra term that may be interpreted as the x-matter, providing a possible phenomenological explanation for the accelerated expansion of the universe. We obtain the general solution of the field equations in an exact parametric form for both Bianchi type I and V space-times. In the special case of a Bianchi type I the solutions of the field equations are obtained in an exact analytic form. Finally, we study the behavior of the observationally important parameters.
Anisotropic brane gravity with a confining potential
Energy Technology Data Exchange (ETDEWEB)
Heydari-Fard, M. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839 (Iran, Islamic Republic of)]. E-mail: m-heydarifard@sbu.ac.ir; Sepangi, H.R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839 (Iran, Islamic Republic of)]. E-mail: hr-sepangi@sbu.ac.ir
2007-05-24
We consider an anisotropic brane world with Bianchi type I and V geometries where the mechanism of confining the matter on the brane is through the use of a confining potential. The resulting equations on the anisotropic brane are modified by an extra term that may be interpreted as the x-matter, providing a possible phenomenological explanation for the accelerated expansion of the universe. We obtain the general solution of the field equations in an exact parametric form for both Bianchi type I and V space-times. In the special case of a Bianchi type I the solutions of the field equations are obtained in an exact analytic form. Finally, we study the behavior of the observationally important parameters.
Comparing anisotropic displacement parameters in protein structures.
Merritt, E A
1999-12-01
The increasingly widespread use of synchrotron-radiation sources and cryo-preparation of samples in macromolecular crystallography has led to a dramatic increase in the number of macromolecular structures determined at atomic or near-atomic resolution. This permits expansion of the structural model to include anisotropic displacement parameters U(ij) for individual atoms. In order to explore the physical significance of these parameters in protein structures, it is useful to be able to compare quantitatively the electron-density distribution described by the refined U(ij) values associated with corresponding crystallographically independent atoms. This paper presents the derivation of an easily calculated correlation coefficient in real space between two atoms modeled with anisotropic displacement parameters. This measure is used to investigate the degree of similarity between chemically equivalent but crystallographically independent atoms in the set of protein structural models currently available from the Protein Data Bank.
Anisotropic permeability in deterministic lateral displacement arrays
Vernekar, Rohan; Loutherback, Kevin; Morton, Keith; Inglis, David
2016-01-01
We investigate anisotropic permeability of microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of micro-particles, including bioparticles such as cells. Correct operation requires that the fluid flow remains at a fixed angle with respect to the periodic obstacle array. We show via experiments and lattice-Boltzmann simulations that subtle array design features cause anisotropic permeability. The anisotropy, which indicates the array's intrinsic tendency to induce an undesired lateral pressure gradient, can lead to off-axis flows and therefore local changes in the critical separation size. Thus, particle trajectories can become unpredictable and the device useless for the desired separation duty. We show that for circular posts the rotated-square layout, unlike the parallelogram layout, does not suffer from anisotropy and is the preferred geometry. Furthermore, anisotropy becomes severe for arrays with unequal axial and lateral gaps...
Anisotropic fluid from nonlocal tidal effects
Culetu, Hristu
2014-01-01
The Shiromizu et al. \\cite{SMS} covariant decomposition formalism is used to find out the brane properties rooted from the 5-dimensional Witten bubble spacetime. The non-local tensor $E_{ab}$ generated by the 5-dimensional Weyl tensor gives rise at an anisotropic energy-momentum tensor on the brane with negative energy density and $p = \\rho/3$ as equation of state. The tidal acceleration is towards the brane and that is in accordance with the negative energy density on the brane. The anisotropic fluid has vanishing "bulk" viscosity but the shear viscosity coefficient is $r$- and $t$- dependent. The brane is endowed with an apparent horizon which is exactly the radial null geodesic.
Polarimetric characterization of optically anisotropic flexible substrates
Energy Technology Data Exchange (ETDEWEB)
Stchakovsky, M. [HORIBA Jobin-Yvon SAS, Z.A. de la Vigne aux Loups, 5 Avenue Arago, 91380 Chilly-Mazarin (France)], E-mail: michel.stchakovsky@jobinyvon.fr; Caillaud, C. [HORIBA Jobin-Yvon SAS, Z.A. de la Vigne aux Loups, 5 Avenue Arago, 91380 Chilly-Mazarin (France); Foldyna, M.; Ossikovski, R.; Garcia-Caurel, E. [Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, 91128 Palaiseau (France)
2008-02-15
Phase Modulated Spectroscopic Ellipsometry as well as Liquid Crystal Mueller Matrix Polarimetry in reflection and in transmission configurations were used to systematically study five types of anisotropic polymer sheets: polyethylene-terephtalate (PET), polyethylene-naphtalate (PEN), polycarbonate (PC), polypropylene (PP) and triacetylcellulose (TAC). The measurements were performed at different sample azimuths in two ellipsometric configurations giving access to both standard ellipsometric data as well as to the entire Mueller matrix. Biaxial anisotropy, a common characteristic to all polymer types, as well as the in-depth optical properties, inhomogeneity present in the sheets were clearly evidenced. The data were interpreted in terms of a model consisting of a thick substrate (several microns) coated with a simple layer. Both, substrate and layer were anisotropic and characterized by a triplet of principal refractive indexes. The orientation of the principal indexes of the bulk and the layer were different revealing the in-depth inhomogeniety of the samples.
Observation of an Anisotropic Wigner Crystal
Liu, Yang; Hasdemir, S.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.
2016-09-01
We report a new correlated phase of two-dimensional charged carriers in high magnetic fields, manifested by an anisotropic insulating behavior at low temperatures. It appears in a large range of low Landau level fillings 1 /3 ≲ν ≲2 /3 in hole systems confined to wide GaAs quantum wells when the sample is tilted in magnetic field to an intermediate angle. The parallel field component (B∥) leads to a crossing of the lowest two Landau levels, and an elongated hole wave function in the direction of B∥. Under these conditions, the in-plane resistance exhibits an insulating behavior, with the resistance along B∥ about 10 times smaller than the resistance perpendicular to B∥. We interpret this anisotropic insulating phase as a two-component, striped Wigner crystal.
Anomalous anisotropic magnetoresistance effects in graphene
Directory of Open Access Journals (Sweden)
Yiwei Liu
2014-09-01
Full Text Available We investigate the effect of external stimulus (temperature, magnetic field, and gases adsorptions on anisotropic magnetoresistance (AMR in multilayer graphene. The graphene sample shows superlinear magnetoresistance when magnetic field is perpendicular to the plane of graphene. A non-saturated AMR with a value of −33% is found at 10 K under a magnetic field of 7 T. It is surprisingly to observe that a two-fold symmetric AMR at high temperature is changed into a one-fold one at low temperature for a sample with an irregular shape. The anomalous AMR behaviors may be understood by considering the anisotropic scattering of carriers from two asymmetric edges and the boundaries of V+(V- electrodes which serve as active adsorption sites for gas molecules at low temperature. Our results indicate that AMR in graphene can be optimized by tuning the adsorptions, sample shape and electrode distribution in the future application.
Anisotropic silica mesostructures for DNA encapsulation
Indian Academy of Sciences (India)
Aparna Ganguly; Ashok K Ganguli
2013-04-01
The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ∼8 g mg-1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups.
Unstructured Mesh Movement and Viscous Mesh Generation for CFD-Based Design Optimization Project
National Aeronautics and Space Administration — The innovations proposed by ResearchSouth are: 1) a robust method to automatically insert high quality anisotropic prismatic (viscous boundary layer) cells into any...
Rotor Airloads Prediction Using Unstructured Meshes and Loose CFD/CSD Coupling
Biedron, Robert T.; Lee-Rausch, Elizabeth M.
2008-01-01
The FUN3D unsteady Reynolds-averaged Navier-Stokes solver for unstructured grids has been modified to allow prediction of trimmed rotorcraft airloads. The trim of the rotorcraft and the aeroelastic deformation of the rotor blades are accounted for via loose coupling with the CAMRAD II rotorcraft computational structural dynamics code. The set of codes is used to analyze the HART-II Baseline, Minimum Noise and Minimum Vibration test conditions. The loose coupling approach is found to be stable and convergent for the cases considered. Comparison of the resulting airloads and structural deformations with experimentally measured data is presented. The effect of grid resolution and temporal accuracy is examined. Rotorcraft airloads prediction presents a very substantial challenge for Computational Fluid Dynamics (CFD). Not only must the unsteady nature of the flow be accurately modeled, but since most rotorcraft blades are not structurally stiff, an accurate simulation must account for the blade structural dynamics. In addition, trim of the rotorcraft to desired thrust and moment targets depends on both aerodynamic loads and structural deformation, and vice versa. Further, interaction of the fuselage with the rotor flow field can be important, so that relative motion between the blades and the fuselage must be accommodated. Thus a complete simulation requires coupled aerodynamics, structures and trim, with the ability to model geometrically complex configurations. NASA has recently initiated a Subsonic Rotary Wing (SRW) Project under the overall Fundamental Aeronautics Program. Within the context of SRW are efforts aimed at furthering the state of the art of high-fidelity rotorcraft flow simulations, using both structured and unstructured meshes. Structured-mesh solvers have an advantage in computation speed, but even though remarkably complex configurations may be accommodated using the overset grid approach, generation of complex structured-mesh systems can require
Unstructured medical image query using big data - An epilepsy case study.
Istephan, Sarmad; Siadat, Mohammad-Reza
2016-02-01
Big data technologies are critical to the medical field which requires new frameworks to leverage them. Such frameworks would benefit medical experts to test hypotheses by querying huge volumes of unstructured medical data to provide better patient care. The objective of this work is to implement and examine the feasibility of having such a framework to provide efficient querying of unstructured data in unlimited ways. The feasibility study was conducted specifically in the epilepsy field. The proposed framework evaluates a query in two phases. In phase 1, structured data is used to filter the clinical data warehouse. In phase 2, feature extraction modules are executed on the unstructured data in a distributed manner via Hadoop to complete the query. Three modules have been created, volume comparer, surface to volume conversion and average intensity. The framework allows for user-defined modules to be imported to provide unlimited ways to process the unstructured data hence potentially extending the application of this framework beyond epilepsy field. Two types of criteria were used to validate the feasibility of the proposed framework - the ability/accuracy of fulfilling an advanced medical query and the efficiency that Hadoop provides. For the first criterion, the framework executed an advanced medical query that spanned both structured and unstructured data with accurate results. For the second criterion, different architectures were explored to evaluate the performance of various Hadoop configurations and were compared to a traditional Single Server Architecture (SSA). The surface to volume conversion module performed up to 40 times faster than the SSA (using a 20 node Hadoop cluster) and the average intensity module performed up to 85 times faster than the SSA (using a 40 node Hadoop cluster). Furthermore, the 40 node Hadoop cluster executed the average intensity module on 10,000 models in 3h which was not even practical for the SSA. The current study is
Unstructured medical image query using big data - An epilepsy case study.
Istephan, Sarmad; Siadat, Mohammad-Reza
2016-02-01
Big data technologies are critical to the medical field which requires new frameworks to leverage them. Such frameworks would benefit medical experts to test hypotheses by querying huge volumes of unstructured medical data to provide better patient care. The objective of this work is to implement and examine the feasibility of having such a framework to provide efficient querying of unstructured data in unlimited ways. The feasibility study was conducted specifically in the epilepsy field. The proposed framework evaluates a query in two phases. In phase 1, structured data is used to filter the clinical data warehouse. In phase 2, feature extraction modules are executed on the unstructured data in a distributed manner via Hadoop to complete the query. Three modules have been created, volume comparer, surface to volume conversion and average intensity. The framework allows for user-defined modules to be imported to provide unlimited ways to process the unstructured data hence potentially extending the application of this framework beyond epilepsy field. Two types of criteria were used to validate the feasibility of the proposed framework - the ability/accuracy of fulfilling an advanced medical query and the efficiency that Hadoop provides. For the first criterion, the framework executed an advanced medical query that spanned both structured and unstructured data with accurate results. For the second criterion, different architectures were explored to evaluate the performance of various Hadoop configurations and were compared to a traditional Single Server Architecture (SSA). The surface to volume conversion module performed up to 40 times faster than the SSA (using a 20 node Hadoop cluster) and the average intensity module performed up to 85 times faster than the SSA (using a 40 node Hadoop cluster). Furthermore, the 40 node Hadoop cluster executed the average intensity module on 10,000 models in 3h which was not even practical for the SSA. The current study is
Analysis and modeling of scale-invariance in plankton abundance
Pelletier, J D
1996-01-01
The power spectrum, $S$, of horizontal transects of plankton abundance are often observed to have a power-law dependence on wavenumber, $k$, with exponent close to $-2$: $S(k)\\propto k^{-2}$ over a wide range of scales. I present power spectral analyses of aircraft lidar measurements of phytoplankton abundance from scales of 1 to 100 km. A power spectrum $S(k)\\propto k^{-2}$ is obtained. As a model for this observation, I consider a stochastic growth equation where the rate of change of plankton abundance is determined by turbulent mixing, modeled as a diffusion process in two dimensions, and exponential growth with a stochastically variable net growth rate representing a fluctuating environment. The model predicts a lognormal distribution of abundance and a power spectrum of horizontal transects $S(k)\\propto k^{-1.8}$, close to the observed spectrum. The model equation predicts that the power spectrum of variations in abundance in time at a point in space is $S(f)\\propto f^{-1.5}$ (where $f$ is the frequency...
Classically Scale Invariant Inflation, WIMPzilla, and (A)gravity
Farzinnia, Arsham
2015-01-01
We introduce a minimal and yet comprehensive framework with $CP$- and classical scale-symmetries, in order to simultaneously address the hierarchy problem, neutrino masses, dark matter, and inflation. One complex gauge singlet scalar and three flavors of the right-handed Majorana neutrinos are added to the standard model content, facilitating the see-saw mechanism, among others. An adimensional theory of gravity (Agravity) is employed as the UV-completion candidate, allowing for the trans-Planckian field excursions. The electroweak and the Planck scales are induced by the Higgs portal and the scalar non-minimal couplings, respectively, once a Coleman-Weinberg dynamically-generated vacuum expectation value for the singlet scalar is obtained. All scales are free of any mutual quadratic destabilization. The $CP$-symmetry prevents a decay of the pseudoscalar singlet, rendering it a suitable WIMPzilla dark matter candidate with the correct observational relic abundance. Identifying the pseudo-Nambu-Goldstone boson...
Scale-invariant properties of public-debt growth
Petersen, A. M.; Podobnik, B.; Horvatic, D.; Stanley, H. E.
2010-05-01
Public debt is one of the important economic variables that quantitatively describes a nation's economy. Because bankruptcy is a risk faced even by institutions as large as governments (e.g., Iceland), national debt should be strictly controlled with respect to national wealth. Also, the problem of eliminating extreme poverty in the world is closely connected to the study of extremely poor debtor nations. We analyze the time evolution of national public debt and find "convergence": initially less-indebted countries increase their debt more quickly than initially more-indebted countries. We also analyze the public debt-to-GDP ratio {\\cal R} , a proxy for default risk, and approximate the probability density function P({\\cal R}) with a Gamma distribution, which can be used to establish thresholds for sustainable debt. We also observe "convergence" in {\\cal R} : countries with initially small {\\cal R} increase their {\\cal R} more quickly than countries with initially large {\\cal R} . The scaling relationships for debt and {\\cal R} have practical applications, e.g. the Maastricht Treaty requires members of the European Monetary Union to maintain {\\cal R} < 0.6 .
Coherent noise, scale invariance and intermittency in large systems
Sneppen, Kim; Newman, M. E. J.
1996-01-01
We introduce a new class of models in which a large number of "agents" organize under the influence of an externally imposed coherent noise. The model shows reorganization events whose size distribution closely follows a power law over many decades, even in the case where the agents do not interact with each other. In addition the system displays "aftershock" events in which large disturbances are followed by a string of others at times which are distributed according to a 1/t law. We also fi...
Curing Black Hole Singularities with Local Scale Invariance
Directory of Open Access Journals (Sweden)
Predrag Dominis Prester
2016-01-01
Full Text Available We show that Weyl-invariant dilaton gravity provides a description of black holes without classical space-time singularities. Singularities appear due to the ill behaviour of gauge fixing conditions, one example being the gauge in which theory is classically equivalent to standard General Relativity. The main conclusions of our analysis are as follows: (1 singularities signal a phase transition from broken to unbroken phase of Weyl symmetry; (2 instead of a singularity, there is a “baby universe” or a white hole inside a black hole; (3 in the baby universe scenario, there is a critical mass after which reducing mass makes the black hole larger as viewed by outside observers; (4 if a black hole could be connected with white hole through the “singularity,” this would require breakdown of (classical geometric description; (5 the singularity of Schwarzschild BH solution is nongeneric and so it is dangerous to rely on it in deriving general results. Our results may have important consequences for resolving issues related to information loss puzzle. Though quantum effects are still crucial and may change the proposed classical picture, a position of building quantum theory around essentially regular classical solutions normally provides a much better starting point.
Dynamical Volume Element in Scale-Invariant and Supergravity Theories
Guendelman, Eduardo; Pacheva, Svetlana; Vasihoun, Mahary
2013-01-01
The use in the action integral of a volume element of the form $\\Phi d^{D}x$, where $\\Phi$ is a metric-independent measure density, can yield new interesting results in all types of known generally coordinate-invariant theories: (1) 4-D theories of gravity plus matter fields; (2) reparametrization invariant theories of extended objects (strings and branes); (3) supergravity theories. In case (1) we obtain interesting insights concerning the cosmological constant problem, inflation and quintessence without the fifth force problem. In case (2) the above formalism leads to dynamically induced tension and to string models of non-abelian confinement. In case (3), we show that the modified-measure supergravity generates an arbitrary dynamically induced cosmological constant.
A Scale Invariant Distribution of the Prime Numbers
Directory of Open Access Journals (Sweden)
Wayne S. Kendal
2015-10-01
Full Text Available The irregular distribution of prime numbers amongst the integers has found multiple uses, from engineering applications of cryptography to quantum theory. The degree to which this distribution can be predicted thus has become a subject of current interest. Here, we present a computational analysis of the deviations between the actual positions of the prime numbers and their predicted positions from Riemann’s counting formula, focused on the variance function of these deviations from sequential enumerative bins. We show empirically that these deviations can be described by a class of probabilistic models known as the Tweedie exponential dispersion models that are characterized by a power law relationship between the variance and the mean, known by biologists as Taylor’s power law and by engineers as fluctuation scaling. This power law behavior of the prime number deviations is remarkable in that the same behavior has been found within the distribution of genes and single nucleotide polymorphisms (SNPs within the human genome, the distribution of animals and plants within their habitats, as well as within many other biological and physical processes. We explain the common features of this behavior through a statistical convergence effect related to the central limit theorem that also generates 1/f noise.
Scale Invariance in Gravity On The Light-Front
Shyam, Vasudev
2015-01-01
In general relativity, the double null foliation is one for which $d$-dimensional spacetime is foliated by two families of intersecting null hyper surfaces (i.e. surfaces whose normal vectors are null) of $(d-1)$ dimensions. Their intersection is at space like surfaces of dimension $(d-2)$. This means that the leaves of this foliation are the space like surfaces of two dimensions lower than that of spacetime which are located by looking at the bundles of light rays that are going into, and emanating from them. Using this foliation, we present a reformulation of the theory which makes explicit the true dynamical degrees of freedom. This is accompanied by making manifest a hidden local conformal invariance. Revealing this local symmetry comes at the cost of preferring a parameterisation of the null hyper surfaces. More precisely, a preferred ruling of the null surfaces by their generators needs to be chosen so that the theory whose gauge symmetries are enhanced by Weyl invariance restricted to preserve the foli...
Broken Scale Invariance, Alpha-Attractors and Vector Impurity
Akarsu, Ozgur; Kahya, Emre O; Ozdemir, Nese; Ozkan, Mehmet
2016-01-01
We show that if the {\\alpha}-attractor model is realized by the spontaneous breaking of the scale symmetry, then the stability and the dynamics of the vector field that gauges the scale symmetry severely constrains the {\\alpha}-parameter as 5/6 < {\\alpha} < 1, restricting the inflationary predictions in a very tiny region in the n_s vs r plane that are in great agreement with the latest Planck data. Although the different values of {\\alpha} do not make a tangible difference for n_s and r, they provide radically different scenarios for the post-inflationary dynamics which determines the standard BBN processes and the large scale isotropy of the universe.
Levy multiplicative chaos and star scale invariant random measures
Rhodes, Rémi; Sohier, Julien; Vargas, Vincent
2014-01-01
In this article, we consider the continuous analog of the celebrated Mandelbrot star equation with infinitely divisible weights. Mandelbrot introduced this equation to characterize the law of multiplicative cascades. We show existence and uniqueness of measures satisfying the aforementioned continuous equation. We obtain an explicit characterization of the structure of these measures, which reflects the constraints imposed by the continuous setting. In particular, we show that the continuous ...
Scale-invariant radio jets and varying black hole spin
Moscibrodzka, Monika; Noble, Scott
2016-01-01
Compact radio cores associated with relativistic jets are often observed in both active galactic nuclei and X-ray binaries. Their radiative properties follow some general scaling laws which primarily depend on their masses and accretion rates. However, it has been suggested that the black hole spin can also strongly influence the power and radio flux of these. Here, we attempt to estimate the dependency of the radio luminosity of steady jets launched by accretion disks on black hole mass, accretion rate and spin using numerical simulations. We make use of 3D GRMHD simulations of accretion disks around low-luminosity black holes in which the jet radio emission is produced by the jet sheath. We find that the radio flux increases roughly by a factor of 6 as the back hole spin increases from a~0 to a=0.98. This is comparable to the increase in accretion power with spin, meaning that the ratio between radio jet and accretion power is hardly changing. Although our jet spine power scales as expected for the Blandfor...
Global scale-invariant dissipation in collisionless plasma turbulence
Kiyani, K H; Khotyaintsev, Yu V; Dunlop, M W
2009-01-01
A higher-order multiscale analysis of the dissipation range of collisionless plasma turbulence is presented using in-situ high-frequency magnetic field measurements from the Cluster spacecraft in a stationary interval of fast ambient solar wind. The observations, spanning five decades in temporal scales, show a crossover from multifractal intermittent turbulence in the inertial range to non-Gaussian monoscaling in the dissipation range. This presents a strong observational constraint on theories of dissipation mechanisms in turbulent collisionless plasmas.
Scale invariance analysis of the premature ECG signals
Wang, Jun; Cheng, Keqiang
2012-06-01
The multifractal detrended fluctuation analysis and detrending moving average algorithm were introduced in detail and applied to the study of the multifractal characteristics of the normal signals, the atrial premature beat (APB) signals and the premature ventricular contraction (PVC) signals. By analyzing the generalized Hurst exponents, Renyi exponents and multifractal spectrum and comparing the relation of h∼h(q) for original signals and their shuffled time series, the result indicated that the three signals have multifractality and present long-range correlation in a certain range. According to the mean value of Δα, we found that the strength of the multifractality is varying. The PVC signals is the strongest, and the Normal signals is the weakest. It is useful for clinical practice of medicine to distinguish APB signals with PVC signals.
Acoustic anisotropic wavefields through perturbation theory
Alkhalifah, Tariq Ali
2013-09-01
Solving the anisotropic acoustic wave equation numerically using finite-difference methods introduces many problems and media restriction requirements, and it rarely contributes to the ability to resolve the anisotropy parameters. Among these restrictions are the inability to handle media with η<0 and the presence of shear-wave artifacts in the solution. Both limitations do not exist in the solution of the elliptical anisotropic acoustic wave equation. Using perturbation theory in developing the solution of the anisotropic acoustic wave equation allows direct access to the desired limitation-free solutions, that is, solutions perturbed from the elliptical anisotropic background medium. It also provides a platform for parameter estimation because of the ability to isolate the wavefield dependency on the perturbed anisotropy parameters. As a result, I derive partial differential equations that relate changes in the wavefield to perturbations in the anisotropy parameters. The solutions of the perturbation equations represented the coefficients of a Taylor-series-type expansion of the wavefield as a function of the perturbed parameter, which is in this case η or the tilt of the symmetry axis. The expansion with respect to the symmetry axis allows use of an acoustic transversely isotropic media with a vertical symmetry axis (VTI) kernel to estimate the background wavefield and the corresponding perturbation coefficients. The VTI extrapolation kernel is about one-fourth the cost of the transversely isotropic model with a tilt in the symmetry axis kernel. Thus, for a small symmetry axis tilt, the cost of migration using a first-order expansion can be reduced. The effectiveness of the approach was demonstrated on the Marmousi model.
Crossing Statistics of Anisotropic Stochastic Surface
Nezhadhaghighi, M Ghasemi; Yasseri, T; Allaei, S M Vaez
2015-01-01
We use crossing statistics and its generalization to determine the anisotropic direction imposed on a stochastic fields in $(2+1)$Dimension. This approach enables us to examine not only the rotational invariance of morphology but also we can determine the Gaussianity of underlying stochastic field in various dimensions. Theoretical prediction of up-crossing statistics (crossing with positive slope at a given threshold $\\alpha$ of height fluctuation), $\
Mesoscopic Phase Separation in Anisotropic Superconductors
V. I. Yukalov; Yukalova, E. P.
2005-01-01
General properties of anisotropic superconductors with mesoscopic phase separation are analysed. The main conclusions are as follows: Mesoscopic phase separation can be thermodynamically stable only in the presence of repulsive Coulomb interactions. Phase separation enables the appearance of superconductivity in a heterophase sample even if it were impossible in pure-phase matter. Phase separation is crucial for the occurrence of superconductivity in bad conductors. Critical temperature for a...
Anisotropic magnetocapacitance in ferromagnetic-plate capacitors
Haigh, J. A.; Ciccarelli, C.; Betz, A. C.; Irvine, A.; Novák, V.; Jungwirth, T.; Wunderlich, J.
2015-04-01
The capacitance of a parallel-plate capacitor can depend on the applied magnetic field. Previous studies have identified capacitance changes induced via classical Lorentz force or spin-dependent Zeeman effects. Here we measure a magnetization direction-dependent capacitance in parallel-plate capacitors where one plate is a ferromagnetic semiconductor, gallium manganese arsenide. This anisotropic magnetocapacitance is due to the anisotropy in the density of states dependent on the magnetization through the strong spin-orbit interaction.
Anisotropic solutions in f(R) Gravity
Tripathy, S K
2016-01-01
Anisotropic cosmological models are investigated in the frame work of $f(R)$ gravity in the metric formalism. Plane symmetric models are considered to incorporate anisotropy in the expansion rates along different spatial directions. The anisotropy in expansion rates are assumed to be maintained throughout the cosmic evolution. Two accelerating models are constructed by considering different functional forms for f(R). The viability of these models are tested through a stability analysis.