1,724 research outputs found
Mutual Interference of Frequency Hopping with Collision Avoidance Systems
The aim of this article is to quantify and analyze mutual interference of Frequency Hopping with Collision Avoidance (FH/CA) systems. The FH/CA system is a frequency hopping system where stations select the least jammed channel from several possible before the next jump. The article describes a mathematical model that allows determining the upper limit of the probability of collision of multiple FH/CA systems operated in a common band. The dependence obtained for mutual interference of FH/CA systems is compared with the dependence for mutual interference of conventional FH systems. The result of the comparison is a conclusion that, in terms of mutual interference, it is more advantageous to operate the FH/CA systems than the conventional FH systems
Application of Mössbauer spectroscopy in study of selected biochemical processes
The Fe, Sn, I, and Eu Mössbauer spectroscopy, scanning force microscopy, and optical fluorescence method were applied to study biological systems starting from porphyrins, through cytochromes and cell membranes until such a complex system as photosystem II. In Fe-porphyrin aggregates iron atoms are able to trap an electron exhibiting the mixed valence Fe-Fe relaxation process. In ironcytochrome c the presence of two different Fe states are indicated, while in tincytochrome Sn appears in Sn and Sn states. From the temperature dependence of the mean square displacement of the resonance nuclei and from the diffusional broadening of the Mössbauer line it was possible to separate the vibrational, fast collective and slow collective motions in tinporphyrin and in iron- and tin-cytochrome c. The electronic state of iodine in oleic acid, the main constituent of cellular membranes, was determined. The molecular mechanism of triphenyltin interaction with membrane of red blood cells has been suggested and the model of haemolysis has been proposed. In photosystem II, Eu ions replacing calcium showed Eu to Eu transition after illumination with light, which points out the possible role of Ca ions in electron transfer in the process of photosynthetic water splitting process
Average distance in growing trees
Two kinds of evolving trees are considered here: the exponential trees, where
subsequent nodes are linked to old nodes without any preference, and the
Barab\'asi--Albert scale-free networks, where the probability of linking to a
node is proportional to the number of its pre-existing links. In both cases,
new nodes are linked to nodes. Average node-node distance is
calculated numerically in evolving trees as dependent on the number of nodes
. The results for not less than a thousand are averaged over a thousand
of growing trees. The results on the mean node-node distance for large
can be approximated by for the exponential trees, and
for the scale-free trees, where the are constant. We
derive also iterative equations for and its dispersion for the exponential
trees. The simulation and the analytical approach give the same results.Comment: 6 pages, 3 figures, Int. J. Mod. Phys. C14 (2003) - in prin
Finite size scaling analysis of intermittency moments in the two dimensional Ising model
Finite size scaling is shown to work very well for the block variables used
in intermittency studies on a 2-d Ising lattice. The intermittency exponents so
derived exhibit the expected relations to the magnetic critical exponent of the
model. Email contact: [email protected]: Saclay-T93/063 Email: [email protected]
The Strong-Coupling Expansion in Simplicial Quantum Gravity
We construct the strong-coupling series in 4d simplicial quantum gravity up
to volume 38. It is used to calculate estimates for the string susceptibility
exponent gamma for various modifications of the theory. It provides a very
efficient way to get a first view of the phase structure of the models.Comment: LATTICE98(surfaces), 3 pages, 4 eps figure
Maximal-entropy random walk unifies centrality measures
In this paper analogies between different (dis)similarity matrices are
derived. These matrices, which are connected to path enumeration and random
walks, are used in community detection methods or in computation of centrality
measures for complex networks. The focus is on a number of known centrality
measures, which inherit the connections established for similarity matrices.
These measures are based on the principal eigenvector of the adjacency matrix,
path enumeration, as well as on the stationary state, stochastic matrix or mean
first-passage times of a random walk. Particular attention is paid to the
maximal-entropy random walk, which serves as a very distinct alternative to the
ordinary random walk used in network analysis.
The various importance measures, defined both with the use of ordinary random
walk and the maximal-entropy random walk, are compared numerically on a set of
benchmark graphs. It is shown that groups of centrality measures defined with
the two random walks cluster into two separate families. In particular, the
group of centralities for the maximal-entropy random walk, connected to the
eigenvector centrality and path enumeration, is strongly distinct from all the
other measures and produces largely equivalent results.Comment: 7 pages, 2 figure
From simple to complex networks: inherent structures, barriers and valleys in the context of spin glasses
Given discrete degrees of freedom (spins) on a graph interacting via an
energy function, what can be said about the energy local minima and associated
inherent structures? Using the lid algorithm in the context of a spin glass
energy function, we investigate the properties of the energy landscape for a
variety of graph topologies. First, we find that the multiplicity Ns of the
inherent structures generically has a lognormal distribution. In addition, the
large volume limit of ln/ differs from unity, except for the
Sherrington-Kirkpatrick model. Second, we find simple scaling laws for the
growth of the height of the energy barrier between the two degenerate ground
states and the size of the associated valleys. For finite connectivity models,
changing the topology of the underlying graph does not modify qualitatively the
energy landscape, but at the quantitative level the models can differ
substantially.Comment: 10 pages, 9 figs, slightly improved presentation, more references,
accepted for publication in Phys Rev
Maximal entropy random walk in community finding
The aim of this paper is to check feasibility of using the maximal-entropy
random walk in algorithms finding communities in complex networks. A number of
such algorithms exploit an ordinary or a biased random walk for this purpose.
Their key part is a (dis)similarity matrix, according to which nodes are
grouped. This study encompasses the use of the stochastic matrix of a random
walk, its mean first-passage time matrix, and a matrix of weighted paths count.
We briefly indicate the connection between those quantities and propose
substituting the maximal-entropy random walk for the previously chosen models.
This unique random walk maximises the entropy of ensembles of paths of given
length and endpoints, which results in equiprobability of those paths. We
compare performance of the selected algorithms on LFR benchmark graphs. The
results show that the change in performance depends very strongly on the
particular algorithm, and can lead to slight improvements as well as
significant deterioration.Comment: 7 pages, 4 figures, submitted to European Physical Journal Special
Topics following the 4-th Conference on Statistical Physics: Modern Trends
and Applications, July 3-6, 2012 Lviv, Ukrain
Evolution of scale-free random graphs: Potts model formulation
We study the bond percolation problem in random graphs of weighted
vertices, where each vertex has a prescribed weight and an edge can
connect vertices and with rate . The problem is solved by the
limit of the -state Potts model with inhomogeneous interactions for
all pairs of spins. We apply this approach to the static model having
so that the resulting graph is scale-free with
the degree exponent . The number of loops as well as the giant
cluster size and the mean cluster size are obtained in the thermodynamic limit
as a function of the edge density, and their associated critical exponents are
also obtained. Finite-size scaling behaviors are derived using the largest
cluster size in the critical regime, which is calculated from the cluster size
distribution, and checked against numerical simulation results. We find that
the process of forming the giant cluster is qualitatively different between the
cases of and . While for the former, the giant
cluster forms abruptly at the percolation transition, for the latter, however,
the formation of the giant cluster is gradual and the mean cluster size for
finite shows double peaks.Comment: 34 pages, 9 figures, elsart.cls, final version appeared in NP
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