Sample records for binary power law

  1. Power laws and market crashes

    E-print Network

    Kaizoji, T

    2006-01-01

    In this paper, we quantitatively investigate the statistical properties of a statistical ensemble of stock prices. We selected 1200 stocks traded on the Tokyo Stock Exchange, and formed a statistical ensemble of daily stock prices for each trading day in the 3-year period from January 4, 1999 to December 28, 2001, corresponding to the period of the forming of the internet bubble in Japn, and its bursting in the Japanese stock market. We found that the tail of the complementary cumulative distribution function of the ensemble of stock prices in the high value of the price is well described by a power-law distribution, $ P(S>x) \\sim x^{-\\alpha} $, with an exponent that moves in the range of $ 1.09 < \\alpha < 1.27 $. Furthermore, we found that as the power-law exponents $ \\alpha $ approached unity, the bubbles collapsed. This suggests that Zipf's law for stock prices is a sign that bubbles are going to burst. PACS: 89.65.Gh

  2. First Law of Mechanics for Black Hole Binaries with Spins

    E-print Network

    Blanchet, Luc; Tiec, Alexandre Le

    2013-01-01

    We use the canonical Hamiltonian formalism to generalize to spinning point particles the first law of mechanics established for binary systems of non-spinning point masses moving on circular orbits [Le Tiec, Blanchet, and Whiting, Phys. Rev. D 85, 064039 (2012)]. We find that the redshift observable of each particle is related in a very simple manner to the canonical Hamiltonian and, more generally, to a class of Fokker-type Hamiltonians. Our results are valid through linear order in the spin of each particle, but hold also for quadratic couplings between the spins of different particles. The knowledge of spin effects in the Hamiltonian allows us to compute spin-orbit terms in the redshift variable through 2.5PN order, for circular orbits and spins aligned or anti-aligned with the orbital angular momentum. To describe extended bodies such as black holes, we supplement the first law for spinning point-particle binaries with some "constitutive relations" that can be used for diagnosis of spin measurements in qu...

  3. Limit Laws for Functions of Fringe trees for Binary Search Trees and Recursive Trees

    E-print Network

    Janson, Svante

    Limit Laws for Functions of Fringe trees for Binary Search Trees and Recursive Trees Cecilia of binary search trees and random recursive trees. In particular, we give simple new proofs of the fact that the number of fringe trees of size k = kn in the binary search tree and the random recursive tree (of total

  4. Power law inflation with electromagnetism

    SciTech Connect

    Luo, Xianghui; Isenberg, James, E-mail: isenberg@uoregon.edu

    2013-07-15

    We generalize Ringström’s global future causal stability results (Ringström 2009) [11] for certain expanding cosmological solutions of the Einstein-scalar field equations to solutions of the Einstein–Maxwell-scalar field system. In particular, after noting that the power law inflationary spacetimes (M{sup n+1},g{sup -hat}, ?{sup -hat}) considered by Ringström (2009) in [11] are solutions of the Einstein–Maxwell-scalar field system (with exponential potential) as well as of the Einstein-scalar field system (with the same exponential potential), we consider (nonlinear) perturbations of initial data sets of these spacetimes which include electromagnetic perturbations as well as gravitational and scalar perturbations. We show that if (as in Ringström (2009) [11]) we focus on pairs of relatively scaled open sets U{sub R{sub 0}}?U{sub 4R{sub 0}} on an initial slice of (M{sup n+1},g{sup -hat}), and if we choose a set of perturbed data which on U{sub 4R{sub 0}} is sufficiently close to that of (M{sup n+1},g{sup -hat},?{sup -hat}, A{sup -hat} = 0), then in the maximal globally hyperbolic spacetime development (M{sup n+1},g,?,A) of this data via the Einstein–Maxwell-scalar field equations, all causal geodesics emanating from U{sub R{sub 0}} are future complete (just as in (M{sup n+1},g{sup -hat})). We also verify that, in a certain sense, the future asymptotic behavior of the fields in the spacetime developments of the perturbed data sets does not differ significantly from the future asymptotic behavior of (M{sup n+1},g{sup -hat}, ?{sup -hat}, A{sup -hat} = 0). -- Highlights: •We prove stability of expanding solutions of the Einstein–Maxwell-scalar field equations. •All nearby solutions are geodesically complete. •The topology of the initial slice is irrelevant to our stability results.

  5. Henry's law, surface tension, and surface adsorption in dilute binary mixtures

    E-print Network

    Henry's law, surface tension, and surface adsorption in dilute binary mixtures Akira Onukia. The solute partitioning between gas and liquid Henry's law and the surface tension change are discussed. A derivation of the Gibbs law =-T is given with being the surface adsorption. Calculated quantities include

  6. The elliptical power law profile lens

    E-print Network

    Tessore, Nicolas

    2015-01-01

    The deflection, potential, shear and magnification of a gravitational lens following an elliptical power law mass model are investigated. This mass model is derived from the circular power law profile through a rescaling of the axes, similar to the case of a singular isothermal ellipsoid. The resulting deflection can be calculated explicitly and given in terms of the Gaussian hypergeometric function. Analytic expressions for the remaining lensing properties are found as well. Because the power law profile lens contains a number of well-known lens models as special cases, the equivalence of the new expressions with known results is checked. Finally, it is shown how these results naturally lead to a fast and accurate numerical scheme for computing the deflection and other lens quantities, making this method a useful tool for realistically modelling observed lenses.

  7. Memory Constraints for Power-Law Series

    E-print Network

    Guo, Fangjian; Zhao, Zhi-Dan; Zhou, Tao

    2015-01-01

    Many time series produced by complex systems are empirically found to follow power-law distributions with different exponents $\\alpha$. By permuting the independently drawn samples from a power-law distribution, we present non-trivial bounds on the memory (1st-order autocorrelation) as a function of $\\alpha$, which are markedly different from the ordinary $\\pm 1$ bounds for Gaussian or uniform distributions. When $1 3$, the upper bound remains +1 while the lower bound descends below 0. Theoretical bounds agree well with numerical simulations. Based on the ratings of MovieLens and posts in Twitter, we also find that empirical power-law distributed data produced by human activities conform to such constraints.

  8. On Power Law Inflation in DBI Models

    E-print Network

    Michal Spalinski

    2007-04-26

    Inflationary models in string theory which identify the inflaton with an open string modulus lead to effective field theories with non-canonical kinetic terms: Dirac-Born-Infeld scalar field theories. In the case of a $D$-brane moving in an AdS throat with a quadratic scalar field potential DBI kinetic terms allow a novel realization of power law inflation. This note adresses the question of whether this behaviour is special to this particular choice of throat geometry and potential. The answer is that for any throat geometry one can explicitly find a potential which leads to power law inflation. This generalizes the well known fact that an exponential potential gives power law inflation in the case of canonical kinetic terms.

  9. Relativity, nonextensivity, and extended power law distributions.

    PubMed

    Silva, R; Lima, J A S

    2005-11-01

    A proof of the relativistic theorem by including nonextensive effects is given. As it happens in the nonrelativistic limit, the molecular chaos hypothesis advanced by Boltzmann does not remain valid, and the second law of thermodynamics combined with a duality transformation implies that the parameter lies on the interval [0,2]. It is also proven that the collisional equilibrium states (null entropy source term) are described by the relativistic power law extension of the exponential Juttner distribution which reduces, in the nonrelativistic domain, to the Tsallis power law function. As a simple illustration of the basic approach, we derive the relativistic nonextensive equilibrium distribution for a dilute charged gas under the action of an electromagnetic field . Such results reduce to the standard ones in the extensive limit, thereby showing that the nonextensive entropic framework can be harmonized with the space-time ideas contained in the special relativity theory. PMID:16383791

  10. Robust model comparison disfavors power law cosmology

    NASA Astrophysics Data System (ADS)

    Shafer, Daniel L.

    2015-05-01

    Late-time power law expansion has been proposed as an alternative to the standard cosmological model and shown to be consistent with some low-redshift data. We test power law expansion against the standard flat ? CDM cosmology using goodness-of-fit and model comparison criteria. We consider type Ia supernova (SN Ia) data from two current compilations (JLA and Union2.1) along with a current set of baryon acoustic oscillation (BAO) measurements that includes the high-redshift Lyman-? forest measurements from BOSS quasars. We find that neither power law expansion nor ? CDM is strongly preferred over the other when the SN Ia and BAO data are analyzed separately but that power law expansion is strongly disfavored by the combination. We treat the Rh=c t cosmology (a constant rate of expansion) separately and find that it is conclusively disfavored by all combinations of data that include SN Ia observations and a poor overall fit when systematic errors in the SN Ia measurements are ignored, despite a recent claim to the contrary. We discuss this claim and some concerns regarding hidden model dependence in the SN Ia data.

  11. Small power systems for law enforcement applications

    Microsoft Academic Search

    Paul E. Sims; Michael G. Mauk; Oleg V. Sulima

    2002-01-01

    Recent events have increased interest in the use of sensors by law enforcement and homeland defense related organizations. Autonomous sensors such as those under development for the Unattended Ground Sensor (UGS) program are suitable for some of these applications. The operational lifetime of a UGS depends on the power consumption of the package and the space allocated for batteries. We

  12. Power-laws and Non-Power-laws in Dark Matter Halos

    E-print Network

    R. N. Henriksen

    2006-09-05

    Simulated dark matter profiles are often modelled as a `NFW' density profile rather than a single power law. Recently, attention has turned to the rather rigorous power-law behaviour exhibited by the `pseudo phase-space density' of the dark matter halo, which is defined dimensionally in terms of the local density and velocity dispersion of the dark matter particles. The non-power-law behaviour of the density profile is generally taken to exclude simple scale-free, in-fall models; however the power-law behaviour of the `pseudo-density' is a counter indication. We argue in this paper that both behaviours may be at least qualitatively understood in terms of a dynamically evolving self-similarity, rather than the form for self-similar infall that is fixed by cosmological initial conditions. The evolution is likely due to collective relaxation such as that provided by the radial-orbit instability on large scales. We deduce, from a distribution function given by first order coarse-graining, both the NFW-type density profile and the power-law pseudo-density profile. The results are not greatly sensitive to variation about 3 in the power of the velocity dispersion used in the definition of the phase space pseudo-density. We suggest that the power 2 may create the more physical quantity, whose deviations from a power-law are a diagnostic of incomplete relaxation.

  13. Universal power law governing pedestrian interactions

    E-print Network

    Karamouzas, Ioannis; Guy, Stephen J

    2014-01-01

    Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory in nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena.

  14. Power laws in economics and elsewhere J. Doyne Farmer

    E-print Network

    Power laws in economics and elsewhere J. Doyne Farmer and John Geanakoplos May 14, 2008 Abstract We review power laws in financial economics. This is a chapter from a preliminary draft of a book called of it applies to power laws in general ­ the nouns may change, but the underlying questions are similar in many

  15. Binary vapor cycle method of electrical power generation

    Microsoft Academic Search

    Humiston

    1982-01-01

    A binary vapor cycle method of electrical power generation is disclosed wherein two refrigerant fluids can be used to operate an apparatus for the generation of mechanical power as well as electrical power generation. This method, which is essentially a dual heat pump system, offers an approach to utilizing the advantages of two different refrigerants within a single apparatus. This

  16. Finite Disks with Power-Law Potentials

    E-print Network

    R. Brada; M. Milgrom

    1994-08-08

    We describe a family of circular, and elliptical, finite disks with a disk potential that is a power of the radius. These are all flattened ellipsoids, obtained by squashing finite spheres with a power-law density distribution, and cutoff at some radius Ro. First we discuss circular disks whose circular rotation speed v is proportional to r^alpha, with any alpha> -1/2. The surface-density of the disks is expressed in terms of hypergeometric functions of 1-(Ro/r)^2. We give closed expressions for the full 3-D potentials in terms of hypergeometric functions of two variables. We express the potential and acceleration in the plane at r>Ro, and along the rotation axis, in terms of simple hypergeometric functions. All the multipoles of the disk are given. We then generalize to non-axisymmetric disks. The potential in the midplane is given in terms of the hypergeometric function of two variables. For integer values of 2 alpha the above quantities are given in more elementary terms. All these results follow straightforwardly from formulae we derive for the general, cutoff, power-law, triaxial ellipsoid.

  17. Existence Theory for Stochastic Power Law Fluids

    NASA Astrophysics Data System (ADS)

    Breit, Dominic

    2015-06-01

    We consider the equations of motion for an incompressible non-Newtonian fluid in a bounded Lipschitz domain during the time interval (0, T) together with a stochastic perturbation driven by a Brownian motion W. The balance of momentum reads as where v is the velocity, the pressure and f an external volume force. We assume the common power law model and show the existence of martingale weak solution provided . Our approach is based on the -truncation and a harmonic pressure decomposition which are adapted to the stochastic setting.

  18. A Universal Power Law Governing Pedestrian Interactions

    NASA Astrophysics Data System (ADS)

    Karamouzas, Ioannis; Skinner, Brian; Guy, Stephen J.

    2015-03-01

    Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory in nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena. Work at Argonne National Laboratory is supported by the U.S. Department of Energy, under Contract No. DE-AC02-06CH11357. Work at the University of Minnesota is supported by MnDRIVE Initiative on Robotics, Sensors, and Advanced Manufacturing.

  19. Advanced law enforcement vehicle electronics and associated power

    Microsoft Academic Search

    J. A. Ochoa; J. Witz; M. Eshani; J. Morgan

    1999-01-01

    An ever-increasing role of technology in law enforcement has led to the integration of numerous electronic devices into the advanced law enforcement vehicle. Along with improved safety and efficiency of law enforcement personnel, the addition of these electronics has resulted in significant vehicle power management challenges. The Texas Transportation Institute has developed the Advanced Law Enforcement and Response Technology (ALERT(R))

  20. Power laws and fragility in flow networks?

    PubMed Central

    Shore, Jesse; Chu, Catherine J.; Bianchi, Matt T.

    2015-01-01

    What makes economic and ecological networks so unlike other highly skewed networks in their tendency toward turbulence and collapse? Here, we explore the consequences of a defining feature of these networks: their nodes are tied together by flow. We show that flow networks tend to the power law degree distribution (PLDD) due to a self-reinforcing process involving position within the global network structure, and thus present the first random graph model for PLDDs that does not depend on a rich-get-richer function of nodal degree. We also show that in contrast to non-flow networks, PLDD flow networks are dramatically more vulnerable to catastrophic failure than non-PLDD flow networks, a finding with potential explanatory power in our age of resource- and financial-interdependence and turbulence.

  1. The POWER7 Binary Floating-Point Unit

    Microsoft Academic Search

    Maarten Boersma; Michael Kroner; Christophe Layer; Petra Leber; Silvia M. Muller; Kerstin Schelm

    2011-01-01

    The binary Floating-Point Unit (FPU) of the POWER7 processor is a 5.5 cycle Fused Multiply-Add (FMA) design, fully compliant with the IEEE 754-2008 standard. Unlike previous PowerPC designs, the POWER7 FPU merges the scalar and vector FPUs into a single unit executing three floating-point instruction sets: the single and double precision scalar set, the single precision VMX vector set, and

  2. Power Law Distributions of Seismic Rates

    E-print Network

    A. Saichev; D. Sornette

    2004-12-09

    We report an empirical determination of the probability density functions $P_{\\text{data}}(r)$ of the number $r$ of earthquakes in finite space-time windows for the California catalog. We find a stable power law tail $P_{\\text{data}}(r) \\sim 1/r^{1+\\mu}$ with exponent $\\mu \\approx 1.6$ for all space ($5 \\times 5$ to $20 \\times 20$ km$^2$) and time intervals (0.1 to 1000 days). These observations, as well as the non-universal dependence on space-time windows for all different space-time windows simultaneously, are explained by solving one of the most used reference model in seismology (ETAS), which assumes that each earthquake can trigger other earthquakes. The data imposes that active seismic regions are Cauchy-like fractals, whose exponent $\\delta =0.1 \\pm 0.1$ is well-constrained by the seismic rate data.

  3. Power-law parametrized quintessence model

    SciTech Connect

    Rahvar, Sohrab [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Movahed, M. Sadegh [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

    2007-01-15

    We propose a simple power-law parametrized quintessence model with time-varying equation of state and obtain corresponding quintessence potential of this model. This model is compared with Supernova Type Ia (SNIa) Gold sample data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the position of the acoustic peak from the CMB observations and structure formation from the 2dFGRS survey and put constrain on the parameters of model. The parameters from the best fit indicates that the equation of state of this model at the present time is w{sub 0}=-1.40{sub -0.65}{sup +0.40} at 1{sigma} confidence level. Finally we calculate the age of universe in this model and compare it with the age of old cosmological objects.

  4. On Power-law Relationships of the Internet Topology

    Microsoft Academic Search

    Michalis Faloutsos; Petros Faloutsos; Christos Faloutsos

    1999-01-01

    Despite the apparent randomness of the Internet, we discover some surprisingly simple power-laws of the Internet topology. These power-laws hold for three snapshots of the Internet, between November 1997 and December 1998, despite a 45% growth of its size during that period. We show that our power-laws fit the real data very well resulting in correlation coefficients of 96% or

  5. Use of power law models in detecting region of interest

    Microsoft Academic Search

    Yves Caron; Pascal Makris; Nicole Vincent

    2007-01-01

    Abstract In this paper, we shall address the issue of semantic extraction of different regions of interest. The proposed approach is based on statistical methods and models inspired from linguistic analysis. Here, the models used are Zipf law and inverse Zipf law. They are used to model the frequency of appearance,of the patterns contained in images,as power law distributions. The

  6. Rate-Controlling Mechanisms in Five-Power-Law Creep

    SciTech Connect

    Michael E. Kassner

    2004-04-20

    OAK-B135 Rate-Controlling Mechanisms in Five-Power-Law Creep. The initial grant emphasized the rate-controlling processes for five power-law creep. The effort has six aspects: (1) Theory of Taylor hardening from the Frank dislocation network in five power law substructures. (2) The dual dynamical and hardening nature of dislocations in five power law substructures. (3) Determination of the existence of long-range internal stress in five-power law creep dislocation substructures. (4) Dynamic recovery mechanisms associated with dislocation heterogeneities during five power law creep. (5) Versatility of five power law creep concept to other (hcp) crystal structures. (6) Writing of a book on ''Fundamental of Creep in Metals and Alloys'' by M.E. Kassner and Maria-Teresa Perez-Frado (postdoctoral scholar, funded by this project) Elsevier Press, 2004, in press. These areas are consistent with the original goals of this project as delineated in the original proposal to Basic Energy Sciences. The progress in each of these areas will be discussed separately and there will be an attempt to tie each aspect together so as to allow a summary regarding the conclusions with respect to the rate-controlling mechanisms of five power-law creep.

  7. Power-Laws and Structure in Functional Programs Ron Coleman

    E-print Network

    Coleman, Ron

    of power- law distributions of software complexity in functional programs. Keywords--Power-laws; minimum]. Software complexity metrics have been developed, more than 100 by some estimates, to quantify to devise a new type of software complexity metric founded on fractal statistics [6, 7]. Indeed, Kokol

  8. Power law of dust devil diameters on Mars and Earth

    Microsoft Academic Search

    Ralph D. Lorenz

    2009-01-01

    Estimates from visual surveys of the frequency of dust devils, even at terrestrial localities known for their abundance, vary by some four orders of magnitude, making a quantitative hazard assessment difficult. Here I show (1) that new high-quality observations from Mars fit a power law size distribution, (2) that such a power law population can unify the discrepant terrestrial surveys,

  9. Advanced binary geothermal power plants: Limits of performance

    SciTech Connect

    Bliem, C.J.; Mines, G.L.

    1990-01-01

    The Heat Cycle Research Program is currently investigating the potential improvements to power cycles utilizing moderate temperature geothermal resources to produce electrical power. Investigations have specifically examined Rankine cycle binary power systems. Binary Rankine cycles are more efficient than the flash steam cycles at moderate resource temperatures, achieving a higher net brine effectiveness. At resource conditions similar to those at the Heber binary plant, it has been shown that mixtures of saturated hydrocarbons (alkanes) or halogenated hydrocarbons operating with a supercritical Rankine cycle gave improved performance over Rankine cycles with the pure working fluids executing single boiling cycles. Recently, in addition to the supercritical Rankine Cycle, other types of cycles have been proposed for binary geothermal service. This paper explores the limits on efficiency of a feasibility plant and discusses the methods used in these advanced concept plants to achieve the maximum possible efficiency. The advanced plants considered appear to be approaching the feasible limit of performance so that the designer must weigh all considerations to find the best plant for a given service. 16 refs., 12 figs.

  10. Power law models of stock indices

    NASA Astrophysics Data System (ADS)

    Tse, Man Kit

    Viewing the stock market as a self-organized system, Sornette and Johansen introduced physics-based models to study the dynamics of stock market crashes from the perspective of complex systems. This involved modeling stock market Indices using a mathematical power law exhibiting log-periodicity as the system approaches a market crash, which acts like a critical point in a thermodynamic system. In this dissertation, I aim to investigate stock indices to determine whether or not they exhibit log-periodic oscillations, according to the models proposed by Sornette, as they approach a crash. In addition to analyzing stock market crashes in the frequency domain using the discrete Fourier transform and the Lomb-Scargle periodogram, I perform a detailed analysis of the stock market crash models through parameter estimation and model testing. I find that the probability landscapes have a complex topography and that there is very little evidence that these phase transition-based models accurately describe stock market crashes.

  11. Power-law confusion: You say incremental, I say differential

    NASA Technical Reports Server (NTRS)

    Colwell, Joshua E.

    1993-01-01

    Power-law distributions are commonly used to describe the frequency of occurrences of crater diameters, stellar masses, ring particle sizes, planetesimal sizes, and meteoroid masses to name a few. The distributions are simple, and this simplicity has led to a number of misstatements in the literature about the kind of power-law that is being used: differential, cumulative, or incremental. Although differential and cumulative power-laws are mathematically trivial, it is a hybrid incremental distribution that is often used and the relationship between the incremental distribution and the differential or cumulative distributions is not trivial. In many cases the slope of an incremental power-law will be nearly identical to the slope of the cumulative power-law of the same distribution, not the differential slope. The discussion that follows argues for a consistent usage of these terms and against the oft-made implicit claim that incremental and differential distributions are indistinguishable.

  12. Distortion of power law blinking with binning and thresholding

    SciTech Connect

    Amecke, Nicole; Heber, André; Cichos, Frank, E-mail: cichos@physik.uni-leipzig.de [Molecular Nanophotonics Group, Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig (Germany)] [Molecular Nanophotonics Group, Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig (Germany)

    2014-03-21

    Fluorescence intermittency is a random switching between emitting (on) and non-emitting (off) periods found for many single chromophores such as semiconductor quantum dots and organic molecules. The statistics of the duration of on- and off-periods are commonly determined by thresholding the emission time trace of a single chromophore and appear to be power law distributed. Here we test with the help of simulations if the experimentally determined power law distributions can actually reflect the underlying statistics. We find that with the experimentally limited time resolution real power law statistics with exponents ?{sub on/off} ? 1.6, especially if ?{sub on} ? ?{sub off} would not be observed as such in the experimental data after binning and thresholding. Instead, a power law appearance could simply be obtained from the continuous distribution of intermediate intensity levels. This challenges much of the obtained data and the models describing the so-called power law blinking.

  13. Do wealth distributions follow power laws? Evidence from ‘rich lists’

    NASA Astrophysics Data System (ADS)

    Brzezinski, Michal

    2014-07-01

    We use data on the wealth of the richest persons taken from the ‘rich lists’ provided by business magazines like Forbes to verify if the upper tails of wealth distributions follow, as often claimed, a power-law behaviour. The data sets used cover the world’s richest persons over 1996-2012, the richest Americans over 1988-2012, the richest Chinese over 2006-2012, and the richest Russians over 2004-2011. Using a recently introduced comprehensive empirical methodology for detecting power laws, which allows for testing the goodness of fit as well as for comparing the power-law model with rival distributions, we find that a power-law model is consistent with data only in 35% of the analysed data sets. Moreover, even if wealth data are consistent with the power-law model, they are usually also consistent with some rivals like the log-normal or stretched exponential distributions.

  14. Development of Jet Noise Power Spectral Laws

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James

    2011-01-01

    High-quality jet noise spectral data measured at the Aero-Acoustic Propulsion Laboratory (AAPL) at NASA Glenn is used to develop jet noise scaling laws. A FORTRAN algorithm was written that provides detailed spectral prediction of component jet noise at user-specified conditions. The model generates quick estimates of the jet mixing noise and the broadband shock-associated noise (BBSN) in single-stream, axis-symmetric jets within a wide range of nozzle operating conditions. Shock noise is emitted when supersonic jets exit a nozzle at imperfectly expanded conditions. A successful scaling of the BBSN allows for this noise component to be predicted in both convergent and convergent-divergent nozzles. Configurations considered in this study consisted of convergent and convergent- divergent nozzles. Velocity exponents for the jet mixing noise were evaluated as a function of observer angle and jet temperature. Similar intensity laws were developed for the broadband shock-associated noise in supersonic jets. A computer program called sJet was developed that provides a quick estimate of component noise in single-stream jets at a wide range of operating conditions. A number of features have been incorporated into the data bank and subsequent scaling in order to improve jet noise predictions. Measurements have been converted to a lossless format. Set points have been carefully selected to minimize the instability-related noise at small aft angles. Regression parameters have been scrutinized for error bounds at each angle. Screech-related amplification noise has been kept to a minimum to ensure that the velocity exponents for the jet mixing noise remain free of amplifications. A shock-noise-intensity scaling has been developed independent of the nozzle design point. The computer program provides detailed narrow-band spectral predictions for component noise (mixing noise and shock associated noise), as well as the total noise. Although the methodology is confined to single streams, efforts are underway to generate a data bank and algorithm applicable to dual-stream jets. Shock-associated noise in high-powered jets such as military aircraft can benefit from these predictions.

  15. Shifted powers in binary recurrence sequences

    NASA Astrophysics Data System (ADS)

    Bennett, Michael A.; Dahmen, Sander R.; Mignotte, Maurice; Siksek, Samir

    2015-03-01

    Let $u_k$ be a Lucas sequence. A standard technique for determining the perfect powers in the sequence $u_k$ combines bounds coming from linear forms in logarithms with local information obtained via Frey curves and modularity. The key to this approach is the fact that the equation $u_k=x^n$ can be translated into a ternary equation of the form $a y^2=b x^{2n}+c$ (with $a$, $b$, $c \\in \\mathbb{Z}$) for which Frey curves are available. In this paper we consider shifted powers in Lucas sequences, and consequently equations of the form $u_k=x^n+c$ which do not typically correspond to ternary equations with rational unknowns. However, they do, under certain hypotheses, lead to ternary equations with unknowns in totally real fields, allowing us to employ Frey curves over those fields instead of Frey curves defined over $\\mathbb{Q}$. We illustrate this approach by showing that the quaternary Diophantine equation $x^{2n} \\pm 6 x^n+1=8 y^2$ has no solutions in positive integers $x$, $y$, $n$ with $x$, $n>1$.

  16. Statistical analyses support power law distributions found in neuronal avalanches.

    PubMed

    Klaus, Andreas; Yu, Shan; Plenz, Dietmar

    2011-01-01

    The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i) analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii) model parameter estimation to determine the specific exponent of the power law, and (iii) comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect). This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex. PMID:21720544

  17. QUANTITATIVE FINANCE COMMENTARY On the origin of power-law

    E-print Network

    Stanley, H. Eugene

    QUANTITATIVE FINANCE COMMENTARY On the origin of power-law fluctuations in stock prices Vasiliki clearly does not imply the same for C11 #12;COMMENTARY QUANTITATIVE FINANCE returns, so FL's criticisms-law behaviour with exponent 1.5--in contrast to FL's claim. Define Si as the price of the stock after trade i

  18. 14 CFR 406.109 - Administrative law judges-powers and limitations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 false Administrative law judges-powers and limitations...Adjudications § 406.109 Administrative law judges—powers and limitations. (a) Powers of an administrative law judge. In accordance...

  19. 14 CFR 406.109 - Administrative law judges-powers and limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 2010-01-01 false Administrative law judges-powers and limitations...Adjudications § 406.109 Administrative law judges—powers and limitations. (a) Powers of an administrative law judge. In accordance...

  20. 14 CFR 406.109 - Administrative law judges-powers and limitations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 false Administrative law judges-powers and limitations...Adjudications § 406.109 Administrative law judges—powers and limitations. (a) Powers of an administrative law judge. In accordance...

  1. Fractal ladder models and power law wave equations

    PubMed Central

    Kelly, James F.; McGough, Robert J.

    2009-01-01

    The ultrasonic attenuation coefficient in mammalian tissue is approximated by a frequency-dependent power law for frequencies less than 100 MHz. To describe this power law behavior in soft tissue, a hierarchical fractal network model is proposed. The viscoelastic and self-similar properties of tissue are captured by a constitutive equation based on a lumped parameter infinite-ladder topology involving alternating springs and dashpots. In the low-frequency limit, this ladder network yields a stress-strain constitutive equation with a time-fractional derivative. By combining this constitutive equation with linearized conservation principles and an adiabatic equation of state, a fractional partial differential equation that describes power law attenuation is derived. The resulting attenuation coefficient is a power law with exponent ranging between 1 and 2, while the phase velocity is in agreement with the Kramers–Kronig relations. The fractal ladder model is compared to published attenuation coefficient data, thus providing equivalent lumped parameters. PMID:19813816

  2. 29 CFR 417.6 - Powers of Administrative Law Judge.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...LABOR-MANAGEMENT STANDARDS PROCEDURE FOR REMOVAL OF LOCAL LABOR ORGANIZATION OFFICERS Procedures To Determine Adequacy of Constitution and Bylaws for Removal of Officers of Local Labor Organizations § 417.6 Powers of Administrative Law Judge....

  3. 29 CFR 417.6 - Powers of Administrative Law Judge.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...LABOR-MANAGEMENT STANDARDS PROCEDURE FOR REMOVAL OF LOCAL LABOR ORGANIZATION OFFICERS Procedures To Determine Adequacy of Constitution and Bylaws for Removal of Officers of Local Labor Organizations § 417.6 Powers of Administrative Law Judge....

  4. 29 CFR 417.6 - Powers of Administrative Law Judge.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...LABOR-MANAGEMENT STANDARDS PROCEDURE FOR REMOVAL OF LOCAL LABOR ORGANIZATION OFFICERS Procedures To Determine Adequacy of Constitution and Bylaws for Removal of Officers of Local Labor Organizations § 417.6 Powers of Administrative Law Judge....

  5. 29 CFR 417.6 - Powers of Administrative Law Judge.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...LABOR-MANAGEMENT STANDARDS PROCEDURE FOR REMOVAL OF LOCAL LABOR ORGANIZATION OFFICERS Procedures To Determine Adequacy of Constitution and Bylaws for Removal of Officers of Local Labor Organizations § 417.6 Powers of Administrative Law Judge....

  6. 29 CFR 417.6 - Powers of Administrative Law Judge.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...LABOR-MANAGEMENT STANDARDS PROCEDURE FOR REMOVAL OF LOCAL LABOR ORGANIZATION OFFICERS Procedures To Determine Adequacy of Constitution and Bylaws for Removal of Officers of Local Labor Organizations § 417.6 Powers of Administrative Law Judge....

  7. Power Law Discounting for N-Gram Language Models 

    E-print Network

    Huang, Songfang; Renals, Steve

    2010-01-01

    We present an approximation to the Bayesian hierarchical Pitman-Yor process language model which maintains the power law distribution over word tokens, while not requiring a computationally expensive approximate inference process. This approximation...

  8. Hidden power law patterns in the top European football leagues

    NASA Astrophysics Data System (ADS)

    Da Silva, Sergio; Matsushita, Raul; Silveira, Eliza

    2013-11-01

    Because sports are stylized combat, sports may follow power laws similar to those found for wars, individual clashes, and acts of terrorism. We show this fact for football (soccer) by adjusting power laws that show a close relationship between rank and points won by the clubs participating in the latest seasons of the top fifteen European football leagues. In addition, we use Shannon entropy for gauging league competitive balance. As a result, we are able to rank the leagues according to competitiveness.

  9. Risk and power-laws in natural hazards

    Microsoft Academic Search

    B. Malamud

    2003-01-01

    There is increasing evidence that many natural hazards satisfy power-law frequency-size statistics. Examples include earthquakes, volcanic eruptions, landslides, snow avalanches, forest and wildfires, meteorite impacts, and possibly floods. Although power-law (fat-tail) distributions are commonly associated with the frequency-size distribution of earthquakes, the frequency-size statistics of many other natural hazards are presently associated (e.g. by government agencies and reinsurance companies) with

  10. Singularity problems of the power law for modeling creep compliance

    NASA Technical Reports Server (NTRS)

    Dillard, D. A.; Hiel, C.

    1985-01-01

    An explanation is offered for the extreme sensitivity that has been observed in the power law parameters of the T300/934 graphite epoxy material systems during experiments to evaluate the system's viscoelastic response. It is shown that the singularity associated with the power law can explain the sensitivity as well as the observed variability in the calculated parameters. Techniques for minimizing errors are suggested.

  11. Arrhenius' law in turbulent media and an equivalent tunnel effect. [in binary exchange chemical reactions

    NASA Technical Reports Server (NTRS)

    Tsuge, S.; Sagara, K.

    1978-01-01

    The indeterminacy inherent to the formal extension of Arrhenius' law to reactions in turbulent flows is shown to be surmountable in the case of a binary exchange reaction with a sufficiently high activation energy. A preliminary calculation predicts that the turbulent reaction rate is invariant in the Arrhenius form except for an equivalently lowered activation energy. This is a reflection of turbulence-augmented molecular vigor, and causes an appreciable increase in the reaction rate. A similarity to the tunnel effect in quantum mechanics is indicated. The anomaly associated with the mild ignition of oxy-hydrogen mixtures is discussed in this light.

  12. Power Law Fluids with Random Forcing

    Microsoft Academic Search

    Nobuo Yoshida

    The unknown process in the SPDE are the velocity field u = u(t, x) = (ui(t, x))d i=1 and the pressure ? = ?(t, x). The Brownian motion W = W (t, x) = (Wi(t, x))d i=1 with values in L2(Td ! Rd) is added as the random perturbation. Physical interpretation of (0.2) and (0.3) are the conservation laws of

  13. 5 CFR 2423.31 - Powers and duties of the Administrative Law Judge at the hearing.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Powers and duties of the Administrative Law Judge at the hearing. 2423... Powers and duties of the Administrative Law Judge at the hearing. (a) Conduct of hearing. The Administrative Law Judge shall conduct...

  14. 5 CFR 2423.31 - Powers and duties of the Administrative Law Judge at the hearing.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Powers and duties of the Administrative Law Judge at the hearing. 2423... Powers and duties of the Administrative Law Judge at the hearing. (a) Conduct of hearing. The Administrative Law Judge shall conduct...

  15. 5 CFR 2423.31 - Powers and duties of the Administrative Law Judge at the hearing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Powers and duties of the Administrative Law Judge at the hearing. 2423... Powers and duties of the Administrative Law Judge at the hearing. (a) Conduct of hearing. The Administrative Law Judge shall conduct...

  16. 5 CFR 2423.31 - Powers and duties of the Administrative Law Judge at the hearing.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Powers and duties of the Administrative Law Judge at the hearing. 2423... Powers and duties of the Administrative Law Judge at the hearing. (a) Conduct of hearing. The Administrative Law Judge shall conduct...

  17. Power-law connections: From Zipf to Heaps and beyond

    SciTech Connect

    Eliazar, Iddo I., E-mail: eliazar@post.tau.ac.il [Holon Institute of Technology, P.O. Box 305, Holon 58102 (Israel); Cohen, Morrel H., E-mail: mcohen@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019 (United States); Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

    2013-05-15

    In this paper we explore the asymptotic statistics of a general model of rank distributions in the large-ensemble limit; the construction of the general model is motivated by recent empirical studies of rank distributions. Applying Lorenzian, oligarchic, and Heapsian asymptotic analyses we establish a comprehensive set of closed-form results linking together rank distributions, probability distributions, oligarchy sizes, and innovation rates. In particular, the general results reveal the fundamental underlying connections between Zipf’s law, Pareto’s law, and Heaps’ law—three elemental empirical power-laws that are ubiquitously observed in the sciences. -- Highlights: ? The large-ensemble asymptotic statistics of rank distributions are explored. ? Lorenzian, oligarchic, and Heapsian asymptotic analyses are applied. ? Associated oligarchy sizes and induced innovation rates are analyzed. ? General elemental statistical connections are established. ? The underlying connections between Zipf’s, Pareto’s and Heaps’ laws are unveiled.

  18. Transient ultrasonic fields in power law attenuation media

    NASA Astrophysics Data System (ADS)

    Kelly, James F.

    Ultrasonic waves in biological media experience frequency dependent attenuation. Extensive measurement of the attenuation coefficient in human and mammalian tissue in the ultrasonic range has revealed a power law dependence on frequency, where the power law exponent ranges between 0 and 2. For most tissue, the power law exponent ranges between 1 and 1.7, which cannot be explained by classical theories for ultrasonic absorption, such as thermo-viscosity or molecular relaxation. The purpose of this thesis is threefold: (1) to understand the analytical structure of transient fields in power law media, (2) to provide a possible description of the physical mechanism responsible for power law attenuation in biological media, and (3) to develop analytical models for transient, three-dimensional sound beams in power law media. Insight into general dissipative media is gained by studying the approximations available in viscous media. The Stokes wave equation is considered in the time domain, and an asymptotic, causal Green's function is rigorously derived and verified using the material impulse response function (MIRF) approach. A lossy impulse response for the Stokes wave equation is derived for calculations of transient fields generated by finite aperture radiators. Expressions for the uniform circular aperture (in both the nearfield and the farfield), the uniform rectangular aperture in the nearfield, and the spherical shell in the nearfield are then derived. Power-law media is then studied using fractional partial differential equations (FPDEs), which add loss to the wave equation with a time-fractional or space-fractional derivative. A FPDE is derived that exactly describes power law attenuation, and analytical, time-domain James F. Kelly Green's functions in power law media are derived for exponents between 0 and 2. To construct solutions, stable law probability distributions are utilized, which are widely used in the study of anomalous diffusion and in the study of fractal media. For exponents strictly less than 1, the Green's functions are causal, while for exponents greater than or equal than 1, the Green's functions are noncausal. To address the lack of causality, alternate power law FPDEs based on fractional spatial operators are considered: the Chen-Holm wave equation and a spatially dispersive wave equation. Green's functions are derived for both equations, yielding causal solutions for all applicable power law exponents. The Chen-Holm equation is shown to be non-dispersive, while the spatially dispersive wave equation supports a phase velocity predicted by the Kramers-Kronig relations. To address the physical basis for FPDEs, a fractal ladder network is proposed as a model for the stress-strain relationship in tissue. This constitutive equation is based on a lumped-parameter infinite-ladder topology involving alternating springs and dashpots to capture the viscoelastic and self-similar properties of tissue. This ladder network yields a stress-strain constitutive equation involving a time-fractional derivative. The Caputo-Wismer FPDE is derived from this constitutive equation. Finally, the impulse response derived for viscous media is generalized to power law media. Expressions for finite apertures are then derived in dispersive media, thus forming the basis for ultrasonic image simulation in biological media.

  19. MHD micropumping of power-law fluids: A numerical solution

    NASA Astrophysics Data System (ADS)

    Moghaddam, Saied

    2013-02-01

    The performance of MHD micropumps is studied numerically assuming that the viscosity of the fluid is shear-dependent. Using power-law model to represent the fluid of interest, the effect of power-law exponent, N, is investigated on the volumetric flow rate in a rectangular channel. Assuming that the flow is laminar, incompressible, two-dimensional, but (approximately) unidirectional, finite difference method (FDM) is used to solve the governing equations. It is found that shear-thinning fluids provide a larger flow rate as compared to Newtonian fluids provided that the Hartmann number is above a critical value. There exists also an optimum Hartmann number (which is larger than the critical Hartmann number) at which the flow rate is maximum. The power-law exponent, N, strongly affects the optimum geometry depending on the Hartmann number being smaller or larger than the critical Hartmann number.

  20. Modelling power-law spread of infectious diseases

    E-print Network

    Meyer, Sebastian

    2013-01-01

    Short-time human travel behaviour can be well described by a power law with respect to distance. We incorporate this information in space-time models for infectious disease surveillance data to better capture the dynamics of disease spread. Two previously established model classes are extended, which both decompose disease risk additively into endemic and epidemic components: a space-time point process model for individual point-referenced data, and a multivariate time series model for aggregated count data. In both frameworks, the power-law spread is embedded into the epidemic component and its decay parameter is estimated simultaneously with all other unknown parameters using (penalised) likelihood inference. The performance of the new approach is investigated by a re-analysis of individual cases of invasive meningococcal disease in Germany (2002-2008), and count data on influenza in 140 administrative districts of Southern Germany (2001-2008). In both applications, the power-law formulations substantially ...

  1. Power-law hereditariness of hierarchical fractal bones.

    PubMed

    Deseri, Luca; Di Paola, Mario; Zingales, Massimiliano; Pollaci, Pietro

    2013-12-01

    In this paper, the authors introduce a hierarchic fractal model to describe bone hereditariness. Indeed, experimental data of stress relaxation or creep functions obtained by compressive/tensile tests have been proved to be fit by power law with real exponent 0 ? ? ?1. The rheological behavior of the material has therefore been obtained, using the Boltzmann-Volterra superposition principle, in terms of real order integrals and derivatives (fractional-order calculus). It is shown that the power laws describing creep/relaxation of bone tissue may be obtained by introducing a fractal description of bone cross-section, and the Hausdorff dimension of the fractal geometry is then related to the exponent of the power law. PMID:23836622

  2. Testing power-law cross-correlations: rescaled covariance test

    NASA Astrophysics Data System (ADS)

    Kristoufek, Ladislav

    2013-10-01

    We introduce a new test for detection of power-law cross-correlations among a pair of time series - the rescaled covariance test. The test is based on a power-law divergence of the covariance of the partial sums of the long-range cross-correlated processes. Utilizing a heteroskedasticity and auto-correlation robust estimator of the long-term covariance, we develop a test with desirable statistical properties which is well able to distinguish between short- and long-range cross-correlations. Such test should be used as a starting point in the analysis of long-range cross-correlations prior to an estimation of bivariate long-term memory parameters. As an application, we show that the relationship between volatility and traded volume, and volatility and returns in the financial markets can be labeled as the power-law cross-correlated one.

  3. Binary generators - you'll wonder where the power went

    SciTech Connect

    Ryan, G.P.

    1983-02-01

    There has been a surge of interest in electric power generation from low-temperature geothermal energy. The organic Rankine cycle is reviewed for efficiency. A pressure-enthalpy diagram for R-114 (the refrigerant chosen for this study) is given. In the cycle, refrigerant is vaporized, then expanded, to turn the shaft, then condensed, then pumped back into the cycle. The cycle depends on the difference between the evaporating pressure and the condensing pressure. The higher the geothermal water temperature, and the lower the cooling water temperature, the higher the work. Heat loss due to radiation and convection, the movement of refrigerant fluid through the evaporator, in the conversion of expanded power to electrical power, and in use of some actual produced power to pump the cooling water and drive the tower fans--all these heat losses are calculated. The overall saleable power efficiency of the cycle is determined. The efficiency is low, but the binary generator can find a place in a carefully conceived process.

  4. Power-law correlated processes with asymmetric distributions

    NASA Astrophysics Data System (ADS)

    Podobnik, Boris; Ivanov, Plamen Ch.; Jazbinsek, Vojko; Trontelj, Zvonko; Stanley, H. Eugene; Grosse, Ivo

    2005-02-01

    Motivated by the fact that many physical systems display (i) power-law correlations together with (ii) an asymmetry in the probability distribution, we propose a stochastic process that can model both properties. The process depends on only two parameters, where one controls the scaling exponent of the power-law correlations, and the other controls the degree of asymmetry in the distributions leaving the correlations unaffected. We apply the process to air humidity data and find that the statistical properties of the process are in a good agreement with those observed in the data.

  5. Turbulent pipe flow of power-law fluids

    SciTech Connect

    Malin, M.R. [CHAM Ltd., London (United Kingdom)] [CHAM Ltd., London (United Kingdom)

    1997-11-01

    Flows of non-Newtonian fluids through pipes are relevant in many engineering applications, especially within the manufacturing, process and wastewater industries. This paper reports on the numerical computation of the turbulent flow of power-law fluids in smooth circular tubes. The turbulence is represented by means of a modified version of an existing two-equation turbulence model. Numerical results are presented for the fully-developed friction factor and velocity profile, and compared with experimental data. The model is shown to produce fairly good agreement with experiment over a wide range of values for the power-law index and generalized Reynolds number.

  6. Power-law cosmologies in minimal and maximal gauged supergravity

    E-print Network

    J. Blåbäck; A. Borghese; S. S. Haque

    2013-03-13

    In this paper we search for accelerating power-law solutions and ekpyrotic solutions within minimal and maximal four dimensional supergravity theories. We focus on the STU model for N=1 and on the new CSO(p,q,r) theories, which were recently obtained exploiting electromagnetic duality, for N=8. In the minimal case we find some new ekpyrotic solutions, while in the maximal case we find some new generic power-law solutions. We do not find any new accelerating solutions for these models.

  7. Chaotic and Power Law Turbulent States in Jerky Flow

    NASA Astrophysics Data System (ADS)

    Ananthakrishna, G.; Bharathi, M. S.

    Recent studies on the Portevin-Le Chatelier effect report an intriguing crossover phenomenon from a low dimensional chaotic to an infinite dimensional scale invariant power law regime in experiments on CuAl single crystals and AlMg polycrystals, as a function of strain rate. We devise a fully dynamical model which reproduces this crossover. At low and medium strain rates, the model is chaotic with the structure of the attractor resembling the reconstructed experimental attractor. At high strain rates, power law statistics for the magnitudes and durations of the stress drops emerge as in experiments and concomitantly, the largest Lyapunov exponent is zero.

  8. Power-law creep from discrete dislocation dynamics.

    PubMed

    Keralavarma, Shyam M; Cagin, T; Arsenlis, A; Benzerga, A Amine

    2012-12-28

    We report two-dimensional discrete dislocation dynamics simulations of combined dislocation glide and climb leading to "power-law" creep in a model aluminum crystal. The approach fully accounts for matter transport due to vacancy diffusion and its coupling with dislocation motion. The existence of quasiequilibrium or jammed states under the applied creep stresses enables observations of diffusion and climb over time scales relevant to power-law creep. The predictions for the creep rates and stress exponents fall within experimental ranges, indicating that the underlying physics is well captured. PMID:23368581

  9. Lensing Basics: IV. Power-law mass model

    E-print Network

    : the COSmological MOnitoring of GRAvItational Lenses · time delays of lensed quasars from optical monitoringLensing Basics: IV. Power-law mass model and its applications Sherry Suyu Academia Sinica Institute, how do we determine the lens mass distribution? i.e., how to use lenses to measure mass? Use

  10. Constraints on cosmological parameters in power-law cosmology

    E-print Network

    Sarita Rani; A. Altaibayeva; M. Shahalam; J. K. Singh; R. Myrzakulov

    2015-03-19

    In this paper, we examine observational constraints on the power law cosmology; essentially dependent on two parameters $H_0$ (Hubble constant) and $q$ (deceleration parameter). We investigate the constraints on these parameters using the latest 28 points of H(z) data and 580 points of Union2.1 compilation data and, compare the results with the results of $\\Lambda$CDM. We also forecast constraints using a simulated data set for the future JDEM, supernovae survey. Our studies give better insight into power law cosmology than the earlier done analysis by Kumar [arXiv:1109.6924] indicating it tuning well with Union2.1 compilation data but not with H(z) data. However, the constraints obtained on $$ and $$ i.e. $H_0$ average and $q$ average using the simulated data set for the future JDEM, supernovae survey are found to be inconsistent with the values obtained from the H(z) and Union2.1 compilation data. We also perform the statefinder analysis and find that the power-law cosmological models approach the standard $\\Lambda$CDM model as $q\\rightarrow -1$. Finally, we observe that although the power law cosmology explains several prominent features of evolution of the Universe, it fails in details.

  11. Parameter identifiability of power-law biochemical system models.

    PubMed

    Srinath, Sridharan; Gunawan, Rudiyanto

    2010-09-01

    Mathematical modeling has become an integral component in biotechnology, in which these models are frequently used to design and optimize bioprocesses. Canonical models, like power-laws within the Biochemical Systems Theory, offer numerous mathematical and numerical advantages, including built-in flexibility to simulate general nonlinear behavior. The construction of such models relies on the estimation of unknown case-specific model parameters by way of experimental data fitting, also known as inverse modeling. Despite the large number of publications on this topic, this task remains the bottleneck in canonical modeling of biochemical systems. The focus of this paper concerns with the question of identifiability of power-law models from dynamic data, that is, whether the parameter values can be uniquely and accurately identified from time-series data. Existing and newly developed parameter identifiability methods were applied to two power-law models of biochemical systems, and the results pointed to the lack of parametric identifiability as the root cause of the difficulty faced in the inverse modeling. Despite the focus on power-law models, the analyses and conclusions are extendable to other canonical models, and the issue of parameter identifiability is expected to be a common problem in biochemical system modeling. PMID:20197073

  12. Squeeze flow of a power-law viscoplastic solid

    Microsoft Academic Search

    J. D. Sherwood; D. Durban

    1996-01-01

    A cylinder of height h is squeezed between two parallel circular plates of radius R >>h. The cylinder is assumed to behave as a generalised Newtonian material in which the stress and strain rate are coaxial: the particular cases of a rigid-plastic solid and power-law fluid are considered in detail. It is assumed that the frictional stress at the walls

  13. A power-law description of heavy ion collision centrality

    E-print Network

    Thomas A. Trainor; Duncan J. Prindle

    2007-01-30

    The minimum-bias distribution on heavy ion collision multiplicity $n_{ch}$ is well approximated by power-law form $n_{ch}^{-3/4}$, suggesting that a change of variable to $n_{ch}^{1/4}$ may provide more precise access to the structure of the distribution and to A-A collision centrality. We present a detailed centrality study of Hijing-1.37 Monte Carlo data at 200 GeV using the power-law format. We find that the minimum-bias distribution on $n_{participant}^{1/4}$, determined with a Glauber Monte Carlo simulation, is uniform except for a 5% sinusoidal variation. The power-law format reveals precise linear relations between Glauber parameters $n_{part}$ and $n_{bin}$ and the fractional cross section. The power-law format applied to RHIC data facilitates incorporation of extrapolation constraints on data and Glauber distributions to obtain a ten-fold improvement in centrality accuracy for peripheral collisions.

  14. Henry's law, surface tension, and surface adsorption in dilute binary mixtures

    E-print Network

    Akira Onuki

    2009-02-07

    Equilibrium properties of dilute binary fluid mixtures are studied in two-phase states on the basis of a Helmholtz free energy including the gradient free energy. The solute partitioning between gas and liquid (Henry's law) and the surface tension change $\\Delta\\gamma$ are discussed. A derivation of the Gibbs law $\\Delta\\gamma=-T\\Gamma$ is given with $\\Gamma$ being the surface adsorption. Calculated quantities include the derivatives $d T_c/dX$ and $d p_c/dX$ of the critical temperature and pressure with respect to the solute molar fraction $X$ and the temperature-derivative $(\\p \\gamma/\\p T)_{{\\rm cx},p}$ of the surface tension at fixed pressure $p$ on the coexistence surface. Here $(\\p \\gamma/\\p T)_{{\\rm cx},p}$ can be both positive and negative, depending on the solute molecular size and the solute-solvent interaction,and diverges on the azeptropic line. Explicit expressions are given for all these quantities in the van der Waals model.

  15. Thermal emission in fatigue described by power laws

    NASA Astrophysics Data System (ADS)

    Curti, G.; Curã, F.; Gallinatti, A. E.; Sesana, R.

    2010-06-01

    In the present work, a theoretical model proposed by the literature and focused on the relationship between microplasticizations thermal behaviour and fatigue scatter is analysed and applied to fatigue test results of standard and notched steel specimens. The same experimental data are subjected to the TCM (Two Curves Method) thermographic elaboration technique, in order to quickly evaluate fatigue limit values. TCM method has been modified, aiming at interpolating thermal data referred to the region of loads upper than fatigue limit with a non linear regression law having the same mathematical structure of the theoretical model equations (power laws).

  16. Generalized Second Law of Thermodynamics for FRW Cosmology with Power-Law Entropy Correction

    E-print Network

    Ujjal Debnath; Surajit Chattopadhyay; Ibrar Hussain; Mubasher Jamil; Ratbay Myrzakulov

    2012-02-23

    In this work, we have considered the power law correction of entropy on the horizon. If the flat FRW Universe is filled with the n components fluid with interactions, the GSL of thermodynamics for apparent and event horizons have been investigated for equilibrium and non-equilibrium cases. If we consider a small perturbation around the de Sitter space-time, the general conditions of the validity of GSL have been found. Also if a phantom dominated Universe has a polelike type scale factor, the validity of GSL has also been analyzed. Further we have obtained constraints on the power-law parameter {\\alpha} in the phantom and quintessence dominated regimes. Finally we obtain conditions under which GSL breaks down in a cosmological background.

  17. Power law rank-abundance relationships in marine phage populations

    NASA Astrophysics Data System (ADS)

    Salamon, Peter; Hoffmann, Karl Heinz; Rodriguez-Brito, Beltran

    2005-03-01

    Phage are the most abundant biological entities in the biosphere, with an estimated 10^31 particles on the planet. About 25% of oceanic organic carbon is cycled through phage every day. Metagenomic analyses show that the rank-abundance curve for marine phage communities follows a power law distribution. This distribution is consistent with a proposed, modified version of Lotka-Volterra predator-prey dynamics, where blooms of a specific microbial species leads to blooms of their corresponding phage and a subsequent decrease in abundance. The model predicts that the majority of phage types in a population will be rare and it is unlikely that the most abundant phage will be the same at different time points. The model is based on spatial-temporal heterogeneity and a power law phage decay, which are both supported by empirical data.

  18. Power-laws in recurrence networks from dynamical systems

    E-print Network

    Y. Zou; J. Heitzig; R. V. Donner; J. F. Donges; J. D. Farmer; R. Meucci; S. Euzzor; N. Marwan; J. Kurths

    2012-03-15

    Recurrence networks are a novel tool of nonlinear time series analysis allowing the characterisation of higher-order geometric properties of complex dynamical systems based on recurrences in phase space, which are a fundamental concept in classical mechanics. In this Letter, we demonstrate that recurrence networks obtained from various deterministic model systems as well as experimental data naturally display power-law degree distributions with scaling exponents $\\gamma$ that can be derived exclusively from the systems' invariant densities. For one-dimensional maps, we show analytically that $\\gamma$ is not related to the fractal dimension. For continuous systems, we find two distinct types of behaviour: power-laws with an exponent $\\gamma$ depending on a suitable notion of local dimension, and such with fixed $\\gamma=1$.

  19. Statistical Power-Law Spectra due to Reservoir Fluctuations

    E-print Network

    T. S. Biró; G. G. Barnaföldi; P. Ván; K. Ürmössy

    2014-04-04

    LHC ALICE data are interpreted in terms of statistical power-law tailed pT spectra. As explanation we derive such statistical distributions for particular particle number fluctuation patterns in a finite heat bath exactly, and for general thermodynamical systems in the subleading canonical expansion approximately. Our general result, $q = 1 - 1/C + \\Delta T^2 / T^2$, demonstrates how the heat capacity and the temperature fluctuation effects compete, and cancel only in the standard Gaussian approximation.

  20. Weak power law rheology of soft glassy and gelled materials

    E-print Network

    Patricio, Pedro

    2015-01-01

    We make a parallel excursion to the generalised Maxwell and Kelvin-Voigt models to find which general conditions may lead to the weak power law behaviours of the elastic and viscous moduli, $G'(w)\\sim G''(w)\\sim w^\\alpha$, with $0 y\\approx \\alpha$ and $y> x\\approx \\alpha$ for respectively the generalised Maxwell and Kelvin-Voigt models. Beyond this region, we find very different and interesting exponents.

  1. Luttinger liquids with boundaries: Power-laws and energy scales

    NASA Astrophysics Data System (ADS)

    Meden, V.; Metzner, W.; Schollwöck, U.; Schneider, O.; Stauber, T.; Schönhammer, K.

    2000-08-01

    We present a study of the one-particle spectral properties for a variety of models of Luttinger liquids with open boundaries. We first consider the Tomonaga-Luttinger model using bosonization. For weak interactions the boundary exponent of the power-law suppression of the spectral weight close to the chemical potential is dominated by a term linear in the interaction. This motivates us to study the spectral properties also within the Hartree-Fock approximation. It already gives power-law behavior and qualitative agreement with the exact spectral function. For the lattice model of spinless fermions and the Hubbard model we present numerically exact results obtained using the density-matrix renormalization-group algorithm. We show that many aspects of the behavior of the spectral function close to the boundary can again be understood within the Hartree-Fock approximation. For the repulsive Hubbard model with interaction U the spectral weight is enhanced in a large energy range around the chemical potential. At smaller energies a power-law suppression, as predicted by bosonization, sets in. We present an analytical discussion of the crossover and show that for small U it occurs at energies exponentially (in -1/U) close to the chemical potential, i.e. that bosonization only holds on exponentially small energy scales. We show that such a crossover can also be found in other models.

  2. Power law scaling in Universal Extra Dimension scenarios

    E-print Network

    Gautam Bhattacharyya; Anindya Datta; Swarup Kumar Majee; Amitava Raychaudhuri

    2006-11-14

    We study the power law running of gauge, Yukawa and quartic scalar couplings in the universal extra dimension scenario where the extra dimension is accessed by all the standard model fields. After compactifying on an $S_1 /Z_2$ orbifold, we compute one-loop contributions of the relevant Kaluza-Klein (KK) towers to the above couplings up to a cutoff scale $\\Lambda$. Beyond the scale of inverse radius, once the KK states are excited, these couplings exhibit power law dependence on $\\Lambda$. As a result of faster running, the gauge couplings tend to unify at a relatively low scale, and we choose our cutoff also around that scale. For example, for a radius $R \\sim 1 TeV^{-1}$, the cutoff is around 30 TeV. We then examine the consequences of power law running on the triviality and vacuum stability bounds on the Higgs mass. We also comment that the supersymmetric extension of the scenario requires $R^{-1}$ to be larger than $\\sim 10^{10}$ GeV in order that the gauge couplings remain perturbative up to the scale where they tend to unify.

  3. Quasi-power laws in multiparticle production processes

    E-print Network

    Grzegorz Wilk; Zbigniew W?odarczyk

    2015-03-30

    We review the ubiquitous presence in multiparticle production processes of quasi-power law distributions (i.e., distributions following pure power laws for large values of the argument but remaining finite, usually exponential, for small values). Special emphasis is placed on the conjecture that this reflects the presence in the produced hadronic systems of some intrinsic fluctuations. If described by parameter q they form, together with the scale parameter $T$ ("temperature"), basis of Tsallis distribution, ${f(X)\\sim [1 - (1-q)X/T]^{1/(1-q)}}$, frequently used to describe the relevant distributions (the X being usually a transverse momentum). We discuss the origin of such quasi-power law behavior based on our experience with the description of multiparticle production processes. In particular, we discuss Tsallis distribution with complex nonextensivity parameter q and argue that it is needed to describe log-oscillations as apparently observed in recent data on large momentum distributions in very high energy p-p collisions.

  4. Advanced binary geothermal power plants working fluid property determination and heat exchanger design

    Microsoft Academic Search

    C. J. Bliem; G. L. Mines

    1989-01-01

    The performance of binary geothermal power plants can be improved through the proper choice of a working fluid, and optimization of component designs and operating conditions. This paper reviews the investigations at the Idaho National Engineering Laboratory (INEL) which are examining binary cycle performance improvements for moderate temperature (350 to 400 F) resources with emphasis on how the improvements may

  5. Development of Jet Noise Power Spectral Laws Using SHJAR Data

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James

    2009-01-01

    High quality jet noise spectral data measured at the Aeroacoustic Propulsion Laboratory at the NASA Glenn Research Center is used to examine a number of jet noise scaling laws. Configurations considered in the present study consist of convergent and convergent-divergent axisymmetric nozzles. Following the work of Viswanathan, velocity power factors are estimated using a least squares fit on spectral power density as a function of jet temperature and observer angle. The regression parameters are scrutinized for their uncertainty within the desired confidence margins. As an immediate application of the velocity power laws, spectral density in supersonic jets are decomposed into their respective components attributed to the jet mixing noise and broadband shock associated noise. Subsequent application of the least squares method on the shock power intensity shows that the latter also scales with some power of the shock parameter. A modified shock parameter is defined in order to reduce the dependency of the regression factors on the nozzle design point within the uncertainty margins of the least squares method.

  6. Published online 1 May 2002 The fractal nature of nature: power laws, ecological

    E-print Network

    Brown, James H.

    Published online 1 May 2002 The fractal nature of nature: power laws, ecological complexity of ecology is order that re ects the operation of funda- mental physical and biological processes. Power laws of magnitude. Power laws allow extrapolation and predic- tion over a wide range of scales. Some appear

  7. Low power correlation detector for binary FSK direct-conversion receivers

    Microsoft Academic Search

    J. Min; A. Rofougaran; S. Khorram; H. Samueli; A. A. Abidi

    1995-01-01

    A multiplierless binary FSK detector with 82 dB of dynamic range is presented. The proposed detector is well-suited for low-power direct-conversion receivers used in wireless communications systems employ- ing FSK modulation.

  8. Weak power law rheology of soft glassy and gelled materials

    E-print Network

    Pedro Patricio; Catarina R. Leal

    2015-06-05

    We make a parallel excursion to the generalised Maxwell and Kelvin-Voigt models to find which general conditions may lead to the weak power law behaviours of the elastic and viscous moduli, $G'(w)\\sim G''(w)\\sim w^\\alpha$, with $0law spectra of relaxation and retardation times, stemming from the different nature of the models. The first, based on the generalised Maxwell model, retains the fluid properties of a soft glassy material (SGM) above the glass transition. The second, based on the generalised Kelvin-Voigt model, retains the elastic properties of a soft solid or gelled material. Using these models, we calculate with accuracy the power law exponents of $G'(w)\\sim w^x$ and $G''(w)\\sim w^y$, for the whole families of relaxation and retardation spectra previously obtained. Within the region corresponding to $0 y\\approx \\alpha$ and $y> x\\approx \\alpha$ for respectively the generalised Maxwell and Kelvin-Voigt models. Beyond this region, we find very different and interesting exponents.

  9. Interfacial pattern formation in confined power-law fluids.

    PubMed

    Brandão, Rodolfo; Fontana, João V; Miranda, José A

    2014-07-01

    The interfacial pattern formation problem in an injection-driven radial Hele-Shaw flow is studied for the situation in which a Newtonian fluid of negligible viscosity displaces a viscous non-Newtonian power-law fluid. By utilizing a Darcy-law-like formulation, we tackle the fluid-fluid interface evolution problem perturbatively, and we derive second-order mode-coupling equations that describe the time evolution of the perturbation amplitudes. This allows us to investigate analytically how the non-Newtonian nature of the dislocated fluid determines the morphology of the emerging interfacial patterns. If the pushed fluid is shear-thinning, our results indicate the development of side-branching structures. On the other hand, if the displaced fluid is shear-thickening, one detects the formation of petal-like shapes, markedly characterized by strong tip-splitting events. Finally, a time-dependent injection protocol is presented that is able to restrain finger proliferation via side-branching and tip-splitting. This permits the emergence of symmetric n-fold interfacial shapes for which the number of fingers remains fixed as time progresses. This procedure generalizes existing controlling strategies for purely Newtonian flow circumstances to the case of a non-Newtonian, displaced power-law fluid. PMID:25122375

  10. Stochastic mixing model with power law decay of variance

    NASA Astrophysics Data System (ADS)

    Fedotov, Sergei; Ihme, Matthias; Pitsch, Heinz

    2005-01-01

    A stochastic mixing model based on the law of large numbers is presented that describes the decay of the variance of a conserved scalar in decaying turbulence as a power law, ?c2?t-? . A general Lagrangian mixing process is modeled by a stochastic difference equation where the mixing frequency and the ambient concentration are random processes. The mixing parameter ? is introduced as a coefficient in the mixing frequency in order to account for initial length-scale ratio of the velocity and scalar field and other physical dependencies. We derive a nonlinear integral equation for the probability density function (pdf) of a conserved scalar that describes the relaxation of an arbitrary initial distribution to a ? -function. Numerical studies of this equation are conducted, and it is shown that ? has a distinct influence on the decay rate of the scalar. Results obtained from the model for the evolution of the pdf are in a good agreement with direct numerical simulation (DNS) data.

  11. Phase morphology and bulk strength in power-law materials

    NASA Astrophysics Data System (ADS)

    Gerbi, Christopher; Johnson, Scott; Cook, Alden; Vel, Senthil

    2015-04-01

    The strength of a polyphase aggregate depends on the constitutive laws of the phases present, the arrangement of those phases, and environmental conditions such as temperature and stress. In this contribution, we consider the degree to which the arrangement of the phases influences the bulk strength of geological materials. Calculations using current single-mineral experimental data indicate that the absolute and relative strength differences between the upper and lower theoretical bounds vary widely with mineral pair and environmental conditions. For example, at 850?C, some pairs, such as plagioclase-clinopyroxene, are highly sensitive to phase morphology, whereas others, such as quartz-plagioclase, are not. Using a finite element implementation of asymptotic expansion homogenization and assuming power-law flow for the phases present, we can calculate the bulk strength of natural microstructures across macroscale strain gradients. We find that phase morphology does not change sufficiently in most cases to be the dominant factor in bulk strength variation. Thus on its own, phase morphology in an aggregate of power-law materials does not appear to be a major control on bulk strength under typical viscous geological conditions. However, phase morphology does affect microscale stress and strain rate patterns which in turn can induce microscale variations in constitutive laws and diffusional pathways. These factors, including reactions and changing deformation mechanisms, are strongly influenced by phase morphology and do cause strength variation in rocks. As a result, any parameterization of rock strength cannot rely on morphology alone, but also needs to account for microscale variation in deformation mechanisms, including - in most instances - mass transfer.

  12. SHJAR Jet Noise Data and Power Spectral Laws

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James

    2009-01-01

    High quality jet noise spectral data measured at the Aeroacoustic Propulsion Laboratory at the NASA Glenn Research Center is used to examine a number of jet noise scaling laws. Configurations considered in the present study consist of convergent and convergent-divergent axisymmetric nozzles. The measured spectral data are shown in narrow band and cover 8193 equally spaced points in a typical Strouhal number range of 0.0 to 10.0. The measured data are reported as lossless (i.e., atmospheric attenuation is added to measurements), and at 24 equally spaced angles (50deg to 165deg) on a 100-diameter (200-in.) arc. Following the work of Viswanathan, velocity power factors are evaluated using a least squares fit on spectral power density as a function of jet temperature and observer angle. The goodness of the fit and the confidence margins for the two regression parameters are studied at each angle, and alternative relationships are proposed to improve the spectral collapse when certain conditions are met. As an immediate application of the velocity power laws, spectral density in shockcontaining jets are decomposed into components attributed to jet mixing noise and shock noise. From this analysis, jet noise prediction tools can be developed with different spectral components derived from different physics.

  13. The p-sphere and the geometric substratum of power-law probability distributions [rapid communication

    NASA Astrophysics Data System (ADS)

    Vignat, C.; Plastino, A.

    2005-08-01

    Links between power law probability distributions and marginal distributions of uniform laws on p-spheres in R show that a mathematical derivation of the Boltzmann Gibbs distribution necessarily passes through power law ones. Results are also given that link parameters p and n to the value of the non-extensivity parameter q that characterizes these power laws in the context of non-extensive statistics.

  14. Power laws, discontinuities and regional city size distributions

    USGS Publications Warehouse

    Garmestani, A.S.; Allen, C.R.; Gallagher, C.M.

    2008-01-01

    Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classes in the city size distributions are snapshots of stable states within urban systems in flux. ?? 2008.

  15. Elastohydrodynamic analysis using a power law pressure-viscosity relation

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Zaretsky, E. V.

    1973-01-01

    An isothermal elastohydrodynamic (EHD) inlet analysis of the Grubin type which considers a power law pressure-viscosity relation and a finite pressure at the inlet edge of the Hertzian contact zone was performed. Comparisons made with published X-ray EHD film thickness data for a synthetic paraffinic oil and when conventional EHD theory showed that the present theory exhibits a slightly stronger film thickness load dependence than do previous isothermal EHD theories but far less than that exhibited by the measured data.

  16. A reservoir for inverse power law decoherence of a qubit

    E-print Network

    Filippo Giraldi; Francesco Petruccione

    2011-01-24

    The exact dynamics of a Jaynes-Cummings model for a qubit interacting with a continuous distribution of bosons, characterized by a special form of the spectral density, is evaluated analytically. The special reservoir is designed to induce anomalous decoherence, resulting in an inverse power law relaxation, of power 3/2, over an evaluated long time scale. If compared to the exponential-like relaxation obtained from the original Jaynes-Cummings model for Lorentzian-type spectral density functions, decoherence is strongly suppressed. The special reservoir exhibits an upper band edge frequency coinciding with the qubit transition frequency. Known theoretical models of photonic band gap media suitable for the realization of the designed reservoir are proposed.

  17. Optimized dynamical decoupling for power-law noise spectra

    SciTech Connect

    Pasini, S.; Uhrig, G. S. [Lehrstuhl fuer Theoretische Physik I, TU Dortmund, Otto-Hahn Strasse 4, D-44221 Dortmund (Germany)

    2010-01-15

    We analyze the suppression of decoherence by means of dynamical decoupling in the pure-dephasing spin-boson model for baths with power law spectra. The sequence of ideal pi pulses is optimized according to the power of the bath. We expand the decoherence function and separate the canceling divergences from the relevant terms. The proposed sequence is chosen to be the one minimizing the decoherence function. By construction, it provides the best performance. We analytically derive the conditions that must be satisfied. The resulting equations are solved numerically. The solutions are very close to the Carr-Purcell-Meiboom-Gill sequence for a soft cutoff of the bath while they approach the Uhrig dynamical-decoupling sequence as the cutoff becomes harder.

  18. Power Law Distributions of Patents as Indicators of Innovation

    E-print Network

    O'Neale, D R J

    2012-01-01

    The total number of patents produced by a country (or the number of patents produced per capita) is often used as an indicator for innovation. Here we present evidence that the distribution of patents amongst applicants within many OECD countries is well-described by power laws with exponents that vary between 1.66 (Japan) and 2.37 (Poland). Using simulations based on simple preferential attachment-type rules that generate power laws, we find we can explain some of the variation in exponents between countries, with countries that have larger numbers of patents per applicant generally exhibiting smaller exponents in both the simulated and actual data. Similarly we find that the exponents for most countries are inversely correlated with other indicators of innovation, such as R&D intensity or the ubiquity of export baskets. This suggests that in more advanced economies, which tend to have smaller values of the exponent, a greater proportion of the total number of patents are filed by large companies than in...

  19. Beyond the power law: Uncovering stylized facts in interbank networks

    NASA Astrophysics Data System (ADS)

    Vandermarliere, Benjamin; Karas, Alexei; Ryckebusch, Jan; Schoors, Koen

    2015-06-01

    We use daily data on bilateral interbank exposures and monthly bank balance sheets to study network characteristics of the Russian interbank market over August 1998-October 2004. Specifically, we examine the distributions of (un)directed (un)weighted degree, nodal attributes (bank assets, capital and capital-to-assets ratio) and edge weights (loan size and counterparty exposure). We search for the theoretical distribution that fits the data best and report the "best" fit parameters. We observe that all studied distributions are heavy tailed. The fat tail typically contains 20% of the data and can be mostly described well by a truncated power law. Also the power law, stretched exponential and log-normal provide reasonably good fits to the tails of the data. In most cases, however, separating the bulk and tail parts of the data is hard, so we proceed to study the full range of the events. We find that the stretched exponential and the log-normal distributions fit the full range of the data best. These conclusions are robust to (1) whether we aggregate the data over a week, month, quarter or year; (2) whether we look at the "growth" versus "maturity" phases of interbank market development; and (3) with minor exceptions, whether we look at the "normal" versus "crisis" operation periods. In line with prior research, we find that the network topology changes greatly as the interbank market moves from a "normal" to a "crisis" operation period.

  20. An inverse method for rheometry of power-law fluids

    NASA Astrophysics Data System (ADS)

    Hemaka Bandulasena, H. C.; Zimmerman, William B.; Rees, Julia M.

    2011-12-01

    This paper is concerned with the determination of the constitutive viscous parameters of dilute solutions of xanthan gum by means of an inverse method used in conjunction with finite element modeling of the governing system of partial differential equations. At low concentrations xanthan gum behaves as a shear-thinning, power-law non-Newtonian fluid. Finite element modeling is used to simulate the pressure-driven flow of xanthan gum solutions in a microchannel T-junction. As the flow is forced to turn the corner of the T-junction a range of shear rates, and hence viscosities, is produced. It is shown that the statistical properties of the velocity field are sensitive to the constitutive parameters of the power-law model. The inverse method is shown to be stable and accurate, with measurement error in the velocity field translating to small errors in the rheological parameter estimation. Due to the particular structure of the inverse map, the error propagation is substantially less than the estimate from the Hadamard criterion.

  1. Power Laws in Real Estate Prices during Bubble Periods

    NASA Astrophysics Data System (ADS)

    Ohnishi, Takaaki; Mizuno, Takayuki; Shimizu, Chihiro; Watanabe, Tsutomu

    How can we detect real estate bubbles? In this paper, we propose making use of information on the cross-sectional dispersion of real estate prices. During bubble periods, prices tend to go up considerably for some properties, but less so for others, so that price inequality across properties increases. In other words, a key characteristic of real estate bubbles is not the rapid price hike itself but a rise in price dispersion. Given this, the purpose of this paper is to examine whether developments in the dispersion in real estate prices can be used to detect bubbles in property markets as they arise, using data from Japan and the U.S. First, we show that the land price distribution in Tokyo had a power-law tail during the bubble period in the late 1980s, while it was very close to a lognormal before and after the bubble period. Second, in the U.S. data we find that the tail of the house price distribution tends to be heavier in those states which experienced a housing bubble. We also provide evidence suggesting that the power-law tail observed during bubble periods arises due to the lack of price arbitrage across regions.

  2. Fractional Action Cosmology: Emergent, Logamediate, Intermediate, Power law Scenarios of the Universe and Generalized Second Law of Thermodynamics

    E-print Network

    Ujjal Debnath; Mubasher Jamil; Surajit Chattopadhyay

    2011-09-07

    In the framework of Fractional Action Cosmology (FAC), we study the generalized second law of thermodynamics for the Friedmann Universe enclosed by a boundary. We use the four well-known cosmic horizons as boundaries namely, apparent horizon, future event horizon, Hubble horizon and particle horizon. We construct the generalized second law (GSL) using and without using the first law of thermodynamics. To check the validity of GSL, we express the law in the form of four different scale factors namely emergent, logamediate, intermediate and power law. For Hubble, apparent and particle horizons, the GSL holds for emergent and logamediate expansions of the universe when we apply with and without using first law. For intermediate scenario, the GSL is valid for Hubble, apparent, particle horizons when we apply with and without first law. Also for intermediate scenario, the GSL is valid for event horizon when we apply first law but it breaks down without using first law. But for power law expansion, the GSL may be valid for some cases and breaks down otherwise.

  3. Stevens' Power Law in 3D Tele-immersion Towards Subjective Modeling of Multimodal Cyber Interaction

    E-print Network

    Nahrstedt, Klara

    Stevens' Power Law in 3D Tele-immersion Towards Subjective Modeling of Multimodal Cyber Interaction? Psychophysical laws are results of quantitative psychology [5], a study with long history that well serves

  4. Power law violation of the area law in quantum spin chains

    E-print Network

    Ramis Movassagh; Peter W. Shor

    2014-10-03

    The sub-volume scaling of the entanglement entropy with the system's size, $n$, has been a subject of vigorous study in the last decade [1]. The area law provably holds for gapped one dimensional systems [2] and it was believed to be violated by at most a factor of $\\log\\left(n\\right)$ in physically reasonable models such as critical systems. In this paper, we generalize the spin$-1$ model of Bravyi et al [3] to all integer spin-$s$ chains, whereby we introduce a class of exactly solvable models that are physical and exhibit signatures of criticality, yet violate the area law by a power law. The proposed Hamiltonian is local and translationally invariant in the bulk. We prove that it is frustration free and has a unique ground state. Moreover, we prove that the energy gap scales as $n^{-c}$, where using the theory of Brownian excursions, we prove $c\\ge2$. This rules out the possibility of these models being described by a conformal field theory. We analytically show that the Schmidt rank grows exponentially with $n$ and that the half-chain entanglement entropy to the leading order scales as $\\sqrt{n}$ (Eq. 16). Geometrically, the ground state is seen as a uniform superposition of all $s-$colored Motzkin walks. Lastly, we introduce an external field which allows us to remove the boundary terms yet retain the desired properties of the model. Our techniques for obtaining the asymptotic form of the entanglement entropy, the gap upper bound and the self-contained expositions of the combinatorial techniques, more akin to lattice paths, may be of independent interest.

  5. Power-law inflation with a nonminimally coupled scalar field

    E-print Network

    Tsujikawa, S

    2000-01-01

    We consider the dynamics of power-law inflation with a nonminimally coupled scalar field $\\phi$. It is well known that multiple scalar fields with exponential potentials $V(\\phi)=V_0 {\\rm exp}(-\\sqrt{16\\pi/p m_{\\rm pl}^2} \\phi)$ lead to an inflationary solution even if the each scalar field is not capable to sustain inflation. In this paper, we show that inflation can be assisted even in the one-field case by the effect of nonminimal coupling. When $\\xi$ is positive, since an effective potential which arises by a conformal transformation becomes flatter compared with the case of $\\xi=0$ for $\\phi>0$, we have an inflationary solution even when the universe evolves as non-inflationary in the minimally coupled case. For the negative $\\xi$, the assisted inflation can take place when $\\phi$ evolves in the region of $\\phi<0$ \\.

  6. Radiative corrections in the (varying power)-law modified gravity

    NASA Astrophysics Data System (ADS)

    Hammad, Fayçal

    2015-06-01

    Although the (varying power)-law modified gravity toy model has the attractive feature of unifying the early- and late-time expansions of the Universe, thanks to the peculiar dependence of the scalar field's potential on the scalar curvature, the model still suffers from the fine-tuning problem when used to explain the actually observed Hubble parameter. Indeed, a more correct estimate of the mass of the scalar field needed to comply with actual observations gives an unnaturally small value. On the other hand, for a massless scalar field the potential would have no minimum and hence the field would always remain massless. What solves these issues are the radiative corrections that modify the field's effective potential. These corrections raise the field's effective mass, rendering the model free from fine-tuning, immune against positive fifth-force tests, and better suited to tackle the dark matter sector.

  7. Power-law distribution of pressure fluctuations in multiphase flow.

    PubMed

    Gheorghiu, S; van Ommen, J R; Coppens, M-O

    2003-04-01

    Bubbling fluidized beds are granular systems, in which a deep layer of particles is set in motion by a vertical gas stream, with the excess gas rising as bubbles through the bed. We show that pressure fluctuations in such a system have non-Gaussian statistics. The probability density function has a power-law drop-off and is very well represented by a Tsallis distribution. Its shape is explained through the folding of the Gaussian distribution of pressure fluctuations produced by a monodisperse set of bubbles, onto the actual distribution of bubble sizes in the bed, assuming that bubbles coalesce via a Smoluchowski-type aggregation process. Therefore, the Tsallis statistics arise as a result of bubble polydispersity, rather than system nonextensivity. PMID:12786360

  8. Persistence of Locality in Systems with Power-Law Interactions

    NASA Astrophysics Data System (ADS)

    Gong, Zhe-Xuan; Foss-Feig, Michael; Michalakis, Spyridon; Gorshkov, Alexey V.

    2014-07-01

    Motivated by recent experiments with ultracold matter, we derive a new bound on the propagation of information in D-dimensional lattice models exhibiting 1/r? interactions with ?>D. The bound contains two terms: One accounts for the short-ranged part of the interactions, giving rise to a bounded velocity and reflecting the persistence of locality out to intermediate distances, whereas the other contributes a power-law decay at longer distances. We demonstrate that these two contributions not only bound but, except at long times, qualitatively reproduce the short- and long-distance dynamical behavior following a local quench in an XY chain and a transverse-field Ising chain. In addition to describing dynamics in numerous intractable long-range interacting lattice models, our results can be experimentally verified in a variety of ultracold-atomic and solid-state systems.

  9. An effective quintessence field with a power-law potential

    E-print Network

    M. Khurshudyan; B. Pourhassan; R. Myrzakulov; S. Chattopadhyay

    2014-10-28

    In this paper, we consider an effective quintessence scalar field with a power-law potential interacting with a $P_{b}=\\xi q\\rho_{b}$ barotropic fluid as a first model, where $q$ is a deceleration parameter. For the second model we assume viscous polytropic gas interacting with the scalar field. We investigate problem numerically and analyze behavior of different cosmological parameter concerning to components and behavior of Universe. We also compare our results with observational data to fix parameters of the models. We find some instabilities in the first model which may disappear in the second model for the appropriate parameters. Therefore, we can propose interacting quintessence dark energy with viscous polytropic gas as a successful model to describe Universe.

  10. Persistence of locality in systems with power-law interactions

    E-print Network

    Zhe-Xuan Gong; Michael Foss-Feig; Spyridon Michalakis; Alexey V. Gorshkov

    2014-07-07

    Motivated by recent experiments with ultra-cold matter, we derive a new bound on the propagation of information in $D$-dimensional lattice models exhibiting $1/r^{\\alpha}$ interactions with $\\alpha>D$. The bound contains two terms: One accounts for the short-ranged part of the interactions, giving rise to a bounded velocity and reflecting the persistence of locality out to intermediate distances, while the other contributes a power-law decay at longer distances. We demonstrate that these two contributions not only bound but, except at long times, \\emph{qualitatively reproduce} the short- and long-distance dynamical behavior following a local quench in an $XY$ chain and a transverse-field Ising chain. In addition to describing dynamics in numerous intractable long-range interacting lattice models, our results can be experimentally verified in a variety of ultracold-atomic and solid-state systems.

  11. Persistence of locality in systems with power-law interactions.

    PubMed

    Gong, Zhe-Xuan; Foss-Feig, Michael; Michalakis, Spyridon; Gorshkov, Alexey V

    2014-07-18

    Motivated by recent experiments with ultracold matter, we derive a new bound on the propagation of information in D-dimensional lattice models exhibiting 1/r^{?} interactions with ?>D. The bound contains two terms: One accounts for the short-ranged part of the interactions, giving rise to a bounded velocity and reflecting the persistence of locality out to intermediate distances, whereas the other contributes a power-law decay at longer distances. We demonstrate that these two contributions not only bound but, except at long times, qualitatively reproduce the short- and long-distance dynamical behavior following a local quench in an XY chain and a transverse-field Ising chain. In addition to describing dynamics in numerous intractable long-range interacting lattice models, our results can be experimentally verified in a variety of ultracold-atomic and solid-state systems. PMID:25083624

  12. Giant Planet Migration in Viscous Power-Law Discs

    E-print Network

    R. G. Edgar

    2007-04-03

    Many extra-solar planets discovered over the past decade are gas giants in tight orbits around their host stars. Due to the difficulties of forming these `hot Jupiters' in situ, they are generally assumed to have migrated to their present orbits through interactions with their nascent discs. In this paper, we present a systematic study of giant planet migration in power law discs. We find that the planetary migration rate is proportional to the disc surface density. This is inconsistent with the assumption that the migration rate is simply the viscous drift speed of the disc. However, this result can be obtained by balancing the angular momentum of the planet with the viscous torque in the disc. We have verified that this result is not affected by adjusting the resolution of the grid, the smoothing length used, or the time at which the planet is released to migrate.

  13. Second-law based thermodynamic analysis of Brayton\\/Rankine combined power cycle with reheat

    Microsoft Academic Search

    A. Khaliq; S. C. Kaushik

    2004-01-01

    The aim of the present paper is to use the second-law approach for the thermodynamic analysis of the reheat combined Brayton\\/Rankine power cycle. Expressions involving the variables for specific power-output, thermal efficiency, exergy destruction in components of the combined cycle, second-law efficiency of each process of the gas-turbine cycle, and second-law efficiency of the steam power cycle have been derived.

  14. Relation of the second law of thermodynamics to the power conversion of energy fluctuations

    Microsoft Academic Search

    Joseph C. Yater

    1979-01-01

    The relation of the second law of thermodynamics to the power conversion of fluctuation energy is analyzed using the master equation of the model for the conversion circuit. The performance equation for independent particles shows that the power-conversion performance is given by the second law both for classical and quantum-effect diodes. The relation of the second law to power-conversion models

  15. Power-Law Template for IR Point Source Clustering

    NASA Technical Reports Server (NTRS)

    Addison, Graeme E.; Dunkley, Joanna; Hajian, Amir; Viero, Marco; Bond, J. Richard; Das, Sudeep; Devlin, Mark; Halpern, Mark; Hincks, Adam; Hlozek, Renee; Marriage, Tobias A.; Moodley, Kavilan; Page, Lyman A.; Reese, Erik D.; Scott, Douglass; Spergel, David N.; Staggs,Suzanne T.; Wollack, Edward

    2011-01-01

    We perform a combined fit to angular power spectra of unresolved infrared (IR) point sources from the Planck satellite (at 217,353,545 and 857 GHz, over angular scales 100 < I < 2200), the Balloonborne Large-Aperture Submillimeter Telescope (BLAST; 250, 350 and 500 microns; 1000 < I < 9000), and from correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps. We find that the clustered power over the range of angular scales and frequencies considered is well fit by a simple power law of the form C_l\\propto I(sup -n) with n = 1.25 +/- 0.06. While the IR sources are understood to lie at a range of redshifts, with a variety of dust properties, we find that the frequency dependence of the clustering power can be described by the square of a modified blackbody, nu(sup beta) B(nu,T_eff), with a single emissivity index beta = 2.20 +/- 0.07 and effective temperature T_eff= 9.7 K. Our predictions for the clustering amplitude are consistent with existing ACT and South Pole Telescope results at around 150 and 220 GHz, as is our prediction for the effective dust spectral index, which we find to be alpha_150-220 = 3.68 +/- 0.07 between 150 and 220 GHz. Our constraints on the clustering shape and frequency dependence can be used to model the IR clustering as a contaminant in Cosmic Microwave Background anisotropy measurements. The combined Planck and BLAST data also rule out a linear bias clustering model.

  16. A mechanism to derive multi-power law functions: An application in the econophysics framework

    NASA Astrophysics Data System (ADS)

    Scarfone, A. M.

    2007-08-01

    It is generally recognized that economical systems, and more in general complex systems, are characterized by power law distributions. Sometime, these distributions show a changing of the slope in the tail so that, more appropriately, they show a multi-power law behavior. We present a method to derive analytically a two-power law distribution starting from a single power law function recently obtained, in the frameworks of the generalized statistical mechanics based on the Sharma-Taneja-Mittal information measure. In order to test the method, we fit the cumulative distribution of personal income and gross domestic production of several countries, obtaining a good agreement for a wide range of data.

  17. One loop back reaction on power law inflation

    NASA Astrophysics Data System (ADS)

    Abramo, L. R.; Woodard, R. P.

    1999-08-01

    We consider quantum-mechanical corrections to a homogeneous, isotropic, and spatially flat geometry whose scale factor expands classically as a general power of the comoving time. The effects of both gravitons and the scalar inflaton are computed at one loop using the manifestly causal formalism of Schwinger [J. Math. Phys. 2, 407 (1961); Particles, Sources and Fields (Addison, Wesley, Reading, MA, 1970)] with the Feynman rules recently developed by Iliopoulos et al. [Nucl. Phys. B 534, 419 (1998)]. We find no significant effect, in marked contrast to the result obtained by Mukhanov and co-workers [Phys. Rev. Lett. 78, 1624 (1998); Phys. Rev. D 56, 3248 (1997)] for chaotic inflation based on a quadratic potential. By applying the canonical technique of Mukhanov and co-workers to the exponential potentials of power law inflation, we show that the two methods produce the same results, within the approximations employed, for these backgrounds. We therefore conclude that the shape of the inflaton potential can have an enormous impact on the one loop back reaction.

  18. Gaussian Random Field Power Spectrum and the Sérsic Law

    NASA Astrophysics Data System (ADS)

    Nipoti, Carlo

    2015-06-01

    The surface-brightness profiles of galaxies are well described by the Sérsic law: systems with high Sérsic index m have steep central profiles and shallow outer profiles, while systems with low m have shallow central profiles and steep outer profiles. R. Cen has conjectured that these profiles arise naturally in the standard cosmological model with initial density fluctuations represented by a Gaussian random field (GRF). We explore and confirm this hypothesis with N-body simulations of dissipationless collapses in which the initial conditions are generated from GRFs with different power spectra. The numerical results show that GRFs with more power on small scales lead to systems with higher m. In our purely dissipationless simulations, the Sérsic index is in the range 2? m? 6.5. It follows that systems with Sérsic index as low as m? 2 can be produced by coherent dissipationless collapse, while high-m systems can be obtained if the assembly history is characterized by several mergers. As expected, dissipative processes appear to be required to obtain exponential profiles (m? 1).

  19. Implementation of a low power adaptive binary encoder 

    E-print Network

    Herrin, Scott W

    1999-01-01

    The demand for a low power implementation of a data compression technique is driven by the need for small, light-weight portable electronic devices that need to operate on battery power for extended periods of time at ...

  20. Numerical Simulation of the Flow of a Power Law Fluid in an Elbow Bend 

    E-print Network

    Kanakamedala, Karthik

    2010-07-14

    A numerical study of flow of power law fluid in an elbow bend has been carried out. The motivation behind this study is to analyze the velocity profiles, especially the pattern of the secondary flow of power law fluid in a bend as there are several...

  1. Power-law tail probabilities of drainage areas in river basins

    USGS Publications Warehouse

    Veitzer, S.A.; Troutman, B.M.; Gupta, V.K.

    2003-01-01

    The significance of power-law tail probabilities of drainage areas in river basins was discussed. The convergence to a power law was not observed for all underlying distributions, but for a large class of statistical distributions with specific limiting properties. The article also discussed about the scaling properties of topologic and geometric network properties in river basins.

  2. Bayesian and Empirical Bayes approaches to power law process and microarray analysis

    Microsoft Academic Search

    Zhao Chen

    2004-01-01

    In this dissertation, we apply Bayesian and Empirical Bayes methods for reliability growth models based on the power law process. We also apply Bayes methods for the study of microarrays, in particular, in the selection of differentially expressed genes. The power law process has been used extensively in reliability growth models. Chapter 1 reviews some basic concepts in reliability growth

  3. Folding of a finite length power law layer Daniel W. Schmid1

    E-print Network

    Podladchikov, Yuri

    layer embedded in a weaker Newtonian matrix subjected to plane strain, pure shear far-field flow in two of an isolated finite length power law layer embedded in a Newtonian viscous matrix is investigated and compared and illustrates the folding of finite length layers up to large strains. The configuration studied is a power law

  4. Can Power-Law Scaling and Neuronal Avalanches Arise from Stochastic Dynamics?

    E-print Network

    Destexhe, Alain

    Can Power-Law Scaling and Neuronal Avalanches Arise from Stochastic Dynamics? Jonathan Touboul1 with no ambiguity that the avalanche size is distributed as a power-law. We conclude that logarithmic and Neuronal Avalanches Arise from Stochastic Dynamics? PLoS ONE 5(2): e8982. doi:10.1371/ journal.pone.0008982

  5. Similarity flow solutions of a non-Newtonian power-law fluid Mohamed Guedda, Zakia Hammouch

    E-print Network

    Paris-Sud XI, Université de

    Similarity flow solutions of a non-Newtonian power-law fluid Mohamed Guedda, Zakia Hammouch LAMFA of an incompressible non- Newtonian fluid past a semi-infinite power-law stretched flat plate with uniform free stream mathematical features presented their equations, boundary-layer flows of non-Newtonian fluids have motivated

  6. The Berners-Lee Hypothesis: Power laws and Group Structure in Flickr

    E-print Network

    TAGora project

    by Tim Berners-Lee, is that the structure of online groups should conform to a power law distribution. We.1 The Berners-Lee Hypothesis Tim Berners-Lee, widely acclaimed as the inventor of the Web, has put forwardThe Berners-Lee Hypothesis: Power laws and Group Structure in Flickr Andrea Baldassarri, Alain

  7. A Low-Power Correlation Detector For Binary FSK Direct-Conversion Receivers

    E-print Network

    Arslan, Hüseyin

    A Low-Power Correlation Detector For Binary FSK Direct-Conversion Receivers J. Min, H-C. Liu, A detector must handle this range to avoid any gain control at RF. A CMOS limiting amplifier [6] capable detector, Tone detection, Correlation, Direct-conversion wireless receivers Abstract A multiplierless

  8. Importance of the specific heat anomaly in the design of binary Rankine cycle power plants

    Microsoft Academic Search

    W. L. Pope; P. A. Doyle; R. L. Fulton; L. F. Silvester

    1980-01-01

    The transposed critical temperature (TPCT) is shown to be an extremely important thermodynamic property in the selection of working fluids and turbine states for geothermal power plants operating on a closed organic (binary) Rankine cycle. When the optimum working fluid composition and process states are determined for specified source and sink conditions, turbine inlet states consistently lie adjacent to the

  9. Folding in power-law viscous multi-layers.

    PubMed

    Schmalholz, Stefan M; Schmid, Daniel W

    2012-04-28

    We study high-amplitude folding in layered rocks with two-dimensional numerical simulations. We employ the finite-element method to model shortening of an incompressible multi-layer with power-law viscous rheology. The Lagrangian numerical mesh is deformed and re-meshed to accurately follow the layer interfaces. Three settings are considered: (i) pure shearing of a confined multi-layer, (ii) simple shearing of a multi-layer above a detachment, and (iii) slump folding owing to gravity sliding. In our pure shear simulations, finite-amplitude folds always develop despite confinement and thin weak interlayers. The fold shapes can be significantly irregular, resulting from initial geometrical heterogeneities that are perturbations of the layer interfaces and differences in layer thickness. The bulk normal viscosity of the multi-layer decreases significantly with progressive folding. This structural softening decreases the bulk normal viscosities by a factor of 2-20. For simple shear, the multi-layer does not develop asymmetric fold shapes significantly. Fold axial planes in the multi-layer are mostly curved and not parallel. For slump folding, fold shapes can be significantly asymmetric exhibiting strongly curved fold axial planes and overturned fold limbs. The rheology of the competent layers has a major impact on the fold shapes for gravity-driven multi-layer folding. PMID:22431758

  10. Statistical tests for power-law cross-correlated processes

    NASA Astrophysics Data System (ADS)

    Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

    2011-12-01

    For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ?DCCA(T,n), where T is the total length of the time series and n the window size. For ?DCCA(T,n), we numerically calculated the Cauchy inequality -1??DCCA(T,n)?1. Here we derive -1??DCCA(T,n)?1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ?DCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ?DCCA(T,n) tends with increasing T to 1/T. Using ?DCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

  11. Power law distribution in high frequency financial data? An econometric analysis

    NASA Astrophysics Data System (ADS)

    Todorova, Lora; Vogt, Bodo

    2011-11-01

    Power law distributions are very common in natural sciences. We analyze high frequency financial data from XETRA and the NYSE using maximum likelihood estimation and the Kolmogorov-Smirnov statistic to test whether the power law hypothesis holds also for these data. We find that the universality and scale invariance properties of the power law are violated. Furthermore, the returns of Daimler Chrysler and SAP traded simultaneously on both exchanges follow a power law at one exchange, but not at the other. These results raise some questions about the no-arbitrage condition. Finally, we find that an exponential function provides a better fit for the tails of the sample distributions than a power law function.

  12. Power-law and exponential rank distributions: A panoramic Gibbsian perspective

    NASA Astrophysics Data System (ADS)

    Eliazar, Iddo

    2015-04-01

    Rank distributions are collections of positive sizes ordered either increasingly or decreasingly. Many decreasing rank distributions, formed by the collective collaboration of human actions, follow an inverse power-law relation between ranks and sizes. This remarkable empirical fact is termed Zipf's law, and one of its quintessential manifestations is the demography of human settlements - which exhibits a harmonic relation between ranks and sizes. In this paper we present a comprehensive statistical-physics analysis of rank distributions, establish that power-law and exponential rank distributions stand out as optimal in various entropy-based senses, and unveil the special role of the harmonic relation between ranks and sizes. Our results extend the contemporary entropy-maximization view of Zipf's law to a broader, panoramic, Gibbsian perspective of increasing and decreasing power-law and exponential rank distributions - of which Zipf's law is one out of four pillars.

  13. Out of the Ordinary: Law, Power, Culture, and the Commonplace

    Microsoft Academic Search

    Naomi Mezey

    2001-01-01

    Review of The Common Place of Law: Stories From Everyday Life by Patricia Ewick & Susan S. Silbey (1998).\\u000aSometimes a work's intellectual influences reveal both its strengths and its shortcomings. This is certainly the case with Patricia Ewick and Susan Silbey's The Common Place of Law: Stories From Everyday Life, and its indebtedness to the thinking of Michel Foucault

  14. Liquid-metal binary cycles for stationary power

    NASA Technical Reports Server (NTRS)

    Gutstein, M.; Furman, E. R.; Kaplan, G. M.

    1975-01-01

    The use of topping cycles to increase electric power plant efficiency is discussed, with particular attention to mercury and alkali metal Rankine cycle systems that could be considered for topping cycle applications. An overview of this technology, possible system applications, the required development, and possible problem areas is presented.

  15. Can power-law scaling and neuronal avalanches arise from stochastic dynamics?

    PubMed

    Touboul, Jonathan; Destexhe, Alain

    2010-01-01

    The presence of self-organized criticality in biology is often evidenced by a power-law scaling of event size distributions, which can be measured by linear regression on logarithmic axes. We show here that such a procedure does not necessarily mean that the system exhibits self-organized criticality. We first provide an analysis of multisite local field potential (LFP) recordings of brain activity and show that event size distributions defined as negative LFP peaks can be close to power-law distributions. However, this result is not robust to change in detection threshold, or when tested using more rigorous statistical analyses such as the Kolmogorov-Smirnov test. Similar power-law scaling is observed for surrogate signals, suggesting that power-law scaling may be a generic property of thresholded stochastic processes. We next investigate this problem analytically, and show that, indeed, stochastic processes can produce spurious power-law scaling without the presence of underlying self-organized criticality. However, this power-law is only apparent in logarithmic representations, and does not survive more rigorous analysis such as the Kolmogorov-Smirnov test. The same analysis was also performed on an artificial network known to display self-organized criticality. In this case, both the graphical representations and the rigorous statistical analysis reveal with no ambiguity that the avalanche size is distributed as a power-law. We conclude that logarithmic representations can lead to spurious power-law scaling induced by the stochastic nature of the phenomenon. This apparent power-law scaling does not constitute a proof of self-organized criticality, which should be demonstrated by more stringent statistical tests. PMID:20161798

  16. Evaluation of Hybrid Air-Cooled Flash/Binary Power Cycle

    SciTech Connect

    Greg Mines

    2005-10-01

    Geothermal binary power plants reject a significant portion of the heat removed from the geothermal fluid. Because of the relatively low temperature of the heat source (geothermal fluid), the performance of these plants is quite sensitive to the sink temperature to which heat is rejected. This is particularly true of air-cooled binary plants. Recent efforts by the geothermal industry have examined the potential to evaporatively cool the air entering the air-cooled condensers during the hotter portions of a summer day. While the work has shown the benefit of this concept, air-cooled binary plants are typically located in regions that lack an adequate supply of clean water for use in this evaporative cooling. In the work presented, this water issue is addressed by pre-flashing the geothermal fluid to produce a clean condensate that can be utilized during the hotter portions of the year to evaporatively cool the air. This study examines both the impact of this pre-flash on the performance of the binary plant, and the increase in power output due to the ability to incorporate an evaporative component to the heat rejection process.

  17. Binary generators - you'll wonder where the power went

    Microsoft Academic Search

    Ryan

    1983-01-01

    There has been a surge of interest in electric power generation from low-temperature geothermal energy. The organic Rankine cycle is reviewed for efficiency. A pressure-enthalpy diagram for R-114 (the refrigerant chosen for this study) is given. In the cycle, refrigerant is vaporized, then expanded, to turn the shaft, then condensed, then pumped back into the cycle. The cycle depends on

  18. Asymptotic power law of moments in a random multiplicative process with weak additive noise

    E-print Network

    Hiroya Nakao

    1998-02-03

    It is well known that a random multiplicative process with weak additive noise generates a power-law probability distribution. It has recently been recognized that this process exhibits another type of power law: the moment of the stochastic variable scales as a function of the additive noise strength. We clarify the mechanism for this power-law behavior of moments by treating a simple Langevin-type model both approximately and exactly, and argue this mechanism is universal. We also discuss the relevance of our findings to noisy on-off intermittency and to singular spatio-temporal chaos recently observed in systems of non-locally coupled elements.

  19. Asymptotic Power-Law Index in Aggregation and Weighted-Chipping Processes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroshi; Sekiyama, Makoto; Ohtsuki, Toshiya

    2015-05-01

    The asymptotic power-law behavior of the distribution function P(X) for X clusters is analyzed for aggregation and weighted-chipping processes. Here, chipping off of a cluster of size n takes place with the probability function ˜1/n?. An exact value of a noninteger power-law index is obtained, that is, P(X) ˜ 1/X? with ? = ? in the case of 1 < ? ? 2. This gives thresholds of ? = 2 for the emergence of a condensed cluster and ? = 1 for the appearance of a power-law distribution. Numerical analysis supports well this result.

  20. Two universal physical principles shape the power-law statistics of real-world networks

    E-print Network

    Lorimer, Tom; Stoop, Ruedi

    2015-01-01

    The study of complex networks has pursued an understanding of macroscopic behavior by focusing on power-laws in microscopic observables. Here, we uncover two universal fundamental physical principles that are at the basis of complex networks generation. These principles together predict the generic emergence of deviations from ideal power laws, which were previously discussed away by reference to the thermodynamic limit. Our approach proposes a paradigm shift in the physics of complex networks, toward the use of power-law deviations to infer meso-scale structure from macroscopic observations.

  1. Power-law solution for anisotropic universe in f( G) gravity

    NASA Astrophysics Data System (ADS)

    Fayaz, V.; Hossienkhani, H.; Aghamohammadi, A.

    2015-06-01

    We try to study the theory of modified Gauss-Bonnet gravity in non-isotope universe. It is considered the exact power-law solution in modified gravity models. A f( G) function corresponding with power law solutions for given scale factor are calculated. We show that BI-like power-law solutions only exist for a very special class of f( G) theories. It is shown that transition to phantom phase is happened by applied some bound on free parameters. We also explore the stability issue of modified gravitational models.

  2. Power Spectra, Power Law Exponents, and Anisotropy of Solar Wind Turbulence at Small Scales

    NASA Technical Reports Server (NTRS)

    Podesta, J. J.; Roberts, D. A.; Goldstein, M. L.

    2006-01-01

    The Wind spacecraft provides simultaneous solar wind velocity and magnetic field measurements with 3- second time resolution, roughly an order of magnitude faster than previous measurements, enabling the small scale features of solar wind turbulence to be studied in unprecedented detail. Almost the entire inertial range can now be explored (the inertial range extends from approximately 1 to 10(exp 3) seconds in the spacecraft frame) although the dissipation range of the velocity fluctuations is still out of reach. Improved measurements of solar wind turbulence spectra at 1 AU in the ecliptic plane are presented including spectra of the energy and cross-helicity, the magnetic and kinetic energies, the Alfven ratio, the normalized cross-helicity, and the Elsasser ratio. Some recent observations and theoretical challenges are discussed including the observation that the velocity and magnetic field spectra often show different power law exponents with values close to 3/2 and 5/3, respectively; the energy (kinetic plus magnetic) and cross-helicity often have approximately equal power law exponents with values intermediate between 3/2 and 5/3; and the Alfven ratio, the ratio of the kinetic to magnetic energy spectra, is often a slowly increasing function of frequency increasing from around 0.4 to 1 for frequencies in the inertial range. Differences between high- and low-speed wind are also discussed. Comparisons with phenomenological turbulence theories show that important aspects of the physics are yet unexplained.

  3. Logarithmic and Power Law Input-Output Relations in Sensory Systems with Fold-Change Detection

    PubMed Central

    Adler, Miri; Mayo, Avi; Alon, Uri

    2014-01-01

    Two central biophysical laws describe sensory responses to input signals. One is a logarithmic relationship between input and output, and the other is a power law relationship. These laws are sometimes called the Weber-Fechner law and the Stevens power law, respectively. The two laws are found in a wide variety of human sensory systems including hearing, vision, taste, and weight perception; they also occur in the responses of cells to stimuli. However the mechanistic origin of these laws is not fully understood. To address this, we consider a class of biological circuits exhibiting a property called fold-change detection (FCD). In these circuits the response dynamics depend only on the relative change in input signal and not its absolute level, a property which applies to many physiological and cellular sensory systems. We show analytically that by changing a single parameter in the FCD circuits, both logarithmic and power-law relationships emerge; these laws are modified versions of the Weber-Fechner and Stevens laws. The parameter that determines which law is found is the steepness (effective Hill coefficient) of the effect of the internal variable on the output. This finding applies to major circuit architectures found in biological systems, including the incoherent feed-forward loop and nonlinear integral feedback loops. Therefore, if one measures the response to different fold changes in input signal and observes a logarithmic or power law, the present theory can be used to rule out certain FCD mechanisms, and to predict their cooperativity parameter. We demonstrate this approach using data from eukaryotic chemotaxis signaling. PMID:25121598

  4. Next Generation Geothermal Power Plants (NGGPP) process data for binary cycle plants

    SciTech Connect

    Not Available

    1996-10-02

    The Next Generation Geothermal Power Plants (NGGPP) study provides the firm estimates - in the public domain - of the cost and performance of U.S. geothermal systems and their main components in the early 1990s. The study was funded by the U.S. Department of Energy Geothermal Research Program, managed for DOE by Evan Hughes of the Electric Power Research Institute, Palo Alto, CA, and conducted by John Brugman and others of the CE Holt Consulting Firm, Pasadena, CA. The printed NGGPP reports contain detailed data on the cost and performance for the flash steam cycles that were characterized, but not for the binary cycles. The nine Tables in this document are the detailed data sheets on cost and performance for the air cooled binary systems that were studied in the NGGPP.

  5. Second law analysis of a waste heat recovery based power generation system

    Microsoft Academic Search

    C. J. Butcher; B. V. Reddy

    2007-01-01

    In the present paper the performance of a waste heat recovery power generation system based on second law analysis is investigated for various operating conditions. The temperature profiles across the heat recovery steam generator (HRSG), network output, second law efficiency and entropy generation number are simulated for various operating conditions. The variation in specific heat with exhaust gas composition and

  6. ANN based optimization of supercritical ORC-Binary geothermal power plant: Simav case study

    Microsoft Academic Search

    Oguz Arslan; Ozge Yetik

    2011-01-01

    Artificial neural network is a new tool, which works rapidly for decision making and modeling of the processes within the expertise. Therefore, ANN can be a solution for the design and optimization of complex power cycles, such as ORC-Binary. In the present study, the back-propagation learning algorithm with three different variants, namely Levenberg–Marguardt (LM), Pola-Ribiere Conjugate Gradient (CGP), and Scaled

  7. Ultra-relativistic nonthermal power-law ensembles: Cosmic-ray electrons and positron fraction

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2014-01-01

    Thermodynamically stable ultra-relativistic power-law distributions are employed to model the recently measured cosmic-ray electron flux and the positron fraction. The probability density of power-law ensembles in phase space is derived, as well as an extensive entropy functional. The phase-space measure is transformed into a spectral number density, parameterized with the Lorentz factor of the charges and quantized in Fermi statistics. Relativistic power-law ensembles admit positive heat capacities and compressibilities ensuring mechanical stability as well as positive root mean squares quantifying thermodynamic fluctuations. The wideband spectral fitting of dilute nonthermal electron-positron plasmas with ultra-relativistic power-law densities is explained.

  8. Tunable power law in the desynchronization events of coupled chaotic electronic circuits

    NASA Astrophysics Data System (ADS)

    de Oliveira, Gilson F.; de Souza Cavalcante, Hugo L. D.; di Lorenzo, Orlando; Chevrollier, Martine; Passerat de Silans, Thierry; Oriá, Marcos

    2014-03-01

    We study the statistics of the amplitude of the synchronization error in chaotic electronic circuits coupled through linear feedback. Depending on the coupling strength, our system exhibits three qualitatively different regimes of synchronization: weak coupling yields independent oscillations; moderate to strong coupling produces a regime of intermittent synchronization known as attractor bubbling; and stronger coupling produces complete synchronization. In the regime of moderate coupling, the probability distribution for the sizes of desynchronization events follows a power law, with an exponent that can be adjusted by changing the coupling strength. Such power-law distributions are interesting, as they appear in many complex systems. However, most of the systems with such a behavior have a fixed value for the exponent of the power law, while here we present an example of a system where the exponent of the power law is easily tuned in real time.

  9. Tunable power law in the desynchronization events of coupled chaotic electronic circuits

    E-print Network

    Gilson F. de Oliveira Jr.; Hugo L. D. de Souza Cavalcante; Orlando di Lorenzo; Martine Chevrollier; Thierry Passerat de Silans; Marcos Oriá

    2013-09-12

    We study the statistics of the amplitude of the synchronization error in chaotic electronic circuits coupled through linear feedback. Depending on the coupling strength, our system exhibits three qualitatively different regimes of synchronization: weak coupling yields independent oscillations; moderate to strong coupling produces a regime of intermittent synchronization known as attractor bubbling; and stronger coupling produces complete synchronization. In the regime of moderate coupling, the probability distribution for the sizes of desynchronization events follows a power law, with an exponent that can be adjusted by changing the coupling strength. Such power-law distributions are interesting, as they appear in many complex systems. However, most of the systems with such a behavior have a fixed value for the exponent of the power law, while here we present an example of a system where the exponent of the power law is easily tuned in real time.

  10. The power-law reaction rate coefficient for an elementary bimolecular reaction

    NASA Astrophysics Data System (ADS)

    Yin, Cangtao; Du, Jiulin

    2014-02-01

    The power-law TST reaction rate coefficient for an elementary bimolecular reaction is studied when the reaction takes place in a nonequilibrium system with power-law distributions. We derive a generalized TST rate coefficient, which not only depends on a power-law parameter but also on the reaction coordinate frequency of transition state. The numerical analyses show a very strong dependence of the TST rate coefficient on the power-law parameter, and clearly indicate that a tiny deviation from unity in the parameter (thus from a Boltzmann-Gibbs distribution) would result in significant changes in the rate coefficient. We take an elementary reaction, F+H?FH+H, as an application example to calculate the reaction rate coefficient, and yield the rate values being exactly in agreement with the measurement values in all the experimental studies in the temperature range 190-765 K.

  11. Multiple Random Walks to Uncover Short Paths in Power Law Networks

    E-print Network

    Kurose, Jim

    in network science. Consider the following routing problem in the context of a large power law network G is a problem of great interest in network science. In this work we focus on network topolo- gies characterized

  12. Power-law Relationship in Describing Temporal and Spatial Precipitation Pattern in Turkey

    NASA Astrophysics Data System (ADS)

    Kadi?lu, M.; ?en, Z.

    Wet and dry spell properties of monthly rainfall series at five meteorology stations in Turkey are examined by plotting successive wet and dry month duration versus their number of occurrences on the double-logarithmic paper. Straight line relationships on such graphs show that power-laws govern the pattern of successive persistent wet and dry monthly spells. Functional power law relationships between the number of dry and wet spells for a given monthly period are derived from the available monthly precipitation data. The probability statements for wet and dry period spells are obtained from the power law expressions. Comparison of power-law behaviours at five distinct sites in Turkey provides useful interpretation about the temporal and spatial rainfall pattern. As in temperate areas such as Turkey the rainfall amounts change mostly due to one-month-long dry or wet spells.

  13. Research on power-law acoustic transient signal detection based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Han, Jian-hui; Yang, Ri-jie; Wang, Wei

    2007-11-01

    Aiming at the characteristics of acoustic transient signal emitted from antisubmarine weapon which is being dropped into water (torpedo, aerial sonobuoy and rocket assisted depth charge etc.), such as short duration, low SNR, abruptness and instability, based on traditional power-law detector, a new method to detect acoustic transient signal is proposed. Firstly wavelet transform is used to de-noise signal, removes random spectrum components and improves SNR. Then Power- Law detector is adopted to detect transient signal. The simulation results show the method can effectively extract envelop characteristic of transient signal on the condition of low SNR. The performance of WT-Power-Law markedly outgoes that of traditional Power-Law detection method.

  14. Double power law for basic creep of concrete

    Microsoft Academic Search

    Z. P. Bažant; E. Osman

    1976-01-01

    The dependence of creep on load duration (t?t?) as well as age at loading t? is described by the law [1+?\\u000a 1\\u000a t?-m\\u000a (t-t?)\\u000a n\\u000a ]\\/E\\u000a 0 in which m, n,?\\u000a 1 E0=material parameters which are determined from test data by optimization techniques. The law is limited to basic creep, but\\u000a with different values of material parameters it can also

  15. Quasilinear relaxation of a beam with power law injected electrons propagating through solar corona

    NASA Astrophysics Data System (ADS)

    Khalilpour, H.

    2015-06-01

    It is assumed that the electron beam propagating thorough the Maxwellian solar corona plasma has a power law spectra. Using numerical simulations of the quasilinear equations, the effects of power law injected electrons on the generation of Langmuir waves are compared with a Maxwellian beam. It is found that the level of Langmuir waves increases in the presence of power law injected electrons. The average velocity of the beam propagation is constant for both Maxwellian and power law injected electrons but its value increases in the second case. The influence of the power law injected electrons on the evolution of gas-dynamical parameters such as the height of the plateau in the beam distribution function in velocity space, its upper and lower velocities boundary, and the local velocity of the beam and its spread is investigated. It is shown that the these parameters are dependent on the characteristics of the power law injected electrons, p (spectral index), and v 0 (the break speed). The upper boundary of plateau decreases (increases) with the p( v 0) but the lower boundary has inverse behavior. The height of plateau p( x, t) is a decreasing function of p and for a fixed value of p it has a maximum in a certain value of v 0 at a given time and position.

  16. Exponentially Convergent Control Laws for Nonholonomic Systems in Power Form?

    E-print Network

    Tsiotras, Panagiotis

    nonholonomic systems. Hybrid time-varying feedback control laws are proposed in 10] for a class of cascade nonlinear systems, which could also be used to stabilize a class of nonholonomic systems, as well that all controllable driftless systems could be stabilized to an equilibriumpoint using smooth, periodic

  17. Effects of multiplicative power law neural noise in visual information processing.

    PubMed

    Medina, Jos M

    2011-04-01

    The human visual system is intrinsically noisy. The benefits of internal noise as part of visual code are controversial. Here the information-theoretic properties of multiplicative (i.e. signal-dependent) neural noise are investigated. A quasi-linear communication channel model is presented. The model shows that multiplicative power law neural noise promotes the minimum information transfer after efficient coding. It is demonstrated that Weber's law and the human contrast sensitivity function arise on the basis of minimum transfer of information and power law neural noise. The implications of minimum information transfer in self-organized neural networks and weakly coupled neurons are discussed. PMID:21222525

  18. Taylor's power law of fluctuation scaling and the growth-rate theorem.

    PubMed

    Cohen, Joel E

    2013-09-01

    Taylor's law (TL), a widely verified empirical relationship in ecology, states that the variance of population density is approximately a power-law function of mean density. The growth-rate theorem (GR) states that, in a subdivided population, the rate of change of the overall growth rate is proportional to the variance of the subpopulations' growth rates. We show that continuous-time exponential change implies GR at every time and, asymptotically for large time, TL with power-law exponent 2. We also show why diverse population-dynamic models predict TL in the limit of large time by identifying simple features these models share: If the mean population density and the variance of population density are (exactly or asymptotically) non-constant exponential functions of a parameter (e.g., time), then the variance of density is (exactly or asymptotically) a power-law function of mean density. PMID:23689021

  19. On the Power-Law Tail in the Mass Function of Protostellar Condensations and Stars

    E-print Network

    Shantanu Basu; C. E. Jones

    2003-11-16

    We explore the idea that the power-law tail in the mass function of protostellar condensations and stars arises from the accretion of ambient cloud material on to a condensation, coupled with a nonuniform (exponential) distribution of accretion lifetimes. This model allows for the generation of power-law distributions in all star-forming regions, even if condensations start with a lognormal mass distribution, as may be expected from the central limit theorem, and supported by some recent numerical simulations of turbulent molecular clouds. For a condensation mass $m$ with growth rate $dm/dt \\propto m$, an analytic three-parameter probability density function is derived; it resembles a lognormal at low mass and has a pure power-law high-mass tail. An approximate power-law tail is also expected for other growth laws, and we calculate the distribution for the plausible case $dm/dt \\propto m^{2/3}$. Furthermore, any single time snapshot of the masses of condensations that are still accreting (and are of varying ages) also yields a distribution with a power-law tail similar to that of the IMF.

  20. Timing of continuous motor imagery: the two-thirds power law originates in trajectory planning.

    PubMed

    Karklinsky, Matan; Flash, Tamar

    2015-04-01

    The two-thirds power law, v = ??(-1/3), expresses a robust local relationship between the geometrical and temporal aspects of human movement, represented by curvature ? and speed v, with a piecewise constant ?. This law is equivalent to moving at a constant equi-affine speed and thus constitutes an important example of motor invariance. Whether this kinematic regularity reflects central planning or peripheral biomechanical effects has been strongly debated. Motor imagery, i.e., forming mental images of a motor action, allows unique access to the temporal structure of motor planning. Earlier studies have shown that imagined discrete movements obey Fitts's law and their durations are well correlated with those of actual movements. Hence, it is natural to examine whether the temporal properties of continuous imagined movements comply with the two-thirds power law. A novel experimental paradigm for recording sparse imagery data from a continuous cyclic tracing task was developed. Using the likelihood ratio test, we concluded that for most subjects the distributions of the marked positions describing the imagined trajectory were significantly better explained by the two-thirds power law than by a constant Euclidean speed or by two other power law models. With nonlinear regression, the ? parameter values in a generalized power law, v = ??(-?), were inferred from the marked position records. This resulted in highly variable yet mostly positive ? values. Our results imply that imagined trajectories do follow the two-thirds power law. Our findings therefore support the conclusion that the coupling between velocity and curvature originates in centrally represented motion planning. PMID:25609105

  1. Power, Resistance, and Emotional Economies in Women's Relationships with Mothers-in-Law in Chinese Immigrant Families

    ERIC Educational Resources Information Center

    Shih, Kristy Y.; Pyke, Karen

    2010-01-01

    This interview study interrogates how cultural values of filial piety inform Chinese American daughters-in-law's understanding of their relationship and power dynamics with immigrant Chinese American mothers-in-law. Ideals of filial respect accord limited authority to mothers-in-law, who engage other mechanisms of power, such as their domestic…

  2. Determination of tidal distortion in the eclipsing binary system V621 Cen by means of deviations from the third Kepler law

    Microsoft Academic Search

    Lorenzo Iorio

    2008-01-01

    In this paper we determine the tidal distortion parameter km of the secondary partner (mass loser) of the semi-detached eclipsing binary system V621 Cen by comparing the phenomenologically determined orbital period Pb=3.683549(11)d to the Keplerian one PKep computed with the values of the relevant system’s parameters determined independently of the third Kepler law itself. Our result is km=-1.5±0.6. Using the

  3. Power-law decay of the view times of scientific courses on YouTube

    NASA Astrophysics Data System (ADS)

    Gao, Lingling

    2012-11-01

    The temporal power-law decay is one class of interesting decay processes, usually indicating a long-time correlation and benefiting for a system to perform functions in various time-scales. In this work, I collect the data of the view times versus lectures of some scientific courses on YouTube, according to some special principles. These data can reflect the dynamical property of the spontaneous learning behavior, influenced by the decay of learning interest. The view times versus lectures show an obviously power-law decay process. The power approximates to 1, a universal constant. This finding brings the learning process into the interesting power-law family. It will be of interest in the fields of the human dynamics, psychology and education.

  4. Statistical evidence for power law temporal correlations in exploratory behaviour of rats.

    PubMed

    Yadav, Chetan K; Verma, Mahendra K; Ghosh, Subhendu

    2010-01-01

    Dynamics of exploratory behaviour of rats and home base establishment is investigated. Time series of instantaneous speed of rats was computed from their position during exploration. The probability distribution function (PDF) of the speed obeys a power law distribution with exponents ranging from 2.1 to 2.32. The PDF of the recurrence time of large speed also exhibits a power law, P(?) ~ ?(??) with ? from 1.56 to 2.30. The power spectrum of the speed is in general agreement with the 1/f spectrum reported earlier. These observations indicate that the acquisition of spatial information during exploration is self-organized with power law temporal correlations. This provides a possible explanation for the home base behaviour of rats during exploration. The exploratory behaviour of rats resembles other systems exhibiting self-organized criticality, e.g., earthquakes, solar flares etc. PMID:20688133

  5. The fractal nature of nature: power laws, ecological complexity and biodiversity.

    PubMed Central

    Brown, James H; Gupta, Vijay K; Li, Bai-Lian; Milne, Bruce T; Restrepo, Carla; West, Geoffrey B

    2002-01-01

    Underlying the diversity of life and the complexity of ecology is order that reflects the operation of fundamental physical and biological processes. Power laws describe empirical scaling relationships that are emergent quantitative features of biodiversity. These features are patterns of structure or dynamics that are self-similar or fractal-like over many orders of magnitude. Power laws allow extrapolation and prediction over a wide range of scales. Some appear to be universal, occurring in virtually all taxa of organisms and types of environments. They offer clues to underlying mechanisms that powerfully constrain biodiversity. We describe recent progress and future prospects for understanding the mechanisms that generate these power laws, and for explaining the diversity of species and complexity of ecosystems in terms of fundamental principles of physical and biological science. PMID:12079523

  6. On the Hardness and Inapproximability of Optimization Problems on Power Law Graphs

    NASA Astrophysics Data System (ADS)

    Shen, Yilin; Nguyen, Dung T.; Thai, My T.

    The discovery of power law distribution in degree sequence (i.e. the number of vertices with degree i is proportional to i - ? for some constant ?) of many large-scale real networks creates a belief that it may be easier to solve many optimization problems in such networks. Our works focus on the hardness and inapproximability of optimization problems on power law graphs (PLG). In this paper, we show that the Minimum Dominating Set, Minimum Vertex Cover and Maximum Independent Set are still APX-hard on power law graphs. We further show the inapproximability factors of these optimization problems and a more general problem (?-Minimum Dominating Set), which proved that a belief of (1 + o(1))-approximation algorithm for these problems on power law graphs is not always true. In order to show the above theoretical results, we propose a general cycle-based embedding technique to embed any d-bounded graphs into a power law graph. In addition, we present a brief description of the relationship between the exponential factor ? and constant greedy approximation algorithms.

  7. Prediction of radio frequency power generation of Neptune's magnetosphere from generalized radiometric Bode's law

    NASA Astrophysics Data System (ADS)

    Millon, M. A.; Goertz, C. K.

    1988-01-01

    Magnetospheric radio frequency emission power has been shown to vary as a function of both solar wind and planetary values such as magnetic field by Kaiser and Desch. Planetary magnetic fields have been shown to scale with planetary variables such as density and angular momentum by numerous researchers. This paper combines two magnetic scaling laws (Busse's and Curtis Ness') with the radiometric law to yield "Bode's"-type laws governing planetary radio emission. Further analysis allows the reduction of variables to planetary mass and orbital distance. These generalized laws are then used to predict the power output of Neptune to be about 1.6×107W; with the intensity peaking at about 3 MHz.

  8. Excessive loss of information by the power-law ansatz for complex systems

    E-print Network

    Tsai, Sun-Ting; Chang, Ching-Hao; Tsai, Meng-Xue; Hsu, Nan-Jung; Hong, Tzay-Ming

    2015-01-01

    Physicists love simple laws and uncovering common causes among seemingly unrelated phenomena. An example is the connection between earthquakes and crumpling of a paper, built through the simple power law (SPL) believed to exist between the occurrence rate of their crackling noise and the pulse intensity. We provide, however, evidence to weaken such a link by showing that both systems in fact obey different and more complex laws. Our analyses are based on the Akaike information criterion (AIC) that is a direct measurement of information loss and emphasizes the need to strike a balance between model simplicity and goodness of fit. AIC found that a shifted power law retains more information than SPL in the cases of crumpling sound, duration-time frequency of solar flare, web link, protein-domain frequency, and stock-market fluctuations. In the mean time, double power laws (DPL) should replace the Gutenberg-Richter law for earthquake, and the scale-free model for brain functional network, two-dimensional sandpile...

  9. Power-law X-ray and gamma-ray emission from relativistic thermal plasmas

    NASA Technical Reports Server (NTRS)

    Zdziarski, A. A.

    1985-01-01

    A common characteristic of cosmic sources is power-law X-ray emission. Extragalactic sources of this type include compact components of active galactic nuclei (AGN). The present study is concerned with a theoretical model of such sources, taking into account the assumption that the power-law spectra are produced by repeated Compton scatterings of soft photons by relativistic thermal electrons. This is one of several possible physical mechanisms leading to the formation of a power-law spectrum. Attention is given to the Comptonization of soft photon sources, the rates of pair processes, the solution of the pair equilibrium equation, and the constraints on a soft photon source and an energy source. It is concluded that the compactness parameters L/R of most of the cosmic sources observed to date lie below the maximum luminosity curves considered.

  10. Absence of Power-law Mid-Infrared Conductivity in Gravitational Crystals

    E-print Network

    Langley, Brandon W; Phillips, Philip W

    2015-01-01

    In a Reissner-Nordstr\\"om spacetime that is asymptotically anti de Sitter, we compute the boundary conductivity as a function of frequency of a charged black hole in the presence of a periodic potential that generates a non-uniform charge density. We choose a periodic potential that interpolates between that used in two previous studies, one that reports power-law scaling for the optical conductivity and one that does not. We find no evidence for a power-law scaling of the optical conductivity, thereby corroborating the previous negative result that gravitational crystals are insufficient to generate the power-law scaling observed in the mid-infrared of the cuprate superconductors.

  11. Phase diagram of power law and Lennard-Jones systems: crystal phases.

    PubMed

    Travesset, Alex

    2014-10-28

    An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists with the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed. PMID:25362319

  12. Power law distribution of the duration and magnitude of recessions in capitalist economies: breakdown of scaling

    NASA Astrophysics Data System (ADS)

    Ormerod, Paul; Mounfield, Craig

    2001-04-01

    Power law distributions of macroscopic observables are ubiquitous in both the natural and social sciences. They are indicative of correlated, cooperative phenomena between groups of interacting agents at the microscopic level. In this paper, we argue that when one is considering aggregate macroeconomic data (annual growth rates in real per capita GDP in the seventeen leading capitalist economies from 1870 through to 1994) the magnitude and duration of recessions over the business cycle do indeed follow power law like behaviour for a significant proportion of the data (demonstrating the existence of cooperative phenomena amongst economic agents). Crucially, however, there are systematic deviations from this behaviour when one considers the frequency of occurrence of large recessions. Under these circumstances the power law scaling breaks down. It is argued that it is the adaptive behaviour of the agents (their ability to recognise the changing economic environment) which modifies their cooperative behaviour.

  13. Explaining the Power-law Distribution of Human Mobility Through Transportation Modality Decomposition

    E-print Network

    Zhao, Kai; Hui, Pan; Rao, Weixiong; Tarkoma, Sasu

    2014-01-01

    Human mobility has been empirically observed to exhibit Levy flight characteristics and behaviour with power-law distributed jump size. The fundamental mechanisms behind this behaviour has not yet been fully explained. In this paper, we analyze urban human mobility and we propose to explain the Levy walk behaviour observed in human mobility patterns by decomposing them into different classes according to the different transportation modes, such as Walk/Run, Bicycle, Train/Subway or Car/Taxi/Bus. Our analysis is based on two real-life GPS datasets containing approximately 10 and 20 million GPS samples with transportation mode information. We show that human mobility can be modelled as a mixture of different transportation modes, and that these single movement patterns can be approximated by a lognormal distribution rather than a power-law distribution. Then, we demonstrate that the mixture of the decomposed lognormal flight distributions associated with each modality is a power-law distribution, providing an e...

  14. Determining scalar field potential in power-law cosmology with observational data

    E-print Network

    Kiattisak Thepsuriya; Burin Gumjudpai

    2011-11-24

    In power-law cosmology, we determine potential function of a canonical scalar field in FLRW universe in presence of barotropic perfect fluid. The combined WMAP5+BAO+SN dataset and WMAP5 dataset are used here to determine the value of the potential. The datasets suggest slightly closed universe. If the universe is closed, the exponents of the power-law cosmology are $q = 1.01$ (WMAP5 dataset) and $q=0.985$ (combined dataset). The lower limits of $a_0$ (closed geometry) are $5.1\\E{26}$ for WMAP5 dataset and $9.85\\E{26}$ for the combined dataset. The domination of the power-law term over the curvature and barotropic density terms is characterised by the inflection of the potential curve. This happens when the universe is 5.3 Gyr old for both datasets.

  15. Phase diagram of power law and Lennard-Jones systems: Crystal phases

    SciTech Connect

    Travesset, Alex [Ames Laboratory

    2014-10-28

    An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists with the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed.

  16. Power law singularities in the scale covariant theory

    SciTech Connect

    Beesham, A.

    1986-12-01

    Power asymptote singularities are discussed in the scale covariant theory of gravitation. Some general results are derived. Special attention is paid to the Friedmann (A. Friedmann, Z. Phys. 10, 377 (1922)) and Kasner (E. Kasner, Am. J. Math. 43, 217 (1921)) models. A wider class of behavior is exhibited and it is shown that the results obtained constitute a generalization of the corresponding general relativistic results.

  17. Power law scaling of topographic depressions and their hydrologic connectivity

    NASA Astrophysics Data System (ADS)

    Le, Phong V. V.; Kumar, Praveen

    2014-03-01

    Topographic depressions, areas of no lateral surface flow, are ubiquitous characteristics of the land surface that control many ecosystem and biogeochemical processes. High density of depressions increases the surface storage capacity, whereas lower depression density increases runoff, thus influencing soil moisture states, hydrologic connectivity, and the climate-soil-vegetation interactions. With the widespread availability of high-resolution lidar-based digital elevation model (lDEM) data, it is now possible to identify and characterize the structure of the spatial distribution of topographic depressions for incorporation in ecohydrologic and biogeochemical studies. Here we use lDEM data to document the prevalence and patterns of topographic depressions across five different landscapes in the United States and quantitatively characterize the probability distribution of attributes, such as surface area, storage volume, and the distance to the nearest neighbor. Through the use of a depression identification algorithm, we show that these probability distributions of attributes follow scaling laws indicative of a structure in which a large fraction of land surface areas can consist of high number of topographic depressions of all sizes and can account for 4 to 21 mm of depression storage. This implies that the impacts of small-scale topographic depressions in the landscapes on the redistribution of material fluxes, evaporation, and hydrologic connectivity are quite significant.

  18. Stochastic Mixing Model with Power Law Decay of Variance

    NASA Technical Reports Server (NTRS)

    Fedotov, S.; Ihme, M.; Pitsch, H.

    2003-01-01

    Here we present a simple stochastic mixing model based on the law of large numbers (LLN). The reason why the LLN is involved in our formulation of the mixing problem is that the random conserved scalar c = c(t,x(t)) appears to behave as a sample mean. It converges to the mean value mu, while the variance sigma(sup 2)(sub c) (t) decays approximately as t(exp -1). Since the variance of the scalar decays faster than a sample mean (typically is greater than unity), we will introduce some non-linear modifications into the corresponding pdf-equation. The main idea is to develop a robust model which is independent from restrictive assumptions about the shape of the pdf. The remainder of this paper is organized as follows. In Section 2 we derive the integral equation from a stochastic difference equation describing the evolution of the pdf of a passive scalar in time. The stochastic difference equation introduces an exchange rate gamma(sub n) which we model in a first step as a deterministic function. In a second step, we generalize gamma(sub n) as a stochastic variable taking fluctuations in the inhomogeneous environment into account. In Section 3 we solve the non-linear integral equation numerically and analyze the influence of the different parameters on the decay rate. The paper finishes with a conclusion.

  19. The equivalence of isothermal and non-isothermal power law distributions with temperature duality

    NASA Astrophysics Data System (ADS)

    Zheng, Yahui; Du, Jiulin

    2015-06-01

    The concept of temperature duality states that the physical temperature and Lagrange temperature both have physical sense in the nonextensive system. By use of this concept, the isothermal power law distribution and the non-isothermal power law distribution are equivalent to each other when the detailed balance is satisfied. Also, the polytropic equation in stellar system and self-gravitating gaseous system can be deduced from both of these two distributions. This indicates that the polytropic system exhibits some 'equilibrium' configuration which, in the stellar system, is probably the result of so called 'violent relaxation'.

  20. On the origin and robustness of power-law species–area relationships in ecology

    PubMed Central

    García Martín, Héctor; Goldenfeld, Nigel

    2006-01-01

    We present an explanation for the widely reported power-law species–area relationship (SAR), which relates the area occupied by a biome to the number of species that it supports. We argue that power-law SARs are a robust consequence of a skewed species abundance distribution resembling a lognormal with higher rarity, together with the observation that individuals of a given species tend to cluster. We show that the precise form of the SAR transcends the specific details of organism interactions, enabling us to characterize its broad trends across taxa. PMID:16801556

  1. Power-law Behavior of High Energy String Scatterings in Compact Spaces

    E-print Network

    Jen-Chi Lee; Yi Yang

    2007-09-28

    We calculate high energy massive scattering amplitudes of closed bosonic string compactified on the torus. We obtain infinite linear relations among high energy scattering amplitudes. For some kinematic regimes, we discover that some linear relations break down and, simultaneously, the amplitudes enhance to power-law behavior due to the space-time T-duality symmetry in the compact direction. This result is consistent with the coexistence of the linear relations and the softer exponential fall-off behavior of high energy string scattering amplitudes as we pointed out prevously. It is also reminiscent of hard (power-law) string scatterings in warped spacetime proposed by Polchinski and Strassler.

  2. Power Law Entropy Corrected New-Agegraphic Dark Energy in Ho?ava-Lifshitz Cosmology

    E-print Network

    K. Karami; A. Sheykhi; Mubasher Jamil; R. Myrzakulov; S. Ghaffari; A. Abdolmaleki

    2012-03-31

    We investigate the new agegraphic dark energy (NADE) model with power-law corrected entropy in the framework of Ho\\v{r}ava-Lifshitz cosmology. For a non-flat universe containing the interacting power-law entropy-corrected NADE (PLECNADE) with dark matter, we obtain the differential equation of the evolution of density parameter as well as the deceleration parameter. To study parametric behavior, we used an interesting form of state parameter as function of redshift $\\omega_{\\Lambda}(z)=\\omega_0+\\omega_1 z$. We found that phantom crossing occurs for the state parameter for a non-zero coupling parameter, thus supporting interacting dark energy model.

  3. Chaotic and power law states in the Portevin-Le Chatelier effect

    NASA Astrophysics Data System (ADS)

    Bharathi, M. S.; Ananthakrishna, G.

    2002-10-01

    Recent studies on the Portevin-Le Chatelier effect report an intriguing crossover phenomenon from a low-dimensional chaotic to an infinite-dimensional scale-invariant power law regime in experiments on CuAl single crystals and AlMg polycrystals, as a function of strain rate. We devise a fully dynamical model which reproduces these results. At low and medium strain rates, the model is chaotic with the structure of the attractor resembling the reconstructed experimental attractor. At high strain rates, power law statistics for the magnitudes and durations of the stress drops emerge as in experiments and concomitantly, the largest Lyapunov exponent is zero.

  4. Tweedie convergence: A mathematical basis for Taylor's power law, 1/f noise, and multifractality

    NASA Astrophysics Data System (ADS)

    Kendal, Wayne S.; Jørgensen, Bent

    2011-12-01

    Plants and animals of a given species tend to cluster within their habitats in accordance with a power function between their mean density and the variance. This relationship, Taylor's power law, has been variously explained by ecologists in terms of animal behavior, interspecies interactions, demographic effects, etc., all without consensus. Taylor's law also manifests within a wide range of other biological and physical processes, sometimes being referred to as fluctuation scaling and attributed to effects of the second law of thermodynamics. 1/f noise refers to power spectra that have an approximately inverse dependence on frequency. Like Taylor's law these spectra manifest from a wide range of biological and physical processes, without general agreement as to cause. One contemporary paradigm for 1/f noise has been based on the physics of self-organized criticality. We show here that Taylor's law (when derived from sequential data using the method of expanding bins) implies 1/f noise, and that both phenomena can be explained by a central limit-like effect that establishes the class of Tweedie exponential dispersion models as foci for this convergence. These Tweedie models are probabilistic models characterized by closure under additive and reproductive convolution as well as under scale transformation, and consequently manifest a variance to mean power function. We provide examples of Taylor's law, 1/f noise, and multifractality within the eigenvalue deviations of the Gaussian unitary and orthogonal ensembles, and show that these deviations conform to the Tweedie compound Poisson distribution. The Tweedie convergence theorem provides a unified mathematical explanation for the origin of Taylor's law and 1/f noise applicable to a wide range of biological, physical, and mathematical processes, as well as to multifractality.

  5. Tweedie convergence: a mathematical basis for Taylor's power law, 1/f noise, and multifractality.

    PubMed

    Kendal, Wayne S; Jørgensen, Bent

    2011-12-01

    Plants and animals of a given species tend to cluster within their habitats in accordance with a power function between their mean density and the variance. This relationship, Taylor's power law, has been variously explained by ecologists in terms of animal behavior, interspecies interactions, demographic effects, etc., all without consensus. Taylor's law also manifests within a wide range of other biological and physical processes, sometimes being referred to as fluctuation scaling and attributed to effects of the second law of thermodynamics. 1/f noise refers to power spectra that have an approximately inverse dependence on frequency. Like Taylor's law these spectra manifest from a wide range of biological and physical processes, without general agreement as to cause. One contemporary paradigm for 1/f noise has been based on the physics of self-organized criticality. We show here that Taylor's law (when derived from sequential data using the method of expanding bins) implies 1/f noise, and that both phenomena can be explained by a central limit-like effect that establishes the class of Tweedie exponential dispersion models as foci for this convergence. These Tweedie models are probabilistic models characterized by closure under additive and reproductive convolution as well as under scale transformation, and consequently manifest a variance to mean power function. We provide examples of Taylor's law, 1/f noise, and multifractality within the eigenvalue deviations of the Gaussian unitary and orthogonal ensembles, and show that these deviations conform to the Tweedie compound Poisson distribution. The Tweedie convergence theorem provides a unified mathematical explanation for the origin of Taylor's law and 1/f noise applicable to a wide range of biological, physical, and mathematical processes, as well as to multifractality. PMID:22304168

  6. Powerful Exact Unconditional Tests for Agreement between Two Raters with Binary Endpoints

    PubMed Central

    Shan, Guogen; Wilding, Gregory E.

    2014-01-01

    Asymptotic and exact conditional approaches have often been used for testing agreement between two raters with binary outcomes. The exact conditional approach is guaranteed to respect the test size as compared to the traditionally used asymptotic approach based on the standardized Cohen's kappa coefficient. An alternative to the conditional approach is an unconditional strategy which relaxes the restriction of fixed marginal totals as in the conditional approach. Three exact unconditional hypothesis testing procedures are considered in this article: an approach based on maximization, an approach based on the conditional p-value and maximization, and an approach based on estimation and maximization. We compared these testing procedures based on the commonly used Cohen's kappa with regards to test size and power. We recommend the following two exact approaches for use in practice due to power advantages: the approach based on conditional p-value and maximization and the approach based on estimation and maximization. PMID:24837970

  7. Geomorphological and hydrological implications of a given hydraulic geometry relationship, beyond the power-law

    NASA Astrophysics Data System (ADS)

    Kim, JongChun; Paik, Kyungrock

    2015-04-01

    Channel geometry and hydraulic characteristics of a given river network, i.e., spatio-temporal variability of width, depth, and velocity, can be described as power functional relationships of flow discharge, named 'hydraulic geometry' (Leopold and Maddock, 1953). Many studies have focused on the implication of this power-law itself, i.e., self-similarity, and accordingly its exponents. Coefficients of the power functional relationships, on the contrary, have received little attention. They are often regarded as empirical constants, determined by 'best fitting' to the power-law without significant scientific implications. Here, we investigate and claim that power-law coefficients of hydraulic geometry relationships carry vital information of a given river system. We approach the given problem on the basis of 'basin hydraulic geometry' formulation (Stall and Fok, 1968) which decomposes power-law coefficients into more elementary constants. The linkage between classical power-law relationship (Leopold and Maddock, 1953) and the basin hydraulic geometry is provided by Paik and Kumar (2004). On the basis of this earlier study, it can be shown that coefficients and exponents of power-law hydraulic geometry are interrelated. In this sense, we argue that more elementary constants that constitute both exponents and coefficients carry important messages. In this presentation, we will demonstrate how these elementary constants vary over a wide range of catchments provided from Stall and Fok (1968) and Stall and Yang (1970). Findings of this study can provide new insights on fundamental understanding about hydraulic geometry relationships. Further, we expect that this understanding can help interpretation of hydraulic geometry relationship in the context of flood propagation through a river system as well. Keywords: Hydraulic geometry; Power-law; River network References Leopold, L. B., & Maddock, T. J. (1953). The hydraulic geometry of stream channels and some physiographic implications. U. S. Geological Survey Professional Paper, 252. Paik, K., & Kumar, P. (2004). Hydraulic geometry and the nonlinearity of the network instantaneous response, Water Resource Research, 40, W03602. Stall, J. B., & Fok, Y. S. (1968). Hydraulic geometry of Illinois streams. University of Illinois Water Resources Center Research Report, 15. Stall, J. B., & Yang, C. T. (1970). Hydraulic geometry of 12 selected stream systems of the United States. University of Illinois Water Resources Center Research Report, 32.

  8. Power loss in open cavity diodes and a modified Child-Langmuir law

    SciTech Connect

    Biswas, Debabrata; Kumar, Raghwendra; Puri, R.R. [Theoretical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Human Resource Development Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2005-09-15

    Diodes used in most high power devices are inherently open. It is shown that under such circumstances, there is a loss of electromagnetic radiation leading to a lower critical current as compared to closed diodes. The power loss can be incorporated in the standard Child-Langmuir framework by introducing an effective potential. The modified Child-Langmuir law can be used to predict the maximum power loss for a given plate separation and potential difference as well as the maximum transmitted current for this power loss. The effectiveness of the theory is tested numerically.

  9. A Spectral Model for RF Oscillators With Power-Law Phase Noise

    Microsoft Academic Search

    Arsenia Chorti; Mike Brookes

    2006-01-01

    In this paper, we apply correlation theory methods to obtain a model for the near-carrier oscillator power-spectral density (PSD). Based on the measurement-driven representation of phase noise as a sum of power-law processes, we evaluate closed form expressions for the relevant oscillator autocorrelation functions. These expressions form the basis of an enhanced oscillator spectral model that has a Gaussian PSD

  10. The power law J–V model of an illuminated solar cell

    Microsoft Academic Search

    Shreepad Karmalkar; H. Saleem

    2011-01-01

    We have earlier introduced the power law equation, j=1?(1??)v??vm, where j=J\\/Jsc and v=V\\/V?, to simplify determination of the J–V curve, fill-factor and peak power point of an illuminated solar cell from a few measurements as well as physical parameters. However, the validity of the various formulae and parameter extraction procedure was established for a limited class of cells, having moderately

  11. Power-Law Rheology of Isolated Nuclei with Deformation Mapping of Nuclear Substructures

    E-print Network

    Discher, Dennis

    are an order of magnitude softer, with the lamina sustaining much of the load. In both cases, nuclearPower-Law Rheology of Isolated Nuclei with Deformation Mapping of Nuclear Substructures Kris Noel-induced changes in genome expression as well as remodeling of nuclear architecture in development and disease

  12. Power law in a gauge-invariant cut-off regularization

    SciTech Connect

    Varin, T.; Welzel, J.; Deandrea, A.; Davesne, D. [Universite de Lyon, Villeurbanne, F-69622 (France) and Universite Lyon 1, Institut de Physique Nucleaire de Lyon, 4 rue Enrico Fermi, F-69622 Villeurbanne (France)

    2006-12-15

    We study one-loop quantum corrections of a compactified Abelian 5d gauge field theory. We use a cut-off regularization procedure which respects the symmetries of the model, i.e. gauge invariance, exhibits the expected powerlike divergences and therefore allows the derivation of power-law behavior of the effective 4d gauge coupling in a coherent manner.

  13. Predictive analyses for nonhomogeneous Poisson processes with power law using Bayesian approach

    Microsoft Academic Search

    Jun-wu Yu; Guo-liang Tian; Man-lai Tang

    2007-01-01

    Nonhomogeneous Poisson process (NHPP) also known as Weibull process with power law, has been widely used in modeling hardware reliability growth and detecting software failures. Although statistical inferences on the Weibull process have been studied extensively by various authors, relevant discussions on predictive analysis are scattered in the literature. It is well known that the predictive analysis is very useful

  14. Power law Starobinsky model of inflation from no-scale SUGRA

    NASA Astrophysics Data System (ADS)

    Chakravarty, Girish Kumar; Mohanty, Subhendra

    2015-06-01

    We consider a power law 1M2R? correction to Einstein gravity as a model for inflation. The interesting feature of this form of generalization is that small deviations from the Starobinsky limit ? = 2 can change the value of tensor-to-scalar ratio from r ? O (10-3) to r ? O (0.1). We find that in order to get large tensor perturbation r ? 0.1 as indicated by BKP measurements, we require the value of ? ? 1.83 thereby breaking global Weyl symmetry. We show that the general R? model can be obtained from a SUGRA construction by adding a power law (? + ? bar) n term to the minimal no-scale SUGRA Kähler potential. We further show that this two-parameter power law generalization of the Starobinsky model is equivalent to generalized non-minimal curvature coupled models of the form ??aRb + ?? 4 (1 + ?) and thus the power law Starobinsky model is the most economical parametrization of such models.

  15. Is ALOHA Causing Power Law Delays? Predrag R. Jelenkovic and Jian Tan

    E-print Network

    Jelenkovic, Predrag

    Is ALOHA Causing Power Law Delays? Predrag R. Jelenkovi´c and Jian Tan Department of Electrical interest in ALOHA-based Medium Access Con- trol (MAC) protocols stems from their proposed applications study the distributional properties of packet transmission delays over an ALOHA channel. We discover

  16. The origin of tablet boudinage: Results from experiments using power–law rock analogs

    Microsoft Academic Search

    J. Zulauf; G. Zulauf; R. Kraus; G. Gutiérrez-Alonso; F. Zanella

    2011-01-01

    We used power–law viscous plasticine (n=ca. 7) as a rock analog to simulate boudinage of rocks undergoing dislocation creep and brittle fracture. A competent plasticine layer, oriented perpendicular to the main shortening direction, Z, underwent bulk pure flattening inside a less competent plasticine matrix. Computer tomographic analyses of the deformed samples revealed that boudinage results from an initial phase of

  17. A theory of power-law distributions in financial market fluctuations.

    PubMed

    Gabaix, Xavier; Gopikrishnan, Parameswaran; Plerou, Vasiliki; Stanley, H Eugene

    2003-05-15

    Insights into the dynamics of a complex system are often gained by focusing on large fluctuations. For the financial system, huge databases now exist that facilitate the analysis of large fluctuations and the characterization of their statistical behaviour. Power laws appear to describe histograms of relevant financial fluctuations, such as fluctuations in stock price, trading volume and the number of trades. Surprisingly, the exponents that characterize these power laws are similar for different types and sizes of markets, for different market trends and even for different countries--suggesting that a generic theoretical basis may underlie these phenomena. Here we propose a model, based on a plausible set of assumptions, which provides an explanation for these empirical power laws. Our model is based on the hypothesis that large movements in stock market activity arise from the trades of large participants. Starting from an empirical characterization of the size distribution of those large market participants (mutual funds), we show that the power laws observed in financial data arise when the trading behaviour is performed in an optimal way. Our model additionally explains certain striking empirical regularities that describe the relationship between large fluctuations in prices, trading volume and the number of trades. PMID:12748636

  18. Power Law Signature in Indonesian Population Empirical Studies of Kabupaten and Kotamadya Population in Indonesia

    Microsoft Academic Search

    Ivan Mulianta; Hokky Situngkir; Yohanes Surya

    The paper analyzes the spreading of population in Indonesia. The spreading of population in Indonesia is clustered in two regional terms, i.e.: kabupaten and kotamadya. It is interestingly found that the rank in all kabupaten respect to the population does not have fat tail properties, while in the other hand; there exists power-law signature in kotamadya. We analyzed that this

  19. Christos Faloutsos Speaks Out on Power Laws, Fractals, the Future of Data Mining, Sabbaticals, and More

    E-print Network

    Christos Faloutsos Speaks Out on Power Laws, Fractals, the Future of Data Mining, Sabbaticals-ranging interests in data mining, database performance, and spatial and multimedia databases. His PhD is from in an area and do deep work there, and other people enjoy collaborations. I was extremely lucky to have

  20. The horizontal dam break problem for slow non-Newtonian power-law fluids

    E-print Network

    The horizontal dam break problem for slow non-Newtonian power-law fluids P. Saramito a C. Smutek bLaboratoire g´eosciences ­ IPGP et universit´e de La R´eunion, France Abstract ­ The dam break problem shallow for the horizontal dam break problem. Keywords ­ viscoplastic fluid; dam break problem; shallow flows. 1

  1. Constitutional Law: Government Powers PSC 330, Fall 2013 [last updated 8/14/2013

    E-print Network

    Ahmad, Sajjad

    Constitutional Law: Government Powers PSC 330, Fall 2013 [last updated 8/14/2013] Instructor of other constitutional democracies. We know that our constitution was the first of its kind, and most of us know that it starts with something like "We the people..." We also know that the Constitution

  2. Power-law distribution as a result of asynchronous random switching between Malthus and Verhulst kinetics.

    PubMed

    Zygad?o, Ryszard

    2008-02-01

    It is shown analytically that the flashing annihilation term of a Verhulst kinetic leads to the power-law distribution in the stationary state. For the frequency of switching slower than twice the free growth rate this provides the quasideterministic source of a Lévy noise at the macroscopic level. PMID:18352010

  3. An approach to power-law phase-noise models through generalized functions

    NASA Astrophysics Data System (ADS)

    Greenhall, Charles A.

    2010-10-01

    This paper has two purposes: first, as a tutorial on the use of generalized autocovariances for deriving covariance properties of phase-noise models with power-law spectra; second, to connect the subject to the theory of generalized functions, also called tempered distributions. Proofs of theorems are available in an online supplement (http://stacks.iop.org/0026-1394/47/605/mmedia).

  4. Power-law cosmic expansion in f(R) gravity models

    SciTech Connect

    Goheer, Naureen; Larena, Julien [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch, Cape Town (South Africa); Dunsby, Peter K. S. [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch, Cape Town (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa)

    2009-09-15

    We show that within the class of f(R) gravity theories, Friedmann-Lemaitre-Robertson-Walker power-law perfect fluid solutions only exist for R{sup n} gravity. This significantly restricts the set of exact cosmological solutions which have similar properties to what is found in standard general relativity.

  5. Thermodynamics of higher dimensional topological dilaton black holes with power-law Maxwell field

    E-print Network

    M. Kord Zangeneh; A. Sheykhi; M. H. Dehghani

    2015-05-02

    In this paper, we extend the study on the nonlinear power-law Maxwell field to dilaton gravity. We introduce the $(n+1)$-dimensional action in which gravity is coupled to a dilaton and power-law nonlinear Maxwell field, and obtain the field equations by varying the action. We construct a new class of higher dimensional topological black hole solutions of Einstein-dilaton theory coupled to a power-law nonlinear Maxwell field and investigate the effects of the nonlinearity of the Maxwell source as well as the dilaton field on the properties of the spacetime. Interestingly enough, we find that the solutions exist provided one assumes three Liouville-type potentials for the dilaton field, and in case of the Maxwell field one of the Liouville potential vanishes. After studying the physical properties of the solutions, we compute the mass, charge, electric potential and temperature of the topological dilaton black holes. We also study thermodynamics and thermal stability of the solutions and disclose the effects of the dilaton field and the power-law Maxwell field on the thermodynamics of these black holes. Finally, we comment on the dynamical stability of the obtained solutions in four-dimensions.

  6. Power-law cosmic expansion in f(R) gravity models

    E-print Network

    Naureen Goheer; Julien Larena; Peter K. S. Dunsby

    2009-06-21

    We show that within the class of f(R) gravity theories, FLRW power-law perfect fluid solutions only exist for R^n gravity. This significantly restricts the set of exact cosmological solutions which have similar properties to what is found in standard General Relativity.

  7. Comment on ``Power-law correlations in the southern-oscillation-index fluctuations characterizing El Niño''

    Microsoft Academic Search

    Richard Metzler

    2003-01-01

    In a recent publication [Phys. Rev. E 63, 047201 (2001)], Ausloos and Ivanova report power-law probability distributions, fractal properties, and antipersistent long-range correlations in the southern oscillation index. As a comparison with artificial short-range correlated data shows, most of these findings are possibly due to misleading interpretation of the analysis techniques used.

  8. Imaging viscoelastic properties of live cells by AFM: power-law rheology on the nanoscale.

    PubMed

    Hecht, Fabian M; Rheinlaender, Johannes; Schierbaum, Nicolas; Goldmann, Wolfgang H; Fabry, Ben; Schäffer, Tilman E

    2015-06-01

    We developed force clamp force mapping (FCFM), an atomic force microscopy (AFM) technique for measuring the viscoelastic creep behavior of live cells with sub-micrometer spatial resolution. FCFM combines force-distance curves with an added force clamp phase during tip-sample contact. From the creep behavior measured during the force clamp phase, quantitative viscoelastic sample properties are extracted. We validate FCFM on soft polyacrylamide gels. We find that the creep behavior of living cells conforms to a power-law material model. By recording short (50-60 ms) force clamp measurements in rapid succession, we generate, for the first time, two-dimensional maps of power-law exponent and modulus scaling parameter. Although these maps reveal large spatial variations of both parameters across the cell surface, we obtain robust mean values from the several hundreds of measurements performed on each cell. Measurements on mouse embryonic fibroblasts show that the mean power-law exponents and the mean modulus scaling parameters differ greatly among individual cells, but both parameters are highly correlated: stiffer cells consistently show a smaller power-law exponent. This correlation allows us to distinguish between wild-type cells and cells that lack vinculin, a dominant protein of the focal adhesion complex, even though the mean values of viscoelastic properties between wildtype and knockout cells did not differ significantly. Therefore, FCFM spatially resolves viscoelastic sample properties and can uncover subtle mechanical signatures of proteins in living cells. PMID:25891371

  9. Power-laws and the Conservation of Information in discrete token systems

    E-print Network

    Hatton, Les

    Hatton leshatton.org August 11, 2013 Abstract The Conservation of Energy plays a pivotal part as the Conservation of Energy does in physical systems. I will go on to prove that this implies power-law behaviour@oakcomp.co.uk 1 #12;1 Preliminaries 1.1 Conservation of Energy The Conservation of Energy is one of a few

  10. The Berners-Lee Hypothesis: Power laws and Group Structure in Flickr

    Microsoft Academic Search

    Andrea Baldassarri; Alain Barrat; A. Capocci; Harry Halpin; Ulrike Lehner; Jose Ramasco; Valentin Robu; Dario Taraborelli

    2008-01-01

    An intriguing hypothesis, first suggested by Tim Berners-Lee, is that the structure of online groups should conform to a power law distribution. We relate this hypothesis to earlier work around the Dunbar Number, which is a sup- posed limit to the number of social contacts a user can have in a group. As pre- liminary results, we show that the

  11. Research on power-law acoustic transient signal detection based on wavelet transform

    Microsoft Academic Search

    Jian-hui Han; Ri-jie Yang; Wei Wang

    2007-01-01

    Aiming at the characteristics of acoustic transient signal emitted from antisubmarine weapon which is being dropped into water (torpedo, aerial sonobuoy and rocket assisted depth charge etc.), such as short duration, low SNR, abruptness and instability, based on traditional power-law detector, a new method to detect acoustic transient signal is proposed. Firstly wavelet transform is used to de-noise signal, removes

  12. Simulation of mass transfer during osmotic dehydration of apple: a power law approximation method

    NASA Astrophysics Data System (ADS)

    Abbasi Souraki, B.; Tondro, H.; Ghavami, M.

    2014-10-01

    In this study, unsteady one-dimensional mass transfer during osmotic dehydration of apple was modeled using an approximate mathematical model. The mathematical model has been developed based on a power law profile approximation for moisture and solute concentrations in the spatial direction. The proposed model was validated by the experimental water loss and solute gain data, obtained from osmotic dehydration of infinite slab and cylindrical shape samples of apple in sucrose solutions (30, 40 and 50 % w/w), at different temperatures (30, 40 and 50 °C). The proposed model's predictions were also compared with the exact analytical and also a parabolic approximation model's predictions. The values of mean relative errors respect to the experimental data were estimated between 4.5 and 8.1 %, 6.5 and 10.2 %, and 15.0 and 19.1 %, for exact analytical, power law and parabolic approximation methods, respectively. Although the parabolic approximation leads to simpler relations, the power law approximation method results in higher accuracy of average concentrations over the whole domain of dehydration time. Considering both simplicity and precision of the mathematical models, the power law model for short dehydration times and the simplified exact analytical model for long dehydration times could be used for explanation of the variations of the average water loss and solute gain in the whole domain of dimensionless times.

  13. Interim Report on the Power Law Index of Interplanetary Suprathermal Ion Spectra

    Microsoft Academic Search

    M. E. Hill; D. C. Hamilton

    2010-01-01

    There is a continuing debate about the applicability of the theory presented by Fisk and Gloeckler (FG) regarding the formation of suprathermal ion tails in phase space density vs. velocity spectra; in the solar wind frame the FG theory predicts a power law index of-5 (which is equivalent to a differential intensity vs. energy index of-1.5). There has also been

  14. Thermodynamic laws, economic methods and the productive power of energy

    NASA Astrophysics Data System (ADS)

    Kümmel, Reiner; Ayres, Robert U.; Lindenberger, Dietmar

    2010-07-01

    Energy plays only a minor role in orthodox theories of economic growth, because standard economic equilibrium conditions say that the output elasticity of a production factor, which measures the factor's productive power, is equal to the factor's share in total factor cost. Having commanded only a tiny cost share of about 5 percent so far, energy is often neglected altogether. On the other hand, energy conversion in the machines of the capital stock has been the basis of industrial growth. How can the physically obvious economic importance of energy be reconciled with the conditions for economic equilibrium, which result from the maximization of profit or overall welfare? We show that these equilibrium conditions no longer yield the equality of cost shares and output elasticities, if the optimization calculus takes technological constraints on the combinations of capital, labor, and energy into account. New econometric analyses of economic growth in Germany, Japan, and the USA yield output elasticities that are for energy much larger and for labor much smaller than their cost shares. Social consequences are discussed.

  15. Gravity darkening in binary stars

    NASA Astrophysics Data System (ADS)

    Espinosa Lara, F.; Rieutord, M.

    2012-11-01

    Context. Interpretation of light curves of many types of binary stars requires the inclusion of the (cor)relation between surface brightness and local effective gravity. Until recently, this correlation has always been modeled by a power law relating the flux or the effective temperature and the effective gravity, namely Teff ? geff? . Aims: We look for a simple model that can describe the variations of the flux at the surface of stars belonging to a binary system. Methods: This model assumes that the energy flux is a divergence-free vector anti-parallel to the effective gravity. The effective gravity is computed from the Roche model. Results: After explaining in a simple manner the old result of Lucy (1967, Z. Astrophys., 65, 89), which says that ? ~ 0.08 for solar type stars, we first argue that one-dimensional models should no longer be used to evaluate gravity darkening laws. We compute the correlation between log Teff and log geff using a new approach that is valid for synchronous, weakly magnetized, weakly irradiated binaries. We show that this correlation is approximately linear, validating the use of a power law relation between effective temperature and effective gravity as a first approximation. We further show that the exponent ? of this power law is a slowly varying function, which we tabulate, of the mass ratio of the binary star and the Roche lobe filling factor of the stars of the system. The exponent ? remains mostly in the interval [0.20,0.25] if extreme mass ratios are eliminated. Conclusions: For binary stars that are synchronous, weakly magnetized and weakly irradiated, the gravity darkening exponent is well constrained and may be removed from the free parameters of the models.

  16. Interim Report: Air-Cooled Condensers for Next Generation Geothermal Power Plants Improved Binary Cycle Performance

    SciTech Connect

    Daniel S. Wendt; Greg L. Mines

    2010-09-01

    As geothermal resources that are more expensive to develop are utilized for power generation, there will be increased incentive to use more efficient power plants. This is expected to be the case with Enhanced Geothermal System (EGS) resources. These resources will likely require wells drilled to depths greater than encountered with hydrothermal resources, and will have the added costs for stimulation to create the subsurface reservoir. It is postulated that plants generating power from these resources will likely utilize the binary cycle technology where heat is rejected sensibly to the ambient. The consumptive use of a portion of the produced geothermal fluid for evaporative heat rejection in the conventional flash-steam conversion cycle is likely to preclude its use with EGS resources. This will be especially true in those areas where there is a high demand for finite supplies of water. Though they have no consumptive use of water, using air-cooling systems for heat rejection has disadvantages. These systems have higher capital costs, reduced power output (heat is rejected at the higher dry-bulb temperature), increased parasitics (fan power), and greater variability in power generation on both a diurnal and annual basis (larger variation in the dry-bulb temperature). This is an interim report for the task ‘Air-Cooled Condensers in Next- Generation Conversion Systems’. The work performed was specifically aimed at a plant that uses commercially available binary cycle technologies with an EGS resource. Concepts were evaluated that have the potential to increase performance, lower cost, or mitigate the adverse effects of off-design operation. The impact on both cost and performance were determined for the concepts considered, and the scenarios identified where a particular concept is best suited. Most, but not all, of the concepts evaluated are associated with the rejection of heat. This report specifically addresses three of the concepts evaluated: the use of recuperation, the use of turbine reheat, and the non-consumptive use of EGS make-up water to supplement heat rejection

  17. Electromagnetic Transients Powered by Nuclear Decay in the Tidal Tails of Coalescing Compact Binaries

    NASA Astrophysics Data System (ADS)

    Roberts, L. F.; Kasen, D.; Lee, W. H.; Ramirez-Ruiz, E.

    2011-07-01

    We investigate the possibility that long tidal tails formed during compact object mergers may produce optical transients powered by the decay of freshly synthesized r-process material. Precise modeling of the merger dynamics allows for a realistic determination of the thermodynamic conditions in the ejected debris. We combine hydrodynamic and full nuclear network calculations to determine the resultant r-process abundances and the heating of the material by their decays. The subsequent homologous structure is mapped into a radiative transfer code to synthesize emergent model light curves and determine how their properties (variability and color evolution) depend on the mass ratio and orientation of the merging binary. The radiation emanating from the ejected debris, though less spectacular than a typical supernova, should be observable in transient surveys and we estimate the associated detection rates. We find that it is unlikely that photometry alone will be able to distinguish between different binary mass ratios and the nature of the compact objects, emphasizing the need for spectroscopic follow-up of these events. The case for (or against) compact object mergers as the progenitors of short gamma-ray bursts can be tested if such electromagnetic transients are detected (or not) in coincidence with some bursts, although they may be obscured by on-axis afterglows.

  18. ELECTROMAGNETIC TRANSIENTS POWERED BY NUCLEAR DECAY IN THE TIDAL TAILS OF COALESCING COMPACT BINARIES

    SciTech Connect

    Roberts, L. F.; Ramirez-Ruiz, E. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Kasen, D. [Departments of Physics and Astronomy, University of California, Berkeley, CA 94270 (United States); Lee, W. H. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Cd. Universitaria, Mexico DF 04510 (Mexico)

    2011-07-20

    We investigate the possibility that long tidal tails formed during compact object mergers may produce optical transients powered by the decay of freshly synthesized r-process material. Precise modeling of the merger dynamics allows for a realistic determination of the thermodynamic conditions in the ejected debris. We combine hydrodynamic and full nuclear network calculations to determine the resultant r-process abundances and the heating of the material by their decays. The subsequent homologous structure is mapped into a radiative transfer code to synthesize emergent model light curves and determine how their properties (variability and color evolution) depend on the mass ratio and orientation of the merging binary. The radiation emanating from the ejected debris, though less spectacular than a typical supernova, should be observable in transient surveys and we estimate the associated detection rates. We find that it is unlikely that photometry alone will be able to distinguish between different binary mass ratios and the nature of the compact objects, emphasizing the need for spectroscopic follow-up of these events. The case for (or against) compact object mergers as the progenitors of short gamma-ray bursts can be tested if such electromagnetic transients are detected (or not) in coincidence with some bursts, although they may be obscured by on-axis afterglows.

  19. Stress-dependent power-law flow in the upper mantle following the 2002 Denali, Alaska, earthquake

    E-print Network

    Freed, Andrew

    Stress-dependent power-law flow in the upper mantle following the 2002 Denali, Alaska, earthquake-field continuous Global Positioning System (GPS) time-series data following the 2002 M7.9 Denali, Alaska earthquake. © 2006 Elsevier B.V. All rights reserved. Keywords: postseismic; power-law; Denali; viscoelastic

  20. Using likelihood to test for Lévy flight search patterns and for general power-law distributions in nature

    Microsoft Academic Search

    Andrew M. Edwards

    2008-01-01

    Summary 1. Ecologists are obtaining ever-increasing amounts of data concerning animal movement. A movement strategy that has been concluded for a broad variety of animals is that of Lévy flights, which are random walks whose step lengths come from probability distributions with heavy power-law tails. 2. The exponent that parameterizes the power-law tail, denoted ? , has repeatedly been found

  1. Universal inverse power-law distribution for temperature and rainfall in the UK region

    E-print Network

    A. M. Selvam

    2013-06-15

    Meteorological parameters, such as temperature, rainfall, pressure etc., exhibit selfsimilar space-time fractal fluctuations generic to dynamical systems in nature such as fluid flows, spread of forest fires, earthquakes, etc. The power spectra of fractal fluctuations display inverse power-law form signifying long-range correlations. The author has developed a general systems theory which predicts universal inverse power-law form incorporating the golden mean for the fractal fluctuations of all size scales, i.e., small, large and extreme values. The model predicted distribution is in close agreement with observed fractal fluctuations in the historic month-wise temperature (maximum and minimum) and rainfall in the UK region. The present study suggests that fractal fluctuations result from the superimposition of an eddy continuum fluctuations. The observed extreme values result from superimposition of maxima (or minima) of dominant eddies (waves) in the eddy continuum.

  2. Taylor's power law and fluctuation scaling explained by a central-limit-like convergence.

    PubMed

    Kendal, Wayne S; Jørgensen, Bent

    2011-06-01

    A power function relationship observed between the variance and the mean of many types of biological and physical systems has generated much debate as to its origins. This Taylor's law (or fluctuation scaling) has been recently hypothesized to result from the second law of thermodynamics and the behavior of the density of states. This hypothesis is predicated on physical quantities like free energy and an external field; the correspondence of these quantities with biological systems, though, remains unproven. Questions can be posed as to the applicability of this hypothesis to the diversity of observed phenomena as well as the range of spatial and temporal scales observed with Taylor's law. We note that the cumulant generating functions derived from this thermodynamic model correspond to those derived over a quarter century earlier for a class of probabilistic models known as the Tweedie exponential dispersion models. These latter models are characterized by variance-to-mean power functions; their phenomenological basis rests with a central-limit-theorem-like property that causes many statistical systems to converge mathematically toward a Tweedie form. We review evaluations of the Tweedie Poisson-gamma model for Taylor's law and provide three further cases to test: the clustering of single nucleotide polymorphisms (SNPs) within the horse chromosome 1, the clustering of genes within human chromosome 8, and the Mertens function. This latter case is a number theoretic function for which a thermodynamic model cannot explain Taylor's law, but where Tweedie convergence remains applicable. The Tweedie models are applicable to diverse biological, physical, and mathematical phenomena that express power variance functions over a wide range of measurement scales; they provide a probabilistic description for Taylor's law that allows mechanistic insight into complex systems without the assumption of a thermodynamic mechanism. PMID:21797449

  3. A more powerful exact test of noninferiority from binary matched-pairs data.

    PubMed

    Lloyd, Chris J; Moldovan, Max V

    2008-08-15

    Assessing the therapeutic noninferiority of one medical treatment compared with another is often based on the difference in response rates from a matched binary pairs design. This paper develops a new exact unconditional test for noninferiority that is more powerful than available alternatives. There are two new elements presented in this paper. First, we introduce the likelihood ratio statistic as an alternative to the previously proposed score statistic of Nam (Biometrics 1997; 53:1422-1430). Second, we eliminate the nuisance parameter by estimation followed by maximization as an alternative to the partial maximization of Berger and Boos (Am. Stat. Assoc. 1994; 89:1012-1016) or traditional full maximization. Based on an extensive numerical study, we recommend tests based on the score statistic, the nuisance parameter being controlled by estimation followed by maximization. PMID:18314932

  4. Exploring the powering source of the TeV X-ray binary LS 5039

    E-print Network

    J. Moldon; M. Ribo; Josep M. Paredes; J. Marti; M. Massi

    2008-12-04

    LS 5039 is one of the four TeV emitting X-ray binaries detected up to now. The powering source of its multi-wavelength emission can be accretion in a microquasar scenario or wind interaction in a young non-accreting pulsar scenario. These two scenarios predict different morphologic and peak position changes along the orbital cycle of 3.9 days, which can be tested at milliarcsecond scales using VLBI techniques. Here we present a campaign of 5 GHz VLBA observations conducted in June 2000 (2 runs five days apart). The results show a core component with a constant flux density, and a fast change in the morphology and the position angle of the elongated extended emission, but maintaining a stable flux density. These results are difficult to fit comfortably within a microquasar scenario, whereas they appear to be compatible with the predicted behavior for a non-accreting pulsar.

  5. The quest for obscured AGN at cosmological distances: Infrared Power-Law Galaxies

    E-print Network

    Almudena Alonso-Herrero; Jennifer L. Donley; George H. Rieke; Jane R. Rigby; Pablo G. Perez-Gonzalez

    2006-12-04

    We summarize multiwavelength properties of a sample of galaxies in the CDF-N and CDF-S whose Spectral Energy Distributions (SEDs) exhibit the characteristic power-law behavior expected for AGN in the Spitzer/IRAC 3.6-8micron bands. AGN selected this way tend to comprise the majority of high X-ray luminosity AGN, whereas AGN selected via other IRAC color-color criteria might contain more star-formation dominated galaxies. Approximately half of these IR power-law galaxies in the CDF-S are detected in deep (1Ms) Chandra X-ray imaging, although in the CDF-N (2Ms) about 77% are detected at the 3sigma level. The SEDs and X-ray upper limits of the sources not detected in X-rays are consistent with those of obscured AGN, and are significantly different from those of massive star-forming galaxies. About 40% of IR power-law galaxies detected in X-rays have SEDs resembling that of an optical QSO and morphologies dominated by bright point source emission. The remaining 60% have SEDs whose UV and optical continuum are much steeper (obscured) and more extended morphologies than those detected in X-rays. Most of the IR power-law galaxies not detected in X-rays have IR (8-1000micron above 10^12Lsun, and X-ray (upper limits) to mid-IR ratios similar to those of local warm (ie, hosting an AGN) ULIRGs. The SED shapes of power-law galaxies are consistent with the obscured fraction (4:1) as derived from the X-ray column densities, if we assume that all the sources not detected in X-rays are heavily absorbed. IR power-law galaxies may account for between 20% and 50% of the predicted number density of mid-IR detected obscured AGN. The remaining obscured AGN probably have rest-frame SEDs dominated by stellar emission.

  6. High-index asymptotics of spherical Bessel products averaged with modulated Gaussian power laws

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2014-12-01

    Bessel integrals of type are investigated, where the kernel g( k) is a modulated Gaussian power-law distribution , and the jl ( m) are multiple derivatives of spherical Bessel functions. These integrals define the multipole moments of Gaussian random fields on the unit sphere, arising in multipole fits of temperature and polarization power spectra of the cosmic microwave background. Two methods allowing efficient numerical calculation of these integrals are presented, covering Bessel indices l in the currently accessible multipole range 0 ? l ? 104 and beyond. The first method is based on a representation of spherical Bessel functions by Lommel polynomials. Gaussian power-law averages can then be calculated in closed form as finite Hankel series of parabolic cylinder functions, which allow high-precision evaluation. The second method is asymptotic, covering the high- l regime, and is applicable to general distribution functions g( k) in the integrand; it is based on the uniform Nicholson approximation of the Bessel derivatives in conjunction with an integral representation of squared Airy functions. A numerical comparison of these two methods is performed, employing Gaussian power laws and Kummer distributions to average the Bessel products.

  7. Fractional Action Cosmology: Emergent, Logamediate, Intermediate, Power Law Scenarios of the Universe and Generalized Second Law of Thermodynamics

    Microsoft Academic Search

    Ujjal Debnath; Mubasher Jamil; Surajit Chattopadhyay

    2011-01-01

    In the framework of Fractional Action Cosmology (FAC), we study the generalized second law of thermodynamics for the Friedmann Universe enclosed by a boundary. We use the four well-known cosmic horizons as boundaries namely, apparent horizon, future event horizon, Hubble horizon and particle horizon. We construct the generalized second law (GSL) using and without using the first law of thermodynamics.

  8. The MLP Distribution: A Modified Lognormal Power-Law Model for the Stellar Initial Mass Function

    E-print Network

    Basu, Shantanu; Auddy, Sayantan

    2015-01-01

    This work explores the mathematical properties of a distribution introduced by Basu & Jones (2004), and applies it to model the stellar initial mass function (IMF). The distribution arises simply from an initial lognormal distribution, requiring that each object in it subsequently undergoes exponential growth but with an exponential distribution of growth lifetimes. This leads to a modified lognormal with a power-law tail (MLP) distribution, which can in fact be applied to a wide range of fields where distributions are observed to have a lognormal-like body and a power-law tail. We derive important properties of the MLP distribution, like the cumulative distribution, the mean, variance, arbitrary raw moments, and a random number generator. These analytic properties of the distribution can be used to facilitate application to modeling the IMF. We demonstrate how the MLP function provides an excellent fit to the IMF compiled by Chabrier (2005) and how this fit can be used to quickly identify quantities like...

  9. Input-anticipating critical reservoirs show power law forgetting of unexpected input events.

    PubMed

    Mayer, Norbert Michael

    2015-05-01

    Usually reservoir computing shows an exponential memory decay. This letter investigates under which circumstances echo state networks can show a power law forgetting. That means traces of earlier events can be found in the reservoir for very long time spans. Such a setting requires critical connectivity exactly at the limit of what is permissible according to the echo state condition. However, for general matrices, the limit cannot be determined exactly from theory. In addition, the behavior of the network is strongly influenced by the input flow. Results are presented that use certain types of restricted recurrent connectivity and anticipation learning with regard to the input, where power law forgetting can indeed be achieved. PMID:25774542

  10. Power Law in Micro-Canonical Ensemble with Scaling Volume Fluctuations

    E-print Network

    V. V. Begun; M. Ga?dzicki; M. I. Gorenstein

    2008-08-11

    Volume fluctuations are introduced in a statistical modelling of relativistic particle collisions. The micro-canonical ensemble is used, and the volume fluctuations are assumed to have the specific scaling properties. This leads to the KNO scaling of the particle multiplicity distributions as measured in p+p interactions. A striking prediction of the model is a power law form of the single particle momentum spectrum at high momenta. Moreover, the mean multiplicity of heavy particles also decreases as a function of the particle mass according to a power law. Finally, it is shown that the dependence of the momentum spectrum on the particle mass and momentum reduces to the dependence on the particle energy. These results resemble the properties of particle production in collisions of high energy particles.

  11. Mixed convection heat transfer to power law fluids in arbitrary cross-sectional ducts

    NASA Astrophysics Data System (ADS)

    Lawal, A.

    1989-05-01

    An analytical investigation of three-dimensional mixed conveciton flow and heat transfer to power-law fluids in horizontal arbitrary cross-sectional ducts is undertaken. The continuity equation and parabolic forms of the energy and momentum equations in rectangular coordinates are transformed into new orthogonal coordinates with the boundaries of the duct coinciding with the coordinate surfaces. The transformed equations are solved by the finite difference technique. The fluid enters the duct with constant velocity and temperature profiles with the wall of the duct subjected to constant temperature. Local heat transfer coefficients and pressure drop for several values of Gr/Re and power-law index n are computed for the triangular, square, trapezoidal, pentagonal, and circular ducts. The buoyancy force is found to increase both the Nusselt number and the pressure drop.

  12. Power-law behavior in the quantum-resonant evolution of the ? -kicked accelerator

    NASA Astrophysics Data System (ADS)

    Halkyard, P. L.; Saunders, M.; Gardiner, S. A.; Challis, K. J.

    2008-12-01

    We consider the atom-optical ? -kicked accelerator when the initial momentum distribution is symmetric. We demonstrate the existence of quantum-resonant dynamics, and derive analytic expressions for the system evolution. In particular, we consider the dynamical evolution of the momentum moments and find that all even-ordered momentum moments exhibit a power-law growth. In the ultracold (zero-temperature) limit the exponent is determined by the order of the moment, whereas for a broad, thermal initial momentum distribution the exponent is reduced by 1. To demonstrate the power-law behavior explicitly we consider the evolutions of the second- and fourth-order momentum moments, and cumulants, for an initially Gaussian momentum distribution corresponding to the Maxwell-Boltzmann distribution of an ideal gas at thermal equilibrium.

  13. The Decay of Magnetohydrodynamic Turbulence from Power-Law Initial Conditions

    E-print Network

    Chirag Kalelkar; Rahul Pandit

    2004-01-30

    We derive relations for the decay of the kinetic and magnetic energies and the growth of the Taylor and integral scales in unforced, incompressible, homogeneous and isotropic three-dimensional magnetohydrodynamic (3DMHD) turbulence with power-law initial energy spectra. We also derive bounds for the decay of the cross- and magnetic helicities. We then present results from systematic numerical studies of such decay both within the context of an MHD shell model and direct numerical simulations (DNS) of 3DMHD. We show explicitly that our results about the power-law decay of the energies hold for times $t

  14. Fractionally integrated process with power-law correlations in variables and magnitudes

    NASA Astrophysics Data System (ADS)

    Podobnik, Boris; Ivanov, Plamen Ch.; Biljakovic, Katica; Horvatic, Davor; Stanley, H. Eugene; Grosse, Ivo

    2005-08-01

    Motivated by the fact that many empirical time series—including changes of heartbeat intervals, physical activity levels, intertrade times in finance, and river flux values—exhibit power-law anticorrelations in the variables and power-law correlations in their magnitudes, we propose a simple stochastic process that can account for both types of correlations. The process depends on only two parameters, where one controls the correlations in the variables and the other controls the correlations in their magnitudes. We apply the process to time series of heartbeat interval changes and air temperature changes and find that the statistical properties of the modeled time series are in agreement with those observed in the data.

  15. The relationship between randomness and power-law distributed move lengths in random walk algorithms

    NASA Astrophysics Data System (ADS)

    Sakiyama, Tomoko; Gunji, Yukio-Pegio

    2014-05-01

    Recently, we proposed a new random walk algorithm, termed the REV algorithm, in which the agent alters the directional rule that governs it using the most recent four random numbers. Here, we examined how a non-bounded number, i.e., "randomness" regarding move direction, was important for optimal searching and power-law distributed step lengths in rule change. We proposed two algorithms: the REV and REV-bounded algorithms. In the REV algorithm, one of the four random numbers used to change the rule is non-bounded. In contrast, all four random numbers in the REV-bounded algorithm are bounded. We showed that the REV algorithm exhibited more consistent power-law distributed step lengths and flexible searching behavior.

  16. Power Laws in Solar Flares: Self-Organized Criticality or Turbulence?

    E-print Network

    Guido Boffetta; Vincenzo Carbone; Paolo Giuliani; Pierluigi Veltri; Angelo Vulpiani

    1999-04-23

    We study the time evolution of Solar Flares activity by looking at the statistics of quiescent times $\\tau_{L}$ between successive bursts. The analysis of 20 years of data reveals a power law distribution with exponent $\\alpha \\simeq 2.4$ which is an indication of complex dynamics with long correlation times. The observed scaling behavior is in contradiction with the Self-Organized Criticality models of Solar Flares which predict Poisson-like statistics. Chaotic models, including the destabilization of the laminar phases and subsequent restabilization due to nonlinear dynamics, are able to reproduce the power law for the quiescent times. In the case of the more realistic Shell Model of MHD turbulence we are able to reproduce all the observed distributions.

  17. Formation of hard power laws in the energetic particle spectra resulting from relativistic magnetic reconnection.

    PubMed

    Guo, Fan; Li, Hui; Daughton, William; Liu, Yi-Hsin

    2014-10-10

    Using fully kinetic simulations, we demonstrate that magnetic reconnection in relativistic plasmas is highly efficient at accelerating particles through a first-order Fermi process resulting from the curvature drift of particles in the direction of the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra in parameter regimes where the energy density in the reconnecting field exceeds the rest mass energy density ? ? B(2)/(4?nm(e)c(2))>1 and when the system size is sufficiently large. In the limit ? ? 1, the spectral index approaches p = 1 and most of the available energy is converted into nonthermal particles. A simple analytic model is proposed which explains these key features and predicts a general condition under which hard power-law spectra will be generated from magnetic reconnection. PMID:25375716

  18. Nonlinear Acoustics FDTD method including Frequency Power Law Attenuation for Soft Tissue Modeling

    E-print Network

    Jiménez, Noé; Sánchez-Morcillo, Víctor; Camarena, Francisco; Hou, Yi; Konofagou, Elisa E

    2014-01-01

    This paper describes a model for nonlinear acoustic wave propagation through absorbing and weakly dispersive media, and its numerical solution by means of finite differences in time domain method (FDTD). The attenuation is based on multiple relaxation processes, and provides frequency dependent absorption and dispersion without using computational expensive convolutional operators. In this way, by using an optimization algorithm the coefficients for the relaxation processes can be obtained in order to fit a frequency power law that agrees the experimentally measured attenuation data for heterogeneous media over the typical frequency range for ultrasound medical applications. Our results show that two relaxation processes are enough to fit attenuation data for most soft tissues in this frequency range including the fundamental and the first ten harmonics. Furthermore, this model can fit experimental attenuation data that do not follow exactly a frequency power law over the frequency range of interest. The main...

  19. Correlations of Power-law Spectral and QPO Features In Black Hole Candidate Sources

    NASA Technical Reports Server (NTRS)

    Fiorito, Ralph; Titarchuk, Lev

    2004-01-01

    Recent studies have shown that strong correlations are observed between low frequency QPO s and the spectral power law index for a number of black hole candidate sources (BHCs), when these sources exhibit quasi-steady hard x-ray emission states. The dominant long standing interpretation of QPO's is that they are produced in and are the signature of the thermal accretion disk. Paradoxically, strong QPO's are present even in the cases where the thermal component is negligible. We present a model which identifies the origin of the QPO's and relates them directly to the properties of a compact coronal region which is bounded by the adjustment from Kepleriaa to sub-Kelperian inflow into the BH, and is primarily responsible for the observed power law spectrum. The model also predicts the relationship between high and low frequency QPO's and shows how BH's can be unique identified from observations of the soft states of NS's and BHC's.

  20. Hypersonic aerodynamic characteristics of a family of power-law, wing body configurations

    NASA Technical Reports Server (NTRS)

    Townsend, J. C.

    1973-01-01

    The configurations analyzed are half-axisymmetric, power-law bodies surmounted by thin, flat wings. The wing planform matches the body shock-wave shape. Analytic solutions of the hypersonic small disturbance equations form a basis for calculating the longitudinal aerodynamic characteristics. Boundary-layer displacement effects on the body and the wing upper surface are approximated. Skin friction is estimated by using compressible, laminar boundary-layer solutions. Good agreement was obtained with available experimental data for which the basic theoretical assumptions were satisfied. The method is used to estimate the effects of power-law, fineness ratio, and Mach number variations at full-scale conditions. The computer program is included.

  1. Power-law behavior in the quantum-resonant evolution of the delta-kicked accelerator

    E-print Network

    P. L. Halkyard; M. Saunders; S. A. Gardiner; K. J. Challis

    2008-09-25

    We consider the atom-optical delta-kicked accelerator when the initial momentum distribution is symmetric. We demonstrate the existence of quantum-resonant dynamics, and derive analytic expressions for the system evolution. In particular, we consider the dynamical evolution of the momentum moments and find that all even-ordered momentum moments exhibit a power law growth. In the ultracold (zero-temperature) limit the exponent is determined by the order of the moment, whereas for a broad, thermal initial momentum distribution the exponent is reduced by one. To demonstrate the power law behavior explicitly we consider the evolutions of the second- and fourth-order momentum moments, and cumulants, for an initially Gaussian momentum distribution corresponding to the Maxwell-Boltzmann distribution of an ideal gas at thermal equilibrium.

  2. Zeotropic mixtures of halocarbons as working fluids in binary geothermal power generation cycles

    SciTech Connect

    Bliem, C.J.

    1987-01-01

    The performance of Rankine cycle binary systems for geothermal power generation using a hydrothermal resource has been investigated. To date, in addition to many pure fluids, mixtures of Paraffin-type hydrocarbons and water-ammonia mixtures have been investigated. This paper gives the results of consideration of mixtures of halocarbons as working fluids in these power cycles. The performance of mixtures of Refrigerant-114 (R-114) and Refrigerant-22 (R-22) in combinations from pure R-114 to pure R-22 was calculated for such cycles. Various alternatives were considered: (1) minimum geofluid outlet temperature constraint/no constraint, (2) dry turbine expansion/expansion through vapor dome, and (3) use of turbine exhaust gas recuperator/no recuperator. Results of the study indicate that the halocarbon mixtures are at least as good as the hydrocarbon mixtures previously analyzed for a 360 F resource. The magnitude of the net geofluid effectiveness (net energy produced per unit mass geofluid flow) for the R-114/R-22 mixtures is the same as for the best hydrocarbon mixture previously analyzed. The percentage improvement in effectiveness in using mixtures over using the pure fluids as working fluids is comparable for both classes of working fluids.

  3. Power-law tail of gravitational waves from a uniformly accelerating black hole

    NASA Astrophysics Data System (ADS)

    Tomimatsu, Akira

    1998-02-01

    To investigate the late-time behavior of gravitational waves at future null infinity, we reexamine the vacuum C-metric describing a uniformly accelerating Schwarzschild black hole. By using the mass function defined in the Bondi-Metzner-Sachs coordinate system, it is clearly shown that the power-law tail predicted by linearized perturbation theory develops also in this fully nonlinear axisymmetric dynamics.

  4. Power-law relationship and self-similarity in the itemset support distribution: analysis and applications

    Microsoft Academic Search

    Kun-ta Chuang; Jiun-long Huang; Ming-syan Chen

    2008-01-01

    In this paper, we identify and explore that the power-law relationship and the self-similar phenomenon appear in the itemset\\u000a support distribution. The itemset support distribution refers to the distribution of the count of itemsets versus their supports.\\u000a Exploring the characteristics of these natural phenomena is useful to many applications such as providing the direction of\\u000a tuning the performance of the

  5. Relaxation Dynamics of Langmuir Polymer Films: A Power-Law Analysis

    Microsoft Academic Search

    Francisco Monroy; Hani M. Hilles; Francisco Ortega; Ramón G. Rubio

    2003-01-01

    We report an experimental study on the mechanical relaxation of Langmuir films of a flexible polymer: polyvinylacetate, a good example of a two-dimensional polymeric system at good-solvent conditions. This study allows us to explore the dependence of the relaxation times and the surface viscosity on the concentration. In the semidilute regime, both dynamical properties follow well-defined power laws, which are

  6. Determination of Constant Parameters of Copper as Power-Law Hardening Material at Different Test Conditions

    NASA Astrophysics Data System (ADS)

    Kowser, Md. A.; Mahiuddin, Md.

    2014-11-01

    In this paper a technique has been developed to determine constant parameters of copper as a power-law hardening material by tensile test approach. A work-hardening process is used to describe the increase of the stress level necessary to continue plastic deformation. A computer program is used to show the variation of the stress-strain relation for different values of stress hardening exponent, n and power-law hardening constant, ? . Due to its close tolerances, excellent corrosion resistance and high material strength, in this analysis copper (Cu) has been selected as the material. As a power-law hardening material, Cu has been used to compute stress hardening exponent, n and power-law hardening constant, ? from tensile test experiment without heat treatment and after heat treatment. A wealth of information about mechanical behavior of a material can be determined by conducting a simple tensile test in which a cylindrical specimen of a uniform cross-section is pulled until it ruptures or fractures into separate pieces. The original cross sectional area and gauge length are measured prior to conducting the test and the applied load and gauge deformation are continuously measured throughout the test. Based on the initial geometry of the sample, the engineering stress-strain behavior (stress-strain curve) can be easily generated from which numerous mechanical properties, such as the yield strength and elastic modulus, can be determined. A universal testing machine is utilized to apply the load in a continuously increasing (ramp) manner according to ASTM specifications. Finally, theoretical results are compared with these obtained from experiments where the nature of curves is found similar to each other. It is observed that there is a significant change of the value of n obtained with and without heat treatment it means the value of n should be determined for the heat treated condition of copper material for their applications in engineering fields.

  7. Power-law cosmological solution derived from DGP brane with a brane tachyon field

    E-print Network

    Yongli Ping; Lixin Xu; Hongya Liu; Ying Shao

    2008-01-01

    By studying a tachyon field on the DGP brane model, in order to embed the 4D standard Friedmann equation with a brane tachyon field in 5D bulk, the metric of the 5D spacetime is presented. Then, adopting the inverse square potential of tachyon field, we obtain an expanding universe with power-law on the brane and an exact 5D solution.

  8. Deviation from power law of the global earthquake seismic moment distribution

    E-print Network

    Serra, Isabel

    2015-01-01

    The distribution of earthquake seismic moment is of capital importance to evaluate seismic hazard, in particular regarding the most extreme events. Likelihood-ratio tests let to compare the performance of the most suitable probabilistic models when ?tted to the global CMT catalog. The conclusion is that the truncated gamma model outperforms the power law and the tapered Gutenberg-Richter models, being able to explain the empirical data both before and after the great Sumatra-Andaman earthquake of 2004.

  9. Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information

    NASA Technical Reports Server (NTRS)

    Howell, L. W., Jr.

    2003-01-01

    A simple power law model consisting of a single spectral index, sigma(sub 2), is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at the knee energy, E(sub k), to a steeper spectral index sigma(sub 2) greater than sigma(sub 1) above E(sub k). The maximum likelihood (ML) procedure was developed for estimating the single parameter sigma(sub 1) of a simple power law energy spectrum and generalized to estimate the three spectral parameters of the broken power law energy spectrum from simulated detector responses and real cosmic-ray data. The statistical properties of the ML estimator were investigated and shown to have the three desirable properties: (Pl) consistency (asymptotically unbiased), (P2) efficiency (asymptotically attains the Cramer-Rao minimum variance bound), and (P3) asymptotically normally distributed, under a wide range of potential detector response functions. Attainment of these properties necessarily implies that the ML estimation procedure provides the best unbiased estimator possible. While simulation studies can easily determine if a given estimation procedure provides an unbiased estimate of the spectra information, and whether or not the estimator is approximately normally distributed, attainment of the Cramer-Rao bound (CRB) can only be ascertained by calculating the CRB for an assumed energy spectrum- detector response function combination, which can be quite formidable in practice. However, the effort in calculating the CRB is very worthwhile because it provides the necessary means to compare the efficiency of competing estimation techniques and, furthermore, provides a stopping rule in the search for the best unbiased estimator. Consequently, the CRB for both the simple and broken power law energy spectra are derived herein and the conditions under which they are stained in practice are investigated.

  10. Observation of power-Law scaling for phase transitions in linear trapped ion crystals

    PubMed

    Enzer; Schauer; Gomez; Gulley; Holzscheiter; Kwiat; Lamoreaux; Peterson; Sandberg; Tupa; White; Hughes; James

    2000-09-18

    We report an experimental confirmation of the power-law relationship between the critical anisotropy parameter and ion number for the linear-to-zigzag phase transition in an ionic crystal. Our experiment uses laser cooled calcium ions confined in a linear radio-frequency trap. Measurements for up to ten ions are in good agreement with theoretical and numeric predictions. Implications on an upper limit to the size of data registers in ion trap quantum computers are discussed. PMID:10978083

  11. Power Laws in Solar Flares: Self-Organized Criticality or Turbulence?

    Microsoft Academic Search

    Guido Boffetta; Vincenzo Carbone; Paolo Giuliani; Pierluigi Veltri; Angelo Vulpiani

    1999-01-01

    The statistics of quiescent times tauL between successive bursts of solar flares activity, performed using 20 years of data, displays a power law distribution with exponent alpha~=2.4. This is an indication of an underlying complex dynamics with long correlation times. The observed scaling behavior is in contradiction with the self-organized criticality models of solar flares which predict Poisson-like statistics. Chaotic

  12. Stochastic modeling of aphid population growth with nonlinear, power-law dynamics

    Microsoft Academic Search

    James H. Matis; Thomas R. Kiffe; Timothy I. Matis; Douglass E. Stevenson

    2007-01-01

    This paper develops a deterministic and a stochastic population size model based on power-law kinetics for the black-margined pecan aphid. The deterministic model in current use incorporates cumulative-size dependency, but its solution is symmetric. The analogous stochastic model incorporates the prolific reproductive capacity of the aphid. These models are generalized in this paper to include a delayed feedback mechanism for

  13. On the use of log-transformation vs. nonlinear regression for analyzing biological power laws

    USGS Publications Warehouse

    Xiao, X.; White, E.P.; Hooten, M.B.; Durham, S.L.

    2011-01-01

    Power-law relationships are among the most well-studied functional relationships in biology. Recently the common practice of fitting power laws using linear regression (LR) on log-transformed data has been criticized, calling into question the conclusions of hundreds of studies. It has been suggested that nonlinear regression (NLR) is preferable, but no rigorous comparison of these two methods has been conducted. Using Monte Carlo simulations, we demonstrate that the error distribution determines which method performs better, with NLR better characterizing data with additive, homoscedastic, normal error and LR better characterizing data with multiplicative, heteroscedastic, lognormal error. Analysis of 471 biological power laws shows that both forms of error occur in nature. While previous analyses based on log-transformation appear to be generally valid, future analyses should choose methods based on a combination of biological plausibility and analysis of the error distribution. We provide detailed guidelines and associated computer code for doing so, including a model averaging approach for cases where the error structure is uncertain. ?? 2011 by the Ecological Society of America.

  14. Empirical analysis on the connection between power-law distributions and allometries for urban indicators

    NASA Astrophysics Data System (ADS)

    Alves, L. G. A.; Ribeiro, H. V.; Lenzi, E. K.; Mendes, R. S.

    2014-09-01

    We report on the existing connection between power-law distributions and allometries. As it was first reported in Gomez-Lievano et al. (2012) for the relationship between homicides and population, when these urban indicators present asymptotic power-law distributions, they can also display specific allometries among themselves. Here, we present an extensive characterization of this connection when considering all possible pairs of relationships from twelve urban indicators of Brazilian cities (such as child labor, illiteracy, income, sanitation and unemployment). Our analysis reveals that all our urban indicators are asymptotically distributed as power laws and that the proposed connection also holds for our data when the allometric relationship displays enough correlations. We have also found that not all allometric relationships are independent and that they can be understood as a consequence of the allometric relationship between the urban indicator and the population size. We further show that the residuals fluctuations surrounding the allometries are characterized by an almost constant variance and log-normal distributions.

  15. Explaining the power-law distribution of human mobility through transportation modality decomposition

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Musolesi, Mirco; Hui, Pan; Rao, Weixiong; Tarkoma, Sasu

    2015-03-01

    Human mobility has been empirically observed to exhibit Lévy flight characteristics and behaviour with power-law distributed jump size. The fundamental mechanisms behind this behaviour has not yet been fully explained. In this paper, we propose to explain the Lévy walk behaviour observed in human mobility patterns by decomposing them into different classes according to the different transportation modes, such as Walk/Run, Bike, Train/Subway or Car/Taxi/Bus. Our analysis is based on two real-life GPS datasets containing approximately 10 and 20 million GPS samples with transportation mode information. We show that human mobility can be modelled as a mixture of different transportation modes, and that these single movement patterns can be approximated by a lognormal distribution rather than a power-law distribution. Then, we demonstrate that the mixture of the decomposed lognormal flight distributions associated with each modality is a power-law distribution, providing an explanation to the emergence of Lévy Walk patterns that characterize human mobility patterns.

  16. Comment on "Time needed to board an airplane: a power law and the structure behind it".

    PubMed

    Bernstein, Noam

    2012-08-01

    Frette and Hemmer [Phys. Rev. E 85, 011130 (2012)] recently showed that for a simple model for the boarding of an airplane, the mean time to board scales as a power law with the number of passengers N and the exponent is less than 1. They note that this scaling leads to the prediction that the "back-to-front" strategy, where passengers are divided into groups from contiguous ranges of rows and each group is allowed to board in turn from back to front once the previous group has found their seats, has a longer boarding time than would a single group. Here I extend their results to a larger number of passengers using a sampling approach and explore a scenario where the queue is presorted into groups from back to front, but allowed to enter the plane as soon as they can. I show that the power law dependence on passenger numbers is different for large N and that there is a boarding time reduction for presorted groups, with a power law dependence on the number of presorted groups. PMID:23005813

  17. Interacting cosmic fluids in power-law Friedmann-Robertson-Walker cosmological models

    E-print Network

    Mauricio Cataldo; Patricio Mella; Paul Minning; Joel Saavedra

    2008-03-07

    We provide a detailed description for power--law scaling Friedmann-Robertson-Walker cosmological scenarios dominated by two interacting perfect fluid components during the expansion. As a consequence of the mutual interaction between the two fluids, neither component is conserved separately and the energy densities are proportional to $1/t^{2}$. It is shown that in flat FRW cosmological models there can exist interacting superpositions of two perfect fluids (each of them having a positive energy density) which accelerate the expansion of the universe. In this family there also exist flat power law cosmological scenarios where one of the fluids may have a ``cosmological constant" or "vacuum energy" equation of state ($p =-\\rho$) interacting with the other component; this scenario exactly mimics the behavior of the standard flat Friedmann solution for a single fluid with a barotropic equation of state. These possibilities of combining interacting perfect fluids do not exist for the non-interacting mixtures of two perfect cosmic fluids, where the general solution for the scale factor is not described by power--law expressions and has a more complicated behavior. In this study is considered also the associated single fluid model interpretation for the interaction between two fluids.

  18. Power-law behavior in complex organizational communication networks during crisis

    NASA Astrophysics Data System (ADS)

    Uddin, Shahadat; Murshed, Shahriar Tanvir Hasan; Hossain, Liaquat

    2011-08-01

    Communication networks can be described as patterns of contacts which are created due to the flow of messages and information shared among participating actors. Contemporary organizations are now commonly viewed as dynamic systems of adaptation and evolution containing several parts, which interact with one another both in internal and in external environment. Although there is limited consensus among researchers on the precise definition of organizational crisis, there is evidence of shared meaning: crisis produces individual crisis, crisis can be associated with positive or negative conditions, crises can be situations having been precipitated quickly or suddenly or situations that have developed over time and are predictable etc. In this research, we study the power-law behavior of an organizational email communication network during crisis from complexity perspective. Power law simply describes that, the probability that a randomly selected node has k links (i.e. degree k) follows P(k)?k, where ? is the degree exponent. We used social network analysis tools and techniques to analyze the email communication dataset. We tested two propositions: (1) as organization goes through crisis, a few actors, who are prominent or more active, will become central, and (2) the daily communication network as well as the actors in the communication network exhibit power-law behavior. Our preliminary results support these two propositions. The outcome of this study may provide significant advancement in exploring organizational communication network behavior during crisis.

  19. Effects of diversity and procrastination in priority queuing theory: The different power law regimes

    NASA Astrophysics Data System (ADS)

    Saichev, A.; Sornette, D.

    2010-01-01

    Empirical analyses show that after the update of a browser, or the publication of the vulnerability of a software, or the discovery of a cyber worm, the fraction of computers still using the older browser or software version, or not yet patched, or exhibiting worm activity decays as a power law ˜1/t? with 0power law tail ˜1/t1/2 , resulting from a first-passage solution of an equivalent Wiener process. Taking into account a diversity of time deficit parameters in a population of individuals, the power law tail is changed into 1/t? , with ??(0.5,?) , including the well-known case 1/t . We also study the effect of “procrastination,” defined as the situation in which the target task may be postponed or delayed even after the individual has solved all other pending tasks. This regime provides an explanation for even slower apparent decay and longer persistence.

  20. Power law behavior of the isotope yield distributions in the multifragmentation regime of heavy ion reactions

    SciTech Connect

    Huang, M. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Wada, R.; Hagel, K.; Barbui, M.; Bottosso, C.; Materna, T.; Natowitz, J. B.; Qin, L.; Rodrigues, M. R. D.; Sahu, P. K.; Schmidt, K. J. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Chen, Z. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Keutgen, T. [FNRS and IPN, Universite Catholique de Louvain, B-1348 Louvain-Neuve (Belgium); Kowalski, S. [Institute of Physics, Silesia University, Katowice (Poland); Bonasera, A. [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States); Laboratori Nazionali del Sud, INFN, via Santa Sofia, 62, I-95123 Catania (Italy); Wang, J. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2010-11-15

    Isotope yield distributions in the multifragmentation regime were studied with high-quality isotope identification, focusing on the intermediate mass fragments (IMFs) produced in semiviolent collisions. The yields were analyzed within the framework of a modified Fisher model. Using the ratio of the mass-dependent symmetry energy coefficient relative to the temperature, a{sub sym}/T, extracted in previous work and that of the pairing term, a{sub p}/T, extracted from this work, and assuming that both reflect secondary decay processes, the experimentally observed isotope yields were corrected for these effects. For a given I=N-Z value, the corrected yields of isotopes relative to the yield of {sup 12}C show a power law distribution Y(N,Z)/Y({sup 12}C){approx}A{sup -}{tau} in the mass range 1{<=}A{<=}30, and the distributions are almost identical for the different reactions studied. The observed power law distributions change systematically when I of the isotopes changes and the extracted {tau} value decreases from 3.9 to 1.0 as I increases from -1 to 3. These observations are well reproduced by a simple deexcitation model, with which the power law distribution of the primary isotopes is determined to be {tau}{sup prim}=2.4{+-}0.2, suggesting that the disassembling system at the time of the fragment formation is indeed at, or very near, the critical point.

  1. Dust-acoustic waves and stability in the permeating dusty plasma. II. Power-law distributions

    NASA Astrophysics Data System (ADS)

    Gong, Jingyu; Liu, Zhipeng; Du, Jiulin

    2012-08-01

    The dust-acoustic waves and the stability theory for the permeating dusty plasma with power-law distributions are studied by using nonextensive q-statistics. In two limiting physical cases, when the thermal velocity of the flowing dusty plasma is much larger than, and much smaller than the phase velocity of the waves, we derived the dust-acoustic wave frequency, the instability growth rate, and the instability critical flowing velocity. As compared with the formulae obtained in part I [Gong et al., Phys. Plasmas 19, 043704 (2012)], all formulae of the present cases and the resulting plasma characteristics are q-dependent, and the power-law distribution of each plasma component of the permeating dusty plasma has a different q-parameter and thus has a different nonextensive effect. Further, we make numerical analyses of an example that a cometary plasma tail is passing through the interplanetary space dusty plasma and we show that these power-law distributions have significant effects on the plasma characteristics of this kind of plasma environment.

  2. Power law behavior of the isotope yield distributions in the multifragmentation regime of heavy ion reactions

    NASA Astrophysics Data System (ADS)

    Huang, M.; Wada, R.; Chen, Z.; Keutgen, T.; Kowalski, S.; Hagel, K.; Barbui, M.; Bonasera, A.; Bottosso, C.; Materna, T.; Natowitz, J. B.; Qin, L.; Rodrigues, M. R. D.; Sahu, P. K.; Schmidt, K. J.; Wang, J.

    2010-11-01

    Isotope yield distributions in the multifragmentation regime were studied with high-quality isotope identification, focusing on the intermediate mass fragments (IMFs) produced in semiviolent collisions. The yields were analyzed within the framework of a modified Fisher model. Using the ratio of the mass-dependent symmetry energy coefficient relative to the temperature, asym/T, extracted in previous work and that of the pairing term, ap/T, extracted from this work, and assuming that both reflect secondary decay processes, the experimentally observed isotope yields were corrected for these effects. For a given I=N-Z value, the corrected yields of isotopes relative to the yield of C12 show a power law distribution Y(N,Z)/Y(12C)~A-? in the mass range 1?A?30, and the distributions are almost identical for the different reactions studied. The observed power law distributions change systematically when I of the isotopes changes and the extracted ? value decreases from 3.9 to 1.0 as I increases from -1 to 3. These observations are well reproduced by a simple deexcitation model, with which the power law distribution of the primary isotopes is determined to be ?prim=2.4±0.2, suggesting that the disassembling system at the time of the fragment formation is indeed at, or very near, the critical point.

  3. Electroosmotic flows of non-Newtonian power-law fluids in a cylindrical microchannel.

    PubMed

    Zhao, Cunlu; Yang, Chun

    2013-03-01

    EOF of non-Newtonian power-law fluids in a cylindrical microchannel is analyzed theoretically. Specially, exact solutions of electroosmotic velocity corresponding to two special fluid behavior indices (n = 0.5 and 1.0) are found, while approximate solutions are derived for arbitrary values of fluid behavior index. It is found that because of the approximation for the first-order modified Bessel function of the first kind, the approximate solutions introduce largest errors for predicting electroosmotic velocity when the thickness of electric double layer is comparable to channel radius, but can accurately predict the electroosmotic velocity when the thickness of electric double layer is much smaller or larger than the channel radius. Importantly, the analysis reveals that the Helmholtz-Smoluchowski velocity of power-law fluids in cylindrical microchannels becomes dependent on geometric dimensions (radius of channel), standing in stark contrast to the Helmholtz-Smoluchowski velocity over planar surfaces or in parallel-plate microchannels. Such interesting and counterintuitive effects can be attributed to the nonlinear coupling among the electrostatics, channel geometry, and non-Newtonian hydrodynamics. Furthermore, a method for enhancement of EOFs of power-law fluids is proposed under a combined DC and AC electric field. PMID:23229874

  4. Analysis of electroosmotic flow of power-law fluids in a slit microchannel.

    PubMed

    Zhao, Cunlu; Zholkovskij, Emilijk; Masliyah, Jacob H; Yang, Chun

    2008-10-15

    Electroosmotic flow of power-law fluids in a slit channel is analyzed. The governing equations including the linearized Poisson-Boltzmann equation, the Cauchy momentum equation, and the continuity equation are solved to seek analytical expressions for the shear stress, dynamic viscosity, and velocity distribution. Specifically, exact solutions of the velocity distributions are explicitly found for several special values of the flow behavior index. Furthermore, with the implementation of an approximate scheme for the hyperbolic cosine function, approximate solutions of the velocity distributions are obtained. In addition, a generalized Smoluchowski velocity is introduced by taking into account contributions due to the finite thickness of the electric double layer and the flow behavior index of power-law fluids. Calculations are performed to examine the effects of kappaH, flow behavior index, double layer thickness, and applied electric field on the shear stress, dynamic viscosity, velocity distribution, and average velocity/flow rate of the electroosmotic flow of power-law fluids. PMID:18656891

  5. Length of inflation and WMAP data in the case of power-law inflation

    E-print Network

    Shiro Hirai; Tomoyuki Takami

    2005-06-21

    The effect of the length of inflation on the power spectra of scalar and tensor perturbations is estimated using the power-law inflation model with a scale factor of a(t) = t^q. Considering various pre-inflation models with radiation-dominated or matter-dominated periods before inflation in combination with two matching conditions, the power spectrum of curvature perturbations at large scales is calculated. Comparison of the derived angular power spectrum with the Wilkinson Microwave Anisotropy Probe (WMAP) data reveals a possibility that the WMAP can be explained by the finite length of inflation model if the length of inflation is near 60 e-folds and q>200.

  6. Shock Acceleration with Focused Transport Equation: Power-Law Energy Spectrum and Injection Efficiency

    NASA Astrophysics Data System (ADS)

    Zuo, P.; Zhang, M.; Gamayunov, K.; Luo, X.; Rassoul, H. K.

    2011-12-01

    The focused transport equation (FTE) includes all the necessary physics for modeling the shock acceleration of energetic particles with a unified description of first-order Fermi acceleration, shock drift acceleration, and shock surfing acceleration. In recent years, the FTE-based theory has been proved to be an efficient tool for reproducing the observational features of the lower energy Termination Shock Particles (TSPs) by Voyagers (e. g. le Roux et al. 2007; Florinski 2009). In this study we investigate the energy spectrum of pickup ions accelerated at shocks of various obliquities with FTE by using a stochastic approach model. Here we focus our discussion on how the focused transport acceleration using FTE is transformed to diffusive shock acceleration. The shock acceleration leads to two-component energy spectra. The low-energy component of the spectrum is made of particles that interact with shock one to a few times. For a parallel shock, the high energy component of the spectrum of power law with the spectral index being the same as the prediction of DSA theory, starts just a few times injection speed. For an oblique or quasi-perpendicular shock, the high-energy component of the spectrum exhibits a double power-law distribution: a harder power-law spectrum followed by another power-law spectrum with a slope the same as the spectral index of DSA. It can be concluded that the shock acceleration will eventually go into the DSA regime at higher energies even if the particle anisotropy is not small. The intensity of the energy spectrum given by the FTE, in the high-energy range where particles get efficient acceleration in the DSA regime, is different from that given by the standard DSA theory for the same injection source. We define the injection efficiency ? as the ratio between the two theoretical intensities. One of the advantages of the focused transport theory is that it allows calculation of the injection efficiency problem, something that is not easy to solve using other popular shock acceleration theories. In addition, our simulation is able to qualitatively explain the production of multiple power-law energy spectra of TSPs observed by Voyagers.

  7. Second law analysis of advanced power generation systems using variable temperature heat sources

    SciTech Connect

    Bliem, C.J.; Mines, G.L.

    1990-01-01

    Many systems produce power using variable temperature (sensible) heat sources. The Heat Cycle Research Program is currently investigating the potential improvements to such power cycles utilizing moderate temperature geothermal resources to produce electrical power. It has been shown that mixtures of saturated hydrocarbons (alkanes) or halogenated hydrocarbons operating with a supercritical Rankine cycle gave improved performance over boiling Rankine cycles with the pure working fluids for typical applications. Recently, in addition to the supercritical Rankine Cycle, other types of cycles have been proposed for binary geothermal service. This paper explores the limits on efficiency of a feasible plant and discusses the methods used in these advanced concept plants to achieve the maximum possible efficiency. The advanced plants considered appear to be approaching the feasible limit of performance so that the designer must weigh all considerations to fine the best plant for a given service. These results would apply to power systems in other services as well as to geothermal power plants. 17 refs., 15 figs.

  8. Power-law viscous materials for analogue experiments: New data on the rheology of highly-filled silicone polymers

    NASA Astrophysics Data System (ADS)

    Boutelier, D.; Schrank, C.; Cruden, A.

    2008-03-01

    The selection of appropriate analogue materials is a central consideration in the design of realistic physical models. We investigate the rheology of highly-filled silicone polymers in order to find materials with a power-law strain-rate softening rheology suitable for modelling rock deformation by dislocation creep and report the rheological properties of the materials as functions of the filler content. The mixtures exhibit strain-rate softening behaviour but with increasing amounts of filler become strain-dependent. For the strain-independent viscous materials, flow laws are presented while for strain-dependent materials the relative importance of strain and strain rate softening/hardening is reported. If the stress or strain rate is above a threshold value some highly-filled silicone polymers may be considered linear visco-elastic (strain independent) and power-law strain-rate softening. The power-law exponent can be raised from 1 to ˜3 by using mixtures of high-viscosity silicone and plasticine. However, the need for high shear strain rates to obtain the power-law rheology imposes some restrictions on the usage of such materials for geodynamic modelling. Two simple shear experiments are presented that use Newtonian and power-law strain-rate softening materials. The results demonstrate how materials with power-law rheology result in better strain localization in analogue experiments.

  9. Edge effect on the power law distribution of granular avalanches Kinga A. Lrincz and Rinke J. Wijngaarden

    E-print Network

    Wijngaarden, Rinke J.

    Edge effect on the power law distribution of granular avalanches Kinga A. Lrincz and Rinke J-law-distributed avalanche sizes to quasiperiodic system-spanning avalanches. Conversely, by removing ledges the incidence of system- spanning avalanches is significantly reduced. This may offer a perspective on new avalanche

  10. Fertility Heterogeneity as a Mechanism for Power Law Distributions of Recurrence Times

    E-print Network

    Saichev, A

    2012-01-01

    We study the statistical properties of recurrence times in the self-excited Hawkes conditional Poisson process, the simplest extension of the Poisson process that takes into account how the past events influence the occurrence of future events. Specifically, we analyze the impact of the power law distribution of fertilities with exponent \\alpha, where the fertility of an event is the number of aftershocks of first generation that it triggers, on the probability distribution function (pdf) f(\\tau) of the recurrence times \\tau between successive events. The other input of the model is an exponential Omori law quantifying the pdf of waiting times between an event and its first generation aftershocks, whose characteristic time scale is taken as our time unit. At short time scales, we discover two intermediate power law asymptotics, f(\\tau) ~ \\tau^{-(2-\\alpha)} for \\tau << \\tau_c and f(\\tau) ~ \\tau^{-\\alpha} for \\tau_c << \\tau << 1, where \\tau_c is associated with the self-excited cascades of aft...

  11. Power-law dynamics in neuronal and behavioral data introduce spurious correlations.

    PubMed

    Schaworonkow, Natalie; Blythe, Duncan A J; Kegeles, Jewgeni; Curio, Gabriel; Nikulin, Vadim V

    2015-08-01

    Relating behavioral and neuroimaging measures is essential to understanding human brain function. Often, this is achieved by computing a correlation between behavioral measures, e.g., reaction times, and neurophysiological recordings, e.g., prestimulus EEG alpha-power, on a single-trial-basis. This approach treats individual trials as independent measurements and ignores the fact that data are acquired in a temporal order. It has already been shown that behavioral measures as well as neurophysiological recordings display power-law dynamics, which implies that trials are not in fact independent. Critically, computing the correlation coefficient between two measures exhibiting long-range temporal dependencies may introduce spurious correlations, thus leading to erroneous conclusions about the relationship between brain activity and behavioral measures. Here, we address data-analytic pitfalls which may arise when long-range temporal dependencies in neural as well as behavioral measures are ignored. We quantify the influence of temporal dependencies of neural and behavioral measures on the observed correlations through simulations. Results are further supported in analysis of real EEG data recorded in a simple reaction time task, where the aim is to predict the latency of responses on the basis of prestimulus alpha oscillations. We show that it is possible to "predict" reaction times from one subject on the basis of EEG activity recorded in another subject simply owing to the fact that both measures display power-law dynamics. The same is true when correlating EEG activity obtained from different subjects. A surrogate-data procedure is described which correctly tests for the presence of correlation while controlling for the effect of power-law dynamics. Hum Brain Mapp 36:2901-2914, 2015. © 2015 Wiley Periodicals, Inc. PMID:25930148

  12. A Qualitative Comparison of Power Law Generators Javier Martin Hernandez, Tom Kleiberg, Huijuan Wang and Piet Van Mieghem

    E-print Network

    Van Mieghem, Piet

    A Qualitative Comparison of Power Law Generators Javier Martin Hernandez, Tom Kleiberg, Huijuan & Informatics (EWI) Mekelweg 4, 2628 CD Delft The Netherlands Email: {J.M.Hernandez, T.Kleiberg, H.Wang, P

  13. Thermionic power-law decay of excited aluminum-cluster anions and its dependence on storage-device temperature

    NASA Astrophysics Data System (ADS)

    Froese, M. W.; Blaum, K.; Fellenberger, F.; Grieser, M.; Lange, M.; Laux, F.; Menk, S.; Orlov, D. A.; Repnow, R.; Sieber, T.; Toker, Y.; von Hahn, R.; Wolf, A.

    2011-02-01

    The decay of excited aluminum-cluster anions (Aln-, n=4 and 5) has been investigated in a cryogenic linear ion-beam trap. A power-law is found to accurately reproduce the time dependence of the observed decay rates at early storage times, although the exponents are significantly larger than the typically observed 1/t decay. It is shown that the power-law exponent is, at most, weakly dependent on the cluster electron affinity and heat capacity. A previous power-law exponent model for small clusters is also shown to be in disagreement with both investigated species. The attribution of a drop in the decay rate at later times to radiative cooling as observed in larger molecules also does not appear justified in our case. A strong dependence of the power-law exponent on the ambient temperature was observed.

  14. Crossover from exponential to power-law scaling for human mobility pattern in urban, suburban and rural areas

    NASA Astrophysics Data System (ADS)

    Liu, Hsing; Chen, Ying-Hsing; Lih, Jiann-Shing

    2015-05-01

    Empirical analysis on human mobility has caught extensive attentions due to the accumulated human dynamical data and the advance of data mining technique. But the results of related research still have to further investigate on some issues such as spatial scale. In this paper, we explore human mobility in greater Kaohsiung area by using long-term taxicabs' GPS data. The trip distance in our dataset exhibits exponential decay for short trips and power-law scaling for long trips. We propose an approach to investigate the possible mechanism of the power-law tail. Moreover, we utilize the method of simulation and random relinking trip path to explain the empirical observation. Our results show that the origin of power-law movement distribution may be largely due to the power-law population distribution.

  15. Power Laws from Linear Neuronal Cable Theory: Power Spectral Densities of the Soma Potential, Soma Membrane Current and Single-Neuron Contribution to the EEG

    PubMed Central

    Pettersen, Klas H.; Lindén, Henrik; Tetzlaff, Tom; Einevoll, Gaute T.

    2014-01-01

    Power laws, that is, power spectral densities (PSDs) exhibiting behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency power laws with power-law exponents analytically identified as for the soma membrane current, for the current-dipole moment, and for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink () noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how power laws with a wide range of values for the power-law exponent ? may arise from a simple, linear partial differential equation. PMID:25393030

  16. Exploring parameter constraints on quintessential dark energy: The inverse power law model

    SciTech Connect

    Yashar, Mark; Bozek, Brandon; Abrahamse, Augusta; Albrecht, Andreas; Barnard, Michael [Department of Physics, University of California at Davis, One Shields Avenue, Davis, California 95616 (United States)

    2009-05-15

    We report on the results of a Markov chain Monte Carlo analysis of an inverse power law (IPL) quintessence model using the Dark Energy Task Force (DETF) simulated data sets as a representation of future dark energy experiments. We generate simulated data sets for a {lambda}CDM background cosmology as well as a case where the dark energy is provided by a specific IPL fiducial model, and present our results in the form of likelihood contours generated by these two background cosmologies. We find that the relative constraining power of the various DETF data sets on the IPL model parameters is broadly equivalent to the DETF results for the w{sub 0}-w{sub a} parametrization of dark energy. Finally, we gauge the power of DETF 'stage 4' data by demonstrating a specific IPL model which, if realized in the universe, would allow stage 4 data to exclude a cosmological constant at better than the 3{sigma} level.

  17. Effect of the length of inflation on angular TT and TE power spectra in power-law inflation

    E-print Network

    Shiro Hirai; Tomoyuki Takami

    2005-12-13

    The effect of the length of inflation on the power spectra of scalar and tensor perturbations is estimated using the power-law inflation model with a scale factor of a(t) = t^q. Considering various pre-inflation models with radiation-dominated or scalar matter-dominated periods before inflation in combination with two matching conditions, the temperature angular power spectrum (TT) and temperature-polarization cross-power spectrum (TE) are calculated and a likelihood analysis is performed. It is shown that the discrepancies between the Wilkinson Microwave Anisotropy Probe (WMAP) data and the LCDM model, such as suppression of the spectrum at l = 2,3 and oscillatory behavior, may be explained by the finite length of inflation model if the length of inflation is near 60 e-folds and q > 300. The proposed models retain similar values of chi^2 to that achieved by the LCDM model with respect to fit to the WMAP data, but display different characteristics of the angular TE power spectra at l < 20.

  18. Design of a condenser-boiler for a binary mercury-organic Rankine cycle solar dynamic space power system

    Microsoft Academic Search

    Randy M. Cotton

    1987-01-01

    A theoretical design was performed for the condenser\\/boiler of a space-based solar dynamic power system. The base system is a binary Rankine cycle with mercury and toluene as the working fluids. System output is 75 KWe with a combined efficiency of 41.1%. Design goals were to develop the most reliable, mass efficient unit possible for delivery to a space station.

  19. Exploiting the power law distribution properties of satellite fire radiative power retrievals: A method to estimate fire radiative energy and biomass burned from sparse satellite observations

    Microsoft Academic Search

    S. S. Kumar; D. P. Roy; L. Boschetti; R. Kremens

    2011-01-01

    Biomass burned retrieved conventionally from FRP significantly sensitive to samplingNew method based on observed FRP power law properties solves this sensitivityNew method demonstrated with ground and satellite fire observations

  20. Maximum likelihood estimators for truncated and censored power-law distributions show how neuronal avalanches may be misevaluated.

    PubMed

    Langlois, Dominic; Cousineau, Denis; Thivierge, J P

    2014-01-01

    The coordination of activity amongst populations of neurons in the brain is critical to cognition and behavior. One form of coordinated activity that has been widely studied in recent years is the so-called neuronal avalanche, whereby ongoing bursts of activity follow a power-law distribution. Avalanches that follow a power law are not unique to neuroscience, but arise in a broad range of natural systems, including earthquakes, magnetic fields, biological extinctions, fluid dynamics, and superconductors. Here, we show that common techniques that estimate this distribution fail to take into account important characteristics of the data and may lead to a sizable misestimation of the slope of power laws. We develop an alternative series of maximum likelihood estimators for discrete, continuous, bounded, and censored data. Using numerical simulations, we show that these estimators lead to accurate evaluations of power-law distributions, improving on common approaches. Next, we apply these estimators to recordings of in vitro rat neocortical activity. We show that different estimators lead to marked discrepancies in the evaluation of power-law distributions. These results call into question a broad range of findings that may misestimate the slope of power laws by failing to take into account key aspects of the observed data. PMID:24580259

  1. Effects of diversity and procrastination in priority queuing theory: the different power law regimes.

    PubMed

    Saichev, A; Sornette, D

    2010-01-01

    Empirical analyses show that after the update of a browser, or the publication of the vulnerability of a software, or the discovery of a cyber worm, the fraction of computers still using the older browser or software version, or not yet patched, or exhibiting worm activity decays as a power law approximately 1/t(alpha) with 0power law tail approximately 1/t(1/2), resulting from a first-passage solution of an equivalent Wiener process. Taking into account a diversity of time deficit parameters in a population of individuals, the power law tail is changed into 1/t(alpha), with alpha is an element of (0.5,infinity), including the well-known case 1/t. We also study the effect of "procrastination," defined as the situation in which the target task may be postponed or delayed even after the individual has solved all other pending tasks. This regime provides an explanation for even slower apparent decay and longer persistence. PMID:20365433

  2. Power laws in microrheology experiments on living cells: Comparative analysis and modeling.

    PubMed

    Balland, Martial; Desprat, Nicolas; Icard, Delphine; Féréol, Sophie; Asnacios, Atef; Browaeys, Julien; Hénon, Sylvie; Gallet, François

    2006-08-01

    We compare and synthesize the results of two microrheological experiments on the cytoskeleton of single cells. In the first one, the creep function J(t) of a cell stretched between two glass plates is measured after applying a constant force step. In the second one, a microbead specifically bound to transmembrane receptors is driven by an oscillating optical trap, and the viscoelastic coefficient Ge(omega) is retrieved. Both J(t) and Ge(omega) exhibit power law behaviors: J(t) = A0(t/t0)alpha and absolute value (Ge(omega)) = G0(omega/omega0)alpha, with the same exponent alpha approximately 0.2. This power law behavior is very robust; alpha is distributed over a narrow range, and shows almost no dependence on the cell type, on the nature of the protein complex which transmits the mechanical stress, nor on the typical length scale of the experiment. On the contrary, the prefactors A0 and G0 appear very sensitive to these parameters. Whereas the exponents alpha are normally distributed over the cell population, the prefactors A0 and G0 follow a log-normal repartition. These results are compared with other data published in the literature. We propose a global interpretation, based on a semiphenomenological model, which involves a broad distribution of relaxation times in the system. The model predicts the power law behavior and the statistical repartition of the mechanical parameters, as experimentally observed for the cells. Moreover, it leads to an estimate of the largest response time in the cytoskeletal network: tau(m) approximately 1000 s. PMID:17025476

  3. Maxwell's Demon at work: Two types of Bose condensate fluctuations in power-law traps.

    PubMed

    Grossmann, S; Holthaus, M

    1997-11-10

    After discussing the idea underlying the Maxwell's Demon ensemble, we employ this ensemble for calculating fluctuations of ideal Bose gas condensates in traps with power-law single-particle energy spectra. Two essentially different cases have to be distinguished. If the heat capacity is continuous at the condensation point, the fluctuations of the number of condensate particles vanish linearly with temperature, independent of the trap characteristics. In this case, microcanonical and canonical fluctuations are practically indistinguishable. If the heat capacity is discontinuous, the fluctuations vanish algebraically with temperature, with an exponent determined by the trap, and the micro-canonical fluctuations are lower than their canonical counterparts. PMID:19373412

  4. Anisotropic Power-law Inflation:A counter example to the cosmic no-hair conjecture

    NASA Astrophysics Data System (ADS)

    Soda, Jiro

    2015-04-01

    It is widely believed that anisotropy in the expansion of the universe will decay exponentially fast during inflation. This is often referred to as the cosmic no-hair conjecture. However, we find a counter example to the cosmic no-hair conjecture in the context of supergravity. As a demonstration, we present an exact anisotropic power-law inflationary solution which is an attractor in the phase space. We emphasize that anisotropic inflation is quite generic in the presence of anisotropic sources which couple with an inflaton.

  5. On global minimizers of repulsive–attractive power-law interaction energies

    PubMed Central

    Carrillo, José Antonio; Chipot, Michel; Huang, Yanghong

    2014-01-01

    We consider the minimization of the repulsive–attractive power-law interaction energies that occur in many biological and physical situations. We show the existence of global minimizers in the discrete setting and obtain bounds for their supports independently of the number of Dirac deltas in a certain range of exponents. These global discrete minimizers correspond to the stable spatial profiles of flock patterns in swarming models. Global minimizers of the continuum problem are obtained by compactness. We also illustrate our results through numerical simulations. PMID:25288810

  6. Anisotropic Power-law Inflation: A counter example to the cosmic no-hair conjecture

    E-print Network

    Jiro Soda

    2014-10-31

    It is widely believed that anisotropy in the expansion of the universe will decay exponentially fast during inflation. This is often referred to as the cosmic no-hair conjecture. However, we find a counter example to the cosmic no-hair conjecture in the context of supergravity. As a demonstration, we present an exact anisotropic power-law inflationary solution which is an attractor in the phase space. We emphasize that anisotropic inflation is quite generic in the presence of anisotropic sources which couple with an inflaton.

  7. Laboratory constraints on chameleon dark energy and power-law fields

    SciTech Connect

    Steffen, Jason H.; /Fermilab; Upadhye, Amol; /KICP, Chicago; Baumbaugh, Al; Chou, Aaron S.; Mazur, Peter O.; Tomlin, Ray; /Fermilab; Weltman, Amanda; /Cape Town U.; Wester, William; /Fermilab

    2010-10-01

    We report results from the GammeV Chameleon Afterglow Search - a search for chameleon particles created via photon/chameleon oscillations within a magnetic field. This experiment is sensitive to a wide class of chameleon power-law models and dark energy models not previously explored. These results exclude five orders of magnitude in the coupling of chameleons to photons covering a range of four orders of magnitude in chameleon effective mass and, for individual chameleon models, exclude between 4 and 12 orders of magnitude in chameleon couplings to matter.

  8. Precision of quantization of the hall conductivity in a finite-size sample: Power law

    SciTech Connect

    Greshnov, A. A.; Kolesnikova, E. N.; Zegrya, G. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)], E-mail: zegrya@mail.ioffe.ru

    2006-01-15

    A microscopic calculation of the conductivity in the integer quantum Hall effect (IQHE) mode is carried out. The precision of quantization is analyzed for finite-size samples. The precision of quantization shows a power-law dependence on the sample size. A new scaling parameter describing this dependence is introduced. It is also demonstrated that the precision of quantization linearly depends on the ratio between the amplitude of the disorder potential and the cyclotron energy. The data obtained are compared with the results of magnetotransport measurements in mesoscopic samples.

  9. Quantifying the geometric sensitivity of attractor basins: Power law dependence on parameter variations and noise

    NASA Astrophysics Data System (ADS)

    Siapas, Athanassios G.

    1994-10-01

    We show that for many physical systems the dependence of attractor basin geometry on parameter variations and noise can be characterized by power laws. We introduce new invariants-the basin immunities-that quantify this dependence and we analyze their origin and properties. Results from extensive numerical experiments are presented; examples include the driven pendulum and the Hénon map. Potential applications of basin immunities include quantifying the effect of parameter uncertainties and noise on the behavior of nonlinear devices, as well as improving parameter estimation algorithms.

  10. Onset of power-law scaling behavior in idiotypic random and scale-free networks

    NASA Astrophysics Data System (ADS)

    Claudino, Elder S.; Lyra, M. L.; Gleria, Iram; Campos, Paulo R. A.; Bertrand, Delvis

    2012-10-01

    We numerically study the dynamics of model immune networks with random and scale-free topologies. We observe that a memory state is reached when the antigen is attached to the most connected sites of the network, whereas a percolation state may occur when the antigen attaches to the less connected sites. For increasing values of the connectivity of the antibody directly binded to the antigen, its population converges exponentially to the asymptotic value of the memory state. On the other hand, the next-nearest populations evolve slowly as power-laws towards the virgin-like state.

  11. Laboratory constraints on chameleon dark energy and power-law fields

    E-print Network

    Jason H. Steffen; Amol Upadhye; Al Baumbaugh; Aaron S. Chou; Peter O. Mazur; Ray Tomlin; Amanda Weltman; William Wester

    2010-10-05

    We report results from the GammeV Chameleon Afterglow Search---a search for chameleon particles created via photon/chameleon oscillations within a magnetic field. This experiment is sensitive to a wide class of chameleon power-law models and dark energy models not previously explored. These results exclude five orders of magnitude in the coupling of chameleons to photons covering a range of four orders of magnitude in chameleon effective mass and, for individual chameleon models, exclude between 4 and 12 orders of magnitude in chameleon couplings to matter.

  12. Crossover of two power laws in the anomalous diffusion of a two lipid membrane.

    PubMed

    Bakalis, Evangelos; Höfinger, Siegfried; Venturini, Alessandro; Zerbetto, Francesco

    2015-06-01

    Molecular dynamics simulations of a bi-layer membrane made by the same number of 1-palmitoyl-2-oleoyl-glycero-3-phospho-ethanolamine and palmitoyl-oleoyl phosphatidylserine lipids reveal sub-diffusional motion, which presents a crossover between two different power laws. Fractional Brownian motion is the stochastic mechanism that governs the motion in both regimes. The location of the crossover point is justified with simple geometrical arguments and is due to the activation of the mechanism of circumrotation of lipids about each other. PMID:26049526

  13. Analysis of power-law exponents by maximum-likelihood maps.

    PubMed

    Baró, Jordi; Vives, Eduard

    2012-06-01

    Maximum-likelihood exponent maps have been studied as a technique to increase the understanding and improve the fit of power-law exponents to experimental and numerical simulation data, especially when they exhibit both upper and lower cutoffs. The use of the technique is tested by analyzing seismological data, acoustic emission data, and avalanches in numerical simulations of the three-dimensional random field Ising model. In the different examples we discuss the nature of the deviations observed in the exponent maps and some relevant conclusions are drawn for the physics behind each phenomenon. PMID:23005176

  14. Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information

    NASA Technical Reports Server (NTRS)

    Howell, L. W.

    2002-01-01

    A simple power law model consisting of a single spectral index, a is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at the knee energy, E(sub k), to a steeper spectral index alpha(sub 2) greater than alpha(sub 1) above E(sub k). The Maximum likelihood (ML) procedure was developed for estimating the single parameter alpha(sub 1) of a simple power law energy spectrum and generalized to estimate the three spectral parameters of the broken power law energy spectrum from simulated detector responses and real cosmic-ray data. The statistical properties of the ML estimator were investigated and shown to have the three desirable properties: (P1) consistency (asymptotically unbiased). (P2) efficiency asymptotically attains the Cramer-Rao minimum variance bound), and (P3) asymptotically normally distributed, under a wide range of potential detector response functions. Attainment of these properties necessarily implies that the ML estimation procedure provides the best unbiased estimator possible. While simulation studies can easily determine if a given estimation procedure provides an unbiased estimate of the spectra information, and whether or not the estimator is approximately normally distributed, attainment of the Cramer-Rao bound (CRB) can only he ascertained by calculating the CRB for an assumed energy spectrum-detector response function combination, which can be quite formidable in practice. However. the effort in calculating the CRB is very worthwhile because it provides the necessary means to compare the efficiency of competing estimation techniques and, furthermore, provides a stopping rule in the search for the best unbiased estimator. Consequently, the CRB for both the simple and broken power law energy spectra are derived herein and the conditions under which they are attained in practice are investigated. The ML technique is then extended to estimate spectra information from an arbitrary number of astrophysics data sets produced by vastly different science instruments. This theory and its successful implementation will facilitate the interpretation of spectral information from multiple astrophysics missions and thereby permit the derivation of superior spectral parameter estimates based on the combination of data sets.

  15. Unification of Small and Large Time Scales for Biological Evolution: Deviations from Power Law

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debashish; Stauffer, Dietrich; Kunwar, Ambarish

    2003-02-01

    We develop a unified model that describes both “micro” and “macro” evolutions within a single theoretical framework. The ecosystem is described as a dynamic network; the population dynamics at each node of this network describes the “microevolution” over ecological time scales (i.e., birth, ageing, and natural death of individual organisms), while the appearance of new nodes, the slow changes of the links, and the disappearance of existing nodes accounts for the “macroevolution” over geological time scales (i.e., the origination, evolution, and extinction of species). In contrast to several earlier claims in the literature, we observe strong deviations from power law in the regime of long lifetimes.

  16. Power-law-distributed dark states are the main pathway for photobleaching of single organic molecules.

    PubMed

    Hoogenboom, Jacob P; van Dijk, Erik M H P; Hernando, Jordi; van Hulst, Niek F; García-Parajó, María F

    2005-08-26

    We exploit the strong excitonic coupling in a superradiant trimer molecule to distinguish between long-lived collective dark states and photobleaching events. The population and depopulation kinetics of the dark states in a single molecule follow power-law statistics over 5 orders of magnitude in time. This result is consistent with the formation of a radical unit via electron tunneling to a time-varying distribution of trapping sites in the surrounding polymer matrix. We furthermore demonstrate that this radicalization process forms the dominant pathway for molecular photobleaching. PMID:16197247

  17. Power-law behavior in the power spectrum induced by Brownian motion of a domain wall

    NASA Astrophysics Data System (ADS)

    Takesue, Shinji; Mitsudo, Tetsuya; Hayakawa, Hisao

    2003-07-01

    We show that Brownian motion of a one-dimensional domain wall in a large but finite system yields a ?-3/2 power spectrum. This is successfully applied to the totally asymmetric simple exclusion process with open boundaries. An excellent agreement between our theory and numerical results is obtained in a frequency range where the domain wall motion dominates and the discreteness of the system is not effective.

  18. The Common Law Power of the Legislature: Insurer Conversions and Charitable Funds

    PubMed Central

    Horwitz, Jill R; Fremont-Smith, Marion R

    2005-01-01

    New York's Empire Blue Cross and Blue Shield conversion from nonprofit to for-profit form has considerable legal significance. Three aspects of the conversion make the case unique: the role of the state legislature in directing the disposition of the conversion assets, the fact that it made itself the primary beneficiary of those assets, and the actions of the state attorney general defending the state rather than the public interest in the charitable assets. Drawing on several centuries of common law rejecting the legislative power to direct the disposition of charitable funds, this article argues that the legislature lacked power to control the conversion and direct the disposition of its proceeds and that its actions not only undermined the nonprofit form but also raised constitutional concerns. PMID:15960770

  19. Statistical properties of the energy in time-dependent homogeneous power law potentials

    NASA Astrophysics Data System (ADS)

    Andresas, Dimitris; Robnik, Marko

    2014-09-01

    We study classical 1D Hamilton systems with a homogeneous power law potential and their statistical behavior, assuming a microcanonical distribution of the initial conditions and describing its change under a monotonically increasing time-dependent function a(t) (the prefactor of the potential). Using the nonlinear Wentzel-Kramers-Brillouin-like method of Papamikos and Robnik 2012 J. Phys. A: Math. Theor. 44 315102 and following a previous work by Papamikos and Robnik 2011 J. Phys. A: Math. Theor. 45 015206, we specifically analyze the mean energy, the variance and the adiabatic invariant (action) of the systems for large time t\\to \\infty and we show that the mean energy and variance increase as powers of a(t), while the action oscillates and finally remains constant. By means of a number of detailed case studies, we show that the theoretical prediction is excellent, which demonstrates the usefulness of the method in such applications.

  20. Underestimating extreme events in power-law behavior due to machine-dependent cutoffs

    NASA Astrophysics Data System (ADS)

    Radicchi, Filippo

    2014-11-01

    Power-law distributions are typical macroscopic features occurring in almost all complex systems observable in nature. As a result, researchers in quantitative analyses must often generate random synthetic variates obeying power-law distributions. The task is usually performed through standard methods that map uniform random variates into the desired probability space. Whereas all these algorithms are theoretically solid, in this paper we show that they are subject to severe machine-dependent limitations. As a result, two dramatic consequences arise: (i) the sampling in the tail of the distribution is not random but deterministic; (ii) the moments of the sample distribution, which are theoretically expected to diverge as functions of the sample sizes, converge instead to finite values. We provide quantitative indications for the range of distribution parameters that can be safely handled by standard libraries used in computational analyses. Whereas our findings indicate possible reinterpretations of numerical results obtained through flawed sampling methodologies, they also pave the way for the search for a concrete solution to this central issue shared by all quantitative sciences dealing with complexity.

  1. Theoretical and semiempirical correction to the long-range dispersion power law of stretched graphite

    NASA Astrophysics Data System (ADS)

    Gould, Tim; Simpkins, Ken; Dobson, John F.

    2008-04-01

    In recent years, intercalated and pillared graphitic systems have come under increasing scrutiny because of their potential for modern energy technologies. While traditional ab initio methods such as the local density approximation give accurate geometries for graphite, they are poorer at predicting physical properties such as cohesive energies and elastic constants perpendicular to the layers because of the strong dependence on long-range dispersion forces. “Stretching” the layers via pillars or intercalation further highlights these weaknesses. We use the ideas developed by Dobson [Phys. Rev. Lett. 96, 073201 (2006)] as a starting point to show that the asymptotic C3D-3 dependence of the cohesive energy on layer spacing D in bigraphene is universal to all graphitic systems with evenly spaced layers. At spacings appropriate to intercalates, this differs from and begins to dominate the C4D-4 power law for dispersion that has been widely used previously. The corrected power law (and a calculated C3 coefficient) is then applied to the semiempirical approach of Hasegawa and Nishidate (HN) [Phys. Rev. B 70, 205431 (2004)]; however, a meaningful result cannot be obtained in this approach. A modified, physically motivated semiempirical method adding some C4D-4 effects allows the HN method to be employed and gives an absolute increase of about 2%-3% to the predicted cohesive energy, while still maintaining the correct C3D-3 asymptotics.

  2. Power-law scaling for macroscopic entropy and microscopic complexity: Evidence from human movement and posture

    NASA Astrophysics Data System (ADS)

    Hong, S. Lee; Bodfish, James W.; Newell, Karl M.

    2006-03-01

    We investigated the relationship between macroscopic entropy and microscopic complexity of the dynamics of body rocking and sitting still across adults with stereotyped movement disorder and mental retardation (profound and severe) against controls matched for age, height, and weight. This analysis was performed through the examination of center of pressure (COP) motion on the mediolateral (side-to-side) and anteroposterior (fore-aft) dimensions and the entropy of the relative phase between the two dimensions of motion. Intentional body rocking and stereotypical body rocking possessed similar slopes for their respective frequency spectra, but differences were revealed during maintenance of sitting postures. The dynamics of sitting in the control group produced lower spectral slopes and higher complexity (approximate entropy). In the controls, the higher complexity found on each dimension of motion was related to a weaker coupling between dimensions. Information entropy of the relative phase between the two dimensions of COP motion and irregularity (complexity) of their respective motions fitted a power-law function, revealing a relationship between macroscopic entropy and microscopic complexity across both groups and behaviors. This power-law relation affords the postulation that the organization of movement and posture dynamics occurs as a fractal process.

  3. Transition from Exponential to Power Law Distributions in a Chaotic Market

    E-print Network

    Carmen Pellicer-Lostao; Ricardo Lopez-Ruiz

    2010-11-23

    Economy is demanding new models, able to understand and predict the evolution of markets. To this respect, Econophysics offers models of markets as complex systems, that try to comprehend macro-, system-wide states of the economy from the interaction of many agents at micro-level. One of these models is the gas-like model for trading markets. This tries to predict money distributions in closed economies and quite simply, obtains the ones observed in real economies. However, it reveals technical hitches to explain the power law distribution, observed in individuals with high incomes. In this work, non linear dynamics is introduced in the gas-like model in way that an effort to overcome these flaws. A particular chaotic dynamics is used to break the pairing symmetry of agents $(i,j)\\Leftrightarrow(j,i)$. The results demonstrate that a "chaotic gas-like model" can reproduce the Exponential and Power law distributions observed in real economies. Moreover, it controls the transition between them. This may give some insight of the micro-level causes that originate unfair distributions of money in a global society. Ultimately, the chaotic model makes obvious the inherent instability of asymmetric scenarios, where sinks of wealth appear and doom the market to extreme inequality.

  4. The MLP distribution: a modified lognormal power-law model for the stellar initial mass function

    NASA Astrophysics Data System (ADS)

    Basu, Shantanu; Gil, M.; Auddy, Sayantan

    2015-05-01

    This work explores the mathematical properties of a distribution introduced by Basu & Jones (2004), and applies it to model the stellar initial mass function (IMF). The distribution arises simply from an initial lognormal distribution, requiring that each object in it subsequently undergoes exponential growth but with an exponential distribution of growth lifetimes. This leads to a modified lognormal with a power-law (MLP) distribution, which can in fact be applied to a wide range of fields where distributions are observed to have a lognormal-like body and a power-law tail. We derive important properties of the MLP distribution, like the cumulative distribution, the mean, variance, arbitrary raw moments, and a random number generator. These analytic properties of the distribution can be used to facilitate application to modelling the IMF. We demonstrate how the MLP function provides an excellent fit to the IMF compiled by Chabrier and how this fit can be used to quickly identify quantities like the mean, median, and mode, as well as number and mass fractions in different mass intervals.

  5. Power-law scaling for macroscopic entropy and microscopic complexity: evidence from human movement and posture.

    PubMed

    Hong, S Lee; Bodfish, James W; Newell, Karl M

    2006-03-01

    We investigated the relationship between macroscopic entropy and microscopic complexity of the dynamics of body rocking and sitting still across adults with stereotyped movement disorder and mental retardation (profound and severe) against controls matched for age, height, and weight. This analysis was performed through the examination of center of pressure (COP) motion on the mediolateral (side-to-side) and anteroposterior (fore-aft) dimensions and the entropy of the relative phase between the two dimensions of motion. Intentional body rocking and stereotypical body rocking possessed similar slopes for their respective frequency spectra, but differences were revealed during maintenance of sitting postures. The dynamics of sitting in the control group produced lower spectral slopes and higher complexity (approximate entropy). In the controls, the higher complexity found on each dimension of motion was related to a weaker coupling between dimensions. Information entropy of the relative phase between the two dimensions of COP motion and irregularity (complexity) of their respective motions fitted a power-law function, revealing a relationship between macroscopic entropy and microscopic complexity across both groups and behaviors. This power-law relation affords the postulation that the organization of movement and posture dynamics occurs as a fractal process. PMID:16599766

  6. The Power-law Spectra of Energetic Particles during Multi-island Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Drake, J. F.; Swisdak, M.; Fermo, R.

    2013-01-01

    Power-law distributions are a near-universal feature of energetic particle spectra in the heliosphere. Anomalous cosmic rays (ACRs), super-Alfvénic ions in the solar wind, and the hardest energetic electron spectra in flares all have energy fluxes with power laws that depend on energy E approximately as E -1.5. We present a new model of particle acceleration in systems with a bath of merging magnetic islands that self-consistently describes the development of velocity-space anisotropy parallel and perpendicular to the local magnetic field and includes the self-consistent feedback of pressure anisotropy on the merging dynamics. By including pitch-angle scattering we obtain an equation for the omnidirectional particle distribution f (v, t) that is solved in closed form to reveal v -5 (corresponding to an energy flux varying as E -1.5) as a near-universal solution as long as the characteristic acceleration time is short compared with the characteristic loss time. In such a state, the total energy in the energetic particles reaches parity with the remaining magnetic free energy. More generally, the resulting transport equation can serve as the basis for calculating the distribution of energetic particles resulting from reconnection in large-scale inhomogeneous systems.

  7. New multi-parametric analytical approximations of exponential distribution with power law tails for new cars sells and other applications

    NASA Astrophysics Data System (ADS)

    Garanina, O. S.; Romanovsky, M. Yu.

    2015-06-01

    A multi-parametric family of exponential distributions with various power law tails is introduced and is shown to describe adequately the known distributions of incomes and wealth as well as the recently measured distributions of new car sales. The three or four-parametric families are characterized by effective temperature in the exponential part, the power exponent in the power-law asymptotic part, the coefficient for the transition between the above two parts, and the starting value, if it is not equal to zero. Since the new car sales distributions are found to correspond to known distributions of incomes, the latter may be inferred from the former.

  8. Scaling-law for the energy dependence of anatomic power spectrum in dedicated breast CT

    SciTech Connect

    Vedantham, Srinivasan; Shi, Linxi; Glick, Stephen J.; Karellas, Andrew [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States)

    2013-01-15

    Purpose: To determine the x-ray photon energy dependence of the anatomic power spectrum of the breast when imaged with dedicated breast computed tomography (CT). Methods: A theoretical framework for scaling the empirically determined anatomic power spectrum at one x-ray photon energy to that at any given x-ray photon energy when imaged with dedicated breast CT was developed. Theory predicted that when the anatomic power spectrum is fitted with a power curve of the form k f{sup -{beta}}, where k and {beta} are fit coefficients and f is spatial frequency, the exponent {beta} would be independent of x-ray photon energy (E), and the amplitude k scales with the square of the difference in energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues. Twenty mastectomy specimens based numerical phantoms that were previously imaged with a benchtop flat-panel cone-beam CT system were converted to 3D distribution of glandular weight fraction (f{sub g}) and were used to verify the theoretical findings. The 3D power spectrum was computed in terms of f{sub g} and after converting to linear attenuation coefficients at monoenergetic x-ray photon energies of 20-80 keV in 5 keV intervals. The 1D power spectra along the axes were extracted and fitted with a power curve of the form k f{sup -{beta}}. The energy dependence of k and {beta} were analyzed. Results: For the 20 mastectomy specimen based numerical phantoms used in the study, the exponent {beta} was found to be in the range of 2.34-2.42, depending on the axis of measurement. Numerical simulations agreed with the theoretical predictions that for a power-law anatomic spectrum of the form k f{sup -{beta}}, {beta} was independent of E and k(E) =k{sub 1}[{mu}{sub g}(E) -{mu}{sub a}(E)]{sup 2}, where k{sub 1} is a constant, and {mu}{sub g}(E) and {mu}{sub a}(E) represent the energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues, respectively. Conclusions: Numerical simulations confirmed the theoretical predictions that in dedicated breast CT, the spatial frequency dependence of the anatomic power spectrum will be independent of x-ray photon energy, and the amplitude of the anatomic power spectrum scales by the square of difference in linear attenuation coefficients of fibroglandular and adipose tissues.

  9. 29 CFR 102.35 - Duties and powers of administrative law judges; stipulations of cases to administrative law...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Regulations Relating to Labor NATIONAL LABOR RELATIONS BOARD RULES AND REGULATIONS, SERIES...of oral argument, in conformity with Public Law 89-554, 5 U.S.C. 557; ...positions concerning any issue in the case or theory in support thereof; (13) To...

  10. Self-similar non-equilibrium dynamics of a many-body system with power-law interactions

    E-print Network

    Gutiérrez, Ricardo; Lesanovsky, Igor

    2015-01-01

    The influence of power-law interactions on the dynamics of many-body systems far from equilibrium is much less explored than their effect on static and thermodynamic properties. To gain insight into this problem we introduce and analyze here an out-of-equilibrium deposition process in which the deposition rate of a given particle depends as a power-law on the distance to previously deposited particles. Although rather simplistic this model draws its relevance from recent experimental progress in the domain of cold atomic gases which are studied in a setting where atoms that are excited to high-lying Rydberg states interact through power-law potentials that translate into power-law excitation rates. The out-of-equilibrium dynamics of this system turns out to be surprisingly rich. It features a self-similar evolution which leads to a characteristic power-law time dependence of observables such as the particle concentration and results in a scale invariance of the structure factor. Moreover, it displays a crosso...

  11. Wavelet-based analysis and power law classification of C/NOFS high-resolution electron density data

    NASA Astrophysics Data System (ADS)

    Rino, C. L.; Carrano, C. S.; Roddy, Patrick

    2014-08-01

    This paper applies new wavelet-based analysis procedures to low Earth-orbiting satellite measurements of equatorial ionospheric structure. The analysis was applied to high-resolution data from 285 Communications/Navigation Outage Forecasting System (C/NOFS) satellite orbits sampling the postsunset period at geomagnetic equatorial latitudes. The data were acquired during a period of progressively intensifying equatorial structure. The sampled altitude range varied from 400 to 800 km. The varying scan velocity remained within 20° of the cross-field direction. Time-to-space interpolation generated uniform samples at approximately 8 m. A maximum segmentation length that supports stochastic structure characterization was identified. A two-component inverse power law model was fit to scale spectra derived from each segment together with a goodness-of-fit measure. Inverse power law parameters derived from the scale spectra were used to classify the scale spectra by type. The largest category was characterized by a single inverse power law with a mean spectral index somewhat larger than 2. No systematic departure from the inverse power law was observed to scales greater than 100 km. A small subset of the most highly disturbed passes at the lowest sampled altitudes could be categorized by two-component power law spectra with a range of break scales from less than 100 m to several kilometers. The results are discussed within the context of other analyses of in situ data and spectral characteristics used for scintillation analyses.

  12. Selection of patients for lung volume reduction surgery using a power law analysis of the computed tomographic scan

    PubMed Central

    Coxson, H; Whittall, K; Nakano, Y; Rogers, R; Sciurba, F; Keenan, R; Hogg, J

    2003-01-01

    Background: A study was undertaken to test the hypothesis that patients respond better to lung volume reduction surgery (LVRS) if their emphysema is confluent and predominantly located in the upper lobes. Methods: A density mask analysis was used to identify voxels inflated beyond 10.2 ml gas/g tissue (-910 HU) on preoperative and postoperative CT scans from patients receiving LVRS. These hyperinflated regions were considered to represent emphysematous lesions. A power law analysis was used to determine the relationship between the number (K) and size (A) of the emphysematous lesions in the whole lung and two anatomical regions using the power law equation Y=KA-D. Results: The analysis showed a positive correlation between the change in the power law exponent (D) and the change in exercise (Watts) after surgery (r=0.47, p=0.03). There was also a negative correlation between the power law exponent D in the upper region of the lung preoperatively and the change in exercise following surgery (r=-0.60, p<0.05). Conclusions: These results confirm that patients with large upper lobe lesions respond better to LVRS than patients with small uniformly distributed disease. Power law analysis of lung CT scans provides a quantitative method for determining the extent and location of emphysema within the lungs of patients with COPD. PMID:12775863

  13. Power-law behavior of beat-rate variability in monolayer cultures of neonatal rat ventricular myocytes.

    PubMed

    Kucera, J P; Heuschkel, M O; Renaud, P; Rohr, S

    2000-06-01

    It is known that extracardiac factors (nervous, humoral, and hemodynamic) participate in the power-law behavior of heart-rate variability. To assess whether intrinsic properties of cardiac tissue might also be involved, beat-rate variability was studied in spontaneously beating cell cultures devoid of extracardiac influences. Extracellular electrograms were recorded from monolayer cultures of neonatal rat ventricular myocytes under stable incubating conditions for up to 9 hours. The beat-rate time series of these recordings were examined in terms of their Fourier spectra and their Hurst scaling exponents. A non-0 Hurst exponent was found in 21 of 22 preparations (0.29+/-0.09; range, 0.11 to 0.45), indicating the presence of fractal self-similarity in the beat-rate time series. The same preparations exhibited power-law behavior of the power spectra with a power-law exponent of -1.36+/-0.24 (range, -1.04 to -1.96) in the frequency range of 0.001 to 1 Hz. Furthermore, it was found that the power-law exponent was nonstationary over time. These results indicate that the power-law behavior of heart-rate variability is determined not only by extracardiac influences but also by components intrinsic to cardiac tissue. Furthermore, the presence of power-law behavior in monolayer cultures of cardiomyocytes suggests that beat-rate variability might be determined by the complex nonlinear dynamics of processes occurring at the level of the cellular network, eg, interactions among a large number of cell oscillators or metabolic regulatory systems. PMID:10850965

  14. From Migmatites to Plutons: Power Law Relationships in the Evolution of Magmatic Bodies

    NASA Astrophysics Data System (ADS)

    Soesoo, Alvar; Bons, Paul D.

    2015-07-01

    Magma is generated by partial melting from micrometre-scale droplets at the source and may accumulate to form >100 km-scale plutons. Magma accumulation thus spans well over ten orders of magnitude in scale. Here we provide measurements of migmatitic leucosomes and granitic veins in drill cores from the Estonian Proterozoic basement and outcrops at Masku in SW Finland and Montemor-o-Novo, central Portugal. Despite the differences in size and number of measured leucosomes and magmatic veins, differences in host rock types and metamorphic grades, the cumulative width distribution of the studied magmatic leucosomes/veins follows a power law with exponents usually between 0.7 and 1.8. Published maps of the SE Australian Lachlan Fold Belt were used to investigate the distribution of granitoid pluton sizes. The granites occupy ca. 22 % of the 2.6 × 105 km2 area. The cumulative pluton area distributions show good power law distributions with exponents between 0.6 and 0.8 depending on pluton area group. Using the self-affine nature of pluton shapes, it is possible to estimate the total volume of magma that was expelled from the source in the 2.6 × 105 km2 map area, giving an estimated 0.8 km3 of magma per km2. It has been suggested in the literature that magma batches in the source merge to form ever-bigger batches in a self-organized way. This leads to a power law for the cumulative distribution of magma volumes, with an exponent m V between 1 for inefficient melt extraction, and 2/3 for maximum accumulation efficiency as most of the volume resides in the largest batches that can escape from the source. If m V ? 1, the mass of the magma is dominated by small batches; in case m = 2/3, about 50 % of all magma in the system is placed in a single largest batch. Our observations support the model that the crust develops a self-organized critical state during magma generation. In this state, magma batches accumulate in a non-continuous, step-wise manner to form ever-larger accumulations. There is no characteristic length or time scale in the partial melting process or its products. Smallest melt segregations and >km-scale plotuns form the end members of a continuous chain of mergers of magma batches.

  15. Thermodynamics of charged rotating dilaton black branes with power-law Maxwell field

    E-print Network

    Zangeneh, M Kord; Dehghani, M H

    2015-01-01

    In this paper, we construct a new class of charged rotating dilaton black brane solutions, with complete set of rotation parameters, which is coupled to a nonlinear Maxwell field. The Lagrangian of the matter field has the form of the power-law Maxwell field. We study the casual structure of the spacetime and its physical properties in ample details. We also compute thermodynamic and conserved quantities of the spacetime such as the temperature, entropy, mass, charge, and angular momentum. We find a Smarr-formula for the mass and verify the validity of the first law of thermodynamics on the black brane horizon. Finally, we investigate the thermal stability of solutions in both the canonical and grand canonical ensembles and disclose the effects of the dilaton field on the thermal stability of the solutions. We find that for $\\alpha \\leq 1$, charged rotating black brane solutions are thermally stable independent of the value of the other parameters. For $\\alpha>1$, the solutions can encounter an unstable phase...

  16. Thermodynamics of charged rotating dilaton black branes with power-law Maxwell field

    E-print Network

    M. Kord Zangeneh; A. Sheykhi; M. H. Dehghani

    2015-06-26

    In this paper, we construct a new class of charged rotating dilaton black brane solutions, with complete set of rotation parameters, which is coupled to a nonlinear Maxwell field. The Lagrangian of the matter field has the form of the power-law Maxwell field. We study the causal structure of the spacetime and its physical properties in ample details. We also compute thermodynamic and conserved quantities of the spacetime such as the temperature, entropy, mass, charge, and angular momentum. We find a Smarr-formula for the mass and verify the validity of the first law of thermodynamics on the black brane horizon. Finally, we investigate the thermal stability of solutions in both canonical and grand-canonical ensembles and disclose the effects of dilaton field and nonlinearity of Maxwell field on the thermal stability of the solutions. We find that for $\\alpha \\leq 1$, charged rotating black brane solutions are thermally stable independent of the values of the other parameters. For $\\alpha>1$, the solutions can encounter an unstable phase depending on the metric parameters.

  17. Random sampling of skewed distributions implies Taylor's power law of fluctuation scaling.

    PubMed

    Cohen, Joel E; Xu, Meng

    2015-06-23

    Taylor's law (TL), a widely verified quantitative pattern in ecology and other sciences, describes the variance in a species' population density (or other nonnegative quantity) as a power-law function of the mean density (or other nonnegative quantity): Approximately, variance = a(mean)(b), a > 0. Multiple mechanisms have been proposed to explain and interpret TL. Here, we show analytically that observations randomly sampled in blocks from any skewed frequency distribution with four finite moments give rise to TL. We do not claim this is the only way TL arises. We give approximate formulae for the TL parameters and their uncertainty. In computer simulations and an empirical example using basal area densities of red oak trees from Black Rock Forest, our formulae agree with the estimates obtained by least-squares regression. Our results show that the correlated sampling variation of the mean and variance of skewed distributions is statistically sufficient to explain TL under random sampling, without the intervention of any biological or behavioral mechanisms. This finding connects TL with the underlying distribution of population density (or other nonnegative quantity) and provides a baseline against which more complex mechanisms of TL can be compared. PMID:25852144

  18. A growth model for directed complex networks with power-law shape in the out-degree distribution

    PubMed Central

    Esquivel-Gómez, J.; Stevens-Navarro, E.; Pineda-Rico, U.; Acosta-Elias, J.

    2015-01-01

    Many growth models have been published to model the behavior of real complex networks. These models are able to reproduce several of the topological properties of such networks. However, in most of these growth models, the number of outgoing links (i.e., out-degree) of nodes added to the network is constant, that is all nodes in the network are born with the same number of outgoing links. In other models, the resultant out-degree distribution decays as a poisson or an exponential distribution. However, it has been found that in real complex networks, the out-degree distribution decays as a power-law. In order to obtain out-degree distribution with power-law behavior some models have been proposed. This work introduces a new model that allows to obtain out-degree distributions that decay as a power-law with an exponent in the range from 0 to 1. PMID:25567141

  19. A growth model for directed complex networks with power-law shape in the out-degree distribution

    NASA Astrophysics Data System (ADS)

    Esquivel-Gómez, J.; Stevens-Navarro, E.; Pineda-Rico, U.; Acosta-Elias, J.

    2015-01-01

    Many growth models have been published to model the behavior of real complex networks. These models are able to reproduce several of the topological properties of such networks. However, in most of these growth models, the number of outgoing links (i.e., out-degree) of nodes added to the network is constant, that is all nodes in the network are born with the same number of outgoing links. In other models, the resultant out-degree distribution decays as a poisson or an exponential distribution. However, it has been found that in real complex networks, the out-degree distribution decays as a power-law. In order to obtain out-degree distribution with power-law behavior some models have been proposed. This work introduces a new model that allows to obtain out-degree distributions that decay as a power-law with an exponent in the range from 0 to 1.

  20. The Power (Law) of Indian Markets: Analysing NSE and BSE Trading Statistics

    NASA Astrophysics Data System (ADS)

    Sinha, Sitabhra; Pan, Raj Kumar

    The nature of fluctuations in the Indian financial market is analyzed in this paper. We have looked at the price returns of individual stocks, with tick-by-tick data from the National Stock Exchange (NSE) and daily closing price data from both NSE and the Bombay Stock Exchange (BSE), the two largest exchanges in India. We find that the price returns in Indian markets follow a fat-tailed cumulative distribution, consistent with a power law having exponent ? ˜ 3, similar to that observed in developed markets. However, the distributions of trading volume and the number of trades have a different nature than that seen in the New York Stock Exchange (NYSE). Further, the price movement of different stocks are highly correlated in Indian markets.

  1. Evidence of power law decay of superexchange coupling in a disordered two-dimensional ? -electron system

    NASA Astrophysics Data System (ADS)

    Bagani, K.; Ray, M. K.; Sardar, M.; Banerjee, S.

    2015-04-01

    We report the specific heat of graphite, highly oriented pyrolytic graphite (HOPG), graphene oxide (GO), and reduced graphene oxide (RGO) from 300 K to 50 mK. Graphite and HOPG exhibits transition from three dimensions (Cv?T3) to two dimensions (Cv?T2) as the temperature increases above 4 K and approaching linearity in temperature for both around room temperature is observed. We observe a Schottky-like peak in specific heat of graphene oxide and reduced graphene oxide near 0.1 K, whose intensity and peak position varies with external magnetic field. We find that the random Heisenberg superexchange interaction between the Anderson (disorder) localized ? electrons of GO/RGO is responsible for the specific-heat peak. The exchange interaction strength between the localized spins falls off with distance as a weak power law (?1/r2.5) , rather than the usual exponential fall in insulating magnets.

  2. Collision-dependent power law scalings in two dimensional gyrokinetic turbulence

    SciTech Connect

    Cerri, S. S., E-mail: silvio.sergio.cerri@ipp.mpg.de; Bañón Navarro, A.; Told, D. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Jenko, F. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany)

    2014-08-15

    Nonlinear gyrokinetics provides a suitable framework to describe short-wavelength turbulence in magnetized laboratory and astrophysical plasmas. In the electrostatic limit, this system is known to exhibit a free energy cascade towards small scales in (perpendicular) real and/or velocity space. The dissipation of free energy is always due to collisions (no matter how weak the collisionality), but may be spread out across a wide range of scales. Here, we focus on freely decaying two dimensional electrostatic turbulence on sub-ion-gyroradius scales. An existing scaling theory for the turbulent cascade in the weakly collisional limit is generalized to the moderately collisional regime. In this context, non-universal power law scalings due to multiscale dissipation are predicted, and this prediction is confirmed by means of direct numerical simulations.

  3. Power law scaling of lateral deformations with universal Poissons index for randomly folded thin sheets

    E-print Network

    Alexander S. Balankin; Didier Samayoa Ochoa; Ernesto Pineda Leon; Rolando Cortes Montes de Oca; Antonio Horta Rangel; Miguel Angel Martinez Cruz

    2008-08-24

    We study the lateral deformations of randomly folded elastoplastic and predominantly plastic thin sheets under the uniaxial and radial compressions. We found that the lateral deformations of cylinders folded from elastoplastic sheets of paper obey a power law behavior with the universal Poissons index nu = 0.17 pm 0.01, which does not depend neither the paper kind and sheet sizes, nor the folding confinement ratio. In contrast to this, the lateral deformations of randomly folded predominantly plastic aluminum foils display the linear dependence on the axial compression with the universal Poissons ratio nu_e = 0.33 pm 0.01. This difference is consistent with the difference in fractal topology of randomly folded elastoplastic and predominantly plastic sheets, which is found to belong to different universality classes. The general form of constitutive stress-deformation relations for randomly folded elastoplastic sheets is suggested.

  4. Constraints on transient and power-law rheologies from rapid uplift in the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    King, M. A.; Barletta, V. R.; Bordoni, A.; Nield, G. A.; Spada, G.; Memin, A.

    2013-12-01

    Commencement of large glacial unloading in the Antarctic Peninsula since 1995, and especially 2002, is now well observed in terms of the unloading and the solid Earth response. The observed uplift requires a viscoelastic response to the unloading, and modelling based on a linear Maxwell rheology closely reproduces the observations. However, wider geophysical and laboratory studies suggest that a more complex rheological model may be required to correctly interpret the observed deformation. This well observed event offers a rare opportunity to constrain the rheology of the upper mantle using post-glacial rebound data and without large ambiguity in the ice history. Here, we report on two separate modelling efforts, respectively adopting a linear viscoelastic Burgers and power-law rheology, and discuss the constraints placed on such models by this dataset.

  5. Power law breakthrough curve tailing in a fracture: The role of advection

    NASA Astrophysics Data System (ADS)

    Fiori, Aldo; Becker, Matthew W.

    2015-06-01

    We offer an explanation of the strongly tailed solute breakthrough curve typically observed when a tracer test is conducted in fractured bedrock. In this example, we limit the model to a single planar fracture of varying aperture. Flow heterogeneity derives from variable fracture aperture, which implies variable transmissivity (T). The analysis employs a physically based model well-suited to strong heterogeneity and relies only upon advective transport. The purely advective model is able to explain a power-law trend of magnitude -2 to -3 in the breakthrough curve tail; a range that has been found in field tracer experiments. The principle cause of this trend is the comparatively slow transport in zones of small transmissivity (tight aperture). Slow advection occurs when either heterogeneity (variance of lnT) is strong or when the assumed heterogeneity distribution is non-Gaussian. Thus, we link breakthrough tailing to the statistical parameters for the transmissivity field.

  6. Stochastic population dynamics in a Markovian environment implies Taylor's power law of fluctuation scaling.

    PubMed

    Cohen, Joel E

    2014-05-01

    Taylor's power law of fluctuation scaling (TL) states that for population density, population abundance, biomass density, biomass abundance, cell mass, protein copy number, or any other nonnegative-valued random variable in which the mean and the variance are positive, variance=a(mean)(b),a>0, or equivalently log variance=loga+b×log mean. Many empirical examples and practical applications of TL are known, but understanding of TL's origins and interpretations remains incomplete. We show here that, as time becomes large, TL arises from multiplicative population growth in which successive random factors are chosen by a Markov chain. We give exact formulas for a and b in terms of the Markov transition matrix and the values of the successive multiplicative factors. In this model, the mean and variance asymptotically increase exponentially if and only if b>2 and asymptotically decrease exponentially if and only if b<2. PMID:24444811

  7. Power law classification scheme of time series correlations. On the example of G20 group

    NASA Astrophysics Data System (ADS)

    Mi?kiewicz, Janusz

    2013-05-01

    A power law classification scheme (PLCS) of time series correlations is proposed. It is shown that PLCS provides the ability to classify nonlinear correlations and measure their stability. PLCS has been applied to gross domestic product (GDP) per capita of G20 members and their correlations analysed. It has been shown that the method does not only recognise linear correlations properly, but also allows to point out converging time series as well as to distinguish nonlinear correlations. PLCS is capable of crash recognition as it is shown in the Argentina example. Finally the strength of correlations and the stability of correlation matrices have been used to construct a minimum spanning tree (MST). The results were compared with those based on the ultrametric distance (UD). Comparing the structures of MST, UD and PLCS indicates that the latter one is more complicated, but better fits the expected economic relations within the G20.

  8. Power law signature of media exposure in human response waiting time distributions

    NASA Astrophysics Data System (ADS)

    Crane, Riley; Schweitzer, Frank; Sornette, Didier

    2010-05-01

    We study the humanitarian response to the destruction brought by the tsunami generated by the Sumatra earthquake of December 26, 2004, as measured by donations, and find that it decays in time as a power law ˜1/t? with ?=2.5±0.1 . This behavior is suggested to be the rare outcome of a priority queuing process in which individuals execute tasks at a rate slightly faster than the rate at which new tasks arise. We believe this to be an empirical evidence documenting the recently predicted [G. Grinstein and R. Linsker, Phys. Rev. E 77, 012101 (2008)] regime, and provide additional independent evidence that suggests that this “highly attentive regime” arises as a result of the intense focus placed on this donation “task” by the media.

  9. Slow synaptic dynamics in a network: From exponential to power-law forgetting

    NASA Astrophysics Data System (ADS)

    Luck, J. M.; Mehta, A.

    2014-09-01

    We investigate a mean-field model of interacting synapses on a directed neural network. Our interest lies in the slow adaptive dynamics of synapses, which are driven by the fast dynamics of the neurons they connect. Cooperation is modeled from the usual Hebbian perspective, while competition is modeled by an original polarity-driven rule. The emergence of a critical manifold culminating in a tricritical point is crucially dependent on the presence of synaptic competition. This leads to a universal 1/t power-law relaxation of the mean synaptic strength along the critical manifold and an equally universal 1/?t relaxation at the tricritical point, to be contrasted with the exponential relaxation that is otherwise generic. In turn, this leads to the natural emergence of long- and short-term memory from different parts of parameter space in a synaptic network, which is the most original and important result of our present investigations.

  10. Extreme power law in a driven many-particle system without threshold dynamics.

    PubMed

    Mani, Roman; Böttcher, Lucas; Herrmann, Hans J; Helbing, Dirk

    2014-10-01

    We study a one-dimensional system of spatially extended particles, which are attached to regularly spaced locations by means of elastic springs. The particles are assumed to be driven by Gaussian noise and to have dissipative, energy-conserving, or antidissipative (pinball-like) interactions, when the particle density exceeds a critical threshold. While each particle in separation shows a well-behaved behavior characterized by a Gaussian velocity distribution, the interaction of particles at high densities can cause an avalanchelike momentum and energy transfer, which can generate extreme (steep) power laws without a well-defined variance and mean value. Specifically, the velocity variance increases dramatically towards the free boundaries of the driven many-particle system. The model might also have some relevance for better understanding of crowd disasters. Our results suggest that these are most likely caused by passive momentum transfers, not by active pushing. PMID:25375483

  11. Power-law persistence in the atmosphere A detailed study of long temperature records

    E-print Network

    Eichner, J F; Bunde, A; Havlin, S; Schellnhuber, H J; Eichner, Jan F.; Koscielny-Bunde, Eva; Bunde, Armin; Havlin, Shlomo; Schellnhuber, Hans J.

    2002-01-01

    We use several variants of the detrended fluctuation analysis to study the appearance of long-term persistence in temperature records, obtained at 95 stations all over the globe. Our results basically confirm earlier studies. We find that the persistence, characterized by the correlation C(s) of temperature variations separated by s days, decays for large s as a power law, C(s) ~ s^(-gamma). For continental stations, including stations along the coast lines, we find that gamma is always close to 0.7. For stations on islands, we find that gamma ranges between 0.3 and 0.7, with a maximum at gamma = 0.4. This is consistent with earlier studies of the persistence in sea surface temperature records where gamma is close to 0.4. By varying the degree of detrending in the fluctuation analysis we obtain also information about trends in the temperature records.

  12. Holographic power-law traps for the efficient production of Bose-Einstein condensates

    SciTech Connect

    Bruce, Graham D.; Bromley, Sarah L.; Smirne, Giuseppe; Torralbo-Campo, Lara; Cassettari, Donatella [Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom)

    2011-11-15

    We use a phase-only spatial light modulator to generate light distributions in which the intensity decays as a power law from a central maximum with order ranging from 2 (parabolic) to 0.5. We suggest that a sequence of these can be used as a time-dependent optical dipole trap for all-optical production of Bose-Einstein condensates (BECs) in two stages: efficient evaporative cooling in a trap with adjustable strength and depth, followed by an adiabatic transformation of the trap order to cross the BEC transition in a reversible way. Realistic experimental parameters are used to verify the capability of this approach in producing larger BECs than by evaporative cooling alone.

  13. Sudden expansion of a one-dimensional bose gas from power-law traps.

    PubMed

    Campbell, A S; Gangardt, D M; Kheruntsyan, K V

    2015-03-27

    We analyze free expansion of a trapped one-dimensional Bose gas after a sudden release from the confining trap potential. By using the stationary phase and local density approximations, we show that the long-time asymptotic density profile and the momentum distribution of the gas are determined by the initial distribution of Bethe rapidities (quasimomenta) and hence can be obtained from the solutions to the Lieb-Liniger equations in the thermodynamic limit. For expansion from a harmonic trap, and in the limits of very weak and very strong interactions, we recover the self-similar scaling solutions known from the hydrodynamic approach. For all other power-law traps and arbitrary interaction strengths, the expansion is not self-similar and shows strong dependence of the density profile evolution on the trap anharmonicity. We also characterize dynamical fermionization of the expanding cloud in terms of correlation functions describing phase and density fluctuations. PMID:25860753

  14. Extreme power law in a driven many-particle system without threshold dynamics

    NASA Astrophysics Data System (ADS)

    Mani, Roman; Böttcher, Lucas; Herrmann, Hans J.; Helbing, Dirk

    2014-10-01

    We study a one-dimensional system of spatially extended particles, which are attached to regularly spaced locations by means of elastic springs. The particles are assumed to be driven by Gaussian noise and to have dissipative, energy-conserving, or antidissipative (pinball-like) interactions, when the particle density exceeds a critical threshold. While each particle in separation shows a well-behaved behavior characterized by a Gaussian velocity distribution, the interaction of particles at high densities can cause an avalanchelike momentum and energy transfer, which can generate extreme (steep) power laws without a well-defined variance and mean value. Specifically, the velocity variance increases dramatically towards the free boundaries of the driven many-particle system. The model might also have some relevance for better understanding of crowd disasters. Our results suggest that these are most likely caused by passive momentum transfers, not by active pushing.

  15. Power law relationship between cell cycle duration and cell volume in the early embryonic development of Caenorhabditis elegans

    PubMed Central

    Arata, Yukinobu; Takagi, Hiroaki; Sako, Yasushi; Sawa, Hitoshi

    2015-01-01

    Cell size is a critical factor for cell cycle regulation. In Xenopus embryos after midblastula transition (MBT), the cell cycle duration elongates in a power law relationship with the cell radius squared. This correlation has been explained by the model that cell surface area is a candidate to determine cell cycle duration. However, it remains unknown whether this second power law is conserved in other animal embryos. Here, we found that the relationship between cell cycle duration and cell size in Caenorhabditis elegans embryos exhibited a power law distribution. Interestingly, the powers of the time-size relationship could be grouped into at least three classes: highly size-correlated, moderately size-correlated, and potentially a size-non-correlated class according to C. elegans founder cell lineages (1.2, 0.81, and <0.39 in radius, respectively). Thus, the power law relationship is conserved in Xenopus and C. elegans, while the absolute powers in C. elegans were different from that in Xenopus. Furthermore, we found that the volume ratio between the nucleus and cell exhibited a power law relationship in the size-correlated classes. The power of the volume relationship was closest to that of the time-size relationship in the highly size-correlated class. This correlation raised the possibility that the time-size relationship, at least in the highly size-correlated class, is explained by the volume ratio of nuclear size and cell size. Thus, our quantitative measurements shed a light on the possibility that early embryonic C. elegans cell cycle duration is coordinated with cell size as a result of geometric constraints between intracellular structures. PMID:25674063

  16. Undersampling power-law size distributions: effect on the assessment of extreme natural hazards

    USGS Publications Warehouse

    Geist, Eric L.; Parsons, Thomas E.

    2014-01-01

    The effect of undersampling on estimating the size of extreme natural hazards from historical data is examined. Tests using synthetic catalogs indicate that the tail of an empirical size distribution sampled from a pure Pareto probability distribution can range from having one-to-several unusually large events to appearing depleted, relative to the parent distribution. Both of these effects are artifacts caused by limited catalog length. It is more difficult to diagnose the artificially depleted empirical distributions, since one expects that a pure Pareto distribution is physically limited in some way. Using maximum likelihood methods and the method of moments, we estimate the power-law exponent and the corner size parameter of tapered Pareto distributions for several natural hazard examples: tsunamis, floods, and earthquakes. Each of these examples has varying catalog lengths and measurement thresholds, relative to the largest event sizes. In many cases where there are only several orders of magnitude between the measurement threshold and the largest events, joint two-parameter estimation techniques are necessary to account for estimation dependence between the power-law scaling exponent and the corner size parameter. Results indicate that whereas the corner size parameter of a tapered Pareto distribution can be estimated, its upper confidence bound cannot be determined and the estimate itself is often unstable with time. Correspondingly, one cannot statistically reject a pure Pareto null hypothesis using natural hazard catalog data. Although physical limits to the hazard source size and by attenuation mechanisms from source to site constrain the maximum hazard size, historical data alone often cannot reliably determine the corner size parameter. Probabilistic assessments incorporating theoretical constraints on source size and propagation effects are preferred over deterministic assessments of extreme natural hazards based on historic data.

  17. Critical properties of homogeneous binary trees

    E-print Network

    P. Silvi; V. Giovannetti; S. Montangero; M. Rizzi; J. I. Cirac; R. Fazio

    2010-09-10

    Many-body states whose wave-function admits a representation in terms of a uniform binary-tree tensor decomposition are shown to obey to power-law two-body correlations functions. Any such state can be associated with the ground state of a translational invariant Hamiltonian which, depending on the dimension of the systems sites, involve at most couplings between third-neighboring sites. A detailed analysis of their spectra shows that they admit an exponentially large ground space.

  18. Fully developed turbulence in accretion discs of binary stars: turbulent viscosity coefficient and power spectrum

    Microsoft Academic Search

    A. M. Fridman; D. V. Bisikalo; A. A. Boyarchuk; L. Pustil’nik; Y. M. Torgashin

    Summary. Using 3D numerical simulations we show the existence of a “spiralvortex” structure in an accretion disc in close binary stars. This structure is not related to the tidal influence of the companion star. It is a density wave containing a one-armed spiral and an anticyclone vortex, centered at the corotation circle. The latter results were obtained by 2D numerical

  19. A Derivation of the Luminosity Function of the Kuiper Belt from a Broken Power-Law Size Distribution

    E-print Network

    W. C. Fraser; JJ. Kavelaars

    2008-09-01

    We have derived a model of the Kuiper belt luminosity function exhibited by a broken power-law size distribution. This model allows direct comparison of the observed luminosity function to the underlying size distribution. We discuss the importance of the radial distribution model in determining the break diameter. We determine a best-fit break-diameter of the Kuiper belt size-distribution of 30function. We also confirm that the observed luminosity function for m(R) ~ 21-28 is consistent with a broken power-law size distribution, and exhibits a break at m(R)=26.0+0.7-1.8.

  20. In search of temporal power laws in the orientational relaxation near isotropic-nematic phase transition in model nematogens.

    PubMed

    Jose, Prasanth P; Bagchi, Biman

    2004-06-15

    Recent Kerr relaxation experiments by Gottke et al. have revealed the existence of a pronounced temporal power law decay in the orientational relaxation near the isotropic-nematic phase transition (INPT) of nematogens of rather small aspect ratio, kappa (kappa approximately 3-4). We have carried out very long (50 ns) molecular dynamics simulations of model (Gay-Berne) prolate ellipsoids with aspect ratio 3 in order to investigate the origin of this power law. The model chosen is known to undergo an isotropic to nematic phase transition for a range of density and temperature. The distance dependence of the calculated angular pair correlation function correctly shows the emergence of a long range correlation as the INPT is approached along the density axis. In the vicinity of INPT, the single particle second rank orientational time correlation function exhibits power law decay, (t(-alpha)) with exponent alpha approximately 2/3. More importantly, we find the sudden appearance of a pronounced power-law decay in the collective part of the second rank orientational time correlation function at short times when the density is very close to the transition density. The power law has an exponent close to unity, that is, the correlation function decays almost linearly with time. At long times, the decay is exponential-like, as predicted by Landau-de Gennes mean field theory. Since Kerr relaxation experiments measure the time derivative of the collective second rank orientational pair correlation function, the simulations recover the near independence of the signal on time observed in experiments. In order to capture the microscopic essence of the dynamics of pseudonematic domains inside the isotropic phase, we introduce and calculate a dynamic orientational pair correlation function (DOPCF) obtained from the coefficients in the expansion of the distinct part of orientational van Hove time correlation function in terms of spherical harmonics. The DOPCF exhibits power law relaxation when the pair separation length is below certain critical length. The orientational relaxation of a local director, defined in terms of the sum of unit vectors of all the ellipsoidal molecules, is also found to show slow power law relaxation over a long time scale. These results have been interpreted in terms of a newly developed mode coupling theory of orientational dynamics near the INPT. In the present case, the difference between the single particle and the collective orientational relaxation is huge which can be explained by the frequency dependence of the memory kernel, calculated from the mode coupling theory. The relationship of this power law with the one observed in a supercooled liquid near its glass transition temperature is explored. PMID:15268154

  1. Instability of collective excitations and power laws of an attractive Bose-Einstein condensate in an anharmonic trap

    NASA Astrophysics Data System (ADS)

    Debnath, P. K.; Chakrabarti, Barnali

    2010-10-01

    We study the instability of collective excitations of a three-dimensional Bose-Einstein condensate with repulsive and attractive interactions in a shallow trap designed as a quadratic plus a quartic potential. By using a correlated many-body theory, we determine the excitation modes and probe the critical behavior of collective modes, having a crucial dependence on the anharmonic parameter. We examine the power-law behavior of monopole frequency near criticality. In Gross-Pitaevskii variational treatment [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.80.1576 80, 1576 (1998)] the power-law exponent is determined as one-fourth power of (1-(A)/(Acr)), A is the number of condensate atoms and Acr is the critical number near collapse. We observe that the power-law exponent becomes (1)/(6) in our calculation for the pure harmonic trap and it becomes (1)/(7), for traps with a small anharmonic distortion. However for large anharmonicity the power law breaks down.

  2. Dynamical Fractional Chaotic Inflation -- Dynamical Generation of a Fractional Power-Law Potential for Chaotic Inflation

    E-print Network

    Keisuke Harigaya; Masahiro Ibe; Kai Schmitz; Tsutomu T. Yanagida

    2014-07-11

    Chaotic inflation based on a simple monomial scalar potential, V(phi) ~ phi^p, is an attractive large-field model of inflation capable of generating a sizable tensor-to-scalar ratio r. Therefore, assuming that future CMB observations will confirm the large r value reported by BICEP2, it is important to determine what kind of dynamical mechanism could possibly endow the inflaton field with such a simple effective potential. In this paper, we answer this question in the context of field theory, i.e. in the framework of dynamical chaotic inflation (DCI), where strongly interacting supersymmetric gauge dynamics around the scale of grand unification dynamically generate a fractional power-law potential via the quantum effect of dimensional transmutation. In constructing explicit models, we significantly extend our previous work, as we now consider a large variety of possible underlying gauge dynamics and relax our conditions on the field content of the model. This allows us to realize almost arbitrary rational values for the power p in the inflaton potential. The present paper may hence be regarded as a first step towards a more complete theory of dynamical chaotic inflation.

  3. Cascade model of gamma-ray bursts: Power-law and annihilation-line components

    NASA Astrophysics Data System (ADS)

    Harding, A. K.; Sturrock, P. A.; Daugherty, J. K.

    1988-08-01

    If, in a neutron star magnetosphere, an electron is accelerated to an energy of 10 to the 11th or 12th power eV by an electric field parallel to the magnetic field, motion of the electron along the curved field line leads to a cascade of gamma rays and electron-positron pairs. This process is believed to occur in radio pulsars and gamma ray burst sources. Results are presented from numerical simulations of the radiation and photon annihilation pair production processes, using a computer code previously developed for the study of radio pulsars. A range of values of initial energy of a primary electron was considered along with initial injection position, and magnetic dipole moment of the neutron star. The resulting spectra was found to exhibit complex forms that are typically power law over a substantial range of photon energy, and typically include a dip in the spectrum near the electron gyro-frequency at the injection point. The results of a number of models are compared with data for the 5 Mar., 1979 gamma ray burst. A good fit was found to the gamma ray part of the spectrum, including the equivalent width of the annihilation line.

  4. Exploiting the power law distribution properties of satellite fire radiative power retrievals: A method to estimate fire radiative energy and biomass burned from sparse satellite observations

    NASA Astrophysics Data System (ADS)

    Kumar, S. S.; Roy, D. P.; Boschetti, L.; Kremens, R.

    2011-10-01

    Instantaneous estimates of the power released by fire (fire radiative power, FRP) are available with satellite active fire detection products. The temporal integral of FRP provides an estimate of the fire radiative energy (FRE) that is related linearly to the amount of biomass burned needed by the atmospheric emissions modeling community. The FRE, however, is sensitive to satellite temporal and spatial FRP undersampling due to infrequent satellite overpasses, cloud and smoke obscuration, and failure to detect cool and/or small fires. Satellite FRPs derived over individual burned areas and fires have been observed to exhibit power law distributions. This property is exploited to develop a new way to derive FRE, as the product of the fire duration and the expected FRP value derived from the FRP power law probability distribution function. The method is demonstrated and validated by the use of FRP data measured with a dual-band radiometer over prescribed fires in the United States and by the use of FRP data retrieved from moderate resolution imaging spectroradiometer (MODIS) active-fire detections over Brazilian deforestation and Australian savanna fires. The biomass burned derived using the conventional FRP temporal integration and power law FRE estimation methods is compared with biomass burned measurements (prescribed fires) and available fuel load information reported in the literature (Australian and Brazilian fires). The results indicate that the FRE power law derivation method may provide more reliable burned biomass estimates under sparse satellite FRP sampling conditions and correct for satellite active-fire detection omission errors if the FRP power law distribution parameters and the fire duration are known.

  5. Power-law decay characteristic of coda envelopes revealed from the analysis of regional earthquakes

    NASA Astrophysics Data System (ADS)

    Lee, W.; Sato, H.

    2005-12-01

    So far, coda envelopes for wide frequency bands with long lapse time range have been described by bending curves which have several systematic changes in decay rate with lapse time. However, for NS component seismograms of regional earthquakes, applying the Hilbert Transform to make envelope curves and taking regression analysis on the envelopes in period bands from 24 s to 1/6 s for a wide lapse time range up to 4,000 s instead of measuring the peak amplitudes of the coda used previously, we found coda envelopes show the feature of ``power-law'' decay and there is no systematic change of decay gradient except for once occurring around ScS arrival with lapse time. 157 seismic events recorded by 11 IRIS broadband seismic network stations during the period from 1988 to 2005 with focal depths shallower than 50 km (shallow events) and deeper than 150 km (deep events) and with epicentral distance less than 1,000 km from individual seismic station were collected in this study. The moment magnitude of selected events ranges from 4.7 to 7.8. The ``power-law'' decay characteristic of seismic envelopes indicates that the power spectrum of seismic coda could be simply expressed as of the form P( T, t) ~ t - ?, where t is lapse time and T is central period. We find that ? = 1.6-6.2 for before ScS arrival in all period bands and 0.6-5.3 for after ScS arrival ranging from 24 s to 3/2 s periods. The coda decay gradient at short periods is steeper than that at longer periods for both cases of before and after ScS arrival. In particular, a clear offset of coda amplitude associated with ScS arrival appears in Turkey, Kyrgyzstan and Bolivia at 4-8 s and 8-16 s period bands. These coda decay gradient change and offset behavior in coda envelopes around ScS arrival are not clear in seismograms of shallow events. The simple and distinct characteristics of seismic coda envelopes could provide reliable information to determine physical values such as seismic source parameters and to identify the regional difference of medium heterogeneity in the deep Earth.

  6. Understanding Zipf's law with playing dice: history-dependent stochastic processes with collapsing sample-space have power-law rank distributions

    E-print Network

    Corominas-Murtra, Bernat; Thurner, Stefan

    2014-01-01

    History-dependent processes are ubiquitous in natural and social systems. Many such processes, especially those that are associated with complex systems, become more constrained as they unfold: The set of possible outcomes of such processes reduces as they 'age'. We demonstrate that stochastic processes of this kind necessarily lead to Zipf's law in the overall rank distributions of their outcomes. Furthermore, if iid noise is added to such sample-space-reducing processes, the corresponding rank distributions are exact power laws, $p(x)\\sim x^{-\\lambda}$, where the exponent $0\\leq \\lambda \\leq 1$ directly corresponds to the mixing ratio of process and noise. We illustrate sample-space-reducing processes with an intuitive example using a set of dice with different numbers of faces. Sample-space-reducing processes provide a new alternative to understand the origin of scaling in complex systems without the recourse to multiplicative, preferential, or self-organised-critical processes. Potential applications are ...

  7. Design of a condenser-boiler for a binary mercury-organic Rankine cycle solar dynamic space power system

    NASA Astrophysics Data System (ADS)

    Cotton, Randy M.

    1987-05-01

    A theoretical design was performed for the condenser/boiler of a space-based solar dynamic power system. The base system is a binary Rankine cycle with mercury and toluene as the working fluids. System output is 75 KWe with a combined efficiency of 41.1%. Design goals were to develop the most reliable, mass efficient unit possible for delivery to a space station. The design sized the unit based on toluene properties and used a computer generated heat balance to thermodynamically match the two fluids. Molybdenum was chosen as the material due to mass effectiveness in heat transfer, strength, and resistance to mercury corrosion. The unit transferred 137.46 kilowatts of thermal power and can operate at varying mass flow rates. Effectiveness in heat transfer is 0.96 and mass performance is 0.016 kg/KWth transferred. The design depends on using only existing technologies and the results call for no new developments.

  8. Multiple Glasses in Asymmetric Binary Hard Spheres

    E-print Network

    Th. Voigtmann

    2010-10-03

    Multiple distinct glass states occur in binary hard-sphere mixtures with constituents of very disparate sizes according to the mode-coupling theory of the glass transition (MCT), distinguished by considering whether small particles remain mobile or not, and whether small particles contribute significantly to perturb the big-particle structure or not. In the idealized glass, the four different glasses are separated by sharp transitions that give rise to higher-order transition phenomena involving logarithmic decay laws, and to anomalous power-law-like diffusion. The phenomena are argued to be expected generally in glass-forming mixtures.

  9. Stress-dependent power-law flow in the upper mantle following the 2002 Denali, Alaska, earthquake

    Microsoft Academic Search

    Andrew M. Freed; Roland Bürgmann; Eric Calais; Jeff Freymueller

    2006-01-01

    Far-field continuous Global Positioning System (GPS) time-series data following the 2002 M7.9 Denali, Alaska earthquake imply that mantle viscoelastic rheology is stress-dependent. A linear viscous mantle cannot explain fast early displacement rates at the surface that rapidly decay with time, whereas a power-law rheology where strain rate is proportional to stress raised to the power of 3.5±0.5 provides decay rates

  10. Propagation of Gravity Currents of non-Newtonian Power-Law Fluids in Porous Media

    NASA Astrophysics Data System (ADS)

    Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.

    2014-12-01

    A comprehensive analytical and experimental framework is presented to describe gravity-driven motions of rheologically complex fluids through porous media. These phenomena are relevant in geophysical, environmental, industrial and biological applications. The fluid is characterized by an Ostwald-DeWaele constitutive equation with behaviour index n. The flow is driven by the release of fluid at the origin of an infinite porous domain. In order to represent several possible spreading scenarios, we consider: i) different domain geometries: plane, radial, and channelized, with the channel shape parameterized by k; ii) instantaneous or continuous injection, depending on the time exponent of the volume of fluid in the current, ?; iii) horizontal or inclined impermeable boundaries. Systematic heterogeneity along the streamwise and/or transverse direction is added to the conceptualization upon considering a power-law permeability variation governed by two additional parameters ? and ?. Scalings for current length and thickness are derived in self similar form coupling the modified Darcy's law accounting for the fluid rheology with the mass balance equation. The length, thickness, and aspect ratio of the current are studied as functions of model parameters; several different critical values of ? emerge and govern the type of dependency, as well as the tendency of the current to accelerate or decelerate and become thicker or thinner at a given point. The asymptotic validity of the solutions is limited to certain ranges of model parameters. Experimental validation is performed under constant volume, constant and variable flux regimes in tanks/channels filled with transparent glass beads of uniform or variable diameter, using shear-thinning suspensions and Newtonian mixtures. The experimental results for the length and profile of the current agree well with the self-similar solutions at intermediate and late times.

  11. THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. IV. A PROBABILISTIC APPROACH TO INFERRING THE HIGH-MASS STELLAR INITIAL MASS FUNCTION AND OTHER POWER-LAW FUNCTIONS

    SciTech Connect

    Weisz, Daniel R.; Fouesneau, Morgan; Dalcanton, Julianne J.; Clifton Johnson, L.; Beerman, Lori C.; Williams, Benjamin F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)] [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Hogg, David W.; Foreman-Mackey, Daniel T. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)] [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Rix, Hans-Walter; Gouliermis, Dimitrios [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)] [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States)] [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Lang, Dustin [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)] [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)] [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Gordon, Karl D.; Kalirai, Jason S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)] [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Skillman, Evan D., E-mail: dweisz@astro.washington.edu [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

    2013-01-10

    We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M {approx}> 1 M {sub Sun }). Using simulated clusters and Markov Chain Monte Carlo sampling of the probability distribution functions, we show that estimates of the MF slope, {alpha}, are unbiased and that the uncertainty, {Delta}{alpha}, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on {alpha}, and provide an analytic approximation for {Delta}{alpha} as a function of the observed number of stars and mass range. Comparison with literature studies shows that {approx}3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield ({alpha}) = 2.46, with a 1{sigma} dispersion of 0.35 dex. We verify that it is impossible for a power-law MF to obtain meaningful constraints on the upper mass limit of the initial mass function, beyond the lower bound of the most massive star actually observed. We show that avoiding substantial biases in the MF slope requires (1) including the MF as a prior when deriving individual stellar mass estimates, (2) modeling the uncertainties in the individual stellar masses, and (3) fully characterizing and then explicitly modeling the completeness for stars of a given mass. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations. We briefly discuss how each of these effects can be incorporated into extensions of the present framework. Finally, we emphasize that the technique and lessons learned are applicable to more general problems involving power-law fitting.

  12. The Panchromatic Hubble Andromeda Treasury. IV. A Probabilistic Approach to Inferring the High-mass Stellar Initial Mass Function and Other Power-law Functions

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Fouesneau, Morgan; Hogg, David W.; Rix, Hans-Walter; Dolphin, Andrew E.; Dalcanton, Julianne J.; Foreman-Mackey, Daniel T.; Lang, Dustin; Johnson, L. Clifton; Beerman, Lori C.; Bell, Eric F.; Gordon, Karl D.; Gouliermis, Dimitrios; Kalirai, Jason S.; Skillman, Evan D.; Williams, Benjamin F.

    2013-01-01

    We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M >~ 1 M ?). Using simulated clusters and Markov Chain Monte Carlo sampling of the probability distribution functions, we show that estimates of the MF slope, ?, are unbiased and that the uncertainty, ??, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on ?, and provide an analytic approximation for ?? as a function of the observed number of stars and mass range. Comparison with literature studies shows that ~3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield lang?rang = 2.46, with a 1? dispersion of 0.35 dex. We verify that it is impossible for a power-law MF to obtain meaningful constraints on the upper mass limit of the initial mass function, beyond the lower bound of the most massive star actually observed. We show that avoiding substantial biases in the MF slope requires (1) including the MF as a prior when deriving individual stellar mass estimates, (2) modeling the uncertainties in the individual stellar masses, and (3) fully characterizing and then explicitly modeling the completeness for stars of a given mass. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations. We briefly discuss how each of these effects can be incorporated into extensions of the present framework. Finally, we emphasize that the technique and lessons learned are applicable to more general problems involving power-law fitting. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  13. A THEORETICAL VARIATION OF THE WIND PROFILE POWER-LAW EXPONENT AS A FUNCTION OF SURFACE ROUGHNESS AND STABILITY

    EPA Science Inventory

    The variation of the wind profile power-law exponent with respect to changes in surface roughness and atmospheric stability is depicted using the formulation of Nickerson and Smiley for specifying the vertical variations of the horizontal wind. The theoretical estimates of the po...

  14. Weibull Analysis of the Strength of Carbon Fibers Using Linear and Power Law Models for the Length Effect

    Microsoft Academic Search

    W. J. Padgett; S. D. Durham; A. M. Mason

    1995-01-01

    The single-filament test measurements for strength of carbon fibers obtained by Bader and Priest [5] are analyzed using a broader class of Weibull models with the scale parameter assumed to be a function of fiber gauge length. Two specific models are proposed for the fiber gauge length effect on tensile strength: The power law model and a linear model. The

  15. Thermal entrance region for laminar forced convection in a circular tube with a power law wall heat flux

    Microsoft Academic Search

    A. Barletta; E. Zanchini

    1996-01-01

    Laminar forced convection in a circular tube is investigated with a boundary condition of prescribed axially varying wall heat flux, under the assumptions of hydrodynamically developed flow and of negligible axial conduction and viscous dissipation in the fluid. A condition on the asymptotic behaviour of the axial distribution of wall heat flux is established which is fulfilled by power-law varying

  16. EVIDENCE FOR DEPARTURE FROM A POWER-LAW FLARE SIZE DISTRIBUTION FOR A SMALL SOLAR ACTIVE REGION

    SciTech Connect

    Wheatland, M. S., E-mail: m.wheatland@physics.usyd.edu.a [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

    2010-02-20

    Active region 11029 was a small, highly flare-productive solar active region observed at a time of extremely low solar activity. The region produced only small flares: the largest of the >70 Geostationary Observational Environmental Satellite (GOES) events for the region has a peak 1-8 A flux of 2.2 x 10{sup -6} W m{sup -2} (GOES C2.2). The background-subtracted GOES peak-flux distribution suggests departure from power-law behavior above 10{sup -6} W m{sup -2}, and a Bayesian model comparison strongly favors a power-law plus rollover model for the distribution over a simple power-law model. The departure from the power law is attributed to this small active region having a finite amount of energy. The rate of flaring in the region varies with time, becoming very high for 2 days coinciding with the onset of an increase in complexity of the photospheric magnetic field. The observed waiting-time distribution for events is consistent with a piecewise-constant Poisson model. These results present challenges for models of flare statistics and of energy balance in solar active regions.

  17. Study on the Electromagnetic Scattering from Non-Gaussian Rough Surface Based on the Modified Power-Law Spectrum

    Microsoft Academic Search

    Yan Peiwen; Tong Chuangming

    2007-01-01

    In microwave remote sensing, the brightness temperature is an important parameter. In order to model more realistic and real natural rough surfaces such as soil and ocean surface, we use exponential, power-law and modified spectral densities to model rough surfaces, which are all named as non-Gaussian surfaces. Then, we obtain the simulations of the scattering coefficient and the brightness temperature

  18. In-Degree and PageRank of Web pages: Why do they follow similar power laws?

    E-print Network

    Litvak, Nelly

    In-Degree and PageRank of Web pages: Why do they follow similar power laws? N. Litvak , W, The Netherlands; e-mail: {n.litvak, w.r.w.scheinhardt, y.volkovich}@ewi.utwente.nl Abstract PageRank is a popularity measure designed by Google to rank Web pages. Experiments confirm that PageRank values obey

  19. A Study of University Students' Understanding of Simple Electric Circuits. Part 2: Batteries, Ohm's Law, Power Dissipated, Resistors in Parallel.

    ERIC Educational Resources Information Center

    Picciarelli, V.; And Others

    1991-01-01

    Results of a systematic investigation into university students' (n=236) misunderstandings of d.c. simple circuit operations are reported. These results provide evidence of various misconceptions present before and after teaching the following topics: a battery as a source of constant current; the functional relation expressed by Ohm's law; power

  20. Research of Reducing the Peak to Average Power Ratio of OFDM System with Mu_Law-PTS

    Microsoft Academic Search

    Kai Zhou; Jian Zhang

    2010-01-01

    This paper aims at the high Peak to Average Power Ratio (PAPR) problem, which will occasionally reach the amplifier saturation region and therefore result in signal distortion in OFDM system. By combining the improved C transformation (?_law compression) and the Partial Transmit Sequence (PTS), we present a new method to modify the PAPR property of OFDM system. The simulation results

  1. Single and Double Power Laws for Cyber-Crimes Richard E Overill and Jantje A M Silomon

    E-print Network

    Overill, Richard E.

    of quantitative analytic treatment. Cyber-crime can be viewed as an asymmetric conflict, in that the resourcesSingle and Double Power Laws for Cyber-Crimes Richard E Overill and Jantje A M Silomon Department are interpreted in terms of the modus operandi of cyber-criminals as revealed in the CSI survey data

  2. Approximations of the self-similar solution for blastwave in a medium with power-law density variation

    E-print Network

    O. Petruk

    2000-02-04

    Approximations of the Sedov self-similar solution for a strong point explosion in a medium with the power-law density distribution \\rho^o\\propto r^{-m} are reviewed and their accuracy are analyzed. Taylor approximation is extended to cases m\

  3. Second Law analysis of a Rankine heat engine with reheat and regenerative options for solar thermal power generation

    Microsoft Academic Search

    S. C. Kaushik; R. D. Misra; N. Singh

    2000-01-01

    This communication presents the Second Law analysis based on the exergy concept for the performance of Simple and Regenerative-Reheat Rankine heat engines generally used in Solar Thermal Power Systems. Basic energy and exergy analysis for the heat engine system components are carried out for evaluating the energy and exergy losses as well as the exergetic efficiencies for both the Simple

  4. An effective antecedent precipitation model derived from the power-law relationship between landslide occurrence and rainfall level

    E-print Network

    Lu, Zhiming

    landslide occurrence and rainfall level Tuhua Ma a , Changjiang Li a, , Zhiming Lu b , Baoxin Wang c antecedent precipitation Lower bound rainfall threshold determination Power-law distributions Fractals Antecedent rainfall is an important predisposing factor in triggering landslides because it reduces soil

  5. The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies

    NASA Astrophysics Data System (ADS)

    Castelló-Mor, N.; Carrera, F. J.; Alonso-Herrero, A.; Mateos, S.; Barcons, X.; Ranalli, P.; Pérez-González, P. G.; Comastri, A.; Vignali, C.; Georgantopoulos, I.

    2013-08-01

    Context. Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Aims: Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012, ApJ, 748, 142; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed NH > 1022 cm-2). Methods: We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component. Results: We find 21/147 sources to be heavily absorbed but the uncertainties in their obscuring column densities do not allow us to confirm their Compton-Thick nature without resorting to additional criteria. Although IR power-law galaxies are less numerous in our sample than IR non-power-law galaxies (60 versus 87 respectively), we find that the fraction of absorbed (NHintr > 1022 cm-2) AGN is significantly higher (at about 3 sigma level) for IR-power-law sources (~2/3) than for those sources that do not meet this IR selection criteria (~1/2). This behaviour is particularly notable at low luminosities, but it appears to be present, although with a marginal significance, at all luminosities. Conclusions: We therefore conclude that the IR power-law method is efficient in finding X-ray-absorbed sources. We would then expect that the long-sought dominant population of absorbed AGN is abundant among IR power-law spectral shape sources not detected in X-rays.

  6. Describing the development of submarine canyons using stream-power erosion laws

    NASA Astrophysics Data System (ADS)

    Mitchell, N. C.

    2004-12-01

    The problem of how turbidity currents erode their beds is important for understanding how canyons develop, but is complex because flow power also varies as a result of incorporation and deposition of the current's suspended load. In some canyons where the total sedimentary mass passing through the canyon has been much larger than the excavated mass, the loads of the eroding currents changed little during passage down-canyon. Canyon morphology can then potentially reveal how gradient and other factors affect erosion rate, illustrated here with two datasets from tectonically active margins. The first dataset is from Tenryu Canyon off Japan, which was entrenched by up to 1200 m by steepening of the Tokai accretionary prism. Incision depth and channel gradient S data [Soh and Tokuyama, 2002] suggest an erosion law in which incision rate E~S0.8, which is remarkably similar to laws for detachment-limited erosion of river beds. In the second dataset, folds of the Barbados prism have created knickpoints [Huyghe et al., 2004]. Numerical modeling reveals that the knickpoints have partly smoothed out, a property of transport-limited erosion, but primarily have translated, a property of detachment-limited erosion. This mixed style of knickpoint development has also been inferred from some bedrock eroding streams on land. If scaling arguments for erosion with flow velocity apply here [Hancock et al., 1998], the inferred dependence of erosion rate on gradient implies that plucking and shear failure rather than abrasion are the main mechanisms in these channels. Hancock, G.S., Anderson, R.S., and Whipple, K.X., 1998, Beyond power: bedrock river incision process and form, in Tinkler, K.J., and Wohl, E.E., eds., Rivers over rock: Fluvial processes in bedrock channels, American Geophysical Union Monogr. 107: p. 35-60. Huyghe, P., M. Foata, E. Deville, and the Caramba Working Group, Channel profiles through the active thrust front of the southern Barbados prism, Geology, 32, 429-432, 2004. Soh, W., and H. Tokuyama, Rejuvination of submarine canyon associated with ridge subduction, Tenryu Canyon, off Tokai, central Japan, Mar. Geol., 187, 203-230, 2002.

  7. IMPACT OF TYPE Ia SUPERNOVA EJECTA ON A HELIUM-STAR BINARY COMPANION

    SciTech Connect

    Pan, Kuo-Chuan; Ricker, Paul M. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, IL 61801 (United States); Taam, Ronald E., E-mail: kpan2@astro.illinois.ed, E-mail: pmricker@astro.illinois.ed, E-mail: taam@tonic.astro.northwestern.ed [Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

    2010-05-20

    The impact of Type Ia supernova (SN) ejecta on a helium-star companion is investigated via high-resolution, two-dimensional hydrodynamic simulations. For a range of helium-star models and initial binary separations, it is found that the mass unbound in the interaction, {delta}M{sub ub}, is related to the initial binary separation, a, by a power law of the form {delta}M{sub ub} {proportional_to} a{sup m} . This power-law index is found to vary from -3.1 to -4.0, depending on the mass of the helium star. The small range of this index brackets values found previously for hydrogen-rich companions, suggesting that the dependence of the unbound mass on orbital separation is not strongly sensitive to the nature of the binary companion. The kick velocity is also related to the initial binary separation by a power law with an index in a range from -2.7 to -3.3, but the power-law index differs from those found in previous studies for hydrogen-rich companions. The space motion of the companion after the SN is dominated by its orbital velocity in the pre-SN binary system. The level of Ni/Fe contamination of the companion resulting from the passage of the SN ejecta is difficult to estimate, but an upper limit on the mass of bound nickel is found to be {approx}5 x 10{sup -4} M{sub sun}.

  8. A new exact and more powerful unconditional test of no treatment effect from binary matched pairs.

    PubMed

    Lloyd, Chris J

    2008-09-01

    We consider the problem of testing for a difference in the probability of success from matched binary pairs. Starting with three standard inexact tests, the nuisance parameter is first estimated and then the residual dependence is eliminated by maximization, producing what I call an E+M P-value. The E+M P-value based on McNemar's statistic is shown numerically to dominate previous suggestions, including partially maximized P-values as described in Berger and Sidik (2003, Statistical Methods in Medical Research 12, 91-108). The latter method, however, may have computational advantages for large samples. PMID:18047530

  9. The upstream-propagating Alfvénic fluctuations with power law spectra in the upstream region of the Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Tu, Chuanyi; Wang, Linghua; He, Jiansen; Marsch, Eckart

    2015-05-01

    Based on theories, the beam instability induced by shock-accelerated ions can generate upstream-propagating Alfvén waves (UPAWs) with a power spectral bump near 0.03 Hz, while the nonlinear wave-wave interaction favors an inverse cascade to create a power law spectrum. Here we present the first observational evidence for the upstream-propagating Alfvénic fluctuations (UPAFs) with power law spectra. We utilize a new criterion to identify the upstream-propagating Alfvénic intervals: the propagation direction is opposite to that of solar wind strahl electron outflow. Besides 35 UPAWs, we find 47 UPAFs with power law spectra, and ˜47% of these UPAFs are associated with energetic ion events (>30 keV). These UPAWs and UPAFs are mostly observed in the slow solar wind. However, their occurrence rate and power behave differently in dependence on the radial distance from the Earth. These results provide new clues on understanding the dynamic equilibrium between the nonlinear inverse cascade and the linear ion beam instability.

  10. Three-Dimensional Structures of the Spatiotemporal Nonlinear Schrödinger Equation with Power-Law Nonlinearity in PT-Symmetric Potentials

    PubMed Central

    Dai, Chao-Qing; Wang, Yan

    2014-01-01

    The spatiotemporal nonlinear Schrödinger equation with power-law nonlinearity in -symmetric potentials is investigated, and two families of analytical three-dimensional spatiotemporal structure solutions are obtained. The stability of these solutions is tested by the linear stability analysis and the direct numerical simulation. Results indicate that solutions are stable below some thresholds for the imaginary part of -symmetric potentials in the self-focusing medium, while they are always unstable for all parameters in the self-defocusing medium. Moreover, some dynamical properties of these solutions are discussed, such as the phase switch, power and transverse power-flow density. The span of phase switch gradually enlarges with the decrease of the competing parameter k in -symmetric potentials. The power and power-flow density are all positive, which implies that the power flow and exchange from the gain toward the loss domains in the cell. PMID:24983624

  11. Three-dimensional structures of the spatiotemporal nonlinear Schrödinger equation with power-law nonlinearity in PT-symmetric potentials.

    PubMed

    Dai, Chao-Qing; Wang, Yan

    2014-01-01

    The spatiotemporal nonlinear Schrödinger equation with power-law nonlinearity in PT-symmetric potentials is investigated, and two families of analytical three-dimensional spatiotemporal structure solutions are obtained. The stability of these solutions is tested by the linear stability analysis and the direct numerical simulation. Results indicate that solutions are stable below some thresholds for the imaginary part of PT-symmetric potentials in the self-focusing medium, while they are always unstable for all parameters in the self-defocusing medium. Moreover, some dynamical properties of these solutions are discussed, such as the phase switch, power and transverse power-flow density. The span of phase switch gradually enlarges with the decrease of the competing parameter k in PT-symmetric potentials. The power and power-flow density are all positive, which implies that the power flow and exchange from the gain toward the loss domains in the PT cell. PMID:24983624

  12. HST Morphologies of z~2 Dust Obscured Galaxies I: Power-law Sources

    E-print Network

    Bussmann, R S; Lotz, J; Armus, L; Brand, K; Brown, M J I; Desai, V; Eisenhardt, P; Higdon, J; Higdon, S; Jannuzi, B T; Le Floc'h, E; Melbourne, J; Soifer, B T; Weedman, D

    2008-01-01

    We present high spatial resolution optical and near-infrared imaging obtained using the ACS, WFPC2 and NICMOS cameras aboard the Hubble Space Telescope of 31 24um--bright z~2 Dust Obscured Galaxies (DOGs) identified in the Bootes Field of the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IR spectral energy distributions dominated by a power-law component suggestive of an AGN, all but one of the galaxies are spatially extended and not dominated by an unresolved component at rest-frame UV or optical wavelengths. The observed V-H and I-H colors of the extended components are 0.2-3 magnitudes redder than normal star-forming galaxies. All but 1 have axial ratios >0.3, making it unlikely that DOGs are composed of an edge-on star-forming disk. We model the spatially extended component of the surface brightness distributions of the DOGs with a Sersic profile and find effective radii of 1-6 kpc. This sample of DOGs is smaller than most sub-millimeter galaxies (SMGs), but larger than quiescent high...

  13. Exact, E = 0, classical and quantum solutions for general power-law oscillators

    NASA Technical Reports Server (NTRS)

    Nieto, Michael Martin; Daboul, Jamil

    1995-01-01

    For zero energy, E = 0, we derive exact, classical and quantum solutions for all power-law oscillators with potentials V(r) = -gamma/r(exp nu), gamma greater than 0 and -infinity less than nu less than infinity. When the angular momentum is non-zero, these solutions lead to the classical orbits (p(t) = (cos mu(phi(t) - phi(sub 0)t))(exp 1/mu) with mu = nu/2 - 1 does not equal 0. For nu greater than 2, the orbits are bound and go through the origin. We calculate the periods and precessions of these bound orbits, and graph a number of specific examples. The unbound orbits are also discussed in detail. Quantum mechanically, this system is also exactly solvable. We find that when nu is greater than 2 the solutions are normalizable (bound), as in the classical case. Further, there are normalizable discrete, yet unbound, states. They correspond to unbound classical particles which reach infinity in a finite time. Finally, the number of space dimensions of the system can determine whether or not an E = 0 state is bound. These and other interesting comparisons to the classical system will be discussed.

  14. Ice Shelves as Floating Channel Flows of Viscous Power-Law Fluids

    E-print Network

    Banik, Indranil

    2013-01-01

    We attempt to better understand the flow of marine ice sheets. Treating ice as a viscous shear-thinning power law fluid, we develop an asymptotic (late-time) theory in two cases - the presence or absence of contact with sidewalls. Most real-world situations fall somewhere between the two extreme cases considered. When sidewalls are absent, we obtain the equilibrium grounding line thickness using a simple computer model and have an analytic approximation. For shelves in contact with sidewalls, we obtain an asymptotic theory, valid for long shelves. Our theory is based on the velocity profile across the channel being a generalised version of Poiseuille flow, which works when lateral shear dominates the force balance. We determine when this is. We conducted experiments using a laboratory model for ice. This was a suspension of xanthan in water, at a concentration of 0.5% by mass. The lab model has $n \\approx 3.8$ (similar to that of ice). The experiments agreed extremely well with our theories for all relevant p...

  15. Power-law tails in probability density functions of molecular cloud column density

    NASA Astrophysics Data System (ADS)

    Brunt, C. M.

    2015-06-01

    Power-law tails are often seen in probability density functions (PDFs) of molecular cloud column densities, and have been attributed to the effect of gravity. We show that extinction PDFs of a sample of five molecular clouds obtained at a few tenths of a parsec resolution, probing extinctions up to AV ˜ 10 mag, are very well described by lognormal functions provided that the field selection is tightly constrained to the cold, molecular zone and that noise and foreground contamination are appropriately accounted for. In general, field selections that incorporate warm, diffuse material in addition to the cold, molecular material will display apparent core+tail PDFs. The apparent tail, however, is best understood as the high extinction part of a lognormal PDF arising from the cold, molecular part of the cloud. We also describe the effects of noise and foreground/background contamination on the PDF structure, and show that these can, if not appropriately accounted for, induce spurious tails or amplify any that are truly present.

  16. Cosmic histories of star formation and reionization: an analysis with a power-law approximation

    SciTech Connect

    Yu, Yun-Wei [Institute of Astrophysics, Central China Normal University, 152 Luoyu Road, Wuhan 430079 (China); Cheng, K.S. [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Chu, M.C.; Yeung, S., E-mail: yuyw@phy.ccnu.edu.cn, E-mail: hrspksc@hku.hk, E-mail: mcchu@phy.cuhk.edu.hk, E-mail: terryys@gmail.com [Department of Physics and Institute of Theoretical Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (China)

    2012-07-01

    With a simple power-law approximation of high-redshift (?>3.5) star formation history, i.e., ?-dot {sub *}(z)?[(1+z)/4.5]{sup ??}, we investigate the reionization of intergalactic medium (IGM) and the consequent Thomson scattering optical depth for cosmic microwave background (CMB) photons. A constraint on the evolution index ? is derived from the CMB optical depth measured by the Wilkinson Microwave Anisotropy Probe (WMAP) experiment, which reads ? ? 2.18 lg N{sub ?}?3.89, where the free parameter N{sub ?} is the number of the escaped ionizing ultraviolet photons per baryon. At the same time, the redshift z{sub f} at which the IGM is fully ionized can also be expressed as a function of ? as well as N{sub ?}. By further taking into account the implication of the Gunn-Peterson trough observations to quasars for the full reionization redshift, i.e., 6?

  17. Power-Laws and the Conservation of Information in discrete token systems: Part 1 General Theory

    E-print Network

    Les Hatton

    2012-07-20

    The Conservation of Energy plays a pivotal part in the development of the physical sciences. With the growth of computation and the study of other discrete token based systems such as the genome, it is useful to ask if there are conservation principles which apply to such systems and what kind of functional behaviour they imply for such systems. Here I propose that the Conservation of Hartley-Shannon Information plays the same over-arching role in discrete token based systems as the Conservation of Energy does in physical systems. I will go on to prove that this implies power-law behaviour in component sizes in software systems no matter what they do or how they were built, and also implies the constancy of average gene length in biological systems as reported for example by Lin Xu et al (10.1093/molbev/msk019). These propositions are supported by very large amounts of experimental data extending the first presentation of these ideas in Hatton (2011, IFIP / SIAM / NIST Working Conference on Uncertainty Quantification in Scientific Computing, Boulder, August 2011).

  18. Bond length estimates for oxide crystals with a molecular power law expression

    NASA Astrophysics Data System (ADS)

    Gibbs, G. V.; Ross, Nancy L.; Cox, David F.

    2015-07-01

    A molecular power law bond length regression expression, R(M-O) = 1.39( s/ r)-0.22, defined in terms of the quotient, s/ r, where s is the averaged Pauling bond strength for the bonded interaction comprising a given molecular coordination polyhedron and r is the periodic table row number for the M atom, serves to replicate the bulk of the 470 individual experimental M-O average bond lengths estimated with Shannon's (Acta Crystallogr A 32(5):751-767, 1976) crystal radii for oxides to within 0.10 Å. The success of the molecular expression is ascribed to a one-to-one deep-seated connection that obtains between the electron density accumulated between bonded pairs of atoms and the average Pauling bond strength. It also implies that the bonded interactions that constitute oxide crystals are governed in large part by local forces. Although the expression reproduces the bond lengths involving rare earth atoms typically to within ~0.05 Å, it does not reproduce the lanthanide ionic radius contraction. It also fails to reproduce the experimental bond lengths for selected transition cations like Cu1+, Ag1+ and VILSFe2+ and for cations like IVK+, VIBa2+ and IIU6+.

  19. Cosmological Evolution of Einstein-Aether Models with Power-law-like Potential

    E-print Network

    Hao Wei; Xiao-Peng Yan; Ya-Nan Zhou

    2014-04-15

    The so-called Einstein-Aether theory is General Relativity coupled (at second derivative order) to a dynamical unit time-like vector field (the aether). It is a Lorentz-violating theory, and gained much attention in the recent years. In the present work, we study the cosmological evolution of Einstein-Aether models with power-law-like potential, by using the method of dynamical system. In the case without matter, there are two attractors which correspond to an inflationary universe in the early epoch, or a de Sitter universe in the late time. In the case with matter but there is no interaction between dark energy and matter, there are only two de Sitter attractors, and no scaling attractor exists. So, it is difficult to alleviate the cosmological coincidence problem. Therefore, we then allow the interaction between dark energy and matter. In this case, several scaling attractors can exist under some complicated conditions, and hence the cosmological coincidence problem could be alleviated.

  20. Power Law Regression Analysis of Heat Flux Width in Type I ELMs

    NASA Astrophysics Data System (ADS)

    Stephens, C. D.; Makowski, M. A.; Leonard, A. W.; Osborne, T. H.

    2014-10-01

    In this project, a database of Type I ELM characteristics has been assembled and will be used to investigate possible dependencies of the heat flux width on physics and engineering parameters. At the edge near the divertor, high impulsive heat loads are imparted onto the surface. The impact of these ELMs can cause a reduction in divertor lifetime if the heat flux is great enough due to material erosion. A program will be used to analyze data, extract relevant, measurable quantities, and record the quantities in the table. Care is taken to accurately capture the complex space/time structure of the ELM. Then correlations between discharge and equilibrium parameters will be investigated. Power law regression analysis will be used to help determine the dependence of the heat flux width on these various measurable quantities and parameters. This will enable us to better understand the physics of heat flux at the edge. Work supported in part by the National Undergraduate Fellowship Program in Plasma Physics and Fusion Energy Sciences and the US DOE under DE-FG02-04ER54761, DE-AC52-07NA27344, DE-FC02-04ER54698.

  1. Interim Report on the Power Law Index of Interplanetary Suprathermal Ion Spectra

    NASA Astrophysics Data System (ADS)

    Hill, M. E.; Hamilton, D. C.

    2010-12-01

    There is a continuing debate about the applicability of the theory presented by Fisk and Gloeckler (FG) regarding the formation of suprathermal ion tails in phase space density vs. velocity spectra; in the solar wind frame the FG theory predicts a power law index of-5 (which is equivalent to a differential intensity vs. energy index of-1.5). There has also been uncertainty and perhaps misunderstanding regarding the extent to which such spectra are actually observed; i.e., is there really a significant preference for the -5 index? Here we report the results of an interim technique we use to analyze ~1-100 keV/nucleon interplanetary suprathermal H+, He+, and He++, spectra measured at the Cassini spacecraft by the Charge Energy Mass Spectrometer (CHEMS) instrument of the Magnetospheric Imaging Instrument (MIMI) suite during the cruise to Saturn. We analyzed 18 active periods and report a mean index in the solar wind frame of 4.9+/-0.4 for protons, 5.2+/-0.5 for He+, and 4.7+/-0.2 for alpha particles. MIMI/CHEMS offers much needed independent observations of heliospheric ions in the suprathermal energy range.

  2. Interim Report on the Power Law Index of Interplanetary Suprathermal Ion Spectra

    SciTech Connect

    Hill, M. E. [Johns Hopkins Applied Physics Laboratory, Laurel, Maryland 20723 (United States); Hamilton, D. C. [University of Maryland College Park, Maryland 20742 (United States)

    2010-12-30

    There is a continuing debate about the applicability of the theory presented by Fisk and Gloeckler (FG) regarding the formation of suprathermal ion tails in phase space density vs. velocity spectra; in the solar wind frame the FG theory predicts a power law index of-5 (which is equivalent to a differential intensity vs. energy index of-1.5). There has also been uncertainty and perhaps misunderstanding regarding the extent to which such spectra are actually observed; i.e., is there really a significant preference for the -5 index? Here we report the results of an interim technique we use to analyze {approx}1-100 keV/nucleon interplanetary suprathermal H{sup +}, He{sup +}, and He{sup ++}, spectra measured at the Cassini spacecraft by the Charge Energy Mass Spectrometer (CHEMS) instrument of the Magnetospheric Imaging Instrument (MIMI) suite during the cruise to Saturn. We analyzed 18 active periods and report a mean index in the solar wind frame of 4.9{+-}0.4 for protons, 5.2{+-}0.5 for He{sup +}, and 4.7{+-}0.2 for alpha particles. MIMI/CHEMS offers much needed independent observations of heliospheric ions in the suprathermal energy range.

  3. Cupid is Still Doomed: Overlapping Power Laws and the Stability of the Inner Uranian Satellites

    NASA Astrophysics Data System (ADS)

    French, Robert S.; Showalter, M. R.

    2012-05-01

    We have continued our exploration of the stability of the inner Uranian satellites (French & Showalter 2011, DDA abstract) using simulations based on recent observational data. We find that the moon subsets Cressida/Desdemona/Juliet and Cupid/Belinda/Perdita are unstable in isolation, crossing orbits in 106-107 years. The presence of the other inner moons reduces this time to 104-106 years. The stability of the inner moons is not changed by the presence of the five classical satellites but Perdita, a very small moon, has a surprisingly large effect on the stability of Cupid and Belinda. We extend the power law previously discovered by Duncan & Lissauer (1997, Icarus, 125, 1-12), in which the crossing time of a pair of moons can be predicted using multiple simulations with higher moon masses, to the case of two unstable moon pairs. We use this new formalism to predict the lifetimes of Cupid/Belinda and Cressida/Desdemona using a conservative density assumption, ?=0.5 g/cm3. The inner satellites continue to exhibit instability with crossing times of 105-107 years in this case. Such short crossing times imply the continuing, rapid evolution of the Uranian satellites.

  4. A stable and robust calibration scheme of the log-periodic power law model

    NASA Astrophysics Data System (ADS)

    Filimonov, V.; Sornette, D.

    2013-09-01

    We present a simple transformation of the formulation of the log-periodic power law formula of the Johansen-Ledoit-Sornette (JLS) model of financial bubbles that reduces it to a function of only three nonlinear parameters. The transformation significantly decreases the complexity of the fitting procedure and improves its stability tremendously because the modified cost function is now characterized by good smooth properties with in general a single minimum in the case where the model is appropriate to the empirical data. We complement the approach with an additional subordination procedure that slaves two of the nonlinear parameters to the most crucial nonlinear parameter, the critical time tc, defined in the JLS model as the end of the bubble and the most probable time for a crash to occur. This further decreases the complexity of the search and provides an intuitive representation of the results of the calibration. With our proposed methodology, metaheuristic searches are not longer necessary and one can resort solely to rigorous controlled local search algorithms, leading to a dramatic increase in efficiency. Empirical tests on the Shanghai Composite index (SSE) from January 2007 to March 2008 illustrate our findings.

  5. Estimators for the exponent and upper limit, and goodness-of-fit tests for (truncated) power-law distributions

    NASA Astrophysics Data System (ADS)

    Maschberger, Thomas; Kroupa, Pavel

    2009-05-01

    Many objects studied in astronomy follow a power-law distribution function (DF), for example the masses of stars or star clusters. A still used method by which such data is analysed is to generate a histogram and fit a straight line to it. The parameters obtained in this way can be severely biased, and the properties of the underlying DF, such as its shape or a possible upper limit, are difficult to extract. In this work, we review techniques available in the literature and present newly developed (effectively) bias-free estimators for the exponent and the upper limit. Furthermore, we discuss various graphical representations of the data and powerful goodness-of-fit tests to assess the validity of a power law for describing the distribution of data. As an example, we apply the presented methods to the data set of massive stars in R136 and the young star clusters in the Large Magellanic Cloud. For R136 we confirm the result of Koen of a truncated power law with a bias-free estimate for the exponent of 2.20 +/- 0.78/2.87 +/- 0.98 (where the Salpeter-Massey value is 2.35) and for the upper limit of 143 +/- 9/163 +/- 9Msolar, depending on the stellar models used. The star clusters in the Large Magellanic Cloud (with ages up to 107.5yr) follow a truncated power-law distribution with exponent 1.62 +/- 0.06 and upper limit 68 +/- 12 × 103Msolar. Using the graphical data representation, a significant change in the form of the mass function below 102.5Msolar can be detected, which is likely caused by incompleteness in the data.

  6. Binary Particle Swarm Optimization Based Defensive Islanding Of Large Scale Power Systems

    Microsoft Academic Search

    Wenxin Liu; Li Liu; David A. Cartes; Ganesh K. Venayagamoorthy

    2007-01-01

    Power system defensive islanding is an efficient way to avoid catastrophic wide area blackouts, such as the 2003 North American Blackout. Finding defensive islands of large -scale power systems is a combinatorial explosion problem. Thus, it is very difficult to find an optimal solution, if it exists, within reasonable time using analytical methods. This paper presents to utilize the computational

  7. Second Law Analysis for Process and Energy Engineering: Use in a Steam/Power Cycle 

    E-print Network

    Sama, D.; Sanhong, Q.

    1988-01-01

    The objective of this paper is to demonstrate how the use of the 2nd Law can help an engineer make intelligent process design decisions in a relatively simple and straightforward manner. A sensitivity to 2nd Law inefficiencies, when used with common...

  8. HST Morphologies of z~2 Dust Obscured Galaxies I: Power-law Sources

    E-print Network

    R. S. Bussmann; Arjun Dey; J. Lotz; L. Armus; K. Brand; M. J. I. Brown; V. Desai; P. Eisenhardt; J. Higdon; S. Higdon; B. T. Jannuzi; E. Le Floc'h; J. Melbourne; B. T. Soifer; D. Weedman

    2009-02-19

    We present high spatial resolution optical and near-infrared imaging obtained using the ACS, WFPC2 and NICMOS cameras aboard the Hubble Space Telescope of 31 24um--bright z~2 Dust Obscured Galaxies (DOGs) identified in the Bootes Field of the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IR spectral energy distributions dominated by a power-law component suggestive of an AGN, all but one of the galaxies are spatially extended and not dominated by an unresolved component at rest-frame UV or optical wavelengths. The observed V-H and I-H colors of the extended components are 0.2-3 magnitudes redder than normal star-forming galaxies. All but 1 have axial ratios >0.3, making it unlikely that DOGs are composed of an edge-on star-forming disk. We model the spatially extended component of the surface brightness distributions of the DOGs with a Sersic profile and find effective radii of 1-6 kpc. This sample of DOGs is smaller than most sub-millimeter galaxies (SMGs), but larger than quiescent high-redshift galaxies. Non-parametric measures (Gini and M20) of DOG morphologies suggest that these galaxies are more dynamically relaxed than local ULIRGs. We estimate lower limits to the stellar masses of DOGs based on the rest-frame optical photometry and find that these range from ~10^(9-11) M_sun. If major mergers are the progenitors of DOGs, then these observations suggest that DOGs may represent a post-merger evolutionary stage.

  9. The origin of tablet boudinage: Results from experiments using power-law rock analogs

    NASA Astrophysics Data System (ADS)

    Zulauf, J.; Zulauf, G.; Kraus, R.; Gutiérrez-Alonso, G.; Zanella, F.

    2011-10-01

    We used power-law viscous plasticine ( n = ca. 7) as a rock analog to simulate boudinage of rocks undergoing dislocation creep and brittle fracture. A competent plasticine layer, oriented perpendicular to the main shortening direction, Z, underwent bulk pure flattening inside a less competent plasticine matrix. Computer tomographic analyses of the deformed samples revealed that boudinage results from an initial phase of viscous necking followed by tensile failure along the previously formed necks. The resulting boudins display a polygonal shape in plan-view and are referred to as 'tablet boudins' (in contrast to the square to rectangular shaped chocolate-tablet boudins). The ratio between the plan-view long and short axis, R, ranges from 1.2 to 2.6. The polygonal, non-isometric shape of the tablet boudins can be explained by the strong interaction of concentric and radial tensile fractures. With increasing layer thickness, Hi, the mean diameter of the boudin tablets, Wa, increases, while the number of boudins, N, decreases. Progressive finite strain results in a higher number of the boudins and a smaller mean diameter. The thickness of the boudins, Hf, is almost the same as the initial layer thickness, Hi, while the aspect ratio ( Wd = Wa / Hf) decreases with layer thickness and finite strain. The mean Wd values obtained from all experiments span from ca. 4 to ca. 11. Tablet boudins, described in the present paper, have yet not been described from natural outcrops. The reasons might be that pure flattening strain is not common in nature, and the characterization and evaluation of tablet boudins requires geometrical analysis in three dimensions, which is a difficult task when such structures occur in nature.

  10. Riemannian geometry of thermodynamics and systems with repulsive power-law interactions.

    PubMed

    Ruppeiner, George

    2005-07-01

    A Riemannian geometric theory of thermodynamics based on the postulate that the curvature scalar R is proportional to the inverse free energy density is used to investigate three-dimensional fluid systems of identical classical point particles interacting with each other via a power-law potential energy gamma r(-alpha) . Such systems are useful in modeling melting transitions. The limit alpha-->infinity corresponds to the hard sphere gas. A thermodynamic limit exists only for short-range (alpha>3) and repulsive (gamma>0) interactions. The geometric theory solutions for given alpha>3 , gamma>0 , and any constant temperature T have the following properties: (1) the thermodynamics follows from a single function b (rho T(-3/alpha) ) , where rho is the density; (2) all solutions are equivalent up to a single scaling constant for rho T(-3/alpha) , related to gamma via the virial theorem; (3) at low density, solutions correspond to the ideal gas; (4) at high density there are solutions with pressure and energy depending on density as expected from solid state physics, though not with a Dulong-Petit heat capacity limit; (5) for 33.7913 a phase transition is required to go between these regimes; (7) for any alpha>3 we may include a first-order phase transition, which is expected from computer simulations; and (8) if alpha-->infinity, the density approaches a finite value as the pressure increases to infinity, with the pressure diverging logarithmically in the density difference. PMID:16090049

  11. Global scale analysis of the stream power law parameters based on worldwide 10Be denudation rates

    NASA Astrophysics Data System (ADS)

    Harel, Marie-Alice; Mudd, Simon; Attal, Mikael

    2015-04-01

    The stream power law, expressed as E = KAmSn where E is erosion rate [LT-1], K is erodibility [T-1L(1-2m)], A is drainage area [L2], S is channel gradient [L/L] and m and n are constants, is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for a large number of applications such as topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of uplift patterns and rates. However, the unknown parameters K, m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably alters the use and interpretation of the model. In this study, we compile published 10Be basin-wide erosion rates (n = 1335) in order to assess the m/n ratio (or concavity index), the slope exponent n and erodibility coefficient K using the integral method of channel profile analysis. These three parameters are calculated for 66 areas and allow for a global scale analysis in terms of climatic, tectonic and environmental settings. Our results suggest that (i) many sites are too noisy or do not have enough data to predict n and K with a satisfying level of confidence; (ii) the slope exponent is predominantly greater than one, meaning that the relationship between erosion rate and the channel gradient is non-linear, supporting the idea that incision is a threshold controlled process. Furthermore, a multi-regression analysis and the calculation of n and K using a reference concavity index m/n = 0.45 demonstrate that (iii) many intuitive or previously demonstrated local-scale trends, such as the correlation between erosion rate and climate, do not appear at a global scale.

  12. The JKR-type adhesive contact problems for power-law shaped axisymmetric punches

    NASA Astrophysics Data System (ADS)

    Borodich, Feodor M.; Galanov, Boris A.; Suarez-Alvarez, Maria M.

    2014-08-01

    The JKR (Johnson, Kendall, and Roberts) and Boussinesq-Kendall models describe adhesive frictionless contact between two isotropic elastic spheres, and between a flat-ended axisymmetric punch and an elastic half-space respectively. However, the shapes of contacting solids may be more general than spherical or flat ones. In addition, the derivation of the main formulae of these models is based on the assumption that the material points within the contact region can move along the punch surface without any friction. However, it is more natural to assume that a material point that came to contact with the punch sticks to its surface, i.e. to assume that the non-slipping boundary conditions are valid. It is shown that the frictionless JKR model may be generalized to arbitrary convex, blunt axisymmetric body, in particular to the case of the punch shape being described by monomial (power-law) punches of an arbitrary degree d?1. The JKR and Boussinesq-Kendall models are particular cases of the problems for monomial punches, when the degree of the punch d is equal to two or it goes to infinity respectively. The generalized problems for monomial punches are studied under both frictionless and non-slipping (or no-slip) boundary conditions. It is shown that regardless of the boundary conditions, the solution to the problems is reduced to the same dimensionless relations among the actual force, displacements and contact radius. The explicit expressions are derived for the values of the pull-off force and for the corresponding critical contact radius. Connections of the results obtained for problems of nanoindentation in the case of the indenter shape near the tip has some deviation from its nominal shape and the shape function can be approximated by a monomial function of radius, are discussed.

  13. Fractional power-law spectral response of CaCu3Ti4O12 dielectric: Many-body effects

    NASA Astrophysics Data System (ADS)

    Kumar, Jitender; Awasthi, A. M.

    2012-08-01

    Spectral character of dielectric response in CaCu3Ti4O12 across 0.5 Hz-4MHz over 45-200 K corresponding to neither the Debyean nor the KWW relaxation patterns rather indicates a random-walk like diffusive dynamics of moments. Non-linear relaxation here is due to the many body dipole-interactions, as confirmed by spectral-fits of our measured permittivity to the Dissado-Hill behaviour. Fractional power-laws observed in ?*(?) macroscopically reflect the fractal microscopic configurations. Below ˜100 K, the power-law exponent m (n) steeply decreases (increases), indicating finite length-scale collective response of moment-bearing entities. At higher temperatures, m gradually approaches 1 and n falls to low values, reflecting tendency towards the single-particle/Debyean relaxation.

  14. Power-law in pedestrian crossing flow under the interference of vehicles at an un-signalized midblock crosswalk

    NASA Astrophysics Data System (ADS)

    Xin, Xiuying; Jia, Ning; Zheng, Liang; Ma, Shoufeng

    2014-07-01

    Mixed traffic without signal control is complicated. This paper proposes a pedestrian-vehicle cellular automata (CA) model to study the characteristics of the mixed traffic. The model includes two sub models. One is the pedestrian model, in which the heterogeneity is taken into consideration. The other is the vehicle model, in which a safely running mode and a normally running mode are introduced. Simulation results show that (1) the traffic flow experiences four phases, that is, free flow, pedestrians-free flow, vehicles-free flow and jams, (2) pedestrians cross the crosswalk in groups and the sizes of the groups obey power law distribution, and (3) the heterogeneity of pedestrians acts an important role in the system. If the pedestrians are simultaneously homogeneous, the mixed traffic flow shows a “polarization” and these power-laws disappear under high arrival rates of vehicles and pedestrians.

  15. Power law burst and inter-burst interval distributions in the solar wind: turbulence or dissipative SOC ?

    E-print Network

    M. P. Freeman; N. W. Watkins; D. J. Riley

    2000-06-28

    We calculate for the first time the probability density functions (PDFs) P of burst energy e, duration T and inter-burst interval tau for a known turbulent system in nature. Bursts in the earth-sun component of the Poynting flux at 1 AU in the solar wind were measured using the MFI and SWE experiments on the NASA WIND spacecraft. We find P(e) and P(T) to be power laws, consistent with self-organised criticality (SOC). We find also a power law form for P(tau) that distinguishes this turbulent cascade from the exponential P(tau) of ideal SOC, but not from some other SOC-like sandpile models. We discuss the implications for the relation between SOC and turbulence.

  16. Lifetime assessment by intermittent inspection under the mixture Weibull power law model with application to XLPE cables.

    PubMed

    Hirose, H

    1997-01-01

    This paper proposes a new treatment for electrical insulation degradation. Some types of insulation which have been used under various circumstances are considered to degrade at various rates in accordance with their stress circumstances. The cross-linked polyethylene (XLPE) insulated cables inspected by major Japanese electric companies clearly indicate such phenomena. By assuming that the inspected specimen is sampled from one of the clustered groups, a mixed degradation model can be constructed. Since the degradation of the insulation under common circumstances is considered to follow a Weibull distribution, a mixture model and a Weibull power law can be combined. This is called The mixture Weibull power law model. By using the maximum likelihood estimation for the newly proposed model to Japanese 22 and 33 kV insulation class cables, they are clustered into a certain number of groups by using the AIC and the generalized likelihood ratio test method. The reliability of the cables at specified years are assessed. PMID:9384621

  17. Power-Law Behavior of Beat-Rate Variability in Monolayer Cultures of Neonatal Rat Ventricular Myocytes

    Microsoft Academic Search

    Jan P. Kucera; Marc O. Heuschkel; Philippe Renaud; Stephan Rohr

    2010-01-01

    It is known that extracardiac factors (nervous, humoral, and hemodynamic) participate in the power-law behavior of heart-rate variability. To assess whether intrinsic properties of cardiac tissue might also be involved, beat-rate variability was studied in spontaneously beating cell cultures devoid of extracardiac influences. Extracellular electrograms were recorded from monolayer cultures of neonatal rat ventricular myocytes under stable incubating conditions for

  18. A variational principle for the two-dimensional boundary-layer flow of non-newtonian power-law fluids

    Microsoft Academic Search

    Djordje S. Djukic; Bozidar D. Vujanovic

    1975-01-01

    Summary This paper is devoted to the theoretical analysis of steady and unsteady boundary layer problems for non-Newtonian power-law fluid flow using a new variational principle ofHamilton's type. The standard method of variational calculus in the form of partial integration is a basic tool for obtaining approximative solutions. The main characteristic of the variational principle developed here is that all

  19. Analysis of power-law self-similar solutions to the problem of hydraulic fracture crack formation

    Microsoft Academic Search

    N. N. Smirnov; V. R. Tagirova

    2007-01-01

    The problem of hydraulic fracture crack propagation in a porous medium is studied in the approximation of small crack opening\\u000a and the inertialess flow of an incompressible Newtonian hydraulic fracturing fluid inside the crack. A one-parameter family\\u000a of power-law self-similar solutions is considered in order to determine the crack width evolution, the fluid velocity in the\\u000a crack, and the seepage

  20. Contact line instability of gravity-driven flow of power-law fluids: Comparison of Experiments and Simulations

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Clever, Henry; Kieweg, Sarah

    2013-11-01

    We previously studied the fingering instabilities of power-law fluids using linear stability analysis (LSA). We also developed a 3D FEM model to simulate a constant-volume power-law fluid flowing down an incline. In this study, we try to perform 3D simulations with constant-flux condition and perturbed contact line, and compare the results to LSA. Moreover, we develop a fluid depth measurement experiment based on fluorescence imaging for further comparison to the numerical results. Instead of using laser-induced fluorescence, we try a simple quantitative way of using LEDs, which is much less expensive. The impact of inclination angle, surface tension, and especially shear-thinning effect on contact line instabilities is investigated. We previously studied the fingering instabilities of power-law fluids using linear stability analysis (LSA). We also developed a 3D FEM model to simulate a constant-volume power-law fluid flowing down an incline. In this study, we try to perform 3D simulations with constant-flux condition and perturbed contact line, and compare the results to LSA. Moreover, we develop a fluid depth measurement experiment based on fluorescence imaging for further comparison to the numerical results. Instead of using laser-induced fluorescence, we try a simple quantitative way of using LEDs, which is much less expensive. The impact of inclination angle, surface tension, and especially shear-thinning effect on contact line instabilities is investigated. This work is supported by NIH R21/R33 Microbicide Innovation Program.

  1. Peak power control of MC-CDMA with special classes of binary sequences

    Microsoft Academic Search

    Xin Gao; Nam Yul Yu; Zhiwei Mao

    2010-01-01

    In this paper, the peak-to-average power ratio (PAPR) properties of m-sequences, 3-term, 5-term and Welch-Gong sequences are discussed as the spreading codes for downlink MC-CDMA. It is shown that for single or multiple users, the orthogonal codes generated by these sequences provide lower peak-to-mean-envelope-power ratios (PMEPR) than Walsh-Hadamard sequences. Therefore, these sequences can be considered as good alternatives to replace

  2. Conserved Noncoding Elements Follow Power-Law-Like Distributions in Several Genomes as a Result of Genome Dynamics

    PubMed Central

    Polychronopoulos, Dimitris; Sellis, Diamantis; Almirantis, Yannis

    2014-01-01

    Conserved, ultraconserved and other classes of constrained elements (collectively referred as CNEs here), identified by comparative genomics in a wide variety of genomes, are non-randomly distributed across chromosomes. These elements are defined using various degrees of conservation between organisms and several thresholds of minimal length. We here investigate the chromosomal distribution of CNEs by studying the statistical properties of distances between consecutive CNEs. We find widespread power-law-like distributions, i.e. linearity in double logarithmic scale, in the inter-CNE distances, a feature which is connected with fractality and self-similarity. Given that CNEs are often found to be spatially associated with genes, especially with those that regulate developmental processes, we verify by appropriate gene masking that a power-law-like pattern emerges irrespectively of whether elements found close or inside genes are excluded or not. An evolutionary model is put forward for the understanding of these findings that includes segmental or whole genome duplication events and eliminations (loss) of most of the duplicated CNEs. Simulations reproduce the main features of the observed size distributions. Power-law-like patterns in the genomic distributions of CNEs are in accordance with current knowledge about their evolutionary history in several genomes. PMID:24787386

  3. Estimating the power law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic data

    NASA Astrophysics Data System (ADS)

    Beskardes, G. D.; Weiss, C. J.; Everett, M. E.

    2013-12-01

    Electromagnetic methods of geophysical exploration are a reflection of the spatio-temporal variability in ground conductivity, a macroscopic physical property that is a function of lithology, pore-scale surface chemistry, fracture networks, and the presence and distribution of fluids and partial melts. As such, the bulk electrical properties of some representative elementary volume within the subsurface derive from the macroscopic effect of charge buildup and current pathways across a range of length scales within. Quantifying this relationship between multiscale electrical properties and the observed geophysical data is a critical step toward meaningful geologic interpretation. Previously we presented evidence of near-surface electromagnetic data whose small scale fluctuations are both repeatable and fractally distributed -- an observation that supports the notion of a spatially hierarchical Earth. Bounded by the end member cases from homogenized isotropic and anisotropic media, we present numerical modeling results from textured and spatially-correlated, stochastic geologic media, demonstrating that the electromagnetic response is a power law distribution similar to that seen in the earlier observational data, rather than a smooth response polluted with Gaussian noise as is commonly assumed. Furthermore, we show that such power law behavior is dependent on correlation length within the medium and that the power law distribution of Earth conductivity can be estimated from that of the observed electromagnetic data.

  4. Capillary force between a probe tip with a power-law profile and a surface or a nanoparticle

    NASA Astrophysics Data System (ADS)

    Wang, Lefeng; Régnier, Stéphane

    2015-01-01

    This paper presents a method to exactly calculate the capillary bridge profile and capillary force between a probe tip with a power-law profile and a surface or nanoparticle at various humidities. The shape of the probe tip is denoted by a power-law profile including a shape index, which is a general extension of the usual parabolids. The accuracy of the usual circular approximation of the capillary bridge is investigated, and it is found that great deviations may occur for capillary bridges and capillary forces at nanoscales, especially for the probe tip with a small shape index. The proportion of the capillary pressure force and the surface tension force which constitute the capillary force is also considered. The results show that the surface tension force can even be dominant at nanoscales. The influences of various parameters, including the shape index, equivalent radius of the tip, relative humidity, contact angles and separation distances, on the capillary force between a probe tip with a power-law profile and a surface or nanoparticle are studied. The rupture distances of the liquid bridges at condensation equilibrium and constant volume conditions are also compared.

  5. Full wave modeling of therapeutic ultrasound: efficient time-domain implementation of the frequency power-law attenuation.

    PubMed

    Liebler, Marko; Ginter, Siegfried; Dreyer, Thomas; Riedlinger, Rainer E

    2004-11-01

    For the simulation of therapeutic ultrasound applications, a method including frequency-dependent attenuation effects directly in the time domain is highly desirable. This paper describes an efficient numerical time-domain implementation of the power-law attenuation model presented by Szabo [Szabo, J. Acoust. Soc. Am. 96, 491-500 (1994)]. Simulations of therapeutic ultrasound applications are feasible in conjunction with a previously presented finite differences time-domain (FDTD) algorithm for nonlinear ultrasound propagation [Ginter et al., J. Acoust. Soc. Am. 111, 2049-2059 (2002)]. Szabo implemented the empirical frequency power-law attenuation using a causal convolutional operator directly in the time-domain equation. Though a variety of time-domain models has been published in recent years, no efficient numerical implementation has been presented so far for frequency power-law attenuation models. Solving a convolutional integral with standard time-domain techniques requires enormous computational effort and therefore often limits the application of such models to 1D problems. In contrast, the presented method is based on a recursive algorithm and requires only three time levels and a few auxiliary data to approximate the convolutional integral with high accuracy. The simulation results are validated by comparison with analytical solutions and measurements. PMID:15603120

  6. Power law relaxation and glassy dynamics in Lebwohl-Lasher model near isotropic-nematic phase transition

    E-print Network

    Suman Chakrabarty; Dwaipayan Chakrabarti; Biman Bagchi

    2006-03-14

    Orientational dynamics in a liquid crystalline system near the isotropic-nematic (I-N) phase transition is studied using Molecular Dynamics simulations of the well-known Lebwohl-Lasher (LL) model. As the I-N transition temperature is approached from the isotropic side, we find that the decay of the orientational time correlation functions (OTCF) slows down noticeably, giving rise to a power law decay at intermediate timescales. The angular velocity time correlation function also exhibits a rather pronounced power law decay near the I-N boundary. In the mean squared angular displacement at comparable timescales, we observe the emergence of a \\emph{subdiffusive regime} which is followed by a \\emph{superdiffusive regime} before the onset of the long-time diffusive behavior. We observe signature of dynamical heterogeneity through \\emph{pronounced non-Gaussian behavior in orientational motion} particularly at lower temperatures. This behavior closely resembles what is usually observed in supercooled liquids. We obtain the free energy as a function of orientational order parameter by the use of transition matrix Monte Carlo method. The free energy surface is flat for the system considered here and the barrier between isotropic and nematic phases is vanishingly small for this weakly first-order phase transition, hence allowing large scale, collective and correlated orientational density fluctuations. This might be responsible for the observed power law decay of the OTCFs.

  7. Accretion-powered Pulsations in an Apparently Quiescent Neutron Star Binary

    NASA Astrophysics Data System (ADS)

    Archibald, Anne M.; Bogdanov, Slavko; Patruno, Alessandro; Hessels, Jason W. T.; Deller, Adam T.; Bassa, Cees; Janssen, Gemma H.; Kaspi, Vicky M.; Lyne, Andrew G.; Stappers, Ben W.; Tendulkar, Shriharsh P.; D’Angelo, Caroline R.; Wijnands, Rudy

    2015-07-01

    Accreting millisecond X-ray pulsars (AMXPs) are an important subset of low-mass X-ray binaries (LMXBs) in which coherent X-ray pulsations can be observed during occasional, bright outbursts (X-ray luminosity {L}{{X}}? {10}36 {erg} {{{s}}}-1). These pulsations show that matter is being channeled onto the neutron star’s magnetic poles. However, such sources spend most of their time in a low-luminosity, quiescent state ({L}{{X}}? {10}34 {erg} {{{s}}}-1), where the nature of the accretion flow onto the neutron star (if any) is not well understood. Here we report that the millisecond pulsar/LMXB transition object PSR J1023+0038 intermittently shows coherent X-ray pulsations at luminosities nearly 100 times fainter than observed in any other AMXP. We conclude that in spite of its low luminosity, PSR J1023+0038 experiences episodes of channeled accretion, a discovery that challenges existing models for accretion onto magnetized neutron stars.

  8. 14 CFR 406.109 - Administrative law judges-powers and limitations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...instruct the party to file with the FDMS, a copy of each document that is submitted to the administrative law judge that has not bee filed with FDMS, except the portions of those documents that contain confidential information. (2) The...

  9. Simple strategies for minimization of cooling water usage in binary power plants

    Microsoft Academic Search

    C. J. Bliem; G. L. Mines

    1989-01-01

    The geothermal resources which could be used for the production of electrical power in the United States are located for the most part in the semi-arid western regions of the country. The availability of ground or surface water in the quantity or quality desired for a conventional wet'' heat rejections system represents a barrier to the development of these resources

  10. XMMNEWTON OBSERVATION DIFFUSE GAS AND LOWMASS XRAY BINARIES THE ELLIPTICAL GALAXY NGC 4649 (M60)

    E-print Network

    Sarazin, Craig

    XMM­NEWTON OBSERVATION DIFFUSE GAS AND LOW­MASS X­RAY BINARIES THE ELLIPTICAL GALAXY NGC 4649 (M60­Newton X­ray observation X­ray--bright elliptical galaxy NGC 4649. In addition bright diffuse emission sources power law, while diffuse spectrum requires a hard and a soft component, presumably relatively

  11. Detection performance of power-law processors for random signals of unknown location, structure, extent, and strength

    SciTech Connect

    Nuttall, A.H. [Naval Undersea Warfare Center, New London, Connecticut 06320 (United States)

    1996-06-01

    A signal (if present) is located somewhere in a band of frequencies characterized by a total of N search bins. The signal occupies an arbitrary set of M{underscore} of these bins, where not only is M{underscore} unknown, but also, the locations of the particular M{underscore} occupied bins are unknown. Also, the signal strength is unknown. A class of processors, called the power-law processors, is investigated, in which the available data is raised to the {nu}-th power prior to summation over all data values. The receiver operating characteristics have been determined for values of power {nu}=1, 2, 2.5, 3, {infinity} for a wide range of values of M{underscore}. These results allow for accurate extraction of required signal-to-noise ratios to achieve a specified level of performance, as measured by the false alarm and detection probabilities, P{sub f} and P{sub d}. One of the most surprising and useful results of this study is the discovery that the power-law processor with {nu}=2.4 performs near the absolute optimum, even without any knowledge of the number of occupied bins M{underscore} or the signal-to-noise ratio. {copyright} {ital 1996 American Institute of Physics.}

  12. The design of linear binary wavelet transforms and their application to binary image compression

    Microsoft Academic Search

    Lute Kamstra

    2003-01-01

    This papers investigates linear binary wavelet transforms: convo- lutions of finite sequences of binary numbers with binary filters. These wavelets can be implemented using binary arithmetic only, which makes calculations simple and fast in practice. The paper presents some results that characterize binary wavelets completely for signal lengths that are powers of two. In addition, a design strategy is proposed

  13. A Low-Power All-Digital Phase-Locked Loop Using Binary Frequency Searching

    Microsoft Academic Search

    Chua-Chin Wang; Tzung-Je Lee; Sheng-Lun Tseng

    We propose a low power ADPLL (All-digital phase-locked loop) by using a controller which employs a bi- nary frequency searching method in this paper. Glitch hazards and timing violations which occurred very often in the prior ADPLL designs are avoided by the control method and the modified DCO (Digital-controlled oscillator) with multiplexers. The proposed design is implemented by only using

  14. A TWO-COMPONENT POWER LAW COVERING NEARLY FOUR ORDERS OF MAGNITUDE IN THE POWER SPECTRUM OF SPITZER FAR-INFRARED EMISSION FROM THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Block, David L. [School of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, WITS 2050 (South Africa); Puerari, Ivanio [Instituto Nacional de Astrofisica, Optica y Electronica, Calle Luis Enrique Erro 1, 72840 Santa MarIa Tonantzintla, Puebla (Mexico); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Bournaud, Frederic, E-mail: bge@us.ibm.co [CEA, IRFU, SAp, F-91191 Gif-sur-Yvette (France)

    2010-07-20

    Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70, and 160 {mu}m observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at k {sup -1} {approx} 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum (PS) covers {approx}3.5 orders of magnitude, and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves, and bars, presumably causes the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks causes the high-k structure in a three-dimensional geometry. This transition in dimensionality corresponds to the observed change in PS slope. A companion paper models the observed power law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.

  15. Analytical and Numerical Solutions for the Case of a Horizontal Well with a Radial Power-Law Permeability Distribution--Comparison to the Multi-Fracture Horizontal Case 

    E-print Network

    Broussard, Ryan Sawyer

    2013-02-08

    with an impermeable outer boundary. The composite reservoir consists of two regions. The cylindrical region closest to the wellbore is stimulated, and the permeability within this region follows a power-law function of the radial distance from the wellbore...

  16. SCALE RESISTANT HEAT EXCHANGER FOR LOW TEMPERATURE GEOTHERMAL BINARY CYCLE POWER PLANT

    SciTech Connect

    HAYS, LANCE G

    2014-11-18

    Phase 1 of the investigation of improvements to low temperature geothermal power systems was completed. The improvements considered were reduction of scaling in heat exchangers and a hermetic turbine generator (eliminating seals, seal system, gearbox, and lube oil system). A scaling test system with several experiments was designed and operated at Coso geothermal resource with brine having a high scaling potential. Several methods were investigated at the brine temperature of 235 ºF. One method, circulation of abradable balls through the brine passages, was found to substantially reduce scale deposits. The test heat exchanger was operated with brine outlet temperatures as low as 125 ºF, which enables increased heat input available to power conversion systems. For advanced low temperature cycles, such as the Variable Phase Cycle (VPC) or Kalina Cycle, the lower brine temperature will result in a 20-30% increase in power production from low temperature resources. A preliminary design of an abradable ball system (ABS) was done for the heat exchanger of the 1 megawatt VPC system at Coso resource. The ABS will be installed and demonstrated in Phase 2 of this project, increasing the power production above that possible with the present 175 ºF brine outlet limit. A hermetic turbine generator (TGH) was designed and manufacturing drawings produced. This unit will use the working fluid (R134a) to lubricate the bearings and cool the generator. The 200 kW turbine directly drives the generator, eliminating a gearbox and lube oil system. Elimination of external seals eliminates the potential of leakage of the refrigerant or hydrocarbon working fluids, resulting in environmental improvement. A similar design has been demonstrated by Energent in an ORC waste heat recovery system. The existing VPC power plant at Coso was modified to enable the “piggyback” demonstration of the TGH. The existing heat exchanger, pumps, and condenser will be operated to provide the required process conditions for the TGH demonstration. Operation of the TGH with and without the ABS system will demonstrate an increase in geothermal resource productivity for the VPC from 1 MW/(million lb) of brine to 1.75 MW/(million lb) of brine, a 75% increase.

  17. Accountability, administrative law and social work practice: Redressing or reinforcing the power imbalance?

    Microsoft Academic Search

    Suzy Braye; Michael Preston-Shoot

    1999-01-01

    Accountability in social care services involves a complex web of obligations to different stakeholders whose demands are not necessarily compatible. This article locates administrative law within the range of mechanisms for ensuring accountability, and evaluates its contribution. It is argued that, in the current policy context, some forms of accountability are promoted over others, and that accountabilities to service users

  18. Feature Extraction for Robust Speech Recognition using a Power-Law Nonlinearity and Power-Bias Subtraction

    E-print Network

    Stern, Richard

    on the gammatone filter shape [3] rather than the triangular frequency weighting or the trape- zoidal frequency.6 ms, with 10 ms between frames for a sampling frequency of 16 kHz, 40 gammatone channels. After passing through the gammatone channel, the power is normalized using peak power (i.e. the Figure 1

  19. What if the power-law model did not apply for the prediction of very large rockfall events?

    NASA Astrophysics Data System (ADS)

    Rohmer, J.; Dewez, T.

    2012-04-01

    Extreme events are of primary importance for risk management in a variety of natural phenomena, and more particularly for landslides and rockfalls, because they might be associated with huge losses. Numerous research works have addressed this problem based on the same paradigm: if events exhibit the same statistical properties across a broad range of sizes, the probability of extreme events can be evaluated by extrapolating the frequency-size distribution. Considering landslides' areas or rockfalls' volumes, the frequency distribution has been found to be heavy-tailed and the well-known power law distribution has been proposed to model it. Yet, the vision of very large extreme event (catastrophic) frequency being an extrapolation of the power laws fitted on small and intermediate events has been challenged in various contexts, in particular by Sornette and co-authors, who proposed viewing such catastrophic events as "outliers" from the power-law model, i.e. they deviate by an abnormal large distance from the extrapolated prediction. In this study, we address such an issue considering a rockfall inventory, containing >8500 events spanning 8 orders of magnitudes of volume and collated from 2.5 years of high-accuracy repeated terrestrial laser scanning (TLS) surveys on a coastal chalk cliff in Normandy (France). This inventory contains a particularly large event of 70,949 m3 which occurred some time between February 1 and 7 April 2008. It is the second largest cliff failure reported in Normandy, and is larger than those collated in historical cliff failure inventories across various geological and geomorphological coastal settings. Is this event an outlier of the power-law volume-frequency distribution ? And if so, why? This largest event recorded appears to stand out of the rest of the sample. We use it to revisit the techniques to fit power-law distribution with robust techniques (robust weighted maximum likelihood estimator), rarely used in rockfall studies, and presenting the appealing feature to be less sensitive to the presence of outliers by assigning a weight within [0 ; 1] to each observation according to its representativeness. Through a bootstrap-based technique, we demonstrate the statistical significance (with p-value <1 %, i.e. not arising by chance) of the low weight assigned to the largest rockfall event i.e. of the deviation from the fractal set of the smaller events. Excluding gross volumetric error on our observation since we used a high-accuracy TLS, we discuss possible mechanisms and their implications for prediction, focusing on two main issues: 1. normal faults bounding the largest rockfall and along which the rupture occurred, which may suggest the hypothesis of a "characteristic" rockfall, i.e. presenting a characteristic scale of the same order of the fault length, as suggested for earthquakes; 2. possible log-periodic signature that decorates the pure power law and linked with the concept of Discrete Scale Invariance. This concept means that scale invariance is kept, but only for specific scales organized in a discrete hierarchy and with some fixed preferred scaling ratio. Such scaling ratio may itself be linked to pre-existing fracture networks.

  20. Design of a condenser-boiler for a binary mercury-organic Rankine-cycle solar-dynamic space-power system. Final report

    Microsoft Academic Search

    1987-01-01

    A theoretical design was performed for the condenser\\/boiler of a space-based solar-dynamic power system. The base system is a binary Rankine cycle with mercury and toluene, as the working fluids. System output is 75 KWe with a combined efficiency of 41.1%. Design goals were to develop the most-reliable, mass-efficient unit possible for delivery to a space station. The design sized

  1. Power-Law Fading of the Frustration Effect in a Periodic Rectangular Superconducting Network with Increasing Aspect Ratio 

    E-print Network

    Hu, Chia-Ren; CHEN, RL.

    1988-01-01

    PHYSICAL REVIEWS 8 VOLUME 37, NUMBER 13 1 MAY 1988 Power-law fading of the frnstration eS'ect in a periodic rectanlnlar snpercondncting neiwork with increasing aspect ratio Chia-Ren Hu and Raymond Lei Chen Department of Physics, Center.... This means that those cusps in the T,2/T, o vs @/@p curve asso- ciated with a larger integer denominator q fade away fas- ter than those associated with a smaller q, leaving a less CHIA-REN HU AND RAYMOND I.EI CHEN "jerky" T,q/T, o vs +/4p curve at larger...

  2. Hydraulic properties of two-dimensional random fracture networks following a power law length distribution: 1. Effective connectivity

    NASA Astrophysics Data System (ADS)

    de Dreuzy, Jean-Raynald; Davy, Philippe; Bour, Olivier

    2001-08-01

    Natural fracture networks involve a very broad range of fractures of variable lengths and apertures, modeled, in general, by a power law length distribution and a lognormal aperture distribution. The objective of this two-part paper is to characterize the permeability variations as well as the relevant flow structure of two-dimensional isotropic models of fracture networks as determined by the fracture length and aperture distributions and by the other parameters of the model (such as density and scale). In this paper we study the sole influence of the fracture length distribution on permeability by assigning the same aperture to all fractures. In the following paper [de Dreuzy et al., this issue] we study the more general case of networks in which fractures have both length and aperture distributions. Theoretical and numerical studies show that the hydraulic properties of power law length fracture networks can be classified into three types of simplified model. If a power law length distribution n (l) ˜ l-a is used in the network design, the classical percolation model based on a population of small fractures is applicable for a power law exponent a higher than 3. For a lower than 2, on the contrary, the applicable model is the one made up of the largest fractures of the network. Between these two limits, i.e., for a in the range 2-3, neither of the previous simplified models can be applied so that a simplified two-scale structure is proposed. For this latter model the crossover scale is the classical correlation length, defined in the percolation theory, above which networks can be homogenized and below which networks have a multipath, multisegment structure. Moreover, the determination of the effective fracture length range, within which fractures significantly contribute to flow, corroborates the relevance of the previous models and clarifies their geometrical characteristics. Finally, whatever the exponent a, the sole significant scale effect is a decrease of the equivalent permeability for networks below or at percolation threshold.

  3. Origins of Taylor's power law for fluctuation scaling in complex systems

    NASA Astrophysics Data System (ADS)

    Fronczak, Agata; Fronczak, Piotr

    2010-06-01

    Taylor’s fluctuation scaling (FS) has been observed in many natural and man-made systems revealing an amazing universality of the law. Here, we give a reliable explanation for the origins and abundance of Taylor’s FS in different complex systems. The universality of our approach is validated against real world data ranging from bird and insect populations through human chromosomes and traffic intensity in transportation networks to stock market dynamics. Using fundamental principles of statistical physics (both equilibrium and nonequilibrium) we prove that Taylor’s law results from the well-defined number of states of a system characterized by the same value of a macroscopic parameter (i.e., the number of birds observed in a given area, traffic intensity measured as a number of cars passing trough a given observation point or daily activity in the stock market measured in millions of dollars).

  4. A DEEP CHANDRA OBSERVATION OF THE WOLF-RAYET + BLACK HOLE BINARY NGC 300 X-1

    SciTech Connect

    Binder, B.; Williams, B. F.; Anderson, S. F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Eracleous, M. [Department of Astronomy and Astrophysics and Center for Gravitational Wave Physics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Garcia, M. R.; Gaetz, T. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2011-12-01

    We have obtained a 63 ks Chandra ACIS-I observation of the Wolf-Rayet + black hole binary NGC 300 X-1. We measure rapid low-amplitude variability in the 0.35-8 keV light curve. The power density spectrum has a power-law index {gamma} = 1.02 {+-} 0.15 consistent with an accreting black hole in a steep power-law state. When compared to previous studies of NGC 300 X-1 performed with XMM-Newton, we find the source at the low end of the previously measured 0.3-10 keV luminosity. The spectrum of NGC 300 X-1 is dominated by a power law ({Gamma} = 2.0 {+-} 0.3) with a contribution at low energies by a thermal component. We estimate the 0.3-10 keV luminosity to be 2.6{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 38} erg s{sup -1}. The timing and spectroscopic properties of NGC 300 X-1 are consistent with being in a steep power-law state, similar to earlier observations performed with XMM-Newton. We additionally compare our observations to known high-mass X-ray binaries and ultraluminous X-ray sources, and find the properties of NGC 300 X-1 are most consistent with black hole high-mass X-ray binaries.

  5. Imaging surface contacts: Power law contact distributions and contact stresses in quartz, calcite, glass and acrylic plastic

    USGS Publications Warehouse

    Dieterich, J.H.; Kilgore, B.D.

    1996-01-01

    A procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials, while the surfaces are subjected to static loads or undergoing frictional slip. Static loading experiments with quartz, calcite, soda-lime glass and acrylic plastic at normal stresses to 30 MPa yield power law distributions of contact areas from the smallest contacts that can be resolved (3.5 ??m2) up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces. In each material, increasing normal stress results in a roughly linear increase of the real area of contact. Mechanisms of contact area increase are by growth of existing contacts, coalescence of contacts and appearance of new contacts. Mean contacts stresses are consistent with the indentation strength of each material. Contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self-similar. The contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies. The contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap. Synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography.

  6. One-dimensional lattice of oscillators coupled through power-law interactions: continuum limit and dynamics of spatial Fourier modes.

    PubMed

    Gupta, Shamik; Potters, Max; Ruffo, Stefano

    2012-06-01

    We study synchronization in a system of phase-only oscillators residing on the sites of a one-dimensional periodic lattice. The oscillators interact with a strength that decays as a power law of the separation along the lattice length and is normalized by a size-dependent constant. The exponent ? of the power law is taken in the range 0??<1. The oscillator frequency distribution is symmetric about its mean (taken to be zero) and is nonincreasing on [0,?). In the continuum limit, the local density of oscillators evolves in time following the continuity equation that expresses the conservation of the number of oscillators of each frequency under the dynamics. This equation admits as a stationary solution the unsynchronized state uniform both in phase and over the space of the lattice. We perform a linear stability analysis of this state to show that when it is unstable, different spatial Fourier modes of fluctuations have different stability thresholds beyond which they grow exponentially in time with rates that depend on the Fourier modes. However, numerical simulations show that at long times all the nonzero Fourier modes decay in time, while only the zero Fourier mode (i.e., the "mean-field" mode) grows in time, thereby dominating the instability process and driving the system to a synchronized state. Our theoretical analysis is supported by extensive numerical simulations. PMID:23005190

  7. Improving the air coupling of bulk piezoelectric transducers with wedges of power-law profiles: a numerical study.

    PubMed

    Remillieux, Marcel C; Anderson, Brian E; Le Bas, Pierre-Yves; Ulrich, T J

    2014-07-01

    An air-coupled ultrasonic transducer is created by bonding a bulk piezoelectric element onto the surface of a thick plate with a wedge of power-law profile. The wedge is used to improve the ultrasonic radiation efficiency. The power-law profile provides a smooth, impedance-matching transition for the mechanical energy to be transferred from the thick plate to the air, through the large-amplitude flexural waves observed in the thinnest region of the wedge. The performance of the proposed transducer is examined numerically and compared to that of a design where the piezoelectric element is isolated and where it is affixed to a thin plate of uniform thickness. The numerical analysis is first focused on the free-field radiation of the transducers. Then, time-reversal experiments are simulated by placing the transducers inside a cavity of arbitrary shape with some perfectly reflecting boundaries. In addition to time-reversal mirrors, the proposed concept could be integrated in the design of phased arrays and parametric arrays. PMID:24636675

  8. Evidence for mild deviation from power-law distribution of electrons in relativistic shocks: GRB 090902B

    E-print Network

    Duran, Rodolfo Barniol

    2011-01-01

    Many previous studies have determined that the long lasting emission at X-ray, optical and radio wavelengths from gamma-ray bursts (GRBs), called the afterglow, is likely produced by the external forward shock model. In this model, the GRB jet interacts with the circum-stellar medium and drives a shock that heats the medium, which radiates via synchrotron emission. In this work, we carried out a detailed analysis of the late time afterglow data of GRB 090902B using a very careful accounting of the Inverse Compton losses. We find that in the context of the external forward shock model, the only viable option to explain the X-ray and optical data of GRB 090920B is to have the electron energy distribution deviate from a power-law shape and exhibit some slight curvature immediately downstream of the shock front (we explored other models that rely on a single power-law assumption, but they all fail to explain the observations). We find the fraction of the energy of shocked plasma in magnetic field to be ~10^{-6} u...

  9. Analytic and finite element solutions of the power-law Euler-Bernoulli beams

    Microsoft Academic Search

    Dongming Wei; Yu Liu

    2012-01-01

    In this paper, we use Hermite cubic finite elements to approximate the solutions\\u000aof a nonlinear Euler-Bernoulli beam equation. The equation is derived\\u000afrom Hollomon’s generalized Hooke’s law for work hardening materials with\\u000athe assumptions of the Euler-Bernoulli beam theory. The Ritz-Galerkin finite\\u000aelement procedure is used to form a finite dimensional nonlinear program\\u000aproblem, and a nonlinear conjugate gradient

  10. Output power analyses of an endoreversible Carnot heat engine with irreversible heat transfer processes based on generalized heat transfer law

    NASA Astrophysics Data System (ADS)

    Wu, Yan-Qiu

    2015-07-01

    In this paper, an endoreversible Carnot heat engine with irreversible heat transfer processes is analyzed based on generalized heat transfer law. The applicability of the entropy generation minimization, exergy analyses method, and entransy theory to the analyses is discussed. Three numerical cases are presented. It is shown that the results obtained from the entransy theory are different from those from the entropy generation minimization, which is equivalent to the exergy analyses method. For the first case in which the application preconditions of the entropy generation minimization and entransy loss maximization are satisfied, both smaller entropy generation rate and larger entransy loss rate lead to larger output power. For the second and third cases in which the preconditions are not satisfied, the entropy generation minimization does not lead to the maximum output power, while larger entransy loss rate still leads to larger output power in the third case. For the discussed cases, the concept of entransy dissipation is not applicable for the analyses of output power. The problems in the negative comments on the entransy theory are pointed out and discussed. The related researchers are advised to focus on some new specific application cases to show if the entransy theory is the same as some other theories. Project supported by the Youth Programs of Chongqing Three Gorges University, China (Grant No. 13QN18).

  11. Human Embryonic and Induced Pluripotent Stem Cell–Derived Cardiomyocytes Exhibit Beat Rate Variability and Power-Law Behavior

    PubMed Central

    Mandel, Yael; Weissman, Amir; Schick, Revital; Barad, Lili; Novak, Atara; Meiry, Gideon; Goldberg, Stanislav; Lorber, Avraham; Rosen, Michael R.; Itskovitz-Eldor, Joseph; Binah, Ofer

    2013-01-01

    Background The sinoatrial node is the main impulse-generating tissue in the heart. Atrioventricular conduction block and arrhythmias caused by sinoatrial node dysfunction are clinically important and generally treated with electronic pacemakers. Although an excellent solution, electronic pacemakers incorporate limitations that have stimulated research on biological pacing. To assess the suitability of potential biological pacemakers, we tested the hypothesis that the spontaneous electric activity of human embryonic stem cell– derived cardiomyocytes (hESC-CMs) and induced pluripotent stem cell– derived cardiomyocytes (iPSC-CMs) exhibit beat rate variability and power-law behavior comparable to those of human sinoatrial node. Methods and Results We recorded extracellular electrograms from hESC-CMs and iPSC-CMs under stable conditions for up to 15 days. The beat rate time series of the spontaneous activity were examined in terms of their power spectral density and additional methods derived from nonlinear dynamics. The major findings were that the mean beat rate of hESC-CMs and iPSC-CMs was stable throughout the 15-day follow-up period and was similar in both cell types, that hESC-CMs and iPSC-CMs exhibited intrinsic beat rate variability and fractal behavior, and that isoproterenol increased and carbamylcholine decreased the beating rate in both hESC-CMs and iPSC-CMs. Conclusions This is the first study demonstrating that hESC-CMs and iPSC-CMs exhibit beat rate variability and power-law behavior as in humans, thus supporting the potential capability of these cell sources to serve as biological pacemakers. Our ability to generate sinoatrial-compatible spontaneous cardiomyocytes from the patient’s own hair (via keratinocyte-derived iPSCs), thus eliminating the critical need for immunosuppression, renders these myocytes an attractive cell source as biological pacemakers. PMID:22261196

  12. The orbital eccentricities of binary millisecond pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Rasio, Frederic A.; Heggie, Douglas C.

    1995-01-01

    Low-mass binary millisecond pulsars (LMBPs) are born with very small orbital eccentricities, typically of order e(sub i) approximately 10(exp -6) to 10(exp -3). In globular clusters, however, higher eccentricities e(sub f) much greater than e(sub i) can be induced by dynamical interactions with passing stars. Here we show that the cross section for this process is much larger than previously estimated. This is becuse, even for initially circular binaries, the induced eccentricity e(sub f) for an encounter with pericenter separation r(sub p) beyond a few times the binary semimajor axis a declines only as a power law (e(sub f) varies as (r(sub p)/a)(exp -5/2), and not as an exponential. We find that all currently known LMBPs in clusters were probably affected by interactions, with their current eccentricities typically greater than at birth by an order of magnitude or more.

  13. Power law rheology of ice and the relaxation style and retention of craters on Ganymede

    NASA Technical Reports Server (NTRS)

    Thomas, Paul J.; Schubert, Gerald

    1988-01-01

    A numerical finite element model of viscous relaxation of craters in ice is presented which incorporates rheological data for ice at temperatures and pressures appropriated to the near-surface regions of Ganymede. For temperature gradients in reasonable agreement with those obtained from thermal and structural models of Ganymede, relaxation times greater than 10 to the 7th years were obtained for craters with diameters less than 100 km. For all craters with diameters greater than 10 km, the dependence of viscosity on stress was found to significantly shorten the relaxation time. The rheological laws which dominate crater relaxation are discussed for craters of various sizes. The results are compared with imagery from Voyager.

  14. Raising food hygiene standards--could customer power and the new laws hold the key?

    PubMed

    Leach, J C

    1996-12-01

    In September 1995 new general food hygiene regulations came into force. The new law, quite rightly, requires proprietors of food businesses to focus their thoughts and actions on risks to food safety. Proprietors are required to identify and assess risks and ensure that adequate management procedures are put into place to ensure food safety. This is a welcome move as contributing factors in most cases of food poisoning involve poor food hygiene practices. At the same time there has been a large increase in the amount of advice and guidance to local authority enforcement officers, particularly to assess risks to food safety when considering what action to take in any situation - the lower the risk the less appropriate it is to take legal action. However, there are many conditions found in food premises which present little or no risk to health, such as routine cleanliness in non-high risk areas, but lower standards on these might be viewed by the public as inappropriate for food businesses. With an increasing amount of choice available to customers, proprietors and managers of food businesses need to be more aware than ever of the complex pattern of consumer demands including that of supplying a clean and safe product in its broadest sense. The notion of consumer sovereignty is not a new concept. Combined with the new laws could it hold the key to genuine improved standards in food hygiene? This article reviews the subject and draws attention to a research programme being undertaken at the University of Brighton to identify, compare and contrast factors which the public perceive as important in terms of food hygiene in public eating places with those considered important by professionals with an interest in the subject. The results could bring benefits to the catering industry and customers. PMID:8987337

  15. From Hillary Clinton to Lady Macbeth: Or, Historicizing Gender, Law, and Power Through Shakespeare's Scottish Play

    Microsoft Academic Search

    Carla Spivack

    2008-01-01

    Female rule was anomalous in the sixteenth century, therefore, Elizabeth I developed a complex set of symbols, rooted in claims traditionally made by male rulers, to legitimate her claim to rule. Nonetheless, her reign was anxiety-provoking, and this article argues that the years after her death saw a backlash against female power. Part of this backlash consisted of the reworking

  16. Inverse power-law like crack growth in earth materials and its possible origin as an emergent property of localisation

    NASA Astrophysics Data System (ADS)

    Lennartz, S.; Main, I. G.; Zaiser, M.; Graham, C. C.; Stanchits, S.; Dresen, G.

    2012-04-01

    The origin and development of cracks in Earth materials is a subject of general interest and wide application: from seismologists studying earthquakes to engineers studying the strength of materials. Therefore many laboratory experiments have been carried out to investigate the response of rocks to an applied differential stress, often using acoustic emissions (AE) to track intermittent crack growth inside the rock specimen prior to system-sized sample failure. Under a constant applied stress in double-torsion tensile tests with a guide groove and a single dominant crack, independent observations of the stress intensity factor and crack growth velocity imply the size of the largest (sub-) critical crack C grows with time t according to an inverse power-law C(t)=C(0)(1-t/t_f)-nu, where tf is the failure time and the exponent {nu} is a constant. A similar law holds for the mean crack length in a population of micro-cracks growing under compressional stress with no pre-defined fault plane, often treated using mean field models that ignore localisation of damage clearly seen in the experiments. Here we present a new hypothesis for the origin of this formula by combining expressions for crack population growth and localisation in a single model. The model is tested and some of its parameters inferred from analysis of the AE rate and the spatial clustering of its source locations from laboratory data.

  17. Power-law correlations in finance-related Google searches, and their cross-correlations with volatility and traded volume: Evidence from the Dow Jones Industrial components

    E-print Network

    Kristoufek, Ladislav

    2015-01-01

    We study power-law correlations properties of the Google search queries for Dow Jones Industrial Average (DJIA) component stocks. Examining the daily data of the searched terms with a combination of the rescaled range and rescaled variance tests together with the detrended fluctuation analysis, we show that the searches are in fact power-law correlated with Hurst exponents between 0.8 and 1.1. The general interest in the DJIA stocks is thus strongly persistent. We further reinvestigate the cross-correlation structure between the searches, traded volume and volatility of the component stocks using the detrended cross-correlation and detrending moving-average cross-correlation coefficients. Contrary to the universal power-law correlations structure of the related Google searches, the results suggest that there is no universal relationship between the online search queries and the analyzed financial measures. Even though we confirm positive correlation for a majority of pairs, there are several pairs with insign...

  18. Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

    NASA Astrophysics Data System (ADS)

    Wen, Rui-Tao; Granqvist, Claes G.; Niklasson, Gunnar A.

    2014-10-01

    Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 104 cycles when the applied voltage was limited to 4.1 V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a "smart window" for energy-efficient buildings.

  19. Evidence for mild deviation from power-law distribution of electrons in relativistic shocks: GRB 090902B

    NASA Astrophysics Data System (ADS)

    Barniol Duran, R.; Kumar, P.

    2011-10-01

    Many previous studies have determined that the long lasting emission at X-ray, optical and radio wavelengths from gamma-ray bursts (GRBs), called the afterglow, is likely produced by the external forward shock model. In this model, the GRB jet interacts with the circum-stellar medium and drives a shock that heats the medium, which radiates via synchrotron emission. In this work, we carried out a detailed analysis of the late time afterglow data of GRB 090902B using a very careful accounting of the Inverse Compton losses. We find that in the context of the external forward shock model, the only viable option to explain the X-ray and optical data of GRB 090920B is to have the electron energy distribution deviate from a power-law shape and exhibit some slight curvature immediately downstream of the shock front (we explored other models that rely on a single power-law assumption, but they all fail to explain the observations). We find the fraction of the energy of shocked plasma in magnetic field to be ˜10-6 using late time afterglow data, which is consistent with the value obtained using early gamma-ray data. Studies like the present one might be able to provide a link between GRB afterglow modelling and numerical simulations of particle acceleration in collisionless shocks. We also provide detailed calculations for the early (? 103 s) high-energy (>100 MeV) emission and confirm that it is consistent with origin in the external forward shock. We investigated the possibility that the ˜10 keV excess observed in the spectrum during the prompt phase also has its origin in the external shock and found the answer to be negative.

  20. The effect of NPS calculation method on power-law coefficient estimation accuracy in breast texture modeling

    NASA Astrophysics Data System (ADS)

    Li, Zhijin; Carton, Ann-Katherine; Muller, Serge; Iordache, R?zvan; Desolneux, Agnès.

    2015-03-01

    In breast X-ray imaging, breast texture has been characterized by a radial noise power spectrum (NPS) that has an inverse power-law shape with exponent ?. The technique to estimate the radial power-law coefficient ? is typically based on averaging 2-dimensional noise power spectra (NPS), calculated from partly overlapping image regions each weighted by a suitable window function. The linear regression applied over a selected frequency range to the logarithm of the 1- dimensional NPS as a function of the logarithm of the radial frequencies, gives ?. For each step in this process, several alternative techniques have been proposed. This paper investigates the effect of image region of interest (ROI) size, image data windowing and alternative ways to determine radial frequency in terms of bias, variance and root mean square error (RMSE) in the estimated ?. The effects of these three factors were analytically derived and evaluated using synthetic images with known ? varying from 1 to 4 to cover the range of textures encountered in 2D and 3D breast X-ray imaging. Our results indicate that the RMSE in estimated ? is smallest when the ROIs are multiplied with an appropriate window function and either no radial averaging or radial averaging with small frequency bins is applied. The ROI size yielding the smallest RMSE depends on several factors and needs to be validated with numerical simulations. In clinical practice however, there might be a need to compromise in the choice of the ROI size to balance between the RMSE magnitudes inherent to the applied ? estimation technique and encompass the breast texture range so as to obtain an accurate shape of the NPS. When using 2.56 cm x 2.56 cm ROI sizes, applying a 2D Hann window and no radial frequency averaging, the RMSE in the estimated ? ranges from 0.04 to 0.1 for true ? values equal to 1 and 4. While many subtleties in real images were not modeled to simplify the mathematics in deriving our results, this work is illustrative in demonstrating the limits of commonly used algorithm steps to estimate accurate ? values.

  1. A Novel Redundant Binary Number to Natural Binary Number Converter

    Microsoft Academic Search

    S. K. Sahoo; Anu Gupta; Abhijit R. Asati; Chandra Shekhar

    2010-01-01

    Redundant binary number appears to be appropriate for high-speed arithmetic operation, but the delay and hardware cost associated\\u000a with the conversion from redundant binary (RB) to natural binary (NB) number is still a challenging task. In the present investigation\\u000a a simple approach has been adopted to achieve high speed with lesser hardware and power saving. A circuit level approach has

  2. Power-Law NLED-Based Magnetic Universe Can Mimic Phantom Behavior

    E-print Network

    Ricardo García-Salcedo; Tame Gonzalez; Claudia Moreno; Israel Quiros

    2010-09-27

    We study the cosmic dynamics of a magnetic universe supported by non-linear electrodynamics (NLED) Lagrangeans that are proportional to powers of the electromagnetic invariant $\\propto F^{1/(1-m)}$ ($m$ is an overall constant). For simplicity we focus in the case when $F$ depends on the magnetic field alone, a case dubbed in the bibliography as ''magnetic universe''. Our results demonstrate that, depending on the values of the free parameter $m$, the magnetic field can mimic phantom field behavior, an effect previously found in other contexts. It is demonstrated that, since there are found equilibrium points in the phase space of these models that can be associated with magnetic-dominated past and future attractors, a combination of positive and negative powers of $F$ may lead to interesting cosmological behavior. In particular, a cosmological scenario where the universe might evolve from a past NLED-driven (non-inflationary) state into a future (late-time) -- also NLED-driven -- inflationary stage, transiting through a matter-dominated solution, is envisioned. The impact of braneworld gravity on the dynamics driven by such NLED Lagrangeans is also investigated. It is demonstrated that, due to phantom property at late times, the non-linear electromagnetic effects may play an important role in deciding the fate of the cosmic evolution. Randall-Sundrum brane effects, in particular, modify the nature of the starting point of the cosmic evolution, as well as the fate of the expansion: both, the big bang singularity and the big rip event -- inherent in general relativity with phantom matter source --, may be avoided.

  3. ACCURACY IN THE DETERMINATIONOF THE NIR EXTINCTION POWER LAW INDEX. D. Froebrich, C. del Burgo, Dublin Institute for Advanced Studies, School of Cosmic Physics, Ireland (df@cp.dias.ie).

    E-print Network

    Froebrich, Dirk

    ACCURACY IN THE DETERMINATIONOF THE NIR EXTINCTION POWER LAW INDEX. D. Froebrich, C. del Burgo of extinction (absorption plus scattering) and how it depends on the wavelength (reddening law), allows us­ versal extinction law for the diffuse ISM (Draine 2003). In translucent and dense regions, however

  4. Analytical Derivation of the Closed-Form Power Law $J$ –$V$ Model of an Illuminated Solar Cell From the Physics Based Implicit Model

    Microsoft Academic Search

    Abhik Kumar Das; Shreepad Karmalkar

    2011-01-01

    Recently, we introduced a simple power law model (PLM) to represent the J -V characteristics of an illuminated solar cell with parasitic resistances. The model is useful for design, characterization, and parameter extraction of solar cells and mod- ules. The form of this model was arrived at by intuition, and its applicability to a few moderate-quality cells with bias-independent photocurrent

  5. Low-frequency crossover of the fractional power-law conductivity in SrRuO3 J.S. Dodge,

    E-print Network

    Low-frequency crossover of the fractional power-law conductivity in SrRuO3 * J.S. Dodge, 1,2 C optical conductivity (, T) of one such material, the ferromagnetic metal SrRuO3 [5­8], behaves according reflectivity studies indicate that both high-Tc superconductors and SrRuO3 exhibit conductivity

  6. A compact split step Padé scheme for higher-order nonlinear Schrödinger equation (HNLS) with power law nonlinearity and fourth order dispersion

    Microsoft Academic Search

    Moussa Smadi; Derradji Bahloul

    2011-01-01

    In this paper we propose a compact split step Padé scheme (CSSPS) to solve the scalar higher-order nonlinear Schrödinger equation (HNLS) with higher-order linear and nonlinear effects such as the third and fourth order dispersion effects, Kerr dispersion, stimulated Raman scattering and power law nonlinearity. The stability of this method has been proved. It has been shown as well that

  7. Detecting Long-range Power-law Correlations in Financial Time Series: A Case on Listed Companies of Taiwan Stock Market

    Microsoft Academic Search

    Huei-Huang Chen; Yi-Lin Huang

    2004-01-01

    In time series analysis, there have been many statistic models widely used; some models could estimate long memory. A new idea for analyzing time series is Detrended Fluctuation Analysis (DFA), which was originally developed for finding long-rage power-law correlations in DNA sequences. We apply DFA to Taiwan stock market for three categories of data: TAIEX (Taiwan Stock Exchange Capitalization Weighted

  8. Power law behavior of RR-interval variability in healthy middle-aged persons, patients with recent acute myocardial infarction, and patients with heart transplants

    NASA Technical Reports Server (NTRS)

    Bigger, J. T. Jr; Steinman, R. C.; Rolnitzky, L. M.; Fleiss, J. L.; Albrecht, P.; Cohen, R. J.

    1996-01-01

    BACKGROUND. The purposes of the present study were (1) to establish normal values for the regression of log(power) on log(frequency) for, RR-interval fluctuations in healthy middle-aged persons, (2) to determine the effects of myocardial infarction on the regression of log(power) on log(frequency), (3) to determine the effect of cardiac denervation on the regression of log(power) on log(frequency), and (4) to assess the ability of power law regression parameters to predict death after myocardial infarction. METHODS AND RESULTS. We studied three groups: (1) 715 patients with recent myocardial infarction; (2) 274 healthy persons age and sex matched to the infarct sample; and (3) 19 patients with heart transplants. Twenty-four-hour RR-interval power spectra were computed using fast Fourier transforms and log(power) was regressed on log(frequency) between 10(-4) and 10(-2) Hz. There was a power law relation between log(power) and log(frequency). That is, the function described a descending straight line that had a slope of approximately -1 in healthy subjects. For the myocardial infarction group, the regression line for log(power) on log(frequency) was shifted downward and had a steeper negative slope (-1.15). The transplant (denervated) group showed a larger downward shift in the regression line and a much steeper negative slope (-2.08). The correlation between traditional power spectral bands and slope was weak, and that with log(power) at 10(-4) Hz was only moderate. Slope and log(power) at 10(-4) Hz were used to predict mortality and were compared with the predictive value of traditional power spectral bands. Slope and log(power) at 10(-4) Hz were excellent predictors of all-cause mortality or arrhythmic death. To optimize the prediction of death, we calculated a log(power) intercept that was uncorrelated with the slope of the power law regression line. We found that the combination of slope and zero-correlation log(power) was an outstanding predictor, with a relative risk of > 10, and was better than any combination of the traditional power spectral bands. The combination of slope and log(power) at 10(-4) Hz also was an excellent predictor of death after myocardial infarction. CONCLUSIONS. Myocardial infarction or denervation of the heart causes a steeper slope and decreased height of the power law regression relation between log(power) and log(frequency) of RR-interval fluctuations. Individually and, especially, combined, the power law regression parameters are excellent predictors of death of any cause or arrhythmic death and predict these outcomes better than the traditional power spectral bands.

  9. Profitability Comparison Between Gas Turbines and Gas Engine in Biomass-Based Power Plants Using Binary Particle Swarm Optimization

    Microsoft Academic Search

    P. Reche López; M. Gómez González; N. Ruiz Reyes; F. Jurado

    2007-01-01

    This paper employs a binary discrete version of the classical Particle Swarm Optimization to compare the maximum net present\\u000a value achieved by a gas turbines biomass plant and a gas engine biomass plant. The proposed algorithm determines the optimal\\u000a location for biomass turbines plant and biomass gas engine plant in order to choose the most profitable between them. Forest\\u000a residues

  10. A GENERALIZED POWER-LAW DIAGNOSTIC FOR INFRARED GALAXIES AT z > 1: ACTIVE GALACTIC NUCLEI AND HOT INTERSTELLAR DUST

    SciTech Connect

    Caputi, K. I., E-mail: karina@astro.rug.nl [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)

    2013-05-10

    I present a generalized power-law (PL) diagnostic which allows one to identify the presence of active galactic nuclei (AGNs) in infrared (IR) galaxies at z > 1, down to flux densities at which the extragalactic IR background is mostly resolved. I derive this diagnostic from the analysis of 174 galaxies with S{sub {nu}}(24 {mu}m)>80 {mu}Jy and spectroscopic redshifts z{sub spec} > 1 in the Chandra Deep Field South, for which I study the rest-frame UV/optical/near-IR spectral energy distributions (SEDs), after subtracting a hot-dust, PL component with three possible spectral indices {alpha} = 1.3, 2.0, and 3.0. I obtain that 35% of these 24 {mu}m sources are power-law composite galaxies (PLCGs), which I define as those galaxies for which the SED fitting with stellar templates, without any previous PL subtraction, can be rejected with >2{sigma} confidence. Subtracting the PL component from the PLCG SEDs produces stellar mass correction factors <1.5 in >80% of cases. The PLCG incidence is especially high (47%) at 1.0 < z < 1.5. To unveil which PLCGs host AGNs, I conduct a combined analysis of 4 Ms X-ray data, galaxy morphologies, and a graybody modeling of the hot dust. I find that (1) 77% of all the X-ray AGNs in my 24 {mu}m sample at 1.0 < z < 1.5 are recognized by the PLCG criterion; (2) PLCGs with {alpha} = 1.3 or 2.0 have regular morphologies and T{sub dust} {approx}> 1000 K, indicating nuclear activity. Instead, PLCGs with {alpha} = 3.0 are characterized by disturbed galaxy dynamics, and a hot interstellar medium can explain their dust temperatures T{sub dust} {approx} 700-800 K. Overall, my results indicate that the fraction of AGNs among 24 {mu}m sources is between {approx}30% and 52% at 1.0 < z < 1.5.

  11. An Inverse Power-Law Distribution of Molecular Bond Lifetimes Predicts Fractional Derivative Viscoelasticity in Biological Tissue

    PubMed Central

    Palmer, Bradley M.; Tanner, Bertrand C.W.; Toth, Michael J.; Miller, Mark S.

    2013-01-01

    Viscoelastic characteristics of many materials falling under the category of soft glassy substances, including biological tissue, often exhibit a mechanical complex modulus Y(?) well described by a fractional derivative model: Y(?) = E(i?/?)k, where E = a generalized viscoelastic stiffness; i = (?1)1/2; ? = angular frequency; ? = scaling factor; and k = an exponent valued between 0 and 1. The term “fractional derivative” refers to the value of k: when k = 0 the viscoelastic response is purely elastic, and when k = 1 the response is purely viscous. We provide an analytical derivation of the fractional derivative complex modulus based on the hypothesis that the viscoelastic response arises from many intermittent molecular crosslinks, whose lifetimes longer than a critical threshold lifetime, tcrit, are distributed with an inverse power law proportional to t-(k+2). We demonstrate that E is proportional to the number and stiffness of crosslinks formed at any moment; the scaling factor ? is equivalent to reciprocal of tcrit; and the relative mean lifetime of the attached crosslinks is inversely proportional to the parameter k. To test whether electrostatic molecular bonds could be responsible for the fractional derivative viscoelasticity, we used chemically skinned human skeletal muscle as a one-dimensional model of a soft glassy substance. A reduction in ionic strength from 175 to 110 mEq resulted in a larger E with no change in k, consistent with a higher probability of interfilament molecular interactions. Thick to thin filament spacing was reduced by applying 4% w/v of the osmolyte Dextran T500, which also resulted in a larger E, indicating a greater probability of crosslink formation in proportion to proximity. A 10°C increase in temperature resulted in an increase in k, which corresponded to a decrease in cross-bridge attachment lifetime expected with higher temperatures. These theoretical and experimental results suggest that the fractional derivative viscoelasticity observed in some biological tissue arises as a mechanical consequence of electrostatic interactions, whose longest lifetimes are distributed with an inverse power law. PMID:23746527

  12. Wavelength-dependent power-law Josephson photoresponse of a Tl2Ba2CaCu2O8 thin film

    NASA Astrophysics Data System (ADS)

    Huggard, P. G.; Schneider, Gi.; Richter, C.; Rickler, R.; Prettl, W.

    1994-04-01

    The Josephson photoresponse of a current biased granular Tl2Ba2CaCu2O8 thin film has been measured at 4.2 K for radiation frequencies ? in the range 20-111 cm-1. The resulting photosignal s depends nonlinearly on the incident power P satisfying the relationship s=K(?)P?(?), where K is a frequency-dependent constant. The value of ? increases monotonically from 0.5 at 20.2 cm-1 to 0.9 at 111 cm-1. At 20.2 cm-1 this power law is valid for incident powers between 5 mW and 1 kW, a range of more than 105. These limits are imposed by experimental constraints and not by deviations from the power-law behavior. As the frequency increases, the responsivity of the film drops strongly, K(?) decreasing approximately as ?-3, so that the power-law validity is established over three orders of magnitude at 111 cm-1. Such a behavior of the Josephson photoresponse has been previously observed, albeit over reduced dynamic ranges, in granular superconducting films of other materials. Thus we believe it to be an inherent characteristic of the random arrays of Josephson junctions contained in such films.

  13. Statistical mechanics of aggregation in anisotropic solvents: kinetic energy of aggregates and universal power-law behavior far from criticality

    NASA Astrophysics Data System (ADS)

    Pergamenshchik, V. M.

    2012-05-01

    We propose and study analytically a statistical mechanical model of reversible aggregation in anisotropic and isotropic solvents for small solute concentrations c. An aggregate comprising n solute molecules is a one-dimensional structureless flexible rod, n-mer, which interacts with the solvent anisotropy. The solvent is a nematic liquid crystal described by its scalar order parameter. The kinetic energy of n-mers is shown to play a unique role in the thermodynamic equilibrium. The kinetic energy contribution to the partition function is modeled by the term nq, where q is determined by the persistence lengths of different translation-rotation modes (e.g. q = 5 for a rigid rod and q?0 for a very flexible chain). The n-mer concentration is found to depend on c via its powers which are fully determined by the parameter q. The solvent anisotropy results in a larger fraction of longer aggregates and gives rise to two different aggregation regimes: a low n regime for lower solute concentration c and a high n regime for higher c. The total aggregate concentration is found to be a sum of universal power laws of c with the exponents that are different for anisotropic and isotropic solvents, but in both cases are determined solely by the parameter q. The analytical formulae for the two regimes and the crossover point (which can be naturally associated with the critical micelle concentration) are in a quantitative agreement with the numerical solution of the model. The model is pertinent to self-assemblies of plank-like dye molecules dissolved in an isotropic solvent (related to chromonic liquid crystals) and in a nematic liquid crystal.

  14. The critical behaviour of a power law between preseismic electric signals and earthquakes of different mechanism in Greece and Japan

    NASA Astrophysics Data System (ADS)

    Dologlou, Elizabeth

    2014-09-01

    The consistency of the critical exponent in the power law relation between the stress drop of the earthquake and the lead time of the precursory seismic electric signal is checked using new data from the recent M w 4.9 earthquake of strike-slip mechanism that occurred on 12 November 2013 in northern Evia island, Greece and the megathrust M w 9.0 Tohoku earthquake on 11 March 2011, in Japan. For the first case, the derived exponent is in excellent agreement with previous ones obtained from all non thrust events analysed by the author and matches the value of critical exponent for fracture. On the other hand, the megathrust Tohoku earthquake follows the behaviour of all thrust events studied by the author, and thus, the calculated exponent significantly deviates from this critical value. The different behaviour between non thrust and thrust-type events could be attributed to the fact that thrust mechanism earthquakes usually occur in collision or subduction zones which are characterised by high accumulation of strain. However, a larger number of thrust events are required in order to obtain reliable results and shed light in the above experimental findings.

  15. Further analysis of the Binary Euclidean algorithm

    Microsoft Academic Search

    Richard P. Brent

    1999-01-01

    The binary Euclidean algorithm is a variant of the classical Euclidean algorithm. It avoids multiplications and divisions, except by powers of two, so is potentially faster than the classical algorithm on a binary machine. We describe the binary algorithm and consider its average case behaviour. In particular, we correct some errors in the literature, discuss some recent results of Vallee,

  16. Low-energy Galactic centre gamma-rays from low-mass X-ray binaries

    NASA Technical Reports Server (NTRS)

    Kluzniak, W.; Ruderman, M.; Shaham, J.; Tavani, M.

    1988-01-01

    Nonthermal processes in low-mass X-ray binaries concentrated in the Galactic bulge are proposed as the direct source of the three continuum components of the emission from the Galactic center region (GCR) and also, possibly, as the indirect source of the 511-keV electron-positron annihilation line. It is suggested that the softer power-law component of the GCR continuum arises from synchrotron emission of relativistic electrons in the strongly nonuniform magnetic field of the neutron star and, more tentatively, that the MeV bump is the result of interaction of harder gamma rays with power-law photons. The hardest power law may be due to Compton scattering of relativistic electrons or photons.

  17. Black hole candidates in binaries

    Microsoft Academic Search

    Yasuo Tanaka

    The X-ray properties of the galactic black hole candidates are briefly reviewed. These sources show either of the two types of energy spectrum: (1) a hard spectrum of approximately a single power-law form, or (2) a composite of an ultrasoft component and a hard, power-law type tail. The power-law component of either spectral class exhibits distinct spectral features associated with

  18. Derivation of energy conservation law by complex line integral for the direct energy method of power system stability

    Microsoft Academic Search

    Young-Hyun Moon; Byoung-Hoon Cho; Yong-Hoon Lee; Hyun-Jong Kook

    1999-01-01

    This paper presents a complex line integral approach to derive an energy conservation law which reflects the resistance, flux-decaying effects, saliency with wide adaptability to various detailed generator models including the governor and exciter control loops. Especially, the previous work has shown that an exact energy conservation law can be derived under the assumption of stator network transients being negligible.

  19. Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 21 November 2001 (MN L A T E X style file v1.4) An electrically powered binary star?

    E-print Network

    Ramsay, Gavin

    propose that binary stars consisting of a magnetic and a non­magnetic white dwarf can also be cosmic unipo of a magnetic and a non­magnetic white­dwarf pair which is powered principally by electrical energy. In our unipolar inductor could be a planet orbiting around a magnetic white dwarf (Li, Fer­ rario & Wickramasinghe

  20. Methods of Using Existing Wire Lines (power lines, phone lines, internet lines) for Totally Secure Classical Communication Utilizing Kirchoff's Law and Johnson-like Noise

    E-print Network

    Laszlo B. Kish

    2006-10-02

    We outline some general solutions to use already existing and currently used wire lines, such as power lines, phone lines, internet lines, etc, for the unconditionally secure communication method based on Kirchoff's Law and Johnson-like Noise (KLJN). Two different methods are shown. One is based on filters used at single wires and the other one utilizes a common mode voltage superimposed on a three-phase powerline.

  1. Closed Loop System with Feedback Control MISO control laws SISO control law

    E-print Network

    Ben-Yakar, Adela

    Closed Loop System with Feedback Control MISO control laws SISO control law Switching Control Advanced Power Systems and Controls Laboratory Methodology: · Supervisory switching control based on power Control MISO SISO Future Work: · Stability of switched nonlinear system · Control law robustness

  2. Steady shear rheological characteristics of model system meat emulsions: Power law and exponential type models to describe effect of corn oil concentration.

    PubMed

    Karaman, Safa; Yilmaz, Mustafa Tahsin; Kayacier, Ahmed; Dogan, Mahmut; Yetim, Hasan

    2015-06-01

    The effect of oil concentration (57.50, 58.75, 60.00 and 61.25 %) and temperature (5, 10 and 15?ºC) on steady shear rheological properties of O/W model system meat emulsions were investigated. The effect of temperature and oil concentration was modeled using power law and exponential type functions. The meat emulsions showed non-Newtonian flow behavior because flow behavior index was lower than unity. Consistency coefficient and flow behavior index values of O/W model system meat emulsions were calculated using Oswald de Waele model with higher coefficients of determination. Apparent viscosities of emulsions at a specified shear rate (50 s(-1)) were in the range of 0.652-0.941 Pa s. Increasing oil concentration provided an increase in apparent viscosity and increase in temperature levels resulted a decrease in consistency coefficient values. The exponential function performed better than the power-law function (R (2)?>?0.922) in terms of describing the effect of oil concentration on the steady shear rheological properties of the model system meat emulsions. Higher coefficients of determination (R (2)?=?0.979-0.999) were observed in exponential-type function compared to a power law function (R (2)?=?0.880-0.946). PMID:26028770

  3. Observation of the Anomalously Slow (Power-Law) Relaxation of the System of Interacting Liquid Nanoclusters in the Disordered Confinement of a Random Porous Medium

    E-print Network

    V. D. Borman; A. A. Belogorlov; V. N. Tronin

    2015-05-20

    The time evolution of the system of water in the Libersorb 23 (L23) disordered nanoporous medium after the complete filling at excess pressure and the subsequent removal of excess pressure has been studied. It has been found that three stages can be identified in the relaxation of the L23-water system under study. At the first stage, a portion of water at the removal of excess pressure rapidly flows out in the pressure reduction time, i.e., following a decrease in the pressure. It has been shown that, at temperatures below the dispersion transition temperature $T power law ${\\theta} \\sim t^{-\\alpha}$ with the exponent ${\\alpha} 10^5$ s, the formed metastable state decays, which is manifested in the transition to a power-law dependence ${\\theta}(t)$ with a larger exponent. The extrusion-time distribution function of pores has been calculated along with the time dependence of the degree of filling, which qualitatively describes the observed anomalously slow relaxation and crossover of the transition to the stage of decay with a power-law dependence ${\\theta}(t)$ with a larger exponent. It has been shown that the relaxation and decay of the metastable state of the confined nonwetting liquid at ${\\theta}>{\\theta_c}$ are attributed to the appearance of local configurations of liquid clusters in confinement and their interaction inside the infinite percolation cluster of filled pores.

  4. Power-law correlations in finance-related Google searches, and their cross-correlations with volatility and traded volume: Evidence from the Dow Jones Industrial components

    NASA Astrophysics Data System (ADS)

    Kristoufek, Ladislav

    2015-06-01

    We study power-law correlations properties of the Google search queries for Dow Jones Industrial Average (DJIA) component stocks. Examining the daily data of the searched terms with a combination of the rescaled range and rescaled variance tests together with the detrended fluctuation analysis, we show that the searches are in fact power-law correlated with Hurst exponents between 0.8 and 1.1. The general interest in the DJIA stocks is thus strongly persistent. We further reinvestigate the cross-correlation structure between the searches, traded volume and volatility of the component stocks using the detrended cross-correlation and detrending moving-average cross-correlation coefficients. Contrary to the universal power-law correlations structure of the related Google searches, the results suggest that there is no universal relationship between the online search queries and the analyzed financial measures. Even though we confirm positive correlation for a majority of pairs, there are several pairs with insignificant or even negative correlations. In addition, the correlations vary quite strongly across scales.

  5. A double power-law fit to the computed stellar $\\log(\\tau/{\\rm y})$-$\\log(m/m_\\odot)$ relation

    E-print Network

    Caimmi, R

    2015-01-01

    The computed $\\log(\\tau/{\\rm y})$-$\\log(m/m_\\odot)$ relation for the stellar initial mass range, 0.6-120.0, and the stellar initial metallicity range, 0.0004-0.0500, tabulated in an earlier attempt (Portinari et al. 1998) is fitted to a good extent by a four-parameter curve, expressed by a double power-law, for assigned stellar initial metallicity, which can be reduced to a three-parameter curve, expressed by a single power-law, for the whole set of stellar initial metallicities. The relative errors do not exceed about 2% and 4%, respectively. The extent to which the interpolation curve, expressed by a single power-law, can be extrapolated towards both high-mass and low-mass stars, is also investigated. High-mass star lifetimes are understimated by a factor less than 2 up to $m/m_\\odot= 1000$ and by a fiducial factor less than 4 up to infinite. Low-mass star lifetimes are overstimated by a factor of about 3 down to $m/m_\\odot=0.25$ and by an unacceptably large factor down to $m/m_\\odot=0.08$. The interpolatio...

  6. Binary stars.

    PubMed

    Paczynacuteski, B

    1984-07-20

    Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars. PMID:17749544

  7. Turbulent Binary Fluids: A Shell Model Study

    E-print Network

    Mogens H. Jensen; Poul Olesen

    1997-06-09

    We introduce a shell (``GOY'') model for turbulent binary fluids. The variation in the concentration between the two fluids acts as an active scalar leading to a redefined conservation law for the energy, which is incorporated into the model together with a conservation law for the scalar. The model is studied numerically at very high values of the Prandtl and Reynolds numbers and we investigate the properties close to the critical point of the miscibility gap where the diffusivity vanishes. A peak develops in the spectrum of the scalar, showing that a strongly turbulent flow leads to an increase in the mixing time. The peak is, however, not very pronounced. The mixing time diverges with the Prandtl number as a power law with an exponent of approximately 0.9. The continuum limit of the shell equations leads to a set of equations which can be solved by a scaling ansatz, consistent with an exact scaling of the Navier-Stokes equations in the inertial range. In this case a weak peak also persists for a certain time in the spectrum of the scalar. Exact analytic solutions of the continuous shell equations are derived in the inertial range. Starting with fluids at rest, from an initial variation of the concentration difference, one can provoke a ``spontaneous'' generation of a velocity field, analogous to MHD in the early universe.

  8. Evaluation of a binary optimization approach to find the optimum locations of energy storage devices in a power grid with stochastically varying loads and wind generation

    NASA Astrophysics Data System (ADS)

    Dar, Zamiyad

    The prices in the electricity market change every five minutes. The prices in peak demand hours can be four or five times more than the prices in normal off peak hours. Renewable energy such as wind power has zero marginal cost and a large percentage of wind energy in a power grid can reduce the price significantly. The variability of wind power prevents it from being constantly available in peak hours. The price differentials between off-peak and on-peak hours due to wind power variations provide an opportunity for a storage device owner to buy energy at a low price and sell it in high price hours. In a large and complex power grid, there are many locations for installation of a storage device. Storage device owners prefer to install their device at locations that allow them to maximize profit. Market participants do not possess much information about the system operator's dispatch, power grid, competing generators and transmission system. The publicly available data from the system operator usually consists of Locational Marginal Prices (LMP), load, reserve prices and regulation prices. In this thesis, we develop a method to find the optimum location of a storage device without using the grid, transmission or generator data. We formulate and solve an optimization problem to find the most profitable location for a storage device using only the publicly available market pricing data such as LMPs, and reserve prices. We consider constraints arising due to storage device operation limitations in our objective function. We use binary optimization and branch and bound method to optimize the operation of a storage device at a given location to earn maximum profit. We use two different versions of our method and optimize the profitability of a storage unit at each location in a 36 bus model of north eastern United States and south eastern Canada for four representative days representing four seasons in a year. Finally, we compare our results from the two versions of our method with a multi period stochastically optimized economic dispatch of the same power system with storage device at locations proposed by our method. We observe a small gap in profit values arising due to the effect of storage device on market prices. However, we observe that the ranking of different locations in terms of profitability remains almost unchanged. This leads us to conclude that our method can successfully predict the optimum locations for installation of storage units in a complex grid using only the publicly available electricity market data.

  9. A statistical methodology to derive the scaling law for the H-mode power threshold using a large multi-machine database

    NASA Astrophysics Data System (ADS)

    Murari, A.; Lupelli, I.; Gaudio, P.; Gelfusa, M.; Vega, J.

    2012-06-01

    In this paper, a refined set of statistical techniques is developed and then applied to the problem of deriving the scaling law for the threshold power to access the H-mode of confinement in tokamaks. This statistical methodology is applied to the 2010 version of the ITPA International Global Threshold Data Base v6b(IGDBTHv6b). To increase the engineering and operative relevance of the results, only macroscopic physical quantities, measured in the vast majority of experiments, have been considered as candidate variables in the models. Different principled methods, such as agglomerative hierarchical variables clustering, without assumption about the functional form of the scaling, and nonlinear regression, are implemented to select the best subset of candidate independent variables and to improve the regression model accuracy. Two independent model selection criteria, based on the classical (Akaike information criterion) and Bayesian formalism (Bayesian information criterion), are then used to identify the most efficient scaling law from candidate models. The results derived from the full multi-machine database confirm the results of previous analysis but emphasize the importance of shaping quantities, elongation and triangularity. On the other hand, the scaling laws for the different machines and at different currents are different from each other at the level of confidence well above 95%, suggesting caution in the use of the global scaling laws for both interpretation and extrapolation purposes.

  10. Universal Inverse Power law distribution for Fractal Fluctuations in Dynamical Systems: Applications for Predictability of Inter - annual Variability of Indian and USA Region Rainfall

    E-print Network

    A. M. Selvam

    2010-02-17

    Dynamical systems in nature exhibit self-similar fractal space-time fluctuations on all scales indicating long-range correlations and therefore the statistical normal distribution with implicit assumption of independence, fixed mean and standard deviation cannot be used for description and quantification of fractal data sets. The author has developed a general systems theory which predicts the following (i) The fractal fluctuations signify an underlying eddy continuum, the larger eddies being the integrated mean of enclosed smaller-scale fluctuations. (ii) The probability distribution of eddy amplitudes and the variance (square of eddy amplitude) spectrum of fractal fluctuations follow the universal Boltzmann inverse power law expressed as a function of the golden mean. The predicted distribution is very close to statistical normal distribution for moderate events within two standard deviations from the mean but exhibits a fat long tail that are associated with hazardous extreme events. Continuous periodogram power spectral analyses of available GHCN annual total rainfall time series for the period 1900 to 2008 for Indian and USA stations show that the power spectra and the corresponding probability distributions follow model predicted universal inverse power law form signifying an eddy continuum structure underlying the observed inter-annual variability of rainfall. Global warming related atmospheric energy input will result in intensification of fluctuations of all scales and can be seen immediately in high frequency (short-term) fluctuations such as devastating floods/droughts resulting from excess/deficit annual, quasi-biennial and other shorter period (years) rainfall cycles.

  11. Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales

    E-print Network

    Joseph F. Hennawi; Michael A. Strauss; Masamune Oguri; Naohisa Inada; Gordon T. Richards; Bartosz Pindor; Donald P. Schneider; Robert H. Becker; Michael D. Gregg; Patrick B. Hall; David E. Johnston; Xiaohui Fan; Scott Burles; David J. Schlegel; James E. Gunn; Robert Lupton; Neta A. Bahcall; Robert J. Brunner; Jon Brinkman

    2005-04-25

    We present a sample of 218 new quasar pairs with proper transverse separations R_prop Quasar Redshift Survey quasars. This sample includes 26 new binary quasars with separations R_prop binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10 kpc/h 3 Mpc/h quasar correlation function, extrapolated down as a power law to the separations probed by our binaries. The excess grows to ~ 30 at R_prop ~ 10 kpc/h, and provides compelling evidence that the quasar autocorrelation function gets progressively steeper on sub-Mpc scales. This small scale excess can likely be attributed to dissipative interaction events which trigger quasar activity in rich environments. Recent small scale measurements of galaxy clustering and quasar-galaxy clustering are reviewed and discussed in relation to our measurement of small scale quasar clustering.

  12. Quark-novae in neutron star - white dwarf binaries: a model for luminous (spin-down powered) sub-Chandrasekhar-mass Type Ia supernovae?

    NASA Astrophysics Data System (ADS)

    Ouyed, Rachid; Staff, Jan

    2013-04-01

    We show that, by appealing to a Quark-Nova (QN) in a tight binary system containing a massive neutron star and a CO white dwarf (WD), a Type Ia explosion could occur. The QN ejecta collides with the WD, driving a shock that triggers carbon burning under degenerate conditions (the QN-Ia). The conditions in the compressed low-mass WD (MWD < 0.9 Msolar) in our model mimic those of a Chandrasekhar mass WD. The spin-down luminosity from the QN compact remnant (the quark star) provides additional power that makes the QN-Ia light-curve brighter and broader than a standard SN-Ia with similar 56Ni yield. In QNe-Ia, photometry and spectroscopy are not necessarily linked since the kinetic energy of the ejecta has a contribution from spin-down power and nuclear decay. Although QNe-Ia may not obey the Phillips relationship, their brightness and their relatively “normal looking" light-curves mean they could be included in the cosmological sample. Light-curve fitters would be confused by the discrepancy between spectroscopy at peak and photometry and would correct for it by effectively brightening or dimming the QNe-Ia apparent magnitudes, thus over- or under-estimating the true magnitude of these spin-down powered SNe-Ia. Contamination of QNe-Ia in samples of SNe-Ia used for cosmological analyses could systematically bias measurements of cosmological parameters if QNe-Ia are numerous enough at high-redshift. The strong mixing induced by spin-down wind combined with the low 56Ni yields in QNe-Ia means that these would lack a secondary maximum in the i-band despite their luminous nature. We discuss possible QNe-Ia progenitors.

  13. Time development of a perturbed-spherical nucleus in a pure supercooled liquid. I - Power-law growth of morphological instabilities. II - Nonlinear development

    NASA Technical Reports Server (NTRS)

    Pines, V.; Zlatkowski, M.; Chait, A.

    1990-01-01

    The linear growth stage of the morphological instabilities developing at the liquid-solid interface during crystal growth from an axisymmetric spherical nucleus is analyzed. The corresponding growth rate parameters are calculated numerically, and it is shown that morphological instabilities for free growth evolve according to a power law in agreement with WKB results and contrary to an exponential law found in a quasi-stationary approximation. The time evolution of an arbitrary perturbed liquid-solid interface from a linear into the nonlinear stage is studied. The initial perturbations include the eigenfunctions for the linear problem, localized perturbations of the grain-boundary type, and a stochastic noise. It is shown that the perturbations grow and spread in a wavelike manner. The formation of a predendritic growth stage is characterized by establishment of constant values of tip radius and velocity.

  14. Power law and exponential ejecta size distributions from the dynamic fragmentation of shock-loaded Cu and Sn metals under melt conditions

    SciTech Connect

    Durand, O.; Soulard, L. [CEA, DAM, DIF, F-91297 Arpajon (France)

    2013-11-21

    Large scale molecular dynamics (MD) simulations are performed to study and to model the ejecta production from the dynamic fragmentation of shock-loaded metals under melt conditions. A generic 3D crystal in contact with vacuum containing about 10{sup 8} atoms and with a sinusoidal free surface roughness is shock loaded so as to undergo a solid-liquid phase change on shock. The reflection of the shock wave at the interface metal/vacuum gives rise to the ejection of 2D jets/sheets of atoms (Richtmyer-Meshkov instabilities in the continuum limit), which develop and break up, forming ejecta (fragments) of different volumes (or mass). The fragmentation process is investigated by analyzing the evolution of the resulting volume distribution of the ejecta as a function of time. Two metals are studied (Cu and Sn) and the amplitude of the roughness is varied. The simulations show that the associated distributions exhibit a generic behavior with the sum of two distinct terms of varying weight, following the expansion rate of the jets: in the small size limit, the distribution obeys a power law dependence with an exponent equal to 1.15?±?0.08; and in the large size limit, it obeys an exponential form. These two components are interpreted, with the help of additional simple simulations, as the signature of two different basic mechanisms of fragmentation. The power law dependence results from the fragmentation of a 2D network of ligaments arranged following a fractal (scale free) geometry and generated when the sheets of liquid metal expand and tear. The exponential distribution results from a 1D Poisson fragmentation process of the largest ligaments previously generated. Unlike the power law distribution, it is governed by a characteristic length scale, which may be provided by energy balance principle.

  15. Developmental biologists' choice of subjects approximates to a power law, with no evidence for the existence of a special group of 'model organisms'

    PubMed Central

    Davies, Jamie A

    2007-01-01

    Background This report describes an unexpected aspect of the structure and development of developmental biology research, rather than the development of a specific embryo. Descriptions of modern developmental biology emphasize investigators' concentration on a small number of 'model' organisms and it is assumed that a clear division exists between the attention paid to these 'model' organisms and that paid to other species. This report describes a quantitative analysis of the organisms that were the subjects of studies reported in developmental biology journals published in the years 1965, 1975, 1985, 1995 and 2005, chosen to represent five decades of modern developmental biology. Results The results demonstrate that the distribution of attention paid to different organisms has a smooth distribution that approximates to a scale-free power law, in which there is no clear discontinuity that divides organisms into 'models' and the rest. This is true for both individual years and for the aggregate of all years' data. In other systems (eg connections in the World Wide Web), such power-law distributions arise from mechanisms of preferential attachment ('the rich get richer'). Detailed analysis of the progress of different organisms over the years under study shows that, while preferential attachment may be part of the mechanism that generates the power law distribution, it is insufficient to explain it. Conclusion The smoothness of the distribution suggests that there is no empirical basis for dividing species under study into 'model' organisms and 'the rest', and that the widely-held view about organism choice in developmental biology is distorted. PMID:17472742

  16. AJ Ohm's Law Calculator

    NSDL National Science Digital Library

    Jimmy Raymond

    The electrical relationships between resistance (R), current (I), power (P) and voltage (E) is defined by Ohm's Law. One ohm is defined as the resistance which allow the current of one ampere under a potential difference of 1 volt.

  17. Ohm's Law I

    NSDL National Science Digital Library

    2014-09-18

    Students work to increase the intensity of a light bulb by testing batteries in series and parallel circuits. They learn about Ohm's law, power, parallel and series circuits, and ways to measure voltage and current.

  18. Binary quasars

    E-print Network

    Daniel J. Mortlock; Rachel L. Webster; Paul J. Francis

    2000-08-03

    Quasar pairs are either physically distinct binary quasars or the result of gravitational lensing. The majority of known pairs are in fact lenses, with a few confirmed as binaries, leaving a population of objects that have not yet been successfully classified. Building on the arguments of Kochanek, Falco & Munoz (1999), it is shown that there are no objective reasons to reject the binary interpretation for most of these. In particular, the similarity of the spectra of the quasar pairs appears to be an artifact of the generic nature of quasar spectra. The two ambiguous pairs discovered as part of the Large Bright Quasar Survey (Q 1429-053 and Q 2153-0256) are analysed using principle components analysis, which shows that their spectral similarities are not greater than expected for a randomly chosen pair of quasars from the survey. The assumption of the binary hypothesis allows the dynamics, time-scales and separation distribution of binary quasars to be investigated and constrained. The most plausible model is that the quasars' activity is triggered by tidal interactions in a galatic merger, but that the (re-)activation of the galactic nuclei occurs quite late in the interaction, when the nuclei are within 80+/-30 kpc of each other. A simple dynamical friction model for the decaying orbits reproduces the observed distribution of projected separations, but the decay time inferred is comparable to a Hubble time. Hence it is predicted that binary quasars are only observable as such in the early stages of galactic collisions, after which the quiescent super-massive black holes orbit in the merger remnant for some time.

  19. Integral solutions to transient nonlinear heat (mass) diffusion with a power-law diffusivity: a semi-infinite medium with fixed boundary conditions

    NASA Astrophysics Data System (ADS)

    Hristov, Jordan

    2015-05-01

    Closed form approximate solutions to nonlinear heat (mass) diffusion equation with power-law nonlinearity of the thermal (mass) diffusivity have been developed by the integral-balance method avoiding the commonly used linearization by the Kirchhoff transformation. The main improvement of the solution is based on the double-integration technique and a new approach to the space derivative. Solutions to Dirichlet and Neumann boundary condition problems have been developed and benchmarked against exact numerical and approximate analytical solutions available in the literature.

  20. SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS

    SciTech Connect

    Morales, Farisa Y.; Werner, M. W.; Bryden, G.; Stapelfeldt, K. R.; Beichman, C. A.; Grogan, K. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Plavchan, P. [NASA Exoplanet Science Institute (NExScI), California Institute of Technology, 770 S. Wilson Ave, Pasadena, CA 91125 (United States); Rieke, G. H.; Su, K. Y. L. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Chen, C. H. [Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore, MD 21218 (United States); Kenyon, S. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Moro-Martin, A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540 (United States); Wolf, S. [Institut fuer Theor. Physik und Astrophysik, Christian-Albrechts-Universitaet zu Kiel, Leibnizstr. 15, 24118 Kiel (Germany)], E-mail: Farisa@jpl.nasa.gov

    2009-07-10

    Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 {mu}m, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) to have excess infrared emission at 24 {mu}m above that expected from the stellar photosphere. The mid-IR excess is confirmed in all cases but two. While prominent spectral features are not evident in any of the spectra, we observed a striking diversity in the overall shape of the spectral energy distributions. Most of the IRS excess spectra are consistent with single-temperature blackbody emission, suggestive of dust located at a single orbital radius-a narrow ring. Assuming the excess emission originates from a population of large blackbody grains, dust temperatures range from 70 to 324 K, with a median of 190 K corresponding to a distance of 10 AU. Thirteen stars however, have dust emission that follows a power-law distribution, F {sub {nu}} = F {sub 0}{lambda}{sup {alpha}}, with exponent {alpha} ranging from 1.0 to 2.9. The warm dust in these systems must span a greater range of orbital locations-an extended disk. All of the stars have also been observed with Spitzer/MIPS at 70 {mu}m, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 {mu}m fluxes are suggestive of a cooler, Kuiper Belt-like component that may be completely independent of the asteroid belt-like warm emission detected at the IRS wavelengths. Fourteen of 37 sources with blackbody-like fits are detected at 70 {mu}m. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 {mu}m (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 {mu}m emission may be related for these sources. Overall, the observed blackbody and power-law thermal profiles reveal debris distributed in a wide variety of radial structures that do not appear to be correlated with spectral type or stellar age. An additional 43 fainter A and late B type stars without 70 {mu}m photometry were also observed with Spitzer/IRS; results are summarized in Appendix B.

  1. THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

    SciTech Connect

    Zabalza, V.; Paredes, J. M. [Departament d'Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

    2011-12-10

    Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

  2. Flight-test of the glide-slope track and flare-control laws for an automatic landing system for a powered-lift STOL airplane

    NASA Technical Reports Server (NTRS)

    Watson, D. M.; Hardy, G. H.; Warner, D. N., Jr.

    1983-01-01

    An automatic landing system was developed for the Augmentor Wing Jet STOL Research Airplane to establish the feasibility and examine the operating characteristics of a powered-lift STOL transport flying a steep, microwave landing system (MLS) glide slope to automatically land on a STOL port. The flight test results address the longitudinal aspects of automatic powered lift STOL airplane operation including glide slope tracking on the backside of the power curve, flare, and touchdown. Three different autoland control laws were evaluated to demonstrate the tradeoff between control complexity and the resulting performance. The flight test and simulation methodology used in developing conventional jet transport systems was applied to the powered-lift STOL airplane. The results obtained suggest that an automatic landing system for a powered-lift STOL airplane operating into an MLS-equipped STOL port is feasible. However, the airplane must be provided with a means of rapidly regulation lift to satisfactorily provide the glide slope tracking and control of touchdown sink rate needed for automatic landings.

  3. Power-law scaling of spatially correlated porosity and log(permeability) sequences from north-central North Sea Brae oilfield well core

    NASA Astrophysics Data System (ADS)

    Leary, P. C.; Al-Kindy, F.

    2002-03-01

    The spatial cross-correlation and power spectra of porosity and log(permeability) sequences are analysed for a total of 750 m of reservoir rock drill-core from four vertical wells in the Brae Formation, an important coarse-grained clastic North Sea hydrocarbon reservoir rock. The well core sequences are 80+/-4 per cent cross-correlated at zero lag and have power-law-scaling spatial power spectra S (k )~1/k ? , ? ~ 1+/-0.4, for spatial frequencies 5km-1 power-law scaling of log(permeability) spatial fluctuation spectra fit into a broad physical context of (1) the 1/k spectral scaling observed in several hundred well logs of sedimentary and crystalline rock recorded world-wide; (2) the 1/f spectral scaling of temporal sequences in a wide range of physical systems; and (3) analogy with power-law-scaling spatial fluctuation spectra in a wide range of critical-state thermodynamic systems. In this physical context, the spatial fluctuations of log(permeability) of clastic reservoir rock are interpreted as due to long-range correlated random fracture-permeability networks in a fluid-saturated granular medium where the range ? of spatial correlation is effectively infinite. Fracture-permeability spatial fluctuations with long-range correlations and 1/k -scaling spectra have practical implications for geofluid reservoir management. Inadequate models of reservoir flow structure are widely attributed to uncertainty in fault and fracture location and connectivity. As a general phenomenon, spatial configurations of large-amplitude, long-range spatially correlated random fluctuations are unpredictable from the statistics of small-scale samples. The observed 1/k spectral scaling of porosity and log(permeability) distributions thus implies that large-scale, large-amplitude fracture-related flow heterogeneity (1) can determine the drainage pattern of crustal reservoirs but (2) cannot be accurately predicted using statistical techniques based on small-scale reservoir samples. Incompatibility of the physics of reservoir heterogeneity and the statistical approaches to reservoir models can thus explain the persistent under-performance of stochastic reservoir models. Accurate reservoir flow models can, however, be determined by direct observation of fluid flow at the reservoir scale. Recent advances in seismic time-lapse reservoir-fluid monitoring may provide data for significantly more effective management of hydrocarbon reservoirs, waste burial sites, mining works and groundwater aquifers.

  4. Distribution pattern of benthic invertebrates in Danish estuaries: The use of Taylor's power law as a species-specific indicator of dispersion and behavior

    NASA Astrophysics Data System (ADS)

    Kristensen, Erik; Delefosse, Matthieu; Quintana, Cintia O.; Banta, Gary T.; Petersen, Hans Christian; Jørgensen, Bent

    2013-03-01

    The lack of a common statistical approach describing the distribution and dispersion pattern of marine benthic animals has often hampered the comparability among studies. The purpose of this study is therefore to apply an alternative approach, Taylor's power law, to data on spatial and temporal distribution of 9 dominating benthic invertebrate species from two study areas, the estuaries Odense Fjord and Roskilde Fjord, Denmark. The slope (b) obtained from the power relationship of sample variance (s2) versus mean (?) appears to be species-specific and independent of location and time. It ranges from a low of ~ 1 for large-bodied (> 1 mg AFDW) species (e.g. Marenzelleria viridis, Nereis diversicolor) to a high of 1.6-1.9 for small-bodied (< 1 mg AFDW) species (e.g. Pygospio elegans and Tubificoides benedii). Accordingly, b is apparently a valuable species-specific dispersion index based on biological factors such as behavior and intraspecific interactions. Thus, at the examined spatial scale, the more intense intraspecific interactions (e.g. territoriality) cause less aggregated distribution patterns among large- than small-bodied invertebrates. The species-specific interactions seem sufficiently strong to override environmental influences (e.g. water depth and sediment type). The strong linear relationship between the slope b and intercept log(a) from the power relationship is remarkably similar for all surveys providing a common slope of - 1.63 with the present sampling approach. We suggest that this relationship is an inherent characteristic of Taylor's power law, and that b as a dispersion index may be biased by e.g. sampling errors when this relationship is weak. The correlation strength between b and log(a) could therefore be envisioned as a data quality check.

  5. Binary Planets

    NASA Astrophysics Data System (ADS)

    Ryan, Keegan; Nakajima, Miki; Stevenson, David J.

    2014-11-01

    Can a bound pair of similar mass terrestrial planets exist? We are interested here in bodies with a mass ratio of ~ 3:1 or less (so Pluto/Charon or Earth/Moon do not qualify) and we do not regard the absence of any such discoveries in the Kepler data set to be significant since the tidal decay and merger of a close binary is prohibitively fast well inside of 1AU. SPH simulations of equal mass “Earths” were carried out to seek an answer to this question, assuming encounters that were only slightly more energetic than parabolic (zero energy). We were interested in whether the collision or near collision of two similar mass bodies would lead to a binary in which the two bodies remain largely intact, effectively a tidal capture hypothesis though with the tidal distortion being very large. Necessarily, the angular momentum of such an encounter will lead to bodies separated by only a few planetary radii if capture occurs. Consistent with previous work, mostly by Canup, we find that most impacts are disruptive, leading to a dominant mass body surrounded by a disk from which a secondary forms whose mass is small compared to the primary, hence not a binary planet by our adopted definition. However, larger impact parameter “kissing” collisions were found to produce binaries because the dissipation upon first encounter was sufficient to provide a bound orbit that was then rung down by tides to an end state where the planets are only a few planetary radii apart. The long computational times for these simulation make it difficult to fully map the phase space of encounters for which this outcome is likely but the indications are that the probability is not vanishingly small and since planetary encounters are a plausible part of planet formation, we expect binary planets to exist and be a non-negligible fraction of the larger orbital radius exoplanets awaiting discovery.

  6. On Hack's Law

    NASA Astrophysics Data System (ADS)

    Rigon, Riccardo; Rodriguez-Iturbe, Ignacio; Maritan, Amos; Giacometti, Achille; Tarboton, David G.; Rinaldo, Andrea

    1996-11-01

    Hack's law is reviewed, emphasizing its implications for the elongation of river basins as well as its connections with their fractal characteristics. The relation between Hack's law and the internal structure of river basins is investigated experimentally through digital elevation models. It is found that Hack's exponent, elongation, and some relevant fractal characters are closely related. The self-affine character of basin boundaries is shown to be connected to the power law decay of the probability of total contributing areas at any link and to Hack's law. An explanation for Hack's law is derived from scaling arguments. From the results we suggest that a statistical framework referring to the scaling invariance of the entire basin structure should be used in the interpretation of Hack's law.

  7. Asteroseismology of Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Huber, Daniel

    Eclipsing binaries have long served as benchmark systems to measure fundamental properties of stars. In recent decades, asteroseismology—the study of stellar pulsations—has emerged as a powerful new tool to study the structure and evolution of stars across the H-R diagram. Pulsating stars in eclipsing binary systems are particularly valuable since fundamental properties such as radii and masses can then be determined using two independent techniques. Furthermore, independently measured properties from binary orbits can be used to improve asteroseismic modelling for pulsating stars in which mode identifications are not straightforward. This chapter provides a review of asteroseismic detections in eclipsing binary stars, with a focus on space-based missions such as CoRoT and Kepler and empirical tests of asteroseismic scaling relations for stochastic (`solar-like') oscillations.

  8. Comment on 'Power loss in open cavity diodes and a modified Child-Langmuir law' [Phys. Plasmas 12, 093102 (2005)

    SciTech Connect

    Swanekamp, S. B.; Ottinger, P. F. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2007-09-15

    In this Comment, it is shown that no modification of the Child-Langmuir law [Phys. Rev.32, 492 (1911); Phys. Rev. 2, 450 (1913)] is necessary to treat the space-charge-limited flow from a diode with an open boundary as reported in Phys. Plasmas 12, 093102 (2005). The open boundary condition in their simulations can be represented by a voltage source and a resistor whose value is the vacuum-wave impedance of the opening. The diode can be represented as a variable resistor whose value depends on the voltage drop across the diode (as measured by the line integral of E across the diode gap). This is a simple voltage-divider circuit whose analysis shows that the real diode voltage drops as the vacuum-wave impedance increases. Furthermore, it is shown that in equilibrium, the voltage drop between the anode and cathode is independent of the path chosen for the line integral of the electric field so that E=-{nabla}{phi} is valid. In this case, the equations of electrostatics are applicable. This clearly demonstrates that the electric field is electrostatic and static fields DO NOT RADIATE. It is shown that the diode voltage drops as the vacuum wave impedance increases and the current drops according to the Child-Langmuir law. Therefore, the observed drop in circuit current can be explained by a real drop in voltage across the diode and not an effective drop as claimed by the authors.

  9. Session 9: Heber Geothermal Binary Demonstration Project

    Microsoft Academic Search

    Richard F. Allen; Tiffany T. Nelson

    1983-01-01

    The Heber Binary Project had its beginning in studies performed for the Electric Power Research Institute (EPRI), which identified the need for commercial scale (50 Mw or larger) demonstration of the binary cycle technology. In late 1980, SDG&E and the Department of Energy (DOE) signed a Cooperative Agreement calling for DOE to share in 50 percent of the Project costs.

  10. On Binary Driven Hypernovae and their nested late X-ray emission

    E-print Network

    Ruffini, R; Bianco, C L; Enderli, M; Izzo, L; Kovacevic, M; Penacchioni, A V; Pisani, G B; Rueda, J A; Wang, Y

    2014-01-01

    Context: The induced gravitational collapse (IGC) paradigm addresses the very energetic (10^{52}-10^{54}erg) long gamma-ray bursts (GRBs) associated to supernovae (SNe). In alternative to the traditional "collapsar" model, an evolved FeCO core with a companion neutron star (NS) in a tight binary system is considered as progenitor. This special class of sources, here named "binary driven hypernovae" (BdHNe), presents a composite sequence made by four different episodes [...]. Aims: a) To compare and contrast the steep decay, the plateau and the power-law decay of the X-ray luminosities of three selected BdHNe [...]; b) to explain the different sizes and Lorentz factors of the emitting regions of the four Episodes, [...]; c) to evidence the possible role of r-process, originating in the binary system of the progenitor. Methods: We compare and contrast the late X-ray luminosity of the above three BdHNe. We examine correlations between the time at the starting point of the constant late power-law decay, t^*_a, th...

  11. Health care law versus constitutional law.

    PubMed

    Hall, Mark A

    2013-04-01

    National Federation of Independent Business v. Sebelius, the Supreme Court's ruling on the Patient Protection and Affordable Care Act, is a landmark decision - both for constitutional law and for health care law and policy. Others will study its implications for constitutional limits on a range of federal powers beyond health care. This article considers to what extent the decision is also about health care law, properly conceived. Under one view, health care law is the subdiscipline that inquires how courts and government actors take account of the special features of medicine that make legal or policy issues especially problematic - rather than regarding health care delivery and finance more generically, like most any other economic or social enterprise. Viewed this way, the opinions from the Court's conservative justices are mainly about general constitutional law principles. In contrast, Justice Ruth Bader Ginsburg's dissenting opinion for the four more liberal justices is just as much about health care law as it is about constitutional law. Her opinion gives detailed attention to the unique features of health care finance and delivery in order to inform her analysis of constitutional precedents and principles. Thus, the Court's multiple opinions give a vivid depiction of the compelling contrasts between communal versus individualistic conceptions of caring for those in need, and between health care and health insurance as ordinary commodities versus ones that merit special economic, social, and legal status. PMID:23262771

  12. Dynamics of the Binary Euclidean Algorithm: Functional Analysis and Operators

    Microsoft Academic Search

    Brigitte Vallée

    1998-01-01

    We provide here a complete average-case analysis of the binary continued fraction representation of a random rational whose numerator and denominator are odd and less than N. We analyze the three main parameters of the binary continued fraction expansion, namely, the height, the number of steps of the binary Euclidean algorithm, and finally the sum of the exponents of powers

  13. Determination of the type of PSK-signal modulation on the basis of power-law transformations and spectrum analysis

    NASA Astrophysics Data System (ADS)

    Loginov, A. A.; Morozov, O. A.; Khmelev, S. L.

    2013-03-01

    We propose an algorithm for determining the PSK-signal type from a short sample under the conditions of absence of information on the center frequency and modulation rate. The algorithm is based on the analysis of averaged characteristics of the spectrum of a signal and its even powers.

  14. The influence of hydrogen on the transition from power-law creep to low-temperature plasticity of olivine at lithospheric temperatures

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob; Zimmerman, Mark; Kohlstedt, David

    2015-04-01

    At high-temperature (asthenospheric) conditions, strain rate of olivine-rich mantle rocks follows a power-law dependence on stress. At lower-temperature (lithospheric) conditions, strain rate exhibits an exponential dependence on stress. However, the influence of water (hydrogen) on the transition from high-temperature to low-temperature behavior is poorly constrained. To investigate the influence of water on the transition in flow regimes at lithospheric conditions, deformation experiments on single crystals of San Carlos olivine under both wet (hydrogen-rich) and dry (hydrogen-poor) conditions were carried out. Crystals were oriented relative to the applied load to exert the maximum shear stress on the (100)[001] and (001)[100] dislocation slip systems, which are the dominate (weakest) slip systems at both low temperatures and under wet conditions. Experiments were carried out using a gas-medium apparatus with high resolution in stress (±2 MPa) and temperature (±2°C). For the wet experiments, hydrogen was supplied to the crystals using talc sealed in nickel jackets. Deformation experiments were carried out in either triaxial compression or direct shear geometries at 1000-1300°C, differential stresses of 120 to 670 MPa, and resultant strain rates of 6 x 10-6 to 4 x 10-4 s-1. At high-temperature, under dry conditions, strain rate is a power-law function of stress with a stress exponent of 3.5 and an Arrhenius function of temperature with an activation energy of 520 kJ/mol. At low-temperature and high-stress conditions, under dry conditions, strain rate increases exponentially with increasing stress with an activation energy of 360 kJ/mol. These observations are consistent with a transition from a climb-controlled dislocation mechanism at higher temperatures to a glide-controlled dislocation mechanism at lower temperatures for hydrogen-poor olivine crystals. Under wet conditions, the strain rate dependence on stress follows a power-law relationship with a stress exponent of 3.5 and an activation energy of 330 kJ/mol and does not transition to an exponential dependence on stress. Post-deformation electron-backscatter diffraction analyses indicate development of low-angle boundaries with rotation about the [010] axis, consistent with deformation resulting from glide of dislocations on the (100)[001] and (001)[100] slip systems. Water concentrations in crystals from wet experiments determined using Fourier transform infrared spectroscopy were 157 to 190 ppm H/Si, similar to values obtained from xenoliths derived from the lithospheric mantle. These analyses indicate that the presence of water in the lithospheric mantle results in considerable weakening and that power-law flow behavior of mantle rocks may operate at shallower depths than previously thought.

  15. Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

    PubMed Central

    Mondal, Sourav; De, Sirshendu

    2013-01-01

    Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed. PMID:24404046

  16. Investigation on average void fraction for air/non-Newtonian power-law fluids two-phase flow in downward inclined pipes

    SciTech Connect

    Xu, Jing-yu [LHO, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)

    2010-11-15

    The present work has been carried out to investigate on the average void fraction of gas/non-Newtonian fluids flow in downward inclined pipes. The influences of pipe inclination angle on the average void fraction were studied experimentally. A simple correlation, which incorporated the method of Vlachos et al. for gas/Newtonain fluid horizontal flow, the correction factor of Farooqi and Richardson and the pipe inclination angle, was proposed to predict the average void fraction of gas/non-Newtonian power-law stratified flow in downward inclined pipes. The correlation was based on 470 data points covering a wide range of flow rates for different systems at diverse angles. A good agreement was obtained between theory and data and the fitting results could describe the majority of the experimental data within {+-}20%. (author)

  17. A compact split step Padé scheme for higher-order nonlinear Schrödinger equation (HNLS) with power law nonlinearity and fourth order dispersion

    NASA Astrophysics Data System (ADS)

    Smadi, Moussa; Bahloul, Derradji

    2011-02-01

    In this paper we propose a compact split step Padé scheme (CSSPS) to solve the scalar higher-order nonlinear Schrödinger equation (HNLS) with higher-order linear and nonlinear effects such as the third and fourth order dispersion effects, Kerr dispersion, stimulated Raman scattering and power law nonlinearity. The stability of this method has been proved. It has been shown as well that the CSSPS method gives the same results as classical numerical methods like the split step Fourier method and Crank-Nicholson (CN) method but it presents many advantages over theme. It is more efficient. This proposed scheme is well suited to higher-order dispersion effects and readily generalized for nonlinear and dispersion managed fibers. We tested this scheme for the case of the quintic nonlinearity and confirmed that this effect has no significant role on the propagation of single solitons.

  18. Universal Inverse Power law distribution for Fractal Fluctuations in Dynamical Systems: Applications for Predictability of Inter - annual Variability of Indian and USA Region Rainfall

    E-print Network

    Selvam, A M

    2010-01-01

    Dynamical systems in nature exhibit self-similar fractal space-time fluctuations on all scales indicating long-range correlations and therefore the statistical normal distribution with implicit assumption of independence, fixed mean and standard deviation cannot be used for description and quantification of fractal data sets. The author has developed a general systems theory which predicts the following (i) The fractal fluctuations signify an underlying eddy continuum, the larger eddies being the integrated mean of enclosed smaller-scale fluctuations. (ii) The probability distribution of eddy amplitudes and the variance (square of eddy amplitude) spectrum of fractal fluctuations follow the universal Boltzmann inverse power law expressed as a function of the golden mean. The predicted distribution is very close to statistical normal distribution for moderate events within two standard deviations from the mean but exhibits a fat long tail that are associated with hazardous extreme events. Continuous periodogram...

  19. Estimation of the hydraulic conductivity of a two-dimensional fracture network using effective medium theory and power-law averaging

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. W.; Leung, C. T.

    2009-12-01

    Most oil and gas reservoirs, as well as most potential sites for nuclear waste disposal, are naturally fractured. In these sites, the network of fractures will provide the main path for fluid to flow through the rock mass. In many cases, the fracture density is so high as to make it impractical to model it with a discrete fracture network (DFN) approach. For such rock masses, it would be useful to have recourse to analytical, or semi-analytical, methods to estimate the macroscopic hydraulic conductivity of the fracture network. We have investigated single-phase fluid flow through generated stochastically two-dimensional fracture networks. The centers and orientations of the fractures are uniformly distributed, whereas their lengths follow a lognormal distribution. The aperture of each fracture is correlated with its length, either through direct proportionality, or through a nonlinear relationship. The discrete fracture network flow and transport simulator NAPSAC, developed by Serco (Didcot, UK), is used to establish the “true” macroscopic hydraulic conductivity of the network. We then attempt to match this value by starting with the individual fracture conductances, and using various upscaling methods. Kirkpatrick’s effective medium approximation, which works well for pore networks on a core scale, generally underestimates the conductivity of the fracture networks. We attribute this to the fact that the conductances of individual fracture segments (between adjacent intersections with other fractures) are correlated with each other, whereas Kirkpatrick’s approximation assumes no correlation. The power-law averaging approach proposed by Desbarats for porous media is able to match the numerical value, using power-law exponents that generally lie between 0 (geometric mean) and 1 (harmonic mean). The appropriate exponent can be correlated with statistical parameters that characterize the fracture density.

  20. Helmet Laws

    MedlinePLUS

    ... universal motorcycle helmet laws to qualify for certain highway safety funds. By 1975, all but three had ... here. For more information, consult the appropriate State Highway Safety Office . State Motorcyclists Bicyclists Universal Helmet Law ( ...