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1

An electrically powered binary star?  

E-print Network

We propose a model for stellar binary systems consisting of a magnetic and a non-magnetic white-dwarf pair which is powered principally by electrical energy. In our model the luminosity is caused by resistive heating of the stellar atmospheres due to induced currents driven within the binary. This process is reminiscent of the Jupiter-Io system, but greatly increased in power because of the larger companion and stronger magnetic field of the primary. Electrical power is an alternative stellar luminosity source, following on from nuclear fusion and accretion. We find that this source of heating is sufficient to account for the observed X-ray luminosity of the 9.5-min binary RX J1914+24, and provides an explanation for its puzzling characteristics.

Kinwah Wu; Mark Cropper; Gavin Ramsay; Kazuhiro Sekiguchi

2001-11-19

2

Entropic force in black hole binaries and Newton's law from an adiabatic Hilbert action  

Microsoft Academic Search

We give an exact solution for the static force between two black holes at the turning points in their binary motion. The results are derived by Gibbs' principle and the Bekenstein-Hawking entropy applied to the apparent horizon surfaces in time-symmetric initial data. New power laws are derived for the entropy jump in mergers, while Newton's law is shown to derive

2011-01-01

3

Anisotropic power-law inflation  

SciTech Connect

We study an inflationary scenario in supergravity model with a gauge kinetic function. We find exact anisotropic power-law inflationary solutions when both the potential function for an inflaton and the gauge kinetic function are exponential type. The dynamical system analysis tells us that the anisotropic power-law inflation is an attractor for a large parameter region.

Kanno, Sugumi [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, 212 College Ave., Medford, MA 02155 (United States); Soda, Jiro; Watanabe, Masa-aki, E-mail: sugumi@cosmos.phy.tufts.edu, E-mail: jiro@tap.scphys.kyoto-u.ac.jp, E-mail: mwatanabe@tap.scphys.kyoto-u.ac.jp [Department of Physics, Kyoto University, Kyoto, 606-8501 (Japan)

2010-12-01

4

The Broadband Power Spectra of X-Ray Binaries  

Microsoft Academic Search

We analyze the rapid, aperiodic X-ray variability of different types of X-ray binaries (black hole candidates, atoll sources, the recently discovered millisecond X-ray pulsar, and Z sources) at their lowest inferred mass accretion rates. At these accretion rates, the power spectra of all sources are dominated by a strong band-limited noise component, which follows a power law with an index

Rudy Wijnands; Michiel van der Klis

1999-01-01

5

Power Law Distribution in Education  

NASA Astrophysics Data System (ADS)

We studied the statistical distribution of student's performance, which is measured through their marks, in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) with respect to (i) period of study-day versus night period (ii) teaching conditions - private versus public school (iii) economical conditions - high versus low family income. We observed long ubiquitous power law tails in physical and biological sciences in all cases. The mean value increases with better study conditions followed by better teaching and economical conditions. In humanities, the distribution is close to normal distribution with very small tail. This indicates that these power law tails in science subjects are due to the nature of the subjects themselves. Further and better study, teaching and economical conditions are more important for physical and biological sciences in comparison to humanities at this level of study. We explain these statistical distributions through Gradually Truncated Power law distributions. We discuss the possible reason for this peculiar behavior.

Gupta, Hari M.; Campanha, José R.; Chavarette, Fábio R.

6

Power law in firms bankruptcy  

NASA Astrophysics Data System (ADS)

We consider the scaling behaviors for fluctuations of the number of Korean firms bankrupted in the period from 1 August 2002 to 28 October 2003. We observe a power law for the distribution of the number of the bankrupted firms. The Pareto exponent is close to unity. We also consider the daily increments of the number of firms bankrupted. The probability distribution of the daily increments for the firms bankrupted follows the Gaussian distribution in central part and has a fat tail. The tail parts of the probability distribution of the daily increments for the firms bankrupted follow a power law.

Hong, Byoung Hee; Lee, Kyoung Eun; Lee, Jae Woo

2007-01-01

7

Power Laws in Firm Productivity  

NASA Astrophysics Data System (ADS)

We estimate firm productivity for about 3.2 million firms from30 countries. We find that the distribution of firm productivity in each country, which is measured by total factor productivity (TFP), has a power law upper tail. However, the power law exponent of a TFP distribution in a country tends to be greater than that of a sales distribution in that country, indicating that the upper tail of a TFP distribution is less heavy compared to that of a sales distribution. We also find that the power law exponent of a TFP distribution tends to be greater than the power law exponents associated with the number of workers or tangible fixed assets. Given the idea that the sales of a firm is determined by the amount of various inputs employed by the firm (i.e., ``production function'' in the terminology of economics), these results suggest that the heavy tail of a sales distribution in a country comes not from the tail of a TFP distribution, but from the tail of the distribution of the number of workers or tangible fixed assets.

Mizuno, T.; Ishikawa, A.; Fujimoto, S.; Watanabe, T.

8

Geothermal power generation using the binary cycle  

Microsoft Academic Search

Geothermal resources of the world are comparable in magnitude to fossil ; fuel and nuclear energy resources. It is evident that the technology exists to ; exploit economically many of the world's known geothermal reservoirs and that the ; impact on the environment will be minimal. A flowsheet for a typical binary ; power cycle is shown. The geothermal fluid

B. Holt; A. J. L. Hutchinson; D. S. Cortez

1973-01-01

9

Accretion-powered Compact Binaries  

NASA Astrophysics Data System (ADS)

Preface; The workshop logo; A short history of the CV workshop F. A. Córdova; Part I. Observations: 1. Low mass x-ray binaries A. P. Cowley, P. C. Schmidtke, D. Crampton, J. B. Hutchings, C. A. Haswell, E. L. Robinson, K. D. Horne, H. M. Johnston, S. R. Kulkarni, S. Kitamoto, X. Han, R. M. Hjellming, R. M. Wagner, S. L. Morris, P. Hertz, A. N. Parmar, L. Stella, P. Giommi, P. J. Callanan, T. Naylor, P. A. Charles, C. D. Bailyn, J. N. Imamura, T. Steiman-Cameron, J. Kristian, J. Middleditch, L. Angelini and J. P. Noris; 2. Nonmagnetic cataclysmic variables R. S. Polidan, C. W. Mauche, R. A. Wade, R. H. Kaitchuck, E. M. Schlegel, P. A. Hantzios, R. C. Smith, J. H. Wood, F. Hessman, A. Fiedler, D. H. P. Jones, J. Casares, P. A. Charles, J. van Paradijs, E. Harlaftis, T. Naylor, G. Sonneborn, B. J. M. Hassall, K. Horne, C. A. la Dous, A. W. Shafter, N. A. Hawkins, D. A. H. Buckley, D. J. Sullivan, F. V. Hessman, V. S. Dhillon, T. R. Marsh, J. Singh, S. Seetha, F. Giovannelli, A. Bianchini, E. M. Sion, D. J. Mullan, H. L. Shipman, G. Machin, P. J. Callanan, S. B. Howell, P. Szkody, E. M. Schlegel and R. F. Webbink; 3. Magnetic cataclysmic variables C. Hellier, K. O. Mason, C. W. Mauche, G. S. Miller, J. C. Raymond, F. K. Lamb, J. Patterson, A. J. Norton, M. G. Watson, A. R. King, I. M. McHardy, H. Lehto, J. P. Osborne, E. L. Robinson, A. W. Shafter, S. Balachandran, S. R. Rosen, J. Krautter, W. Buchholz, D. A. H. Buckley, I. R. Tuoly, D. Crampton, B. Warner, R. M. Prestage, B. N. Ashoka, M. Mouchet, J. M. Bonnet-Bidaud, J. M. Hameury, P. Szkody, P. Garnavich, S. Howell, T. Kii, M. Cropper, K. Mason, J. Bailey, D. T. Wickramasinghe, L. Ferrario, K. Beuermann, A. D. Schwope, H.-C. Thomas, S. Jordan, J. Schachter, A. V. Filippenko, S. M. Kahn, F. B. S. Paerels, K. Mukai, M. L. Edgar, S. Larsson, R. F. Jameson, A. R. King, A. Silber, R. Remillard, H. Bradt, M. Ishida, T. Ohashi and G. D. Schmidt; Part II. Accretion Theory: 4. Nonmagnetic W. Kley, F. Geyer, H. Herold, H. Ruder, R. Whitehurst, A. King, J. C. Wheeler, S. Mineshige, M. Huang, S. W. Kim, Y. Tuchman, T. R. Kallman and J. A. Woods; 5. Magnetic M. T. Wolff, J. N. Imamura, K. S. Wood, J. H. Gardner, S. J. Litchfield, J. J. Brainerd, G. Chanmugan, K. Wu, J. Frank, T. Hanawa, K. Hirotani and N. Kawai; Part III. Novae S. Starrfield, R. M. Hjellming, A. B. Tomaney, A. W. Shafter, A. Cassatella, P. L. Selvelli, R. Gilmozzi, A. Bianchini, M. Friedjung, H. Ritter, M. J. Politano, M. Livio, R. F. Webbink, K. Horne, W. F. Welsh, R. A. Wade, J. Krauttler, M. A. J. Snijders, N. Vogt, L. H. Barrera, H. Barwig, K.-H Mantel, R. Gilmozzi, A. Shankar, A. Burkert, J. W. Truran and J. Hayes: Part IV. Evolution I. Iben Jr, M. S. Hjellming, R. E. Taam, M. Politano, F. D'Antona, I. Mazzitelli, H. Ritter, J. M. Hameury, A. R. King, J. P. Lasota, R. Popham, R. Narayan, J. Isern, J. Laybay, R. Canal, D. García, A. S. Fruchter, S. R. Kulkarni, R. W. Romani, A. Ray, W. Kluzniak, S. Miyaji and G. Chanmugam; Subject index; Star index.

Mauche, Christopher W.

2003-12-01

10

The Pareto, Zipf and other power laws  

Microsoft Academic Search

Many empirical size distributions in economics and elsewhere exhibit power-law behaviour in the upper tail. This article contains a simple explanation for this. It also predicts lower-tail power- law behaviour, which is verified empirically for income and city-size data. Many empirical distributions encountered in economics and other realms of inquiry exhibit power-law behaviour. In economics prime examples are the distributions

William J. Reed

2001-01-01

11

Tachyonic (phantom) power-law cosmology  

NASA Astrophysics Data System (ADS)

Tachyonic scalar field-driven late universe with dust matter content is considered. The cosmic expansion is modeled with power-law and phantom power-law expansion at late time, i.e. z?0.45. WMAP7 and its combined data are used to constraint the model. The forms of potential and the field solution are different for quintessence and tachyonic cases. Power-law cosmology model (driven by either quintessence or tachyonic field) predicts unmatched equation of state parameter to the observational value, hence the power-law model is excluded for both quintessence and tachyonic field. In the opposite, the phantom power-law model predicts agreeing valued of equation of state parameter with the observational data for both quintessence and tachyonic cases, i.e. (WMAP7+BAO+ H 0) and (WMAP7). The phantom-power law exponent ? must be less than about -6, so that the -2< w ?,0<-1. The phantom power-law tachyonic potential is reconstructed. We found that dimensionless potential slope variable ? at present is about 1.5. The tachyonic potential reduced to V= V 0 ? -2 in the limit ? m,0?0.

Rangdee, Rachan; Gumjudpai, Burin

2014-02-01

12

Power law inflation with electromagnetism  

SciTech Connect

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.

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

2013-07-15

13

Power Laws and Market Crashes ---Empirical Laws on Bursting Bubbles---  

NASA Astrophysics Data System (ADS)

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) ˜ x^{-?}, with an exponent that moves in the range of 1.09 < ? < 1.27. Furthermore, we found that as the power-law exponents ? approached unity, the bubbles collapsed. This suggests that Zipf's law for stock prices is a sign that bubbles are going to burst.

Kaizoji, T.

14

Injection molding of power-law polymer  

NSDL National Science Digital Library

A polymer in injected with a constant pressure gradient between two parallel plates. The progression of the polymer front is modeled for a power law fluid (typical of a polymer) and compared to results for a Newtonian fluid.

Krane, Matthew J.

2008-10-25

15

Executive Power v. International Law  

Microsoft Academic Search

Critics of the Bush administration's conduct of the war on terrorism and the wars in Afghanistan and Iraq have made the claim that the President cannot order conduct that is inconsistent with international law. Not only is the argument under-theorized, it runs counter to the best reading of the constitutional text, structure, and the history of American practice. A careful

John C Yoo; Robert J Delahunty

2007-01-01

16

A probabilistic walk up power laws  

NASA Astrophysics Data System (ADS)

We establish a path leading from Pareto’s law to anomalous diffusion, and present along the way a panoramic overview of power-law statistics. Pareto’s law is shown to universally emerge from “Central Limit Theorems” for rank distributions and exceedances, and is further shown to be a finite-dimensional projection of an infinite-dimensional underlying object - Pareto’s Poisson process. The fundamental importance and centrality of Pareto’s Poisson process is described, and we demonstrate how this process universally generates an array of anomalous diffusion statistics characterized by intrinsic power-law structures: sub-diffusion and super-diffusion, Lévy laws and the “Noah effect”, long-range dependence and the “Joseph effect”, 1/f noises, and anomalous relaxation.

Eliazar, Iddo; Klafter, Joseph

2012-02-01

17

A signature of power law network dynamics  

E-print Network

Can one hear the 'sound' of a growing network? We address the problem of recognizing the topology of evolving biological or social networks. Starting from percolation theory, we analytically prove a linear inverse relationship between two simple graph parameters--the logarithm of the average cluster size and logarithm of the ratio of the edges of the graph to the theoretically maximum number of edges for that graph--that holds for all growing power law graphs. The result establishes a novel property of evolving power-law networks in the asymptotic limit of network size. Numerical simulations as well as fitting to real-world citation co-authorship networks demonstrate that the result holds for networks of finite sizes, and provides a convenient measure of the extent to which an evolving family of networks belongs to the same power-law class.

Bhan, Ashish

2014-01-01

18

A Music Information Retrieval Approach Based on Power Laws  

Microsoft Academic Search

We present a music information retrieval approach based on power laws. Research in cognitive science and neuroscience reveals connections between power laws, human cognition, and human physiology. Empirical studies also demonstrate connections between power laws and human aesthetics. We utilize 250+ power-law metrics to extract statistical proportions of music-theoretic and other attributes of music pieces. We discuss an experiment where

Patrick Roos; Bill Manaris

2007-01-01

19

Power-aware FPGA logic synthesis using binary decision diagrams  

Microsoft Academic Search

Power consumption in field programmable gate arrays (FPGAs) has become an important issue as the FPGA market has grown to include mobile platforms. In this work we present a power-aware logic optimization tool that is specialized to facilitate subsequent power-aware technology mapping. Our synthesis framework uses binary decision diagram (BDD) based collapsing and decomposition techniques in conjunction with signal switching

Kevin Oo Tinmaung; David Howland; Russell Tessier

2007-01-01

20

Information Ranking and Power Laws on Trees  

Microsoft Academic Search

We study the situations when the solution to a weighted stochastic recursion has a power law tail. To this end, we develop two complementary approaches, the first one extends Goldie's (1991) implicit renewal theorem to cover recursions on trees; and the second one is based on a direct sample path large deviations analysis of weighted recursive random sums. We believe

Predrag R. Jelenkovic; Mariana Olvera-Cravioto

2009-01-01

21

Temporal analysis of power law liquid jets  

Microsoft Academic Search

In this paper we investigate the breakup mechanisms of power law liquid jets. The viscosity of the liquid is represented the Carreau–Yasuda model, and the surface tension of the liquid jet has a variation (gradient) along the jet axial direction. The surface tension gradient may be introduced by the thermal disturbance of the jet surface as it comes of out

Zhanjun Gao; Kam Ng

2010-01-01

22

Application of power laws for wind energy assessment  

Microsoft Academic Search

Variations in the exponent in the power law relating height to wind velocity are investigated for a series of measurements of nocturnal low-level winds in northern Illinois in order to determine the applicability of power laws in estimates of attainable wind power. Hourly, seasonal and annual frequency distributions of power law exponents representing the best fit to wind profiles obtained

D. L. Sisterson; B. B. Hicks

1979-01-01

23

Fractal power law in literary English  

NASA Astrophysics Data System (ADS)

We present in this paper a numerical investigation of literary texts by various well-known English writers, covering the first half of the twentieth century, based upon the results obtained through corpus analysis of the texts. A fractal power law is obtained for the lexical wealth defined as the ratio between the number of different words and the total number of words of a given text. By considering as a signature of each author the exponent and the amplitude of the power law, and the standard deviation of the lexical wealth, it is possible to discriminate works of different genres and writers and show that each writer has a very distinct signature, either considered among other literary writers or compared with writers of non-literary texts. It is also shown that, for a given author, the signature is able to discriminate between short stories and novels.

Gonçalves, L. L.; Gonçalves, L. B.

2006-02-01

24

On power law inflation in DBI models  

Microsoft Academic Search

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 addresses the

Michal Spalinski

2007-01-01

25

Power-law Solutions from Heterotic Strings  

E-print Network

In this paper we search for accelerating power-law and ekpyrotic solutions in heterotic string theory with NS-NS fluxes compactified on half-flat and generalized half-flat manifolds. We restrict our searches to the STZ sector of the theory and include linear order $\\alpha'$ corrections when looking for accelerating solutions. We find two ekpyrotic solutions in the case when the heterotic string theory is compactified on generalized half-flat manifolds. We do not find accelerating solutions in any of the models.

Tibra Ali; S. Shajidul Haque

2014-03-11

26

Parameter estimation of power law process  

SciTech Connect

Power law process is an important model in reliability analysis of engineering systems experiencing reliability growth or decay. Existing articles mainly deal with the estimation of the shape parameter. The estimation of the scale parameter is either ignored or dealt with very inefficiently. In this article, we are going to explain why those methods can estimate the shape parameter well, but fail to estimate the scale parameter effectively. It is still open problem if we can obtain an estimate to the scale parameter as good as the one to the shape parameter. We try to explore a new way to improve the estimate of the scale parameter. which will be proven better than the existing methods in theory and practice.

Qiao, H. [Fort Valley State Univ., Fort Valley, GA (United States); Tsokos, C.P. [Univ. of South Florida, Tampa, FL (United States)

1994-12-31

27

Modulated power-law behaviour in Stirling's approximation  

E-print Network

Modulated power-law behaviour in Stirling's approximation Les Hatton CISM, University of Kingston. This argument used Stirling's approximation which limits its relevance to larger component sizes. Although power to broaden Stirling's approximation to see if it corresponds with the departures from power-law observed

Hatton, Les

28

On powers of words occurring in binary codings of rotations  

Microsoft Academic Search

We discuss combinatorial properties of a class of binary sequences generalizing Sturmian sequences and obtained as a coding of an irrational rotation on the circle with respect to a partition in two intervals. We give a characterization of those having a finite index in terms of a two-dimensional continued fraction like algorithm, the so-called D-expansion. Then, we discuss powers occurring

Boris Adamczewski

2005-01-01

29

On Power-law Relationships of the Internet Topology  

Microsoft Academic Search

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

Michalis Faloutsos; Petros Faloutsos; Christos Faloutsos

1999-01-01

30

A review of power laws in real life phenomena  

NASA Astrophysics Data System (ADS)

Power law distributions, also known as heavy tail distributions, model distinct real life phenomena in the areas of biology, demography, computer science, economics, information theory, language, and astronomy, amongst others. In this paper, it is presented a review of the literature having in mind applications and possible explanations for the use of power laws in real phenomena. We also unravel some controversies around power laws.

Pinto, Carla M. A.; Mendes Lopes, A.; Machado, J. A. Tenreiro

2012-09-01

31

Power-law spatial dispersion from fractional Liouville equation  

SciTech Connect

A microscopic model in the framework of fractional kinetics to describe spatial dispersion of power-law type is suggested. The Liouville equation with the Caputo fractional derivatives is used to obtain the power-law dependence of the absolute permittivity on the wave vector. The fractional differential equations for electrostatic potential in the media with power-law spatial dispersion are derived. The particular solutions of these equations for the electric potential of point charge in this media are considered.

Tarasov, Vasily E. [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)] [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

2013-10-15

32

Testing the power law model for discrete size data.  

PubMed

It is sometimes claimed that different types of size data in biology follow a power law. Here, a formal statistical test of the power law for discrete size data is described. The test is based on embedding the power law in the nonparametric family of distributions for which frequency is nonincreasing with size. A parametric bootstrap is used to assess significance. The test is applied to four data sets concerning the frequency of genera of different sizes. The power law is rejected in three out of four cases. PMID:14618544

Solow, Andrew R; Costello, Christopher J; Ward, Michael

2003-11-01

33

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

NASA Astrophysics Data System (ADS)

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 ?? are discussed. A derivation of the Gibbs law ?? =-T? is given with ? being the surface adsorption. Calculated quantities include the derivatives dTc/dX and dpc/dX of the critical temperature and pressure with respect to the solute molar fraction X and the temperature-derivative (??/?T)cx,p of the surface tension at fixed pressure p on the coexistence surface. Here (??/?T)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.

Onuki, Akira

2009-03-01

34

Small power systems for law enforcement applications  

NASA Astrophysics Data System (ADS)

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 survey and assess options for powering these devices ina long-term scenario. These alternatives are in various stages of development, and range from conventional batteries and solar cells that are ready for deployment and are now commercially available; to technologies developed for other applications (e.g., power for deep-space probes, man portable power for soldiers, or for sensors in oil drilling bore holes) that would need to be adapted to UGS's; to new and often speculative concepts that are in the laboratory or are still on the drawing board. Ideally, unattended ground sensors do not require servicing, re- energizing or refueling; and are capable of autonomous operation for weeks or even years. Further, UGS's may need to be used covertly, which restricts schemes that would provide a detectable signature. Reliability, ruggedness, cost, weight, size, camouflaging, use of toxic materials and other safety or disposal aspects, restrictions on their deployment (e.g., whether UGS's can be dropped form the air or whether they need to be uprighted or favorably oriented), storage and inventorying considerations, temperature ranges of operation, and complexity of associated electronics are also important issues. In this paper, we will limit the discussion to systems where operating power does not exceed 5 watts since larger systems are commercially available. Some subjectivity in comparisons is perhaps inevitable, but despite the disparate physics upon which these devices are based, a few common criteria can be invoked for discussing their suitability for energy storage and powering UGS's. Metrics can be developed to assess and compare options, but since most of the options are in very different stages of development, one is sometimes forced to use performance specifications that are predicted, rather than demonstrated. Thus, in some cases the comparisons are tentative or speculative.

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

2002-08-01

35

ON CYCLOTOMIC POLYNOMIALS, POWER RESIDUES, AND RECIPROCITY LAWS  

E-print Network

ON CYCLOTOMIC POLYNOMIALS, POWER RESIDUES, AND RECIPROCITY LAWS ROMYAR T. SHARIFI Abstract of quadratic reciprocity. Indeed, this problem was one of the main motivations for the formulation of this law conjectures use reciprocity laws which arose as generalizations of quadratic reciprocity. For arbitrary nth

Sharifi, Romyar

36

A law of mixtures for transport properties in binary particulate composites  

SciTech Connect

A connected-grain model was developed earlier to explain mechanical and thermal properties of porous ceramics and sedimentary rocks. We have now generalized this model for binary particulate composites, based on simulation of a connected-grain structure of individual components of the composites by randomly selecting individual grains and shrinking them. Repetition of this procedure results in a structure of a binary particulate composite that contains channels of individual components, through which transport occurs. We developed a generalized law of mixtures in which transport properties are expressed as scaling relationships that depend on the shrinking parameter expressed as an exponent. This parameter provides the skewness of the distribution of the grains. The model is compared with various transport properties of binary composites reported in the literature. In addition, the model is tested on YBa{sub 2}Cu{sub 3}O{sub x} superconductors and Ag composites that were fabricated in our laboratory and tested for electrical conductivity and elastic modulus. This test demonstrates how the model predicts two entirely different transport properties through their common microstructure and grain-size distribution. {copyright} {ital 1998 American Institute of Physics.}

Duncan, K.L.; Lodenquai, J.F. [Physics Department, University of the West Indies, Mona, Kingston 7 (Jamaica)] [Physics Department, University of the West Indies, Mona, Kingston 7 (Jamaica); Wagh, A.S.; Goretta, K.C. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439-4838 (United States)] [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439-4838 (United States)

1998-09-01

37

Power-law entropic corrections to Newton's law and Friedmann equations  

Microsoft Academic Search

A possible source of black hole entropy could be the entanglement of quantum fields inside and outside the horizon. The entanglement entropy of the ground state obeys the area law. However, a correction term proportional to a fractional power of area results when the field is in a superposition of ground and excited states. Inspired by the power-law corrections to

A. Sheykhi; S. H. Hendi

2011-01-01

38

Low Power Reversible Parallel Binary Adder/Subtractor  

E-print Network

In recent years, Reversible Logic is becoming more and more prominent technology having its applications in Low Power CMOS, Quantum Computing, Nanotechnology, and Optical Computing. Reversibility plays an important role when energy efficient computations are considered. In this paper, Reversible eight-bit Parallel Binary Adder/Subtractor with Design I, Design II and Design III are proposed. In all the three design approaches, the full Adder and Subtractors are realized in a single unit as compared to only full Subtractor in the existing design. The performance analysis is verified using number reversible gates, Garbage input/outputs and Quantum Cost. It is observed that Reversible eight-bit Parallel Binary Adder/Subtractor with Design III is efficient compared to Design I, Design II and existing design.

Rangaraju, H G; Muralidhara, K N; Raja, K B; 10.5121/vlsic.2010.1303

2010-01-01

39

Power-law mass distribution of aggregation systems with injection  

Microsoft Academic Search

We introduce a new family of aggregation models with constant interjection. In our models, the asymptotic distribution of particle mass, s, always follows a power law, P(>=s)~s-alpha, where (1\\/3<=alpha<= 1) \\/ 2 . It is clarified that this power law is realized by a balance of two effects, injection and aggregation.

Hideki Takayasu; Ikuko Nishikawa; Hal Tasaki

1988-01-01

40

On the inverse power laws for accelerated random fatigue testing  

Microsoft Academic Search

This paper addresses the usage of inverse power laws in accelerated fatigue testing under wide-band Gaussian random loading. The aim is not at predicting an absolute value of fatigue life but assessing the fatigue damage relative accumulation. The widely accepted inverse power scaling laws in fatigue damage assessment is discussed, reviewing the engineering standards and pointing out their inherent limitations.

G. Allegri; X. Zhang

2008-01-01

41

On the inverse power laws for accelerated random fatigue testing  

Microsoft Academic Search

This paper addresses the usage of inverse power laws in accelerated fatigue testing under wide-band Gaussian random loading. The aim is not at predicting an ab- solute value of fatigue life but assessing the fatigue damage relative accumulation. The widely accepted inverse power scaling laws in fatigue damage assessment is discussed, reviewing the engineering standards and pointing out their inherent

G. Allegri; X. Zhang

2009-01-01

42

Functionality, power-laws and defect evolution in software systems  

Microsoft Academic Search

In a previous paper, an intimate link between power-law distri- bution of component sizes and defect growth in maturing software systems, independently of their representation language, was revealed by the use of a variational method built on statistical mechanical ar- guments. Building on the above work, this paper first of all demonstrates ex- perimentally that power-law behaviour in component sizes

Les Hatton

43

Construction of Russia's pilot binary power unit at the pauzhet geothermal power station  

NASA Astrophysics Data System (ADS)

The basic process diagram and main technical solutions adopted in constructing the pilot 2.5-MW Pauzhet binary geothermal power station are described. Results obtained from an analysis of some principles of selecting the working fluid and optimizing the working parameters and operating modes of this power unit are presented.

Tomarov, G. V.; Nikol'Skii, A. I.; Semenov, V. N.; Shipkov, A. A.

2010-11-01

44

Power-Law Entropic Corrections to Newton's Law and Friedmann Equations  

E-print Network

A possible source of black hole entropy could be the entanglement of quantum fields in and out the horizon. The entanglement entropy of the ground state obeys the area law. However, a correction term proportional to a fractional power of area results when the field is in a superposition of ground and excited states. Inspired by the power-law corrections to entropy and adopting the viewpoint that gravity emerges as an entropic force, we derive modified Newton's law of gravitation as well as the corrections to Friedmann equations. In a different approach, we obtained power-law corrected Friedmann equation by starting from the first law of thermodynamics at apparent horizon of a FRW universe, and assuming that the associated entropy with apparent horizon has a power-law corrected relation. Our study shows a consistency between the obtained results of these two approaches. We also examine the time evolution of the total entropy including the power-law corrected entropy associated with the apparent horizon together with the matter field entropy inside the apparent horizon and show that the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon.

Ahmad Sheykhi; Seyed Hossein Hendi

2010-11-02

45

Refraction of power-law spatial solitons — The Helmholtz-Snell law  

Microsoft Academic Search

The behaviour of a scalar optical beam at the boundary between two dissimilar nonlinear media is of fundamental interest in photonics. Here, we report the first systematic generalization of our Kerr analyses to a wider class of power-law materials. Universal refraction laws will be given, and theory-simulation agreement demonstrated.

J. M. Christian; J. Sa?nchez-Curto; P. Chamorro-Posada; G. S. McDonald; E. A. McCoy

2010-01-01

46

A Cosmic Coincidence: The Power-law Galaxy Correlation Function  

NASA Astrophysics Data System (ADS)

We model the evolution of galaxy clustering through cosmic time to investigate the nature of the power-law shape of ?(r), the galaxy two-point correlation function. While ?(r) at large scales is set by primordial fluctuations, departures from a power law are governed by galaxy pair counts at small scales, subject to nonlinear dynamics. We assume that galaxies reside within dark matter halos and subhalos. Therefore, the shape of the correlation function at small scales depends on the amount of halo substructure. We use a semi-analytic substructure evolution model to study subhalo populations within host halos. We find that tidal mass loss and, to a lesser extent, dynamical friction dramatically deplete the number of subhalos within larger host halos over time, resulting in a ~90% reduction by z = 0 compared to the number of distinct mergers that occur during the assembly of a host halo. We show that these nonlinear processes resulting in this depletion are essential for achieving a power law ?(r). We investigate how the shape of ?(r) depends on subhalo mass (or luminosity) and redshift. We find that ?(r) breaks from a power law at high masses, implying that only galaxies of luminosities <~ L * should exhibit power-law clustering. Moreover, we demonstrate that ?(r) evolves from being far from a power law at high redshift, toward a near power-law shape at z = 0. We argue that ?(r) will once again evolve away from a power law in the future. This is in large part caused by the evolving competition between the accretion and destruction rates of subhalos over time, which happen to strike just the right balance at z ? 0. We then investigate the conditions required for ?(r) to be a power law in a general context. We use the halo model, along with simple parameterizations of the halo occupation distribution, to probe galaxy occupation at various masses and redshifts. We show that the key ingredients determining the shape of ?(r) are the fraction of galaxies that are satellites, the relative difference in mass between the halos of isolated galaxies and halos that contain a single satellite on average, and the rareness of halos that host galaxies. These pieces are intertwined and we find no simple, universal rule for which a power law ?(r) will occur. However, we do show that the physics responsible for setting the galaxy content of halos do not care about the conditions needed to achieve a power law ?(r) and that these conditions are met only in a narrow mass and redshift range. We conclude that the power-law nature of ?(r) for L * and fainter galaxy samples at low redshift is a cosmic coincidence.

Watson, Douglas F.; Berlind, Andreas A.; Zentner, Andrew R.

2011-09-01

47

ISPM, Division of Biostatistics Modelling power-law spread  

E-print Network

ISPM, Division of Biostatistics Modelling power-law spread of infectious diseases Sebastian Meyer 2013 Page 1 #12;ISPM, Division of Biostatistics Epidemic Modelling ­ Prospective surveillance: outbreak-law spread of infectious diseases Page 2 #12;ISPM, Division of Biostatistics Mobility networks determine

Zurich, University of

48

Binary generators - you'll wonder where the power went  

SciTech Connect

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.

Ryan, G.P.

1983-02-01

49

Fractal ladder models and power law wave equations  

PubMed Central

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

Kelly, James F.; McGough, Robert J.

2009-01-01

50

Quantum power correction to the Newton law  

Microsoft Academic Search

A graviton contribution to the one-loop quantum correction to the Newton law is found. This correction corresponds to an interaction\\u000a decreasing with distance as 1\\/r\\u000a 3, in which the graviton contribution numerically dominates. Previous calculations of this contribution to the discussed effect\\u000a are demonstrated to be incorrect.

G. G. Kirilin; I. B. Khriplovich

2002-01-01

51

Quantum power correction to the Newton law  

E-print Network

We have found the graviton contribution to the one-loop quantum correction to the Newton law. This correction results in interaction decreasing with distance as 1/r^3 and is dominated numerically by the graviton contribution. The previous calculations of this contribution to the discussed effect are demonstrated to be incorrect.

I. B. Khriplovich; G. G. Kirilin

2002-07-30

52

On the Packet Delay Distribution in Power-Law Networks  

Microsoft Academic Search

Measurement studies of the Internet topology have revealed that the degree distribution exhibits a power-law attribute. That is, the probability P(k) that a node has k outgoing links follows P(k) ~ k-gamma. However, it is known that the power-law degree distribution alone does not determine traffic-level behaviors in Internet topologies. In this paper, we investigate packet-level delay behavior of topologies

Takahiro Hirayama; S. Arakawa; K.-i. Arai; M. Murata

2009-01-01

53

Singularity problems of the power law for modeling creep compliance  

NASA Technical Reports Server (NTRS)

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.

Dillard, D. A.; Hiel, C.

1985-01-01

54

Leakage Current: Moore's Law Meets Static Power  

Microsoft Academic Search

Abstract: for some time. Figure 1shows total chip dynamic and static power consumptiontrends based on 2002 statistics normalizedto the 2001 International Technology Roadmapfor Semiconductors.The ITRS projects adecrease in dynamic power per device over time.However, if we assume a doubling of on-chipdevices every two years, total dynamic power willincrease on a per-chip basis. Packaging and coolingcosts as well as the limited

Nam Sung Kim; Todd M. Austin; David Blaauw; Trevor N. Mudge; Krisztián Flautner; Jie S. Hu; Mary Jane Irwin; Mahmut T. Kandemir; Narayanan Vijaykrishnan

2003-01-01

55

Power-Law Entropic Corrections to Newton's Law and Friedmann Equations From Entropic Force  

Microsoft Academic Search

A possible source of black hole entropy could be the entanglement of quantum\\u000afields in and out the horizon. The entanglement entropy of the ground state\\u000aobeys the area law. However, a correction term proportional to a fractional\\u000apower of area results when the field is in a superposition of ground and\\u000aexcited states. Inspired by the power-law corrections to

Ahmad Sheykhi; Seyed Hossein Hendi

2010-01-01

56

Power-law friction in closely-packed granular materials  

E-print Network

In order to understand the nature of friction in closely-packed granular materials, a discrete element simulation on granular layers subjected to isobaric plain shear is performed. It is found that the friction coefficient increases as the power of the shear rate, the exponent of which does not depend on the material constants. Using a nondimensional parameter that is known as the inertial number, the power-law can be cast in a generalized form so that the friction coefficients at different confining pressures collapse on the same curve. We show that the volume fraction also obeys a power-law.

Takahiro Hatano

2006-12-14

57

Primordial scalar perturbations in tachyonic power-law inflation  

NASA Astrophysics Data System (ADS)

In this work we determine the power spectrum of the gravitational potential of the primordial fluctuations for an inflationary model whose inflaton is a noncanonical scalar field of the tachyon-type. The respective background field equations for an inverse-square potential produce a power-law inflation, and it is explicitly shown that for such a potential the power spectrum tends to be scale independent for highly accelerated regimes in the inflationary expansion.

de Souza, Rudinei C.; Kremer, Gilberto M.

2014-01-01

58

A COSMIC COINCIDENCE: THE POWER-LAW GALAXY CORRELATION FUNCTION  

SciTech Connect

We model the evolution of galaxy clustering through cosmic time to investigate the nature of the power-law shape of {xi}(r), the galaxy two-point correlation function. While {xi}(r) at large scales is set by primordial fluctuations, departures from a power law are governed by galaxy pair counts at small scales, subject to nonlinear dynamics. We assume that galaxies reside within dark matter halos and subhalos. Therefore, the shape of the correlation function at small scales depends on the amount of halo substructure. We use a semi-analytic substructure evolution model to study subhalo populations within host halos. We find that tidal mass loss and, to a lesser extent, dynamical friction dramatically deplete the number of subhalos within larger host halos over time, resulting in a {approx}90% reduction by z = 0 compared to the number of distinct mergers that occur during the assembly of a host halo. We show that these nonlinear processes resulting in this depletion are essential for achieving a power law {xi}(r). We investigate how the shape of {xi}(r) depends on subhalo mass (or luminosity) and redshift. We find that {xi}(r) breaks from a power law at high masses, implying that only galaxies of luminosities {approx}< L{sub *} should exhibit power-law clustering. Moreover, we demonstrate that {xi}(r) evolves from being far from a power law at high redshift, toward a near power-law shape at z = 0. We argue that {xi}(r) will once again evolve away from a power law in the future. This is in large part caused by the evolving competition between the accretion and destruction rates of subhalos over time, which happen to strike just the right balance at z {approx} 0. We then investigate the conditions required for {xi}(r) to be a power law in a general context. We use the halo model, along with simple parameterizations of the halo occupation distribution, to probe galaxy occupation at various masses and redshifts. We show that the key ingredients determining the shape of {xi}(r) are the fraction of galaxies that are satellites, the relative difference in mass between the halos of isolated galaxies and halos that contain a single satellite on average, and the rareness of halos that host galaxies. These pieces are intertwined and we find no simple, universal rule for which a power law {xi}(r) will occur. However, we do show that the physics responsible for setting the galaxy content of halos do not care about the conditions needed to achieve a power law {xi}(r) and that these conditions are met only in a narrow mass and redshift range. We conclude that the power-law nature of {xi}(r) for L{sub *} and fainter galaxy samples at low redshift is a cosmic coincidence.

Watson, Douglas F.; Berlind, Andreas A. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Zentner, Andrew R. [Department of Physics and Astronomy, The University of Pittsburgh, Pittsburgh, PA 15260 (United States)

2011-09-01

59

Testing power-law cross-correlations: rescaled covariance test  

NASA Astrophysics Data System (ADS)

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.

Kristoufek, Ladislav

2013-10-01

60

Modelling power-law spread of infectious diseases  

E-print Network

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 ...

Meyer, Sebastian

2013-01-01

61

Universal power law in crossover from integrability to quantum chaos  

NASA Astrophysics Data System (ADS)

We study models of interacting fermions in one dimension to investigate the crossover from integrability to nonintegrability, i.e., quantum chaos, as a function of system size. Using exact diagonalization of finite-sized systems, we study this crossover by obtaining the energy level statistics and Drude weight associated with transport. Our results reinforce the idea that for system size L ?? nonintegrability sets in for an arbitrarily small integrability-breaking perturbation. The crossover value of the perturbation scales as a power law ˜L-? when the integrable system is gapless. The exponent ? ?3 appears to be robust to microscopic details and the precise form of the perturbation. We conjecture that the exponent in the power law is characteristic of the random matrix ensemble describing the nonintegrable system. For systems with a gap, the crossover scaling appears to be faster than a power law.

Modak, Ranjan; Mukerjee, Subroto; Ramaswamy, Sriram

2014-08-01

62

Statistical Models of Power-law Distributions in Homogeneous Plasmas  

SciTech Connect

A variety of in-situ measurements in space plasmas point out to an intermittent formation of distribution functions with elongated tails and power-law at high energies. Power-laws form ubiquitous signature of many complex systems, plasma being a good example of a non-Boltzmann behavior for distribution functions of energetic particles. Particles, which either undergo mutual collisions or are scattered in phase space by electromagnetic fluctuations, exhibit statistical properties, which are determined by the transition probability density function of a single interaction, while their non-asymptotic evolution may determine the observed high-energy populations. It is shown that relaxation of the Brownian motion assumptions leads to non-analytical characteristic functions and to generalization of the Fokker-Planck equation with fractional derivatives that result in power law solutions parameterized by the probability density function.

Roth, Ilan [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2011-01-04

63

Describing the properties of compressed expanded graphite through power laws  

NASA Astrophysics Data System (ADS)

In this paper, valuable formulae describing the behaviour of a number of physical properties of moderately compressed expanded graphite (CEG) are given. Many of these relationships provide confirmations of empirical power law equations which had remained unexplained. Other physical properties are also described for the first time with power laws whose exponents are derived rigorously. On the basis of early works by the authors, the origins of the observed behaviours are explained, hence providing a better understanding of the material. Thus, the variations with the density of CEG of the thermal and electrical conductivities, elastic moduli, mosaicities, permeabilities, formation factors, characteristic pore radii and diameters, surface areas and open pore volumes are described. Power laws are shown to apply, and the values of the corresponding exponents are compared both with the results of the authors and with those from the literature.

Celzard, A.; Marêché, J. F.; Furdin, G.

2003-11-01

64

The power law relationship for landslide fatality data  

NASA Astrophysics Data System (ADS)

In recent years there has been considerable interest in the nature of the power law relationship in landslide area and volume datsets. In other hazards, similar fat-tailed power law distributions have been observed for loss data. For example, both earthquake fatality datasets for large events (Knopoff and Sornette 1995) and for flood losses (Pisarenko 1998) have been shown to display power law distributions. Data from very large rockslope failures also suggests that fat tailed power law distributions may describe the occurrence of fatalities associated with these events (Evans et al. 2006). However, there has been a lack of rigorous analysis of the statistical distributions for fatality datasets for all landslide events, which is unfortunate given the potential use of this data to examine potential losses from forecast events. This paper examines nine years of rainfall induced landslide data from the Durham Fatal Landslide database, which provides records losses of life from landslides on a global basis. It is demonstrated that the landslide fatality data exhibits a clear fat tailed power law distribution. A roll-over is noted for events with small numbers of fatalities (i.e. one or two deaths per event), suggesting under-sampling in that part of the distribution. Examination of this roll-over for the data for individual years suggests that its magnitude is becoming smaller, which in turn implies that the quality of the dataset may be improving with time. An examination is made of the power law distribution for different geographical areas; it is suggested that differences in the scaling of the dataset may be related to a combination of the physical conditions associated with the landslides themselves (e.g. topography, climate, geology and land cover) and the social setting (e.g. population density, household size and wealth).

Petley, D. N.

2011-12-01

65

Local Gravity Constraints and Power Law f(R) Theories  

E-print Network

There is a conformal equivalence between power law $f(R)$ theories and scalar field theories in which the scalar degree of freedom evolves under the action of an exponential potential function. In the scalar field representation there is a strong coupling of the scalar field with the matter sector due to the conformal transformation. We use chameleon mechanism to implement constraints on the potential function of the scalar field in order that the resulting model be in accord with Solar System experiments. Investigation of these constraints reveals that there may be no possibility to distinguish between a power law $f(R)$ function and the usual Einstein-Hilbert Lagrangian density.

Yousef Bisabr

2010-05-31

66

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

Microsoft Academic Search

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

C. J. Bliem; G. L. Mines

1989-01-01

67

Inapproximability of Dominating Set in Power Law Mikael Gast  

E-print Network

Inapproximability of Dominating Set in Power Law Graphs Mikael Gast Mathias Hauptmann Marek01; Gue+02; Sig+03; Eub+04b; Ses+08]. In the research of epidemic spreading of diseases across for disease detection inside social net- works Eubank et al. [Eub+04b] studied near-optimal Minimum Dominating

Karpinski, Marek

68

Power scaling laws and dimensional transitions in solid mechanics  

Microsoft Academic Search

Physicists have often observed a scaling behaviour of the main physical quantities during experiments on systems exhibiting a phase transition. The main assumption of a scaling theory is that these characteristic quantities are self-similar functions of the independent variables of the phenomenon and, therefore, such a scaling can be interpreted be means of power-laws. Since a characteristic feature of phase

Alberto Carpinteri; Bernardino Chiaia

1996-01-01

69

Brief Announcement: Efficient Flooding in Power-Law Networks  

E-print Network

Brief Announcement: Efficient Flooding in Power-Law Networks Farnoush Banaei-Kashani University California Los Angeles, California 90089 shahabi@usc.edu ABSTRACT Flooding is an effective mechanism for both and guaranteeing minimum delay. However, flooding is not a scalable communication mech- anism, mainly because

Shahabi, Cyrus

70

On the origin of power laws in Internet topologies  

Microsoft Academic Search

Recent empirical studies [6] have shown that Internet topologies exhibit power laws of the form y = x ? for the following relationships: (P1) outdegree of node (domain or router) versus rank; (P2) number of nodes versus outdegree; (P3) number of node pairs within a neighborhood versus neighborhood size (in hops); and (P4) eigenvalues of the adjacency matrix versus rank.

Alberto Medina; Ibrahim Matta; John W. Byers

2000-01-01

71

The Origin of Power-Laws in Internet Topologies Revisited  

Microsoft Academic Search

In a recent paper, Faloutsos et al. (1) found that the inter Autonomous System (AS) topology exhibits a power-law vertex degree dis- tribution. This result was quite unexpected in the networking community and stirred significant interest in exploring the possible causes of this phe- nomenon. The work of Barabasi and Albert (2) and its application to net- work topology generation

Qian Chen; Hyunseok Chang; Ramesh Govindan; Sugih Jamin; Scott J. Shenker; Walter Willinger

2002-01-01

72

A consistency relation for power law inflation in DBI models  

Microsoft Academic Search

Brane inflation in string theory leads to a new realization of power law inflation which can give rise to significant non-gaussianity. This can happen for any throat geometry if the scalar potential is appropriate. This Letter presents a consistency relation connecting the running of the nonlinearity parameter characterizing the non-gaussianity and the scalar and tensor indices. The relationship is valid

Micha? Spali?ski

2007-01-01

73

Diapiric ascent of magmas through power law crust and mantle  

Microsoft Academic Search

There has never been a convincing explanation of the way in which diapirs of molten granite can effectively rise through mantle and crust. We argue here that this is mainly because the country rocks have previously been assumed to be Newtonian, and we show that granitoid diapirs rising through thermally graded power law crust may indeed rise to shallow crustal

Roberto Ferrez Weinberg; Yuri Podladchikov

1994-01-01

74

Second law analysis of a conventional steam power plant  

NASA Technical Reports Server (NTRS)

A numerical investigation of exergy destroyed by operation of a conventional steam power plant is computed via an exergy cascade. An order of magnitude analysis shows that exergy destruction is dominated by combustion and heat transfer across temperature differences inside the boiler, and conversion of energy entering the turbine/generator sets from thermal to electrical. Combustion and heat transfer inside the boiler accounts for 53.83 percent of the total exergy destruction. Converting thermal energy into electrical energy is responsible for 41.34 percent of the total exergy destruction. Heat transfer across the condenser accounts for 2.89 percent of the total exergy destruction. Fluid flow with friction is responsible for 0.50 percent of the total exergy destruction. The boiler feed pump turbine accounts for 0.25 percent of the total exergy destruction. Fluid flow mixing is responsible for 0.23 percent of the total exergy destruction. Other equipment including gland steam condenser, drain cooler, deaerator and heat exchangers are, in the aggregate, responsible for less than one percent of the total exergy destruction. An energy analysis is also given for comparison of exergy cascade to energy cascade. Efficiencies based on both the first law and second law of thermodynamics are calculated for a number of components and for the plant. The results show that high first law efficiency does not mean high second law efficiency. Therefore, the second law analysis has been proven to be a more powerful tool in pinpointing real losses. The procedure used to determine total exergy destruction and second law efficiency can be used in a conceptual design and parametric study to evaluate the performance of other steam power plants and other thermal systems.

Liu, Geng; Turner, Robert H.; Cengel, Yunus A.

1993-01-01

75

Spectral geometry of power-law potentials in quantum mechanics  

NASA Astrophysics Data System (ADS)

It is supposed that a single particle moves in openR3 in an attractive central power-law potential V(q)(r)=sgn(q)rq, q>-2, and obeys nonrelativistic quantum mechanics. This paper is concerned with the question: How do the discrete eigenvalues Enl(q) of the Hamiltonian H=-?+V(q) depend on the power parameter q\\? Pure power-law potentials have the elementary property that, for p

Hall, Richard L.

1989-06-01

76

Automated piecewise power-law modeling of biological systems.  

PubMed

Recent trends suggest that future biotechnology will increasingly rely on mathematical models of the biological systems under investigation. In particular, metabolic engineering will make wider use of metabolic pathway models in stoichiometric or fully kinetic format. A significant obstacle to the use of pathway models is the identification of suitable process descriptions and their parameters. We recently showed that, at least under favorable conditions, Dynamic Flux Estimation (DFE) permits the numerical characterization of fluxes from sets of metabolic time series data. However, DFE does not prescribe how to convert these numerical results into functional representations. In some cases, Michaelis-Menten rate laws or canonical formats are well suited, in which case the estimation of parameter values is easy. However, in other cases, appropriate functional forms are not evident, and exhaustive searches among all possible candidate models are not feasible. We show here how piecewise power-law functions of one or more variables offer an effective default solution for the almost unbiased representation of uni- and multivariate time series data. The results of an automated algorithm for their determination are piecewise power-law fits, whose accuracy is only limited by the available data. The individual power-law pieces may lead to discontinuities at break points or boundaries between sub-domains. In many practical applications, these boundary gaps do not cause problems. Potential smoothing techniques, based on differential inclusions and Filippov's theory, are discussed in Appendix A. PMID:20060428

Machina, Anna; Ponosov, Arkady; Voit, Eberhard O

2010-09-01

77

Deviation from Power Law Behavior in Landslide Phenomenon  

NASA Astrophysics Data System (ADS)

Power law distribution of magnitude is widely observed in many natural hazards (e.g., earthquake, floods, tornadoes, and forest fires). Landslide is unique as the size distribution of landslide is characterized by a power law decrease with a rollover in the small size end. Yet, the emergence of the rollover, i.e., the deviation from power law behavior for small size landslides, remains a mystery. In this contribution, we grouped the forces applied on landslide bodies into two categories: 1) the forces proportional to the volume of failure mass (gravity and friction), and 2) the forces proportional to the area of failure surface (cohesion). Failure occurs when the forces proportional to volume exceed the forces proportional to surface area. As such, given a certain mechanical configuration, the failure volume to failure surface area ratio must exceed a corresponding threshold to guarantee a failure. Assuming all landslides share a uniform shape, which means the volume to surface area ratio of landslide regularly increase with the landslide volume, a cutoff of landslide volume distribution in the small size end can be defined. However, in realistic landslide phenomena, where heterogeneities of landslide shape and mechanical configuration are existent, a simple cutoff of landslide volume distribution does not exist. The stochasticity of landslide shape introduce a probability distribution of the volume to surface area ratio with regard to landslide volume, with which the probability that the volume to surface ratio exceed the threshold can be estimated regarding values of landslide volume. An experiment based on empirical data showed that this probability can induce the power law distribution of landslide volume roll down in the small size end. We therefore proposed that the constraints on the failure volume to failure surface area ratio together with the heterogeneity of landslide geometry and mechanical configuration attribute for the deviation from power law behavior in landslide phenomenon. Figure shows that a rollover of landslide size distribution in the small size end is produced as the probability for V/S (the failure volume to failure surface ratio of landslide) exceeding the mechanical threshold applied to the power law distribution of landslide volume.

Li, L.; Lan, H.; Wu, Y.

2013-12-01

78

Value at Risk in the Presence of the Power Laws  

NASA Astrophysics Data System (ADS)

The aim of this paper is to determine the Value at Risk (VaR) of the portfolio consisting of several long positions in risky assets. We consider the case when the tail parts of distributions of logarithmic returns of these assets follow the power law of the same degree and the lower tail of associated copula C follows the power law of degree 1. We provide the asymptotic formula for Value at Risk and determine the optimal portfolio. We show that the part of the capital invested in the i-th asset should be equal to the conditional probability that the drop of the value of the i-th asset will be smaller than the others under the condition that the value of the all assets will be smaller than c times their initial value (c << 1).

Jaworski, P.

2005-08-01

79

Ising Models on Power-Law Random Graphs  

NASA Astrophysics Data System (ADS)

We study a ferromagnetic Ising model on random graphs with a power-law degree distribution and compute the thermodynamic limit of the pressure when the mean degree is finite (degree exponent ?>2), for which the random graph has a tree-like structure. For this, we closely follow the analysis by Dembo and Montanari (Ann. Appl. Probab. 20(2):565-592, 2010) which assumes finite variance degrees ( ?>3), adapting it when necessary and also simplifying it when possible. Our results also apply in cases where the degree distribution does not obey a power law. We further identify the thermodynamic limits of various physical quantities, such as the magnetization and the internal energy.

Dommers, Sander; Giardinà, Cristian; van der Hofstad, Remco

2010-11-01

80

New exact solutions for power-law inflation Friedmann models  

E-print Network

We consider the spatially flat Friedmann model. For a(t) = t^p, especially, if p is larger or equal to 1, this is called power-law inflation. For the Lagrangian L = R^m with p = - (m - 1)(2m - 1)/(m - 2), power-law inflation is an exact solution, as it is for Einstein gravity with a minimally coupled scalar field Phi in an exponential potential V(Phi) = exp(mu Phi) and also for the higher-dimensional Einstein equation with a special Kaluza-Klein ansatz. The synchronized coordinates are not adapted to allow a closed-form solution, so we use another gauge. Finally, special solutions for the closed and open Friedmann model are found.

H. -J. Schmidt

2001-09-04

81

Power-law cosmology, SN Ia, and BAO  

NASA Astrophysics Data System (ADS)

We revise observational constraints on the class of models of modified gravity which at low redshifts lead to a power-law cosmology. To this end we use available public data on Supernova Ia and on baryon acoustic oscillations. We show that the expansion regime a(t) ~ t? with ? close to 3/2 in a spatially flat universe is a good fit to these data.

Dolgov, Aleksander; Halenka, Vitali; Tkachev, Igor

2014-10-01

82

London house prices are power-law distributed  

E-print Network

In this pilot study we explore the house price distributions for London, Manchester, Bristol, Newcastle, Birmingham and Leeds. We find Pareto (power law) behaviour in their upper tails, which is clearly distinct from lognormal behaviour in the cases of London and Manchester. We propose an index of Housing Wealth Inequality based on the Pareto exponent and analogous to the Gini coefficient, and comment on its possible uses.

MacKay, Niall

2010-01-01

83

Power-Law Testing for Fault Attributes Distributions  

NASA Astrophysics Data System (ADS)

This paper is devoted to statistical analysis of faults' attributes. The distributions of lengths, widths of damage zones, displacements and thicknesses of fault cores are studied. Truncated power-law (TPL) is considered in comparison with commonly used simple power-law (PL) (or Pareto) distribution. The maximal likelihood and the confidence interval of the exponent for both PL and TPL are estimated by appropriate statistical methods. The Kolmogorov-Smirnov (KS) test and the likelihood ratio test with alternative non-nested hypothesis for exponential distribution are used to verify the statistical approximation. Furthermore, the advantage of TPL is proved by Bayesian information criterion. Our results suggest that a TPL is more suitable for describing fault attributes, and that its condition is satisfied for a wide range of fault scales. We propose that using truncated power laws in general might eliminate or relax the bias related to sampling strategy and the resolution of measurements (such as censoring, truncation, and cut effect) and; therefore, the most reliable range of data can be considered for the statistical approximation of fault attributes.

Kolyukhin, Dmitry; Torabi, Anita

2013-12-01

84

Peristaltic transport of two-layered power-law fluids.  

PubMed

Peristaltic transport of two-layered power-law fluids in axisymmetric tubes is studied. Use of the power-law fluid model permits independent choice of shear thinning, shear thickening, or Newtonian fluids for the core and the peripheral layer. The interface between the two layers is determined from a transcendental equation in the core radius. The variation of the time-mean flow Q with the pressure rise or drop over one wavelength delta p is studied. It is observed that a negative time-mean flow is achieved under free pumping (delta p = 0) for the wave forms considered here if one of the peripheral layer and core fluids is non-Newtonian. The rheology of the peripheral layer fluid is a dominant factor in producing a negative or positive mean flow. It is noticed that a sinusoidal wave always yields a positive mean flow for power-law fluids. The trapped bolus volume for sinusoidal peristaltic wave is observed to decrease with an increase in the rate of shear thinning of the core and the peripheral layer fluids. PMID:9407289

Usha, S; Rao, A R

1997-11-01

85

Development of Jet Noise Power Spectral Laws Using SHJAR Data  

NASA Technical Reports Server (NTRS)

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.

Khavaran, Abbas; Bridges, James

2009-01-01

86

Binary Power Control for Sum Rate Maximization over Multiple Interfering Links  

Microsoft Academic Search

We consider allocating the transmit powers for a wireless multi-link (N-link) system, in order to maximize the total system throughput under interference and noise impairments, and short term power constraints. Employing dynamic spectral reuse, we allow for centralized control. In the two-link case, the optimal power allocation then has a remarkably simple nature termed binary power control: depending on the

Anders Gjendemsjø; David Gesbert; Geir E. Øien; Saad G. Kiani

2008-01-01

87

Phantom phase power-law solution in $f(G)$ gravity  

E-print Network

Power-law solutions for $f(G)$ gravity coupled with perfect fluid have been studied for spatially flat universe. It is shown that despite the matter dominated and accelerating power-law solutions, the power-law solution exists for an special form of $f(G)$ when this universe enters a Phantom phase.

A. R. Rastkar; M. R. Setare; F. Darabi

2011-04-11

88

Interfacial pattern formation in confined power-law fluids.  

PubMed

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

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

2014-07-01

89

Interfacial pattern formation in confined power-law fluids  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

90

Critical Multiplicities and Power Law in Spontaneous Magnetization  

NASA Astrophysics Data System (ADS)

Spontaneous magnetization of a finite system of particles has been modeled via a genetic algorithm based on mutation and selection. As the critical temperature is approached, distinct critical multiplicities are attained notwithstanding a constant power law is observed all along the evolution of the system, in agreement with Fisher theory of nucleation. The constant critical exponent obtained is the same as the critical exponent for the Heavy Ions Collisions universality class. Computations were performed at UAMA Supercomputing Lab and UT-El Paso supercomputing facilities. Authors acknowledge financial support from NSF through fund PHYS-96-00038.

Barranon, Armando; Lopez, Jorge A.

2001-10-01

91

Power-law time distribution of large earthquakes.  

PubMed

We study the statistical properties of time distribution of seismicity in California by means of a new method of analysis, the diffusion entropy. We find that the distribution of time intervals between a large earthquake (the main shock of a given seismic sequence) and the next one does not obey Poisson statistics, as assumed by the current models. We prove that this distribution is an inverse power law with an exponent mu=2.06+/-0.01. We propose the long-range model, reproducing the main properties of the diffusion entropy and describing the seismic triggering mechanisms induced by large earthquakes. PMID:12786049

Mega, Mirko S; Allegrini, Paolo; Grigolini, Paolo; Latora, Vito; Palatella, Luigi; Rapisarda, Andrea; Vinciguerra, Sergio

2003-05-01

92

Adhesion of nanoscale asperities with power-law profiles  

NASA Astrophysics Data System (ADS)

The behavior of single-asperity micro- and nanoscale contacts in which adhesion is present is important for the performance of many small-scale mechanical systems and processes, such as atomic force microscopy (AFM). When analyzing such problems, the bodies in contact are often assumed to have paraboloidal shapes, thus allowing the application of the familiar Johnson-Kendall-Roberts (JKR), Derjaguin-Müller-Toporov (DMT), or Maugis-Dugdale (M-D) adhesive contact models. However, in many situations the asperities do not have paraboloidal shapes and, instead, have geometries that may be better described by a power-law function. An M-D-n analytical model has recently been developed to extend the M-D model to asperities with power-law profiles. We use a combination of M-D-n analytical modeling, finite element (FE) analysis, and experimental measurements to investigate the behavior of nanoscale adhesive contacts with non-paraboloidal geometries. Specifically, we examine the relationship between pull-off force, work of adhesion, and range of adhesion for asperities with power-law-shaped geometries. FE analysis is used to validate the M-D-n model and examine the effect of the shape of the adhesive interaction potential on the pull-off force. In the experiments, the extended M-D model is applied to analyze pull-off force measurements made on nanoscale tips that are engineered via gradual wear to have power-law shapes. The experimental and modeling results demonstrate that the range of the adhesive interaction is a crucial parameter when quantifying the adhesion of non-paraboloidal tips, quite different than the familiar paraboloidal case. The application of the M-D-n model to the experimental results yields an unusually large adhesion range of 4-5 nm, a finding we attribute to either the presence of long-range van der Waals forces or deviations from continuum theory due to atomic-scale roughness of the tips. Finally, an adhesion map to aid in analysis of pull-off force measurements of non-paraboloidal tips is presented. The map delineates the cases in which a simplified rigid analysis can be used to analyze experimental data.

Grierson, David S.; Liu, Jingjing; Carpick, Robert W.; Turner, Kevin T.

2013-02-01

93

Dust-Raising and Power Law Statistics of Dust Devils  

NASA Astrophysics Data System (ADS)

Are Martian dust devils really larger than Earth's? What is the dust injection rate into the atmosphere? These important questions cannot be answered without a rigorous discussion of the observed size population, and consideration of the size-dependent efficiency of detection of the relevant observations. There is some evidence in both optical diameters, and in-situ meteorological measurements, that Martian dust devils follow a power-law diameter distribution. Remarkably, terrestrial data is often too poorlybinned to permit meaningful comparison with Mars. Requirements for future field data are identified: better-determined diameter measurements, and statistically-significant populations of unbiased insitu measurements from fixed stations or arrays.

Lorenz, R. D.

2011-10-01

94

Power-law expansion cosmology in Schrödinger-type formulation  

NASA Astrophysics Data System (ADS)

We investigate non-linear Schrödinger-type formulation of cosmology of which our cosmological system is a general relativistic FRLW universe containing canonical scalar field under arbitrary potential and a barotropic fluid with arbitrary spatial curvatures. We extend the formulation to include phantom field case and we have found that Schrödinger wave function in this formulation is generally non-normalizable. Assuming power-law expansion, a˜tq, we obtain scalar field potential as function of time. The corresponding quantities in Schrödinger-type formulation such as Schrödinger total energy, Schrödinger potential and wave function are also presented.

Gumjudpai, Burin

2008-11-01

95

Multiple Wannier power laws for 3 e escape  

SciTech Connect

A pair of generalized coordinates is introduced to describe Wannier threshold effects in three- and four-particle systems. In the case of four-particle breakup, they indicate the presence of multiple {ital unstable} normal modes in the breakup configuration and thus reveal a new feature in the Wannier formalism: the occurrence of a secondary Wannier power law. This prediction is in accord with recent experimental observations of a break in the cross section near threshold for triple photoionization in oxygen and in neon.

Feagin, J.M.; Filipczyk, R.D. (Department of Physics, California State University, Fullerton, California 92634 (US))

1990-01-22

96

Minimal Letter Frequency in n-th Power-Free Binary Words  

Microsoft Academic Search

We show that the minimal proportion of one letter in an n-th power-free binary word is asymptotically 1\\/n. We also consider a generalization of n-th power-free words defined through the notion of exponent: a word is -th power-free for a real , if it does not contain subwords of exponent or more. We study the minimal proportion of one letter

Roman M. Kolpakov; Gregory Kucherov

1997-01-01

97

Power Law Distributions of Patents as Indicators of Innovation  

PubMed Central

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 countries is well-described by power laws with exponents that vary between 1.66 (Japan) and 2.37 (Poland). We suggest that this exponent is a useful new metric for studying innovation. 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 research and development 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 less advanced countries. PMID:23227144

O'Neale, Dion R. J.; Hendy, Shaun C.

2012-01-01

98

Power Law Distributions of Patents as Indicators of Innovation  

E-print Network

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...

O'Neale, D R J

2012-01-01

99

Raft River 5MW Power Plant: a small binary power plant  

SciTech Connect

The Raft River 5MW power plant is a binary cycle pilot plant. The system uses isobutane in a dual boiling cycle. This cycle was selected because the well field and temperatures were not well known at the time of cycle selection, and therefore, a boiling cycle was desirable. The dual boiling feature provides about 15 to 20% more power and makes the output less sensitive to changes in geothermal temperature changes than a single boiler system. The plant design was based upon a 290F geothermal fluid temperature at the inlet to the plant and has a gross nominal generator rating of 5MW; however, actual output will vary according to ambient wet bulb temperatures over a range from 4.4MW to 6.2MW with the actual plant inlet temperature of 278F being obtained. The plant is supplied by three production wells. Geothermal fluid boost pumps within the plant inlet provide the pressure necessary to overcome plant pressure drop and return the fluid to the two injection sites. All long runs of the buried geothermal piping external to the plant boundaries use cement-asbestos pipe. The physical size and manpower requirements for the Raft River facility, the economics of small plant operation, and operational experience are discussed.

Whitbeck, J.F.; DiBello, E.G.; Walrath, L.F.

1982-01-01

100

Power-law versus log-law in wall-bounded turbulence: A large-eddy simulation perspective  

NASA Astrophysics Data System (ADS)

The debate whether the mean streamwise velocity in wall-bounded turbulent flows obeys a log-law or a power-law scaling originated over two decades ago, and continues to ferment in recent years. As experiments and direct numerical simulation can not provide sufficient clues, in this study we present an insight into this debate from a large-eddy simulation (LES) viewpoint. The LES organically combines state-of-the-art models (the stretched-vortex model and inflow rescaling method) with a virtual-wall model derived under different scaling law assumptions (the log-law or the power-law by George and Castillo ["Zero-pressure-gradient turbulent boundary layer," Appl. Mech. Rev. 50, 689 (1997)]). Comparison of LES results for Re? ranging from 105 to 1011 for zero-pressure-gradient turbulent boundary layer flows are carried out for the mean streamwise velocity, its gradient and its scaled gradient. Our results provide strong evidence that for both sets of modeling assumption (log law or power law), the turbulence gravitates naturally towards the log-law scaling at extremely large Reynolds numbers.

Cheng, W.; Samtaney, R.

2014-01-01

101

Power-Law Template for IR Point Source Clustering  

E-print Network

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 Balloon-borne Large-Aperture Submillimeter Telescope (BLAST; 250, 350 and 500 um; 1000 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 l^-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^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 arou...

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

2011-01-01

102

Power-law Template for Infrared Point-source Clustering  

NASA Astrophysics Data System (ADS)

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 <~ l <~ 2200), the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST; 250, 350, and 500 ?m 1000 <~ l <~ 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 fitted by a simple power law of the form C clust lvpropl-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, ?? B(?, T eff), with a single emissivity index ? = 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 ?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.

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

2012-06-01

103

The use of mixture working fluids in geothermal binary power cycles  

Microsoft Academic Search

The use of hydrocarbon mixtures as working fluids in the geothermal binary power cycles provides certain advantages over systems based on pure component working fluids. The composition of the working fluid can be changed in response to long-term variations in the available geothermal resource temperature. The dew point of a mixture can be customized to permit a lower turbine exhaust

K. E. Starling; L. W. Fish; K. Z. Iqbal; H. H. West

1977-01-01

104

Sample Size and Power Calculations Based on Generalized Linear Mixed Models with Correlated Binary Outcomes  

PubMed Central

The generalized linear mixed model (GLIMMIX) provides a powerful technique to model correlated outcomes with different types of distributions. The model can now be easily implemented with SAS PROC GLIMMIX in version 9.1. For binary outcomes, linearization methods of penalized quasilikelihood (PQL) or marginal quasi-likelihood (MQL) provide relatively accurate variance estimates for fixed effects. Using GLIMMIX based on these linearization methods, we derived formulas for power and sample size calculations for longitudinal designs with attrition over time. We found that the power and sample size estimates depend on the within-subject correlation and the size of random effects. In this article, we present tables of minimum sample sizes commonly used to test hypotheses for longitudinal studies. A simulation study was used to compare the results. We also provide a Web link to the SAS macro that we developed to compute power and sample sizes for correlated binary outcomes. PMID:18462826

Dang, Qianyu; Mazumdar, Sati; Houck, Patricia R.

2008-01-01

105

Raft River binary-cycle geothermal pilot power plant final report  

SciTech Connect

The design and performance of a 5-MW(e) binary-cycle pilot power plant that used a moderate-temperature hydrothermal resource, with isobutane as a working fluid, are examined. Operating problems experienced and solutions found are discussed and recommendations are made for improvements to future power plant designs. The plant and individual systems are analyzed for design specification versus actual performance figures.

Bliem, C.J.; Walrath, L.F.

1983-04-01

106

Avoiding Abelian powers in binary words with bounded Abelian complexity  

Microsoft Academic Search

The notion of Abelian complexity of infinite words was recently used by the\\u000athree last authors to investigate various Abelian properties of words. In\\u000aparticular, using van der Waerden's theorem, they proved that if a word avoids\\u000aAbelian $k$-powers for some integer $k$, then its Abelian complexity is\\u000aunbounded. This suggests the following question: How frequently do Abelian\\u000a$k$-powers occur

Julien Cassaigne; Gwénaël Richomme; Kalle Saari; Luca Q. Zamboni

2010-01-01

107

Swings between rotation and accretion power in a binary millisecond pulsar.  

PubMed

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales. PMID:24067710

Papitto, A; Ferrigno, C; Bozzo, E; Rea, N; Pavan, L; Burderi, L; Burgay, M; Campana, S; Di Salvo, T; Falanga, M; Filipovi?, M D; Freire, P C C; Hessels, J W T; Possenti, A; Ransom, S M; Riggio, A; Romano, P; Sarkissian, J M; Stairs, I H; Stella, L; Torres, D F; Wieringa, M H; Wong, G F

2013-09-26

108

Power-law distribution of pressure fluctuations in multiphase flow  

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

109

Power-law distribution of pressure fluctuations in multiphase flow.  

PubMed

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

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

2003-04-01

110

An effective quintessence field with a power-law potential  

E-print Network

In this paper, we will 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.

Khurshudyan, M; Myrzakulov, R; Chattopadhyay, S; Kahya, E O

2014-01-01

111

An effective quintessence field with a power-law potential  

E-print Network

In this paper, we will 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.

M. Khurshudyan; B. Pourhassan; R. Myrzakulov; S. Chattopadhyay; E. O Kahya

2014-03-15

112

Deviations from uniform power law scaling in nonstationary time series  

NASA Technical Reports Server (NTRS)

A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

1997-01-01

113

Power law tails in the Italian personal income distribution  

NASA Astrophysics Data System (ADS)

We investigate the shape of the Italian personal income distribution using microdata from the Survey on Household Income and Wealth, made publicly available by the Bank of Italy for the years 1977-2002. We find that the upper tail of the distribution is consistent with a Pareto-power law type distribution, while the rest follows a two-parameter lognormal distribution. The results of our analysis show a shift of the distribution and a change of the indexes specifying it over time. As regards the first issue, we test the hypothesis that the evolution of both gross domestic product and personal income is governed by similar mechanisms, pointing to the existence of correlation between these quantities. The fluctuations of the shape of income distribution are instead quantified by establishing some links with the business cycle phases experienced by the Italian economy over the years covered by our dataset.

Clementi, F.; Gallegati, M.

2005-05-01

114

Bootstrap Percolation in Power-Law Random Graphs  

NASA Astrophysics Data System (ADS)

A bootstrap percolation process on a graph is an "infection" process which evolves in rounds. Initially, there is a subset of infected nodes and in each subsequent round each uninfected node which has at least infected neighbours becomes infected and remains so forever. The parameter is fixed. Such processes have been used as models for the spread of ideas or trends within a network of individuals. We analyse this process in the case where the underlying graph is an inhomogeneous random graph, which exhibits a power-law degree distribution, and initially there are randomly infected nodes. The main focus of this paper is the number of vertices that will have been infected by the end of the process. The main result of this work is that if the degree sequence of the random graph follows a power law with exponent , where , then a sublinear number of initially infected vertices is enough to spread the infection over a linear fraction of the nodes of the random graph, with high probability. More specifically, we determine explicitly a critical function such that with the following property. Assuming that is the number of vertices of the underlying random graph, if , then the process does not evolve at all, with high probability as grows, whereas if , then there is a constant such that, with high probability, the final set of infected vertices has size at least . This behaviour is in sharp contrast with the case where the underlying graph is a random graph with . It follows from an observation of Balogh and Bollobás that in this case if the number of initially infected vertices is sublinear, then there is lack of evolution of the process. It turns out that when the maximum degree is , then depends also on . But when the maximum degree is , then.

Amini, Hamed; Fountoulakis, Nikolaos

2014-04-01

115

Virial theorem and energy partitioning in systems with mixed power-law potentials  

Microsoft Academic Search

Clausius’ Virial Theorem is often invoked to predict the partitioning of kinetic and potential energies in either classical or quantum systems with simple power-law potentials. Here, the Virial Theorem, and related statistical mechanical identities, are used to investigate energy partitioning in classical systems with mixed power-law potentials, in either one or three dimensions, with either positive or negative mixed power-law

Dor Ben-Amotz

2008-01-01

116

Universal fractional noncubic power law for density of metallic glasses.  

PubMed

As a fundamental property of a material, density is controlled by the interatomic distances and the packing of microscopic constituents. The most prominent atomistic feature in a metallic glass (MG) that can be measured is its principal diffraction peak position (q1) observable by x-ray, electron, or neutron diffraction, which is closely associated with the average interatomic distance in the first shell. Density (and volume) would naturally be expected to vary under compression in proportion to the cube of the one-dimensional interatomic distance. However, by using high pressure as a clean tuning parameter and high-resolution in situ techniques developed specifically for probing the density of amorphous materials, we surprisingly found that the density of a MG varies with the 5/2 power of q1, instead of the expected cubic relationship. Further studies of MGs of different compositions repeatedly produced the same fractional power law of 5/2 in all three MGs we investigated, suggesting a universal feature in MG. PMID:24856706

Zeng, Qiaoshi; Kono, Yoshio; Lin, Yu; Zeng, Zhidan; Wang, Junyue; Sinogeikin, Stanislav V; Park, Changyong; Meng, Yue; Yang, Wenge; Mao, Ho-Kwang; Mao, Wendy L

2014-05-01

117

Quantum healing of classical singularities in power-law spacetimes  

NASA Astrophysics Data System (ADS)

We study a broad class of spacetimes whose metric coefficients reduce to powers of a radius r in the limit of small r. Among these four-parameter 'power-law' metrics, we identify those parameters for which the spacetimes have classical singularities as r ? 0. We show that a large set of such classically-singular spacetimes is nevertheless non-singular quantum mechanically, in that the Hamiltonian operator is essentially self-adjoint, so that the evolution of quantum wave packets lacks the ambiguity associated with scattering off singularities. Using these metrics, the broadest class yet studied to compare classical with quantum singularities, we explore the physical reasons why some that are singular classically are 'healed' quantum mechanically, while others are not. We show that most (but not all) of the remaining quantum-mechanically singular spacetimes can be excluded if either the weak energy condition or the dominant energy condition is invoked, and we briefly discuss the effect of this work on the strong cosmic censorship conjecture.

Helliwell, T. M.; Konkowski, D. A.

2007-07-01

118

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

E-print Network

In this paper we determine the tidal distortion parameter k_m of the secondary partner (mass loser) of the semi-detached eclipsing binary system V621 Cen by comparing the phenomenologically determined orbital period P_b=3.683549(11) d to the Keplerian one P^Kep computed with the values of the relevant system's parameters determined independently of the third Kepler law itself. Our result is k_m = -1.5 +/- 0.6. Using the periastron precession, as traditionally done with other eclipsing binaries in eccentric orbits, would have not been possible because of the circularity of the V621 Cen path.

Lorenzo Iorio

2008-01-06

119

GRASPING "THE INFLUENCE OF LAW ON SEA POWER" Commander James Kraska, JAGC, U.S. Navy  

E-print Network

GRASPING "THE INFLUENCE OF LAW ON SEA POWER" Commander James Kraska, JAGC, U.S. Navy Over the past in the International Law Department, Center for Naval Warfare Studies, U.S. Naval War College, and a Guest Investigator two decades international maritime law has evolved from a set of rules designed to avoid naval warfare

Acton, Scott

120

Transient Anomaly Imaging in Visco-Elastic Media Obeying a Frequency Power-Law  

E-print Network

-31May2010 #12;In an ideal medium; without attenuation, Hooke's law gives the following rela- tionship) For a medium obeying a power-law attenuation model and under the smallness condition (4), a generalized Hooke and denotes the gamma function. Note that for the common case, y = 2, the generalized Hooke's law (5) reduces

Boyer, Edmond

121

On the number of ? -power-free binary words for 2 < ? ? 7 \\/ 3  

Microsoft Academic Search

We study the number u?(n) of ?-power-free binary words of length n, and the asymptotics of this number when n tends to infinity, for a fixed rational number ? in (2,7\\/3]. For any such ?, we prove a structure result that allows us to describe constructively the sequence u?(n) as a 2-regular sequence. This provides an algorithm that computes the

Vincent D. Blondel; Julien Cassaigne; Raphaël M. Jungers

2009-01-01

122

Reciprocity and the Emergence of Power Laws in Social Networks  

NASA Astrophysics Data System (ADS)

Research in network science has shown that many naturally occurring and technologically constructed networks are scale free, that means a power law degree distribution emerges from a growth model in which each new node attaches to the existing network with a probability proportional to its number of links (= degree). Little is known about whether the same principles of local attachment and global properties apply to societies as well. Empirical evidence from six ethnographic case studies shows that complex social networks have significantly lower scaling exponents ? ~ 1 than have been assumed in the past. Apparently humans do not only look for the most prominent players to play with. Moreover cooperation in humans is characterized through reciprocity, the tendency to give to those from whom one has received in the past. Both variables — reciprocity and the scaling exponent — are negatively correlated (r = -0.767, sig = 0.075). If we include this effect in simulations of growing networks, degree distributions emerge that are much closer to those empirically observed. While the proportion of nodes with small degrees decreases drastically as we introduce reciprocity, the scaling exponent is more robust and changes only when a relatively large proportion of attachment decisions follow this rule. If social networks are less scale free than previously assumed this has far reaching implications for policy makers, public health programs and marketing alike.

Schnegg, Michael

123

Statistical tests for power-law cross-correlated processes  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

124

Statistical tests for power-law cross-correlated processes.  

PubMed

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. PMID:22304166

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

2011-12-01

125

Folding in power-law viscous multi-layers.  

PubMed

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

Schmalholz, Stefan M; Schmid, Daniel W

2012-04-28

126

Consistency relation in power law G-inflation  

NASA Astrophysics Data System (ADS)

In the standard inflationary scenario based on a minimally coupled scalar field, canonical or non-canonical, the subluminal propagation of speed of scalar perturbations ensures the following consistency relation: r <= -8nT, where r is the tensor-to-scalar-ratio and nT is the spectral index for tensor perturbations. However, recently, it has been demonstrated that this consistency relation could be violated in Galilean inflation models even in the absence of superluminal propagation of scalar perturbations. It is therefore interesting to investigate whether the subluminal propagation of scalar field perturbations impose any bound on the ratio r/|nT| in G-inflation models. In this paper, we derive the consistency relation for a class of G-inflation models that lead to power law inflation. Within these class of models, it turns out that one can have r > -8nT or r <= -8nT depending on the model parameters. However, the subluminal propagation of speed of scalar field perturbations, as required by causality, restricts r <= -(32/3) nT.

Unnikrishnan, Sanil; Shankaranarayanan, S.

2014-07-01

127

Inverse Power Law Quintessence with Non-Tracking Initial Conditions  

E-print Network

A common property of popular models of quintessence dark energy is the convergence to a common solution from a large range of the initial conditions. We re-examine the popular inverse power-law model of quintessence (where the common solution is dubbed as the 'tracker') with particular attention to the initial conditions for the field and their influence on the evolution. We find that previously derived limits on the parameters of the potential in this model are valid only in a range of initial conditions. A reasonably sharp boundary lies where the initial energy density of the scalar field is equal to that of the background radiation component. An initial quintessence energy density above this equipartition value lead to a solution that will not have joined the tracker solution by the present epoch. These non-tracker solutions possess the property that their present equation of state is very compatible with the observed bounds and independent of the exponent of the potential.

James P. Kneller; Louis E. Strigari

2003-02-09

128

Power law distributions and dynamic behaviour of stock markets  

NASA Astrophysics Data System (ADS)

A simple agent model is introduced by analogy with the mean field approach to the Ising model for a magnetic system. Our model is characterised by a generalised Langevin equation = F ? + G ? t where t is the usual Gaussian white noise, i.e.: t t' = 2D? t-t' and t = 0. Both the associated Fokker Planck equation and the long time probability distribution function can be obtained analytically. A steady state solution may be expressed as P ? = exp{ - ? ? - ln G(?)} where ? ? = - F/ G d? and Z is a normalization factor. This is explored for the simple case where F ? = J? + b?2 - c?3 and fluctuations characterised by the amplitude G ? = ? + ? when it readily yields for ?>>?, a distribution function with power law tails, viz: P ? = exp{ 2b?-c?2 /D}. The parameter c ensures convergence of the distribution function for large values of ?. It might be loosely associated with the activity of so-called value traders. The parameter J may be associated with the activity of noise traders. Output for the associated time series show all the characteristics of familiar financial time series providing J < 0 and D | J|.

Richmond, P.

2001-04-01

129

Transport coefficients in Lorentz plasmas with the power-law kappa-distribution  

SciTech Connect

Transport coefficients in Lorentz plasma with the power-law ?-distribution are studied by means of using the transport equation and macroscopic laws of Lorentz plasma without magnetic field. Expressions of electric conductivity, thermoelectric coefficient, and thermal conductivity for the power-law ?-distribution are accurately derived. It is shown that these transport coefficients are significantly modified by the ?-parameter, and in the limit of the parameter ??? they are reduced to the standard forms for a Maxwellian distribution.

Jiulin, Du [Department of Physics, School of Science, Tianjin University, Tianjin 300072 (China)] [Department of Physics, School of Science, Tianjin University, Tianjin 300072 (China)

2013-09-15

130

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

E-print Network

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...

Kanakamedala, Karthik

2010-07-14

131

Damping of flexural vibrations in rectangular plates by slots of power-law profile  

E-print Network

investigations are described: the effect of power-law tapered slots on vibration damping in steel and composite method of damping flexural vibrations, which is comparable with the method using power-law wedges Eleven samples were designed for this investigation; six of which were manufactured from 5 mm thick hot

Paris-Sud XI, Université de

132

Power-law tail probabilities of drainage areas in river basins  

USGS Publications Warehouse

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.

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

2003-01-01

133

Interpolating between types and tokens by estimating power-law generators  

Microsoft Academic Search

Standard statistical models of language fail to capture one of the most striking properties of natural languages: the power-law distribution in the frequencies of word tokens. We present a framework for developing statistical models that generically produce power-laws, augmenting stan- dard generative models with an adaptor that produces the appropriate pattern of token frequencies. We show that taking a particular

Sharon Goldwater; Tom Griffiths; Mark Johnson

2005-01-01

134

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

E-print Network

is dilatant or shear-thickening and for 0 shear-thinning, in these cases the fluidSimilarity 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

Paris-Sud XI, Université de

135

Public Health Law for a Brave New World; Book Review: Lawrence O. Gostin, Public Health Law: Power, Duty, Restraint  

Microsoft Academic Search

This is book review of Lawrence O. Gostin's new edition of Public Health Law: Power, Duty, Restraint (University of California Press, Berkeley, California, 2d ed., 2008). A review of a second edition of a book may be somewhat unusual as subsequent editions of already published works typically do not break new ground. But this book is different. Gostin's first edition,

2008-01-01

136

Exponential and power-law mass distributions in brittle fragmentation.  

PubMed

Generic arguments, a minimal numerical model, and fragmentation experiments with gypsum disk are used to investigate the fragment-size distribution that results from dynamic brittle fragmentation. Fragmentation is initiated by random nucleation of cracks due to material inhomogeneities, and its dynamics are pictured as a process of propagating cracks that are unstable against side-branch formation. The initial cracks and side branches both merge mutually to form fragments. The side branches have a finite penetration depth as a result of inherent damping. Generic arguments imply that close to the minimum strain (or impact energy) required for fragmentation, the number of fragments of size s scales as s(-(2D-1)/D) f(1) (- (2/lambda)(D) s)+ f(2) (- s(-1 )(0 ) (lambda+ s(1/D) )(D) ), where D is the Euclidean dimension of the space, lambda is the penetration depth, and f(1) and f(2) can be approximated by exponential functions. Simulation results and experiments can both be described by this theoretical fragment-size distribution. The typical largest fragment size s(0) was found to diverge at the minimum strain required for fragmentation as it is inversely related to the density of initially formed cracks. Our results also indicate that scaling of s(0) close to this divergence depends on, e.g., loading conditions, and thus is not universal. At the same time, the density of fragment surface vanishes as L-1, L being the linear dimension of the brittle solid. The results obtained provide an explanation as to why the fragment-size distributions found in nature can have two components, an exponential as well as a power-law component, with varying relative weights. PMID:15447542

Aström, J A; Linna, R P; Timonen, J; Møller, Peder Friis; Oddershede, Lene

2004-08-01

137

Electromagnetic power loss in open coaxial diodes and the Langmuir-Blodgett law  

SciTech Connect

The space charge limited current in coaxial diodes with electromagnetic power loss is studied. The Langmuir-Blodgett law is expressed in terms of the electromagnetic power loss and the applied voltage. Particle-in-cell simulations of photodiode-like situations and high power diodes confirm the relation between the applied voltage, diode voltage, and electromagnetic power loss.

Kumar, Raghwendra; Biswas, Debabrata [Theoretical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2010-10-15

138

Power-law modeling based on least-squares minimization criteria.  

PubMed

The power-law formalism has been successfully used as a modeling tool in many applications. The resulting models, either as Generalized Mass Action or as S-systems models, allow one to characterize the target system and to simulate its dynamical behavior in response to external perturbations and parameter changes. The power-law formalism was first derived as a Taylor series approximation in logarithmic space for kinetic rate-laws. The especial characteristics of this approximation produce an extremely useful systemic representation that allows a complete system characterization. Furthermore, their parameters have a precise interpretation as local sensitivities of each of the individual processes and as rate-constants. This facilitates a qualitative discussion and a quantitative estimation of their possible values in relation to the kinetic properties. Following this interpretation, parameter estimation is also possible by relating the systemic behavior to the underlying processes. Without leaving the general formalism, in this paper we suggest deriving the power-law representation in an alternative way that uses least-squares minimization. The resulting power-law mimics the target rate-law in a wider range of concentration values than the classical power-law. Although the implications of this alternative approach remain to be established, our results show that the predicted steady-state using the least-squares power-law is closest to the actual steady-state of the target system. PMID:10546442

Hernández-Bermejo, B; Fairén, V; Sorribas, A

1999-10-01

139

The broad-band power spectra of X-ray binaries  

Microsoft Academic Search

We analyzed the rapid aperiodic X-ray variability of different types of X-ray\\u000abinaries (black hole candidates, atoll sources, the recently discovered\\u000amillisecond X-ray pulsar, and Z sources) at their lowest inferred mass\\u000aaccretion rates. At these accretion rates, the power spectra of all sources are\\u000adominated by a strong band-limited noise component, which follows a power law\\u000awith an index

Rudy Wijnands; Michiel van der Klis

1998-01-01

140

Detailed empirical study of the term structure of interest rates. Emergence of power laws and scaling laws  

NASA Astrophysics Data System (ADS)

The technique of Padé approximants, introduced in a previous work, is applied to extended recent data on the distribution of variations of interest rates compiled by the Federal Reserve System in the US. It is shown that new power laws and new scaling laws emerge for any maturity not only as a function of the Lag but also as a function of the average inital rate. This is especially true for the one year maturity where critical forms and critical exponents are obtained. This suggests future work in the direction of constructing a theory of variations of interest rates at a more “microscopic” level.

Alderweireld, Thomas; Nuyts, Jean

2004-01-01

141

Are power-law distributions an equilibrium distribution or a stationary nonequilibrium distribution?  

NASA Astrophysics Data System (ADS)

We examine whether the principle of detailed balance holds for the power-law distributions that are generated from the well-known two-variable Langevin equation and the associated Fokker-Planck equations. With the detailed balance and the generalized fluctuation-dissipation relation, we derive analytically the stationary power-law distribution from the Ito’s, Stratonovich’s and Zwanzig’s Fokker-Planck equations, and conclude that the power-law distributions can either be a stationary nonequilibrium distribution or an equilibrium distribution, which depend on information about the form of the diffusion coefficient function and the existence and uniqueness of an equilibrium state.

Guo, Ran; Du, Jiulin

2014-07-01

142

Unbounded Binary Search for a Fast and Accurate Maximum Power Point Tracking  

NASA Astrophysics Data System (ADS)

This paper presents a technique for maximum power point tracking (MPPT) of a concentrating photovoltaic system using cell level power optimization. Perturb and observe (P&O) has been a standard for an MPPT, but it introduces a tradeoff between the tacking speed and the accuracy of the maximum power delivered. The P&O algorithm is not suitable for a rapid environmental condition change by partial shading and self-shading due to its tracking time being linear to the length of the voltage range. Some of researches have been worked on fast tracking but they come with internal ad hoc parameters. In this paper, by using the proposed unbounded binary search algorithm for the MPPT, tracking time becomes a logarithmic function of the voltage search range without ad hoc parameters.

Kim, Yong Sin; Winston, Roland

2011-12-01

143

Gamma-rays from nebulae around binary systems containing energetic rotation-powered pulsars  

NASA Astrophysics Data System (ADS)

We consider nebulae which are created around binary systems containing rotation-powered pulsars and companion stars with strong stellar winds. It is proposed that the stellar and pulsar winds have to mix at some distance from the binary system, defined by the orbital period of the companion stars and the velocity of the stellar wind. The mixed pulsar-stellar wind expands with a specific velocity determined by the pulsar power and the mass loss rate of the companion star. Relativistic particles, either from the inner pulsar magnetosphere and/or accelerated at the shocks between stellar and pulsar winds, are expected to be captured and isotropized in the reference frame of the mixed wind. Therefore, they can efficiently Comptonize stellar radiation producing GeV-TeV ?-rays in the inverse Compton process. We calculate the ?-ray spectra expected in such scenario for the two example binary systems: J1816+4510 which is the Redback-type millisecond binary and LS 5039 which is supposed to contain energetic pulsar. It is concluded that the steady TeV ?-ray emission from J1816+4510 should be on the 100 h sensitivity limit of the planned Cherenkov Telescope Array, provided that ? ˜ 10 per cent of the rotational energy lost by the pulsar is transferred to TeV electrons. On the other hand, the comparison of the predicted steady TeV ?-ray emission, expected from ?-ray binary LS 5039, with the observations of the TeV emission in a low state, reported by the High Energy Stereoscopic System Collaboration, allows us to put stringent upper limit on the product of the part of the hemisphere in which the mixed pulsar-stellar wind is confined, ?mix, and the energy conversion efficiency, ?, from the supposed pulsar to the TeV electrons injected in this system, ?mix ? < 1 per cent. This lower limit can be understood provided that either the acceleration efficiency of electrons is rather low (? ˜ 1 per cent), or the parameters of the stellar wind from the companion star are less extreme than expected, or the injection/acceleration process of electrons occurs highly anisotropically with the predominance towards the companion star.

Bednarek, W.; Sitarek, J.

2013-04-01

144

The power law of sensory adaptation: simulation by a model of excitability in spider mechanoreceptor neurons.  

PubMed

The power law of sensory adaptation was introduced more than 50 years ago. It is characterized by action potential adaptation that follows fractional powers of time or frequency, rather than exponential decays and corresponding frequency responses. Power law adaptation describes the responses of a range of vertebrate and invertebrate sensory receptors to deterministic stimuli, such as steps or sinusoids, and to random (white noise) stimulation. Hypotheses about the physical basis of power law adaptation have existed since its discovery. Its cause remains enigmatic, but the site of power law adaptation has been located in the conversion of receptor potentials into action potentials in some preparations. Here, we used pseudorandom noise stimulation and direct spectral estimation to show that simulations containing only two voltage activated currents can reproduce the power law adaptation in two types of spider mechanoreceptors. Identical simulations were previously used to explain the different responses of these two types of sensory neurons to step inputs. We conclude that power law adaptation results during action potential encoding by nonlinear combination of a small number of activation and inactivation processes with different exponential time constants. PMID:17952602

French, Andrew S; Torkkeli, Päivi H

2008-01-01

145

Log-Periodic Power Law as a Predictor of Catastrophic Events: A New Mathematical  

E-print Network

Log-Periodic Power Law as a Predictor of Catastrophic Events: A New Mathematical Justification of a catastrophic event, many parame- ters exhibit log-periodic power behavior, with oscillations of increasing to vastly different systems seems to indicate that the log-periodic power behavior is not related

Kreinovich, Vladik

146

Two Power-Law States of the Ultraluminous X-Ray Source IC 342 X-1  

NASA Astrophysics Data System (ADS)

In order to elucidate the emission properties of ultraluminous X-ray sources (ULXs) during their power-law (PL) state, we examined long-term X-ray spectral data of IC 342 X-1 during its PL state by using our own Suzaku data and archival data by XMM-Newton, Chandra, and Swift observations. The PL state of this source seems to be classified into two sub-states in terms of the X-ray luminosities in the 0.5-10 keV band: the low-luminosity PL state with (4-6) × 1039 erg s-1 and the high-luminosity one with (1.1-1.4) × 1040 erg s-1 . During Suzaku observations, which were made in 2010 August and 2011 March, X-1 stayed in the low-luminosity PL state. The observed X-ray luminosity (4.9-5.6 × 1039 erg s-1) and the spectral shape (photon index = 1.67-1.83) slightly changed between the two observations. Using the Suzaku PIN detector, we for the first time confirmed a PL tail extending up to at least 20 keV with no signatures of a high-energy turnover in both of the Suzaku observations. In contrast, a turnover at about 6 keV was observed during the high-luminosity PL state in 2004 and 2005 with XMM-Newton. Importantly, the photon indices are similar between the two PL states, and so are the Compton y-parameters of y ˜ 1, which indicates a similar energy balance (between the corona and the accretion disk) holding in the two PL states despite different electron temperatures. From spectral similarities with recent studies about other ULXs, and the Galactic black-hole binary GRS 1915+ 105, IC 342 X-1 is also likely to be in a state with a supercritical accretion rate, although more sensitive higher energy observations would be necessary to make any conclusion.

Yoshida, Tessei; Isobe, Naoki; Mineshige, Shin; Kubota, Aya; Mizuno, Tsunefumi; Saitou, Kei

2013-04-01

147

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

E-print Network

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 ...

Crane, Riley

148

The power-law TST reaction rate coefficient with tunneling correction  

NASA Astrophysics Data System (ADS)

We study the TST reaction rate for the systems with power-law distributions. We derive the expressions of the reaction rate coefficient with tunneling correction, which strongly depends on the power-law parameter. The numerical results show that a small deviation from one in the parameter can result in a significant change in the rate coefficient, but only cause a small change in the tunneling correction. Thus the tunneling correction is not sensitive to the power-law distributions. As an application example, we take the H+H2 reaction to calculate the power-law reaction rate coefficient with the tunneling correction, the results of which with the parameter slightly different from one are in good agreement with all the experimental studies in temperature range 2×102˜103 K.

Yin, Cangtao; Zhou, Yanjun; Du, Jiulin

2014-11-01

149

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

E-print Network

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.

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

150

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

PubMed

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. PMID:24697367

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

2014-03-01

151

POWER LAW DISCOUNTING FOR N-GRAM LANGUAGE MODELS Songfang Huang, Steve Renals  

E-print Network

probability. It follows that a stochastic process, such as the Pitman-Yor process [7], that has the "rich-get- richer" capacity to generate a power law distribution is able to take advantage of this property

Edinburgh, University of

152

Important Property of GRB Pulse: Power-Law Indices of Time Properties on Energy  

NASA Astrophysics Data System (ADS)

The dependence of pulse temporal properties (pulse width, pulse rise width and pulse decay width) on energy is power-law function. Some correlated relationships between the power-law indices of the pulse time properties on energy and the spectral lags, relative spectral lags, spectral parameters of band function, and photon flux using a well-separated long-duration ?-ray burst (GRB) pulse sample is demonstrated here. We argue that the curvature effect can explain the correlated properties.

Peng, Zhao-Yang

2014-11-01

153

Scalar field reconstruction of power-law entropy-corrected holographic dark energy  

Microsoft Academic Search

A so-called 'power-law entropy-corrected holographic dark energy' (PLECHDE) was recently proposed to explain the dark energy (DE)-dominated universe. This model is based on the power-law corrections to black hole entropy that appear when dealing with the entanglement of quantum fields between the inside and the outside of the horizon. In this paper, we suggest a correspondence between the interacting PLECHDE

Esmaeil Ebrahimi; Ahmad Sheykhi

2011-01-01

154

Relationships between power-law long-range interactions and fractional mechanics  

NASA Astrophysics Data System (ADS)

We investigate the relationships between models of power-law long-range interactions and mechanics based on fractional derivatives. We present the fractional Lagrangian density which gives the Euler-Lagrange equation that serves as the equation of motion for fractional-power-law long-range interactions. We derive this equation by the fractional variational method. In addition, we derive a Noether-like current from the fractional Lagrangian density.

Ishiwata, Ryosuke; Sugiyama, Y?ki

2012-12-01

155

Species-area relationship for power-law species abundance distribution  

Microsoft Academic Search

We studied the mathematical relations between species abundance distributions (SADs) and species-area relationships (SARs) and found that a power-law SAR can be generally derived from a power-law SAD without a special assumption such as the ``canonical hypothesis''. In the present analysis, an SAR-exponent is obtained as a function of an SAD-exponent for a finite number of species. We also studied

Haruyuki Irie; Kei Tokita

2006-01-01

156

Power-law behaviour evaluation from foreign exchange market data using a wavelet transform method  

NASA Astrophysics Data System (ADS)

Numerous studies in the literature have shown that the dynamics of many time series including observations in foreign exchange markets exhibit scaling behaviours. A simple new statistical approach, derived from the concept of the continuous wavelet transform correlation function (WTCF), is proposed for the evaluation of power-law properties from observed data. The new method reveals that foreign exchange rates obey power-laws and thus belong to the class of self-similarity processes.

Wei, H. L.; Billings, S. A.

2009-09-01

157

Power-law expansion and Higgs-type potential in a scalar-tensor model  

E-print Network

In the scalar-tensor model with Gauss-Bonnet and kinetic couplings, the power-law dark energy solution may be described by Higgs-type potential. It was found that in the solution describing early time epoch of matter dominance, the potential presents symmetry breaking phase, and the power law solution leading to accelerated expansion corresponds to Higgs-type potential in its symmetric shape.

Granda, L N

2014-01-01

158

The steadily propagating crack in an elastic\\/power-law material: Second order solutions  

Microsoft Academic Search

We present second-order asymptotic solutions to the near-tip field for a crack propagating under steady-state, antiplane strain conditions in an elastic\\/power-law material. First-order solutions to this problem were originally given by Hui and Riedel. For values of the power-law exponent n < 3, the second-order solution is found to satisfy a linear, inhomogeneous equation. For n > 3, however, an

T. J. Delph; P. A. Blythe

1995-01-01

159

Power-law expansion and Higgs-type potential in a scalar-tensor model  

NASA Astrophysics Data System (ADS)

In the scalar-tensor model with Gauss-Bonnet and kinetic couplings, the power-law dark-energy solution may be described by a Higgs-type potential. It was found that in the solution describing the early time epoch of matter dominance, the potential presents a symmetry breaking phase, and the power-law solution leading to accelerated expansion corresponds to a Higgs-type potential in its symmetric shape.

Granda, L. N.

2014-01-01

160

Frequency dependence of solar flare occurrence rates—inferred from power-law distribution  

NASA Astrophysics Data System (ADS)

Based on the frequency dependence of the power-law distribution of the peak fluxes in 486 radio bursts in 1-35 GHz observed by Nobeyama Radio Polarimeters (see Song et al. in Astrophys. J. 750:160, 2012), we have first suggested in this paper that the events with power-law behaviors may be emitted from the optically-thin regions, which can be considered as a good measure for the flare energy release. This result is supported by that both the power-law and optical-thin events gradually increase with radio frequencies, which are well fitted by a power-law function with similar indices of 0.48 and 0.80, respectively. Moreover, a flare occurrence rate is newly defined by the power-law event number in per unit frequency. Its values in lower frequencies are evidently larger than those in higher frequencies, which just imply that most flares are trigged in higher corona. Hence, the frequency variation of power-law event number may indicate different energy dissipation rates on different coronal heights.

Song, Qiwu; Huang, Guangli; Huang, Yu

2013-09-01

161

Theories of Power, Poverty, and Law: In Commemoration of the Contributions of Peter Bachrach--Power, Law, and Final Thoughts: The Contributions of Peter Bachrach  

ERIC Educational Resources Information Center

I am pleased to be part of this symposium to celebrate the life and work of Peter Bachrach. Although my focus is the relevance of Peter's ideas of power to law, I want to begin with some personal comments as well as raise some final thoughts, drawing on others' contributions. Like so many of Peter's other students, I adored him. Peter's joy in…

Schneider, Elizabeth M.

2010-01-01

162

Polarized X-rays from Neutron Stars in X-ray Binaries and Rotation Powered Pulsars  

NASA Astrophysics Data System (ADS)

We give an overview of the expected polarization properties of X-rays emitted by neutron stars in X-ray binaries, including both accretion powered pulsars and low-mass X-ray binaries, as well as in rotation powered pulsars. We summarize the model calculations that lead to these expected properties, highlighting those properties of X-ray production and transfer in strong magnetic fields which leave their signature in the degree and direction of polarization. We emphasize the crucial role played by the quantum electrodynamical (QED) phenomenon of vacuum resonance in determining the transition point in X-ray polarization properties. We discuss how a comparison of the above expected properties with those observed with NASA's X-ray polarimetry mission GEMS will probe the essential dynamical and electromagnetic processes involved in our understanding of the X-ray emission from neutron stars in a variety of astrophysical situations. We indicate how such probes will discriminate between models and constrain model parameters. We comment on the exciting possibility of the demonstration of a fundamental QED effect, the vacuum resonance, through these GEMS studies.

Ghosh, Pranab

2012-07-01

163

Raft River 5MW(e) binary geothermal-electric power plant: operation and performance  

SciTech Connect

A 5MW(e) Pilot Geothermal Power Plant was built at Raft River, Idaho, as an integral part of the Department of Energy's plan for commercial development of geothermal energy. The purpose of the plant was to investigate the technical feasibility of utilizing a moderate temperature hydrothermal resource (275 to 300/sup 0/F) to generate electrical power in an environmentally acceptable manner. The plant used a dual-boiling binary cycle with isobutane as the working fluid, and drew thermal energy from a 280/sup 0/F liquid-dominated resource. This paper presents the results of that testing, comparing the system performance to the performance predicted prior to operation along with a summary of operational experience.

Bliem, C.J. Jr.

1983-01-01

164

On the scaling range of power-laws originated from fluctuation analysis  

E-print Network

We extend our previous study of scaling range properties done for detrended fluctuation analysis (DFA) \\cite{former_paper} to other techniques of fluctuation analysis (FA). The new technique called Modified Detrended Moving Average Analysis (MDMA) is introduced and its scaling range properties are examined and compared with those of detrended moving average analysis (DMA) and DFA. It is shown that contrary to DFA, DMA and MDMA techniques exhibit power law dependence of the scaling range with respect to the length of the searched signal and with respect to the accuracy $R^2$ of the fit to the considered scaling law imposed by DMA or MDMA schemes. This power law dependence is satisfied for both uncorrelated and autocorrelated data. We find also a simple generalization of this power law relation for series with different level of autocorrelations measured in terms of the Hurst exponent. Basic relations between scaling ranges for different techniques are also discussed. Our findings should be particularly useful ...

Dariusz, Grech

2012-01-01

165

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

SciTech Connect

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.

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

166

State Courts as Agents of Federalism: Power and Interpretation in State Constitutional Law  

Microsoft Academic Search

In the American constitutional tradition, federalism is commonly understood as a mechanism designed to institutionalize a kind of permanent struggle between state and national power. The same American constitutional tradition also holds that courts are basically passive institutions whose mission is to apply the law impartially while avoiding inherently political power struggles. These two commonplace understandings conflict on their face.

James A. Gardner

2003-01-01

167

Exact solutions for the fourth order nonlinear Schrodinger equations with cubic and power law nonlinearities  

Microsoft Academic Search

The tanh method and the sine–cosine method are used for solving the fourth order nonlinear Schrodinger equations with cubic and power law nonlinearities. Several exact solutions with distinct structures are formally obtained for each type of nonlinearity. The study reveals the power of the two proposed algorithms.

Abdul-Majid Wazwaz

2006-01-01

168

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

SciTech Connect

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

Daniel S. Wendt; Greg L. Mines

2010-09-01

169

Power law behavior associated with a Fibonacci Lucas model and generalized statistical models  

E-print Network

A Fibonacci-Lucas based statistical model and several other related models are studied. The canonical and grand canonical partition functions for these models are developed.Partition structure such as the distribution of sizes as in a cluster distribution is explored.Ensemble averaging over all partitions leads to a scale invariant power law behavior at a particular critical like point. The canonical ensemble of the Fibonacci-Lucas case involves the Gegenbauer polynomial.The model has a hyperbolic power law behavior, a feature linked to the golden mean ratio of two adjacent Fibonacci numbers and also the connection of Lucas numbers to the golden mean. The relation to other power law behavior, such as Zipf and Pareto laws, is mentioned. For the cases considered, the grand canonical ensemble involves the Gauss hypergeometric function F(a,b,c,z) with specific values for a,b,c. The general case has a variable power law behavior with tau exponent equal to1+c-a-b. An application with a=1/2, b=1, c=3 and thus tau=5/2 very closely approximates Bose-Einstein condensation. The zeta function zeta(3/2)=2.61 of the exact theory is replaced with 8/3 and zeta(5/2)= 1.34 with 4/3. At the condensation point the number of cycles of length falls as a scale invariant power law. The cycles, which arise from permutation symmetries associated with Bose-Einstein statistics, can be viewed as links in a complex network of connections between particles. This scale invariant power law parallels that seen in complex networks. The growth of the network is developed using recurrence properties of the model. Constraints imposed by the canonical ensemble and associates correlations lead to some number theoretic connections between Fibonacci and Lucas numbers as an incidental consequence of this approach.

Aram Z. Mekjian

2009-10-13

170

Excitation of Langmuir waves by the lower energy cutoff behavior of power-law electrons  

E-print Network

Langmuir waves (LWs), which are believed to play a crucial role in the plasma emission of solar radio bursts, can be excited by streaming instability of energetic electron beams. However, solar hard X-ray observations imply that the energetic flare electrons usually have a power-law energy distribution with a lower energy cutoff. In this paper, we investigate LWs driven by the power-law electrons. The results show that power-law electrons with the steepness cutoff behavior can excite LWs effectively because of the population inversion distribution below the cutoff energy ($E_c$). The growth rate of LWs increases with the steepness index ($\\delta$) and decreases with the power-law index ($\\alpha$). The wave number of the fastest growing LWs ($k\\lambda_D$), decreases with the characteristic velocity of the power-law electrons ($v_{c}=\\sqrt{2E_{c}/m_{e}}$) and increases with the thermal velocity of ambient electrons ($v_T$). This can be helpful for us to understand better the physics of LWs and the dynamics of e...

Tang, Jianfei; Zhao, Guoqing; Chen, Ling; Tan, Chengming

2014-01-01

171

Alpha-power law MOSFET model and its applications to CMOS inverter delay and other formulas  

Microsoft Academic Search

An ?-power-law MOS model that includes the carrier velocity saturation effect, which becomes prominent in short-channel MOSFETs, is introduced. The model is an extension of Shockley's square-law MOS model in the saturation region. Since the model is simple, it can be used to handle MOSFET circuits analytically and can predict the circuit behavior in the submicrometer region. Using the model,

T. Sakurai; A. R. Newton

1990-01-01

172

All Bright Cold Classical KBOs are Binary  

NASA Astrophysics Data System (ADS)

When sorted by absolute magnitude as seen in ground based observations, an extremely high fraction of the brightest Cold Classical (CC) Kuiper Belt objects (KBO) are, in fact resolved as binaries when observed at higher angular resolution. Of the 22 CCs brighter than H=6.1 observed by HST, 16 have been found to be binary yielding a binary fraction of 73±10%. When low inclination interlopers from the hot population and close binaries are considered, this very high fraction is consistent with 100% of bright CCs being binary. At fainter absolute magnitudes, this fraction drops to ~20%. Such a situation is a natural outcome of a broken size distribution with a steep drop-off in the number of CCs with individual component diameters larger than 150 km (for an assumed albedo of 0.15). A sharp cutoff in the size distribution for CCs is consistent with formation models that suggest that most planetesimals form at a preferred modal size of order 100 km.The very high fraction of binaries among the largest CCs also serves to limit the separation distribution of KBO binaries. At most, 27% of the brightest CCs are possible unresolved binaries. The apparent power law distribution of binary separation must cut off near the current observational limits of HST ( 1800 km at 43 AU). It is worth noting, however, that this observation does not constrain how many components of resolved binaries may themselves be unresolved multiples like 47171 1999 TC36. Finally, it is important to point out that, when sorted by the size of the primary rather than absolute magnitude of the unresolved pair, the fraction of binaries is relatively constant with size (Nesvorny et al. 2011, AJ 141, 159) eliminating observational bias as cause of the pile up of binaries among the brightest Cold Classical Kuiper Belt objects.The very high fraction of binaries among the brightest CCs appears to be an effect of the underlying CC size distribution.

Noll, Keith S.; Parker, Alex H.; Grundy, William M.

2014-11-01

173

Forced convection of power-law fluids flow over a rotating nonisothermal body  

SciTech Connect

Presented is an analysis of steady laminar flow of power-law fluids past a rotating body with nonisothermal surfaces. A coordinate transformation combined with the Merk-type series expansion is employed to transform the governing momentum equations into a set of coupled ordinary differential equations. The equations are numerically integrated to obtain the axial and tangential velocity gradients for determining the friction coefficient. For forced convection, a generalized coordinate transformation is used to analyze the temperature field of the power-law flow. Solutions to the transformed energy equations are obtained in the form of universal functions. The heat transfer coefficients in terms of NuRe exp 1/(n + 1) are presented for a rotating sphere. The effects of power-law index, rotation parameter, Prandtl number, and the location of step discontinuity in surface temperature on the local Nusselt number are fully investigated and demonstrated. 13 refs.

Kim, H.W.; Esseniyi, A.J. (Youngstown State Univ., OH (United States))

1993-12-01

174

Tanner's simple model of crystallization for power-law fluids extended  

NASA Astrophysics Data System (ADS)

Tanner et al. (Rheol. Acta, 48, 2009, 499-507) presented a simple model for power-law fluids in which it was possible to derive semi-analytical solutions based on some key simplifying assumptions. These include shear flows in tubes and channels, a 'step function' or 'amorphous-frozen' model of the viscosity changes due to crystallization, and a power-law index of 1/3 valid for a crystallizing poly(butene-1) polymer for which experiments were available. Their work compared favorably with experimental data for the onset of crystallization times. In the present work, we have repeated and verified the Tanner model and extended it to power-law indices from 1 (Newtonian behavior) down to 0 (extreme shear thinning) in order to study the effect of the different problem parameters and place a set of results that will act as reference for future and more detailed computational calculations through the Finite Element Method.

Mitsoulis, E.; Zisis, Th.

2014-05-01

175

Transient volume of evaporating sessile droplets: 2/3, 1/1, or another power law?  

PubMed

The transient shape and volume of evaporating sessile droplets are critical to our understanding and prediction of deposits left over on the solid surface after droplet evaporation. The 2/3 power law of scaling, (V/Vo)(?) = 1 - t/tf with ? = 2/3, has been widely used. The 1/1 power law of scaling with ? = 1 was also obtained for vanishingly small contact angles. Here we show that ? significantly deviates from 2/3 and 1 when the droplet base is pinned: ? depends on both initial and transient contact angles. The 1/1 power law presents the upper limit of ? = 1, while ? = 2/3 is the lower limit if contact angles are smaller than 148°. Unexpectedly, ? can be smaller than 2/3 if contact angles are larger than 148°. We also present a semianalytical approximation for ? as a function of the initial contact angle. PMID:24873776

Nguyen, Tuan A H; Nguyen, Anh V

2014-06-10

176

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

E-print Network

We report on the existing connection between power-law distributions and allometries. As it was first reported in [PLoS ONE 7, e40393 (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 labour, illiteracy, income, sanitation and unemployment). Our analysis reveal 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 residua...

Alves, Luiz G A; Lenzi, Ervin K; Mendes, Renio S

2014-01-01

177

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

PubMed

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

Travesset, Alex

2014-10-28

178

Power-law decay of the spatial correlation function in exciton-polariton condensates  

PubMed Central

We create a large exciton-polariton condensate and employ a Michelson interferometer setup to characterize the short- and long-distance behavior of the first order spatial correlation function. Our experimental results show distinct features of both the two-dimensional and nonequilibrium characters of the condensate. We find that the gaussian short-distance decay is followed by a power-law decay at longer distances, as expected for a two-dimensional condensate. The exponent of the power law is measured in the range 0.9–1.2, larger than is possible in equilibrium. We compare the experimental results to a theoretical model to understand the features required to observe a power law and to clarify the influence of external noise on spatial coherence in nonequilibrium phase transitions. Our results indicate that Berezinskii–Kosterlitz–Thouless-like phase order survives in open-dissipative systems. PMID:22496595

Roumpos, Georgios; Lohse, Michael; Nitsche, Wolfgang H.; Keeling, Jonathan; Szymanska, Marzena Hanna; Littlewood, Peter B.; Loffler, Andreas; Hofling, Sven; Worschech, Lukas; Forchel, Alfred; Yamamoto, Yoshihisa

2012-01-01

179

Fertility heterogeneity as a mechanism for power law distributions of recurrence times  

NASA Astrophysics Data System (ADS)

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 ?, where the fertility of an event is the number of triggered events of first generation, on the probability distribution function (PDF) f(?) of the recurrence times ? between successive events. The other input of the model is an exponential law quantifying the PDF of waiting times between an event and its first generation triggered events, whose characteristic time scale is taken as our time unit. At short-time scales, we discover two intermediate power law asymptotics, f(?)˜?-(2-?) for ???c and f(?)˜?-? for ?c???1, where ?c is associated with the self-excited cascades of triggered events. For 1???1/?, we find a constant plateau f(?)?const, while at long times, 1/???, f(?)?e-?? has an exponential tail controlled by the arrival rate ? of exogenous events. These results demonstrate a novel mechanism for the generation of power laws in the distribution of recurrence times, which results from a power law distribution of fertilities in the presence of self-excitation and cascades of triggering.

Saichev, A.; Sornette, D.

2013-02-01

180

Fertility heterogeneity as a mechanism for power law distributions of recurrence times.  

PubMed

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 ?, where the fertility of an event is the number of triggered events of first generation, on the probability distribution function (PDF) f(?) of the recurrence times ? between successive events. The other input of the model is an exponential law quantifying the PDF of waiting times between an event and its first generation triggered events, whose characteristic time scale is taken as our time unit. At short-time scales, we discover two intermediate power law asymptotics, f(?)~?(-(2-?)) for ?power laws in the distribution of recurrence times, which results from a power law distribution of fertilities in the presence of self-excitation and cascades of triggering. PMID:23496576

Saichev, A; Sornette, D

2013-02-01

181

Finite sample properties of power-law cross-correlations estimators  

E-print Network

We study finite sample properties of estimators of power-law cross-correlations -- detrended cross-correlation analysis (DCCA), height cross-correlation analysis (HXA) and detrending moving-average cross-correlation analysis (DMCA) -- with a special focus on short-term memory bias as well as power-law coherency. Presented broad Monte Carlo simulation study focuses on different time series lengths, specific methods' parameter setting, and memory strength. We find that each method is best suited for different time series dynamics so that there is no clear winner between the three. The method selection should be then made based on observed dynamic properties of the analyzed series.

Kristoufek, Ladislav

2014-01-01

182

The process of coevolutionary competitive exclusion: speciation, multifractality and power-laws in correlations  

NASA Astrophysics Data System (ADS)

Competitive exclusion, a key principle of ecology, can be generalized to understand many other complex systems. Individuals under surviving pressure tend to be different from others, and correlations among them change correspondingly to the updating of their states. We show with numerical simulation that these aptitudes can contribute to group formation or speciation in social fields. Moreover, they can lead to power-law topological correlations of complex networks. By coupling updating states of nodes with variation of connections in a network, structural properties with power-laws and functions like multifractality, spontaneous ranking and evolutionary branching of node states can emerge simultaneously from the present self-organized model of coevolutionary processes.

Zhu, Chen-Ping; Zhou, Tao; Yang, Hui-Jie; Xiong, Shi-Jie; Gu, Zhi-Ming; Shi, Da-Ning; He, Da-Ren; Wang, Bing-Hong

2008-02-01

183

Effect of Body Perturbations on Hypersonic Flow Over Slender Power Law Bodies  

NASA Technical Reports Server (NTRS)

Hypersonic-slender-body theory, in the limit as the free-stream Mach number becomes infinite, is used to find the effect of slightly perturbing the surface of slender two-dimensional and axisymmetric power law bodies, The body perturbations are assumed to have a power law variation (with streamwise distance downstream of the nose of the body). Numerical results are presented for (1) the effect of boundary-layer development on two dimensional and axisymmetric bodies, (2) the effect of very small angles of attack (on tow[dimensional bodies), and (3) the effect of blunting the nose of very slender wedges and cones.

Mirels, Harold; Thornton, Philip R.

1959-01-01

184

The extent of power-law energy spectra in collisionless relativistic magnetic reconnection in pair plasmas  

E-print Network

Using two-dimensional particle-in-cell simulations, we characterize the energy spectra of particles accelerated by relativistic magnetic reconnection (without guide field) in collisionless electron-positron plasmas, for a wide range of upstream magnetizations $\\sigma$ and system sizes $L$. The particle spectra are well-represented by a power law $\\gamma^{-\\alpha}$, with a combination of exponential and super-exponential high-energy cutoffs, proportional to $\\sigma$ and $L$, respectively. For large $L$ and $\\sigma$, the power-law index $\\alpha$ approaches about 1.2.

Werner, G R; Cerutti, B; Nalewajko, K; Begelman, M C

2014-01-01

185

Bose-Einstein condensation in dark power-law laser traps  

E-print Network

We investigate theoretically the phase transition of interacting Bose gases in shaped optical traps. One-, two- and three-dimensional power-law trapping potentials are created using two crossing blue-detuned Laguerre-Gaussian laser beams. Controlling their associated azimuthal order l allows for the exploration of a multitude of power-law trapping situations ranging from the harmonic trap to a quasi-homogeneous Bose gas. For an arbitrary condensate occupation number and when compared to a harmonic trap of the same size, higher transition temperatures can be obtained with larger values of l. This effect results in a substantial acceleration of the condensation dynamics.

Jaouadi, Amine; Telmini, Mourad; De Lesegno, Bruno Viaris; Pruvost, Laurence; Charron, Eric

2009-01-01

186

LRS Bianchi type-I cosmological model with power law expansion in f(R) gravity  

NASA Astrophysics Data System (ADS)

We reconstruct the f(R) theory of gravity in the framework of Locally Rotationally Symmetric Bianchi type-I space-time by considering the power law expansion of the Universe. We find the exact solution of field equations and investigate the possible ranges of parameters in power laws for the consistency of the theory. The model exhibits the decelerated and present accelerated phase of the universe at early time and late time of the evolution of the Universe, respectively. We found that f(R) theory of gravity may be the alternative of dark energy and dark matter. We also discuss the physical behaviors of other cosmological parameters.

Singh, Vijay; Singh, C. P.

2012-07-01

187

Inverse free steering law for small satellite attitude control and power tracking with VSCMGs  

NASA Astrophysics Data System (ADS)

Recent developments in integrated power and attitude control systems (IPACSs) for small satellite, has opened a new dimension to more complex and demanding space missions. This paper presents a new inverse free steering approach for integrated power and attitude control systems using variable-speed single gimbal control moment gyroscope. The proposed inverse free steering law computes the VSCMG steering commands (gimbal rates and wheel accelerations) such that error signal (difference in command and output) in feedback loop is driven to zero. H? norm optimization approach is employed to synthesize the static matrix elements of steering law for a static state of VSCMG. Later these matrix elements are suitably made dynamic in order for the adaptation. In order to improve the performance of proposed steering law while passing through a singular state of CMG cluster (no torque output), the matrix element of steering law is suitably modified. Therefore, this steering law is capable of escaping internal singularities and using the full momentum capacity of CMG cluster. Finally, two numerical examples for a satellite in a low earth orbit are simulated to test the proposed steering law.

Malik, M. S. I.; Asghar, Sajjad

2014-01-01

188

Power law shapes for leading-edge blunting with minimal standoff distance in low-density hypersonic flow  

NASA Astrophysics Data System (ADS)

The steady-state aerodynamic characteristics of power law shaped leading edges immersed in high-speed rarefied air flow are examined by using a Direct Simulation Monte Carlo method. The work is motivated by interest in investigating power-law shaped leading edges as possible candidates for blunting geometries of hypersonic configurations. The aerodynamic performance of power law shapes is compared to a corresponding round leading edge shape based on equivalent shock standoff distance. For the flow conditions considered, the analysis shows that round leading edges provide smaller stagnation point heating and smaller drag than power law shapes for equivalent shock standoff distance.

Santos, W. F. N.

189

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

SciTech Connect

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.

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

190

Fokker–Planck equation of distributions of financial returns and power laws  

Microsoft Academic Search

Our purpose is to relate the Fokker–Planck formalism proposed by [Friedrich et al., Phys. Rev. Lett. 84 (2000) 5224] for the distribution of stock market returns to the empirically well-established power-law distribution with an exponent in the range 3–5. We show how to use Friedrich et al.'s formalism to predict that the distribution of returns is indeed asymptotically a power

Didier Sornette

2001-01-01

191

The Lawful Acquisition and Exercise of Monopoly Power and Its Implications for the Objectives of Antitrust  

Microsoft Academic Search

The antitrust laws of the United States have, from their inception, allowed firms to acquire significant market power, to charge prices that reflect that market power, and to enjoy supra-competitive returns. This article shows that this policy, which was established by the U.S. Congress and affirmed repeatedly by the U.S. courts, reflects a tradeoff between the dynamic benefits that society

David Evans; Keith Hylton

2008-01-01

192

Protein fold and family occurrence in genomes: power-law behaviour and evolutionary model  

Microsoft Academic Search

Global surveys of genomes measure the usage of essential molecular parts, defined here as protein families, superfamilies or folds, in different organisms. Based on surveys of the first 20 completely sequenced gen- omes, we observe that the occurrence of these parts follows a power-law distribution. That is, the number of distinct parts (F) with a given geno- mic occurrence (V)

Jiang Qian; Nicholas M Luscombe; Mark Gerstein

2001-01-01

193

Dark optical solitons in power law media with time-dependent coefficients  

Microsoft Academic Search

This Letter talks about the dynamics of dark optical solitons that are governed by the nonlinear Schrödinger's equation with power law nonlinearity. The solitons are considered in presence of linear attenuation, third order dispersion and self-steepening terms, all with time-dependent coefficients. The solitary wave ansatz is used to carry out the integration and an exact soliton solution is obtained. It

Manirupa Saha; Amarendra K. Sarma; Anjan Biswas

2009-01-01

194

Power-law spin correlations in pyrochlore antiferromagnets C. L. Henley  

E-print Network

Power-law spin correlations in pyrochlore antiferromagnets C. L. Henley Department of Physics The ground state ensemble of the highly frustrated pyrochlore-lattice antiferromagnet can be mapped specifically the pyrochlore lattice, consisting of corner-sharing tetrahedra, partly because of its simplicity

Henley, Christopher L.

195

A numerical study of nonlinear viscoelastic flow and nonisothermal power-law flow  

Microsoft Academic Search

The energy equation for power law fluids is solved under various circumstances including a temperature dependent viscosity, viscous dissipation and heat convection across streamlines induced by the abrupt change of boundary temperature and subsequent velocity field rearrangement. In addition to the numerical solutions given, an analytical approximation method for the Graetz-Nusselt problem is also presented for comparison. This method divides

Y. T. Lin

1980-01-01

196

Forced convection of power-law fluids flow over a rotating nonisothermal body  

Microsoft Academic Search

Presented is an analysis of steady laminar flow of power-law fluids past a rotating body with nonisothermal surfaces. A coordinate transformation combined with the Merk-type series expansion is employed to transform the governing momentum equations into a set of coupled ordinary differential equations. The equations are numerically integrated to obtain the axial and tangential velocity gradients for determining the friction

H. W. Kim; A. J. Esseniyi

1993-01-01

197

Black swans or dragon kings? A simple test for deviations from the power law  

E-print Network

We develop a simple test for deviations from power law tails, which is based on the asymptotic properties of the empirical distribution function. We use this test to answer the question whether great natural disasters, financial crashes or electricity price spikes should be classified as dragon kings or 'only' as black swans.

Janczura, Joanna

2011-01-01

198

Large amplitude oscillatory shear flow of gluten dough: A model power-law gel  

E-print Network

In a previous paper [T. S. K. Ng and G. H. McKinley, J. Rheol.52(2), 417–449 (2008)], we demonstrated that gluten gels can best be understood as a polymericnetwork with a power-law frequency response that reflects the ...

Ng, Trevor S. K.

199

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

200

114Exploring Power-Law Functions Using WISE Data! The Wide-field Infrared Survey Experiment  

E-print Network

, galaxies, asteroids and other objects that shine brightly in the infrared spectrum. The image to the left114Exploring Power-Law Functions Using WISE Data! The Wide-field Infrared Survey Experiment (WISE 'First Light' image near the bright star V482 Carinae seen to the right. Astronomers not only study

201

Power law thinning relationships for fall deposits: The example of Kilauea Iki 1959  

NASA Astrophysics Data System (ADS)

Quantitative measures of tephra dispersal, such as Walker's D index or Pyle's bt parameter, are dependent critically on an exponential thinning relationship for fall deposits. Several recent studies have show that some well-constrained Plinian and subplinian deposits cannot be modeled this way and require either power law thinning relationships or multiple exponential segments linked to contrasting settling behaviors of particles of contrasting Reynolds number. It appears that this holds true also for weaker, cone-forming explosive eruptions and the widespread component of the tephra fall from the 1959 Kilauea Iki eruption in Hawai'i shows a clear power law geometry. The 1959 eruption is an outstanding example of Hawaiian volcanism in which vigorous lava fountains reached heights as great as 580 m and discharge rates of 105 kg m-3, equivalent to time-averaged discharge rates of historical subplinian eruptions. Seventeen lava fountaining episodes over 37 days built a 50 m high, 40 hectare steep-sided cone and deposited a tephra sheet extending beyond 15 km down wind from the cone. Data gathered at the time of the eruption and in the current study show that the tephra sheet thins according to a power law relationship of the form Thickness = 485.95*sqrt(Area)^{-3.293}. In detail the form of the sheet is complex and reflects the superposition of at least 5 pulses of tephra with slightly different dispersal axes, each with its own separate power law geometry.

Fagents, S. A.; Houghton, B. F.; Swanson, D. A.

2006-12-01

202

Cosmological dynamics of the tachyon with an inverse power-law potential  

E-print Network

We investigate tachyon dynamics with an inverse power-law potential $V(\\phi) \\propto \\phi^{-\\alpha}$. We find global attractors of the dynamics leading to a dust behaviour for $\\alpha > 2$ and to an accelerating universe for $0 dark energy.

L. Raul W. Abramo; Fabio Finelli

2003-07-10

203

Ozone's effects on power-law particle size distribution in recirculating aquaculture systems  

Microsoft Academic Search

A power law model for particle size distributions has been applied by several researchers to aquacultural and aquatic systems Rueter and Johnson [Aquacult. Eng. 14 (1995) 123] demonstrated that ozonation of trout hatchery water increased the proportion of large particles in the water. Summerfelt et al. [Aquaculture 158 (1997) 57] speculated that this increase in particle size led to their

Valdis Krumins; James M. Ebeling; Fred Wheaton

2001-01-01

204

Does Stevens's Power Law for Brightness Extend to Perceptual Brightness Averaging?  

ERIC Educational Resources Information Center

Stevens's power law ([Psi][infinity][Phi][beta]) captures the relationship between physical ([Phi]) and perceived ([Psi]) magnitude for many stimulus continua (e.g., luminance and brightness, weight and heaviness, area and size). The exponent ([beta]) indicates whether perceptual magnitude grows more slowly than physical magnitude ([beta] less…

Bauer, Ben

2009-01-01

205

Evidence of power-law flow in the Mojave desert mantle  

E-print Network

............................................................................................................................................................................. Studies of the Earth's response to large earthquakes can be viewed as large rock deformation experiments to observable postseismic surface deformation1 . Laboratory experiments suggest that viscous flow of deforming hot lithospheric rocks is characterized by a power law in which strain rate is proportional to stress

Freed, Andrew

206

'Power law scaling during physical vapor deposition under extreme shadowing conditions  

E-print Network

interisland separation, which scales for metallic systems with the homologous growth temperature =Ts'Power law scaling during physical vapor deposition under extreme shadowing conditions S. Mukherjee as well as surface islands on the rod growth fronts control the morphological evolution which

Gall, Daniel

207

Graph Structure in Three National Academic Webs: Power Laws with Anomalies.  

ERIC Educational Resources Information Center

Explains how the Web can be modeled as a mathematical graph and analyzes the graph structures of three national university publicly indexable Web sites from Australia, New Zealand, and the United Kingdom. Topics include commercial search engines and academic Web link research; method-analysis environment and data sets; and power laws. (LRW)

Thelwall, Mike; Wilkinson, David

2003-01-01

208

A theory of power-law distributions in financial market fluctuations  

Microsoft Academic Search

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

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

2003-01-01

209

Evidence of power-law flow in the Mojave desert mantle.  

PubMed

Studies of the Earth's response to large earthquakes can be viewed as large rock deformation experiments in which sudden stress changes induce viscous flow in the lower crust and upper mantle that lead to observable postseismic surface deformation. Laboratory experiments suggest that viscous flow of deforming hot lithospheric rocks is characterized by a power law in which strain rate is proportional to stress raised to a power, n (refs 2, 3). Most geodynamic models of flow in the lower crust and upper mantle, however, resort to newtonian (linear) stress-strain rate relations. Here we show that a power-law model of viscous flow in the mantle with n = 3.5 successfully explains the spatial and temporal evolution of transient surface deformation following the 1992 Landers and 1999 Hector Mine earthquakes in southern California. A power-law rheology implies that viscosity varies spatially with stress causing localization of strain, and varies temporally as stress evolves, rendering newtonian models untenable. Our findings are consistent with laboratory-derived flow law parameters for hot and wet olivine--the most abundant mineral in the upper mantle--and support the contention that, at least beneath the Mojave desert, the upper mantle is weaker than the lower crust. PMID:15282602

Freed, Andrew M; Bürgmann, Roland

2004-07-29

210

Power Laws on Weighted Branching Trees Predrag R. Jelenkovic and Mariana Olvera-Cravioto  

E-print Network

Power Laws on Weighted Branching Trees Predrag R. Jelenkovi´c and Mariana Olvera-Cravioto 1 ranking schemes of large information sets, e.g., the World Wide Web (WWW); see [46, 47, 26 weight that measures its rela- tive importance with respect to other pages. We think of the Web as a very

Olvera-Cravioto, Mariana

211

Power Laws on Weighted Branching Trees Predrag R. Jelenkovic and Mariana Olvera-Cravioto  

E-print Network

Power Laws on Weighted Branching Trees Predrag R. Jelenkovi´c and Mariana Olvera-Cravioto Abstract of Electrical Engineering, e-mail: predrag@ee.columbia.edu Mariana Olvera-Cravioto Columbia University;2 Predrag R. Jelenkovi´c and Mariana Olvera-Cravioto where (Q,N,C1,C2,...) is a real-valued random vector

Jelenkovic, Predrag

212

Bose-Einstein condensation in dark power-law laser traps A. Jaouadi,1, 2, 3  

E-print Network

power-law laser traps. We propose to create such traps with two crossing blue-detuned Laguerre- Gaussian of a "finger" or of a "hockey puck" in such Laguerre-Gaussian traps. In addition, for a fixed atom number, requires a better but still reasonable focusing of the Laguerre-Gaussian beams. PACS numbers: 03.75.Hh, 03

Paris-Sud XI, Université de

213

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

NASA Astrophysics Data System (ADS)

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.

Metzler, Richard

2003-01-01

214

On the distributions of seasonal river flows: Lognormal or power law?  

NASA Astrophysics Data System (ADS)

Distributional analysis of river discharge time series is an important task in many areas of hydrological engineering, including optimal design of water storage and drainage networks, management of extreme events, risk assessment for water supply, and environmental flow management, among many others. Having diverging moments, heavy-tailed power law distributions have attracted widespread attention, especially for the modeling of the likelihood of extreme events such as floods and droughts. However, straightforward distributional analysis does not connect well with the complicated dynamics of river flows, including fractal and multifractal behavior, chaos-like dynamics, and seasonality. To better reflect river flow dynamics, we propose to carry out distributional analysis of river flow time series according to three "flow seasons": dry, wet, and transitional. We present a concrete statistical procedure to partition river flow data into three such seasons and fit data in these seasons using two types of distributions, power law and lognormal. The latter distribution is a salient property of the cascade multiplicative multifractal model, which is among the best models for turbulence and rainfall. We show that while both power law and lognormal distributions are relevant to dry seasons, river flow data in wet seasons are typically better fitted by lognormal distributions than by power law distributions.

Bowers, M. C.; Tung, W. W.; Gao, J. B.

2012-05-01

215

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

E-print Network

and the thin plate approximation for the linear stability analysis and is verified by finite element models imposed by the analyt- ical methods, we use a finite element model that allows us to verify the resultsFolding of a finite length power law layer Daniel W. Schmid1 and Yuri Y. Podladchikov Geologisches

Podladchikov, Yuri

216

Determination of power-law attenuation coefficient and dispersion spectra in multi-wall carbon nanotube  

E-print Network

for a set of multi-wall carbon nanotube MWCNT -nylon composites from pure nylon to 20% MWCNT by weight conductivity of copper. Incorporating nano-scale particles into a matrix to construct a macro-scale compositeDetermination of power-law attenuation coefficient and dispersion spectra in multi-wall carbon

Gladden, Josh

217

A stochastic evolutionary model exhibiting power-law behaviour with an exponential cutoff  

NASA Astrophysics Data System (ADS)

Recently several authors have proposed stochastic evolutionary models for the growth of complex networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the “rich get richer” phenomenon. Despite the generality of the proposed stochastic models, there are still some unexplained phenomena, which may arise due to the limited size of networks such as protein and e-mail networks. Such networks may in fact exhibit an exponential cutoff in the power-law scaling, although this cutoff may only be observable in the tail of the distribution for extremely large networks. We propose a modification of the basic stochastic evolutionary model, so that after a node is chosen preferentially, say according to the number of its inlinks, there is a small probability that this node will be discarded. We show that as a result of this modification, by viewing the stochastic process in terms of an urn transfer model, we obtain a power-law distribution with an exponential cutoff. Unlike many other models, the current model can capture instances where the exponent of the distribution is less than or equal to two. As a proof of concept, we demonstrate the consistency of our model by analysing a yeast protein interaction network, the distribution of which is known to follow a power law with an exponential cutoff.

Fenner, Trevor; Levene, Mark; Loizou, George

2005-09-01

218

A Stochastic Evolutionary Model Exhibiting Power-Law Behaviour with an Exponential Cutoff  

E-print Network

Recently several authors have proposed stochastic evolutionary models for the growth of complex networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the ``rich get richer'' phenomenon. Despite the generality of the proposed stochastic models, there are still some unexplained phenomena, which may arise due to the limited size of networks such as protein and e-mail networks. Such networks may in fact exhibit an exponential cutoff in the power-law scaling, although this cutoff may only be observable in the tail of the distribution for extremely large networks. We propose a modification of the basic stochastic evolutionary model, so that after a node is chosen preferentially, say according to the number of its inlinks, there is a small probability that this node will be discarded. We show that as a result of this modification, by viewing the stochastic process in terms of an urn transfer model, we obtain a power-law distribution with an exponential cutoff. Unlike many other models, the current model can capture instances where the exponent of the distribution is less than or equal to two. As a proof of concept, we demonstrate the consistency of our model by analysing a yeast protein interaction network, the distribution of which is known to follow a power law with an exponential cutoff.

Trevor Fenner; Mark Levene; George Loizou

2002-09-19

219

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

220

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

E-print Network

force vector. When n = 1, the fluid is Newtonian, with the classical Navier-Stokes equations. The shear thinning behavior is associated with 0 shear thickening behavior to n > 1. The notation |DThe horizontal dam break problem for slow non-Newtonian power-law fluids P. Saramito a C. Smutek b

221

Stochastic Power Law Fluids : the Existence and the Uniqueness of the Weak Solution  

E-print Network

,... · Shear thickening fluid: (F is in |e(u)|) bullet proof vests, automobile 4WD systems,... #12;· PDE "shear thinning" = 2 "Newtonian" > 2 "shear thickening" #12;· SPDE for Stochastic Power Law Fluids: u: (SPLF)p = (SNS) for p = 2, stochastic non-Newtonian fluid for p = 2. ("shear thinning" for p shear

Yoshida, Nobuo

222

DC Circuit Powered by Orbital Motion: Magnetic Interactions in Compact Object Binaries and Exoplanetary Systems  

E-print Network

The unipolar induction DC circuit model, originally developed by Goldreich & Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultra-compact white dwarf binaries, we find that DC circuit does not provide adequate energy dissipation to explain the observed X-ray luminosities of seve...

Lai, Dong

2012-01-01

223

Optical solitons with power-law asymptotics Robert W. Micallef, Vsevolod V. Afanasjev, Yuri S. Kivshar, and John D. Love  

E-print Network

Optical solitons with power-law asymptotics Robert W. Micallef, Vsevolod V. Afanasjev, Yuri S. Kivshar, and John D. Love Optical Sciences Centre, The Australian National University Canberra, Australian with power-law asymptotics, i.e., algebraic optical solitons, can be regarded as a special case of sech

224

Phase diagram of softly repulsive systems: The Gaussian and inverse-power-law potentials  

E-print Network

We redraw, using state-of-the-art methods for free-energy calculations, the phase diagrams of two reference models for the liquid state: the Gaussian and inverse-power-law repulsive potentials. Notwithstanding the different behavior of the two potentials for vanishing interparticle distances, their thermodynamic properties are similar in a range of densities and temperatures, being ruled by the competition between the body-centered-cubic (BCC) and face-centered-cubic (FCC) crystalline structures and the fluid phase. We confirm the existence of a reentrant BCC phase in the phase diagram of the Gaussian-core model, just above the triple point. We also trace the BCC-FCC coexistence line of the inverse-power-law model as a function of the power exponent $n$ and relate the common features in the phase diagrams of such systems to the softness degree of the interaction.

S. Prestipino; F. Saija; P. V. Giaquinta

2005-10-19

225

Bianchi-V string cosmology with power law expansion in f (R, T) gravity  

NASA Astrophysics Data System (ADS)

In this paper, we search the existence of the Bianchi-V string cosmological model in the f ( R, T) gravity with power law expansion. Einstein's field equations have been solved by taking into account the law of variation of Hubble's parameter that yields the constant value of the deceleration parameter (DP). We observe that the massive strings dominate the early universe but they do not survive for long time and finally disappear from the universe. We examine the nature of classical potential and also discuss the physical properties of the universe.

Kumar Yadav, Anil

2014-09-01

226

Bianchi-V string cosmology with power law expansion in $f(R, T)$ Gravity  

E-print Network

In this paper, we search the existence of Bianchi-V string cosmological model in $f(R,T)$ gravity with power law expansion. Einstein's field equations have been solved by taking into account the law of variation of Hubble's parameter that yields the constant value of deceleration parameter (DP). We observe that the massive strings dominate the early universe but they do not survive for long time and finally disappear from the universe. We examine the nature of classical potential and also discuss the physical properties of universe.

Anil Kumar Yadav

2013-11-22

227

Simple power law for transport ratio with bimodal distributions of coarse sediments under waves  

NASA Astrophysics Data System (ADS)

Morphodynamic models of coastal evolution require relatively simple parameterizations of sediment transport for application over larger scales. Here we present a transport parameterization for bimodal distributions of coarse quartz grains using simulations from a discrete particle model for sheet flow and near sheet flow conditions. The discrete particle model simulates the simplest one-dimensional fluid using a turbulent eddy viscosity determined from a mixing length coupled to particle motions. The motions of individual sand grains are simulated using spherical elements. Newton's second law in translational and rotational forms is solved for every particle in the domain as determined by both grain-grain and grain-fluid interactions. The forcing from idealized monochromatic waves is accomplished by specifying a spatially constant, time varying horizontal pressure gradient acting on the simulation domain. Consequently, the time series of the free-stream fluid acceleration and velocity are also fixed. Simulations cover a range of wave forcing, diameter ratios for the large and small grains in the bimodal size distribution, and mass ratios of large to small grains in the simulation domain, for a total of 243 unique simulation conditions. The simulation results are successfully parameterized with a simple power law that allows for the prediction of the transport rates of each size fraction in the bimodal distribution. The simple power law determined from simulations provides favorable predictions of transport rates for each size fraction when applied to available laboratory data for sheet flow with bimodal size distributions. It is important to note that rapid vertical kinematic sorting of grains by size is explicitly simulated with the model and thus implicitly captured by the power law. Discussion focuses on practical application of the power law.

Calantoni, Joseph; Thaxton, Christopher S.

2008-03-01

228

Strain-rate Dependence of Power-law Creep and Folding of Rocks  

NASA Astrophysics Data System (ADS)

Kocks (1987) proposed how the kinetics of deformation associated with different stress levels results in different shear stress-shear strain rate behaviours, with a cross-over or threshold from thermally activated dislocation motion at low stresses to viscous glide at some critical shear stress. Cordier (pers. comm.; Carrez et al., 2010) clarified this transition at least for MgO through atomistic, single dislocation and Dislocation Dynamics calculations. These studies indicate that the power-law relations observed experimentally for deforming rocks may be different for geological strain-rates, in that rate laws may become relatively strain-rate insensitive at low strain-rates. This transition from power law behaviour with relatively small values of the stress exponent, N, (N = 1 to 5) to large values of N (N = 5 to 20) has important implications for the development of localised behaviour during deformation as has been demonstrated at the other end of the spectrum for high stresses by Schmalholz and Fletcher (2011). Since localisation of fold systems arises from softening of the tangential viscosity, large values of N mean that little softening occurs with changes in strain rate, and sinusoidal folds are expected. There is therefore a critical range of N-values where localised, natural looking, folds develop. We explore the implications for folding of linear viscous single layers embedded in power-law viscous materials with N that varies with the stress level. The strain-rate dependence of the power law parameters results in strongly localised, aperiodic folding as opposed to the fold styles that arise from the linear Biot theory of folding. Also developed are axial plane shear fabrics. These structures resemble natural ones more than those that arise from simple Newtonian viscous or power-law behaviour with constant N. The results show that new studies of folded rocks and associated axial plane structures in the field may give important information on the transition from thermally activated dislocation motion to viscous glide. References. Amodeo, J., Carrez, Ph., Devincre, B., & Cordier, P. 2011. Multiscale modelling of MgO plasticity. Acta Materialia, 59, 2291-2301. Kocks, U. F. 1987. Constitutive behavior based on crystal plasticity. In: Unified Constitutive Equations for Creep and Plasticity. Ed. by A. K. Miller, Elsevier, pp. 1-88. Schmalholz, S. M., & Fletcher, R. C. 2011. The exponential flow law applied to necking and folding of a ductile layer. Geophys. J. Int., 184, 83-89.

Ord, A.; Hobbs, B. E.

2011-12-01

229

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

Code of Federal Regulations, 2010 CFR

...duty of the administrative law judge to inquire fully...complaint. The administrative law judge shall have authority...applications for subpoenas; (3) To rule upon petitions...contemptuous conduct and to strike all related testimony of...referred to the administrative law judge by the...

2010-07-01

230

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

Code of Federal Regulations, 2012 CFR

...duty of the administrative law judge to inquire fully...complaint. The administrative law judge shall have authority...applications for subpoenas; (3) To rule upon petitions...contemptuous conduct and to strike all related testimony of...referred to the administrative law judge by the...

2012-07-01

231

Superdiffusive transport and the power law distribution of pitch angle scattering times in solar wind turbulence  

NASA Astrophysics Data System (ADS)

Energetic particle transport in the interplanetary space is strongly influenced by turbulence and by the properties of magnetic field fluctuations. For istance, normalized magnetic field variances play a crucial role in the determination of the pitch angle scattering times and then of the transport regime. We have analyzed the time behavior of the normalized variances of the magnetic field fluctuations, measured by the Ulysses spacecraft upstream of some corotating interaction region (CIR) shocks. Recently, analyzing the accelerated particle time profiles upstream of CIRs, we found that energetic electrons exhibit superdiffusive transport, since their profiles decay as a power law in time (in the case of normal diffusion an exponential decay is expected). Superdiffusion can be described in terms of a Levy random walk, which is a statistical process implying a power law distribution of free path lengths and free path durations. The latter can be estimated from the pitch angle scattering time, which can be obtained from the normalized magnetic variance at the gyroresonant scale. The analysis presented shows that the normalized magnetic field variances are quasi steady-state in time from about 10 hours to 100 hours from the shock front. This rules out the presence of a spatially varying diffusion coefficient, which might produce a power law time profile for energetic particles upstream of a shock even in the case of normal transport, and confirms the possibility of superdiffusion for energetic electrons. A statistical analysis of the scattering times obtained from the magnetic fluctuations upstream of the CIRs events has also been performed. These power law distributions imply long free paths, long range correlations and weak pitch angle scattering. The power law slopes are often between 2 and 3, in good agreement with superdiffusive processes described by a Levy random walk. This shows that the power law distribution of pitch angle scattering times can be the physical origin of superdiffusion in the solar wind. We have also extended the theory of diffusive shock acceleration to the superdiffusive case: the main results will be presented, including a new expression for the energy spectral index of accelerated particles, which depends on the exponent of the mean square displacement growth, i.e., = 2Da*t? with ? > 1 for superdiffusion, as well as on the shock compression ratio.

Zimbardo, G.; Perri, S.

2012-12-01

232

Second-order small-disturbance solutions for hypersonic flow over power-law bodies  

NASA Technical Reports Server (NTRS)

Similarity solutions were found which give the adiabatic flow of an ideal gas about two-dimensional and axisymmetric power-law bodies at infinite Mach number to second order in the body slenderness parameter. The flow variables were expressed as a sum of zero-order and perturbation similarity functions for which the axial variations in the flow equations separated out. The resulting similarity equations were integrated numerically. The solutions, which are universal functions, are presented in graphic and tabular form. To avoid a singularity in the calculations, the results are limited to body power-law exponents greater than about 0.85 for the two-dimensional case and 0.75 for the axisymmetric case. Because of the entropy layer induced by the nose bluntness (for power-law bodies other than cones and wedges), only the pressure function is valid at the body surface. The similarity results give excellent agreement with the exact solutions for inviscid flow over wedges and cones having half-angles up to about 20 deg. They give good agreement with experimental shock-wave shapes and surface-pressure distributions for 3/4-power axisymmetric bodies, considering that Mach number and boundary-layer displacement effects are not included in the theory.

Townsend, J. C.

1975-01-01

233

Power laws, scale invariance, and generalized Frobenius series: Applications to Newtonian and TOV stars near criticality  

E-print Network

We present a self-contained formalism for analyzing scale invariant differential equations. We first cast the scale invariant model into its equidimensional and autonomous forms, find its fixed points, and then obtain power-law background solutions. After linearizing about these fixed points, we find a second linearized solution, which provides a distinct collection of power laws characterizing the deviations from the fixed point. We prove that generically there will be a region surrounding the fixed point in which the complete general solution can be represented as a generalized Frobenius-like power series with exponents that are integer multiples of the exponents arising in the linearized problem. This Frobenius-like series can be viewed as a variant of Liapunov's expansion theorem. As specific examples we apply these ideas to Newtonian and relativistic isothermal stars and demonstrate (both numerically and analytically) that the solution exhibits oscillatory power-law behaviour as the star approaches the point of collapse. These series solutions extend classical results. (Lane, Emden, and Chandrasekhar in the Newtonian case; Harrison, Thorne, Wakano, and Wheeler in the relativistic case.) We also indicate how to extend these ideas to situations where fixed points may not exist -- either due to ``monotone'' flow or due to the presence of limit cycles. Monotone flow generically leads to logarithmic deviations from scaling, while limit cycles generally lead to discrete self-similar solutions.

Nicolas Yunes; Matt Visser

2002-10-31

234

A generalized power-law detection algorithm for humpback whale vocalizations.  

PubMed

Conventional detection of humpback vocalizations is often based on frequency summation of band-limited spectrograms under the assumption that energy (square of the Fourier amplitude) is the appropriate metric. Power-law detectors allow for a higher power of the Fourier amplitude, appropriate when the signal occupies a limited but unknown subset of these frequencies. Shipping noise is non-stationary and colored and problematic for many marine mammal detection algorithms. Modifications to the standard power-law form are introduced to minimize the effects of this noise. These same modifications also allow for a fixed detection threshold, applicable to broadly varying ocean acoustic environments. The detection algorithm is general enough to detect all types of humpback vocalizations. Tests presented in this paper show this algorithm matches human detection performance with an acceptably small probability of false alarms (P(FA) < 6%) for even the noisiest environments. The detector outperforms energy detection techniques, providing a probability of detection P(D) = 95% for P(FA) < 5% for three acoustic deployments, compared to P(FA) > 40% for two energy-based techniques. The generalized power-law detector also can be used for basic parameter estimation and can be adapted for other types of transient sounds. PMID:22501048

Helble, Tyler A; Ierley, Glenn R; D'Spain, Gerald L; Roch, Marie A; Hildebrand, John A

2012-04-01

235

Bessel integrals in epsilon expansion: Squared spherical Bessel functions averaged with Gaussian power-law distributions  

NASA Astrophysics Data System (ADS)

Bessel integrals of type {int_0^infty {k^{?+2}{e}^{-ak2-(b+{i} ?)k}j_l^{2} (pk)dk}} are studied, where the squared spherical Bessel function j {/l 2} is averaged with a modulated Gaussian power-law density. 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. The averages can be calculated in closed form as finite Hankel series, which allow high-precision evaluation. In the case of integer power-law exponents ?, singularities emerge in the series coefficients, which requires ? expansion. The pole extraction and regularization of singular Hankel series is performed, for integer Gaussian power-law densities as well as for the special case of Kummer averages (a = 0 in the exponential of the integrand). The singular ? residuals are used to derive combinatorial identities (sum rules) for the rational Hankel coefficients, which serve as consistency checks in precision calculations of the integrals. Numerical examples are given, and the Hankel evaluation of Gaussian and Kummer averages is compared with their high-index Airy approximation over a wide range of integer Bessel indices l.

Tomaschitz, Roman

2013-12-01

236

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

E-print Network

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...

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

2014-01-01

237

Speed-invariant encoding of looming object distance requires power law spike rate adaptation  

PubMed Central

Neural representations of a moving object’s distance and approach speed are essential for determining appropriate orienting responses, such as those observed in the localization behaviors of the weakly electric fish, Apteronotus leptorhynchus. We demonstrate that a power law form of spike rate adaptation transforms an electroreceptor afferent’s response to “looming” object motion, effectively parsing information about distance and approach speed into distinct measures of the firing rate. Neurons with dynamics characterized by fixed time scales are shown to confound estimates of object distance and speed. Conversely, power law adaptation modifies an electroreceptor afferent’s response according to the time scales present in the stimulus, generating a rate code for looming object distance that is invariant to speed and acceleration. Consequently, estimates of both object distance and approach speed can be uniquely determined from an electroreceptor afferent’s firing rate, a multiplexed neural code operating over the extended time scales associated with behaviorally relevant stimuli. PMID:23898185

Clarke, Stephen E.; Naud, Richard; Longtin, Andre; Maler, Leonard

2013-01-01

238

Creep substructure formation in sodium chloride single crystals in the power law and exponential creep regimes  

NASA Technical Reports Server (NTRS)

Creep tests conducted on NaCl single crystals in the temperature range from 373 to 1023 K show that true steady state creep is obtained only above 873 K when the ratio of the applied stress to the shear modulus is less than or equal to 0.0001. Under other stress and temperature conditions, corresponding to both power law and exponential creep, the creep rate decreases monotonically with increasing strain. The transition from power law to exponential creep is shown to be associated with increases in the dislocation density, the cell boundary width, and the aspect ratio of the subgrains along the primary slip planes. The relation between dislocation structure and creep behavior is also assessed.

Raj, S. V.; Pharr, G. M.

1989-01-01

239

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

E-print Network

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.

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

2008-07-16

240

Scalar field reconstruction of power-law entropy-corrected holographic dark energy  

NASA Astrophysics Data System (ADS)

A so-called 'power-law entropy-corrected holographic dark energy' (PLECHDE) was recently proposed to explain the dark energy (DE)-dominated universe. This model is based on the power-law corrections to black hole entropy that appear when dealing with the entanglement of quantum fields between the inside and the outside of the horizon. In this paper, we suggest a correspondence between the interacting PLECHDE and the tachyon, quintessence, K-essence and dilaton scalar field models of DE in a non-flat Friedmann-Robertson-Walker universe. Then, we reconstruct the potential terms accordingly, and present the dynamical equations that describe the evolution of the scalar field DE models.

Ebrahimi, Esmaeil; Sheykhi, Ahmad

2011-10-01

241

Comparison of fractional wave equations for power law attenuation in ultrasound and elastography.  

PubMed

A set of wave equations with fractional loss operators in time and space are analyzed. The fractional Szabo equation, the power law wave equation and the causal fractional Laplacian wave equation are all found to be low-frequency approximations of the fractional Kelvin-Voigt wave equation and the more general fractional Zener wave equation. The latter two equations are based on fractional constitutive equations, whereas the former wave equations have been derived from the desire to model power law attenuation in applications like medical ultrasound. This has consequences for use in modeling and simulation, especially for applications that do not satisfy the low-frequency approximation, such as shear wave elastography. In such applications, the wave equations based on constitutive equations are the viable ones. PMID:24433745

Holm, Sverre; Näsholm, Sven Peter

2014-04-01

242

Market reaction to a bid-ask spread change: a power-law relaxation dynamics.  

PubMed

We study the relaxation dynamics of the bid-ask spread and of the midprice after a sudden variation of the spread in a double auction financial market. We find that the spread decays as a power law to its normal value. We measure the price reversion dynamics and the permanent impact, i.e., the long-time effect on price, of a generic event altering the spread and we find an approximately linear relation between immediate and permanent impact. We hypothesize that the power-law decay of the spread is a consequence of the strategic limit order placement of liquidity providers. We support this hypothesis by investigating several quantities, such as order placement rates and distribution of prices and times of submitted orders, which affect the decay of the spread. PMID:19658779

Ponzi, Adam; Lillo, Fabrizio; Mantegna, Rosario N

2009-07-01

243

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

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

244

Market reaction to a bid-ask spread change: A power-law relaxation dynamics  

NASA Astrophysics Data System (ADS)

We study the relaxation dynamics of the bid-ask spread and of the midprice after a sudden variation of the spread in a double auction financial market. We find that the spread decays as a power law to its normal value. We measure the price reversion dynamics and the permanent impact, i.e., the long-time effect on price, of a generic event altering the spread and we find an approximately linear relation between immediate and permanent impact. We hypothesize that the power-law decay of the spread is a consequence of the strategic limit order placement of liquidity providers. We support this hypothesis by investigating several quantities, such as order placement rates and distribution of prices and times of submitted orders, which affect the decay of the spread.

Ponzi, Adam; Lillo, Fabrizio; Mantegna, Rosario N.

2009-07-01

245

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

E-print Network

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.

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

1999-04-23

246

Power law for the permeabiltiy in a two dimensional disordered porous medium  

NASA Astrophysics Data System (ADS)

We report numerical calculations of the permeability as a function of porosity for a two-dimensional disordered porous medium. This medium is modeled using the well known “Swiss Cheese” model. The fluid is simulated using a cellular automata algorithm. We find that for relatively high porosities the permeability decays exponentially with the density of obstacles. As a consequence of this exponential behavior, a power-law dependence of the permeability as a function of the porosity is obtained, for this model system. We find that the power-law exponent is given by the ratio between two characteristic scales. One scale is given by the inverse of the area of one obstacle, and is approximately equal to the density of obstacles necessary to reach the percolation threshold. The other scale is equal to the average change in the density of obstacles necessary for the permeability to be reduced to about 1/ e of its original value.

Reyes, Leonardo I.; V, Ricardo Parades; Gutiérrez, Gustavo

1999-12-01

247

Formation of Hard Power Laws in the Energetic Particle Spectra Resulting from Relativistic Magnetic Reconnection  

NASA Astrophysics Data System (ADS)

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 ??B2/(4?nmec2)>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.

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

2014-10-01

248

Two-phase power-law modeling of pipe flows displaying shear-thinning phenomena  

SciTech Connect

This paper describes work in modeling concentrated liquid-solids flows in pipes. COMMIX-M, a three-dimensional transient and steady-state computer program developed at Argonne National Laboratory, was used to compute velocities and concentrations. Based on the authors` previous analyses, some concentrated liquid-solids suspension flows display shear-thinning rather than Newtonian phenomena. Therefore, they developed a two-phase non-Newtonian power-law model that includes the effect of solids concentration on solids viscosity. With this new two-phase power-law solids-viscosity model, and with constitutive relationships for interfacial drag, virtual mass effect, shear lift force, and solids partial-slip boundary condition at the pipe walls, COMMIX-M is capable of analyzing concentrated three-dimensional liquid-solids flows.

Ding, Jianmin; Lyczkowski, R.W.; Sha, W.T.

1993-12-31

249

Power-law solutions and accelerated expansion in scalar-tensor theories  

NASA Astrophysics Data System (ADS)

We find exact power-law solutions for scalar-tensor theories and clarify the conditions under which they can account for an accelerated expansion of the Universe. These solutions have the property that the signs of both the Hubble rate and the deceleration parameter in the Jordan frame may be different from the signs of their Einstein-frame counterparts. For special parameter combinations we identify these solutions with asymptotic attractors that have been obtained in the literature through dynamical-system analysis. We establish an effective general-relativistic description for which the geometrical equivalent of dark energy is associated with a time dependent equation of state. The present value of the latter is consistent with the observed cosmological “constant.” We demonstrate that this type of power-law solution for accelerated expansion cannot be realized in f(R) theories.

Batista, C. E. M.; Zimdahl, W.

2010-07-01

250

Deviations from uniform power-law scaling due to exposure to high altitude  

NASA Astrophysics Data System (ADS)

A major challenge in biological physics is the analysis of time series that are typically highly nonstationary. Viswanathan et al. (Phys. Rev. E 55 (1) (1997) 845-899) using techniques based on the Fano factor and the Allan factor functions, as well as on detrended fluctuation analysis showed that the scaling properties of the dynamics of healthy physiological systems in normal conditions are more stable than those of pathological systems-there is underlying loss of uniform power-law scaling in disease. Here we test, using the same techniques as Viswanathan et al. (1997), the hypothesis that deviations from uniform power-law scaling, similar to those seen in heart failure and deep apnea syndrome occur also for healthy subjects under pathological conditions (hypoxaemic stress during exposure to high altitude, over 6000 m).

Posiewnik, A.

2002-12-01

251

Energy Conditions Constraints and Stability of Power Law Solutions in f(R,T) Gravity  

E-print Network

The energy conditions are derived in the context of $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor, which can reduce to the well-known conditions in $f(R)$ gravity and general relativity. We present the general inequalities set by the energy conditions in terms of Hubble, deceleration, jerk and snap parameters. In this study, we concentrate on two particular models of $f(R,T)$ gravity namely, $f(R)+\\lambda{T}$ and $R+2f(T)$. The exact power-law solutions are obtained for these two cases in homogeneous and isotropic $f(R,T)$ cosmology. Finally, we find certain constraints which have to be satisfied to ensure that power law solutions may be stable and match the bounds prescribed by the energy conditions.

Muhammad Sharif; Muhammad Zubair

2012-10-15

252

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

NASA Astrophysics Data System (ADS)

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.

Sakiyama, Tomoko; Gunji, Yukio-Pegio

2014-05-01

253

ENERGY-DEPENDENT POWER SPECTRAL STATES AND ORIGIN OF APERIODIC VARIABILITY IN BLACK HOLE BINARIES  

SciTech Connect

We found that the black hole candidate MAXI J1659-152 showed distinct power spectra, i.e., power-law noise (PLN) versus band-limited noise (BLN) plus quasi-periodic oscillations (QPOs) below and above about 2 keV, respectively, in observations with Swift and the Rossi X-ray Timing Explorer during the 2010 outburst, indicating a high energy cutoff of the PLN and a low energy cutoff of the BLN and QPOs around 2 keV. The emergence of the PLN and the fading of the BLN and QPOs initially took place below 2 keV when the source entered the hard intermediate state and settled in the soft state three weeks later. The evolution was accompanied by the emergence of the disk spectral component and decreases in the amplitudes of variability in the soft and hard X-ray bands. Our results indicate that the PLN is associated with an optically thick disk in both hard and intermediate states, and the power spectral state is independent of the X-ray energy spectral state in a broadband view. We suggest that in the hard or intermediate state, the BLN and QPOs emerge from the innermost hot flow subjected to Comptonization, while the PLN originates from the optically thick disk farther out. The energy cutoffs of the PLN and the BLN or QPOs then follow the temperature of the seed photons from the inner edge of the optically thick disk, while the high frequency cutoff of the PLN follows the orbital frequency of the inner edge of the optically thick disk as well.

Yu Wenfei; Zhang Wenda, E-mail: wenfei@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

2013-06-20

254

Universal scaling of dissolved oxygen distribution at the sediment-water interface: A power law  

Microsoft Academic Search

Dissolved oxygen (DO) distribution at the sediment-water interface of a flow over a smooth bed is investigated for Reynolds numbers .360 and ,4,090. These conditions are commonly encountered in streams, wetlands, and lakes. A power-law scaling of DO distribution is derived and compared with experimental data. The scaling analysis is based on DO flux at the sediment-water interface in a

Miki Hondzo; Tom Feyaerts; Richard Donovan; Ben L. O'Connor

2005-01-01

255

Power laws and STM image of standing wave of the topological surface states  

Microsoft Academic Search

We have theoretically and experimentally studied the quasiparticle interference pattern caused by scattering off the step edges of topological surface states in Bi2Te3 and Bi2Se3. We propose a general formalism to identify the power law that governs the decaying spatial oscillations of standing wave of the quasiparticle. With strong hexagonal warping of the surface states in Bi2Te3, the standing wave

Bang-Fen Zhu; Jing Wang; Wei Li; Peng Cheng; Canli Song; Tong Zhang; Xi Chen; Xucun Ma; Ke He; Jin-Feng Jia; Qi-Kun Xue

2011-01-01

256

Fine structure and complex exponents in power-law distributions from random maps  

Microsoft Academic Search

Discrete scale invariance (DSI) has been suggested recently in time-to-failure rupture, earthquake processes, financial crashes, the fractal geometry of growth processes, and random systems. The main signature of DSI is the presence of log-periodic oscillations correcting the usual power laws, corresponding to complex exponents. Log-periodic structures are important because they reveal the presence of preferred scaling ratios of the underlying

Per Jögi; Didier Sornette; Michael Blank

1998-01-01

257

Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information  

NASA Technical Reports Server (NTRS)

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.

Howell, L. W., Jr.

2003-01-01

258

Effects of Multiplicative Power Law Neural Noise in Visual Information Processing  

Microsoft Academic Search

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

José M. Medina

2011-01-01

259

Forced convection of a power-law fluid in a porous channel – numerical solutions  

Microsoft Academic Search

A detailed numerical study of laminar forced convection in a porous channel which contains a fibrous medium saturated with\\u000a a power-law fluid was performed. Hydrodynamic and heat transfer results are presented for a configuration that has uniform\\u000a heat flux or uniform temperature heating at the walls. The flow in the porous medium was modeled using the modified Brinkman-Forchheimer-extended\\u000a Darcy model

G. Chen; H. A. Hadim

1998-01-01

260

Radial power-law position-dependent mass; Cylindrical coordinates, separability, and spectral signatures  

E-print Network

We discuss the separability of the position-dependent mass Hamiltonian in cylindrical coordinates in the framework of a radial power-law position-dependent mass. We consider two particular radial mass settings; a harmonic oscillator type, and a Coulombic type. We subject the radial harmonic oscillator type mass to a radial harmonic oscillator potential and the radial Coulombic mass to a radial Coulombic potential. Azimuthal symmetry is assumed and spectral signatures of various z-dependent interaction potentials are reported.

Omar Mustafa

2011-04-07

261

A power-law distribution for tenure lengths of sports managers  

NASA Astrophysics Data System (ADS)

We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level.

Aidt, Toke S.; Leong, Bernard; Saslaw, William C.; Sgroi, Daniel

2006-10-01

262

Bifurcation phenomena in the rigid inclusion power law matrix composite sphere  

Microsoft Academic Search

Bifurcation of interface separation related to cavity nucleation is analyzed for a radially loaded composite sphere consisting of a rigid inclusion separated from a power law matrix by a uniform, non-linear cohesive zone. Equations for the spherically symmetric and non-symmetric problems are obtained from a hyperelastic finite strain theory by a limiting process that preserves non-linear matrix and interface response

Alan J. Levy

2003-01-01

263

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

PubMed

We report results from a search for chameleon particles created via photon-chameleon oscillations within a magnetic field. This experiment is sensitive to a wide class of unexplored chameleon power-law and dark energy models. These results exclude 5 orders of magnitude in the coupling of chameleons to photons covering a range of 4 orders of magnitude in chameleon effective mass and, for individual models, exclude between 4 and 12 orders of magnitude in chameleon couplings to matter. PMID:21231645

Steffen, J H; Upadhye, A; Baumbaugh, A; Chou, A S; Mazur, P O; Tomlin, R; Weltman, A; Wester, W

2010-12-31

264

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

Microsoft Academic Search

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

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

1999-01-01

265

Power-law relationships for estimating mass, fuel consumption and costs of energy conversion equipments.  

PubMed

To perform life-cycle assessment studies, data on the production and use of the products is required. However, often only few data or measurements are available. Estimation of properties can be performed by applying scaling relationships. In many disciplines, they are used to either predict data or to search for underlying patterns, but they have not been considered in the context of product assessments hitherto. The goal of this study was to explore size scaling for commonly used energy conversion equipment, that is, boilers, engines, and generators. The variables mass M, fuel consumption Q, and costs C were related to power P. The established power-law relationships were M = 10(0.73.. 1.89)P(0.64.. 1.23) (R(2) ? 0.94), Q = 10(0.06.. 0.68)P(0.82.. 1.02) (R(2) ? 0.98) and C = 10(2.46.. 2.86)P(0.83.. 0.85) (R(2) ? 0.83). Mass versus power and costs versus power showed that none of the equipment types scaled isometrically, that is, with a slope of 1. Fuel consumption versus power scaled approximately isometrically for steam boilers, the other equipments scaled significantly lower than 1. This nonlinear scaling behavior induces a significant size effect. The power laws we established can be applied to scale the mass, fuel consumption and costs of energy conversion equipments up or down. Our findings suggest that empirical scaling laws can be used to estimate properties, particularly relevant in studies focusing on early product development for which generally only little information is available. PMID:21133374

Caduff, Marloes; Huijbregts, Mark A J; Althaus, Hans-Joerg; Hendriks, A Jan

2011-01-15

266

Single and Binary Black Holes and their Influence on Nuclear Structure  

E-print Network

Massive central objects affect both the structure and evolution of galactic nuclei. Adiabatic growth of black holes generates power-law central density profiles with logarithmic slopes in the range from ~1.5 to ~2.5, in good agreement with the profiles observed in the nuclei of galaxies fainter than visual magnitude -20. However the shallow nuclear profiles of bright galaxies require a different explanation. Binary black holes are an inevitable result of galactic mergers, and the ejection of stars by a massive binary displaces a mass of order the binary's own mass, creating a core or shallow power-law cusp. This model is at least crudely consistent with core sizes in bright galaxies. Uncertainties remain about the effectiveness of stellar- and gas-dynamical processes at inducing coalescence of binary black holes, and uncoalesced binaries may be common in low-density nuclei.

David Merritt

2003-01-14

267

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

SciTech Connect

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.

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

268

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

E-print Network

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.

Mauricio Cataldo; Patricio Mella; Paul Minning; Joel Saavedra

2008-03-07

269

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

SciTech Connect

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.

Gong Jingyu; Du Jiulin [Department of Physics, School of Science, Tianjin University, Tianjin 300072 (China); Liu Zhipeng [Department of Physics, School of Science, Tianjin University, Tianjin 300072 (China); Department of Fundamental Subject, Tianjin Institute of Urban Construction, Tianjin 300384 (China)

2012-08-15

270

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

271

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

NASA Astrophysics Data System (ADS)

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.

Saichev, A.; Sornette, D.

2010-01-01

272

Dynamics of threads and polymers in turbulence: power-law distributions and synchronization  

NASA Astrophysics Data System (ADS)

We study the behavior of threads and polymers in a turbulent flow. These objects have finite spatial extension, so the flow along them differs slightly. The corresponding drag forces produce a finite average stretching and the thread is stretched most of the time. Nevertheless, the probability of shrinking fluctuations is significant and is known to decay only as a power law. We show that the exponent of the power law is a universal number independent of the statistics of the flow. For polymers the coil-stretch transition exists: the flow must have a sufficiently large Lyapunov exponent to overcome the elastic resistance and stretch the polymer from the coiled state it takes otherwise. The probability of shrinking from the stretched state above the transition again obeys a power law but with a non-universal exponent. We show that well above the transition the exponent becomes universal and derive the corresponding expression. Furthermore, we demonstrate synchronization: the end-to-end distances of threads or polymers above the transition are synchronized by the flow and become identical. Thus, the transition from Newtonian to non-Newtonian behavior in dilute polymer solutions can be seen as an ordering transition.

Fouxon, Itzhak; Posch, Harald A.

2012-01-01

273

Power-law behavior in complex organizational communication networks during crisis  

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

274

Fast Spectral Fitting of Hard X-Ray Bremsstrahlung from Truncated Power-Law Electron Spectra  

E-print Network

Hard X-Ray bremsstrahlung continuum spectra, such as from solar flares, are commonly described in terms of power-law fits, either to the photon spectra themselves or to the electron spectra responsible for them. In applications various approximate relations between electron and photon spectral indices are often used for energies both above and below electron low-energy cutoffs. We examine the form of the exact relationships in various situations, and for various cross-sections, showing that empirical relations sometimes used can be highly misleading and consider how to improve fitting procedures. We obtain expressions for photon spectra from single, double and truncated power-law electron spectra for a variety of cross-sections and for the thin and thick target models and simple analytic expressions for the Bethe-Heitler cases. We show that above a low-energy cutoff the Kramers and Bethe-Heitler results match reasonably well with results for exact cross-sections up to energies around 100 keV; that below the low-energy cutoff, Kramers and other constant spectral index forms commonly used are very poor approximations to accurate results; but that our analytical forms are a very good match. Analytical forms of the Bethe-Heitler photon spectra from general power-law electron spectra are an excellent match to exact results for both thin and thick targets and they enable much faster spectral fitting than evaluation of the full spectral integrations.

J. C. Brown; J. Kasparova; A. M. Massone; M. Piana

2008-02-05

275

Energy Spectrum of the Electrons Accelerated by a Reconnection Electric Field: Exponential or Power Law?  

E-print Network

The direct current (DC) electric field near the reconnection region has been proposed as an effective mechanism to accelerate protons and electrons in solar flares. A power-law energy spectrum was generally claimed in the simulations of electron acceleration by the reconnection electric field. However in most of the literature, the electric and magnetic fields were chosen independently. In this paper, we perform test-particle simulations of electron acceleration in a reconnecting magnetic field, where both the electric and magnetic fields are adopted from numerical simulations of the MHD equations. It is found that the accelerated electrons present a truncated power-law energy spectrum with an exponential tail at high energies, which is analogous to the case of diffusive shock acceleration. The influences of reconnection parameters on the spectral feature are also investigated, such as the longitudinal and transverse components of the magnetic field and the size of the current sheet. It is suggested that the DC electric field alone might not be able to reproduce the observed single or double power-law distributions.

W. J. Liu; P. F. Chen; M. D. Ding; C. Fang

2008-09-07

276

Power-law tails in nonstationary stochastic processes with asymmetrically multiplicative interactions  

NASA Astrophysics Data System (ADS)

We consider stochastic processes where randomly chosen particles with positive quantities x,y(>0) interact and exchange the quantities asymmetrically by the rule x'=c{(1-a)x+by} , y'=d{ax+(1-b)y} (x?y) , where (0?)a,b(?1) and c,d(>0) are interaction parameters. Noninteger power-law tails in the probability distribution function of scaled quantities are analyzed in a similar way as in inelastic Maxwell models. A transcendental equation to determine the growth rate ? of the processes and the exponent s of the tails is derived formally from moment equations in Fourier space. In the case c=d or a+b=1(a?0,1) , the first-order moment equation admits a closed form solution and ? and s are calculated analytically from the transcendental equation. It becomes evident that at c=d , exchange rate b of small quantities is irrelevant to power-law tails. In the case c?d and a+b?1 , a closed form solution of the first-order moment equation cannot be obtained because of asymmetry of interactions. However, the moment equation for a singular term formally forms a closed solution and possibility for the presence of power-law tails is shown. Continuity of the exponent s with respect to parameters a,b,c,d is discussed. Then numerical simulations are carried out and campared with the theory. Good agreement is achieved for both ? and s .

Fujihara, Akihiro; Ohtsuki, Toshiya; Yamamoto, Hiroshi

2004-09-01

277

Fitting and goodness-of-fit test of non-truncated and truncated power-law distributions  

E-print Network

Power-law distributions contain precious information about a large variety of processes in geoscience and elsewhere. Although there are sound theoretical grounds for these distributions, the empirical evidence in favor of power laws has been traditionally weak. Recently, Clauset et al. have proposed a systematic method to find over which range (if any) a certain distribution behaves as a power law. However, their method has been found to fail, in the sense that true (simulated) power-law tails are not recognized as such in some instances, and then the power-law hypothesis is rejected. Moreover, the method does not work well when extended to power-law distributions with an upper truncation. We explain in detail a similar but alternative procedure, valid for truncated as well as for non-truncated power-law distributions, based in maximum likelihood estimation, the Kolmogorov-Smirnov goodness-of-fit test, and Monte Carlo simulations. An overview of the main concepts as well as a recipe for their practical implem...

Corral, Alvaro

2012-01-01

278

Disorder induced power-law response of a superconducting vortex on a plane  

E-print Network

We report drive-response experiments on individual superconducting vortices on a plane, a realization for a 1+1-dimensional directed polymer in random media. For this we use magnetic force microscopy (MFM) to image and manipulate individual vortices trapped on a twin boundary in YBCO near optimal doping. We find that when we drag a vortex with the magnetic tip it moves in a series of jumps. As theory suggests the jump-size distribution does not depend on the applied force and is consistent with power-law behavior. The measured power is much larger than widely accepted theoretical calculations.

N. Shapira; Y. Lamhot; O. Shpielberg; Y. Kafri; B. J. Ramshaw; D. A. Bonn; Ruixing Liang; W. N. Hardy; O. M. Auslaender

2014-01-06

279

DC Circuit Powered by Orbital Motion: Magnetic Interactions in Compact Object Binaries and Exoplanetary Systems  

E-print Network

The unipolar induction DC circuit model, originally developed by Goldreich & Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultra-compact white dwarf binaries, we find that DC circuit does not provide adequate energy dissipation to explain the observed X-ray luminosities of several sources. For exoplanetary systems containing close-in Jupiters or super-Earths, magnetic torque and dissipation are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 10^3G.

Dong Lai

2012-06-17

280

DC Circuit Powered by Orbital Motion: Magnetic Interactions in Compact Object Binaries and Exoplanetary Systems  

NASA Astrophysics Data System (ADS)

The unipolar induction DC circuit model, originally developed by Goldreich and Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such a model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to the breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultracompact white dwarf binaries, we find that unipolar induction does not provide adequate energy dissipation to explain the observed X-ray luminosities of several sources. For exoplanetary systems containing close-in Jupiters or super-Earths, the magnetic torque and energy dissipation induced by the orbital motion are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 103 G.

Lai, Dong

2012-09-01

281

Streamwater ages derived from tritium show power law variation with discharge like silica concentrations  

NASA Astrophysics Data System (ADS)

Understanding runoff generation is important for management of freshwater systems. Determining transit time distributions of streamwaters and how they change with discharge gives information on the flowpaths and recharge sources of streams - vital information for determining the responses of streams to stressors such as pollution, landuse change, or climate change. This work takes a first look at unique information on how transit time distributions change with discharge in some New Zealand catchments. Transit time distributions of streamwaters have been determined from tritium measurements on single samples in this work. This allows changes with stream discharge to be observed, in contrast to previous isotope studies which have given averaged transit time distributions based on series of samples. In addition, tritium reveals the wide spectrum of ages present in streams whereas oxygen-18 or chloride variations only show the younger ages (Stewart et al., 2010). It was found that the mean transit time (MTT) data could be reasonably represented by straight lines in log-log plots, indicating power law relationships between MTT and discharge. Similar power law behaviour has been observed for the rock forming elements such as silica in streamwaters (Godsey et al., 2009). Case studies are presented for two New Zealand catchments, both with volcanic ash substrates. Toenepi is a dairy catchment near Hamilton, which shows well-constrained power law relationships between MTT and discharge, and between silica concentration and discharge (Morgenstern et al., 2010). Baseflow MTTs vary from 2.5 to 157 years. Tutaeuaua is a pastoral farming catchment near Taupo. Results for nested catchments along the stream also show power law relationships for both MTT and silica with discharge. Streamwater MTTs vary from 1 to 11 years. The results indicate that (1) relatively old waters dominate many streams, (2) streamwater ages vary with discharge, and (3) age, like silica, varies according to power law relationships with stream discharge. References: Godsey, S.E., Kirchner, J.W., Clow, D.W. Hydrological Processes 23, 1844-1864, 2009. Morgenstern, U., Stewart M. K., Stenger, R. Hydrology and Earth System Sciences 14, 2289-2301, 2010. Stewart, M.K., Morgenstern, U., McDonnell, J.J. Hydrological Processes 24(12), 1646-1659, 2010.

Stewart, Michael; Morgenstern, Uwe

2013-04-01

282

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

E-print Network

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...

Saichev, A

2012-01-01

283

Numerical study of unsteady stenosis flow: parametric evaluation of power-law model.  

PubMed

Currently the best indicator for surgical treatment of arterio-sclerosis is the degree of stenosis. Although X-ray angiography is currently the standard, cost and morbidity are distinct disadvantages. By modelling stenosis and studying its biofluid mechanics, one can apply its results in the field of arterial disease research. This formed the motivation for this work. A non-Newtonian (power law) incompressible Navier-Stokes (N-S) solver was developed using the method of operator splitting and artificial compressibility. The vehicle used is the computational fluid dynamics (CFD) numerical library FASTFLO. The power-law model developed is then used to do a parametric study of the effect of 'n' on blood flow mechanics where 'n' is the power index that determines the haematocrit of blood. A pulsatile pressure wave over a cardiac cycle of a second was used to simulate transient flow over a hypothetical two-dimensional stenotic geometry. By comparing the different velocity pressure, wall shear stress and viscosity profiles, it has been found when 'n' increases, the vortex formation and peak wall shear stress decreases (magnitudes of < 1.5 Pa). Since the formation of vortices and low oscillatory wall shear stress on the stenotic wall is detrimental to the well-being of the arterial tract, it can therefore be inferred that there might be a relationship between the diseased state of blood (power law) and early genesis of atherosclerosis. However, the conclusion of this paper marks the advent of new research directions in this field of study. PMID:11204243

Ng, E Y; Siauw, W L; Goh, W E

2000-01-01

284

Mathematical modeling of genome evolution: Where do the power laws come from  

NASA Astrophysics Data System (ADS)

Power law distributions appear in numerous biological, physical, social and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interaction partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution. A simple model of evolution of the domain composition of proteomes was developed, with the following elementary processes: i) domain birth (duplication with divergence), ii) death (inactivation and/or deletion), and iii) innovation (emergence from non-coding or non-globular sequences or acquisition via horizontal gene transfer). This formalism can be described as a birth, death and innovation model (BDIM). The formulas for equilibrium frequencies of domain families of different size and the total number of families at equilibrium were derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models were found and their appearance depending on model parameters was investigated. It was proved that the power law asymptotics appears if, and only if, the model is balanced, i.e., domain duplication (birth) and deletion (death) rates are asymptotically equal up to the second order. It was further proved that any power asymptotic with the degree not equal to -1 can appear only if the assumption of independence of the birth/death rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, were explored in detail and the distributions of the equilibrium frequencies of domain families of different size were determined for each case. The BDIM formalism was applied to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and an excellent fit was observed between these empirical data and a particular form of the model, the second-order balanced linear BDIM. Calculation of the parameters of these models suggests surprisingly high innovation rates, comparable to the total domain birth (duplication) and death (elimination) rates, particularly for prokaryotic genomes. Thus, a straightforward model of genome evolution, which does not explicitly include selection, seems to be sufficient to explain the observed distributions of domain family sizes, in which power laws appear as asymptotic. However, for the model to be compatible with the data, there has to be a precise balance between domain birth, death and innovation rates, and this is likely to be maintained by selection. The developed approach is oriented at a mathematical description of evolution of domain composition of proteomes, but a simple reformulation could be applied to models of other evolving networks with preferential attachment.

Koonin, Eugene

2003-03-01

285

Multiple Binary Classifications via Linear Discriminant Analysis for Improved Controllability of a Powered Prosthesis  

Microsoft Academic Search

This paper describes a novel pattern recognition based myoelectric control system that uses parallel binary classification and class specific thresholds. The system was designed with an intuitive configuration interface, similar to existing conventional myoelectric control systems. The system was assessed quantitatively with a classification error metric and functionally with a clothespin test implemented in a virtual environment. For each case,

Levi J. Hargrove; Kevin B. Englehart; Bernard S. Hudgins

2010-01-01

286

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

SciTech Connect

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.

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

287

A Hard X-Ray Power-Law Spectral Cutoff in Centaurus X-4  

E-print Network

The low-mass X-ray binary Cen X-4 is the brightest and closest (law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1 x 10^(33) erg/s (for D=1kpc), with around 60 percent in the thermal component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with an 18 keV electron temperature, which can be understood as...

Chakrabarty, Deepto; Grefenstette, Brian W; Psaltis, Dimitrios; Bachetti, Matteo; Barret, Didier; Boggs, Steven E; Christensen, Finn E; Craig, William W; Fuerst, Felix; Hailey, Charles J; Harrison, Fiona A; Kaspi, Victoria A; Miller, Jon M; Nowak, Michael A; Rana, Vikram; Stern, Daniel; Wik, Daniel R; Wilms, Joern; Zhang, William W

2014-01-01

288

On the interplay between short and long term memory in the power-law cross-correlations setting  

E-print Network

We focus on emergence of the power-law cross-correlations from processes with both short and long term memory properties. In the case of correlated error-terms, the power-law decay of the cross-correlation function comes automatically with the characteristics of the separate processes. The bivariate Hurst exponent is then equal to an average of the separate Hurst exponents of the analysed processes. Strength of the short term memory has no effect on these asymptotic properties.

Kristoufek, Ladislav

2014-01-01

289

The Cultural Power of Law and the Cultural Enactment of Legality: The Case of Same-Sex Marriage  

Microsoft Academic Search

legal marriage. Approaching marriage from the perspective of same-sex cou-ples, this research demonstrates that the legal and cultural aspects of marriage are deeply intertwined. Cultural enactments of marriage enact legality even in the absence of official law, and many actors ascribe to law a cultural power that transcends its specific benefits and protections, the power to pro-duce social and cultural

Kathleen E. Hull

2003-01-01

290

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

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

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

2014-01-01

291

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

Power laws, that is, power spectral densities (PSDs) exhibiting [Formula: see text] 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 [Formula: see text] power laws with power-law exponents analytically identified as [Formula: see text] for the soma membrane current, [Formula: see text] for the current-dipole moment, and [Formula: see text] 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 ([Formula: see text]) 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 [Formula: see text] power laws with a wide range of values for the power-law exponent ? may arise from a simple, linear partial differential equation. PMID:25393030

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

2014-11-01

292

Lower Energy Cutoff Behavior of Negative Power-Law Electrons and Electron-Cyclotron Maser Emission  

NASA Astrophysics Data System (ADS)

The electron-cyclotron maser (ECM) emission is one of the most important radio emission mechanisms in astrophysics. It was first pointed out in the late 1950s. Because of the limitation of the nonrelativistic resonant condition, it is difficult to produce an amplified radiation that can escape from plasma. The ECM instability has been extensively applied to various coherent radio-burst phenomena since Wu & Lee (1979) utilized the weakly relativistic resonant condition. Several loss-cone like electron distribution functions have been put forward. Astrophysical observations demonstrate that energetic electrons usually have a negative power-law distribution. However, the negative power-law spectrum of energetic electrons can depress the ECM instability effectively. We need a new and more effective mechanism to drive the radiation. In this thesis, we investigate the ECM emission driven by the lower energy cutoff behavior of power-law electrons, and the effects of anisotropy of energetic electrons in velocity space on ECM. Firstly, Chapter 1 introduces the general knowledge of the observational characteristics of solar radio bursts, and the excitation mechanisms of radio emission. Then, combining with the observations of hard X-ray spectrum, in Chapter 2 we overview the properties of energetic electrons driving the radio emission, and discuss the lower energy cutoff behavior of the negative power-law electrons. We suggest a hyperbolic tangent function to describe the lower energy cutoff behavior. In Chapter 3 we discuss the ECM driven by the lower energy cutoff behavior, and the effects of anisotropy in velocity space on the ECM instability. It is found that: (1) even with isotropic distribution, the power-law electrons with the steepness cutoff can efficiently excite the ECM instability; (2) same as the isotropy case, the power-law electrons with anisotropic distributions can also excite ECM instability efficiently, which have an important effect on the ECM emission. Energetic electrons observed in situ are ubiquitous in the near Earth space plasmas. They are commonly modeled as the so-called Kappa distribution. In Chapter 4 we investigate the ECM instability in space plasmas driven by the Kappa loss-cone distribution. Chapter 5 reports a novel kind of fine structures in solar radio bursts, solar microwave drifting spikes (SMDSs) on 2004 November 3, and makes statistical analysis of microwave spikes on 2006 December 13. We investigate the observational parameters of SMDSs observed on 2004 November 3. The electrons trapped within the solitary kinetic Alfven waves (SKAWs) can be accelerated by the SKAW electric fields, and directly trigger the observed SMDSs by the ECM mechanism. According to the GOES soft X-ray observations, the flare on 2006 December 13 can be separated into the rising phase, peak phase, and decay phase. We make statistical analysis of the observational parameters of the radio spikes, which occurred in all the three phases, and investigate their temporal evolution. Finally, the summary of the whole thesis and outlook are presented in Chapter 6.

Tang, J. F.

2014-01-01

293

Learning curves in highly skilled chess players: a test of the generality of the power law of practice.  

PubMed

The power law of practice holds that a power function best interrelates skill performance and amount of practice. However, the law's validity and generality are moot. Some researchers argue that it is an artifact of averaging individual exponential curves while others question whether the law generalizes to complex skills and to performance measures other than response time. The present study tested the power law's generality to development over many years of a very complex cognitive skill, chess playing, with 387 skilled participants, most of whom were grandmasters. A power or logarithmic function best fit grouped data but individuals showed much variability. An exponential function usually was the worst fit to individual data. Groups differing in chess talent were compared and a power function best fit the group curve for the more talented players while a quadratic function best fit that for the less talented. After extreme amounts of practice, a logarithmic function best fit grouped data but a quadratic function best fit most individual curves. Individual variability is great and the power law or an exponential law are not the best descriptions of individual chess skill development. PMID:24915472

Howard, Robert W

2014-09-01

294

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

295

Entropy and the Cosmic Ray Particle Energy Distribution Power Law Exponent  

E-print Network

We consider the hypothesis that cosmic rays are emitted from the surfaces of neutron stars by a process of evaporation from an internal nuclear liquid to a dilute external gas which constitutes the "vacuum". On this basis, we find an inverse power in the energy distribution with a power law exponent of 2.701178 in excellent agreement with the experimental value of 2.7. The heat of nuclear matter evaporation via the entropy allows for the computation of the exponent. The evaporation model employed is based on the entropy considerations of Landau and Fermi that have been applied to the liquid drop model of evaporation in a heavy nucleus excited by a collision. This model provides a new means of obtaining power law distributions for cosmic ray energy distributions and, remarkably, an actual value for the exponent which is in agreement with experiment and explains the otherwise puzzling smoothness of the cosmic ray energy distribution over a wide range of energies without discontinuities due to contributions from...

Widom, A; Srivastava, Y N

2014-01-01

296

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

NASA Astrophysics Data System (ADS)

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. A general systems theory model predicts universal inverse power-law form incorporating the golden mean for the fractal fluctuations. The model predicted distribution was compared with observed distribution of fractal fluctuations of all size scales (small, large and extreme values) in the historic month-wise temperature (maximum and minimum) and total rainfall for the four stations Oxford, Armagh, Durham and Stornoway in the UK region, for data periods ranging from 92 years to 160 years. For each parameter, the two cumulative probability distributions, namely cmax and cmin starting from respectively maximum and minimum data value were used. The results of the study show that (i) temperature distributions (maximum and minimum) follow model predicted distribution except for Stornowy, minimum temperature cmin. (ii) Rainfall distribution for cmin follow model predicted distribution for all the four stations. (iii) Rainfall distribution for cmax follows model predicted distribution for the two stations Armagh and Stornoway. The present study suggests that fractal fluctuations result from the superimposition of eddy continuum fluctuations.

Selvam, A. M.

2014-06-01

297

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

PubMed

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

Saichev, A; Sornette, D

2010-01-01

298

CT-based Diagnosis of Diffuse Coronary Artery Disease on the Basis of Scaling Power Laws  

PubMed Central

Purpose: To provide proof of concept for a diagnostic method to assess diffuse coronary artery disease (CAD) on the basis of coronary computed tomography (CT) angiography. Materials and Methods: The study was approved by the Cleveland Clinic Institutional Review Board, and all subjects gave informed consent. Morphometric data from the epicardial coronary artery tree, determined with CT angiography in 120 subjects (89 patients with metabolic syndrome and 31 age- and sex-matched control subjects) were analyzed on the basis of the scaling power law. Results obtained in patients with metabolic syndrome and control subjects were compared statistically. Results: The mean lumen cross-sectional area (ie, lumen cross-sectional area averaged over each vessel of an epicardial coronary artery tree) and sum of intravascular volume in patients with metabolic syndrome (0.039 cm2 ± 0.015 [standard deviation] and 2.71 cm3 ± 1.75, respectively) were significantly less than those in control subjects (0.054 cm2± 0.015 and 3.29 cm3± 1.77, respectively; P < .05). The length-volume power law showed coefficients of 27.0 cm?4/3 ± 9.0 (R2 = 0.91 ± 0.08) for patients with metabolic syndrome and 19.9 cm?4/3 ± 4.3 (R2 = 0.92 ± 0.07) for control subjects (P < .05). The probability frequency shows that more than 65% of patients with metabolic syndrome had a coefficient of 23 or more for the length-volume scaling power law, whereas approximately 90% of the control subjects had a coefficient of less than 23. Conclusion: The retrospective scaling analysis provides a quantitative rationale for diagnosis of diffuse CAD. © RSNA, 2013 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122181/-/DC1 PMID:23616633

Huo, Yunlong; Wischgoll, Thomas; Choy, Jenny Susana; Sola, Srikanth; Navia, Jose L.; Teague, Shawn D.; Bhatt, Deepak L.

2013-01-01

299

Integrating connectivity, power law, and alternative stable state paradigms of dryland ecosystem structure and dynamics  

NASA Astrophysics Data System (ADS)

Drylands are important ecosystems that cover about 40% of the Earth's land surface and provide goods and services for about 30% of the Earth's inhabitants. Dryland vegetation is almost universally patchy reflecting the resource limitation endemic to these areas and this patchiness unquestionably results from some type of self-organization. Understanding the function of these ecosystems is critical for their effective management and for understanding how they will be affected by changes in climate and land use as well as by invasion of non-native species. There are three main paradigms that have emerged in the literature to explain dryland ecosystem structure and dynamics. The connectivity paradigm posits that spatiotemporal patterns of vegetation observed in drylands are a result of the lateral movement of resources and disturbance along connected pathways. Other authors have examined the impact of local-scale interactions that give rise to large-scale patterns in the form of power law distributions of vegetation patches. Deviation from power law distributions as a sign of imminent, catastrophic change has been a common thread in this line of research. The sudden and often irreversible change observed in dryland ecosystems has led others to emphasize the importance of feedbacks that lead to the existence of alternative stable states and hysteresis in drylands. This latter view is closely aligned with the state-and-transition model approach. Here we show, through a series of conceptual and mathematical model arguments, that these three approaches - connectivity, power law distributions, and alternative stable states - can in many circumstances be considered equivalent. They are, in essence, different facets of a common set underlying processes. This transdisciplinary, integrated perspective should help understand how spatial processes interact to create pattern and patchiness in dryalnds as well as other ecosystems worldwide.

Okin, Gregory; D'Odorico, Paolo

2013-04-01

300

Anisotropic Power Law Strain Correlations in Sheared Amorphous 2D Solids  

SciTech Connect

The local deformation of steadily sheared two-dimensional Lennard-Jones glasses is studied via computer simulations at zero temperature. In the quasistatic limit, spatial correlations in the incremental strain field are highly anisotropic. The data show power law behavior with a strong angular dependence of the scaling exponent, and the strongest correlations along the directions of maximal shear stress. These results support the notion that the jamming transition at the onset of flow is critical, but suggest unusual critical behavior. The predicted behavior is testable through experiments on sheared amorphous materials such as bubble rafts, foams, emulsions, granular packings, and other systems where particle displacements can be tracked.

Maloney, C. E. [Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Robbins, M. O. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

2009-06-05

301

Power-law spin correlations in the pyrochlore antiferromagnet Tb(2)Ti(2)O(7).  

PubMed

We investigate the low-temperature state of the rare-earth pyrochlore Tb(2)Ti(2)O(7) using polarized neutron scattering. Tb(2)Ti(2)O(7) is often described as an antiferromagnetic spin liquid with spin correlations extending over lengths comparable to individual tetrahedra of the pyrochlore lattice. We confirm this picture at 20 K but find that at 0.05 K the data contain evidence of pinch-point scattering, suggesting that the low temperature state of Tb(2)Ti(2)O(7) has power-law spin correlations. PMID:23031127

Fennell, T; Kenzelmann, M; Roessli, B; Haas, M K; Cava, R J

2012-07-01

302

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

SciTech Connect

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.

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

303

Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information  

NASA Technical Reports Server (NTRS)

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.

Howell, L. W.

2002-01-01

304

On global minimizers of repulsive-attractive power-law interaction energies  

PubMed Central

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

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

2014-01-01

305

The Anderson-Darling test of fit for the power law distribution from left censored samples  

E-print Network

Maximum likelihood estimation and a test of fit based on the Anderson-Darling statistic is presented for the case of the power law distribution when the parameters are estimated from a left-censored sample. Expressions for the maximum likelihood estimators and tables of asymptotic percentage points for the A^2 statistic are given. The technique is illustrated for data from the Dow Jones Industrial Average index, an example of high theoretical and practical importance in Econophysics, Finance, Physics, Biology and, in general, in other related Sciences such as Complexity Sciences.

Coronel-Brizio, H F

2010-01-01

306

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

NASA Astrophysics Data System (ADS)

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.

Chowdhury, Debashish; Stauffer, Dietrich; Kunwar, Ambarish

2003-02-01

307

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

PubMed

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

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

2014-11-13

308

Orbital period variability in the eclipsing pulsar binary PSR B1957+20: Evidence for a tidally powered star  

NASA Technical Reports Server (NTRS)

Recent observations indicate that the eclipsing pulsar binary PSR B1957+20 undergoes alternating epochs of orbital period increase and decrease. We apply a model developed to explain orbital period changes of alternating sign in other binaries to the PSR B1957+20 system and find that it fits the pulsars observations well. The novel feature of the PSR B1957+20 system is that the energy flow in the companion needed to power the orbital period change mechanism can be supplied by tidal dissipation, making the companion the first identified tidally powered star. The flow of energy in the companion drives magnetic activity, which underlies the observed orbital period variations. The magnetic activity and the wind driven by the pulsar irradiation results in a torque on the spin of the companion. This torque holds the companion out of synchronous rotation, causing tidal dissipation of energy. We propose that the progenitor had a approximately 2 hr orbital period and a companion mass of 0.1-0.2 solar mass, and the system is evolving to longer orbital periods by mass and angular momentum loss on a timescale of 10(exp 8) yr.

Applegate, James H.; Shaham, Jacob

1994-01-01

309

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

E-print Network

We study 1D Hamilton systems with homogeneous power law potential and their statistical behaviour, assuming the microcanonical distribution of the initial conditions and describing its change under monotonically increasing time-dependent function $a(t)$ (prefactor of the potential). Using the nonlinear WKB-like method by Papamikos and Robnik {\\em J. Phys. A: Math. Theor. {\\bf 44} (2012) 315102} and following a previous work by Papamikos G and Robnik M {\\em J. Phys. A: Math. Theor. {\\bf 45} (2011) 015206} we specifically analyze the mean energy, the variance and the adiabatic invariant (action) of the systems for large time $t\\rightarrow\\infty$ 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.

Dimitris Andresas; Marko Robnik

2014-05-22

310

Semiclassical trace formula for the two-dimensional radial power-law potentials  

NASA Astrophysics Data System (ADS)

The trace formula for the density of single-particle levels in the two-dimensional radial power-law potentials, which nicely approximate up to a constant shift the radial dependence of the Woods-Saxon potential and its quantum spectra in a bound region, was derived by the improved stationary phase method. The specific analytical results are obtained for the powers ?=4 and 6. The enhancement of periodic-orbit contribution to the level density near the bifurcations are found to be significant for the description of the fine shell structure. The semiclassical trace formulas for the shell corrections to the level density and the energy of many-fermion systems reproduce the quantum results with good accuracy through all the bifurcation (symmetry breaking) catastrophe points, where the standard stationary-phase method breaks down. Various limits (including the harmonic oscillator and the spherical billiard) are obtained from the same analytical trace formula.

Magner, A. G.; Vlasenko, A. A.; Arita, K.

2013-06-01

311

Validation of a power-law noise model for simulating small-scale breast tissue  

PubMed Central

We have validated a small-scale breast tissue model based on power-law noise. A set of 110 patient images served as truth. The statistical model parameters were determined by matching the radially-averaged power-spectrum of the projected simulated tissue with that of the central tomosynthesis patient breast projections. Observer performance in a signal-known exactly detection task in simulated and actual breast backgrounds was compared. Observers included human readers, a pre-whitening observer model and a channelized Hotelling observer model. For all observers, good agreement between performance in the simulated and actual backgrounds was found, both in the tomosynthesis central projections and the reconstructed images. This tissue model can be used for breast x-ray imaging system optimization. The complete statistical description of the model is provided. PMID:23938858

Reiser, I.; Edwards, A.; Nishikawa, R. M.

2013-01-01

312

Highly optimized tolerance and power laws in dense and sparse resource regimes  

E-print Network

Power law cumulative frequency $(P)$ vs. event size $(l)$ distributions $P(\\geq l)\\sim l^{-\\alpha}$ are frequently cited as evidence for complexity and serve as a starting point for linking theoretical models and mechanisms with observed data. Systems exhibiting this behavior present fundamental mathematical challenges in probability and statistics. The broad span of length and time scales associated with heavy tailed processes often require special sensitivity to distinctions between discrete and continuous phenomena. A discrete Highly Optimized Tolerance (HOT) model, referred to as the Probability, Loss, Resource (PLR) model, gives the exponent $\\alpha=1/d$ as a function of the dimension $d$ of the underlying substrate in the sparse resource regime. This agrees well with data for wildfires, web file sizes, and electric power outages. However, another HOT model, based on a continuous (dense) distribution of resources, predicts $\\alpha= 1+ 1/d $. In this paper we describe and analyze a third model, the cuts m...

Manning, M; Doyle, J

2005-01-01

313

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

NASA Astrophysics Data System (ADS)

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.

Cotton, Randy M.

1987-05-01

314

Bose-Einstein condensation in dark power-law laser traps  

NASA Astrophysics Data System (ADS)

We investigate theoretically an original route to achieve Bose-Einstein condensation using dark power-law laser traps. We propose to create such traps with two crossing blue-detuned Laguerre-Gaussian optical beams. Controlling their azimuthal order ? allows for the exploration of a multitude of power-law trapping situations in one, two, and three dimensions, ranging from the usual harmonic trap to an almost square-well potential, in which a quasihomogeneous Bose gas can be formed. The usual cigar-shaped and disk-shaped Bose-Einstein condensates obtained in a 1D or 2D harmonic trap take the generic form of a “finger” or of a “hockey puck” in such Laguerre-Gaussian traps. In addition, for a fixed atom number, higher transition temperatures are obtained in such configurations when compared with a harmonic trap of the same volume. This effect, which results in a substantial acceleration of the condensation dynamics, requires a better but still reasonable focusing of the Laguerre-Gaussian beams.

Jaouadi, A.; Gaaloul, N.; Viaris de Lesegno, B.; Telmini, M.; Pruvost, L.; Charron, E.

2010-08-01

315

Finite and Infinite Width Stokes Layers in a Power-Law Fluid  

NASA Astrophysics Data System (ADS)

Self-similar solutions for the oscillatory boundary layer (the ``Stokes layer'') in a semi-infinite power-law fluid bounded by an oscillating wall (the so-called Stokes problem) are obtained and analysed. These semi-analytical solutions differ qualitatively from the classical solution for a Newtonian fluid, both in the non-sinusoidal form of the velocity oscillations and in the manner at which their amplitude decays with distance from the wall. In particular, for shear-thickening fluids the velocity reaches zero at a finite distance from the wall, and for shear-thinning fluids it decays algebraically with distance, in contrast to the exponential decay for a Newtonian fluid. We demonstrate numerically that these self-similar solutions provide a good approximation to the flow driven by a sinusoidally oscillating wall. Further details can be found in the recent paper by D. Pritchard, C. R. McArdle and S. K. Wilson entitled ``The Stokes boundary layer for a power-law fluid,'' in Journal of Non-Newtonian Fluid Mechanics 166, 745--753 (2011).

Wilson, Stephen; Pritchard, David; McArdle, Catriona

2011-11-01

316

The power-law spectra of energetic particles during multi-island magnetic reconnection  

E-print Network

Power-law distributions are a near universal feature of energetic particle spectra in the heliosphere. Anomalous Cosmic Rays (ACRs), super-Alfv\\'enic 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 omni-directional 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 ...

Drake, J F; Fermo, R L

2012-01-01

317

On the sensitivity of tidal network characterization to power law estimation  

NASA Astrophysics Data System (ADS)

Long-term simulations (3000 yr) of an idealized basin using different tidal ranges (1, 2 and 3 m) and grain sizes (120, 480 and 960 ?m) have been performed in order to cover a range of hydrodynamic and sedimentary conditions. Two different cell sizes (50 and 100 m) have been used to study the impact of cell size on tidal network development. The probability distributions of the drainage area and the drainage volume have been computed for every simulation (during an ebb and a flood phase). Power law distributions are observed in drainage area and drainage volume distribution. As an objective estimation of the exponent of a power law is an open issue, different approaches (linear binning, normalized logarithmic binning, cumulative distribution function and maximum likelihood) proposed by White et al. (2008) to estimate the exponent have been used to carry out a sensitivity analysis. Our findings indicate that although all methods results in high and significant correlation coefficients, more work is needed to develop a universal, objective estimation of the exponent.

Jiménez, M.; Castanedo, S.; Zhou, Z.; Coco, G.; Medina, R.; Rodriguez-Iturbe, I.

2014-04-01

318

Extended power-law scaling of self-affine signals exhibiting apparent multifractality  

NASA Astrophysics Data System (ADS)

Many earth and environmental variables appear to scale as multiplicative (multifractal) processes with spatial or temporal increments possessing Gaussian or heavy-tailed distributions. The behavior, characterized by power-law scaling, is typically limited to intermediate ranges of separation scales (lags) considered, in the case of fully developed turbulence, to be dominated by inertia. It has been established empirically that, in numerous cases (e.g. turbulence, diffusion-limited aggregates, natural images, kinetic surface roughening, fluvial turbulence, sand wave dynamics, Martian topography, river morphometry, gravel-bed mobility, barometric pressure, low-energy cosmic rays, cosmic microwave background radiation, metal-insulator transition, irregularities in human heartbeat time series, turbulence in edge magnetized plasma of fusion devices and turbulent boundary layers of the Earth's magnetosphere), this range of lags can be enlarged significantly, at both ends of the spectrum, via a procedure known as Extended Self-Similarity (ESS). We demonstrate numerically that a similar procedure extends the power-law scaling range over which additive (self-affine) signals exhibit apparent multifractality. We conclude that signals appearing to exhibit either standard or extended (such as those listed) multifractal scaling may potentially represent self-affine processes.

Guadagnini, Alberto; Neuman, Shlomo P.

2011-07-01

319

Power law approximations of movement network data for modeling infectious disease spread.  

PubMed

Globalization and increased mobility of individuals enable person-to-person transmitted infectious diseases to spread faster to distant places around the world, making good models for the spread increasingly important. We study the spatiotemporal pattern of spread in the remotely located and sparsely populated region of North Norway in various models with fixed, seasonal, and random effects. The models are applied to influenza A counts using data from positive microbiology laboratory tests as proxy for the underlying disease incidence. Human travel patterns with local air, road, and sea traffic data are incorporated as well as power law approximations thereof, both with quasi-Poisson regression and based on the adjacency structure of the relevant municipalities. We investigate model extensions using information about the proportion of positive laboratory tests, data on immigration from outside North Norway and by connecting population to the movement network. Furthermore, we perform two separate analyses for nonadults and adults as children are an important driver for influenza A. Comparisons of one-step-ahead predictions generally yield better or comparable results using power law approximations. PMID:24843881

Geilhufe, Marc; Held, Leonhard; Skrøvseth, Stein Olav; Simonsen, Gunnar S; Godtliebsen, Fred

2014-05-01

320

So You Think the Crab is Described by a Power-Law Spectrum  

NASA Technical Reports Server (NTRS)

X-ray observations of the Crab Nebula and its pulsar have played a prominent role in the history of X-ray astronomy. Discoveries range from the detection of the X-ray Nebula and pulsar and the measurement of the Nebula-averaged X-ray polarization, to the observation of complex X-ray morphology, including jets emanating from the pulsar and the ring defining the shocked pulsar wind. The synchrotron origin of much of the radiation has been deduced by detailed studies across the electromagnetic spectrum, yet has fooled many X-ray astronomers into believing that the integrated spectrum from this system ought to be a power law. In many cases, this assumption has led observers to adjust the experiment response function(s) to guarantee such a result. We shall discuss why one should not observe a power-law spectrum, and present simulations using the latest available response matrices showing what should have been observed for a number of representative cases including the ROSAT IPC, XMM-Newton, and RXTE. We then discuss the implications, if any, for current calibrations.

Weisskopf, Martin C.

2008-01-01

321

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

NASA Astrophysics Data System (ADS)

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.

Radicchi, Filippo

2014-11-01

322

Nonuniversal power law scaling in the probability distribution of scientific citations  

PubMed Central

We develop a model for the distribution of scientific citations. The model involves a dual mechanism: in the direct mechanism, the author of a new paper finds an old paper A and cites it. In the indirect mechanism, the author of a new paper finds an old paper A only via the reference list of a newer intermediary paper B, which has previously cited A. By comparison to citation databases, we find that papers having few citations are cited mainly by the direct mechanism. Papers already having many citations (“classics”) are cited mainly by the indirect mechanism. The indirect mechanism gives a power-law tail. The “tipping point” at which a paper becomes a classic is about 25 citations for papers published in the Institute for Scientific Information (ISI) Web of Science database in 1981, 31 for Physical Review D papers published from 1975–1994, and 37 for all publications from a list of high h-index chemists assembled in 2007. The power-law exponent is not universal. Individuals who are highly cited have a systematically smaller exponent than individuals who are less cited. PMID:20805513

Peterson, George J.; Presse, Steve; Dill, Ken A.

2010-01-01

323

Ruling out the power-law form of the scalar primordial spectrum  

NASA Astrophysics Data System (ADS)

Combining Planck CMB temperature [1] and BICEP2 B-mode polarization data [2,3] we show qualitatively that, assuming inflationary consistency relation, the power-law form of the scalar primordial spectrum is ruled out at more than 3? CL. This is an important finding, since the power-law form of the scalar primordial spectrum is one of the main assumptions of concordance model of cosmology and also a direct prediction of many inflationary scenarios. We show that a break or step in the form of the primordial scalar perturbation spectrum, similar to what we studied recently analyzing Planck data [4], can address both Planck and BICEP2 results simultaneously. Our findings also indicate that the data may require more flexibilities than what running of scalar spectral index can provide. Finally we show that an inflaton potential, originally appeared in [5], can generate both the step and the break model of scalar primordial spectrum in two different limits. The discussed potential is found to be favored by Planck data but marginally disfavored by BICEP2 results as it produces slightly lower amplitude of tensor primordial spectrum. Hence, if the tensor-to-scalar ratio (r) quoted by BICEP2 persists, it is of importance that we generate inflationary models with large r and at the same time provide suppression in scalar primordial spectrum at large scales.

Hazra, Dhiraj Kumar; Shafieloo, Arman; Smoot, George F.; Starobinsky, Alexei A.

2014-06-01

324

Robust statistical tests of Dragon-Kings beyond power law distributions  

NASA Astrophysics Data System (ADS)

We ask the question whether it is possible to diagnose the existence of "Dragon-Kings" (DK), namely anomalous observations compared to a power law background distribution of event sizes. We present two new statistical tests, the U-test and the DK-test, aimed at identifying the existence of even a single anomalous event in the tail of the distribution of just a few tens of observations. The DK-test in particular is derived such that the p-value of its statistic is independent of the exponent characterizing the null hypothesis, which can use an exponential or power law distribution. We demonstrate how to apply these two tests on the distributions of cities and of agglomerations in a number of countries. We find the following evidence for Dragon-Kings: London in the distribution of city sizes of Great Britain; Moscow and St-Petersburg in the distribution of city sizes in the Russian Federation; and Paris in the distribution of agglomeration sizes in France. True negatives are also reported, for instance the absence of Dragon-Kings in the distribution of cities in Germany.

Pisarenko, V. F.; Sornette, D.

2012-05-01

325

Spin glassiness and power law scaling in anisotropic triangular spin-1/2 antiferromagnets  

NASA Astrophysics Data System (ADS)

We present data on the magnetic properties of two classes of layered spin S=1/2 antiferromagnetic quasi-triangular lattice materials: Cu2(1-x)Zn2x(OH)3NO3(0<=x<=0.65) and its long-organic-chain-intercalated derivatives Cu2(1-x)Zn2x(OH)3(C7H15COO)·mH2O(0<=x<=0.29), where non-magnetic Zn substitutes for Cu isostructurally. It is found that the intercalated compounds, even in a clean system in the absence of dilution, x=0, show spin glass behaviour, as evidenced by DC and AC susceptibility, and by time-dependent magnetization measurements. A striking feature is the observation of a sharp crossover between two successive power law regimes in the DC susceptibility above the freezing temperature. In constrast to standard theoretical expectations, these power laws are insensitive to doping. Specific heat data are consistent with a conventional phase transition in the unintercalated compounds, and glassy behaviour in the intercalated compounds.

Wu, Jian; Wildeboer, Julia S.; Werner, Fletcher; Seidel, Alexander; Nussinov, Z.; Solin, S. A.

2011-03-01

326

Beyond power laws: A new approach for analyzing single molecule photoluminescence intermittency  

NASA Astrophysics Data System (ADS)

The photoluminescence intermittency (PI) exhibited by single emitters has been studied for over a decade. To date, the vast majority of PI analyses involve parsing the data into emissive and non-emissive events, constructing histograms of event durations, and fitting these histograms to either exponential or power law probability distributions functions (PDFs). Here, a new method for analyzing PI data is presented where the data are used directly to construct a cumulative distribution function (CDF), and maximum-likelihood estimation techniques are used to determine the best fit of a model PDF to the CDF. Statistical tests are then employed to quantitatively evaluate the hypothesis that the CDF (data) is represented by the model PDF. The analysis method is outlined and applied to PI exhibited by single CdSe/CdS core-shell nanocrystals and the organic chromophore violamine R isolated in single crystals of potassium-acid phthalate. Contrary to previous studies, the analysis presented here demonstrates that the PI exhibited by these systems is not described by a power law. The analysis developed here is also used to quantify heterogeneity within PI data obtained from a collection of CdSe/CdS nanocrytals, and for the determination of statistically significant changes in PI accompanying perturbation of the emitter. In summary, the analysis methodology presented here provides a more statistically robust approach for analyzing PI data.

Riley, E. A.; Hess, C. M.; Whitham, P. J.; Reid, P. J.

2012-05-01

327

Influence of the power law index on the fiber breakage during injection molding by numerical simulations  

NASA Astrophysics Data System (ADS)

In predictive engineering for polymer processes, the proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step forward properly predicting bulk properties in the finished composite. Operating within the context of long-fiber thermoplastics (LFT, length > 15mm) this investigation concentrates on the influence of the power law index on the final fiber length distribution within the injection molded part. To realize this, the Autodesk Simulation Moldflow Insight Scandium 2013 software has been used. In this software, a fiber breakage algorithm is available from this release on. Using virtual material data with realistic viscosity levels allows to separate the influence of the power law index on the fiber breakage from the other material and process parameters. Applying standard settings for the fiber breakage parameters results in an obvious influence on the fiber length distribution through the thickness of the part and also as function of position in the part. Finally, the influence of the shear rate constant within the fiber breakage model has been investigated illustrating the possibility to fit the virtual fiber length distribution to the possible experimentally available data.

Desplentere, Frederik; Six, Wim; Bonte, Hilde; Debrabandere, Eric

2013-04-01

328

Power-law scaling during shadowing growth of nanocolumns by oblique angle deposition  

SciTech Connect

The authors have investigated the power-law behaviors of various morphological parameters during the shadowing growth of ruthenium (Ru) nanocolumns by an oblique angle sputter deposition technique with substrate rotation. Particularly, wavelength and column number density were measured at different column heights (h). The exponents associated with the wavelength (p{sub {lambda}}) and column number density (p{sub n}), correlated by the geometrical relationship p{sub {lambda}}{approx_equal}-(1/2)p{sub n}, were measured by atomic force microscopy to be {approx}0.5 and {approx}-1.0, respectively. Using a one-dimensional facet growth model based upon the principle of evolutionary selection under oblique angle deposition, they showed that the exponents associated with the column number density and wavelength can be predicted. The authors also illustrated that the exponent value associated with column number density originates from the competitive growth among columns that have different vertical growth rates. The simulated exponent values are independent of the shape of the facet, which indicates the universality of these power-law exponents.

Tang, F.; Karabacak, T.; Li, L.; Pelliccione, M.; Wang, G.-C.; Lu, T.-M. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States); Department of Applied Science, University of Arkansas at Little Rock, Little Rock, Arkansas 72204 (United States); Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States)

2007-01-15

329

Is a data set distributed as a power law? A test, with application to gamma-ray burst brightnesses  

NASA Technical Reports Server (NTRS)

We present a method to determine whether an observed sample of data is drawn from a parent distribution that is pure power law. The method starts from a class of statistics which have zero expectation value under the null hypothesis, H(sub 0), that the distribution is a pure power law: F(x) varies as x(exp -alpha). We study one simple member of the class, named the `bending statistic' B, in detail. It is most effective for detection a type of deviation from a power law where the power-law slope varies slowly and monotonically as a function of x. Our estimator of B has a distribution under H(sub 0) that depends only on the size of the sample, not on the parameters of the parent population, and is approximated well by a normal distribution even for modest sample sizes. The bending statistic can therefore be used to test a set of numbers is drawn from any power-law parent population. Since many measurable quantities in astrophysics have distriibutions that are approximately power laws, and since deviations from the ideal power law often provide interesting information about the object of study (e.g., a `bend' or `break' in a luminosity function, a line in an X- or gamma-ray spectrum), we believe that a test of this type will be useful in many different contexts. In the present paper, we apply our test to various subsamples of gamma-ray burst brightness from the first-year Burst and Transient Source Experiment (BATSE) catalog and show that we can only marginally detect the expected steepening of the log (N (greater than C(sub max))) - log (C(sub max)) distribution.

Wijers, Ralph A. M. J.; Lubin, Lori M.

1994-01-01

330

Non-Gaussian features of primordial magnetic fields in power-law inflation  

E-print Network

We show that a conformal-invariance violating coupling of the inflaton to electromagnetism produces a cross correlation between curvature fluctuations and a spectrum of primordial magnetic fields. According to this model, in the case of power-law inflation, a primordial magnetic field is generated with a nearly flat power spectrum and rms amplitude ranging from nG to pG. We study the cross correlation, a three-point function of the curvature perturbation and two powers of the magnetic field, in real and momentum space. The cross-correlation coefficient, a dimensionless ratio of the three-point function with the curvature perturbation and magnetic field power spectra, can be several orders of magnitude larger than expected as based on the amplitude of scalar metric perturbations from inflation. In momentum space, the cross-correlation peaks for flattened triangle configurations, and is three orders of magnitude larger than the squeezed triangle configuration. These results suggest likely methods for distinguishing the observational signatures of the model.

Leonardo Motta; Robert R. Caldwell

2012-03-05

331

Non-Gaussian features of primordial magnetic fields in power-law inflation  

E-print Network

We show that a conformal-invariance violating coupling of the inflaton to electromagnetism produces a cross correlation between curvature fluctuations and a spectrum of primordial magnetic fields. According to this model, in the case of power-law inflation, a primordial magnetic field is generated with a nearly flat power spectrum and rms amplitude ranging from nG to pG. We study the cross correlation, a three-point function of the curvature perturbation and two powers of the magnetic field, in real and momentum space. The cross-correlation coefficient, a dimensionless ratio of the three-point function with the curvature perturbation and magnetic field power spectra, can be several orders of magnitude larger than expected as based on the amplitude of scalar metric perturbations from inflation. In momentum space, the cross-correlation peaks for flattened triangle configurations, and is three orders of magnitude larger than the squeezed triangle configuration. These results suggest likely methods for distinguis...

Motta, Leonardo

2012-01-01

332

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

333

Anomalous Power Law Decay in Solvation Dynamics of DNA: A Mode Coupling Theory Analysis of Ion Contribution  

E-print Network

Several time domain fluorescence Stokes shift (TDFSS) experiments have reported a slow power law decay in the hydration dynamics of a DNA molecule. Such a power law has neither been observed in computer simulations nor in some other TDFSS experiments. Here we observe that a slow decay may originate from collective ion contribution because in experiments DNA is immersed in a buffer solution, and also from groove bound water and lastly from DNA dynamics itself. In this work we first express the solvation time correlation function in terms of dynamic structure factors of the solution. We use mode coupling theory to calculate analytically the time dependence of collective ionic contribution. A power law decay in seen to originate from an interplay between long range probe-ion direct correlation function and ion-ion dynamic structure factor. Although the power law decay is reminiscent of Debye-Falkenhagen effect yet solvation dynamics is dominated by ion atmosphere relaxation times at longer length scales (small wave number) than in electrolyte friction. We further discuss why this power law may not originate from water motions which have been computed by molecular dynamics simulations. Lastly, we propose several experiments to check the prediction of the present theoretical work.

Biman Bagchi

2014-04-20

334

˜A carnival of crime on our border: International Law, Imperial Power, and Extradition in Canada, 1865“1883  

Microsoft Academic Search

: This paper traces the development of Canadian extradition law from the formation of a pro-extradition consensus in the 1860s to the passage of a new Canadian statute in 1877, to that act’s final ratification by Britain in 1883. This process of law reform illustrates Britain’s continuing legal power in Canada. Throughout the 1870s and 1880s imperial authorities suppressed, delayed,

Bradley Miller

2009-01-01

335

˜A carnival of crime on our border: International Law, Imperial Power, and Extradition in Canada, 1865“1883  

Microsoft Academic Search

This paper traces the development of Canadian extradition law from the formation of a pro-extradition consensus in the 1860s to the passage of a new Canadian statute in 1877, to that act’s final ratification by Britain in 1883. This process of law reform illustrates Britain’s continuing legal power in Canada. Throughout the 1870s and 1880s imperial authorities suppressed, delayed, and

Bradley Miller

2009-01-01

336

Listing triangles in expected linear time on a class of power law graphs.  

SciTech Connect

Enumerating triangles (3-cycles) in graphs is a kernel operation for social network analysis. For example, many community detection methods depend upon finding common neighbors of two related entities. We consider Cohen's simple and elegant solution for listing triangles: give each node a 'bucket.' Place each edge into the bucket of its endpoint of lowest degree, breaking ties consistently. Each node then checks each pair of edges in its bucket, testing for the adjacency that would complete that triangle. Cohen presents an informal argument that his algorithm should run well on real graphs. We formalize this argument by providing an analysis for the expected running time on a class of random graphs, including power law graphs. We consider a rigorously defined method for generating a random simple graph, the erased configuration model (ECM). In the ECM each node draws a degree independently from a marginal degree distribution, endpoints pair randomly, and we erase self loops and multiedges. If the marginal degree distribution has a finite second moment, it follows immediately that Cohen's algorithm runs in expected linear time. Furthermore, it can still run in expected linear time even when the degree distribution has such a heavy tail that the second moment is not finite. We prove that Cohen's algorithm runs in expected linear time when the marginal degree distribution has finite 4/3 moment and no vertex has degree larger than {radical}n. In fact we give the precise asymptotic value of the expected number of edge pairs per bucket. A finite 4/3 moment is required; if it is unbounded, then so is the number of pairs. The marginal degree distribution of a power law graph has bounded 4/3 moment when its exponent {alpha} is more than 7/3. Thus for this class of power law graphs, with degree at most {radical}n, Cohen's algorithm runs in expected linear time. This is precisely the value of {alpha} for which the clustering coefficient tends to zero asymptotically, and it is in the range that is relevant for the degree distribution of the World-Wide Web.

Nordman, Daniel J. (Iowa State University, Ames, Iowa); Wilson, Alyson G. (Iowa State University, Ames, Iowa); Phillips, Cynthia Ann; Berry, Jonathan W.

2010-07-01

337

Low-Power Memory-Reduced Traceback MAP Decoding for Double-Binary Convolutional Turbo Decoder  

Microsoft Academic Search

Iterative decoding of convolutional turbo code (CTC) has a large memory power consumption. To reduce the power consumption of the state metrics cache (SMC), low-power memory-reduced traceback maximum a posteriori algorithm (MAP) decoding is proposed. Instead of storing all state metrics, the traceback MAP decoding reduces the size of the SMC by accessing difference metrics. The proposed traceback computation requires

Cheng-Hung Lin; Chun-Yu Chen; Tsung-Han Tsai; An-Yeu Wu

2009-01-01

338

On syntheses of the X-ray background with power-law sources  

NASA Astrophysics Data System (ADS)

The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

De Zotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

1981-08-01

339

Maximum Likelihood Estimation of the Broken Power Law Spectral Parameters with Detector Design Applications  

NASA Technical Reports Server (NTRS)

The maximum likelihood procedure is developed for estimating the three spectral parameters of an assumed broken power law energy spectrum from simulated detector responses and their statistical properties investigated. The estimation procedure is then generalized for application to real cosmic-ray data. To illustrate the procedure and its utility, analytical methods were developed in conjunction with a Monte Carlo simulation to explore the combination of the expected cosmic-ray environment with a generic space-based detector and its planned life cycle, allowing us to explore various detector features and their subsequent influence on estimating the spectral parameters. This study permits instrument developers to make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope.

Howell, Leonard W.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

340

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

341

Power-law entropy-corrected Ricci dark energy and dynamics of scalar fields  

NASA Astrophysics Data System (ADS)

Motivated by the holographic principle, it has previously been suggested that the dark energy (DE) density can be inversely proportional to the area A of the event horizon of the Universe. However, this kind of model would have a casuality problem. In this work, we study the power-law entropy-corrected holographic DE (PLECHDE) model in the non-flat Friedmann-Robertson-Walker universe, with the future event horizon replaced by the average radius of the Ricci scalar curvature. We derive the equation of state parameter ??, the deceleration parameter q and the evolution of energy density parameter ?D? in the presence of interaction between DE and dark matter. We consider the correspondence between our Ricci-PLECHDE model and the modified Chaplygin gas and the tachyon, K-essence, dilaton and quintessence scalar fields. The potential and dynamics of the scalar field models have been reconstructed according to the evolutionary behaviour of the interacting entropy-corrected holographic DE model.

Pasqua, Antonio; Jamil, Mubasher; Myrzakulov, Ratbay; Majeed, Bushra

2012-10-01

342

Power Law Versus Exponential Form of Slow Crack Growth of Advanced Structural Ceramics: Dynamic Fatigue  

NASA Technical Reports Server (NTRS)

The life prediction analysis based on an exponential crack velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ("dynamic fatigue") and preload testing at ambient and elevated temperatures. The data fit to the strength versus In (stress rate) relation was found to be very reasonable for most of the materials. It was also found that preloading technique was equally applicable for the case of slow crack growth (SCG) parameter n > 30. The major limitation in the exponential crack velocity formulation, however, was that an inert strength of a material must be known priori to evaluate the important SCG parameter n, a significant drawback as compared to the conventional power-law crack velocity formulation.

Choi, Sung R.; Gyekenyesi, John P.

2002-01-01

343

3-d quantum stabilizer codes with a power law energy barrier  

E-print Network

We introduce a new primitive, called welding, for combining two stabilizer codes to produce a new stabilizer code. We apply welding to construct surface codes and then use the surface codes to construct solid codes, a variant of a 3-d toric code with rough and smooth boundaries. Finally, we weld solid codes together to produce a $(O(L^3),1,O(L^{4/3}))$ stabilizer code with an energy barrier of $O(L^{2/3})$, which solves an open problem of whether a power law energy barrier is possible for local stabilizer code Hamiltonians in three-dimensions. The previous highest energy barrier is $O(\\log L)$. Previous no-go results are avoided by breaking translation invariance.

Kamil Michnicki

2012-08-16

344

Correspondence between $f(G)$ Gravity and Holographic Dark Energy via Power-law Solution  

E-print Network

In this paper, we discuss cosmological application of holographic Dark Energy (HDE) in the framework of $f(G)$ modified gravity. For this purpose, we construct $f(G)$ model with the inclusion of HDE and a well-known power law form of the scale factor $a(t)$. The reconstructed $f(G)$ is found to satisfy a sufficient condition for a realistic modified gravity model. We find quintessence behavior of effective equation of state (EoS) parameter $\\omega_{DE}$ through energy conditions in this context. Also, we observe that the squared speed of sound $v_s^2$ remains negative which shows the instability of HDE $f(G)$ model.

Abdul Jawad; Antonio Pasqua; Surajit Chattopadhyay

2012-11-22

345

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

E-print Network

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.

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

346

On syntheses of the X-ray background with power-law sources  

NASA Technical Reports Server (NTRS)

The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

Dezotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

1981-01-01

347

Persistent fluctuations of activity in undriven continuum neural field models with power-law connections  

NASA Astrophysics Data System (ADS)

We study the effect of random inhomogeneous connections on a continuous field description of neural tissue. We focus on a regime in which persistent random fluctuations in activity arise spontaneously in the absence of either time-varying or spatially inhomogeneous input. While present in real tissue and network models of discrete neurons, such behavior has not been reported in continuum models of this type. The activity contains frequencies similar to those seen experimentally. We consider a power-law envelope r-? for the inhomogeneity and present evidence that the statistical coherence (a measure of two-point correlation) rapidly percolates across the system as ? is reduced below ?c?1,2 in one and two dimensions, respectively.

Brackley, C. A.; Turner, M. S.

2009-01-01

348

Collision-dependent power law scalings in 2D gyrokinetic turbulence  

E-print Network

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 2D 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.

Cerri, S S; Jenko, F; Told, D

2014-01-01

349

Leptonic decays of vector mesons in a power-law potential model of independent quarks  

NASA Astrophysics Data System (ADS)

A relativistic power-law potential model of independent quarks is used to study the leptonic decays of neutral vector mesons. Here, the transition probability amplitude for leptonic decay of meson is determined from the momentum distribution function which is found from the assumption of a strong correlation existing between the momenta of quark and antiquark inside the meson. The model parameters are first determined from the application of the model to study the ground state spectra of ?, ?, ?, ? and ? mesons together with the radiative decay widths of mesons. The same model with no adjustable parameters is then used to evaluate the leptonic decay widths and the electromagnetic decay constants for the vector mesons ?, ?, ?, ? and ?. The calculated results are in remarkable agreement with the corresponding experimental values.

Jena, S. N.; Nanda, P. K.; Sahoo, S.; Panda, P.

2014-04-01

350

Comparison of fractional wave equations for power law attenuation in ultrasound and elastography  

E-print Network

A set of wave equations with fractional loss operators in time and space are analyzed. It is shown that the fractional Szabo equation, the power law wave equation, and the fractional Laplacian wave equation in the causal and non-causal forms all are low frequency approximations of the fractional Kelvin-Voigt wave equation and the more general fractional Zener wave equation. The latter two equations are based on fractional constitutive equations while the former wave equations are ad hoc, heuristic equations. We show that this has consequences for use in modelling and simulation especially for applications that do not satisfy the low frequency approximation, such as shear wave elastography. In such applications the wave equations based on constitutive equations are the preferred ones.

Holm, Sverre

2013-01-01

351

A study of dynamic contact angles of shear-thickening power-law fluids  

NASA Astrophysics Data System (ADS)

We study the dynamic wetting of shear-thickening power-law fluids in a liquid-solid-gas contact system. In the previous model based on hydrodynamic analysis, microscopic effects near the contact line are neglected. In this work, we adopt two different physical models, slip boundary model and molecular force model, to incorporate microscopic effects and relieve the stress singularity at the moving contact line in hydrodynamics analysis. The two models, which are mathematically equivalent for Newtonian fluids, lead to different results on the dependence of the liquid's dynamic contact angle on its moving speed in both complete wetting and partial wetting cases. By comparing with experiments, we find that the slip boundary model matches the experiments better than the previous model and the molecular force model.

Wang, Yu; Zhu, Ke-Qin

2014-05-01

352

Evidence for power-law tail of the wealth distribution in India  

NASA Astrophysics Data System (ADS)

The higher-end tail of the wealth distribution in India is studied using recently published lists of the wealth of richest Indians between the years 2002-2004. The resulting rank distribution seems to imply a power-law tail for the wealth distribution, with a Pareto exponent between 0.81 and 0.92 (depending on the year under analysis). This provides a comparison with previous studies of wealth distribution, which have all been confined to Western advanced capitalist economies. We conclude with a discussion on the appropriateness of multiplicative stochastic process as a model for asset accumulation, the relation between the wealth and income distributions (we estimate the Pareto exponent for the latter to be around 1.5 for India), as well as possible sources of error in measuring the Pareto exponent for wealth.

Sinha, Sitabhra

2006-01-01

353

Functional form of f( R) with power-law expansion in anisotropic model  

NASA Astrophysics Data System (ADS)

In this paper, we study an anisotropic Bianchi-I space-time model in f( R) theory of gravity in the presence of perfect fluid as a matter contains. The aim of this paper is to find the functional form of f( R) from the field equations and hence the solution of various cosmological parameters. We assume that the deceleration parameter to be a constant, and the shear scalar proportional to the expansion scalar to obtain the power-law form of the scale factors. We find that the model describes the decelerated phases of the universe under the choice of certain constraints on the parameters. The model does not show the acceleration expansion and also transition from past deceleration to present accelerating epoch. We discuss the stability of the functional form of f( R) and find that it is completely stable for describing the decelerating phase of the universe.

Singh, Vijay; Singh, C. P.

2013-07-01

354

Protecting prosecution: exploring the powers of law in an intervention program for domestic violence.  

PubMed

This article critically analyzes how the criminal justice system centrally situates itself in an intervention program intended to protect victims of domestic abuse and stalking. Based on the first empirical, in-depth study in the Netherlands of an intervention program using electronic technology that is increasingly used in the United States, results indicate how the central role of the criminal justice actors can evoke a shift toward foregrounding prosecutorial interests. Drawing from a critical theoretical understanding of the powers of law and the legal system, the author argues that current tendencies toward criminalization in domestic violence interventions can have an unintended violent impact for victims who are either excluded from the program or are forced into a criminal justice regime that might not be in their primary interest. In this study, women seem to actively navigate the use of the criminal justice system to receive the protection they need. PMID:16382030

Römkens, Renée

2006-02-01

355

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

NASA Astrophysics Data System (ADS)

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.

Luck, J. M.; Mehta, A.

2014-09-01

356

Black swans, power laws, and dragon-kings: Earthquakes, volcanic eruptions, landslides, wildfires, floods, and SOC models  

NASA Astrophysics Data System (ADS)

Extreme events that change global society have been characterized as black swans. The frequency-size distributions of many natural phenomena are often well approximated by power-law (fractal) distributions. An important question is whether the probability of extreme events can be estimated by extrapolating the power-law distributions. Events that exceed these extrapolations have been characterized as dragon-kings. In this paper we consider extreme events for earthquakes, volcanic eruptions, wildfires, landslides and floods. We also consider the extreme event behavior of three models that exhibit self-organized criticality (SOC): the slider-block, forest-fire, and sand-pile models. Since extrapolations using power-laws are widely used in probabilistic hazard assessment, the occurrence of dragon-king events have important practical implications.

Sachs, M. K.; Yoder, M. R.; Turcotte, D. L.; Rundle, J. B.; Malamud, B. D.

2012-05-01

357

Musical rhythm spectra from Bach to Joplin obey a 1/f power law.  

PubMed

Much of our enjoyment of music comes from its balance of predictability and surprise. Musical pitch fluctuations follow a 1/f power law that precisely achieves this balance. Musical rhythms, especially those of Western classical music, are considered highly regular and predictable, and this predictability has been hypothesized to underlie rhythm's contribution to our enjoyment of music. Are musical rhythms indeed entirely predictable and how do they vary with genre and composer? To answer this question, we analyzed the rhythm spectra of 1,788 movements from 558 compositions of Western classical music. We found that an overwhelming majority of rhythms obeyed a 1/f(?) power law across 16 subgenres and 40 composers, with ? ranging from ?0.5-1. Notably, classical composers, whose compositions are known to exhibit nearly identical 1/f pitch spectra, demonstrated distinctive 1/f rhythm spectra: Beethoven's rhythms were among the most predictable, and Mozart's among the least. Our finding of the ubiquity of 1/f rhythm spectra in compositions spanning nearly four centuries demonstrates that, as with musical pitch, musical rhythms also exhibit a balance of predictability and surprise that could contribute in a fundamental way to our aesthetic experience of music. Although music compositions are intended to be performed, the fact that the notated rhythms follow a 1/f spectrum indicates that such structure is no mere artifact of performance or perception, but rather, exists within the written composition before the music is performed. Furthermore, composers systematically manipulate (consciously or otherwise) the predictability in 1/f rhythms to give their compositions unique identities. PMID:22355125

Levitin, Daniel J; Chordia, Parag; Menon, Vinod

2012-03-01

358

Musical rhythm spectra from Bach to Joplin obey a 1/f power law  

PubMed Central

Much of our enjoyment of music comes from its balance of predictability and surprise. Musical pitch fluctuations follow a 1/f power law that precisely achieves this balance. Musical rhythms, especially those of Western classical music, are considered highly regular and predictable, and this predictability has been hypothesized to underlie rhythm's contribution to our enjoyment of music. Are musical rhythms indeed entirely predictable and how do they vary with genre and composer? To answer this question, we analyzed the rhythm spectra of 1,788 movements from 558 compositions of Western classical music. We found that an overwhelming majority of rhythms obeyed a 1/f? power law across 16 subgenres and 40 composers, with ? ranging from ?0.5–1. Notably, classical composers, whose compositions are known to exhibit nearly identical 1/f pitch spectra, demonstrated distinctive 1/f rhythm spectra: Beethoven's rhythms were among the most predictable, and Mozart's among the least. Our finding of the ubiquity of 1/f rhythm spectra in compositions spanning nearly four centuries demonstrates that, as with musical pitch, musical rhythms also exhibit a balance of predictability and surprise that could contribute in a fundamental way to our aesthetic experience of music. Although music compositions are intended to be performed, the fact that the notated rhythms follow a 1/f spectrum indicates that such structure is no mere artifact of performance or perception, but rather, exists within the written composition before the music is performed. Furthermore, composers systematically manipulate (consciously or otherwise) the predictability in 1/f rhythms to give their compositions unique identities. PMID:22355125

Levitin, Daniel J.; Chordia, Parag; Menon, Vinod

2012-01-01

359

Deterministic excitable media under Poisson drive: Power law responses, spiral waves, and dynamic range  

NASA Astrophysics Data System (ADS)

When each site of a spatially extended excitable medium is independently driven by a Poisson stimulus with rate h , the interplay between creation and annihilation of excitable waves leads to an average activity F . It has recently been suggested that in the low-stimulus regime ( htilde 0) the response function F(h) of hypercubic deterministic systems behaves as a power law, Ftilde hm . Moreover, the response exponent m has been predicted to depend only on the dimensionality d of the lattice, m=1/(1+d) [T. Ohta and T. Yoshimura, Physica D 205, 189 (2005)]. In order to test this prediction, we study the response function of excitable lattices modeled by either coupled Morris-Lecar equations or Greenberg-Hastings cellular automata. We show that the prediction is verified in our model systems for d=1 , 2, and 3, provided that a minimum set of conditions is satisfied. Under these conditions, the dynamic range—which measures the range of stimulus intensities that can be coded by the network activity—increases with the dimensionality d of the network. The power law scenario breaks down, however, if the system can exhibit self-sustained activity (spiral waves). In this case, we recover a scenario that is common to probabilistic excitable media: as a function of the conductance coupling G among the excitable elements, the dynamic range is maximized precisely at the critical value Gc above which self-sustained activity becomes stable. We discuss the implications of these results in the context of neural coding.

Ribeiro, Tiago L.; Copelli, Mauro

2008-05-01

360

Truncated Power Laws Reveal a Link between Low-Level Behavioral Processes and Grouping Patterns in a Colonial Bird  

PubMed Central

Background Departures from power law group size frequency distributions have been proposed as a useful tool to link individual behavior with population patterns and dynamics, although examples are scarce for wild animal populations. Methodology/Principal Findings We studied a population of Lesser kestrels (Falco naumanni) breeding in groups (colonies) from one to ca. 40 breeding pairs in 10,000 km2 in NE Spain. A 3.5 fold steady population increase occurred during the eight-year study period, accompanied by a geographical expansion from an initial subpopulation which in turn remained stable in numbers. This population instability was mainly driven by first-breeders, which are less competitive at breeding sites, being relegated to breed solitarily or in small colony sizes, and disperse farther than adults. Colony size frequency distributions shifted from an initial power law to a truncated power law mirroring population increase. Thus, we hypothesized that population instability was behind the truncation of the power law. Accordingly, we found a power law distribution through years in the initial subpopulation, and a match between the power law breakpoint (at ca. ten pairs) and those colony sizes from which the despotic behavior of colony owners started to impair the settlement of newcomers. Moreover, the instability hypothesis was further supported by snapshot data from another population of Lesser kestrels in SW Spain suffering a population decline. Conclusions/Significance Appropriate analysis of the scaling properties of grouping patterns has unraveled the link between local agonistic processes and large-scale (population) grouping patterns in a wild bird population. PMID:18431479

Jovani, Roger; Serrano, David; Ursua, Esperanza; Tella, Jose L.

2008-01-01

361

Nonextensivity and the power-law distributions for the systems with self-gravitating long-range interactions  

Microsoft Academic Search

By a natural nonextensive generalization of the conservation of energy in the q-kinetic theory, we study the nonextensivity and the power-law distributions for the many-body systems with the self-gravitating\\u000a long-range interactions. It is shown that the power-law distributions describe the long-range nature of the interactions and\\u000a the non-local correlations within the self-gravitating system with the inhomogeneous velocity dispersion. A relation

Du Jiulin

2007-01-01

362

Power laws behavior in multi-state elastic models with different constraints in the statistical distribution of elements  

NASA Astrophysics Data System (ADS)

Often materials exhibit nonlinearity and hysteresis in their response to an elastic excitation and the dependence of the nonlinear indicator on the excitation energy is a power law function. From the theoretical point of view, such behavior could be described using multistate elastic models based on a generalized Preisach-Mayergoyz (PM) approach. In these models a statistical distribution of transition parameters is usually introduced. We show in this paper the existence of a link between the power law exponent predicted by the model and the properties of the chosen distribution. Numerical results are discussed, based on an implementation in the PM formalism of an adhesion model.

Scalerandi, M.; Gliozzi, A. S.; Idjimarene, S.

2014-10-01

363

Highly optimized tolerance and power laws in dense and sparse resource regimes  

NASA Astrophysics Data System (ADS)

Power law cumulative frequency (P) versus event size (l) distributions P(?l)˜l-? are frequently cited as evidence for complexity and serve as a starting point for linking theoretical models and mechanisms with observed data. Systems exhibiting this behavior present fundamental mathematical challenges in probability and statistics. The broad span of length and time scales associated with heavy tailed processes often require special sensitivity to distinctions between discrete and continuous phenomena. A discrete highly optimized tolerance (HOT) model, referred to as the probability, loss, resource (PLR) model, gives the exponent ?=1/d as a function of the dimension d of the underlying substrate in the sparse resource regime. This agrees well with data for wildfires, web file sizes, and electric power outages. However, another HOT model, based on a continuous (dense) distribution of resources, predicts ?=1+1/d . In this paper we describe and analyze a third model, the cuts model, which exhibits both behaviors but in different regimes. We use the cuts model to show all three models agree in the dense resource limit. In the sparse resource regime, the continuum model breaks down, but in this case, the cuts and PLR models are described by the same exponent.

Manning, M.; Carlson, J. M.; Doyle, J.

2005-07-01

364

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

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.

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

365

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)

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.

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

366

22 CFR 1423.19 - Duties and powers of the Administrative Law Judge.  

Code of Federal Regulations, 2012 CFR

...duty of the Administrative Law Judge to inquire fully...Counsel, an Administrative Law Judge presiding at a hearing...contemptuous conduct and strike all related testimony of...referred to the Administrative Law Judge by the Regional...11(e) (2) and (3); (q) Grant or...

2012-04-01

367

22 CFR 1423.19 - Duties and powers of the Administrative Law Judge.  

Code of Federal Regulations, 2013 CFR

...duty of the Administrative Law Judge to inquire fully...Counsel, an Administrative Law Judge presiding at a hearing...contemptuous conduct and strike all related testimony of...referred to the Administrative Law Judge by the Regional...11(e) (2) and (3); (q) Grant or...

2013-04-01

368

Why credit risk markets are predestined for exhibiting log-periodic power law structures  

NASA Astrophysics Data System (ADS)

Recent research has established the existence of log-periodic power law (LPPL) patterns in financial institutions’ credit default swap (CDS) spreads. The main purpose of this paper is to clarify why credit risk markets are predestined for exhibiting LPPL structures. To this end, the credit risk prediction of two variants of logistic regression, i.e. polynomial logistic regression (PLR) and kernel logistic regression (KLR), are firstly compared to the standard logistic regression (SLR). In doing so, the question whether the performances of rating systems based on balance sheet ratios can be improved by nonlinear transformations of the explanatory variables is resolved. Building on the result that nonlinear balance sheet ratio transformations hardly improve the SLR’s predictive power in our case, we secondly compare the classification performance of a multivariate SLR to the discriminative powers of probabilities of default derived from three different capital market data, namely bonds, CDSs, and stocks. Benefiting from the prompt inclusion of relevant information, the capital market data in general and CDSs in particular increasingly outperform the SLR while approaching the time of the credit event. Due to the higher classification performances, it seems plausible for creditors to align their investment decisions with capital market-based default indicators, i.e., to imitate the aggregate opinion of the market participants. Since imitation is considered to be the source of LPPL structures in financial time series, it is highly plausible to scan CDS spread developments for LPPL patterns. By establishing LPPL patterns in governmental CDS spread trajectories of some European crisis countries, the LPPL’s application to credit risk markets is extended. This novel piece of evidence further strengthens the claim that credit risk markets are adequate breeding grounds for LPPL patterns.

Wosnitza, Jan Henrik; Leker, Jens

2014-01-01

369

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)

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.

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

2011-10-01

370

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

Microsoft Academic Search

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

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

2006-01-01

371

Single and Double Power Laws for Cyber-Crimes Richard E Overill and Jantje A M Silomon  

E-print Network

.overill|jantje.silomon}@kcl.ac.uk Abstract Eleven years of financial loss data from the CSI annual Computer Crime and Security surveys have losses due to cyber-crimes as reported in the Computer Security Institute (CSI) annual surveys do indeedSingle and Double Power Laws for Cyber-Crimes Richard E Overill and Jantje A M Silomon Department

Overill, Richard E.

372

Power law in properties of sulfur near the polymerization transition V. F. Kozhevnikov, J. M. Viner, and P. C. Taylor  

E-print Network

polymerization. However, neither dispersion in the sound velocity nor any appreciable change in sound attenuationPower law in properties of sulfur near the polymerization transition V. F. Kozhevnikov, J. M. Viner to estimate the extent of polymerization as a function of the temperature. Both quantities exhibit a similar

Kozhevnikov, Vladimir

373

A Weibull distribution with power-law tails that describes the first passage time processes of foreign currency exchanges  

Microsoft Academic Search

A Weibull distribution with power-law tails is confirmed as a good candidate to describe the first passage time process of foreign currency exchange rates. The Lorentz curve and the corresponding Gini coefficient for a Weibull distribution are derived analytically. We show that the coefficient is in good agreement with the same quantity calculated from the empirical data. We also calculate

Naoya Sazuka; Jun-Ichi Inoue

2007-01-01

374

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

E-print Network

Stress-dependent power-law flow in the upper mantle following the 2002 Denali, Alaska, earthquake of Alaska Fairbanks, Fairbanks, Alaska, USA Received 27 March 2006; received in revised form 3 October 2006-field continuous Global Positioning System (GPS) time-series data following the 2002 M7.9 Denali, Alaska earthquake

Freed, Andrew

375

Anomalous Power Law Decay in Solvation Dynamics of DNA: A Mode Coupling Theory Analysis of Ion Contribution  

E-print Network

Several time domain fluorescence Stokes shift (TDFSS) experiments have reported a slow power law decay in the hydration dynamics of a DNA molecule. Such a power law has neither been observed in computer simulations nor in some other TDFSS experiments. Here we observe that a slow decay may originate from collective ion contribution because in experiments DNA is immersed in a buffer solution, and also from groove bound water and lastly from DNA dynamics itself. In this work we first express the solvation time correlation function in terms of dynamic structure factors of the solution. We use mode coupling theory to calculate analytically the time dependence of collective ionic contribution. A power law decay in seen to originate from an interplay between long range probe-ion direct correlation function and ion-ion dynamic structure factor. Although the power law decay is reminiscent of Debye-Falkenhagen effect yet solvation dynamics is dominated by ion atmosphere relaxation times at longer length scales (small w...

Bagchi, Biman

2014-01-01

376

Different Power-law Indices in the Frequency Distributions of Flares with and without Coronal Mass Ejections  

E-print Network

We investigated the frequency distributions of flares with and without coronal mass ejections (CMEs) as a function of flare parameters (peak flux, fluence, and duration of soft X-ray flares). We used CMEs observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) mission and soft X-ray flares (C3.2 and above) observed by the GOES satellites during 1996 to 2005. We found that the distributions obey a power-law of the form: dN/dX~X^-alpha, where X is a flare parameter and dN is the number of events recorded within the interval [X, X+dX]. For the flares with (without) CMEs, we obtained the power-law index alpha=1.98+-0.05 (alpha=2.52+-0.03) for the peak flux, alpha=1.79+-0.05 (alpha=2.47+-0.11) for the fluence, and alpha=2.49+-0.11 (alpha=3.22+-0.15) for the duration. The power-law indices for flares without CMEs are steeper than those for flares with CMEs. The larger power-law index for flares without CMEs supports the possibility that nanoflares contribute to coronal heating.

S. Yashiro; S. Akiyama; N. Gopalswamy; R. A. Howard

2006-09-07

377

Exact Solutions of Nonlinear Schrodinger's Equation with Dual Power-Law Nonlinearity by Extended Trial Equation Method  

E-print Network

In this paper, we acquire the soliton solutions of the nonlinear Schrodinger's equation with dual power-law nonlinearity. Primiraly, we use the extended trial equation method to find exact solutions of this equation. Then, we attain some exact solutions including soliton solutions, rational and elliptic function solutions of this equation by using the extended trial equation method.

Hasan Bulut; Yusuf Pandir; Seyma Tuluce Demiray

2014-02-04

378

Advances in Applied Probability, 42(4), 2010, to appear. (28 July 2010) INFORMATION RANKING AND POWER LAWS ON TREES  

E-print Network

AND POWER LAWS ON TREES PREDRAG R. JELENKOVI´C, Columbia University MARIANA OLVERA-CRAVIOTO, Columbia interconnected data sets, e.g. Google's PageRank algorithm for ranking pages on the World Wide Web interconnected information (data) sets, e.g., ranking pages on the World Wide Web (Web). A solution

Jelenkovic, Predrag

379

Advances in Applied Probability, 42(4), 2010, to appear. (29 July 2010) INFORMATION RANKING AND POWER LAWS ON TREES  

E-print Network

AND POWER LAWS ON TREES PREDRAG R. JELENKOVI´C, Columbia University MARIANA OLVERA-CRAVIOTO, Columbia interconnected data sets, e.g. Google's PageRank algorithm for ranking pages on the World Wide Web interconnected information (data) sets, e.g., ranking pages on the World Wide Web (Web). A solution

Olvera-Cravioto, Mariana

380

Analytical solution for the evolution of a binary with stable mass transfer from a giant  

Microsoft Academic Search

We derive a simple analytical solution for the evolution of a close binary with nuclear time-scale driven mass transfer from a giant. This solution is based on the well-known fact that the luminosity and the radius of a giant scale to a good approximation as simple power laws of the mass Mc of the degenerate helium core. Comparison with results

H. Ritter

1999-01-01

381

A stable and robust calibration scheme of the log-periodic power law model  

NASA Astrophysics Data System (ADS)

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.

Filimonov, V.; Sornette, D.

2013-09-01

382

A unified econophysics explanation for the power-law exponents of stock market activity  

NASA Astrophysics Data System (ADS)

We survey a theory (first sketched in Nature in 2003, then fleshed out in the Quarterly Journal of Economics in 2006) of the economic underpinnings of the fat-tailed distributions of a number of financial variables, such as returns and trading volume. Our theory posits that they have a common origin in the strategic trading behavior of very large financial institutions in a relatively illiquid market. We show how the fat-tailed distribution of fund sizes can indeed generate extreme returns and volumes, even in the absence of fundamental news. Moreover, we are able to replicate the individually different empirical values of the power-law exponents for each distribution: 3 for returns, 3/2 for volumes, 1 for the assets under management of large investors. Large investors moderate their trades to reduce their price impact; coupled with a concave price impact function, this leads to volumes being more fat-tailed than returns but less fat-tailed than fund sizes. The trades of large institutions also offer a unified explanation for apparently disconnected empirical regularities that are otherwise a challenge for economic theory.

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

2007-08-01

383

Motion of a random walker in a quenched power law correlated velocity field  

E-print Network

We study the motion of a random walker in one longitudinal and d transverse dimensions with a quenched power law correlated velocity field in the longitudinal x-direction. The model is a modification of the Matheron-de Marsily (MdM) model, with long-range velocity correlation. For a velocity correlation function, dependent on transverse co-ordinates y as 1/(a+|{y_1 - y_2}|)^alpha, we analytically calculate the two-time correlation function of the x-coordinate. We find that the motion of the x-coordinate is a fractional Brownian motion (fBm), with a Hurst exponent H = max [1/2, (1- alpha/4), (1-d/4)]. From this and known properties of fBM, we calculate the disorder averaged persistence probability of x(t) up to time t. We also find the lines in the parameter space of d and alpha along which there is marginal behaviour. We present results of simulations which support our analytical calculation.

Soumen Roy; Dibyendu Das

2005-11-01

384

Generic emergence of power law distributions and Lévy-Stable intermittent fluctuations in discrete logistic systems  

NASA Astrophysics Data System (ADS)

The dynamics of generic stochastic Lotka-Volterra (discrete logistic) systems of the form wi(t+1)=?(t)wi(t)+aw¯(t)-bwi(t)w¯(t) is studied by computer simulations. The variables wi, i=1,...,N, are the individual system components and w¯(t)=(1/N)?iwi(t) is their average. The parameters a and b are constants, while ?(t) is randomly chosen at each time step from a given distribution. Models of this type describe the temporal evolution of a large variety of systems such as stock markets and city populations. These systems are characterized by a large number of interacting objects and the dynamics is dominated by multiplicative processes. The instantaneous probability distribution P(w,t) of the system components wi turns out to fulfill a Pareto power law P(w,t)~w-1-?. The time evolution of w¯(t) presents intermittent fluctuations parametrized by a Lévy-stable distribution with the same index ?, showing an intricate relation between the distribution of the wi's at a given time and the temporal fluctuations of their average.

Biham, Ofer; Malcai, Ofer; Levy, Moshe; Solomon, Sorin

1998-08-01

385

Robust Statistical Tests of Dragon-Kings beyond Power Law Distributions  

E-print Network

We ask the question whether it is possible to diagnose the existence of "Dragon-Kings" (DK), namely anomalous observations compared to a power law background distribution of event sizes. We present two new statistical tests, the U-test and the DK-test, aimed at identifying the existence of even a single anomalous event in the tail of the distribution of just a few tens of observations. The DK-test in particular is derived such that the p-value of its statistic is independent of the exponent characterizing the null hypothesis. We demonstrate how to apply these two tests on the distributions of cities and of agglomerations in a number of countries. We find the following evidence for Dragon-Kings: London in the distribution of city sizes of Great Britain; Moscow and St-Petersburg in the distribution of city sizes in the Russian Federation; and Paris in the distribution of agglomeration sizes in France. True negatives are also reported, for instance the absence of Dragon-Kings in the distribution of cities in Ger...

Pisarenko, V F

2011-01-01

386

Liquidity crisis detection: An application of log-periodic power law structures to default prediction  

NASA Astrophysics Data System (ADS)

We employ the log-periodic power law (LPPL) to analyze the late-2000 financial crisis from the perspective of critical phenomena. The main purpose of this study is to examine whether LPPL structures in the development of credit default swap (CDS) spreads can be used for default classification. Based on the different triggers of Bear Stearns’ near bankruptcy during the late-2000 financial crisis and Ford’s insolvency in 2009, this study provides a quantitative description of the mechanism behind bank runs. We apply the Johansen-Ledoit-Sornette (JLS) positive feedback model to explain the rise of financial institutions’ CDS spreads during the global financial crisis 2007-2009. This investigation is based on CDS spreads of 40 major banks over the period from June 2007 to April 2009 which includes a significant CDS spread increase. The qualitative data analysis indicates that the CDS spread variations have followed LPPL patterns during the global financial crisis. Furthermore, the univariate classification performances of seven LPPL parameters as default indicators are measured by Mann-Whitney U tests. The present study supports the hypothesis that discrete scale-invariance governs the dynamics of financial markets and suggests the application of new and fast updateable default indicators to capture the buildup of long-range correlations between creditors.

Wosnitza, Jan Henrik; Denz, Cornelia

2013-09-01

387

Breakup characteristics of power-law liquid sheets formed by two impinging jets  

NASA Astrophysics Data System (ADS)

The breakup characteristics of the shear-thinning power-law liquid sheets formed by two impinging jets have been investigated with the shadowgraph technique. This paper focuses on the effects of spray parameters (jet velocity), physical parameters (viscosity) and geometry parameters (impinging angle and nozzle cross-sectional shape) on the breakup behaviors of liquid sheets. The breakup mode, sheet length and expansion angle of the sheet are extracted from the spray images obtained by a high speed camera. Impinging angle and Weber number play the similar roles in promoting the breakup of liquid sheets. With the increase of jet velocity, five different breakup modes are observed and the expansion angle increases consistently after the closed-rim mode while the sheet length first increases and then decreases. But there exists a concave consisting of a fierce drop and a second rising process on the sheet length curve for the fluid with smaller viscosity. Different nozzle cross-sectional shapes emphasize significant effects on the sheet length and expansion angle of liquid sheets. At a fixed Weber number, the liquid sheet with greater viscosity has a greater sheet length and a smaller expansion angle due to the damping effect of viscosity.

Bai, Fuqiang; Diao, Hai; Zhang, Mengzheng; Chang, Qing; Wang, Endong; Du, Qing

2014-10-01

388

Power-Law Entropy Corrected Ricci Dark Energy and Dynamics of Scalar Fields  

E-print Network

Motivated by the holographic principle, it has been suggested that the Dark Energy (DE) density can be inversely proportional to the area $A$ of the event horizon of the universe. However, this kind of model would have a casuality problem. In this work, we study the power-law entropy corrected holographic DE (PLECHDE) model in the non-flat Friedmann-Robertson-Walker universe, with the future event horizon replaced by the average radius of the Ricci scalar curvature. We derive the equation of state parameter $\\omega_{\\Lambda}$, the deceleration parameter $q$ and the evolution of energy density parameter $\\Omega_D'$ in presence of interaction between DE and Dark Matter (DM). We consider the correspondence between our Ricci-PLECHDE model and the Modified Chaplygin Gas (MCG) and the tachyon, K-essence, dilaton and quintessence scalar fields. The potential and the dynamics of the scalar field models have been reconstructed according to the evolutionary behaviour of the interacting entropy-corrected holographic DE model.

Antonio Pasqua; Mubasher Jamil; Ratbay Myrzakulov; Bushra Majeed

2012-10-27

389

Contracting bubbles in Hele-Shaw cells with a power-law fluid  

NASA Astrophysics Data System (ADS)

The problem of bubble contraction in a Hele-Shaw cell is studied for the case in which the surrounding fluid is of power-law type. A small perturbation of the radially symmetric problem is first considered, focussing on the behaviour just before the bubble vanishes, it being found that for shear-thinning fluids the radially symmetric solution is stable, while for shear-thickening fluids the aspect ratio of the bubble boundary increases. The borderline (Newtonian) case considered previously is neutrally stable, the bubble boundary becoming elliptic in shape with the eccentricity of the ellipse depending on the initial data. Further light is shed on the bubble contraction problem by considering a long thin Hele-Shaw cell: for early times the leading-order behaviour is one-dimensional in this limit; however, as the bubble contracts its evolution is ultimately determined by the solution of a Wiener-Hopf problem, the transition between the long thin limit and the extinction limit in which the bubble vanishes being described by what is in effect a similarity solution of the second kind. This same solution describes the generic (slit-like) extinction behaviour for shear-thickening fluids, the interface profiles that generalize the ellipses that characterize the Newtonian case being constructed by the Wiener-Hopf calculation.

McCue, Scott W.; King, John R.

2011-02-01

390

Exact, E = 0, classical and quantum solutions for general power-law oscillators  

NASA Technical Reports Server (NTRS)

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.

Nieto, Michael Martin; Daboul, Jamil

1995-01-01

391

Power Law and Logarithmic Ricci Dark Energy Models in Ho?ava-Lifshitz Cosmology  

NASA Astrophysics Data System (ADS)

In this work, we studied the Power Law and the Logarithmic Entropy Corrected versions of the Ricci Dark Energy (RDE) model in a spatially non-flat universe and in the framework of Ho?ava-Lifshitz cosmology. For the two cases containing non-interacting and interacting RDE and Dark Matter (DM), we obtained the exact differential equation that determines the evolutionary form of the RDE energy density. Moreover, we obtained the expressions of the deceleration parameter q and, using a parametrization of the equation of state (EoS) parameter ? D given by the relation ? D (z) = ? 0+? 1 z, we derived the expressions of both ? 0 and ? 1. We interestingly found that the expression of ? 0 is the same for both non-interacting and interacting case. The expression of ? 1 for the interacting case has strong dependence from the interacting parameter b 2. The parameters derived in this work are done in small redshift approximation and for low redshift expansion of the EoS parameter.

Pasqua, Antonio; Chattopadhyay, Surajit; Khurshudyan, Martiros; Myrzakulov, Ratbay; Hakobyan, Margarit; Movsisyan, Artashes

2014-08-01

392

Measurement of power-law creep parameters by instrumented indentation methods  

NASA Astrophysics Data System (ADS)

New experimental methods are developed to measure the uniaxial power-law creep parameters ? and n in the relation ??=?? (?? is the creep strain rate and ? is the creep stress) from indentation data obtained with a conical or pyramidal indenter. The methods are based on an analysis of Bower et al., which relates the indentation creep rate to the uniaxial creep parameters based on simple assumptions about the constitutive behavior (Bower et al., 1993). Using finite element simulations to establish the influences of finite indenter geometry and transients caused by elasticity, the proposed methods are explored experimentally using amorphous selenium as a model material. This material is well suited for the study because it creeps at temperatures slightly above ambient in a load-history independent fashion with a stress exponent close to unity. Indentation creep tests were conducted with a Berkovich indenter using three different loading methods. With a few notable exceptions, the values of both ? and n derived from the indentation data are generally in good agreement with those measured in uniaxial compression tests, thus demonstrating the validity of the approach.

Su, Caijun; Herbert, Erik G.; Sohn, Sangjoon; LaManna, James A.; Oliver, Warren C.; Pharr, George M.

2013-02-01

393

Influence of power-law rheology on cell injury during microbubble flows.  

PubMed

The reopening of fluid-occluded pulmonary airways generates microbubble flows which impart complex hydrodynamic stresses to the epithelial cells lining airway walls. In this study we used boundary element solutions and finite element techniques to investigate how cell rheology influences the deformation and injury of cells during microbubble flows. An optimized Prony-Dirichlet series was used to model the cells' power-law rheology (PLR) and results were compared with a Maxwell fluid model. Results indicate that membrane strain and the risk for cell injury decreases with increasing channel height and bubble speed. In addition, the Maxwell and PLR models both indicate that increased viscous damping results in less cellular deformation/injury. However, only the PLR model was consistent with the experimental observation that cell injury is not a function of stress exposure duration. Correlation of our models with experimental observations therefore highlights the importance of using PLR in computational models of cell mechanics/deformation. These computational models also indicate that altering the cell's viscoelastic properties may be a clinically relevant way to mitigate microbubble-induced cell injury. PMID:19865840

Dailey, H L; Ghadiali, S N

2010-06-01

394

Pressure effects on electroosmotic flow of power-law fluids in rectangular microchannels  

NASA Astrophysics Data System (ADS)

In this paper, the fully developed electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A complete parametric study reveals that the pressure effects are more pronounced at higher values of the channel aspect ratio and smaller values of the flow behavior index. The Poiseuille number is found to be an increasing function of the channel aspect ratio for pressure assisted flow and a decreasing function of this parameter for pressure opposed flow. It is also observed that the Poiseuille number is increased by increasing the zeta potential. Furthermore, the results show that an increase in the flow behavior index results in a lower flow rate ratio, defined to be the ratio of the flow rate to that of a Newtonian fluid at the same conditions. Moreover, whereas the flow rate ratio in the presence of an opposed pressure gradient is smaller than that of a favorable pressure force for shear thinnings, the opposite is true for shear-thickening fluids.

Vakili, Mohammad Ali; Sadeghi, Arman; Saidi, Mohammad Hassan

2014-08-01

395

Power-Law Expansion and Scalar Field Cosmology in Higher Derivative Theory  

NASA Astrophysics Data System (ADS)

In this paper we study the evolution of a flat Friedmann-Robertson-Walker model filled with a perfect fluid and a scalar field minimally coupled to gravity in higher derivative theory of gravitation. Exact solution of the field equations are obtained by the assumption of power-law form of the scale factor. A number of evolutionary phases of the universe including the present accelerating phase are found to exist with scalar field in the higher derivative theory of gravitation. The properties of scalar field and other physical parameters are discussed in detail. We find that the equation of state parameter for matter and scalar field are same at late time in each case. We observe that a higher derivative term can hardly be a candidate to describe the presently observed accelerated expansion. It is only the hypothetical fluids, which provide the late time acceleration. It is also remarkable that the higher derivative theory does not effect the radiating model of scalar field cosmology.

Singh, C. P.; Singh, Vijay

2012-06-01

396

Black hole in the expanding universe with arbitrary power-law expansion  

NASA Astrophysics Data System (ADS)

We present a time-dependent and spatially inhomogeneous solution that interpolates the extremal Reissner-Nordström (RN) black hole and the Friedmann-Lemaître-Robertson-Walker (FLRW) universe with arbitrary power-law expansion. It is an exact solution of the D-dimensional Einstein-Maxwell-dilaton system, where two Abelian gauge fields couple to the dilaton with different coupling constants, and the dilaton field has a Liouville-type exponential potential. It is shown that the system satisfies the weak energy condition. The solution involves two harmonic functions on a (D-1)-dimensional Ricci-flat base space. In the case where the harmonics have a single-point source on the Euclidean space, we find that the spacetime describes a spherically symmetric charged black hole in the FLRW universe, which is characterized by three parameters: the steepness parameter of the dilaton potential nT, the U(1) charge Q, and the nonextremality ?. In contrast with the extremal RN solution, the spacetime admits a nondegenerate Killing horizon unless these parameters are finely tuned. The global spacetime structures are discussed in detail.

Maeda, Kei-Ichi; Nozawa, Masato

2010-06-01

397

Momentum and Heat Transfer Phenomena for Power–Law Liquids in Assemblages of Solid Spheres of Moderate to Large Void Fractions  

Microsoft Academic Search

This work extends our previously reported results for the flow of and heat transfer from expanded beds of solid spheres to power–law fluids by using a modified and more accurate numerical solution procedure. Extensive results have been obtained to elucidate the effects of the Reynolds number (Re), the Prandtl number (Pr), the power–law index (n), and the bed voidage (?)

N. Kishore; S. D. Dhole; R. P. Chhabra; V. Eswaran

2009-01-01

398

Scale-free relaxation of a wave packet in a quantum well with power-law tails  

E-print Network

We propose a setup for which a power-law decay is predicted to be observable for generic and realistic conditions. The system we study is very simple: A quantum wave packet initially prepared in a potential well with (i) tails asymptotically decaying like ~ x^{-2} and (ii) an eigenvalues spectrum that shows a continuous part attached to the ground or equilibrium state. We analytically derive the asymptotic decay law from the spectral properties for generic, confined initial states. Our findings are supported by realistic numerical simulations for state-of-the-art expansion experiments with cold atoms.

Salvatore Miccichè; Andreas Buchleitner; Fabrizio Lillo; Rosario N. Mantegna; Tobias Paul; Sandro Wimberger

2012-11-27

399

Expansion of Scaling Law of Field-Aligned Potential Difference with Increased Plug ECRH Power in GAMMA 10  

NASA Astrophysics Data System (ADS)

The high power operation of gyrotrons exceeding their nominal powers has been carried out for ECRH at the plug region in the GAMMA 10 tandem mirror device. The highest recorded value of the axial ion confining potential for a hot ion mode plasma has been obtained. The mean energy Teff of the axially flowing electrons driven by the plug ECRH increases to 3 keV according to the increase in the heating power up to 260 kW. The maximum field-aligned potential difference ?? has reached 5.5 kV and the scaling law between ?? and Teff has expanded.

Saito, Teruo; Tatematsu, Yoshinori; Ikegami, Hirokazu; Sekine, Takayuki; Nagai, Daichi; Nozaki, Kiyoshi; Yoshida, Maiko; Ishii, Kameo; Cho, Teruji

400

Peptide kinetics from picoseconds to microseconds using boxed molecular dynamics: power law rate coefficients in cyclisation reactions.  

PubMed

Molecular dynamics (MD) methods are increasingly widespread, but simulation of rare events in complex molecular systems remains a challenge. We recently introduced the boxed molecular dynamics (BXD) method, which accelerates rare events, and simultaneously provides both kinetic and thermodynamic information. We illustrate how the BXD method may be used to obtain high-resolution kinetic data from explicit MD simulations, spanning picoseconds to microseconds. The method is applied to investigate the loop formation dynamics and kinetics of cyclisation for a range of polypeptides, and recovers a power law dependence of the instantaneous rate coefficient over six orders of magnitude in time, in good agreement with experimental observations. Analysis of our BXD results shows that this power law behaviour arises when there is a broad and nearly uniform spectrum of reaction rate coefficients. For the systems investigated in this work, where the free energy surfaces have relatively small barriers, the kinetics is very sensitive to the initial conditions: strongly non-equilibrium conditions give rise to power law kinetics, while equilibrium initial conditions result in a rate coefficient with only a weak dependence on time. These results suggest that BXD may offer us a powerful and general algorithm for describing kinetics and thermodynamics in chemical and biochemical systems. PMID:23126740

Shalashilin, Dmitrii V; Beddard, Godfrey S; Paci, Emanuele; Glowacki, David R

2012-10-28

401

Peptide kinetics from picoseconds to microseconds using boxed molecular dynamics: Power law rate coefficients in cyclisation reactions  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) methods are increasingly widespread, but simulation of rare events in complex molecular systems remains a challenge. We recently introduced the boxed molecular dynamics (BXD) method, which accelerates rare events, and simultaneously provides both kinetic and thermodynamic information. We illustrate how the BXD method may be used to obtain high-resolution kinetic data from explicit MD simulations, spanning picoseconds to microseconds. The method is applied to investigate the loop formation dynamics and kinetics of cyclisation for a range of polypeptides, and recovers a power law dependence of the instantaneous rate coefficient over six orders of magnitude in time, in good agreement with experimental observations. Analysis of our BXD results shows that this power law behaviour arises when there is a broad and nearly uniform spectrum of reaction rate coefficients. For the systems investigated in this work, where the free energy surfaces have relatively small barriers, the kinetics is very sensitive to the initial conditions: strongly non-equilibrium conditions give rise to power law kinetics, while equilibrium initial conditions result in a rate coefficient with only a weak dependence on time. These results suggest that BXD may offer us a powerful and general algorithm for describing kinetics and thermodynamics in chemical and biochemical systems.

Shalashilin, Dmitrii V.; Beddard, Godfrey S.; Paci, Emanuele; Glowacki, David R.

2012-10-01

402

Iterative method for generating correlated binary sequences  

NASA Astrophysics Data System (ADS)

We propose an efficient iterative method for generating random correlated binary sequences with a prescribed correlation function. The method is based on consecutive linear modulations of an initially uncorrelated sequence into a correlated one. Each step of modulation increases the correlations until the desired level has been reached. The robustness and efficiency of the proposed algorithm are tested by generating sequences with inverse power-law correlations. The substantial increase in the strength of correlation in the iterative method with respect to single-step filtering generation is shown for all studied correlation functions. Our results can be used for design of disordered superlattices, waveguides, and surfaces with selective transport properties.

Usatenko, O. V.; Melnik, S. S.; Apostolov, S. S.; Makarov, N. M.; Krokhin, A. A.

2014-11-01

403

New version of PLNoise: a package for exact numerical simulation of power-law noises  

NASA Astrophysics Data System (ADS)

In a recent paper I have introduced a package for the exact simulation of power-law noises and other colored noises [E. Milotti, Comput. Phys. Comm. 175 (2006) 212]: in particular, the algorithm generates 1/f noises with 0power-law spectrum for any arbitrary sequence of sampling intervals, i.e. the sampling times may be unevenly spaced. Program summaryTitle of program: PLNoise Catalogue identifier:ADXV_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXV_v2_0.html Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Programming language used: ANSI C Computer: Any computer with an ANSI C compiler: the package has been tested with gcc version 3.2.3 on Red Hat Linux 3.2.3-52 and gcc version 4.0.0 and 4.0.1 on Apple Mac OS X-10.4 Operating system: All operating systems capable of running an ANSI C compiler RAM: The code of the test program is very compact (about 60 Kbytes), but the program works with list management and allocates memory dynamically; in a typical run with average list length 2?10, the RAM taken by the list is 200 Kbytes External routines: The package needs external routines to generate uniform and exponential deviates. The implementation described here uses the random number generation library ranlib freely available from Netlib [B.W. Brown, J. Lovato, K. Russell: ranlib, available from Netlib, http://www.netlib.org/random/index.html, select the C version ranlib.c], but it has also been successfully tested with the random number routines in Numerical Recipes [W.H. Press, S.A. Teulkolsky, W.T. Vetterling, B.P. Flannery, Numerical Recipes in C: The Art of Scientific Computing, second ed., Cambridge Univ. Press., Cambridge, 1992, pp. 274-290]. Notice that ranlib requires a pair of routines from the linear algebra package LINPACK, and that the distribution of ranlib includes the C source of these routines, in case LINPACK is not installed on the target machine. No. of lines in distributed program, including test data, etc.:2975 No. of bytes in distributed program, including test data, etc.:194 588 Distribution format:tar.gz Catalogue identifier of previous version: ADXV_v1_0 Journal reference of previous version: Comput. Phys. Comm. 175 (2006) 212 Does the new version supersede the previous version?: Yes Nature of problem: Exact generation of different types of colored noise. Solution method: Random superposition of relaxation processes [E. Milotti, Phys. Rev. E 72 (2005) 056701], possibly followed by an integration step to produce noise with spectral index >2. Reasons for the new version: Extension to 1/f noises with spectral index 2

Milotti, Edoardo

2007-08-01

404

PLNoise: a package for exact numerical simulation of power-law noises  

NASA Astrophysics Data System (ADS)

Many simulations of stochastic processes require colored noises: here I describe a small program library that generates samples with a tunable power-law spectral density: the algorithm can be modified to generate more general colored noises, and is exact for all time steps, even when they are unevenly spaced (as may often happen in the case of astronomical data, see e.g. [N.R. Lomb, Astrophys. Space Sci. 39 (1976) 447]. The method is exact in the sense that it reproduces a process that is theoretically guaranteed to produce a range-limited power-law spectrum 1/f with -1

Milotti, Edoardo

2006-08-01

405

Bubble Motion through a Generalized Power-Law Fluid Flowing in a Vertical Tube  

PubMed Central

Intravascular gas embolism may occur with decompression in space flight, as well as during cardiac and vascular surgery. Intravascular bubbles may be deposited into any end organ, such as the heart or the brain. Surface interactions between the bubble and the endothelial cells lining the vasculature result in serious impairment of blood flow and can lead to heart attack, stroke, or even death. To develop effective therapeutic strategies, there is a need for understanding the dynamics of bubble motion through blood and its interaction with the vessel wall through which it moves. Toward this goal, we numerically investigate the axisymmetric motion of a bubble moving through a vertical circular tube in a shear-thinning generalized power-law fluid, using a front-tracking method. The formulation is characterized by the inlet Reynolds number, capillary number, Weber number, and Froude number. The flow dynamics and the associated wall shear stresses are documented for a combination of two different inlet flow conditions (inlet Reynolds numbers) and three different effective bubble radii (ratio of the undeformed bubble radii to the tube radii). The results of the non-Newtonian model are then compared with that of the model assuming a Newtonian blood viscosity. Specifically, for an almost occluding bubble (effective bubble radius = 0.9), the wall shear stress and the bubble residence time are compared for both Newtonian and non-Newtonian cases. Results show that at low shear rates, for a given pressure gradient the residence time for a non-Newtonian flow is higher than that for a Newtonian flow. PMID:19426324

Mukundakrishnan, Karthik; Eckmann, David M.; Ayyaswamy, P. S.

2009-01-01

406

Generalized power-law stiffness model for nonlinear dynamics of in-plane cable networks  

NASA Astrophysics Data System (ADS)

Cross-ties are used for mitigating stay-cable vibration, induced by wind and wind-rain on cable-stayed bridges. In-plane cable networks are obtained by connecting the stays by transverse cross-ties. While taut-cable theory has been traditionally employed for simulating the dynamics of cable networks, the use of a nonlinear restoring-force discrete element in each cross-tie has been recently proposed to more realistically replicate the network vibration when snapping or slackening of the restrainer may be anticipated. The solution to the free-vibration dynamics can be determined by "equivalent linearization method". In an exploratory study by the authors a cubic-stiffness spring element, in parallel with a linear one, was used to analyze the restoring-force effect in a cross-tie on the nonlinear dynamics of two simplified systems. This preliminary investigation is generalized in this paper by considering a power-law stiffness model with a generic integer exponent and applied to a prototype network installed on an existing bridge. The study is restricted to the fundamental mode and some of the higher ones. A time-domain lumped-mass algorithm is used for validating the equivalent linearization method. For the prototype network with quadratic-stiffness spring and a positive stiffness coefficient, a stiffening effect is observed, with a ten percent increment in the equivalent frequency for the fundamental mode. Results also show dependency on vibration amplitude. For higher modes the equivalent nonlinear effects can be responsible for an alteration of the linear mode shapes and a transition from a "localized mode" to a "global mode".

Giaccu, Gian Felice; Caracoglia, Luca

2013-04-01

407

Maximal planar networks with large clustering coefficient and power-law degree distribution  

NASA Astrophysics Data System (ADS)

In this article, we propose a simple rule that generates scale-free networks with very large clustering coefficient and very small average distance. These networks are called random Apollonian networks (RANs) as they can be considered as a variation of Apollonian networks. We obtain the analytic results of power-law exponent ?=3 and clustering coefficient C=(46)/(3)-36ln(3)/(2)?0.74 , which agree with the simulation results very well. We prove that the increasing tendency of average distance of RANs is a little slower than the logarithm of the number of nodes in RANs. Since most real-life networks are both scale-free and small-world networks, RANs may perform well in mimicking the reality. The RANs possess hierarchical structure as C(k)˜k-1 that are in accord with the observations of many real-life networks. In addition, we prove that RANs are maximal planar networks, which are of particular practicability for layout of printed circuits and so on. The percolation and epidemic spreading process are also studied and the comparisons between RANs and Barabási-Albert (BA) as well as Newman-Watts (NW) networks are shown. We find that, when the network order N (the total number of nodes) is relatively small (as Ñ104 ), the performance of RANs under intentional attack is not sensitive to N , while that of BA networks is much affected by N . And the diseases spread slower in RANs than BA networks in the early stage of the suseptible-infected process, indicating that the large clustering coefficient may slow the spreading velocity, especially in the outbreaks.

Zhou, Tao; Yan, Gang; Wang, Bing-Hong

2005-04-01

408

Pulsatile flow of power-law fluid model for blood flow under periodic body acceleration.  

PubMed

A mathematical model has been proposed to study the pulsatile flow of a power-law fluid through rigid circular tubes under the influence of a periodic body acceleration. Numerical solutions have been obtained by using finite difference method. The accuracy of the numerical procedure has been checked by comparing the obtained numerical results with other numerical and analytical solutions. It is found that the agreement between them is quite good. Interaction of non-Newtonian nature of fluid with the body acceleration has been investigated by using the physiological data for two particular cases (coronary and femoral arteries). The axial velocity, fluid acceleration, wall shear stress and instantaneous volume flow rate have been computed and their variations with different parameters have been analyzed. The following important observations have been made: (i) The velocity and acceleration profiles can have more than one maxima, this is in contrast with usual parabolic profiles where they have only one maximum at the axis. As n increases, the maxima shift towards the axis; (ii) For the flow with no body acceleration, the amplitude of both, wall shear and flow rate, increases with n, whereas for the flow with body acceleration, the amplitude of wall shear (flow rate) increases (decreases) as n increases; (iii) In the absence of body acceleration, pseudoplastic (dilatant) fluids, with low frequency pulsations, have higher (lower) value of maximum flow rate Qmax than Newtonian fluids, whereas for high frequencies, opposite behavior has been observed; for flow with body acceleration pulsations gives higher (lower) value of Qmax for pseudoplastic (dilatant) fluids than Newtonian fluids. PMID:2271765

Chaturani, P; Palanisamy, V

1990-01-01

409

The JKR-type adhesive contact problems for power-law shaped axisymmetric punches  

NASA Astrophysics Data System (ADS)

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.

Borodich, Feodor M.; Galanov, Boris A.; Suarez-Alvarez, Maria M.

2014-08-01

410

Power-Law and Logarithmic Entropy-Corrected Ricci Viscous Dark Energy and Dynamics of Scalar Fields  

E-print Network

In this work, I consider the logarithmic-corrected and the power-law corrected versions of the holographic dark energy (HDE) model in the non-flat FRW universe filled with a viscous Dark Energy (DE) interacting with Dark Matter (DM). We propose to replace the infra-red cut-off with the inverse of the Ricci scalar curvature $R$. I obtain the equation of state (EoS) parameter $\\omega_{\\Lambda}$, the deceleration parameter $q$ and the evolution of energy density parameter $\\Omega_D'$ in the presence of interaction between DE and DM for both corrections. I study the correspondence of the logarithmic entropy corrected Ricci Dark Dnergy (LECRDE) and power-law entropy corrected Ricci Dark Energy (PLECRDE) models with the the Modified Chaplygin Gas (MCG) and some scalar fields including tachyon, K-essence, dilaton and quintessence. I also make comparisons with previous results.

Antonio Pasqua

2013-03-12

411

Anomalous diffusion and power-law relaxation of the time averaged mean squared displacement in worm-like micellar solutions  

NASA Astrophysics Data System (ADS)

We report the results of single tracer particle tracking by optical tweezers and video microscopy in micellar solutions. From careful analysis in terms of different stochastic models, we show that the polystyrene tracer beads of size 0.52-2.5 ?m after short-time normal diffusion turn over to perform anomalous diffusion of the form ? t? with ? ? 0.3. This free anomalous diffusion is ergodic and consistent with a description in terms of the generalized Langevin equation with a power-law memory kernel. With optical tweezers tracking, we unveil a power-law relaxation over several decades in time to the thermal plateau value under the confinement of the harmonic tweezer potential, as predicted previously (Phys. Rev. E 85 021147 (2012)). After the subdiffusive motion in the millisecond range, the motion becomes faster and turns either back to normal Brownian diffusion or to even faster superdiffusion, depending on the size of the tracer beads.

Jeon, Jae-Hyung; Leijnse, Natascha; Oddershede, Lene B.; Metzler, Ralf

2013-04-01

412

Power-law and logarithmic entropy-corrected Ricci viscous dark energy and dynamics of scalar fields  

NASA Astrophysics Data System (ADS)

In this work, I consider the logarithmic-corrected and the power-law corrected versions of the holographic dark energy (HDE) model in the non-flat FRW universe filled with a viscous Dark Energy (DE) interacting with Dark Matter (DM). I propose to replace the infra-red cut-off with the inverse of the Ricci scalar curvature R. I obtain the equation of state (EoS) parameter ? ? , the deceleration parameter q and the evolution of energy density parameter \\varOmegaD' in the presence of interaction between DE and DM for both corrections. I study the correspondence of the logarithmic entropy corrected Ricci Dark Dnergy (LECRDE) and power-law entropy corrected Ricci Dark Energy (PLECRDE) models with the the Modified Chaplygin Gas (MCG) and some scalar fields including tachyon, K-essence, dilaton and quintessence. I also make comparisons with previous results.

Pasqua, Antonio

2013-08-01

413

Power law burst and inter-burst interval distributions in the solar wind: turbulence or dissipative SOC ?  

E-print Network

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.

M. P. Freeman; N. W. Watkins; D. J. Riley

2000-03-08

414

Simple empirical relation for the exponent of a power law in a two dimensional disordered porous system  

NASA Astrophysics Data System (ADS)

We study experimentally, the conductance as a function of porosity for a two dimensional disordered porous media far from the percolation treshold. We used photolithography and electron beam lithography to fabricate a "swiss cheese'' two dimensional porous media. We obtain a power law dependence for the conductance as a function of the porosity in the high porosity region. The exponent is found to be the ratio of two characteristic scales. One of them is not affected by the shape of the obstacles and is equal to the area of the system divided by the area of a single obstacle. The other one is expected to be sensitive to transport properties. The exponent of the power law varies with the size of the system. A simple empirical relation is found for the exponent as a function of the ratio of the area of the system over the area of a single obstacle.

Sánchez, Iván; Reyes, Leonardo; Donoso, Arnaldo; Paredes, Ricardo; Gutiérrez, Gustavo

2003-03-01

415

Fire Radiative Energy and Biomass Burned Estimation Under Sparse Satellite Sampling Conditions: Using Power Law Probability Distribution Properties of MODIS Fire Radiative Power Retrievals  

NASA Astrophysics Data System (ADS)

Spatially and temporally explicit mapping of the amount of biomass burned by fire is needed to estimate atmospheric emissions of green house gases and aerosols. The instantaneous Fire Radiative Power (FRP) [units: W] is retrieved at active fire detections from mid-infrared wavelength remotely sensed data and can be used to estimate the rate of biomass consumed. Temporal integration of FRP measurements over the duration of the fire provides the Fire Radiative Energy (FRE) [units: J] that has been shown to be linearly related to the total biomass burned [units: g]. However, FRE, and thus biomass burned retrieval, is sensitive to the satellite spatial and temporal sampling of FRP which can be sparse under cloudy conditions and with polar orbiting sensors such as MODIS. In this paper the FRE is derived in a new way as the product of the fire duration and the first moment of the FRP power law probability distribution. MODIS FRP data retrieved over savanna fires in Australia and deforestation fires in Brazil are shown to have power law distributions with different scaling parameters that are related to the fire energy in these two contrasting systems. The FRE derived burned biomass estimates computed using this new method are compared to estimates using the conventional temporal FRP integration method and with literature values. The results of the comparison suggest that the new method may provide more reliable burned biomass estimates under sparse satellite sampling conditions if the fire duration and the power law distribution parameters are characterized a priori.

Sathyachandran, S.; Roy, D. P.; Boschetti, L.

2010-12-01

416

On a Finite Branch and Bound Algorithm for the Global Minimization of a Concave Power Law Over a Polytope  

Microsoft Academic Search

In this paper, a finite branch-and-bound algorithm is developed for the minimization of a concave power law over a polytope.\\u000a Linear terms are also included in the objective function. Using the first order necessary conditions of optimality, the optimization\\u000a problem is transformed into an equivalent problem consisting of a linear objective function, a set of linear constraints,\\u000a a set of

Vasilios I. Manousiouthakis; Neil Thomas; Ahmad M. Justanieah

417

Soliton solution and bifurcation analysis of the Zakharov-Kuznetsov-Benjamin-Bona-Mahoney equation with power law nonlinearity  

NASA Astrophysics Data System (ADS)

This paper addresses the Zakharov-Kuznetsov-Benjamin-Bona-Mahoney equation with power law nonlinearity. First the soliton solution is obtained by the aid of traveling wave hypothesis and along with it the constraint conditions fall out naturally, in order for the soliton solution to exist. Subsequently, the bifurcation analysis of this equation is carried out and the fixed points are obtained. The phase portraits are also analyzed for the existence of other solutions.

Biswas, Anjan; Song, Ming

2013-07-01

418

A new approach to quantify power-law cross-correlation and its application to commodity markets  

Microsoft Academic Search

We proposed a new method: Detrended Moving-average Cross-correlation Analysis (DMCA) to detect the power-law cross-correlation between two correlated non-stationary time series by combining Detrended Cross-Correlation Analysis (DCCA) and Detrended Moving Average (DMA). In order to compare the performance of DMCA and DCCA in the detection of cross-correlation, and to estimate the influence of periodic trend, we generate two cross-correlated time

Ling-Yun He; Shu-Peng Chen

2011-01-01

419

Fourier, Gegenbauer and Jacobi Expansions for a Power-Law Fundamental Solution of the Polyharmonic Equation and Polyspherical Addition Theorems  

NASA Astrophysics Data System (ADS)

We develop complex Jacobi, Gegenbauer and Chebyshev polynomial expansions for the kernels associated with power-law fundamental solutions of the polyharmonic equation on d-dimensional Euclidean space. From these series representations we derive Fourier expansions in certain rotationally-invariant coordinate systems and Gegenbauer polynomial expansions in Vilenkin's polyspherical coordinates. We compare both of these expansions to generate addition theorems for the azimuthal Fourier coefficients.

Cohl, Howard S.

2013-06-01

420

Binary Inspirals in Nordström's Second Theory  

E-print Network

We investigate Nordstr\\"om's second theory of gravitation, with a focus on utilizing it as a testbed for developing techniques in numerical relativity. Numerical simulations of inspiraling compact star binaries are performed for this theory, and compared to the predictions of semi-analytic calculations (which are similar to Peters and Mathews' results for GR). The simulations are based on a co-rotating spherical coordinate system, where both finite difference and pseudo-spectral methods are used. We also adopt the "Hydro without Hydro" approximation, and the Weak Radiation Reaction approximation when the orbital motion is quasi-circular. We evolve a binary with quasi-circular initial data for hundreds of orbits and find that the resulting inspiral closely matches the 1/4 power law profile given by the semi-analytical calculations. We additionally find that an eccentric binary circularizes and precesses at the expected rates. The methods investigated thus provide a promising line of attack for the numerical modeling of long binary inspirals in general relativity.

Travis Garrett

2011-02-25

421

Estimating the power law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic data  

NASA Astrophysics Data System (ADS)

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.

Beskardes, G. D.; Weiss, C. J.; Everett, M. E.

2013-12-01

422

Power laws in cities population, financial markets and internet sites (scaling in systems with a variable number of components)  

NASA Astrophysics Data System (ADS)

We study a few dynamical systems composed of many components whose sizes evolve according to multiplicative stochastic rules. We compare them with respect to the emergence of power laws in the size distribution of their components. We show that the details specifying and enforcing the smallest size of the components are crucial as well as the rules for creating new components. In particular, a growing system with a fixed number of components and a fixed smallest component size does not converge to a power law. We present a new model with variable number of components that converges to a power law for a very wide range of parameters. In a very large subset of this range, one obtains for the exponent ? the special value 1 specific for the city populations distribution. We discuss the conditions in which ? can take different values. In the case of the stock market, the distribution of the investors’ wealth is related to the ratio between the new capital invested in stock and the rate of increase of the stock index.

Blank, Aharon; Solomon, Sorin

2000-11-01

423

Conserved Noncoding Elements Follow Power-Law-Like Distributions in Several Genomes as a Result of Genome Dynamics  

PubMed Central

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

Polychronopoulos, Dimitris; Sellis, Diamantis; Almirantis, Yannis

2014-01-01

424

Impacts of a power-law non-thermal electron tail on the ionization and recombination rates  

E-print Network

We have investigated the effects of a non-thermal electron population on the ionization and recombination rates. The considered electron distribution is defined as a Maxwellian function below a break energy E_b and as a power-law function of index alpha above this energy. We have calculated the collisional (direct and excitation autoionization) ionization coefficient rates as well as the (radiative and dielectronic) recombination rates. Practical methods are given to calculate these rates in order to be easily included in a computer code. The ionization rates are very sensitive to the non-thermal electron population and can be increased by several orders of magnitude depending on the temperature and parameters of the power-law function (E_b and alpha). The non-thermal electrons have a much weaker effect on the (radiative and dielectronic) recombination rates. We have determined the mean electric charge of elements C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni for different values of the break energy and power-law index. The ionization balance is affected significantly, whereas the effect is smaller in ionizing plasmas.

D. Porquet; M. Arnaud; A. Decourchelle

2001-05-22

425

Universal power-law diet partitioning by marine fish and squid with surprising stability-diversity implications.  

PubMed

A central question in community ecology is how the number of trophic links relates to community species richness. For simple dynamical food-web models, link density (the ratio of links to species) is bounded from above as the number of species increases; but empirical data suggest that it increases without bounds. We found a new empirical upper bound on link density in large marine communities with emphasis on fish and squid, using novel methods that avoid known sources of bias in traditional approaches. Bounds are expressed in terms of the diet-partitioning function (DPF): the average number of resources contributing more than a fraction f to a consumer's diet, as a function of f. All observed DPF follow a functional form closely related to a power law, with power-law exponents independent of species richness at the measurement accuracy. Results imply universal upper bounds on link density across the oceans. However, the inherently scale-free nature of power-law diet partitioning suggests that the DPF itself is a better defined characterization of network structure than link density. PMID:21068048

Rossberg, Axel G; Farnsworth, Keith D; Satoh, Keisuke; Pinnegar, John K

2011-06-01

426

Power law relation between size-resolved vertical dust flux and friction velocity measured in a fallow wheat field  

NASA Astrophysics Data System (ADS)

Size-resolved dust flux measurements are important for estimation of concentration and physical properties of dust particles in the atmosphere and their impacts on cloud and radiation transfer. In this study, we evaluate the power law relationship between size-resolved dust flux, Fair,d, and friction velocity, u?. During the Japan-Australia Dust Experiment, size-resolved dust fluxes were estimated with the gradient method by using data from optical particle counters and profile measurements of wind speed and air temperature in a dry, non-crusted fallow wheat field in Australia. When a power law is fitted to the u?-Fair,d relation, i.e., Fair,d-u?n, the coefficient of determination R2 is largest for n = 4. However, when a power law is fitted separately to data of each particle size range, n is found to depend on the particle size with values of 2.54 (0.7 ?m), 3.40 (1.1 ?m), 3.80 (1.7 ?m), 4.32 (2.6 ?m), 4.67 (4.6 ?m), and 4.53 (7.0 ?m), respectively, and maximum n was 4.67 for the 4.6 ?m diameter. This suggests that the Fair,d-u?n relationship is not universal, and embedded in n is the nature of soil aggregation. For practical purposes, n should be determined separately for each particle size range when estimating size-resolved dust fluxes.

Ishizuka, Masahide; Mikami, Masao; Leys, John F.; Shao, Yaping; Yamada, Yutaka; Heidenreich, Stephan

2014-03-01

427

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

...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...

2014-01-01

428

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

Code of Federal Regulations, 2011 CFR

...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...

2011-01-01

429

The puzzling dynamic nebula powered by the pulsar B1259-63 in a high-mass binary  

NASA Astrophysics Data System (ADS)

PSR B1259-63/LS 2883 is the famous eccentric gamma-ray binary (Pbin=3.4 yr, e=0.87) in which a pulsar orbits a massive O-type star. Its X-ray emission is produced by colliding winds of the pulsar and the massive companion. Using ACIS observations, we discovered an extended structure apparently moving away from the binary with v = 0.05-0.1 c. Such a moving X-ray nebula has never been seen before. To understand the nature of the dynamic nebula, the extended emission must be monitored throughout the binary orbit. As a first step in the monitoring program, we propose 2 ACIS observations to examine repeatability of the extended emission in different binary cycles and study the properties of the colliding winds and the emitting material.

Pavlov, George

2014-09-01

430

Orbital period variability in the eclipsing pulsar binary PSR B1957+20: Evidence for a tidally powered star  

Microsoft Academic Search

Recent observations indicate that the eclipsing pulsar binary PSR B1957+20 undergoes alternating epochs of orbital period increase and decrease. We apply a model developed to explain orbital period changes of alternating sign in other binaries to the PSR B1957+20 system and find that it fits the pulsars observations well. The novel feature of the PSR B1957+20 system is that the

James H. Applegate; Jacob Shaham

1994-01-01

431

A DEEP CHANDRA OBSERVATION OF THE WOLF-RAYET + BLACK HOLE BINARY NGC 300 X-1  

SciTech Connect

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.

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

432

Calibration Binaries  

NASA Astrophysics Data System (ADS)

Two Excel Spreadsheet files are offered to help calibrate telescope or camera image scale and orientation with binary stars for any time. One is a personally selected list of fixed position binaries and binaries with well-determined orbits, and the other contains all binaries with published orbits. Both are derived from the web site of the Washington Double Star Library. The spreadsheets give the position angle and separation of the binaries for any entered time by taking advantage of Excel's built in iteration function to solve Kepler's transcendental equation.

Drummond, J.

2011-09-01

433

THE ORBITAL ECCENTRICITIES OF BINARY MILLISECOND PULSARS IN GLOBULAR CLUSTERS  

E-print Network

Low-mass binary millisecond pulsars (LMBPs) are born with very small orbital eccentricities, typically of order $e_i\\sim10^{-6}$--$10^{-3}$. In globular clusters, however, higher eccentricities $e_f\\gg e_i$ 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 because, even for initially circular binaries, the induced eccentricity $e_f$ for an encounter with pericenter separation $r_{\\rm p}$ beyond a few times the binary semi-major axis $a$ declines only as a power-law, $e_f\\propto(r_{\\rm p}/a)^ {-5/2}$, and {\\it not\\/} as an exponential. We find that {\\it all\\/} currently known \\lmbps in clusters were probably affected by interactions, with their current eccentricities typically an order of magnitude or more greater than at birth.

Frederic A. Rasio; Douglas C. Heggie

1995-02-28

434

Origins of Taylor's power law for fluctuation scaling in complex systems  

Microsoft Academic Search

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

Agata Fronczakand; Piotr Fronczak

2010-01-01

435

High School Forum: Boyle's/Hooke's/Towneley and Power's/Mariotte's Law.  

ERIC Educational Resources Information Center

This column for high school teachers, written by high school teachers, discusses several interesting anecdotes related to the formulation of laws and the determination of constants. Science history is presented in a manner that can enliven classroom presentations and aid in understanding the principle itself. (Authur/SA)

Hawthorne, Robert M.; Herron, J. Dudley, Ed.

1979-01-01

436

Effects of suction or blowing on the velocity and temperature distribution in the flow past a porous flat plate of a power-law fluid  

Microsoft Academic Search

An analysis is made of the steady flow of a non-Newtonian fluid past an infinite porous flat plate subject to suction or blowing. The incompressible fluid obeys Ostwald-de Waele power-law model. It is shown that steady solutions for velocity distribution exist only for a pseudoplastic (shear-thinning) fluid for which the power-law index n satisfies 0 < n < 1 provided

A. S. Gupta; J. C. Misra; M. Reza

2003-01-01

437

Effects of suction or blowing on the velocity and temperature distribution in the flow past a porous flat plate of a power-law fluid  

Microsoft Academic Search

An analysis is made of the steady flow of a non-Newtonian fluid past an infinite porous flat plate subject to suction or blowing. The incompressible fluid obeys Ostwald-de Waele power-law model. It is shown that steady solutions for velocity distribution exist only for a pseudoplastic (shear-thinning) fluid for which the power-law index n satisfies 0

A. S. Gupta; J. C. Misra; M. Reza

2003-01-01

438

Log-periodic power law bubbles in Latin-American and Asian markets and correlated anti-bubbles in Western stock markets: An empirical study  

Microsoft Academic Search

Twenty-two significant bubbles followed by large crashes or by severe corrections in the Argentinian, Brazilian, Chilean, Mexican, Peruvian, Venezuelan, Hong-Kong, Indonesian, Korean, Malaysian, Philippine and Thai stock markets indices are identified and analysed for log-periodic signatures decorating an average power law acceleration. We find that log-periodic power laws adequately describe speculative bubbles on these emerging markets with very few exceptions

Anders Johansen; Didier Sornette

1999-01-01

439

Estimation of drought and flood recurrence interval from historical discharge data: a case study utilising the power law distribution  

NASA Astrophysics Data System (ADS)

The choice of which statistical distribution to fit to historical discharge data is critical when attempting to predict the most extreme flows. It has been shown that depending upon the distribution selected, the calculated return periods can vary dramatically. Cunnane (1985) discussed the factors affecting the choice of distribution for river flow series data, and was able to show that small differences in the Extreme Value Type 1 (Gumbel), Type 2, and Type 3 can lead to large differences in the predicted return period. Indeed this divergence increases as the return period becomes larger: a finding which has obvious implications for fluvial management. Despite this, in many studies which fit a frequency-magnitude distribution to fluvial discharge data, the choice of distribution appears driven by regional convention, or even by some other apparently arbitrary factor. Benson (1968) analysed data for ten US stations, and compared the fit using the log-normal, gamma, Gumbel, log-Gumbel, Hazen and log-Pearson type 3 distributions. On the basis of this study alone, the standard approach to flow frequency estimation in the USA became the fitting of a log-Pearson type 3 (LP3) distribution (US Water Resources Council, 1982). While several other countries have adopted a similar approach, usage of the LP3 distribution is not geographically universal. Hydrologists in the United Kingdom conventionally utilise a fitted generalised logistic distribution for flow frequency estimation (Robson and Reed, 1999) while Chinese hydrologists utilise the log-normal distribution (Singh, 2002). Choice of fitted distribution is obviously crucial, since selecting one distribution rather than another will change the estimated probabilities of future droughts and floods, particularly the largest and rarest events. Malamud et al. (1996) showed that a flood of equivalent size to that experienced on the Mississippi in 1993 has a recurrence interval on the order of 100 years when a power-law distribution is fitted, but a much longer recurrence interval — on the order of 1000 years — using the USA's standard LP3 method. In addition Pandey et al. (1998) found that fitting a power-law distribution, compared with fitting a Generalized Extreme Value distribution, can lead to a large decrease in the predicted return period for a given flood event. Both these findings have obvious implications for river management design. Power-law distributions have been fitted to fluvial discharge data by many authors (most notably by Malamud et al., 1996 and Pandey et al., 1998), who then use these fitted distributions to estimate flow probabilities. These authors found that the power-law performed as well or better than many of the distributions currently used around the world, despite utilising fewer pa