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1.
Are citations of scientific papers a case of nonextensivity? 总被引:1,自引:0,他引:1
C. Tsallis M.P. de Albuquerque 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):777-780
The distribution N(x) of citations of scientific papers has recently been illustrated (on ISI and PRE data sets) and analyzed by Redner (Eur.
Phys. J. B 4, 131 (1998)). To fit the data, a stretched exponential () has been used with only partial success. The success is not complete because the data exhibit, for large citation count
x, a power law (roughly for the ISI data), which, clearly, the stretched exponential does not reproduce. This fact is then attributed to a possibly
different nature of rarely cited and largely cited papers. We show here that, within a nonextensive thermostatistical formalism,
the same data can be quite satisfactorily fitted with a single curve (namely, [0pt] for the available values of x. This is consistent with the connection recently established by Denisov (Phys. Lett. A 235, 447 (1997)) between this nonextensive formalism and the Zipf-Mandelbrot law. What the present analysis ultimately suggests
is that, in contrast to Redner's conclusion, the phenomenon might essentially be one and the same along the entire range of the citation number x.
Received 13 April 1999 相似文献
2.
J.A. Davies 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):445-447
Over the last five years or so, a number of studies have focussed on the distribution of `success' in physics and other sciences;
in these studies, `success' is measured by the number of times a paper, or an author, is cited. The distribution of citations
of individual papers approximates to a power-law [S. Redner, Eur. Phys. J. B 4, 131 (1998)], while lifetime total citations of the 1120 most-cited physicists follows a stretched exponential [J. Laherrère,
D. Sornette, Eur. Phys. J. B 2, 525 (1998)]. Here, I examine the distribution of success in popular music, a field of creativity that has social structures
very different from those of physics, and which is generally held to be controlled primarily by fashion. For this study, the
lifetime total success of bands was measured by the total number of weeks they were in the weekly `top 75' list of best-selling
recordings. Like the lifetime success of physicists reported by Laherrere and Sornette, the success of the 6107 bands that
appeared in the UK `top 75' from 1950 until 2000 follows a stretched exponential of the form P(x)dx = c(x
c - 1/x
0
c)exp[- (x/x
0)c]dx; for the music data, c = 0.5 and x
0 = 9.37.
Received 23 October 2001 Published online 25 June 2002 相似文献
3.
K. Pomorski K. Dietrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):353-364
We investigate the existence of stable charged metallic bubbles using the shell correction method. We find that for a given
mesoscopic system of n atoms of a given metal and (positive) elementary charges, a metallic bubble turns out to have a lower total energy than a compact spherical cluster,
whenever the charge number q is larger than a critical charge number qc. For a magic number (n-q) of free electrons, the spherical metallic bubble may become stable against fission.
Received: 17 November 1997 / Revised: 28 May 1998 / Accepted: 20 July 1998 相似文献
4.
K. Ramesh S. Asokan K.S. Sangunni E.S.R. Gopal 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):207-212
Differential Scanning Calorimetric (DSC) studies on AgxGe15Te85-x glasses have been undertaken over a wide range of compositions, to understand the effect of topological thresholds on thermal
properties. It is found that the compositional dependence of glass transition temperature (T
g
), crystallization temperature (T
c
), activation energy for crystallization and thermal stability show anomalies at the rigidity percolation threshold. Unusual variations also observed in different thermal properties at
the composition x = 20, clearly establishes the occurrence of chemical threshold in these glasses.
Received: 27 January 1998 / Revised: 12 June 1998 / Accepted: 3 July 1998 相似文献
5.
M.-L. Almazor O. Dulieu M. Elbs E. Tiemann F. Masnou-Seeuws 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):237-242
Due to competition between ionic and covalent dissociation, the excited potential curves of the alkali dimers display long
range structures, leading in some cases to secondary wells. We discuss the possibility of populating the well (with a depth
of 1614.8 cm-1, located at R
e
= 30.5a
0
) that is present in the Na2
potential curve and propose detection schemes.
Received: 28 May 1998 / Revised: 5 August 1998 / Accepted: 24 September 1998 相似文献
6.
B. O'Shaughnessy D. Vavylonis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):363-372
We study the reaction kinetics of end-functionalized polymer chains dispersed in an unreactive polymer melt. Starting from
an infinite hierarchy of coupled equations for many-chain correlation functions, a closed equation is derived for the 2nd
order rate constant k after postulating simple physical bounds. Our results generalize previous 2-chain treatments (valid in dilute reactants limit)
by Doi [#!doi:inter2!#], de Gennes [#!gennes:polreactionsiandii!#], and Friedman and O'Shaughnessy [#!ben:interdil_all_aip!#],
to arbitrary initial reactive group density n0 and local chemical reactivity Q. Simple mean field (MF) kinetics apply at short times, .For high Q, a transition occurs to diffusion-controlled (DC) kinetics with (where xt is rms monomer displacement in time t) leading to a density decay . If n0 exceeds the chain overlap threshold, this behavior is followed by a regime where during which k has the same power law dependence in time, , but possibly different numerical coefficient. For unentangled melts this gives while for entangled cases one or more of the successive regimes ,t
-3/8
and t
-3/4
may be realized depending on the magnitudes of Q and n0. Kinetics at times longer than the longest polymer relaxation time are always MF. If a DC regime has developed before then the long time rate constant is where R is the coil radius. We propose measuring the above kinetics in a model experiment where radical end groups are generated
by photolysis.
Received: 2 June 1998 / Revised: 9 July 1998 / Accepted: 10 July 1998 相似文献
7.
B.A. Berg U.H.E. Hansmann 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):395-398
Applied to statistical physics models, the random cost algorithm enforces a Random Walk (RW) in energy (or possibly other
thermodynamic quantities). The dynamics of this procedure is distinct from fixed weight updates. The probability for a configuration
to be sampled depends on a number of unusual quantities, which are explained in this paper. This has been overlooked in recent
literature, where the method is advertised for the calculation of canonical expectation values. We illustrate these points
for the 2d Ising model. In addition, we prove a previously conjectured equation which relates microcanonical expectation values to the
spectral density.
Received: 13 May 1998 / Received in final form and Accepted: 26 May 1998 相似文献
8.
A. Nossov J. Pierre J. Beille V. Vassiliev B. Slobodin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(4):467-472
The influence of hydrostatic pressure on the transport properties of (La1-xRx)0.67Ca0.33MnO3 (,Tb) ferromagnetic manganites is investigated. The enhancement of the Curie temperature TC under pressure agrees with previous data. In the paramagnetic range, the resistivity can be represented by a Mott localisation
law, with a characteristic temperature T0 decreasing with pressure. The variation of TC with pressure is compared to the effect induced by replacing La by a magnetic rare earth in (La1-xRx)0.67Sr0.33MnO3 manganites (, ..., Tm). The main effect is not related to the decrease of the mean radius of the cation, but to an additional scattering
by the magnetic moment of the rare earth.
Received: 15 May 1998 / Revised: 6 July 1998 / Accepted: 16 July 1998 相似文献
9.
K. Mølmer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):301-305
We discuss the possibility of preparing an atomic sample of atoms with minimum fluctuations in the difference between populations
of two levels. A first scheme involves absorption of twin beams of light, and it presents a variant of a recent proposal for
atomic spin squeezing within an excited state manifold [Kuzmich et al., Phys. Rev. Lett. 79, 4782 (1997)]. A second scheme involves atoms with two stable states, and we suggest that by use of quantum non-demolition
detection and feed-back optical pumping, we may ensure a perfect agreement between the number of atoms in these two states.
Received: 14 May 1998 / Revised: 10 August 1998 / Accepted: 8 October 1998 相似文献
10.
X. Waintal D. Weinmann J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(3):451-456
For two particles in a disordered chain of length L with on-site interaction U, a duality transformation maps the behavior at weak interaction onto the behavior at strong interaction. Around the fixed
point of this transformation, the interaction yields a maximum mixing of the one body states. When (the one particle localization length), this mixing results in weak chaos accompanied by multifractal wave functions and
critical spectral statistics, as in the one particle problem at the mobility edge or in certain pseudo-integrable billiards.
In one dimension, a local interaction can only yield this weak chaos but can never drive the two particle system to full chaos
with Wigner-Dyson statistics.
Received: 22 May 1998 / Received in final form: 24 August 1998 / Accepted: 4 September 1998 相似文献