Percolation with multiple giant clusters
International Nuclear Information System (INIS)
Ben-Naim, E; Krapivsky, P L
2005-01-01
We study mean-field percolation with freezing. Specifically, we consider cluster formation via two competing processes: irreversible aggregation and freezing. We find that when the freezing rate exceeds a certain threshold, the percolation transition is suppressed. Below this threshold, the system undergoes a series of percolation transitions with multiple giant clusters ('gels') formed. Giant clusters are not self-averaging as their total number and their sizes fluctuate from realization to realization. The size distribution F k , of frozen clusters of size k, has a universal tail, F k ∼ k -3 . We propose freezing as a practical mechanism for controlling the gel size. (letter to the editor)
Percolation Systems away from the Critical Point
Dhar, Deepak
2001-01-01
This article reviews some effects of disorder in percolation systems even away from the critical density p_c. For densities below p_c, the statistics of large clusters defines the animals problem. Its relation to the directed animals problem and the Lee-Yang edge singularity problem is described. Rare compact clusters give rise to Griffiths singuraties in the free energy of diluted ferromagnets, and lead to a very slow relaxation of magnetization. In biassed diffusion on percolation clusters,...
Percolation technique for galaxy clustering
Klypin, Anatoly; Shandarin, Sergei F.
1993-01-01
We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.
Geometric structure of percolation clusters.
Xu, Xiao; Wang, Junfeng; Zhou, Zongzheng; Garoni, Timothy M; Deng, Youjin
2014-01-01
We investigate the geometric properties of percolation clusters by studying square-lattice bond percolation on the torus. We show that the density of bridges and nonbridges both tend to 1/4 for large system sizes. Using Monte Carlo simulations, we study the probability that a given edge is not a bridge but has both its loop arcs in the same loop and find that it is governed by the two-arm exponent. We then classify bridges into two types: branches and junctions. A bridge is a branch iff at least one of the two clusters produced by its deletion is a tree. Starting from a percolation configuration and deleting the branches results in a leaf-free configuration, whereas, deleting all bridges produces a bridge-free configuration. Although branches account for ≈43% of all occupied bonds, we find that the fractal dimensions of the cluster size and hull length of leaf-free configurations are consistent with those for standard percolation configurations. By contrast, we find that the fractal dimensions of the cluster size and hull length of bridge-free configurations are given by the backbone and external perimeter dimensions, respectively. We estimate the backbone fractal dimension to be 1.643 36(10).
Percolation and epidemics in random clustered networks
Miller, Joel C.
2009-08-01
The social networks that infectious diseases spread along are typically clustered. Because of the close relation between percolation and epidemic spread, the behavior of percolation in such networks gives insight into infectious disease dynamics. A number of authors have studied percolation or epidemics in clustered networks, but the networks often contain preferential contacts in high degree nodes. We introduce a class of random clustered networks and a class of random unclustered networks with the same preferential mixing. Percolation in the clustered networks reduces the component sizes and increases the epidemic threshold compared to the unclustered networks.
Fragmentation of percolation cluster perimeters
Debierre, Jean-Marc; Bradley, R. Mark
1996-05-01
We introduce a model for the fragmentation of porous random solids under the action of an external agent. In our model, the solid is represented by a bond percolation cluster on the square lattice and bonds are removed only at the external perimeter (or `hull') of the cluster. This model is shown to be related to the self-avoiding walk on the Manhattan lattice and to the disconnection events at a diffusion front. These correspondences are used to predict the leading and the first correction-to-scaling exponents for several quantities defined for hull fragmentation. Our numerical results support these predictions. In addition, the algorithm used to construct the perimeters reveals itself to be a very efficient tool for detecting subtle correlations in the pseudo-random number generator used. We present a quantitative test of two generators which supports recent results reported in more systematic studies.
Percolation of Monte Carlo clusters
International Nuclear Information System (INIS)
Wanzeller, W.G.; Krein, G.; Cucchieri, A.; Mendes, T.
2004-01-01
Percolation theory is of interest in problems of phase transitions in condensed matter physics, and in biology and chemistry. More recently, concepts of percolation theory have been invoked in studies of color deconfinement at high temperatures in Quantum Chromodynamics. In the present paper we briefly review the basic concept of percolation theory, exemplify its application to the Ising model, and present the arguments for a possible relevance of percolation theory to the problem of color deconfinement. (author)
Percolating cluster of center vortices and confinement
International Nuclear Information System (INIS)
Gliozzi, Ferdinando; Panero, Marco; Provero, Paolo
2003-01-01
We study the role of percolating clusters of center vortices in configurations of an Ising gauge theory in 3D. It is known that low energy features of gauge theories can be described in terms of an 'effective string picture', and that confinement properties are associated with topologically non-trivial configurations. We focus our attention upon percolating clusters of center vortices, and present numerical evidence for the fact that these objects play a preminent role in confinement phenomenon, since their removal sweeps off confinement altogether. Moreover, numerical simulations show that the string fluctuations, and in particular the Mischer term, are completely encoded in the percolating cluster
Fractal properties of percolation clusters in Euclidian neural networks
International Nuclear Information System (INIS)
Franovic, Igor; Miljkovic, Vladimir
2009-01-01
The process of spike packet propagation is observed in two-dimensional recurrent networks, consisting of locally coupled neuron pools. Local population dynamics is characterized by three key parameters - probability for pool connectedness, synaptic strength and neuron refractoriness. The formation of dynamic attractors in our model, synfire chains, exhibits critical behavior, corresponding to percolation phase transition, with probability for non-zero synaptic strength values representing the critical parameter. Applying the finite-size scaling method, we infer a family of critical lines for various synaptic strengths and refractoriness values, and determine the Hausdorff-Besicovitch fractal dimension of the percolation clusters.
Percolation systems away from the critical point
Indian Academy of Sciences (India)
DEEPAK DHAR. Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India ... There is more to percolation theory than the critical exponents. Of course, an experi- .... simple qualitative arguments. In the summation ...
Inequality for the infinite-cluster density in Bernoulli percolation
International Nuclear Information System (INIS)
Chayes, J.T.; Chayes, L.
1986-01-01
Under a certain assumption (which is satisfied whenever there is a dense infinite cluster in the half-space), we prove a differential inequality for the infinite-cluster density, P/sub infinity/(p), in Bernoulli percolation. The principal implication of this result is that if P/sub infinity/(p) vanishes with critical exponent β, then β obeys the mean-field bound β< or =1. As a corollary, we also derive an inequality relating the backbone density, the truncated susceptibility, and the infinite-cluster density
International Nuclear Information System (INIS)
Fontes, L.R.G.; Sidoravicius, V.
2004-01-01
Percolation is the phenomenon of transport of a fluid through a porous medium. For example, oil or gas through rock, or water through coffee powder. The medium consists of microscopic pores and channels through which the fluid might pass. In a simple situation, each channel will be open or closed to the passage of the fluid, depending on several characteristics of the medium which could be summed up in a few parameters. The distribution of open and closed channels could be described probabilistically. In the simplest case, each channel, independently of the others, is open with probability p, the single parameter of the model, and closed with probability 1 - p. We will model the medium microscopically by the d-dimensional hipercubic lattice, Z d , whose sites and (nearest neighbor) bonds represent the pores and channels, respectively. This constitutes what we will call the independent (Bernoulli) bond percolation model (in Z d ). It will be focused on in Part I of these notes. A basic question is the occurrence or not of percolation, that is, the existence of an infinite path, through open bonds only, cutting through the medium. In the next sections of this introduction, we will define the model in detail and show its first non-trivial result, establishing the existence of a phase transition in 2 and higher dimensions, that is, establishing the existence of a critical value for the parameter p, p c is an element of (0, 1), such that the model does not exhibit percolation almost surely for values of p below p c , and does exhibit percolation almost surely for values of p above p c . In Part II, we consider an oriented percolation model in a random environment which is related to several interesting questions in discrete probability. In Part III, we depart further from the initial model, and consider stochastic Ising models at zero temperature, which are not immediately related to the models in the previous parts, but rather to a dynamical percolation model called
Simple method to calculate percolation, Ising and Potts clusters
International Nuclear Information System (INIS)
Tsallis, C.
1981-01-01
A procedure ('break-collapse method') is introduced which considerably simplifies the calculation of two - or multirooted clusters like those commonly appearing in real space renormalization group (RG) treatments of bond-percolation, and pure and random Ising and Potts problems. The method is illustrated through two applications for the q-state Potts ferromagnet. The first of them concerns a RG calculation of the critical exponent ν for the isotropic square lattice: numerical consistence is obtained (particularly for q→0) with den Nijs conjecture. The second application is a compact reformulation of the standard star-triangle and duality transformations which provide the exact critical temperature for the anisotropic triangular and honeycomb lattices. (Author) [pt
Percolation approach for atomic and molecular cluster formation
International Nuclear Information System (INIS)
Knospe, O.; Seifert, G.
1987-12-01
We apply a percolation approach for the theoretical analysis of mass spectra of molecular microclusters obtained by adiabatic expansion technique. The evolution of the shape of the experimental size distributions as function of stagnation pressure and stagnation temperature are theoretically reproduced by varying the percolation parameter. Remaining discrepancies between theory and experiment are discussed. In addition, the even-odd alternation as well as the 'magic' shell structure within metallic, secondary ion mass spectra are investigated by introducing statistical weights for the cluster formation probabilities. Shell correction energies of atomic clusters as function of cluster-size are deduced from the experimental data. (orig.)
Mirrorless lasing from light emitters in percolating clusters
Burlak, Gennadiy; Rubo, Y. G.
2015-07-01
We describe the lasing effect in the three-dimensional percolation system, where the percolating cluster is filled by active media composed by light emitters excited noncoherently. We show that, due to the presence of a topologically nontrivial photonic structure, the stimulated emission is modified with respect to both conventional and random lasers. The time dynamics and spectra of the lasing output are studied numerically with finite-difference time-domain approach. The Fermat principle and Monte Carlo approach are applied to characterize the optimal optical path and interconnection between the radiating emitters. The spatial structure of the laser mode is found by a long-time FDTD simulation.
Cluster concentrations in correlated and non-correlated continuum percolation problems
International Nuclear Information System (INIS)
Borstnik, B.; Jesudason, C.G.; Lukman, D.
1996-01-01
The methodologies are developed how to evaluate properties of clusters of correlated and non-correlated particles. As an example of correlated particles, the two dimensional hard core disks with attractive square well potential are taken. Narrow and deep square well potential is used in order to mimic the adhesive potential, suitable for modeling of colloidal systems. Permeable disks in two dimensions are taken as an example of non-correlated systems. In both cases the dependence of cluster concentrations upon the density of particles is studied. Percolation threshold densities and critical exponents which govern the zeroth, first and second moments of cluster distributions are evaluated. It is found that the calculation of density dependence of cluster concentrations gives enough information to evaluate the percolation threshold density, some critical exponents, as well as to reproduce the Rushbrooke scaling law
Logarithmic corrections to scaling in critical percolation and random resistor networks.
Stenull, Olaf; Janssen, Hans-Karl
2003-09-01
We study the critical behavior of various geometrical and transport properties of percolation in six dimensions. By employing field theory and renormalization group methods we analyze fluctuation induced logarithmic corrections to scaling up to and including the next-to-leading order correction. Our study comprehends the percolation correlation function, i.e., the probability that two given points are connected, and some of the fractal masses describing percolation clusters. To be specific, we calculate the mass of the backbone, the red bonds, and the shortest path. Moreover, we study key transport properties of percolation as represented by the random resistor network. We investigate the average two-point resistance as well as the entire family of multifractal moments of the current distribution.
Kolesnikov, B. P.
2017-11-01
The presented work belongs to the issue of searching for the effective kinetic properties of macroscopically disordered environments (MDE). These properties characterize MDE in general on the sizes which significantly exceed the sizes of macro inhomogeneity. The structure of MDE is considered as a complex of interpenetrating percolating and finite clusters consolidated from homonymous components, topological characteristics of which influence on the properties of the whole environment. The influence of percolating clusters’ fractal substructures (backbone, skeleton of backbone, red bonds) on the transfer processes during crossover (a structure transition from fractal to homogeneous condition) is investigated based on the offered mathematical approach for finding the effective conductivity of MDEs and on the percolating cluster model. The nature of the change of the critical conductivity index t during crossover from the characteristic value for the area close to percolation threshold to the value corresponded to homogeneous condition is demonstrated. The offered model describes the transfer processes in MDE with the finite conductivity relation of «conductive» and «low conductive» phases above and below percolation threshold and in smearing area (an analogue of a blur area of the second-order phase transfer).
The abundance threshold for plague as a critical percolation phenomenon
DEFF Research Database (Denmark)
Davis, S; Trapman, P; Leirs, H
2008-01-01
. However, no natural examples have been reported. The central question of interest in percolation theory 4 , the possibility of an infinite connected cluster, corresponds in infectious disease to a positive probability of an epidemic. Archived records of plague (infection with Yersinia pestis....... Abundance thresholds are the theoretical basis for attempts to manage infectious disease by reducing the abundance of susceptibles, including vaccination and the culling of wildlife 6, 7, 8 . This first natural example of a percolation threshold in a disease system invites a re-appraisal of other invasion...
Critical current simulation in granular superconductors above the percolation threshold
Riedinger, Roland
1992-02-01
In the phase-coherent regime without applied external magnetic field, the critical superconducting current is limited by intragranular junctions which behave like Josephson junctions. We study the percolation aspects specific to lattices of such junctions and/or the mixing of superconductor with normal grains by averaging over configurations. We illustrate on 2 and 3 dimensional examples. The power laws valid near the percolation threshold are valid well above it, in two and three dimensions. We discuss the other models limiting the superconducting current, the vortex creep and superconducting order parameter fluctuations. Dans la limite de champ magnétique nul et de cohérence de phase du paramètre d'ordre supraconducteur, le courant supraconducteur maximal dans un réseau est limité par les jonctions intergranulaires qui se comportent comme des jonctions Josephson. Nous analysons les problèmes de percolation spécifiques aux réseaux de jonctions et du mélange de grains normaux et supraconducteurs. Nous donnons des exemples bidimensionnels et tridimensionnels ; après moyenne sur les configurations et analyse en taille finie, nous montrons que les lois de puissance valables au voisinage du seuil de percolation s'étendent sur un grand domaine au-delà du seuil de percolation, à deux et trois dimensions. Nous discutons les autres modèles limitant le courant supraconducteur, ancrage de vortex et fluctuations du paramètre d'ordre.
Percolation and cooperation with mobile agents: geometric and strategy clusters.
Vainstein, Mendeli H; Brito, Carolina; Arenzon, Jeferson J
2014-08-01
We study the conditions for persistent cooperation in an off-lattice model of mobile agents playing the Prisoner's Dilemma game with pure, unconditional strategies. Each agent has an exclusion radius r(P), which accounts for the population viscosity, and an interaction radius r(int), which defines the instantaneous contact network for the game dynamics. We show that, differently from the r(P)=0 case, the model with finite-sized agents presents a coexistence phase with both cooperators and defectors, besides the two absorbing phases, in which either cooperators or defectors dominate. We provide, in addition, a geometric interpretation of the transitions between phases. In analogy with lattice models, the geometric percolation of the contact network (i.e., irrespective of the strategy) enhances cooperation. More importantly, we show that the percolation of defectors is an essential condition for their survival. Differently from compact clusters of cooperators, isolated groups of defectors will eventually become extinct if not percolating, independently of their size.
Hybrid Percolation Transition in Cluster Merging Processes: Continuously Varying Exponents
Cho, Y. S.; Lee, J. S.; Herrmann, H. J.; Kahng, B.
2016-01-01
Consider growing a network, in which every new connection is made between two disconnected nodes. At least one node is chosen randomly from a subset consisting of g fraction of the entire population in the smallest clusters. Here we show that this simple strategy for improving connection exhibits a more unusual phase transition, namely a hybrid percolation transition exhibiting the properties of both first-order and second-order phase transitions. The cluster size distribution of finite clusters at a transition point exhibits power-law behavior with a continuously varying exponent τ in the range 2 power-law behavior of the avalanche size distribution arising in models with link-deleting processes in interdependent networks.
On the upper critical dimension of Bernoulli percolation
International Nuclear Information System (INIS)
Chayes, J.T.; Chayes, L.
1987-01-01
Derived is a set of inequalities for the d-dimensional independent percolation problem. Assuming the existence of critical exponents, these inequalities imply: f + nu ≥ 1 + β/sub Q/, μ + nu ≥ 1 + β/sub Q/, zeta ≥ min (1, nu'/nu), where the above exponents are f: the flow constant exponent, nu (nu'): the correlation length exponent below (above) threshold, μ: the surface tension exponent, β/sub Q/: the backbone density exponent and zeta: the chemical distance exponent. Note that all of these inequalities are mean-field bounds, and that they relate the exponent nu defined from below the percolation threshold to exponents defined from above threshold. Furthermore, we combine the strategy of the proofs these inequalities with notions of finite-size scaling to derive: max (d nu, d nu') ≥ 1 + β/sub Q/, where d is the lattice dimension. Since β/sub Q/ ≥ 2β, where β is the percolation density exponent, the final bound implies that, below six dimensions, the standard order parameter and correlation length exponents cannot simultaneously assume their mean-field values; hence an implicit bound on the upper critical dimension: d/sub c/ ≥ 6
International Nuclear Information System (INIS)
Herrmann, H.J.
1989-01-01
Electrical conductivity diffusion or phonons, have an anomalous behaviour on percolation clusters at the percolation threshold due to the fractality of these clusters. The results that have been found numerically for this anomalous behaviour are reviewed. A special purpose computer built for this purpose is described and the evaluation of the data from this machine is discussed
Ding, Jian; Li, Li
2018-06-01
We initiate the study on chemical distances of percolation clusters for level sets of two-dimensional discrete Gaussian free fields as well as loop clusters generated by two-dimensional random walk loop soups. One of our results states that the chemical distance between two macroscopic annuli away from the boundary for the random walk loop soup at the critical intensity is of dimension 1 with positive probability. Our proof method is based on an interesting combination of a theorem of Makarov, isomorphism theory, and an entropic repulsion estimate for Gaussian free fields in the presence of a hard wall.
Walking on fractals: diffusion and self-avoiding walks on percolation clusters
International Nuclear Information System (INIS)
Blavatska, V; Janke, W
2009-01-01
We consider random walks (RWs) and self-avoiding walks (SAWs) on disordered lattices directly at the percolation threshold. Applying numerical simulations, we study the scaling behavior of the models on the incipient percolation cluster in space dimensions d = 2, 3, 4. Our analysis yields estimates of universal exponents, governing the scaling laws for configurational properties of RWs and SAWs
Anomalous critical and supercritical phenomena in explosive percolation
D'Souza, Raissa M.; Nagler, Jan
2015-07-01
The emergence of large-scale connectivity on an underlying network or lattice, the so-called percolation transition, has a profound impact on the system’s macroscopic behaviours. There is thus great interest in controlling the location of the percolation transition to either enhance or delay its onset and, more generally, in understanding the consequences of such control interventions. Here we review explosive percolation, the sudden emergence of large-scale connectivity that results from repeated, small interventions designed to delay the percolation transition. These transitions exhibit drastic, unanticipated and exciting consequences that make explosive percolation an emerging paradigm for modelling real-world systems ranging from social networks to nanotubes.
The selected models of the mesostructure of composites percolation, clusters, and force fields
Herega, Alexander
2018-01-01
This book presents the role of mesostructure on the properties of composite materials. A complex percolation model is developed for the material structure containing percolation clusters of phases and interior boundaries. Modeling of technological cracks and the percolation in the Sierpinski carpet are described. The interaction of mesoscopic interior boundaries of the material, including the fractal nature of interior boundaries, the oscillatory nature of it interaction and also the stochastic model of the interior boundaries’ interaction, the genesis, structure, and properties are discussed. One of part of the book introduces the percolation model of the long-range effect which is based on the notion on the multifractal clusters with transforming elements, and the theorem on the field interaction of multifractals is described. In addition small clusters, their characteristic properties and the criterion of stability are presented.
Percolation and nucleation approaches to nuclear fragmentation: criticality in very small systems
Energy Technology Data Exchange (ETDEWEB)
Santiago, A.J. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Inst. de Fisica; Chung, K.C.
1994-12-01
Different criteria for criticality in very small systems are discussed in the context of percolation and nucleation approaches to nuclear fragmentation. It is shown that the probability threshold in percolation and interaction radius threshold in nucleation are very strongly dependent upon the adopted criterion. By using Monte Carlo method, similarities and dissimilarities between nucleation and percolation pictures are also pointed out. (author). 17 refs, 5 figs, 2 tabs.
Percolation and nucleation approaches to nuclear fragmentation: criticality in very small systems
International Nuclear Information System (INIS)
Santiago, A.J.; Chung, K.C.
1994-12-01
Different criteria for criticality in very small systems are discussed in the context of percolation and nucleation approaches to nuclear fragmentation. It is shown that the probability threshold in percolation and interaction radius threshold in nucleation are very strongly dependent upon the adopted criterion. By using Monte Carlo method, similarities and dissimilarities between nucleation and percolation pictures are also pointed out. (author). 17 refs, 5 figs, 2 tabs
On Equivalence between Critical Probabilities of Dynamic Gossip Protocol and Static Site Percolation
Ishikawa, Tetsuya; Hayakawa, Tomohisa
The relationship between the critical probability of gossip protocol on the square lattice and the critical probability of site percolation on the square lattice is discussed. Specifically, these two critical probabilities are analytically shown to be equal to each other. Furthermore, we present a way of evaluating the critical probability of site percolation by approximating the saturation of gossip protocol. Finally, we provide numerical results which support the theoretical analysis.
Ac hopping conduction at extreme disorder takes place on the percolating cluster
DEFF Research Database (Denmark)
Schrøder, Thomas; Dyre, J. C.
2008-01-01
Simulations of the random barrier model show that ac currents at extreme disorder are carried almost entirely by the percolating cluster slightly above threshold; thus contributions from isolated low activation-energy clusters are negligible. The effective medium approximation in conjunction...
Bond percolation on a class of correlated and clustered random graphs
International Nuclear Information System (INIS)
Allard, A; Hébert-Dufresne, L; Noël, P-A; Marceau, V; Dubé, L J
2012-01-01
We introduce a formalism for computing bond percolation properties of a class of correlated and clustered random graphs. This class of graphs is a generalization of the configuration model where nodes of different types are connected via different types of hyperedges, edges that can link more than two nodes. We argue that the multitype approach coupled with the use of clustered hyperedges can reproduce a wide spectrum of complex patterns, and thus enhances our capability to model real complex networks. As an illustration of this claim, we use our formalism to highlight unusual behaviours of the size and composition of the components (small and giant) in a synthetic, albeit realistic, social network. (paper)
Critical percolation in the slow cooling of the bi-dimensional ferromagnetic Ising model
Ricateau, Hugo; Cugliandolo, Leticia F.; Picco, Marco
2018-01-01
We study, with numerical methods, the fractal properties of the domain walls found in slow quenches of the kinetic Ising model to its critical temperature. We show that the equilibrium interfaces in the disordered phase have critical percolation fractal dimension over a wide range of length scales. We confirm that the system falls out of equilibrium at a temperature that depends on the cooling rate as predicted by the Kibble-Zurek argument and we prove that the dynamic growing length once the cooling reaches the critical point satisfies the same scaling. We determine the dynamic scaling properties of the interface winding angle variance and we show that the crossover between critical Ising and critical percolation properties is determined by the growing length reached when the system fell out of equilibrium.
Nonlinear random resistor diode networks and fractal dimensions of directed percolation clusters.
Stenull, O; Janssen, H K
2001-07-01
We study nonlinear random resistor diode networks at the transition from the nonpercolating to the directed percolating phase. The resistor-like bonds and the diode-like bonds under forward bias voltage obey a generalized Ohm's law V approximately I(r). Based on general grounds such as symmetries and relevance we develop a field theoretic model. We focus on the average two-port resistance, which is governed at the transition by the resistance exponent straight phi(r). By employing renormalization group methods we calculate straight phi(r) for arbitrary r to one-loop order. Then we address the fractal dimensions characterizing directed percolation clusters. Via considering distinct values of the nonlinearity r, we determine the dimension of the red bonds, the chemical path, and the backbone to two-loop order.
Clustering and percolation threshold in diphase systems of random centered quantum dots of ZnSe
International Nuclear Information System (INIS)
Bondar', N.V.
2009-01-01
A characteristic feature due to the formation of a percolation phase transition of carriers has been observed in a two-phase system consisting of borosilicate glass with ZnSe quantum dots. For near-threshold quantum-dot concentrations, changes due to microscopic fluctuations of the quantum-dot density have been observed in the intensities of radiation emission bands. This phenomenon is reminiscent of critical opalescence, where similar fluctuations of the density of a pure substance arise near a phase transition. It is proposed that the dielectric mismatch between the matrix and ZnSe plays a large role in the carrier (exciton) delocalization, resulting in the appearance of a 'dielectric trap' on the interface and the formation there of surface states of excitons. The spatial overlapping of states which occurs at the critical concentration of quantum dots results in carrier tunneling and the appearance of a percolation transition in such a system
Berger, Noam; Mukherjee, Chiranjib; Okamura, Kazuki
2018-03-01
We prove a quenched large deviation principle (LDP) for a simple random walk on a supercritical percolation cluster (SRWPC) on {Z^d} ({d ≥ 2}). The models under interest include classical Bernoulli bond and site percolation as well as models that exhibit long range correlations, like the random cluster model, the random interlacement and the vacant set of random interlacements (for {d ≥ 3}) and the level sets of the Gaussian free field ({d≥ 3}). Inspired by the methods developed by Kosygina et al. (Commun Pure Appl Math 59:1489-1521, 2006) for proving quenched LDP for elliptic diffusions with a random drift, and by Yilmaz (Commun Pure Appl Math 62(8):1033-1075, 2009) and Rosenbluth (Quenched large deviations for multidimensional random walks in a random environment: a variational formula. Ph.D. thesis, NYU, arXiv:0804.1444v1) for similar results regarding elliptic random walks in random environment, we take the point of view of the moving particle and prove a large deviation principle for the quenched distribution of the pair empirical measures of the environment Markov chain in the non-elliptic case of SRWPC. Via a contraction principle, this reduces easily to a quenched LDP for the distribution of the mean velocity of the random walk and both rate functions admit explicit variational formulas. The main difficulty in our set up lies in the inherent non-ellipticity as well as the lack of translation-invariance stemming from conditioning on the fact that the origin belongs to the infinite cluster. We develop a unifying approach for proving quenched large deviations for SRWPC based on exploiting coercivity properties of the relative entropies in the context of convex variational analysis, combined with input from ergodic theory and invoking geometric properties of the supercritical percolation cluster.
Order parameter fluctuations at a critical point - an exact result about percolation -
International Nuclear Information System (INIS)
Botet, Robert
2011-01-01
The order parameter of the system in the critical state, is expected to undergo large non-Gaussian fluctuations. However, almost nothing is known about the mathematical forms of the possible probability distributions of the order parameter. A remarkable exception is the site-percolation on the Bethe lattice, for which the complete order-parameter distribution has been recently derived at the critical point. Surprisingly, it appears to be the Kolmogorov-Smirnov distribution, well known in very different areas of mathematical statistics. In the present paper, we explain first how this special distribution could appear naturally in the context of the critical systems, under the assumption (still virtually unstudied) of the exponential distribution of the number of domains of a given size. In a second part, we present for the first time the complete derivation of the order-parameter distribution for the critical percolation model on the Bethe lattice, thus completing a recent publication announcing this result.
Self-Organized Percolation and Critical Sales Fluctuations
Weisbuch, Gérard; Solomon, Sorin
There is a discrepancy between the standard view of equilibrium through price adjustment in economics and the observation of large fluctuations in stock markets. We study here a simple model where agents decisions not only depend upon their individual preferences but also upon information obtained from their neighbors in a social network. The model shows that information diffusion coupled to the adjustment process drives the system to criticality with large fluctuations rather than converging smoothly to equilibrium.
Entanglement percolation on a quantum internet with scale-free and clustering characters
International Nuclear Information System (INIS)
Wu Liang; Zhu Shiqun
2011-01-01
The applicability of entanglement percolation protocol to real Internet structure is investigated. If the current Internet can be used directly in the quantum regime, the protocol can provide a way to establish long-distance entanglement when the links are pure nonmaximally entangled states. This applicability is primarily due to the combination of scale-free degree distribution and a high level of clustering, both of which are widely observed in many natural and artificial networks including the current Internet. It suggests that the topology of real Internet may play an important role in entanglement establishment.
Entanglement percolation on a quantum internet with scale-free and clustering characters
Energy Technology Data Exchange (ETDEWEB)
Wu Liang; Zhu Shiqun [School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006 (China)
2011-11-15
The applicability of entanglement percolation protocol to real Internet structure is investigated. If the current Internet can be used directly in the quantum regime, the protocol can provide a way to establish long-distance entanglement when the links are pure nonmaximally entangled states. This applicability is primarily due to the combination of scale-free degree distribution and a high level of clustering, both of which are widely observed in many natural and artificial networks including the current Internet. It suggests that the topology of real Internet may play an important role in entanglement establishment.
Hara, T.; Hofstad, van der R.W.; Slade, G.
2003-01-01
We consider spread-out models of self-avoiding walk, bond percolation, lattice trees and bond lattice animals on ${\\mathbb{Z}^d}$, having long finite-range connections, above their upper critical dimensions $d=4$ (self-avoiding walk), $d=6$ (percolation) and $d=8$ (trees and animals). The two-point
Non-criticality of interaction network over system's crises: A percolation analysis.
Shirazi, Amir Hossein; Saberi, Abbas Ali; Hosseiny, Ali; Amirzadeh, Ehsan; Toranj Simin, Pourya
2017-11-20
Extraction of interaction networks from multi-variate time-series is one of the topics of broad interest in complex systems. Although this method has a wide range of applications, most of the previous analyses have focused on the pairwise relations. Here we establish the potential of such a method to elicit aggregated behavior of the system by making a connection with the concepts from percolation theory. We study the dynamical interaction networks of a financial market extracted from the correlation network of indices, and build a weighted network. In correspondence with the percolation model, we find that away from financial crises the interaction network behaves like a critical random network of Erdős-Rényi, while close to a financial crisis, our model deviates from the critical random network and behaves differently at different size scales. We perform further analysis to clarify that our observation is not a simple consequence of the growth in correlations over the crises.
Anisotropic Percolation Analysis of Discharge
Matsumoto, Shogo; Odagaki, Takashi
2014-03-01
Exploiting a nonlinear resistor network on a square lattice in two dimensions, we investigate discharge when two opposite sides of the lattice are subjected to a constant voltage difference. Each site is ionized randomly with a probability in proportion to the square of the strength of the electric field, and the resistivity between two ionized sites is assumed to be 10-6 times smaller than the original resistivity. Using Monte Carlo simulation, we obtain the current and distribution of clusters of ionized sites as functions of the fraction of ionized sites. It is found that a wall of potential drop is formed as the fraction approaches a critical value, which is followed by discharge. The critical value is much smaller than the critical percolation probability of the standard site percolation on the square lattice. We also find that a singular behavior of the cluster distribution is expected at a critical fraction differently from that for the current, and that the critical exponents characterizing the cluster distribution satisfy the scaling relation known for two-dimensional percolation, while the critical exponent of the percolation probability is close to the value reported for a directed percolation.
International Nuclear Information System (INIS)
Riera, R.; Oliveira, P.M.C. de; Chaves, C.M.G.F.; Queiroz, S.L.A. de.
1980-04-01
A real-space renormalization group approach for the bond percolation problem in a square lattice with first- and second- neighbour bonds is proposed. The respective probabilities are treated, as independent variables. Two types of cells are constructed. In one of them the lattice is considered as two interpenetrating sublattices, first-neighbour bonds playing the role of intersublattice links. This allows the calculation of both critical exponents ν and γ, without resorting to any external field. Values found for the critical indices are in good agreement with data available in the literature. The phase diagram in parameter space is also obtained in each case. (Author) [pt
Spatial correlations, clustering and percolation-like transitions in homicide crimes
Alves, L. G. A.; Lenzi, E. K.; Mendes, R. S.; Ribeiro, H. V.
2015-07-01
The spatial dynamics of criminal activities has been recently studied through statistical physics methods; however, models and results have been focusing on local scales (city level) and much less is known about these patterns at larger scales, e.g. at a country level. Here we report on a characterization of the spatial dynamics of the homicide crimes along the Brazilian territory using data from all cities (˜5000) in a period of more than thirty years. Our results show that the spatial correlation function in the per capita homicides decays exponentially with the distance between cities and that the characteristic correlation length displays an acute increasing trend in the latest years. We also investigate the formation of spatial clusters of cities via a percolation-like analysis, where clustering of cities and a phase-transition-like behavior describing the size of the largest cluster as a function of a homicide threshold are observed. This transition-like behavior presents evolutive features characterized by an increasing in the homicide threshold (where the transitions occur) and by a decreasing in the transition magnitudes (length of the jumps in the cluster size). We believe that our work sheds new light on the spatial patterns of criminal activities at large scales, which may contribute for better political decisions and resources allocation as well as opens new possibilities for modeling criminal activities by setting up fundamental empirical patterns at large scales.
Directory of Open Access Journals (Sweden)
Zhou Zongzheng
2017-01-01
Full Text Available The underlying microstructure and dynamics of a dense granular material as it evolves towards the “critical state”, a limit state in which the system deforms with an essentially constant volume and stress ratio, remains widely debated in the micromechanics of granular media community. Strain localization, a common mechanism in the large strain regime, further complicates the characterization of this limit state. Here we revisit the evolution to this limit state within the framework of modern percolation theory. Attention is paid to motion transfer: in this context, percolation translates to the emergence of a large-scale connectivity in graphs that embody information on individual grain displacements. We construct each graph G(r by connecting nodes, representing the grains, within a distance r in the displacement-state-space. As r increases, we observe a percolation transition on G(r. The size of the jump discontinuity increases in the lead up to failure, indicating that the nature of percolation transition changes from continuous to explosive. We attribute this to the emergence of collective motion, which manifests in increasingly isolated communities in G(r. At the limit state, where the jump discontinuity is highest and invariant across the different unjamming cycles (drops in stress ratio, G(r encapsulates multiple kinematically distinct communities that are mediated by nodes corresponding to those grains in the shear band. This finding casts light on the dual and opposing roles of the shear band: a mechanism that creates powder keg divisions in the sample, while simultaneously acting as a mechanical link that transfers motion through such subdivisions moving in relative rigid-body motion.
Zhou, Zongzheng; Tordesillas, Antoinette
2017-06-01
The underlying microstructure and dynamics of a dense granular material as it evolves towards the "critical state", a limit state in which the system deforms with an essentially constant volume and stress ratio, remains widely debated in the micromechanics of granular media community. Strain localization, a common mechanism in the large strain regime, further complicates the characterization of this limit state. Here we revisit the evolution to this limit state within the framework of modern percolation theory. Attention is paid to motion transfer: in this context, percolation translates to the emergence of a large-scale connectivity in graphs that embody information on individual grain displacements. We construct each graph G(r) by connecting nodes, representing the grains, within a distance r in the displacement-state-space. As r increases, we observe a percolation transition on G(r). The size of the jump discontinuity increases in the lead up to failure, indicating that the nature of percolation transition changes from continuous to explosive. We attribute this to the emergence of collective motion, which manifests in increasingly isolated communities in G(r). At the limit state, where the jump discontinuity is highest and invariant across the different unjamming cycles (drops in stress ratio), G(r) encapsulates multiple kinematically distinct communities that are mediated by nodes corresponding to those grains in the shear band. This finding casts light on the dual and opposing roles of the shear band: a mechanism that creates powder keg divisions in the sample, while simultaneously acting as a mechanical link that transfers motion through such subdivisions moving in relative rigid-body motion.
Ultrathin percolated WO{sub 3} cluster film and its resistive response to H{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Zhao, Meng [Research Center for Solid State Physics and Materials, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009 (China); Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Wong, Man Hon; Huang, Jian Xing [Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Ong, Chung Wo, E-mail: c.w.ong@polyu.edu.hk [Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)
2014-11-05
Highlights: • Ultrathin percolated network of WO{sub 3} clusters was fabricated. • The WO{sub 3} clusters are modeled by spherical caps connected by ultrafine linkages. • The ultrathin percolated network of WO{sub 3} clusters shows fast response rate to H{sub 2}. • The fast response is attributed to the rapid electrical switching of the linkages. • Improved H{sub 2} sensing properties may be achieved if narrower linkages are used. - Abstract: Thin films composed of tungsten oxide (WO{sub 3}) nanoclusters were fabricated by oxidizing supersonic cluster beam deposited tungsten films at various temperatures. Oxidation at 700 °C resulted in aggregation of the deposits, forming a percolated network of WO{sub 3} spherical caps connected by fine links. The resistance response of the palladium-(Pd-) coated film sample to hydrogen (H{sub 2}) was investigated. The response rate was faster than those of other samples oxidized at lower temperatures. This is the result of the rapid electrical switching of the intercluster links between the highly resistive depleted state and conducting hydrogenated state. The possibility of improving the H{sub 2} sensing response rate with the use of the percolated WO{sub 3} film structure is illustrated.
Signature of Thermal Rigidity Percolation
International Nuclear Information System (INIS)
Huerta, Adrián
2013-01-01
To explore the role that temperature and percolation of rigidity play in determining the macroscopic properties, we propose a model that adds translational degrees of freedom to the spins of the well known Ising hamiltonian. In particular, the Ising model illustrate the longstanding idea that the growth of correlations on approach to a critical point could be describable in terms of the percolation of some sort of p hysical cluster . For certain parameters of this model we observe two well defined peaks of C V , that suggest the existence of two kinds of p hysical percolation , namely connectivity and rigidity percolation. Thermal fluctuations give rise to two different kinds of elementary excitations, i.e. droplets and configuron, as suggested by Angell in the framework of a bond lattice model approach. The later is reflected in the fluctuations of redundant constraints that gives stability to the structure and correlate with the order parameter
Torres, V. J. B.; Hajj Hussein, R.; Pagès, O.; Rayson, M. J.
2017-02-01
We test a presumed ability behind the phenomenological percolation scheme used for the basic description of the multi-mode Raman spectra of mixed crystals at one dimension along the linear chain approximation, to determine, via the Raman intensities, the nature of the atom substitution, as to whether this is random or due to local clustering/anticlustering. For doing so, we focus on the model percolation-type GeySi1-y system characterized by six oscillators { 1 × ( G e - G e ) , 3 × ( G e - S i ) , 2 × ( S i - S i ) } and place the study around the critical compositions y ˜ (0.16, 0.71, and 0.84) corresponding to nearly matching of intensities between the like Raman modes from a given multiplet ( G e - S i triplet or S i - S i doublet). The interplay between the GeySi1-y Raman intensities predicted by the percolation scheme depending on a suitable order parameter κ of local clustering/anticlustering is found to be consistent with ab initio calculations of the GeySi1-y Raman spectra done with the Ab Initio Modeling PROgram code using large (64-, 216-, and 512-atoms) disordered cubic supercells matching the required ( y , κ ) values. The actual "percolation vs. ab initio" comparative insight at moderate/dilute-(Ge,Si) limits, with an emphasis on the κ -induced intra-bond transfer of oscillator strength, extends a pioneering one earlier achieved at an intermediate composition ( y ˜ 0.50) by using small (32-atom) supercells [O. Pagès et al., J. Appl. Phys. 114, 033513 (2013)], mainly concerned with the inter-bond transfer of oscillator strength, providing altogether a complete picture.
Distribution of the minimum path on percolation clusters: A renormalization group calculation
International Nuclear Information System (INIS)
Hipsh, Lior.
1993-06-01
This thesis uses the renormalization group for the research of the chemical distance or the minimal path on percolation clusters on a 2 dimensional square lattice. Our aims are to calculate analytically (iterative calculation) the fractal dimension of the minimal path. d min. , and the distributions of the minimum paths, l min for different lattice sizes and for different starting densities (including the threshold value p c ). For the distributions. We seek for an analytic form which describes them. The probability to get a minimum path for each linear size L is calculated by iterating the distribution of l min for the basic cell of size 2*2 to the next scale sizes, using the H cell renormalization group. For the threshold value of p and for values near to p c . We confirm a scaling in the form: P(l,L) =f1/l(l/(L d min ). L - the linear size, l - the minimum path. The distribution can be also represented in the Fourier space, so we will try to solve the renormalization group equations in this space. A numerical fitting is produced and compared to existing numerical results. In order to improve the agreement between the renormalization group and the numerical simulations, we also present attempts to generalize the renormalization group by adding more parameters, e.g. correlations between bonds in different directions or finite densities for occupation of bonds and sites. (author) 17 refs
International Nuclear Information System (INIS)
Magalhaes, A.C.N. de.
1982-01-01
By using real space renormalization group methods, bond percolation on d-dimensional hypercubic (d = 2, 3, 4), first - and second - neighbour isotropic square, anisotropic square and 'inhomogeneous' 4-8 lattices is studied. Through some extrapolation methods, critical points and/or frontiers are obtained (as well as the critical exponent ν sub(p) in the isotropic cases) for these lattices that, or agree well with other available results, or are new as far as it is know (first - and second - neighbour isotropic square and 'inhomogeneous' 4-8 lattices). A conjecture concerning approximate (eventually exact) critical points and, in certain situations, critical frontiers of q-state Potts ferromagnets on d-dimensional lattices (d > 1) is formulated. This conjecture is verified within good accuracy for all the lattices whose critical points are known, and it allows the prediction of a great number of new results, some of them it is believed to be exact. Within a real space renomalization group framework, accurate approximations for the critical frontiers associated with the quenched bond-diluted first-neighbour spin-1/2 Ising ferromagnet on triangular and honeycomb lattices are calculated. The best numerical proposals lead, in both pure bond percolation (p = p sub(c)) and pure Ising (p = 1) limits, to the exact critical points and (dt 0 /dp) sub(p = p sub(c)) (where t 0 identical to tanh J/K sub(B) T), and to a 0.15% (0.96%) error in (dt 0 /dp) sub(p = 1) for the triangular (honeycomb) lattice; for p sub(c) 0 (for fixed p) of 0.27% (0.14%) is estimated for the triangular (honeycomb) lattice. It is exhibited, for many star-triangle graph pairs with any number of terminals and different sizes, that the exact q = 1, 2, 3, 4 critical points of Potts ferromagnets can aZZ of them, be obtained from any one of such graph pairs. (Author) [pt
Hofstad, van der R.W.; Sakai, A.
2005-01-01
We consider self-avoiding walk and percolation in d, oriented percolation in d×+, and the contact process in d, with p D(·) being the coupling function whose range is proportional to L. For percolation, for example, each bond is independently occupied with probability p D(y–x). The above models are
The computation of bond percolation critical polynomials by the deletion–contraction algorithm
International Nuclear Information System (INIS)
Scullard, Christian R
2012-01-01
Although every exactly known bond percolation critical threshold is the root in [0,1] of a lattice-dependent polynomial, it has recently been shown that the notion of a critical polynomial can be extended to any periodic lattice. The polynomial is computed on a finite subgraph, called the base, of an infinite lattice. For any problem with exactly known solution, the prediction of the bond threshold is always correct for any base containing an arbitrary number of unit cells. For unsolved problems, the polynomial is referred to as the generalized critical polynomial and provides an approximation that becomes more accurate with increasing number of bonds in the base, appearing to approach the exact answer. The polynomials are computed using the deletion–contraction algorithm, which quickly becomes intractable by hand for more than about 18 bonds. Here, I present generalized critical polynomials calculated with a computer program for bases of up to 36 bonds for all the unsolved Archimedean lattices, except the kagome lattice, which was considered in an earlier work. The polynomial estimates are generally within 10 −5 –10 −7 of the numerical values, but the prediction for the (4,8 2 ) lattice, though not exact, is not ruled out by simulations. (paper)
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Mulet, R.; Diaz, O.; Altshuler, E.
1997-01-01
The percolative character of the current paths and the self-field effects were considered to estimate optimal sample dimensions for the transport current of a granular superconductor by means of a Monte Carlo algorithm and critical-state model calculations. We showed that, under certain conditions, self-field effects are negligible and the J c dependence on sample dimensions is determined by the percolative character of the current. Optimal dimensions are demonstrated to be a function of the fraction of superconducting phase in the sample. (author)
Conformal partition functions of critical percolation from D 3 thermodynamic Bethe Ansatz equations
Morin-Duchesne, Alexi; Klümper, Andreas; Pearce, Paul A.
2017-08-01
Using the planar Temperley-Lieb algebra, critical bond percolation on the square lattice can be reformulated as a loop model. In this form, it is incorporated as {{ L}}{{ M}}(2, 3) in the Yang-Baxter integrable family of logarithmic minimal models {{ L}}{{ M}}( p, p\\prime) . We consider this model of percolation in the presence of boundaries and with periodic boundary conditions. Inspired by Kuniba, Sakai and Suzuki, we rewrite the recently obtained infinite Y-system of functional equations. In this way, we obtain nonlinear integral equations in the form of a closed finite set of TBA equations described by a D 3 Dynkin diagram. Following the methods of Klümper and Pearce, we solve the TBA equations for the conformal finite-size corrections. For the ground states of the standard modules on the strip, these agree with the known central charge c = 0 and conformal weights Δ1, s for \\renewcommand≥≥slant} s\\in {{ Z}≥slant 1} with Δr, s=\\big((3r-2s){\\hspace{0pt}}^2-1\\big)/24 . For the periodic case, the finite-size corrections agree with the conformal weights Δ0, s , Δ1, s with \\renewcommand{≥{≥slant} s\\in\\frac{1}{2}{{ Z}≥slant 0} . These are obtained analytically using Rogers dilogarithm identities. We incorporate all finite excitations by formulating empirical selection rules for the patterns of zeros of all the eigenvalues of the standard modules. We thus obtain the conformal partition functions on the cylinder and the modular invariant partition function (MIPF) on the torus. By applying q-binomial and q-Narayana identities, it is shown that our refined finitized characters on the strip agree with those of Pearce, Rasmussen and Zuber. For percolation on the torus, the MIPF is a non-diagonal sesquilinear form in affine u(1) characters given by the u(1) partition function Z2, 3(q)=Z2, 3{Circ}(q) . The u(1) operator content is {{ N}}Δ, \\barΔ=1 for Δ=\\barΔ=-\\frac{1}{24}, \\frac{35}{24} and {{ N}}Δ, \\barΔ=2 for
Recent advances in percolation theory and its applications
Energy Technology Data Exchange (ETDEWEB)
Saberi, Abbas Ali, E-mail: ab.saberi@ut.ac.ir
2015-05-24
Percolation is the simplest fundamental model in statistical mechanics that exhibits phase transitions signaled by the emergence of a giant connected component. Despite its very simple rules, percolation theory has successfully been applied to describe a large variety of natural, technological and social systems. Percolation models serve as important universality classes in critical phenomena characterized by a set of critical exponents which correspond to a rich fractal and scaling structure of their geometric features. We will first outline the basic features of the ordinary model. Over the years a variety of percolation models has been introduced some of which with completely different scaling and universal properties from the original model with either continuous or discontinuous transitions depending on the control parameter, dimensionality and the type of the underlying rules and networks. We will try to take a glimpse at a number of selective variations including Achlioptas process, half-restricted process and spanning cluster-avoiding process as examples of the so-called explosive percolation. We will also introduce non-self-averaging percolation and discuss correlated percolation and bootstrap percolation with special emphasis on their recent progress. Directed percolation process will be also discussed as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. In the past decade, after the invention of stochastic Löwner evolution (SLE) by Oded Schramm, two-dimensional (2D) percolation has become a central problem in probability theory leading to the two recent Fields medals. After a short review on SLE, we will provide an overview on existence of the scaling limit and conformal invariance of the critical percolation. We will also establish a connection with the magnetic models based on the percolation properties of the Fortuin–Kasteleyn and geometric spin clusters. As an application we will discuss how percolation
Recent advances in percolation theory and its applications
International Nuclear Information System (INIS)
Saberi, Abbas Ali
2015-01-01
Percolation is the simplest fundamental model in statistical mechanics that exhibits phase transitions signaled by the emergence of a giant connected component. Despite its very simple rules, percolation theory has successfully been applied to describe a large variety of natural, technological and social systems. Percolation models serve as important universality classes in critical phenomena characterized by a set of critical exponents which correspond to a rich fractal and scaling structure of their geometric features. We will first outline the basic features of the ordinary model. Over the years a variety of percolation models has been introduced some of which with completely different scaling and universal properties from the original model with either continuous or discontinuous transitions depending on the control parameter, dimensionality and the type of the underlying rules and networks. We will try to take a glimpse at a number of selective variations including Achlioptas process, half-restricted process and spanning cluster-avoiding process as examples of the so-called explosive percolation. We will also introduce non-self-averaging percolation and discuss correlated percolation and bootstrap percolation with special emphasis on their recent progress. Directed percolation process will be also discussed as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. In the past decade, after the invention of stochastic Löwner evolution (SLE) by Oded Schramm, two-dimensional (2D) percolation has become a central problem in probability theory leading to the two recent Fields medals. After a short review on SLE, we will provide an overview on existence of the scaling limit and conformal invariance of the critical percolation. We will also establish a connection with the magnetic models based on the percolation properties of the Fortuin–Kasteleyn and geometric spin clusters. As an application we will discuss how percolation
Recent advances in percolation theory and its applications
Saberi, Abbas Ali
2015-05-01
Percolation is the simplest fundamental model in statistical mechanics that exhibits phase transitions signaled by the emergence of a giant connected component. Despite its very simple rules, percolation theory has successfully been applied to describe a large variety of natural, technological and social systems. Percolation models serve as important universality classes in critical phenomena characterized by a set of critical exponents which correspond to a rich fractal and scaling structure of their geometric features. We will first outline the basic features of the ordinary model. Over the years a variety of percolation models has been introduced some of which with completely different scaling and universal properties from the original model with either continuous or discontinuous transitions depending on the control parameter, dimensionality and the type of the underlying rules and networks. We will try to take a glimpse at a number of selective variations including Achlioptas process, half-restricted process and spanning cluster-avoiding process as examples of the so-called explosive percolation. We will also introduce non-self-averaging percolation and discuss correlated percolation and bootstrap percolation with special emphasis on their recent progress. Directed percolation process will be also discussed as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. In the past decade, after the invention of stochastic Löwner evolution (SLE) by Oded Schramm, two-dimensional (2D) percolation has become a central problem in probability theory leading to the two recent Fields medals. After a short review on SLE, we will provide an overview on existence of the scaling limit and conformal invariance of the critical percolation. We will also establish a connection with the magnetic models based on the percolation properties of the Fortuin-Kasteleyn and geometric spin clusters. As an application we will discuss how percolation
Ranjbar, Zahra; Moradian, Siamak; Rastegar, Saeed
2003-08-15
The electrodeposition behavior of blends of primary dispersions of a lower and a higher molecular weight epoxy-amine adduct has been investigated. The throwing power of the above-mentioned blends showed a voltage-dependent critical composition at which the throwing power dropped to a much lower value. This was assigned to the formation of an infinite conducting cluster, the extension of which is dependent on the rate of the electrocoagulation process at the cathode boundary. The random resistor network approach of Stauffer (RRNS) and the random resistor network approach of Miller and Abrahams (RRNMA) were applied to the experimental data with high correlations (r2=0.9314 and 0.9699). The percolating cluster formed within the film, however, gave a critical exponent of conductivity equal to 1.1028, much less than expected from a classical three-dimensional lattice (i.e., 1.5-2.0). This discrepancy was explained in terms of the changed behavior of the film resulting from the bubbles formed near the cathode and its effect on the infinite conducting cluster.
Introduction to percolation theory
Stauffer, Dietrich
1991-01-01
Percolation theory deals with clustering, criticallity, diffusion, fractals, phase transitions and disordered systems. This book covers the basic theory for the graduate, and also professionals dealing with it for the first time
Boundary rules and breaking of self-organized criticality in 2D frozen percolation
J. van den Berg (Rob); P. Nolin (Pierre)
2016-01-01
htmlabstractWe study frozen percolation on the (planar) triangular lattice, where connected components stop growing ("freeze") as soon as their "size" becomes at least N, for some parameter N ≥ 1. The size of a connected component can be measured in several natural ways, and we
Boundary rules and breaking of self-organized criticality in 2D frozen percolation
J. van den Berg (Rob); P. Nolin (Pierre)
2017-01-01
htmlabstractWe study frozen percolation on the (planar) triangular lattice, where connected components stop growing (“freeze”) as soon as their “size” becomes at least N, for some parameter N ≥ 1. The size of a connected component can be measured in several natural ways, and we
International Nuclear Information System (INIS)
Kunz, H.
1980-01-01
Percolation is a unifying which appeared to be rather useful in trying to understand some properties of disordered physical systems, or some phase transitions in polymers, like gelation or vulcanisation. Although implicitely used in the pioneering work of Flory in 1941 on the sol-gel transition of polymers, it was first introduced in a well-defined way by the mathematicians Hammersley and Broadbent in 1957, who obtained the first rigorous result. Since then, the subject has seen a variety of new applications and its recent study has largely benefited from the vigorous development of critical phenomena after the introduction of the RG ideas and techniques. (author)
A generalized model for site percolation with two independent concentrations
International Nuclear Information System (INIS)
Lin Jiancheng.
1987-05-01
In this paper the usual site percolation problem with single concentration is generalized to the one that contains two independent concentrations. Using the real space renormalization technique we derive an exact transformation for the one dimensional lattice and a cluster transformation for triangle lattice in two dimensions. The critical exponents and the percolation threshold concentrations obtained are the same as those of the usual single concentration percolation problem. Critical line and flow diagram in the two concentration parameters space are also given. (author). 10 refs, 6 figs
Finite-size scaling of clique percolation on two-dimensional Moore lattices
Dong, Jia-Qi; Shen, Zhou; Zhang, Yongwen; Huang, Zi-Gang; Huang, Liang; Chen, Xiaosong
2018-05-01
Clique percolation has attracted much attention due to its significance in understanding topological overlap among communities and dynamical instability of structured systems. Rich critical behavior has been observed in clique percolation on Erdős-Rényi (ER) random graphs, but few works have discussed clique percolation on finite dimensional systems. In this paper, we have defined a series of characteristic events, i.e., the historically largest size jumps of the clusters, in the percolating process of adding bonds and developed a new finite-size scaling scheme based on the interval of the characteristic events. Through the finite-size scaling analysis, we have found, interestingly, that, in contrast to the clique percolation on an ER graph where the critical exponents are parameter dependent, the two-dimensional (2D) clique percolation simply shares the same critical exponents with traditional site or bond percolation, independent of the clique percolation parameters. This has been corroborated by bridging two special types of clique percolation to site percolation on 2D lattices. Mechanisms for the difference of the critical behaviors between clique percolation on ER graphs and on 2D lattices are also discussed.
Solomon, Sorin; Weisbuch, Gerard; de Arcangelis, Lucilla; Jan, Naeem; Stauffer, Dietrich
2000-03-01
We here relate the occurrence of extreme market shares, close to either 0 or 100%, in the media industry to a percolation phenomenon across the social network of customers. We further discuss the possibility of observing self-organized criticality when customers and cinema producers adjust their preferences and the quality of the produced films according to previous experience. Comprehensive computer simulations on square lattices do indeed exhibit self-organized criticality towards the usual percolation threshold and related scaling behaviour.
Multifragmentation and percolation
International Nuclear Information System (INIS)
Campi, X.; Desbois, J.
1985-01-01
Percolation theory is applied to the problem of nucleus break-up. A model of nuclear percolation is proposed in which the rules for linkage of nucleons to form a cluster are defined in real and momentum spaces. This model exhibits a rather well defined threshold at rho ≅ 0.6. Analytical expressions for cluster size distributions at fixed concentration rho are given. Decay of excited clusters (by evaporation and fission) to give stable nuclear fragments is incorporated. The distribution law for rho in inclusive reactions is studied and the calculated mass yields are compared to experimental results
A percolation process on the square lattice where large finite clusters are frozen
van den Berg, J.; de Lima, B.N.B.; Nolin, P.
2012-01-01
In (Aldous, Math. Proc. Cambridge Philos. Soc. 128 (2000), 465-477), Aldous constructed a growth process for the binary tree where clusters freeze as soon as they become infinite. It was pointed out by Benjamini and Schramm that such a process does not exist for the square lattice. This motivated us
Goldenberg, J.; Libai, B.; Solomon, S.; Jan, N.; Stauffer, D.
2000-09-01
A percolation model is presented, with computer simulations for illustrations, to show how the sales of a new product may penetrate the consumer market. We review the traditional approach in the marketing literature, which is based on differential or difference equations similar to the logistic equation (Bass, Manage. Sci. 15 (1969) 215). This mean-field approach is contrasted with the discrete percolation on a lattice, with simulations of "social percolation" (Solomon et al., Physica A 277 (2000) 239) in two to five dimensions giving power laws instead of exponential growth, and strong fluctuations right at the percolation threshold.
Integral hierarchies and percolation
International Nuclear Information System (INIS)
Klein, W.; Stell, G.
1985-01-01
For a variation of the Potts model which has been shown to describe continuum percolation, we derive a hierarchy of integral equations of Kirkwood-Salsburg type. The distribution functions which are the solutions of this hierarchy can be simply related to the connectedness functions in continuum percolation. From this hierarchy a second set of equations is derived from which the connectedness functions can be obtained directly. This approach is extremely useful when investigating properties of systems far from the percolation transition. These hierarchies are solved exactly in the mean-field (Kac-Baker) limit and possible implications for cluster growth are discussed. The relation between the Potts model for continuum percolation and the Widom-Rowlinson model is also noted
The internal percolation problem
International Nuclear Information System (INIS)
Bezsudnov, I.V.; Snarskii, A.A.
2010-01-01
The internal percolation problem (IP) as a new type of the percolation problem is introduced and investigated. In spite of the usual (or external) percolation problem (EP) when the percolation current flows from the top to the bottom of the system, in IP case the voltage is applied through bars which are present in the hole located within the system. The EP problem has two major parameters: M-size of the system and a 0 -size of inclusions, bond size, etc. The IP problem holds one parameter more: size of the hole L. Numerical simulation shows that the critical indexes of conductance for the IP problem are very close to those in the EP problem. On the contrary, the indexes of the relative spectral noise density of 1/f noise and higher moments differ from those in the EP problem. The basics of these facts is discussed.
Bondar', N. V.
2009-03-01
A characteristic feature due to the formation of a percolation phase transition of carriers has been observed in a two-phase system consisting of borosilicate glass with ZnSe quantum dots. For near-threshold quantum-dot concentrations, changes due to microscopic fluctuations of the quantum-dot density have been observed in the intensities of radiation emission bands. This phenomenon is reminiscent of critical opalescence, where similar fluctuations of the density of a pure substance arise near a phase transition. It is proposed that the dielectric mismatch between the matrix and ZnSe plays a large role in the carrier (exciton) delocalization, resulting in the appearance of a "dielectric trap" on the interface and the formation there of surface states of excitons. The spatial overlapping of states which occurs at the critical concentration of quantum dots results in carrier tunneling and the appearance of a percolation transition in such a system.
Interactions and ``puff clustering'' close to the critical point in pipe flow
Vasudevan, Mukund; Hof, Björn
2017-11-01
The first turbulent structures to arise in pipe flow are puffs. Albeit transient in nature, their spreading determines if eventually turbulence becomes sustained. Due to the extremely long time scales involved in these processes it is virtually impossible to directly observe the transition and the flow patterns that are eventually assumed in the long time limit. We present a new experimental approach where, based on the memoryless nature of turbulent puffs, we continuously recreate the flow pattern exiting the pipe. These periodic boundary conditions enable us to show that the flow pattern eventually settles to a statistically steady state. While our study confirms the value of the critical point of Rec 2040 , the flow fields show that puffs interact over longer ranges than previously suspected. As a consequence puffs tend to cluster and these regions of large puff densities travel across the puff pattern in a wave like fashion. While transition in Couette flow has been shown to fall into the ``directed percolation'', pipe flow may be more complicated since long range interactions are prohibited for the percolation transition type. Extensive measurements at the critical point will be presented to clarify the nature of the transition.
Percolation via Combined Electrostatic and Chemical Doping in Complex Oxide Films
Orth, Peter P.; Fernandes, Rafael M.; Walter, Jeff; Leighton, C.; Shklovskii, B. I.
2017-03-01
Stimulated by experimental advances in electrolyte gating methods, we investigate theoretically percolation in thin films of inhomogeneous complex oxides, such as La1 -xSrxCoO3 (LSCO), induced by a combination of bulk chemical and surface electrostatic doping. Using numerical and analytical methods, we identify two mechanisms that describe how bulk dopants reduce the amount of electrostatic surface charge required to reach percolation: (i) bulk-assisted surface percolation and (ii) surface-assisted bulk percolation. We show that the critical surface charge strongly depends on the film thickness when the film is close to the chemical percolation threshold. In particular, thin films can be driven across the percolation transition by modest surface charge densities. If percolation is associated with the onset of ferromagnetism, as in LSCO, we further demonstrate that the presence of critical magnetic clusters extending from the film surface into the bulk results in considerable enhancement of the saturation magnetization, with pronounced experimental consequences. These results should significantly guide experimental work seeking to verify gate-induced percolation transitions in such materials.
Generalized bond percolation and statistical mechanics
International Nuclear Information System (INIS)
Tsallis, C.
1978-05-01
A generalization of traditional bond percolation is performed, in the sens that bonds have now the possibility of partially transmitting the information (a fact which leads to the concept of 'fidelity' of the bond), and also in the sens that, besides the normal tendency to equiprobability, the bonds are allowed to substantially change the information. Furthermore the fidelity is allowed, to become an aleatory variable, and the operational rules concerning the associated distribution laws are determined. Thermally quenched random bonds and the whole body of Statistical Mechanics become particular cases of this formalism, which is in general adapted to the treatment of all problems whose main characteristic is to preserve a part of the information through a long path or array (critical phenomena, regime changements, thermal random models, etc). Operationally it provides a quick method for the calculation of the equivalent probability of complex clusters within the traditional bond percolation problem [pt
Percolation and spin glass transition
International Nuclear Information System (INIS)
Sadiq, A.; Tahir-Kheli, R.A.; Wortis, M.; Bhatti, N.A.
1980-10-01
The behaviour of clusters of curved and normal plaquette particles in a bond random, +-J, Ising model is studied in finite square and triangular lattices. Computer results for the concentration of antiferromagnetic bonds when percolating clusters first appears are found to be close to those reported for the occurrence and disappearance of spin glass phases in these systems. (author)
Target-Searching on Percolation
International Nuclear Information System (INIS)
Yang Shijie
2005-01-01
We study target-searching processes on a percolation, on which a hunter tracks a target by smelling odors it emits. The odor intensity is supposed to be inversely proportional to the distance it propagates. The Monte Carlo simulation is performed on a 2-dimensional bond-percolation above the threshold. Having no idea of the location of the target, the hunter determines its moves only by random attempts in each direction. For lager percolation connectivity p ∼> 0.90, it reveals a scaling law for the searching time versus the distance to the position of the target. The scaling exponent is dependent on the sensitivity of the hunter. For smaller p, the scaling law is broken and the probability of finding out the target significantly reduces. The hunter seems trapped in the cluster of the percolation and can hardly reach the goal.
Unusual percolation in simple small-world networks.
Cohen, Reuven; Dawid, Daryush Jonathan; Kardar, Mehran; Bar-Yam, Yaneer
2009-06-01
We present an exact solution of percolation in a generalized class of Watts-Strogatz graphs defined on a one-dimensional underlying lattice. We find a nonclassical critical point in the limit of the number of long-range bonds in the system going to zero, with a discontinuity in the percolation probability and a divergence in the mean finite-cluster size. We show that the critical behavior falls into one of three regimes depending on the proportion of occupied long-range to unoccupied nearest-neighbor bonds, with each regime being characterized by different critical exponents. The three regimes can be united by a single scaling function around the critical point. These results can be used to identify the number of long-range links necessary to secure connectivity in a communication or transportation chain. As an example, we can resolve the communication problem in a game of "telephone."
Percolation and multifragmentation of nuclei
International Nuclear Information System (INIS)
Shmakov, S.Yu.; Uzhinskij, V.V.
1989-01-01
A method to build the 'cold' nuclei as percolation clusters is suggested. Within the framework of definite assumptions of the character of nucleon-nucleon couplings breaking resulting from the nuclear reactions as description of the multifragmentation process in the hadron-nucleus and nucleus-nucleus reactions at high energies is obtained. 19 refs.; 6 figs
Percolation Threshold Parameters of Fluids
Czech Academy of Sciences Publication Activity Database
Škvor, J.; Nezbeda, Ivo
2009-01-01
Roč. 79, č. 4 (2009), 041141-041147 ISSN 1539-3755 Institutional research plan: CEZ:AV0Z40720504 Keywords : percolation threshold * universality * infinite cluster Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.400, year: 2009
Attacks and infections in percolation processes
International Nuclear Information System (INIS)
Janssen, Hans-Karl; Stenull, Olaf
2017-01-01
We discuss attacks and infections at propagating fronts of percolation processes based on the extended general epidemic process. The scaling behavior of the number of the attacked and infected sites in the long time limit at the ordinary and tricritical percolation transitions is governed by specific composite operators of the field-theoretic representation of this process. We calculate corresponding critical exponents for tricritical percolation in mean-field theory and for ordinary percolation to 1-loop order. Our results agree well with the available numerical data. (paper)
Polymer Percolation Threshold in Multi-Component HPMC Matrices Tablets
Directory of Open Access Journals (Sweden)
Maryam Maghsoodi
2011-06-01
Full Text Available Introduction: The percolation theory studies the critical points or percolation thresholds of the system, where onecomponent of the system undergoes a geometrical phase transition, starting to connect the whole system. The application of this theory to study the release rate of hydrophilic matrices allows toexplain the changes in release kinetics of swellable matrix type system and results in a clear improvement of the design of controlled release dosage forms. Methods: In this study, the percolation theory has been applied to multi-component hydroxypropylmethylcellulose (HPMC hydrophilic matrices. Matrix tablets have been prepared using phenobarbital as drug,magnesium stearate as a lubricant employing different amount of lactose and HPMC K4M as a fillerandmatrix forming material, respectively. Ethylcelullose (EC as a polymeric excipient was also examined. Dissolution studies were carried out using the paddle method. In order to estimate the percolation threshold, the behaviour of the kinetic parameters with respect to the volumetric fraction of HPMC at time zero, was studied. Results: In both HPMC/lactose and HPMC/EC/lactose matrices, from the point of view of the percolation theory, the optimum concentration for HPMC, to obtain a hydrophilic matrix system for the controlled release of phenobarbital is higher than 18.1% (v/v HPMC. Above 18.1% (v/v HPMC, an infinite cluster of HPMC would be formed maintaining integrity of the system and controlling the drug release from the matrices. According to results, EC had no significant influence on the HPMC percolation threshold. Conclusion: This may be related to broad functionality of the swelling hydrophilic matrices.
Cluster tails for critical power-law inhomogeneous random graphs
van der Hofstad, R.; Kliem, S.; van Leeuwaarden, J.S.H.
2018-01-01
Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299–2361, 2012). It was proved that when the degrees obey a power law with exponent τ∈ (3 , 4)
Critical machine cluster identification using the equal area criterion
DEFF Research Database (Denmark)
Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob
2015-01-01
The paper introduces a new method to early identify the critical machine cluster (CMC) after a transient disturbance. For transient stability assessment with methods based on the equal area criterion it is necessary to split the generators into a group of critical and non-critical machines....... The generators in the CMC are those likely to lose synchronism. The early and reliable identification of the CMC is crucial and one of the major challenges. The proposed new approach is based on the assessment of the rotor dynamics between two machines and the evaluation of their coupling strength. A novel...
Percolation in Heterogeneous Media
International Nuclear Information System (INIS)
Vocka, Radim
1999-01-01
This work is a theoretical reflection on the problematic of the modeling of heterogeneous media, that is on the way of their simple representation conserving their characteristic features. Two particular problems are addressed in this thesis. Firstly, we study the transport in porous media, that is in a heterogeneous media which structure is quenched. A pore space is represented in a simple way - a pore is symbolized as a tube of a given length and a given diameter. The fact that the correlations in the distribution of pore sizes are taken into account by a construction of a hierarchical network makes possible the modeling of porous media with a porosity distributed over several length scales. The transport in the hierarchical network shows qualitatively different phenomena from those observed in simpler models. A comparison of numerical results with experimental data shows that the hierarchical network gives a good qualitative representation of the structure of real porous media. Secondly, we study a problem of the transport in a heterogeneous media which structure is evolving during the time. The models where the evolution of the structure is not influenced by the transport are studied in detail. These models present a phase transition of the same nature as that observed on the percolation networks. We propose a new theoretical description of this transition, and we express critical exponents describing the evolution of the conductivity as a function of fundamental exponents of percolation theory. (author) [fr
Degree product rule tempers explosive percolation in the absence of global information
Trevelyan, Alexander J.; Tsekenis, Georgios; Corwin, Eric I.
2018-02-01
We introduce a guided network growth model, which we call the degree product rule process, that uses solely local information when adding new edges. For small numbers of candidate edges our process gives rise to a second-order phase transition, but becomes first order in the limit of global choice. We provide the set of critical exponents required to characterize the nature of this percolation transition. Such a process permits interventions which can delay the onset of percolation while tempering the explosiveness caused by cluster product rule processes.
Bootstrap percolation: a renormalisation group approach
International Nuclear Information System (INIS)
Branco, N.S.; Santos, Raimundo R. dos; Queiroz, S.L.A. de.
1984-02-01
In bootstrap percolation, sites are occupied at random with probability p, but each site is considered active only if at least m of its neighbours are also active. Within an approximate position-space renormalization group framework on a square lattice we obtain the behaviour of the critical concentration p (sub)c and of the critical exponents ν and β for m = 0 (ordinary percolation), 1,2 and 3. We find that the bootstrap percolation problem can be cast into different universality classes, characterized by the values of m. (author) [pt
Porous media: Analysis, reconstruction and percolation
DEFF Research Database (Denmark)
Rogon, Thomas Alexander
1995-01-01
functions of Gaussian fields and spatial autocorrelation functions of binary fields. An enhanced approach which embodies semi-analytical solutions for the conversions has been made. The scope and limitations of the method have been analysed in terms of realizability of different model correlation functions...... stereological methods. The measured sample autocorrelations are modeled by analytical correlation functions. A method for simulating porous networks from their porosity and spatial correlation originally developed by Joshi (14) is presented. This method is based on a conversion between spatial autocorrelation...... in binary fields. Percolation threshold of reconstructed porous media has been determined for different discretizations of a selected model correlation function. Also critical exponents such as the correlation length exponent v, the strength of the infinite network and the mean size of finite clusters have...
Percolation and lasing in real 3D crystals with inhomogeneous distributed random pores
Energy Technology Data Exchange (ETDEWEB)
Burlak, Gennadiy, E-mail: gburlak@uaem.mx; Calderón-Segura, Yessica
2014-11-15
We systematically study the percolation phase transition in real 3D crystals where not only the state of pores but also their radius r and displacement s are random valued numbers. The mean values R=〈r〉 and S=〈s〉 emerge as additional spatial scales in such an extended network. This leads to variations of the threshold (critical) percolation probability p{sub C} and the percolation order parameter P that become to be the intricate functions of R and S. Our numerical simulations have shown that in such extended system the incipient spanning cluster can arise even for situations where for simple periodical system the percolation does not exist. We analyzed the validity of the nearest neighbor's approximation and found that such approximation is not valid for materials with large dispersivity of pores. The lasing of nanoemitters incorporated in such percolating spanning cluster is studied too. This effect can open interesting perspectives in modern nano- and micro-information technologies.
Reversible first-order transition in Pauli percolation
Maksymenko, Mykola; Moessner, Roderich; Shtengel, Kirill
2015-06-01
Percolation plays an important role in fields and phenomena as diverse as the study of social networks, the dynamics of epidemics, the robustness of electricity grids, conduction in disordered media, and geometric properties in statistical physics. We analyze a new percolation problem in which the first-order nature of an equilibrium percolation transition can be established analytically and verified numerically. The rules for this site percolation model are physical and very simple, requiring only the introduction of a weight W (n )=n +1 for a cluster of size n . This establishes that a discontinuous percolation transition can occur with qualitatively more local interactions than in all currently considered examples of explosive percolation; and that, unlike these, it can be reversible. This greatly extends both the applicability of such percolation models in principle and their reach in practice.
Long-range correlated percolation
International Nuclear Information System (INIS)
Weinrib, A.
1984-01-01
This paper is a study of the percolation problem with long-range correlations in the site or bond occupations. An extension of the Harris criterion for the relevance of the correlations is derived for the case that the correlations decay as x/sup -a/ for large distances x. For a d the correlations are relevant if dν-2<0. Applying this criterion to the behavior that results when the correlations are relevant, we argue that the new behavior will have ν/sub long/ = 2/a. It is shown that the correlated bond percolation problem is equivalent to a q-state Potts model with quenched disorder in the limit q→1. With the use of this result, a renormalization-group study of the problem is presented, expanding in epsilon = 6-d and in delta = 4-a. In addition to the normal percolation fixed point, we find a new long-range fixed point. The crossover to this new fixed point follows the extended Harris criterion, and the fixed point has exponents ν/sub long/ = 2/a (as predicted) and eta/sub long/ = (1/11)(delta-epsilon). Finally, several results on the percolation properties of the Ising model at its critical point are shown to be in agreement with the predictions of this paper
PERCOLATION TRANSITION AND TOPOLOGY
Directory of Open Access Journals (Sweden)
Patricia Jouannot-Chesney
2017-06-01
Full Text Available A number of bidimensional random structures with increasing densities are simulated to explore possible links between Euler-Poincaré characteristic (EPC, or connectivity, and percolation threshold. For each structure model, the percolation threshold is compared with a number of typical points (extrema, zero crossings... of the EPC curve. From these exercises, it can be concluded that the percolation threshold cannot be generally predicted using the evolution of the EPC.
Cluster Tails for Critical Power-Law Inhomogeneous Random Graphs
van der Hofstad, Remco; Kliem, Sandra; van Leeuwaarden, Johan S. H.
2018-04-01
Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299-2361, 2012). It was proved that when the degrees obey a power law with exponent τ \\in (3,4), the sequence of clusters ordered in decreasing size and multiplied through by n^{-(τ -2)/(τ -1)} converges as n→ ∞ to a sequence of decreasing non-degenerate random variables. Here, we study the tails of the limit of the rescaled largest cluster, i.e., the probability that the scaling limit of the largest cluster takes a large value u, as a function of u. This extends a related result of Pittel (J Combin Theory Ser B 82(2):237-269, 2001) for the Erdős-Rényi random graph to the setting of rank-1 inhomogeneous random graphs with infinite third moment degrees. We make use of delicate large deviations and weak convergence arguments.
Cluster monte carlo method for nuclear criticality safety calculation
International Nuclear Information System (INIS)
Pei Lucheng
1984-01-01
One of the most important applications of the Monte Carlo method is the calculation of the nuclear criticality safety. The fair source game problem was presented at almost the same time as the Monte Carlo method was applied to calculating the nuclear criticality safety. The source iteration cost may be reduced as much as possible or no need for any source iteration. This kind of problems all belongs to the fair source game prolems, among which, the optimal source game is without any source iteration. Although the single neutron Monte Carlo method solved the problem without the source iteration, there is still quite an apparent shortcoming in it, that is, it solves the problem without the source iteration only in the asymptotic sense. In this work, a new Monte Carlo method called the cluster Monte Carlo method is given to solve the problem further
Standard and inverse bond percolation of straight rigid rods on square lattices
Ramirez, L. S.; Centres, P. M.; Ramirez-Pastor, A. J.
2018-04-01
Numerical simulations and finite-size scaling analysis have been carried out to study standard and inverse bond percolation of straight rigid rods on square lattices. In the case of standard percolation, the lattice is initially empty. Then, linear bond k -mers (sets of k linear nearest-neighbor bonds) are randomly and sequentially deposited on the lattice. Jamming coverage pj ,k and percolation threshold pc ,k are determined for a wide range of k (1 ≤k ≤120 ). pj ,k and pc ,k exhibit a decreasing behavior with increasing k , pj ,k →∞=0.7476 (1 ) and pc ,k →∞=0.0033 (9 ) being the limit values for large k -mer sizes. pj ,k is always greater than pc ,k, and consequently, the percolation phase transition occurs for all values of k . In the case of inverse percolation, the process starts with an initial configuration where all lattice bonds are occupied and, given that periodic boundary conditions are used, the opposite sides of the lattice are connected by nearest-neighbor occupied bonds. Then, the system is diluted by randomly removing linear bond k -mers from the lattice. The central idea here is based on finding the maximum concentration of occupied bonds (minimum concentration of empty bonds) for which connectivity disappears. This particular value of concentration is called the inverse percolation threshold pc,k i, and determines a geometrical phase transition in the system. On the other hand, the inverse jamming coverage pj,k i is the coverage of the limit state, in which no more objects can be removed from the lattice due to the absence of linear clusters of nearest-neighbor bonds of appropriate size. It is easy to understand that pj,k i=1 -pj ,k . The obtained results for pc,k i show that the inverse percolation threshold is a decreasing function of k in the range 1 ≤k ≤18 . For k >18 , all jammed configurations are percolating states, and consequently, there is no nonpercolating phase. In other words, the lattice remains connected even when
Quantum mechanical cluster calculations of critical scintillation processes
International Nuclear Information System (INIS)
Derenzo, Stephen E.; Klintenberg, Mattias K.; Weber, Marvin J.
2000-01-01
This paper describes the use of commercial quantum chemistry codes to simulate several critical scintillation processes. The crystal is modeled as a cluster of typically 50 atoms embedded in an array of typically 5,000 point charges designed to reproduce the electrostatic field of the infinite crystal. The Schrodinger equation is solved for the ground, ionized, and excited states of the system to determine the energy and electron wave function. Computational methods for the following critical processes are described: (1) the formation and diffusion of relaxed holes, (2) the formation of excitons, (3) the trapping of electrons and holes by activator atoms, (4) the excitation of activator atoms, and (5) thermal quenching. Examples include hole diffusion in CsI, the exciton in CsI, the excited state of CsI:Tl, the energy barrier for the diffusion of relaxed holes in CaF2 and PbF2, and prompt hole trapping by activator atoms in CaF2:Eu and CdS:Te leading to an ultra-fast (<50ps) scintillation rise time.
Integral equation hierarchy for continuum percolation
International Nuclear Information System (INIS)
Given, J.A.
1988-01-01
In this thesis a projection operator technique is presented that yields hierarchies of integral equations satisfied exactly by the n-point connectedness functions in a continuum version of the site-bond percolation problem. The n-point connectedness functions carry the same structural information for a percolation problem as then-point correlation functions do for a thermal problem. This method extends the Potts model mapping of Fortuin and Kastelyn to the continuum by exploiting an s-state generalization of the Widom-Rowlinson model, a continuum model for phase separation. The projection operator technique is used to produce an integral equation hierarchy for percolation similar to the Born-Green heirarchy. The Kirkwood superposition approximation (SA) is extended to percolation in order to close this hierarchy and yield a nonlinear integral equation for the two-point connectedness function. The fact that this function, in the SA, is the analytic continuation to negative density of the two-point correlation function in a corresponding thermal problem is discussed. The BGY equation for percolation is solved numerically, both by an expansion in powers of the density, and by an iterative technique due to Kirkwood. It is argued both analytically and numerically, that the BYG equation for percolation, unlike its thermal counterpart, shows non-classical critical behavior, with η = 1 and γ = 0.05 ± .1. Finally a sequence of refinements to the superposition approximations based in the theory of fluids by Rice and Lekner is discussed
Seyrich, Maximilian; Sornette, Didier
2016-04-01
We present a plausible micro-founded model for the previously postulated power law finite time singular form of the crash hazard rate in the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles. The model is based on a percolation picture of the network of traders and the concept that clusters of connected traders share the same opinion. The key ingredient is the notion that a shift of position from buyer to seller of a sufficiently large group of traders can trigger a crash. This provides a formula to estimate the crash hazard rate by summation over percolation clusters above a minimum size of a power sa (with a>1) of the cluster sizes s, similarly to a generalized percolation susceptibility. The power sa of cluster sizes emerges from the super-linear dependence of group activity as a function of group size, previously documented in the literature. The crash hazard rate exhibits explosive finite time singular behaviors when the control parameter (fraction of occupied sites, or density of traders in the network) approaches the percolation threshold pc. Realistic dynamics are generated by modeling the density of traders on the percolation network by an Ornstein-Uhlenbeck process, whose memory controls the spontaneous excursion of the control parameter close to the critical region of bubble formation. Our numerical simulations recover the main stylized properties of the JLS model with intermittent explosive super-exponential bubbles interrupted by crashes.
Quasiuniversal Connectedness Percolation of Polydisperse Rod Systems
Nigro, B.; Grimaldi, C.; Chatterjee, A.P.; van der Schoot, P. P. A. M.
2013-01-01
The connectedness percolation threshold (ηc) and critical coordination number (Zc) of systems of penetrable spherocylinders characterized by a length polydispersity are studied by way of Monte Carlo simulations for several aspect ratio distributions. We find that (i) ηc is a nearly universal
Conformal Field Theory of Percolation (1)
CERN. Geneva
2015-01-01
This series of 5 lectures will describe what is known about the Logarithmic CFT describing the critical point of percolation. The subsequent lectures will take place in TH Conference room on: (2) Wednesday Sep 16 at 10am (3) Thursday Sep 17 at 10am (4) Thursday Sep 17 at 2pm (5) Friday Sep 18 at 10am
Fluid leakage near the percolation threshold
Dapp, Wolf B.; Müser, Martin H.
2016-02-01
Percolation is a concept widely used in many fields of research and refers to the propagation of substances through porous media (e.g., coffee filtering), or the behaviour of complex networks (e.g., spreading of diseases). Percolation theory asserts that most percolative processes are universal, that is, the emergent powerlaws only depend on the general, statistical features of the macroscopic system, but not on specific details of the random realisation. In contrast, our computer simulations of the leakage through a seal—applying common assumptions of elasticity, contact mechanics, and fluid dynamics—show that the critical behaviour (how the flow ceases near the sealing point) solely depends on the microscopic details of the last constriction. It appears fundamentally impossible to accurately predict from statistical properties of the surfaces alone how strongly we have to tighten a water tap to make it stop dripping and also how it starts dripping once we loosen it again.
Using a dynamic point-source percolation model to simulate bubble growth
International Nuclear Information System (INIS)
Zimmerman, Jonathan A.; Zeigler, David A.; Cowgill, Donald F.
2004-01-01
Accurate modeling of nucleation, growth and clustering of helium bubbles within metal tritide alloys is of high scientific and technological importance. Of interest is the ability to predict both the distribution of these bubbles and the manner in which these bubbles interact at a critical concentration of helium-to-metal atoms to produce an accelerated release of helium gas. One technique that has been used in the past to model these materials, and again revisited in this research, is percolation theory. Previous efforts have used classical percolation theory to qualitatively and quantitatively model the behavior of interstitial helium atoms in a metal tritide lattice; however, higher fidelity models are needed to predict the distribution of helium bubbles and include features that capture the underlying physical mechanisms present in these materials. In this work, we enhance classical percolation theory by developing the dynamic point-source percolation model. This model alters the traditionally binary character of site occupation probabilities by enabling them to vary depending on proximity to existing occupied sites, i.e. nucleated bubbles. This revised model produces characteristics for one and two dimensional systems that are extremely comparable with measurements from three dimensional physical samples. Future directions for continued development of the dynamic model are also outlined
Dynamics of bootstrap percolation
Indian Academy of Sciences (India)
precise criterion for the occurrence of a mixed transition is not very clear, and has been the subject ... ology, electronic communication, and social networks. It has also acquired a ... percolation theory is to start with a lattice with a fraction p of its sites occupied randomly, and ..... samples of a 104-node network. Probability is ...
Phase transition approach to bursting in neuronal cultures: quorum percolation models
Monceau, P.; Renault, R.; Métens, S.; Bottani, S.; Fardet, T.
2017-10-01
The Quorum Percolation model has been designed in the context of neurobiology to describe bursts of activity occurring in neuronal cultures from the point of view of statistical physics rather than from a dynamical synchronization approach. It is based upon information propagation on a directed graph with a threshold activation rule; this leads to a phase diagram which exhibits a giant percolation cluster below some critical value mC of the excitability. We describe the main characteristics of the original model and derive extensions according to additional relevant biological features. Firstly, we investigate the effects of an excitability variability on the phase diagram and show that the percolation transition can be destroyed by a sufficient amount of such a disorder; we stress the weakly averaging character of the order parameter and show that connectivity and excitability can be seen as two overlapping aspects of the same reality. Secondly, we elaborate a discrete time stochastic model taking into account the decay originating from ionic leakage through the membrane of neurons and synaptic depression; we give evidence that the decay softens and shifts the transition, and conjecture than decay destroys the transition in the thermodynamical limit. We were able to develop mean-field theories associated with each of the two effects; we discuss the framework of their agreement with Monte Carlo simulations. It turns out that the the critical point mC from which information on the connectivity of the network can be inferred is affected by each of these additional effects. Lastly, we show how dynamical simulations of bursts with an adaptive exponential integrateand- fire model can be interpreted in terms of Quorum Percolation. Moreover, the usefulness of the percolation model including the set of sophistication we investigated can be extended to many scientific fields involving information propagation, such as the spread of rumors in sociology, ethology, ecology.
Scaling and percolation in the small-world network model
Energy Technology Data Exchange (ETDEWEB)
Newman, M. E. J. [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States); Watts, D. J. [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States)
1999-12-01
In this paper we study the small-world network model of Watts and Strogatz, which mimics some aspects of the structure of networks of social interactions. We argue that there is one nontrivial length-scale in the model, analogous to the correlation length in other systems, which is well-defined in the limit of infinite system size and which diverges continuously as the randomness in the network tends to zero, giving a normal critical point in this limit. This length-scale governs the crossover from large- to small-world behavior in the model, as well as the number of vertices in a neighborhood of given radius on the network. We derive the value of the single critical exponent controlling behavior in the critical region and the finite size scaling form for the average vertex-vertex distance on the network, and, using series expansion and Pade approximants, find an approximate analytic form for the scaling function. We calculate the effective dimension of small-world graphs and show that this dimension varies as a function of the length-scale on which it is measured, in a manner reminiscent of multifractals. We also study the problem of site percolation on small-world networks as a simple model of disease propagation, and derive an approximate expression for the percolation probability at which a giant component of connected vertices first forms (in epidemiological terms, the point at which an epidemic occurs). The typical cluster radius satisfies the expected finite size scaling form with a cluster size exponent close to that for a random graph. All our analytic results are confirmed by extensive numerical simulations of the model. (c) 1999 The American Physical Society.
Scaling and percolation in the small-world network model
International Nuclear Information System (INIS)
Newman, M. E. J.; Watts, D. J.
1999-01-01
In this paper we study the small-world network model of Watts and Strogatz, which mimics some aspects of the structure of networks of social interactions. We argue that there is one nontrivial length-scale in the model, analogous to the correlation length in other systems, which is well-defined in the limit of infinite system size and which diverges continuously as the randomness in the network tends to zero, giving a normal critical point in this limit. This length-scale governs the crossover from large- to small-world behavior in the model, as well as the number of vertices in a neighborhood of given radius on the network. We derive the value of the single critical exponent controlling behavior in the critical region and the finite size scaling form for the average vertex-vertex distance on the network, and, using series expansion and Pade approximants, find an approximate analytic form for the scaling function. We calculate the effective dimension of small-world graphs and show that this dimension varies as a function of the length-scale on which it is measured, in a manner reminiscent of multifractals. We also study the problem of site percolation on small-world networks as a simple model of disease propagation, and derive an approximate expression for the percolation probability at which a giant component of connected vertices first forms (in epidemiological terms, the point at which an epidemic occurs). The typical cluster radius satisfies the expected finite size scaling form with a cluster size exponent close to that for a random graph. All our analytic results are confirmed by extensive numerical simulations of the model. (c) 1999 The American Physical Society
Statistical mechanics of high-density bond percolation
Timonin, P. N.
2018-05-01
High-density (HD) percolation describes the percolation of specific κ -clusters, which are the compact sets of sites each connected to κ nearest filled sites at least. It takes place in the classical patterns of independently distributed sites or bonds in which the ordinary percolation transition also exists. Hence, the study of series of κ -type HD percolations amounts to the description of classical clusters' structure for which κ -clusters constitute κ -cores nested one into another. Such data are needed for description of a number of physical, biological, and information properties of complex systems on random lattices, graphs, and networks. They range from magnetic properties of semiconductor alloys to anomalies in supercooled water and clustering in biological and social networks. Here we present the statistical mechanics approach to study HD bond percolation on an arbitrary graph. It is shown that the generating function for κ -clusters' size distribution can be obtained from the partition function of the specific q -state Potts-Ising model in the q →1 limit. Using this approach we find exact κ -clusters' size distributions for the Bethe lattice and Erdos-Renyi graph. The application of the method to Euclidean lattices is also discussed.
Short-term memory and critical clusterization in brain neurons spike series
Bershadskii, A.; Dremencov, E.; Yadid, G.
2003-06-01
A new phenomenon: critical clusterization, is observed in the neuron firing of a genetically defined rat model of depression. The critical clusterization is studied using a multiscaling analysis of the data obtained from the neurons belonging to the Red Nucleus area of the depressive brains. It is suggested that this critical phenomenon can be partially responsible for the observed ill behavior of the depressive brains: loss of short-term motor memory and slow motor reaction.
Percolation Model for the Existence of a Mitochondrial Eve
Neves, A G M
2005-01-01
We look at the process of inheritance of mitochondrial DNA as a percolation model on trees equivalent to the Galton-Watson process. The model is exactly solvable for its percolation threshold $p_c$ and percolation probability critical exponent. In the approximation of small percolation probability, and assuming limited progeny number, we are also able to find the maximum and minimum percolation probabilities over all probability distributions for the progeny number constrained to a given $p_c$. As a consequence, we can relate existence of a mitochondrial Eve to quantitative knowledge about demographic evolution of early mankind. In particular, we show that a mitochondrial Eve may exist even in an exponentially growing population, provided that the average number of children per individual is constrained to a small range depending on the probability $p$ that a newborn child is a female.
DIRECTIONAL OPPORTUNISTIC MECHANISM IN CLUSTER MESSAGE CRITICALITY LEVEL BASED ZIGBEE ROUTING
B.Rajeshkanna *1, Dr.M.Anitha 2
2018-01-01
The cluster message criticality level based zigbee routing(CMCLZOR) has been proposed for routing the cluster messages in wireless smart energy home area networks. It employs zigbee opportunistic shortcut tree routing(ZOSTR) and AODV individually for routing normal messages and highly critical messages respectively. ZOSTR allows the receiving nodes to compete for forwarding a packet with the priority of left-over hops rather than stating single next hop node like unicast protocols. Since it h...
Dimensional crossover in directed percolation
International Nuclear Information System (INIS)
Chame, A.M.N.; Queiroz, S.L.A. de; Santos, Raimundo R. dos.
1984-04-01
We study the dimensional crossover in directed percolation in three dimensions. Bonds are allowed to have different concentrations along the three cartesian axes of the lattice. Through a Position Space Renormalization Group we obtain the phase-diagrama where non-percolating, 1-D, 2-D and 3-D percolating phases are present. We find that the isotropic fixed points are unstable with respect to anisotropy, thus driving the system into a different universality class. (author) [pt
Diao, K; Farmani, R; Fu, G; Astaraie-Imani, M; Ward, S; Butler, D
2014-01-01
Large water distribution systems (WDSs) are networks with both topological and behavioural complexity. Thereby, it is usually difficult to identify the key features of the properties of the system, and subsequently all the critical components within the system for a given purpose of design or control. One way is, however, to more explicitly visualize the network structure and interactions between components by dividing a WDS into a number of clusters (subsystems). Accordingly, this paper introduces a clustering strategy that decomposes WDSs into clusters with stronger internal connections than external connections. The detected cluster layout is very similar to the community structure of the served urban area. As WDSs may expand along with urban development in a community-by-community manner, the correspondingly formed distribution clusters may reveal some crucial configurations of WDSs. For verification, the method is applied to identify all the critical links during firefighting for the vulnerability analysis of a real-world WDS. Moreover, both the most critical pipes and clusters are addressed, given the consequences of pipe failure. Compared with the enumeration method, the method used in this study identifies the same group of the most critical components, and provides similar criticality prioritizations of them in a more computationally efficient time.
Percolation-enhanced nonlinear scattering from semicontinuous metal films
Breit, M.; von Plessen, G.; Feldmann, J.; Podolskiy, V. A.; Sarychev, A. K.; Shalaev, V. M.; Gresillon, S.; Rivoal, J. C.; Gadenne, P.
2001-03-01
Strongly enhanced second-harmonic generation (SHG), which is characterized by nearly isotropic distribution, is observed for gold-glass films near the percolation threshold. The diffuse-like SHG scattering, which can be thought of as nonlinear critical opalescence, is in sharp contrast with highly collimated linear reflection and transmission from these nanostructured semicontinuous metal films. Our observations, which can be explained by giant fluctuations of local nonlinear sources for SHG, verify recent predictions of percolation-enhanced nonlinear scattering.
Statistical mechanics of semi-supervised clustering in sparse graphs
International Nuclear Information System (INIS)
Ver Steeg, Greg; Galstyan, Aram; Allahverdyan, Armen E
2011-01-01
We theoretically study semi-supervised clustering in sparse graphs in the presence of pair-wise constraints on the cluster assignments of nodes. We focus on bi-cluster graphs and study the impact of semi-supervision for varying constraint density and overlap between the clusters. Recent results for unsupervised clustering in sparse graphs indicate that there is a critical ratio of within-cluster and between-cluster connectivities below which clusters cannot be recovered with better than random accuracy. The goal of this paper is to examine the impact of pair-wise constraints on the clustering accuracy. Our results suggest that the addition of constraints does not provide automatic improvement over the unsupervised case. When the density of the constraints is sufficiently small, their only impact is to shift the detection threshold while preserving the criticality. Conversely, if the density of (hard) constraints is above the percolation threshold, the criticality is suppressed and the detection threshold disappears
Group percolation in interdependent networks
Wang, Zexun; Zhou, Dong; Hu, Yanqing
2018-03-01
In many real network systems, nodes usually cooperate with each other and form groups to enhance their robustness to risks. This motivates us to study an alternative type of percolation, group percolation, in interdependent networks under attack. In this model, nodes belonging to the same group survive or fail together. We develop a theoretical framework for this group percolation and find that the formation of groups can improve the resilience of interdependent networks significantly. However, the percolation transition is always of first order, regardless of the distribution of group sizes. As an application, we map the interdependent networks with intersimilarity structures, which have attracted much attention recently, onto the group percolation and confirm the nonexistence of continuous phase transitions.
Scala, Antonio
2015-03-01
We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. Self-healing is a crucial in implementing the next generation of smart grids allowing to ensure a high quality of service to the users. We then map our self-healing procedure in a percolation problem and analyse the interplay between redundancies and topology in improving the resilience of networked infrastructures to multiple failures. We find exact results both for planar lattices and for random lattices, hinting the role of duality in the design of resilient networks. Finally, we introduce a cavity method approach to study the recovery of connectivity after damage in self-healing networks. CNR-PNR National Project ``Crisis-Lab,'' EU HOME/2013/CIPS/AG/4000005013 project CI2C and EU FET project MULTIPLEX nr.317532.
Percolation on the institute-enterprise R
Directory of Open Access Journals (Sweden)
Li Chenguang
2015-01-01
Full Text Available Realistic network-like systems are usually composed of multiple networks with interacting relations such as school-enterprise research and development (R&D collaboration networks. Here, we study the percolation properties of a special class of R&D collaboration network, namely institute-enterprise R&D collaboration networks (IERDCNs. We introduce two actual IERDCNs to show their structural properties, and we present a mathematical framework based on generating functions for analyzing an interacting network with any connection probability. Then,we illustrate the percolation threshold and structural parameter arithmetic in the sub-critical and supercritical regimes.We compare the predictions of our mathematical framework and arithmetic to data for two real R&D collaboration networks and a number of simulations. We find that our predictions are in remarkable agreement with the data. We show applications of the framework to electronics R&D collaboration networks
New scaling results in quantum percolation
International Nuclear Information System (INIS)
Srivastava, V.; Chaturvedi, M.
1983-06-01
Scaling arguments for distribution of cluster size and size of localized states have been developed to calculate average number of lattice sites falling under a localized wave function as a function of concentration for a model binary system with ''infinite disorder''. We find distinct features near classical and quantum percolation thresholds. Analytical results are compared with computer-experiment results and the predicted features are found to be confirmed. Possibility of appearance of extended states in two-dimensional binary systems even at infinite disorder is pointed out. (author)
Dielectric and diamagnetic susceptibilities near percolative superconductor-insulator transitions.
Loh, Yen Lee; Karki, Pragalv
2017-10-25
Coarse-grained superconductor-insulator composites exhibit a superconductor-insulator transition governed by classical percolation, which should be describable by networks of inductors and capacitors. We study several classes of random inductor-capacitor networks on square lattices. We present a unifying framework for defining electric and magnetic response functions, and we extend the Frank-Lobb bond-propagation algorithm to compute these quantities by network reduction. We confirm that the superfluid stiffness scales approximately as [Formula: see text] as the superconducting bond fraction p approaches the percolation threshold p c . We find that the diamagnetic susceptibility scales as [Formula: see text] below percolation, and as [Formula: see text] above percolation. For models lacking self-capacitances, the electric susceptibility scales as [Formula: see text]. Including a self-capacitance on each node changes the critical behavior to approximately [Formula: see text].
International Nuclear Information System (INIS)
Cloots, R.; Liege Univ.; Dang, A.; Vanderbemden, P.; Vanderschueren, A.; Vanderschueren, H.W.; Bougrine, H.; Liege Univ.; Rulmont, A.; Ausloos, M.
1996-01-01
We measured the AC susceptibility of magnetically textured (123) 80%/211(20%) DyBaCuO composite in a special set-up in order to enhance the intergrain contribution. The synthesis process led to very clean weak links at grain boundaries. At the percolation threshold bulk shielding paths were such that the intergrain critical current density J C was above 10 5 A/cm 2 . The field dependence of J C was understood through an analytical form indicating a distribution of currents similar to the law of clusters at fracture/percolation thresholds. (orig.)
International Nuclear Information System (INIS)
Jaqaman, H.R.; Birzeit Univ.; Papp, G.; Eoetvoes Lorand Tudomanyegyetem, Budapest; Gross, D.H.E.; Freie Univ. Berlin
1990-01-01
The distributions of fragments produced by microcanonical multifragmentation of hot nuclei are compared with the cluster distributions predicted by a bond percolation model on a finite lattice. The conditional moments of these distributions are used together with the correlations between the largest three fragments in each event. Whereas percolation and statistical nuclear fragmentation agree in many details as in the usual plots of the averaged moments of the fragment distributions which yield the critical exponents, they turn out to be essentially different when less averaged quantities or correlations are considered. The differences between the predictions of the two models are mainly due to the particularities of the nuclear problem, especially the effect of the long-range Coulomb force which favours the break-up of the highly excited nucleus into two large fragments (pseudo-fission) and, to a somewhat lesser extent, enhances the possibility for the cracking of the nucleus into more than two large fragments. The fission events are, however, clearly separated from a second branch of critical correlations which shows up clearly in both nuclear fragmentation and percolation. We think that this critical correlation branch is due to the liquid-gas phase transition in finite nuclei. (orig.)
Percolation in real multiplex networks
Bianconi, Ginestra; Radicchi, Filippo
2016-12-01
We present an exact mathematical framework able to describe site-percolation transitions in real multiplex networks. Specifically, we consider the average percolation diagram valid over an infinite number of random configurations where nodes are present in the system with given probability. The approach relies on the locally treelike ansatz, so that it is expected to accurately reproduce the true percolation diagram of sparse multiplex networks with negligible number of short loops. The performance of our theory is tested in social, biological, and transportation multiplex graphs. When compared against previously introduced methods, we observe improvements in the prediction of the percolation diagrams in all networks analyzed. Results from our method confirm previous claims about the robustness of real multiplex networks, in the sense that the average connectedness of the system does not exhibit any significant abrupt change as its individual components are randomly destroyed.
Nuclear fragmentation with secondary decay in the context of conventional percolation model
International Nuclear Information System (INIS)
Santiago, A.J.
1989-09-01
Mass and energy spectra arising from proton-nucleus collisions at energies between 80 and 350 GeV were studied, using the conventional percolation model coupled with secondary decay of the clusters. (L.C.J.A.)
Multifractal properties of resistor diode percolation.
Stenull, Olaf; Janssen, Hans-Karl
2002-03-01
Focusing on multifractal properties we investigate electric transport on random resistor diode networks at the phase transition between the nonpercolating and the directed percolating phase. Building on first principles such as symmetries and relevance we derive a field theoretic Hamiltonian. Based on this Hamiltonian we determine the multifractal moments of the current distribution that are governed by a family of critical exponents [psi(l)]. We calculate the family [psi(l)] to two-loop order in a diagrammatic perturbation calculation augmented by renormalization group methods.
The field theory approach to percolation processes
International Nuclear Information System (INIS)
Janssen, Hans-Karl; Taeuber, Uwe C.
2005-01-01
We review the field theory approach to percolation processes. Specifically, we focus on the so-called simple and general epidemic processes that display continuous non-equilibrium active to absorbing state phase transitions whose asymptotic features are governed, respectively, by the directed (DP) and dynamic isotropic percolation (dIP) universality classes. We discuss the construction of a field theory representation for these Markovian stochastic processes based on fundamental phenomenological considerations, as well as from a specific microscopic reaction-diffusion model realization. Subsequently we explain how dynamic renormalization group (RG) methods can be applied to obtain the universal properties near the critical point in an expansion about the upper critical dimensions d c = 4 (DP) and 6 (dIP). We provide a detailed overview of results for critical exponents, scaling functions, crossover phenomena, finite-size scaling, and also briefly comment on the influence of long-range spreading, the presence of a boundary, multispecies generalizations, coupling of the order parameter to other conserved modes, and quenched disorder
Percolation Magnetism in Ferroelectric Nanoparticles
Golovina, Iryna S.; Lemishko, Serhii V.; Morozovska, Anna N.
2017-06-01
Nanoparticles of potassium tantalate (KTaO3) and potassium niobate (KNbO3) were synthesized by oxidation of metallic tantalum in molten potassium nitrate with the addition of potassium hydroxide. Magnetization curves obtained on these ferroelectric nanoparticles exhibit a weak ferromagnetism, while these compounds are nonmagnetic in a bulk. The experimental data are used as a start point for theoretical calculations. We consider a microscopic mechanism that leads to the emerging of a ferromagnetic ordering in ferroelectric nanoparticles. Our approach is based on the percolation of magnetic polarons assuming the dominant role of the oxygen vacancies. It describes the formation of surface magnetic polarons, in which an exchange interaction between electrons trapped in oxygen vacancies is mediated by magnetic impurity Fe3+ ions. The dependences of percolation radius on concentration of the oxygen vacancies and magnetic defects are determined in the framework of percolation theory.
Percolation Magnetism in Ferroelectric Nanoparticles.
Golovina, Iryna S; Lemishko, Serhii V; Morozovska, Anna N
2017-12-01
Nanoparticles of potassium tantalate (KTaO 3 ) and potassium niobate (KNbO 3 ) were synthesized by oxidation of metallic tantalum in molten potassium nitrate with the addition of potassium hydroxide. Magnetization curves obtained on these ferroelectric nanoparticles exhibit a weak ferromagnetism, while these compounds are nonmagnetic in a bulk. The experimental data are used as a start point for theoretical calculations. We consider a microscopic mechanism that leads to the emerging of a ferromagnetic ordering in ferroelectric nanoparticles. Our approach is based on the percolation of magnetic polarons assuming the dominant role of the oxygen vacancies. It describes the formation of surface magnetic polarons, in which an exchange interaction between electrons trapped in oxygen vacancies is mediated by magnetic impurity Fe 3+ ions. The dependences of percolation radius on concentration of the oxygen vacancies and magnetic defects are determined in the framework of percolation theory.
Percolation effect in thick film superconductors
Energy Technology Data Exchange (ETDEWEB)
Sali, R.; Harsanyi, G. [Technical Univ. of Budapest (Hungary)
1994-12-31
A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to high T{sub c} and advantageous current density properties the base of the paste was chosen to be of Bi(Pb)SrCaCuO system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density at the boiling temperature of the liquid He- was between 200-300 A/cm{sup 2}. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency and the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.
Percolation effect in thick film superconductors
International Nuclear Information System (INIS)
Sali, R.; Harsanyi, G.
1994-01-01
A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to high T c and advantageous current density properties the base of the paste was chosen to be of Bi(Pb)SrCaCuO system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density at the boiling temperature of the liquid He- was between 200-300 A/cm 2 . The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency and the losses were determined. Finally, some fundamental advantages and problems of the process were discussed
Finite-Size Effects for Some Bootstrap Percolation Models
Enter, A.C.D. van; Adler, Joan; Duarte, J.A.M.S.
The consequences of Schonmann's new proof that the critical threshold is unity for certain bootstrap percolation models are explored. It is shown that this proof provides an upper bound for the finite-size scaling in these systems. Comparison with data for one case demonstrates that this scaling
Cooperation percolation in spatial prisoner's dilemma game
International Nuclear Information System (INIS)
Yang, Han-Xin; Rong, Zhihai; Wang, Wen-Xu
2014-01-01
The paradox of cooperation among selfish individuals still puzzles scientific communities. Although a large amount of evidence has demonstrated that the cooperator clusters in spatial games are effective in protecting the cooperators against the invasion of defectors, we continue to lack the condition for the formation of a giant cooperator cluster that ensures the prevalence of cooperation in a system. Here, we study the dynamical organization of the cooperator clusters in spatial prisoner's dilemma game to offer the condition for the dominance of cooperation, finding that a phase transition characterized by the emergence of a large spanning cooperator cluster occurs when the initial fraction of the cooperators exceeds a certain threshold. Interestingly, the phase transition belongs to different universality classes of percolation determined by the temptation to defect b. Specifically, on square lattices, 1 < b < 4/3 leads to a phase transition pertaining to the class of regular site percolation, whereas 3/2 < b < 2 gives rise to a phase transition subject to invasion percolation with trapping. Our findings offer a deeper understanding of cooperative behavior in nature and society. (paper)
Percolation transitions in two dimensions
Feng, X.; Deng, Y.; Blöte, H.W.J.
2008-01-01
We investigate bond- and site-percolation models on several two-dimensional lattices numerically, by means of transfer-matrix calculations and Monte Carlo simulations. The lattices include the square, triangular, honeycomb kagome, and diced lattices with nearest-neighbor bonds, and the square
DISCOVERY OF THE LARGEST KNOWN LENSED IMAGES FORMED BY A CRITICALLY CONVERGENT LENSING CLUSTER
International Nuclear Information System (INIS)
Zitrin, Adi; Broadhurst, Tom
2009-01-01
We identify the largest known lensed images of a single spiral galaxy, lying close to the center of the distant cluster MACS J1149.5+2223 (z = 0.544). These images cover a total area of ≅150 mbox '' and are magnified ≅200 times. Unusually, there is very little image distortion, implying that the central mass distribution is almost uniform over a wide area (r ≅ 200 kpc) with a surface density equal to the critical density for lensing, corresponding to maximal lens magnification. Many fainter multiply lensed galaxies are also uncovered by our model, outlining a very large tangential critical curve, of radius r ≅ 170 kpc, posing a potential challenge for the standard LCDM cosmology. Because of the uniform central mass distribution, a particularly clean measurement of the mass of the brightest cluster galaxy is possible here, for which we infer stars contribute most of the mass within a limiting radius of ≅30 kpc, with a mass-to-light ratio of M/L B ≅ 4.5(M/L) sun . This cluster with its uniform and central mass distribution acts analogously to a regular magnifying glass, converging light without distorting the images, resulting in the most powerful lens yet discovered for accessing the faint high-z universe.
One-dimensional long-range percolation: A numerical study
Gori, G.; Michelangeli, M.; Defenu, N.; Trombettoni, A.
2017-07-01
In this paper we study bond percolation on a one-dimensional chain with power-law bond probability C /rd +σ , where r is the distance length between distinct sites and d =1 . We introduce and test an order-N Monte Carlo algorithm and we determine as a function of σ the critical value Cc at which percolation occurs. The critical exponents in the range 0 values for Cc are compared with a known exact bound, while the critical exponent ν is compared with results from mean-field theory, from an expansion around the point σ =1 and from the ɛ -expansion used with the introduction of a suitably defined effective dimension deff relating the long-range model with a short-range one in dimension deff. We finally present a formulation of our algorithm for bond percolation on general graphs, with order N efficiency on a large class of graphs including short-range percolation and translationally invariant long-range models in any spatial dimension d with σ >0 .
Formation of clusters composed of C60 molecules via self-assembly in critical fluids
International Nuclear Information System (INIS)
Fukuda, Takahiro; Ishii, Koji; Kurosu, Shunji; Whitby, Raymond; Maekawa, Toru
2007-01-01
Fullerenes are promising candidates for intelligent, functional nanomaterials because of their unique mechanical, electronic and chemical properties. However, it is necessary to invent some efficient but relatively simple methods of producing structures composed of fullerenes for the development of nanomechatronic, nanoelectronic and biochemical devices and sensors. In this paper, we show that various structures such as straight fibres, networks formed by fibres, wide sheets and helical structures, which are composed of C 60 molecules, are created by placing C 60 -crystals in critical ethane, carbon dioxide and xenon even though C 60 molecules do not dissolve or disperse in the above fluids. It is supposed, judging by the intermolecular potentials between C 60 and C 60 , between C 60 and ethane, and between ethane and ethane, that C 60 -clusters grow with the assistance of solvent molecules, which are trapped between C 60 molecules under critical conditions. This room-temperature self-assembly cluster growth process in critical fluids may open up a new methodology of forming structures built up with fullerenes without the need for any ultra-fine processing technologies
Veerman, C.; Ruis, H.G.M.; Sagis, L.M.C.; Linden, van der E.
2002-01-01
The effect of electrostatic interactions on the critical percolation concentration (cp) of fibrillar -lactoglobulin gels at pH 2 was investigated using rheological measurements, transmission electron microscopy (TEM), and performing conversion experiments. A decreasing cp with increasing ionic
Influence of the growth process on some laws deduced from percolation theory
International Nuclear Information System (INIS)
Hachi, M.; Olivier, G.
1985-09-01
A brutal application of the percolation theory to some physical problems can lead to erroneous interpretation of the experimental results. Among these problems, the influence of the growth process on the percolation laws is studied. The behaviour of nsub(s)(t), the number of clusters of size s, at time t, is analyzed and linked to a macroscopic property of the system for a comparison to experimental laws. (author)
Cities and regions in Britain through hierarchical percolation
Arcaute, Elsa; Molinero, Carlos; Hatna, Erez; Murcio, Roberto; Vargas-Ruiz, Camilo; Masucci, A. Paolo; Batty, Michael
2016-04-01
Urban systems present hierarchical structures at many different scales. These are observed as administrative regional delimitations which are the outcome of complex geographical, political and historical processes which leave almost indelible footprints on infrastructure such as the street network. In this work, we uncover a set of hierarchies in Britain at different scales using percolation theory on the street network and on its intersections which are the primary points of interaction and urban agglomeration. At the larger scales, the observed hierarchical structures can be interpreted as regional fractures of Britain, observed in various forms, from natural boundaries, such as National Parks, to regional divisions based on social class and wealth such as the well-known North-South divide. At smaller scales, cities are generated through recursive percolations on each of the emerging regional clusters. We examine the evolution of the morphology of the system as a whole, by measuring the fractal dimension of the clusters at each distance threshold in the percolation. We observe that this reaches a maximum plateau at a specific distance. The clusters defined at this distance threshold are in excellent correspondence with the boundaries of cities recovered from satellite images, and from previous methods using population density.
Influence of polyethylene glycol on percolation dynamics of reverse microemulsions
Geethu, P. M.; Yadav, Indresh; Aswal, V. K.; Satapathy, D. K.
2018-04-01
We explore the influence of a hydrophilic polymer, polyethylene glycol (PEG), on the structure and the percolation dynamics of reverse microemulsions (ME) stabilized by an anionic surfactant AOT (sodium bis(2-ethylhexyl) sulfosuccinate). The percolation transition of MEs is probed using dielectric relaxation spectroscopy (DRS). Notably, an increase in percolation temperature is observed by the incorporation of PEG-polymer into larger ME droplets which is explained by considering the model of polymer adsorption at surfactant-water interface. The stability of the droplet phase of microemulsion after the incorporation of PEG is confirmed by small-angle neutron scattering (SANS) experiment. Further, a net decrease in percolation transition temperature is observed with the addition of PEG polymer for smaller ME droplets and is discussed in relation with the destabilization of droplets owing to the polymer induced bridging and the associated clustering of droplets. We conjecture that the adsorption of PEG polymer chains at the surfactant-water interface as well as the PEG-induced bridging of droplets are due to the strong ion-dipole interaction between anionic head group of AOT surfactant and dipoles present in PEG polymer chains.
Ising percolation in a three-state majority vote model
Energy Technology Data Exchange (ETDEWEB)
Balankin, Alexander S., E-mail: abalankin@ipn.mx [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico); Martínez-Cruz, M.A.; Gayosso Martínez, Felipe [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico); Mena, Baltasar [Laboratorio de Ingeniería y Procesos Costeros, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Sisal, Yucatán, 97355 (Mexico); Tobon, Atalo; Patiño-Ortiz, Julián; Patiño-Ortiz, Miguel; Samayoa, Didier [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico)
2017-02-05
Highlights: • Three-state non-consensus majority voter model is introduced. • Phase transition in the absorbing state non-consensus is revealed. • The percolation transition belongs to the universality class of Ising percolation. • The effect of an updating rule for a tie between voter neighbors is highlighted. - Abstract: In this Letter, we introduce a three-state majority vote model in which each voter adopts a state of a majority of its active neighbors, if exist, but the voter becomes uncommitted if its active neighbors are in a tie, or all neighbors are the uncommitted. Numerical simulations were performed on square lattices of different linear size with periodic boundary conditions. Starting from a random distribution of active voters, the model leads to a stable non-consensus state in which three opinions coexist. We found that the “magnetization” of the non-consensus state and the concentration of uncommitted voters in it are governed by an initial composition of system and are independent of the lattice size. Furthermore, we found that a configuration of the stable non-consensus state undergoes a second order percolation transition at a critical concentration of voters holding the same opinion. Numerical simulations suggest that this transition belongs to the same universality class as the Ising percolation. These findings highlight the effect of an updating rule for a tie between voter neighbors on the critical behavior of models obeying the majority vote rule whenever a strict majority exists.
Ising percolation in a three-state majority vote model
International Nuclear Information System (INIS)
Balankin, Alexander S.; Martínez-Cruz, M.A.; Gayosso Martínez, Felipe; Mena, Baltasar; Tobon, Atalo; Patiño-Ortiz, Julián; Patiño-Ortiz, Miguel; Samayoa, Didier
2017-01-01
Highlights: • Three-state non-consensus majority voter model is introduced. • Phase transition in the absorbing state non-consensus is revealed. • The percolation transition belongs to the universality class of Ising percolation. • The effect of an updating rule for a tie between voter neighbors is highlighted. - Abstract: In this Letter, we introduce a three-state majority vote model in which each voter adopts a state of a majority of its active neighbors, if exist, but the voter becomes uncommitted if its active neighbors are in a tie, or all neighbors are the uncommitted. Numerical simulations were performed on square lattices of different linear size with periodic boundary conditions. Starting from a random distribution of active voters, the model leads to a stable non-consensus state in which three opinions coexist. We found that the “magnetization” of the non-consensus state and the concentration of uncommitted voters in it are governed by an initial composition of system and are independent of the lattice size. Furthermore, we found that a configuration of the stable non-consensus state undergoes a second order percolation transition at a critical concentration of voters holding the same opinion. Numerical simulations suggest that this transition belongs to the same universality class as the Ising percolation. These findings highlight the effect of an updating rule for a tie between voter neighbors on the critical behavior of models obeying the majority vote rule whenever a strict majority exists.
Hattori, Y.; Ushiki, H.; Engl, W.; Courbin, L.; Panizza, P.
2005-08-01
Within the framework of an effective medium approach and a mean-field approximation, we present a simple lattice model to treat electrical percolation in the presence of attractive interactions. We show that the percolation line depends on the magnitude of interactions. In 2 dimensions, the percolation line meets the binodal line at the critical point. A good qualitative agreement is observed with experimental results on a ternary AOT-based water-in-oil microemulsion system.
Controlling percolation with limited resources
Schröder, Malte; Araújo, Nuno A. M.; Sornette, Didier; Nagler, Jan
2017-12-01
Connectivity, or the lack thereof, is crucial for the function of many man-made systems, from financial and economic networks over epidemic spreading in social networks to technical infrastructure. Often, connections are deliberately established or removed to induce, maintain, or destroy global connectivity. Thus, there has been a great interest in understanding how to control percolation, the transition to large-scale connectivity. Previous work, however, studied control strategies assuming unlimited resources. Here, we depart from this unrealistic assumption and consider the effect of limited resources on the effectiveness of control. We show that, even for scarce resources, percolation can be controlled with an efficient intervention strategy. We derive such an efficient strategy and study its implications, revealing a discontinuous transition as an unintended side effect of optimal control.
Regularity of the Speed of Biased Random Walk in a One-Dimensional Percolation Model
Gantert, Nina; Meiners, Matthias; Müller, Sebastian
2018-03-01
We consider biased random walks on the infinite cluster of a conditional bond percolation model on the infinite ladder graph. Axelson-Fisk and Häggström established for this model a phase transition for the asymptotic linear speed \\overline{v} of the walk. Namely, there exists some critical value λ c>0 such that \\overline{v}>0 if λ \\in (0,λ c) and \\overline{v}=0 if λ ≥ λ c. We show that the speed \\overline{v} is continuous in λ on (0,∞) and differentiable on (0,λ c/2). Moreover, we characterize the derivative as a covariance. For the proof of the differentiability of \\overline{v} on (0,λ c/2), we require and prove a central limit theorem for the biased random walk. Additionally, we prove that the central limit theorem fails to hold for λ ≥ λ c/2.
Liao, Hung-Chang; Wang, Ya-Huei
2016-04-01
This study examined whether students studying literature in complementary learning clusters would show more improvement in medical humanities literacy, critical thinking skills, and English proficiency compared to those in conventional learning clusters. Ninety-three students participated in the study (M age = 18.2 years, SD = 0.4; 36 men, 57 women). A quasi-experimental design was used over 16 weeks, with the control group (n = 47) working in conventional learning clusters and the experimental group (n = 46) working in complementary learning clusters. Complementary learning clusters were those in which individuals had complementary strengths enabling them to learn from and offer assistance to other cluster members, hypothetically facilitating the learning process. Measures included the Medical Humanities Literacy Scale, Critical Thinking Disposition Assessment, English proficiency tests, and Analytic Critical Thinking Scoring Rubric. The results showed that complementary learning clusters have the potential to improve students' medical humanities literacy, critical thinking skills, and English proficiency. © The Author(s) 2016.
Percolation theory for flow in porous media
Hunt, Allen; Ghanbarian, Behzad
2014-01-01
This monograph presents, for the first time, a unified and comprehensive introduction to some of the basic transport properties of porous media, such as electrical and hydraulic conductivity, air permeability and diffusion. The approach is based on critical path analysis and the scaling of transport properties, which are individually described as functions of saturation. At the same time, the book supplies a tutorial on percolation theory for hydrologists, providing them with the tools for solving actual problems. In turn, a separate chapter serves to introduce physicists to some of the language and complications of groundwater hydrology necessary for successful modeling. The end-of-chapter problems often indicate open questions, which young researchers entering the field can readily start working on. This significantly revised and expanded third edition includes in particular two new chapters: one on advanced fractal-based models, and one devoted to the discussion of various open issues such as the role of d...
Physical-depth architectural requirements for generating universal photonic cluster states
Morley-Short, Sam; Bartolucci, Sara; Gimeno-Segovia, Mercedes; Shadbolt, Pete; Cable, Hugo; Rudolph, Terry
2018-01-01
Most leading proposals for linear-optical quantum computing (LOQC) use cluster states, which act as a universal resource for measurement-based (one-way) quantum computation. In ballistic approaches to LOQC, cluster states are generated passively from small entangled resource states using so-called fusion operations. Results from percolation theory have previously been used to argue that universal cluster states can be generated in the ballistic approach using schemes which exceed the critical threshold for percolation, but these results consider cluster states with unbounded size. Here we consider how successful percolation can be maintained using a physical architecture with fixed physical depth, assuming that the cluster state is continuously generated and measured, and therefore that only a finite portion of it is visible at any one point in time. We show that universal LOQC can be implemented using a constant-size device with modest physical depth, and that percolation can be exploited using simple pathfinding strategies without the need for high-complexity algorithms.
Percolation for a model of statistically inhomogeneous random media
International Nuclear Information System (INIS)
Quintanilla, J.; Torquato, S.
1999-01-01
We study clustering and percolation phenomena for a model of statistically inhomogeneous two-phase random media, including functionally graded materials. This model consists of inhomogeneous fully penetrable (Poisson distributed) disks and can be constructed for any specified variation of volume fraction. We quantify the transition zone in the model, defined by the frontier of the cluster of disks which are connected to the disk-covered portion of the model, by defining the coastline function and correlation functions for the coastline. We find that the behavior of these functions becomes largely independent of the specific choice of grade in volume fraction as the separation of length scales becomes large. We also show that the correlation function behaves in a manner similar to that of fractal Brownian motion. Finally, we study fractal characteristics of the frontier itself and compare to similar properties for two-dimensional percolation on a lattice. In particular, we show that the average location of the frontier appears to be related to the percolation threshold for homogeneous fully penetrable disks. copyright 1999 American Institute of Physics
Progress in high-dimensional percolation and random graphs
Heydenreich, Markus
2017-01-01
This text presents an engaging exposition of the active field of high-dimensional percolation that will likely provide an impetus for future work. With over 90 exercises designed to enhance the reader’s understanding of the material, as well as many open problems, the book is aimed at graduate students and researchers who wish to enter the world of this rich topic. The text may also be useful in advanced courses and seminars, as well as for reference and individual study. Part I, consisting of 3 chapters, presents a general introduction to percolation, stating the main results, defining the central objects, and proving its main properties. No prior knowledge of percolation is assumed. Part II, consisting of Chapters 4–9, discusses mean-field critical behavior by describing the two main techniques used, namely, differential inequalities and the lace expansion. In Parts I and II, all results are proved, making this the first self-contained text discussing high-dimensiona l percolation. Part III, consist...
Percolation bounds for decoding thresholds with correlated erasures in quantum LDPC codes
Hamilton, Kathleen; Pryadko, Leonid
Correlations between errors can dramatically affect decoding thresholds, in some cases eliminating the threshold altogether. We analyze the existence of a threshold for quantum low-density parity-check (LDPC) codes in the case of correlated erasures. When erasures are positively correlated, the corresponding multi-variate Bernoulli distribution can be modeled in terms of cluster errors, where qubits in clusters of various size can be marked all at once. In a code family with distance scaling as a power law of the code length, erasures can be always corrected below percolation on a qubit adjacency graph associated with the code. We bound this correlated percolation transition by weighted (uncorrelated) percolation on a specially constructed cluster connectivity graph, and apply our recent results to construct several bounds for the latter. This research was supported in part by the NSF Grant PHY-1416578 and by the ARO Grant W911NF-14-1-0272.
A special percolation problem in ceramic composites
International Nuclear Information System (INIS)
Ang Chen; Xi Dai; Yu Zhi; Yahua Bao
1993-11-01
The interface effect is taken into consideration, and a special percolation model is proposed for a two-phases metal/ceramic composite in the present paper. The computer simulation shows that the percolation threshold of this interface-controlled percolation behaviour is 4.5% in the three dimensional f.c.c. lattices, which is in good agreement with the experimental data. (author). 9 refs, 3 figs
Directed polymers versus directed percolation
Halpin-Healy, Timothy
1998-10-01
Universality plays a central role within the rubric of modern statistical mechanics, wherein an insightful continuum formulation rises above irrelevant microscopic details, capturing essential scaling behaviors. Nevertheless, occasions do arise where the lattice or another discrete aspect can constitute a formidable legacy. Directed polymers in random media, along with its close sibling, directed percolation, provide an intriguing case in point. Indeed, the deep blood relation between these two models may have sabotaged past efforts to fully characterize the Kardar-Parisi-Zhang universality class, to which the directed polymer belongs.
Spin dynamics on percolating networks
International Nuclear Information System (INIS)
Aeppli, G.; Guggenheim, H.; Uemura, Y.J.
1985-01-01
We have used inelastic neutron scattering to measure the order parameter relaxation rate GAMMA in the dilute, two-dimensional Ising antiferromagnet Rb 2 CoMg/sub 1-c/F 4 with c very close to the magnetic percolation threshold. Where kappa is the inverse magnetic correlation length, GAMMA approx. kappa/sup z/ with z = 2.4/sub -0.1//sup +0.2/. Our results are discussed in terms of current ideas about spin relaxation on fractals. 13 refs., 1 fig
Temporal percolation of the susceptible network in an epidemic spreading.
Valdez, Lucas Daniel; Macri, Pablo Alejandro; Braunstein, Lidia Adriana
2012-01-01
In this work, we study the evolution of the susceptible individuals during the spread of an epidemic modeled by the susceptible-infected-recovered (SIR) process spreading on the top of complex networks. Using an edge-based compartmental approach and percolation tools, we find that a time-dependent quantity ΦS(t), namely, the probability that a given neighbor of a node is susceptible at time t, is the control parameter of a node void percolation process involving those nodes on the network not-reached by the disease. We show that there exists a critical time t(c) above which the giant susceptible component is destroyed. As a consequence, in order to preserve a macroscopic connected fraction of the network composed by healthy individuals which guarantee its functionality, any mitigation strategy should be implemented before this critical time t(c). Our theoretical results are confirmed by extensive simulations of the SIR process.
Directory of Open Access Journals (Sweden)
Eric Dumonteil
2017-09-01
Full Text Available The Monte Carlo criticality simulation of decoupled systems, as for instance in large reactor cores, has been a challenging issue for a long time. In particular, due to limited computer time resources, the number of neutrons simulated per generation is still many order of magnitudes below realistic statistics, even during the start-up phases of reactors. This limited number of neutrons triggers a strong clustering effect of the neutron population that affects Monte Carlo tallies. Below a certain threshold, not only is the variance affected but also the estimation of the eigenvectors. In this paper we will build a time-dependent diffusion equation that takes into account both spatial correlations and population control (fixed number of neutrons along generations. We will show that its solution obeys a traveling wave dynamic, and we will discuss the mechanism that explains this biasing of local tallies whenever leakage boundary conditions are applied to the system.
Inward Cationic Diffusion and Percolation Transition in Glass-Ceramics
DEFF Research Database (Denmark)
Smedsklaer, Morten Mattrup; Yue, Yuanzheng; Mørup, Steen
2010-01-01
We show the quantitative correlation between the degree of crystallization and the cationic diffusion extent in iron-containing diopside glass–ceramics at the glass transition temperature. We find a critical degree of crystallization, above which the diffusion extent sharply drops with the degree...... of crystallization. Below the critical value, the diffusion extent decreases only slightly with the degree of crystallization. No cationic diffusion is observed in the fully crystalline materials. The critical value might be associated with a percolation transition from an interconnected to a disconnected glass...
Emergent Percolation Length and Localization in Random Elastic Networks
Directory of Open Access Journals (Sweden)
Ariel Amir
2013-06-01
Full Text Available We study, theoretically and numerically, a minimal model for phonons in a disordered system. For sufficient disorder, the vibrational modes of this classical system can become Anderson localized, yet this problem has received significantly less attention than its electronic counterpart. We find rich behavior in the localization properties of the phonons as a function of the density, frequency, and spatial dimension. We use a percolation analysis to argue for a Debye spectrum at low frequencies for dimensions higher than one, and for a localization-delocalization transition (at a critical frequency above two dimensions. We show that in contrast to the behavior in electronic systems, the transition exists for arbitrarily large disorder, albeit with an exponentially small critical frequency. The structure of the modes reflects a divergent percolation length that arises from the disorder in the springs without being explicitly present in the definition of our model. Within the percolation approach, we calculate the speed of sound of the delocalized modes (phonons, which we corroborate with numerics. We find the critical frequency of the localization transition at a given density and find good agreement of these predictions with numerical results using a recursive Green-function method that was adapted for this problem. The connection of our results to recent experiments on amorphous solids is discussed.
Critical and Exponential Experiments on 19-Rod Clusters (R3 Fuel) in Heavy Water
Energy Technology Data Exchange (ETDEWEB)
Persson, R; Wikdahl, C E; Zadworski, Z
1962-03-15
Buckling measurements on clusters of 19 UO{sub 2} rods in heavy water have been performed in an exponential assembly and by means of substitution measurements in a critical facility. The material buckling was determined as a function of lattice pitch (range of V{sub mod} /V{sub fuel}: 7-22), internal spacing, void, and temperature (20 < T < 90 deg C). The change of diffusion coefficients (about 6-8 per cent) caused by voids was studied with single test fuel assemblies. The progressive substitution measurements have been analysed by means of a modified one-group perturbation theory in combination with an unconventional cell definition. The buckling differences between test and reference lattices are of the order of -1.0 to -3.5/m{sup 2}, The results of the exponential and the critical experiments are compared with similar measurements on the same kind of fuel at the Savannah River Laboratory. This comparison shows that the results of the various experiments agree quite well, whereas theoretical predictions fail in the extreme ranges.
Electrical and percolative behavior of Sr2YSbO6-YBa2Cu3O7-δ composites
International Nuclear Information System (INIS)
Ortiz-Diaz, O.; Landinez Tellez, D.A.; Perez, F.; Tovar, H.; Roa-Rojas, J.
2007-01-01
We found that a mixture of materials Sr 2 YSbO 6 insulator with YBa 2 Cu 3 O 7-δ superconductor is a system where the particles of superconductor and insulator materials are found coexisting in a composite with two well-defined separate phases. Electrical transport properties and percolation behavior have been studied by electrical resistivity measurements at room temperature on several samples of composites with different vol.% of YBa 2 Cu 3 O 7-δ . Resistivity measurements agree with the equation which describes the conductivity in percolation theory. However, critical exponent t=6.65 is greater than universal value t∼2. Furthermore, there is a non-negligible conductivity below percolation threshold while it is expected to be zero in ideal percolative systems. Nevertheless, percolative behavior in this region was found and, critical exponent value s was determined to be s=0.75 in agreement with universal value
Percolation, statistical topography, and transport in random media
International Nuclear Information System (INIS)
Isichenko, M.B.
1992-01-01
A review of classical percolation theory is presented, with an emphasis on novel applications to statistical topography, turbulent diffusion, and heterogeneous media. Statistical topography involves the geometrical properties of the isosets (contour lines or surfaces) of a random potential ψ(x). For rapidly decaying correlations of ψ, the isopotentials fall into the same universality class as the perimeters of percolation clusters. The topography of long-range correlated potentials involves many length scales and is associated either with the correlated percolation problem or with Mandelbrot's fractional Brownian reliefs. In all cases, the concept of fractal dimension is particularly fruitful in characterizing the geometry of random fields. The physical applications of statistical topography include diffusion in random velocity fields, heat and particle transport in turbulent plasmas, quantum Hall effect, magnetoresistance in inhomogeneous conductors with the classical Hall effect, and many others where random isopotentials are relevant. A geometrical approach to studying transport in random media, which captures essential qualitative features of the described phenomena, is advocated
Loopless nontrapping invasion-percolation model for fracking.
Norris, J Quinn; Turcotte, Donald L; Rundle, John B
2014-02-01
Recent developments in hydraulic fracturing (fracking) have enabled the recovery of large quantities of natural gas and oil from old, low-permeability shales. These developments include a change from low-volume, high-viscosity fluid injection to high-volume, low-viscosity injection. The injected fluid introduces distributed damage that provides fracture permeability for the extraction of the gas and oil. In order to model this process, we utilize a loopless nontrapping invasion percolation previously introduced to model optimal polymers in a strongly disordered medium and for determining minimum energy spanning trees on a lattice. We performed numerical simulations on a two-dimensional square lattice and find significant differences from other percolation models. Additionally, we find that the growing fracture network satisfies both Horton-Strahler and Tokunaga network statistics. As with other invasion percolation models, our model displays burst dynamics, in which the cluster extends rapidly into a connected region. We introduce an alternative definition of bursts to be a consecutive series of opened bonds whose strengths are all below a specified value. Using this definition of bursts, we find good agreement with a power-law frequency-area distribution. These results are generally consistent with the observed distribution of microseismicity observed during a high-volume frack.
International Nuclear Information System (INIS)
Banerjee, Saikat; Furtado, Jonathan; Bagchi, Biman
2014-01-01
Water–tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with x TBA ≈ 0.03–0.07. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at x TBA ≈ 0.05. We note that “islands” of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak nonlinearity. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration, x TBA ≈ 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of largest water cluster. This second transition gives rise to another set of anomalies around. Both the percolation transitions can be regarded as manifestations of Janus effect at small molecular level
Mutoru, J W; Smith, W; O'Hern, C S; Firoozabadi, A
2013-01-14
Understanding the transport properties of molecular fluids in the critical region is important for a number of industrial and natural systems. In the literature, there are conflicting reports on the behavior of the self diffusion coefficient D(s) in the critical region of single-component molecular systems. For example, D(s) could decrease to zero, reach a maximum, or remain unchanged and finite at the critical point. Moreover, there is no molecular-scale understanding of the behavior of diffusion coefficients in molecular fluids in the critical regime. We perform extensive molecular dynamics simulations in the critical region of single-component fluids composed of medium-chain n-alkanes-n-pentane, n-decane, and n-dodecane-that interact via anisotropic united-atom potentials. For each system, we calculate D(s), and average molecular cluster sizes κ(cl) and numbers N(cl) at various cluster lifetimes τ, as a function of density ρ in the range 0.2ρ(c) ≤ ρ ≤ 2.0ρ(c) at the critical temperature T(c). We find that D(s) decreases with increasing ρ but remains finite at the critical point. Moreover, for any given τ critical point.
Percolator: Scalable Pattern Discovery in Dynamic Graphs
Energy Technology Data Exchange (ETDEWEB)
Choudhury, Sutanay; Purohit, Sumit; Lin, Peng; Wu, Yinghui; Holder, Lawrence B.; Agarwal, Khushbu
2018-02-06
We demonstrate Percolator, a distributed system for graph pattern discovery in dynamic graphs. In contrast to conventional mining systems, Percolator advocates efficient pattern mining schemes that (1) support pattern detection with keywords; (2) integrate incremental and parallel pattern mining; and (3) support analytical queries such as trend analysis. The core idea of Percolator is to dynamically decide and verify a small fraction of patterns and their in- stances that must be inspected in response to buffered updates in dynamic graphs, with a total mining cost independent of graph size. We demonstrate a) the feasibility of incremental pattern mining by walking through each component of Percolator, b) the efficiency and scalability of Percolator over the sheer size of real-world dynamic graphs, and c) how the user-friendly GUI of Percolator inter- acts with users to support keyword-based queries that detect, browse and inspect trending patterns. We also demonstrate two user cases of Percolator, in social media trend analysis and academic collaboration analysis, respectively.
Indian Academy of Sciences (India)
2017-09-27
Sep 27, 2017 ... Author for correspondence (zh4403701@126.com). MS received 15 ... lic clusters using density functional theory (DFT)-GGA of the DMOL3 package. ... In the process of geometric optimization, con- vergence thresholds ..... and Postgraduate Research & Practice Innovation Program of. Jiangsu Province ...
Indian Academy of Sciences (India)
environmental as well as technical problems during fuel gas utilization. ... adsorption on some alloys of Pd, namely PdAu, PdAg ... ried out on small neutral and charged Au24,26,27, Cu,28 ... study of Zanti et al.29 on Pdn (n = 1–9) clusters.
Generalized model for k -core percolation and interdependent networks
Panduranga, Nagendra K.; Gao, Jianxi; Yuan, Xin; Stanley, H. Eugene; Havlin, Shlomo
2017-09-01
Cascading failures in complex systems have been studied extensively using two different models: k -core percolation and interdependent networks. We combine the two models into a general model, solve it analytically, and validate our theoretical results through extensive simulations. We also study the complete phase diagram of the percolation transition as we tune the average local k -core threshold and the coupling between networks. We find that the phase diagram of the combined processes is very rich and includes novel features that do not appear in the models studying each of the processes separately. For example, the phase diagram consists of first- and second-order transition regions separated by two tricritical lines that merge and enclose a two-stage transition region. In the two-stage transition, the size of the giant component undergoes a first-order jump at a certain occupation probability followed by a continuous second-order transition at a lower occupation probability. Furthermore, at certain fixed interdependencies, the percolation transition changes from first-order → second-order → two-stage → first-order as the k -core threshold is increased. The analytic equations describing the phase boundaries of the two-stage transition region are set up, and the critical exponents for each type of transition are derived analytically.
Disorder-induced quantum bond percolation
International Nuclear Information System (INIS)
Nishino, Shinya; Katsuno, Shuji; Goda, Masaki
2009-01-01
We investigate the effects of off-diagonal disorder on localization properties in quantum bond percolation networks on cubic lattices, motivated by the finding that the off-diagonal disorder does not always enhance the quantum localization of wavefunctions. We numerically construct a diagram of the 'percolation threshold', distinguishing extended states from localized states as a function of two degrees of disorder, by using the level statistics and finite-size scaling. The percolation threshold increases in a characteristic way on increasing the disorder in the connected bonds, while it gradually decreases on increasing the disorder in the disconnected bonds. Furthermore, the exchange of connected and disconnected bonds induced by the disorder causes a dramatic change of the percolation threshold.
The Beasts' model of percolative transport
International Nuclear Information System (INIS)
Dubois, M.A.; Beaufume, P.; Fromont, B.
1991-12-01
A class of nonlinear dynamical systems is introduced: it is aimed to be a tool in order to study anomalous transport and percolation phenomena. We study a simple example of this system, and explore different regimes of transport exhibited
SmBa2NbO6 Nanopowders, an Effective Percolation Network Medium for YBCO Superconductors
Directory of Open Access Journals (Sweden)
S. Vidya
2013-01-01
Full Text Available The percolation behavior of superconductor-insulator composite, YBa2Cu3O7–δ, and nano SmBa2NbO2 synthesized by modified combustion technique was studied. Particle size of nano SmBa2NBO6 was determined using transmission electron microscopy. The chemical nonreactivity of nano SmBa2NbO6 with YBCO is evident from the X-Ray diffraction study which makes it a suitable nanoceramic substrate material for high temperature superconducting films. A systematic increase in the sintered density, approaching the optimum value of the insulating nanophase is clearly observed, as the vol.% of YBCO in the composite decreases. SEM micrograph showed uniform distribution of nanopowder among the large clusters of YBCO. The obtained percolation threshold is ~26 vol% of YBCO in the composite. All the composites below the threshold value showed TC(0~92 K even though the room resistivity increases with increase in vol.% of nano SmBa2NbO6. The values of critical exponents obtained matches well with the theoretically expected ones for an ideal superconductor-insulator system.
Percolation of secret correlations in a network
Leverrier, Anthony; García-Patrón, Raúl
2011-01-01
In this work, we explore the analogy between entanglement and secret classical correlations in the context of large networks, more precisely the question of percolation of secret correlations in a network. It is known that entanglement percolation in quantum networks can display a highly nontrivial behavior depending on the topology of the network and on the presence of entanglement between the nodes. Here we show that this behavior, thought to be of a genuine quantum nature, also occurs in a...
Percolation of secret correlations in a network
Energy Technology Data Exchange (ETDEWEB)
Leverrier, Anthony; Garcia-Patron, Raul [ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona) (Spain); Research Laboratory of Electronics, MIT, Cambridge, MA 02139 (United States) and Max-Planck Institut fur Quantenoptik, Hans-Kopfermann Str. 1, D-85748 Garching (Germany)
2011-09-15
In this work, we explore the analogy between entanglement and secret classical correlations in the context of large networks--more precisely, the question of percolation of secret correlations in a network. It is known that entanglement percolation in quantum networks can display a highly nontrivial behavior depending on the topology of the network and on the presence of entanglement between the nodes. Here we show that this behavior, thought to be of a genuine quantum nature, also occurs in a classical context.
Percolation of secret correlations in a network
International Nuclear Information System (INIS)
Leverrier, Anthony; Garcia-Patron, Raul
2011-01-01
In this work, we explore the analogy between entanglement and secret classical correlations in the context of large networks--more precisely, the question of percolation of secret correlations in a network. It is known that entanglement percolation in quantum networks can display a highly nontrivial behavior depending on the topology of the network and on the presence of entanglement between the nodes. Here we show that this behavior, thought to be of a genuine quantum nature, also occurs in a classical context.
The threshold of coexistence and critical behaviour of a predator-prey cellular automaton
International Nuclear Information System (INIS)
Arashiro, Everaldo; Tome, Tania
2007-01-01
We study a probabilistic cellular automaton to describe two population biology problems: the threshold of species coexistence in a predator-prey system and the spreading of an epidemic in a population. By carrying out mean-field approximations and numerical simulations we obtain the phase boundaries (thresholds) related to the transition between an active state, where prey and predators present a stable coexistence, and a prey absorbing state. The numerical estimates for the critical exponents show that the transition belongs to the directed percolation universality class. In the limit where the cellular automaton maps into a model for the spreading of an epidemic with immunization we observe a crossover from directed percolation class to the dynamic percolation class. Patterns of growing clusters related to species coexistence and spreading of epidemic are shown and discussed
Range of plasma ions in cold cluster gases near the critical point
International Nuclear Information System (INIS)
Zhang, G.; Quevedo, H.J.; Bonasera, A.; Donovan, M.; Dyer, G.; Gaul, E.; Guardo, G.L.; Gulino, M.; La Cognata, M.; Lattuada, D.; Palmerini, S.; Pizzone, R.G.; Romano, S.; Smith, H.; Trippella, O.; Anzalone, A.; Spitaleri, C.; Ditmire, T.
2017-01-01
We measure the range of plasma ions in cold cluster gases by using the Petawatt laser at the University of Texas-Austin. The produced plasma propagated in all directions some hitting the cold cluster gas not illuminated by the laser. From the ratio of the measured ion distributions at different angles we can estimate the range of the ions in the cold cluster gas. It is much smaller than estimated using popular models, which take only into account the slowing down of charged particles in uniform matter. We discuss the ion range in systems prepared near a liquid–gas phase transition. - Highlights: • We present experimental results obtained at the UT Petawatt laser facility, Austin, TX. • The ion range is strongly modified for cluster gases as compared to its value in a homogeneous system. • Large fluctuations are found if the cluster gas is prepared near the liquid–gas phase transition region.
Range of plasma ions in cold cluster gases near the critical point
Energy Technology Data Exchange (ETDEWEB)
Zhang, G. [Cyclotron Institute, Texas A& M University, 77843 College Station, TX (United States); Quevedo, H.J. [Center for High Energy Density Science, C1510, University of Texas at Austin, Austin, TX 78712 (United States); Bonasera, A., E-mail: abonasera@comp.tamu.edu [Cyclotron Institute, Texas A& M University, 77843 College Station, TX (United States); Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Donovan, M.; Dyer, G.; Gaul, E. [Center for High Energy Density Science, C1510, University of Texas at Austin, Austin, TX 78712 (United States); Guardo, G.L. [Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Gulino, M. [Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Libera Universita' Kore, 94100 Enna (Italy); La Cognata, M.; Lattuada, D. [Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Palmerini, S. [Department of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia (Italy); Istituto Nazionale di Fisica Nucleare, Section of Perugia, Via A. Pascoli, 06123 Perugia (Italy); Pizzone, R.G.; Romano, S. [Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Smith, H. [Center for High Energy Density Science, C1510, University of Texas at Austin, Austin, TX 78712 (United States); Trippella, O. [Department of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia (Italy); Istituto Nazionale di Fisica Nucleare, Section of Perugia, Via A. Pascoli, 06123 Perugia (Italy); Anzalone, A.; Spitaleri, C. [Laboratori Nazionali del Sud-INFN, via S. Sofia 64, 95123 Catania (Italy); Ditmire, T. [Center for High Energy Density Science, C1510, University of Texas at Austin, Austin, TX 78712 (United States)
2017-05-18
We measure the range of plasma ions in cold cluster gases by using the Petawatt laser at the University of Texas-Austin. The produced plasma propagated in all directions some hitting the cold cluster gas not illuminated by the laser. From the ratio of the measured ion distributions at different angles we can estimate the range of the ions in the cold cluster gas. It is much smaller than estimated using popular models, which take only into account the slowing down of charged particles in uniform matter. We discuss the ion range in systems prepared near a liquid–gas phase transition. - Highlights: • We present experimental results obtained at the UT Petawatt laser facility, Austin, TX. • The ion range is strongly modified for cluster gases as compared to its value in a homogeneous system. • Large fluctuations are found if the cluster gas is prepared near the liquid–gas phase transition region.
International Nuclear Information System (INIS)
Korzhenevskii, A.L.; Luzhkov, A.A.
1991-01-01
The development of a theory of phase transitions in disordered materials is still one of the central problems in solid-state physics. The model of a percolation phase transition plays the same role among the models put forward to account for phase transitions in disordered media as does the Ising model for second-order phase transitions in ideal crystals. In addition to the clear picture of the processes occurring in the course of a percolation phase transition, a scaling theory has been developed and various techniques have been used to calculate the critical exponents describing the thermodynamics of a medium in the vicinity of the percolation threshold. The authors adopt a field-theoretic approach in a study of acoustic properties of disordered solids undergoing percolation phase transitions characterized by h ∼ 1. Among these transitions they concentrate on the case with the simplest type of striction interaction when the solution of a stochastic vector differential equation of motion describing the behavior of an elastic medium in the critical region can be reduced to a scalar equation. The results of their calculations by the field renormalization group method confirmed the existence of the scaling relationships between the critical exponents and also the conclusion on the nature of short- and long-wavelength vibrations near the percolation threshold, which follow from phenomenological considerations of the scaling theory. The values of the upper critical dimensionality and of the critical exponents of the problem are shown to differ from the values applicable to percolation phase transitions characterized by h much-lt 1
Real-space renormalization group; application to site percolation in square lattice
International Nuclear Information System (INIS)
Tsallis, C.; Schwachheim, G.
1978-05-01
The real-space renormalization group proposed by Reynolds, Klein and Stanley 1977 to treat the site percolation is analysed and extended . The best among 3 possible definitions of 'percolating' configurations and among 5 possible methods to weight these configurations, are established for percolation in square lattices. The use of n xn square clusters leads, for n = 2 (RKS), n = 3 and n = 4, to √ sub (p) approximately equal to 1.635, √ sub(p) approximately equal to 1.533 and √ sub(p) approximately equal to 1.498, and also to P sub(c) approximately equal to 0.382, P sub(c) approximately equal to 0.388 and P sub(c) approximately equal to 0.398, exhibiting in this way the correct (but slow) tendency towards the best up to date values [pt
Weak link behaviour in YBa2Cu3O7-δ system studied by a site percolation model
International Nuclear Information System (INIS)
Arulgnanam, A.; Balasubramanian, A.
1992-01-01
The superconductivity in the YBaCuO system can be explained in terms of the superconducting percolation of 90 K orthorhombic microdomain. Kubo et al. have studied the percolation behaviour of the 123 system and estimated the total critical oxygen occupancy P c to be 0.75 for the orthorhombic I structure using at 150x180 lattice model. In this paper, we report our work on the percolative behaviour of the 123 system, using a Monte Carlo method. We have studied the effect on P c of increasing the lattice dimension up to 500x500. For P c ≤0.60 no percolative behaviour was observed, suggesting the tetragonal phase. Few times percolation was observed for 0.60≤P≤0.65 indicating the phase transformation from tetragonal to orthorhombic. For 0.65≤P≤0.77 (or 0.230≤δ≤0.35) weak percolative behaviour was observed suggesting the formation of orthorhombic II structure, which is in good agreement with the value observed by Cava et al. For 0.77≤P≤1.0 strong percolation was exhibited indicating the formation of orthorhombic I phase. We have explained the weak link region observed for 0.60≤P≤0.77. We estimated the total critical oxygen occupancy P c =0.766 for an orthorhombic I structure for the lattice. (orig.)
A critical cluster analysis of 44 indicators of author-level performance
DEFF Research Database (Denmark)
Wildgaard, Lorna Elizabeth
2016-01-01
-four indicators of individual researcher performance were computed using the data. The clustering solution was supported by continued reference to the researcher’s curriculum vitae, an effect analysis and a risk analysis. Disciplinary appropriate indicators were identified and used to divide the researchers......This paper explores a 7-stage cluster methodology as a process to identify appropriate indicators for evaluation of individual researchers at a disciplinary and seniority level. Publication and citation data for 741 researchers from 4 disciplines was collected in Web of Science. Forty...... of statistics in research evaluation. The strength of the 7-stage cluster methodology is that it makes clear that in the evaluation of individual researchers, statistics cannot stand alone. The methodology is reliant on contextual information to verify the bibliometric values and cluster solution...
Growth dominates choice in network percolation
Vijayaraghavan, Vikram S.; Noël, Pierre-André; Waagen, Alex; D'Souza, Raissa M.
2013-09-01
The onset of large-scale connectivity in a network (i.e., percolation) often has a major impact on the function of the system. Traditionally, graph percolation is analyzed by adding edges to a fixed set of initially isolated nodes. Several years ago, it was shown that adding nodes as well as edges to the graph can yield an infinite order transition, which is much smoother than the traditional second-order transition. More recently, it was shown that adding edges via a competitive process to a fixed set of initially isolated nodes can lead to a delayed, extremely abrupt percolation transition with a significant jump in large but finite systems. Here we analyze a process that combines both node arrival and edge competition. If started from a small collection of seed nodes, we show that the impact of node arrival dominates: although we can significantly delay percolation, the transition is of infinite order. Thus, node arrival can mitigate the trade-off between delay and abruptness that is characteristic of explosive percolation transitions. This realization may inspire new design rules where network growth can temper the effects of delay, creating opportunities for network intervention and control.
Percolation analysis for cosmic web with discrete points
Zhang, Jiajun; Cheng, Dalong; Chu, Ming-Chung
2018-01-01
Percolation analysis has long been used to quantify the connectivity of the cosmic web. Most of the previous work is based on density fields on grids. By smoothing into fields, we lose information about galaxy properties like shape or luminosity. The lack of mathematical modeling also limits our understanding for the percolation analysis. To overcome these difficulties, we have studied percolation analysis based on discrete points. Using a friends-of-friends (FoF) algorithm, we generate the S -b b relation, between the fractional mass of the largest connected group (S ) and the FoF linking length (b b ). We propose a new model, the probability cloud cluster expansion theory to relate the S -b b relation with correlation functions. We show that the S -b b relation reflects a combination of all orders of correlation functions. Using N-body simulation, we find that the S -b b relation is robust against redshift distortion and incompleteness in observation. From the Bolshoi simulation, with halo abundance matching (HAM), we have generated a mock galaxy catalog. Good matching of the projected two-point correlation function with observation is confirmed. However, comparing the mock catalog with the latest galaxy catalog from Sloan Digital Sky Survey (SDSS) Data Release (DR)12, we have found significant differences in their S -b b relations. This indicates that the mock galaxy catalog cannot accurately retain higher-order correlation functions than the two-point correlation function, which reveals the limit of the HAM method. As a new measurement, the S -b b relation is applicable to a wide range of data types, fast to compute, and robust against redshift distortion and incompleteness and contains information of all orders of correlation functions.
International Nuclear Information System (INIS)
Kind, Hans Jarle; Osmundsen, Petter; Tverteraas, Ragnar
2001-10-01
Enhanced understanding of the factors determining trans national companies' localisation decisions is important for regulators and other stake holders concerned about maintaining current activity levels in a petroleum producing country. This article discusses localisation decisions in the context of theories of industrial clusters and real portfolio optimisation theory (materiality), which we argue are two fruitful lines of explanation for trans national companies' behaviour. The industrial cluster literature is concerned about the level of positive externalities associated with geographic clustering of related production activities. The concept of materiality, implying that investment projects in an oil province must be of a certain minimum size in order to be interesting for oil companies, is evaluated empirically and compared to predictions of mainstream economic theory. (author)
Energy Technology Data Exchange (ETDEWEB)
Kind, Hans Jarle; Osmundsen, Petter; Tverteraas, Ragnar
2001-10-01
Enhanced understanding of the factors determining transnational companies' localisation decisions is important for regulators and other stakeholders concerned about maintaining current activity levels in a petroleum producing country. This article discusses localisation decisions in the context of theories of industrial clusters and real portfolio optimisation theory (materiality), which we argue are two fruitful lines of explanation for transnational companies' behaviour. The industrial cluster literature is concerned about the level of positive externalities associated with geographic clustering of related production activities. The concept of materiality, implying that investment projects in an oil province must be of a certain minimum size in order to be interesting for oil companies, is evaluated empirically and compared to predictions of mainstream economic theory. (author)
Percolation under noise: Detecting explosive percolation using the second-largest component
Viles, Wes; Ginestet, Cedric E.; Tang, Ariana; Kramer, Mark A.; Kolaczyk, Eric D.
2016-05-01
We consider the problem of distinguishing between different rates of percolation under noise. A statistical model of percolation is constructed allowing for the birth and death of edges as well as the presence of noise in the observations. This graph-valued stochastic process is composed of a latent and an observed nonstationary process, where the observed graph process is corrupted by type-I and type-II errors. This produces a hidden Markov graph model. We show that for certain choices of parameters controlling the noise, the classical (Erdős-Rényi) percolation is visually indistinguishable from a more rapid form of percolation. In this setting, we compare two different criteria for discriminating between these two percolation models, based on the interquartile range (IQR) of the first component's size, and on the maximal size of the second-largest component. We show through data simulations that this second criterion outperforms the IQR of the first component's size, in terms of discriminatory power. The maximal size of the second component therefore provides a useful statistic for distinguishing between different rates of percolation, under physically motivated conditions for the birth and death of edges, and under noise. The potential application of the proposed criteria for the detection of clinically relevant percolation in the context of applied neuroscience is also discussed.
A critical cluster analysis of 44 indicators of author-level performance
DEFF Research Database (Denmark)
Wildgaard, Lorna Elizabeth
2015-01-01
. Publication and citation data for 741 researchers across Astronomy, Environmental Science, Philosophy and Public Health was collected in Web of Science (WoS). Forty-four indicators of individual performance were computed using the data. A two-step cluster analysis using IBM SPSS version 22 was performed...
Emerging critical roles of Fe-S clusters in DNA replication and repair
Fuss, Jill O.; Tsai, Chi-Lin; Ishida, Justin P.; Tainer, John A.
2015-01-01
Fe-S clusters are partners in the origin of life that predate cells, acetyl-CoA metabolism, DNA, and the RNA world. The double helix solved the mystery of DNA replication by base pairing for accurate copying. Yet, for genome stability necessary to life, the double helix has equally important implications for damage repair. Here we examine striking advances that uncover Fe-S cluster roles both in copying the genetic sequence by DNA polymerases and in crucial repair processes for genome maintenance, as mutational defects cause cancer and degenerative disease. Moreover, we examine an exciting, controversial role for Fe-S clusters in a third element required for life – the long-range coordination and regulation of replication and repair events. By their ability to delocalize electrons over both Fe and S centers, Fe-S clusters have unbeatable features for protein conformational control and charge transfer via double-stranded DNA that may fundamentally transform our understanding of life, replication, and repair. PMID:25655665
Ising percolation in a three-state majority vote model
Balankin, Alexander S.; Martínez-Cruz, M. A.; Gayosso Martínez, Felipe; Mena, Baltasar; Tobon, Atalo; Patiño-Ortiz, Julián; Patiño-Ortiz, Miguel; Samayoa, Didier
2017-02-01
In this Letter, we introduce a three-state majority vote model in which each voter adopts a state of a majority of its active neighbors, if exist, but the voter becomes uncommitted if its active neighbors are in a tie, or all neighbors are the uncommitted. Numerical simulations were performed on square lattices of different linear size with periodic boundary conditions. Starting from a random distribution of active voters, the model leads to a stable non-consensus state in which three opinions coexist. We found that the "magnetization" of the non-consensus state and the concentration of uncommitted voters in it are governed by an initial composition of system and are independent of the lattice size. Furthermore, we found that a configuration of the stable non-consensus state undergoes a second order percolation transition at a critical concentration of voters holding the same opinion. Numerical simulations suggest that this transition belongs to the same universality class as the Ising percolation. These findings highlight the effect of an updating rule for a tie between voter neighbors on the critical behavior of models obeying the majority vote rule whenever a strict majority exists.
Cell percolation model for electrical conduction of granular superconducting composites. 2
International Nuclear Information System (INIS)
Horvath, G.; Bankuti, J.
1990-01-01
The percolation of the electrical conductivity of the uniform cells is studied in an in-situ elongated granular superconducting composite on the basis of the uniform cell model improved previously. The critical temperatures are determined in the macroscopic superconducting state of the two- and the three-dimensional composites. (author)
Computer simulation of current percolation in polycrystalline high-temperature superconductors
Energy Technology Data Exchange (ETDEWEB)
Zeimetz, B [Department of Materials Science and Interdisciplinary Research Centre in Superconductivity, Cambridge University, Pembroke Street, Cambridge (United Kingdom); Rutter, N A; Glowacki, B A; Evetts, J E [Department of Materials Science and Interdisciplinary Research Centre in Superconductivity, Cambridge University, Pembroke Street, Cambridge (United Kingdom)
2001-09-01
YBCO-coated conductors were modelled in a computer simulation using a resistor network concept, with the resistors representing the grain boundaries. Dissipation above the critical current, accompanied by flux penetration into the grain boundaries, was described by a linear (flux-flow) resistivity. The model allowed calculation of the combined percolation of current and magnetic flux. Current-voltage data showed scaling in agreement with percolation theory for two-dimensional systems. The influence of grain alignment and electromagnetic parameters on conductor performance was investigated. (author)
Breit, M.; Podolskiy, V. A.; Grésillon, S.; von Plessen, G.; Feldmann, J.; Rivoal, J. C.; Gadenne, P.; Sarychev, Andrey K.; Shalaev, Vladimir M.
2001-09-01
Strongly enhanced second-harmonic generation (SHG), which is characterized by a nearly isotropic intensity distribution, is observed for gold-glass films near the percolation threshold. The diffuselike SHG scattering, which can be thought of as nonlinear critical opalescence, is in sharp contrast with highly collimated linear reflection and transmission from these nanostructured semicontinuous metal films. Our observations, which can be explained by giant fluctuations of local nonlinear sources for SHG due to plasmon localization, verify recent predictions of percolation-enhanced nonlinear scattering.
Percolation of interdependent network of networks
International Nuclear Information System (INIS)
Havlin, Shlomo; Stanley, H. Eugene; Bashan, Amir; Gao, Jianxi; Kenett, Dror Y.
2015-01-01
Complex networks appear in almost every aspect of science and technology. Previous work in network theory has focused primarily on analyzing single networks that do not interact with other networks, despite the fact that many real-world networks interact with and depend on each other. Very recently an analytical framework for studying the percolation properties of interacting networks has been introduced. Here we review the analytical framework and the results for percolation laws for a Network Of Networks (NONs) formed by n interdependent random networks. The percolation properties of a network of networks differ greatly from those of single isolated networks. In particular, because the constituent networks of a NON are connected by node dependencies, a NON is subject to cascading failure. When there is strong interdependent coupling between networks, the percolation transition is discontinuous (first-order) phase transition, unlike the well-known continuous second-order transition in single isolated networks. Moreover, although networks with broader degree distributions, e.g., scale-free networks, are more robust when analyzed as single networks, they become more vulnerable in a NON. We also review the effect of space embedding on network vulnerability. It is shown that for spatially embedded networks any finite fraction of dependency nodes will lead to abrupt transition
The geometry of percolation fronts in two-dimensional lattices with spatially varying densities
International Nuclear Information System (INIS)
Gastner, Michael T; Oborny, Beáta
2012-01-01
Percolation theory is usually applied to lattices with a uniform probability p that a site is occupied or that a bond is closed. The more general case, where p is a function of the position x, has received less attention. Previous studies with long-range spatial variations in p(x) have only investigated cases where p has a finite, non-zero gradient at the critical point p c . Here we extend the theory to two-dimensional cases in which the gradient can change from zero to infinity. We present scaling laws for the width and length of the hull (i.e. the boundary of the spanning cluster). We show that the scaling exponents for the width and the length depend on the shape of p(x), but they always have a constant ratio 4/3 so that the hull's fractal dimension D = 7/4 is invariant. On this basis, we derive and verify numerically an asymptotic expression for the probability h(x) that a site at a given distance x from p c is on the hull. (paper)
Benefits of current percolation in superconducting coated conductors
International Nuclear Information System (INIS)
Rutter, N.A.; Durrell, J.H.; Blamire, M.G.; MacManus-Driscoll, J.L.; Wang, H.; Foltyn, S.R.
2005-01-01
The critical currents of coated conductors fabricated by metal-organic deposition (MOD) on rolling-assisted biaxially textured substrates (RABiTS) and by pulsed laser deposition (PLD) on ion-beam assisted deposition (IBAD) templates have been measured as a function of magnetic field orientation and compared to films grown on single crystal substrates. By varying the orientation of magnetic field applied in the plane of the film, we are able to determine the extent to which current flow in each type of conductor is percolative. Standard MOD/RABiTS conductors have also been compared to samples whose grain boundaries have been doped by diffusing Ca from an overlayer. We find that undoped MOD/RABiTS tapes have a less anisotropic in-plane field dependence than PLD/IBAD tapes and that the uniformity of critical current as a function of in-plane field angle is greater for MOD/RABiTS samples doped with Ca
Nezlobin, David; Pariente, Sarah; Lavee, Hanoch; Sachs, Eyal
2017-04-01
Source-sink systems are very common in hydrology; in particular, some land cover types often generate runoff (e.g. embedded rocks, bare soil) , while other obstruct it (e.g. vegetation, cracked soil). Surface runoff coefficients of patchy slopes/plots covered by runoff generating and obstructing covers (e.g., bare soil and vegetation) depend critically on the percentage cover (i.e. sources/sinks abundance) and decrease strongly with observation scale. The classic mathematical percolation theory provides a powerful apparatus for describing the runoff connectivity on patchy hillslopes, but it ignores strong effect of the overland flow directionality. To overcome this and other difficulties, modified percolation theory approaches can be considered, such as straight percolation (for the planar slopes), quasi-straight percolation and models with limited obstruction. These approaches may explain both the observed critical dependence of runoff coefficients on percentage cover and their scale decrease in systems with strong flow directionality (e.g. planar slopes). The contributing area increases sharply when the runoff generating percentage cover approaches the straight percolation threshold. This explains the strong increase of the surface runoff and erosion for relatively low values (normally less than 35%) of the obstructing cover (e.g., vegetation). Combinatorial models of urns with restricted occupancy can be applied for the analytic evaluation of meaningful straight percolation quantities, such as NOGA's (Non-Obstructed Generating Area) expected value and straight percolation probability. It is shown that the nature of the cover-related runoff scale decrease is combinatorial - the probability for the generated runoff to avoid obstruction in unit area decreases with scale for the non-trivial percentage cover values. The magnitude of the scale effect is found to be a skewed non-monotonous function of the percentage cover. It is shown that the cover-related scale
Anisotropy in Fracking: A Percolation Model for Observed Microseismicity
Norris, J. Quinn; Turcotte, Donald L.; Rundle, John B.
2015-01-01
Hydraulic fracturing (fracking), using high pressures and a low viscosity fluid, allow the extraction of large quantiles of oil and gas from very low permeability shale formations. The initial production of oil and gas at depth leads to high pressures and an extensive distribution of natural fractures which reduce the pressures. With time these fractures heal, sealing the remaining oil and gas in place. High volume fracking opens the healed fractures allowing the oil and gas to flow to horizontal production wells. We model the injection process using invasion percolation. We use a 2D square lattice of bonds to model the sealed natural fractures. The bonds are assigned random strengths and the fluid, injected at a point, opens the weakest bond adjacent to the growing cluster of opened bonds. Our model exhibits burst dynamics in which the clusters extend rapidly into regions with weak bonds. We associate these bursts with the microseismic activity generated by fracking injections. A principal object of this paper is to study the role of anisotropic stress distributions. Bonds in the y-direction are assigned higher random strengths than bonds in the x-direction. We illustrate the spatial distribution of clusters and the spatial distribution of bursts (small earthquakes) for several degrees of anisotropy. The results are compared with observed distributions of microseismicity in a fracking injection. Both our bursts and the observed microseismicity satisfy Gutenberg-Richter frequency-size statistics.
Olivet, Jeffrey; Zerger, Suzanne; Greene, R. Neil; Kenney, Rachael R.; Herman, Daniel B.
2016-01-01
This study examined the effectiveness of online education to providers who serve people experiencing homelessness, comparing online and face-to-face training of Critical Time Intervention (CTI), an evidence-based case management model. The authors recruited 184 staff from nineteen homeless service agencies to participate in one of two training…
Percolation Analysis as a Tool to Describe the Topology of the Large Scale Structure of the Universe
Yess, Capp D.
1997-09-01
Percolation analysis is the study of the properties of clusters. In cosmology, it is the statistics of the size and number of clusters. This thesis presents a refinement of percolation analysis and its application to astronomical data. An overview of the standard model of the universe and the development of large scale structure is presented in order to place the study in historical and scientific context. Then using percolation statistics we, for the first time, demonstrate the universal character of a network pattern in the real space, mass distributions resulting from nonlinear gravitational instability of initial Gaussian fluctuations. We also find that the maximum of the number of clusters statistic in the evolved, nonlinear distributions is determined by the effective slope of the power spectrum. Next, we present percolation analyses of Wiener Reconstructions of the IRAS 1.2 Jy Redshift Survey. There are ten reconstructions of galaxy density fields in real space spanning the range β = 0.1 to 1.0, where β=Ω0.6/b,/ Ω is the present dimensionless density and b is the linear bias factor. Our method uses the growth of the largest cluster statistic to characterize the topology of a density field, where Gaussian randomized versions of the reconstructions are used as standards for analysis. For the reconstruction volume of radius, R≈100h-1 Mpc, percolation analysis reveals a slight 'meatball' topology for the real space, galaxy distribution of the IRAS survey. Finally, we employ a percolation technique developed for pointwise distributions to analyze two-dimensional projections of the three northern and three southern slices in the Las Campanas Redshift Survey and then give consideration to further study of the methodology, errors and application of percolation. We track the growth of the largest cluster as a topological indicator to a depth of 400 h-1 Mpc, and report an unambiguous signal, with high signal-to-noise ratio, indicating a network topology which in
Hing, P.
2011-11-01
Percolation theory deals with the behaviour of connected clusters in a system. Originally developed for studying the flow of liquid in a porous body, the percolation theory has been extended to quantum computation and communication, entanglement percolation in quantum networks, cosmology, chaotic situations, properties of disordered solids, pandemics, petroleum industry, finance, control of traffic and so on. In this paper, the application of various models of the percolation theory to predict and explain the properties of a specially developed family of dense sintered and highly refractory Al2O3-W composites for potential application in high intensity discharge light sources such as high pressure sodium lamps and ceramic metal halide lamps are presented and discussed. The low cost, core-shell concept can be extended to develop functional composite materials with unusual dielectric, electrical, magnetic, superconducting, and piezoelectric properties starting from a classical insulator. The core shell concept can also be applied to develop catalysts with high specific surface areas with minimal amount of expensive platinium, palladium or rare earth nano structured materials for light harvesting, replicating natural photosynthesis, in synthetic zeolite composites for the cracking and separation of crude oil. There is also possibility of developing micron and nanosize Faraday cages for quantum devices, nano electronics and spintronics. The possibilities are limitless.
Two-dimensional fractal geometry, critical phenomena and conformal invariance
International Nuclear Information System (INIS)
Duplantier, B.
1988-01-01
The universal properties of critical geometrical systems in two-dimensions (2D) like the O (n) and Potts models, are described in the framework of Coulomb gas methods and conformal invariance. The conformal spectrum of geometrical critical systems obtained is made of a discrete infinite series of scaling dimensions. Specific applications involve the fractal properties of self-avoiding walks, percolation clusters, and also some non trivial critical exponents or fractal dimensions associated with subsets of the planar Brownian motion. The statistical mechanics of the same critical models on a random 2D lattice (namely in presence of a critically-fluctuating metric, in the so-called 2D quantum gravity) is also addressed, and the above critical geometrical systems are shown to be exactly solvable in this case. The new ''gravitational'' conformal spectrum so derived is found to satisfy the recent Knizhnik, Polyakov and Zamolodchikov quadratic relation which links it to the standard conformal spectrum in the plane
Phenomenology of quarkyonic percolation at FAIR
International Nuclear Information System (INIS)
Torrieri, Giorgio; Lottini, Stefano
2013-01-01
We will give an introduction to the concept of quarkyonic matter, presenting an overview of what is meant by this term in the literature. We will then argue that the quarkyonic phase, as defined in the original paper, is a percolation-type phase transition whose phase transition line is strongly curved in ρ B − N c space, where N C is the number of colors and ρ B the baryon density. With a toy model estimate, we show that it might be possible to obtain a percolating but confined phase at N c = 3, N f = 2 at densities larger than one baryon per one baryon size. We conclude by discussing how this phase can be observed at FAIR.
Modified Invasion Percolation Models for Multiphase Processes
Energy Technology Data Exchange (ETDEWEB)
Karpyn, Zuleima [Pennsylvania State Univ., State College, PA (United States)
2015-01-31
This project extends current understanding and modeling capabilities of pore-scale multiphase flow physics in porous media. High-resolution X-ray computed tomography imaging experiments are used to investigate structural and surface properties of the medium that influence immiscible displacement. Using experimental and computational tools, we investigate the impact of wetting characteristics, as well as radial and axial loading conditions, on the development of percolation pathways, residual phase trapping and fluid-fluid interfacial areas.
Nuzhnyy, D.; Savinov, M.; Bovtun, V.; Kempa, M.; Petzelt, J.; Mayoral, B.; McNally, T.
2013-02-01
Composites of multiwalled carbon nanotubes with poly(ethylene terephthalate) (PET-MWCNT) with up to 3 vol% MWCNTs were prepared and characterized by broad-band AC conductivity and dielectric spectroscopy up to the infrared range using several techniques. A very low electrical percolation threshold of 0.07 vol% MWCNTs was revealed from the low-frequency conductivity plateau as well as from DC conductivity, whose values show the same critical power dependence on MWCNT concentration with the exponent t = 4.3. Above the plateau, the AC conductivity increases with frequency up to the THz range, where it becomes overlapped with the absorption of vibrational modes. The temperature dependence down to ˜5 K has shown semiconductor behaviour with a concentration-independent but weakly temperature-dependent small activation energy of ˜3 meV. The behaviour is compatible with the previously suggested fluctuation-induced tunnelling conductivity model through a thin (˜1 nm) polymer contact layer among the adjacent MWCNTs within percolated clusters. At higher frequencies, deviations from the simple universal conductivity behaviour are observed, indicating some distribution of energy barriers for an electron hopping mechanism.
Experimental percolation studies of random networks
Feinerman, A.; Weddell, J.
2017-06-01
This report establishes an experimental method of studying electrically percolating networks at a higher resolution than previously implemented. This method measures the current across a conductive sheet as a function of time as elliptical pores are cut into the sheet. This is done utilizing a Universal Laser System X2-600 100 W CO2 laser system with a 76 × 46 cm2 field and 394 dpc (dots/cm) resolution. This laser can cut a random system of elliptical pores into a conductive sheet with a potential voltage applied across it and measures the current versus time. This allows for experimental verification of a percolation threshold as a function of the ellipse's aspect ratio (minor/major diameter). We show that as an ellipse's aspect ratio approaches zero, the percolation threshold approaches one. The benefit of this method is that it can experimentally measure the effect of removing small pores, as well as pores with complex geometries, such as an asterisk from a conductive sheet.
Percolation Model of Adhesion at Polymer Interfaces
Wool, Richard P.
1998-03-01
Adhesion at polymer interfaces is treated as a percolation problem, where an areal density of chains Σ, of length L, contribute a number of entanglements to the interface of thickness X. The fracture energy G, is determined by the fraction of entanglements P, fractured or disentangled in the deformation zone preceding the crack tip, via G ~ P-P_c, where Pc is the percolation threshold, given by Pc = 1- M_e/Mc . For incompatible A/B interfaces reinforced with Σ diblocks or random A-B copolymers of effective length L'(L' ~ 0 for brushes and strongly adsorbed chains), we obtain P ~ ΣL/X, Pc ~ Σ _cL/X, such that G = K(Σ - Σ _c)+ G_o, where K and Go ~ 1 J/m^2 are constants. Note that Log G vs Log Σ will have an apparent slope of about 2, incorrectly suggesting that G ~ Σ ^2. For cohesive fracture, disentanglement dominates at M M*, G = G*[1-M_c/M]. For fatigue crack propagation da/dN, at welding interfaces, we obtain da/dN ~ M-5/2(t/Tr)-5/4, where t is the welding time and Tr is the reptation time. For polymer-solid interfaces, G ~ (X/R)^2. where X is the conformational width of the first layer of chains of random coil size R. The fractal nature of the percolation process is relevant to the fracture mechanism and fractography.
Energy Technology Data Exchange (ETDEWEB)
Brodie, Jean P.; Conroy, Charlie; Arnold, Jacob A.; Romanowsky, Aaron J. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Usher, Christopher; Forbes, Duncan A. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Strader, Jay, E-mail: brodie@ucolick.org [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
2012-11-10
Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.
International Nuclear Information System (INIS)
Brodie, Jean P.; Conroy, Charlie; Arnold, Jacob A.; Romanowsky, Aaron J.; Usher, Christopher; Forbes, Duncan A.; Strader, Jay
2012-01-01
Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.
Guettari, Moez; Aferni, Ahmed E. L.; Tajouri, Tahar
2017-12-01
The main aim of this paper is the analysis of micellar collisions and polymer confinement effects on the electrical conductivity percolative behavior of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles. Firstly, we have performed conductance measurements of the system for three AOT to isooctane volume ratio, φm = 0.1 , 0.15 and 0.2 to examine the influence of micellar collisions on the percolation parameters. All the measurements were carried out over the 298.15 K-333.15 K temperature range at a fixed water to AOT molar ratio, W0 = 45 . We have assessed that the rise of micellar collisions frequency enhances the conductance percolation. Secondly, the confinement effect of a water-soluble polymer, polyvinylpyrrolidone (PVP), on the reverse micelles conductance behavior was investigated. Temperature-induced percolation, Tp , have shown a dependence on the polymer concentration, CPVP . It was also observed that for various PVP concentrations, the activation energy of percolation decreases. Finally, the values of the critical exponents determined in the presence and absence of PVP prove that the polymer affects the dynamic of percolation.
Evaluation of percolation rate of bedrock aquifer in coastal area
Energy Technology Data Exchange (ETDEWEB)
Lee, Jeong Hwan; Jung, Hae Ryong; Park, Joo Wan; Yoon, Jeong Hyoun; Cheong, Jae Yeol [Korea Radioactive Waste Agency, Daejeon (Korea, Republic of); Park, Sun Ju [NEXGEO Co. Ltd, Seoul (Korea, Republic of); Jun, Seong Chun [GeoGreen21 Co. Ltd, Seoul (Korea, Republic of)
2016-03-15
Estimation of groundwater hydrologic cycle pattern is one of the most critical issues in sustainable management of groundwater resources in coastal area. This study estimated groundwater percolation by using the water balance methodology and hydrogeological characteristics of land use and soil. Evapotranspiration was computed by using the Thornthwaite method, and surface runoff was determined by using the SCS-CN technique. Groundwater storage change was obtained as 229 mm/a (17.8% of the average annual rainfall, 1286 mm/a), with 693 mm/a (60.1%) of evapotranspiration and 124 mm/a (9.6%) of surface runoff. Rainfall and groundwater storage change was highly correlated, comparing with the relationships between rainfall and evapotranspiration, and between rainfall and surface runoff. This result indicates that groundwater storage change responds more sensitively to precipitation than evapotranspiration and surface runoff.
Evaluation of percolation rate of bedrock aquifer in coastal area
International Nuclear Information System (INIS)
Lee, Jeong Hwan; Jung, Hae Ryong; Park, Joo Wan; Yoon, Jeong Hyoun; Cheong, Jae Yeol; Park, Sun Ju; Jun, Seong Chun
2016-01-01
Estimation of groundwater hydrologic cycle pattern is one of the most critical issues in sustainable management of groundwater resources in coastal area. This study estimated groundwater percolation by using the water balance methodology and hydrogeological characteristics of land use and soil. Evapotranspiration was computed by using the Thornthwaite method, and surface runoff was determined by using the SCS-CN technique. Groundwater storage change was obtained as 229 mm/a (17.8% of the average annual rainfall, 1286 mm/a), with 693 mm/a (60.1%) of evapotranspiration and 124 mm/a (9.6%) of surface runoff. Rainfall and groundwater storage change was highly correlated, comparing with the relationships between rainfall and evapotranspiration, and between rainfall and surface runoff. This result indicates that groundwater storage change responds more sensitively to precipitation than evapotranspiration and surface runoff
Hybrid phase transition into an absorbing state: Percolation and avalanches
Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.
2016-04-01
Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .
Donado-Garzon, L. D.; Pardo, Y.
2013-12-01
percolation theory, the latter is applicable to such networks. Under these conditions, percolation theory permit us to reduced the number of elements (90% in average) that form clusters of the 100 DFNs, preserving the so-called backbone. In this way the calibration runs in these networks changed from several hours to just a second obtaining much better results.
Quantum walks of two interacting particles on percolation graphs
Siloi, Ilaria; Benedetti, Claudia; Piccinini, Enrico; Paris, Matteo G. A.; Bordone, Paolo
2017-10-01
We address the dynamics of two indistinguishable interacting particles moving on a dynamical percolation graph, i.e., a graph where the edges are independent random telegraph processes whose values jump between 0 and 1, thus mimicking percolation. The interplay between the particle interaction strength, initial state and the percolation rate determine different dynamical regimes for the walkers. We show that, whenever the walkers are initially localised within the interaction range, fast noise enhances the particle spread compared to the noiseless case.
Eising, G.; Kooi, B. J.
2012-01-01
Growth and decay of clusters at temperatures below T-c have been studied for a two-dimensional Ising model for both square and triangular lattices using Monte Carlo (MC) simulations and the enumeration of lattice animals. For the lattice animals, all unique cluster configurations with their internal
Benallou, Amina; Hadri, Baghdad; Martinez-Vega, Juan; El Islam Boukortt, Nour
2018-04-01
The effect of percolation threshold on the behaviour of electrical conductivity at high electric field of insulating polymers has been briefly investigated in literature. Sometimes the dead ends links are not taken into account in the study of the electric field effect on the electrical properties. In this work, we present a theoretical framework and Monte Carlo simulation of the behaviour of the electric conductivity at high electric field based on the percolation theory using the traps energies levels which are distributed according to distribution law (uniform, Gaussian, and power-law). When a solid insulating material is subjected to a high electric field, and during trapping mechanism the dead ends of traps affect with decreasing the electric conductivity according to the traps energies levels, the correlation length of the clusters, the length of the dead ends, and the concentration of the accessible positions for the electrons. A reasonably good agreement is obtained between simulation results and the theoretical framework.
Percolation Analysis of a Wiener Reconstruction of the IRAS 1.2 Jy Redshift Catalog
Yess, Capp; Shandarin, Sergei F.; Fisher, Karl B.
1997-01-01
We present percolation analyses of Wiener reconstructions of the IRAS 1.2 Jy redshift survey. There are 10 reconstructions of galaxy density fields in real space spanning the range β = 0.1-1.0, where β = Ω0.6/b, Ω is the present dimensionless density, and b is the bias factor. Our method uses the growth of the largest cluster statistic to characterize the topology of a density field, where Gaussian randomized versions of the reconstructions are used as standards for analysis. For the reconstruction volume of radius R ~ 100 h-1 Mpc, percolation analysis reveals a slight ``meatball'' topology for the real space, galaxy distribution of the IRAS survey.
Volatility Behaviors of Financial Time Series by Percolation System on Sierpinski Carpet Lattice
Pei, Anqi; Wang, Jun
2015-01-01
The financial time series is simulated and investigated by the percolation system on the Sierpinski carpet lattice, where percolation is usually employed to describe the behavior of connected clusters in a random graph, and the Sierpinski carpet lattice is a graph which corresponds the fractal — Sierpinski carpet. To study the fluctuation behavior of returns for the financial model and the Shanghai Composite Index, we establish a daily volatility measure — multifractal volatility (MFV) measure to obtain MFV series, which have long-range cross-correlations with squared daily return series. The autoregressive fractionally integrated moving average (ARFIMA) model is used to analyze the MFV series, which performs better when compared to other volatility series. By a comparative study of the multifractality and volatility analysis of the data, the simulation data of the proposed model exhibits very similar behaviors to those of the real stock index, which indicates somewhat rationality of the model to the market application.
Nonlinear Analysis on Cross-Correlation of Financial Time Series by Continuum Percolation System
Niu, Hongli; Wang, Jun
We establish a financial price process by continuum percolation system, in which we attribute price fluctuations to the investors’ attitudes towards the financial market, and consider the clusters in continuum percolation as the investors share the same investment opinion. We investigate the cross-correlations in two return time series, and analyze the multifractal behaviors in this relationship. Further, we study the corresponding behaviors for the real stock indexes of SSE and HSI as well as the liquid stocks pair of SPD and PAB by comparison. To quantify the multifractality in cross-correlation relationship, we employ multifractal detrended cross-correlation analysis method to perform an empirical research for the simulation data and the real markets data.
Estimating filtration coefficients for straining from percolation and random walk theories
DEFF Research Database (Denmark)
Yuan, Hao; Shapiro, Alexander; You, Zhenjiang
2012-01-01
In this paper, laboratory challenge tests are carried out under unfavorable attachment conditions, so that size exclusion or straining is the only particle capture mechanism. The experimental results show that far above the percolation threshold the filtration coefficients are not proportional...... size exclusion theory or the model of parallel tubes with mixing chambers, where the filtration coefficients are proportional to the flux through smaller pores, and the predicted penetration depths are much lower. A special capture mechanism is proposed, which makes it possible to explain...... the experimentally observed power law dependencies of filtration coefficients and large penetration depths of particles. Such a capture mechanism is realized in a 2D pore network model with periodical boundaries with the random walk of particles on the percolation lattice. Geometries of infinite and finite clusters...
Percolation Theory and Modern Hydraulic Fracturing
Norris, J. Q.; Turcotte, D. L.; Rundle, J. B.
2015-12-01
During the past few years, we have been developing a percolation model for fracking. This model provides a powerful tool for understanding the growth and properties of the complex fracture networks generated during a modern high volume hydraulic fracture stimulations of tight shale reservoirs. The model can also be used to understand the interaction between the growing fracture network and natural reservoir features such as joint sets and faults. Additionally, the model produces a power-law distribution of bursts which can easily be compared to observed microseismicity.
Use of Invasion Percolation Models To Study the Secondary Migration of Oil and Related Problems
Energy Technology Data Exchange (ETDEWEB)
Wagner, G.
1997-09-01
In oil reservoir engineering, multi-phase displacement processes are important. This doctoral thesis describes simulations of the slow displacement of a wetting fluid by a non-wetting fluid in a complex, random porous medium and in a single fracture. The study is restricted to two-phase flow in the quasi-static limit in which viscous forces can be neglected. The secondary migration of oil takes place in this regime, however, the discussion is broader in scope. The thesis connects the problem of slow two-phase flow to percolation theory and discusses the mechanisms that control immiscible displacements. A new, modified version of the invasion percolation model is used to simulate an imbibition process in a porous medium and the migration of a cluster of non-wetting fluid through a porous medium saturated with a wetting fluid. The simulations include the secondary migration of oil through porous homogeneous rock. Fluid migration through heterogeneous porous media is simulated qualitatively. Slow displacement of a wetting fluid by a non-wetting fluid in a single rock fracture is simulated by using the standard invasion percolation model. Experiments and simulations are performed to study the fragmentation of invasion percolation-like structures of non-wetting fluid in a porous medium saturated with a wetting fluid. A scenario is studied in which a cluster of non-wettable fluid migrates through a porous medium that is saturated with a wetting fluid, the migration being driven by continuously increasing buoyancy forces. There is a simulation of the secondary migration of oil in both two- and three-dimensional media. 361 refs., 115 figs.
International Nuclear Information System (INIS)
Barnes, J.; Dekel, A.; Efstathiou, G.; Frenk, C.S.; Yale Univ., New Haven, CT; California Univ., Santa Barbara; Cambridge Univ., England; Sussex Univ., Brighton, England)
1985-01-01
The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales. 30 references
Plasmonic percolation: Plasmon-manifested dielectric-to-metal transition
Chen, Huanjun
2012-08-28
Percolation generally refers to the phenomenon of abrupt variations in electrical, magnetic, or optical properties caused by gradual volume fraction changes of one component across a threshold in bicomponent systems. Percolation behaviors have usually been observed in macroscopic systems, with most studies devoted to electrical percolation. We report on our observation of plasmonic percolation in Au nanorod core-Pd shell nanostructures. When the Pd volume fraction in the shell consisting of palladium and water approaches the plasmonic percolation threshold, ∼70%, the plasmon of the nanostructure transits from red to blue shifts with respect to that of the unshelled Au nanorod. This plasmonic percolation behavior is also confirmed by the scattering measurements on the individual core-shell nanostructures. Quasistatic theory and numerical simulations show that the plasmonic percolation originates from a positive-to-negative transition in the real part of the dielectric function of the shell as the Pd volume fraction is increased. The observed plasmonic percolation is found to be independent of the metal type in the shell. Moreover, compared to the unshelled Au nanorods with similar plasmon wavelengths, the Au nanorod core-Pd shell nanostructures exhibit larger refractive index sensitivities, which is ascribed to the expulsion of the electric field intensity from the Au nanorod core by the adsorbed Pd nanoparticles. © 2012 American Chemical Society.
Innovation diffusion in networks : the microeconomics of percolation
Zeppini, P.; Frenken, K.; Izquierdo, L.R.
2013-01-01
We implement a diffusion model for an innovative product in a market with a structure of social relationships. Diffusion is described with a percolation approach in the price space. Percolation shows a phase transition from a diffusion to a no-diffusion regime. This has strong implications for
Innovation diffusion in networks: the microeconomics of percolation
Zeppini, P.; Frenken, K.; Izquierdo, L.R.
2013-01-01
We implement a diffusion model for an innovative product in a market with a structure of social relationships. Diffusion is described with a percolation approach in the price space. Percolation shows a phase transition from a diffusion to a no-diffusion regime. This has strong implications for
Percolation of overlapping squares or cubes on a lattice
International Nuclear Information System (INIS)
Koza, Zbigniew; Kondrat, Grzegorz; Suszczyński, Karol
2014-01-01
Porous media are often modeled as systems of overlapping obstacles, which leads to the problem of two percolation thresholds in such systems, one for the porous matrix and the other for the void space. Here we investigate these percolation thresholds in the model of overlapping squares or cubes of linear size k > 1 randomly distributed on a regular lattice. We find that the percolation threshold of obstacles is a nonmonotonic function of k, whereas the percolation threshold of the void space is well approximated by a function linear in 1/k. We propose a generalization of the excluded volume approximation to discrete systems and use it to investigate the transition between continuous and discrete percolation, finding a remarkable agreement between the theory and numerical results. We argue that the continuous percolation threshold of aligned squares on a plane is the same for the solid and void phases and estimate the continuous percolation threshold of the void space around aligned cubes in a 3D space as 0.036(1). We also discuss the connection of the model to the standard site percolation with complex neighborhood. (paper)
Plasmonic percolation: Plasmon-manifested dielectric-to-metal transition
Chen, Huanjun; Wang, Feng; Li, Kun; Woo, Katchoi; Wang, Jianfang; Li, Quan; Sun, Ling Dong; Zhang, Xixiang; Lin, Haiqing; YAN, Chunhua
2012-01-01
Percolation generally refers to the phenomenon of abrupt variations in electrical, magnetic, or optical properties caused by gradual volume fraction changes of one component across a threshold in bicomponent systems. Percolation behaviors have usually been observed in macroscopic systems, with most studies devoted to electrical percolation. We report on our observation of plasmonic percolation in Au nanorod core-Pd shell nanostructures. When the Pd volume fraction in the shell consisting of palladium and water approaches the plasmonic percolation threshold, ∼70%, the plasmon of the nanostructure transits from red to blue shifts with respect to that of the unshelled Au nanorod. This plasmonic percolation behavior is also confirmed by the scattering measurements on the individual core-shell nanostructures. Quasistatic theory and numerical simulations show that the plasmonic percolation originates from a positive-to-negative transition in the real part of the dielectric function of the shell as the Pd volume fraction is increased. The observed plasmonic percolation is found to be independent of the metal type in the shell. Moreover, compared to the unshelled Au nanorods with similar plasmon wavelengths, the Au nanorod core-Pd shell nanostructures exhibit larger refractive index sensitivities, which is ascribed to the expulsion of the electric field intensity from the Au nanorod core by the adsorbed Pd nanoparticles. © 2012 American Chemical Society.
Anaerobic Treatment Of Percolate From Faecal Sludge Drying Beds ...
African Journals Online (AJOL)
Composite percolate samples, from sludge drying beds of a pilot co-composting plant in Kumasi, Ghana, were characterised and subjected to laboratory scale anaerobic treatment. Two categories of percolate samples were investigated; samples seeded with anaerobic sludge and samples without seeding. The average ...
Definition of percolation thresholds on self-affine surfaces
Marrink, S.J.; Paterson, Lincoln; Knackstedt, Mark A.
2000-01-01
We study the percolation transition on a two-dimensional substrate with long-range self-affine correlations. We find that the position of the percolation threshold on a correlated lattice is no longer unique and depends on the spanning rule employed. Numerical results are provided for spanning
Inactivation of VHSV by Percolation and Salt Under Experimental Conditions
DEFF Research Database (Denmark)
Skall, Helle Frank; Olesen, Niels Jørgen; Jørgensen, Claus
2012-01-01
At the moment the only legal method in Denmark to sanitize wastewater from fish cutting plants is by percolation. To evaluate the inactivation effect of percolation on VHSV an experimental examination was initiated. A column packed with gravel as top- and bottom layer (total of 22 cm) and a mid l...
The relationship between synchronization and percolation for regular networks
Li, Zhe; Ren, Tao; Xu, Yanjie; Jin, Jianyu
2018-02-01
Synchronization and percolation are two essential phenomena in complex dynamical networks. They have been studied widely, but previously treated as unrelated. In this paper, the relationship between synchronization and percolation are revealed for regular networks. Firstly, we discovered a bridge between synchronization and percolation by using the eigenvalues of the Laplacian matrix to describe the synchronizability and using the eigenvalues of the adjacency matrix to describe the percolation threshold. Then, we proposed a method to find the relationship for regular networks based on the topology of networks. Particularly, if the degree distribution of the network is subject to delta function, we show that only the eigenvalues of the adjacency matrix need to be calculated. Finally, several examples are provided to demonstrate how to apply our proposed method to discover the relationship between synchronization and percolation for regular networks.
Nazarieh, F.; Ansari, H.; Ziaei, A. N.; Izady, A.; Davari, K.; Brunner, P.
2018-05-01
The time required for deep percolating water to reach the water table can be considerable in areas with a thick vadose zone. Sustainable groundwater management, therefore, has to consider the spatial and temporal dynamics of groundwater recharge. The key parameters that control the lag time have been widely examined in soil physics using small-scale lysimeters and modeling studies. However, only a small number of studies have analyzed how deep-percolation rates affect groundwater recharge dynamics over large spatial scales. This study examined how the parameters influencing lag time affect groundwater recharge in a semi-arid catchment under irrigation (in northeastern Iran) using a numerical modeling approach. Flow simulations were performed by the MODFLOW-NWT code with the Vadose-Zone Flow (UZF) Package. Calibration of the groundwater model was based on data from 48 observation wells. Flow simulations showed that lag times vary from 1 to more than 100 months. A sensitivity analysis demonstrated that during drought conditions, the lag time was highly sensitive to the rate of deep percolation. The study illustrated two critical points: (1) the importance of providing estimates of the lag time as a basis for sustainable groundwater management, and (2) lag time not only depends on factors such as soil hydraulic conductivity or vadose zone depth but also depends on the deep-percolation rates and the antecedent soil-moisture condition. Therefore, estimates of the lag time have to be associated with specific percolation rates, in addition to depth to groundwater and soil properties.
Leveraging percolation theory to single out influential spreaders in networks
Radicchi, Filippo; Castellano, Claudio
2016-06-01
Among the consequences of the disordered interaction topology underlying many social, technological, and biological systems, a particularly important one is that some nodes, just because of their position in the network, may have a disproportionate effect on dynamical processes mediated by the complex interaction pattern. For example, the early adoption of a commercial product by an opinion leader in a social network may change its fate or just a few superspreaders may determine the virality of a meme in social media. Despite many recent efforts, the formulation of an accurate method to optimally identify influential nodes in complex network topologies remains an unsolved challenge. Here, we present the exact solution of the problem for the specific, but highly relevant, case of the susceptible-infected-removed (SIR) model for epidemic spreading at criticality. By exploiting the mapping between bond percolation and the static properties of the SIR model, we prove that the recently introduced nonbacktracking centrality is the optimal criterion for the identification of influential spreaders in locally tree-like networks at criticality. By means of simulations on synthetic networks and on a very extensive set of real-world networks, we show that the nonbacktracking centrality is a highly reliable metric to identify top influential spreaders also in generic graphs not embedded in space and for noncritical spreading.
Simoes, Ricardo; Silva, Jaime; Vaia, Richard; Sencadas, Vítor; Costa, Pedro; Gomes, João; Lanceros-Méndez, Senentxu
2009-01-21
The low concentration behaviour and the increase of the dielectric constant in carbon nanotubes/polymer nanocomposites near the percolation threshold are still not well understood. In this work, a numerical model has been developed which focuses on the effect of the inclusion of conductive fillers in a dielectric polymer matrix on the dielectric constant and the dielectric strength. Experiments have been carried out in carbon nanotubes/poly(vinylidene fluoride) nanocomposites in order to compare to the simulation results. This work shows how the critical concentration is related to the formation of capacitor networks and that these networks give rise to high variations in the electrical properties of the composites. Based on numerical studies, the dependence of the percolation transition on the preparation of the nanocomposite is discussed. Finally, based on numerical and experimental results, both ours and from other authors, the causes of anomalous percolation behaviour of the dielectric constant are identified.
Frozen into stripes: fate of the critical Ising model after a quench.
Blanchard, T; Picco, M
2013-09-01
In this article we study numerically the final state of the two-dimensional ferromagnetic critical Ising model after a quench to zero temperature. Beginning from equilibrium at T_{c}, the system can be blocked in a variety of infinitely long lived stripe states in addition to the ground state. Similar results have already been obtained for an infinite temperature initial condition and an interesting connection to exact percolation crossing probabilities has emerged. Here we complete this picture by providing an example of stripe states precisely related to initial crossing probabilities for various boundary conditions. We thus show that this is not specific to percolation but rather that it depends on the properties of spanning clusters in the initial state.
Effects of surfaces on resistor percolation.
Stenull, O; Janssen, H K; Oerding, K
2001-05-01
We study the effects of surfaces on resistor percolation at the instance of a semi-infinite geometry. Particularly we are interested in the average resistance between two connected ports located on the surface. Based on general grounds as symmetries and relevance we introduce a field theoretic Hamiltonian for semi-infinite random resistor networks. We show that the surface contributes to the average resistance only in terms of corrections to scaling. These corrections are governed by surface resistance exponents. We carry out renormalization-group improved perturbation calculations for the special and the ordinary transition. We calculate the surface resistance exponents phiS and phiS(infinity) for the special and the ordinary transition, respectively, to one-loop order.
Kocic, Aleksandar; Wang, K C
1993-01-01
We simulate four flavor noncompact lattice QED using the Hybrid Monte Carlo algorithm on $10^4$ and $16^4$ lattices. Measurements of the monopole susceptibility and the percolation order parameter indicate a transition at $\\beta = {1/e^2} = .205(5)$ with critical behavior in the universality class of four dimensional percolation. We present accurate chiral condensate measurements and monitor finite size effects carefully. The chiral condensate data supports the existence of a power-law transition at $\\beta = .205$ in the same universality class as the chiral transition in the two flavor model. The resulting equation of state predicts the mass ratio $m_\\pi^2/m_\\sigma^2$ in good agreement with spectrum calculations while the hypothesis of a logarithmically improved mean field theory fails qualitatively.
Current flow in random resistor networks: the role of percolation in weak and strong disorder.
Wu, Zhenhua; López, Eduardo; Buldyrev, Sergey V; Braunstein, Lidia A; Havlin, Shlomo; Stanley, H Eugene
2005-04-01
We study the current flow paths between two edges in a random resistor network on a L X L square lattice. Each resistor has resistance e(ax) , where x is a uniformly distributed random variable and a controls the broadness of the distribution. We find that: (a) The scaled variable u identical with u congruent to L/a(nu) , where nu is the percolation connectedness exponent, fully determines the distribution of the current path length l for all values of u . For u > 1, the behavior corresponds to the weak disorder limit and l scales as l approximately L, while for u < 1 , the behavior corresponds to the strong disorder limit with l approximately L(d(opt) ), where d(opt) =1.22+/-0.01 is the optimal path exponent. (b) In the weak disorder regime, there is a length scale xi approximately a(nu), below which strong disorder and critical percolation characterize the current path.
Percolation transition in carbon composite on the basis of fullerenes and exfoliated graphite
Berezkin, V. I.; Popov, V. V.
2018-01-01
The electrical conductivity of a carbon composite on the basis of C60 fullerenes and exfoliated graphite is investigated in the range of relative contents of components from 0 to 100%. The samples are obtained by the thermal treatment of the initial dispersed mixtures in vacuum in the diffusion-adsorption process and their further cold pressing. The resistivity of the samples gradually increases with an increase in the fraction of fullerenes, and a sharp transition from the conductive state to the dielectric one is observed after achieving certain concentrations of C60. The interpretation of the results within the percolation theory makes it possible to evaluate the percolation threshold (expressed as a relative content of graphite) as equal to 4.45 wt % and the critical conductivity index as equal to 1.85 (which is typical for three-dimensional twocomponent disordered media including those having pores).
Ji, Shenggong; Lü, Linyuan; Yeung, Chi Ho; Hu, Yanqing
2017-07-01
Social networks constitute a new platform for information propagation, but its success is crucially dependent on the choice of spreaders who initiate the spreading of information. In this paper, we remove edges in a network at random and the network segments into isolated clusters. The most important nodes in each cluster then form a set of influential spreaders, such that news propagating from them would lead to extensive coverage and minimal redundancy. The method utilizes the similarities between the segmented networks before percolation and the coverage of information propagation in each social cluster to obtain a set of distributed and coordinated spreaders. Our tests of implementing the susceptible-infected-recovered model on Facebook and Enron email networks show that this method outperforms conventional centrality-based methods in terms of spreadability and coverage redundancy. The suggested way of identifying influential spreaders thus sheds light on a new paradigm of information propagation in social networks.
Effect of diffusion on percolation threshold in thick-film resistors
International Nuclear Information System (INIS)
Abdurakhmanov, G.
2009-01-01
Resistivity ρ(C) of thick-film resistors doped by metal oxides is simulated as a function of volume content C of the ligature, firing temperature T f and firing time τ. It is proved that the doping of a glass during firing of the thick film resistor is rather uniform. It is shown also, that conductance takes place in the whole volume of the sample, but not through the sole infinite cluster only, even the content of a conductive phase is below than the theoretical percolation threshold value.
Connectivity: a primer in phase transitions and critical phenomena for students of particle physics
International Nuclear Information System (INIS)
Stanley, H.E.
1983-01-01
This introduction to the phase transitions and critical phenomena focuses on the theme of connectivity, and illustrates concepts with a paradigm of connectivity, such as the percolation problem. The phenomenon of bond percolation, where a finite section of ''fence'' has both conducting and insulating links, is described. Three approaches to the study of connectivity phenomena are described: exact enumeration procedures, Monte Carlo simulation, and renormalization groups. Exact enumeration probabilities are calculated. Lattice animals are discussed. Computer simulation is described as simple: assign random numbers, then design algorithms that recognize clusters. The Monte Carlo simulations have not lead to higher accuracy in predicting critical exponents, but have given a graphic illustration of what a million-site cluster looks like. The incipient infinite cluster can also be described. In this case, the magnetic correlations of a dilute magnetic system will spread along the ''backbone bonds'' rather than by ''dangling ends.'' Renormalization group approaches are also treated. Finally, relations between connectivity and models of critical thermal phenomena such as the Ising Model, the Potts model, and polychromatic generalization of the Potts Model, are discussed
Energy Technology Data Exchange (ETDEWEB)
Rubio, B; Nombela, M. A; Vilas, F [Departamento de Geociencias Marinas y Ordenacion del Territorio, Vigo, Espana (Spain)
2001-06-01
The indiscriminate use of cluster analysis to distinguish contaminated and non-contaminated sediments has led us to make a comparative evaluation of different cluster analysis procedures as applied to heavy metal concentrations in subtidal sediments from the Ria de Vigo, NW Spain. The use of different clusters algorithms and other transformations from the same departing set of data lead to the formation of different clusters with a clear inconclusive result about the contamination status of the sediments. The results show that this approach is better suited to identifying groups of samples differing in sedimentological characteristics, such as grain size, rather than in the degree of contamination. Our main aim is to call attention to these aspects in cluster analysis and to suggest that researches should be rigorous with this kind of analysis. Finally, the use of discriminate analysis allows us to find a discriminate function that separates the samples into two clearly differentiated groups, which should not be treated jointly. [Spanish] El uso indiscriminado del analisis cluster para distinguir sedimentos contaminados y no contaminados nos ha llevado a realizar una evaluacion comparativa entre los diferentes procedimientos de estos analisis aplicada a la concentracion de metales pesados en sedimentos submareales de la Ria de Vigo, NW de Espana. La utilizacion de distintos algoritmos de cluster, asi como otras transformaciones de la misma matriz de datos conduce a la formacion de diferentes clusters con un resultado inconcluso sobre el estado de contaminacion de los sedimentos. Los resultados muestran que esta aproximacion se ajusta mejor para identificar grupos de muestras que difieren en caracteristicas sedimentologicas, tal como el tamano de grano, mas que el grado de contaminacion. El principal objetivo es llamar la atencion sobre estos aspectos del analisis cluster y sugerir a los investigadores que sean rigurosos con este tipo de analisis. Finalmente el uso
Percolation dans des reseaux realistes de nanostructures de carbone
Simoneau, Louis-Philippe
versatility in the choice of network components that can be simulated. The tools we have developed, grouped together in the RPH-HPN software Reseaux percolatifs hybrides - Hybrid Percolation Networks, construct random networks, detect contact between the tubes, translate the systems to equivalent electrical circuits and calculate global properties. An infinity of networks can have the same basic characteristics (size, diameter, etc.) and therefore the properties of a particular random network are not necessarily representative of the average properties of all networks. To obtain those general properties, we simulate a large number of random networks with the same basic characteristics and the average of the quantities is determined. The network constituent elements can be spheres, rods or snakes. The use of such geometries for network elements makes contact detection simple and quick, and more faithfully reproduce the form of carbon nanotubes. We closely monitor the geometrical and electrical properties of these elements through stochastic distributions of our choice. We can choose the length, diameter, orientation, chirality, tortuosity and impenetrable nature of the elements in order to properly reproduce real networks characteristics. We have considered statistical distribution functions that are rectangular, Gaussian, and Lorentzian, but all other distributions that can be expressed mathematically can also be envisioned. During the creation of a particular network, we generate the elements one by one. Each of their properties is sampled from a preselected distribution. Efficient algorithms used in various fields were adapted to our needs to manage the detection of contacts, clusters and percolation. In addition, we model more realistic contact between rigid nanotubes using an original method used to create the network that does not require a relaxation phase. Finally, we use Kirchhoff's laws to solve the equivalent electrical circuit conventionally. First, we evaluated
Percolation on shopping and cashback electronic commerce networks
Fu, Tao; Chen, Yini; Qin, Zhen; Guo, Liping
2013-06-01
Many realistic networks live in the form of multiple networks, including interacting networks and interdependent networks. Here we study percolation properties of a special kind of interacting networks, namely Shopping and Cashback Electronic Commerce Networks (SCECNs). We investigate two actual SCECNs to extract their structural properties, and develop a mathematical framework based on generating functions for analyzing directed interacting networks. Then we derive the necessary and sufficient condition for the absence of the system-wide giant in- and out- component, and propose arithmetic to calculate the corresponding structural measures in the sub-critical and supercritical regimes. We apply our mathematical framework and arithmetic to those two actual SCECNs to observe its accuracy, and give some explanations on the discrepancies. We show those structural measures based on our mathematical framework and arithmetic are useful to appraise the status of SCECNs. We also find that the supercritical regime of the whole network is maintained mainly by hyperlinks between different kinds of websites, while those hyperlinks between the same kinds of websites can only enlarge the sizes of in-components and out-components.
Practical Guidelines for Water Percolation Capacity Determination of the Ground
Directory of Open Access Journals (Sweden)
Mihael Brenčič
2011-06-01
Full Text Available Determination of water infiltration capacity of ground soils and rocks represents important part of design and construction procedures of the facilities for the infiltration of clean precipitation water. With their help percolation capacity of ground as well as response of the infiltration facilities to the inflowing precipitation water is estimated.Comparing to other in situ hydrogeological tests they can be understood as simple. However, in every day’s practiceseveral problems during their on site application and desk interpretation can arise. Paper represents review of existingpractical engineering procedures during the performance of percolation tests. Procedures are described for the borehole and shaft percolation tests execution and calculation theory for stationary and non‑stationary percolation tests are given. Theory is illustrated with practical exercises. Interpretations of typical departures from theoretical presumptions according to Hvorslev test of non-stationary test are illustrated.
Percolation of polyatomic species on site diluted lattices
International Nuclear Information System (INIS)
Cornette, V.; Ramirez-Pastor, A.J.; Nieto, F.
2006-01-01
In this Letter, the percolation of (a) linear segments of size k and (b) k-mers (particles occupying k adjacent sites) of different structures and forms deposited on a diluted square lattice have been studied. The diluted lattice is built by randomly selecting a fraction of sites which are considered forbidden for deposition. The analysis of the obtained results is made in the framework of the finite size scaling theory. The characteristic parameters of the percolation problem are dependent not only on the form and structure of the k-mers but also on the properties of the lattice where they are deposited. A phase diagram separating a percolating from a non-percolating region is determined and discussed
Aerodynamics and Percolation: Unfolding Laminar Separation Bubble on Airfoils
Traphan, Dominik; Wester, Tom T. B.; Gülker, Gerd; Peinke, Joachim; Lind, Pedro G.
2018-04-01
As a fundamental phenomenon of fluid mechanics, recent studies suggested laminar-turbulent transition belonging to the universality class of directed percolation. Here, the onset of a laminar separation bubble on an airfoil is analyzed in terms of the directed percolation model using particle image velocimetry data. Our findings indicate a clear significance of percolation models in a general flow situation beyond fundamental ones. We show that our results are robust against fluctuations of the parameter, namely, the threshold of turbulence intensity, that maps velocimetry data into binary cells (turbulent or laminar). In particular, this percolation approach enables the precise determination of the transition point of the laminar separation bubble, an important problem in aerodynamics.
50 years of first-passage percolation
Auffinger, Antonio; Hanson, Jack
2017-01-01
First-passage percolation (FPP) is a fundamental model in probability theory that has a wide range of applications to other scientific areas (growth and infection in biology, optimization in computer science, disordered media in physics), as well as other areas of mathematics, including analysis and geometry. FPP was introduced in the 1960s as a random metric space. Although it is simple to define, and despite years of work by leading researchers, many of its central problems remain unsolved. In this book, the authors describe the main results of FPP, with two purposes in mind. First, they give self-contained proofs of seminal results obtained until the 1990s on limit shapes and geodesics. Second, they discuss recent perspectives and directions including (1) tools from metric geometry, (2) applications of concentration of measure, and (3) related growth and competition models. The authors also provide a collection of old and new open questions. This book is intended as a textbook for a graduate course or as a...
Long range correlations, event simulation and parton percolation
International Nuclear Information System (INIS)
Pajares, C.
2011-01-01
We study the RHIC data on long range rapidity correlations, comparing their main trends with different string model simulations. Particular attention is paid to color percolation model and its similarities with color glass condensate. As both approaches corresponds, at high density, to a similar physical picture, both of them give rise to a similar behavior on the energy and the centrality of the main observables. Color percolation explains the transition from low density to high density.
Application of percolation leaching in Fuzhou uranium mine
International Nuclear Information System (INIS)
Jiang Lang; Wang Haita; He Jiangming
2006-01-01
In order to solve these problems such as high cost by conventional agitation leaching, low permeability and low leaching rate by heap leach, a percolation leaching method was developed. Two-year's production results show that leaching rate of uranium is up to 90% by this method. Compared with conventional agitation leaching, the power, sulfuric acid and lime consumption by the percolation leaching decreased by 60%, 27% and 77% respectively. (authors)
Estimation of water percolation by different methods using TDR
Directory of Open Access Journals (Sweden)
Alisson Jadavi Pereira da Silva
2014-02-01
Full Text Available Detailed knowledge on water percolation into the soil in irrigated areas is fundamental for solving problems of drainage, pollution and the recharge of underground aquifers. The aim of this study was to evaluate the percolation estimated by time-domain-reflectometry (TDR in a drainage lysimeter. We used Darcy's law with K(θ functions determined by field and laboratory methods and by the change in water storage in the soil profile at 16 points of moisture measurement at different time intervals. A sandy clay soil was saturated and covered with plastic sheet to prevent evaporation and an internal drainage trial in a drainage lysimeter was installed. The relationship between the observed and estimated percolation values was evaluated by linear regression analysis. The results suggest that percolation in the field or laboratory can be estimated based on continuous monitoring with TDR, and at short time intervals, of the variations in soil water storage. The precision and accuracy of this approach are similar to those of the lysimeter and it has advantages over the other evaluated methods, of which the most relevant are the possibility of estimating percolation in short time intervals and exemption from the predetermination of soil hydraulic properties such as water retention and hydraulic conductivity. The estimates obtained by the Darcy-Buckingham equation for percolation levels using function K(θ predicted by the method of Hillel et al. (1972 provided compatible water percolation estimates with those obtained in the lysimeter at time intervals greater than 1 h. The methods of Libardi et al. (1980, Sisson et al. (1980 and van Genuchten (1980 underestimated water percolation.
Social percolation and the influence of mass media
Proykova, Ana; Stauffer, Dietrich
2002-09-01
In the marketing model of Solomon and Weisbuch, people buy a product only if their neighbours tell them of its quality, and if this quality is higher than their own quality expectations. Now we introduce additional information from the mass media, which is analogous to the ghost field in percolation theory. The mass media shift the percolative phase transition observed in the model, and decrease the time after which the stationary state is reached.
A new approach for multicriticality in directed and diode percolation
International Nuclear Information System (INIS)
Tsallis, C.; Boston Univ., MA; Redner, S.
1983-01-01
A new and very simple model for treating directed and more general diode percolation problems is presented, by allowing neighboring sites to be joined by up to two independent bonds of opposite orientations. A generalized 'break-collapse' method is developed to calculate renormalization group recursion relations. On the square lattice, a very symmetric phase diagram is obtained which displays multicritical percolation phenomena, and a variety of interesting conductivity transitions are predicted. (Author) [pt
Analysis of radionuclide transport through fracture networks by percolation theory
International Nuclear Information System (INIS)
Ahn, Joonhong; Furuhama, Yutaka; Li, Yadong; Suzuki, Atsuyuki
1991-01-01
Presented are results of numerical simulations for radionuclide diffusion through fracture networks in geologic layers. Actual fracture networks are expressed as two-dimensional honeycomb percolation lattices. Random-walk simulations of diffusion on percolation lattices are made by the exact-enumeration method, and compared with those from Fickian diffusion with constant and decreasing diffusion coefficients. Mean-square displacement of a random-walker on percolation lattices increases more slowly with time than that for Fickian diffusion with the constant diffusion coefficient. Though the same relation of mean-square displacement vs. time as for the percolation lattices can be obtained for a continuum with decreasing diffusion coefficients, spatial distribution of probability densities of finding the random-walker on the percolation lattice differs from that on a continuum with the decreasing diffusion coefficient. The percolation model results in slow spreading near the origin and fast spreading in the outer region, whereas the decreasing-diffusion coefficient model shows the reverse because of smaller diffusion coefficient in the outer region. We could derive a general formula that can include both Fickian and anomalous diffusion in terms of fractal and fracton dimensionalities and the anomalous diffusion exponent. (author)
Multiscale synchrony behaviors of paired financial time series by 3D multi-continuum percolation
Wang, M.; Wang, J.; Wang, B. T.
2018-02-01
Multiscale synchrony behaviors and nonlinear dynamics of paired financial time series are investigated, in an attempt to study the cross correlation relationships between two stock markets. A random stock price model is developed by a new system called three-dimensional (3D) multi-continuum percolation system, which is utilized to imitate the formation mechanism of price dynamics and explain the nonlinear behaviors found in financial time series. We assume that the price fluctuations are caused by the spread of investment information. The cluster of 3D multi-continuum percolation represents the cluster of investors who share the same investment attitude. In this paper, we focus on the paired return series, the paired volatility series, and the paired intrinsic mode functions which are decomposed by empirical mode decomposition. A new cross recurrence quantification analysis is put forward, combining with multiscale cross-sample entropy, to investigate the multiscale synchrony of these paired series from the proposed model. The corresponding research is also carried out for two China stock markets as comparison.
Use of Invasion Percolation Models To Study the Secondary Migration of Oil and Related Problems
Energy Technology Data Exchange (ETDEWEB)
Wagner, G.
1997-12-31
This thesis studies simulations of the slow displacement of a wetting fluid by a non-wetting fluid in porous media and in a single fracture. The simulations are based on the invasion percolation model. New modified versions of the model are presented that simulate migration, fragmentation and coalescence processes of the clusters of non-wetting fluid. The resulting displacement patterns are characterized by scaling laws. In particular, simulations of the secondary migration of oil through porous homogeneous rock are discussed. Fractured rocks are extreme cases of inhomogeneous porous media. Simulations of the slow displacement of a wetting fluid by a non-wetting fluid in a single fracture using the standard invasion model are presented. There is a discussion of a scenario in which a cluster of non-wetting fluid migrates through a porous medium that was saturated with a wetting fluid. The migration is driven by continuously driven buoyancy forces. Both experiments and simulations are described. The same scenario is also studied theoretically and by simulations using a simplified percolation model of fluid migration in one dimension. The migration model in two dimensions, with constant buoyancy forces, is also discussed. Simulations of fluid migration, such as the secondary migration of oil, in two- and three-dimensional media are examined, the media having multi-affine properties rather than being homogeneous. Slow immiscible displacement processes in single fractures are studied using fractal geometries to model single fractures. 167 refs., 123 figs.
Negishi, Yuichi; Nakazaki, Tafu; Malola, Sami; Takano, Shinjiro; Niihori, Yoshiki; Kurashige, Wataru; Yamazoe, Seiji; Tsukuda, Tatsuya; Häkkinen, Hannu
2015-01-28
We report on how the transition from the bulk structure to the cluster-specific structure occurs in n-dodecanethiolate-protected gold clusters, Au(n)(SC12)m. To elucidate this transition, we isolated a series of Au(n)(SC12)m in the n range from 38 to ∼520, containing five newly identified or newly isolated clusters, Au104(SC12)45, Au(∼226)(SC12)(∼76), Au(∼253)(SC12)(∼90), Au(∼356)(SC12)(∼112), and Au(∼520)(SC12)(∼130), using reverse-phase high-performance liquid chromatography. Low-temperature optical absorption spectroscopy, powder X-ray diffractometry, and density functional theory (DFT) calculations revealed that the Au cores of Au144(SC12)60 and smaller clusters have molecular-like electronic structures and non-fcc geometric structures, whereas the structures of the Au cores of larger clusters resemble those of the bulk gold. A new structure model is proposed for Au104(SC12)45 based on combined approach between experiments and DFT calculations.
Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials
International Nuclear Information System (INIS)
Suzdalev, I.P.
2005-01-01
Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered
Buick, Otto; Falcon, Pat; Alexander, G.; Siegel, Edward Carl-Ludwig
2013-03-01
Einstein[Dover(03)] critical-slowing-down(CSD)[Pais, Subtle in The Lord; Life & Sci. of Albert Einstein(81)] is Siegel CyberWar denial-of-access(DOA) operations-research queuing theory/pinning/jamming/.../Read [Aikido, Aikibojitsu & Natural-Law(90)]/Aikido(!!!) phase-transition critical-phenomenon via Siegel DIGIT-Physics (Newcomb[Am.J.Math. 4,39(1881)]-{Planck[(1901)]-Einstein[(1905)])-Poincare[Calcul Probabilités(12)-p.313]-Weyl [Goett.Nachr.(14); Math.Ann.77,313 (16)]-{Bose[(24)-Einstein[(25)]-Fermi[(27)]-Dirac[(1927)]}-``Benford''[Proc.Am.Phil.Soc. 78,4,551 (38)]-Kac[Maths.Stat.-Reasoning(55)]-Raimi[Sci.Am. 221,109 (69)...]-Jech[preprint, PSU(95)]-Hill[Proc.AMS 123,3,887(95)]-Browne[NYT(8/98)]-Antonoff-Smith-Siegel[AMS Joint-Mtg.,S.-D.(02)] algebraic-inversion to yield ONLY BOSE-EINSTEIN QUANTUM-statistics (BEQS) with ZERO-digit Bose-Einstein CONDENSATION(BEC) ``INTERSECTION''-BECOME-UNION to Barabasi[PRL 876,5632(01); Rev.Mod.Phys.74,47(02)...] Network /Net/GRAPH(!!!)-physics BEC: Strutt/Rayleigh(1881)-Polya(21)-``Anderson''(58)-Siegel[J.Non-crystalline-Sol.40,453(80)
Lignes de percolation dans un fluide supercritique
Sator , Nicolas
2000-01-01
Daniel BEYSENS rapporteur Xavier CAMPI directeur de thèse Antonio CONIGLIO Hans HERRMANN rapporteur Hendrik-Jan HILHORST président Hubert KRIVINE co-directeur de thèse Dominique LEVESQUE invité; The aim of this thesis is to establish the correspondence between the phase diagram of a simple fluid and its microscopic structure in terms of clusters of particles. Large scale Monte-Carlo and molecular dynamics calculations suggest that self-bound clusters are present in the supercritical phase, th...
Sharma, Manu; Sharma, Vinay; Majumdar, Dipak K.
2014-01-01
The binary mixture tablets of papain and microcrystalline cellulose (MCC), dicalcium phosphate dihydrate (DCP), carrageenan, tragacanth, and agar were prepared by direct compression. Carrageenan, tragacanth, and agar provided maximum protection to enzyme activity compared to MCC and DCP. However, stability studies indicated highest loss of enzyme activity with carrageenan, tragacanth, and agar. Therefore, compression behaviour of different binary mixtures of papain with MCC at different compaction pressures, that is, 40–280 MPa, was studied according to Heckel equation. The compressibility studies of binary mixtures indicated brittle behavior of papain. The application of percolation theory on the relationship between critical density as a function of enzyme activity and mixture composition revealed the presence of percolation threshold for binary mixture. Papain-MCC mixture composition showed significant percolation threshold at 18.48% (w/w) papain loading. Microcrystalline cellulose provided higher protection during stability study. However, higher concentrations of microcrystalline cellulose, probably as dominant particles, do not protect the enzyme with their plastic deformation. Below the percolation threshold, that is, 18.48% (w/w) papain amount in mixture with plastic excipient, activity loss increases strongly because of higher shearing forces during compaction due to system dominance of plastic particles. This mixture range should therefore be avoided to get robust formulation of papain. PMID:27350972
Bondar, N. V.; Brodyn, M. S.
2010-03-01
In two-phase disordered media composed of borosilicate glass with ZnSe or CdS quantum dots, the formation of a phase percolation transition of carriers for near-threshold concentrations that are manifested in optical spectra has been observed. Microscopic fluctuations of the quantum-dot density near the percolation threshold were found that resembled the phenomenon of critical opalescence, where similar fluctuations of the density of a pure substance appear near to a phase transition. It is proposed that the dielectric mismatch between a matrix and ZnSe or CdS quantum dots plays a significant role in the carrier (exciton) delocalization, resulting in the appearance of a “dielectric Coulomb trap” beyond the QD border and the formation of surface states of excitons. The spatial overlapping of excitonic states at the critical density of quantum dots results in a tunneling of carriers and the formation of a phase percolation transition in such media.
Effect of sorbic acid doping on flux pinning in bulk MgB2 with the percolation model
International Nuclear Information System (INIS)
Yang, Y.; Cheng, C.H.; Wang, L.; Sun, H.H.; Zhao, Y.
2010-01-01
In this paper, we study the doping effect of sorbic acid (C 6 H 8 O 2 ), from 0 to 20 wt.% of the total MgB 2 , on critical temperature (T c ), critical current density (J c ), irreversibility field (H irr ) and crystalline structure. The XRD patterns of samples show a slightly decrease in a-axis lattice parameter for doped samples, due to the partial substitution of carbon at boron site. On the other hand, we investigate the influence of doping on the behavior of flux pinning and J c (B) in the framework of percolation theory and it is found that the J c (B) behavior could be well fitted in high field region. The two key parameters, anisotropy and percolation threshold, play very important roles. It is believed that the enhancement of J c is due to the reduction of anisotropy in high field region.
Percolation effects in supercapacitors with thin, transparent carbon nanotube electrodes.
King, Paul J; Higgins, Thomas M; De, Sukanta; Nicoloso, Norbert; Coleman, Jonathan N
2012-02-28
We have explored the effects of percolation on the properties of supercapacitors with thin nanotube networks as electrodes. We find the equivalent series resistance, R(ESR), and volumetric capacitance, C(V), to be thickness independent for relatively thick electrodes. However, once the electrode thickness falls below a threshold thickness (∼100 nm for R(ESR) and ∼20 nm for C(V)), the properties of the electrode become thickness dependent. We show the thickness dependence of both R(ESR) and C(V) to be consistent with percolation theory. While this is expected for R(ESR), that the capacitance follows a percolation scaling law is not. This occurs because, for sparse networks, the capacitance is proportional to the fraction of nanotubes connected to the main network. This fraction, in turn, follows a percolation scaling law. This allows us to understand and quantify the limitations on the achievable capacitance for transparent supercapacitors. We find that supercapacitors with thickness independent R(ESR) and C(V) occupy a well-defined region of the Ragone plot. However, supercapacitors whose electrodes are limited by percolation occupy a long tail to lower values of energy and power density. For example, replacing electrodes with transparency of T = 80% with thinner networks displaying T = 97% will result in a 20-fold reduction of both power and energy density.
Bounds for percolation thresholds on directed and undirected graphs
Hamilton, Kathleen; Pryadko, Leonid
2015-03-01
Percolation theory is an efficient approach to problems with strong disorder, e.g., in quantum or classical transport, composite materials, and diluted magnets. Recently, the growing role of big data in scientific and industrial applications has led to a renewed interest in graph theory as a tool for describing complex connections in various kinds of networks: social, biological, technological, etc. In particular, percolation on graphs has been used to describe internet stability, spread of contagious diseases and computer viruses; related models describe market crashes and viral spread in social networks. We consider site-dependent percolation on directed and undirected graphs, and present several exact bounds for location of the percolation transition in terms of the eigenvalues of matrices associated with graphs, including the adjacency matrix and the Hashimoto matrix used to enumerate non-backtracking walks. These bounds correspond t0 a mean field approximation and become asymptotically exact for graphs with no short cycles. We illustrate this convergence numerically by simulating percolation on several families of graphs with different cycle lengths. This research was supported in part by the NSF Grant PHY-1416578 and by the ARO Grant W911NF-11-1-0027.
Multi-Type Directed Scale-Free Percolation
International Nuclear Information System (INIS)
Shang Yilun
2012-01-01
In this paper, we study a long-range percolation model on the lattice ℤ d with multi-type vertices and directed edges. Each vertex x in ℤ d is independently assigned a non-negative weight W x and a type ψ x , where (W x ) xinℤ d are i.i.d. random variables, and (ψ x ) xinℤ d are also i.i.d. Conditionally on weights and types, and given λ, α > 0, the edges are independent and the probability that there is a directed edge from x to y is given by p xy = 1 - exp(-λφ ψ x ψ y W x W y /|x-y| α ), where φ ij 's are entries from a type matrix Φ. We show that, when the tail of the distribution of W x is regularly varying with exponent τ - 1, the tails of the out/in-degree distributions are both regularly varying with exponent γ = α(τ - 1)/d. We formulate conditions under which there exist critical values λ c WCC in (0, ∞) and λ c SCC in (0, ∞) such that an infinite weak component and an infinite strong component emerge, respectively, when λ exceeds them. A phase transition is established for the shortest path lengths of directed and undirected edges in the infinite component at the point γ = 2, where the out/in-degrees switch from having finite to infinite variances. The random graph model studied here features some structures of multi-type vertices and directed edges which appear naturally in many real-world networks, such as the SNS networks and computer communication networks. (condensed matter: structural, mechanical, and thermal properties)
Percolation of binary disk systems: Modeling and theory
International Nuclear Information System (INIS)
Meeks, Kelsey; Pantoya, Michelle L.
2017-01-01
The dispersion and connectivity of particles with a high degree of polydispersity is relevant to problems involving composite material properties and reaction decomposition prediction and has been the subject of much study in the literature. This paper utilizes Monte Carlo models to predict percolation thresholds for a two-dimensional systems containing disks of two different radii. Monte Carlo simulations and spanning probability are used to extend prior models into regions of higher polydispersity than those previously considered. A correlation to predict the percolation threshold for binary disk systems is proposed based on the extended dataset presented in this work and compared to previously published correlations. Finally, a set of boundary conditions necessary for a good fit is presented, and a condition for maximizing percolation threshold for binary disk systems is suggested.
Connectivity percolation in suspensions of attractive square-well spherocylinders.
Dixit, Mohit; Meyer, Hugues; Schilling, Tanja
2016-01-01
We have studied the connectivity percolation transition in suspensions of attractive square-well spherocylinders by means of Monte Carlo simulation and connectedness percolation theory. In the 1980s the percolation threshold of slender fibers has been predicted to scale as the fibers' inverse aspect ratio [Phys. Rev. B 30, 3933 (1984)PRBMDO1098-012110.1103/PhysRevB.30.3933]. The main finding of our study is that the attractive spherocylinder system reaches this inverse scaling regime at much lower aspect ratios than found in suspensions of hard spherocylinders. We explain this difference by showing that third virial corrections of the pair connectedness functions, which are responsible for the deviation from the scaling regime, are less important for attractive potentials than for hard particles.
Renormalization group theory for percolation in time-varying networks.
Karschau, Jens; Zimmerling, Marco; Friedrich, Benjamin M
2018-05-22
Motivated by multi-hop communication in unreliable wireless networks, we present a percolation theory for time-varying networks. We develop a renormalization group theory for a prototypical network on a regular grid, where individual links switch stochastically between active and inactive states. The question whether a given source node can communicate with a destination node along paths of active links is equivalent to a percolation problem. Our theory maps the temporal existence of multi-hop paths on an effective two-state Markov process. We show analytically how this Markov process converges towards a memoryless Bernoulli process as the hop distance between source and destination node increases. Our work extends classical percolation theory to the dynamic case and elucidates temporal correlations of message losses. Quantification of temporal correlations has implications for the design of wireless communication and control protocols, e.g. in cyber-physical systems such as self-organized swarms of drones or smart traffic networks.
Controlling electrical percolation in multicomponent carbon nanotube dispersions.
Kyrylyuk, Andriy V; Hermant, Marie Claire; Schilling, Tanja; Klumperman, Bert; Koning, Cor E; van der Schoot, Paul
2011-04-10
Carbon nanotube reinforced polymeric composites can have favourable electrical properties, which make them useful for applications such as flat-panel displays and photovoltaic devices. However, using aqueous dispersions to fabricate composites with specific physical properties requires that the processing of the nanotube dispersion be understood and controlled while in the liquid phase. Here, using a combination of experiment and theory, we study the electrical percolation of carbon nanotubes introduced into a polymer matrix, and show that the percolation threshold can be substantially lowered by adding small quantities of a conductive polymer latex. Mixing colloidal particles of different sizes and shapes (in this case, spherical latex particles and rod-like nanotubes) introduces competing length scales that can strongly influence the formation of the system-spanning networks that are needed to produce electrically conductive composites. Interplay between the different species in the dispersions leads to synergetic or antagonistic percolation, depending on the ease of charge transport between the various conductive components.
International Nuclear Information System (INIS)
Mookerjee, A.
1984-09-01
The problem of spin-glass to ferromagnetic transition with increasing concentration is then one of the familiar nearest neighbour percolation but on the background of IIC. In the regime p<=psub(c) at T=Tsub(g)(p), the IIC forms a fractal background on which ferromagnetic percolation takes place. The equivalent statement is that the mobility edge Jsub(c)(p) moves outwards as p increases and at a critical psub(c) coincides with the band edge Jsub(B). At and above these concentrations the mode with highest energy is extended and we have the familiar paramagnetic to ferromagnetic transition as temperature is lowered across Jsub(B)/ksub(B). The physical justification of this picture is not at all transparent as in the case of the cluster percolation ideas. To this date no reliable estimates of the behaviour of Jsub(c)(p) as a function of p, for a purely off diagonal random matrix J(R) have been made
Percolation temperature and the 'instability' of the effective potential
International Nuclear Information System (INIS)
Carvalho, C.A. de; Bazeia Filho, D.; Eboli, O.J.P.; Marques, G.C.; Silva, A.J. da; Ventura, I.
1984-01-01
It is shown that in spontaneously broken lambda phi 4 theory the percolation temperature coincides with the temperature at which the semiclassical (loop) expansion of the effective potential (free energy) of the system around a uniform field configuration fails. This allows us to extract the percolation temperature directly from the effective potential. The addition of fermions or gauge fields does not alter the result as long as they are weakly coupled to the scalars. The coincidence holds in the high temperature limit at every order in the loop expansion. (Author) [pt
Kalfon, Pierre; Mimoz, Olivier; Loundou, Anderson; Geantot, Marie-Agnès; Revel, Nathalie; Villard, Isabelle; Amour, Julien; Azoulay, Elie; Garrouste-Orgeas, Maïté; Martin, Claude; Sharshar, Tarek; Baumstarck, Karine; Auquier, Pascal
2016-02-16
It is now well documented that critically ill patients are exposed to stressful conditions and experience discomforts from multiple sources. Improved identification of the discomforts of patients in intensive care units (ICUs) may have implications for managing their care, including consideration of ethical issues, and may assist clinicians in choosing the most appropriate interventions. The primary objective of this study was to assess the effectiveness of a multicomponent program of discomfort reduction in critically ill patients. The secondary objectives were to assess the sustainability of the impact of the program and the potential seasonality effect. We conducted a multicenter, cluster-randomized, controlled, single (patient)-blind study involving 34 French adult ICUs. The experimental intervention was a 6-month period during which the multicomponent program was implemented in the ICU and included the following steps: identification of discomforts, immediate feedback to the healthcare team, and implementation of targeted interventions. The control intervention was a 6-month period during which any program was implemented. The primary endpoint was the monthly overall score of self-reported discomfort from the French questionnaire on discomforts in ICU patients (IPREA). The secondary endpoints were the scores of the discomfort items of IPREA. The sample size was 660 individuals to obtain 80% power to detect a 25% difference in the overall discomfort score of IPREA between the two groups (design effect: 2.9). The results of this cluster-randomized controlled study are expected to confirm that a multicomponent program of discomfort reduction may be a new strategy in the management of care for critically ill patients. ClinicalTrials.gov NCT02442934, registered 11 May 2015.
Rigidity percolation in dispersions with a structured viscoelastic matrix
Wilbrink, M.W.L.; Michels, M.A.J.; Vellinga, W.P.; Meijer, H.E.H.
2005-01-01
This paper deals with rigidity percolation in composite materials consisting of a dispersion of mineral particles in a microstructured viscoelastic matrix. The viscoelastic matrix in this specific case is a hydrocarbon refinery residue. In a set of model random composites the mean interparticle
Universality for first passage percolation on sparse random graphs
Bhamidi, S.; Hofstad, van der R.W.; Hooghiemstra, G.
2014-01-01
We consider first passage percolation on the conguration model with n vertices, and general independent and identically distributed edge weights assumed to have a density. Assuming that the degree distribution satisfies a uniform X2 logX-condition, we analyze the asymptotic distribution for the
Large Dielectric Constant Enhancement in MXene Percolative Polymer Composites
Tu, Shao Bo; Jiang, Qiu; Zhang, Xixiang; Alshareef, Husam N.
2018-01-01
near the percolation limit of about 15.0 wt % MXene loading, which surpasses all previously reported composites made of carbon-based fillers in the same polymer. With up to 10 wt % MXene loading, the dielectric loss of the MXene
Remarks on the percolation problem in anisotropic systems
International Nuclear Information System (INIS)
Chaves, C.M.G.F.; Oliveira, P.M.C. de; Queiroz, S.L.A. de; Riera, R.
1979-07-01
The bond percolation problem is discused in an anisotropic square lattice using the position space renormalization group. It is shown that, due to symmetry, this treatment reproduces known exact results for this problem. The phase diagram and the flow lines in parameter space are also shown. Results are in agreement with universality.(Author) [pt
Universality for first passage percolation on sparse random graphs
Bhamidi, S.; Van Der Hofstad, R.W.; Hooghiemstra, G.
2017-01-01
We consider first passage percolation on the configuration model with n vertices, and general independent and identically distributed edge weights assumed to have a density. Assuming that the degree distribution satisfies a uniform X2 logX-condition, we analyze the asymptotic distribution for the
First-passage percolation on the random graph
Hofstad, van der R.W.; Hooghiemstra, G.; Van Mieghem, P.
2001-01-01
We study first-passage percolation on the random graph Gp(N) with exponentially distributed weights on the links. For the special case of the complete graph, this problem can be described in terms of a continuous-time Markov chain and recursive trees. The Markov chain X(t) describes the number of
Finite-size effects for anisotropic bootstrap percolation : Logarithmic corrections
van Enter, Aernout C. D.; Hulshof, Tim
In this note we analyse an anisotropic, two-dimensional bootstrap percolation model introduced by Gravner and Griffeath. We present upper and lower bounds on the finite-size effects. We discuss the similarities with the semi-oriented model introduced by Duarte.
Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions
Enter, Aernout C.D. van; Fey, Anne
In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the
Finite-size effects for anisotropic bootstrap percolation: logerithmic corrections
Enter, van A.C.D.; Hulshof, T.
2007-01-01
In this note we analyse an anisotropic, two-dimensional bootstrap percolation model introduced by Gravner and Griffeath. We present upper and lower bounds on the finite-size effects. We discuss the similarities with the semi-oriented model introduced by Duarte.
Directory of Open Access Journals (Sweden)
Sergey L’vovich Molchatsky
2017-10-01
Full Text Available The objective of the research was to determine of neuronic ensembles in the brain. The research was based that neuronic ensembles of a brain are considered as the percolating clusters. In the basic part of the study the main concern was determination of the following parameters: fractal dimension on a passing threshold df; for geodetic lines on a fractal dθ and for trajectories of particles in a turbulence field dw. In the same part of a research the index of a compendency (θ of neuronic ensembles of animals and the human brain is defined. As well as it was supposed has a negative value θ 1. Numerical calculations with use of results of computer analysis frontal section images of a hypothalamus of a brain of animals and human are shown, that the considered objects can be ranked to the special class of fractal objects. Such class of objects is called asymptotically arcwise connected.
Built-up structure criticality
Czech Academy of Sciences Publication Activity Database
Vašata, D.; Exner, Pavel; Seba, P.
2011-01-01
Roč. 390, 21-22 (2011), s. 3922-3931 ISSN 0378-4371 R&D Projects: GA MŠk LC06002 Institutional research plan: CEZ:AV0Z10480505 Keywords : SELF-ORGANIZED CRITICALITY * URBAN-GROWTH PATTERNS * PERCOLATION Subject RIV: BE - Theoretical Physics Impact factor: 1.373, year: 2011
Cardoso, L. S.; Gonçalves, G. E.; Kanda, D. H. F.; Bianchi, R. F.; Nagashima, H. N.
2017-12-01
This paper describes a new statistical model to predict the frequency dependence of the conductivity of conjugated polymer-semiconductor nanoparticle composites. The model considers AC conduction in an inhomogeneous medium represented by a two-dimensional model of resistor network. The conductivity between two neighboring sites in the polymer matrix and the semiconductor particles is assumed to obey the random free energy barrier model and the Drude model, respectively. The real and imaginary parts of the AC conductivity were determined using the transfer-matrix technique, and the statistical model was applied to experimental data of thin films composed of polyaniline (PANI) and indium-tin-oxide (ITO) nanoparticles. The conductivity critical exponent ( s) obtained in two dimensions for PANI/ITO films below the percolation threshold was found to be 2.7, which is greater than the universal value of s described by the classical percolation theory ( s = 1.3). This non-universality is explained by the existence of a local electric field distribution in the bulk of the nanocomposite. Finally, these results are discussed in terms of the distribution of potential barriers that vary according to the concentration of ITO amount in the composite.
On a random area variable arising in discrete-time queues and compact directed percolation
International Nuclear Information System (INIS)
Kearney, Michael J
2004-01-01
A well-known discrete-time, single-server queueing system with mean arrival rate λ and mean departure rate μ is considered from the perspective of the area, A, swept out by the queue occupation process during a busy period. We determine the exact form of the tail of the distribution, Pr(A > x); in particular, we show that Pr(A > x) ∼ Cx -1/4 exp(-Dx 1/2 ) for all ρ ≠ 1, where ρ ≡ λ/μ, and expressions for C and D are given. For the critical case ρ = 1 we show that Pr(A > x) ∼ C'x -1/3 , with C' also given. A simple mapping, used in the derivation, establishes a connection with compact directed percolation on a square lattice. As a corollary, therefore, we are also able to specify the large-area asymptotic behaviour of this model at all points in the phase diagram. This extends previous scaling results, which are only valid close to the percolation threshold
Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition
Schrenk, K. J.; Felder, A.; Deflorin, S.; Araújo, N. A. M.; D'Souza, R. M.; Herrmann, H. J.
2012-03-01
The BFW model introduced by Bohman, Frieze, and Wormald [Random Struct. Algorithms1042-983210.1002/rsa.20038, 25, 432 (2004)], and recently investigated in the framework of discontinuous percolation by Chen and D'Souza [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.106.115701 106, 115701 (2011)], is studied on the square and simple-cubic lattices. In two and three dimensions, we find numerical evidence for a strongly discontinuous transition. In two dimensions, the clusters at the threshold are compact with a fractal surface of fractal dimension df=1.49±0.02. On the simple-cubic lattice, distinct jumps in the size of the largest cluster are observed. We proceed to analyze the tree-like version of the model, where only merging bonds are sampled, for dimension two to seven. The transition is again discontinuous in any considered dimension. Finally, the dependence of the cluster-size distribution at the threshold on the spatial dimension is also investigated.
Pilot test of bacterial percolation leaching at Fuzhou uranium mine
International Nuclear Information System (INIS)
Fan Baotuan; Liu Jian; Jiang Yngqiong; Cai Chunhui; Jiang Lang; Zhou Renhua; Tong Changning; Zhang Hongli
2006-01-01
Total 18 t uranium ores of Fuzhou Uranium Mine packed in three or four columns in series were leached by bacterial percolation. The results show that without adding any other chemical oxidant such as sodium chlorate, the leaching rate measured by residue is 91.45%-94.48%, leaching time is 50-60 d, acid consumption is 6.17%-7.75%, and residue grade is 0.0149%-0.0208%. Compared with conventional percolation leaching process, the leaching rate is improved by 3%, leaching time is shorted by 26%, and acid consumption is saved by 34%. Accumulation pattern of ΣFe and F - in the process of leaching is discussed. Influence of F - on bacterial growth, regeneration of barren solution as well as correlative techniques are reviewed. (authors)
Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring
Directory of Open Access Journals (Sweden)
Matias Soto
2015-09-01
Full Text Available A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss–Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature.
Damage percolation during stretch flange forming of aluminum alloy sheet
Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.
2005-12-01
A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.
Schreiner-McGraw, A.; Vivoni, E. R.; Browning, D. M.
2017-12-01
A critical hydrologic process in arid regions is the contribution of episodic streamflow in ephemeral channels to groundwater recharge. This process has traditionally been studied in channels that drain large watersheds (10s to 100s km2). In this study, we aim to characterize the provision of the ecosystem services of surface and groundwater supply in a first-order watershed (4.6 ha) in an arid piedmont slope of the Jornada Experimental Range (JER). We use an observational and modeling approach to estimate deep percolation. During a 6 year study period, we observed 428 mm of percolation (P) and 39 mm of runoff (Q); ratios of P to rainfall (R) of P/R = 0.27 and Q/R = 0.02. Utilizing an instrument network and site measurements, we determine that percolation occurs primarily inside channel reaches when these receive runoff from upland hillslopes and find that a monthly rainfall threshold of 62 mm is needed for significant percolation to be generated. In order to quantify the mechanisms leading to this threshold response, we develop a channel transmission loss module for the TIN-based Real-time Integrated Basin Simulator (tRIBS) and test the model thoroughly against the available observations over the study period. For these purposes, we make use of image classifications from Unmanned Aerial Vehicle flights, a ground-based phenocam, and species-level measurements to parameterize vegetation processes in the model. We then conduct an extensive set of sensitivity experiments to determine the relative roles of channel, soil, and vegetation properties on modifying the relation between monthly rainfall and percolation. Additionally, we test how the observed vegetation transitions in the JER over the last 150 years affect the deep percolation and runoff estimates. By quantifying mechanisms through which vegetation changes affect water resource provision, this work provides new insights on the ecohydrological controls on the water yield of arid piedmont slopes.
International Nuclear Information System (INIS)
Risi, Celso L.S.; Hattenhauer, Irineu; Ramos, Airton; Coelho, Luiz A.F.; Pezzin, Sérgio H.
2015-01-01
The formation of percolation networks in epoxy matrix nanocomposites reinforced with multi-wall carbon nanotubes (MWNT) during the curing process, at different MWNT contents, was studied by using a parallel plate cell subjected to a 300 V/cm AC electric field at 1 kHz. The percolation was verified by the electrical current output measured during and after the resin curing. The behavior of electric dipoles was characterized by impedance spectroscopy and followed the Debye first order dispersion model, by which an average relaxation time of 6.0 × 10 −4 s and a cut-off frequency of 1.7 kHz were experimentally found. By applying the theory of percolation, a critical probability, p c , equal to 0.038 vol% and an exponent of conductivity of 2.0 were found. Both aligned and random samples showed dipole relaxation times typical of interfacial and/or charge-hopping polarization, while the permittivity exhibited an exponential decrease with frequency. This behavior can be related to the increased ability to trap electrical charges due to the formation of the carbon nanotubes network. Optical and electron microscopies confirm the theoretical prediction that the application of an electric field during cure helps the process of MWNT debundling in epoxy resin. - Highlights: • We report the formation of percolating networks of MWNTs under AC electric field. • MWNT/epoxy dielectric properties were measured by impedance spectroscopy. • Lower percolation thresholds were obtained for composites with aligned CNTs. • Application of AC electric field helps the debundling of CNTs. • CNT/Epoxy with percolated networks presents interfacial and hopping polarizations
Fardet, Tanguy; Bottani, Samuel; Métens, Stéphane; Monceau, Pascal
2018-06-01
The Quorum Percolation model (QP) has been designed in the context of neurobiology to describe the initiation of activity bursts occurring in neuronal cultures from the point of view of statistical physics rather than from a dynamical synchronization approach. This paper aims at investigating an extension of the original QP model by taking into account the presence of inhibitory neurons in the cultures (IQP model). The first part of this paper is focused on an equivalence between the presence of inhibitory neurons and a reduction of the network connectivity. By relying on a simple topological argument, we show that the mean activation behavior of networks containing a fraction η of inhibitory neurons can be mapped onto purely excitatory networks with an appropriately modified wiring, provided that η remains in the range usually observed in neuronal cultures, namely η ⪅ 20%. As a striking result, we show that such a mapping enables to predict the evolution of the critical point of the IQP model with the fraction of inhibitory neurons. In a second part, we bridge the gap between the description of bursts in the framework of percolation and the temporal description of neural networks activity by showing how dynamical simulations of bursts with an adaptive exponential integrate-and-fire model lead to a mean description of bursts activation which is captured by Quorum Percolation.
Levitation and percolation in quantum Hall systems with correlated disorder
Song, Hui; Maruyama, Isao; Hatsugai, Yasuhiro
2007-01-01
We investigate the integer quantum Hall system in a two dimensional lattice model with spatially correlated disorder by using the efficient method to calculate the Chern number proposed by Fukui et al. [J. Phys. Soc. Jpn. 74, 1674 (2005)]. Distribution of charge density indicates that the extended states at the center of each Landau band have percolating current paths, which are topologically equivalent to the edge states that exist in a system with boundaries. As increasing the strength of d...
Double site-bond percolation model for biomaterial implants
Mely, H.; Mathiot, J. -F.
2011-01-01
9 figures - 10 pages; We present a double site-bond percolation model to account, on the one hand, for the vascularization and/or resorption of biomaterial implant in bones, and on the other hand, for its mechanical continuity. The transformation of the implant into osseous material, and the dynamical formation/destruction of this osseous material is accounted for by creation and destruction of links and sites in two, entangled, networks. We identify the relevant parameters to describe the im...
Electrical Properties of Zinc-Kaolin Composites below its Percolation ...
African Journals Online (AJOL)
In this paper, we present some electrical properties of the zinc-kaolin cermet resistors with zinc metal fillers below the percolation threshold. Rectangular cermet rods of dimensions 65 mm by 6.5 mm by 3.2 mm were produced in a mould with semi-dry the zinc/kaolin powder mixture which is compressed with a force of about ...
Fractional scaling of quantum walks on percolation lattices
International Nuclear Information System (INIS)
Kendon, Viv; Knott, Paul; Leung, Godfrey; Bailey, Joe
2011-01-01
Quantum walks can be used to model processes such as transport in spin chains and bio-molecules. The enhanced spreading and mixing properties of quantum walks compared with their classical counterparts have been well-studied on regular structures and also shown to be sensitive to defects and imperfections. Using numerical simulation, we study the spreading properties of quantum walks on percolation lattices for both bond and site percolation. The randomly missing edges or sites provide a controlled amount of disorder in the regular Cartesian lattice. In one dimension (the line) we introduce a simple model of quantum tunneling to allow the walk to proceed past the missing edges or sites. This allows the quantum walk to spread faster than a classical random walk for short times, but at longer times the disorder localises the quantum walk. In two dimensions, we observe fractional scaling of the spreading with the number of steps of the walk. For percolation above the 85% level, we obtain faster spreading than classical random walks on the full lattice.
Interdependent networks - Topological percolation research and application in finance
Zhou, Di
This dissertation covers the two major parts of my Ph.D. research: i) developing a theoretical framework of complex networks and applying simulation and numerical methods to study the robustness of the network system, and ii) applying statistical physics concepts and methods to quantitatively analyze complex systems and applying the theoretical framework to study real-world systems. In part I, we focus on developing theories of interdependent networks as well as building computer simulation models, which includes three parts: 1) We report on the effects of topology on failure propagation for a model system consisting of two interdependent networks. We find that the internal node correlations in each of the networks significantly changes the critical density of failures, which can trigger the total disruption of the two-network system. Specifically, we find that the assortativity within a single network decreases the robustness of the entire system. 2) We study the percolation behavior of two interdependent scale-free (SF) networks under random failure of 1-p fraction of nodes. We find that as the coupling strength q between the two networks reduces from 1 (fully coupled) to 0 (no coupling), there exist two critical coupling strengths q1 and q2 , which separate the behaviors of the giant component as a function of p into three different regions, and for q2 relationship both analytically and numerically. We study a starlike network of n Erdos-Renyi (ER), SF networks and a looplike network of n ER networks, and we find for starlike networks, their phase transition regions change with n, but for looplike networks the phase regions change with average degree k . In part II, we apply concepts and methods developed in statistical physics to study economic systems. We analyze stock market indices and foreign exchange daily returns for 60 countries over the period of 1999-2012. We build a multi-layer network model based on different correlation measures, and introduce a
Clustering of near clusters versus cluster compactness
International Nuclear Information System (INIS)
Yu Gao; Yipeng Jing
1989-01-01
The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)
Spin-glass-like dynamics of ferromagnetic clusters in La0.75Ba0.25CoO3
International Nuclear Information System (INIS)
Kumar, Devendra
2014-01-01
We report a magnetization study of the compound La 0.75 Ba 0.25 CoO 3 where the Ba 2+ doping is just above the critical limit for percolation of ferromagnetic clusters. The field cooled and zero-field cooled (ZFC) magnetization exhibit thermomagnetic irreversibility and the ac susceptibility shows a frequency dependent peak at the ferromagnetic ordering temperature (T C ≈ 203 K) of the clusters. These features indicate the presence of a non-equilibrium state below T C . For the non-equilibrium state, the dynamic scaling of the imaginary part of the ac susceptibility and the static scaling of the nonlinear susceptibility clearly establish a spin-glass-like cooperative freezing of ferromagnetic clusters at 200.9(2) K. The assertion of the occurrence of spin-glass-like freezing of ferromagnetic clusters is further substantiated by ZFC ageing and memory experiments. We also observe certain dynamical features which are not present in a typical spin glass, such as: the initial magnetization after ZFC ageing first increases and then decreases with the waiting time; and there is an imperfect recovery of relaxation in negative temperature cycling experiments. This imperfect recovery transforms to perfect recovery for concurrent field cycling. Our analysis suggests that these additional dynamical features have their origin in the inter-cluster exchange interaction and cluster size distribution. The inter-cluster exchange interaction above the magnetic percolation level gives a superferromagnetic state in some granular thin films, but our results show the absence of a typical superferromagnetic-like state in La 0.75 Ba 0.25 CoO 3 . (paper)
Priour, D. J.
2014-01-01
The percolation threshold for flow or conduction through voids surrounding randomly placed spheres is calculated. With large-scale Monte Carlo simulations, we give a rigorous continuum treatment to the geometry of the impenetrable spheres and the spaces between them. To properly exploit finite-size scaling, we examine multiple systems of differing sizes, with suitable averaging over disorder, and extrapolate to the thermodynamic limit. An order parameter based on the statistical sampling of stochastically driven dynamical excursions and amenable to finite-size scaling analysis is defined, calculated for various system sizes, and used to determine the critical volume fraction ϕc=0.0317±0.0004 and the correlation length exponent ν =0.92±0.05.
Percolation Model of Sensory Transmission and Loss of Consciousness Under General Anesthesia
Zhou, David W.; Mowrey, David D.; Tang, Pei; Xu, Yan
2015-09-01
Neurons communicate with each other dynamically; how such communications lead to consciousness remains unclear. Here, we present a theoretical model to understand the dynamic nature of sensory activity and information integration in a hierarchical network, in which edges are stochastically defined by a single parameter p representing the percolation probability of information transmission. We validate the model by comparing the transmitted and original signal distributions, and we show that a basic version of this model can reproduce key spectral features clinically observed in electroencephalographic recordings of transitions from conscious to unconscious brain activities during general anesthesia. As p decreases, a steep divergence of the transmitted signal from the original was observed, along with a loss of signal synchrony and a sharp increase in information entropy in a critical manner; this resembles the precipitous loss of consciousness during anesthesia. The model offers mechanistic insights into the emergence of information integration from a stochastic process, laying the foundation for understanding the origin of cognition.
Memory effects, two color percolation, and the temperature dependence of Mott variable-range hopping
Agam, Oded; Aleiner, Igor L.
2014-06-01
There are three basic processes that determine hopping transport: (a) hopping between normally empty sites (i.e., having exponentially small occupation numbers at equilibrium), (b) hopping between normally occupied sites, and (c) transitions between normally occupied and unoccupied sites. In conventional theories all these processes are considered Markovian and the correlations of occupation numbers of different sites are believed to be small (i.e., not exponential in temperature). We show that, contrary to this belief, memory effects suppress the processes of type (c) and manifest themselves in a subleading exponential temperature dependence of the variable-range hopping conductivity. This temperature dependence originates from the property that sites of type (a) and (b) form two independent resistor networks that are weakly coupled to each other by processes of type (c). This leads to a two-color percolation problem which we solve in the critical region.
Far from Equilibrium Percolation, Stochastic and Shape Resonances in the Physics of Life
Directory of Open Access Journals (Sweden)
Antonio Bianconi
2011-10-01
Full Text Available Key physical concepts, relevant for the cross-fertilization between condensed matter physics and the physics of life seen as a collective phenomenon in a system out-of-equilibrium, are discussed. The onset of life can be driven by: (a the critical fluctuations at the protonic percolation threshold in membrane transport; (b the stochastic resonance in biological systems, a mechanism that can exploit external and self-generated noise in order to gain efficiency in signal processing; and (c the shape resonance (or Fano resonance or Feshbach resonance in the association and dissociation processes of bio-molecules (a quantum mechanism that could play a key role to establish a macroscopic quantum coherence in the cell.
Perrier, E. M. A.; Bird, N. R. A.; Rieutord, T. B.
2010-10-01
Quantifying the connectivity of pore networks is a key issue not only for modelling fluid flow and solute transport in porous media but also for assessing the ability of soil ecosystems to filter bacteria, viruses and any type of living microorganisms as well inert particles which pose a contamination risk. Straining is the main mechanical component of filtration processes: it is due to size effects, when a given soil retains a conveyed entity larger than the pores through which it is attempting to pass. We postulate that the range of sizes of entities which can be trapped inside soils has to be associated with the large range of scales involved in natural soil structures and that information on the pore size distribution has to be complemented by information on a critical filtration size (CFS) delimiting the transition between percolating and non percolating regimes in multiscale pore networks. We show that the mass fractal dimensions which are classically used in soil science to quantify scaling laws in observed pore size distributions can also be used to build 3-D multiscale models of pore networks exhibiting such a critical transition. We extend to the 3-D case a new theoretical approach recently developed to address the connectivity of 2-D fractal networks (Bird and Perrier, 2009). Theoretical arguments based on renormalisation functions provide insight into multi-scale connectivity and a first estimation of CFS. Numerical experiments on 3-D prefractal media confirm the qualitative theory. These results open the way towards a new methodology to estimate soil filtration efficiency from the construction of soil structural models to be calibrated on available multiscale data.
Directory of Open Access Journals (Sweden)
E. M. A. Perrier
2010-10-01
Full Text Available Quantifying the connectivity of pore networks is a key issue not only for modelling fluid flow and solute transport in porous media but also for assessing the ability of soil ecosystems to filter bacteria, viruses and any type of living microorganisms as well inert particles which pose a contamination risk. Straining is the main mechanical component of filtration processes: it is due to size effects, when a given soil retains a conveyed entity larger than the pores through which it is attempting to pass. We postulate that the range of sizes of entities which can be trapped inside soils has to be associated with the large range of scales involved in natural soil structures and that information on the pore size distribution has to be complemented by information on a critical filtration size (CFS delimiting the transition between percolating and non percolating regimes in multiscale pore networks. We show that the mass fractal dimensions which are classically used in soil science to quantify scaling laws in observed pore size distributions can also be used to build 3-D multiscale models of pore networks exhibiting such a critical transition. We extend to the 3-D case a new theoretical approach recently developed to address the connectivity of 2-D fractal networks (Bird and Perrier, 2009. Theoretical arguments based on renormalisation functions provide insight into multi-scale connectivity and a first estimation of CFS. Numerical experiments on 3-D prefractal media confirm the qualitative theory. These results open the way towards a new methodology to estimate soil filtration efficiency from the construction of soil structural models to be calibrated on available multiscale data.
A stratified percolation model for saturated and unsaturated flow through natural fractures
International Nuclear Information System (INIS)
Pyrak-Nolte, L.J.
1990-01-01
The geometry of the asperities of contact between the two surfaces of a fracture and of the adjacent void spaces determines fluid flow through a fracture and the mechanical deformation across a fracture. Heuristically we have developed a stratified continuum percolation model to describe this geometry based on a fractal construction that includes scale invariance and correlation of void apertures. Deformation under stress is analyzed using conservation of rock volume to correct for asperity interpenetration. Single phase flow is analyzed using a critical path along which the principal resistance is a result of laminar flow across the critical neck in this path. Results show that flow decreases with apparent aperture raised to a variable power greater than cubic, as is observed in flow experiments on natural fractures. For two phases, flow of the non-wetting phase is likewise governed by the critical neck along the critical path of largest aperture but flow of the wetting phase is governed by tortuosity. 17 refs., 10 figs
International Nuclear Information System (INIS)
Zeng Yanwei; Tian Changan; Liu Junliang
2006-01-01
The XPS and GISAXS have been employed as useful tools to probe the chemical compositional and microstructural evolutions in the surface layers formed via phase separation and percolation in polystyren/Ti(OBut) 4 /alumina composite thick films. The surface enrichment of Ti species due to the migration of Ti(OBut) 4 molecules in the films was found to show an incubation period of ∼15 h while the samples were treated at 100 deg. C before a remarkable progress can be identified. According to the XPS and GISAXS data, Key mechanism to govern this surface process is phenomenologically considered to be the specific phase separation behavior in Ti(OBut) 4 /PS blend and the subsequent percolating process. The extended thermal treatment was found to make the surface layer microstructure evolve from local phase separation featured with an increasing population of individual microbeads of Ti(OBut) 4 (∼1.5 nm in radius) to the formation of large size clusters of microbeads due to their interconnections, accompanied by the growth of every microbead itself to ∼10 nm on the average, which provokes and then enhances the surface enrichment of Ti(OBut) 4 since these clusters act as a fast diffusion network due to percolation effect
International Nuclear Information System (INIS)
Lemieux, M.A.; Breton, P.; Tremblay, A.M.S.
1985-01-01
It is shown that the Negative Eigenvalue Theorem and transfer matrix methods may be considered within a unified framework and generalized to compute projected densities of states or, more generally, any linear combination of matrix elements of the inverse of large symmetric random matrices. As examples of applications, extensive simulations for one- and two-mode behaviour in the Raman spectrum of one-dimensional mixed crystals and a finite-size analysis of critical exponents for the central force percolation universality class are presented
Statistical analysis and Monte Carlo simulation of growing self-avoiding walks on percolation
Energy Technology Data Exchange (ETDEWEB)
Zhang Yuxia [Department of Physics, Wuhan University, Wuhan 430072 (China); Sang Jianping [Department of Physics, Wuhan University, Wuhan 430072 (China); Department of Physics, Jianghan University, Wuhan 430056 (China); Zou Xianwu [Department of Physics, Wuhan University, Wuhan 430072 (China)]. E-mail: xwzou@whu.edu.cn; Jin Zhunzhi [Department of Physics, Wuhan University, Wuhan 430072 (China)
2005-09-26
The two-dimensional growing self-avoiding walk on percolation was investigated by statistical analysis and Monte Carlo simulation. We obtained the expression of the mean square displacement and effective exponent as functions of time and percolation probability by statistical analysis and made a comparison with simulations. We got a reduced time to scale the motion of walkers in growing self-avoiding walks on regular and percolation lattices.
Critical behavior and correlations on scale-free small-world networks: Application to network design
Ostilli, M.; Ferreira, A. L.; Mendes, J. F. F.
2011-06-01
We analyze critical phenomena on networks generated as the union of hidden variable models (networks with any desired degree sequence) with arbitrary graphs. The resulting networks are general small worlds similar to those à la Watts and Strogatz, but with a heterogeneous degree distribution. We prove that the critical behavior (thermal or percolative) remains completely unchanged by the presence of finite loops (or finite clustering). Then, we show that, in large but finite networks, correlations of two given spins may be strong, i.e., approximately power-law-like, at any temperature. Quite interestingly, if γ is the exponent for the power-law distribution of the vertex degree, for γ⩽3 and with or without short-range couplings, such strong correlations persist even in the thermodynamic limit, contradicting the common opinion that, in mean-field models, correlations always disappear in this limit. Finally, we provide the optimal choice of rewiring under which percolation phenomena in the rewired network are best performed, a natural criterion to reach best communication features, at least in noncongested regimes.
Predicting deep percolation with eddy covariance under mulch drip irrigation
Ming, Guanghui; Tian, Fuqiang; Hu, Hongchang
2016-04-01
Water is essential for the agricultural development and ecological sustainability of the arid and semi-arid oasis with rare precipitation input and high evaporation demand. Deep percolation (DP) defined as excess irrigation water percolating below the plant root zone will reduce irrigation water use efficiency (WUE). But the DP was often ignored in mulch drip irrigation (MDI) which has reached the area of 1.6 million hectares in Xinjiang, the northwest of China. In this study DP experiments were conducted at an agricultural experiment station located within an irrigation district in the Tarim River Basin for four cotton growing periods. First it was detected the irrigation water infiltrated into the soil layers below 100cm and the groundwater level responded to the irrigation events well. Then DP below 100cm soil layers was calculated using the soil water balance method with the aid of eddy covariance (with the energy balance closure of 0.72). The negative DP (groundwater contribution to the crop-water use through capillary rising) at the seedling and harvesting stages can reach 77mm and has a good negative correlation with the groundwater level and positive correlation with potential evaporation. During the drip irrigation stage approximately 45% of the irrigation became DP and resulted in the low irrigation WUE of 0.6. The DP can be 164mm to 270mm per year which was positive linearly correlated to irrigation depth and negative linear correlated to irrigation interval. It is better to establish the irrigation schedule with small irrigation depth and given frequently to reduce deep percolation and meet crop needs.
Percolative Theory of Organic Magnetoresistance and Fringe-Field Magnetoresistance
Flatté, Michael E.
2013-03-01
A recently-introduced percolation theory for spin transport and magnetoresistance in organic semiconductors describes the effects of spin dynamics on hopping transport by considering changes in the effective density of hopping sites, a key quantity determining the properties of percolative transport. Increases in the spin-flip rate open up ``spin-blocked'' pathways to become viable conduction channels and hence, as the spin-flip rate changes with magnetic field, produce magnetoresistance. Features of this percolative magnetoresistance can be found analytically in several regimes, and agree with measurements of the shape and saturation of measured magnetoresistance curves. We find that the threshold hopping distance is analogous to the branching parameter of a phenomenological two-site model, and that the distinction between slow and fast hopping is contingent on the threshold hopping distance. Regimes of slow and fast hopping magnetoresistance are uniquely characterized by their line shapes. Studies of magnetoresistance in known systems with controllable positional disorder would provide an additional stringent test of this theory. Extensions to this theory also describe fringe-field magnetoresistance, which is the influence of fringe magnetic fields from a nearby unsaturated magnetic electrode on the conductance of an organic film. This theory agrees with several key features of the experimental fringe-field magnetoresistance, including the applied fields where the magnetoresistance reaches extrema, the applied field range of large magnetoresistance effects from the fringe fields, and the sign of the effect. All work done in collaboration with N. J. Harmon, and fringe-field magnetoresistance work in collaboration also with F. Macià, F. Wang, M. Wohlgenannt and A. D. Kent. This work was supported by an ARO MURI.
Percolation modelling for highly aligned polycrystalline superconducting tapes
Energy Technology Data Exchange (ETDEWEB)
Rutter, N A; Glowacki, B A; Evetts, J E [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); IRC in Superconductivity, Madingley Road, Cambridge CB3 0HE (United Kingdom)
2000-11-01
Surface and bulk texture measurements have been carried out on highly aligned NiFe tapes, suitable for use as coated conductor substrates. Data from small-area electron backscatter diffraction measurements are compared with those from bulk x-ray analysis in the development of a two-dimensional percolation model, and the two are shown to give very similar results. No evidence of grain-to-grain correlation is found. The model is then developed to assess how the properties of a superconducting layer grown epitaxially on buffered tapes will depend on parameters such as sample size, grain size and the extent of grain alignment. (author)
Percolation simulation of laser-guided electrical discharges.
Sasaki, Akira; Kishimoto, Yasuaki; Takahashi, Eiichi; Kato, Susumu; Fujii, Takashi; Kanazawa, Seiji
2010-08-13
A three-dimensional simulation of laser-guided discharges based on percolation is presented. The model includes both local growth of a streamer due to the enhanced electric field at the streamer's tip and propagation of a leader by remote ionization such as that caused by runaway electrons. The stochastic behavior of the discharge through a preformed plasma channel is reproduced by the calculation, which shows complex path with detouring and bifurcation. The probability of guiding is investigated with respect to the ionized, conductive fraction along the channel.
On the genre-fication of music: a percolation approach
Lambiotte, R.; Ausloos, M.
2006-03-01
We analyze web-downloaded data on people sharing their music library. By attributing to each music group usual music genres (Rock, Pop ...), and analysing correlations between music groups of different genres with percolation-idea based methods, we probe the reality of these subdivisions and construct a music genre cartography, with a tree representation. We also discuss an alternative objective way to classify music, that is based on the complex structure of the groups audience. Finally, a link is drawn with the theory of hidden variables in complex networks.
Capillary condensation, invasion percolation, hysteresis, and discrete memory
International Nuclear Information System (INIS)
Guyer, R.A.; McCall, K.R.
1996-01-01
A model of the capillary condensation process, i.e., of adsorption-desorption isotherms, having only pore-pore interactions is constructed. The model yields (1) hysteretic isotherms, (2) invasion percolation on desorption, and (3) hysteresis with discrete memory for interior chemical potential loops. All of these features are seen in experiment. The model is compared to a model with no pore-pore interactions (the Preisach model) and to a related model of interacting pore systems (the random field Ising model). The capillary condensation model differs from both. copyright 1996 The American Physical Society
Singh, A.; Holt, R. M.; Ramarao, B.; Clemo, T.
2011-12-01
Three radioactive waste disposal landfills at the Waste Control Specialists (WCS) facility in Andrews County, Texas are constructed below grade, within the low-permeability Dockum Group mudrocks (Cooper Canyon Formation) of Triassic age. Recent site investigations at the WCS disposal facilities indicate the presence of a trapped and compressed gas phase in the mudrocks. The Dockum is a low-permeability medium with vertical and horizontal effective hydraulic conductivities of 1.2E-9 cm/s and 2.9E-7 cm/s. The upper 300+ feet of the Dockum is in the unsaturated zone, with an average saturation of 0.87 and average capillary pressure of 2.8 MPa determined from core samples. Air entry pressures on core samples range from from 0.016 to 9.8 MPa, with a mean of 1.0 MPa. Heat dissipation sensors, thermocouple psychrometers, and advanced tensiometers installed in Dockum borehole arrays generally show capillary pressures one order of magnitude less than those measured on core samples. These differences with core data are attributed to the presence of a trapped and compressed gas phase within Dockum materials. In the vicinity of an instrumented borehole, the gas phase pressure equilibrates with atmospheric pressure, lowering the capillary pressure. We have developed a new macroscopic invasion percolation (MIP) model to illustrate the origin of the trapped gas phase in the Dockum rocks. An MIP model differs from invasion percolation (IP) through the definition of macro-scale capillarity. Individual pore throats and necks are not considered. Instead, a near pore-scale block is defined and characterized by a local threshold spanning pressure (a local block-scale breakthrough pressure) that represents the behavior of the subscale network. The model domain is discretized into an array of grid blocks with assigned spanning pressures. An invasion pressure for each block is then determined by the sum of spanning pressure, buoyance forces, and viscous forces. An IP algorithm sorts the
Rapid self-organised initiation of ad hoc sensor networks close above the percolation threshold
Korsnes, Reinert
2010-07-01
This work shows potentials for rapid self-organisation of sensor networks where nodes collaborate to relay messages to a common data collecting unit (sink node). The study problem is, in the sense of graph theory, to find a shortest path tree spanning a weighted graph. This is a well-studied problem where for example Dijkstra’s algorithm provides a solution for non-negative edge weights. The present contribution shows by simulation examples that simple modifications of known distributed approaches here can provide significant improvements in performance. Phase transition phenomena, which are known to take place in networks close to percolation thresholds, may explain these observations. An initial method, which here serves as reference, assumes the sink node starts organisation of the network (tree) by transmitting a control message advertising its availability for its neighbours. These neighbours then advertise their current cost estimate for routing a message to the sink. A node which in this way receives a message implying an improved route to the sink, advertises its new finding and remembers which neighbouring node the message came from. This activity proceeds until there are no more improvements to advertise to neighbours. The result is a tree network for cost effective transmission of messages to the sink (root). This distributed approach has potential for simple improvements which are of interest when minimisation of storage and communication of network information are a concern. Fast organisation of the network takes place when the number k of connections for each node ( degree) is close above its critical value for global network percolation and at the same time there is a threshold for the nodes to decide to advertise network route updates.
Percolation Diffusion into Self-Assembled Mesoporous Silica Microfibres
Directory of Open Access Journals (Sweden)
John Canning
2014-03-01
Full Text Available Percolation diffusion into long (11.5 cm self-assembled, ordered mesoporous microfibres is studied using optical transmission and laser ablation inductive coupled mass spectrometry (LA-ICP-MS. Optical transmission based diffusion studies reveal rapid penetration (<5 s, D > 80 μm2∙s−1 of Rhodamine B with very little percolation of larger molecules such as zinc tetraphenylporphyrin (ZnTPP observed under similar loading conditions. The failure of ZnTPP to enter the microfibre was confirmed, in higher resolution, using LA-ICP-MS. In the latter case, LA-ICP-MS was used to determine the diffusion of zinc acetate dihydrate, D~3 × 10−4 nm2∙s−1. The large differences between the molecules are accounted for by proposing ordered solvent and structure assisted accelerated diffusion of the Rhodamine B based on its hydrophilicity relative to the zinc compounds. The broader implications and applications for filtration, molecular sieves and a range of devices and uses are described.
Percolation behavior of tritiated water into a soil packed bed
Energy Technology Data Exchange (ETDEWEB)
Honda, T.; Katayama, K.; Uehara, K.; Fukada, S. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka (Japan); Takeishi, T. [Faculty of Engineering, Kyushu University, Motooka Nishi-ku, Fukuoka (Japan)
2015-03-15
A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)
Percolation behavior of tritiated water into a soil packed bed
International Nuclear Information System (INIS)
Honda, T.; Katayama, K.; Uehara, K.; Fukada, S.; Takeishi, T.
2015-01-01
A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)
Accelerating Gas Adsorption on 3D Percolating Carbon Nanotubes.
Li, Hui; Wen, Chenyu; Zhang, Youwei; Wu, Dongping; Zhang, Shi-Li; Qiu, Zhi-Jun
2016-02-18
In the field of electronic gas sensing, low-dimensional semiconductors such as single-walled carbon nanotubes (SWCNTs) can offer high detection sensitivity owing to their unprecedentedly large surface-to-volume ratio. The sensitivity and responsivity can further improve by increasing their areal density. Here, an accelerated gas adsorption is demonstrated by exploiting volumetric effects via dispersion of SWCNTs into a percolating three-dimensional (3D) network in a semiconducting polymer. The resultant semiconducting composite film is evaluated as a sensing membrane in field effect transistor (FET) sensors. In order to attain reproducible characteristics of the FET sensors, a pulsed-gate-bias measurement technique is adopted to eliminate current hysteresis and drift of sensing baseline. The rate of gas adsorption follows the Langmuir-type isotherm as a function of gas concentration and scales with film thickness. This rate is up to 5 times higher in the composite than only with an SWCNT network in the transistor channel, which in turn results in a 7-fold shorter time constant of adsorption with the composite. The description of gas adsorption developed in the present work is generic for all semiconductors and the demonstrated composite with 3D percolating SWCNTs dispersed in functional polymer represents a promising new type of material for advanced gas sensors.
Electron percolation in realistic models of carbon nanotube networks
International Nuclear Information System (INIS)
Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain
2015-01-01
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models
Link overlap, viability, and mutual percolation in multiplex networks
International Nuclear Information System (INIS)
Min, Byungjoon; Lee, Sangchul; Lee, Kyu-Min; Goh, K.-I.
2015-01-01
Many real-world complex systems are best modeled by multiplex networks. The multiplexity has proved to have broad impact on the system’s structure and function. Most theoretical studies on multiplex networks to date, however, have largely ignored the effect of the link overlap across layers despite strong empirical evidences for its significance. In this article, we investigate the effect of the link overlap in the viability of multiplex networks, both analytically and numerically. After a short recap of the original multiplex viability study, the distinctive role of overlapping links in viability and mutual connectivity is emphasized and exploited for setting up a proper analytic framework. A rich phase diagram for viability is obtained and greatly diversified patterns of hysteretic behavior in viability are observed in the presence of link overlap. Mutual percolation with link overlap is revisited as a limit of multiplex viability problem, and the controversy between existing results is clarified. The distinctive role of overlapping links is further demonstrated by the different responses of networks under random removals of overlapping and non-overlapping links, respectively, as well as under several link-removal strategies. Our results show that the link overlap facilitates the viability and mutual percolation; at the same time, the presence of link overlap poses a challenge in analytical approaches to the problem
Polymer collapse, protein folding, and the percolation threshold.
Meirovitch, Hagai
2002-01-15
We study the transition of polymers in the dilute regime from a swollen shape at high temperatures to their low-temperature structures. The polymers are modeled by a single self-avoiding walk (SAW) on a lattice for which l of the monomers (the H monomers) are self-attracting, i.e., if two nonbonded H monomers become nearest neighbors on the lattice they gain energy of interaction (epsilon = -/epsilon/); the second type of monomers, denoted P, are neutral. This HP model was suggested by Lau and Dill (Macromolecules 1989, 22, 3986-3997) to study protein folding, where H and P are the hydrophobic and polar amino acid residues, respectively. The model is simulated on the square and simple cubic (SC) lattices using the scanning method. We show that the ground state and the sharpness of the transition depend on the lattice, the fraction g of the H monomers, as well as on their arrangement along the chain. In particular, if the H monomers are distributed at random and g is larger than the site percolation threshold of the lattice, a collapsed transition is very likely to occur. This conclusion, drawn for the lattice models, is also applicable to proteins where an effective lattice with coordination number between that of the SC lattice and the body centered cubic lattice is defined. Thus, the average fraction of hydrophobic amino acid residues in globular proteins is found to be close to the percolation threshold of the effective lattice.
Rubber elasticity for percolation network consisting of Gaussian chains
International Nuclear Information System (INIS)
Nishi, Kengo; Noguchi, Hiroshi; Shibayama, Mitsuhiro; Sakai, Takamasa
2015-01-01
A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G 0 , must be equal to G/G 0 = (p − 2/f)/(1 − 2/f) if the position of sites can be determined so as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels
Rubber elasticity for percolation network consisting of Gaussian chains
Energy Technology Data Exchange (ETDEWEB)
Nishi, Kengo, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp; Noguchi, Hiroshi; Shibayama, Mitsuhiro, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp [Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Sakai, Takamasa, E-mail: kengo.nishi@phys.uni-goettingen.de, E-mail: sakai@tetrapod.t.u-tokyo.ac.jp, E-mail: sibayama@issp.u-tokyo.ac.jp [Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)
2015-11-14
A theory describing the elastic modulus for percolation networks of Gaussian chains on general lattices such as square and cubic lattices is proposed and its validity is examined with simulation and mechanical experiments on well-defined polymer networks. The theory was developed by generalizing the effective medium approximation (EMA) for Hookian spring network to Gaussian chain networks. From EMA theory, we found that the ratio of the elastic modulus at p, G to that at p = 1, G{sub 0}, must be equal to G/G{sub 0} = (p − 2/f)/(1 − 2/f) if the position of sites can be determined so as to meet the force balance, where p is the degree of cross-linking reaction. However, the EMA prediction cannot be applicable near its percolation threshold because EMA is a mean field theory. Thus, we combine real-space renormalization and EMA and propose a theory called real-space renormalized EMA, i.e., REMA. The elastic modulus predicted by REMA is in excellent agreement with the results of simulations and experiments of near-ideal diamond lattice gels.
Electron percolation in realistic models of carbon nanotube networks
Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain
2015-09-01
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Tayyib, Nahla; Coyer, Fiona; Lewis, Peter A
2015-05-01
This study tested the effectiveness of a pressure ulcer (PU) prevention bundle in reducing the incidence of PUs in critically ill patients in two Saudi intensive care units (ICUs). A two-arm cluster randomized experimental control trial. Participants in the intervention group received the PU prevention bundle, while the control group received standard skin care as per the local ICU policies. Data collected included demographic variables (age, diagnosis, comorbidities, admission trajectory, length of stay) and clinical variables (Braden Scale score, severity of organ function score, mechanical ventilation, PU presence, and staging). All patients were followed every two days from admission through to discharge, death, or up to a maximum of 28 days. Data were analyzed with descriptive correlation statistics, Kaplan-Meier survival analysis, and Poisson regression. The total number of participants recruited was 140: 70 control participants (with a total of 728 days of observation) and 70 intervention participants (784 days of observation). PU cumulative incidence was significantly lower in the intervention group (7.14%) compared to the control group (32.86%). Poisson regression revealed the likelihood of PU development was 70% lower in the intervention group. The intervention group had significantly less Stage I (p = .002) and Stage II PU development (p = .026). Significant improvements were observed in PU-related outcomes with the implementation of the PU prevention bundle in the ICU; PU incidence, severity, and total number of PUs per patient were reduced. Utilizing a bundle approach and standardized nursing language through skin assessment and translation of the knowledge to practice has the potential to impact positively on the quality of care and patient outcome. © 2015 Sigma Theta Tau International.
Directory of Open Access Journals (Sweden)
Balázs Gönci
2010-12-01
Full Text Available Because of its relevance to everyday life, the spreading of viral infections has been of central interest in a variety of scientific communities involved in fighting, preventing and theoretically interpreting epidemic processes. Recent large scale observations have resulted in major discoveries concerning the overall features of the spreading process in systems with highly mobile susceptible units, but virtually no data are available about observations of infection spreading for a very large number of immobile units. Here we present the first detailed quantitative documentation of percolation-type viral epidemics in a highly reproducible in vitro system consisting of tens of thousands of virtually motionless cells. We use a confluent astroglial monolayer in a Petri dish and induce productive infection in a limited number of cells with a genetically modified herpesvirus strain. This approach allows extreme high resolution tracking of the spatio-temporal development of the epidemic. We show that a simple model is capable of reproducing the basic features of our observations, i.e., the observed behaviour is likely to be applicable to many different kinds of systems. Statistical physics inspired approaches to our data, such as fractal dimension of the infected clusters as well as their size distribution, seem to fit into a percolation theory based interpretation. We suggest that our observations may be used to model epidemics in more complex systems, which are difficult to study in isolation.
Gönci, Balázs; Németh, Valéria; Balogh, Emeric; Szabó, Bálint; Dénes, Ádám; Környei, Zsuzsanna; Vicsek, Tamás
2010-12-20
Because of its relevance to everyday life, the spreading of viral infections has been of central interest in a variety of scientific communities involved in fighting, preventing and theoretically interpreting epidemic processes. Recent large scale observations have resulted in major discoveries concerning the overall features of the spreading process in systems with highly mobile susceptible units, but virtually no data are available about observations of infection spreading for a very large number of immobile units. Here we present the first detailed quantitative documentation of percolation-type viral epidemics in a highly reproducible in vitro system consisting of tens of thousands of virtually motionless cells. We use a confluent astroglial monolayer in a Petri dish and induce productive infection in a limited number of cells with a genetically modified herpesvirus strain. This approach allows extreme high resolution tracking of the spatio-temporal development of the epidemic. We show that a simple model is capable of reproducing the basic features of our observations, i.e., the observed behaviour is likely to be applicable to many different kinds of systems. Statistical physics inspired approaches to our data, such as fractal dimension of the infected clusters as well as their size distribution, seem to fit into a percolation theory based interpretation. We suggest that our observations may be used to model epidemics in more complex systems, which are difficult to study in isolation.
Effect of sorbic acid doping on flux pinning in bulk MgB{sub 2} with the percolation model
Energy Technology Data Exchange (ETDEWEB)
Yang, Y. [Key Laboratory of Advanced Technologies of Materials (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Key Laboratory of Magnetic Levitation and Maglev Train (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, C.H. [School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia); Wang, L.; Sun, H.H. [Key Laboratory of Advanced Technologies of Materials (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Key Laboratory of Magnetic Levitation and Maglev Train (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhao, Y., E-mail: yzhao@swjtu.edu.c [Key Laboratory of Advanced Technologies of Materials (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Key Laboratory of Magnetic Levitation and Maglev Train (Ministry of Education of China), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia)
2010-11-01
In this paper, we study the doping effect of sorbic acid (C{sub 6}H{sub 8}O{sub 2}), from 0 to 20 wt.% of the total MgB{sub 2}, on critical temperature (T{sub c}), critical current density (J{sub c}), irreversibility field (H{sub irr}) and crystalline structure. The XRD patterns of samples show a slightly decrease in a-axis lattice parameter for doped samples, due to the partial substitution of carbon at boron site. On the other hand, we investigate the influence of doping on the behavior of flux pinning and J{sub c}(B) in the framework of percolation theory and it is found that the J{sub c}(B) behavior could be well fitted in high field region. The two key parameters, anisotropy and percolation threshold, play very important roles. It is believed that the enhancement of J{sub c} is due to the reduction of anisotropy in high field region.
A Matter of Time: Faster Percolator Analysis via Efficient SVM Learning for Large-Scale Proteomics.
Halloran, John T; Rocke, David M
2018-05-04
Percolator is an important tool for greatly improving the results of a database search and subsequent downstream analysis. Using support vector machines (SVMs), Percolator recalibrates peptide-spectrum matches based on the learned decision boundary between targets and decoys. To improve analysis time for large-scale data sets, we update Percolator's SVM learning engine through software and algorithmic optimizations rather than heuristic approaches that necessitate the careful study of their impact on learned parameters across different search settings and data sets. We show that by optimizing Percolator's original learning algorithm, l 2 -SVM-MFN, large-scale SVM learning requires nearly only a third of the original runtime. Furthermore, we show that by employing the widely used Trust Region Newton (TRON) algorithm instead of l 2 -SVM-MFN, large-scale Percolator SVM learning is reduced to nearly only a fifth of the original runtime. Importantly, these speedups only affect the speed at which Percolator converges to a global solution and do not alter recalibration performance. The upgraded versions of both l 2 -SVM-MFN and TRON are optimized within the Percolator codebase for multithreaded and single-thread use and are available under Apache license at bitbucket.org/jthalloran/percolator_upgrade .
Pseudo-random-number generators and the square site percolation threshold.
Lee, Michael J
2008-09-01
Selected pseudo-random-number generators are applied to a Monte Carlo study of the two-dimensional square-lattice site percolation model. A generator suitable for high precision calculations is identified from an application specific test of randomness. After extended computation and analysis, an ostensibly reliable value of p_{c}=0.59274598(4) is obtained for the percolation threshold.
Current Percolation in Medium with Boundaries under Quantum Hall Effect Conditions
Directory of Open Access Journals (Sweden)
M. U. Malakeeva
2012-01-01
Full Text Available The current percolation has been considered in the medium with boundaries under quantum Hall effect conditions. It has been shown that in that case the effective Hall conductivity has a nonzero value due to percolation of the Hall current through the finite number of singular points (in our model these are corners at the phase joints.
Mikami, Masato; Saputro, Herman; Seo, Takehiko; Oyagi, Hiroshi
2018-03-01
Stable operation of liquid-fueled combustors requires the group combustion of fuel spray. Our study employs a percolation approach to describe unsteady group-combustion excitation based on findings obtained from microgravity experiments on the flame spread of fuel droplets. We focus on droplet clouds distributed randomly in three-dimensional square lattices with a low-volatility fuel, such as n-decane in room-temperature air, where the pre-vaporization effect is negligible. We also focus on the flame spread in dilute droplet clouds near the group-combustion-excitation limit, where the droplet interactive effect is assumed negligible. The results show that the occurrence probability of group combustion sharply decreases with the increase in mean droplet spacing around a specific value, which is termed the critical mean droplet spacing. If the lattice size is at smallest about ten times as large as the flame-spread limit distance, the flame-spread characteristics are similar to those over an infinitely large cluster. The number density of unburned droplets remaining after completion of burning attained maximum around the critical mean droplet spacing. Therefore, the critical mean droplet spacing is a good index for stable combustion and unburned hydrocarbon. In the critical condition, the flame spreads through complicated paths, and thus the characteristic time scale of flame spread over droplet clouds has a very large value. The overall flame-spread rate of randomly distributed droplet clouds is almost the same as the flame-spread rate of a linear droplet array except over the flame-spread limit.
International Nuclear Information System (INIS)
He Da; Ekere, N N
2004-01-01
In this paper, we apply Monte Carlo simulation to investigate the conductive percolation threshold of granular composite of conductive and insulating powders with amorphous structure. We focus on the effect of insulating to conductive particle size ratio λ = d i /d c on the conducting percolation threshold p c (the volume fraction of the conductive powder). Simulation results show that, for λ = 1, the percolation threshold p c lies between simple cubic and body centred cubic site percolation thresholds, and that as λ increases the percolation threshold decreases. We also use the structural information obtained by the simulation to study the nonlinear current-voltage characteristics of composite with solid volume fraction of conductive powder below p c in terms of electron tunnelling for nanoscale powders, dielectric breakdown for microscale or larger powders, and pressing induced conduction for non-rigid insulating powders
The critical current of granular superconductor
International Nuclear Information System (INIS)
Ignat'ev, V.K.
1998-01-01
A mechanism of hyper vortex pinning in granular superconductors is proposed to describe the field dependence of the critical current density and pinning potential. The results are in a good agreement with the experiment. The model represents the peak effect and the percolation mechanism of conductivity in ceramic superconductors
Pretreatment Characteristics of Waste Oak Wood by Ammonia Percolation
Kim, Jun-Seok; Kim, Hyunjoon; Lee, Jin-Suk; Lee, Joon-Pyo; Park, Soon-Chul
A log of waste oak wood collected from a Korean mushroom farm has been tested for ammonia percolation pretreatment. The waste log has different physical characteristics from that of virgin oak wood. The density of the waste wood was 30% lower than that of virgin oak wood. However, there is little difference in the chemical compositions between the woods. Due to the difference in physical characteristics, the optimal pretreatment conditions were also quite different. While for waste oak the optimum temperature was determined to be 130°C, for virgin oak wood the optimum pretreatment was only achieved at 170°C. Presoaking for 12 h with ammonia solution before pretreatment was helpful to increase the delignification efficiency.
Large Dielectric Constant Enhancement in MXene Percolative Polymer Composites
Tu, Shao Bo
2018-04-06
near the percolation limit of about 15.0 wt % MXene loading, which surpasses all previously reported composites made of carbon-based fillers in the same polymer. With up to 10 wt % MXene loading, the dielectric loss of the MXene/P(VDF-TrFE-CFE) composite indicates only an approximately 5-fold increase (from 0.06 to 0.35), while the dielectric constant increased by 25 times over the same composition range. Furthermore, the ratio of permittivity to loss factor of the MXene-polymer composite is superior to that of all previously reported fillers in this same polymer. The dielectric constant enhancement effect is demonstrated to exist in other polymers as well when loaded with MXene. We show that the dielectric constant enhancement is largely due to the charge accumulation caused by the formation of microscopic dipoles at the surfaces between the MXene sheets and the polymer matrix under an external applied electric field.
Mesoscopic Percolating Resistance Network in a Strained Manganite Thin Film
Lai, K.; Nakamura, M.; Kundhikanjana, W.; Kawasaki, M.; Tokura, Y.; Kelly, M. A.; Shen, Z.-X.
2010-01-01
Many unusual behaviors in complex oxides are deeply associated with the spontaneous emergence of microscopic phase separation. Depending on the underlying mechanism, the competing phases can form ordered or random patterns at vastly different length scales. By using a microwave impedance microscope, we observed an orientation-ordered percolating network in strained Nd 1/2Sr1/2MnO3 thin films with a large period of 100 nanometers. The filamentary metallic domains align preferentially along certain crystal axes of the substrate, suggesting the anisotropic elastic strain as the key interaction in this system. The local impedance maps provide microscopic electrical information of the hysteretic behavior in strained thin film manganites, suggesting close connection between the glassy order and the colossal magnetoresistance effects at low temperatures.
Mesoscopic Percolating Resistance Network in a Strained Manganite Thin Film
Lai, K.
2010-07-08
Many unusual behaviors in complex oxides are deeply associated with the spontaneous emergence of microscopic phase separation. Depending on the underlying mechanism, the competing phases can form ordered or random patterns at vastly different length scales. By using a microwave impedance microscope, we observed an orientation-ordered percolating network in strained Nd 1/2Sr1/2MnO3 thin films with a large period of 100 nanometers. The filamentary metallic domains align preferentially along certain crystal axes of the substrate, suggesting the anisotropic elastic strain as the key interaction in this system. The local impedance maps provide microscopic electrical information of the hysteretic behavior in strained thin film manganites, suggesting close connection between the glassy order and the colossal magnetoresistance effects at low temperatures.
Percolation Effects in Very-High-Energy Cosmic Rays
International Nuclear Information System (INIS)
Dias de Deus, J.; Santo, M.C. Espirito; Pimenta, M.; Pajares, C.
2006-01-01
Cosmic ray data at high energies present a number of well-known puzzles. At very high energies (E∼10 20 eV) there are indications of a discrepancy between ground array experiments and fluorescence detectors. On the other hand, the dependence of the depth of the shower maximum X max with the primary energy shows a change in slope (E∼10 17 eV) which is usually explained assuming a composition change. Both effects could be accounted for in models predicting that above a certain energy showers would develop deeper in the atmosphere. In this Letter we argue that this can be done naturally by including percolation effects in the description of the shower development, which cause a change in the behavior of the inelasticity K above E≅10 17 eV
Mesoscopic percolating resistance network in a strained manganite thin film.
Lai, Keji; Nakamura, Masao; Kundhikanjana, Worasom; Kawasaki, Masashi; Tokura, Yoshinori; Kelly, Michael A; Shen, Zhi-Xun
2010-07-09
Many unusual behaviors in complex oxides are deeply associated with the spontaneous emergence of microscopic phase separation. Depending on the underlying mechanism, the competing phases can form ordered or random patterns at vastly different length scales. By using a microwave impedance microscope, we observed an orientation-ordered percolating network in strained Nd(1/2)Sr(1/2)MnO3 thin films with a large period of 100 nanometers. The filamentary metallic domains align preferentially along certain crystal axes of the substrate, suggesting the anisotropic elastic strain as the key interaction in this system. The local impedance maps provide microscopic electrical information of the hysteretic behavior in strained thin film manganites, suggesting close connection between the glassy order and the colossal magnetoresistance effects at low temperatures.
Factors affecting water balance and percolate production for a landfill in operation.
Poulsen, Tjalfe G; Møoldrup, Per
2005-02-01
Percolate production and precipitation data for a full-scale landfill in operation measured over a 13-year period were used to evaluate the impact and importance of the hydrological conditions of landfill sections on the percolate production rates. Both active (open) and closed landfill sections were included in the evaluation. A simple top cover model requiring a minimum of input data was used to simulate the percolate production as a function of precipitation and landfill section hydrology. The results showed that changes over time in the hydrology of individual landfill sections (such as section closure or plantation of trees on top of closed sections) can change total landfill percolate production by more than 100%; thus, percolate production at an active landfill can be very different from percolate production at the same landfill after closure. Furthermore, plantation of willow on top of closed sections can increase the evapotranspiration rate thereby reducing percolate production rates by up to 47% compared to a grass cover. This process, however, depends upon the availability of water in the top layer, and so the evaporation rate will be less than optimal during the summer where soil-water contents in the top cover are low.
International Nuclear Information System (INIS)
O'Sullivan, W.J.; Mockler, R.C.
1985-08-01
We have completed a program of small angle scattering Rayleigh linewidth measurements on thin films of a 2,6-lutidine + water mixture. No statistically significant departures from three dimensional dynamic response were seen, although the conditions set by the theory of Calvo and Ferrell were met. We have applied digital image processing to evaluate fractal scale invariance in two dimensional particle aggregates arising from the induced coagulation of colloidal particle monolayer crystals. Our system gives us the capability of calculating the pair correlation function for both small and very large (2 x 10 4 particles) particle clusters. We find evidence of an apparent crossover between kinetic clustering aggregation at small distances (about 20 particle diameters) to percolation or gel/sol transition-behavior at large distances. This is evident in both isolated clusters and in final state ''giant'' aggregates. We are carrying through a parallel program of computer calculations whose motivation is to assess the sensitivity of experimental measures of self similarity to cluster size and image resolution, and to generate efficient algorithms which can be applied to calculate fractal ''critical exponents'' other than the Hausdorff dimension. We have succeeded in measuring the surface tension of a water surface covered by a colloidal particle monolayer crystal, in both its repulsive-dipole and close-packed van der Waals phases
Invasion percolation of single component, multiphase fluids with lattice Boltzmann models
International Nuclear Information System (INIS)
Sukop, M.C.; Or, Dani
2003-01-01
Application of the lattice Boltzmann method (LBM) to invasion percolation of single component multiphase fluids in porous media offers an opportunity for more realistic modeling of the configurations and dynamics of liquid/vapor and liquid/solid interfaces. The complex geometry of connected paths in standard invasion percolation models arises solely from the spatial arrangement of simple elements on a lattice. In reality, fluid interfaces and connectivity in porous media are naturally controlled by the details of the pore geometry, its dynamic interaction with the fluid, and the ambient fluid potential. The multiphase LBM approach admits realistic pore geometry derived from imaging techniques and incorporation of realistic hydrodynamics into invasion percolation models
Picu, R. C.; Pal, A.; Lupulescu, M. V.
2016-04-01
We study the mechanical behavior of two-dimensional, stochastically microcracked continua in the range of crack densities close to, and above, the transport percolation threshold. We show that these materials retain stiffness up to crack densities much larger than the transport percolation threshold due to topological interlocking of sample subdomains. Even with a linear constitutive law for the continuum, the mechanical behavior becomes nonlinear in the range of crack densities bounded by the transport and stiffness percolation thresholds. The effect is due to the fractal nature of the fragmentation process and is not linked to the roughness of individual cracks.
Equation of states for the infinite cluster and backbone in anisotropic square lattice
International Nuclear Information System (INIS)
Silva, L.R. da; Almeida, N.S.; Tsallis, C.
1985-01-01
A real space renormalization group procedure recently developed for calculating equations of states for geometrical problems is used, to treat bond percolation in the anisotropic square lattice. By choosing a convenient self-dual cluster, for all values of the occupancy probabilities P sub(x) and P sub(y) (along the x and y axes respectively), the order parameters P infinity (P sub(x),P sub(y)) and P sup(B) infinity (P sub(x),P sub(y)) respectively associated with the complete percolating infinite cluster and with its backbone are calculated. An interesting difference appears between these two quantities whenever one of the occupancy probabilities, say P sub(y), equals unity: lim sub(P sub(y) → l) P infinity (P sub(x),P sub(y) is discontinuous at P sub(x)=0 (where P sub(infinity) jumps from 0 to 1), whereas lim sub(P sub(y) → 1) P sup(B) sub(infinity) (P sub(x),P sub(y)) continuously increases from 0 to 1 when P sub(x) increases from 0 to 1. Through a convenient extrapolation procedure which includes the use of the best available values for the critical exponents β and β sup(B), values for P sub(infinity) and P sup(B) sub(infinity) which are believed to be numerically quite reliable are obtained. In particular, P sub(infinity) (p,p) approx. A (p-1/2) sup(β) (β=5/36 and A approx. 1.25) and P sup(B) sub(infinity) (p,p) approx. A sup(B) (p-1/2) sup(β) sup(B) (β sup(B) approx. 0.53 and A sup(B) approx. 1.92). (Author) [pt
Shin, Kyounghee; Gong, Gyeonghyeon; Cuadrado, Jonas; Jeon, Serim; Seo, Mintae; Choi, Hong Sung; Hwang, Jae Sung; Lee, Youngbok; Fernandez-Nieves, Alberto; Kim, Jin Woong
2017-03-28
This study introduces an extremely stable attractive nanoscale emulsion fluid, in which the amphiphilic block copolymer, poly(ethylene oxide)-block-poly(ϵ-caprolactone) (PEO-b-PCL), is tightly packed with lecithin, thereby forming a mechanically robust thin-film at the oil-water interface. The molecular association of PEO-b-PCL with lecithin is critical for formation of a tighter and denser molecular assembly at the interface, which is systematically confirmed by T 2 relaxation and DSC analyses. Moreover, suspension rheology studies also reflect the interdroplet attractions over a wide volume fraction range of the dispersed oil phase; this results in a percolated network of stable drops that exhibit no signs of coalescence or phase separation. This unique rheological behavior is attributed to the dipolar interaction between the phosphorylcholine groups of lecithin and the methoxy end groups of PEO-b-PCL. Finally, the nanoemulsion system significantly enhances transdermal delivery efficiency due to its favorable attraction to the skin, as well as high diffusivity of the nanoscale emulsion drops. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites
Rowley, S. E.; Vojta, T.; Jones, A. T.; Guo, W.; Oliveira, J.; Morrison, F. D.; Lindfield, N.; Baggio Saitovitch, E.; Watts, B. E.; Scott, J. F.
2017-07-01
Hexagonal ferrites not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultrahigh-density memories, credit-card stripes, magnetic bar codes, small motors, and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbF e12 -xG axO19 to zero by chemical substitution x . The phase transition boundary is found to vary as TN˜(1-x /xc ) 2 /3 with xc very close to the calculated spin percolation threshold, which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven. We find that this produces a form of compositionally tuned, insulating, ferrimagnetic quantum criticality. Close to the zero-temperature phase transition, we observe the emergence of an electric dipole glass induced by magnetoelectric coupling. The strong frequency behavior of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero-frequency limit, depending on composition x . These quantum-mechanical properties, along with the multiplicity of low-lying modes near the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.
Percolation-theoretic bounds on the cache size of nodes in mobile opportunistic networks.
Yuan, Peiyan; Wu, Honghai; Zhao, Xiaoyan; Dong, Zhengnan
2017-07-18
The node buffer size has a large influence on the performance of Mobile Opportunistic Networks (MONs). This is mainly because each node should temporarily cache packets to deal with the intermittently connected links. In this paper, we study fundamental bounds on node buffer size below which the network system can not achieve the expected performance such as the transmission delay and packet delivery ratio. Given the condition that each link has the same probability p to be active in the next time slot when the link is inactive and q to be inactive when the link is active, there exists a critical value p c from a percolation perspective. If p > p c , the network is in the supercritical case, where we found that there is an achievable upper bound on the buffer size of nodes, independent of the inactive probability q. When p network is in the subcritical case, and there exists a closed-form solution for buffer occupation, which is independent of the size of the network.
International Nuclear Information System (INIS)
Botet, R.
1996-01-01
A novel scaling of the multiplicity distributions is found in the shattering phase of the sequential fragmentation process with inhibition. The same scaling law is shown to hold in the percolation process. (author)
PRETREATMENT AND FRACTIONATION OF CORN STOVER BY AMMONIA RECYCLE PERCOLATION PROCESS. (R831645)
Corn stover was pretreated with aqueous ammonia in a flow-through column reactor,a process termed as Ammonia Recycle Percolation (ARP). The aqueous ammonia causesswelling and efficient delignification of biomass at high temperatures. The ARPprocess solubilizes abou...
Percolation pond as a method of managed aquifer recharge in a ...
Indian Academy of Sciences (India)
Raicy Mani Christy
2017-07-17
Jul 17, 2017 ... Percolation ponds have become very popular methods of managed aquifer recharge due to their low ... effect of recharge structures by some researchers .... qualitative comparison of observed responses of .... Two types of.
Percolation testing at the F- and H-Area Seepage Basins
International Nuclear Information System (INIS)
McHood, M.D.
1993-01-01
The design of the F- and H-Area Seepage Basin contaminated groundwater remediation system requires information from multiple well pump tests (Reference 1). Soil percolation rates are needed in order to support the multiple well pump test planning. The objective of this task was to determine characteristic percolation rates for soils in four select areas where infiltration galleries are proposed. These infiltration galleries will be temporary installations built on the ground surface and used to disposes of water from the multiple well pump tests. A procedure defining the specific work process for collecting percolation rate data is contained in Appendix 3. Results from these percolation tests will be used in the design of infiltration galleries for the disposal of well water extracted during the multiple well pump tests
Diffusion of test particles in stochastic magnetic fields in the percolative regime
International Nuclear Information System (INIS)
Neuer, Marcus; Spatschek, Karl H.
2006-01-01
For stochastic magnetic flux functions with percolative contours the test particle transport is investigated. The calculations make use of the stochastic Liouville approach. They start from the so-called A-Langevin equations, including stochastic magnetic field components and binary collisions. Using the decorrelation trajectory method, a relation between the Lagrangian velocity correlation function and the Eulerian magnetic field correlation is derived and introduced into the Green-Kubo formalism. Finite Larmor radius effects are included. Interesting results are presented in the percolation regime corresponding to high Kubo numbers. Previous results are found to be limiting cases for small Kubo numbers. For different percolative scenarios the diffusion is analyzed and strong influences of the percolative structures on the transport scaling are found. The finite Larmor radius effects are discussed in detail. Numerical simulations of the A-Langevin equation confirm the semianalytical predictions
Influence maximization in complex networks through optimal percolation
Morone, Flaviano; Makse, Hernán A.
2015-08-01
The whole frame of interconnections in complex networks hinges on a specific set of structural nodes, much smaller than the total size, which, if activated, would cause the spread of information to the whole network, or, if immunized, would prevent the diffusion of a large scale epidemic. Localizing this optimal, that is, minimal, set of structural nodes, called influencers, is one of the most important problems in network science. Despite the vast use of heuristic strategies to identify influential spreaders, the problem remains unsolved. Here we map the problem onto optimal percolation in random networks to identify the minimal set of influencers, which arises by minimizing the energy of a many-body system, where the form of the interactions is fixed by the non-backtracking matrix of the network. Big data analyses reveal that the set of optimal influencers is much smaller than the one predicted by previous heuristic centralities. Remarkably, a large number of previously neglected weakly connected nodes emerges among the optimal influencers. These are topologically tagged as low-degree nodes surrounded by hierarchical coronas of hubs, and are uncovered only through the optimal collective interplay of all the influencers in the network. The present theoretical framework may hold a larger degree of universality, being applicable to other hard optimization problems exhibiting a continuous transition from a known phase.
Inorganic arsenic removal in rice bran by percolating cooking water.
Signes-Pastor, Antonio J; Carey, Manus; Meharg, Andrew A
2017-11-01
Rice bran, a by-product of milling rice, is highly nutritious but contains very high levels of the non-threshold carcinogen inorganic arsenic (i-As), at concentrations around 1mg/kg. This i-As content needs to be reduced to make rice bran a useful food ingredient. Evaluated here is a novel approach to minimizing rice bran i-As content which is also suitable for its stabilization namely, cooking bran in percolating arsenic-free boiling water. Up to 96% of i-As removal was observed for a range of rice bran products, with i-As removal related to the volume of cooking water used. This process reduced the copper, potassium, and phosphorus content, but had little effect on other trace- and macro-nutrient elements in the rice bran. There was little change in organic composition, as assayed by NIR, except for a decrease in the soluble sugar and an increase, due to biomass loss, in dietary fiber. Copyright © 2017 Elsevier Ltd. All rights reserved.
Influence maximization in complex networks through optimal percolation
Morone, Flaviano; Makse, Hernan; CUNY Collaboration; CUNY Collaboration
The whole frame of interconnections in complex networks hinges on a specific set of structural nodes, much smaller than the total size, which, if activated, would cause the spread of information to the whole network, or, if immunized, would prevent the diffusion of a large scale epidemic. Localizing this optimal, that is, minimal, set of structural nodes, called influencers, is one of the most important problems in network science. Here we map the problem onto optimal percolation in random networks to identify the minimal set of influencers, which arises by minimizing the energy of a many-body system, where the form of the interactions is fixed by the non-backtracking matrix of the network. Big data analyses reveal that the set of optimal influencers is much smaller than the one predicted by previous heuristic centralities. Remarkably, a large number of previously neglected weakly connected nodes emerges among the optimal influencers. Reference: F. Morone, H. A. Makse, Nature 524,65-68 (2015)
Energy Technology Data Exchange (ETDEWEB)
Moscicki, J. K.; Sokolowska, D.; Dziob, D.; Nowak, J. [Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Kwiatkowski, L. [Department of Econometrics and Operations Research, Cracow University of Economics, Rakowicka 27, 31-510 Krakow (Poland)
2014-02-15
A simplified data analysis protocol, for dielectric spectroscopy use to study conductivity percolation in dehydrating granular media is discussed. To enhance visibility of the protonic conductivity contribution to the dielectric loss spectrum, detrimental effects of either low-frequency dielectric relaxation or electrode polarization are removed. Use of the directly measurable monofrequency dielectric loss factor rather than estimated DC conductivity to parameterize the percolation transition substantially reduces the analysis work and time.
Effective modelling of percolation at the landscape scale using data-based approaches
Selle, Benny; Lischeid, Gunnar; Huwe, Bernd
2008-06-01
Process-based models have been extensively applied to assess the impact of landuse change on water quantity and quality at landscape scales. However, the routine application of those models suffers from large computational efforts, lack of transparency and the requirement of many input parameters. Data-based models such as Feed-Forward Multilayer Perceptrons (MLP) and Classification and Regression Trees (CART) may be used as effective models, i.e. simple approximations of complex process-based models. These data-based approaches can subsequently be applied for scenario analysis and as a transparent management tool provided climatic boundary conditions and the basic model assumptions of the process-based models do not change dramatically. In this study, we apply MLP, CART and Multiple Linear Regression (LR) to model the spatially distributed and spatially aggregated percolation in soils using weather, groundwater and soil data. The percolation data is obtained via numerical experiments with Hydrus1D. Thus, the complex process-based model is approximated using simpler data-based approaches. The MLP model explains most of the percolation variance in time and space without using any soil information. This reflects the effective dimensionality of the process-based model and suggests that percolation in the study area may be modelled much simpler than using Hydrus1D. The CART model shows that soil properties play a negligible role for percolation under wet climatic conditions. However, they become more important if the conditions turn drier. The LR method does not yield satisfactory predictions for the spatially distributed percolation however the spatially aggregated percolation is well approximated. This may indicate that the soils behave simpler (i.e. more linear) when percolation dynamics are upscaled.
TreeCluster: Massively scalable transmission clustering using phylogenetic trees
Moshiri, Alexander
2018-01-01
Background: The ability to infer transmission clusters from molecular data is critical to designing and evaluating viral control strategies. Viral sequencing datasets are growing rapidly, but standard methods of transmission cluster inference do not scale well beyond thousands of sequences. Results: I present TreeCluster, a cross-platform tool that performs transmission cluster inference on a given phylogenetic tree orders of magnitude faster than existing inference methods and supports multi...
Universality of Critically Pinned Interfaces in Two-Dimensional Isotropic Random Media
Grassberger, Peter
2018-05-01
Based on extensive simulations, we conjecture that critically pinned interfaces in two-dimensional isotropic random media with short-range correlations are always in the universality class of ordinary percolation. Thus, in contrast to interfaces in >2 dimensions, there is no distinction between fractal (i.e., percolative) and rough but nonfractal interfaces. Our claim includes interfaces in zero-temperature random field Ising models (both with and without spontaneous nucleation), in heterogeneous bootstrap percolation, and in susceptible-weakened-infected-removed epidemics. It does not include models with long-range correlations in the randomness and models where overhangs are explicitly forbidden (which would imply nonisotropy of the medium).
Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache; Vascular headache - cluster ... Doctors do not know exactly what causes cluster headaches. They ... (chemical in the body released during an allergic response) or ...
Directory of Open Access Journals (Sweden)
Zhida Du
2014-05-01
Full Text Available To reduce the deep percolation during greenhouse vegetable cultivation, the technique of subsurface film strips placement was tested. Four treatments with two kinds of cross-sections (flat and U-shaped and two different spacings (10 cm and 40 cm of subsurface film strips were arranged in a greenhouse before planting celery. At the same time, a non-film treatment was arranged for comparison. Soil water content was measured and irrigation time was adjusted according to the soil water content. Evapotranspiration of celery during growth was calculated by the method of energy balance and the deep percolation was calculated by the equation of water balance. Deep percolation was reduced in all experimental treatments. Greater reduction in deep percolation was observed when using U-shaped cross-section strips compared with that using the flat cross-section strips. In addition, greater reduction in deep percolation was observed when the spacing between the film strips was smaller. The results of this test showed that the technique of subsurface film strips placement can reduce deep percolation and conserve irrigation water for greenhouse vegetables cultivation. However, the optimal layout variables for the use of the technique of subsurface film strips placement need further experimental and numerical analysis.
Monte Carlo simulations of electrical percolation in multicomponent thin films with nanofillers
Ni, Xiaojuan; Hui, Chao; Su, Ninghai; Jiang, Wei; Liu, Feng
2018-02-01
We developed a 2D disk-stick percolation model to investigate the electrical percolation behavior of an insulating thin film reinforced with 1D and 2D conductive nanofillers via Monte Carlo simulation. Numerical predictions of the percolation threshold in single component thin films showed good agreement with the previous published work, validating our model for investigating the characteristics of the percolation phenomena. Parametric studies of size effect, i.e., length of 1D nanofiller and diameter of 2D nanofiller, were carried out to predict the electrical percolation threshold for hybrid systems. The relationships between the nanofillers in two hybrid systems was established, which showed differences from previous linear assumption. The effective electrical conductance was evaluated through Kirchhoff’s current law by transforming it into a resistor network. The equivalent resistance was obtained from the distribution of nodal voltages by solving a system of linear equations with a Gaussian elimination method. We examined the effects of stick length, relative concentration, and contact patterns of 1D/2D inclusions on electrical performance. One novel aspect of our study is its ability to investigate the effective conductance of nanocomposites as a function of relative concentrations, which shows there is a synergistic effect when nanofillers with different dimensionalities combine properly. Our work provides an important theoretical basis for designing the conductive networks and predicting the percolation properties of multicomponent nanocomposites.
Directory of Open Access Journals (Sweden)
Daniel Andres Dos Santos
2014-06-01
Full Text Available Since the tendon is composed by collagen fibrils of various sizes connected between them through molecular cross-links, it sounds logical to model it via a heterogeneous network of fibrils. Using cross sectional images, that network is operatively inferred from the respective Gabriel graph of the fibril mass centers. We focus on network percolation characteristics under an ordered activation of fibrils (progressive recruitment going from the smallest to the largest fibril. Analyses of percolation were carried out on a repository of images of digital flexor tendons obtained from samples of lizards and frogs. Observed percolation thresholds were compared against values derived from hypothetical scenarios of random activation of nodes. Strikingly, we found a significant delay for the occurrence of percolation in actual data. We interpret this finding as the consequence of some non-random packing of fibrillar units into a size-constrained geometric pattern. We erect an ideal geometric model of balanced interspersion of polymorphic units that accounts for the delayed percolating instance. We also address the circumstance of being percolation curves mirrored by the empirical curves of stress-strain obtained from the same studied tendons. By virtue of this isomorphism, we hypothesize that the inflection points of both curves are different quantitative manifestations of a common transitional process during mechanical load transference.
Alizadeh Sahraei, Abolfazl; Ayati, Moosa; Baniassadi, Majid; Rodrigue, Denis; Baghani, Mostafa; Abdi, Yaser
2018-03-01
This study attempts to comprehensively investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the AC and DC electrical conductivity of epoxy nanocomposites. The samples (0.2, 0.3, and 0.5 wt. % MWCNT) were produced using a combination of ultrason and shear mixing methods. DC measurements were performed by continuous measurement of the current-voltage response and the results were analyzed via a numerical percolation approach, while for the AC behavior, the frequency response was studied by analyzing phase difference and impedance in the 10 Hz to 0.2 MHz frequency range. The results showed that the dielectric parameters, including relative permittivity, impedance phase, and magnitude, present completely different behaviors for the frequency range and MWCNT weight fractions studied. To better understand the nanocomposites electrical behavior, equivalent electric circuits were also built for both DC and AC modes. The DC equivalent networks were developed based on the current-voltage curves, while the AC equivalent circuits were proposed by using an optimization problem according to the impedance magnitude and phase at different frequencies. The obtained equivalent electrical circuits were found to be highly useful tools to understand the physical mechanisms involved in MWCNT filled polymer nanocomposites.
Karaoulanis, D; Bacalis, N C
2000-01-01
We have performed Monte Carlo simulations of magnetic semiconductors above and below the nearest-neighbour percolation threshold (NNPT) using a classical Heisenberg Hamiltonian with up to third nearest-neighbour (nn) interactions. Large clusters were created allowing use of realistically low magnetic fields (10 G). Above NNPT our results, apart from confirming the existing picture of this class of materials, also show that the inclusion of the second and third (nn) interactions increases the frustration, thus making the transition temperature smaller and closer to experiment than calculated via the first nn interactions only. A physically plausible explanation is given. Below NNPT our results strongly support the validity of the hypothesis (D. Karaoulanis, J.P. Xanthakis, C. Papatriantafillou, J. Magn. Magn. Mater. 161 (1996) 231), that the experimentally observed susceptibility is the sum of two contributions: a paramagnetic one due to isolated magnetic clusters, and a spin-glass contribution due to an 'infi...
Soil Respiration Controls Ionic Nutrient Concentration In Percolating Water In Rice Fields
Kimura, M.
2004-12-01
Soil water in the plow layer in rice fields contains various kinds of cations and anions, and they are lost from the plow layer by water percolation. Some portions of CO2 produced by respirations of rice roots and soil microorganisms are also leached by water percolation to the subsoil layer as HCO3-. As the electrical neutrality of inorganic substances in percolating water is maintained when they are assumed to be in the form of simple cations and anions, soil respiration accelerates the leaching of ionic nutrients from the plow layer by water percolation. The proportion of inorganic carbon (Σ CO2) originated from photosynthates in the total Σ CO2 in soil solution in the plow layer was from 28 to 36 % in the rice straw amended soil and from 16 to 31 % in the soil without rice straw amendment in a soil pot experiment with rice plant after the maximum tillering stage. Most of Σ CO2 in percolating water from the plow layer accumulates in the subsoil layer. Periodical measurement of Σ CO2 in percolating water at 13 and 40 cm soil depths indicated that 10 % of total soil organic C in the plow layer was leached down from the plow layer (13 cm), and that about 90 % of it was retained in the subsoil layer to the depth of 40 cm. Water soluble organic materials are also leached from the plow layer by water percolation, and the leaching is accelerated by soil reduction. Soil reduction decreased the content of organic materials that were bound with ferric iron in soil (extractable by 0.1M Na4P2O7 + NaBH4) and increased the content of organic materials that were extractable by the neutral chelating solution (0.1M Na4P2O7). In addition, water percolation transformed the latter organic materials to those that were extractable by water and a neutral salt. Considerable portions of organic materials in percolating water are adsorbed in the subsoil layer, and then partially decomposed and polymerized to specific soil organic materials in the subsoil. Organic materials that were
Do diatoms percolate through soil and can they be used for tracing the origin of runoff?
De Graaf, Lenka; Cammeraat, Erik; Pfister, Laurent; Wetzel, Carlos; Klaus, Julian; Hissler, Christophe
2015-04-01
Tracers are widely used to study the movement of water in a catchment. Because of depletion of scientific possibilities with most common tracer types, we proposed the use of diatoms as a natural tracer. Paradoxical results on the contribution of surface runoff to the storm hydrograph were obtained in pioneer research on this idea. Diatom transport via the subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation behavior (speed of percolation, speed of percolation over time, and species distribution) of Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns of contrasting substrates. Co-objective is to study the flowpaths of water through the soil columns. Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on schist, marl and sandstone substrates. Rain simulation experiments were performed to study vertical diatom transport. Rhodamine dye experiments were carried out to gain insight in the active flowpaths of water, and breakthrough experiments were performed to study the responses of the soil columns to applied water. Diatoms were transported through the soil columns of the three substrates. A vast majority of diatom percolation took place within the first 15 minutes, percolation hereafter was marginal but nevertheless present. Peaks in diatom percolation corresponded with a high flux caused by the addition of the diatom culture, but seepage of diatoms along the sides is unlikely according to the species distribution and the rhodamine dye experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp. Significantly more diatoms percolated through the marl columns compared to the schist columns and variance within the sandstone group was very high. Absolute differences between substrates however, were marginal. Most preferential flowpaths were observed in
Leaders of neuronal cultures in a quorum percolation model
Directory of Open Access Journals (Sweden)
Jean-Pierre Eckmann
2010-09-01
Full Text Available We present a theoretical framework using quorum-percolation for describing the initiation of activity in a neural culture. The cultures are modeled as random graphs, whose nodes are neurons with $kin$ inputs and $kout$ outputs, and whose input degrees $kin=k$ obey given distribution functions $p_k$. We examine the firing activity of the population of neurons according to their input degree ($k$ classes and calculate for each class its firing probability $Phi_k(t$ as a function of $t$. The probability of a node to fire is found to be determined by its in-degree $k$, and the first-to-fire neurons are those that have a high $k$. A small minority of high-$k$ classes may be called ``Leaders,'' as they form an inter-connected subnetwork that consistently fires much before the rest of the culture. Once initiated, the activity spreads from the Leaders to the less connected majority of the culture. We then use the distribution of in-degree of the Leaders to study the growth rate of the number of neurons active in a burst, which was experimentally measured to be initially exponential. We find that this kind of growth rate is best described by a population that has an in-degree distribution that is a Gaussian centered around $k=75$ with width $sigma=31$ for the majority of the neurons, but also has a power law tail with exponent $-2$ for ten percent of the population. Neurons in the tail may have as many as $k=4,700$ inputs. We explore and discuss the correspondence between the degree distribution and a dynamic neuronal threshold, showing that from the functional point of view, structure and elementary dynamics are interchangeable. We discuss possible geometric origins of this distribution, and comment on the importance of size, or of having a large number of neurons, in the culture.
DEFF Research Database (Denmark)
Ackerman, Margareta; Ben-David, Shai; Branzei, Simina
2012-01-01
We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both...... the partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...
Guajardo, Olga A; Oyana, Tonny J
2009-01-01
To assess previously determined geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, using a new set of environmental factors. Breast and lung cancer data were acquired from the Michigan Department of Community Health, along with point source pollution data from the U.S. Environmental Protection Agency. The datasets were used to determine whether there is a spatial association between disease risk and environmental contamination. GIS and spatial techniques were combined with statistical analysis to investigate local risk of breast and lung cancer. The study suggests that neighborhoods in close proximity to the river were associated with a high risk of breast cancer, while increased risk of lung cancer was detected among neighborhoods in close proximity to point source pollution and major highways. Statistically significant (P clusters of cancer incidences were observed among residents living near the rivers. These findings are useful to researchers and governmental agencies for risk assessment, regulation, and control of environmental contamination in the floodplains.
Directory of Open Access Journals (Sweden)
Olga A. Guajardo
2009-01-01
Full Text Available Objectives. To assess previously determined geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, using a new set of environmental factors. Materials and Methods. Breast and lung cancer data were acquired from the Michigan Department of Community Health, along with point source pollution data from the U.S. Environmental Protection Agency. The datasets were used to determine whether there is a spatial association between disease risk and environmental contamination. GIS and spatial techniques were combined with statistical analysis to investigate local risk of breast and lung cancer. Results and Conclusion. The study suggests that neighborhoods in close proximity to the river were associated with a high risk of breast cancer, while increased risk of lung cancer was detected among neighborhoods in close proximity to point source pollution and major highways. Statistically significant (P≤.001 clusters of cancer incidences were observed among residents living near the rivers. These findings are useful to researchers and governmental agencies for risk assessment, regulation, and control of environmental contamination in the floodplains.
International Nuclear Information System (INIS)
Guajardo, O.A.; Oyana, T.J.
2010-01-01
Objectives. To assess previously determined geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, using a new set of environmental factors. Materials and Methods. Breast and lung cancer data were acquired from the Michigan Department of Community Health, along with point source pollution data from the U.S. Environmental Protection Agency. The datasets were used to determine whether there is a spatial association between disease risk and environmental contamination. GIS and spatial techniques were combined with statistical analysis to investigate local risk of breast and lung cancer. Results and Conclusion. The study suggests that neighborhoods in close proximity to the river were associated with a high risk of breast cancer, while increased risk of lung cancer was detected among neighborhoods in close proximity to point source pollution and major highways. Statistically significant (P=.001) clusters of cancer incidences were observed among residents living near the rivers. These findings are useful to researchers and governmental agencies for risk assessment, regulation, and control of environmental contamination in the flood plains.
Percolation Line and Response Functions in Simple Supercritical Fluids
Czech Academy of Sciences Publication Activity Database
Škvor, J.; Nezbeda, Ivo
2011-01-01
Roč. 190, 1 Sp.I:Sl (2011), s. 133-139 ISSN 0026-8976. [Liblice Conference on the Statistical Mechanics of Liquids /8./. Brno, 13.06.2010-18.06.2010] Institutional research plan: CEZ:AV0Z40720504 Keywords : primitive models * clusters * voronoi polyhedra Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.819, year: 2011
A percolation model of innovation in complex technology spaces
Silverberg, G.; Verspagen, B.
2002-01-01
Innovations are known to arrive more highly clustered than if they were purely random, and their rate of arrival has been increasing nearly exponentially for several centuries. Their distribution of importance is highly skewed and appears to obey a power law or lognormal distribution. Technological
Barbero, Ever J.; Bedard, Antoine Joseph
2018-04-01
Magnetoelectric composites can be produced by embedding magnetostrictive particles in a piezoelectric matrix derived from a piezoelectric powder precursor. Ferrite magnetostrictive particles, if allowed to percolate, can short the potential difference generated in the piezoelectric phase. Modeling a magnetoelectric composite as an aggregate of bi-disperse hard shells, molecular dynamics was used to explore relationships among relative particle size, particle affinity, and electrical percolation with the goal of maximizing the percolation threshold. It is found that two factors raise the percolation threshold, namely the relative size of magnetostrictive to piezoelectric particles, and the affinity between the magnetostrictive and piezoelectric particles.
CO2 injection into fractured peridotites: a reactive percolation experiment
Escario, S.; Godard, M.; Gouze, P.; Leprovost, R.; Luquot, L.; Garcia-Rios, M.
2017-12-01
Mantle peridotites have the potential to trap CO2 as carbonates. This process observed in ophiolites and in oceanic environments provides a long term and safe storage for CO2. It occurs as a part of a complex suite of fluid-rock reactions involving silicate dissolution and precipitation of hydrous phases, carbonates and minor phases that may in turn modify the hydrodynamic properties and the reactivity of the reacted rocks. The efficiency and lastingness of the process require the renewal of fluids at the mineral-fluid interface. Fractures are dominant flow paths in exhumed mantle sections. This study aims at better understanding the effect of CO2-enriched saline fluids on hydrodynamic and chemical processes through fractured peridotites. Experiments were performed using the reactive percolation bench ICARE Lab 3 - Géosciences Montpellier. It allows monitoring the permeability changes during experiments. Effluents are recurrently sampled for analysing cation concentration, pH and alkalinity. Reacted rock samples were characterized by high resolution X-ray microtomography (ESRF ID19, Grenoble, France) and SEM. Experiments consisted in injecting CO2-enriched brines (NaCl 0.5 M) at a rate of 6 mL.h-1 into artificially fractured cores (9 mm diameter × 20 mm length) of Oman harzburgites at T=170°C and Ptotal = 25 MPa for up to 2 weeks. Fractures are of few µm apertures with rough walls. Three sets of experiments were performed at increasing value of [CO2] (0, 0.1 and 1 mol/kg). All experiments showed a decrease in permeability followed by steady state regime that can be caused by a decrease in the roughness of fracture walls (dissolution dominated process), thus favouring fracture closing, or by the precipitation of secondary phases. Maximum enrichments in Mg, Fe and Ca of the effluent fluids occur during the first 2 hours of the experiments whereas Si displays a maximum enrichment at t = 20 h, suggesting extensive dissolution. Maximum enrichments are observed with
Katz, R
1992-11-01
Cluster management is a management model that fosters decentralization of management, develops leadership potential of staff, and creates ownership of unit-based goals. Unlike shared governance models, there is no formal structure created by committees and it is less threatening for managers. There are two parts to the cluster management model. One is the formation of cluster groups, consisting of all staff and facilitated by a cluster leader. The cluster groups function for communication and problem-solving. The second part of the cluster management model is the creation of task forces. These task forces are designed to work on short-term goals, usually in response to solving one of the unit's goals. Sometimes the task forces are used for quality improvement or system problems. Clusters are groups of not more than five or six staff members, facilitated by a cluster leader. A cluster is made up of individuals who work the same shift. For example, people with job titles who work days would be in a cluster. There would be registered nurses, licensed practical nurses, nursing assistants, and unit clerks in the cluster. The cluster leader is chosen by the manager based on certain criteria and is trained for this specialized role. The concept of cluster management, criteria for choosing leaders, training for leaders, using cluster groups to solve quality improvement issues, and the learning process necessary for manager support are described.
Percolation picture of disintegration of nuclei in the proton-nucleus interaction
International Nuclear Information System (INIS)
Botvina, A.S.; Lanin, L.V.
1992-01-01
Breakup of nuclei into fragments in the proton-nucleus interaction is studied. It is assumed that breakup occurs in two stages. During the first stage the incident particle interacts with individual nucleons of the nucleus, and high-energy reaction products are emitted from the nucleus. This stage is described by means of the intranuclear-cascade model. During the second stage some of the nuclei, whose excitation energy is high, or whose density is very inhomogeneous, break up. This breakup is described by means of a percolation model which takes into account the spatial distribution of nucleons in the nucleus and which generalizes the percolation description of the 'liquid-gas' phase transition for finite nuclei. Features of this breakup mechanism are studied. The analysis of the experimental data indicates that it is not sufficient to consider percolation only in the coordinate space, and that the momentum distribution of the nucleons in the nucleus must be taken into account
A nonsteady-state firn-densification model for the percolation zone of a glacier
DEFF Research Database (Denmark)
Reeh, Niels
2008-01-01
A simple steady state firn-densification model is modified to account for short-term time variations of accumulation rate and surface temperature. The temporal surface-elevation- and mass changes at two sites in the percolation zone of an ice sheet in response to various climate histories...... are determined. It is shown that a straight-forward translation of observed short-term ice-sheet surface-elevation variations into mass changes may be completely misleading, particularly for the percolation zone of the ice sheet, where temperature driven variations of melting/re-freezing rates have a strong...... impact on near surface density. In the lower percolation zone, the mass change associated with a temperature anomaly in respect to the mean climate may for example amount to as little as 10 percent of the observed, simultaneous surface elevation change. Moreover, significant surface elevation change may...
Pal, Anirban; Picu, Catalin; Lupulescu, Marian V.
We study the mechanical behavior of two-dimensional, stochastically microcracked continua in the range of crack densities close to, and above the transport percolation threshold. We show that these materials retain stiffness up to crack densities much larger than the transport percolation threshold, due to topological interlocking of sample sub-domains. Even with a linear constitutive law for the continuum, the mechanical behavior becomes non-linear in the range of crack densities bounded by the transport and stiffness percolation thresholds. The effect is due to the fractal nature of the fragmentation process and is not linked to the roughness of individual cracks. We associate this behavior to that of itacolumite, a sandstone that exhibits unusual flexibility.
Multiscale volatility duration characteristics on financial multi-continuum percolation dynamics
Wang, Min; Wang, Jun
A random stock price model based on the multi-continuum percolation system is developed to investigate the nonlinear dynamics of stock price volatility duration, in an attempt to explain various statistical facts found in financial data, and have a deeper understanding of mechanisms in the financial market. The continuum percolation system is usually referred to be a random coverage process or a Boolean model, it is a member of a class of statistical physics systems. In this paper, the multi-continuum percolation (with different values of radius) is employed to model and reproduce the dispersal of information among the investors. To testify the rationality of the proposed model, the nonlinear analyses of return volatility duration series are preformed by multifractal detrending moving average analysis and Zipf analysis. The comparison empirical results indicate the similar nonlinear behaviors for the proposed model and the actual Chinese stock market.
Notes on scaling and critical behaviour in nuclear fragmentation
International Nuclear Information System (INIS)
Campi, X.; Krivine, H.
1994-01-01
The relevance of the concepts of scaling and critical behaviour in nuclear fragmentation is discussed. Experimental results are reviewed to check whether the signals of a percolation or liquid-gas phase transition manifest themselves in the data. (author). 45 refs., 10 figs., 2 tabs
International Nuclear Information System (INIS)
Geraedts, J.M.P.
1983-01-01
Spectra of isotopically mixed clusters (dimers of SF 6 ) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)
... a role. Unlike migraine and tension headache, cluster headache generally isn't associated with triggers, such as foods, hormonal changes or stress. Once a cluster period begins, however, drinking alcohol ...
Nilsson, Martin; Frenning, Göran; Gråsjö, Johan; Alderborn, Göran; Strømme, Maria
2006-10-19
The present study aims at contributing to a complete understanding of the water-induced ionic charge transport in cellulose. The behavior of this transport in loosely compacted microcrystalline cellulose (MCC) powder was investigated as a function of density utilizing a new type of measurement setup, allowing for dielectric spectroscopy measurement in situ during compaction. The ionic conductivity in MCC was found to increase with increasing density until a leveling-out was observed for densities above approximately 0.7 g/cm3. Further, it was shown that the ionic conductivity vs density followed a percolation type behavior signifying the percolation of conductive paths in a 3D conducting network. The density percolation threshold was found to be between approximately 0.2 and 0.4 g/cm3, depending strongly on the cellulose moisture content. The observed percolation behavior was attributed to the forming of interparticulate bonds in the MCC and the percolation threshold dependence on moisture was linked to the moisture dependence of particle rearrangement and plastic deformation in MCC during compaction. The obtained results add to the understanding of the density-dependent water-induced ionic transport in cellulose showing that, at given moisture content, the two major parameters determining the magnitude of the conductivity are the connectedness of the interparticluate bonds and the connectedness of pores with a diameter in the 5-20 nm size range. At densities between approximately 0.7 and 1.2 g/cm3 both the bond and the pore networks have percolated, facilitating charge transport through the MCC compact.
Continuum percolation of polydisperse rods in quadrupole fields: Theory and simulations
Finner, Shari P.; Kotsev, Mihail I.; Miller, Mark A.; van der Schoot, Paul
2018-01-01
We investigate percolation in mixtures of nanorods in the presence of external fields that align or disalign the particles with the field axis. Such conditions are found in the formulation and processing of nanocomposites, where the field may be electric, magnetic, or due to elongational flow. Our focus is on the effect of length polydispersity, which—in the absence of a field—is known to produce a percolation threshold that scales with the inverse weight average of the particle length. Using a model of non-interacting spherocylinders in conjunction with connectedness percolation theory, we show that a quadrupolar field always increases the percolation threshold and that the universal scaling with the inverse weight average no longer holds if the field couples to the particle length. Instead, the percolation threshold becomes a function of higher moments of the length distribution, where the order of the relevant moments crucially depends on the strength and type of field applied. The theoretical predictions compare well with the results of our Monte Carlo simulations, which eliminate finite size effects by exploiting the fact that the universal scaling of the wrapping probability function holds even in anisotropic systems. Theory and simulation demonstrate that the percolation threshold of a polydisperse mixture can be lower than that of the individual components, confirming recent work based on a mapping onto a Bethe lattice as well as earlier computer simulations involving dipole fields. Our work shows how the formulation of nanocomposites may be used to compensate for the adverse effects of aligning fields that are inevitable under practical manufacturing conditions.
Pearce, Iris
1985-01-01
Cluster headache is the most severe primary headache with recurrent pain attacks described as worse than giving birth. The aim of this paper was to make an overview of current knowledge on cluster headache with a focus on pathophysiology and treatment. This paper presents hypotheses of cluster headache pathophysiology, current treatment options and possible future therapy approaches. For years, the hypothalamus was regarded as the key structure in cluster headache, but is now thought to be pa...
Queiroz, Dayane Andrade
2015-01-01
Neste trabalho apresentamos as categorias cluster, que foram introduzidas por Aslak Bakke Buan, Robert Marsh, Markus Reineke, Idun Reiten e Gordana Todorov, com o objetivo de categoriíicar as algebras cluster criadas em 2002 por Sergey Fomin e Andrei Zelevinsky. Os autores acima, em [4], mostraram que existe uma estreita relação entre algebras cluster e categorias cluster para quivers cujo grafo subjacente é um diagrama de Dynkin. Para isto desenvolveram uma teoria tilting na estrutura triang...
Percolation model of excess electrical noise in transition-edge sensors
International Nuclear Information System (INIS)
Lindeman, M.A.; Anderson, M.B.; Bandler, S.R.; Bilgri, N.; Chervenak, J.; Gwynne Crowder, S.; Fallows, S.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C.A.; Lai, T.; Man, J.; McCammon, D.; Nelms, K.L.; Porter, F.S.; Rocks, L.E.; Saab, T.; Sadleir, J.; Vidugiris, G.
2006-01-01
We present a geometrical model to describe excess electrical noise in transition-edge sensors (TESs). In this model, a network of fluctuating resistors represents the complex dynamics inside a TES. The fluctuations can cause several resistors in series to become superconducting. Such events short out part of the TES and generate noise because much of the current percolates through low resistance paths. The model predicts that excess white noise increases with decreasing TES bias resistance (R/R N ) and that perpendicular zebra stripes reduce noise and alpha of the TES by reducing percolation
The Central Limit Theorem for Supercritical Oriented Percolation in Two Dimensions
Tzioufas, Achillefs
2018-04-01
We consider the cardinality of supercritical oriented bond percolation in two dimensions. We show that, whenever the the origin is conditioned to percolate, the process appropriately normalized converges asymptotically in distribution to the standard normal law. This resolves a longstanding open problem pointed out to in several instances in the literature. The result applies also to the continuous-time analog of the process, viz. the basic one-dimensional contact process. We also derive general random-indices central limit theorems for associated random variables as byproducts of our proof.
White Light Generation and Anisotropic Damage in Gold Films near Percolation Threshold
DEFF Research Database (Denmark)
Novikov, Sergey M.; Frydendahl, Christian; Beermann, Jonas
2017-01-01
in vanishingly small gaps between gold islands in thin films near the electrically determined percolation threshold. Optical explorations using two-photon luminescence (TPL) and near-field microscopies reveals supercubic TPL power dependencies with white-light spectra, establishing unequivocally...... that the strongest TPL signals are generated close to the percolation threshold films, and occurrence of extremely confined (similar to 30 nm) and strongly enhanced (similar to 100 times) fields at the illumination wavelength. For linearly polarized and sufficiently powerful light, we observe pronounced optical...
International Nuclear Information System (INIS)
Neu, V; Schultz, L; Schulze, C; Makarov, D; Albrecht, M; Faustini, M; Grosso, D; Lee, J; Kim, S-K; Suess, D
2013-01-01
Magnetization reversal processes in Co/Pt multilayers prepared on nanoperforated templates are probed by magnetization relaxation measurements. The signature of pinning controlled domain wall movement as expected for percolated media is identified. This contrasts with the nucleation-type reversal mechanism of a Co/Pt reference film prepared on a smooth substrate. A zero field energy barrier of 93k B T is determined by fluctuation field measurements and is elucidated by micromagnetic calculations using the nudged elastic band method. This value is sufficiently large to qualify the material as a promising percolated medium. (paper)
Energy Technology Data Exchange (ETDEWEB)
Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.
2004-05-26
We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.
SHERSTIUK S.V.; POSYLAYEVA K.I.
2013-01-01
In the article there are the theoretical and methodological approaches to the nature and existence of the cluster. The cluster differences from other kinds of cooperative and integration associations. Was develop by scientific-practical recommendations for forming a competitive horticultur cluster.
Cluster formation of network-modifier cations in cesium silicate glasses
Jardón-Álvarez, Daniel; Sanders, Kevin J.; Phyo, Pyae; Baltisberger, Jay H.; Grandinetti, Philip J.
2018-03-01
Natural abundance 29Si two-dimensional magic-angle flipping (2D MAF) NMR spectra were measured in a series of ten cesium silicate glass compositions xCs2O.(1 - x)SiO2, where x is 0.067, 0.113, 0.175, 0.179, 0.218, 0.234, 0.263, 0.298, 0.31, and 0.36. The Q3 shielding anisotropy decreases with increasing Cs content—interpreted as an increase in the non-bridging oxygen (NBO) bond length from increasing Cs coordination (clustering) around the NBO. The 29Si 2D MAF spectra for four glass compositions x = 0.218, 0.234, 0.263, 0.298 exhibit a second co-existing and distinctly smaller shielding anisotropy corresponding to a significantly longer Si-NBO length arising from a higher degree of Cs clustering around the NBO. This second Q3 site appears at a Cs2O mole fraction close to the critical mole fraction of x = 0.24 associated with the percolation threshold of non-bridging oxygen in random close packing of oxygen, thus suggesting that the longer Si-NBO length is associated with an infinite size spanning cluster while the sites with larger anisotropies are associated with shorter Si-NBO lengths and belong to finite size clusters. The equilibrium constant of the Q3 disproportionation reaction was determined as k3 = 0.005, indicating a Qn anionic species distribution close to a binary model as expected for a low field strength modifier such as cesium. It is also found that evolution of the isotropic Q4 and line shapes with increasing Cs content are consistent with a random connectivity model between Qn of differing number of bridging oxygen, n.
Some fractal properties of the percolating backbone in two dimensions
International Nuclear Information System (INIS)
Laidlaw, D.; MacKay, G.; Jan, N.
1987-01-01
A new algorithm is presented, based on elements of artificial intelligence theory, to determine the fractal properties of the backbone of the incipient infinite cluster. It is found that fractal dimensionality of the backbone is d/sub f//sup BB/ = 1.61 +/- 0.01, the chemical dimensionality is d/sub t/ = 1.40 +/- 0.01, and the fractal dimension of the minimum path d/sub min/ = 1.15 +/- 0.02 for the two-dimensional triangular lattice
Salm, van der C.; Verstraten, J.M.; Tiktak, A.
1996-01-01
Weathering rates from laboratory experiments are generally one or two orders of magnitude larger than field weathering rates. To obtain more information on this gap a large undisturbed soil column was percolated with a hydrochloric/sulphuric acid solution at rates of 0.15-0.89 cm/d. The percolate
DEFF Research Database (Denmark)
Gulati, Mukesh; Lund-Thomsen, Peter; Suresh, Sangeetha
2018-01-01
sell their products successfully in international markets, but there is also an increasingly large consumer base within India. Indeed, Indian industrial clusters have contributed to a substantial part of this growth process, and there are several hundred registered clusters within the country...... of this handbook, which focuses on the role of CSR in MSMEs. Hence we contribute to the literature on CSR in industrial clusters and specifically CSR in Indian industrial clusters by investigating the drivers of CSR in India’s industrial clusters....
Compact cluster growth on the half-plane: forest fires in a valley
Kearney, M J
2003-01-01
A two-parameter model on a directed lattice is introduced to represent the growth and spread of clusters on the half-plane. The model exhibits a phase transition in the compact directed percolation universality class between a state where clusters are finite with probability one and a state where clusters are infinite with non-zero probability. In the finite regime, exact expressions are given for the mean perimeter length and area of the generated clusters for a variety of different boundary conditions. An illustrative example is considered, namely a forest fire spreading before a prevailing wind along the floor and sides of an idealized valley.
Energy Technology Data Exchange (ETDEWEB)
Nehm, Frederik, E-mail: frederik.nehm@iapp.de; Schubert, Sylvio; Müller-Meskamp, Lars; Leo, Karl
2014-04-01
The growth behavior of thin silver films on organic layers is investigated during deposition by means of simultaneous in-situ monitoring of sheet resistance and transmittance. Thermally evaporated films up to 11 nm show a distinct percolation behavior with strong resistance drop at the percolation thickness. Additionally, evaporations are divided into a sequence of one nanometer steps. In the deposition breaks, the films exhibit a ripening effect with an inversion at the percolation thickness, by changing from an increasing to decreasing sheet resistance over time. Scanning electron micrographs suggest same ripening mechanisms for islands below the percolation thickness as for holes above. - Highlights: • Fundamental understanding of metal thin film growth is presented. • Optical and electrical in-situ measurements used for optimizing transparent electrodes • Stepwise Ag deposition reveals extraordinary ripening effects. • Feature ripening inversion is discovered at the percolation threshold.
International Nuclear Information System (INIS)
Nehm, Frederik; Schubert, Sylvio; Müller-Meskamp, Lars; Leo, Karl
2014-01-01
The growth behavior of thin silver films on organic layers is investigated during deposition by means of simultaneous in-situ monitoring of sheet resistance and transmittance. Thermally evaporated films up to 11 nm show a distinct percolation behavior with strong resistance drop at the percolation thickness. Additionally, evaporations are divided into a sequence of one nanometer steps. In the deposition breaks, the films exhibit a ripening effect with an inversion at the percolation thickness, by changing from an increasing to decreasing sheet resistance over time. Scanning electron micrographs suggest same ripening mechanisms for islands below the percolation thickness as for holes above. - Highlights: • Fundamental understanding of metal thin film growth is presented. • Optical and electrical in-situ measurements used for optimizing transparent electrodes • Stepwise Ag deposition reveals extraordinary ripening effects. • Feature ripening inversion is discovered at the percolation threshold
White, S
1994-01-01
Galaxy clusters are the largest coherent objects in Universe. It has been known since 1933 that their dynamical properties require either a modification of the theory of gravity, or the presence of a dominant component of unseen material of unknown nature. Clusters still provide the best laboratories for studying the amount and distribution of this dark matter relative to the material which can be observed directly -- the galaxies themselves and the hot,X-ray-emitting gas which lies between them.Imaging and spectroscopy of clusters by satellite-borne X -ray telescopes has greatly improved our knowledge of the structure and composition of this intergalactic medium. The results permit a number of new approaches to some fundamental cosmological questions,but current indications from the data are contradictory. The observed irregularity of real clusters seems to imply recent formation epochs which would require a universe with approximately the critical density. On the other hand, the large baryon fraction observ...
International Nuclear Information System (INIS)
Saïdi, Sami; Bouzitoun, Mouna; Mannaî, Aymen; Gmati, Fethi; Derouiche, Hassen; Mohamed, Abdellatif Belhadj
2013-01-01
Polyaniline–Poly(vinylidene) fluoride (PANI–PVDF) composites were prepared by adding PANI to the PVDF by different weight percentages p % (p = 0, 5, 10, 20, … until 100%). The dc and ac electrical conductivity were studied as a function of PANI percentage in the temperature range 303–453 K. The percolation threshold was found to be equal to 2.95%. When the amount of PANI varies from 5 to 30%, the charge transport mechanism was found to be governed by Mott's three-dimensional variable range hopping model and the dc conductivity decreases within this range. For p > 30%, the conductivity increases and the charge transport mechanism are better fitted by a fluctuation induced tunnelling model (FIT). By calculating the distance ‘s’ between two successive clusters (the distance between two active imines centres (=N + H–) of PANI) from the FIT model, we deduce that electron charge transfer is done by inter-chain hopping for the range [p = 40 to 60%] and by intra-chain hopping for p = 70 to 90%. Some insights about the contribution of the ionic charge transport for PANI concentrations in the interval 5% < p < 30% were obtained using impedance measurements at different frequencies. X-ray diffraction measurements, Fourier transform infrared spectroscopy and scanning electron microscopy were used to investigate the effect of PANI on the structure and morphology of composites. (paper)
Lewis, G.; Osterberg, E. C.; Hawley, R. L.; Marshall, H. P.; Birkel, S. D.; Meehan, T. G.; Graeter, K.; Overly, T. B.; McCarthy, F.
2017-12-01
The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. Increased melting in the GrIS percolation zone over the past several decades has led to increased mass loss at lower elevations due to recent warming. Uncertainties in mass balance are especially large in regions with sparse and/or outdated in situ measurements. This study is the first to calculate in situ accumulation over a large region of western Greenland since the Program for Arctic Regional Climate Assessment campaign during the 1990s. Here we analyze 5000 km of 400 MHz ground penetrating radar data and sixteen 25-33 m-long firn cores in the western GrIS percolation zone to determine snow accumulation over the past 50 years. The cores and radar data were collected as part of the 2016-2017 Greenland Traverse for Accumulation and Climate Studies (GreenTrACS). With the cores and radar profiles we capture spatial accumulation gradients between 1850-2500 m a.s.l and up to Summit Station. We calculate accumulation rates and use them to validate five widely used regional climate models and to compare with IceBridge snow and accumulation radars. Our results indicate that while the models capture most regional spatial climate patterns, they lack the small-scale spatial variability captured by in situ measurements. Additionally, we evaluate temporal trends in accumulation at ice core locations and throughout the traverse. Finally, we use empirical orthogonal function and correlation analyses to investigate the principal drivers of radar-derived accumulation rates across the western GrIS percolation zone, including major North Atlantic climate modes such as the North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and Greenland Blocking Index.
Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films
Ramakrishnan, G.; Planken, P.C.M.
2011-01-01
Emission of pulses of electromagnetic radiation in the terahertz range is observed when ultrathin gold films on glass are illuminated with femtosecond near-IR laser pulses. A distinct maximum is observed in the emitted terahertz amplitude from films of average thickness just above the percolation
Commercial test on uranium ore percolation leaching in Fuzhou uranium mine
International Nuclear Information System (INIS)
Cai Chunhui
2002-01-01
Commercial test on uranium ore percolation leaching was carried out according to ore characteristics of Fuzhou Uranium Mine and results from small test. Technological and economic indexes, such as leaching rate, acid consumption, leaching cycle, etc. are discussed. The general idea applying the test results to commercial production is presented, too
Percolation blockage: A process that enables melt pond formation on first year Arctic sea ice
Polashenski, Chris; Golden, Kenneth M.; Perovich, Donald K.; Skyllingstad, Eric; Arnsten, Alexandra; Stwertka, Carolyn; Wright, Nicholas
2017-01-01
Melt pond formation atop Arctic sea ice is a primary control of shortwave energy balance in the Arctic Ocean. During late spring and summer, the ponds determine sea ice albedo and how much solar radiation is transmitted into the upper ocean through the sea ice. The initial formation of ponds requires that melt water be retained above sea level on the ice surface. Both theory and observations, however, show that first year sea ice is so highly porous prior to the formation of melt ponds that multiday retention of water above hydraulic equilibrium should not be possible. Here we present results of percolation experiments that identify and directly demonstrate a mechanism allowing melt pond formation. The infiltration of fresh water into the pore structure of sea ice is responsible for blocking percolation pathways with ice, sealing the ice against water percolation, and allowing water to pool above sea level. We demonstrate that this mechanism is dependent on fresh water availability, known to be predominantly from snowmelt, and ice temperature at melt onset. We argue that the blockage process has the potential to exert significant control over interannual variability in ice albedo. Finally, we suggest that incorporating the mechanism into models would enhance their physical realism. Full treatment would be complex. We provide a simple temperature threshold-based scheme that may be used to incorporate percolation blockage behavior into existing model frameworks.
Percolation Line, Response Functions, and Voronoi Polyhedra Analysis in Supercritical Water
Czech Academy of Sciences Publication Activity Database
Škvor, J.; Nezbeda, Ivo
2012-01-01
Roč. 15, č. 2 (2012), s. 23301 ISSN 1607-324X R&D Projects: GA AV ČR IAA200760905 Grant - others:GA UJEP(CZ) 53223–15–0010–01 Institutional support: RVO:67985858 Keywords : percolation line * response functions * widom lines Subject RIV: BJ - Thermodynamics Impact factor: 0.757, year: 2012
Is there a delocalization transition in a two-dimensional model for quantum percolation
International Nuclear Information System (INIS)
Dasgupta, I.; Saha, T.; Mookerjee, A.; Chakrabarti, B.K.
1992-01-01
In this paper, the authors estimate the transmittance of the quantum percolation model of Eggarter and Kirkpatrick on the square lattice of various sizes using the vector recursion method. The authors note from finite size scaling that there is no delocalization transition for any degree of disorder in two dimensions
Explosive percolation on directed networks due to monotonic flow of activity
Waagen, Alex; D'Souza, Raissa M.; Lu, Tsai-Ching
2017-07-01
An important class of real-world networks has directed edges, and in addition, some rank ordering on the nodes, for instance the popularity of users in online social networks. Yet, nearly all research related to explosive percolation has been restricted to undirected networks. Furthermore, information on such rank-ordered networks typically flows from higher-ranked to lower-ranked individuals, such as follower relations, replies, and retweets on Twitter. Here we introduce a simple percolation process on an ordered, directed network where edges are added monotonically with respect to the rank ordering. We show with a numerical approach that the emergence of a dominant strongly connected component appears to be discontinuous. Large-scale connectivity occurs at very high density compared with most percolation processes, and this holds not just for the strongly connected component structure but for the weakly connected component structure as well. We present analysis with branching processes, which explains this unusual behavior and gives basic intuition for the underlying mechanisms. We also show that before the emergence of a dominant strongly connected component, multiple giant strongly connected components may exist simultaneously. By adding a competitive percolation rule with a small bias to link uses of similar rank, we show this leads to formation of two distinct components, one of high-ranked users, and one of low-ranked users, with little flow between the two components.
Complex dynamic behaviors of oriented percolation-based financial time series and Hang Seng index
International Nuclear Information System (INIS)
Niu, Hongli; Wang, Jun
2013-01-01
Highlights: • We develop a financial time series model by two-dimensional oriented percolation system. • We investigate the statistical behaviors of returns for HSI and the financial model by chaos-exploring methods. • We forecast the phase point of reconstructed phase space by RBF neural network. -- Abstract: We develop a financial price model by the two-dimensional oriented (directed) percolation system. The oriented percolation model is a directed variant of ordinary (isotropic) percolation, and it is applied to describe the fluctuations of stock prices. In this work, we assume that the price fluctuations result from the participants’ investment attitudes toward the market, and we investigate the information spreading among the traders and the corresponding effect on the price fluctuations. We study the complex dynamic behaviors of return time series of the model by using the multiaspect chaos-exploring methods. And we also explore the corresponding behaviors of the actual market index (Hang Seng Index) for comparison. Further, we introduce the radial basic function (RBF) neural network to train and forecast the phase point of reconstructed phase space
Bhamidi, S.; Van der Hofstad, R.; Hooghiemstra, G.
2010-01-01
We study first passage percolation (FPP) on the configuration model (CM) having power-law degrees with exponent ? ? [1, 2) and exponential edge weights. We derive the distributional limit of the minimal weight of a path between typical vertices in the network and the number of edges on the
Idiotypic networks incorporating T-B cell co-operation. The conditions for percolation
Boer, R.J. de; Hogeweg, P.
1989-01-01
Previous work was concerned with symmetric immune networks of idiotypic interactions amongst B cell clones. The behaviour of these networks was contrary to expectations. This was caused by an extensive percolation of idiotypic signals. Idiotypic activation was thus expected to affect almost all
Simulation of Water Percolation in a FEBEX Bentonite Block using TOUGH2 Program
International Nuclear Information System (INIS)
Bru, A.
2001-01-01
We use Tough2 program to simulate the water percolation in a Febex bentonite Block. From obtained results, we conclude that mean field approximation does not describe this process because the heterogeneity of the medium it is not include in mathematical formalism. (Author) 17 refs
Apparent anomalous critical behaviour of superfluid helium 4 in porous medium
International Nuclear Information System (INIS)
Maynard, R.; Deutscher, G.
1989-01-01
The anomalous critical exponents of the superfluid 4 He density in silica aerogels is analysed by a simple model where the distribution of pore size is assumed to be very broad. The strong modification of the critical behaviour is related to the structure of the aerogels skeleton which is discussed in terms of a percolation or alternatively a hierarchical sponge model
A model for electrode effects using percolation theory
International Nuclear Information System (INIS)
Wuethrich, R.; Bleuler, H.
2004-01-01
Electrode effects are known for more than 150 years. These effects, with undesirable consequences in industrial aluminium electrolysis, can be used to micro-machine glass with Spark Assisted Chemical Engraving (SACE). In this paper, a novel approach for theoretical analysis of the phenomenon is proposed by considering the bubble growth and bubble departure from electrodes as a stochastic process. The critical conditions (critical voltage and current density) are predicted in function of electrode geometry and electrolyte concentration as well as the static mean current-voltage characteristics prior to the onset of the effects. The different regions of the current-voltage characteristics, as identified by previous authors, are described and explained. It is shown that all relevant processes for the onset of the electrodes effects happen in the adherence region of the bubble layer. The model is applied for vertical cylindrical electrodes and compared with experimental data
Wagstaff, Kiri L.
2012-03-01
On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained
Carey, Manus; Jiujin, Xiao; Gomes Farias, Júlia; Meharg, Andrew A
2015-01-01
A novel way of cooking rice to maximize the removal of the carcinogen inorganic arsenic (Asi) is presented here. In conventional rice cooking water and grain are in continuous contact, and it is known that the larger the water:rice cooking ratio, the more Asi removed by cooking, suggesting that the Asi in the grain is mobile in water. Experiments were designed where rice is cooked in a continual stream of percolating near boiling water, either low in Asi, or Asi free. This has the advantage of not only exposing grain to large volumes of cooking water, but also physically removes any Asi leached from the grain into the water receiving vessel. The relationship between cooking water volume and Asi removal in conventional rice cooking was demonstrated for the rice types under study. At a water-to-rice cooking ratio of 12:1, 57±5% of Asi could be removed, average of 6 wholegrain and 6 polished rice samples. Two types of percolating technology were tested, one where the cooking water was recycled through condensing boiling water steam and passing the freshly distilled hot water through the grain in a laboratory setting, and one where tap water was used to cook the rice held in an off-the-shelf coffee percolator in a domestic setting. Both approaches proved highly effective in removing Asi from the cooking rice, with up to 85% of Asi removed from individual rice types. For the recycled water experiment 59±8% and 69±10% of Asi was removed, on average, compared to uncooked rice for polished (n=27) and wholegrain (n=13) rice, respectively. For coffee percolation there was no difference between wholegrain and polished rice, and the effectiveness of Asi removal was 49±7% across 6 wholegrain and 6 polished rice samples. The manuscript explores the potential applications and further optimization of this percolating cooking water, high Asi removal, discovery.
International Nuclear Information System (INIS)
Schaeffer, R.
1987-01-01
The galaxy and cluster luminosity functions are constructed from a model of the mass distribution based on hierarchical clustering at an epoch where the matter distribution is non-linear. These luminosity functions are seen to reproduce the present distribution of objects as can be inferred from the observations. They can be used to deduce the redshift dependence of the cluster distribution and to extrapolate the observations towards the past. The predicted evolution of the cluster distribution is quite strong, although somewhat less rapid than predicted by the linear theory
Pereira, Maria E. S.; Soares-Santos, Marcelle; Makler, Martin; Annis, James; Lin, Huan; Palmese, Antonella; Vitorelli, André Z.; Welch, Brian; Caminha, Gabriel B.; Erben, Thomas; Moraes, Bruno; Shan, Huanyuan
2018-02-01
We present the first weak lensing calibration of μ⋆, a new galaxy cluster mass proxy corresponding to the total stellar mass of red and blue members, in two cluster samples selected from the SDSS Stripe 82 data: 230 red-sequence Matched-filter Probabilistic Percolation (redMaPPer) clusters at redshift 0.1 ≤ z proxy for VT clusters. Catalogues including μ⋆ measurements will enable its use in studies of galaxy evolution in clusters and cluster cosmology.
Energy Technology Data Exchange (ETDEWEB)
Marshall, Margaret A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bess, John D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Briggs, J. Blair [Idaho National Lab. (INL), Idaho Falls, ID (United States); Murphy, Michael F. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mihalczo, John T. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-03-01
Cadmium ratios were measured with enriched uranium metal foils at various locations in the assembly with the fuel tube at the 1.506-cm spacing. They are described in the following subsections. The experiment configuration was the same as the first critical configuration described in HEU-COMP-FAST-004 (Case 1). The experimenter placed 0.75-cm-diameter × 0.010-cm-thick 93.15%-235U-enriched uranium metal foils with and without 0.051-cm-thick cadmium covers at various locations in the core and top reflector. One part of the cadmium cover was cupshape and contained the uranium foil. The other part was a lid that fit over the exposed side of the foil when it was in the cup shaped section of the cover. As can be seen in the logbook, two runs were required to obtain all the measurements necessary for the cadmium ratio. The bare foil measurements within the top reflector were run first as part of the axial foil activation measurements. The results of this run are used for both the axial activation results and the cadmium ratios. Cadmium covered foils were then placed at the same location through the top reflector in a different run. Three pairs of bare and cadmium covered foils were also placed through the core tank. One pair was placed at the axial center of a fuel tube 11.35 cm from the center of the core. Two pairs of foils were placed on top of fuel tubes 3.02 and 12.06 cm from the center of the core. The activation of the uranium metal foils was measured after removal from the assembly using two lead shielded NaI scintillation detectors as follows. The NaI scintillators were carefully matched and had detection efficiencies for counting delayed-fission-product gamma rays with energies above 250 KeV within 5%. In all foil activation measurements, one foil at a specific location was used as a normalizing foil to remove the effects of the decay of fission products during the counting measurements with the NaI detectors. The normalization foil was placed on one Na
Directory of Open Access Journals (Sweden)
B. B. Khatua
2013-06-01
Full Text Available In this work, polycarbonate (PC/multiwall carbon nanotube (MWCNT nanocomposites were prepared by simple melt mixing at a temperature (~350°C well above the processing temperature of PC, followed by compression molding, that exhibited percolation threshold as low as of 0.11 wt% and high electrical conductivity of 1.38x10–3 S•cm–1 at only 0.5 wt% MWCNT loading. Due to the lower interfacial energy between MWCNT and PC, the carbon nanotubes are excellently dispersed and formed continuous conductive network structure throughout the host polymer. AC electrical conductivity and dielectric permittivity of PC/MWCNT nanocomposites were characterized in a broad frequency range, 101–107 Hz. Low percolation threshold (pc of 0.11 wt% and the critical exponent (t of ~3.38 was resulted from scaling law equation. The linear plot of logσDC vs. p–1/3 supported the presence of tunneling conduction among MWCNTs. The thermal property and storage modulus of PC were increased with the incorporation of little amount of MWCNTs. Transmission electron microscopy (TEM and field emission scanning electron microscopy (FESEM confirmed the homogeneous dispersion and distribution of MWCNTs throughout the matrix phase.
Correlation properties of surface and percolation transfer of electrons
International Nuclear Information System (INIS)
Bakunin, O.G.
2002-01-01
In this work was received equation, connecting correlatively properties of surface with electrons distribution function. Usually for equilibrium is necessary a large number of collisions. Collisions are 'destroying' correlations. In case rare collisions large importance have correlations and 'memory' effects. Non-Markov's character of emitting particles by surface lead to strongly nonequilibrium condition of 'gas'. Here kinetic equation of diffusive form does not apply. Classical kinetic equation are described only conditions near to equilibrium. This work offers to use ideas anomal diffusion in phase-space. The correlation properties of surface describe by correlations of velocities of emitting electrons: B(t). We offer to use functional equation for probability collision instead of kinetic equation: ∫ 0 ν 0 W noncoll F(ν) dv = 1 - B(t). This functional allow to consider 'memory' effects. It is important for consideration of electrons and clusters near surfaces. Distribution function become direct connected with correlations. In classical Kubo-Mory theory of transfer is necessary to get nondivergences integral: D ∝ ∫ 0 ∞ B(t). In considering case we can use even 'power function'. It was used 'slow' correlation function as Kohlraush in calculations. The information about kinetics and correlations properties are containing in one functional equation. It was received solution of this equation in form Levy function: F(ν) ∝ 1/ν α exp(-1/ν). The solution of this form can not be get with help asymptotic methods of kinetic theory. Asymptotics of solution have scale-invariant character F(V) ∝ 1/V α . This indicate on fractal properties phase-space. (author)
Minku, Leandro L.
2017-10-06
Background: Software Effort Estimation (SEE) can be formulated as an online learning problem, where new projects are completed over time and may become available for training. In this scenario, a Cross-Company (CC) SEE approach called Dycom can drastically reduce the number of Within-Company (WC) projects needed for training, saving the high cost of collecting such training projects. However, Dycom relies on splitting CC projects into different subsets in order to create its CC models. Such splitting can have a significant impact on Dycom\\'s predictive performance. Aims: This paper investigates whether clustering methods can be used to help finding good CC splits for Dycom. Method: Dycom is extended to use clustering methods for creating the CC subsets. Three different clustering methods are investigated, namely Hierarchical Clustering, K-Means, and Expectation-Maximisation. Clustering Dycom is compared against the original Dycom with CC subsets of different sizes, based on four SEE databases. A baseline WC model is also included in the analysis. Results: Clustering Dycom with K-Means can potentially help to split the CC projects, managing to achieve similar or better predictive performance than Dycom. However, K-Means still requires the number of CC subsets to be pre-defined, and a poor choice can negatively affect predictive performance. EM enables Dycom to automatically set the number of CC subsets while still maintaining or improving predictive performance with respect to the baseline WC model. Clustering Dycom with Hierarchical Clustering did not offer significant advantage in terms of predictive performance. Conclusion: Clustering methods can be an effective way to automatically generate Dycom\\'s CC subsets.
Operator content of the critical Potts model in d dimensions and logarithmic correlations
International Nuclear Information System (INIS)
Vasseur, Romain; Jacobsen, Jesper Lykke
2014-01-01
Using the symmetric group S Q symmetry of the Q-state Potts model, we classify the (scalar) operator content of its underlying field theory in arbitrary dimension. In addition to the usual identity, energy and magnetization operators, we find fields that generalize the N-cluster operators well-known in two dimensions, together with their subleading counterparts. We give the explicit form of all these operators – up to non-universal constants – both on the lattice and in the continuum limit for the Landau theory. We compute exactly their two- and three-point correlation functions on an arbitrary graph in terms of simple probabilities, and give the general form of these correlation functions in the continuum limit at the critical point. Specializing to integer values of the parameter Q, we argue that the analytic continuation of the S Q symmetry yields logarithmic correlations at the critical point in arbitrary dimension, thus implying a mixing of some scaling fields by the scale transformation generator. All these logarithmic correlation functions are given a clear geometrical meaning, which can be checked in numerical simulations. Several physical examples are discussed, including bond percolation, spanning trees and forests, resistor networks and the Ising model. We also briefly address the generalization of our approach to the O(n) model
Criticality of Parasitic Disease Transmission in a Diffusive Population
International Nuclear Information System (INIS)
He Minhua; Zhang Duanming; Yin Yanping; Chen Zhiyuan; Pan Guijun
2008-01-01
Through using the methods of finite-size effect and short time dynamic scaling, we study the critical behavior of parasitic disease spreading process in a diffusive population mediated by a static vector environment. Through comprehensive analysis of parasitic disease spreading we find that this model presents a dynamical phase transition from disease-free state to endemic state with a finite population density. We determine the critical population density, above which the system reaches an epidemic spreading stationary state. We also perform a scaling analysis to determine the order parameter and critical relaxation exponents. The results show that the model does not belong to the usual directed percolation universality class and is compatible with the class of directed percolation with diffusive and conserved fields
International Nuclear Information System (INIS)
Romli
1997-01-01
Cluster analysis is the name of group of multivariate techniques whose principal purpose is to distinguish similar entities from the characteristics they process.To study this analysis, there are several algorithms that can be used. Therefore, this topic focuses to discuss the algorithms, such as, similarity measures, and hierarchical clustering which includes single linkage, complete linkage and average linkage method. also, non-hierarchical clustering method, which is popular name K -mean method ' will be discussed. Finally, this paper will be described the advantages and disadvantages of every methods
Everitt, Brian S; Leese, Morven; Stahl, Daniel
2011-01-01
Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons
DEFF Research Database (Denmark)
Böcker, S.; Baumbach, Jan
2013-01-01
. The problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications......The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side...
Transport processes in macroscopically disordered media from mean field theory to percolation
Snarskii, Andrei A; Sevryukov, Vladimir A; Morozovskiy, Alexander; Malinsky, Joseph
2016-01-01
This book reflects on recent advances in the understanding of percolation systems to present a wide range of transport phenomena in inhomogeneous disordered systems. Further developments in the theory of macroscopically inhomogeneous media are also addressed. These developments include galvano-electric, thermoelectric, elastic properties, 1/f noise and higher current momenta, Anderson localization, and harmonic generation in composites in the vicinity of the percolation threshold. The book describes how one can find effective characteristics, such as conductivity, dielectric permittivity, magnetic permeability, with knowledge of the distribution of different components constituting an inhomogeneous medium. Considered are a wide range of recent studies dedicated to the elucidation of physical properties of macroscopically disordered systems. Aimed at researchers and advanced students, it contains a straightforward set of useful tools which will allow the reader to derive the basic physical properties of compli...
Bedard, Antoine Joseph; Barbero, Ever J.
2018-03-01
Magnetoelectric (ME) composites can be produced by embedding magnetostrictive H particles in a piezoelectric E matrix derived from a piezoelectric powder precursor. Previously, using a bi-disperse hard-shell model (Barbero and Bedard in Comput Part Mech, 2018. https://doi.org/10.1007/s40571-017-0165-4), it has been shown that the electrical percolation threshold of the conductive H phase can be increased by decreasing the piezoelectric E particle size, relative to the H phase particle size, and by increasing short-range affinity between the E and H particles. This study builds on our previous study by exploring what happens during sintering of the ME composite when either the H or E particles undergo deformation. It was found that deformation of the H particles reduces the percolation threshold, and that deformation of E particles increases inter-phase H-E mechanical coupling, thus contributing to enhancing of ME coupling.
Measurement of cation exchange capacity (CEC) on natural zeolite by percolation method
Wiyantoko, Bayu; Rahmah, Nafisa
2017-12-01
The cation exchange capacity (CEC)measurement has been carried out in natural zeolite by percolation method. The natural zeolite samples used for cation exchange capacity measurement were activated beforehand with physical activation and chemical activation. The physically activated zeolite was done by calcination process at 600 °C for 4 hours. The natural zeolite was activated chemically by using sodium hydroxide by refluxing process at 60-80 °C for 3 hours. In summary, cation exchange capacity (CEC) determination was performed by percolation, distillation and titration processes. Based on the measurement that has been done, the exchange rate results from physical activated and chemical activated of natural zeolite were 181.90cmol (+)/kg and 901.49cmol (+)/kg respectively.
A new percolation model for composite solid electrolytes and dispersed ionic conductors
Risyad Hasyim, Muhammad; Lanagan, Michael T.
2018-02-01
Composite solid electrolytes (CSEs) including conductor/insulator composites known as dispersed ionic conductors (DICs) have motivated the development of novel percolation models that describe their conductivity. Despite the long history, existing models lack in one or more key areas: (1) rigorous foundation for their physical theory, (2) explanation for non-universal conductor-insulator transition, (3) classification of DICs, and (4) extension to frequency-domain. This work describes a frequency-domain effective medium approximation (EMA) of a bond percolation model for CSEs. The EMA is derived entirely from Maxwell’s equations and contains basic microstructure parameters. The model was applied successfully to several composite systems from literature. Simulations and fitting of literature data address these key areas and illustrate the interplay between space charge layer properties and bulk microstructure.
Finding influential nodes for integration in brain networks using optimal percolation theory.
Del Ferraro, Gino; Moreno, Andrea; Min, Byungjoon; Morone, Flaviano; Pérez-Ramírez, Úrsula; Pérez-Cervera, Laura; Parra, Lucas C; Holodny, Andrei; Canals, Santiago; Makse, Hernán A
2018-06-11
Global integration of information in the brain results from complex interactions of segregated brain networks. Identifying the most influential neuronal populations that efficiently bind these networks is a fundamental problem of systems neuroscience. Here, we apply optimal percolation theory and pharmacogenetic interventions in vivo to predict and subsequently target nodes that are essential for global integration of a memory network in rodents. The theory predicts that integration in the memory network is mediated by a set of low-degree nodes located in the nucleus accumbens. This result is confirmed with pharmacogenetic inactivation of the nucleus accumbens, which eliminates the formation of the memory network, while inactivations of other brain areas leave the network intact. Thus, optimal percolation theory predicts essential nodes in brain networks. This could be used to identify targets of interventions to modulate brain function.
Dou, Fei; Silva, Carlos; Zhang, Xinping
2013-05-01
We find that the external quantum efficiency of photovoltaic diodes based on finely mixed blends of poly-9,9’-dioctylfluorene-co-bis-N,N’-(4-butylphenyl)-bis-N,N’-phenyl-l,4-phenylenediamine (PFB) and poly-9,9’- dioctylfluorene-co-benzothiadiazole (F8BT) depends strongly on the blend ratio. The peak external quantum efficiency is optimum for a PFB:F8BT ratio of 3:1. The difference of peak efficiency for this composition and a 1:1 ratio is significantly higher than the reported yield of charge-transfer excitons. From a surface topography analysis, we believe that charge percolation plays a crucial role in photocurrent efficiency in PFB:F8BT diodes. Furthermore, we present a qualitative model for different charge percolation pathways in diodes of different blend ratios.
Directory of Open Access Journals (Sweden)
Veras Carlos A. G.
2002-01-01
Full Text Available The chemical percolation devolatilization model (CPD was extended for the prediction of drying and devolatilization of coal particles in high intensity acoustic fields found in Rijke tube reactors. The acoustic oscillations enhance the heat and mass transfer processes in the fuel bed as well as in the freeboard, above the grate. The results from simulations in a Rijke tube combustor have shown an increase in the rate of water evaporation and thermal degradation of the particles. The devolatilization model, based on chemical percolation, applied in pulsating regime allowed the dynamic prediction on the yields of CO, CO2, CH4, H2O, other light gases as well as tar which are important on ignition and stabilization of flames. The model predicted the quantity and form of nitrogen containing species generated during devolatilization, for which knowledge is strategically indispensable for reducing pollutant emissions (NOx in flames under acoustic excitation .
Numerical analysis of a proposed percolation experiment at the Pena Blanca natural analog site
International Nuclear Information System (INIS)
Green, R.T.; Rice, G.
1995-01-01
A field-scale percolation test is proposed for the Pena Blanca natural analog site near Chihuahua, MX. To aid in design of the field test, the V-TOUGH two-phase flow simulator was applied to model percolation of water through 8 to 10 m of partially saturated fractured tuff. The rock was characterized as a composite medium using measured hydraulic properties for the rock matrix and estimated values for the fractures. Measured matrix permeability varied over four orders of magnitude and fracture apertures were estimated to range from 10 to 1,000 μm. Water arrival times were predicted to vary between one day to 10,000 yr. The utility of the composite model and other representations of flow through fractured porous media can be tested using results from the field scale infiltration test data
Cazimajou, T.; Legallais, M.; Mouis, M.; Ternon, C.; Salem, B.; Ghibaudo, G.
2018-05-01
We studied the current-voltage characteristics of percolating networks of silicon nanowires (nanonets), operated in back-gated transistor mode, for future use as gas or biosensors. These devices featured P-type field-effect characteristics. It was found that a Lambert W function-based compact model could be used for parameter extraction of electrical parameters such as apparent low field mobility, threshold voltage and subthreshold slope ideality factor. Their variation with channel length and nanowire density was related to the change of conduction regime from direct source/drain connection by parallel nanowires to percolating channels. Experimental results could be related in part to an influence of the threshold voltage dispersion of individual nanowires.
The importance of stress percolation patterns in rocks and other polycrystalline materials.
Burnley, P C
2013-01-01
A new framework for thinking about the deformation behavior of rocks and other heterogeneous polycrystalline materials is proposed, based on understanding the patterns of stress transmission through these materials. Here, using finite element models, I show that stress percolates through polycrystalline materials that have heterogeneous elastic and plastic properties of the same order as those found in rocks. The pattern of stress percolation is related to the degree of heterogeneity in and statistical distribution of the elastic and plastic properties of the constituent grains in the aggregate. The development of these stress patterns leads directly to shear localization, and their existence provides insight into the formation of rhythmic features such as compositional banding and foliation in rocks that are reacting or dissolving while being deformed. In addition, this framework provides a foundation for understanding and predicting the macroscopic rheology of polycrystalline materials based on single-crystal elastic and plastic mechanical properties.
Elshurafa, Amro M.
2013-06-14
We show that graphene-percolated polymer composites exhibit fractional capacitance response in the frequency range of 50 kHz–2 MHz. In addition, it is shown that by varying the loading of graphene within the matrix from 2.5% to 12%, the phase can be controllably tuned from −67° to −31°, respectively. The electrostatic fractional capacitors proposed herein are easy to fabricate and offer integration capability on electronic printed circuit boards.
Effect of degree correlations above the first shell on the percolation transition
Valdez, L. D.; Buono, C.; Braunstein, L. A.; Macri, P. A.
2011-01-01
The use of degree-degree correlations to model realistic networks which are characterized by their Pearson's coefficient, has become widespread. However the effect on how different correlation algorithms produce different results on processes on top of them, has not yet been discussed. In this letter, using different correlation algorithms to generate assortative networks, we show that for very assortative networks the behavior of the main observables in percolation processes depends on the a...
Effect of percolation rate on water-travel time in deep, partially saturated zones
International Nuclear Information System (INIS)
Peters, R.R.; Gauthier, J.H.; Dudley, A.L.
1986-02-01
The Nevada Nuclear Waste Storage Investigations (NNWSI) project is investigating Yucca Mountain, Nye county, Nevada, as a prospective site for a radioactive-waste repository. The Yucca Mountain site is unique among those currently being investigated by the US Department of Energy (DOE) in that the prospective repository location is in the unsaturated zone, approximately 300 m above the water table. The rock units at Yucca Mountain can be grouped into three types: (1) vitric tuffs with high matrix conductivity and few fractures; (2) zeolitized tuffs with low matrix conductivity and few fractures; and (3) densely welded tuffs with low matrix conductivities and many fractures. The prospective repository zone is in densely welded tuff; the units between it and the water table are of types 1 and 2. Current percolation rates through Yucca Mountain, and those that are currently postulated under future climatic conditions, are thought to be of the order of the saturated matrix conductivity of some of the units. Although it is probable that there is now little or no water movement in fracture, it is necessary to investigate the potential for fracture flow, especially that which could be initiated under future climatic conditions. Significant fracture flow, if present, could reduce the water travel time between the repository and the water table. A composite-porosity, continuum model was developed to model flow in a fractured, porous medium. Simulations using data from the Yucca Mountain site and this model in the one-dimensional code TOSPAC indicate that current estimates of the percolation rate result in water movement confined to the matrix and that the water-travel time from the repository to the water table is on the order of hundreds of thousands of years. this result is sensitive to the percolation rate; an increase in percolation rate of a factor of 10 many initiate water movement in the fractures, reducing the travel time significantly
International Nuclear Information System (INIS)
Kota, Arun K; Cipriano, Bani H; Powell, Dan; Raghavan, Srinivasa R; Bruck, Hugh A
2007-01-01
For the first time, an interpenetrating phase polymer nanocomposite formed by the percolation of multiwalled carbon nanotubes (MWCNTs) in polystyrene (PS) has been quantitatively characterized through electrical conductivity measurements and melt rheology. Both sets of measurements, in conjunction with scanning electron microscopy (SEM) images, indicate the presence of a continuous phase of percolated MWCNTs appearing at particle concentrations exceeding 2 vol% MWCNTs in PS. To quantify the amount of this continuous phase present in the PS/MWCNT composite, electrical conductivity data at various MWCNT concentrations, β, are correlated with a proposed degree of percolation, C-bar(β), developed using a conventional power-law formula with and without a percolation threshold. To quantify the properties of the interpenetrating phase polymer nanocomposite, the PS/MWCNT composite is treated as a combination of two phases: a continuous phase consisting of a pseudo-solid-like network of percolated MWCNTs, and a continuous PS phase reinforced by non-interacting MWCNTs. The proposed degree of percolation is used to quantify the distribution of MWCNTs among the phases, and is then used in a rule-of-mixtures formulation for the storage modulus, G'(β, C-bar(β), ω), and the loss modulus, G''(β, C-bar(β), ω), to quantify the properties of the continuous phase consisting of percolated MWCNTs and the continuous PS phase reinforced by non-interacting MWCNTs from the experimental melt rheology data. The properties of the continuous phase of percolated MWCNTs are indicative of a scaffold-like microstructure exhibiting an elastic behavior with a complex modulus of 360 kPa at lower frequencies and viscoplastic behavior with a complex viscosity of 6 kPa s rad -1 at higher frequencies, most likely due to a stick-slip friction mechanism at the interface of the percolated MWCNTs. Additional evidence of this microstructure was obtained via scanning electron microscopy. This research
Pottawattamie County School System, Council Bluffs, IA.
The 15 occupational clusters (transportation, fine arts and humanities, communications and media, personal service occupations, construction, hospitality and recreation, health occupations, marine science occupations, consumer and homemaking-related occupations, agribusiness and natural resources, environment, public service, business and office…
DEFF Research Database (Denmark)
Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan
2000-01-01
A symptom is a condition indicating the presence of a disease, especially, when regarded as an aid in diagnosis.Symptoms are the smallest units indicating the existence of a disease. A syndrome on the other hand is an aggregate, set or cluster of concurrent symptoms which together indicate...... and clustering are the basic concerns in medicine. Classification depends on definitions of the classes and their required degree of participant of the elements in the cases' symptoms. In medicine imprecise conditions are the rule and therefore fuzzy methods are much more suitable than crisp ones. Fuzzy c......-mean clustering is an easy and well improved tool, which has been applied in many medical fields. We used c-mean fuzzy clustering after feature extraction from an aphasia database. Factor analysis was applied on a correlation matrix of 26 symptoms of language disorders and led to five factors. The factors...
Electrical percolation, morphological and dispersion properties of MWCNT/PMMA nanocomposites
Energy Technology Data Exchange (ETDEWEB)
Coelho, Paulo Henrique da Silva Leite; Marchesin, Marcel Silva; Morales, Ana Rita; Bartoli, Julio Roberto, E-mail: piyke.coelho@gmail.com [Universidade de Campinas (UNICAMP), SP (Brazil). Escola de Engenharia Quimica
2014-08-15
Nanocomposites of poly (methyl methacrylate) (PMMA) and carbon nanotubes have a high potential for applications where conductivity and low specific weight are required. This piece of work concerns investigations of the level of dispersion and morphology on the electrical properties of in situ polymerized nanocomposites in different concentrations of multi-walled carbon nanotubes (MWCNT) in a PMMA matrix. The electrical conductivity was measured by the four point probe. The morphology and dispersion was analyzed by Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). The correlation between electrical conductivity and the MWCNT amount, presented a typical percolation behavior, whose electrical percolation threshold determined by power law relationship was 0.2 vol. (%) The exponent t from the percolation power law indicated the formation of a 3D network of randomly arranged MWCNT. SAXS detected that the structures are intermediate to disks or spheres indicating fractal geometry for the MWCNT aggregates instead of isolated rods. HR-TEM images allowed us to observe the MWCNT individually dispersed into the matrix, revealing their distribution without preferential space orientation and absence of significant damage to the walls. The combined results of SAXS and HR-TEM suggest that MWCNT into the polymeric matrix might present interconnected aggregates and some dispersed single structures. (author)
Electrical percolation, morphological and dispersion properties of MWCNT/PMMA nanocomposites
International Nuclear Information System (INIS)
Coelho, Paulo Henrique da Silva Leite; Marchesin, Marcel Silva; Morales, Ana Rita; Bartoli, Julio Roberto
2014-01-01
Nanocomposites of poly (methyl methacrylate) (PMMA) and carbon nanotubes have a high potential for applications where conductivity and low specific weight are required. This piece of work concerns investigations of the level of dispersion and morphology on the electrical properties of in situ polymerized nanocomposites in different concentrations of multi-walled carbon nanotubes (MWCNT) in a PMMA matrix. The electrical conductivity was measured by the four point probe. The morphology and dispersion was analyzed by Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). The correlation between electrical conductivity and the MWCNT amount, presented a typical percolation behavior, whose electrical percolation threshold determined by power law relationship was 0.2 vol. (%) The exponent t from the percolation power law indicated the formation of a 3D network of randomly arranged MWCNT. SAXS detected that the structures are intermediate to disks or spheres indicating fractal geometry for the MWCNT aggregates instead of isolated rods. HR-TEM images allowed us to observe the MWCNT individually dispersed into the matrix, revealing their distribution without preferential space orientation and absence of significant damage to the walls. The combined results of SAXS and HR-TEM suggest that MWCNT into the polymeric matrix might present interconnected aggregates and some dispersed single structures. (author)
Effect of percolation rate on water-travel time in deep, partially saturated zones
International Nuclear Information System (INIS)
Peters, R.R.; Gauthier, J.H.; Dudley, A.L.
1986-01-01
The Nevada Nuclear Waste Storage Investigations (NNWSI) project is investigating Yucca Mountain, Nye County, Nevada, as a prospective site for a radioactive-waste repository. The Yucca Mountain site is unique among those currently being investigated by the US Department of Energy (DOE) in that the prospective repository location is in the unsaturated zone, approximately 300 m above the water table. A composite-porosity, continuum model was developed to model flow in a fractured, porous medium. Simulations using data from the Yucca Mountain site and this model in the one-dimensional code TOSPAC indicate that current estimates of the percolation rate result in water movement confined to the matrix and that the water-travel time from the repository to the water table in on the order of hundreds of thousands of years. This result is sensitive to the percolation rate; an increase in percolation rate of a factor of 10 may initiate water movement in the fractures, reducing the travel time significantly
When interflow also percolates: downslope travel distances and hillslope process zones.
Energy Technology Data Exchange (ETDEWEB)
Jackson, C. Rhett [Warnell School of Forestry and Natural Resources, University of Georgia, GA 30602 Athens USA; Bitew, Menberu [Warnell School of Forestry and Natural Resources, University of Georgia, GA 30602 Athens USA; Du, Enhao [Climate Science Department, Lawrence Berkeley National Laboratory, CA 94720 Berkeley USA
2014-02-17
In hillslopes with soils characterized by deep regoliths, such as Ultisols,Oxisols, and Alfisols, interflow occurs episodically over impeding layers near and parallel to the soil surface such as low-conductivity B horizons (e.g.Newman et al., 1998; Buttle andMcDonald, 2002; Du et al., In Review), till layers (McGlynn et al., 1999; Bishop et al., 2004), hardpans (McDaniel et al., 2008), C horizons (Detty and McGuire, 2010), and permeable bedrock (Tromp van Meerveld et al., 2007). As perched saturation develops within and above these impeding but permeable horizons, flow moves laterally downslope, but the perched water also continues to percolate through the impeding horizon to the unsaturated soils and saprolite below. Perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon. In such flow situations, only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm.farther up the slope, lateral flow within the zone of perched saturation. will act mainly to shift the point of percolation (location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer) down the hillslope from the point of infiltration. In flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers, lateral flow distances will be negligible.
Percolative ionic conduction in the LiAlSiO4 glass-ceramic system
International Nuclear Information System (INIS)
Biefeld, R.M.; Pike, G.E.; Johnson, R.T. Jr.
1977-01-01
The effect f crystallinity on the lithium ion conductivity in LiAlSiO 4 glass and glass-ceramic solid electrolytes has been determined. The ionic conductivity is thermally activated with an activation energy and pre-exponential factor that change in a marked and nonsimple manner as the volume fraction of crystallinity changes. These results are explained by using a continuum percolation model (effective-medium approximation) which assumes that ionic conduction in the glass-ceramic is almost entirely within the glass phase until the crystalline volume fraction rises above approx. 55%. The LiAlSiO 4 system would seem to be nearly ideal for application of percolation theory since the crystalline phase, β eucryptite, has nearly the same composition as the glass phase. Hence, as the crystallite volume fraction increases in the glass ceramic, the residual glass composition and conductivity remain the same. This is the first application of percolation theory to ionic transport in glass-ceramics and excellent agreement is obtained between theory and experiment for the LiAlSiO 4 system
Donchev, Todor I [Urbana, IL; Petrov, Ivan G [Champaign, IL
2011-05-31
Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.
Massey, Richard; Kitching, Thomas; Nagai, Daisuke
2010-01-01
The unique properties of dark matter are revealed during collisions between clusters of galaxies, such as the bullet cluster (1E 0657−56) and baby bullet (MACS J0025−12). These systems provide evidence for an additional, invisible mass in the separation between the distributions of their total mass, measured via gravitational lensing, and their ordinary ‘baryonic’ matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. C...
Leroux, Elizabeth; Ducros, Anne
2008-01-01
Abstract Cluster headache (CH) is a primary headache disease characterized by recurrent short-lasting attacks (15 to 180 minutes) of excruciating unilateral periorbital pain accompanied by ipsilateral autonomic signs (lacrimation, nasal congestion, ptosis, miosis, lid edema, redness of the eye). It affects young adults, predominantly males. Prevalence is estimated at 0.5–1.0/1,000. CH has a circannual and circadian periodicity, attacks being clustered (hence the name) in bouts that can occur ...
Reproducibility of up-flow column percolation tests for contaminated soils.
Directory of Open Access Journals (Sweden)
Tetsuo Yasutaka
Full Text Available Up-flow column percolation tests are used at laboratory scale to assess the leaching behavior of hazardous substance from contaminated soils in a specific condition as a function of time. Monitoring the quality of these test results inter or within laboratory is crucial, especially if used for Environment-related legal policy or for routine testing purposes. We tested three different sandy loam type soils (Soils I, II and III to determine the reproducibility (variability inter laboratory of test results and to evaluate the difference in the test results within laboratory. Up-flow column percolation tests were performed following the procedure described in the ISO/TS 21268-3. This procedure consists of percolating solution (calcium chloride 1 mM from bottom to top at a flow rate of 12 mL/h through softly compacted soil contained in a column of 5 cm diameter and 30 ± 5 cm height. Eluate samples were collected at liquid-to-solid ratio of 0.1, 0.2, 0.5, 1, 2, 5 and 10 L/kg and analyzed for quantification of the target elements (Cu, As, Se, Cl, Ca, F, Mg, DOC and B in this research. For Soil I, 17 institutions in Japan joined this validation test. The up-flow column experiments were conducted in duplicate, after 48 h of equilibration time and at a flow rate of 12 mL/h. Column percolation test results from Soils II and III were used to evaluate the difference in test results from the experiments conducted in duplicate in a single laboratory, after 16 h of equilibration time and at a flow rate of 36 mL/h. Overall results showed good reproducibility (expressed in terms of the coefficient of variation, CV, calculated by dividing the standard deviation by the mean, as the CV was lower than 30% in more than 90% of the test results associated with Soil I. Moreover, low variability (expressed in terms of difference between the two test results divided by the mean was observed in the test results related to Soils II and III, with a variability lower than 30
Anomalous properties of technetium clusters
International Nuclear Information System (INIS)
Kryuchkov, S.V.
1985-01-01
On the basis of critical evaluation of literature data in the field of chemistry of technetium cluster compounds with ligands of a weak field a conclusion is made on specific, ''anomalous'' properties of technetium cluster complexes which consist in an increased ability of the given element to the formation of a series of binuclear and multinuclear clusters, similar in composition and structure and easily transforming in each other. The majority of technetium clusters unlike similar compounds of other elements are paramagnetic with one unpaired electron on ''metallic'' MO of loosening type. All theoretical conceptions known today on the electronic structure of technetium clusters are considered. It is pointed out, that the best results in the explanation of ''anomalous'' properties of technetium clusters can be obtained in the framework of nonempirical methods of self-consistent field taking into account configuration interactions. It is also shown, that certain properties of technetium clusters can be explained on the basis of qualitative model of Coulomb repulsion of metal atoms in clusters. The conclusion is made, that technetium position in the Periodic table, as well as recently detected technetium property to the decrease of effective charge on its atoms during M-M bond formation promote a high ability of the element to cluster formation both with weak field ligands and with strong field one
Statistical Significance for Hierarchical Clustering
Kimes, Patrick K.; Liu, Yufeng; Hayes, D. Neil; Marron, J. S.
2017-01-01
Summary Cluster analysis has proved to be an invaluable tool for the exploratory and unsupervised analysis of high dimensional datasets. Among methods for clustering, hierarchical approaches have enjoyed substantial popularity in genomics and other fields for their ability to simultaneously uncover multiple layers of clustering structure. A critical and challenging question in cluster analysis is whether the identified clusters represent important underlying structure or are artifacts of natural sampling variation. Few approaches have been proposed for addressing this problem in the context of hierarchical clustering, for which the problem is further complicated by the natural tree structure of the partition, and the multiplicity of tests required to parse the layers of nested clusters. In this paper, we propose a Monte Carlo based approach for testing statistical significance in hierarchical clustering which addresses these issues. The approach is implemented as a sequential testing procedure guaranteeing control of the family-wise error rate. Theoretical justification is provided for our approach, and its power to detect true clustering structure is illustrated through several simulation studies and applications to two cancer gene expression datasets. PMID:28099990
DEFF Research Database (Denmark)
Kjellberg, Caspar Mølholt; Meredith, David
2014-01-01
. Since the comments are not input sequentially, with regard to position, but in arbitrary order, this list must be sorted by copy/pasting the rows into place—an error-prone and time-consuming process. Scholars who produce critical editions typically use off-the-shelf music notation software......The best text method is commonly applied among music scholars engaged in producing critical editions. In this method, a comment list is compiled, consisting of variant readings and editorial emendations. This list is maintained by inserting the comments into a document as the changes are made......, consisting of a Sibelius plug-in, a cross-platform application, called CriticalEd, and a REST-based solution, which handles data storage/retrieval. A prototype has been tested at the Danish Centre for Music Publication, and the results suggest that the system could greatly improve the efficiency...
Cluster Correlation in Mixed Models
Gardini, A.; Bonometto, S. A.; Murante, G.; Yepes, G.
2000-10-01
We evaluate the dependence of the cluster correlation length, rc, on the mean intercluster separation, Dc, for three models with critical matter density, vanishing vacuum energy (Λ=0), and COBE normalization: a tilted cold dark matter (tCDM) model (n=0.8) and two blue mixed models with two light massive neutrinos, yielding Ωh=0.26 and 0.14 (MDM1 and MDM2, respectively). All models approach the observational value of σ8 (and hence the observed cluster abundance) and are consistent with the observed abundance of damped Lyα systems. Mixed models have a motivation in recent results of neutrino physics; they also agree with the observed value of the ratio σ8/σ25, yielding the spectral slope parameter Γ, and nicely fit Las Campanas Redshift Survey (LCRS) reconstructed spectra. We use parallel AP3M simulations, performed in a wide box (of side 360 h-1 Mpc) and with high mass and distance resolution, enabling us to build artificial samples of clusters, whose total number and mass range allow us to cover the same Dc interval inspected through Automatic Plate Measuring Facility (APM) and Abell cluster clustering data. We find that the tCDM model performs substantially better than n=1 critical density CDM models. Our main finding, however, is that mixed models provide a surprisingly good fit to cluster clustering data.
Critical current characteristics in high T/sub c/ oxide superconductors
International Nuclear Information System (INIS)
Matsushita, T.; Ni, B.
1989-01-01
Critical current densities are theoretically estimated for single-crystalline thin films, polycrystalline bulk materials with oriented and random textures of superconducting oxides. The percolation theory is used and the effect of depression of the transport current through grain boundaries is taken into account. A comparison is made with existing experimental results
Minku, Leandro L.; Hou, Siqing
2017-01-01
baseline WC model is also included in the analysis. Results: Clustering Dycom with K-Means can potentially help to split the CC projects, managing to achieve similar or better predictive performance than Dycom. However, K-Means still requires the number
International Nuclear Information System (INIS)
Paces, J.B.; Whelan, J.F.; Peterman, Z.E.; Marshall, B.D.
2000-01-01
Geological, mineralogical, chemical, and isotopic evidence from coatings of calcite and silica on open fractures and lithophysal cavities within welded tuffs at Yucca Mountain indicate an origin from meteoric water percolating through a thick (500 to 700 m) unsaturated zone (UZ) rather than from pulses of ascending ground water. Geologic evidence for a UZ setting includes the presence of coatings in only a small percentage of cavities, the restriction of coatings to fracture footwalls and cavity floors, and an absence of mineral high-water marks indicative of water ponding. Systematic mineral sequences (early calcite, followed by chalcedony with minor quartz and fluorite, and finally calcite with intercalated opal forming the bulk of the coatings) indicate progressive changes in UZ conditions through time, rather than repeated saturation by flooding. Percolation under the influence of gravity also results in mineral textures that vary between steeply dipping sites (thinner coatings of blocky calcite) and shallowly dipping sites (thicker coatings of coarse, commonly bladed calcite, with globules and sheets of opal). Micrometer-scale growth banding in both calcite and opal reflects slow average growth rates (scale of mm/m.y.) over millions of years rather than only a few rapidly deposited growth episodes. Isotopic compositions of C, O, Sr, and U from calcite and opal indicate a percolation-modified meteoric water source, and collectively refute a deeper ground-water source. Chemical and isotopic variations in coatings also indicate long-term evolution of water compositions. Although some compositional changes are related to shifts in climate, growth rates in the deeper UZ are buffered from large changes in meteoric input. Coatings most likely formed from films of water flowing down connected fracture pathways. Mineral precipitation is consistent with water vapor and carbon dioxide loss from films at very slow rates. Data collectively indicate that mineral coatings
Unraveling the atomic structure of ultrafine iron clusters
Wang, Hongtao; Li, Kun; Yao, Yingbang; Wang, Qingxiao; Cheng, Yingchun; Schwingenschlö gl, Udo; Zhang, Xixiang; Yang, Wei
2012-01-01
Unraveling the atomic structures of ultrafine iron clusters is critical to understanding their size-dependent catalytic effects and electronic properties. Here, we describe the stable close-packed structure of ultrafine Fe clusters for the first
A solid-on-solid invasion percolation model for self-affine interfaces
International Nuclear Information System (INIS)
Arizmendi, C.M.; Martin, H.O.; Sanchez, J.R.
1993-08-01
The scaling properties of the interface of a new growth model are studied. The model is based on the standard invasion percolation without trapping in which the solid-on-solid condition is imposed. The local correlation between points of the interface can be controlled through a parameter. The self-affine properties of the interface show strong dependence on the existence of the local correlation. The dependence of the relevant exponents of the interface with the correlation is analysed. (author). 8 refs, 4 figs
Percolation Model of Nuclear Multifragmentation in High Energy Nucleus-Nucleus Interactions
International Nuclear Information System (INIS)
Abdel-Waged, Kh.
1994-01-01
A hybrid model based on Reggeon theory inspired model of nuclear distribution, which was successful in explaining the cascading of particles in high energy nucleus-nucleus interactions, and percolation model is proposed. In the framework of this model the yield of the fragment in p + Ag, Au at 350 GeV and C + Ag, Au at 3.6 GeV/nucleon as well as the charge distribution of fragments in Kr, Xe and U interactions with emulsion at ∼ 1 GeV/nucleon is correctly described. 32 refs., 3 figs
A Percolation Study of Wettability Effect on the Electrical Properties of Reservoir Rocks
DEFF Research Database (Denmark)
Zhou, Dengen; Arbabi, Sepehr; Stenby, Erling Halfdan
1997-01-01
Measurements of the electrical resistivity of oil reservoirs are commonly used to estimate other properties of reservoirs, such as porosity and hydrocarbon reserves. However, the interpretation of the measurements is based on empirical correlations, because the underlying mechanisms that control...... the electrical properties of oil bearing rocks have not been well understood. In this paper, we employ percolation concepts to investigate the effect of wettability on the electrical conductivity of a reservoir formation. A three-dimensional simple cubic network is used to represent an ideal reservoir formation...
Janssen, Hans-Karl; Stenull, Olaf
2004-02-01
We investigate corrections to scaling induced by irrelevant operators in randomly diluted systems near the percolation threshold. The specific systems that we consider are the random resistor network and a class of continuous spin systems, such as the x-y model. We focus on a family of least irrelevant operators and determine the corrections to scaling that originate from this family. Our field theoretic analysis carefully takes into account that irrelevant operators mix under renormalization. It turns out that long standing results on corrections to scaling are respectively incorrect (random resistor networks) or incomplete (continuous spin systems).
Paddle-wheel versus percolation mechanism for cation transport in some sulphate phases
DEFF Research Database (Denmark)
Andersen, N.H.; Bandaranyake, P.W.S.K.; Careem, M.A.
1992-01-01
in these phases. A single-crystal neutron diffraction study has been performed for cubic lithium sulphate. The refinement of the data gives a very complex model for the location of the lithium ions. There is definitely a void at and near the octahedral (1/2, 1/2, 1/2) position. 90% of the lithium ions are located...... and interdiffusion, all studied mono- and divalent cations are very mobile in the rotor phases, which lack the pronounced correlation with ionic radii that is characteristic for diffusion in other classes of solid electrolytes. The quoted studies are to be considered as strong evidence against a percolation model...
Bond percolation in a square lattice in presence of a 'magnetic field'
International Nuclear Information System (INIS)
Oliveira, P.M.C. de; Queiroz, S.L.A. de; Riera, R.; Chaves, C.M.G.F.
1979-10-01
A calculation of the bond percolation problem in a square lattice in presence of a magnetic field is presented using the position space renormalization group and cells of dimension b x b, where b runs from 2 up to 5. Due to symmetry, the calculation splits into two parts, one determining the 'thermal' exponent ν and the other, the magnetic exponent eta. For the largest cell in each case, we get ν = 1.355 (b=5) and eta = 0.244 (b=4), in good agreement with series results of Dunn et al. Comments are made on the extrapolation of the results to b = infinity. (Author) [pt
Herega, Alexander; Sukhanov, Volodymyr; Vyrovoy, Valery
2016-11-01
The multiplicative measure and estimation method of ordering of the nearest neighborhood at the multiscale "site" percolation problem are considered. In the report also is shown the possibility of quantifying a relative degree of order of two nearest neighborhoods, which is based on the algorithm proposed by one of the authors. Moreover, the model of the oscillatory component of interaction of inner boundaries of different scales is proposed. In the context of our report, the concept of lacunarity and effective dimension (introduced by B. Mandelbrot) is discussed as effective tools of mathematical modeling.
The, Matthew; MacCoss, Michael J.; Noble, William S.; Käll, Lukas
2016-11-01
Percolator is a widely used software tool that increases yield in shotgun proteomics experiments and assigns reliable statistical confidence measures, such as q values and posterior error probabilities, to peptides and peptide-spectrum matches (PSMs) from such experiments. Percolator's processing speed has been sufficient for typical data sets consisting of hundreds of thousands of PSMs. With our new scalable approach, we can now also analyze millions of PSMs in a matter of minutes on a commodity computer. Furthermore, with the increasing awareness for the need for reliable statistics on the protein level, we compared several easy-to-understand protein inference methods and implemented the best-performing method—grouping proteins by their corresponding sets of theoretical peptides and then considering only the best-scoring peptide for each protein—in the Percolator package. We used Percolator 3.0 to analyze the data from a recent study of the draft human proteome containing 25 million spectra (PM:24870542). The source code and Ubuntu, Windows, MacOS, and Fedora binary packages are available from http://percolator.ms/ under an Apache 2.0 license.
Directory of Open Access Journals (Sweden)
Yuli Chen
2014-01-01
Full Text Available The electrical percolation of polymer-matrix composites (PMCs containing hybrid fillers of carbon nanotubes (CNTs and carbon black (CB is estimated by studying the connection possibility of the fillers using Monte Carlo simulation. The 3D simulation model of CB-CNT hybrid filler is established, in which CNTs are modeled by slender capped cylinders and CB groups are modeled by hypothetical spheres with interspaces because CB particles are always agglomerated. The observation on the effects of CB and CNT volume fractions and dimensions on the electrical percolation threshold of hybrid filled composites is then carried out. It is found that the composite electrical percolation threshold can be reduced by increasing CNT aspect ratio, as well as increasing the diameter ratio of CB groups to CNTs. And adding CB into CNT composites can decrease the CNT volume needed to convert the composite conductivity, especially when the CNT volume fraction is close to the threshold of PMCs with only CNT filler. Different from previous linear assumption, the nonlinear relation between CB and CNT volume fractions at composite percolation threshold is revealed, which is consistent with the synergistic effect observed in experiments. Based on the nonlinear relation, the estimating equation for the electrical percolation threshold of the PMCs containing CB-CNT hybrid fillers is established.
DEFF Research Database (Denmark)
Christensen, Thomas Budde
The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands...... or management. Both the Accelerate Wales and the Accelerate Cluster programmes target this issue by trying to establish networks between companies that can be used to supply knowledge from research institutions to manufacturing companies. The paper concludes that public sector interventions can make...... businesses. The universities were not considered by the participating companies to be important parts of the local business environment and inputs from universities did not appear to be an important source to access knowledge about new product development or new techniques in production, distribution...
Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...
Mucha, Hans-Joachim; Sofyan, Hizir
2000-01-01
As an explorative technique, duster analysis provides a description or a reduction in the dimension of the data. It classifies a set of observations into two or more mutually exclusive unknown groups based on combinations of many variables. Its aim is to construct groups in such a way that the profiles of objects in the same groups are relatively homogenous whereas the profiles of objects in different groups are relatively heterogeneous. Clustering is distinct from classification techniques, ...
Jeong, Seongmin; Cho, Hyunmin; Han, Seonggeun; Won, Phillip; Lee, Habeom; Hong, Sukjoon; Yeo, Junyeob; Kwon, Jinhyeong; Ko, Seung Hwan
2017-07-12
Air quality has become a major public health issue in Asia including China, Korea, and India. Particulate matters are the major concern in air quality. We present the first environmental application demonstration of Ag nanowire percolation network for a novel, electrical type transparent, reusable, and active PM2.5 air filter although the Ag nanowire percolation network has been studied as a very promising transparent conductor in optoelectronics. Compared with previous particulate matter air filter study using relatively weaker short-range intermolecular force in polar polymeric nanofiber, Ag nanowire percolation network filters use stronger long-range electrostatic force to capture PM2.5, and they are highly efficient (>99.99%), transparent, working on an active mode, low power consumption, antibacterial, and reusable after simple washing. The proposed new particulate matter filter can be applied for a highly efficient, reusable, active and energy efficient filter for wearable electronics application.
International Nuclear Information System (INIS)
Watters, Arianna L; Palmese, Giuseppe R
2014-01-01
Uniform dispersion of single walled carbon nanotubes (SWNTs) in an epoxy was achieved by a streamlined mechano-chemical processing method. SWNT-epoxy composites were synthesized using a room temperature ionic liquid (IL) with an imidazolium cation and dicyanamide anion. The novel approach of using ionic liquid that behaves as a dispersant for SWNTs and initiator for epoxy polymerization greatly simplifies nanocomposite synthesis. The material was processed using simple and scalable three roll milling. The SWNT dispersion of the resultant composite was evaluated by electron microscopy and electrical conductivity measurements in conjunction with percolation theory. Processing conditions were optimized to achieve the lowest possible percolation threshold, 4.29 × 10 −5 volume fraction SWNTs. This percolation threshold is among the best reported in literature yet it was obtained using a streamlined method that greatly simplifies processing. (paper)
Watters, Arianna L.; Palmese, Giuseppe R.
2014-09-01
Uniform dispersion of single walled carbon nanotubes (SWNTs) in an epoxy was achieved by a streamlined mechano-chemical processing method. SWNT-epoxy composites were synthesized using a room temperature ionic liquid (IL) with an imidazolium cation and dicyanamide anion. The novel approach of using ionic liquid that behaves as a dispersant for SWNTs and initiator for epoxy polymerization greatly simplifies nanocomposite synthesis. The material was processed using simple and scalable three roll milling. The SWNT dispersion of the resultant composite was evaluated by electron microscopy and electrical conductivity measurements in conjunction with percolation theory. Processing conditions were optimized to achieve the lowest possible percolation threshold, 4.29 × 10-5 volume fraction SWNTs. This percolation threshold is among the best reported in literature yet it was obtained using a streamlined method that greatly simplifies processing.
Gibbs Measures Over Locally Tree-Like Graphs and Percolative Entropy Over Infinite Regular Trees
Austin, Tim; Podder, Moumanti
2018-03-01
Consider a statistical physical model on the d-regular infinite tree Td described by a set of interactions Φ . Let Gn be a sequence of finite graphs with vertex sets V_n that locally converge to Td. From Φ one can construct a sequence of corresponding models on the graphs G_n. Let μ_n be the resulting Gibbs measures. Here we assume that μ n converges to some limiting Gibbs measure μ on Td in the local weak^* sense, and study the consequences of this convergence for the specific entropies |V_n|^{-1}H(μ _n). We show that the limit supremum of |V_n|^{-1}H(μ _n) is bounded above by the percolative entropy H_{it{perc}}(μ ), a function of μ itself, and that |V_n|^{-1}H(μ _n) actually converges to H_{it{perc}}(μ ) in case Φ exhibits strong spatial mixing on T_d. When it is known to exist, the limit of |V_n|^{-1}H(μ _n) is most commonly shown to be given by the Bethe ansatz. Percolative entropy gives a different formula, and we do not know how to connect it to the Bethe ansatz directly. We discuss a few examples of well-known models for which the latter result holds in the high temperature regime.
Normalized fluctuations, H2O vs n-hexane: Site-correlated percolation
Koga, Yoshikata; Westh, Peter; Sawamura, Seiji; Taniguchi, Yoshihiro
1996-08-01
Entropy, volume and the cross fluctuations were normalized to the average volume of a coarse grain with a fixed number of molecules, within which the local and instantaneous value of interest is evaluated. Comparisons were made between liquid H2O and n-hexane in the range from -10 °C to 120 °C and from 0.1 MPa to 500 MPa. The difference between H2O and n-hexane in temperature and pressure dependencies of these normalized fluctuations was explained in terms of the site-correlated percolation theory for H2O. In particular, the temperature increase was confirmed to reduce the hydrogen bond probability, while the pressure appeared to have little effect on the hydrogen bond probability. According to the Le Chatelier principle, however, the putative formation of ``ice-like'' patches at low temperatures due to the site-correlated percolation requirement is retarded by pressure increases. Thus, only in the limited region of low pressure (<300 MPa) and temperature (<60 °C), the fluctuating ice-like patches are considered to persist.
Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.
Persson, B N J; Prodanov, N; Krick, B A; Rodriguez, N; Mulakaluri, N; Sawyer, W G; Mangiagalli, P
2012-01-01
The dynamics of fluid flow at the interface between elastic solids with rough surfaces depends sensitively on the area of real contact, in particular close to the percolation threshold, where an irregular network of narrow flow channels prevails. In this paper, numerical simulation and experimental results for the contact between elastic solids with isotropic and anisotropic surface roughness are compared with the predictions of a theory based on the Persson contact mechanics theory and the Bruggeman effective medium theory. The theory predictions are in good agreement with the experimental and numerical simulation results and the (small) deviation can be understood as a finite-size effect. The fluid squeeze-out at the interface between elastic solids with randomly rough surfaces is studied. We present results for such high contact pressures that the area of real contact percolates, giving rise to sealed-off domains with pressurized fluid at the interface. The theoretical predictions are compared to experimental data for a simple model system (a rubber block squeezed against a flat glass plate), and for prefilled syringes, where the rubber plunger stopper is lubricated by a high-viscosity silicon oil to ensure functionality of the delivery device. For the latter system we compare the breakloose (or static) friction, as a function of the time of stationary contact, to the theory prediction.
Tiglyene, S; Jaouad, A; Mandi, L
2008-06-01
The aim of this paper was, on one hand, to study the treatment of raw tannery effluent by infiltration percolation system and, on the other hand, to determine the distribution and speciation of chromium in the used soil. The system pilot consisted of columns filled to 15 cm of gravel and 60 cm of soil (88% of sand). The columns irrigated by raw tannery wastewater with a daily hydraulic load of 5 cm per day (approximately 10 L every day). The water flowed vertically through the soil. The speciation of Cr was investigated by using selective five steps sequential extraction method. The results indicated that the pH of the treated wastewater increases by three units in comparison to the raw wastewater. The electrical conductivity of the effluent increases also after treatment. Over the whole experimental period, results revealed significant performances of infiltration percolation system for organic load reduction. The mean elimination rate was 74% for total COD. In addition, there was a significant accumulation of organic carbon (62%) in the surface strata for the system. The total chromium undergoes an overall removal of 98%. After seven months of experiment, the results indicated that the whole retention of Cr occurring in the surface horizon of the soil (69%). Furthermore, the speciation study of Cr in the soil revealed that the oxidizable fraction is the most represented 55%. The reducible and residual phases represent 17.5% and 18.5%, respectively. The carbonate fraction presented 9% while exchangeable fraction presented only 0.02%.
Percolation leaching and uranium recovery of El erediya granitic rocks, eastern desert, Egypt
International Nuclear Information System (INIS)
Abdel Monem, H.M.; Ali, M.M.; Hassan, M.A.
1998-01-01
El erediya uranium occurrence is located in the vicinity of qena-safaga road, central eastern desert. A bulk head sample of about 50 kg was prepared for this study. mineralogically, uranophane is the essential uranium mineral identified in the studied bulk head sample. It occurs as yellow flakes and acicular grains filling fractures, whereas the gangue minerals are mainly composed of quartz, altered potash feldspar, and minor plagioclase. The head sample assays as 74.36% SiO 2 , 13.81% Al 2 O 3 and 0.091% U. Percolation leaching utilizing H 2 SO 4 was performed at a fairly low Ph value. The examined factors include Ph of the leach solution, the grain size beside the duration time. More than 97% leaching of the uranium was reported after percolating the leach solution for 6 weeks at ph 1.4. Thus it could be possible to produce a pregnant leach solution assaying more than 1.2 g U/L by using a multi-stage leaching system. For recovering uranium, tri-octyl-phosphine oxide (TOPO) in kerosene was found to be the most powerful U-extractant. Good U-distribution coefficient (E) of 103 has been obtained with 0.1 M TOPO in the presence of 0.1 M HNO 3
Two percolation thresholds due to geometrical effects: experimental and simulated results
International Nuclear Information System (INIS)
Nettelblad, B; Martensson, E; Oenneby, C; Gaefvert, U; Gustafsson, A
2003-01-01
The electrical properties of a mixture of ethylene-propylene-diene monomer rubber and silicon carbide (SiC) have been measured as a function of filler concentration. It was found that mixtures containing angular SiC grains have a conductivity that displays not one, but two percolation thresholds. Different types of contacts between the conducting particles, being represented by edge and face connections, respectively, can explain the phenomenon. The two percolation thresholds are obtained at volume fractions of about 0.25 and 0.40, respectively. These values are higher than those predicted by theory, which can be explained by dispersion effects with only one phase being granular and the other being continuous. The value of the conductivity at the central plateau was found to be close to the geometric mean of the limiting conductivities at low and high concentrations. This is in good agreement with theory. With rounded SiC grains only one threshold is obtained, which is consistent with only one type of contact. The concentration dependence of the conductivity was simulated using a three-dimensional impedance network model that incorporates both edge and face contacts. The double-threshold behaviour also appears in the calculations. By dispersing the conducting particles more evenly than random, the thresholds are shifted towards higher concentrations as observed in the experiments
Morone, Flaviano; Min, Byungjoon; Bo, Lin; Mari, Romain; Makse, Hernán A.
2016-07-01
We elaborate on a linear-time implementation of Collective-Influence (CI) algorithm introduced by Morone, Makse, Nature 524, 65 (2015) to find the minimal set of influencers in networks via optimal percolation. The computational complexity of CI is O(N log N) when removing nodes one-by-one, made possible through an appropriate data structure to process CI. We introduce two Belief-Propagation (BP) variants of CI that consider global optimization via message-passing: CI propagation (CIP) and Collective-Immunization-Belief-Propagation algorithm (CIBP) based on optimal immunization. Both identify a slightly smaller fraction of influencers than CI and, remarkably, reproduce the exact analytical optimal percolation threshold obtained in Random Struct. Alg. 21, 397 (2002) for cubic random regular graphs, leaving little room for improvement for random graphs. However, the small augmented performance comes at the expense of increasing running time to O(N2), rendering BP prohibitive for modern-day big-data. For instance, for big-data social networks of 200 million users (e.g., Twitter users sending 500 million tweets/day), CI finds influencers in 2.5 hours on a single CPU, while all BP algorithms (CIP, CIBP and BDP) would take more than 3,000 years to accomplish the same task.
Tritium sorption behavior on the percolation of tritiated water into a soil packed bed
Energy Technology Data Exchange (ETDEWEB)
Furuichi, Kazuya, E-mail: kfuruichi@aees.kyushu-u.ac.jp [Department of Advanced Energy Engineering, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Katayama, Kazunari; Date, Hiroyuki [Department of Advanced Energy Engineering, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Takeishi, Toshiharu [Factory of Engineering, Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395 (Japan); Fukada, Satoshi [Department of Advanced Energy Engineering, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)
2016-11-01
Highlights: • We establish the permeation model of tritiated water in the soil layer. • Saturated hydraulic conductivity of water in soil was gained by using the model. • The isotope exchange reaction coefficient was good agreement with experimental data. - Abstract: Development of tritium transport model in natural soil is an important issue from a viewpoint of safety of fusion reactors. The spill of a large amount of tritiated water to the environment is a concern accident because huge tritiated water is handled in a fusion plant. In this work, a simple tritium transport model was proposed based on the tritium transport model in porous materials. The overall mass transfer coefficient representing isotope exchange reaction between tritiated water and structural water in soil particles was obtained by numerically analyzing the result of the percolation experiment of tritiated water into the soil packed bed. Saturated hydraulic conductivity in the natural soil packed bed was obtained to be 0.033 mm/s. By using this value, the overall mass transfer capacity coefficients representing the isotope exchange reaction between tritiated water percolating through the packed bed and overall structural water on soil particles was determined to be 6.0 × 10{sup −4} 1/s. This value is much smaller than the mass transfer capacity coefficient between tritiated water vapor and water on concrete material and metals.
Zeng, Yayun; Wang, Jun; Xu, Kaixuan
2017-04-01
A new financial agent-based time series model is developed and investigated by multiscale-continuum percolation system, which can be viewed as an extended version of continuum percolation system. In this financial model, for different parameters of proportion and density, two Poisson point processes (where the radii of points represent the ability of receiving or transmitting information among investors) are applied to model a random stock price process, in an attempt to investigate the fluctuation dynamics of the financial market. To validate its effectiveness and rationality, we compare the statistical behaviors and the multifractal behaviors of the simulated data derived from the proposed model with those of the real stock markets. Further, the multiscale sample entropy analysis is employed to study the complexity of the returns, and the cross-sample entropy analysis is applied to measure the degree of asynchrony of return autocorrelation time series. The empirical results indicate that the proposed financial model can simulate and reproduce some significant characteristics of the real stock markets to a certain extent.
Energy Technology Data Exchange (ETDEWEB)
Hussein El-Sayed, M
1984-07-01
Phosphatic sandstone of Qatrani area contains high concentrations of uranium and thorium (1450 and 870 ppm respectively). These elements were directly separated from a representative sample of the ore by percolation leaching. Separation made was carried out by using two different leaching reagents, citric and nitric acids for obtaining two separate concentrates of U and Th consecutively from the sample. Uranium was leached first by using citric acid where other rock ingredients were left intact. The effects of: (a) increasing acid input amounts and (b) increasing leaching solution volumes (dilution) on U leaching efficiency were studied. The results revealed that citric acid reaction upon phosphate is limited in spite of higher residual acidity reported in the leach liquors. Regarding uranium, its leaching efficiency increased by increasing acid amounts and/or leaching solution volumes while fixing the acid input amounts. The efficiency of U leaching is more pronounced in the second case than in the first. Increasing U leaching while phosphate dissolution is limited could be interpreted as that the relative complexing affinity of citrate anion for hexavalent uranium is by far much greater than with phosphate. Thorium was thereafter leached by using dilute solutions of nitric acid to avoid dissolution of nitric acid to avoid dissolution of impurities. Percolation leaching experiments were thus performed on the uranium-free samples in the columns used previously in uranium leaching. The effects of increasing acid amounts and increasing leach liquor recycles on Th (and P/sub 2/O/sub 5/) leaching efficiency were studied.
Morone, Flaviano; Min, Byungjoon; Bo, Lin; Mari, Romain; Makse, Hernán A.
2016-01-01
We elaborate on a linear-time implementation of Collective-Influence (CI) algorithm introduced by Morone, Makse, Nature 524, 65 (2015) to find the minimal set of influencers in networks via optimal percolation. The computational complexity of CI is O(N log N) when removing nodes one-by-one, made possible through an appropriate data structure to process CI. We introduce two Belief-Propagation (BP) variants of CI that consider global optimization via message-passing: CI propagation (CIP) and Collective-Immunization-Belief-Propagation algorithm (CIBP) based on optimal immunization. Both identify a slightly smaller fraction of influencers than CI and, remarkably, reproduce the exact analytical optimal percolation threshold obtained in Random Struct. Alg. 21, 397 (2002) for cubic random regular graphs, leaving little room for improvement for random graphs. However, the small augmented performance comes at the expense of increasing running time to O(N2), rendering BP prohibitive for modern-day big-data. For instance, for big-data social networks of 200 million users (e.g., Twitter users sending 500 million tweets/day), CI finds influencers in 2.5 hours on a single CPU, while all BP algorithms (CIP, CIBP and BDP) would take more than 3,000 years to accomplish the same task. PMID:27455878
Bigus-Kwiatkowska, Marta; Fronczak, Agata; Fronczak, Piotr
2018-03-01
Inspired by albatrosses that use thermal lifts to fly across oceans we develop a simple model of gliders that serves us to study theoretical limitations of unlimited exploration of the Earth. Our studies, grounded in physical theory of continuous percolation and biased random walks, allow us to identify a variety of percolation transitions, which are understood as providing potentially unlimited movement through a space in a specified direction. We discover an unexpected phenomenon of self-organization of gliders in clusters, which resembles the flock organization of birds. This self-organization is intriguing, as it occurs thanks to exchange of information only and without any particular rules that could favor the clustering of the gliders (in contrast to the causes well known in literature, like, for example, attractive forces used in the Vicsek-type models or fitness functions used in evolutionary computation).
Misty Mountain clustering: application to fast unsupervised flow cytometry gating
Directory of Open Access Journals (Sweden)
Sealfon Stuart C
2010-10-01
Full Text Available Abstract Background There are many important clustering questions in computational biology for which no satisfactory method exists. Automated clustering algorithms, when applied to large, multidimensional datasets, such as flow cytometry data, prove unsatisfactory in terms of speed, problems with local minima or cluster shape bias. Model-based approaches are restricted by the assumptions of the fitting functions. Furthermore, model based clustering requires serial clustering for all cluster numbers within a user defined interval. The final cluster number is then selected by various criteria. These supervised serial clustering methods are time consuming and frequently different criteria result in different optimal cluster numbers. Various unsupervised heuristic approaches that have been developed such as affinity propagation are too expensive to be applied to datasets on the order of 106 points that are often generated by high throughput experiments. Results To circumvent these limitations, we developed a new, unsupervised density contour clustering algorithm, called Misty Mountain, that is based on percolation theory and that efficiently analyzes large data sets. The approach can be envisioned as a progressive top-down removal of clouds covering a data histogram relief map to identify clusters by the appearance of statistically distinct peaks and ridges. This is a parallel clustering method that finds every cluster after analyzing only once the cross sections of the histogram. The overall run time for the composite steps of the algorithm increases linearly by the number of data points. The clustering of 106 data points in 2D data space takes place within about 15 seconds on a standard laptop PC. Comparison of the performance of this algorithm with other state of the art automated flow cytometry gating methods indicate that Misty Mountain provides substantial improvements in both run time and in the accuracy of cluster assignment. Conclusions
BCS superconductivity for weakly coupled clusters
International Nuclear Information System (INIS)
Friedel, J.
1992-01-01
BCS superconductivity is expected to have fairly high critical temperatures when clusters of moderate sizes are weakly coupled to form a crystal. This remark extends to quasi zerodimensional cases, a remark initially made by Labbe for quasi one-dimensional ones and by Hirsch, Bok and Labbe for quasi twodimensional ones. Possible applications are envisaged for twodimensional clusters (fullerene) or threedimensional ones (metal clusters, Chevrel phases). Conditions for optimal applicability of the scheme are somewhat restricted. (orig.)