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1

Power laws, Pareto distributions and Zipf's law  

NASA Astrophysics Data System (ADS)

When the probability of measuring a particular value of some quantity varies inversely as a power of that value, the quantity is said to follow a power law, also known variously as Zipf's law or the Pareto distribution. Power laws appear widely in physics, biology, earth and planetary sciences, economics and finance, computer science, demography and the social sciences. For instance, the distributions of the sizes of cities, earthquakes, forest fires, solar flares, moon craters and people's personal fortunes all appear to follow power laws. The origin of power-law behaviour has been a topic of debate in the scientific community for more than a century. Here we review some of the empirical evidence for the existence of power-law forms and the theories proposed to explain them.

Newman, Mej

2005-09-01

2

Extended Stevens' power law.  

PubMed

An extension of the Stevens' power law, widely used in psychophysics to relate a physical magnitude of a stimulus (e.g. taste, luminance, weight, sound pressure) with the corresponding experienced magnitude (saltiness, brightness, heaviness, loudness etc.) has been proposed. It takes into account the fact that psychophysical functions are basically of a sigmoid and not power-like type. To model the stimulus-response relationship the S-shaped Gompertz function converted to the power form by the mapping procedure is employed. It provides the extended Stevens' power law y(C) = k(C)C(n(C)) with the scaling factor k(C) and exponent n(C) as function of the stimulus magnitude C. The model will be used in determination of the saltiness and brightness stimulus-response power function correctly reproducing the experimental psychophysical data in a wide range of the stimuli applied. It will be proven that the extended Stevens' power law belongs to the class of self-similar and allometric processes of the fractal nature. PMID:21771605

Molski, Marcin

2011-07-12

3

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

4

Heber Binary Project Binary Cycle Geothermal Demonstration Power Plant  

Microsoft Academic Search

Recognizing the desirability of demonstrating the operation of a commercial scale, binary cycle, geothermal power plant, San Diego Gas and Electric Company (SDGandE) has formed a consortium consisting of three California utilities, the Electric Power Research Institute (EPRI), and the Department of Energy (DOE) to carry out the Heber Binary Project. The overall goal of the Project is to establish

R. G. Lacy; T. T. Nelson

1982-01-01

5

Binary-flashing geothermal power plants  

Microsoft Academic Search

Binary-flashing units utilize new types of geothermal power cycles, which may be used with resources of relatively low temperatures (less than 150 C) where other cycles result in very low efficiencies. The thermodynamic cycles for the binary-flashing units are combinations of the geothermal binary and flashing cycles. They have most of the advantages of these two conventionally used cycles, but

Z. Yuan; E. E. Michaelides

1993-01-01

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 Law Distribution in Education  

Microsoft Academic Search

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

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

2003-01-01

8

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.

9

First law of mechanics for black hole binaries with spins  

NASA Astrophysics Data System (ADS)

We use the canonical Hamiltonian formalism to generalize to spinning point particles the first law of mechanics established for binary systems of nonspinning point masses moving on circular orbits [A. Le Tiec, L. Blanchet, and B. F. Whiting, Phys. Rev. D 85, 064039 (2012)PRVDAQ1550-7998]. We find that the redshift observable of each particle is related in a very simple manner to the canonical Hamiltonian and, more generally, to a class of Fokker-type Hamiltonians. Our results are valid through linear order in the spin of each particle, but hold also for quadratic couplings between the spins of different particles. The knowledge of spin effects in the Hamiltonian allows us to compute spin-orbit terms in the redshift variable through 2.5PN order, for circular orbits and spins aligned or anti-aligned with the orbital angular momentum. To describe extended bodies such as black holes, we supplement the first law for spinning point-particle binaries with some “constitutive relations” that can be used for diagnosis of spin measurements in quasi-equilibrium initial data.

Blanchet, Luc; Buonanno, Alessandra; Le Tiec, Alexandre

2013-01-01

10

Quantum dissipation from power-law memory  

NASA Astrophysics Data System (ADS)

A new quantum dissipation model based on memory mechanism is suggested. Dynamics of open and closed quantum systems with power-law memory is considered. The processes with power-law memory are described by using integration and differentiation of non-integer orders, by methods of fractional calculus. An example of quantum oscillator with linear friction and power-law memory is considered.

Tarasov, Vasily E.

2012-06-01

11

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

12

Power law scaling for rotational energy transfer  

Microsoft Academic Search

We have applied a new scaling law to several sets of rotational energy transfer cross sections. The new law asserts that the square of the T-matrix depends on the amount of energy transferred as a power law. Two different kinds of angular momentum statistics are assumed, one corresponding to mj being conserved and the other corresponding to mj being completely

David E. Pritchard; Neil Smith; Richard D. Driver; Timothy A. Brunner

1979-01-01

13

Heber Binary Project. Binary Cycle Geothermal Demonstration Power Plant (RP1900-1)  

Microsoft Academic Search

The Heber Binary Project (1) demonstrates the potential of moderate temperature (below 410 F) geothermal energy to produce economic electric power with binary cycle conversion technology; (2) allows the scaling up and evaluation of the performance of binary cycle technology in geothermal service; (3) establishes schedule, cost and equipment performance, reservoir performance, and the environmental acceptability of such plants; and

R. G. Lacy; T. T. Nelson

1982-01-01

14

Power-Law Relaxation and Cumulative Information  

NASA Astrophysics Data System (ADS)

We associate the cumulative information of a system relaxing towards equilibrium with a divergent integral when a power-law relaxation holds. We discuss and illustrate numerically how this implies that a system that relaxes to equilibrium through a power-law has a cumulative information content that progressively diverges from that of its equilibrium realization to which it is relaxing. Our findings shed light on some aspects of weak ergodicity breaking and suggest that power-laws imply a form of complexity that does not require dissipation or built-in disorder.

Di Porto, P.; Di Sabatino, S.; Crosignani, B.; DelRe, E.

2013-11-01

15

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.

16

Generalizing Benford's law using power laws: application to integer sequences  

Microsoft Academic Search

A simple method to derive parametric analytical extensions of Benford's law for first digits of numerical data is proposed. Two generalized Benford distributions are considered, namely the two-sided power Benford distribution and the new Pareto Benford distribution. The fitting capabilities of these generalized Benford distributions are illustrated and compared at some interesting and important integer sequences.

Werner Hurlimann

2006-01-01

17

Power-law inflation with exponential potentials  

NASA Astrophysics Data System (ADS)

We investigate some power-law solutions in inflationary cosmology, both by analytic and numerical means, considering first a simple model of a scalar field with an exponential field coupled to gravity. As has been pointed out recently by Yokoyama and Maeda, in power-law inflation viscous forces caused by couplings of the inflation to other particles can be important. We use numerical simulation to examine the effects of this viscosity on the inflation, for both a simple exponential potential and a more realistic potential motivated by particle physics. In general, the viscosity enhances the exponent of the power-law inflation, increasing the efficiency of inflation in power-law models, and we outline a specific inflationary model featuring viscosity. Supported by a University of Glasgow postgraduate scholarship.

Liddle, Andrew R.

1989-04-01

18

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

19

Heber Binary Project. Binary Cycle Geothermal Demonstration Power Plant (RP1900-1)  

NASA Astrophysics Data System (ADS)

The Heber Binary Project (1) demonstrates the potential of moderate temperature (below 410 F) geothermal energy to produce economic electric power with binary cycle conversion technology; (2) allows the scaling up and evaluation of the performance of binary cycle technology in geothermal service; (3) establishes schedule, cost and equipment performance, reservoir performance, and the environmental acceptability of such plants; and (4) resolves uncertainties associated with the reservoir performance, plant operation, and economics.

Lacy, R. G.; Nelson, T. T.

1982-12-01

20

Power-law distributions resulting from %nite resources  

Microsoft Academic Search

An elementary stochastic model, termed the normalization model, is put forward which does demonstrate that power-laws generically occur in systems with %nite resources. The model is capable to exhibit power-law distributions with arbitrary power law exponents; nevertheless, for a large fraction of the parameter space power law exponents near unity are obtained. As an application of the normalization mechanism we

Thomas Wilhelma; Peter H

21

Experimental verification of drag laws for binary, gas-fluidized systems  

Microsoft Academic Search

Axial species segregation measurements were carried out in a fluidized bed with a binary mix- ture of Geldart Group B particles. Several bed loadings with glass-polystyrene and polystyrene- polystyrene mixtures were investigated. The experimental results were then compared with MP- PIC numerical simulations with two drag laws for polydisperse systems, following the method described in the companion work by Leboreiro

Gustavo G. Joseph; Christine M. Hrenya; Matthew D. Lehr; Heather R. Woods; Sibashis S. Banerjee; Dale M. Snider

22

Fractal power law in literary English  

Microsoft Academic Search

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

L. L. Gonçalves; L. B. Gonçalves

2006-01-01

23

Power law damping parameter identification  

NASA Astrophysics Data System (ADS)

The parameter estimation of a nonlinear power damping system is studied. The parameter identification method used here assumes a priori the equation of motion describing the system dynamics. The method, which is based on the measured data (acceleration), was applied to the free and forced vibrations. The identification procedure was found to be robust on the guessed value of parameters at the numerical experimentation. The parameter values were estimated with a good accuracy for both modes of system operation (free and forced) if only the measured time history was sampled at a high enough rate for the noise level contained within. It was shown that the steady state of the harmonically excited system is not the best region for the parameter identification with this method. During the experimentation the method was applied to the free vibrations in different media (air and water). The results obtained by the parameter identification method were compared to the ones obtained by separate tests and good agreement was found. The identification procedure was found to work fine for all models under consideration and the models' responses correspond well to the measured acceleration time histories.

Jakši?, Nikola

2011-11-01

24

43 CFR 4.1121 - Powers of administrative law judges.  

Code of Federal Regulations, 2012 CFR

...administrative law judges. 4...Interior Office of the Secretary...PROCEDURES Special Rules Applicable to...1121 Powers of administrative law judges. ...the regulations of this part, an administrative law judge may...discovery; (4) Rule on...

2012-10-01

25

Variational Principle for the Pareto Power Law  

NASA Astrophysics Data System (ADS)

A mechanism is proposed for the appearance of power-law distributions in various complex systems. It is shown that in a conservative mechanical system composed of subsystems with different numbers of degrees of freedom a robust power-law tail can appear in the equilibrium distribution of energy as a result of certain superpositions of the canonical equilibrium energy densities of the subsystems. The derivation only uses a variational principle based on the Boltzmann entropy, without assumptions outside the framework of canonical equilibrium statistical mechanics. Two examples are discussed, free diffusion on a complex network and a kinetic model of wealth exchange. The mechanism is illustrated in the general case through an exactly solvable mechanical model of a dimensionally heterogeneous system.

Chakraborti, Anirban; Patriarca, Marco

2009-11-01

26

Gibbsian Theory of Power-Law Distributions  

SciTech Connect

It is shown that power-law phase space distributions describe marginally stable Gibbsian equilibria far from thermal equilibrium, which are expected to occur in collisionless plasmas containing fully developed quasistationary turbulence. Gibbsian theory is extended on the fundamental level to statistically dependent subsystems introducing an 'ordering parameter' {kappa}. Particular forms for the entropy and partition functions are derived with superadditive (nonextensive) entropy, and a redefinition of temperature in such systems is given.

Treumann, R. A. [Department of Geophysics and Environmental Sciences, Munich University, D-80333 Munich (Germany); Department of Physics, Dartmouth College, Hanover, New Hampshire 03755 (United States); Jaroschek, C. H. [Department Earth and Planetary Science, University of Tokyo, Tokyo (Japan)

2008-04-18

27

Stochastic Perturbation of Power Law Optical Solitons  

Microsoft Academic Search

The soliton perturbation theory is used to study and analyze the stochastic perturbation of optical solitons, with power law\\u000a nonlinearity, in addition to deterministic perturbations, that is governed by the nonlinear Schrödinger’s equation. The Langevin\\u000a equations are derived and analysed. The deterministic perturbations that are considered here are due to filters and nonlinear\\u000a damping.

Anjan Biswas; Huaizhong Ren; Swapan Konar

2007-01-01

28

Supersaturated Turbine Expansions for Binary Geothermal Power Plants  

Microsoft Academic Search

The Heat Cycle Research project is developing the technology base that will permit a much greater utilization of the moderate-temperature, liquid-dominated geothermal resources, particularly for the generation of electrical power. The emphasis in the project has been the improvement of the performance of binary power cycles. The investigations have been examining concepts projected to improve the brine utilization by 20%

C. J. Bliem; G. L. Mines

1992-01-01

29

Power-law distributions from additive preferential redistributions  

NASA Astrophysics Data System (ADS)

We introduce a nongrowth model that generates the power-law distribution with the Zipf exponent. There are N elements, each of which is characterized by a quantity, and at each time step these quantities are redistributed through binary random interactions with a simple additive preferential rule, while the sum of quantities is conserved. The situation described by this model is similar to those of closed N -particle systems when conservative two-body collisions are only allowed. We obtain stationary distributions of these quantities both analytically and numerically while varying parameters of the model, and find that the model exhibits the scaling behavior for some parameter ranges. Unlike well-known growth models, this alternative mechanism generates the power-law distribution when the growth is not expected and the dynamics of the system is based on interactions between elements. This model can be applied to some examples such as personal wealths, city sizes, and the generation of scale-free networks when only rewiring is allowed.

Ree, Suhan

2006-02-01

30

Kinetic coefficient of normal law of crystallization of macrosystems in the case of a dilute binary solution  

SciTech Connect

In the crystallization of highly diluted macroscopic binary solid solutions in the region of low supercooling in each layer of the transition region in practice only one spontaneous thermal equilibrium fluctuation is possible and, as a result, the concentration of particles in the solid state takes the mean value of the concentration calculated for the case of the corresponding binary microsystems. The growth kinetics of crystals of highly diluted macroscopic binary solid solutions (a particular form of binary metallic macrosystems) in the region of low supercooling of the system binary melt-crystal are described by the normal law (v = K ..delta..T) due to the action of the mechanism of spontaneous fluctuations with a limited spectrum of changes in the concentration of solid particles in the layers of the two-phase transition zone. An expression is obtained for the kinetic coefficient of the normal law of crystallization in the case of highly diluted macroscopic binary solid solutions.

Baikov, Yu.A.; Zelenev, Yu.V.

1987-03-01

31

Power Spectrum of Binary FM Signal with Additional AM  

Microsoft Academic Search

Formulas are derived for the power spectral density function of a sinusoidal carrier, frequency modulated by a random baseband pulse train in which the signaling interval equalsT. The signal pulses of duration2Toverlap. In the analysis presented different shapes of the signal pulses are approximated by staircase functions. Variations of the instantaneous frequency of the binary FM signal are accompanied by

P. Szulakiewicz

1979-01-01

32

Power-law parametrized quintessence model  

SciTech Connect

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

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

2007-01-15

33

Supersaturated Turbine Expansions for Binary Geothermal Power Plants  

SciTech Connect

The Heat Cycle Research project is developing the technology base that will permit a much greater utilization of the moderate-temperature, liquid-dominated geothermal resources, particularly for the generation of electrical power. The emphasis in the project has been the improvement of the performance of binary power cycles. The investigations have been examining concepts projected to improve the brine utilization by 20% relative to a ''Heber-type'' binary plant; these investigations are nearing completion. preparations are currently underway in the project to conduct field investigations of the condensation behavior of supersaturated turbine expansions. These investigations will evaluate whether the projected additional 8% to 10% improvement in brine utilization can be realized by allowing these expansions. Future program efforts will focus on the problems associated with heat rejection and on the transfer of the technology being developed to industry.

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

1992-03-24

34

Outlook for binary power plants using liquid-metal MHD  

Microsoft Academic Search

Preliminary testing and extrapolations thereof indicate that liquid-metal MHD can be used as a topping cycle to increase the efficiency of large central-station power plants. Because maximum temperatures as low as 870° C are effective, such binary plants are possible with existing material technology. The best present choices appear to be a potassium working fluid and either a (helium-or sodium-cooled)

L. L. Prem; W. E. Parkins

1970-01-01

35

The powerful law of the power law and other myths in network biology.  

PubMed

For almost 10 years, topological analysis of different large-scale biological networks (metabolic reactions, protein interactions, transcriptional regulation) has been highlighting some recurrent properties: power law distribution of degree, scale-freeness, small world, which have been proposed to confer functional advantages such as robustness to environmental changes and tolerance to random mutations. Stochastic generative models inspired different scenarios to explain the growth of interaction networks during evolution. The power law and the associated properties appeared so ubiquitous in complex networks that they were qualified as "universal laws". However, these properties are no longer observed when the data are subjected to statistical tests: in most cases, the data do not fit the expected theoretical models, and the cases of good fitting merely result from sampling artefacts or improper data representation. The field of network biology seems to be founded on a series of myths, i.e. widely believed but false ideas. The weaknesses of these foundations should however not be considered as a failure for the entire domain. Network analysis provides a powerful frame for understanding the function and evolution of biological processes, provided it is brought to an appropriate level of description, by focussing on smaller functional modules and establishing the link between their topological properties and their dynamical behaviour. PMID:20023717

Lima-Mendez, Gipsi; van Helden, Jacques

2009-10-02

36

Rate-Controlling Mechanisms in Five-Power-Law Creep  

SciTech Connect

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

Michael E. Kassner

2004-04-20

37

Inverse Power Law distribution and failure initiation of subaerial landslides  

Microsoft Academic Search

Landslides are sometimes considered together with other natural hazards, such as earthquakes and fires, as a cascading avalanche or self-organized critical process, where the disturbance initiates in one or a few locations and propagates to the entire region. This view stems from numerous studies of subaerial landslides that show an inverse power law size distribution. Inverse power law distributions are

R. Barkan; B. D. Andrews; J. D. Chaytor

2009-01-01

38

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

39

Power laws for rough wall turbulent boundary layers  

Microsoft Academic Search

An assessment of the ability of power laws to describe the mean velocity profile in the overlap region of a zero pressure gradient turbulent boundary layer is reported. The experiments were performed in a wind tunnel on smooth and four different types of rough surfaces at moderate Reynolds numbers. A novel modification to the power law velocity profile is proposed

N. A. Kotey; D. J. Bergstrom; M. F. Tachie

2003-01-01

40

Dynamic Power Spectra: Searching for Compact Binary Pulsars  

NASA Astrophysics Data System (ADS)

Some of the most scientifically useful pulsars are those in compact binary orbits (Porb < 4-5 hours), which are often found in the dense stellar environments of globular clusters. Unfortunately, strong Doppler accelerations make finding these pulsars very difficult. One of the more promising techniques to find these objects utilizes Dynamic Power Spectra (DPS), which are sensitive to binary pulsars when the observation length is comparable to the orbital period. A DPS consists of Fourier powers spanning across a large data plane of Fourier frequency and time. A pulsar appears in the DPS as a curve tracing out the Doppler shifted spin frequency as a function of observation time across the plane. We have improved the method by which we create DPS by including a new harmonic summing routine and a constant frequency derivative acceleration search with interbinning in each DPS segment. We have developed a beta version of a DPS search algorithm that is tuned to find pulsars when the orbital period is approximately equal to the observation duration. We have many terabytes of globular cluster data from the Green Bank Telescope which likely contain unknown compact pulsar binaries, many of which are thought to be sought-after millisecond pulsars. A thorough search of this data in ongoing and if new pulsars are found we will then determine "instant" timing solutions using the archival data. Funding for this presentation is made possible by the NSF REU Program, AUI, the NRAO, and Columbia University.

Pennucci, Tim

2009-01-01

41

Resurrecting power law inflation in the light of Planck results  

NASA Astrophysics Data System (ADS)

It is well known that a canonical scalar field with an exponential potential can drive power law inflation (PLI). However, the tensor-to-scalar ratio in such models turns out to be larger than the stringent limit set by recent Planck results. We propose a new model of power law inflation for which the scalar spectra index, the tensor-to-scalar ratio and the non-gaussianity parameter fNLequil are in excellent agreement with Planck results. Inflation, in this model, is driven by a non-canonical scalar field with an inverse power law potential. The Lagrangian for our model is structurally similar to that of a canonical scalar field and has a power law form for the kinetic term. A simple extension of our model resolves the graceful exit problem which usually afflicts models of power law inflation.

Unnikrishnan, Sanil; Sahni, Varun

2013-10-01

42

Filtration law for power-law fluids in anisotropic porous media  

Microsoft Academic Search

This work is concerned with modelling steady-state slow flow of incompressible power-law fluids in porous media. The macroscopic filtration law is derived by upscaling the pore–scale description. The upscaling technique in use is the homogenisation method of multiple scales. Then, the filtration law is investigated by means of the theory of representation of isotropic tensor function of tensor arguments. The

J.-L. Auriault; P. Royer; C. Geindreau

2002-01-01

43

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

Microsoft Academic Search

The basic process diagram and main technical solutions adopted in constructing the pilot 2.5-MW Pauzhet binary geothermal\\u000a power station are described. Results obtained from an analysis of some principles of selecting the working fluid and optimizing\\u000a the working parameters and operating modes of this power unit are presented.

G. V. Tomarov; A. I. Nikol’skii; V. N. Semenov; A. A. Shipkov

2010-01-01

44

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

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

Statistical Analyses Support Power Law Distributions Found in Neuronal Avalanches  

PubMed Central

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

Klaus, Andreas; Yu, Shan; Plenz, Dietmar

2011-01-01

47

Nonuniversal power-law spectra in turbulent systems.  

PubMed

Turbulence is generally associated with universal power-law spectra in scale ranges without significant drive or damping. Although many examples of turbulent systems do not exhibit such an inertial range, power-law spectra may still be observed. As a simple model for such situations, a modified version of the Kuramoto-Sivashinsky equation is studied. By means of semianalytical and numerical studies, one finds power laws with nonuniversal exponents in the spectral range for which the ratio of nonlinear and linear time scales is (roughly) scale independent. PMID:23992072

Bratanov, V; Jenko, F; Hatch, D R; Wilczek, M

2013-08-14

48

Binary optics beam mode transformer and its application in high-power laser processing  

Microsoft Academic Search

Based on the newly developed binary optics, a new kind of optics device used for laser beam mode transforming has been developed. This kind of binary optics device is worked with the principle of optical diffraction. It can be used to transform very efficiently the beam mode of high power laser of long wavelength. Using such a binary optics device

Wenjin Liu; Yanxiang Li; Jie Zhao; Haicheng Zhang; Shusen Deng; Pin Long; Yansong Cheng

1998-01-01

49

43 CFR 4.1121 - Powers of administrative law judges.  

Code of Federal Regulations, 2011 CFR

... Office of the Secretary of the Interior DEPARTMENT HEARINGS AND APPEALS PROCEDURES Special Rules Applicable to Surface Coal Mining Hearings and Appeals Evidentiary Hearings § 4.1121 Powers of administrative law judges. (a) Under the...

2011-10-01

50

Solitary waves of Boussinesq equation in a power law media  

Microsoft Academic Search

In this paper, the solitary wave solution of the Boussinesq equation, with power law nonlinearity, is obtained by virtue of solitary wave ansatze method. The numerical simulations are obtained to support the theory.

Anjan Biswas; Daniela Milovic; Arjuna Ranasinghe

2009-01-01

51

Power-Law entropy corrected holographic dark energy model  

NASA Astrophysics Data System (ADS)

Among various scenarios to explain the acceleration of the universe expansion, the holographic dark energy (HDE) model has got a lot of enthusiasm recently. In the derivation of holographic energy density, the area relation of the black hole entropy plays a crucial role. Indeed, the power-law corrections to entropy appear in dealing with the entanglement of quantum fields in and out the horizon. Inspired by the power-law corrected entropy, we propose the so-called "power-law entropy-corrected holographic dark energy" (PLECHDE) in this Letter. We investigate the cosmological implications of this model and calculate some relevant cosmological parameters and their evolution. We also briefly study the so-called "power-law entropy-corrected agegraphic dark energy" (PLECADE).

Sheykhi, Ahmad; Jamil, Mubasher

2011-10-01

52

Positive influence dominating sets in power-law graphs  

Microsoft Academic Search

Finding the minimum Positive Influence Dominating Set (PIDS) is a problem arisen from the social network applications. The\\u000a problem has been studied on general random graphs. However, the social networks is presented more precisely by power-law graphs.\\u000a One of the most important properties of social networks is the power-law degree distribution. In this paper, we focus on the\\u000a PIDS problem

Wei ZhangWeili; Weili Wu; Feng Wang; Kuai Xu

53

Optical monitoring for power law fluids during spin coating.  

PubMed

Optical monitoring is applied, in situ and in real time, to non-newtonian, power law fluids in the spin coating process. An analytical exact solution is presented for thickness evolution that well fits to most measurement data. As result, typical rheological parameters are obtained for several CMC (carboximetilcelullose) concentrations and rotation speeds. Optical monitoring thus precisely indicates applicability of the model to power law fluids under spin coating. PMID:22330554

Jardim, P L G; Michels, A F; Horowitz, F

2012-01-30

54

The Power Law of Practice in adaptive training The Power Law of Practice in adaptive training The Power Law of Practice in adaptive training The Power Law of Practice in adaptive training applications applications applicationsapplications  

Microsoft Academic Search

Abstract This research paper was inspired by the difference of findings in empirical learning-curve-data collected by ourselves and those of Newell and Rosenbloom (1981), who analysed empirical data-sets from other investigators to prove the ubiquity of the Power Law of Practice. The aim of this paper is to show some fundamental statistical and numerical flaws associated with Power Law analysis

J. J. M. Roessingh; B. G. Hilburn

2000-01-01

55

Hidden power law patterns in the top European football leagues  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

56

Power-law decay in first-order relaxation processes  

NASA Astrophysics Data System (ADS)

Starting from a simple definition of a stationary regime in first-order relaxation processes, we obtain that experimental results are to be fitted to a power law when approaching the stationary limit. On the basis of this result, we propose a graphical representation that allows the discrimination between power-law and stretched exponential time decays. Examples of fittings of magnetic, dielectric, and simulated relaxation data support the results.

Fondado, A.; Mira, J.; Rivas, J.

2005-07-01

57

Power law asymptotics for nonlinear eigenvalue problems  

Microsoft Academic Search

Nonlinear eigenvalue problems arise in a wide variety of phys- ical settings where oscillation amplitudes are too large to justify lineariza- tion. These problems have amplitude dependent frequencies, and one can ask whether scaling laws of the kind that arise in classical Sturm-Liouville theory still pertain. We prove in this paper that in the context of analyzing radially symmetric solutions

Paul K. Newton; Vassilis G. Papanicolaou

58

Power-Law Scaling in the Brain Surface Electric Potential  

PubMed Central

Recent studies have identified broadband phenomena in the electric potentials produced by the brain. We report the finding of power-law scaling in these signals using subdural electrocorticographic recordings from the surface of human cortex. The power spectral density (PSD) of the electric potential has the power-law form from 80 to 500 Hz. This scaling index, , is conserved across subjects, area in the cortex, and local neural activity levels. The shape of the PSD does not change with increases in local cortical activity, but the amplitude, , increases. We observe a “knee” in the spectra at , implying the existence of a characteristic time scale . Below , we explore two-power-law forms of the PSD, and demonstrate that there are activity-related fluctuations in the amplitude of a power-law process lying beneath the rhythms. Finally, we illustrate through simulation how, small-scale, simplified neuronal models could lead to these power-law observations. This suggests a new paradigm of non-oscillatory “asynchronous,” scale-free, changes in cortical potentials, corresponding to changes in mean population-averaged firing rate, to complement the prevalent “synchronous” rhythm-based paradigm.

Miller, Kai J.; Sorensen, Larry B.; Ojemann, Jeffrey G.; den Nijs, Marcel

2009-01-01

59

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

60

MHD micropumping of power-law fluids: A numerical solution  

NASA Astrophysics Data System (ADS)

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

Moghaddam, Saied

2013-02-01

61

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

62

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

63

Isomorphs in the phase diagram of a model liquid without inverse power law repulsion  

NASA Astrophysics Data System (ADS)

It is demonstrated by molecular dynamics simulations that liquids interacting via the Buckingham potential are strongly correlating, i.e., have regions of their phase diagram where constant-volume equilibrium fluctuations in the virial and potential energy are strongly correlated. A binary Buckingham liquid is cooled to a viscous phase and shown to have isomorphs, which are curves in the phase diagram along which structure and dynamics in appropriate units are invariant to a good approximation. To test this, the radial distribution function, and both the incoherent and coherent intermediate scattering function are calculated. The results are shown to reflect a hidden scale invariance; despite its exponential repulsion the Buckingham potential is well approximated by an inverse power-law plus a linear term in the region of the first peak of the radial distribution function. As a consequence the dynamics of the viscous Buckingham liquid is mimicked by a corresponding model with purely repulsive inverse-power-law interactions. The results presented here closely resemble earlier results for Lennard-Jones type liquids, demonstrating that the existence of strong correlations and isomorphs does not depend critically on the mathematical form of the repulsion being an inverse power law.

Veldhorst, A. A.; Bøhling, L.; Dyre, J. C.; Schrøder, T. B.

2012-01-01

64

Universal power law behaviors in genomic sequences and evolutionary models  

NASA Astrophysics Data System (ADS)

We study the length distribution of a particular class of DNA sequences known as the 5' untranslated regions exons. These exons belong to the messenger RNA of protein coding genes, but they are not coding (they are located upstream of the coding portion of the mRNA) and are thus less constrained from an evolutionary point of view. We show that in both mice and humans these exons show a very clean power law decay in their length distribution and suggest a simple evolutionary model, which may explain this finding. We conjecture that this power law behavior could indeed be a general feature of higher eukaryotes.

Martignetti, Loredana; Caselle, Michele

2007-08-01

65

Power-Law Creep from Discrete Dislocation Dynamics  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

66

Cosmic no-hair theorem in power-law inflation  

SciTech Connect

We prove a cosmic no-hair theorem for Bianchi models in power-law inflation. Provided that the potential of an inflaton {phi} is exp({minus}{lambda}{kappa}{phi}) with 0{le}{lambda}{lt} {radical}2/3 , we find that the isotropic power-law solution is the unique attractor for any initially expanding Bianchi-type models except type IX. For Bianchi type IX, this conclusion is also true if the initial ratio of the vacuum energy to the maximum three-curvature is larger than one half.

Kitada, Y. (Department of Physics, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan)); Maeda, K. (Department of Physics, Waseda University, Shinjuku-ku, Tokyo 169 (Japan))

1992-02-15

67

Law  

ERIC Educational Resources Information Center

|A case involving the mental health rights of children is currently working its way toward the Supreme Court. That case, Bartley v. Kremens, challenges the power of parents to institutionalize their children in mental hospitals or institutions for the retarded without due process of law. (Author/RK)|

Ellis, James W.

1976-01-01

68

Exponential and power laws in public procurement markets  

NASA Astrophysics Data System (ADS)

We analyze for the first time a unique public procurement database, which includes information about a number of bidders for a contract, a final price, an identification of a winner and an identification of a contracting authority for each of more than 40000 public procurements in the Czech Republic between 2006 and 2011, focusing on the distributional properties of the variables of interest. We uncover several scaling laws —the exponential law for the number of bidders, and the power laws for the total revenues and total spendings of the participating companies, which even follows Zipf's law for the 100 most spending institutions. We propose an analogy between extensive and non-extensive systems in physics and the public procurement market situations. Through an entropy maximization, such analogy yields some interesting results and policy implications with respect to the Maxwell-Boltzmann and Pareto distributions in the analyzed quantities.

Kristoufek, Ladislav; Skuhrovec, Jiri

2012-07-01

69

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

70

3C 273 and the power-law myth  

Microsoft Academic Search

There is no doubt that power-law representations fit the continuum observations of quasars very well over limited (about one decade) frequency ranges, notably the radio and X-ray. Over the entire observed frequency range (spanning 14 decades), however, the subjective goodness of fit can be distorted by the method used to plot the data. The continuous fall in the log of

Judith J. Perry; Martin J. Ward; Michael Jones

1987-01-01

71

From Power Laws to Fractional Diffusion: the Direct Way  

Microsoft Academic Search

Starting from the model of continuous time random walk, we focus our interest on random walks in which the probability distributions of the waiting times and jumps have fat tails characterized by power laws with exponent between 0 and 1 for the waiting times, between 0 and 2 for the jumps. By stating the relevant lemmata (of Tauber type) for

Rudolf Gorenflo; Entsar A. A. Abdel-Rehim

2007-01-01

72

Power law distribution of dividends in horse races  

Microsoft Academic Search

We discovered that the distribution of dividends in Korean horse races follows a power law. A simple model of betting is proposed, which reproduces the observed distribution. The model provides a mechanism to arrive at the true underlying winning probabilities, which are initially unknown, in a self-organized collective fashion, through the dynamic process of betting. Numerical simulations yield excellent agreement

E. Domany

2001-01-01

73

John Yoo's War Powers: The Law Review and the World  

Microsoft Academic Search

John Yoo’s 1996 The Continuation of Politics by Other Means: The Original Understanding of War Powers is surely among the most consequential articles ever to appear in the California Law Review. Five years after its publication, Yoo became the principal theorist of the Bush administration's War on Terrorism policies. His expansive theory of presidential primacy became the legal basis for

Janet Cooper Alexander

2012-01-01

74

Parameter identifiability of power-law biochemical system models.  

PubMed

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

Srinath, Sridharan; Gunawan, Rudiyanto

2010-03-01

75

Stability of Couette flow of liquids with power law viscosity  

Microsoft Academic Search

The stability of the Couette flow of the liquid with the power law viscosity in a wide annular gap has been investigated theoretically in this work with the aid of the method of small disturbances. The Taylor number, being a criterion of the stability, has been defined using the mean apparent viscosity value in the main flow. In the whole

M. Jastrz?bski; H. A. Zaidani; S. Wro?ski

1992-01-01

76

On the origin of power laws in equilibrium  

NASA Astrophysics Data System (ADS)

A particle in the attractive Coulomb field has an interesting property: its specific heat is constant and negative. We show, both analytically and numerically, that when a classical Hamiltonian system stays in weak contact with one such negative specific heat object, its statistics conforms to a fat-tailed power-law distribution with power index given by C/kB - 1, where kB is the Boltzmann constant and C is the heat capacity.

Campisi, Michele; Zhan, Fei; Hänggi, Peter

2012-09-01

77

Performance and operational experience of a prototype binary geothermal power plant  

Microsoft Academic Search

The production of electric power from a moderate temperature geothermal resource was investigated. The initial production of electrical power was accomplished with the prototype power plant which was built to demonstrate the operation of binary power cycles where the energy in the geothermal fluid is transferred to a secondary working fluid. During the automatic run test the plant produced a

G. L. Mines

1981-01-01

78

Second law analysis of a conventional steam power plant  

NASA Astrophysics Data System (ADS)

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.

1993-11-01

79

Chusho chinetsu binary hatsuden system jisho shiken hokokusho. (Report on demonstration test on small- and medium-size geothermal binary power generation systems (1993)).  

National Technical Information Service (NTIS)

With relation to the geothermal binary power generation system, investigations were made on evaluation of economic efficiency, basic commercialization/introduction study, check and review of the power system, present scale prevention measures, etc. As for...

1995-01-01

80

Thermal emission in fatigue described by power laws  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

81

Scale properties as a basis of power law relaxation processes  

NASA Astrophysics Data System (ADS)

Computer simulations of first-order relaxation processes show that the spatial configurations of the system acquire an invariant shape once the stationary regime is attained. Inspired by them we find that, in any first-order relaxation process, if the interaction that governs the system fulfils a simple scale property, then the relaxation will end up by following a stationary process described by a power law. A scaling law and some invariants are obtained for the time evolution of the system in such a case.

Fondado, A.; Mira, J.; Rivas, J.

2007-04-01

82

The influence of binary drag laws on simulations of species segregation in gas-fluidized beds  

Microsoft Academic Search

Monodisperse drag laws have been traditionally employed in polydisperse systems using ad hoc assumptions due to the lack of adequate drag laws for polydisperse systems. A key component of both continuum and discrete models used to study segregation in gas fluidized beds is the drag law. In this work, both the ad hoc approach and a new drag treatment developed

José Leboreiro; Gustavo G. Joseph; Christine M. Hrenya; Dale M. Snider; Sibashis S. Banerjee; Janine E. Galvin

2008-01-01

83

There is More than a Power Law in Zipf  

PubMed Central

The largest cities, the most frequently used words, the income of the richest countries, and the most wealthy billionaires, can be all described in terms of Zipf’s Law, a rank-size rule capturing the relation between the frequency of a set of objects or events and their size. It is assumed to be one of many manifestations of an underlying power law like Pareto’s or Benford’s, but contrary to popular belief, from a distribution of, say, city sizes and a simple random sampling, one does not obtain Zipf’s law for the largest cities. This pathology is reflected in the fact that Zipf’s Law has a functional form depending on the number of events N. This requires a fundamental property of the sample distribution which we call ‘coherence’ and it corresponds to a ‘screening’ between various elements of the set. We show how it should be accounted for when fitting Zipf’s Law.

Cristelli, Matthieu; Batty, Michael; Pietronero, Luciano

2012-01-01

84

Summary of investigations of the use of modified turbine inlet conditions in a binary power plant  

Microsoft Academic Search

Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of modified inlet conditions in geothermal binary power plant turbines to increase the power generation. An inlet condition of interest allows the expanding vapor to enter

G. L. Mines

2000-01-01

85

Summary of Investigations of the Use of Modified Turbine Inlet Conditions in a Binary Power Plant  

Microsoft Academic Search

Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of modified inlet conditions in geothermal binary power plant turbines to increase the power generation. An inlet condition of interest allows the expanding vapor to enter

Mines; Gregory Lee

2000-01-01

86

COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS  

SciTech Connect

In chameleon field theories, a scalar field can couple to matter with gravitational strength and still evade local gravity constraints due to a combination of self-interactions and the couplings to matter. Originally, these theories were proposed with a constant coupling to matter; however, the chameleon mechanism also extends to the case where the coupling becomes field dependent. We study the cosmology of chameleon models with power-law couplings and power-law potentials. It is found that these generalized chameleons, when viable, have a background expansion very close to {Lambda}CDM, but can in some special cases enhance the growth of the linear perturbations at low redshifts. For the models we consider, it is found that this region of the parameter space is ruled out by local gravity constraints. Imposing a coupling to dark matter only, the local constraints are avoided, and it is possible to have observable signatures on the linear matter perturbations.

Mota, David F.; Winther, Hans A. [Institute of Theoretical Astrophysics, University of Oslo, Box 1029, 0315 Oslo (Norway)

2011-05-20

87

Power law behavior of the zigzag transition in Yukawa clusters  

SciTech Connect

We provide direct experimental evidence that the width of a Yukawa cluster exhibits power law behavior during the one-dimensional (1D) to two-dimensional (2D) zigzag transition. Configurations of small dusty (complex) plasma clusters confined in a biharmonic potential well are characterized as the well anisotropy is varied. When the anisotropy is large the particles are in a 1D straight-line configuration. As the anisotropy is decreased the cluster undergoes a zigzag transition to a 2D configuration. The measured dependence of cluster width on anisotropy follows a power law. A second transition from the zigzag to an elliptical configuration is also observed. The results are in very good agreement with a model of identical particles interacting through a Yukawa potential.

Sheridan, T. E.; Magyar, Andrew L. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

2010-11-15

88

Power law in a microcanonical ensemble with scaling volume fluctuations  

SciTech Connect

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

Begun, V. V. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine); Gazdzicki, M. [Institut fuer Kernphysik, University of Frankfurt, Frankfurt (Germany); Jan Kochanowski University, Kielce (Poland); Gorenstein, M. I. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine); Frankfurt Institute for Advanced Studies, Frankfurt (Germany)

2008-08-15

89

Synchronization of oscillators with long-range power law interactions  

NASA Astrophysics Data System (ADS)

We present analytical calculations and numerical simulations for the synchronization of oscillators interacting via a long-range power law interaction on a one-dimensional lattice. We have identified the critical value of the power law exponent ?c across which a transition from a synchronized to an unsynchronized state takes place for a sufficiently strong but finite coupling strength in the large system limit. We find ?c=3/2 . Frequency entrainment and phase ordering are discussed as a function of ??1 . The calculations are performed using an expansion about the aligned phase state (spin-wave approximation) and a coarse graining approach. We also generalize the spin-wave results to the d -dimensional problem.

Chowdhury, Debanjan; Cross, M. C.

2010-07-01

90

Biasing power law exponents by magnitude estimation instructions  

Microsoft Academic Search

Different sets of magnitude estimation instructions, were given to different subjects in order to see if this could account\\u000a for the reported variation of the exponent in Stevens’ power law. Subiects who were asked to give as an estimate of pulse\\u000a rate (Experiment I) or loudness (Experiment II) the number 50 when it was 1\\/2 of the standard and 150

George H. Robinson

1976-01-01

91

Power law distribution of dividends in horse races  

NASA Astrophysics Data System (ADS)

We discovered that the distribution of dividends in Korean horse races follows a power law. A simple model of betting is proposed, which reproduces the observed distribution. The model provides a mechanism to arrive at the true underlying winning probabilities, which are initially unknown, in a self-organized collective fashion, through the dynamic process of betting. Numerical simulations yield excellent agreement with the empirical data.

Park, K.; Domany, E.

2001-02-01

92

Power-law correlations of landslide areas in central Italy  

Microsoft Academic Search

We have studied the frequency–area statistics of landslides in central Italy. We consider two data sets. Data set A contains 16?809 landslide areas in the Umbria–Marche area of central Italy; they represent a reconnaissance inventory of very old, old, and recent (modern) landslides. The noncumulative frequency–area distribution of these landslides correlates well with a power-law relation, exponent ?2.5, over the

Fausto Guzzetti; Bruce D Malamud; Donald L Turcotte; Paola Reichenbach

2002-01-01

93

Scaling power laws in the Sao Paulo Stock Exchange  

Microsoft Academic Search

The scaling of the probability distribution of the Sao Paulo Stock Exchange index is shown to be described by a Levy stable stochastic process for the modal region of the distribution. Data refer to daily records for the 30-year period 1968-1998. The truncated Levy process is characterized by a scaling index of 1.66. Scaling power laws are also shown to

Sergio Da Silva; Raul Matsushita; Iram Gleria

2002-01-01

94

Modeling cliff erosion using negative power law scaling of rockfalls  

NASA Astrophysics Data System (ADS)

We model cliff erosion using an approach based upon the negative power law scaling properties of rockfall magnitude-frequency distributions. These are derived from an extensive, high resolution, rockfall inventory for a series of sea cliffs near Staithes, North Yorkshire. A comparison between observed volumetric erosion and that produced by the model yields a statistically significant correlation. However, we note that the temporal resolution of the inventory can have an influence on results. Our data indicate that monthly inventories are capable of producing magnitude-frequency relations that model erosion in good correlation with observed events. However, for months that experience high magnitude events, seasonal inventories are more appropriate. Furthermore, increasing the return period between surveys has the effect of increasing the superimposition of rockfall events thereby reducing the slope of the power law, giving an incorrect picture of the scaling properties of rockfalls at this site. Applying observed variations in the negative power law scaling parameters to a probabilistic simulation model of cliff retreat provides a new means of assessing the most likely erosional scenarios and indicates that the current dataset may not be indicative of long term cliff evolution. This may provide a quantitative means of establishing an appropriate time window for characterizing rockfall erosion over decadal time scales.

Barlow, John; Lim, Michael; Rosser, Nick; Petley, David; Brain, Matthew; Norman, Emma; Geer, Melanie

2012-02-01

95

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

96

Power-Law Behavior of Power Spectra in Low Prandtl Number Rayleigh-Bénard Convection  

NASA Astrophysics Data System (ADS)

The origin of the power-law decay measured in the power spectra of low Prandtl number Rayleigh-Bénard convection near the onset of chaos is addressed using long time numerical simulations of the three-dimensional Boussinesq equations in cylindrical domains. The power law is found to arise from quasidiscontinuous changes in the slope of the time series of the heat transport associated with the nucleation of dislocation pairs and roll pinch-off events. For larger frequencies, the power spectra decay exponentially as expected for time continuous deterministic dynamics.

Paul, M. R.; Cross, M. C.; Fischer, P. F.; Greenside, H. S.

2001-10-01

97

Binary conversion cycles for concentrating solar power technology  

Microsoft Academic Search

It is recognized that the temperature potential of concentrated solar energy is much higher than needed by standard conversion cycles. High temperature solar receivers are in the development stage hopefully leading to the use of solarized gas turbines or of solar combined cycles. These systems are analyzed and taken as a reference standard. Binary alkali-metal steam cycles are shown to

Gianfranco Angelino; Costante Invernizzi

2008-01-01

98

Simulator-analyzer for binary-cycle geothermal power plants: Volume 1, Executive summary: Final report  

Microsoft Academic Search

The object was to develop a generic dynamic simulator\\/analyzer for binary-cycle geothermal power plants for use on today's personal computers. The simulator\\/analyzer, as developed, can be used for (1) engineering analyses of static\\/dynamic performance and design trade-offs; (2) operator training and operating procedure evaluation; and (3) binary cycle technology demonstration. The simulator\\/analyzer consists of a set of ordinary non-linear differential

1987-01-01

99

Heber binary-cycle geothermal demonstration power plant: summary of technical characteristics  

Microsoft Academic Search

This report provides a concise summary of the technical characteristics of the Heber Binary-Cycle Geothermal Power Plant Deminstration Project. The purpose of the project is to demonstrate the capability of the binary cycle technology for use in the development of moderate temperature (150 to 210°C (300 to 410°F)) geothermal resources. The primary objective is to show cost, performance, and environmental

1986-01-01

100

Thermal distribution in high power optical devices with power-law thermal conductivity  

NASA Astrophysics Data System (ADS)

We introduce a power-law approximation to model non-linear ranges of the thermal conductivity, and under this approximation derive a simple analytical expression for calculating the temperature profile in high power quantum cascade lasers and light emitting diodes. The thermal conductivity of a type II InAs/GaSb superlattice (T2SL) is used as an example, having negative or positive power-law exponents depending on the thermal range of interest. The result is an increase or decrease in the temperature, respectively, relative to the uniform thermal conductivity assumption.

Zhou, Chuanle; Grayson, M.

2012-01-01

101

Screw Expanders Increase Output and Decrease the Cost of Geothermal Binary Power Plant Systems  

Microsoft Academic Search

1. ABSTRACT A study has been carried out on the feasibility of using screw expanders, as an alternative to turbines, in three types of binary systems, suitable for recovering power from liquid dominated brines. The maximum power that one machine can generate is of the order of 1-3 MW per unit, depending on the type of system, and the brine

Ian K Smith; Nikola Stosic; Ahmed Kovacevic

102

The Influence of Binary Drag Laws on MP-PIC Simulations of Segregation  

Microsoft Academic Search

Gas-fluidized beds with particles of different sizes and\\/or densities are common in industry, and known to exhibit segregation under some operating conditions. A key component of both Eulerian and Lagrangian models used to study segregation is the drag force. Monodisperse drag laws have been traditionally employed in polydisperse systems using ad-hoc assumptions due to the lack of adequate drag laws

José Leboreiro; Gustavo G. Joseph; Christine M. Hrenya; Dale M. Snider; Sibashis S. Banerjee

103

Physical Origin of the Power-Law Tailed Statistical Distributions  

NASA Astrophysics Data System (ADS)

Starting from the BBGKY hierarchy, describing the kinetics of nonlinear particle system, we obtain the relevant entropy and stationary distribution function. Subsequently, by employing the Lorentz transformations we propose the relativistic generalization of the exponential and logarithmic functions. The related particle distribution and entropy represents the relativistic extension of the classical Maxwell-Boltzmann distribution and of the Boltzmann entropy, respectively, and define the statistical mechanics presented in [Phys. Rev. E 66 (2002) 056125] and [Phys. Rev. E 72 (2005) 036108]. The achievements of the present effort, support the idea that the experimentally observed power-law tailed statistical distributions in plasma physics, are enforced by the relativistic microscopic particle dynamics.

Kaniadakis, G.

104

A Note on the Invariance Properties and Conservation Laws of the Kadomstev—Petviashvili Equation with Power Law Nonlinearity  

Microsoft Academic Search

First, we studied the invariance properties of the Kadomstev—Petviashvili equation with power law nonlinearity. Then, we determined the complete class of conservation laws and stated the corresponding conserved densities which are useful in finding the conserved quantities of the equation. The point symmetry generators were also used to reduce the equation to an exact solution and to verify the invariance

A H Bokhari; F D Zaman; K Fakhar; A H Kara

2011-01-01

105

Power-law scaling in dimension-to-biomass relationship of fish schools  

Microsoft Academic Search

Motivated by the finding that there is some biological universality in the relationship between school geometry and school biomass of various pelagic fishes in various conditions, I here establish a scaling law for school dimensions: the school diameter increases as a power-law function of school biomass. The power-law exponent is extracted through the data collapse, and is close to 35.

Hiro-Sato Niwa

2005-01-01

106

Power Law Scaling of Variability of Discrete Signals.  

NASA Astrophysics Data System (ADS)

Data were taken for a variety of systems of discrete signals, including heart rate and background radiation. These sets of data were individually analyzed comparing the standard deviation and the average number of counts as functions of time (or length). It is well known that for random systems, such as nuclear decay, the standard deviation is proportional to the average number of counts raised to the 1/2 power. This was found not to be true for the background radiation and heart rate data. To analyze the data, a computer code was written in C++. The method of analyzing discrete signal data by finding a power-law relationship between standard deviation and average may be used over a wide range of disciplines in areas including, but not limited to, health science, computer science, business, life science, and physics. It may be especially useful in modeling non-linear discrete data.

Thompson, Emily

2004-05-01

107

Optimized dynamical decoupling for power-law noise spectra  

SciTech Connect

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

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

2010-01-15

108

``Slimming'' of power-law tails by increasing market returns  

NASA Astrophysics Data System (ADS)

We introduce a simple generalization of rational bubble models which removes the fundamental problem discovered by Lux and Sornette (J. Money, Credit and Banking, preprint at http://xxx.lanl.gov/abs/cond-mat/9910141) that the distribution of returns is a power law with exponent /<1, in contradiction with empirical data. The idea is that the price fluctuations associated with bubbles must on average grow with the mean market return /r. When /r is larger than the discount rate r?, the distribution of returns of the observable price, sum of the bubble component and of the fundamental price, exhibits an intermediate tail with an exponent which can be larger than 1. This regime r>r? corresponds to a generalization of the rational bubble model in which the fundamental price is no more given by the discounted value of future dividends. We explain how this is possible. Our model predicts that, the higher is the market remuneration /r above the discount rate, the larger is the power-law exponent and thus the thinner is the tail of the distribution of price returns.

Sornette, D.

2002-06-01

109

Inverse Power Law distribution and failure initiation of subaerial landslides  

NASA Astrophysics Data System (ADS)

Landslides are sometimes considered together with other natural hazards, such as earthquakes and fires, as a cascading avalanche or self-organized critical process, where the disturbance initiates in one or a few locations and propagates to the entire region. This view stems from numerous studies of subaerial landslides that show an inverse power law size distribution. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. However, the observation of a large number of small separate subaerial landslides being triggered by a single earthquake, such as the 1994 Northridge earthquake, is incompatible with a cascading hypothesis and suggests instead that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area affected by subaerial landslides is shown to be comparable to the affected area calculated by slope stability analysis for submarine landslides and is thus predictable. We show a statistical similarity between morphological attributes of the affected area and area distribution of the landslides from the Northridge earthquake, which suggests that area distribution of subaerial landslides may be determined by the morphology of the affected area, not by the initiation process.

ten Brink, U. S.; Barkan, R.; Andrews, B. D.; Chaytor, J. D.

2009-12-01

110

Testing Power-Law Relaxation Scenarios in a Metastable Liquid  

NASA Astrophysics Data System (ADS)

The renormalized dynamics described by the equations of nonlinear fluctuating hydrodynamics (NFH) treated at one loop order gives rise to the basic model of the mode coupling theory (MCT). We investigate here by analyzing the density correlation function, a crucial prediction of ideal MCT, namely the validity of the multi step relaxation scenario. The equilibrium density correlation function is calculated here from the direct solutions of NFH equations for a hard sphere system. We make first detailed investigation for the robustness of the correlation functions obtained from the numerical solutions by varying the size of the grid. For an optimum choice of grid size we analyze the decay of the density correlation function to identify the multi-step relaxation process. Weak signatures of two step power law relaxation is seen with exponents which do not match predictions from the one loop MCT. For the final relaxation stretched exponential (KWW) behavior is seen and the relaxation time grows with increase of density. But apparent power law divergences indicate a critical packing fraction much higher than the corresponding MCT predictions for a hard sphere fluid.

Gupta, Bhaskar Sen; Das, Shankar P.

2012-11-01

111

Power Laws in Real Estate Prices during Bubble Periods  

NASA Astrophysics Data System (ADS)

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

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

112

An inverse method for rheometry of power-law fluids  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

113

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

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Administrative law judges-powers and limitations...INVESTIGATIONS, ENFORCEMENT, AND ADMINISTRATIVE REVIEW Rules of Practice in FAA...Transportation Adjudications § 406.109 Administrative law judgesâpowers and...

2009-01-01

114

Implication of the power law cutoff evolution in XTE J1550-564  

NASA Astrophysics Data System (ADS)

We present spectral analysis of data collected using RXTE during two periods of X-ray activity in 1998 and 2000 from the Galactic X-ray black hole binary XTE J1550-564. We particularly concentrate on the behavior of the high energy cutoff of the power law part of the spectrum. The 1998 event was very powerful, showing a quick initial transition from low-hard state to very high state. The power law cutoff energy decreases from low-hard to intermediate states and increased again during transition to very high and high-soft states. For the 2000 outburst we also observe the decrease of the cutoff energy during the start of the state transition, similar to that in 1998 outburst, however the increase of the high energy cutoff (folding energy) is not apparent in this track because the source does not reach the real high-soft state in this event. We attribute this difference in the cutoff energy behavior to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization in photon upscattering. Namely, during the 1998 event higher accretion rate presumably provided more cooling to Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions the bulk motion should take a leading role in boosting the input soft photons. This observational behavior of the cutoff energy presents an additional evidence of the existence of the converging bulk motion region near the central objects and provides further support for the previously reported index saturations effect as a black hole signature.

Titarchuk, Lev; Shaposhnikov, Nikolai

115

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

116

Performance and operational experience of a prototype binary geothermal power plant  

NASA Astrophysics Data System (ADS)

The production of electric power from a moderate temperature geothermal resource was investigated. The initial production of electrical power was accomplished with the prototype power plant which was built to demonstrate the operation of binary power cycles where the energy in the geothermal fluid is transferred to a secondary working fluid. During the automatic run test the plant produced a maximum of 59kW(e). During the automatic run test, the plant operation was stable and the facility was operated for 1357 hours producing electrical power approximately 87% of the time geothermal fluid was available for operation.

Mines, G. L.

1981-12-01

117

Optimization of thermodynamic efficiency in binary-type geothermal electric power generating plants  

Microsoft Academic Search

Calculations and curves are presented which prove that for each turbine entry temperature, there is an entry pressure which will optimize the thermodynamic efficiency of a binary type geothermal power plant. Comparisons are made between thermodynamic efficiency and another method of rating process efficiency.

E. Eno

1975-01-01

118

Exergy analysis of a dual-level binary geothermal power plant  

Microsoft Academic Search

Exergy analysis of a 12.4 MW existing binary geothermal power plant is performed using actual plant data to assess the plant performance and pinpoint sites of primary exergy destruction. Exergy destruction throughout the plant is quantified and illustrated using an exergy flow diagram, and compared to the energy flow diagram. The causes of exergy destruction in the plant include the

Mehmet Kanoglu

2002-01-01

119

A novel fault finding and identification strategy using pseudorandom binary sequences for multicore power cable troubleshooting  

Microsoft Academic Search

A novel fault finding correlation methodology, using pseudorandom binary sequences (PRBS), is presented as an alternative to time domain reflectometry (TDR) for multi-core power cable fault location and identification. The fulcrum of this method is the cross correlation (CCR) of the fault echo response with the input pseudonoise (pN) test sequence which results in a unique signature for identification of

Holger Geisler; Richard A. Guinee

2009-01-01

120

The Autocorrelation Function and Power Spectrum of PCM\\/FM with Random Binary Modulating Waveforms  

Microsoft Academic Search

This paper presents the derivation of exact expressions for the autocorrelation function and power spectrum of PCM\\/FM or FSK when the frequency modulating waveform is a random sequence of binary pulses of length T. The problem treated is that of true frequency modulation of an oscillator, a process which, except for a few special cases, generates waveforms and spectra different

M. G. Pelchat

1964-01-01

121

Performance and parametric investigation of a binary geothermal power plant by exergy  

Microsoft Academic Search

Exergy analysis of a binary geothermal power plant is performed using actual plant data to assess the plant performance and pinpoint sites of primary exergy destruction. Exergy destruction throughout the plant is quantified and illustrated using an exergy diagram, and compared to the energy diagram. The sites with greater exergy destructions include brine reinjection, heat exchanger and condenser losses. Exergetic

Mehmet Kanoglu; Ali Bolatturk

2008-01-01

122

Power laws governing hydrology and carbon dynamics in northern peatlands  

NASA Astrophysics Data System (ADS)

Environmental and biological variables fluctuate over different time scales. On the basis of power spectral analysis of 14 time series at four sites from northern peatlands (fens and raised bogs), the temporal variability of physical environment (temperatures, water tables) and biological variables (CO 2 flux) shows power-law behaviour, with a scaling exponent ranging from about 0.5 to 1.5. The scaling exponents of air temperatures change from 1.5 at high frequency to 0.5 at low frequency, with a break point at diurnal period. Comparison with similar analysis of temperature data from climate stations suggests that the atmosphere above peatlands has more active heat exchange with waterlogged peatlands than with upland terrestrial ecosystems. Water tables from different peatlands show almost identical power spectra, with a scaling exponent of 1.0 over all time scales. CO 2 exchange has more complex spectral structure, with two break points at daily and monthly periods. This spectral structure suggests scale-dependent influence of climatic and hydrological fluctuations on CO 2 fluxes. CO 2 flux responds to air temperature with a distinct diurnal spectral peak. These results indicate that time scales are important in discussing hydrology and carbon dynamics in peatlands, and that scaling up of short-term experimental results may be inadvisable. Further statistical analysis on drained and harvested peatlands would provide insights into understanding shift in peatland dynamics due to human disturbance.

Yu, Zicheng

2006-09-01

123

Power-Law Spectra of Incipient Gas-Curtain Turbulence  

SciTech Connect

We investigate the evolution of a thin curtain of heavy gas (SF{sub 6} ) embedded in a lighter gas (air) and accelerated with a Machthinspthinsp1.2 planar shock wave. The Richtmyer-Meshkov instability leads to growth of the initial perturbations of the curtain and eventually to transition to turbulence. We visualize a time sequence of images of a section of the flow illuminated with a laser sheet. The SF{sub 6} is premixed with tracer (glycol fog), so the intensity of the light scattered off the curtain grows with the local density. As the curtain evolves towards a fully mixed state, real-space correlations of the density, inferred from scattered light intensity, show the emergence of a power-law behavior, indicative of transition to turbulence. {copyright} {ital 1998} {ital The American Physical Society }

Vorobieff, P. [Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 (United States); Vorobieff, P.; Rightley, P.M.; Benjamin, R.F. [Dynamic Experimentation Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 (United States)

1998-09-01

124

Power-law weighted networks from local attachments  

NASA Astrophysics Data System (ADS)

This letter introduces a mechanism for constructing, through a process of distributed decision-making, substrates for the study of collective dynamics on extended power-law weighted networks with both a desired scaling exponent and a fixed clustering coefficient. The analytical results show that the connectivity distribution converges to the scaling behavior often found in social and engineering systems. To illustrate the approach of the proposed framework we generate network substrates that resemble steady state properties of the empirical citation distributions of i) publications indexed by the Institute for Scientific Information from 1981 to 1997; ii) patents granted by the U.S. Patent and Trademark Office from 1975 to 1999; and iii) opinions written by the Supreme Court and the cases they cite from 1754 to 2002.

Moriano, P.; Finke, J.

2012-07-01

125

Stable power laws in variable economies; Lotka-Volterra implies Pareto-Zipf  

NASA Astrophysics Data System (ADS)

In recent years we have found that logistic systems of the Generalized Lotka-Volterra type (GLV) describing statistical systems of auto-catalytic elements posses power law distributions of the Pareto-Zipf type. In particular, when applied to economic systems, GLV leads to power laws in the relative individual wealth distribution and in market returns. These power laws and their exponent ? are invariant to arbitrary variations in the total wealth of the system and to other endogenously and exogenously induced variations.

Solomon, S.; Richmond, P.

2002-05-01

126

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

Microsoft Academic Search

The performance of Rankine cycle binary systems for geothermal power generation using a hydrothermal resource has been investigated. To date, in addition to many pure fluids, mixtures of Paraffin-type hydrocarbons and water-ammonia mixtures have been investigated. This paper gives the results of consideration of mixtures of halocarbons as working fluids in these power cycles. The performance of mixtures of Refrigerant-114

Bliem

1987-01-01

127

Shape of gas flow paths causes power law tailing  

NASA Astrophysics Data System (ADS)

In soil and/or groundwater remediation, we often see prolonged tailings: continuous outflow of low concentration pollutants for very long time, and in many cases power low behavior of late-time time-concentration curves. We considered that this kind of tailing can be caused by the shape of the gaseous flow introduced in saturated/unsaturated porous media. When gas is introduced to porous media, like air-sparging or soil vapor extraction, the shape of the gas flow path would be tree-like, or to some extent "fractal." So, there would be a distribution of the distance that a solute would have to travel by diffusion before getting to a gas/water interface, and we might expect that the distribution of this "diffusion distance" would be power-law-like. In order to see if tailing can be caused by this mechanism, simple column experiments were carried out. A column, 64 mm in inner diameter and 240 mm in height, was prepared and was packed with 1mm diameter glass beads. Nitrogen gas containing 5 % CO2 and 5% He was supplied from the bottom of the column, and after the water in the column is approximately saturated with CO2, the sparging gas was changed to pure nitrogen. The CO2 and He concentrations in the effluent gas was monitored and recorded. As the result, we saw tailing: the double-log plots of the concentration vs. time relationship was practically linear, and the absolute value of the slope in the double-log charts were 1.28, 0.95 and 0.83 according to the gas flow rates of 40, 80 and 120 ml/min, respectively. Slope less than 1.00 showed that these tailings cannot be explained by Freundlich-type adsorption behavior. Model analysis showed that this power low time-concentration behavior with the slope of approximately -1.0 can be explained by the power law distribution of diffusion distance \\textit{a} with PDF p(\\textit{a}) proportional to \\textit{a}^{-1}.

Kawanishi, T.; Sakami, A.; Hayashi, Y.

2004-12-01

128

Swings between rotation and accretion power in a binary millisecond pulsar  

NASA Astrophysics Data System (ADS)

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.

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.

2013-09-01

129

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

130

POWER-LAW TEMPLATE FOR INFRARED POINT-SOURCE CLUSTERING  

SciTech Connect

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 {approx}< l {approx}< 2200), the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST; 250, 350, and 500 {mu}m; 1000 {approx}< l {approx}< 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{sup clust}{sub l}{proportional_to}l{sup -n} with n = 1.25 {+-} 0.06. While the IR sources are understood to lie at a range of redshifts, with a variety of dust properties, we find that the frequency dependence of the clustering power can be described by the square of a modified blackbody, {nu}{sup {beta}} B({nu}, T{sub eff}), with a single emissivity index {beta} = 2.20 {+-} 0.07 and effective temperature T{sub eff} = 9.7 K. Our predictions for the clustering amplitude are consistent with existing ACT and South Pole Telescope results at around 150 and 220 GHz, as is our prediction for the effective dust spectral index, which we find to be {alpha}{sub 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 [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Hajian, Amir; Das, Sudeep; Hincks, Adam D.; Page, Lyman A.; Staggs, Suzanne T. [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Viero, Marco [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Bond, J. Richard [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Devlin, Mark J.; Reese, Erik D. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Halpern, Mark; Scott, Douglas [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Hlozek, Renee; Marriage, Tobias A.; Spergel, David N. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Moodley, Kavilan [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041 (South Africa); Wollack, Edward [NASA/Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)

2012-06-20

131

Summary of Investigations of the Use of Modified Turbine Inlet Conditions in a Binary Power Plant  

SciTech Connect

Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of modified inlet conditions in geothermal binary power plant turbines to increase the power generation. An inlet condition of interest allows the expanding vapor to enter the two-phase region, a mode of operation typically avoided because of concern that condensate would form and damage the turbine, degrading performance. INEEL investigators postulated that initially a supersaturated vapor would be supported, and that no turbine damage would occur. This paper summarizes the investigation of these expansions that began with testing of their condensation behavior, and culminated with the incorporation of these expansions into the operation of several commercial binary plant turbines.

Mines, Gregory Lee

2000-09-01

132

Summary of investigations of the use of modified turbine inlet conditions in a binary power plant  

SciTech Connect

Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of modified inlet conditions in geothermal binary power plant turbines to increase the power generation. An inlet condition of interest allows the expanding vapor to enter the two-phase region, a mode of operation typically avoided because of concern that condensate would form and damage the turbine, degrading performance. INEEL investigators postulated that initially a supersaturated vapor would be supported, and that no turbine damage would occur. This paper summarizes the investigation of these expansions that began with testing of their condensation behavior, and culminated with the incorporation of these expansions into the operation of several commercial binary plant turbines.

G. L. Mines

2000-09-24

133

Special function instruments for binary cycle geothermal power plants  

Microsoft Academic Search

Three special instruments have been designed to support plant operations at the Heber geothermal power plant in Heber, California. All are aids to give operating information which no commercial instruments can provide. The first is a package for determining COâ breakout conditions for a particular brine. Brine is sampled continuously at either the wellhead or the plant inlet. A temperature-pressure

R. J. Robertus; D. W. Shannon; R. G. Sullivan

1984-01-01

134

Performance analysis of the Chena binary geothermal power plant  

Microsoft Academic Search

In this paper, the IPSEpro model of the Chena Geothermal ORC Power Plant had been developed and validated using the real data. The validated model was used to investigate the effect of variation in the geothermal source temperature on plant performance.The analysis showed that the variation of the geothermal source temperature affects the plant behaviour. Increase in the geothermal source

Mathew Aneke; Brian Agnew; Chris Underwood

2011-01-01

135

Binary Cycle Geothermal Demonstration Power Plant New Developments  

Microsoft Academic Search

San Diego Gas and Electric Company (SDG and E) has been associated with geothermal exploration and development in the Imperial Valley since 1971. SDG and E currently has interests in the four geothermal reservoirs shown. Major SDG and E activities have included drilling and flow testing geothermal exploration wells, feasibility and process flow studies, small-scale field testing of power processes

Robert G. Lacy; William O. Jacobson

1980-01-01

136

The power of power laws and an interpretation of Lotkaian informetric systems as self-similar fractals  

Microsoft Academic Search

Although already defined in 1926 by A. Lotka, power laws are becoming more and more important since they have been found valid in social networks such as the Internet. In this paper we prove some unique properties of power laws. We show that they characterise functions with the scale-free property (also called self-similarity property) as well as functions with the

Leo Egghe

2005-01-01

137

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

NASA Astrophysics Data System (ADS)

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

2013-09-01

138

On the Cumulants of Population Size for the Stochastic Power Law Logistic Model  

Microsoft Academic Search

The deterministic power law logistic model is used to describe density-dependent population growth in cases where the ordinary logistic model is insufficient. This paper investigates an analogous stochastic power law logistic model. The exact (unconditional) population size distributions and the cumulant functions for this stochastic model are intractable for large population sizes. Approximating cumulant functions are derived for populations of

James H Matis; Thomas R Kiffe; P. R. Parthasarathy

1998-01-01

139

Origins and Violations of the 2\\/3 Power Law in Rhythmic 3D Arm Movements  

Microsoft Academic Search

The 2\\/3 power law, the nonlinear relationship between tangential velocity and radius of curvature of the endeffector trajectory, has been suggested as a fundamental constraint of the central nervous system in the formation of rhythmic endpoint trajectories. However, studies on the 2\\/3 power law have largely been confined to planar drawing patterns of relatively small size. With the hypothesis that

Stefan Schaal; Dagmar Sternad

2001-01-01

140

Experimental and numerical investigations of pressure drop in a rectangular duct with modified power law fluids  

Microsoft Academic Search

Numerical solutions are presented for fully developed laminar flow for a modified power law fluid (MPL) in a rectangular duct. The solutions are applicable to pseudoplastic fluids over a wide shear rate range from Newtonian behavior at low shear rates, through a transition region, to power law behavior at higher shear rates. The analysis identified a dimensionless shear rate parameter

Dong-Ryul Lee

2003-01-01

141

Self-Similar Criticality: A link between cumulative power law distributions and fractal geometry  

NASA Astrophysics Data System (ADS)

Cumulative number-size distributions associated with many natural phenomena follow a power law. A data set that follows a power law may be considered fractal since both power laws and fractals are scale invariant. To understand the relationship between power law cumulative distributions and fractal geometry, we propose a model called Self-Similar Criticality (SSC). The model is based on a grid containing a self-similar distribution of critical cells. During each step of the model, a unit of material is supplied to the grid at a location selected at random. An event occurs when material is added to a critical cell, causing all material in occupied non-diagonal adjacent cells to leave the grid. The resulting cumulative distribution of event sizes follows an upper-truncated power law with a scaling exponent that depends on the fractal dimension of the critical cells. Unlike self-organized criticality (SOC) systems, which generate non-cumulative distributions with scaling exponents near unity, the SSC model generates power law distributions with a range of scaling exponents depending on the fractal dimension of the critical cells. The SSC model reproduces the observed power law distribution of seamount volumes in the Easter Island/Salas y Gomez Chain by initiating eruptions on a self-similar distribution of critical cells. For many natural systems, the SSC model may provide a link between observed power law distributions and fractal geometry.

Tebbens, S. F.; Burroughs, S. M.

2001-12-01

142

Heat transfer enhancement in laminar slurry pipe flows with power law thermal conductivities  

Microsoft Academic Search

Generalized theoretical results for heat transfer in laminar pipe flow with power law varying thermal conductivities are presented. The study is motivated by experimental observations that above a threshold shear rate the effective thermal conductivity for disperse two-phase mixtures increases with shear rate. Using a relatively general three parameter power law model for conductivity as a function of shear rate,

C. W. Sohn; M. M. Chen

1984-01-01

143

Exploring the origin of power law distribution in single-molecule conformation dynamics: Energy landscape perspectives  

Microsoft Academic Search

We explored the origin of power law distribution observed in single-molecule conformational dynamics experiments. By establishing a kinetic master equation approach to study statistically the microscopic state dynamics, we show that the underlying landscape with exponentially distributed density of states leads to power law distribution of kinetics. The exponential density of states emerges when the system becomes glassy and landscape

Jin Wang; Li Xu; Kang Xue; Erkang Wang

2008-01-01

144

Relative performance of supercritical binary geothermal power cycles with in-tube condensors in different orientations  

SciTech Connect

The Heat Cycle Research Program, which is conducted for the Department of Energy, has as its objective the development of the technology for effecting the improved utilization of moderate temperature geothermal resources. The current testing involves the investigation of the performance of binary power cycles utilizing mixtures of non-adjacent hydrocarbons as the working fluids, with supercritical vaporization and in-tube condensation. The utilization of these concepts will improve the net geofluid effectiveness (net plant output per unit mass of geofluid) about 20% over that of a conventional binary power plant. The major prerequisite for this improvement is the achievement of integral, countercurrent condensation. Results are presented for testing of the performance of the condenser at different tube inclinations. The performance in the vertical orientation is better than in either the horizontal or inclined orientations. 7 refs., 8 figs.

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

1989-01-01

145

Power-Law Correlated Disorder in Graphene and Square Nanoribbons  

NASA Astrophysics Data System (ADS)

Two dimensional metal-insulator transitions have remained an active topic in condensed matter physics do to the lack of a general model that can predict when an MIT occurs. With the creation of truly 2D crystals and nanostructures, the question has become increasingly relevant. Though initially predicted to not contain a MIT transition, the inclusion of electron-electron interactions and/or spatial disorder can drive a MIT in some 2D systems. In the case of graphene, correlated ripples are present even when the nanoribbons are freestanding and can have an effect on the transport properties while electron-electron interactions are normally considered negligible. To explore the effect of ripples, we model graphene with a long-range power-law spatial correlation of the form = 1/(1 + |ri/a|)^? where ?i, r, a, and ? are the on-site energy, position, lattice constant, and strength of the correlation respectively. It should be noted that much work has been completed on short-range correlations but little on truly long-range correlations. We also present our finding for the square lattice for comparison.[4pt] [1] Abrahams E. Phys. Rev. Lett. 42, 673-676 (1979)[0pt] [2] Abrahams E. Ann. Phys. 8 (1999) 7-9, 539-548

Sandler, Nancy; Petersen, Greg

2012-02-01

146

Evaluation of detection model performance in power-law noise  

NASA Astrophysics Data System (ADS)

Two alternative forced-choice (2AFC) nodule detection performances of a number of model observers were evaluated for detection of simulated nodules in filtered power-law (1/f3) noise. The models included the ideal observer, the channelized Fisher-Hotelling (FH) model with two different basis function sets, the non-prewhitening matched filter with an eye filter (NPWE), and the Rose model with no DC response (RoseNDC). Detectability of the designer nodule signal was investigated. It has equation s((rho) )equalsA*Rect((rho) /2)(1-(rho) 2)v, where (rho) is a normalized distance (r/R), R is the nodule radius and A is signal amplitude. The nodule profile can be changed (designed) by changing the value of v. For example, the result is a sharp-edged, flat-topped disc for v equal to zero and the projection of a sphere for v equal to 0.5. Human observer experiments were done with nodules based on v equal to 0, 0.5 and 1.5. For the v equal to 1.5 case, human results could be well fitted using a variety of models. The human CD diagram slopes were -0.12, +0.27 and +0.44 for v equal to 0, 0.5 and 1.5 respectively.

Burgess, Arthur E.

2001-06-01

147

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

NASA Astrophysics Data System (ADS)

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

Todorova, Lora; Vogt, Bodo

2011-11-01

148

Operational upset transients in a dual boiling binary cycle geothermal power plant  

Microsoft Academic Search

The effects of operational upsets (such as a valve or pump failure) on a dual boiling binary power plant with isobutane as the working fluid are discussed. These results are based on a mathematical simulation using vendor specifications of the existing components and materials in the 5MW(e) Raft River Pilot Plant. The major problems which can result are excessive heat-up

D. J. Wiggins; C. J. Bliem

1980-01-01

149

Failure analysis report: Heat exchanger tubes geothermal binary power plant, Magma Electric Company, East Mesa, California  

Microsoft Academic Search

Radian received twelve sections of heat exchanger tubing from the Magma Electric Company's 10MW(e) East Mesa binary geothermal power plant. Three tube sections were received from each of four shell and tube heat exchangers (HX1, Hx6, HX8, and Hx10) of the isobutane vaporizer train. All samples were taken from the upper few rows of tubes. Two months later, four more

Dennis M. Anliker; Peter F. II Ellis

1982-01-01

150

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

Microsoft Academic Search

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

Oguz Arslan; Ozge Yetik

2011-01-01

151

Special function instruments for binary cycle geothermal power plants  

SciTech Connect

Three special instruments have been designed to support plant operations at the Heber geothermal power plant in Heber, California. All are aids to give operating information which no commercial instruments can provide. The first is a package for determining CO/sub 2/ breakout conditions for a particular brine. Brine is sampled continuously at either the wellhead or the plant inlet. A temperature-pressure curve is generated which will span all possible operating combinations. That information tells designers or operators what pump pressures must be used to keep the CO/sub 2/ in solution. A second package unit will detect the presence of ppM levels of isobutane in either brine or water streams. It samples actual flowing brine streams continuously. The function is to alert operators when leaks are occurring in heat exchangers. A final unit senses water in flowing hydrocarbon streams. The sampled streams can be either liquid or vapor. Sensitivity is close to actual solubility limit for water in isobutane. This device warns operators when their hydrocarbon has been contaminated with brine (or cooling water).

Robertus, R.J.; Shannon, D.W.; Sullivan, R.G.

1984-04-01

152

Preliminary Performance Estimates and Value Analyses for Binary Geothermal Power Plants Using Ammonia-Water Mixtures as Working Fluids.  

National Technical Information Service (NTIS)

The use of ammonia-water mixtures as working fluids in binary geothermal power generation systems is investigated. The available thermodynamic data is discussed and the methods of extrapolating this data to give the quantities needed to perform analyses o...

C. J. Bliem

1983-01-01

153

Upper-truncated power laws and self-similar criticality in geophysical processes  

NASA Astrophysics Data System (ADS)

Cumulative number-size distributions associated with many natural phenomena follow a power law. A data set that follows a power law may be fractal since both power laws and fractals are scale invariant. For many data sets of natural processes, the cumulative number-size distribution exhibits a "fall-off" from a power law as the measured object size increases. Previous attempts to analyze such distributions have often either ignored the fall-off region or described this region with a different function. We show that when a data set is abruptly truncated at large object size, fall-off from a power law is expected for the cumulative distribution. We derive functions to describe this fall-off for both linearly and logarithmically binned data. These functions lead to a generalized function, the upper-truncated power law, that is independent of binning method. Fitting the upper-truncated power law to a cumulative number-size distribution determines the parameters of the power law, thus providing the scaling exponent of the data. Using the upper-truncated power law, we analyze distributions associated with the following natural processes: forest fire areas in the Australian Capital Territory, fault offsets in the Vernejoul coal field, hydrocarbon volumes in the Frio Strand Plain exploration play, fault lengths on the plains of Venus, earthquake magnitudes associated with subduction of the Nazca plate, and hotspot seamount volumes in the Easter Island/Salas y Gomez seamount chain (ESC). In all cases, the upper-truncated power law provides a better description of the data than does a single power law. Applying the upper-truncated power law to earthquake cumulative frequency-magnitude distributions provides new insight into the reported change in b-value preceding large earthquakes. To understand hotspot seamount volume distributions, we develop a model where uniform energy input produces events initiated on a self-similar distribution of critical cells. We call this model Self-Similar Criticality (SSC). By allowing the spatial distribution of magma migration to be self-similar, the SSC model recreates the observed ESC seamount volume distribution. The SSC model may provide a connection between fractal geometry and observed power law distributions for other natural systems such as forest fires and landslides.

Burroughs, Stephen M.

2001-07-01

154

Multiplicative processes and power laws in human reaction times derived from hyperbolic functions  

NASA Astrophysics Data System (ADS)

In sensory psychophysics reaction time is a measure of the stochastic latency elapsed from stimulus presentation until a sensory response occurs as soon as possible. A random multiplicative model of reaction time variability is investigated for generating the reaction time probability density functions. The model describes a generic class of hyperbolic functions by Piéron's law. The results demonstrate that reaction time distributions are the combination of log-normal with power law density functions. A transition from log-normal to power law behavior is found and depends on the transfer of information in neurons. The conditions to obtain Zipf's law are analyzed.

Medina, José M.

2012-04-01

155

AEGIS: A Multiwavelength Study of Spitzer Power-law Galaxies  

NASA Astrophysics Data System (ADS)

This paper analyzes a sample of 489 Spitzer/Infrared Array Camera (IRAC) sources in the Extended Groth Strip (EGS), whose spectral energy distributions fit a red power law (PL) from 3.6 to 8.0 ?m. The median redshift for sources with known redshifts is langzrang = 1.6. Though all or nearly all of the sample galaxies are likely to be active galactic nuclei (AGNs), only 33% were detected in the EGS X-ray survey (AEGIS-X) using 200 ks Chandra observations. The detected sources are X-ray luminous with L X>1043 erg s-1 and moderately to heavily obscured with N H>1022 cm-2. Stacking the X-ray-undetected sample members yields a statistically significant X-ray signal, suggesting that they are on average more distant or more obscured than sources with X-ray detections. The ratio of X-ray to mid-infrared fluxes suggests that a substantial fraction of the sources undetected in X-rays are obscured at the Compton-thick level, in contrast to the X-ray-detected sources, all of which appear to be Compton thin. For the X-ray-detected PL sources with redshifts, an X-ray luminosity L X ~ 1044 erg s-1 marks a transition between low-luminosity, blue sources dominated by the host galaxy to high-luminosity, red PL sources dominated by nuclear activity. X-ray-to-optical ratios, infrared variability, and 24 ?m properties of the sample are consistent with the identification of infrared PL sources as active nuclei, but a rough estimate is that only 22% of AGNs are selected by the PL criteria. Comparison of the PL selection technique and various IRAC color criteria for identifying AGNs confirms that high-redshift samples selected via simple IRAC colors may be heavily contaminated by starlight-dominated objects.

Park, S. Q.; Barmby, P.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G.; Georgakakis, A.; Ivison, R. J.; Konidaris, N. P.; Miyazaki, S.; Nandra, K.; Rosario, D. J.

2010-07-01

156

Frequency-power-law scattering by fractal inclusions  

NASA Astrophysics Data System (ADS)

Since the 1980s, the concept of fractals has been increasingly adopted in geophysics. Here, we study scattering by fractal inclusions which, under isothermal conditions, causes energy loss of the directly propagated field. If the medium follows a fractal model, then the effective sound velocity c averaged over the characteristic length is c(?)propto?1-?, where ? is the angular frequency and the parameter ? characterizes the scale dependence of the bulk or shear modulus. This frequency-power-law (FPL) relation leads to a wave equation of hereditary type with a fractional-power derivative operator. The corresponding causal point-source solution has an analytic form. It is expressed in terms of the special function f?(t)=L-1srightarrow t\\{exp(-s?)\\}, where L-1srightarrow t represents the one-sided inverse Laplace transform supported on tin[0,propto]. Memory effects cause smoothing of the wavefield in the vicinity of the wavefront and a rapid amplitude decay far from the wavefront. In addition, a significant FPL pulse delay can be identified. In practice, this time delay can be measured during migration velocity analysis to estimate the fractal dimension D related to the dispersion parameter ?. To examine the FPL dependence of direct body waves propagating in a homogeneous medium containing fractal inhomogeneities, we compute acoustic finite-difference snapshots in the frequency range f= 20-200 Hz. In contrast to regular fractals, the percolation model is constructed using the theory of percolation pertaining to stochastic geometry. This model is universal in the sense that it arises from randomly distributed particles provided their concentration is sufficiently high. This is why the use of percolation models allows quantitative characterization of real fracture/fault patterns and multi-scale interpretation of log data. The fractal structure of the model is very prominent because of frequency-dependent scattering with intrinsic correlation over a wide range of scales. We start by computing the F-K spectrum P for the scattered data. Next, the peak envelope of the k-averaged spectrum (P) is computed as a function of frequency f. The slope of a least-squares fit of the data (P) in the log-log domain gives an estimate of D. Results are important for inelastic depth imaging, inverse Q filtering, fracture detection, and integrated geophysical reservoir monitoring.

Rok, V.; Druzhinin, A.; Evans, J. R.; Li, X.-Y.

2003-04-01

157

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

PubMed Central

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

Touboul, Jonathan; Destexhe, Alain

2010-01-01

158

AEGIS: A MULTIWAVELENGTH STUDY OF SPITZER POWER-LAW GALAXIES  

SciTech Connect

This paper analyzes a sample of 489 Spitzer/Infrared Array Camera (IRAC) sources in the Extended Groth Strip (EGS), whose spectral energy distributions fit a red power law (PL) from 3.6 to 8.0 {mu}m. The median redshift for sources with known redshifts is (z) = 1.6. Though all or nearly all of the sample galaxies are likely to be active galactic nuclei (AGNs), only 33% were detected in the EGS X-ray survey (AEGIS-X) using 200 ks Chandra observations. The detected sources are X-ray luminous with L {sub X}>10{sup 43} erg s{sup -1} and moderately to heavily obscured with N {sub H}>10{sup 22} cm{sup -2}. Stacking the X-ray-undetected sample members yields a statistically significant X-ray signal, suggesting that they are on average more distant or more obscured than sources with X-ray detections. The ratio of X-ray to mid-infrared fluxes suggests that a substantial fraction of the sources undetected in X-rays are obscured at the Compton-thick level, in contrast to the X-ray-detected sources, all of which appear to be Compton thin. For the X-ray-detected PL sources with redshifts, an X-ray luminosity L {sub X} {approx} 10{sup 44} erg s{sup -1} marks a transition between low-luminosity, blue sources dominated by the host galaxy to high-luminosity, red PL sources dominated by nuclear activity. X-ray-to-optical ratios, infrared variability, and 24 {mu}m properties of the sample are consistent with the identification of infrared PL sources as active nuclei, but a rough estimate is that only 22% of AGNs are selected by the PL criteria. Comparison of the PL selection technique and various IRAC color criteria for identifying AGNs confirms that high-redshift samples selected via simple IRAC colors may be heavily contaminated by starlight-dominated objects.

Park, S. Q.; Barmby, P.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Georgakakis, A. [National Observatory of Athens, I. Metaxa and V. Paulou, Athens 15236 (Greece); Ivison, R. J. [UK Astronomy Technology Centre, Science and Technology Facilities Council, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Konidaris, N. P.; Rosario, D. J. [UCO/Lick Observatory, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Miyazaki, S. [National Astronomical Observatory of Japan, Osawa Mitaka, Tokyo 181-8588 (Japan); Nandra, K., E-mail: spark@cfa.harvard.ed [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

2010-07-10

159

The power of power-laws: Or how to save power in SoC  

Microsoft Academic Search

Power and energy issues have signifi- cantly gained in importance in computing environ- ments in the last few decades. In a world of mobile devices and massive-scale data centers, low-power systems are crucial for cost, availability, and the environment. Minimizing power consumption in a computing system is a complex problem that can be addressed with various strategies and on various

Christof Teuscher; Haera Chung; Allen Grimm; Avinash Amarnath; Neha Parashar

2011-01-01

160

The Sliding of a Rigid Indentor Over a Power Law Viscoelastic Halfspace.  

National Technical Information Service (NTIS)

Closed form solutions are obtained for the problem of a rigid asperity sliding with Coulomb friction over a power law viscoelastic halfspace. The dual integral equations relating the unknown normal traction under the contact interval (also unknown) to the...

A. Nachman J. R. Walton R. A. Schapery

1977-01-01

161

Symmetries of boundary layer equations of power-law fluids of second grade  

NASA Astrophysics Data System (ADS)

A modified power-law fluid of second grade is considered. The model is a combination of power-law and second grade fluid in which the fluid may exhibit normal stresses, shear thinning or shear thickening behaviors. The equations of motion are derived for two dimensional incompressible flows, and from which the boundary layer equations are derived. Symmetries of the boundary layer equations are found by using Lie group theory, and then group classification with respect to power-law index is performed. By using one of the symmetries, namely the scaling symmetry, the partial differential system is transformed into an ordinary differential system, which is numerically integrated under the classical boundary layer conditions. Effects of power-law index and second grade coefficient on the boundary layers are shown and solutions are contrasted with the usual second grade fluid solutions.

Pakdemirli, Mehmet; Aksoy, Yi?it; Yürüsoy, Muhammet; Khalique, Chaudry Masood

2008-12-01

162

Restoring phase coherence in a one-dimensional superconductor using power-law electron hopping  

NASA Astrophysics Data System (ADS)

In a one-dimensional (1D) superconductor, zero-temperature quantum fluctuations destroy phase coherence. Here we put forward a mechanism which can restore phase coherence: power-law hopping. We study a 1D attractive-U Hubbard model with power-law hopping using Abelian bosonization and density-matrix renormalization group (DMRG) techniques. The parameter that controls the hopping decay acts as the effective, noninteger spatial dimensionality deff. For real-valued hopping amplitudes we identify analytically a range of parameters for which power-law hopping suppresses fluctuations and restores superconducting long-range order for any deff>1, at zero temperature. A detailed DMRG analysis fully supports these findings. These results are also of direct relevance to quantum magnetism as our model can be mapped onto an S=1/2 XXZ spin chain with power-law decaying couplings, which can be studied experimentally with cold-ion-trap techniques.

Lobos, Alejandro M.; Tezuka, Masaki; García-García, Antonio M.

2013-10-01

163

Explanation of power law behavior of autoregressive conditional duration processes based on the random multiplicative process  

NASA Astrophysics Data System (ADS)

Autoregressive conditional duration (ACD) processes, which have the potential to be applied to power law distributions of complex systems found in natural science, life science, and social science, are analyzed both numerically and theoretically. An ACD(1) process exhibits the singular second order moment, which suggests that its probability density function (PDF) has a power law tail. It is verified that the PDF of the ACD(1) has a power law tail with an arbitrary exponent depending on a model parameter. On the basis of theory of the random multiplicative process a relation between the model parameter and the power law exponent is theoretically derived. It is confirmed that the relation is valid from numerical simulations. An application of the ACD(1) to intervals between two successive transactions in a foreign currency market is shown.

Sato, Aki-Hiro

2004-04-01

164

Explanation of power law behavior of autoregressive conditional duration processes based on the random multiplicative process.  

PubMed

Autoregressive conditional duration (ACD) processes, which have the potential to be applied to power law distributions of complex systems found in natural science, life science, and social science, are analyzed both numerically and theoretically. An ACD(1) process exhibits the singular second order moment, which suggests that its probability density function (PDF) has a power law tail. It is verified that the PDF of the ACD(1) has a power law tail with an arbitrary exponent depending on a model parameter. On the basis of theory of the random multiplicative process a relation between the model parameter and the power law exponent is theoretically derived. It is confirmed that the relation is valid from numerical simulations. An application of the ACD(1) to intervals between two successive transactions in a foreign currency market is shown. PMID:15169127

Sato, Aki-Hiro

2004-04-26

165

Creep Fracture by Coupled Power-Law Creep and Diffusion Under Multiaxial Stress.  

National Technical Information Service (NTIS)

Creep fracture by coupled diffusion and power-law creep is analyzed, using approximate methods, both for uniaxial tension and for axial tension plus a superimposed hydrostatic tension. Over a wide range of stress and temperature, voids grow predominatly b...

A. C. F. Cocks M. F. Ashby

1980-01-01

166

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

167

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

168

Optical solitons with time-dependent dispersion, nonlinearity and attenuation in a power-law media  

Microsoft Academic Search

This paper studies optical solitons in a power-law media with time-dependent coefficients of dispersion, nonlinearity and attenuation. The 1-soliton solution is obtained for the nonlinear Schrödinger’s equation with power-law nonlinearity. In addition, a relation between these coefficients is obtained for the solitons to exist. Finally, the velocity of the soliton is also obtained in terms of these coefficients.

Anjan Biswas

2009-01-01

169

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

170

Momentum and Heat Transfer in Power-Law Fluids Across a Rotating Cylinder: A Numerical Study  

NASA Astrophysics Data System (ADS)

The momentum and energy equations describing the steady cross-flow of power-law fluids past a rotating heated cylinder have been solved numerically. The results highlight the influence of dimensionless rotational velocity (0<=?<=6), power-law index (0.5<=n<=1.5), Prandtl number (1<=Pr<=100) on the drag and lift coefficients for Reynolds number of Re = 40, surface-averaged values of the Nusselt number, detailed flow and temperature fields.

Soares, A. A.; Couto, Nuno T.; Marinho, D.; Rouboa, Abel; Mantha, Vishveshwar; Silva, A.

2011-09-01

171

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

172

Gravity darkening in binary stars  

NASA Astrophysics Data System (ADS)

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

Espinosa Lara, F.; Rieutord, M.

2012-11-01

173

Statistical interpretation of transient current power-law decay in colloidal quantum dot arrays  

NASA Astrophysics Data System (ADS)

A new statistical model of the charge transport in colloidal quantum dot arrays is proposed. It takes into account Coulomb blockade forbidding multiple occupancy of nanocrystals and the influence of energetic disorder of interdot space. The model explains power-law current transients and the presence of the memory effect. The fractional differential analogue of the Ohm law is found phenomenologically for nanocrystal arrays. The model combines ideas that were considered as conflicting by other authors: the Scher-Montroll idea about the power-law distribution of waiting times in localized states for disordered semiconductors is applied taking into account Coulomb blockade; Novikov's condition about the asymptotic power-law distribution of time intervals between successful current pulses in conduction channels is fulfilled; and the carrier injection blocking predicted by Ginger and Greenham (2000 J. Appl. Phys. 87 1361) takes place.

Sibatov, R. T.

2011-08-01

174

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

ERIC Educational Resources Information Center

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

Shih, Kristy Y.; Pyke, Karen

2010-01-01

175

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

176

Performance of a 5-MW(e) binary geothermal-electric power plant  

SciTech Connect

A 5-MW(e) Pilot Geothermal Power Plant was built by the Idaho National Engineering Laboratory (INEL), 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, and compares both component and system performance to the performance predicted prior to operation.

Bliem, C.J.; Fullmer, K.S.; Kochan, R.J.

1983-01-01

177

The causal lossy impulse response of a circular piston evaluated in the time and frequency domains for power law media  

Microsoft Academic Search

Analytical expressions for the time-domain Green's function that exactly solve the wave equation for power-law media with an attenuation term that is proportional to frequency to the power were recently derived. These analytical expressions are causal for power-law exponents less than one and noncausal for power-law exponents greater than or equal to one. A causal expression for the lossy impulse

Christopher T. Johnson; Robert J. McGough

2011-01-01

178

Improved nearside gravity field of the Moon by localizing the power law constraint  

Microsoft Academic Search

The problem associated with the large data gap on the farside of the Moon is addressed for constructing a high-resolution global gravity model. By localizing the power law constraint and making it effective only within the farside and limb regions, we mitigate the undesired power-limiting effect on the nearside. Compared to the solution estimated from Lunar Prospector and other satellite

Shin-Chan Han; Erwan Mazarico; Frank G. Lemoine

2009-01-01

179

Phase scintillations due to equatorial F region irregularities with two-component power law spectrum  

Microsoft Academic Search

Power spectra of weak phase scintillations on a 140-MHz signal, transmitted from the geostationary satellite ATS 6 and observed during premidnight and postmidnight periods at an equatorial station Ootacamund (magnetic dip 6 N), show that the nighttime equatorial F region irregularities in the wavelength range of about hundred meters to a few kilometers exhibit a two-component power law spectrum. The

A. Bhattacharyya; R. G. Rastogi

1986-01-01

180

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

PubMed

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

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

2010-08-03

181

Implications of the Power Law Cutoff Evolution in XTE J1550-564 to the Comptonization Regimes  

NASA Astrophysics Data System (ADS)

We present spectral analysis of data collected using RXTE during two periods of X-ray activity in 1998 and 2000 from the Galactic X-ray black hole binary XTE J1550-564. We particularly concentrate on the behavior of the high energy cutoff (folding energy) of the power law part of the spectrum. The 1998 event was very powerful, showing a quick initial transition from low-hard state to very high state. The power law cutoff energy decreased from low-hard to intermediate states and increased again during transition to very high and high-soft states. For the 2000 outburst we also observe the decrease of the cutoff energy during the start of the state transition, similar to that in 1998 outburst, however the increase of the high energy cutoff is not apparent in this track because the source does not reach the real high-soft state in this event. We attribute this difference in the cutoff energy behavior to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization in photon upscattering. Namely, during the 1998 event higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions the bulk motion should take a leading role in boosting the input soft photons. This observational behavior of the cutoff energy presents an additional evidence of the existence of the converging bulk motion region near the central objects and provides further support for the previously reported index saturations effect as a black hole signature.

Shaposhnikov, Nikolai; Titarchuk, L.

2010-05-01

182

Direct simulation Monte Carlo of rarefied hypersonic flow on power law shaped leading edges  

NASA Astrophysics Data System (ADS)

A numerical study of several parameters that influence the flowfield structure, aerodynamic surface quantities and shock wave structure at rarefied hypersonic flow conditions is conducted on power law shaped leading edges. The calculations are performed with a detailed computer code that properly accounts for nonequilibrium effects and that has been demonstrated to yield excellent comparisons with flight- and ground-test data. The flowfield structure, aerodynamic surface quantities and shock wave structure of power law shaped leading edges are examined in order to provide information on how well these shapes could stand as possible candidates for blunting geometries of hypersonic leading edges. Newtonian flow analysis has shown that these shapes exhibit both blunt and sharp aerodynamic properties. Moreover, computational investigation of minimum-drag bodies at supersonic and moderate hypersonic speeds has indicated that power law shapes for certain exponents yield the lowest wave drag. These qualities make power law shapes strong candidates for leading edge design. A very detailed description of the impact on the flow properties, such as velocity, density, temperature and pressure, has been presented separately in the vicinity of the nose of the leading edges due to changes in their shapes. Numerical solutions show that the shape of the leading edge disturbed the flowfield far upstream, where the domain of influence decreased as the leading edge became aerodynamically sharp. A detailed procedure is presented to predict the pressure gradient along the body surface in a rarefied environment. Numerical solutions show that the pressure gradient behavior follows that predicted by Newtonian theory. It is found that the pressure gradient along the body surface goes to zero at the nose of the leading edge for power law exponents less than 2/3, a characteristic of a blunt body. It is finite for power law exponent of 2/3 and goes to minus infinite for power law exponents larger than 2/3, a characteristic of a sharp body. Numerical solutions show that the stagnation point heating for power law leading edges with finite curvature radius follows that for classical blunt body, i.e., the stagnation point heating is inversely proportional to the square root of the nose radius of the leading edge. For those power law leading edges with zero radius of curvature, the stagnation point heating is not a function of the radius of curvature in the vicinity of the leading edges, but agrees with the continuum prediction far from the stagnation point.

Santos, Wilson Fernando Nogueira Dos

183

Predicting the long tail of book sales: Unearthing the power-law exponent  

NASA Astrophysics Data System (ADS)

The concept of the long tail has recently been used to explain the phenomenon in e-commerce where the total volume of sales of the items in the tail is comparable to that of the most popular items. In the case of online book sales, the proportion of tail sales has been estimated using regression techniques on the assumption that the data obeys a power-law distribution. Here we propose a different technique for estimation based on a generative model of book sales that results in an asymptotic power-law distribution of sales, but which does not suffer from the problems related to power-law regression techniques. We show that the proportion of tail sales predicted is very sensitive to the estimated power-law exponent. In particular, if we assume that the power-law exponent of the cumulative distribution is closer to 1.1 rather than to 1.2 (estimates published in 2003, calculated using regression by two groups of researchers), then our computations suggest that the tail sales of Amazon.com, rather than being 40% as estimated by Brynjolfsson, Hu and Smith in 2003, are actually closer to 20%, the proportion estimated by its CEO.

Fenner, Trevor; Levene, Mark; Loizou, George

2010-06-01

184

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

NASA Astrophysics Data System (ADS)

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

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

185

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

186

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

187

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

188

Failure analysis report: Heat exchanger tubes geothermal binary power plant, Magma Electric Company, East Mesa, California  

SciTech Connect

Radian received twelve sections of heat exchanger tubing from the Magma Electric Company's 10MW(e) East Mesa binary geothermal power plant. Three tube sections were received from each of four shell and tube heat exchangers (HX1, Hx6, HX8, and Hx10) of the isobutane vaporizer train. All samples were taken from the upper few rows of tubes. Two months later, four more tube sections were received. These four sections were taken from the lower rows of heat exchangers 1, 6 (two sections), and 10. Radian was requested to investigate the cause of severe pitting failure of these heat exchanger tubes. This report is part of a continuing DOE effort to gain insight into the service life of component materials employed in geothermal energy utilization.

Anliker, Dennis M.; Ellis, Peter F. II

1982-05-01

189

Power-laws from critical gravitiational collapse: The mass distribution of subsolar objects  

NASA Astrophysics Data System (ADS)

At large mass, the initial mass function [IMF], which describes the size distribution of stellar objects, is characterized by a power-law with the Salpeter exponent. At small [substellar] mass, theory indicates that there must be some change in this power law. Indeed, direct observation indicates that the IMF is certainly modified below approximately one-tenth of a solar mass. We demonstrate that at very low mass the IMF should again be given by a power law with an exponent opposite in sign to the high-mass exponent. Furthermore, we verify that this low-mass exponent is in principle calculable via dynamical systems theory applied to gravitational collapse. Observational data indicate a broad agreement with the sign of the low-mass exponent, and a preponderance of evidence pointing to a critical mass-scaling exponent approximately equal to two.

Yunes, Nicolas; Visser, Matt

2004-05-01

190

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.

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

191

Origin of Power Laws for Reactions at Metal Surfaces Mediated by Hot Electrons  

NASA Astrophysics Data System (ADS)

A wide range of experiments have established that certain chemical reactions at metal surfaces can be driven by multiple hot-electron-mediated excitations of adsorbates. A high transient density of hot electrons is obtained by means of femtosecond laser pulses and a characteristic feature of such experiments is the emergence of a power law dependence of the reaction yield on the laser fluence ?Fn. We propose a model of multiple inelastic scattering by hot electrons which reproduces this power law and the observed exponents of several experiments. All parameters are calculated within density functional theory and the delta self-consistent field method. With a simplifying assumption, the power law becomes exact and we obtain a simple physical interpretation of the exponent n, which represents the number of adsorbate vibrational states participating in the reaction.

Olsen, Thomas; Schiøtz, Jakob

2009-12-01

192

Holographic f(T)-gravity model with power-law entropy correction  

NASA Astrophysics Data System (ADS)

Using the correspondence between the f(T)-gravity model and the holographic dark energy model with the power-law entropy correction, we reconstruct the holographic f(T)-gravity model with the power-law entropy correction. We fit the model parameters by using the latest observational data including type Ia supernovae, baryon acoustic oscillations, cosmic microwave background, and Hubble parameter data. We also check the viability of our model using a cosmographic analysis approach. Using the best-fit values of the model, we obtain the evolutionary behavior of the effective torsion equation-of-state parameter of the power-law entropy-corrected holographic f(T)-gravity model, as well as the deceleration parameter of the Universe. We also investigate different energy conditions in our model. Furthermore, we examine the validity of the generalized second law of gravitational thermodynamics. Finally, we point out the growth rate of the matter density perturbation in our model. We conclude that in the power-law entropy-corrected holographic f(T)-gravity model, the Universe begins a matter-dominated phase and approaches a de Sitter regime at late times, as expected. It also can justify the transition from the quintessence state to the phantom regime in the near past, as indicated by recent observations. Moreover, this model is consistent with current data, it passes the cosmographic test, and it fits the data of the growth factor as well as the ?CDM model.

Karami, K.; Asadzadeh, S.; Abdolmaleki, A.; Safari, Z.

2013-10-01

193

Generating Discrete Power-Law Distributions from a Death- Multiple Immigration Population Process  

NASA Astrophysics Data System (ADS)

We consider the evolution of a simple population process governed by deaths and multiple immigrations that arrive with rates particular to their order. For a particular choice of rates, the equilibrium solution has a discrete power-law form. The model is a generalization of a process investigated previously where immigrants arrived in pairs [1]. The general properties of this model are discussed in a companion paper. The population is initiated with precisely M individuals present and evolves to an equilibrium distribution with a power-law tail. However the power-law tails of the equilibrium distribution are established immediately, so that moments and correlation properties of the population are undefined for any non-zero time. The technique we develop to characterize this process utilizes external monitoring that counts the emigrants leaving the population in specified time intervals. This counting distribution also possesses a power-law tail for all sampling times and the resulting time series exhibits two features worthy of note, a large variation in the strength of the signal, reflecting the power-law PDF; and secondly, intermittency of the emissions. We show that counting with a detector of finite dynamic range regularizes naturally the fluctuations, in effect `clipping' the events. All previously undefined characteristics such as the mean, autocorrelation and probabilities to the first event and time between events are well defined and derived. These properties, although obtained by discarding much data, nevertheless possess embedded power-law regimes that characterize the population in a way that is analogous to box averaging determination of fractal-dimension.

Matthews, J. O.; Jakeman, E.; Hopcraft, K. I.

2003-04-01

194

Universality of the power-law approach to the jamming limit in random sequential adsorption dynamics.  

PubMed

Random sequential adsorption (RSA), on a two-dimensional continuum substrate, of different types of zero area objects that disallow domain formation and hence lead to jamming, is examined by simulation. In all the cases, in the asymptotic time regime, the approach of the number density rho(t) at instant t to jamming density rho(infinity) is found to exhibit power law rho(infinity)-rho(t) approximately t{-p} as that for RSA of finite area objects. These results suggest the possibility of the power law being universal for all jamming systems in RSA on a continuum substrate. A generalized analytical treatment is also proposed. PMID:17677210

Shelke, Pradip B; Khandkar, M D; Banpurkar, A G; Ogale, S B; Limaye, A V

2007-06-07

195

Power Law Inflation and the Cosmic No Hair Theorem in Brane World  

SciTech Connect

We study the cosmic no hair theorem for anisotropic Bianchi models that admit power law inflation with a scalar field in the framework of Brane world. The power law inflationary solution obtained here is driven by the curvature term in the modified field equation in Brane. It is found that all Bianchi models except Bianchi type IX, transit to an inflationary regime with vanishing anisotropy. We note that in the Brane world anisotropic universe isotropizes much faster than that in the general theory of relativity.

Paul, B. C. [Physics Department, North Bengal University, Siliguri, Pin: 734 013 (India); Beesham, A. [Department of Mathematical Sciences, Zululand University, Kwadlangezwa (South Africa)

2006-11-03

196

Power law distribution of the frequency of demises of US firms  

NASA Astrophysics Data System (ADS)

Both theoretical and applied economics have a great deal to say about many aspects of the firm, but the literature on the extinctions, or demises, of firms is very sparse. We use a publicly available data base covering some 6 million firms in the US and show that the underlying statistical distribution which characterises the frequency of firm demises-the disappearances of firms as autonomous entities-is closely approximated by a power law. The exponent of the power law is, intriguingly, close to that reported in the literature on the extinction of biological species.

Cook, William; Ormerod, Paul

2003-06-01

197

Preliminary performance estimates and value analyses for binary geothermal power plants using ammonia-water mixtures as working fluids  

Microsoft Academic Search

The use of ammonia-water mixtures as working fluids in binary geothermal power generation systems is investigated. The available thermodynamic data is discussed and the methods of extrapolating this data to give the quantities needed to perform analyses of the system is given. It is indicated that for a system without a recuperator and with a working fluid which is 50%

C. J. Bliem

1983-01-01

198

Earthquake accelerogram simulation with statistical law of evolutionary power spectrum  

Microsoft Academic Search

By using the technique for evolutionary power spectrum proposed by Nakayama and with reference to the Kameda formula, an evolutionary\\u000a spectrum prediction model for given earthquake magnitude and distance is established based on the 80 near-source acceleration\\u000a records at rock surface with large magnitude from the ground motion database of western U.S.. Then a new iteration method\\u000a is developed for

Cui-Ran Zhang; Hou-Qun Chen; Min Li

2007-01-01

199

Quantization and truncation conditions of fourier power spectrum for good performance in binary subtracted joint transform correlator  

NASA Astrophysics Data System (ADS)

Binary subtracted joint transform correlator (BSJTC) provides sharp autocorrelation peaks and better discrimination for similar targets even though many reference images are arranged regularly in an input scene. The effects of the number of reference patterns, the quantization levels and truncation of the Fourier power spectra on the performance of BSJTC are investigated. The number of effective quantization levels to obtain sharp and clear autocorrelation peaks is estimated by computer simulations using the input scenes with many binary images (alphabetic characters) and halftone images (human portraits). Experimental results of BSJTC are also shown using a hybrid system with a Bi12SiO20 spatial light modulator and a personal computer.

Osugi, Yukihisa; Mizukawa, Hiromitsu; Minemoto, Takumi

1996-05-01

200

Earthquake accelerogram simulation with statistical law of evolutionary power spectrum  

NASA Astrophysics Data System (ADS)

By using the technique for evolutionary power spectrum proposed by Nakayama and with reference to the Kameda formula, an evolutionary spectrum prediction model for given earthquake magnitude and distance is established based on the 80 near-source acceleration records at rock surface with large magnitude from the ground motion database of western U.S.. Then a new iteration method is developed for generation of random accelerograms non-stationary both in amplitude and frequency which are compatible with target evolutionary spectrum. The phase spectra of those simulated accelerograms are also non-stationary in time and frequency domains since the interaction between amplitude and phase angle has been considered during the generation. Furthermore, the sign of the phase spectrum increment is identified to accelerate the iteration. With the proposed statistical model for predicting evolutionary power spectra and the new method for generating compatible time history, the artificial random earthquake accelerograms non-stationary both in amplitude and frequency for certain magnitude and distance can be provided.

Zhang, Cui-Ran; Chen, Hou-Qun; Li, Min

2007-07-01

201

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

202

Percolation and fire spread with power-law flame radiations  

NASA Astrophysics Data System (ADS)

Percolation and non-equilibrium front propagation in a two-dimensional network modeling wildfire spread is studied. The model includes a deterministic long-range interaction induced by flame radiation. It includes also a time weighting process due to the flame residence time and the activation (ignition) energy of the exposed combustible. For the square power decreasing radiation interaction, three weight-dependent regimes were previously found; a dynamical, a static, and a non-propagative regime (Zekri N. et al. Phys. Lett. A, 376 (2012) 2522). The weight effect on the percolation threshold is found here independent of the deterministic interaction. Using the Family-Vicsek scaling ansatz, the front dynamical exponents belong to the Edwards-Wilkinson model universality class at the saturation of the dynamical regime. They are weight dependent beyond saturation.

Khelloufi, K.; Baara, Y.; Zekri, N.

2013-07-01

203

Powering the second 2012 outburst of SN 2009ip by repeating binary interaction  

NASA Astrophysics Data System (ADS)

We propose that the major 2012 outburst of the supernova impostor SN 2009ip was powered by an extended and repeated interaction between the luminous blue variable (LBV) and a more compact companion. Motivated by the recent analysis of Margutti et al. (2013) of ejected clumps and shells, we consider two scenarios. In both scenarios, the major 2012b outburst with total (radiated + kinetic) energy of ˜5 × 1049 erg was powered by accretion of ˜2-5 M? on to the companion during a periastron passage (the first passage) of the binary system approximately 20 d before the observed maximum of the light curve. In the first scenario, the surviving companion scenario, the companion was not destructed and still exists in the system after the outburst. It ejected partial shells (or collimated outflows or clumps) for two consecutive periastron passages after the major one. The orbital period was reduced from ˜38 to ˜25 d as a result of the mass transfer process that took place during the first periastron passage. In the second scenario, the merger scenario, some partial shells/clumps were also ejected in a second periastron passage that took place ˜20 d after the first one. After this second periastron passage, the companion dived too deep into the LBV envelope to launch more outflows and merged with the LBV.

Kashi, Amit; Soker, Noam; Moskovitz, Nitsan

2013-10-01

204

Power-law accelerating growth complex networks with mixed attachment mechanisms  

NASA Astrophysics Data System (ADS)

In this paper, motivated by the thoughts and methods of the mixture of preferential and uniform attachments, we extend the Barabási–Albert (BA) model, and establish a network model with the power-law accelerating growth and the mixture of the two attachment mechanisms. In our model, the number of edges generated by each newly-introduced node is proportional to the power of ? (0??<1) of time t, i.e., mt?. By virtue of the continuum approach, we have deduced the degree distribution P(k,t) of our model with the extended power-law form P(k,t)=A(t)[. When the number of edges k generated by each new node is much greater than the value of B(t), the degree distribution P(k,t) will converge to the power-law form P(k,t)=A(t)k. When k is much less than the value of B(t), the degree distribution P(k,t) will converge to the exponential-law form P(k,t)=A(t)[e. By virtue of numerical simulations, we also discuss the dependence of the degree distribution P(k,t) on the model's parameters (where t is considered as a constant in the simulations). Finally, we investigate the possible application of our model in the spreading and evolution of epidemics in some real-world systems.

Chen, Tao; Shao, Zhi-Gang

2012-04-01

205

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

206

1-soliton solution of ( 1 + 2 )-dimensional nonlinear Schrödinger's equation in dual-power law media  

Microsoft Academic Search

This Letter solves the nonlinear Schrödinger's equation in 1+2 dimensions with dual-power law nonlinearity and obtains the 1-soliton solution. The solitary wave ansatze is used to obtain the solution. A few conserved quantities are calculated using the soliton solution.

Anjan Biswas

2008-01-01

207

Propagation\\/Inversion in viscoelastic power law media: application to ultrasonic laboratory data  

Microsoft Academic Search

Realistic propagation\\/inversion of seismic wave need a model which is mathematically rigorous, physically acceptable and flexible enough. Such a model need to include ab-sorption and dispersion effects and also to satisfy causality principle. Power laws are the simplest models of causal and attenuating media including absorption and dispersion effects. In this work we present an adaptation of viscoelastic inversion originally

A. Ribodetti; A. Hanyga

2003-01-01

208

Optical solitons in a power law media with fourth order dispersion  

Microsoft Academic Search

In this paper, a closed form optical soliton solution is obtained for the nonlinear Schrödinger’s equation with fourth order dispersion in a power law media. The solitary wave ansatze is used to carry out the integration of this equation. Finally, a numerical simulation is given for the closed form soliton solution.

Anjan Biswas; Daniela Milovic

2009-01-01

209

Analysis of Accelerated Life Test Data-Least Squares Methods for the Inverse Power Law Model  

Microsoft Academic Search

This expository paper presents simple least squares methods for analyzing accelerated life test data with the inverse power law model, when all test units are run to failure. These methods are illustrated with accelerated test data on time to break-down of an insulating fluid.

Wayne Nelson; Reader Aids

1975-01-01

210

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

Microsoft Academic Search

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\\/talpha with 0

A. Saichev; D. Sornette

2010-01-01

211

Ideal quantum gases in D-dimensional space and power-law potentials  

Microsoft Academic Search

We investigate ideal quantum gases in D-dimensional space and confined in a generic external potential by using the semiclassical approximation. In particular, we derive density of states, density profiles and critical temperatures for Fermions and Bosons trapped in isotropic power-law potentials. From such results, one can easily obtain those of quantum gases in a rigid box and in a harmonic

Luca Salasnich

2000-01-01

212

Morphological decomposition of sandstone pore–space: fractal power-laws  

Microsoft Academic Search

Morphological decomposition procedure is applied to estimate fractal dimension of a pore–space, which is isolated from a sandstone microphotograph. The fractal dimensions that have been computed by considering various probing rules have precisely followed the universal power-law relationships proposed elsewhere. These results are derived by considering structuring elements such as octagon, square and rhombus that have been used to decompose

Teo Lay Lian; P. Radhakrishnan; B. S. Daya Sagar

2004-01-01

213

Power law for the duration of recession and prosperity in Latin American countries  

NASA Astrophysics Data System (ADS)

Ormerod and Mounfield [P. Ormerod, C. Mounfield, Power law distribution of duration and magnitude of recessions in capitalist economies: Breakdown of scaling, Physica A 293 (2001) 573] and Ausloos et al. [M. Ausloos, J. Mikiewicz, M. Sanglier, The durations of recession and prosperity: Does their distribution follow a power or an exponential law? Physica A 339 (2004) 548] have independently analyzed the duration of recessions for developed countries through the evolution of the GDP in different time windows. It was found that there is a power law governing the duration distribution. We have analyzed data collected from 19 Latin American countries in order to observe whether such results are valid or not for developing countries. The case of prosperity years is also discussed. We observe that the power law of recession time intervals, see Ref. [1], is valid for Latin American countries as well. Thus an interesting point is discovered: the same scaling time is found in the case of recessions for the three data sets (ca. 1 year), and this could represent a universal feature. Other time scale parameters differ significantly from each other.

Redelico, Francisco O.; Proto, Araceli N.; Ausloos, Marcel

2008-11-01

214

Direct simulation Monte Carlo of rarefied hypersonic flow on power law shaped leading edges  

Microsoft Academic Search

A numerical study of several parameters that influence the flowfield structure, aerodynamic surface quantities and shock wave structure at rarefied hypersonic flow conditions is conducted on power law shaped leading edges. The calculations are performed with a detailed computer code that properly accounts for nonequilibrium effects and that has been demonstrated to yield excellent comparisons with flight- and ground-test data.

Wilson Fernando Nogueira Dos Santos

2002-01-01

215

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

NASA Astrophysics Data System (ADS)

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

Greenhall, Charles A.

2010-10-01

216

Semiempirical power-law scaling of new infection rate to model epidemic dynamics with inhomogeneous mixing  

Microsoft Academic Search

The expected number of new infections per day per infectious person during an epidemic has been found to exhibit power-law scaling with respect to the susceptible fraction of the population. This is in contrast to the linear scaling assumed in traditional epidemiologic modeling. Based on simulated epidemic dynamics in synthetic populations representing Los Angeles, Chicago, and Portland, we find city-dependent

Phillip D. Stroud; Stephen J. Sydoriak; Jane M. Riese; James P. Smith; Susan M. Mniszewski; Phillip R. Romero

2006-01-01

217

Hurst exponents, power laws, and efficiency in the Brazilian foreign exchange market  

Microsoft Academic Search

We find evidence of weak informational efficiency in the Brazilian daily foreign exchange market using Hurst exponents (Hurst 1951, 1955, Feder 1988), which offer an alternative (from statistical physics) to traditional econometric gauges. We show that a trend toward efficiency has been reverted since the crisis of 1999. We also find power laws (Mantegna and Stanley 2000) in means, volatilities,

Sergio Da Silva; Annibal Figueiredo; Iram Gleria; Raul Matsushita

2007-01-01

218

Fractal structures and power law spectra in the distant Earth's magnetotail  

Microsoft Academic Search

This paper is aimed at the theoretical understanding of the results obtained from the survey of plasmas and magnetic fields in the Earth's distant magnetotail with the Geotail spacecraft. Our attention is concentrated on the ``kink'' power law spectrum of magnetic field fluctuations proposed by Hoshino et al. [1994] from an analysis of the Geotail data. In the framework of

Alexander V. Milovanov; Lev M. Zelenyi; Gaetano Zimbardo

1996-01-01

219

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

220

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

221

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

SciTech Connect

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

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

2009-09-15

222

On Exploring the Power-Law Relationship in the Itemset Support Distribution  

Microsoft Academic Search

We identify and explore in this paper an important pheno- menon which points out that the power-law relationship appears in the distribution of itemset supports. Characterizing such a relationship will benefit many applications such as providing the direction of tuning the per- formance of the frequent-itemset mining. Nevertheless, due to the explosive number of itemsets, it will be prohibitively expensive

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

2006-01-01

223

Power Density Spectral Analysis as a Method of Compact Object Determination in X-ray Binary Systems  

NASA Astrophysics Data System (ADS)

Mass determinations and X-ray energy spectral analyses are among the methods used to distinguish between the types of compact objects present in X-ray binary systems. We test a method of distinguishing between neutron stars and black holes proposed by Sunyaev and Revnivtsev where power density spectra are used, particularly in the 500-1000Hz range. Sunyaev and Revnivtsev found that only neutron stars appear to have significant power in this frequency range. We apply this criterion to 12 X-ray binary systems (six neutron stars and six black holes) using USA data and cannot reproduce Sunyaev and Revnivtsev's result. The reason for this discrepancy is most likely a USA instrumental effect which manifests itself as excess power in the frequency range of interest. Future work on correcting this problem should provide more accurate analyses that may yield a different result.

Lee, J.

2002-08-01

224

Widespread occurrence of power-law distributions in inter-repeat distances shaped by genome dynamics.  

PubMed

Repetitive DNA sequences derived from transposable elements (TE) are distributed in a non-random way, co-clustering with other classes of repeat elements, genes and other genomic components. In a previous work we reported power-law-like size distributions (linearity in log-log scale) in the spatial arrangement of Alu and LINE1 elements in the human genome. Here we investigate the large-scale features of the spatial arrangement of all principal classes of TEs in 14 genomes from phylogenetically distant organisms by studying the size distribution of inter-repeat distances. Power-law-like size distributions are found to be widespread, extending up to several orders of magnitude. In order to understand the emergence of this distributional pattern, we introduce an evolutionary scenario, which includes (i) Insertions of DNA segments (e.g., more recent repeats) into the considered sequence and (ii) Eliminations of members of the studied TE family. In the proposed model we also incorporate the potential for transposition events (characteristic of the DNA transposons' life-cycle) and segmental duplications. Simulations reproduce the main features of the observed size distributions. Furthermore, we investigate the effects of various genomic features on the presence and extent of power-law size distributions including TE class and age, mode of parental TE transmission, GC content, deletion and recombination rates in the studied genomic region, etc. Our observations corroborate the hypothesis that insertions of genomic material and eliminations of repeats are at the basis of power-laws in inter-repeat distances. The existence of these power-laws could facilitate the formation of the recently proposed "fractal globule" for the confined chromatin organization. PMID:22370293

Klimopoulos, Alexandros; Sellis, Diamantis; Almirantis, Yannis

2012-02-18

225

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

Microsoft Academic Search

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

Andrew M. Edwards

2008-01-01

226

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

227

An Interacting Binary System Powers Precessing Outflows of an Evolved Star  

NASA Astrophysics Data System (ADS)

Stars are generally spherical, yet their gaseous envelopes often appear nonspherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase, when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our finding of a post-common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems.

Boffin, Henri M. J.; Miszalski, Brent; Rauch, Thomas; Jones, David; Corradi, Romano L. M.; Napiwotzki, Ralf; Day-Jones, Avril C.; Köppen, Joachim

2012-11-01

228

An interacting binary system powers precessing outflows of an evolved star.  

PubMed

Stars are generally spherical, yet their gaseous envelopes often appear nonspherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase, when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our finding of a post-common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems. PMID:23139326

Boffin, Henri M J; Miszalski, Brent; Rauch, Thomas; Jones, David; Corradi, Romano L M; Napiwotzki, Ralf; Day-Jones, Avril C; Köppen, Joachim

2012-11-01

229

The Properties of Plane-wave Scintillation Index Curves for 2D Gaussian and Power Law Random Media  

Microsoft Academic Search

The plane-wave fourth-moment equation is solved numerically for two-dimensional homogeneous random media with Gaussian and power-law fluctuation spectra. Scintillation index curves are calculated for scattering strengths ? spanning the range 0·5 to 10. Multiple peaks in the scintillation index curves are found to occur for moderate values of ? (?10) for power-law media with power indices ? greater than ?2·5.

M. C. Cook

1991-01-01

230

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

SciTech Connect

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

Lawal, A. (Univ. of Port Harcourt (Nigeria))

1989-05-01

231

Segmentation of genomic DNA through entropic divergence: Power laws and scaling  

NASA Astrophysics Data System (ADS)

Genomic DNA is fragmented into segments using the Jensen-Shannon divergence. Use of this criterion results in the fragments being entropically homogeneous to within a predefined level of statistical significance. Application of this procedure is made to complete genomes of organisms from archaebacteria, eubacteria, and eukaryotes. The distribution of fragment lengths in bacterial and primitive eukaryotic DNAs shows two distinct regimes of power-law scaling. The characteristic length separating these two regimes appears to be an intrinsic property of the sequence rather than a finite-size artifact, and is independent of the significance level used in segmenting a given genome. Fragment length distributions obtained in the segmentation of the genomes of more highly evolved eukaryotes do not have such distinct regimes of power-law behavior.

Azad, Rajeev K.; Bernaola-Galván, Pedro; Ramaswamy, Ramakrishna; Rao, J. Subba

2002-05-01

232

Modelling memory processes and Internet response times: Weibull or power-law?  

NASA Astrophysics Data System (ADS)

The Weibull distribution is proposed as a model for response times. Theoretical support is offered by classical results for extreme-value distributions. Fits of the Weibull distribution to response time data in different contexts show that this distribution (and the exponential distribution on small time-scales) perform better than the often-suggested power-law and logarithmic function. This study suggests that the power-law can be viewed as an approximation, at neural level, for the aggregate strength of superposed memory traces that have different decay rates in distinct parts of the brain. As we predict, this view does not find support at the level of induced response processes. The distinction between underlying and induced processes might also be considered in other fields, such as engineering, biology and physics.

Chessa, Antonio G.; Murre, Jaap M. J.

2006-07-01

233

Linking multiple relaxation, power-law attenuation, and fractional wave equations.  

PubMed

The acoustic wave attenuation is described by an experimentally established frequency power law in a variety of complex media, e.g., biological tissue, polymers, rocks, and rubber. Recent papers present a variety of acoustical fractional derivative wave equations that have the ability to model power-law attenuation. On the other hand, a multiple relaxation model is widely recognized as a physically based description of the acoustic loss mechanisms as developed by Nachman et al. [J. Acoust. Soc. Am. 88, 1584-1595 (1990)]. Through assumption of a continuum of relaxation mechanisms, each with an effective compressibility described by a distribution related to the Mittag-Leffler function, this paper shows that the wave equation corresponding to the multiple relaxation approach is identical to a given fractional derivative wave equation. This work therefore provides a physically based motivation for use of fractional wave equations in acoustic modeling. PMID:22087931

Näsholm, Sven Peter; Holm, Sverre

2011-11-01

234

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

NASA Astrophysics Data System (ADS)

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

Lawal, A.

1989-05-01

235

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

236

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

237

Power-law singularities in string theory and M-theory  

NASA Astrophysics Data System (ADS)

We extend the definition of the Szekeres Iyer power-law singularities to supergravity, string and M-theory backgrounds, and find that are characterized by Kasner-type exponents. The near singularity geometries of brane and some intersecting brane backgrounds are investigated and the exponents are computed. The Penrose limits of some of these power-law singularities have profiles A ~ u-? for ? >= 2. We find the range of the exponents for which ? = 2 and the frequency squares are bounded by 1/4. We propose some qualitative tests for deciding whether a null or timelike spacetime singularity can be resolved within string theory and M-theory based on the near singularity geometry and its Penrose limits.

Papadopoulos, G.

2004-11-01

238

Flow structure for Power-Law fluids in lid-driven arc-shape cavities  

NASA Astrophysics Data System (ADS)

In this paper the lid-driven flow of a Power-Law fluid in arc-shape cavities is studied. Two different arc cavity cross sections are considered with arc angle ratios r = 1/2 and r = 1/3. The unsteady streamfunction-vorticity formulation is adopted together with a Power-Law constitutive relation. Body-fitted coordinate transformation is applied to generate orthogonal computational grids. The equations are discretized in space using a second order finite difference numerical method. Time integration is performed using fourth order Runge-Kutta explicit scheme. The combined effects of inertia, shear thinning/shear thickening and curved geometry on the vortical structure and velocity profiles are shown. The results are compared to Newtonian fluid case. It is found that under inertia, shear thinning effects lead to the early formation and growth of secondary vortices in the curved cavity, however shear thickening has an opposite effect.

Mercan, Hatice; Atalik, Kunt

2011-06-01

239

Linear current fluctuations in the power-law region of metallic carbon nanotubes  

NASA Astrophysics Data System (ADS)

We study low-frequency noise in a non-Ohmic region of metallic single walled and multiwalled carbon nanotubes. The generalized relative noise appears to be independent of applied bias in the power-law regime of the tubes and in agreement with theoretical predictions. Beyond the power-law regime the suppression of conductance due to scattering with optical phonons is accompanied by a reduction of relative noise by an order of magnitude. Mobility fluctuations in the tubes due to optical phonon scattering cause the unexpected reduction in the relative noise magnitude which is modeled using a modified mobility fluctuation picture. The findings have important implications for metallic nanotubes being used as interconnects in nanoelectronic devices.

Talukdar, D.; Yotprayoonsak, P.; Herranen, O.; Ahlskog, M.

2013-09-01

240

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

SciTech Connect

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. [Universidade Federal do Espirito Santo, Departamento de Fisica, Av. Fernando Ferrari, 514, Campus de Goiabeiras, CEP 29075-910, Vitoria, Espirito Santo (Brazil)

2010-07-15

241

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

Microsoft Academic Search

An analytical investigation of three-dimensional mixed conveciton flow and heat transfer to power-law fluids in horizontal arbitrary cross-sectional ducts is undertaken. The continuity equation and parabolic forms of the energy and momentum equations in rectangular coordinates are transformed into new orthogonal coordinates with the boundaries of the duct coinciding with the coordinate surfaces. The transformed equations are solved by the

A. Lawal

1989-01-01

242

Kinetic Modeling of Hydrodesulphurization of Residual Oils. I. Power Law Model  

Microsoft Academic Search

The kinetics of hydrodesulphurization (HDS) reaction of residual oils at temperatures of 320–440°C has been explored leading to the development of a power law model. The reaction order was found to decrease with increasing temperature from 4.33 to 1.42 while the rate constant increased with temperature from 0.312 to 10.847 kg\\/mol h. The activation energy of 101.0 kJ\\/mol and a frequency factor of

L. O. Oyekunle; B. O. Kalejaiye

2003-01-01

243

Armonique: Experiments in Content-Based Similarity Retrieval using Power-Law Melodic and Timbre Metrics  

Microsoft Academic Search

This paper presents results from an on-going MIR study utilizing hundreds of melodic and timbre features based on power laws for content-based similarity retrieval. These metrics are incorporated into a music search engine prototype, called Armonique. This prototype is used with a corpus of 9153 songs encoded in both MIDI and MP3 to identify pieces similar to and dissimilar from

Bill Z. Manaris; Dwight Krehbiel; Patrick Roos; Thomas Zalonis

2008-01-01

244

Cusp-latitude Pc3 spectra: band-limited and power-law components  

NASA Astrophysics Data System (ADS)

This work attempts to fill a gap in comparative studies of upstream-generated Pc3 4 waves and broad band ULF noise observed at cusp latitudes. We performed a statistical analysis of the spectral properties of three years of cusp-latitude ground magnetometer data, finding that the average daytime Pc3 4 spectra are characterized by two principal components: an upstream-related band-limited enhancement (‘signal’) and a power-law background (‘noise’) with S(f ) a

Ponomarenko, P. V.; Fraser, B. J.; Menk, F. W.; Ables, S. T.; Morris, R. J.

2002-10-01

245

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

246

Convergence of the K2 entropy for random noises with power law spectra  

Microsoft Academic Search

We discuss a counter-example to the traditional expectation that stochastic processes lead to a non-convergence of the K2 entropy in computed or measured time series. We consider a simple class of ``colored'' random noises with power law spectra which have already been shown to generate finite and predictable values of the correlation dimension. We show that the K2 entropy of

A. Provenzale; A. R. Osborne; R. Soj

1991-01-01

247

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

Microsoft Academic Search

We present a time-dependent and spatially inhomogeneous solution that interpolates the extremal Reissner-Nordstroem (RN) black hole and the Friedmann-Lemaitre-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

Kei-ichi Maeda; Masato Nozawa

2010-01-01

248

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

Microsoft Academic Search

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

Kei-Ichi Maeda; Masato Nozawa

2010-01-01

249

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

2010-12-28

250

Laboratory Constraints on Chameleon Dark Energy and Power-Law Fields  

SciTech Connect

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.

Steffen, J. H.; Baumbaugh, A.; Chou, A. S.; Mazur, P. O.; Tomlin, R.; Wester, W. [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510 (United States); Upadhye, A. [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637 (United States); Weltman, A. [Astrophysics, Cosmology and Gravity Centre, University of Cape Town, Rondebosch, Private Bag, 7700 (South Africa)

2010-12-31

251

Evidence of percolation related power law behavior in the thermal conductivity of nanotube/polymer composites  

NASA Astrophysics Data System (ADS)

A power law relation for the thermal conductivity, indicative of percolation, is reported through measurements on carbon nanotube/polymer composites. Our results contradict earlier assertions and indicate that synthesis methodologies may be adapted to facilitate such behavior. Consistent modeling of the experimentally determined electrical and thermal conductivity anisotropy, in addition to the incorporation of interfacial resistance, was used to understand the underlying mechanisms and variations.

Kim, B.-W.; Park, S.-H.; Kapadia, R. S.; Bandaru, P. R.

2013-06-01

252

Single-parameter power law psychophysics of auditory numerosity and the psychological moment hypothesis  

Microsoft Academic Search

In the present study, numerosity estimation was investigated. A two-parameter Stevens power law analysis was performed on\\u000a a total of944 subjects in six experiments. Two pulse ranges (2–17 or 17–253 pulses) and six pulse rates (either constant or\\u000a randomly varied within trial blocks) were used, variously, in an unsuccessful attempt to find evidence for a psychological\\u000a moment, under the supposition

George H. Robinson

1992-01-01

253

Effects of Diversity and Procrastination in Priority Queuing Theory: the Different Power Law Regimes  

Microsoft Academic Search

Empirical analysis show that, after the update of a browser, the publication\\u000aof the vulnerability of a software, or the discovery of a cyber worm, the\\u000afraction of computers still using the older version, or being not yet patched,\\u000aor exhibiting worm activity decays as power laws $\\\\sim 1\\/t^{\\\\alpha}$ with $0 <\\u000a\\\\alpha \\\\leq 1$ over time scales of years.

A. Saichev; Didier Sornette

2009-01-01

254

Universality of the power-law approach to the jamming limit in random sequential adsorption dynamics  

Microsoft Academic Search

Random sequential adsorption (RSA), on a two-dimensional continuum substrate, of different types of zero area objects that disallow domain formation and hence lead to jamming, is examined by simulation. In all the cases, in the asymptotic time regime, the approach of the number density rho(t) at instant t to jamming density rho(?) is found to exhibit power law rho(?)-rho(t)˜t-p as

Pradip B. Shelke; M. D. Khandkar; A. G. Banpurkar; S. B. Ogale; A. V. Limaye

2007-01-01

255

Deterministic Small-World Graphs and the Eigenvalue Power Law of Internet  

Microsoft Academic Search

Many relevant real-life networks like the WWW, Internet, transportation and communication networks, or even biological and social networks can be modelled by small-world scale-free graphs. These graphs have strong local clustering (vertices have many mutual neighbors), a small diameter and a distribution of degrees according to a power law. On the other hand, the knowledge of the spectrum of a

Francesc Comellas; Silvia Gago

2004-01-01

256

On the Power-Law of the Internet and the Hierarchy of BGP Convergence  

Microsoft Academic Search

Border Gateway Protocol (BGP) is the de facto inter-domain routing protocol. With the rapid development of the Internet, the\\u000a convergence problem of BGP attracts more attention. This paper analyzes the relationship between BGP convergence and the characteristics\\u000a of the Internet. The Internet is classified into three hierarchies based on the power-law and commercial relations of autonomous\\u000a systems. The relation of

Peidong Zhu; Jinjing Zhao; Yan Wen; Kaiyu Cai

2007-01-01

257

Power-law numerical solution for post-die extrusion of plastic pipe  

Microsoft Academic Search

In a continuous plastic-pipe extrusion, melt emerges from an annular die and is then drawn freely into a sizing sleeve. Here, we investigate this extensional flow when a pressure difference is applied across the melt cone. A numerical solution to a power-law fluid is presented. Differential equations for the melt-cone shape are derived from a force balance on the melt

Aaron J. Hade; A. Jeffrey Giacomin

2002-01-01

258

Bending the power law: A CMPL theory of strategy shifts and the automatization of cognitive skills  

Microsoft Academic Search

The shift with practice from use of generic, multistep problem-solving strategies to fast and relatively effortless memory-based strategies, was explored in 2 experiments using pseudoa- rithmetic tasks. A complete transition to the memory strategy occurred by about the 60th exposure to each problem. The power law of practice did not hold in the overall data for either the mean or

Timothy C. Rickard

1997-01-01

259

A power-law model of blood flow through a tapered overlapping stenosed artery  

Microsoft Academic Search

A mathematical model of non-Newtonian blood flow through a tapered stenotic artery is considered. The non-Newtonian model chosen is characterized by the generalized power-law model incorporating the effect of tapering due to the pulsatile nature of blood flow. The flow is assumed to be unsteady, laminar, two-dimensional and axisymmetric. The governing equations of motion in terms of the viscous shear

Zuhaila Ismail; Ilyani Abdullah; Norzieha Mustapha; Norsarahaida Amin

2008-01-01

260

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

261

Evidence for intermittency and a truncated power law from highly resolved aphid movement data  

PubMed Central

Power laws are increasingly used to describe animal movement. Despite this, the use of power laws has been criticized on both empirical and theoretical grounds, and alternative models based on extensions of conventional random walk theory (Brownian motion) have been suggested. In this paper, we analyse a large volume of data of aphid walking behaviour (65 068 data points), which provides a highly resolved dataset to investigate the pattern of movement. We show that aphid movement is intermittent—with alternations of a slow movement with frequent change of direction and a fast, relatively directed movement—and that the fast movement consists of two phases—a strongly directed phase that gradually changes into an uncorrelated random walk. By measuring the mean-squared displacement and the duration of non-stop movement episodes we found that both spatial and temporal aspects of aphid movement are best described using a truncated power law approach. We suggest that the observed spatial pattern arises from the duration of non-stop movement phases rather than from correlations in turning angles. We discuss the implications of these findings for interpreting movement data, such as distinguishing between movement and non-movement, and the effect of the range of data used in the analysis on the conclusions.

Mashanova, Alla; Oliver, Tom H.; Jansen, Vincent A. A.

2010-01-01

262

On the transition from power law creep to Harper-Dorn creep  

SciTech Connect

At intermediate to high temperature single and polycrystalline metals, alloys, ceramics and minerals often deform by the diffusion-controlled dislocation mechanism of power law creep at high stresses, but by a mechanism of Harper-Dorn (H-D) creep at low stresses. H-D creep is characterized by a stress exponent n of unity and an activation energy equal to that for power law creep and a strain rate independent of grain size. Several dislocation mechanisms have been proposed for H-D creep. Langdon and Yavari explain H-D creep from the climb of edge dislocations under conditions of vacancy saturation. According to Weertman and Blacic, H-D creep may be produced by a low-amplitude thermal cycling effect which causes a cyclic change in equilibrium point defect concentration. Raj postulated a mechanism with the generation of dislocations from surface sources controlling the strain rate. Ardell and Lee considered H-D creep as the result of a dislocation network coarsening. Based on the assumption of the presence of internal stress, Wu and Sherby and Ruano et al. treated Harper-Dorn creep as an extension of power law creep into the low stress region. It is the intent of this communication to show that H-D creep starts to operate at stresses equal to the Peierls stress.

Wang, J.N. (Monash Univ., Clayton (Australia). Dept. of Earth Science)

1993-09-01

263

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

264

Accuracy analysis of measurements on a stable power-law distributed series of events  

NASA Astrophysics Data System (ADS)

We investigate how finite measurement time limits the accuracy with which the parameters of a stably distributed random series of events can be determined. The model process is generated by timing the emigration of individuals from a population that is subject to deaths and a particular choice of multiple immigration events. This leads to a scale-free discrete random process where customary measures, such as mean value and variance, do not exist. However, converting the number of events occurring in fixed time intervals to a 1-bit 'clipped' process allows the construction of well-behaved statistics that still retain vestiges of the original power-law and fluctuation properties. These statistics include the clipped mean and correlation function, from measurements of which both the power-law index of the distribution of events and the time constant of its fluctuations can be deduced. We report here a theoretical analysis of the accuracy of measurements of the mean of the clipped process. This indicates that, for a fixed experiment time, the error on measurements of the sample mean is minimized by an optimum choice of the number of samples. It is shown furthermore that this choice is sensitive to the power-law index and that the approach to Poisson statistics is dominated by rare events or 'outliers'. Our results are supported by numerical simulation.

Matthews, J. O.; Hopcraft, K. I.; Jakeman, E.; Siviour, G. B.

2006-11-01

265

Point mobility of a cylindrical plate incorporating a tapered hole of power-law profile.  

PubMed

The paper describes the results of experimental measurements of point mobility carried out on circular plates containing tapered holes of quadratic power-law profile with attached damping layers. The obtained results are compared to the developed numerical model, as a means of validation. The profiles of the tapered hole in the plates are designed to replicate near zero reflection of quasi-plane waves from a tapered hole in geometrical acoustics approximation, also known as acoustic black hole effect. The driving point mobility measurements are provided, showing a comparison of the results for a constant thickness circular plate, a constant thickness plate with a layer of damping film applied and a plate with a quadratic power-law profile machined into the center, which is tested with a thin layer of elastic damping material attached. The results indicate a substantial suppression of resonant peaks, agreeing with a numerical model, which is based on the analytical solution available for the vibration of a plate with a central quadratic power-law profile. The paper contains results for the case of free boundary conditions on all edges of the plates, with emphasis placed on the predictions of resonant frequencies and the amplitudes of vibration and loss factor. PMID:21682374

O'Boy, Daniel J; Bowyer, Elizabeth P; Krylov, Victor V

2011-06-01

266

Local cortical circuit model inferred from power-law distributed neuronal avalanches.  

PubMed

How cortical neurons process information crucially depends on how their local circuits are organized. Spontaneous synchronous neuronal activity propagating through neocortical slices displays highly diverse, yet repeatable, activity patterns called "neuronal avalanches". They obey power-law distributions of the event sizes and lifetimes, presumably reflecting the structure of local circuits developed in slice cultures. However, the explicit network structure underlying the power-law statistics remains unclear. Here, we present a neuronal network model of pyramidal and inhibitory neurons that enables stable propagation of avalanche-like spiking activity. We demonstrate a neuronal wiring rule that governs the formation of mutually overlapping cell assemblies during the development of this network. The resultant network comprises a mixture of feedforward chains and recurrent circuits, in which neuronal avalanches are stable if the former structure is predominant. Interestingly, the recurrent synaptic connections formed by this wiring rule limit the number of cell assemblies embeddable in a neuron pool of given size. We investigate how the resultant power laws depend on the details of the cell-assembly formation as well as on the inhibitory feedback. Our model suggests that local cortical circuits may have a more complex topological design than has previously been thought. PMID:17226088

Teramae, Jun-Nosuke; Fukai, Tomoki

2007-01-17

267

Comment on ``Time needed to board an airplane: A power law and the structure behind it''  

NASA Astrophysics Data System (ADS)

Frette and Hemmer [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.011130 85, 011130 (2012)] recently showed that for a simple model for the boarding of an airplane, the mean time to board scales as a power law with the number of passengers N and the exponent is less than 1. They note that this scaling leads to the prediction that the “back-to-front” strategy, where passengers are divided into groups from contiguous ranges of rows and each group is allowed to board in turn from back to front once the previous group has found their seats, has a longer boarding time than would a single group. Here I extend their results to a larger number of passengers using a sampling approach and explore a scenario where the queue is presorted into groups from back to front, but allowed to enter the plane as soon as they can. I show that the power law dependence on passenger numbers is different for large N and that there is a boarding time reduction for presorted groups, with a power law dependence on the number of presorted groups.

Bernstein, Noam

2012-08-01

268

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

269

Against the Use of Power Law Luminosity Functions for ET Beacons  

NASA Astrophysics Data System (ADS)

Not infrequently it is suggested that the luminosity function (the distribution of the space densities of objects as a function of their luminosities) of extraterrestrial transmitters can plausibly be modeled as a power law, L^{-?}, of the luminosity L (Drake 1973; Gulkis 1985; Lampton 2002). This assertion is usually motivated by analogy to the luminosity function for stars in the solar vicinity, which can be (very) roughly modeled as such a power law Fig. 1, data from Mihalas and Binney (1981). The argument then continues that if the power law is sufficiently flat (? < 1.5), then a flux limited sample of transmitters will be dominated by the most luminous, since their relative scarcity is more than made up by the much larger volume in which they can be detected. This is an extreme example of the infamous Malmquist bias (Mihalas &Binney 1981). It is then concluded that if the distribution of ET transmitters were to have such a flat distribution, then the seemingly obvious SETI search strategy of starting with the nearest stars and working outward would be incorrect, and, since we do not know the value of ? it makes sense to ``hedge'' our bets by performing all-sky SETI searches even if such searches are much less sensitive.

Dreher, John W.

2004-06-01

270

Complex scale-free networks with tunable power-law exponent and clustering  

NASA Astrophysics Data System (ADS)

We introduce a network evolution process motivated by the network of citations in the scientific literature. In each iteration of the process a node is born and directed links are created from the new node to a set of target nodes already in the network. This set includes m "ambassador" nodes and l of each ambassador's descendants where m and l are random variables selected from any choice of distributions pl and qm. The process mimics the tendency of authors to cite varying numbers of papers included in the bibliographies of the other papers they cite. We show that the degree distributions of the networks generated after a large number of iterations are scale-free and derive an expression for the power-law exponent. In a particular case of the model where the number of ambassadors is always the constant m and the number of selected descendants from each ambassador is the constant l, the power-law exponent is (2l+1)/l. For this example we derive expressions for the degree distribution and clustering coefficient in terms of l and m. We conclude that the proposed model can be tuned to have the same power law exponent and clustering coefficient of a broad range of the scale-free distributions that have been studied empirically.

Colman, E. R.; Rodgers, G. J.

2013-11-01

271

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas  

NASA Astrophysics Data System (ADS)

Simulations are presented for coronal type III bursts produced by injection of energetic electrons with power law speed spectra onto open magnetic field lines embedded in an otherwise unmagnetized Maxwellian background coronal plasma, including quasi-linear wave-particle interactions and nonlinear wave-wave processes. The simulations show that although fast electrons with speeds >0.3c are injected, they are important only to the onset and not to the peak of fp emission, where fp is the local electron plasma frequency. Instead, slower beam electrons are the major drivers of the peak fp emission. Therefore, the type III beam speeds derived from the drift rates of peak fp emission are less than the typical speeds of c/3 observed for coronal type III bursts. This occurs mainly because the number of fast beam electrons with speeds >0.3c is much less than the slower ones, causing weaker fp emission from these fast beam electrons. Comparisons are made with injected electrons having Maxwellian spectra. We find that type III beams are faster when the injection has power law spectra, since there are more fast electrons injected than for Maxwellian spectra. These results suggest that type III beams produced in the corona with Maxwellian background particle distributions and either power law or Maxwellian spectra can account only for the lower half of the observed range 0.1-0.6c of type III beam speeds but not for the upper half.

Li, Bo; Cairns, Iver H.

2013-08-01

272

Energy-dependent Power Spectral States and Origin of Aperiodic Variability in Black Hole Binaries  

NASA Astrophysics Data System (ADS)

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

2013-06-01

273

Evaluation of the Impact of Off-Design Operation on an Air-Cooled Binary Power Plant  

SciTech Connect

Geothermal power plants are designed and constructed to provide a rated power output at specific resource and ambient conditions. Due to both diurnal and seasonal changes in the ambient air temperature, as well as a decline in resource productivity over time, plants seldom operate at these ''design'' conditions. This paper examines the impact of ''off- design'' operation of an air-cooled binary geothermal power plant. An available energy analysis is used to evaluate operation at these conditions. This evaluation identifies those portions of the power cycle that are most sensitive to changing resource and ambient conditions, as well as where improvements in cycle component or system performance would have the largest impact in increasing power output.

Mines, G.L.

2002-06-17

274

Evaluation of the Impact of Off-Design Operation on an Air-Cooled Binary Power Plant  

SciTech Connect

Geothermal power plants are designed and constructed to provide a rated power output at specific resource and ambient conditions. Due to both diurnal and seasonal changes in the ambient air temperature, as well as a decline in resource productivity over time, plants seldom operate at these "design" conditions. This paper examines the impact of "off- design" operation of an air-cooled binary geothermal power plant. An available energy analysis is used to evaluate operation at these conditions. This evaluation identifies those portions of the power cycle that are most sensitive to changing resource and ambient conditions, as well as where improvements in cycle component or system performance would have the largest impact in increasing power output.

Mines, Gregory Lee

2002-09-01

275

Transient Thermoelastic Analysis for a Multilayered Hollow Cylinder with Piecewise Power Law Nonhomogeneity  

NASA Astrophysics Data System (ADS)

This paper is concerned with the theoretical treatment of transient thermoelastic problem involving a multilayered hollow cylinder with piecewise power law nonhomogeneity due to uniform heat supply. The thermal and thermoelastic constants of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. We obtain the exact solution for the one-dimensional temperature change in a transient state, and thermoelastic response under the state of plane strain. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures.

Ootao, Yoshihiro

276

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

277

GEOLOGICAL AND ENVIRONMENTAL CONSTRAINTS ON THE NEGATIVE POWER LAW SCALING OF ROCKFALLS, YORKSHIRE, UK  

NASA Astrophysics Data System (ADS)

A large body of evidence within the research literature indicates that mass movements follow a negative power law scaling in their magnitude-frequency distributions over several orders of magnitude. Questions remain as to: (1) Whether this relationship holds for the entire range of the magnitude-frequency distribution. The existence of a rollover in the distribution for smaller events has been the topic of much discussion in the research literature with authors regarding it is a geophysical property of mass movements or as caused by data censoring of smaller magnitude events. (2) The effect that different geological and environmental boundary conditions have on constraining the power law. This research makes use of an ongoing sea cliff monitoring project at Boulby, UK to answer these questions. Monthly surveys using terrestrial laser scanning (TLS) over a period of 7 yrs provides one of the most comprehensive datasets for rock fall in existence. Here we demonstrate that the negative power law scaling holds over six orders of magnitude from 0.01m3 up to 1000 m3 with a characteristic rollover in the distribution for smaller failures. The rollover for the Boulby dataset occurs for rock falls that are three orders of magnitude smaller than other mass movements reported in the research literature and supports the view that it is the result of data censoring rather than a geophysical property inherent to mass movements. Furthermore, we can conclude that our TLS method has a resolution that allows the identification of events from as small as 0.01 m3 to those involving the entire cliff face. Previous research demonstrates that the scaling parameter associated with the slope of the negative power law varies considerably according to regional differences in geology, morphology, hydrology, and climate. At Boulby, the cliffs are composed of horizontally interbedded shales, sandstones, and carbonates allowing for detailed investigation into the geological controls on rock fall occurrence under a wide range of environmental conditions. Stratifying the data in this way gives insight into the constraining influence that these factors have on the magnitude-frequency of rock falls in the area. For example, our results indicate that a decrease in the strength of a rock mass has the effect of steepening the magnitude frequency relation when plotted on logarithmic axes. To date, no project has quantified the geological and environmental constraints on the negative power law scaling of mass movements in this way. Such data will be useful for models of landscape evolution and as a management tool for coastal erosion defences.

Barlow, J.; Rosser, N.; Petley, D. N.

2009-12-01

278

Bose-Einstein condensation with a finite number of particles in a power-law trap  

SciTech Connect

Bose-Einstein condensation (BEC) of an ideal gas is investigated, beyond the thermodynamic limit, for a finite number N of particles trapped in a generic three-dimensional power-law potential. We derive an analytical expression for the condensation temperature T{sub c} in terms of a power series in x{sub 0}={epsilon}{sub 0}/k{sub B}T{sub c}, where {epsilon}{sub 0} denotes the zero-point energy of the trapping potential. This expression, which applies in Cartesian, cylindrical, and spherical power-law traps, is given analytically at infinite order. It is also given numerically for specific potential shapes as an expansion in powers of x{sub 0} up to the second order. We show that, for a harmonic trap, the well-known first-order shift of the critical temperature {Delta}T{sub c}/T{sub c{proportional_to}}N{sup -1/3} is inaccurate when N{<=}10{sup 5}, the next order (proportional to N{sup -1/2}) being significant. We also show that finite-size effects on the condensation temperature cancel out in a cubic trapping potential, e.g., V(r){proportional_to}r{sup 3}. Finally, we show that in a generic power-law potential of higher order, e.g., V(r){proportional_to}r{sup {alpha}} with {alpha}>3, the shift of the critical temperature becomes positive. This effect provides a large increase of T{sub c} for relatively small atom numbers. For instance, an increase of about +40% is expected with 10{sup 4} atoms in a V(r){proportional_to}r{sup 12} trapping potential.

Jaouadi, A. [Universite Paris-Sud, Institut des Sciences Moleculaires d'Orsay (ISMO), F-91405 Orsay cedex (France); CNRS, F-91405 Orsay cedex (France); LSAMA, Department of Physics, Faculty of Science of Tunis, University of Tunis El Manar, TN-2092 Tunis (Tunisia); Telmini, M. [LSAMA, Department of Physics, Faculty of Science of Tunis, University of Tunis El Manar, TN-2092 Tunis (Tunisia); National Centre for Nuclear Science and Technology, Sidi Thabet Technopark, TN-2020 Ariana (Tunisia); Charron, E. [Universite Paris-Sud, Institut des Sciences Moleculaires d'Orsay (ISMO), F-91405 Orsay cedex (France); CNRS, F-91405 Orsay cedex (France)

2011-02-15

279

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

SciTech Connect

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

Froese, M. W.; Blaum, K.; Fellenberger, F.; Grieser, M.; Lange, M.; Laux, F.; Menk, S.; Orlov, D. A.; Repnow, R.; Sieber, T.; Hahn, R. von; Wolf, A. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Toker, Y. [Department of Particle Physics, Weizmann Institute of Science, Rehovot, 76100 (Israel)

2011-02-15

280

High-Latitude Emission of a Non-Power-Law Spectrum and Spectral Evolution of GRB X-Ray Tails  

SciTech Connect

The apparent spectral evolution observed in the steep decay phase of many GRB earlyX-ray afterglows raises a great concern of the high-latitude ''curvature effect'' interpretation of this phase. However, previous curvature effect models only invoked a simple power law spectrum upon the cessation of the prompt internal emission. We investigate the 'curvature effect' model of a more general non-power-law spectrum and and test this model with the Swift/XRT observations By comparing the simulated lightcurves/spectra with the observed ones, we show that one can reproduce both the observed lightcurve and the apparent spectral evolution of GRB 050814 using a model invoking a cut-off power-law spectrum. This suggests that at least for some GRBs, the fast spectral evolution in the steep-decay phase can be explained by the curvature effect of a non-power-law spectrum.

Zhang Binbin; Zhang Bing [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States); Liang Enwei [Department of Physics, Guangxi University, Nanning 530004 (China); Wang Xiangyu [Department of Astronomy, Nanjing University, Nanjing 210093 (China)

2009-05-25

281

Extended power-law scaling of heavy-tailed random fields or processes  

NASA Astrophysics Data System (ADS)

We analyze the scaling behaviors of two log permeability data sets showing heavy-tailed frequency distributions in three and two spatial dimensions, respectively. One set consists of 1-m scale pneumatic packer test data from six vertical and inclined boreholes spanning a decameters scale block of unsaturated fractured tuffs near Superior, Arizona, the other of pneumatic minipermeameter data measured at a spacing of 15 cm along two horizontal transects on a 21 m long outcrop of lower-shoreface bioturbated sandstone near Escalante, Utah. Order q sample structure functions of each data set scale as a power ? (q) of separation scale or lag, s, over limited ranges of s. A procedure known as Extended Self-Similarity (ESS) extends this range to all lags and yields a nonlinear (concave) functional relationship between ? (q) and q. Whereas the literature tends to associate extended and nonlinear power-law scaling with multifractals or fractional Laplace motions, we have shown elsewhere that (a) ESS of data having a normal frequency distribution is theoretically consistent with (Gaussian) truncated (additive, self-affine, monofractal) fractional Brownian motion (tfBm), the latter being unique in predicting a breakdown in power-law scaling at small and large lags, and (b) nonlinear power-law scaling of data having either normal or heavy-tailed frequency distributions is consistent with samples from sub-Gaussian random fields or processes subordinated to tfBm, stemming from lack of ergodicity which causes sample moments to scale differently than do their ensemble counterparts. Here we (i) demonstrate that the above two data sets are consistent with sub-Gaussian random fields subordinated to tfBm and (ii) provide maximum likelihood estimates of parameters characterizing the corresponding Lévy stable subordinators and tfBm functions.

Guadagnini, A.; Riva, M.; Neuman, S. P.

2012-06-01

282

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

283

On the quest for power laws in flood events: implications for flood frequency and rainfall-runoff modeling (Invited)  

Microsoft Academic Search

Power laws have been observed in the statistics (quantiles) of annual peak discharge at many locations throughout the US (i.e. annual-scale power laws). Recently, they have also been observed for peak flows during flood events at small experimental watersheds where adequate networks of stream gauges exist as well as at a large (>32,000 km2) basin in Iowa during the devastating

W. F. Krajewski; R. Mantilla; V. K. Gupta; B. M. Troutman

2009-01-01

284

Relation Between Velocity and Curvature in Movement: Equivalence and Divergence Between a Power Law and a Minimum-Jerk Model  

Microsoft Academic Search

Unconstrained hand movements typically display a decrease in hand speed around highly curved sections of a trajectory. It has been suggested that this relation between tangential velocity and radius of curvature conforms to a one-third power law. We demonstrate that a one-third power law can be explained by models taking account of trajectory costs such as a minimum-jerk model. Data

John Wann; Ian Nimmo-Smith; Alan M. Wing

1988-01-01

285

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

286

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

NASA Astrophysics Data System (ADS)

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 ?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 w0-wa 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? level.

Yashar, Mark; Bozek, Brandon; Abrahamse, Augusta; Albrecht, Andreas; Barnard, Michael

2009-05-01

287

Extended power-law scaling of air permeabilities measured on a block of tuff  

NASA Astrophysics Data System (ADS)

We use three methods to identify power law scaling of (natural) log air permeability data collected by Tidwell and Wilson (1999) on the faces of a laboratory-scale block of Topopah Spring tuff: method of moments (M), extended power-law scaling also known as Extended Self-Similarity (ESS) and a generalized version thereof (G-ESS). All three methods focus on qth-order sample structure functions of absolute increments. Most such functions exhibit power-law scaling at best over a limited midrange of experimental separation scales, or lags, which are sometimes difficult to identify unambiguously by means of M. ESS and G-ESS extend this range in a way that renders power-law scaling easier to characterize. Most analyses of this type published to date concern time series or one-dimensional transects of spatial data associated with a unique measurement (support) scale. We consider log air permeability data having diverse support scales on the faces of a cube. Our analysis confirms the superiority of ESS and G-ESS over M in identifying the scaling exponents ?(q) of corresponding structure functions of orders q, suggesting further that ESS is more reliable than G-ESS. The exponents vary in a nonlinear fashion with q as is typical of real or apparent (Guadagnini and Neuman, 2011; Guadagnini et al., 2011) multifractals. Our estimates of the Hurst scaling coefficient increase with support scale, implying a reduction in roughness (anti-persistence) of the log permeability field with measurement volume. ESS and G-ESS ratios between scaling exponents ?(q) associated with various orders q show no distinct dependence on support volume or on two out of three Cartesian directions (there being no distinct power law scaling in the third direction). The finding by Tidwell and Wilson (1999) that log permeabilities associated with all tip sizes can be characterized by stationary variogram models, coupled with our findings that log permeability increments associated with the smallest tip size are approximately Gaussian and those associated with all tip size scales show nonlinear (multifractal) variations in ?(q) with q, are consistent with a view of these data as a sample from a truncated version (tfBm) of self-affine fractional Brownian motion (fBm). Since in theory the scaling exponents, ?(q), of tfBm vary linearly with q we conclude, in accord with Neuman (2010a, b, 2011), that nonlinear scaling in our case is not an indication of multifractality but an artifact of sampling from tfBm. This allows us to explain theoretically how power law scaling is extended by ESS. It further allows us to identify the functional form and estimate all parameters of the corresponding tfBm based on sample structure functions of first and second orders. Our estimate of lower cutoff is consistent with a theoretical support scale of the data.

Siena, M.; Guadagnini, A.; Riva, M.; Neuman, S. P.

2011-08-01

288

Extended Power-Law Scaling of Air Permeabilities Measured on a Block of Tuff  

NASA Astrophysics Data System (ADS)

We use three methods to identify power law scaling of (natural) log air permeability data collected by Tidwell and Wilson (1999) on the faces of a laboratory-scale block of Topopah Spring tuff: method of moments (M), extended power-law scaling also known as Extended Self-Similarity (ESS) and a generalized version thereof (G-ESS). All three methods focus on qth-order sample structure functions of absolute increments. Most such functions exhibit power-law scaling at best over a limited midrange of experimental separation scales, or lags, which are sometimes difficult to identify unambiguously by means of M. ESS and G-ESS extend this range in a way that renders power-law scaling easier to characterize. Most analyses of this type published to date concern time series or one-dimensional transects of spatial data associated with a unique measurement (support) scale. We consider log air permeability data having diverse support scales on the faces of a cube. Our analysis confirms the superiority of ESS and G-ESS over M in identifying the scaling exponents ?(q) of corresponding structure functions of orders q, suggesting further that ESS is more reliable than G-ESS. The exponents vary in a nonlinear fashion with q as is typical of real or apparent (Guadagnini and Neuman, 2011; Guadagnini et al., 2011) multifractals. Our estimates of the Hurst scaling coefficient increase with support scale, implying a reduction in roughness (anti-persistence) of the log permeability field with measurement volume. ESS and G-ESS ratios between scaling exponents ?(q) associated with various orders q show no distinct dependence on support volume or on two out of three Cartesian directions (there being no distinct power law scaling in the third direction). The finding by Tidwell and Wilson (1999) that log permeabilities associated with all tip sizes can be characterized by stationary variogram models, coupled with our findings that log permeability increments associated with the smallest tip size are approximately Gaussian and those associated with all tip size scales show nonlinear (multifractal) variations in ?(q) with q, are consistent with a view of these data as a sample from a truncated version (tfBm) of self-affine fractional Brownian motion (fBm). Since in theory the scaling exponents, ?(q), of tfBm vary linearly with q we conclude, in accord with Neuman (2010a, 2010b, 2011), that nonlinear scaling in our case is not an indication of multifractality but an artifact of sampling from tfBm. This allows us to explain theoretically how power law scaling is extended by ESS. It further allows us to identify the functional form and estimate all parameters of the corresponding tfBm based on sample structure functions of first and second orders. Our estimate of lower cutoff is consistent with a theoretical support scale of the data.

Siena, M.; Guadagnini, A.; Riva, M.; Neuman, S. P.

2011-12-01

289

A new scaling law for analyzing power in hadron production by transversely polarized baryons  

NASA Astrophysics Data System (ADS)

Experimental data on analyzing power for inclusive meson and baryon production in collisions of transversely polarized protons and antiprotons with protons and light nuclei have been analyzed. It is found that the existing data can be described by a simple function of collision energy (sqrt{s}), transverse momentum (pT{}) and a new scaling variable xA{} = E/E^{BEAM}{}. At beam energies above 40 GeV and pT{} above 1.0 GeV/c the analyzing power is described by a function of xA{} and pT{} only (AN{}={F }(pT {}){G }(xA{})) for both polarized proton fragmentation and central regions of proton-hadron collision. Comparison of data from Fermilab and new IHEP data measured using 40 GeV/c polarized proton beam was most decisive for the revelation of the above regularities. This new scaling law allows one to predict the analyzing powers for kinematic regions, not yet explored in experiments and constrains models of strong interactions. The new scaling law allows one also to use some reactions as polarimeters for experiments with a polarized beam.

Abramov, V. V.

2000-06-01

290

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

PubMed

This paper develops a deterministic and a stochastic population size model based on power-law kinetics for the black-margined pecan aphid. The deterministic model in current use incorporates cumulative-size dependency, but its solution is symmetric. The analogous stochastic model incorporates the prolific reproductive capacity of the aphid. These models are generalized in this paper to include a delayed feedback mechanism for aphid death. Whereas the per capita aphid death rate in the current model is proportional to cumulative size, delayed feedback is implemented by assuming that the per capita rate is proportional to some power of cumulative size, leading to so-called power-law dynamics. The solution to the resulting differential equations model is a left-skewed abundance curve. Such skewness is characteristic of observed aphid data, and the generalized model fits data well. The assumed stochastic model is solved using Kolmogrov equations, and differential equations are given for low order cumulants. Moment closure approximations, which are simple to apply, are shown to give accurate predictions of the two endpoints of practical interest, namely (1) a point estimate of peak aphid count and (2) an interval estimate of final cumulative aphid count. The new models should be widely applicable to other aphid species, as they are based on three fundamental properties of aphid population biology. PMID:17306309

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

2006-11-18

291

Design and off-design operation of a dual-boiling binary geothermal power plant  

Microsoft Academic Search

The design of a 5 MW(e) geothermal plant using a binary fluid process is described. The second fluid is isobutane. This plant is presently under construction at Raft River, Idaho. A mathematical simulation of the plant is discussed. The heat exchangers were modeled by dividing them into segments in the direction of flow to permit local adjustments in heat transfer

Bliem; C. J. Jr

1980-01-01

292

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

2010-01-22

293

An Evaluation of Power Law Breakdown in Metals, Alloys, Dispersion Hardened Materials and Compounds  

SciTech Connect

Creep at high stresses often produces strain rates that exceed those that would be predicted by a power law relationship. In this paper, we examine available high stress creep data for pure metals, solid solution alloys, dispersion strengthened powder metallurgy materials and compounds for power law breakdown (PLB). The results show that, if PLB is observed, then the onset of PLB is generally observed at about {epsilon}/D{sub eff} = 10{sup 13} m{sup -2}, where D{sub eff} is the effective diffusion coefficient incorporating lattice and dislocation pipe diffusion. The common origins of PLB for the various systems studied can be found in the production of excess vacancies by plastic deformation. Anomalous behavior in two pure metals (nickel and tungsten) and a solid solution alloy (Fe-25Cr and Fe-26Cr-1Mo) has been analyzed and provides insight into this excess vacancy mechanism. In metal systems, the onset of PLB is related to a change in the nature of the subgrain structure developed. In the PLB region, subgrains become imperfect containing dislocation tangles adjacent to the sub-boundary, and dislocation cells are evident. The dislocation tangles and cells are the source of excess vacancies and increase the creep rate above that predicted from power law creep. If subgrains do not form then PLB is not observed. In solid solution alloys, in which the dominant deformation resistance results from the interaction of solute atoms with moving dislocations, excess vacancies influence the diffusion of these solute atoms. PLB is not observed in many systems. This is attributed either to the presence of a high equilibrium vacancy concentration (because of a low activation energy for vacancy formation) or to the inability to form subgrains.

Lesuer, D.R.; Syn, C.K.; Sherby, O.D.

1999-10-20

294

Power-law decaying oscillations of neutrally buoyant spheres in continuously stratified fluid  

NASA Astrophysics Data System (ADS)

The free sinking motion of small spheres is experimentally investigated in a laboratory tank filled up with continuously stratified salt solutions. Special attention is paid to the late stage oscillations around the gravitational equilibrium level. Such motion is generated by slowly decaying weak internal waves originating from the interaction of the solid sphere with the surrounding fluid. The temporal decay of oscillation amplitudes and velocities can be best described by a power law of exponent value close to -3/2. Up to our best knowledge, none of the existing theories can predict a similar algebraic decay.

Biró, István; Gábor Szabó, K.; Gyüre, Balázs; Jánosi, Imre M.; Tél, Tamás

2008-05-01

295

Steady thermal explosion with power-law thermal absorptivity in microannuli: wavy-roughness effect  

NASA Astrophysics Data System (ADS)

We obtain the approximate solutions for the steady temperature profiles of materials with a temperature-dependent thermal absorptivity inside a microannulus with wavy-rough surfaces considering a quasilinear partial differential equation by the boundary perturbation approach. Our numerical results show that the wave number as well as the small amplitude of the wavy roughness will influence the net temperature significantly especially near the inner wall of a microannulus. Meanwhile we observed that the critical Frank-Kamanestkii parameter depends on the small-amplitude wavy-roughness for specific power-law of thermal absorptivity. Our results could be applied to the relevant fields in MicroElectroMechanical System (MEMS).

Zotin Kwang-Hua, Chu

2009-07-01

296

Extended power-law scaling of air permeabilities measured on a block of tuff  

NASA Astrophysics Data System (ADS)

We use three methods to identify power-law scaling of multi-scale log air permeability data collected by Tidwell and Wilson on the faces of a laboratory-scale block of Topopah Spring tuff: method of moments (M), Extended Self-Similarity (ESS) and a generalized version thereof (G-ESS). All three methods focus on q-th-order sample structure functions of absolute increments. Most such functions exhibit power-law scaling at best over a limited midrange of experimental separation scales, or lags, which are sometimes difficult to identify unambiguously by means of M. ESS and G-ESS extend this range in a way that renders power-law scaling easier to characterize. Our analysis confirms the superiority of ESS and G-ESS over M in identifying the scaling exponents, ?(q), of corresponding structure functions of orders q, suggesting further that ESS is more reliable than G-ESS. The exponents vary in a nonlinear fashion with q as is typical of real or apparent multifractals. Our estimates of the Hurst scaling coefficient increase with support scale, implying a reduction in roughness (anti-persistence) of the log permeability field with measurement volume. The finding by Tidwell and Wilson that log permeabilities associated with all tip sizes can be characterized by stationary variogram models, coupled with our findings that log permeability increments associated with the smallest tip size are approximately Gaussian and those associated with all tip sizes scale show nonlinear variations in ?(q) with q, are consistent with a view of these data as a sample from a truncated version (tfBm) of self-affine fractional Brownian motion (fBm). Since in theory the scaling exponents, ?(q), of tfBm vary linearly with q we conclude that nonlinear scaling in our case is not an indication of multifractality but an artifact of sampling from tfBm. This allows us to explain theoretically how power-law scaling of our data, as well as of non-Gaussian heavy-tailed signals subordinated to tfBm, are extended by ESS. It further allows us to identify the functional form and estimate all parameters of the corresponding tfBm based on sample structure functions of first and second orders.

Siena, M.; Guadagnini, A.; Riva, M.; Neuman, S. P.

2012-01-01

297

Power-Law Slip Profile of the Moving Contact Line in Two-Phase Immiscible Flows  

NASA Astrophysics Data System (ADS)

Large-scale molecular dynamics (MD) simulations on two-phase immiscible flows show that, associated with the moving contact line, there is a very large 1/x partial-slip region where x denotes the distance from the contact line. This power-law partial-slip region is verified in large-scale adaptive continuum calculations based on a local, continuum hydrodynamic formulation, which has proved successful in reproducing MD results at the nanoscale. Both MD simulations and numerical solutions of continuum equations indicate the existence of a universal slip profile in the Stokes-flow regime.

Qian, Tiezheng; Wang, Xiao-Ping; Sheng, Ping

2004-08-01

298

Power-law slip profile of the moving contact line in two-phase immiscible flows.  

PubMed

Large-scale molecular dynamics (MD) simulations on two-phase immiscible flows show that, associated with the moving contact line, there is a very large 1/x partial-slip region where x denotes the distance from the contact line. This power-law partial-slip region is verified in large-scale adaptive continuum calculations based on a local, continuum hydrodynamic formulation, which has proved successful in reproducing MD results at the nanoscale. Both MD simulations and numerical solutions of continuum equations indicate the existence of a universal slip profile in the Stokes-flow regime. PMID:15447105

Qian, Tiezheng; Wang, Xiao-Ping; Sheng, Ping

2004-08-27

299

Power Law and Logarithmic Entropy Corrected Ricci Dark Energy Models in Brans-Dicke Chameleon Cosmology  

NASA Astrophysics Data System (ADS)

In this work, we study the power-law and the logarithmic entropy corrected versions of the Ricci Dark Energy (RDE) model in the framework of the Brans-Dicke cosmology non-minimally coupled with a chameleon scalar field ?. Considering the presence of interaction between Dark Energy (DE) and Dark Matter (DM), we derived the expressions of some relevant cosmological parameters, i.e. the equation of state parameter ? D , the deceleration parameter q and the evolution of the energy density parameter \\varOmega'D.

Pasqua, Antonio; Assaf, Khudhair A.; Aly, Ayman A.

2013-10-01

300

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

2012-07-03

301

Laboratory constraints on chameleon dark energy and power-law fields  

SciTech Connect

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

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

2010-10-01

302

Survivor statistics and damage spreading on social network with power-law degree distributions  

NASA Astrophysics Data System (ADS)

Damage spreading(DS) of the random graph networks with power-law degree distributions is investigated using Glauber dynamics. Various subgraphs defined by the probability of acquaintance show distinct features in DS as measured by Hamming distance. A heuristic understanding of the long-time value of damage is achieved through an analysis of the survivor statistics. All survivors are dynamical, flipping in unison for the controlled sample and the damaged sample. Verification of these dynamic survivors is achieved through the introduction of a new measure of self-damage.

Guo, Z. Z.; Szeto, K. Y.

2007-01-01

303

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

304

Effective permeability of fractured porous media with power-law distribution of fracture sizes.  

PubMed

The permeability of geological formations which contain fractures with a power-law size distribution is addressed numerically by solving the coupled Darcy equations in the fractures and in the surrounding porous medium. Two reduced parameters are introduced which allow for a unified description over a very wide range of the fracture characteristics, including their shape, density, size distribution, and possibly size-dependent permeability. Two general models are proposed for loose and dense fracture networks, and they provide a good representation of the numerical data throughout the investigated parameter range. PMID:17930343

Bogdanov, I I; Mourzenko, V V; Thovert, J-F; Adler, P M

2007-09-21

305

Mathematical analysis of the dimensional scaling technique for the Schroedinger equation with power-law potentials  

SciTech Connect

The dimensional scaling (D-scaling) technique is an innovative asymptotic expansion approach to study the multiparticle systems in molecular quantum mechanics. It enables the calculation of ground and excited state energies of quantum systems without having to solve the Schroedinger equation. In this paper, we present a mathematical analysis of the D-scaling technique for the Schroedinger equation with power-law potentials. By casting the D-scaling technique in an appropriate variational setting and studying the corresponding minimization problem, the D-scaling technique is justified rigorously. A new asymptotic dimensional expansion scheme is introduced to compute asymptotic expansions for ground state energies.

Ding Zhonghai [Department of Mathematical Sciences, University of Nevada Las Vegas, Las Vegas, Nevada 89154-4020 (United States); Department of Mathematics and Taida Institute for Mathematical Sciences, National Taiwan University, Taipei, Taiwan (China); Chen, Goong [Department of Mathematics and Institute for Quantum Science and Engineering, Texas A and M University, College Station, Texas 77843 (United States); Department of Mathematics and Taida Institute for Mathematical Sciences, National Taiwan University, Taipei, Taiwan (China); Lin, Chang-Shou [Department of Mathematics and Taida Institute for Mathematical Sciences, National Taiwan University, Taipei, Taiwan (China)

2010-12-15

306

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

307

Analysis of power-law exponents by maximum-likelihood maps  

NASA Astrophysics Data System (ADS)

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

Baró, Jordi; Vives, Eduard

2012-06-01

308

Birth and death of protein domains: A simple model of evolution explains power law behavior  

PubMed Central

Background Power distributions appear in numerous biological, physical 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 interactions 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. Results 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 are derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models are found and their appearance depending on model parameters is investigated. It is proved that the power law asymptotics appears if, and only if, the model is balanced, i.e. domain duplication and deletion rates are asymptotically equal up to the second order. It is further proved that any power asymptotic with the degree not equal to -1 can appear only if the hypothesis of independence of the duplication/deletion rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, are considered in details and the distributions of the equilibrium frequencies of domain families of different size are determined for each case. We apply the BDIM formalism to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and show an excellent fit 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 elimination rates, particularly for prokaryotic genomes. Conclusions We show that a straightforward model of genome evolution, which does not explicitly include selection, is 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.

Karev, Georgy P; Wolf, Yuri I; Rzhetsky, Andrey Y; Berezovskaya, Faina S; Koonin, Eugene V

2002-01-01

309

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

PubMed

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

2013-08-12

310

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

311

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

PubMed Central

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

Horwitz, Jill R; Fremont-Smith, Marion R

2005-01-01

312

Landau damping in relativistic plasmas with power-law distributions and applications to solar wind electrons  

SciTech Connect

The relativistic plasma dispersion relation is derived for Langmuir waves in a spatially homogeneous unmagnetized plasma in which the electrons have an isotropic power-law distribution in momentum space. The theory is applied to the study of Langmuir waves in the quiescent solar wind near the orbit of the Earth assuming that the electron distribution function can be approximated as a power-law from thermal energies {approx}10 eV to relativistic energies < or approx. 100 keV. Numerical solutions of the dispersion relation show that in the regime of weak Landau damping the phase speeds of the waves match the velocities of the high-energy particles, known in the solar wind literature as the superhalo, which lie in the range 0.09

Podesta, J. J. [Space Science Center, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2008-12-15

313

Power law distribution in statistics of failures in operation of spacecraft onboard equipment  

NASA Astrophysics Data System (ADS)

The possibility of using the statistics of recurrence time for extreme events is studied in this paper having in mind the problems of control and prediction of failures in spacecraft operation. The information about failures onboard satellites of various types presented by the US National Geophysical Data Center was analyzed. It was found that the probability density of recurrence intervals followed a power law of the Pareto type with an index equal to 2.3. The obtained result is consistent both with the theory of normal catastrophes and with the principle of self-organization of criticality for metastable active heterogeneous environment. A practical consequence of the obtained result consists in the fact that predictions of these extreme events should not rely on traditional models with the second-order Pearson statistics. To make predictions, the models are necessary that take into account the power law distribution of recurrence intervals for failures on satellites. The failures should be considered in these models as extreme events connected with manifestation of the space environment factors.

Karimova, L. M.; Kruglun, O. A.; Makarenko, N. G.; Romanova, N. V.

2011-10-01

314

The US business cycle: power law scaling for interacting units with complex internal structure  

NASA Astrophysics Data System (ADS)

In the social sciences, there is increasing evidence of the existence of power law distributions. The distribution of recessions in capitalist economies has recently been shown to follow such a distribution. The preferred explanation for this is self-organised criticality. Gene Stanley and colleagues propose an alternative, namely that power law scaling can arise from the interplay between random multiplicative growth and the complex structure of the units composing the system. This paper offers a parsimonious model of the US business cycle based on similar principles. The business cycle, along with long-term growth, is one of the two features which distinguishes capitalism from all previously existing societies. Yet, economics lacks a satisfactory theory of the cycle. The source of cycles is posited in economic theory to be a series of random shocks which are external to the system. In this model, the cycle is an internal feature of the system, arising from the level of industrial concentration of the agents and the interactions between them. The model-in contrast to existing economic theories of the cycle-accounts for the key features of output growth in the US business cycle in the 20th century.

Ormerod, Paul

2002-11-01

315

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

316

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.

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

2010-01-01

317

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

318

Bose-Einstein condensation in dark power-law laser traps  

SciTech Connect

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 l 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. [Universite Paris-Sud, Institut des Sciences Moleculaires d'Orsay (ISMO), F-91405 Orsay (France); CNRS, Orsay, F-91405 France (France); Laboratoire de Spectroscopie Atomique, Moleculaire et Applications (LSAMA), Department of Physics, Faculty of Science of Tunis, University of Tunis El Manar, T-2092 Tunis (Tunisia); Gaaloul, N. [Institut fuer Quantenoptik, Welfengarten 1, Gottfried Wilhelm Leibniz Universitaet, D-30167 Hannover (Germany); Viaris de Lesegno, B.; Pruvost, L. [CNRS, Laboratoire Aime Cotton (LAC), F-91405 Orsay (France); Universite Paris-Sud, Orsay, F-91405 France (France); Telmini, M. [Laboratoire de Spectroscopie Atomique, Moleculaire et Applications (LSAMA), Department of Physics, Faculty of Science of Tunis, University of Tunis El Manar, T-2092 Tunis (Tunisia); Charron, E. [Universite Paris-Sud, Institut des Sciences Moleculaires d'Orsay (ISMO), F-91405 Orsay (France); CNRS, Orsay, F-91405 (France)

2010-08-15

319

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

320

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

321

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

322

Reconsideration of the power-law (Batho) equation for inhomogeneity corrections  

SciTech Connect

The power-law (Batho) equation for inhomogeneity corrections to the dose calculated in a layered medium has been examined to elucidate the implicit approximations made in its derivation and hence to discover its limitations. Relationships based on primary and first scatter dose calculations are established between the Batho correction and the true correction from which several conclusions can be drawn. For dose corrections within water in a two-layer medium, the Batho method underestimates the correction when the electron density (rho) of the overlaying inhomogeneity relative to water is less than 1, and overestimates it when this density is greater than 1. The Batho method is excellent for small fields and rho<1, but is poor for large fields and rho>1. When the power-law equation is extended to multilayer media, by assuming that the correction factor for each layer multiplies independently, the method gives less accurate results. The largest errors occur inside an inhomogeneity directly underneath a top layer of unit density, since the contribution from such a layer is inherently ignored. All of these conclusions are demonstrated in the paper by experimental measurements. Finally, relationships are shown between the Batho correction and both the correction factor proposed by MacDonald et al. and the differential scatter air ratio correction.

Wong, J.W.; Henkelman, R.M.

1982-07-01

323

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

324

Transition from Exponential to Power Law Income Distributions in a Chaotic Market  

NASA Astrophysics Data System (ADS)

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

Pellicer-Lostao, Carmen; Lopez-Ruiz, Ricardo

325

A power-law approximation for fluvial incision by tools and bed coverage processes  

NASA Astrophysics Data System (ADS)

The stream-power model is widely used to represent fluvial incision in bedrock channels. The model does not account for the amount of sediment in the channel, which can abrade the channel at low concentrations or armor the channel at high concentrations. Here we use a natural example (Clearwater River, Washington State, USA) and numerical experiments to explore how sediment flux influences bedrock incision at a drainage-wide scale. We have generated numerical landscapes with different uplift patterns using the CHILD numerical model and incision rules that include a tools-and-coverage formulation. We then use regression analysis to fit a power-law function I=K*Am*Sn*, where I is incision rate, S slope, and A drainage area, and K*, m*, and n* are fit parameters. We find that this formulation works very well for the Clearwater and all of our numerical experiments. The function has the same form as the stream-power model, but the parameters are empirically defined (as indicated by the asterisks) and can take on values quite different than those inferred from process-based arguments. The best-fit parameters appear to be constant at the scale of a single drainage, but they vary between drainages depending on the pattern of uplift, and whether or not the landscape has reached steady-state. In all cases, slope-area steepness analysis works well for estimating relative incision rates. Our analysis indicates that, in some cases, m* can be quite low, apparently due to the fact that bed coverage increases with increasing area. We conclude that the power-law formulation provides a good functional representation of fluvial incision, but that there are no universal values for m* and n*. These conclusions have important implications for the size of mountain belts and feedbacks between tectonic uplift and surface processes.

Brandon, M. T.; Gasparini, N. M.

2005-12-01

326

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

NASA Astrophysics Data System (ADS)

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

Takesue, Shinji; Mitsudo, Tetsuya; Hayakawa, Hisao

2003-07-01

327

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

328

A computational analysis of natural convection in a vertical channel with a modified power law non-Newtonian fluid  

SciTech Connect

An implicit finite difference method was applied to analyze laminar natural convection in a vertical channel with a modified power law fluid. This fluid model was chosen because it describes the viscous properties of a pseudoplastic fluid over the entire shear rate range likely to be found in natural convection flows since it covers the shear rate range from Newtonian through transition to simple power law behavior. In addition, a dimensionless similarity parameter is identified which specifies in which of the three regions a particular system is operating. The results for the average channel velocity and average Nusselt number in the asymptotic Newtonian and power law regions are compared with numerical data in the literature. Also, graphical results are presented for the velocity and temperature fields and entrance lengths. The results of average channel velocity and Nusselt number are given in the three regions including developing and fully developed flows. As an example, a pseudoplastic fluid (carboxymethyl cellulose) was chosen to compare the different results of average channel velocity and Nusselt number between a modified power law fluid and the conventional power law model. The results show, depending upon the operating conditions, that if the correct model is not used, gross errors can result.

Lee, S.R.; Irvine, T.F. Jr. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Mechanical Engineering; Greene, G.A. [Brookhaven National Lab., Upton, NY (United States). Dept. of Advanced Technology

1998-04-01

329

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

NASA Astrophysics Data System (ADS)

Recently, Clauset, Shalizi, and Newman 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 implementation is provided. The performance of our method is put to test on several empirical data which were previously analyzed with less systematic approaches. We find the functioning of the method very satisfactory.

Deluca, Anna; Corral, Álvaro

2013-12-01

330

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

PubMed Central

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

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

2003-01-01

331

Network-state modulation of power-law frequency-scaling in visual cortical neurons.  

PubMed

Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of V(m) activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the V(m) reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the "effective" connectivity responsible for the dynamical signature of the population signals measured at different integration levels, from Vm to LFP, EEG and fMRI. PMID:19779556

El Boustani, Sami; Marre, Olivier; Béhuret, Sébastien; Baudot, Pierre; Yger, Pierre; Bal, Thierry; Destexhe, Alain; Frégnac, Yves

2009-09-25

332

Impact of Type Ia Supernova Ejecta on a Helium-star Binary Companion  

Microsoft Academic Search

The impact of Type Ia supernova (SN) ejecta on a helium-star companion is investigated via high-resolution, two-dimensional hydrodynamic simulations. For a range of helium-star models and initial binary separations, it is found that the mass unbound in the interaction, deltaM ub, is related to the initial binary separation, a, by a power law of the form deltaM ub vprop am

Kuo-Chuan Pan; Paul M. Ricker; Ronald E. Taam

2010-01-01

333

IMPACT OF TYPE Ia SUPERNOVA EJECTA ON A HELIUM-STAR BINARY COMPANION  

Microsoft Academic Search

The impact of Type Ia supernova (SN) ejecta on a helium-star companion is investigated via high-resolution, two-dimensional hydrodynamic simulations. For a range of helium-star models and initial binary separations, it is found that the mass unbound in the interaction, M{sub ub}, is related to the initial binary separation, a, by a power law of the form M{sub ub} a{sup m}

Kuo-Chuan Pan; Paul M. Ricker; Ronald E. Taam

2010-01-01

334

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

335

Design and off-design operation of a dual-boiling binary geothermal power plant  

SciTech Connect

The design of a 5 MW(e) geothermal plant using a binary fluid process is described. The second fluid is isobutane. This plant is presently under construction at Raft River, Idaho. A mathematical simulation of the plant is discussed. The heat exchangers were modeled by dividing them into segments in the direction of flow to permit local adjustments in heat transfer coefficients and fluid properties. Sensitivity of plant performance to geofluid temperature and flow rate, heat exchanger fouling and cooling water temperatures were investigated. Conventional correlations were used for the heat transfer coefficients except for the condensing coefficient, which was obtained from a recent study at Lawrence Berkeley Laboratory.

Bliem, C.J. Jr.

1980-01-01

336

Universality in rank distributions due to multiplicative processes : from power laws to stretched exponentials  

NASA Astrophysics Data System (ADS)

Although power laws have been used to fit rank distributions in many different contexts, they usually fail at the tails. Stretched exponentials and log-normal distributions have been used to solve the problem, but unfortunately they are not able to fit at the same time both ending tails. Here we show that many different data in rank laws, like in granular materials, codons, author impact in scientific journal, etc. are very well fitted by a beta-like function (a,b distribution). Since this distribution is indeed ubiquitous, it is reasonable to associate it to the product of correlated probability distributions. In particular, we have found that the macrostates of the product of discrete probability distributions imply stretched exponential-like frequency-rank functions, which qualitatively and quantitatively can be fitted with the a,b distribution in the limit of many random variables [1]. We prove this by transforming the problem into an algebraic one: finding the rank of successive products of a given set of numbers. [1] New J. Phys. 9 (2007) 286. (2007).

Naumis, Gerardo; Cocho, Germinal

2008-03-01

337

Phase transition of interacting Bose gases in general power-law potentials  

SciTech Connect

We investigate the phase transition of interacting Bose gases in general power-law traps in the thermodynamic limit. Using energy-shell renormalization and the {epsilon} expansion, we evaluate the partition function for the uncondensed gas phase within a renormalization-group framework. This approach allows a unified description of homogeneous as well as inhomogeneous and anisotropic systems. Results for the critical temperature are compared to mean-field theory as well as to a local-density approximation based on renormalization-group theory for the homogeneous Bose gas. This comparison indicates the consistency of our approach. We also make suggestions for an optimized trap design in experiments that measure the transition temperature.

Zobay, O.; Metikas, G.; Alber, G. [Institut fuer Angewandte Physik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany)

2004-06-01

338

Critical Scaling of Extended Power Law I-V Isotherms near Vortex Glass Transition  

NASA Astrophysics Data System (ADS)

In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau (GL) functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I-V data of Strachan et al. [Phys. Rev. Lett. 87 (2001) 067007]. The puzzling question of the derivative plot for the I-V curves and the controversy surrounding the values of critical exponents are discussed.

Hu, Xiang; He, Li; Ning, Zhen-Hua; Chen, Kai-Xuan; Yin, Lan; Lu, Guo; Xu, Xiao-Lin; Guo, Jian-Dong; Wang, Fu-Ren; Li, Chuan-Yi; Yin, Dao-Le

2006-12-01

339

Modelling of semi-solid processing using a modified temperature-dependent power-law model  

NASA Astrophysics Data System (ADS)

A fairly simple one-phase rheological model has been implemented into a commercial fluid flow finite element software to simulate mould filling during the semi-solid processing (thixoforming) of aluminium alloys. This model is of purely viscous nature. Its temperature-dependent viscosity is a power-law function of the shear rate with a shear rate cut-off. The constitutive parameters of this model were determined for a rheocast A356 alloy. For that purpose, simulation results were compared with instrumented thixoforming experiments performed on a production-scale injection machine. The selected configuration was that of a transient flow near a bifurcation, i.e. obstruction of an established Poiseuille-type flow by a shaft placed at the centre of a tube. Using these parameters, the model was then further validated by comparing the simulation of an axisymmetric reservoir mould filling with the shape of solidified shells obtained after interrupted injection experiments.

Orgéas, L.; Gabathuler, J.-P.; Imwinkelried, Th.; Paradies, Ch.; Rappaz, M.

2003-07-01

340

An Optimal Power-Law for Synchrony and Lognormally Synaptic Weighted Hub Networks  

NASA Astrophysics Data System (ADS)

Details about the structure of a network model are revealed at the spontaneous spike activity level, in which the power-law of synchrony is optimized to that observed in the CA3 hippocampal slice cultures. The network model is subject to spike noise with exponentially distributed interspike intervals. The excitatory (E) and/or inhibitory (I) neurons interact through synapses whose weights show a log-normal distribution. The spike behavior observed in the network model with the appropriate log-normal distributed synaptic weights fits best to that observed in the experiment. The best-fit is then achieved with high activities of I neurons having a hub-like structure, in which the I neurons, subject to optimized spike noise, are intensively projected from low active E neurons.

Yasuomi, D. Sato

2013-09-01

341

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

NASA Astrophysics Data System (ADS)

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

Crane, Riley; Schweitzer, Frank; Sornette, Didier

2010-05-01

342

Discharge Plasma and Sheath as a Stochastic Process —What the |f|-? Power Spectral Law Implies—  

NASA Astrophysics Data System (ADS)

Noise signals detected with a Langmuir probe from a DC magnetron plasma device are discussed. Noise spectra were characterized by the |f|-? power law with ? being the constant stochastic index. ? ranged between 2.5 and 5.5 in the frequency range of 0.1

Tanizuka, Noboru

1991-01-01

343

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

NASA Astrophysics Data System (ADS)

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

Mi?kiewicz, Janusz

2013-05-01

344

Power law distribution of wealth in population based on a modified Equíluz-Zimmermann model  

NASA Astrophysics Data System (ADS)

We propose a money-based model for the power law distribution (PLD) of wealth in an economically interacting population. It is introduced as a modification of the Equíluz and Zimmermann (EZ) model for crowding and information transmission in financial markets. Still, it must be stressed that in the EZ model a PLD without exponential correction is obtained only for a particular parameter, while our pattern will give the exact PLD within a wide range. The PLD exponent depends on the model parameters in a nontrivial way and is exactly calculated in this paper. The numerical results are in excellent agreement with the analytic prediction, and also comparable with empirical data of wealth distribution.

Xie, Yan-Bo; Wang, Bing-Hong; Hu, Bo; Zhou, Tao

2005-04-01

345

Ewald methods for inverse power-law interactions in tridimensional and quasi-two-dimensional systems  

NASA Astrophysics Data System (ADS)

In this paper, we derive the Ewald method for inverse power-law interactions in quasi-two-dimensional systems. The derivation is done by using two different analytical methods. The first uses Parry's limit that considers the Ewald methods for quasi-two-dimensional systems as a limit of the Ewald methods for tridimensional systems; the second uses Poisson-Jacobi identities for lattice sums. Taking into account the equivalence of both derivations, we obtain a new analytical Fourier transform integral involving an incomplete gamma function. Energies of the generalized restrictive primitive model of electrolytes (?-RPM) and of the generalized one-component plasma model (?-OCP) are given for the tridimensional, quasi-two-dimensional and monolayers systems. Few numerical results, using Monte Carlo simulations, for ?-RPM and ?-OCP monolayer systems are reported.

Mazars, Martial

2010-10-01

346

Scalar field probes of power-law space-time singularities  

NASA Astrophysics Data System (ADS)

We analyse the effective potential of the scalar wave equation near generic space-time singularities of power-law type (Szekeres-Iyer metrics) and show that the effective potential exhibits a universal and scale invariant leading inverse square behaviour ~ x-2 in the ``tortoise coordinate'' x provided that the metrics satisfy the strict Dominant Energy Condition (DEC). This result parallels that obtained in [1] for probes consisting of families of massless particles (null geodesic deviation, a.k.a. the Penrose Limit). The detailed properties of the scalar wave operator depend sensitively on the numerical coefficient of the x-2-term, and as one application we show that timelike singularities satisfying the DEC are quantum mechanically singular in the sense of the Horowitz-Marolf (essential self-adjointness) criterion. We also comment on some related issues like the near-singularity behaviour of the scalar fields permitted by the Friedrichs extension.

Blau, Matthias; Frank, Denis; Weiss, Sebastian

2006-08-01

347

Stretched-exponential relaxation and hidden power laws in a solidifying 2D liquid  

NASA Astrophysics Data System (ADS)

In a 2D Lennard-Jones liquid, the number of particles keeping their memorized nearest neighbors is found to decay stretched-exponentially; the probability for a particle to keep the same 6 nearest neighbors for a time t can be fitted with a power law. Using the lists of nearest neighbors (nn-lists) as a topological order parameter, we studied the dynamics of the structure underlying these signature features of complexity in materials. The nn-changes randomly appear along the boundaries of better ordered blocks at a time scale of the order of particles vibration period; these boundaries, and the shapes of the blocks, perform a next time-scale random motion. Particles diffusion includes periods of slow and fast diffusion. We discuss the feed-back interactions between nn-changes, block boundaries motion, and orientation relaxation in the system.

Patashinski, Alexander; Orlik, Rafal; Mitus, Antoni; Grzybowski, Bartosz; Ratner, Mark

2012-02-01

348

Holographic DBI-Essence Dark Energy via Power-Law Solution of the Scale Factor  

NASA Astrophysics Data System (ADS)

The present work reports a Holographic reconstruction of Dirac-Born-Infeld (DBI)-essence Dark Energy (DE) in a flat FRW universe. The scale factor a( t) is chosen in power law form. We have reconstructed the scalar field and potential and subsequently the equation of state (EoS) parameter ? of the DBI-essence DE. The corresponding plots show increasing scalar field, decaying tension and decaying potential. The reconstructed EoS parameter stays below -1, showing a phantom-like behavior. The stability of the reconstructed DBI-essence DE is investigated through squared speed of sound : its negative sign reveals that the holographically reconstructed DBI-essence is classically unstable.

Chattopadhyay, Surajit; Pasqua, Antonio

2013-11-01

349

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

SciTech Connect

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

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

2011-11-15

350

From Lognormal Distribution to Power Law:. a New Classification of the Size Distributions  

NASA Astrophysics Data System (ADS)

We propose a new classification of the size distributions of entities based on an exponent ? defined from the shape of the log-log Rank Size plot. From an inspection of a large number of cases in different fields, one finds three possibilities: ? = 1 giving a power law, ? > 1 (parabola like curve) and 0 < ? < 1 (analogous to a log normal distribution). A fourth possibility that can be defined when ? < 0 was never observed. We present a modified version of models based on a random multiplicative process and an introduction of new entities during the growth. We recover all three kinds of distributions and show that the type of a distribution is conditioned by the rate of the introduction of new entities.

Benguigui, Lucien; Blumenfeld-Lieberthal, Efrat

351

Perihelion precession from power law central force and magnetic-like force  

SciTech Connect

By the Laplace-Runge-Lenz (LRL) vector, we analyzed perihelion precessions of orbit with arbitrary eccentricity from perturbations of 1) power law central force and 2) fThusmagnetic-like force. Exact and analytically closed expressions for the precession rate are derived in both cases. In the central force case, we give a further expansion expression of precession rate in orders of eccentricity, and a rule judging pro- or retrograde precession is also given. We applied the result of central force to precessions of a planet in 1) Schwarzschild space-time, for which the formula for the Mercury's 43''/century is reproduced, and 2) spherically distributed dark matter, for which we find a formula that is a generalization of the result derived by others for circular orbit. In the magnetic case, the use of the LRL vector proves to be simple and efficient. An example of magnetic-like perturbation is also discussed.

Xu Feng [Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093 (China)

2011-04-15

352

Conductance statistics for the power-law banded random matrix model  

SciTech Connect

We study numerically the conductance statistics of the one-dimensional (1D) Anderson model with random long-range hoppings described by the Power-law Banded Random Matrix (PBRM) model. Within a scattering approach to electronic transport, we consider two scattering setups in absence and presence of direct processes: 2M single-mode leads attached to one side and to opposite sides of 1D circular samples. For both setups we show that (i) the probability distribution of the logarithm of the conductance T behaves as w(lnT){proportional_to}T{sup M2/2}, for T<<, for both the critical and the non-critical samples; and (ii) at criticality there is a smooth crossover from localized-like to delocalized-like behavior in the transport properties of the PBRM model by decreasing the fractality of its eigenstates.

Martinez-Mendoza, A. J.; Mendez-Bermudez, J. A. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apartado Postal J-48, Puebla 72570 (Mexico); Varga, Imre [Elmeleti Fizika Tanszek, Fizikai Intezet, Budapesti Mu''szaki es Gazdasagtudomanyi Egyetem, H-1521 Budapest (Hungary); Fachbereich Physik und Wissenschaftliches Zentrum fuer Materialwissenschaften, Philipps Universitaet Marburg, D-35032 Marburg (Germany)

2010-12-21

353

Ideal-Modified Bosonic Gas Trapped in AN Arbitrary Three-Dimensional Power-Law Potential  

NASA Astrophysics Data System (ADS)

We analyze the effects caused by an anomalous single-particle dispersion relation suggested in several quantum-gravity models, upon the thermodynamics of a Bose-Einstein condensate trapped in a generic three-dimensional power-law potential. We prove that the shift in the condensation temperature, caused by a deformed dispersion relation, described as a non-trivial function of the number of particles and the shape associated to the corresponding trap, could provide bounds for the parameters associated to such deformation. In addition, we calculate the fluctuations in the number of particles as a criterium of thermodynamic stability for these systems. We show that the apparent instability caused by the anomalous fluctuations in the thermodynamic limit can be suppressed considering the lowest energy associated to the system in question.

Castellanos, E.; Lämmerzahl, C.

2012-10-01

354

Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling.  

PubMed

We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito et al. [Phys. Rev. Lett. 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines. PMID:22400551

Yan, H; Guo, Hao

2012-01-27

355

Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling  

NASA Astrophysics Data System (ADS)

We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.150603 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines.

Yan, H.; Guo, Hao

2012-01-01

356

Low prevalence, quasi-stationarity and power-law behavior in a model of contagion spreading  

NASA Astrophysics Data System (ADS)

While contagion (information, infection, etc.) spreading has been extensively studied recently, the role of active local agents has not been fully considered. Here, we propose and study a model of spreading which takes into account the strength or quality of contagions as well as the local probabilistic dynamics occurring at various nodes. Transmission occurs only after the quality-based fitness of the contagion has been evaluated by the local agent. We study such spreading dynamics on Erdös-Rényi as well as scale free networks. The model exhibits quality-dependent exponential time scales at early times leading to a slowly evolving quasi-stationary state. Low prevalence is seen for a wide range of contagion quality for arbitrary large networks. We also investigate the activity of nodes and find a power-law distribution with a robust exponent independent of network topology. These properties, while absent in standard theoretical models, are observed in recent empirical observations.

Montakhab, Afshin; Manshour, Pouya

2012-09-01

357

Origins of power-law degree distribution in the heterogeneity of human activity in social networks  

NASA Astrophysics Data System (ADS)

The probability distribution of number of ties of an individual in a social network follows a scale-free power-law. However, how this distribution arises has not been conclusively demonstrated in direct analyses of people's actions in social networks. Here, we perform a causal inference analysis and find an underlying cause for this phenomenon. Our analysis indicates that heavy-tailed degree distribution is causally determined by similarly skewed distribution of human activity. Specifically, the degree of an individual is entirely random - following a ``maximum entropy attachment'' model - except for its mean value which depends deterministically on the volume of the users' activity. This relation cannot be explained by interactive models, like preferential attachment, since the observed actions are not likely to be caused by interactions with other people.

Muchnik, Lev; Pei, Sen; Parra, Lucas C.; Reis, Saulo D. S.; Andrade, José S., Jr.; Havlin, Shlomo; Makse, Hernán A.

2013-05-01

358

The power law relation of spiral waves in the Belousov-Zhabotinsky reaction  

NASA Astrophysics Data System (ADS)

The relationship of the period Ts and the wavelength ?s of spiral waves with the control parameters is systematically studied with the Belousov-Zhabotinksy (BZ) reaction in a spatially extended quasi-two-dimensional system. Our experiments indicate that Ts and ?s not only rely on the concentrations of sulfuric acid and sodium bromate, as indicated in the previous work [A. L. Belmonte, Q. Ouyang, and J. M. Flesselles, J. Phys. II 7, 1425 (1997)] but also have strong relation with the concentration of malonic acid (MA). With the influence of the concentration of MA taken into consideration, a revised power law of spiral waves is suggested, which is qualitatively in agreement with early works of numerical simulations and theoretical analysis.

Li, Yan; Bai, Shufeng; Ouyang, Qi

2000-12-01

359

Quasinormal modes of nearly extremal Kerr spacetimes: Spectrum bifurcation and power-law ringdown  

NASA Astrophysics Data System (ADS)

We provide an in-depth investigation of quasinormal-mode oscillations of Kerr black holes with nearly extremal angular momenta. We first discuss in greater detail the two distinct types of quasinormal-mode frequencies presented in a recent paper [H. Yang et al., Phys. Rev. D 87, 041502 (2013)]. One set of modes that we call “zero-damping modes” has vanishing imaginary part in the extremal limit and exists for all corotating perturbations (i.e. modes with azimuthal index m?0). The other set (the “damped modes”) retains a finite decay rate even for extremal Kerr black holes and exists only for a subset of corotating modes. As the angular momentum approaches its extremal value, the frequency spectrum bifurcates into these two distinct branches when both types of modes are present. We discuss the physical reason for the mode branching by developing and using a bound-state formulation for the perturbations of generic Kerr black holes. We also numerically explore the specific case of the fundamental l=2 modes, which have the greatest astrophysical interest. Using the results of these investigations, we compute the quasinormal-mode response of a nearly extremal Kerr black hole to perturbations. We show that many superimposed overtones result in a slow power-law decay of the quasinormal ringing at early times, which later gives way to exponential decay. This exceptional early-time power-law decay implies that the ringdown phase is long lived for black holes with large angular momentum, which could provide a promising strong source for gravitational-wave detectors.

Yang, Huan; Zimmerman, Aaron; Zengino?lu, An?l; Zhang, Fan; Berti, Emanuele; Chen, Yanbei

2013-08-01

360

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

361

Nonvisual motor learning improves visual motion perception: evidence from violating the two-thirds power law.  

PubMed

Few studies have reported direct effects of motor learning on visual perception, especially when using novel movements for the motor system. Atypical motor behaviors that violate movement constraints provide an excellent opportunity to study action-to-perception transfer. In our study, we passively trained blindfolded participants on movements violating the 2/3 power law. Before and after motor training, participants performed a visual discrimination task in which they decided whether two consecutive movements were same or different. For motor training, we randomly assigned the participants to two motor training groups or a control group. The motor training group experienced either a weak or a strong elliptic velocity profile on a circular trajectory that matched one of the visual test stimuli. The control group was presented with linear trajectories unrelated to the viewed movements. After each training session, participants actively reproduced the movement to assess motor learning. The group trained on the strong elliptic velocity profile reproduced movements with increasing elliptic velocity profiles while circular geometry remained constant. Furthermore, both training groups improved in visual discrimination ability for the learned movement as well as for highly similar movements. Participants in the control group, however, did not show any improvements in the visual discrimination task nor did participants who did not acquire the trained movement. The present results provide evidence for a transfer from action to perception which generalizes to highly related movements and depends on the success of motor learning. Moreover, under specific conditions, it seems to be possible to acquire movements deviating from the 2/3 power law. PMID:20610788

Beets, I A M; Rösler, F; Fiehler, K

2010-07-07

362

A simple marriage model for the power-law behaviour in the frequency distributions of family names  

NASA Astrophysics Data System (ADS)

In many countries, the frequency distributions of family names are found to decay as a power law with an exponent ranging from 1.0 to 2.2. In this work, we propose a simple marriage model which can reproduce this power-law behaviour. Our model, based on the evolution of families, consists of the growth of big families and the formation of new families. Preliminary results from the model show that the name distributions are in good agreement with empirical data from Taiwan and Norway.

Wu, Hao-Yun; Chou, Chung-I.; Tseng, Jie-Jun

2011-01-01

363

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

SciTech Connect

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

Debnath, P. K. [Santoshpur Sri Gouranga Vidyapith (H.S.), P.O. Kulitapara, Howrah 711312 (India); Chakrabarti, Barnali [Department of Physics, Lady Brabourne College, P1/ 2 Surawardi Avenue, Kolkata 700017 (India)

2010-10-15

364

Powerful jets from black hole X-ray binaries in Low\\/Hard X-ray states  

Microsoft Academic Search

Four persistent (Cygnus X-1, GX 339-4, GRS 1758-258 and 1E 1740.7-2942) and\\u000athree transient (GS 2023+38, GRO J0422+32 and GS 1354-64) black hole X-ray\\u000abinary systems have been extensively observed at radio wavelengths during\\u000aextended periods in the Low\\/Hard X-ray state, which is characterised in X-rays\\u000aby a hard power-law spectrum and strong variability. All seven systems show a\\u000apersistent

R. P. Fender

2000-01-01

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

The profound impact of negative power law noise on statistical estimation.  

PubMed

This paper investigates the profound impact of negative power law (neg-p) noise - that is, noise with a power spectral density L(p)(f) proportional variant | f |(p) for p < 0 - on the ability of practical implementations of statistical estimation or fitting techniques, such as a least squares fit (LSQF) or a Kalman filter, to generate valid results. It demonstrates that such negp noise behaves more like systematic error than conventional noise, because neg-p noise is highly correlated, non-stationary, non-mean ergodic, and has an infinite correlation time tau(c). It is further demonstrated that stationary but correlated noise will also cause invalid estimation behavior when the condition T > tau(c) is not met, where T is the data collection interval for estimation. Thus, it is shown that neg-p noise, with its infinite Tau(c), can generate anomalous estimation results for all values of T, except in certain circumstances. A covariant theory is developed explaining much of this anomalous estimation behavior. However, simulations of the estimation behavior of neg-p noise demonstrate that the subject cannot be fully understood in terms of covariant theory or mean ergodicity. It is finally conjectured that one must investigate the variance ergodicity properties of neg-p noise through the use of 4th order correlation theory to fully explain such simulated behavior. PMID:20040429

Reinhardt, Victor S

2010-01-01

367

Signal detection in power-law noise: effect of spectrum exponents.  

PubMed

Many natural backgrounds have approximately isotropic power spectra of the power-law form, P(f)=K/f(beta), where f is radial frequency. For natural scenes and mammograms, the values of the exponent, beta, range from 1.5 to 3.5. The ideal observer model predicts that for signals with certain properties and backgrounds that can be treated as random noise, a plot of log (contrast threshold) versus log (signal size) will be linear with slope, m, given by: m=(beta-2)/2. This plot is referred to as a contrast-detail (CD) diagram. It is interesting that this predicts a detection threshold that is independent of signal size for beta equal to 2. We present two-alternative forced-choice (2AFC) detection results for human and channelized model observers of a simple signal in filtered noise with exponents from 1.5 to 3.5. The CD diagram results are in good agreement with the prediction of this equation. PMID:18059914

Burgess, Arthur E; Judy, Philip F

2007-12-01

368

Binary Quasars Observed by Chandra  

NASA Astrophysics Data System (ADS)

We present analysis of Chandra X-ray imaging and spectroscopy for a sample of 14 quasars in close pairs, targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from Sloan Digital Sky Survey (SDSS). One pair, SDSS J1254+0846 at z=0.44 clearly inhabits an ongoing, pre-coalescence galaxy merger showing obvious tidal tails. We measure the X-ray properties of all 14 QSOs, and study the distribution of X-ray and optical-to-X-ray power-law indices in these binary quasars, and find no significant difference with large control samples of isolated quasars. We present near-IR photometry from UKIDDS, 2MASS or the MMT with SWIRC, and fit simple spectral energy distributions to all 14 QSOs, and find preliminary evidence that substantial contributions from star formation are required, but no more so than for isolated X-ray-detected QSOs. Sensitive searches of the X-ray images for extended emission, and the optical images for optical galaxy excess show that these binary QSOs, while likely occurring in strong peaks of the dark matter distribution, are not preferentially found in rich cluster environments.

Green, Paul J.; Myers, A. D.; Barkhouse, W. A.; Trichas, M.; Aldcroft, T. L.; Ruiz, A.; Hopkins, P.; Richards, G. T.

2011-05-01

369

The effects of viscous dissipation on heat transfer to power law fluids in arbitrary cross-sectional ducts  

Microsoft Academic Search

In this paper, the analytical study of forced convection heat transfer to power-law fluids in arbitrary cross-sectional ducts with finite viscous dissipation is undertaken. Both the flow and heat transfer develop simultaneously from the entrance of the duct the walls of which are maintained at a constant temperature different from the entering fluid temperature. The governing conservation equations written in

A. Lawal; A. S. Mujumdar

1992-01-01

370

Laminar Flow and Heat Transfer in Power-Law Fluids Flowing in Arbitrary Cross-Sectional Ducts  

Microsoft Academic Search

A numerical method capable of handling three-dimensional transport processes is devised to model the developing steady laminar flow and heat transfer to power-law fluids flowing in ducts of arbitrary but uniform cross section. The governing equations are the general momentum and energy equations parabolized in the axial direction and as such are applicable to flow systems with a predominant flow

Adeniyi Lawal; Arun Mujumdar

1985-01-01

371

Convection Heat and Mass Transfer in an Electrical Conducting Power Law Flow over a Heated Vertical Porous Plate  

Microsoft Academic Search

This paper investigates convection heat and mass transfer flow in an electrically conducting power law fluid past a vertical porous plate in presence of a transverse magnetic field, thermal radiation, and thermal diffusion. The non–linear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method and the resulting similarity equations are solved numerically

B. I. Olajuwon

2010-01-01

372

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

SciTech Connect

Active region 11029 was a small, highly flare-productive solar active region observed at a time of extremely low solar activity. The region produced only small flares: the largest of the >70 Geostationary Observational Environmental Satellite (GOES) events for the region has a peak 1-8 A flux of 2.2 x 10{sup -6} W m{sup -2} (GOES C2.2). The background-subtracted GOES peak-flux distribution suggests departure from power-law behavior above 10{sup -6} W m{sup -2}, and a Bayesian model comparison strongly favors a power-law plus rollover model for the distribution over a simple power-law model. The departure from the power law is attributed to this small active region having a finite amount of energy. The rate of flaring in the region varies with time, becoming very high for 2 days coinciding with the onset of an increase in complexity of the photospheric magnetic field. The observed waiting-time distribution for events is consistent with a piecewise-constant Poisson model. These results present challenges for models of flare statistics and of energy balance in solar active regions.

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

2010-02-20

373

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

NASA Astrophysics Data System (ADS)

We develop a simple test for deviations from power law tails. Actually, from the tails of any distribution. We use this test - which is based on the asymptotic properties of the empirical distribution function - 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, J.; Weron, R.

2012-05-01

374

A regional comparison of particle size distributions and the power law approximation in oceanic and estuarine surface waters  

Microsoft Academic Search

The particle size distribution (PSD) is commonly used in studies of sediment fluxes, phytoplankton dynamics, and optical scattering from particulates, but little is known about the spatial and temporal variability of this parameter. Here, we analyze in situ laser diffraction measurements of the PSD from a variety of estuarine and open ocean systems. The power law or “Junge-type” distribution provided

C. J. Buonassissi; H. M. Dierssen

2010-01-01

375

The Origins of the ‘Nonmarket Economy’: Ideas, Pluralism & Power in EC Anti-dumping Law about China  

Microsoft Academic Search

‘Market’ and ‘market economy’ exercise a powerful, even magnetic grip on our collective imagination. But what do we mean by ‘market economy’? Does it make sense to speak of a ‘nonmarket economy’, and if so, what does it mean? How are the ideas of ‘market economy’ and ‘nonmarket economy’ related? Focusing on EC anti-dumping law, this article seeks to answer

Francis Snyder

2001-01-01

376

Exploring the origins of the power-law properties of energy landscapes: An egg-box model  

Microsoft Academic Search

Multidimensional potential energy landscapes (PELs) have a Gaussian distribution for the energies of the minima, but at the same time the distribution of the hyperareas for the basins of attraction surrounding the minima follows a power-law. To explore how both these features can simultaneously be true, we introduce an ``egg-box'' model. In these model landscapes, the Gaussian energy distribution is

Claire P. Massen; Jonathan P. K. Doye; Rupert W. Nash

2007-01-01

377

Exploring the origins of the power-law properties of energy landscapes: An egg-box model  

Microsoft Academic Search

Multidimensional potential energy landscapes (PELs) have a Gaussian distribution for the energies of the minima, but at the same time the distribution of the hyperareas for the basins of attraction surrounding the minima follows a power-law. To explore how both these features can simultaneously be true, we introduce an “egg-box” model. In these model landscapes, the Gaussian energy distribution is

Claire P. Massen; Jonathan P. K. Doye; Rupert W. Nash

2007-01-01

378

Thermostatistical properties of q-deformed bosons trapped in a D-dimensional power-law potential  

NASA Astrophysics Data System (ADS)

The thermostatistical properties of an ideal gas of q-deformed bosons trapped in a D-dimensional power-law potential are studied, based on the q-deformed Bose-Einstein distribution. The effects of q-deformation on the properties of the system are discussed. It is shown that q-deformed bosons (q \

Su, Guozhen; Chen, Jincan; Chen, Lixuan

2003-10-01

379

Viscous timescale in high mass X-ray binaries  

NASA Astrophysics Data System (ADS)

Context. Low mass X-ray binaries are found to have very low frequency breaks in their power density spectra. The power density spectra below these breaks are nearly in white noise structure and at higher frequencies approximately follow the P? ? ?-1.3 law. Aims: To determine whether high mass X-ray binary power density spectra have similar properties and the findings for low mass X-ray binaries are also valid for high mass binaries, we analyzed the time series of high mass X-ray binary sources produced by All Sky Monitor of Rossi X-ray Timing Explorer. Methods: We obtained the power density spectra of the high mass X-ray binaries using the cosine transform of autocorrelation function. Results: We identified break frequencies for seven sources, namely OAO 1657-415, SS 433, Vela X-1, SMC X-1, 4U 1700-377, GX 301-2, and LMC X-1. The normalized break frequencies with respect to the orbital frequency (fbreak/forbit) for sources OAO 1657-415, SS 433, SMC X-1 and LMC X-1 are consistent with those of Roche lobe overflow systems. The other high mass X-ray binary systems, Vela X-1, GX 301-2, and 4U 1700-377, however, have larger break frequency ratios, fbreak/forb, which are indicative of short viscous times. These are all wind-accreting sources and the stellar winds in the systems allow the formation of only short radius discs. Consequently, we qualitatively distinguished the Roche lobe overflow binaries from the wind accreting system by comparing their normalized break frequencies.

Içdem, B.; Baykal, A.

2011-05-01

380

Summary of investigations of the use of modified turbine inlet conditions in a binary power plant.  

National Technical Information Service (NTIS)

Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of ...

G. L. Mines

2000-01-01

381

Performance of a 5MW(e) binary geothermal-electric power plant  

Microsoft Academic Search

A 5-MW(e) Pilot Geothermal Power Plant was built by the Idaho National Engineering Laboratory (INEL), 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°F) to generate electrical power

C. J. Bliem; K. S. Fullmer; R. J. Kochan

1983-01-01

382

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

Microsoft Academic Search

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°F) to generate electrical power in an environmentally acceptable manner. The plant

Bliem; C. J. Jr

1983-01-01

383

Performance of a 5MW(e) binary geothermal-electric power plant  

Microsoft Academic Search

A 5MW(e) Pilot Geothermal Power Plant was built by the Idaho National Engineering Laboratory (INEL), 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°F) to generate electrical power

C. J. Bliem; K. Fullmer; R. J. Kochan

1983-01-01

384

On the numerical simulation of random fields with a truncated power-law correlation function.  

NASA Astrophysics Data System (ADS)

Flow and solute transport in fractured media have become a viable research topic since several countries have decided on or pondering the use of fractured rock as host medium for the deposition of nuclear waste. Due to the highly hazardous potential of nuclear material for the biosphere precise as well as effective computational tools must be provided in order to facilitate risk analysis for decision makers. One of the challenges for the accurate description of fractured media is the fractal nature of the permeability. This means that heterogeneities appear continuous over a wide range of spatial scales, without any preference as well as separation amongst them. Di Federico and Neuman (WRR 1997) showed how such permeability fields can be represented by stochastic fields with a truncated power-law correlation function. The power law accounts for the fractal nature of the heterogeneities, whereas the truncation represents the finite size of any real medium confining the fractal behavior within certain bounds. Common methods for the generation of random fields, like the Fourier method, are not able to adequately generate random fields with such features. In our study we investigate and compare two newer methods; the Randomization method as well as the Fourier-Wavelet method. We evaluate these methods with respect to their ability to represent the correlation function over a number of spatial scales as well as the Gaussianity of the generated fields. We furthermore compare these two methods with respect to computational costs. Results show that the Randomization method performs well if only a few number of spatial scales (4-6 orders of magnitude) need to be represented. Due to its simpler implementation it can be preferred over the Fourier-Wavelet method. For a larger interval of spatial scales (9-12 orders of magnitude) however, the Randomization method fails to represent the correlation function. Under such circumstances the Fourier-Wavelet method should be used. In addition to this comparison we also investigate structural features of the generated permeability fields by means of the Euler number and the chord distribution. Results show the transition from a fractal regime for small length scales to a classic (Gaussian or exponential) regime for larger length scales. We interpret these findings with respect to flow and transport properties.

Hesse, F.; Prykhodko, V.; Attinger, A.

2012-04-01

385

Modeling of magnetic properties and alternate current losses in high-Tc superconductors using a power law voltage-current characteristic  

Microsoft Academic Search

This article presents numerical diffusion models which describe the electromagnetic properties and alternate current (ac) losses of a high-Tc superconducting tape carrying transport current. The models simulate the tape as a highly nonlinear conductor with equivalent resistivity being a function of J, the local current density, as deduced from a power law E-J characteristic of the material. The power law

A. E. Mahdi; A. Tami; R. L. Stoll

1999-01-01

386

Modeling of magnetic properties and alternate current losses in high-Tc superconductors using a power law voltage–current characteristic  

Microsoft Academic Search

This article presents numerical diffusion models which describe the electromagnetic properties and alternate current (ac) losses of a high-Tc superconducting tape carrying transport current. The models simulate the tape as a highly nonlinear conductor with equivalent resistivity being a function of J, the local current density, as deduced from a power law E–J characteristic of the material. The power law

A. E. Mahdi; A. Tami; R. L. Stoll

1999-01-01

387

The nurses' power to detain informal psychiatric patients: a review of the statutory and common law provisions in England and Wales  

Microsoft Academic Search

This paper explores the extent to which nurses can use statutory and common law provisions as lawful authority to detain informal psychiatric patients. The power of a nurse to detain informal psychiatric patients received statutory recognition for the first time in the Mental Health Act 1983. Section 5(4) of this Act, the 'Nurses Holding Power', provides for nurses of the

Gary D. Houlihan; SRN RMN

2000-01-01

388

Preliminary performance estimates and value analyses for binary geothermal power plants using ammonia-water mixtures as working fluids  

NASA Astrophysics Data System (ADS)

The use of ammonia-water mixtures as working fluids in binary geothermal power generation systems is investigated. The available thermodynamic data is discussed and the methods of extrapolating this data to give the quantities needed to perform analyses of the system is given. It is indicated that for a system without a recuperator and with a working fluid which is 50% by mass of each constituent, the geofluid effectiveness is 84% of that for the 50 MW Heber Plant. The cost of generating electric power for this system was estimated to be 9% greater than for the Heber Plant. If a recuperator is incorporated in the system however, the geofluid effectiveness becomes 102% of that for the Heber Plant, and the cost of electricity is 5.25% lower because of less expensive equipment resulting from lower pressure, better heat transfer, and less working fluid to handle for the ammonia water plant. It is concluded that use of nonazeotropic mixtures of fluorocarbons as working fluids should be studied before expending further effort in the investigation of the ammonia water mixtures.

Bliem, C. J.

1983-12-01

389

A TWO-COMPONENT POWER LAW COVERING NEARLY FOUR ORDERS OF MAGNITUDE IN THE POWER SPECTRUM OF SPITZER FAR-INFRARED EMISSION FROM THE LARGE MAGELLANIC CLOUD  

Microsoft Academic Search

Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70, and 160 m observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at k ¹ 100-200 pc, which is interpreted as the line-of-sight thickness of

David L. Block; Ivanio Puerari; Bruce G. Elmegreen; Frederic Bournaud

2010-01-01

390

Oscillatory and fluctuating terms in energies of assemblies of equicharged particles subject to spherically symmetric power-law confining potentials  

NASA Astrophysics Data System (ADS)

Energies E(N) of assemblies of equicharged particles subject to spherically symmetric power-law confining potentials vary in a convoluted fashion with the particle totalities N. Accurate rigorous upper bounds to these energies, which are amenable to detailed mathematical analysis, are found to comprise terms with smooth, oscillatory, and fluctuating dependences on N. The smooth energy component is obtained as a power series in N-2/3 with the first two terms corresponding to the bulk and Madelung energies. The oscillatory component possesses the large-N asymptotics given by a product of N1/(? + 1), where ? is the power-law exponent, and a function periodic in N1/3. The amplitude of the fluctuating component, which originates mostly from the irregular dependence of the Thomson energy ETh(n) on n, also scales like N1/(? + 1).

Cioslowski, Jerzy; Albin, Joanna

2013-09-01

391

Ionization of H Rydberg atoms: Fractals and power-law decay  

NASA Astrophysics Data System (ADS)

Concepts from the theory of transient chaos are applied to study the classical ionization process of a one-dimensional model of kicked hydrogen Rydberg atoms. It is proved analytically that for a range of field parameters the associated classical phase space is devoid of regular islands. In this case, the fraction of atoms PB(t) not ionized after time t decays asymptotically according to PB(t)~t-? with ?~=1.65. The origin of the algebraic decay can be traced back to the fractal structure of the invariant set of never-ionizing phase-space points, and is explained by the symbolic dynamics of this system, which consists of a countably infinite number of symbols. The algebraic decay is reproduced by an analytically solvable diffusion model that predicts ?=3/2. Replacing zero-width ? kicks with smooth finite-width pulses, a subset of phase space is regular. For this case we observe that PB(t) shows a transition between two power-law regimes with ?~=1.65 for short times and ?~=2.1 for long times, where the effect of Cantori and regular islands is felt.

Hillermeier, C. F.; Blümel, R.; Smilansky, U.

1992-03-01

392

Creep characterization of power-law materials through pseudo-steady indentation tests and numerical simulations  

NASA Astrophysics Data System (ADS)

A constant-indentation creep rate test (CICRT) has been carried out for an Al-Mg solid-solution alloy using a microindenter in the temperature range of 636-773 K. When a conical indenter is pressed into the specimen surface under a load condition of F=F0 exp(?t) (F the indentation load, F0 the initial load, ? the loading rate parameter, t the loading time), the indentation pressure and indentation creep rate approach constant values of ps and dot epsilonin(s), respectively. The representative points of the deformation in the underlying material are defined on a contour line of the equivalent stress ?r = C1ps, where C1 is the so-called constraint coefficient of 1/3 reported by Tabor. The finite element simulation of a power-law material subjected to the CICRT shows that the relationship between the equivalent plastic strain rate dot epsilonr at these points and dot epsilonin(s) is dot epsilonr=C2dot epsilonin(s) and that C2 approxeq 1/3.6 in the case of a creep stress exponent of 3.0. The constitutive equation of dot epsilonr versus ?r obtained from experimental data and the computed value of C2 is in good agreement with that evaluated from conventional uniaxial creep tests.

Takagi, Hidenari; Dao, Ming; Fujiwara, M.

2010-07-01

393

Gravitational contributions to gauge Green's functions and asymptotic free power-law running of gauge coupling  

NASA Astrophysics Data System (ADS)

We perform an explicit one-loop calculation for the gravitational contributions to the two-, three- and four-point gauge Green's functions with paying attention to the quadratic divergences. It is shown for the first time in the diagrammatic calculation that the Slavnov-Taylor identities are preserved even if the quantum graviton effects are included at one-loop level, such a conclusion is independent of the choice of regularization schemes. We also present a regularization scheme independent calculation based on the gauge condition independent background field framework of Vilkovisky-DeWitt's effective action with focusing on both the quadratic divergence and quartic divergence that is not discussed before. With the harmonic gauge condition, the results computed by using the traditional background field method can consistently be recovered from the Vilkovisky-DeWitt's effective action approach by simply taking a limiting case, and are found to be the same as the ones yielded by the diagrammatic calculation. As a consequence, in all the calculations, the symmetry-preserving and divergent-behavior-preserving loop regularization method can consistently lead to a nontrivial gravitational contribution to the gauge coupling constant with an asymptotic free power-law running at one loop near the Planck scale.

Tang, Yong; Wu, Yue-Liang

2011-11-01

394

Newtonian and Power-Law fluid flow in a T-junction of rectangular ducts  

NASA Astrophysics Data System (ADS)

The aim of the present study is the numerical investigation of the shear-thinning and shear-thickening effects of flow in a T-junction of rectangular ducts. The employed CFD code incorporates the SIMPLE scheme in conjunction with the finite volume method with collocated arrangement of variables. The code enables multi-block computations in domains with multiple apertures, thus coping with the two-block, two-outlet layout of the current 3D computational domain. The shear-thinning and shear-thickening behaviours of the flow are covered by changing the index n of the Power-Law model within a range from 0.20 to 1.25, and the subsequent effects are investigated by means of different flow parameters namely the Reynolds (Re) number and the boundary conditions at the outlets. Results exhibit the extent of the effect of the Re number on the velocity profiles at different positions in the domain for both Newtonian and non-Newtonian cases. Similarly, the trend of the effect of shear-thinning and shear-thickening behaviours on the flow rate ratio between inlet and outlets, in the case of equal pressure imposed on outlets, is shown.

Neofytou, P.; Housiadas, C.; Tsangaris, S. G.; Stubos, A. K.; Fotiadis, D. I.

2013-08-01

395

Power-law persistence and trends in the atmosphere: a detailed study of long temperature records.  

PubMed

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) approximately s(-gamma). For continental stations, including stations along the coastlines, 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. In all cases, the exponent gamma does not depend on the distance of the stations to the continental coastlines. By varying the degree of detrending in the fluctuation analysis we obtain also information about trends in the temperature records. PMID:14683028

Eichner, J F; Koscielny-Bunde, E; Bunde, A; Havlin, S; Schellnhuber, H-J

2003-10-28

396

Nematic phase in two-dimensional frustrated systems with power-law decaying interactions.  

PubMed

We address the problem of orientational order in frustrated interaction systems as a function of the relative range of the competing interactions. We study a spin model Hamiltonian with short-range ferromagnetic interaction competing with an antiferromagnetic component that decays as a power law of the distance between spins, 1/r(?). These systems may develop a nematic phase between the isotropic disordered and stripe phases. We evaluate the nematic order parameter using a self-consistent mean-field calculation. Our main result indicates that the nematic phase exists, at mean-field level, provided 0

Barci, Daniel G; Ribeiro, Leonardo; Stariolo, Daniel A

2013-06-13

397

Spatiotemporal dynamics of prairie wetland networks: power-law scaling and implications for conservation planning.  

PubMed

Although habitat networks show promise for conservation planning at regional scales, their spatiotemporal dynamics have not been well studied, especially in climate-sensitive landscapes. Here I use satellite remote sensing to compile wetland habitat networks from the Prairie Pothole Region (PPR) of North America. An ensemble of networks assembled across a hydrologic gradient from deluge to drought and a range of representative dispersal distances exhibits power-law scaling of important topological parameters. Prairie wetland networks are "meso-worlds" with mean topological distance increasing faster with network size than small-world networks, but slower than a regular lattice (or "large world"). This scaling implies rapid dispersal through wetland networks without some of the risks associated with "small worlds" (e.g., extremely rapid propagation of disease or disturbance). Retrospective analysis of wetland networks establishes a climatic envelope for landscape connectivity in the PPR, where I show that a changing climate might severely impact metapopulation viability and restrict long-distance dispersal and range shifts. More generally, this study demonstrates an efficient approach to conservation planning at a level of abstraction addressing key drivers of the global biodiversity crisis: habitat fragmentation and climatic change. PMID:20715611

Wright, Christopher K

2010-07-01

398

Cosmic histories of star formation and reionization: an analysis with a power-law approximation  

NASA Astrophysics Data System (ADS)

With a simple power-law approximation of high-redshift (gtrsim3.5) star formation history, i.e., dot rho*(z)propto[(1+z)/4.5]-?, we investigate the reionization of intergalactic medium (IGM) and the consequent Thomson scattering optical depth for cosmic microwave background (CMB) photons. A constraint on the evolution index ? is derived from the CMB optical depth measured by the Wilkinson Microwave Anisotropy Probe (WMAP) experiment, which reads ? ? 2.18 lg Script N?-3.89, where the free parameter Script N? is the number of the escaped ionizing ultraviolet photons per baryon. At the same time, the redshift zf at which the IGM is fully ionized can also be expressed as a function of ? as well as Script N?. By further taking into account the implication of the Gunn-Peterson trough observations to quasars for the full reionization redshift, i.e., 6lesssimzflesssim7, we obtain 0.3lesssim?lesssim1.3 and 80lesssimScript N?lesssim230. For a typical number of ~ 4000 of ionizing photons released per baryon of normal stars, the fraction of these photons escaping from the stars, fesc, can be constrained to within the range of (2.0-5.8)%.

Yu, Yun-Wei; Cheng, K. S.; Chu, M. C.; Yeung, S.

2012-07-01

399

The Aggregation Equation with Power-Law Kernels: Ill-Posedness, Mass Concentration and Similarity Solutions  

NASA Astrophysics Data System (ADS)

We study the multidimensional aggregation equation {u_t+div(uv)=0, v=-nabla K*u} with initial data in {fancyscript{P}_2left(mathbb R^dright)\\cap Lp left(mathbb R^dright)}. We prove that with biological relevant potential K( x) = | x|, the equation is ill-posed in the critical Lebesgue space {L_{d/(d-1)}left(mathbb R^dright)} in the sense that there exists initial data in {fancyscript{P}_2left(mathbb R^dright)\\cap L_{d/(d-1)}left(mathbb R^dright)} such that the unique measure-valued solution leaves {L_{d/(d-1)}left(mathbb R^dright)} immediately. We also extend this result to more general power-law kernels K( x) = | x| ? , 0 < ? < 2 for p = p s := d/( d + ? - 2), and prove a conjecture in Bertozzi et al. (Comm Pure Appl Math 64(1):45-83, 2010) about instantaneous mass concentration for initial data in {fancyscript{P}_2left(mathbb R^dright)\\cap Lpleft(mathbb R^dright)} with p < p s . Finally, we characterize all the "first kind" radially symmetric similarity solutions in dimension greater than two.

Dong, Hongjie

2011-06-01

400

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

2009-10-29

401

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

SciTech Connect

There is a continuing debate about the applicability of the theory presented by Fisk and Gloeckler (FG) regarding the formation of suprathermal ion tails in phase space density vs. velocity spectra; in the solar wind frame the FG theory predicts a power law index of-5 (which is equivalent to a differential intensity vs. energy index of-1.5). There has also been uncertainty and perhaps misunderstanding regarding the extent to which such spectra are actually observed; i.e., is there really a significant preference for the -5 index? Here we report the results of an interim technique we use to analyze {approx}1-100 keV/nucleon interplanetary suprathermal H{sup +}, He{sup +}, and He{sup ++}, spectra measured at the Cassini spacecraft by the Charge Energy Mass Spectrometer (CHEMS) instrument of the Magnetospheric Imaging Instrument (MIMI) suite during the cruise to Saturn. We analyzed 18 active periods and report a mean index in the solar wind frame of 4.9{+-}0.4 for protons, 5.2{+-}0.5 for He{sup +}, and 4.7{+-}0.2 for alpha particles. MIMI/CHEMS offers much needed independent observations of heliospheric ions in the suprathermal energy range.

Hill, M. E. [Johns Hopkins Applied Physics Laboratory, Laurel, Maryland 20723 (United States); Hamilton, D. C. [University of Maryland College Park, Maryland 20742 (United States)

2010-12-30

402

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

NASA Astrophysics Data System (ADS)

There is a continuing debate about the applicability of the theory presented by Fisk and Gloeckler (FG) regarding the formation of suprathermal ion tails in phase space density vs. velocity spectra; in the solar wind frame the FG theory predicts a power law index of-5 (which is equivalent to a differential intensity vs. energy index of-1.5). There has also been uncertainty and perhaps misunderstanding regarding the extent to which such spectra are actually observed; i.e., is there really a significant preference for the -5 index? Here we report the results of an interim technique we use to analyze ~1-100 keV/nucleon interplanetary suprathermal H+, He+, and He++, spectra measured at the Cassini spacecraft by the Charge Energy Mass Spectrometer (CHEMS) instrument of the Magnetospheric Imaging Instrument (MIMI) suite during the cruise to Saturn. We analyzed 18 active periods and report a mean index in the solar wind frame of 4.9+/-0.4 for protons, 5.2+/-0.5 for He+, and 4.7+/-0.2 for alpha particles. MIMI/CHEMS offers much needed independent observations of heliospheric ions in the suprathermal energy range.

Hill, M. E.; Hamilton, D. C.

2010-12-01

403

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

SciTech Connect

For zero energy, E = 0, we derive exact, classical and quantum solutions for all power-law oscillators with potentials V(r) = {minus}{gamma}/r{sup {nu}}, {gamma} > 0 and {minus}{infinity} < {nu} < {infinity}. When the angular momentum is non-zero, these solutions lead to the classical orbits {rho}(t) = [cos {mu}({var_phi}(t) {minus} {var_phi}{sub 0}(t))]{sup 1/{mu}}, with {mu} = {nu}/2 {minus} 1 {ne} 0. For {nu} > 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} > 2 the solutions are normalizable (bound), as in the classical case. Also, there are normalizable discrete, yet unbound, state which correspond to unbound classical particles which reach infinity in a finite time. These and other interesting comparisons to the classical system will be discussed.

Nieto, M.M. [Los Alamos National Lab., NM (United States); Daboul, J. [Ben Gurion Univ. of the Negev, Beer Sheva (Israel)

1994-07-01

404

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

SciTech Connect

We present a time-dependent and spatially inhomogeneous solution that interpolates the extremal Reissner-Nordstroem (RN) black hole and the Friedmann-Lemaitre-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 n{sub T}, the U(1) charge Q, and the nonextremality {tau}. 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 [Department of Physics, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Waseda Research Institute for Science and Engineering, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Nozawa, Masato [Department of Physics, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan)

2010-06-15

405

Performance of a 5-MW(E) Binary Geothermal-Electric Power Plant.  

National Technical Information Service (NTIS)

A 5-MW(e) Pilot Geothermal Power Plant was built by the Idaho National Engineering Laboratory (INEL), 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 wa...

C. J. Bliem K. S. Fullmer R. J. Kochan

1983-01-01

406

Raft River 5MW(E) Binary Geothermal-Electric Power Plant: Operation and Performance.  

National Technical Information Service (NTIS)

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 utilizin...

C. J. Bliem

1983-01-01

407

Uniform Power Method for Sample Size Calculation in Historical Control Studies with Binary Response  

Microsoft Academic Search

Makuch and Simon gave a sample size calculation formula for historical control (HC) studies that assumed that the observed response rate in the control group is the true response rate. We dropped this assumption and computed the expected power and expected sample size to evaluate the performance of the procedure under the omniscient model. When there is uncertainty in the

J. Jack Lee; Chi-hong Tseng

2001-01-01

408

Evaluating power and type 1 error in large pedigree analyses of binary traits.  

PubMed

Studying population isolates with large, complex pedigrees has many advantages for discovering genetic susceptibility loci; however, statistical analyses can be computationally challenging. Allelic association tests need to be corrected for relatedness among study participants, and linkage analyses require subdividing and simplifying the pedigree structures. We have extended GenomeSIMLA to simulate SNP data in complex pedigree structures based on an Amish pedigree to generate the same structure and distribution of sampled individuals. We evaluated type 1 error rates when no disease SNP was simulated and power when disease SNPs with recessive, additive, and dominant modes of inheritance and odds ratios of 1.1, 1.5, 2.0, and 5.0 were simulated. We generated subpedigrees with a maximum bit-size of 24 using PedCut and performed two-point and multipoint linkage using Merlin. We also ran MQLS on the subpedigrees and unified pedigree. We saw no inflation of type 1 error when running MQLS on either the whole pedigrees or the sub-pedigrees, and we saw low type 1 error for two-point and multipoint linkage. Power was reduced when running MQLS on the subpedigrees versus the whole pedigree, and power was low for two-point and multipoint linkage analyses of the subpedigrees. These data suggest that MQLS has appropriate type 1 error rates in our Amish pedigree structure, and while type 1 error does not seem to be affected when dividing the pedigree prior to linkage analysis, power to detect linkage is diminished when the pedigree is divided. PMID:23658753

Cummings, Anna C; Torstenson, Eric; Davis, Mary F; D'Aoust, Laura N; Scott, William K; Pericak-Vance, Margaret A; Bush, William S; Haines, Jonathan L

2013-05-03

409

Minorities, Muslims and Shari: Some Reflections on Islamic Law and Muslims without Political Power  

Microsoft Academic Search

Muslims are defined as Muslims by their sacred law; as such, they constitute a religious community delineated, theoretically and practically, according to a notion of jurisprudence. The comprehensive nature of that law has led many to doubt the ability of Muslims to integrate into non-Muslim societies, and the confusion remains in various ways in the present day, with many continuing

Hisham A. Hellyer

2007-01-01

410

Harnessing the power of multimedia in offender-based law enforcement information systems  

Microsoft Academic Search

Criminal offenders are increasingly administratively processed by automated multimedia information systems. During this processing, case and offender biographical data, mugshot photos, fingerprints and other valuable information and media are collected by law enforcement officers. As part of their criminal investigations, law enforcement officers are routinely called to solve criminal cases based upon limited evidence . . . evidence increasingly comprised

Alan P. Zimmerman

1997-01-01

411

Application of power laws to low Reynolds number boundary layers on smooth and rough surfaces  

Microsoft Academic Search

Scaling laws for the overlap region of near-wall turbulent flows are of particular interest to turbulence researchers and engineers. For the mean flow at sufficiently high Reynolds numbers, the classical boundary layer theory proposes a logarithmic law for the overlap region. On the other hand, at low Reynolds numbers, refined measurements and direct numerical simulation results indicate that the log

D. J. Bergstrom; M. F. Tachie; R. Balachandar

2001-01-01

412

The Power of Comparison in Teaching about Constitutionalism, Law, and Democracy.  

ERIC Educational Resources Information Center

Promoting change in civic education means rethinking what are the important aspects to teach about the Constitution, law, and democracy to equip students to be effective and affective citizens. The scope of instruction needs to broaden to include specific comparisons between the U.S. federal system of law and constitutionalism with counterparts in…

Hall, Kermit L.

413

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

SciTech Connect

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 {gamma}=3 and clustering coefficient C=(46/3)-36 ln (3/2){approx_equal}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){approx}k{sup -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 Barabasi-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 N{approx}10{sup 4}), 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 [Nonlinear Science Center and Department of Modern Physics, University of Science and Technology of China, Hefei Anhui, 230026 (China); Department of Electronic Science and Technology, University of Science and Technology of China, Hefei Anhui, 230026 (China); Yan Gang [Department of Electronic Science and Technology, University of Science and Technology of China, Hefei Anhui, 230026 (China); Wang Binghong [Nonlinear Science Center and Department of Modern Physics, University of Science and Technology of China, Hefei Anhui, 230026 (China)

2005-04-01

414

Negative Power Law Scaling of Rockfalls along the Yorkshire Coast: Implications for Long Term Landscape Evolution  

NASA Astrophysics Data System (ADS)

An increasing body of evidence suggests that rockfalls follow a negative power law scaling in their magnitude-frequency distribution of the form F = aM-b. Where F is the normalized frequency density, M is the event magnitude, and a / b are dimensionless scaling coefficients. Investigation using Terrestrial Laser Scanning (TLS) has produced an extremely high resolution inventory of rockfall magnitudes along the sea cliffs near Staithes, UK. Such data is ideal for erosion modelling. Once the scaling parameters have been estimated, the volume of eroded rock for events of magnitude x (Vx) is derived as Vx = ax-b+1. Therefore, the total volume (V t) of eroded rock between a minimum and maximum magnitude can be calculated by taking by integrating the above. An examination of monthly fluctuations in the scaling coefficients indicates greater variation within the winter months in response to higher deliveries of wave energy during these months. Initial results using geophone data indicate a relationship between the magnitude of the scaling coefficients and the amount of wave energy delivered to the cliff. Such linkages suggest the possibility of a predictive model for erosion based on wave climate, providing a predictive capability for the implications of environmental change. Model testing is to be accomplished using an innovative cliff recession model derived using cosmogenic isotope concentrations and paleoenvironmental data. Our cosmogenic dating model considers marine variables (tidal range, wave climate and inundation duration); Holocene relative sea level change; lateral cliff retreat, and the consequent changes in geometrical and marine shielding to establish the rate of retreat based on a continuum of Be10 concentrations.

Barlow, John; Rosser, Nick; Lime, Michael; Petley, David; Brain, Matthew; Sapsford, Melanie; Norman, Emma

2010-05-01

415

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.

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

2009-01-01

416

Fractional power-law spectral response of CaCu3Ti4O12 dielectric: Many-body effects  

NASA Astrophysics Data System (ADS)

Spectral character of dielectric response in CaCu3Ti4O12 across 0.5 Hz-4MHz over 45-200 K corresponding to neither the Debyean nor the KWW relaxation patterns rather indicates a random-walk like diffusive dynamics of moments. Non-linear relaxation here is due to the many body dipole-interactions, as confirmed by spectral-fits of our measured permittivity to the Dissado-Hill behaviour. Fractional power-laws observed in ?*(?) macroscopically reflect the fractal microscopic configurations. Below ~100 K, the power-law exponent m (n) steeply decreases (increases), indicating finite length-scale collective response of moment-bearing entities. At higher temperatures, m gradually approaches 1 and n falls to low values, reflecting tendency towards the single-particle/Debyean relaxation.

Kumar, Jitender; Awasthi, A. M.

2012-08-01

417

New soliton and periodic solutions of (1 + 2)-dimensional nonlinear Schrödinger equation with dual-power law nonlinearity  

NASA Astrophysics Data System (ADS)

With the aid of symbolic computation, the new generalized algebraic method is extended to the (1 + 2)-dimensional nonlinear Schrödinger equation (NLSE) with dual-power law nonlinearity for constructing a series of new exact solutions. Because of the dual-power law nonlinearity, the equation cannot be directly dealt with by the method and require some kinds of techniques. By means of two proper transformations, we reduce the NLSE to an ordinary differential equation that is easy to solve and find a rich variety of new exact solutions for the equation, which include soliton solutions, combined soliton solutions, triangular periodic solutions and rational function solutions. Numerical simulations are given for a solitary wave solution to illustrate the time evolution of the solitary creation. Finally, conditional stability of the solution in Lyapunov’s sense is discussed.

Zhang, Li-Hua; Si, Jian-Guo

2010-10-01

418

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

419

a Development of Accelerated Life Test Method for Blower Motor for Automobile Using Inverse Power Law Model  

NASA Astrophysics Data System (ADS)

Reliability of automotive parts has been one of the most interesting fields in the automotive industry. Especially small DC motor was issued because of the increasing adoption for passengers' safety and convenience. This study was performed to develop the accelerated life test method using Inverse power law model for small DC motors. The failure mode of small DC motor includes brush wear-out. Inverse power law model is applied effectively the electronic components to reduce the testing time and to achieve the accelerating test conditions. Accelerated life testing method was induced to bring on the brush wear-out as increasing voltage of motor. Life distribution of the small DC motor was supposed to follow Weibull distribution and life test time was calculated under the conditions of B10 life and 90% confidence level.

Shin, Wae-Gyeong; Lee, Soo-Hong

420

Static and free vibration analyses of continuously graded fiber-reinforced cylindrical shells using generalized power-law distribution  

Microsoft Academic Search

In this study, based on the three-dimensional theory of elasticity, static and free vibration characteristics of continuously\\u000a graded fiber-reinforced (CGFR) cylindrical shells are considered by making use of a generalized power-law distribution. In\\u000a the present formulation, the cylindrical shell is assumed to be made of an orthotropic material. The CGFR cylindrical shells\\u000a have a smooth variation of matrix volume fraction

B. Sobhani Aragh; M. H. Yas

2010-01-01

421

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

Microsoft Academic Search

We study the instability of collective excitations of a three-dimensional Bose-Einstein condensate with repulsive and attractive interactions in a shallow trap designed as a quadratic plus a quartic potential. By using a correlated many-body theory, we determine the excitation modes and probe the critical behavior of collective modes, having a crucial dependence on the anharmonic parameter. We examine the power-law

P. K. Debnath; Barnali Chakrabarti

2010-01-01

422

Generalizations of power-law distributions applicable to sampled fault-trace lengths: model choice, parameter estimation and caveats  

Microsoft Academic Search

It has often been observed that fault-trace lengths tend to follow a power-law or Pareto distribution, at least for sufficiently large lengths. A very common method of fitting this type of model to data consists of plotting on log-log axes the number of faults with trace length greater than x against x, and reading off the slope of the resulting

R. M. Clark; S. J. D. Cox; G. M. Laslett

1999-01-01

423

Singular stresses at the tip of a sharp notch in power-law-hardening materials under antisymmetric loading  

Microsoft Academic Search

We studied stresses near the tip of a sharp V-notch in a material with power-law hardening under the action of antisymmetric loading. The problem is reduced to the solution of a fourth-order differential eigenvalue equation. We present the results of numerical analysis of the order of singularity of displacements and the angular distribution of stresses. We also construct the plastic

N. V. Kouzniak; H. P. Rossmanith; M. P. Savruk

1996-01-01

424

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

NASA Astrophysics Data System (ADS)

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 the average waiting time which is an important measure to estimate the time for customers to wait until the next price change after they login to their computer systems. By assuming that the first passage time distribution might change its shape from the Weibull to the power-law at some critical time, we evaluate the averaged waiting time by means of the renewal-reward theorem. We find that our correction of tails of the distribution makes the averaged waiting time much closer to the value obtained from empirical data analysis. We also discuss the deviation from the estimated average waiting time by deriving the waiting time distribution directly. These results make us conclude that the first passage process of the foreign currency exchange rates is well described by a Weibull distribution with power-law tails.

Sazuka, Naoya; Inoue, Jun-Ichi

2007-03-01

425

Power-law variability in rupture phenomena, How and why do PL exponents change toward the failure.  

NASA Astrophysics Data System (ADS)

Damage and sliding events associated with the deformation of brittle materials are observed to obey power-law distributions. This is verified at scales ranging from laboratory samples to the Earth's crust, for various materials and under various loading modes. Besides the claim that this is a universal characteristic of the deformation of heterogeneous media, spatial and temporal variations are observed in the exponent and tail-shape. These have considerable implications for the ability and the reliability of forecasting large events from smaller ones. There is a growing interest in identifying the factors responsible for these variations. In this present work, we first present observations at various scales (laboratory tests, field experiments, landslides, mining induced seismicity, crustal Earthquakes) showing that substantial variations exist in both the slope and the tail-shape of the rupture event size distribution. This review allows us to identify potential explanations for these variations (incorrect statistical methods, heterogeneity, stress, brittle/ductile transition, finite size effects, proximity to the failure). A possible link with the critical point theory is also drawn showing that it is able to explain a part of the observed variations considering the distance to the critical point. Using numerical simulations of progressive failure we investigate the role of mechanical properties on the power-law distributions. The results of simulations agree with the critical point theory for various macroscopic behaviors ranging from ductility to brittleness providing a unified framework for the understanding of power-law variability observed in rupture phenomena.

Amitrano, D.

2012-04-01

426

Full wave modeling of therapeutic ultrasound: Efficient time-domain implementation of the frequency power-law attenuation  

NASA Astrophysics Data System (ADS)

For the simulation of therapeutic ultrasound applications, a method including frequency-dependent attenuation effects directly in the time domain is highly desirable. This paper describes an efficient numerical time-domain implementation of the power-law attenuation model presented by Szabo [Szabo, J. Acoust. Soc. Am. 96, 491-500 (1994)]. Simulations of therapeutic ultrasound applications are feasible in conjunction with a previously presented finite differences time-domain (FDTD) algorithm for nonlinear ultrasound propagation [Ginter et al., J. Acoust. Soc. Am. 111, 2049-2059 (2002)]. Szabo implemented the empirical frequency power-law attenuation using a causal convolutional operator directly in the time-domain equation. Though a variety of time-domain models has been published in recent years, no efficient numerical implementation has been presented so far for frequency power-law attenuation models. Solving a convolutional integral with standard time-domain techniques requires enormous computational effort and therefore often limits the application of such models to 1D problems. In contrast, the presented method is based on a recursive algorithm and requires only three time levels and a few auxiliary data to approximate the convolutional integral with high accuracy. The simulation results are validated by comparison with analytical solutions and measurements. .

Liebler, Marko; Ginter, Siegfried; Dreyer, Thomas; Riedlinger, Rainer E.

2004-11-01

427

Estimating rate uncertainty with maximum likelihood: differences between power-law and flicker-random-walk models  

NASA Astrophysics Data System (ADS)

Recent studies have documented that global positioning system (GPS) time series of position estimates have temporal correlations which have been modeled as a combination of power-law and white noise processes. When estimating quantities such as a constant rate from GPS time series data, the estimated uncertainties on these quantities are more realistic when using a noise model that includes temporal correlations than simply assuming temporally uncorrelated noise. However, the choice of the specific representation of correlated noise can affect the estimate of uncertainty. For many GPS time series, the background noise can be represented by either: (1) a sum of flicker and random-walk noise or, (2) as a power-law noise model that represents an average of the flicker and random-walk noise. For instance, if the underlying noise model is a combination of flicker and random-walk noise, then incorrectly choosing the power-law model could underestimate the rate uncertainty by a factor of two. Distinguishing between the two alternate noise models is difficult since the flicker component can dominate the assessment of the noise properties because it is spread over a significant portion of the measurable frequency band. But, although not necessarily detectable, the random-walk component can be a major constituent of the estimated rate uncertainty. None the less, it is possible to determine the upper bound on the random-walk noise.

Langbein, John

2012-09-01

428

Working fluid and cycle selection criteria for binary geothermal power plants with resource temperatures in the range of 220°F to 400°F  

Microsoft Academic Search

Binary cycles using refrigerants as working fluids are an effective means of developing geothermal resources for power production. In order to maximize the utilization of the geothermal fluid resource over a temperature range of from 220°F to 400°F, a study was performed to optimize plant design with respect to working fluid and thermodynamic cycle. Additionally, system variations due to tolerances

I. J. Ingvarsson; S. E. Turner

1977-01-01

429

1Soliton solution of 1 + 2 dimensional nonlinear Schrödinger’s equation in power law media  

Microsoft Academic Search

This paper obtains the 1-soliton solution of the nonlinear Schrödinger’s equation in 1+2 dimensions for parabolic law nonlinearity. An exact soliton solution is obtained in closed form by the solitary wave ansatze.

Anjan Biswas

2009-01-01

430

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

Code of Federal Regulations, 2013 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...

2013-01-01

431

Statistical fractal adsorption isotherms, linear energy relations, and power-law trapping-time distributions in porous media  

SciTech Connect

Drazer and Zanette [Phys. Rev. E 60, 5858 (1999)] have reported on interesting experiments which show that trapping-time distributions in porous media obey a scaling law of the negative power-law type. Unfortunately, their theoretical interpretation of the experimental data has physical and mathematical inconsistencies and errors. Drazer and Zanette assume the existence of a distribution of local adsorption isotherms for which the random parameter is not a thermodynamic function, but a kinetic parameter, the trapping time. Moreover, they mistakenly identify the reciprocal value of a rate coefficient with the instantaneous (fluctuating) value of the trapping time. Their approach leads to mathematically inconsistent probability densities for the trapping times, which they find to be non-normalizable. We suggest a different theory, which is physically and mathematically consistent. We start with the classical patch approximation, which assumes the existence of a distribution of adsorption heats, and introduce two linear energy relationships between the activation energies of the adsorption and desorption processes and the adsorption heat. If the distribution of the adsorption heat obeys the exponential law of Zeldovich and Roghinsky, then both the adsorption isotherm and the probability density of trapping times can be evaluated analytically in terms of the incomplete beta and gamma functions, respectively. Our probability density of the trapping times is mathematically consistent; that is, it is non-negative and normalized to unity. For large times it has a long tail which obeys a scaling law of the negative power-law type, which is consistent with the experimental data of Drazer and Zanette. By using their data we can evaluate the numerical values of the proportionality coefficients in the linear energy relations. The theory suggests that experimental study of the temperature dependence of the fractal exponents helps to elucidate the mechanism of the adsorption-desorption process. (c) 2000 The American Physical Society.

Vlad, Marcel Ovidiu [Department of Chemistry, Stanford University, Stanford, California 94305-5080 (United States); Center of Mathematical Statistics, Casa Academiei Romane, Calea Septembrie 13, 76100 Bucharest, (Romania); Cerofolini, Gianfranco [ST Microelectronics, 20041 Agrate MI, (Italy); Ross, John [Department of Chemistry, Stanford University, Stanford, California 94305-5080 (United States)

2000-07-01

432

Power-law and exponential segregation in two-dimensional silos of granular mixtures  

Microsoft Academic Search

When a binary mixture of granular materials, differing in shape or size, is poured into a quasi-two-dimensional silo, segregation of the mixture is observed. Depending on the size ratio d2\\/d1 of the species, the mixture segregates completely or partially into the pure species. To study the partial-segregation effect we propose a theoretical model based on the work of Boutreux and

Rajesh K. Goyal; M. Silvina Tomassone

2006-01-01

433

Anomalous Coulomb diamonds and power-law behavior sensitive to back-gate voltages in carbon nanoscale peapod quantum dots  

NASA Astrophysics Data System (ADS)

We report anomalous charging effect of single electrons (Coulomb diamonds) observed in carbon nanoscale peapod quantum dots that encapsulate a series of C60 molecules. We find that behaviors of diamonds are anomalously sensitive to back-gate voltages (Vbg) , exhibiting two evidently different Vbg regions and a large polarity on Vbg . In particular, we find only a sequence of one large diamond followed by three smaller ones existing around ground state. Magnetic-field dependence indicates the presence of shell filling by spin singlet to doubly degenerate electronic levels for these. The encapsulated- C60 molecules indirectly affect this shell filling at low Vbg possibly via nearly free electrons. In contrast, they act as individual quantum dots coupled in series in high Vbg region. It directly contributes to highly overlapped very large diamonds. Moreover, we report power-law behaviors on conductance versus energy relationships observed in the same carbon nanoscale peapods. We find that the values of powers are also highly sensitive to applied Vbg with three different regions and anomalously high at high source-drain voltages. Because the power laws are found at voltages, which are the nearest outside of the above-mentioned fourfold Coulomb diamonds, correlation of the anomalous powers with orbital-related Tomonaga-Luttinger liquid is discussed.

Mizubayashi, J.; Haruyama, J.; Takesue, I.; Okazaki, T.; Shinohara, H.; Harada, Y.; Awano, Y.

2007-05-01

434

Extended power-law scaling of heavy-tailed random air-permeability fields in fractured and sedimentary rocks  

NASA Astrophysics Data System (ADS)

We analyze the scaling behaviors of two field-scale log permeability data sets showing heavy-tailed frequency distributions in three and two spatial dimensions, respectively. One set consists of 1-m scale pneumatic packer test data from six vertical and inclined boreholes spanning a decameters scale block of unsaturated fractured tuffs near Superior, Arizona, the other of pneumatic minipermeameter data measured at a spacing of 15 cm along three horizontal transects on a 21 m long and 6 m high outcrop of the Upper Cretaceous Straight Cliffs Formation, including lower-shoreface bioturbated and cross-bedded sandstone near Escalante, Utah. Order q sample structure functions of each data set scale as a power ?(q) of separation scale or lag, s, over limited ranges of s. A procedure known as extended self-similarity (ESS) extends this range to all lags and yields a nonlinear (concave) functional relationship between ?(q) and q. Whereas the literature tends to associate extended and nonlinear power-law scaling with multifractals or fractional Laplace motions, we have shown elsewhere that (a) ESS of data having a normal frequency distribution is theoretically consistent with (Gaussian) truncated (additive, self-affine, monofractal) fractional Brownian motion (tfBm), the latter being unique in predicting a breakdown in power-law scaling at small and large lags, and (b) nonlinear power-law scaling of data having either normal or heavy-tailed frequency distributions is consistent with samples from sub-Gaussian random fields or processes subordinated to tfBm or truncated fractional Gaussian noise (tfGn), stemming from lack of ergodicity which causes sample moments to scale differently than do their ensemble counterparts. Here we (i) demonstrate that the above two data sets are consistent with sub-Gaussian random fields subordinated to tfBm or tfGn and (ii) provide maximum likelihood estimates of parameters characterizing the corresponding Lévy stable subordinators and tfBm or tfGn functions.

Guadagnini, A.; Riva, M.; Neuman, S. P.

2012-09-01

435

A power-law approximation of the turbulent flow friction factor useful for the design and simulation of urban water networks  

Microsoft Academic Search

An approximation of the friction factor of the Colebrook–White equation is proposed, which is expressed as a power-law function of the pipe diameter and the energy gradient and is combined with the Darcy–Weisbach equation, thus yielding an overall power-law equation for turbulent pressurised pipe flow. This is a generalised Manning equation, whose exponents are not unique but depend on the

D. Koutsoyiannis

2008-01-01

436

Democracy, Sea Power and Institutional Change: An Economic Analysis of the Athenian Naval Law  

Microsoft Academic Search

The present essay attempts to test the validity of the theory of institutional change based on the concept of property rights, in the remote historical setting of Classical Athens. The “Naval Law” introduced by Themistocles in 483-2 BC, established the institution of trierarchy to produce warships to face the Persian invaders. This reform led to the first attempt to define

Nicholas C. Kyriazis; Michel S. Zouboulakis

2004-01-01

437

Mining the Way to Wealth and Power: Late Qing Reform of Mining Law (1895–1911)  

Microsoft Academic Search

This article traces the origins of Chinese alignment with Western mining laws to the last years of the Qing dynasty. I argue that the first decade of the twentieth century was the fundamental watershed in China between early modern views of mining and those held by the Chinese government today.

Shellen X. Wu

2012-01-01

438

A TWO-COMPONENT POWER LAW COVERING NEARLY FOUR ORDERS OF MAGNITUDE IN THE POWER SPECTRUM OF SPITZER FAR-INFRARED EMISSION FROM THE LARGE MAGELLANIC CLOUD  

SciTech Connect

Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70, and 160 {mu}m observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at k {sup -1} {approx} 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum (PS) covers {approx}3.5 orders of magnitude, and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves, and bars, presumably causes the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks causes the high-k structure in a three-dimensional geometry. This transition in dimensionality corresponds to the observed change in PS slope. A companion paper models the observed power law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.

Block, David L. [School of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, WITS 2050 (South Africa); Puerari, Ivanio [Instituto Nacional de Astrofisica, Optica y Electronica, Calle Luis Enrique Erro 1, 72840 Santa MarIa Tonantzintla, Puebla (Mexico); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Bournaud, Frederic, E-mail: bge@us.ibm.co [CEA, IRFU, SAp, F-91191 Gif-sur-Yvette (France)

2010-07-20

439

A Two-component Power Law Covering Nearly Four Orders of Magnitude in the Power Spectrum of Spitzer Far-infrared Emission from the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70, and 160 ?m observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at k -1 ~ 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum (PS) covers ~3.5 orders of magnitude, and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves, and bars, presumably causes the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks causes the high-k structure in a three-dimensional geometry. This transition in dimensionality corresponds to the observed change in PS slope. A companion paper models the observed power law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.

Block, David L.; Puerari, Ivânio; Elmegreen, Bruce G.; Bournaud, Frédéric

2010-07-01

440

What if the power-law model did not apply for the prediction of very large rockfall events?  

NASA Astrophysics Data System (ADS)

Extreme events are of primary importance for risk management in a variety of natural phenomena, and more particularly for landslides and rockfalls, because they might be associated with huge losses. Numerous research works have addressed this problem based on the same paradigm: if events exhibit the same statistical properties across a broad range of sizes, the probability of extreme events can be evaluated by extrapolating the frequency-size distribution. Considering landslides' areas or rockfalls' volumes, the frequency distribution has been found to be heavy-tailed and the well-known power law distribution has been proposed to model it. Yet, the vision of very large extreme event (catastrophic) frequency being an extrapolation of the power laws fitted on small and intermediate events has been challenged in various contexts, in particular by Sornette and co-authors, who proposed viewing such catastrophic events as "outliers" from the power-law model, i.e. they deviate by an abnormal large distance from the extrapolated prediction. In this study, we address such an issue considering a rockfall inventory, containing >8500 events spanning 8 orders of magnitudes of volume and collated from 2.5 years of high-accuracy repeated terrestrial laser scanning (TLS) surveys on a coastal chalk cliff in Normandy (France). This inventory contains a particularly large event of 70,949 m3 which occurred some time between February 1 and 7 April 2008. It is the second largest cliff failure reported in Normandy, and is larger than those collated in historical cliff failure inventories across various geological and geomorphological coastal settings. Is this event an outlier of the power-law volume-frequency distribution ? And if so, why? This largest event recorded appears to stand out of the rest of the sample. We use it to revisit the techniques to fit power-law distribution with robust techniques (robust weighted maximum likelihood estimator), rarely used in rockfall studies, and presenting the appealing feature to be less sensitive to the presence of outliers by assigning a weight within [0 ; 1] to each observation according to its representativeness. Through a bootstrap-based technique, we demonstrate the statistical significance (with p-value <1 %, i.e. not arising by chance) of the low weight assigned to the largest rockfall event i.e. of the deviation from the fractal set of the smaller events. Excluding gross volumetric error on our observation since we used a high-accuracy TLS, we discuss possible mechanisms and their implications for prediction, focusing on two main issues: 1. normal faults bounding the largest rockfall and along which the rupture occurred, which may suggest the hypothesis of a "characteristic" rockfall, i.e. presenting a characteristic scale of the same order of the fault length, as suggested for earthquakes; 2. possible log-periodic signature that decorates the pure power law and linked with the concept of Discrete Scale Invariance. This concept means that scale invariance is kept, but only for specific scales organized in a discrete hierarchy and with some fixed preferred scaling ratio. Such scaling ratio may itself be linked to pre-existing fracture networks.

Rohmer, J.; Dewez, T.

2012-04-01

441

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 parameters. The power-law has not, however, been officially adopted by any country for fitting to fluvial discharge data. This paper demonstrates a statistically robust method, based on Maximum Likelihood Estimation, for fitting a power-law distribution to mean daily streamflows. The fitted distribution is then used to calculate return periods, which are compared to the return periods obtained by other, more commonly used, distributions. The implications for river management, extremes of flow in particular, are then explored.

Eadie, Chris; Favis-Mortlock, David

2010-05-01

442

Variability in the power-law distributions of rupture events. How and why does b-value change  

NASA Astrophysics Data System (ADS)

Rupture events, as the propagation of cracks or the sliding along faults, associated with the deformation of brittle materials are observed to obey power-law distributions. This is verified at scales ranging from laboratory samples to the Earth's crust, for various materials and under various loading modes. Besides the claim that this is a universal characteristic of the deformation of heterogeneous media, spatial and temporal variations are observed in the exponent and tail-shape. These have considerable implications for the ability and the reliability of forecasting large events from smaller ones. There is a growing interest in identifying the factors responsible for these variations. In this work, we first present observations at various scales (laboratory tests, field experiments, landslides, mining induced seismicity, crustal Earthquakes) showing that substantial variations exist in both the slope and the tail-shape of the rupture event size distribution. This review allows us to identify potential explanations for these variations (incorrect statistical methods, heterogeneity, stress, brittle/ductile transition, finite size effects, proximity to the failure). A possible link with the critical point theory is also drawn showing that it is able to explain a part of the observed variations considering the distance to the critical point. Using numerical simulations of progressive failure we investigate the role of mechanical properties on the power-law distributions. The results of simulations agree with the critical point theory for various macroscopic behaviors ranging from ductility to brittleness providing a unified framework for the understanding of power-law variability observed in rupture phenomena.

Amitrano, D.

2012-05-01

443

Asteroseismology of Binary Stars  

NASA Astrophysics Data System (ADS)

The study of stellar oscillations, asteroseismology, enables us to draw conclusions on the inner structure of stars; thereby helping improve stellar models. Given that the majority of stars are found in binary or multiple systems, we expect to find many such systems containing pulsators. Binary stars, and in particular eclipsing binaries, play a crucial role in stellar astrophysics. Eclipse shapes, radial velocities, and other geometric properties of orbits are related to the physical properties of the components, such as radius and mass. These properties can, therefore, easily be derived from spectroscopic and photometric observations by simply applying the laws of physics and without relying on any assumptions of stellar-structure models. Hence, the understanding of eclipsing binary systems with pulsating components provide accurate constraints on the input physics for asteroseismic models. We will study nine different eclipsing binary stars containing pulsating components that range in masses from about 2-8 Mo. We will make use of high-precision photometry provided by the Kepler satellite and combine them with high-resolution spectroscopy gathered with the HERMES spectrograph mounted on the Mercator telescope, located on La Palma, Spain. The prospects of this challenging project will be presented and illustrated by the means of a case study.

Schmid, Valentina; Aerts, Conny; Debosscher, Jonas

2013-06-01

444

Eclipsing Binary Stars  

NSDL National Science Digital Library

Eclipsing Binary Stars model simulates the detection of eclipsing binary stars. In this method, the light curve from the combination of the two stars, and how it changes over time due to each star transiting (or being occulted or eclipsing the other), is observed and then analyzed. In this simulation each star orbits the other in circular motion via Kepler's third law.  When one star passes in front of the other (transits), it blocks part of the starlight of the other star. This decrease in starlight is shown on the graph.  In the simulation the binary star system is shown as seen from Earth (edge on view) and from overhead, but magnified greatly, and with the star sizes not shown to the scale of the orbit. The mass, radius, and temperature of each star can be changed. The simulation uses either simple 3D or Java 3D (if installed) to render the view the stars. If Java 3D is not installed, the simulation defaults to simple 3D using Java. The Eclipsing Binary Stars model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_astronomy_eclipsing_binaries.jar file will run the program if Java is installed.

Belloni, Mario

2010-07-15

445

Optimizing hyperpolarizability through the configuration space of energy spectrum and transition strength spanned by power law potentials  

NASA Astrophysics Data System (ADS)

While sophisticated numerical computational techniques can calculate the hyperpolarizabilities of complex molecules, it is not clear what scale invariant parameters determine a large nonlinear response. We investigate the first and second intrinsic hyperpolarizabilities of one-dimensional power-law potentials with a hybrid analytical semiclassical analysis of energy spectra and numerical calculations of eigenfunctions. By varying the exponent, we determine how key underlying properties drive the nonlinear response as the system smoothly varies from particle in a box, harmonic oscillator, point charge potential, to all multipolar Coulomb potentials. The role of the well-known pathology of the 1/x2 potential is also discussed.

Mossman, Sean M.; Kuzyk, Mark G.

2013-09-01

446

MHD mixed convection flow of a power law nanofluid over a vertical stretching sheet with radiation effect  

NASA Astrophysics Data System (ADS)

A similarity solution of the steady magnetohydrodynamic (MHD) mixed convection boundary lay