Search results for "power law"
showing 10 items of 188 documents
Dynamics of single semiflexible polymers in dilute solution
2016
We study the dynamics of a single semiflexible chain in solution using computer simulations, where we systematically investigate the effect of excluded volume, chain stiffness, and hydrodynamic interactions. We achieve excellent agreement with previous theoretical considerations, but find that the crossover from the time τb, up to which free ballistic motion of the monomers describes the chain dynamics, to the times W−1 or τ0, where anomalous monomer diffusion described by Rouse-type and Zimm-type models sets in, requires two decades of time. While in the limit of fully flexible chains the visibility of the anomalous diffusion behavior is thus rather restricted, the t3/4 power law predicted…
Spectroscopy of Very Hot Plasma in Non-flaring Parts of a Solar Limb Active Region: Spatial and Temporal Properties
2017
In this work we investigate the thermal structure of an off-limb active region (AR) in various non-flaring areas, as it provides key information on the way these structures are heated. In particular, we concentrate on the very hot component (>3 MK) as it is a crucial element to distinguish between different heating mechanisms. We present an analysis using Fe and Ca emission lines from both the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) and the EUV Imaging Spectrometer (EIS) on board Hinode. A data set covering all ionization stages from Fe X to Fe XIX has been used for the thermal analysis (both differential emission …
Timing Properties and Spectral States in Aquila X‐1
2003
We have analyzed five X-ray outbursts of the neutron-star soft X-ray transient Aql X-1 and investigated the timing properties of the source in correlation with its spectral states as defined by different positions in the color-color and hardness-intensity diagrams. The hard color and the source count rate serve as the distinguishing parameters giving rise to three spectral states: a low-intensity hard state, an intermediate state and a high-intensity soft state. These states are respectively identified with the extreme island, island and banana states that characterize the atoll sources. The large amount of data analyzed allowed us to perform for the first time a detailed timing analysis of…
Problems of Clustering of Radiogalaxies
2012
We present the preliminary analysis of clustering of a sample of 1157 radio-identified galaxies from Machalski & Condon (1999). We found that for separations $2-15 h^{-1}$Mpc their redshift space autocorrelation function $\xi(s)$ can be approximated by the power law with the correlation length $\sim 3.75h^{-1}$Mpc and slope $\gamma \sim 1.8$. The correlation length for radiogalaxies is found to be lower and the slope steeper than the corresponding parameters of the control sample of optically observed galaxies. Analysis the projected correlation function $\Xi(r)$ displays possible differences in the clustering properties between active galactic nuclei (AGN) and starburst (SB) galaxies.
The parameterisation of the atmospheric aerosol optical depth using the Ångström power law
1998
Abstract We have analysed the ability of the Angstrom power law to model the spectral aerosol optical depth, τaλ, for the 400–670 nm band, obtained from spectral direct irradiance measurements at normal incidence. The spectra were registered at ground level in Valencia, Spain, using a Li-cor 1800 spectroradiometer. The results obtained showed that the fitting method that introduces lower errors in the determination of the Angstrom power law coefficients is to adjust directly the spectral experimental data. In this way the errors obtained for the turbidity coefficient, β, were about 0.004 and for the wavelength exponent, α, 0.07. The correlation coefficient was always greater than 0.95. Thes…
An exact thermodynamical model of power-law temperature time scaling
2016
In this paper a physical model for the anomalous temperature time evolution (decay) observed in complex thermodynamical system in presence of uniform heat source is provided. Measures involving temperatures T with power-law variation in time as T(t)∝tβ with β∈R shows a different evolution of the temperature time rate T(t) with respect to the temperature time-dependence T(t). Indeed the temperature evolution is a power-law increasing function whereas the temperature time rate is a power-law decreasing function of time. Such a behavior may be captured by a physical model that allows for a fast thermal energy diffusion close to the insulated location but must offer more resistance to the therm…
The relaxation dynamics of a viscous silica melt: II The intermediate scattering functions
2001
We use molecular dynamics computer simulations to study the relaxation dynamics of a viscous melt of silica. The coherent and incoherent intermediate scattering functions, F_d(q,t) and F_s(q,t), show a crossover from a nearly exponential decay at high temperatures to a two-step relaxation at low temperatures. Close to the critical temperature of mode-coupling theory (MCT) the correlators obey in the alpha-regime the time temperature superposition principle (TTSP) and show a weak stretching. We determine the wave-vector dependence of the stretching parameter and find that for F_d(q,t) it shows oscillations which are in phase with the static structure factor. The temperature dependence of the…
Static and dynamic properties of a viscous silica melt
1999
We present the results of a large scale molecular dynamics computer simulation in which we investigated the static and dynamic properties of a silica melt in the temperature range in which the viscosity of the system changes from ${O(10}^{\ensuremath{-}2})$ P to ${O(10}^{2})$ P. We show that even at temperatures as high as 4000 K the structure of this system is very similar to the random tetrahedral network found in silica at lower temperatures. The temperature dependence of the concentration of the defects in this network shows an Arrhenius law. From the partial structure factors we calculate the neutron scattering function and find that it agrees very well with experimental neutron scatte…
A coupled map as a model of the dynamics of the magnetotail current sheet
2001
Abstract A magnetic field model of the magnetotail current sheet in the form of a coupled-map lattice (CML) is presented. It is continuously driven (“running”) and based on the MHD diffusion equation. Solar wind vBS data (solar wind speed multiplied by the southward component of IMF) are used for driving the model, and it is shown to exhibit perturbations (avalanches) with power-law scalings in their distributions of duration and size. Such distributions may indicate self-organized critical (SOC) behavior. Furthermore, it is shown that the power spectra of the model outputs are of bicolor power-law form with different slopes for high and low frequencies. Although the “running” model gives p…
Exponential and power-law mass distributions in brittle fragmentation
2004
Generic arguments, a minimal numerical model, and fragmentation experiments with gypsum disk are used to investigate the fragment-size distribution that results from dynamic brittle fragmentation. Fragmentation is initiated by random nucleation of cracks due to material inhomogeneities, and its dynamics are pictured as a process of propagating cracks that are unstable against side-branch formation. The initial cracks and side branches both merge mutually to form fragments. The side branches have a finite penetration depth as a result of inherent damping. Generic arguments imply that close to the minimum strain (or impact energy) required for fragmentation, the number of fragments of size $s…