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Sample records for critical percolation cluster

  1. Critical percolation clusters in seven dimensions and on a complete graph

    Science.gov (United States)

    Huang, Wei; Hou, Pengcheng; Wang, Junfeng; Ziff, Robert M.; Deng, Youjin

    2018-02-01

    We study critical bond percolation on a seven-dimensional hypercubic lattice with periodic boundary conditions (7D) and on the complete graph (CG) of finite volume (number of vertices) V . We numerically confirm that for both cases, the critical number density n (s ,V ) of clusters of size s obeys a scaling form n (s ,V ) ˜s-τn ˜(s /Vdf*) with identical volume fractal dimension df*=2 /3 and exponent τ =1 +1 /df*=5 /2 . We then classify occupied bonds into bridge bonds, which includes branch and junction bonds, and nonbridge bonds; a bridge bond is a branch bond if and only if its deletion produces at least one tree. Deleting branch bonds from percolation configurations produces leaf-free configurations, whereas deleting all bridge bonds leads to bridge-free configurations composed of blobs. It is shown that the fraction of nonbridge (biconnected) bonds vanishes, ρn ,CG→0 , for large CGs, but converges to a finite value, ρn ,7 D=0.006 193 1 (7 ) , for the 7D hypercube. Further, we observe that while the bridge-free dimension dbf*=1 /3 holds for both the CG and 7D cases, the volume fractal dimensions of the leaf-free clusters are different: dlf,7 D *=0.669 (9 ) ≈2 /3 and dlf,CG *=0.3337 (17 ) ≈1 /3 . On the CG and in 7D, the whole, leaf-free, and bridge-free clusters all have the shortest-path volume fractal dimension dmin*≈1 /3 , characterizing their graph diameters. We also study the behavior of the number and the size distribution of leaf-free and bridge-free clusters. For the number of clusters, we numerically find the number of leaf-free and bridge-free clusters on the CG scale as ˜lnV , while for 7D they scale as ˜V . For the size distribution, we find the behavior on the CG is governed by a modified Fisher exponent τ'=1 , while for leaf-free clusters in 7D, it is governed by Fisher exponent τ =5 /2 . The size distribution of bridge-free clusters in 7D displays two-scaling behavior with exponents τ =4 and τ'=1 . The probability distribution

  2. 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)

  3. Percolation technique for galaxy clustering

    Science.gov (United States)

    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.

  4. Fragmentation of percolation cluster perimeters

    Science.gov (United States)

    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.

  5. 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)

  6. Percolation systems away from the critical point

    Indian Academy of Sciences (India)

    ping in dead-end branches leads to asymptotic drift velocity becoming zero for strong bias, and very slow relaxation of velocity near the critical bias field. Keywords. Percolation; lattice animals ... these systems. It turns out that percolation systems, such as the classical models of disordered media show many interest-. 419 ...

  7. 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.

  8. Double Percolation Phase Transition in Clustered Complex Networks

    Directory of Open Access Journals (Sweden)

    Pol Colomer-de-Simón

    2014-10-01

    Full Text Available The internal organization of complex networks often has striking consequences on either their response to external perturbations or on their dynamical properties. In addition to small-world and scale-free properties, clustering is the most common topological characteristic observed in many real networked systems. In this paper, we report an extensive numerical study on the effects of clustering on the structural properties of complex networks. Strong clustering in heterogeneous networks induces the emergence of a core-periphery organization that has a critical effect on the percolation properties of the networks. We observe a novel double phase transition with an intermediate phase in which only the core of the network is percolated and a final phase in which the periphery percolates regardless of the core. This result implies breaking of the same symmetry at two different values of the control parameter, in stark contrast to the modern theory of continuous phase transitions. Inspired by this core-periphery organization, we introduce a simple model that allows us to analytically prove that such an anomalous phase transition is, in fact, possible.

  9. Percolation properties of complex networks with weak and strong clustering

    Science.gov (United States)

    Serrano, M. Angeles

    2007-03-01

    A diversity of systems in the real world can be analyzed as complex networks. This makes any theoretical development in the field potentially applicable to many different areas. As a germane example, percolation has helped us to understand, for instance, the high resilience of scale-free networks in front of the random removal of a fraction of their constituents, with important implications for communication or biological systems among others. In addition to its high theoretical interest, it serves as a conceptual approach to treat more factual problems on networks, such as the dynamics of epidemic spreading. On the other hand, when large systems of interactions are mapped into comprehensible graphs, just vertices and edges are usually recognized as the primary building blocks. However, transitive relations, represented by triangles and referred to as clustering, should also be taken into account as a basic structure whose presence and self-organization can drastically impact network structure and properties. In this framework, the introduction of clustering in the percolation analysis of complex networks represents a theoretical challenge. Previous approaches were based on the idea of branching process, which works well when the network is locally treelike and thus the clustering coefficient is very small. Real networks, however, are shown to have a significant level of clustering. They can be classified in networks with weak transitivity, in which triangles are disjoint, and networks with strong transitivity, where edges are forced to share many triangles. The class a network belongs to changes its percolation properties. For networks with weak clustering, we find analytically the critical point for the onset of the giant component and its size. By means of numerical simulations, we also prove that, when comparing with the unclustered counterpart, weak clustering hinders the onset of the giant connected component whereas it is favored by strong clustering. This

  10. Percolation

    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

  11. 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

  12. The high temperature Ising model is a critical percolation model

    NARCIS (Netherlands)

    Meester, R.W.J.; Camia, F.; Balint, A.

    2010-01-01

    We define a new percolation model by generalising the FK representation of the Ising model, and show that on the triangular lattice and at high temperatures, the critical point in the new model corresponds to the Ising model. Since the new model can be viewed as Bernoulli percolation on a random

  13. Logarithmic corrections to scaling in critical percolation and random resistor networks.

    Science.gov (United States)

    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.

  14. 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...

  15. Memory decay and loss of criticality in quorum percolation

    Science.gov (United States)

    Renault, Renaud; Monceau, Pascal; Bottani, Samuel

    2013-12-01

    In this paper, we present the effects of memory decay on a bootstrap percolation model applied to random directed graphs (quorum percolation). The addition of decay was motivated by its natural occurrence in physical systems previously described by percolation theory, such as cultured neuronal networks, where decay originates from ionic leakage through the membrane of neurons and/or synaptic depression. Surprisingly, this feature alone appears to change the critical behavior of the percolation transition, where discontinuities are replaced by steep but finite slopes. Using different numerical approaches, we show evidence for this qualitative change even for very small decay values. In experiments where the steepest slopes can not be resolved and still appear as discontinuities, decay produces nonetheless a quantitative difference on the location of the apparent critical point. We discuss how this shift impacts network connectivity previously estimated without considering decay. In addition to this particular example, we believe that other percolation models are worth reinvestigating, taking into account similar sorts of memory decay.

  16. The critical probability for confetti percolation equals 1/2

    NARCIS (Netherlands)

    Müller, Tobias

    2017-01-01

    In the confetti percolation model, or two-coloured dead leaves model, radius one disks arrive on the plane according to a space-time Poisson process. Each disk is coloured black with probability p and white with probability 1 − p. In this paper we show that the critical probability for confetti

  17. The abundance threshold for plague as a critical percolation phenomenon.

    Science.gov (United States)

    Davis, S; Trapman, P; Leirs, H; Begon, M; Heesterbeek, J A P

    2008-07-31

    Percolation theory is most commonly associated with the slow flow of liquid through a porous medium, with applications to the physical sciences. Epidemiological applications have been anticipated for disease systems where the host is a plant or volume of soil, and hence is fixed in space. However, no natural examples have been reported. The central question of interest in percolation theory, 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) in populations of great gerbils (Rhombomys opimus) in Kazakhstan have been used to show that epizootics only occur when more than about 0.33 of the burrow systems built by the host are occupied by family groups. The underlying mechanism for this abundance threshold is unknown. Here we present evidence that it is a percolation threshold, which arises from the difference in scale between the movements that transport infectious fleas between family groups and the vast size of contiguous landscapes colonized by gerbils. Conventional theory predicts that abundance thresholds for the spread of infectious disease arise when transmission between hosts is density dependent such that the basic reproduction number (R(0)) increases with abundance, attaining 1 at the threshold. Percolation thresholds, however, are separate, spatially explicit thresholds that indicate long-range connectivity in a system and do not coincide with R(0) = 1. 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. This first natural example of a percolation threshold in a disease system invites a re-appraisal of other invasion thresholds, such as those for epidemic viral infections in African lions (Panthera leo), and of other disease systems such as bovine tuberculosis (caused by Mycobacterium bovis) in

  18. Numerical calculation of the conductivity of percolation clusters and the use of special purpose computers

    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

  19. Transfer matrix computation of generalized critical polynomials in percolation

    Science.gov (United States)

    Scullard, Christian R.; Lykke Jacobsen, Jesper

    2012-12-01

    Percolation thresholds have recently been studied by means of a graph polynomial PB(p), henceforth referred to as the critical polynomial, that may be defined on any periodic lattice. The polynomial depends on a finite subgraph B, called the basis, and the way in which the basis is tiled to form the lattice. The unique root of PB(p) in [0, 1] either gives the exact percolation threshold for the lattice, or provides an approximation that becomes more accurate with appropriately increasing size of B. Initially PB(p) was defined by a contraction-deletion identity, similar to that satisfied by the Tutte polynomial. Here, we give an alternative probabilistic definition of PB(p), which allows for much more efficient computations, by using the transfer matrix, than was previously possible with contraction-deletion. We present bond percolation polynomials for the (4, 82), kagome, and (3, 122) lattices for bases of up to respectively 96, 162 and 243 edges, much larger than the previous limit of 36 edges using contraction-deletion. We discuss in detail the role of the symmetries and the embedding of B. For the largest bases, we obtain the thresholds pc(4, 82) = 0.676 803 329…, pc(kagome) = 0.524 404 998…, pc(3, 122) = 0.740 420 798…, comparable to the best simulation results. We also show that the alternative definition of PB(p) can be applied to study site percolation problems. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  20. Transfer matrix computation of generalized critical polynomials in percolation

    International Nuclear Information System (INIS)

    Scullard, Christian R; Jacobsen, Jesper Lykke

    2012-01-01

    Percolation thresholds have recently been studied by means of a graph polynomial P B (p), henceforth referred to as the critical polynomial, that may be defined on any periodic lattice. The polynomial depends on a finite subgraph B, called the basis, and the way in which the basis is tiled to form the lattice. The unique root of P B (p) in [0, 1] either gives the exact percolation threshold for the lattice, or provides an approximation that becomes more accurate with appropriately increasing size of B. Initially P B (p) was defined by a contraction-deletion identity, similar to that satisfied by the Tutte polynomial. Here, we give an alternative probabilistic definition of P B (p), which allows for much more efficient computations, by using the transfer matrix, than was previously possible with contraction-deletion. We present bond percolation polynomials for the (4, 8 2 ), kagome, and (3, 12 2 ) lattices for bases of up to respectively 96, 162 and 243 edges, much larger than the previous limit of 36 edges using contraction-deletion. We discuss in detail the role of the symmetries and the embedding of B. For the largest bases, we obtain the thresholds p c (4, 8 2 ) = 0.676 803 329…, p c (kagome) = 0.524 404 998…, p c (3, 12 2 ) = 0.740 420 798…, comparable to the best simulation results. We also show that the alternative definition of P B (p) can be applied to study site percolation problems. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday. (paper)

  1. 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

  2. Anomalous critical and supercritical phenomena in explosive percolation

    Science.gov (United States)

    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.

  3. Trivial, Critical and Near-critical Scaling Limits of Two-dimensional Percolation

    NARCIS (Netherlands)

    Meester, R.W.J.; Camia, F.; Joosten, M.T.

    2009-01-01

    It is natural to expect that there are only three possible types of scaling limits for the collection of all percolation interfaces in the plane: (1) a trivial one, consisting of no curves at all, (2) a critical one, in which all points of the plane are surrounded by arbitrarily large loops and

  4. 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.

  5. 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

  6. 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...... with the Alexander-Orbach conjecture lead to an excellent analytical fit to the universal ac conductivity with no nontrivial fitting parameters....

  7. Directionality effects in percolation

    Science.gov (United States)

    Redner, Sidney

    The percolation properties of random networks containing resistors (two-way streets) and/or diodes (one-way streets) are considered. The directionality constraints of the diodes are found to lead to novel geometrical behavior. As a simple example, various random cluster models with a preferred direction, such as directed random walks or directed lattice animals, are shown to be anisotropic in character. The critical behavior of directed percolation is then treated and its connection with branching Markov processes is explained. A closely related "reverse" percolation problem, a transition from one-way percolation to isotropic percolation, is introduced. Finally, the geometrical properties of a network containing arbitrarily oriented diodes are treated. Symmetry and duality arguments are applied to yield exact results for certain aspects of its critical behavior.

  8. 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)

  9. Percolation Theory

    OpenAIRE

    Wierman, John C.

    1982-01-01

    An introduction is provided to the mathematical tools and problems of percolation theory. A discussion of Bernoulli percolation models shows the role of graph duality and correlation inequalities in the recent determination of the critical probability in the square, triangular, and hexagonal lattice bond models. An introduction to first passage percolation concentrates on the problems of existence of optimal routes, length of optimal routes, and conditions for convergence of first passage tim...

  10. Critical percolation in the slow cooling of the bi-dimensional ferromagnetic Ising model

    Science.gov (United States)

    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.

  11. Nonlinear random resistor diode networks and fractal dimensions of directed percolation clusters.

    Science.gov (United States)

    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.

  12. 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.

  13. Quenched Large Deviations for Simple Random Walks on Percolation Clusters Including Long-Range Correlations

    Science.gov (United States)

    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.

  14. 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.

  15. Factorization of percolation density correlation functions for clusters touching the sides of a rectangle

    Science.gov (United States)

    Simmons, Jacob J H; Ziff, Robert M; Kleban, Peter

    2009-02-01

    In this paper we consider the density, at a point z = x+iy, of critical percolation clusters that touch the left (PL(z)), right (PR(z)), or both (PLR(z)) sides of a rectangular system, with open boundary conditions on the top and bottom sides. While each of these quantities is non-universal and indeed vanishes in the continuum limit, the ratio C(z)=P_{L R}(z) / \\sqrt {P_L(z) P_R(z) \\Pi_{\\mathrm {h}}} , where Πh is the probability of left-right crossing given by Cardy, is a universal function of z. With wired (fixed) boundary conditions on the left- and right-hand sides, high-precision numerical simulations and theoretical arguments show that C(z) goes to a constant C0 = 27/2 3-3/4 π5/2 Γ(1/3)-9/2 = 1.029 9268... for points far from the ends, and varies by no more than a few per cent for all z values. Thus PLR(z) factorizes over the entire rectangle to very good approximation. In addition, the numerical observation that C(z) depends upon x but not upon y leads to an explicit expression for C(z) via conformal field theory for a long rectangle (semi-infinite strip). We also derive explicit expressions for PL(z), PR(z), and PLR(z) in this geometry, first by assuming y independence and then by a full analysis that obtains these quantities exactly with no assumption on the y behavior. In this geometry we obtain, in addition, the corresponding quantities in the case of open boundary conditions, which allows us to calculate C(z) in the open system. We give some theoretical results for an arbitrary rectangle as well. Our results also enable calculation of the finite-size corrections to the factorization near an isolated anchor point, for the case of clusters anchored at points. Finally, we present numerical results for a rectangle with periodic b.c. in the horizontal direction, and find C(z) that approaches a constant value C1≈1.022.

  16. Non-criticality of interaction network over system's crises: A percolation analysis.

    Science.gov (United States)

    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.

  17. Ellipses Percolation

    Science.gov (United States)

    Teixeira, Augusto; Ungaretti, Daniel

    2017-07-01

    We define a continuum percolation model that provides a collection of random ellipses on the plane and study the connectivity behavior of the covered set and the vacant set, the one obtained by removing all ellipses. Our model generalizes a construction that appears implicitly in the Poisson cylinder model of Tykesson and Windisch. The ellipses model has a parameter α > 0 associated with the tail decay of the major axis distribution; we only consider distributions ρ satisfying ρ [r, ∞) \\asymp r^{-α }. We prove that this model presents a double phase transition in α . For α \\in (0,1] the plane is completely covered by the ellipses, almost surely. For α \\in (1,2) the vacant set is not empty but does not percolate for any positive density of ellipses, while the covered set always percolates. For α \\in (2, ∞) the vacant set percolates for small densities of ellipses and the covered set percolates for large densities. Moreover, we prove for the critical parameter α = 2 that there is a non-degenerate interval of densities for which the probability of crossing boxes of a fixed proportion is bounded away from zero and one. In this interval neither the covered set nor the vacant set percolate, a behavior that is similar to critical independent percolation on Z^2.

  18. Spatial correlations, clustering and percolation-like transitions in homicide crimes

    Science.gov (United States)

    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.

  19. Powder keg divisions in the critical state regime: transition from continuous to explosive percolation

    Science.gov (United States)

    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.

  20. 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

  1. Frontiers and critical expoents in percolation and Ising and Potts ferromagnets: renormalization group and others techniques

    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

  2. The critical manifolds of inhomogeneous bond percolation on bow-tie and checkerboard lattices

    Science.gov (United States)

    Ziff, Robert M.; Scullard, Christian R.; Wierman, John C.; Sedlock, Matthew R. A.

    2012-12-01

    We give a conditional derivation of the inhomogeneous critical percolation manifold of the bow-tie lattice with five different probabilities, a problem that does not appear at first to fall into any known solvable class. Although our argument is mathematically rigorous only on a region of the manifold, we conjecture that the formula is correct over its entire domain, and we provide a non-rigorous argument for this that employs the negative probability regime of the triangular lattice critical surface. We discuss how the rigorous portion of our result substantially broadens the range of lattices in the solvable class to include certain inhomogeneous and asymmetric bow-tie lattices, and that, if it could be put on a firm foundation, the negative probability portion of our method would extend this class to many further systems, including F Y Wu’s checkerboard formula for the square lattice. We conclude by showing that this latter problem can in fact be proved using a recent result of Grimmett and Manolescu for isoradial graphs, lending strong evidence in favor of our other conjectured results. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  3. Flow, Transport, and Reaction in Porous Media: Percolation Scaling, Critical-Path Analysis, and Effective Medium Approximation

    Science.gov (United States)

    Hunt, Allen G.; Sahimi, Muhammad

    2017-12-01

    We describe the most important developments in the application of three theoretical tools to modeling of the morphology of porous media and flow and transport processes in them. One tool is percolation theory. Although it was over 40 years ago that the possibility of using percolation theory to describe flow and transport processes in porous media was first raised, new models and concepts, as well as new variants of the original percolation model are still being developed for various applications to flow phenomena in porous media. The other two approaches, closely related to percolation theory, are the critical-path analysis, which is applicable when porous media are highly heterogeneous, and the effective medium approximation—poor man's percolation—that provide a simple and, under certain conditions, quantitatively correct description of transport in porous media in which percolation-type disorder is relevant. Applications to topics in geosciences include predictions of the hydraulic conductivity and air permeability, solute and gas diffusion that are particularly important in ecohydrological applications and land-surface interactions, and multiphase flow in porous media, as well as non-Gaussian solute transport, and flow morphologies associated with imbibition into unsaturated fractures. We describe new applications of percolation theory of solute transport to chemical weathering and soil formation, geomorphology, and elemental cycling through the terrestrial Earth surface. Wherever quantitatively accurate predictions of such quantities are relevant, so are the techniques presented here. Whenever possible, the theoretical predictions are compared with the relevant experimental data. In practically all the cases, the agreement between the theoretical predictions and the data is excellent. Also discussed are possible future directions in the application of such concepts to many other phenomena in geosciences.

  4. 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

  5. Recent advances in percolation theory and its applications

    Science.gov (United States)

    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

  6. Introduction to percolation theory

    CERN Document Server

    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

  7. Sharpness of the percolation transition in the two-dimensional contact process

    NARCIS (Netherlands)

    van den Berg, J.

    2011-01-01

    For ordinary (independent) percolation on a large class of lattices it is well known that below the critical percolation parameter pc the cluster size distribution has exponential decay and that power-law behavior of this distribution can only occur at pc. This behavior is often called "sharpness of

  8. Social percolation models

    Science.gov (United States)

    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.

  9. Percolation in the canonical ensemble

    Science.gov (United States)

    Hu, Hao; Blöte, Henk W. J.; Deng, Youjin

    2012-12-01

    We study the bond percolation problem under the constraint that the total number of occupied bonds is fixed, so that the canonical ensemble applies. We show via an analytical approach that at criticality, the constraint can induce new finite-size corrections with exponent ycan = 2yt - d both in energy-like and magnetic quantities, where yt = 1/ν is the thermal renormalization exponent and d is the spatial dimension. Furthermore, we find that while most of the universal parameters remain unchanged, some universal amplitudes, like the excess cluster number, can be modified and become non-universal. We confirm these predictions by extensive Monte Carlo simulations of the two-dimensional percolation problem which has ycan = -1/2. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  10. Finite size scaling study of a two parameter percolation model: Constant and correlated growth

    Science.gov (United States)

    Roy, Bappaditya; Santra, S. B.

    2018-02-01

    A new percolation model of enhanced parameter space with nucleation and growth is developed taking the initial seed concentration ρ and a growth parameter g as two tunable parameters. Percolation transition is determined by the final static configurations of spanning clusters once taking uniform growth probability for all the clusters and then taking a cluster size dependent dynamic growth probability. The uniform growth probability remains constant over time and leads to a constant growth model whereas the dynamically varying growth probability leads to a correlated growth model. In the first case, the growth of a cluster will encounter partial hindrance due to the presence of other clusters whereas in the second case the growth of a larger cluster will be further suppressed in comparison to the growth of smaller clusters. A finite size scaling theory for percolation transition is developed and numerically verified for both the models. The scaling functions are found to depend on both g and ρ. At the critical growth parameter gc, the values of the critical exponents are found to be same as that of the original percolation at all values of ρ for the constant growth model whereas in the case of correlated growth model the scaling behavior deviates from ordinary percolation in the dilute limit of ρ. The constant growth model then belongs to the same universality class of percolation for a wide range of ρ whereas the correlated growth model displays a continuously varying universality class as ρ decreases towards zero.

  11. Constraint percolation on hyperbolic lattices

    Science.gov (United States)

    Lopez, Jorge H.; Schwarz, J. M.

    2017-11-01

    Hyperbolic lattices interpolate between finite-dimensional lattices and Bethe lattices, and they are interesting in their own right, with ordinary percolation exhibiting not one but two phase transitions. We study four constraint percolation models—k -core percolation (for k =1 ,2 ,3 ) and force-balance percolation—on several tessellations of the hyperbolic plane. By comparing these four different models, our numerical data suggest that all of the k -core models, even for k =3 , exhibit behavior similar to ordinary percolation, while the force-balance percolation transition is discontinuous. We also provide proof, for some hyperbolic lattices, of the existence of a critical probability that is less than unity for the force-balance model, so that we can place our interpretation of the numerical data for this model on a more rigorous footing. Finally, we discuss improved numerical methods for determining the two critical probabilities on the hyperbolic lattice for the k -core percolation models.

  12. Interactions and ``puff clustering'' close to the critical point in pipe flow

    Science.gov (United States)

    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.

  13. Percolation via Combined Electrostatic and Chemical Doping in Complex Oxide Films

    Science.gov (United States)

    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.

  14. 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

  15. Color-avoiding percolation

    Science.gov (United States)

    Krause, Sebastian M.; Danziger, Michael M.; Zlatić, Vinko

    2017-08-01

    Many real world networks have groups of similar nodes which are vulnerable to the same failure or adversary. Nodes can be colored in such a way that colors encode the shared vulnerabilities. Using multiple paths to avoid these vulnerabilities can greatly improve network robustness, if such paths exist. Color-avoiding percolation provides a theoretical framework for analyzing this scenario, focusing on the maximal set of nodes which can be connected via multiple color-avoiding paths. In this paper we extend the basic theory of color-avoiding percolation that was published in S. M. Krause et al. [Phys. Rev. X 6, 041022 (2016)], 10.1103/PhysRevX.6.041022. We explicitly account for the fact that the same particular link can be part of different paths avoiding different colors. This fact was previously accounted for with a heuristic approximation. Here we propose a better method for solving this problem which is substantially more accurate for many avoided colors. Further, we formulate our method with differentiated node functions, either as senders and receivers, or as transmitters. In both functions, nodes can be explicitly trusted or avoided. With only one avoided color we obtain standard percolation. Avoiding additional colors one by one, we can understand the critical behavior of color-avoiding percolation. For unequal color frequencies, we find that the colors with the largest frequencies control the critical threshold and exponent. Colors of small frequencies have only a minor influence on color-avoiding connectivity, thus allowing for approximations.

  16. Quantum mechanical cluster calculations of critical scintillationprocesses

    Energy Technology Data Exchange (ETDEWEB)

    Derenzo, Stephen E.; Klintenberg, Mattias K.; Weber, Marvin J.

    2000-02-22

    This paper describes the use of commercial quantum chemistrycodes to simu-late several critical scintillation processes. The crystalis modeled as a cluster of typically 50 atoms embedded in an array oftypically 5,000 point charges designed to reproduce the electrostaticfield of the infinite crystal. The Schrodinger equation is solved for theground, ionized, and excited states of the system to determine the energyand electron wavefunction. Computational methods for the followingcritical processes are described: (1) the formation and diffusion ofrelaxed holes, (2) the formation of excitons, (3) the trapping ofelectrons and holes by activator atoms, (4) the excitation of activatoratoms, and (5) thermal quenching. Examples include hole diffusion in CsI,the exciton in CsI, the excited state of CsI:Tl, the energy barrier forthe diffusion of relaxed holes in CaF2 and PbF2, and prompt hole trappingby activator atoms in CaF2:Eu and CdS:Te leading to an ultra-fast (<50ps) scintillation risetime.

  17. Percolating magmas in three dimensions

    Directory of Open Access Journals (Sweden)

    H. Gaonac'h

    2007-11-01

    Full Text Available The classical models of volcanic eruptions assume that they originate as a consequence of critical stresses or critical strain rates being exceeded in the magma followed by catastrophic fragmentation. In a recent paper (Gaonac'h et al., 2003 we proposed an additional mechanism based on the properties of complex networks of overlapping bubbles; that extreme multibubble coalescence could lead to catastrophic changes in the magma rheology at a critical vesicularity. This is possible because at a critical vesicularity Pc (the percolation threshold, even in the absence of external stresses the magma fragments. By considering 2-D percolation with the (observed extreme power law bubble distributions, we showed numerically that P2c had the apparently realistic value ≈0.7.

    The properties of percolating systems are, however, significantly different in 2-D and 3-D. In this paper, we discuss various new features relevant to 3-D percolation and compare the model predictions with empirical data on explosive volcanism. The most important points are a bubbles and magma have different 3-D critical percolation points; we show numerically that with power law bubble distributions that the important magma percolation threshold P3c,m has the high value ≈0.97±0.01, b a generic result of 3-D percolation is that the resulting primary fragments will have power law distributions with exponent B3f≈1.186±0.002, near the empirical value (for pumice ≈1.1±0.1; c we review the relevant percolation literature and point out that the elastic properties may have lower – possibly more realistic – critical vesicularities relevant to magmas; d we explore the implications of long range correlations (power law bubble distributions and discuss this in combination with bubble anisotropy; e we propose a new kind of intermediate "elliptical" dimensional percolation involving differentially

  18. 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.

  19. Interplay between thermal percolation and jamming upon dimer adsorption on binary alloys

    Science.gov (United States)

    Loscar, Ernesto S.; Borzi, R. A.; Albano, Ezequiel V.

    2006-11-01

    By means of Monte Carlo simulations we study jamming and percolation processes upon the random sequential adsorption of dimers on binary alloys with different degrees of structural order. The substrates are equimolar mixtures that we simulate using an Ising model with conserved order parameter. After an annealing at temperature T we quench the alloys to freeze the state of order of the surface at this temperature. The deposition is then performed neglecting thermal effects like surface desorption or diffusion. In this way, the annealing temperature is a continuous parameter that characterizes the adsorbing surfaces, shaping the deposition process. As the alloys undergo an order-disorder phase transition at the Onsager critical temperature (Tc) , the jamming and percolating properties of the set of deposited dimers are subjected to nontrivial changes, which we summarize in a density-temperature phase diagram. We find that for Tjamming prevents the onset of percolating clusters, while percolation is possible for T>T* . Particular attention is focused close to T* , where the interplay between jamming and percolation restricts fluctuations, forcing exponents seemingly different from the standard percolation universality class. By analogy with a thermal transition, we study the onset of percolation using the temperature T as a control parameter. We propose thermal scaling Ansätze to analyze the behavior of the percolation threshold and its thermally induced fluctuations. Also, the fractal dimension of the percolating cluster is determined. Based on these measurements and the excellent data collapse, we conclude that the universality class of standard percolation is preserved for all temperatures.

  20. Staircase polygons, scaling functions and asymmetric compact directed percolation

    CERN Document Server

    Kearney, M J

    2002-01-01

    The scaling function for compact directed percolation on a square lattice is investigated for the asymmetric case where two parameters control the critical behaviour. A simple representation for the area-perimeter generating function for staircase polygons is found, which can be recast as a non-linear functional equation. From this, the exact scaling function is extracted. In the process, the most concise derivations to date are given for the exact low order cluster moments. (letter to the editor)

  1. The determination of the full set of characteristic values of percolation, percolation threshold and critical exponents for the artificial composite with ionic conduction Ag4RbI5-(β-AgI)

    International Nuclear Information System (INIS)

    Nozaki, Kiyoshi; Itami, Toshio

    2006-01-01

    The dc electrical conductivity, σ dc , of the composite system Ag 4 RbI 5 -(β-AgI), which is composed of a good ionic conductor and a bad one, was measured by the ac impedance method. The obtained σ dc increases with the volume fraction, φ, of the good conductor, Ag 4 RbI 5 . This φ dependence of σ dc was analysed based on the generalized effective medium (GEM) theory. The scaling law analysis was also applied. The obtained threshold value of the volume fraction, φ c , was 0.162 ± 0.005. The critical exponents, t and s, were determined to be 2.0 ± 0.05 and 0.88 ± 0.005 respectively. These values are in almost complete agreement with the universal values of φ,t and s predicted by the computer simulation for the electrical conduction. So far as the present authors know, this study is the first to provide the full set of universal characteristic values of percolation, φ,t and s, for the electrical conduction from a single experimental study for the artificial composite material

  2. 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

  3. 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

  4. 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)

  5. Search for a signal on QCD critical point in central nucleusnucleus collisions

    Science.gov (United States)

    Suleymanov, M. K.; Khan, E. U.; Ahmed, K.; Haseeb, M. Q.; Tahir, F.; Huseynaliyev, Y. H.; Ajaz, M.; Khan, K. H.; Wazir, Z.

    2011-07-01

    We discuss that the QCD critical point could appear in central collisions in percolation cluster. We suggest to use the effects of nuclear transparency and that of the light nuclear production to identify the critical point.

  6. 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...

  7. 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

  8. Degree product rule tempers explosive percolation in the absence of global information

    Science.gov (United States)

    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.

  9. Percolation study for the capillary ascent of a liquid through a granular soil

    Science.gov (United States)

    Cárdenas-Barrantes, Manuel Antonio; Muñoz, José Daniel; Araujo, Nuno Machado

    2017-06-01

    Capillary rise plays a crucial role in the construction of road embankments in flood zones, where hydrophobic compounds are added to the soil to suppress the rising of water and avoid possible damage of the pavement. Water rises through liquid bridges, menisci and trimers, whose width and connectivity depends on the maximal half-length λ of the capillary bridges among grains. Low λs generate a disconnect structure, with small clusters everywhere. On the contrary, for high λ, create a percolating cluster of trimers and enclosed volumes that form a natural path for capillary rise. Hereby, we study the percolation transition of this geometric structure as a function of λ on a granular media of monodisperse spheres in a random close packing. We determine both the percolating threshold λc = (0.049 ± 0.004)R (with R the radius of the granular spheres), and the critical exponent of the correlation length v = 0.830 ± 0.051, suggesting that the percolation transition falls into the universality class of ordinary percolation.

  10. Roots at the percolation threshold.

    Science.gov (United States)

    Kroener, Eva; Ahmed, Mutez Ali; Carminati, Andrea

    2015-04-01

    The rhizosphere is the layer of soil around the roots where complex and dynamic interactions between plants and soil affect the capacity of plants to take up water. The physical properties of the rhizosphere are affected by mucilage, a gel exuded by roots. Mucilage can absorb large volumes of water, but it becomes hydrophobic after drying. We use a percolation model to describe the rewetting of dry rhizosphere. We find that at a critical mucilage concentration the rhizosphere becomes impermeable. The critical mucilage concentration depends on the radius of the soil particle size. Capillary rise experiments with neutron radiography prove that for concentrations below the critical mucilage concentration water could easily cross the rhizosphere, while above the critical concentration water could no longer percolate through it. Our studies, together with former observations of water dynamics in the rhizosphere, suggest that the rhizosphere is near the percolation threshold, where small variations in mucilage concentration sensitively alter the soil hydraulic conductivity. Is mucilage exudation a plant mechanism to efficiently control the rhizosphere conductivity and the access to water?

  11. 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

  12. 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.

  13. Cluster Tails for Critical Power-Law Inhomogeneous Random Graphs

    Science.gov (United States)

    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.

  14. Network reliability analysis based on percolation theory

    International Nuclear Information System (INIS)

    Li, Daqing; Zhang, Qiong; Zio, Enrico; Havlin, Shlomo; Kang, Rui

    2015-01-01

    In this paper, we propose a new way of looking at the reliability of a network using percolation theory. In this new view, a network failure can be regarded as a percolation process and the critical threshold of percolation can be used as network failure criterion linked to the operational settings under control. To demonstrate our approach, we consider both random network models and real networks with different nodes and/or edges lifetime distributions. We study numerically and theoretically the network reliability and find that the network reliability can be solved as a voting system with threshold given by percolation theory. Then we find that the average lifetime of random network increases linearly with the average lifetime of its nodes with uniform life distributions. Furthermore, the average lifetime of the network becomes saturated when system size is increased. Finally, we demonstrate our method on the transmission network system of IEEE 14 bus. - Highlights: • Based on percolation theory, we address questions of practical interest such as “how many failed nodes/edges will break down the whole network?” • The percolation threshold naturally gives a network failure criterion. • The approach based on percolation theory is suited for calculations of large-scale networks

  15. Directed percolation with incubation times.

    Science.gov (United States)

    Jiménez-Dalmaroni, Andrea

    2006-07-01

    We introduce a model for directed percolation with a long-range temporal diffusion, while the spatial diffusion is kept short ranged. In an interpretation of directed percolation as an epidemic process, this non-Markovian modification can be understood as incubation times, which are distributed accordingly to a Lévy distribution. We argue that the best approach to find the effective action for this problem is through a generalization of the Cardy-Sugar method, adding the non-Markovian features into the geometrical properties of the lattice. We formulate a field theory for this problem and renormalize it up to one loop in a perturbative expansion. We solve the various technical difficulties that the integrations possess by means of an asymptotic analysis of the divergences. We show the absence of field renormalization at one-loop order, and we argue that this would be the case to all orders in perturbation theory. Consequently, in addition to the characteristic scaling relations of directed percolation, we find a scaling relation valid for the critical exponents of this theory. In this universality class, the critical exponents vary continuously with the Lévy parameter.

  16. Standard and inverse bond percolation of straight rigid rods on square lattices

    Science.gov (United States)

    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

  17. Connectivity and percolation of pore networks in a cultivated silt loam soil quantified by X-ray tomography

    Science.gov (United States)

    Jarvis, Nicholas; Koestel, John; Larsbo, Mats

    2016-04-01

    The connectivity of macropore networks is thought to exert an important control on transport processes in soil. However, little progress has been made towards quantifying these effects for natural soils in the field, partly because of the experimental difficulties but also because the concept of connectivity lacks a unique mathematical definition. To investigate this question, X-ray tomography was used to measure pore volume, size distribution and connectivity at an image resolution of 65 microns for 64 samples taken in two consecutive years in the harrowed and ploughed layers of a silt loam soil a few weeks after spring cultivation. Three different connectivity metrics were evaluated and compared: one local metric, the Euler number, and two global measures, the connection probability and the probability of percolation (the fraction of the porosity which is continuous across the sample). The connection probability was found to be a good measure of the long-range connectivity (i.e. continuity) of the pore networks. In contrast, the Euler number was not a sensitive measure of global connectivity, although all samples with negative Euler numbers did percolate. We also found that the way connection is defined in the image analysis (either by 6 or 26 nearest neighbours) did not influence the calculations of percolating porosity. The results also demonstrate that harrowing has a clear homogenizing effect on the distribution of the pore space. However, a comparison with random field simulations and the evidence of small percolation thresholds shows that the macropore system developed in the recently harrowed soil was far from completely random or disordered. In some samples, more than one pore cluster percolated, while in others the percolating cluster was not the largest one. Nevertheless, the macropore networks in this cultivated silt loam soil displayed some key features predicted by percolation theory: a strong relationship was found between the percolating fraction

  18. Criticality calculation for cluster fuel bundles using grey Dancoff factor

    International Nuclear Information System (INIS)

    Hyeong Heon Kim; Nam Zin Cho

    1999-01-01

    This paper applies the grey Dancoff factor calculated by Monte Carlo method to the criticality calculation for cluster fuel bundles. Dancoff factors for five symmetrically different pin positions of CANDU37 and CANFLEX fuel bundles in full three-dimensional geometry are calculated by Monte Carlo method. The concept of equivalent Dancoff factor is introduced to use the grey Dancoff factor in the resonance calculation based on equivalence theorem. The equivalent Dancoff factor which is based on the realistic model produces an exact fuel collision probability and can be used in the resonance calculation just as the black Dancoff factor. The infinite multiplication factors based on the black Dancoff factors calculated by collision probability or Monte Carlo method are overestimated by about 2 mk for normal condition and 4 mk for void condition of CANDU37 and CANFLEX fuel bundles in comparison with those based on the equivalent Dancoff factors

  19. Percolation conductivity in hafnium sub-oxides

    Energy Technology Data Exchange (ETDEWEB)

    Islamov, D. R., E-mail: damir@isp.nsc.ru; Gritsenko, V. A., E-mail: grits@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Cheng, C. H. [Department of Mechatronic Technology, National Taiwan Normal University, Taipei 106, Taiwan (China); Chin, A., E-mail: albert-achin@hotmail.com [National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2014-12-29

    In this study, we demonstrated experimentally that formation of chains and islands of oxygen vacancies in hafnium sub-oxides (HfO{sub x}, x < 2) leads to percolation charge transport in such dielectrics. Basing on the model of Éfros-Shklovskii percolation theory, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics was achieved. Based on the percolation theory suggested model shows that hafnium sub-oxides consist of mixtures of metallic Hf nanoscale clusters of 1–2 nm distributed onto non-stoichiometric HfO{sub x}. It was shown that reported approach might describe low resistance state current-voltage characteristics of resistive memory elements based on HfO{sub x}.

  20. Bond Percolation on Multiplex Networks

    Science.gov (United States)

    Hackett, A.; Cellai, D.; Gómez, S.; Arenas, A.; Gleeson, J. P.

    2016-04-01

    We present an analytical approach for bond percolation on multiplex networks and use it to determine the expected size of the giant connected component and the value of the critical bond occupation probability in these networks. We advocate the relevance of these tools to the modeling of multilayer robustness and contribute to the debate on whether any benefit is to be yielded from studying a full multiplex structure as opposed to its monoplex projection, especially in the seemingly irrelevant case of a bond occupation probability that does not depend on the layer. Although we find that in many cases the predictions of our theory for multiplex networks coincide with previously derived results for monoplex networks, we also uncover the remarkable result that for a certain class of multiplex networks, well described by our theory, new critical phenomena occur as multiple percolation phase transitions are present. We provide an instance of this phenomenon in a multiplex network constructed from London rail and European air transportation data sets.

  1. Conformal Field Theory of Percolation (1)

    CERN Multimedia

    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

  2. Nucleation and mesostrain influence on percolating critical currents of solution derived YBa{sub 2}Cu{sub 3}O{sub 7} superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Obradors, X., E-mail: Xavier.obradors@icmab.es [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Martinez-Julian, F.; Zalamova, K.; Vlad, V.R.; Pomar, A.; Palau, A.; Llordes, A.; Chen, H.; Coll, M.; Ricart, S.; Mestres, N.; Granados, X.; Puig, T. [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Rikel, M. [Nexans Superconductors, 50354 Huerth (Germany)

    2012-11-20

    After briefly reviewing the present understanding of the nucleation process of YBCO films, a new approach is presented to enhance the stability of c-axis nucleation in epitaxial chemical solution deposited YBCO thin films derived from TFA precursors. We show that with silver addition to the TFA precursor c-axis nucleation can be reached in a wide range of temperature thus keeping high percolating J{sub c}. We argue that silver reduces supersaturation and makes more stable the c-axis nuclei without modifying T{sub c}. Additional advantages of silver addition are an enhanced surface smootheness and a reduced porosity of the YBCO films. The second reported topic relates to the discovery of an adverse relationship between percolating J{sub c} and YBCO films mesostrain, as determined through X-ray diffraction line broadening. We show that mesostrain is enhanced in processes leading to inefficient strain healing at grain boundaries, for instance annealing times too short or growth temperatures too low. It is suggested that the strained regions at the low angle grain boundaries lead to a weak link behavior which can be microscopically understood on the basis of pair formation prevention, as proposed by the bond contraction pairing model.

  3. Precise Calculation of a Bond Percolation Transition and Survival Rates of Nodes in a Complex Network

    Science.gov (United States)

    Kawamoto, Hirokazu; Takayasu, Hideki; Jensen, Henrik Jeldtoft; Takayasu, Misako

    2015-01-01

    Through precise numerical analysis, we reveal a new type of universal loopless percolation transition in randomly removed complex networks. As an example of a real-world network, we apply our analysis to a business relation network consisting of approximately 3,000,000 links among 300,000 firms and observe the transition with critical exponents close to the mean-field values taking into account the finite size effect. We focus on the largest cluster at the critical point, and introduce survival probability as a new measure characterizing the robustness of each node. We also discuss the relation between survival probability and k-shell decomposition. PMID:25885791

  4. Phase transition approach to bursting in neuronal cultures: quorum percolation models

    Science.gov (United States)

    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.

  5. 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

  6. Percolation Model for the Existence of a Mitochondrial Eve

    CERN Document Server

    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.

  7. Widom line, dynamical crossover, and percolation transition of supercritical oxygen via molecular dynamics simulations

    Science.gov (United States)

    Raman, Abhinav S.; Li, Huiyong; Chiew, Y. C.

    2018-01-01

    Supercritical oxygen, a cryogenic fluid, is widely used as an oxidizer in jet propulsion systems and is therefore of paramount importance in gaining physical insights into processes such as transcritical and supercritical vaporization. It is well established in the scientific literature that the supercritical state is not homogeneous but, in fact, can be demarcated into regions with liquid-like and vapor-like properties, separated by the "Widom line." In this study, we identified the Widom line for oxygen, constituted by the loci of the extrema of thermodynamic response functions (heat capacity, volumetric thermal expansion coefficient, and isothermal compressibility) in the supercritical region, via atomistic molecular dynamics simulations. We found that the Widom lines derived from these response functions all coincide near the critical point until about 25 bars and 15-20 K, beyond which the isothermal compressibility line begins to deviate. We also obtained the crossover from liquid-like to vapor-like behavior of the translational diffusion coefficient, shear viscosity, and rotational relaxation time of supercritical oxygen. While the crossover of the translational diffusion coefficient and shear viscosity coincided with the Widom lines, the rotational relaxation time showed a crossover that was largely independent of the Widom line. Further, we characterized the clustering behavior and percolation transition of supercritical oxygen molecules, identified the percolation threshold based on the fractal dimension of the largest cluster and the probability of finding a cluster that spans the system in all three dimensions, and found that the locus of the percolation threshold also coincided with the isothermal compressibility Widom line. It is therefore clear that supercritical oxygen is far more complex than originally perceived and that the Widom line, dynamical crossovers, and percolation transitions serve as useful routes to better our understanding of the

  8. 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

  9. Clustering analysis of water distribution systems: identifying critical components and community impacts.

    Science.gov (United States)

    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.

  10. Percolation testing and hydraulic conductivity of soils for percolation areas.

    Science.gov (United States)

    Mulqueen, J; Rodgers, M

    2001-11-01

    The results of specific percolation tests are expressed in terms of field saturated hydraulic conductivity (Kfs) of the soil. The specific tests comprise the Irish SR 6 and the UK BS 6297 standard tests and the inversed auger hole and square hole tests employed for the design of land drainage. Percolation times from these tests are converted to Kfs values using unit gradient theory and the Elrick and Reynolds (Soil Sci. 142(5) (1986) 308) model which takes into account gravitational, pressure head and matric potential gradients. Kfs is then expressed as the inverse of the percolation rate times a constant, in this way the percolation rate can be directly related to Kfs of the soil. A plot of Kfs against percolation rate for the Irish SR 6 and the UK BS 6297 standard tests is asymptotic at Kfs values less than 0.2 m/d and greater than 0.8 m/d. This behaviour creates difficulty in setting limits for percolation rates in standards. Curves are provided which enable Kfs values to be read off from percolation tests without the restrictions of head range currently enforced, for example in the Irish SR 6 and BS 6297 standards. Experimental measurements of percolation rates and Kfs were carried out on two sands in the laboratory and in the field on two soils. Kfs of these four materials was also measured using a tension infiltrometer and the Guelph permeameter. The saturated hydraulic conductivities (Ks) of the sands were also estimated in a falling head laboratory apparatus and by the Hazen formula. There was good agreement between the different tests for Kfs on each material. Because percolation time continued to increase significantly in consecutive tests in the same test hole while Kfs became constant, the latter is a better measure of the suitability of soils for percolation.

  11. Hall effect in quantum critical charge-cluster glass

    Science.gov (United States)

    Wu, Jie; Bollinger, Anthony T.; Sun, Yujie

    2016-04-01

    Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4 (LSCO) samples doped near the quantum critical point at x ˜ 0.06. Dramatic fluctuations in the Hall resistance appear below TCG ˜ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps, Δx ˜ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state.

  12. Group percolation in interdependent networks

    Science.gov (United States)

    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.

  13. 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

  14. 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

  15. Percolation of triplet excitation in restricted geometries

    Science.gov (United States)

    Saha, D. C.; Misra, T. N.; Talukdar, D.

    1996-04-01

    Migration of benzophenone triplet excitations in polymethylmethacrylate and methylmethacrylate-styrene copolymer has been studied under steady state excitation by using 1-chloronapthalene as a trap. The excitation energy capture efficiency by a trap has been obtained as a function of the donor concentration at various trap concentrations. Percolation model has been successfully applied to evaluate the critical exponents. The evaluated critical exponents are in very good agreement with three dimensional triplet excitation migration topology in polymethylmethacrylate and two dimensional one in the copolymer.

  16. Percolative transport in the vicinity of charge-order ferromagnetic ...

    Indian Academy of Sciences (India)

    The electric field driven charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters dispersed in a CO background. Keywords. Hole-doped manganite; percolative transport; charge-order; ferromagnetic transition. PACS Nos 75.30.Vn; 75.50.Dd. 1.

  17. Percolation based enhancement in effective thermal conductivity of ...

    Indian Academy of Sciences (India)

    0.15MnO3 (LBSMO) filler of nanometric grain size in HDPE matrix is investigated. Volume fraction of LBSMO fillers was varied between 0 and 0.30. SEM photographs of the composites show the presence of clusters and percolative paths, ...

  18. Superconductivity of networks. A percolation approach to the effects of disorder

    Science.gov (United States)

    Alexander, S.

    1983-02-01

    Solutions of the linearized Landau-Ginzburg equations on networks of thin wires are studied. We derive linear-difference equations for the value of the order parameter at the junctions of the net with the use of the explicit form of the solutions on the wires. The technique is shown to be applicable to the diffusion equation, to harmonic lattice vibrations, and to the Schrödinger equation and results in equations similar to tight-binding equations. The equations are solved and the upper critical field is determined for some simple finite nets, for the infinite square net, and for the triangular Sierpinski gasket. Dead-end side branches are shown to lead to a mass renormalization. On the square net the equations map on the Azbel-Hofstadter-Aubry model. When the coherence length is small, vortex cores can be accommodated in the holes of the net and there is no upper critical field. The equations on the Sierpinski gasket are solved by an iterative decimation process. The process determines a new length scale proportional to a power of the bare coherence length. The upper critical field is studied for a finite gasket and for a lattice of gaskets. With the use of scaling arguments the results are applied to percolation clusters. Far from the percolation threshold the results are described by a renormalized correlation length of standard form. When this length becomes shorter than the correlation length for the percolation problem the critical field is shown to be constant or decreasing as the threshold is approached. Existing experiments are discussed and the importance of high-field-susceptibility measurements is emphasized.

  19. 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.)

  20. Multifractal properties of resistor diode percolation.

    Science.gov (United States)

    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.

  1. Studies in clustering theory

    Science.gov (United States)

    Stell, George

    In recent years the properties of percolation models have been studied intensively. The purpose of our project was to develop a general theory of percolation and clustering between particles of arbitrary size and shape, with arbitrary correlations between them. The goal of such a theory includes the treatment of continuum percolation as well as a novel treatment of lattice percolation. We made substantial progress toward this goal. The quantities basic to a description of clustering, the mean cluster size, mean number of clusters, etc., were developed. Concise formulas were given for the terms in such series, and proved, at least for sufficiently low densities, that the series are absolutely convergent. These series can now be used to construct Pade approximants that will allow one to probe the percolation transition. A scaled-particle theory of percolation was developed which gives analytic approximants for the mean number of clusters in a large class of two and three dimensional percolation models. Although this quantity is essential in many applications, e.g., explaining colligative properties, and interpreting low-angle light-scattering data, no systematic studies of it have been done before this work. Recently carried out detailed computer simulations show that the mean number of clusters is given to high accuracy by several of there approximations. Extensions of this work will allow calculation of the complete cluster size distribution.

  2. Percolation approach to initial stage effects in high energy collisions

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Brijesh K.

    2014-06-15

    Possible phase transition of strongly interacting matter from hadron to a quark–gluon plasma state have in the past received considerable interest. The clustering of color sources provides a framework of the partonic interactions in the initial stage of the collisions. The onset of deconfinement transition is identified by the spanning percolation cluster in 2D percolation. In this talk results are presented both for the multiplicity and the elliptic flow at RHIC and LHC energies. The thermodynamic quantities temperature, equation of state and transport coefficient are obtained in the framework of clustering of color sources. It is shown that the results are in excellent agreement with the recent lattice QCD calculations (LQCD)

  3. Percolation Magnetism in Ferroelectric Nanoparticles

    Science.gov (United States)

    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.

  4. Percolation Magnetism in Ferroelectric Nanoparticles.

    Science.gov (United States)

    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.

  5. Percolation systems away from the critical point

    Indian Academy of Sciences (India)

    Pramana – Journal of Physics. Current Issue : Vol. 90, Issue 3 · Current Issue Volume 90 | Issue 3. March 2018. Home · Volumes & Issues · Special Issues · Forthcoming Articles · Search · Editorial Board · Information for Authors · Subscription ...

  6. Percolation systems away from the critical point

    Indian Academy of Sciences (India)

    a trap with trapping time bigger than t, and gets stuck there. Eventually, it will exit from this trap, only to get stuck in other traps, some with even larger trapping times. Thus, if we examine all particles at some large time t, typically they would be stuck in, or just emerging from a trap with trapping time of ordert. For B = Bc, the ...

  7. 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

  8. Finite-Size Effects for Some Bootstrap Percolation Models

    NARCIS (Netherlands)

    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

  9. Existence of phase transition for heavy-tailed continuum percolation

    NARCIS (Netherlands)

    A. Sapozhnikov (Artem)

    2007-01-01

    textabstractWe consider a continuum percolation model in $R^d$, where $d >= 2$. It is given by a homogeneous Poisson process of intensity $\\labda$ and independent radii random variables of common distribution of a positive random variable $r$. Let $\\labda_c$ be the critical intensity for the

  10. Heavy ions collisions and the site-bond percolation

    International Nuclear Information System (INIS)

    Desbois, J.

    1986-07-01

    Site-bond percolation on a lattice is used for the investigation of heavy ions reactions. A model characterized by two parameters, p and q, is worked out and a critical zone in the p-q plane is shown up. Analytical expressions for various quantities concerning percolation and evaporation are established. Calculations of energy spectra, linear momentum transfer, fragment multiplicities and mass yields at various bombarding energies are compared with experimental data. Different possibilities for the attainment of the multifragmentation regime are discussed. 17 figs; 43 refs

  11. 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)

  12. Solvable random-decimation model of cluster scaling

    Science.gov (United States)

    Fraser, Simon J.

    1988-07-01

    A percolation model of critical-cluster scaling is studied. The model allows the generation of configurations of strongly self-similar clusters by stochastic decimation on a tree. Tree traversal is controlled by a probability parameter p. At p=0 or 1, the configuration is deterministic, but, for 0decimation algorithm uses the Sierpinski carpet and Vicsek snowflake generators, so that the treelike character (connectedness) of the clusters can be changed continuously. Various dimensions of the (fractal) percolation cluster are calculated using boundary conditions that give correct values at the deterministic limits. The usual cluster distribution law, ns~s-τ with τ=d/D+1, is obeyed for stationary p in (0,1), although τ=d/D, the deterministic value at p=0 or 1. Here d is the space dimension, and D the fractal dimension of the percolation cluster. The sensitivity of τ to changes in p near p=0 or 1 allows anomalous cluster scaling, so that τ may be fixed between d/D and d/D+1, without affecting D. Possible applications of the model are discussed.

  13. Tunneling-percolation model of multicomponent nanocomposites

    Science.gov (United States)

    Kale, Sohan; Karimi, Pouyan; Sabet, Fereshteh A.; Jasiuk, Iwona; Ostoja-Starzewski, Martin

    2018-02-01

    Using a mixture of different types of fillers has been experimentally shown to improve the electrical conductivity of polymer nanocomposites beyond the weighted average due to synergistic effects. In this study, we develop a critical path analysis-based tunneling-percolation model for multicomponent systems of nanocomposites with ellipsoidal fillers. The nature of the interaction between different filler components is controlled by a key modeling parameter capturing the tunneling interactions between fillers. This generalization allows us to examine scenarios where the nature of a given type of filler can be varied continuously from an insulating-type to a conductive-type. The percolation behavior of two-component systems with a combination of prolate, oblate, and spherical fillers is investigated using Monte Carlo simulations for different relative volume fractions and nature of interactions while keeping the total volume fraction fixed. The simulation results are shown to be in semi-quantitative agreement with predictions made by the second-virial-approximation-based theories. Our results suggest that for multicomponent systems with well-dispersed fillers, the synergistic effects are linked directly with the nature of interactions between different filler types. Moreover, addition of prolate fillers to oblate or spherical fillers should generally improve the electrical conductivity of multicomponent nanocomposites.

  14. Fuzzy clustering: critical analysis of the contextual mechanisms employed by three neural network models

    Science.gov (United States)

    Baraldi, Andrea; Parmiggiani, Flavio

    1996-06-01

    cognitive tasks. In this paper, the FLVQ model is critically analyzed in order to stress the meaning of a fuzzy learning mechanism. This study leads to the development of a new NN model, termed the fuzzy competitive/cooperative Kohonen (FCCK) model, which replaces FLVQ. Then, the architectural differences amongst three NN algorithms and the relationships between their fuzzy clustering properties are discussed. These models, which all perform on-line learning, are: (1) SOM; (2) FCCK; and (3) improved neural-gas (INC).

  15. 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)

  16. Cities and regions in Britain through hierarchical percolation

    Science.gov (United States)

    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.

  17. Nontrivial nonequilibrium critical relaxation in cluster algorithms and universal nonequilibrium-to-equilibrium scaling procedure

    Science.gov (United States)

    Nonomura, Yoshihiko; Tomita, Yusuke

    2015-03-01

    Recently we have found that the nonequilibrium relaxation from the perfectly-ordered state of the 2D and 3D Ising models in cluster algorithms shows nontrivial stretched-exponential decay at the transition temperature. Similar nontrivial nonequilibrium critical relaxation is also observed in the 2D XY, 3D XY and 3D Heisenberg models; simple exponential decay in these cases. In order to confirm these behaviors and evaluate the scaling form precisely and robustly, we have proposed a universal scaling procedure to connect nonequilibrium and equilibrium behaviors continuously. For example, when the critical relaxation of the average magnetization of a system with linear size L is observed in local-update algorithms, this quantity decays in a power law in the early-stage relaxation with ~t - β / (zν) and converges to the critical magnetization mc (L) ~L - β / ν in equilibrium. Then, when L β / ν is plotted versus tL-z , data for various system sizes are scaled on a single curve in the whole parameter region. This procedure also holds for the cases with cluster algorithms.

  18. Controlling percolation with limited resources

    Science.gov (United States)

    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.

  19. 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.

  20. 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.

  1. Regularity of the Speed of Biased Random Walk in a One-Dimensional Percolation Model

    Science.gov (United States)

    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.

  2. Percolation theory for flow in porous media

    CERN Document Server

    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...

  3. Critical flow and clustering in a model of granular transport: the interplay between drift and antidiffusion.

    Science.gov (United States)

    Kanellopoulos, Giorgos; van der Weele, Ko

    2012-06-01

    We study the transport of granular matter through a staircaselike array of K vertically vibrated compartments. Given a constant inflow rate Qsystem. However, as soon as Q grows beyond the critical value Q{cr}(K) the particles form a cluster and the flow comes to a halt. Interestingly, this clustering is preceded by a subcritical warning signal: for Q values just below Q{cr}(K) the density profile along the conveyor belt spontaneously develops a pattern in which the compartments are alternatingly densely and sparsely populated. In a previous paper [Kanellopoulos and van der Weele, Int. J. Bifurcation Chaos 21, 2305 (2011)] this pattern was shown to be the result of a period-doubling bifurcation. The present paper aims at unravelling the physical mechanism that lies at the basis of the pattern formation. To this end we study the continuum version of the same system, replacing the compartment number k=1,...,K by a continuous variable x. The dynamics of the system is now described (instead of by K coupled ordinary differential equations) by a single partial differential equation of the Fokker-Planck type, with a drift and a diffusive term that both depend on the density. The drift term turns out to be responsible for the subcritical density oscillations, thereby paving the way for the eventual clustering which sets in when the diffusion coefficient becomes negative. The observed sequence of events in the granular transport system is thus explained as an interplay between drift and (anti)diffusion.

  4. Identifying driving gene clusters in complex diseases through critical transition theory

    Science.gov (United States)

    Wolanyk, Nathaniel; Wang, Xujing; Hessner, Martin; Gao, Shouguo; Chen, Ye; Jia, Shuang

    A novel approach of looking at the human body using critical transition theory has yielded positive results: clusters of genes that act in tandem to drive complex disease progression. This cluster of genes can be thought of as the first part of a large genetic force that pushes the body from a curable, but sick, point to an incurable diseased point through a catastrophic bifurcation. The data analyzed is time course microarray blood assay data of 7 high risk individuals for Type 1 Diabetes who progressed into a clinical onset, with an additional larger study requested to be presented at the conference. The normalized data is 25,000 genes strong, which were narrowed down based on statistical metrics, and finally a machine learning algorithm using critical transition metrics found the driving network. This approach was created to be repeatable across multiple complex diseases with only progression time course data needed so that it would be applicable to identifying when an individual is at risk of developing a complex disease. Thusly, preventative measures can be enacted, and in the longer term, offers a possible solution to prevent all Type 1 Diabetes.

  5. Using Complementary Learning Clusters in Studying Literature to Enhance Students' Medical Humanities Literacy, Critical Thinking, and English Proficiency.

    Science.gov (United States)

    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.

  6. Physical-depth architectural requirements for generating universal photonic cluster states

    Science.gov (United 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.

  7. Progress in high-dimensional percolation and random graphs

    CERN Document Server

    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...

  8. 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

  9. Clustering and traveling waves in the Monte Carlo criticality simulation of decoupled and confined media

    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.

  10. Criticality calculation for cluster fuel bundles using monte carlo generated grey dancoff factor

    International Nuclear Information System (INIS)

    Kim, Hyeong Heon; Cho, Nam Zin

    1999-01-01

    The grey Dancoff factor calculated by Monte Carlo method is applied to the criticality calculation for cluster fuel bundles. Dancoff factors for five symmetrically different pin positions of CANDU37 and CANFLEX fuel bundles in full three-dimensional geometry are calculated by Monte Carlo method. The concept of equivalent Dancoff factor is introduced to use the grey Dancoff factor in the resonance calculation based on equivalence theorem. The equivalent Dancoff factor which is based on the realistic model produces an exact fuel collision probability and can be used in the resonance calculation just as the black Dancoff factor. The infinite multiplication factors based on the black Dancoff factors calculated by collision probability or Monte Carlo method are overestimated by about 2mk for normal condition and 4mk for void condition of CANDU37 and CANFLEX fuel bundles in comparison with those based on the equivalent Dancoff factors

  11. Critical nonequilibrium relaxation in cluster algorithms in the BKT and weak first-order phase transitions

    Science.gov (United States)

    Nonomura, Yoshihiko; Tomita, Yusuke

    Recently we showed that the critical nonequilibrium relaxation in cluster algorithms is widely described by the stretched-exponential decay of physical quantities in the Ising or Heisenberg models. Here we make a similar analysis in the Berezinsky-Kosterlitz-Thouless (BKT) phase transition in the 2D XY model (simple exponential decay) and in the weak first-order phase transition in the 2D q = 5 Potts model (power-law decay), which means that these phase transitions can clearly be characterized by the present analysis. These relaxation behaviors are compared with those in the 3D and 4D XY models (second-order phase transition) and in the 2D q-state Potts models (2 = 6 for strong first-order phase transitions.

  12. 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...... into four groups; low, middle, high and extremely high performers. Seniority-specific indicators were not identified. The practical importance of the recommended disciplinary appropriate indicators is concerning. Our study revealed several critical concerns that should be investigated in the application....... It is important to do studies that investigate the usefulness of statistical evaluation methodologies to help us as a community learn more about the appropriateness of particular bibliometric indicators in the analysis of different researcher profiles....

  13. 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...

  14. Percolation of triplet excitation in sol-gel matrix

    Science.gov (United States)

    Saha, D. C.; Misra, T. N.

    1996-11-01

    Triplet spectroscopy and energy migration among benzophenone chromophores have been studied in sol-gel matrix under steady state excitation. The energy migration process was observed by the rise of sensitised emission from triplet energy acceptors like, 1,4-dibromonaphthalene and 1-chloronaphthalene after excitation of benzophenone chromophore. The probability of donor excitation energy capture by the trap shows a critical concentration dependence on the benzophenone molecules. The percolation model has been applied to evaluate the critical exponents. The evaluated critical exponents are in very good agreement with three dimensional excitation transport.

  15. 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.

  16. 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

  17. Loopless nontrapping invasion-percolation model for fracking.

    Science.gov (United States)

    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.

  18. Loopless nontrapping invasion-percolation model for fracking

    Science.gov (United States)

    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.

  19. Roots at the Percolation Threshold

    Science.gov (United States)

    Kroener, E.; Ahmed, M. A.; Kaestner, A.; Vontobel, P.; Zarebanadkouki, M.; Carminati, A.

    2014-12-01

    Much of the carbon assimilated by plants during photosynthesis is lost to the soil via rhizodepositions. One component of rhizopdeposition is mucilage, a hydrogel that dramatically alters the soil physical properties. Mucilage was assumed to explain unexpectedly low rhizosphere rewetting rates during irrigation (Carminati et al. 2010) and temporarily water repellency in the rhizosphere after severe drying (Moradi et al. 2012).Here, we present an experimental and theoretical study for the rewetting behaviour of a soil mixed with mucilage, which was used as an analogue of the rhizosphere. Our samples were made of two layers of untreated soils separated by a thin layer (ca. 1 mm) of soil treated with mucilage. We prepared soil columns of varying particle size, mucilage concentration and height of the middle layer above the water table. The dry soil columns were re-wetted by capillary rise from the bottom.The rewetting of the middle layer showed a distinct dual behavior. For mucilage concentrations lower than a certain threshold, water could cross the thin layer almost immediately after rewetting of bulk soil. At slightly higher mucilage concentrations, the thin layer was almost impermeable. The mucilage concentration at the threshold strongly depended on particle size: the smaller the particle size the larger the soil specific surface and the more mucilage was needed to cover the entire particle surface and to induce water repellency.We applied a classic pore network model to simulate the experimental observations. In the model a certain fraction of nodes were randomly disconnected to reproduce the effect of mucilage in temporarily blocking the flow. The percolation model could qualitatively reproduce well the threshold characteristics of the experiments. Our experiments, together with former observations of water dynamics in the rhizosphere, suggest that the rhizosphere is near the percolation threshold, where small variations in mucilage concentration sensitively

  20. clusters

    Indian Academy of Sciences (India)

    2017-09-27

    Sep 27, 2017 ... while CuCoNO, Co3NO, Cu3CoNO, Cu2Co3NO, Cu3Co3NO and Cu6CoNO clusters display stronger chemical stability. Magnetic and electronic properties are also discussed. The magnetic moment is affected by charge transfer and the spd hybridization. Keywords. CumConNO (m + n = 2–7) clusters; ...

  1. The price of anarchy is maximized at the percolation threshold

    Science.gov (United States)

    Skinner, Brian

    2015-03-01

    When many independent users try to route traffic through a network, the flow can easily become suboptimal as a consequence of congestion of the most efficient paths. The degree of this suboptimality is quantified by the so-called ``price of anarchy'' (POA), but so far there are no general rules for when to expect a large POA in a random network. Here I address this question by introducing a simple model of flow through a network with randomly-placed ``congestible'' and ``incongestible'' links. I show that the POA is maximized precisely when the fraction of congestible links matches the percolation threshold of the lattice. Both the POA and the total cost demonstrate critical scaling near the percolation threshold.

  2. Price of anarchy is maximized at the percolation threshold

    Science.gov (United States)

    Skinner, Brian

    2015-05-01

    When many independent users try to route traffic through a network, the flow can easily become suboptimal as a consequence of congestion of the most efficient paths. The degree of this suboptimality is quantified by the so-called price of anarchy (POA), but so far there are no general rules for when to expect a large POA in a random network. Here I address this question by introducing a simple model of flow through a network with randomly placed congestible and incongestible links. I show that the POA is maximized precisely when the fraction of congestible links matches the percolation threshold of the lattice. Both the POA and the total cost demonstrate critical scaling near the percolation threshold.

  3. Price of anarchy is maximized at the percolation threshold.

    Science.gov (United States)

    Skinner, Brian

    2015-05-01

    When many independent users try to route traffic through a network, the flow can easily become suboptimal as a consequence of congestion of the most efficient paths. The degree of this suboptimality is quantified by the so-called price of anarchy (POA), but so far there are no general rules for when to expect a large POA in a random network. Here I address this question by introducing a simple model of flow through a network with randomly placed congestible and incongestible links. I show that the POA is maximized precisely when the fraction of congestible links matches the percolation threshold of the lattice. Both the POA and the total cost demonstrate critical scaling near the percolation threshold.

  4. Cyclic Competition and Percolation in Grouping Predator-Prey Populations

    Directory of Open Access Journals (Sweden)

    Alessandra F. Lütz

    2017-02-01

    Full Text Available We study, within the framework of game theory, the properties of a spatially distributed population of both predators and preys that may hunt or defend themselves either isolatedly or in group. Specifically, we show that the properties of the spatial Lett-Auger-Gaillard model, when different strategies coexist, can be understood through the geometric behavior of clusters involving four effective strategies competing cyclically,without neutral states. Moreover, the existence of strong finite-size effects, a form of the survival of the weakest effect, is related to a percolation crossover. These results may be generic and of relevance to other bimatrix games.

  5. Assimilative capacity-based emission load management in a critically polluted industrial cluster.

    Science.gov (United States)

    Panda, Smaranika; Nagendra, S M Shiva

    2017-12-01

    In the present study, a modified approach was adopted to quantify the assimilative capacity (i.e., the maximum emission an area can take without violating the permissible pollutant standards) of a major industrial cluster (Manali, India) and to assess the effectiveness of adopted air pollution control measures at the region. Seasonal analysis of assimilative capacity was carried out corresponding to critical, high, medium, and low pollution levels to know the best and worst conditions for industrial operations. Bottom-up approach was employed to quantify sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and particulate matter (aerodynamic diameter capacity. Results indicated that 22.8 tonnes/day of SO 2 , 7.8 tonnes/day of NO 2 , and 7.1 tonnes/day of PM 10 were emitted from the industries of Manali. The estimated assimilative capacities for SO 2 , NO 2 , and PM 10 were found to be 16.05, 17.36, and 19.78 tonnes/day, respectively. It was observed that the current SO 2 emissions were exceeding the estimated safe load by 6.7 tonnes/day, whereas PM 10 and NO 2 were within the safe limits. Seasonal analysis of assimilative capacity showed that post-monsoon had the lowest load-carrying capacity, followed by winter, summer, and monsoon seasons, and the allowable SO 2 emissions during post-monsoon and winter seasons were found to be 35% and 26% lower, respectively, when compared with monsoon season. The authors present a modified approach for quantitative estimation of assimilative capacity of a critically polluted Indian industrial cluster. The authors developed a geo-coded fine-resolution PM 10 , NO 2 , and SO 2 emission inventory for Manali industrial area and further quantitatively estimated its season-wise assimilative capacities corresponding to various pollution levels. This quantitative representation of assimilative capacity (in terms of emissions), when compared with routine qualitative representation, provides better data for quantifying carrying capacity of an

  6. 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.

  7. Large swelling and percolation in irradiated zircon

    CERN Document Server

    Trachenko, K; Salje, E K H

    2003-01-01

    We study the effect of large swelling in irradiated zircon. We perform molecular dynamics simulation of the overlap of two radiation events and find that the damage produced in the second event scatters away from the densified boundary of the damaged region implanted previously. This serves as the microscopic mechanism of the increase of volume occupied by the damage. The additive nature of this effect results in large swelling observed experimentally. We translate the damage accumulation into the percolation problem, and show that volume swelling is a percolation phenomenon, with the swelling curve increasing rapidly at the percolation threshold. (letter to the editor)

  8. Percolation Transition in Fluids: Scaling Behavior of the Spanning Probability Functions

    Czech Academy of Sciences Publication Activity Database

    Škvor, J.; Nezbeda, Ivo; Brovchenko, I.; Oleinikova, A.

    2007-01-01

    Roč. 99, - (2007), s. 127801 ISSN 0031-9007 R&D Projects: GA ČR(CZ) GA101/05/2214; GA AV ČR(CZ) 1ET400720409 Institutional research plan: CEZ:AV0Z40720504 Keywords : percolation threshold * spanning functions * clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 6.944, year: 2007

  9. cluster

    Indian Academy of Sciences (India)

    has been investigated electrochemically in positive and negative microenvironments, both in solution and in film. Charge nature around the active centre ... in plants, bacteria and also in mammals. This cluster is also an important constituent of a ..... selection of non-cysteine amino acid in the active centre of Rieske proteins.

  10. 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.

  11. The threshold of coexistence and critical behaviour of a predator-prey cellular automaton

    Energy Technology Data Exchange (ETDEWEB)

    Arashiro, Everaldo; Tome, Tania [Instituto de Fisica, Universidade de Sao Paulo, Caixa postal 66318, 05315-970 Sao Paulo, SP (Brazil)

    2007-02-02

    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.

  12. 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.

  13. Percolation analysis for cosmic web with discrete points

    Science.gov (United States)

    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.

  14. Critical temperature for a model quasi-one-dimensional disordered superconductor

    Science.gov (United States)

    Lin, Yi; Yi, Xiao; Kai-lun, Yao

    1993-06-01

    With the help of the decimation ansatz of the renormlization group, the dependence of critical temperature on a transverse magnetic field is calculated analytically for a quasi-one-dimensional disordered superconductor model, based on the de Gennes-Skal-Shklovskii (dGSS) picture of the large cluster in a percolation system. Our results are in good agreement with those given by Halley's scaling theory.

  15. Percolation under noise: Detecting explosive percolation using the second-largest component

    Science.gov (United States)

    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.

  16. Critical Factors in Transnational Oil Companies Localisation Decisions - Clusters and Portfolio Optimisation

    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)

  17. Critical Factors in Transnational Oil Companies Localisation Decisions - Clusters and Portfolio Optimisation

    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)

  18. Modeling stock price dynamics by continuum percolation system and relevant complex systems analysis

    Science.gov (United States)

    Xiao, Di; Wang, Jun

    2012-10-01

    The continuum percolation system is developed to model a random stock price process in this work. Recent empirical research has demonstrated various statistical features of stock price changes, the financial model aiming at understanding price fluctuations needs to define a mechanism for the formation of the price, in an attempt to reproduce and explain this set of empirical facts. The continuum percolation model is usually referred to as a random coverage process or a Boolean model, the local interaction or influence among traders is constructed by the continuum percolation, and a cluster of continuum percolation is applied to define the cluster of traders sharing the same opinion about the market. We investigate and analyze the statistical behaviors of normalized returns of the price model by some analysis methods, including power-law tail distribution analysis, chaotic behavior analysis and Zipf analysis. Moreover, we consider the daily returns of Shanghai Stock Exchange Composite Index from January 1997 to July 2011, and the comparisons of return behaviors between the actual data and the simulation data are exhibited.

  19. Locating critical points on multi-dimensional surfaces by genetic algorithm: test cases including normal and perturbed argon clusters

    Science.gov (United States)

    Chaudhury, Pinaki; Bhattacharyya, S. P.

    1999-03-01

    It is demonstrated that Genetic Algorithm in a floating point realisation can be a viable tool for locating critical points on a multi-dimensional potential energy surface (PES). For small clusters, the standard algorithm works well. For bigger ones, the search for global minimum becomes more efficient when used in conjunction with coordinate stretching, and partitioning of the strings into a core part and an outer part which are alternately optimized The method works with equal facility for locating minima, local as well as global, and saddle points (SP) of arbitrary orders. The search for minima requires computation of the gradient vector, but not the Hessian, while that for SP's requires the information of the gradient vector and the Hessian, the latter only at some specific points on the path. The method proposed is tested on (i) a model 2-d PES (ii) argon clusters (Ar 4-Ar 30) in which argon atoms interact via Lennard-Jones potential, (iii) Ar mX, m=12 clusters where X may be a neutral atom or a cation. We also explore if the method could also be used to construct what may be called a stochastic representation of the reaction path on a given PES with reference to conformational changes in Ar n clusters.

  20. 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...

  1. Hydrogeological deep percolation modelling of groundwater ...

    African Journals Online (AJOL)

    Indirect physical methods of assess groundwater recharge rely on the measurement or estimation of soil physical parameters, which along with soil physical principles; can be used to estimate the potential or actual recharge. However, the deep percolation method uses a daily water- budget approach to simulate deep ...

  2. On Universality of the Wrapping Percolation Transition

    Czech Academy of Sciences Publication Activity Database

    Škvor, J.; Nezbeda, Ivo

    2008-01-01

    Roč. 73, č. 3 (2008), s. 401-412 ISSN 0010-0765 R&D Projects: GA AV ČR 1ET400720409; GA AV ČR IAA400720710 Institutional research plan: CEZ:AV0Z40720504 Keywords : percolation threshold * wrapping probability * spanning probability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.784, year: 2008

  3. Percolation Thresholds in 2-Dimensional Prefractal Models of Porous Media

    NARCIS (Netherlands)

    Sukop, M.C.; Dijk, van G.J.; Perfect, E.; Loon, van W.K.P.

    2002-01-01

    Considerable effort has been directed towards the application of percolation theory and fractal modeling to porous media. We combine these areas of research to investigate percolation in prefractal porous media. We estimated percolation thresholds in the pore space of homogeneous random

  4. Disinfection of secondary effluents by infiltration percolation.

    Science.gov (United States)

    Makni, H

    2001-01-01

    Among the most attractive applications of reclaimed wastewater are: irrigation of public parks, sports fields, golf courses and market gardening. These uses require advanced wastewater treatment including disinfection. According to WHO guidelines (1989) and current rules and regulations in Tunisia, faecal coliform levels have to be reduced to < 10(3) or 10(2) CFU/100 mL. In Tunisia, most wastewater plants are only secondary treatment and, in order to meet health related regulations, the effluents need to be disinfected. However, it is usual for secondary effluents to need filtration prior to disinfection. Effectiveness of conventional disinfection processes, such as chlorination and UV radiation, are dependent upon the oxidation level and the levels of suspended solids of the treated water. Ozonation is relatively expensive and energy consuming. The consideration of the advantages and disadvantages of conventional techniques, their reliability, investment needs and operational costs will lead to the use of less sophisticated alternative techniques for certain facilities. Among alternative techniques, soil aquifer treatment and infiltration percolation through sand beds have been studied in Arizona, Israel, France, Spain and Morocco. Infiltration percolation plants have been intermittently fed with secondary or high quality primary effluents which percolated through 1.5-2 m unsaturated coarse sand and were recovered by under-drains. In such infiltration percolation facilities, microorganisms were eliminated through numerous physical, physicochemical and biological inter-related processes (mechanical filtration, adsorption and microbial degradation respectively). Efficiency of faecal coliform removal was dependent upon the water detention times in the filtering medium and on the oxidation of the filtered water. Effluents of Sfax town aerated ponds were infiltrated through 1.5 m deep sand columns in order to determine the performance of infiltration percolation in the

  5. Overland flow connectivity on planar patchy hillslopes - modified percolation theory approaches and combinatorial model of urns

    Science.gov (United States)

    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

  6. Possible crossover to percolation scenario near superfluid-Bose-glass transition

    Science.gov (United States)

    Syromyatnikov, A. V.; Sizanov, A. V.

    2017-10-01

    We discuss magnetically ordered (;superfluid;) phase near quantum transition to Bose-glass phase in a simple modeling system, Heisenberg antiferromagnet in spatial dimension d > 2 in external magnetic field with disorder in exchange coupling constants. Our analytical consideration is based on hydrodynamic description of long-wavelength excitations and it is valid in the entire critical region near the quantum critical point (QCP). We demonstrate that the system behaves in full agreement with predictions by Fisher et al. (Phys. Rev. B 40, 546 (1989)) in close vicinity of QCP. On the other hand, we show that many recent experimental and numerical results obtained in various 3D systems can be described by our formulas using percolation critical exponents. Then, it is a possibility that a percolation critical regime arises in the ordered phase in some 3D systems not very close to QCP.

  7. Percolation of cadmium across a mercury film

    International Nuclear Information System (INIS)

    Malek, K.; Gobal, F.

    2003-01-01

    Electrodeposition/dissolution of cadmium onto a film of mercury shows some deviations from the natural liquidity of mercury caused by the reduction of Cd onto it. Percolation and fractal analyzes were done on the surface and the bulk of the mercury film during diffusion of Cd species (atoms). These show that the fractal dimensions of the Cd-inserted mercury film are about 2.11 and 2.54 near the surface of the mercury film and at deeper points inside the film, respectively. The insertion process has a negligible effect on the surface morphology of the mercury film and there is a phase transition in the bulk, as well as a geometrical transition during the Cd-insertion (de-insertion) process. This corresponds to a percolation threshold of about 0.2 mol l -1 Cd content

  8. 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.

  9. 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.

  10. THE WORK OF LUCIO RUSSO ON PERCOLATION

    OpenAIRE

    Grimmett, Geoffrey Richard

    2016-01-01

    The contributions of Lucio Russo to the mathematics of percolation and disordered systems are outlined. The context of his work is explained, and its ongoing impact on current work is described and amplified. Engineering and Physical Sciences Research Council(Grant ID: EP/I03372X/1) This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Institute for Mathematics and Mechanics of Complex Systems.

  11. Genomic Identification and Analysis of Shared Cis-regulator Elements in a Developmentally Critical homeobox Cluster

    Energy Technology Data Exchange (ETDEWEB)

    Chris Amemiya

    2003-04-01

    The goals of this project were to isolate, characterize, and sequence the Dlx3/Dlx7 bigene cluster from twelve different species of mammals. The Dlx3 and Dlx7 genes are known to encode homeobox transcription factors involved in patterning of structures in the vertebrate jaw as well as vertebrate limbs. Genomic sequences from the respective taxa will subsequently be compared in order to identify conserved non-coding sequences that are potential cis-regulatory elements. Based on the comparisons they will fashion transgenic mouse experiments to functionally test the strength of the potential cis-regulatory elements. A goal of the project is to attempt to identify those elements that may function in coordinately regulating both Dlx3 and Dlx7 functions.

  12. 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

  13. Experimental percolation studies of random networks

    Science.gov (United States)

    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.

  14. Broad-band conductivity and dielectric spectroscopy of composites of multiwalled carbon nanotubes and poly(ethylene terephthalate) around their low percolation threshold

    Science.gov (United States)

    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.

  15. Effect of micellar collisions and polyvinylpyrrolidone confinement on the electrical conductivity percolation parameters of water/AOT/isooctane reverse micelles

    Science.gov (United States)

    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.

  16. 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

  17. THE SLUGGS SURVEY: NGC 3115, A CRITICAL TEST CASE FOR METALLICITY BIMODALITY IN GLOBULAR CLUSTER SYSTEMS

    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.

  18. The Role of Percolation Theory in Developing Next Generation Smart Nanomaterials

    Science.gov (United States)

    Simien, Daneesh

    2016-01-01

    The incorporation of small volume fractions of nanoscale graphitic particles into varied base materials has been explored across fields ranging from automotive to aerospace to commercial plastics, with the goal of utilizing their enhanced thermal conductivity, electrical conductivity or mechanical strength. Percolation theory has emerged as a useful tool to aid in mapping and predicting the enhancement of properties based on the size and conductivity of incorporated single-walled carbon nanotubes relative to their less conductive base materials. These tools can aid researchers in the development of next generation smart nanomaterials. In this paper, we discuss the use of homogeneous fractions of length- or chirality-sorted single-walled carbon nanotubes (SWNTs) which are incorporated into thin film networks, and cement composites, and are evaluated in terms of their conductivity, mechanical properties and noise spectrum at critical percolation. We demonstrate that, near the percolation threshold, the conductivity of these highly characterized SWNT films exhibits a power law dependence on the network geometrical parameters. We also present our findings on the development of incorporated thin film SWNTs for the development of sensing technology for novel non-destructive failure diagnostic applications. SWNTs are able to be used as benign inclusions, capable of active sensing, when incorporated into cement-based composites for the purpose of detecting crack initiation. As such, we investigate the use of homogeneous length-sorted SWNTs that are randomly distributed in percolated networks capable of being an internal responsive net mechanism. Our findings demonstrate increased microstructure sensitivity of our networks for our shorter length nanotubes near their critical percolation threshold. This shows promise for the development of even more sensitive, embedded piezo-resistive SWNT-based sensors for preemptive failure detection technology.

  19. Percolation in a Proton Exchange Membrane Fuel Cell Catalyst Layer

    Energy Technology Data Exchange (ETDEWEB)

    Stacy, Stephen; Allen, Jeffrey

    2012-07-01

    Water management in the catalyst layers of proton exchange membrane fuel cells (PEMFC) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. At the present time, the data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited. A method and apparatus for measuring the percolation pressure in the catalyst layer has been developed based upon an experimental apparatus used to test water percolation in porous transport layers (PTL). The experimental setup uses a pseudo Hele-Shaw type testing where samples are compressed and a fluid is injected into the sample. Testing the samples gives percolation pressure plots which show trends in increasing percolation pressure with an increase in flow rate. A decrease in pressure was seen as percolation occurred in one sample, however the pressure only had a rising effect in the other sample.

  20. Critical behavior of superfluid {sup 4}He in aerogel

    Energy Technology Data Exchange (ETDEWEB)

    Moon, K. [Department of Physics, University of California, Davis, California 95616 (United States); Girvin, S.M. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

    1995-08-14

    We report Monte Carlo studies of the critical behavior of superfluid {sup 4}He in the presence of quenched disorder with long-range fractal correlations. Modeling aerogel as an incipient percolating cluster in 3D and weakening the bonds at the fractal sites, {ital XY}-model simulations demonstrate an increase in the superfluid density exponent {zeta} from 0.67{plus_minus}0.005 for the pure case to an apparent value of 0.722{plus_minus}0.005 in the presence of the fractal disorder, provided that the helium correlation length does not exceed the fractal correlation length.

  1. Volatility Behaviors of Financial Time Series by Percolation System on Sierpinski Carpet Lattice

    Science.gov (United States)

    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.

  2. Nonlinear Analysis on Cross-Correlation of Financial Time Series by Continuum Percolation System

    Science.gov (United States)

    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.

  3. Fluctuations in percolation of sparse complex networks

    Science.gov (United States)

    Bianconi, Ginestra

    2017-07-01

    We study the role of fluctuations in percolation of sparse complex networks. To this end we consider two random correlated realizations of the initial damage of the nodes and we evaluate the fraction of nodes that are expected to remain in the giant component of the network in both cases or just in one case. Our framework includes a message-passing algorithm able to predict the fluctuations in a single network, and an analytic prediction of the expected fluctuations in ensembles of sparse networks. This approach is applied to real ecological and infrastructure networks and it is shown to characterize the expected fluctuations in their response to external damage.

  4. Percolation Theory and Modern Hydraulic Fracturing

    Science.gov (United States)

    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.

  5. 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.

  6. Topography of phase-separated critical and off-critical polymer mixtures

    Science.gov (United States)

    Cabral, J.; Higgins, J.; Magonov, Sn

    2003-03-01

    We investigate the spinodal decomposition of a polymer mixture, at both critical and off-critical compositions, using atomic force microscopy. Phase separation in the bulk is imaged using tapping mode on the surface of microtomed samples. The generated surface profiles, revealed in height images, are analyzed according to their in-plane spinodal morphology and their (perpendicular) height distribution. The former is characterized in terms of the periodicity of the structure and volume fraction of coexisting phases, both in the percolation and cluster regimes. The average height profiles are shown to be bimodal with a height step, Deltah, ranging from 1 to 7 nm, for the temperature quench depths spanned. Deltah is time-independent but depends linearly on annealing temperature and therefore on the composition difference between coexisting phases. This temperature dependence allows us to extrapolate to the mixture's critical temperature. A blend of tetramethyl bisphenol A polycarbonate and polystyrene was employed for this demonstration.

  7. A simple model for the earthquake cycle combining self-organized complexity with critical point behavior

    Directory of Open Access Journals (Sweden)

    W. I. Newman

    2002-01-01

    Full Text Available We have studied a hybrid model combining the forest-fire model with the site-percolation model in order to better understand the earthquake cycle. We consider a square array of sites. At each time step, a "tree" is dropped on a randomly chosen site and is planted if the site is unoccupied. When a cluster of "trees" spans the site (a percolating cluster, all the trees in the cluster are removed ("burned" in a "fire." The removal of the cluster is analogous to a characteristic earthquake and planting "trees" is analogous to increasing the regional stress. The clusters are analogous to the metastable regions of a fault over which an earthquake rupture can propagate once triggered. We find that the frequency-area statistics of the metastable regions are power-law with a negative exponent of two (as in the forest-fire model. This is analogous to the Gutenberg-Richter distribution of seismicity. This "self-organized critical behavior" can be explained in terms of an inverse cascade of clusters. Small clusters of "trees" coalesce to form larger clusters. Individual trees move from small to larger clusters until they are destroyed. This inverse cascade of clusters is self-similar and the power-law distribution of cluster sizes has been shown to have an exponent of two. We have quantified the forecasting of the spanning fires using error diagrams. The assumption that "fires" (earthquakes are quasi-periodic has moderate predictability. The density of trees gives an improved degree of predictability, while the size of the largest cluster of trees provides a substantial improvement in forecasting a "fire."

  8. Determination of critical exponents in nuclear systems

    International Nuclear Information System (INIS)

    Mueller, W.F.J.; Bassini, R.; Begemann-Blaich, M.

    1996-07-01

    Signatures of critical behaviour in nuclear fragmentation are often based on arguments from percolation theory. We demonstrate with general thermodynamic considerations and studies of the Ising model that the reliance on percolation as a reference model bears the risk of missing parts of the essential physics. (orig.)

  9. Plasmonic percolation: Plasmon-manifested dielectric-to-metal transition

    KAUST Repository

    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.

  10. Optical properties of nanocomposites: Percolation films, nanowires, and nanoholes

    Science.gov (United States)

    Podolskiy, Viktor Anatolyevich

    The optical properties of percolation films, nanowires, nanowire composites, and nanoholes composites were studied theoretically. Developed theory predicts the existence of localized plasmon modes in metal-dielectric percolation films when the metal concentration is close to the percolation threshold. Due to the plasmon localization local fields, local field fluctuations are extremely enhanced on the surface of percolation composite. This explains enormous enhancement of the nonlinear diffuse scattering by the percolation film. Also, localization of the plasmon modes and their coupling to optical phonon modes leads to the enhanced absorption by thick percolation composites. Our simulations show that spatial plasmon modes localization and unique local spectral characteristics of these modes make it possible to produce extremely sharp responses using the percolation composites. The developed technique suggests the existence of propagating polariton modes in the metal nanowire, which explains the unique spatial distribution of the electromagnetic field around the metal nanowire. Our simulations show the existence of sharp plasmon resonance in single nanowire and localized plasmon modes in nanowire percolation composite. The specific nanowire composite, which has negative refractive index is suggested. Development of recent Generalized Ohm's Law (GOL) approach allows us to explain extraordinary light transmittance by metal-nanoholes composite. The theory predicts large local field enhancement in such composite close to the transmittance resonance. The theory also predicts the plausibility of light nano-management using metal-holes composites.

  11. 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 ...

  12. Innovation diffusion in networks: the microeconomics of percolation

    NARCIS (Netherlands)

    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

  13. Leveraging percolation theory to single out influential spreaders in networks

    Science.gov (United States)

    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.

  14. Percolation and permeability of heterogeneous fracture networks

    Science.gov (United States)

    Adler, Pierre; Mourzenko, Valeri; Thovert, Jean-François

    2013-04-01

    Natural fracture fields are almost necessarily heterogeneous with a fracture density varying with space. Two classes of variations are quite frequent. In the first one, the fracture density is decreasing from a given surface; the fracture density is usually (but not always see [1]) an exponential function of depth as it has been shown by many measurements. Another important example of such an exponential decrease consists of the Excavated Damaged Zone (EDZ) which is created by the excavation process of a gallery [2,3]. In the second one, the fracture density undergoes some local random variations around an average value. This presentation is mostly focused on the first class and numerical samples are generated with an exponentially decreasing density from a given plane surface. Their percolation status and hydraulic transmissivity can be calculated by the numerical codes which are detailed in [4]. Percolation is determined by a pseudo diffusion algorithm. Flow determination necessitates the meshing of the fracture networks and the discretisation of the Darcy equation by a finite volume technique; the resulting linear system is solved by a conjugate gradient algorithm. Only the flow properties of the EDZ along the directions which are parallel to the wall are of interest when a pressure gradient parallel to the wall is applied. The transmissivity T which relates the total flow rate per unit width Q along the wall through the whole fractured medium to the pressure gradient grad p, is defined by Q = - T grad p/mu where mu is the fluid viscosity. The percolation status and hydraulic transmissivity are systematically determined for a wide range of decay lengths and anisotropy parameters. They can be modeled by comparison with anisotropic fracture networks with a constant density. A heuristic power-law model is proposed which accurately describes the results for the percolation threshold over the whole investigated range of heterogeneity and anisotropy. Then, the data

  15. Effects of surfaces on resistor percolation.

    Science.gov (United States)

    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.

  16. Monopole percolation and the universality class of the chiral transition in four flavor noncompact lattice QED

    CERN Document Server

    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.

  17. Current flow in random resistor networks: the role of percolation in weak and strong disorder.

    Science.gov (United States)

    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.

  18. Link between hopping models and percolation scaling laws for charge transport in mixtures of small molecules

    Directory of Open Access Journals (Sweden)

    Dong-Gwang Ha

    2016-04-01

    Full Text Available Mixed host compositions that combine charge transport materials with luminescent dyes offer superior control over exciton formation and charge transport in organic light emitting devices (OLEDs. Two approaches are typically used to optimize the fraction of charge transport materials in a mixed host composition: either an empirical percolative model, or a hopping transport model. We show that these two commonly-employed models are linked by an analytic expression which relates the localization length to the percolation threshold and critical exponent. The relation is confirmed both numerically and experimentally through measurements of the relative conductivity of Tris(4-carbazoyl-9-ylphenylamine (TCTA :1,3-bis(3,5-dipyrid-3-yl-phenylbenzene (BmPyPb mixtures with different concentrations, where the TCTA plays a role as hole conductor and the BmPyPb as hole insulator. The analytic relation may allow the rational design of mixed layers of small molecules for high-performance OLEDs.

  19. Effective spreading from multiple leaders identified by percolation in the susceptible-infected-recovered (SIR) model

    Science.gov (United States)

    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.

  20. 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.

  1. Coherent Light Scattering from Semicontinuous Silver Nanoshells near the Percolation Threshold

    Science.gov (United States)

    Rohde, C. A.; Hasegawa, K.; Deutsch, Miriam

    2006-02-01

    We report on measurements of visible extinction spectra of semicontinuous silver nanoshells grown on colloidal silica spheres. We find that thin, fractal shells below the percolation threshold exhibit geometrically tunable plasmon resonances. A modified scaling theory approach is used to model the dielectric response of such shells, which is then utilized to obtain the extinction cross section in a retarded Mie scattering formalism. We show that such spherical resonators support unique plasmon dynamics: in the visible there is a new regime of coherently driven cluster-localized plasmons, while crossover to homogeneous response in the infrared predicts a delocalized shell plasmon.

  2. The application of heterogeneous cluster grouping to reflective writing for medical humanities literature study to enhance students' empathy, critical thinking, and reflective writing.

    Science.gov (United States)

    Liao, Hung-Chang; Wang, Ya-Huei

    2016-09-02

    To facilitate interdisciplinary collaboration and to make connections between patients' diseases and their social/cultural contexts, the study examined whether the use of heterogeneous cluster grouping in reflective writing for medical humanities literature acquisition could have positive effects on medical university students in terms of empathy, critical thinking, and reflective writing. A 15-week quasi-experimental design was conducted to investigate the learning outcomes. After conducting cluster algorithms, heterogeneous learning clusters (experimental group; n = 43) and non-heterogeneous learning clusters (control group; n = 43) were derived for a medical humanities literature study. Before and after the intervention, an Empathy Scale in Patient Care (ES-PC), a critical thinking disposition assessment (CTDA-R), and a reflective writing test were administered to both groups. The findings showed that on the empathy scale, significant differences in the "behavioral empathy," "affective empathy," and overall sections existed between the post-test mean scores of the experimental group and those of the control group, but such differences did not exist in "intelligent empathy." Regarding critical thinking, there were significant differences in "systematicity and analyticity," "skepticism and well-informed," "maturity and skepticism," and overall sections. As for reflective writing, significant differences existed in "ideas," "voice and point of view," "critical thinking and representation," "depth of reflection on personal growth," and overall sections, but not in "focus and context structure" and "language and conventions." This study outlined an alternative for using heterogeneous cluster grouping in reflective writing about medical humanities literature to facilitate interdisciplinary cooperation to provide more humanizing medical care.

  3. Conserved directed percolation: exact quasistationary distribution of small systems and Monte Carlo simulations

    Science.gov (United States)

    César Mansur Filho, Júlio; Dickman, Ronald

    2011-05-01

    We study symmetric sleepy random walkers, a model exhibiting an absorbing-state phase transition in the conserved directed percolation (CDP) universality class. Unlike most examples of this class studied previously, this model possesses a continuously variable control parameter, facilitating analysis of critical properties. We study the model using two complementary approaches: analysis of the numerically exact quasistationary (QS) probability distribution on rings of up to 22 sites, and Monte Carlo simulation of systems of up to 32 000 sites. The resulting estimates for critical exponents β, \\beta /\

  4. Percolation of triplet excitation in molecularly doped polymer, copolymer and rigid solution matrices

    Science.gov (United States)

    Saha, D. C.; Misra, T. N.; Talukdar, D.

    1999-12-01

    The triplet energy migration in benzophenone and 1,4 dibromonaphthalene doped polystyrene, methylmethacrylate-styrene copolymer and ethanol-methanol rigid glassy solution has been studied under steady state excitation. The probability of donor excitation energy capture by the traps shows a critical concentration dependence on benzophenone molecules. The percolation model has been successfully applied to evaluate the critical exponents. It is observed that in rigid glassy solution and in polystyrene matrices a three-dimensional triplet excitation migration topology is observed, whereas in copolymer matrix it is two-dimensional.

  5. Percolation on shopping and cashback electronic commerce networks

    Science.gov (United States)

    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.

  6. Conductive polymer foams with carbon nanofillers – Modeling percolation behavior

    Directory of Open Access Journals (Sweden)

    O. Maxian

    2017-05-01

    Full Text Available A new numerical model considering nanofiller random distribution in a porous polymeric matrix was developed to predict electrical percolation behavior in systems incorporating 1D-carbon nanotubes (CNTs and/or 2D-graphene nanoplatelets (GNPs. The numerical model applies to porous systems with closed-cell morphology. The percolation threshold was found to decrease with increasing porosity due to filler repositioning as a result of foaming. CNTs were more efficient in forming a percolative network than GNPs. High-aspect ratio (AR and randomly oriented fillers were more prone to form a network. Reduced percolation values were determined for misaligned fillers as they connect better in a network compared to aligned ones. Hybrid CNT-GNP fillers show synergistic effects in forming electrically conductive networks by comparison with single fillers.

  7. Percolation Models of Financial Market Dynamics

    Science.gov (United States)

    Stauffer, Dietrich

    Microscopic models dealing with the decisions of traders on the market have tried to reproduce real market behaviour. Possibly the simplest of these models is the herding approach of Cont and Bouchaud. Variations include letting the concentration varying between zero and unity (or zero and percolation threshold); changing the price proportionally not to the difference between demand and supply, but to the square root of this difference; influencing the buy /sell decisions by the actual price and price change. As a result, the probability to find a market change greater than some R was found to vary as R-2.9; this distribution gets wings which might correspond to outliers like the 1929 crash on Wall Street; bubbles lead to sharp peaks separated by flat valleys; and the log-periodic variations after the Japanese crash of 1990 were reproduced to get rich from the prediction made in January 1999 by Johansen and Sornette that Nikkei will rise appreciably during 1999. As it did.

  8. 50 years of first-passage percolation

    CERN Document Server

    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...

  9. A critical evaluation of the use of cluster analysis to identify contaminated sediments in the Ria de Vigo

    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

  10. 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.

  11. Social percolation and the influence of mass media

    Science.gov (United States)

    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.

  12. 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.

  13. Patterns in the English language: phonological networks, percolation and assembly models

    Science.gov (United States)

    Stella, Massimo; Brede, Markus

    2015-05-01

    In this paper we provide a quantitative framework for the study of phonological networks (PNs) for the English language by carrying out principled comparisons to null models, either based on site percolation, randomization techniques, or network growth models. In contrast to previous work, we mainly focus on null models that reproduce lower order characteristics of the empirical data. We find that artificial networks matching connectivity properties of the English PN are exceedingly rare: this leads to the hypothesis that the word repertoire might have been assembled over time by preferentially introducing new words which are small modifications of old words. Our null models are able to explain the ‘power-law-like’ part of the degree distributions and generally retrieve qualitative features of the PN such as high clustering, high assortativity coefficient and small-world characteristics. However, the detailed comparison to expectations from null models also points out significant differences, suggesting the presence of additional constraints in word assembly. Key constraints we identify are the avoidance of large degrees, the avoidance of triadic closure and the avoidance of large non-percolating clusters.

  14. Multiscale synchrony behaviors of paired financial time series by 3D multi-continuum percolation

    Science.gov (United States)

    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.

  15. Einstein Critical-Slowing-Down is Siegel CyberWar Denial-of-Access Queuing/Pinning/ Jamming/Aikido Via Siegel DIGIT-Physics BEC ``Intersection''-BECOME-UNION Barabasi Network/GRAPH-Physics BEC: Strutt/Rayleigh-Siegel Percolation GLOBALITY-to-LOCALITY Phase-Transition Critical-Phenomenon

    Science.gov (United States)

    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)

  16. 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

  17. Lignes de percolation dans un fluide supercritique

    OpenAIRE

    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...

  18. Scaling relation for determining the critical threshold for continuum ...

    Indian Academy of Sciences (India)

    We study continuum percolation of overlapping circular discs of two sizes. We propose a phenomenological scaling equation for the increase in the effective size of the larger discs due to the presence of the smaller discs. The critical percolation threshold as a function of the ratio of sizes of discs, for different values of the ...

  19. Scaling relation for determining the critical threshold for continuum ...

    Indian Academy of Sciences (India)

    Abstract. We study continuum percolation of overlapping circular discs of two sizes. We propose a phenomenological scaling equation for the increase in the effective size of the larger discs due to the presence of the smaller discs. The critical percolation threshold as a function of the ratio of sizes of discs, for different values ...

  20. Relationship between Polymer Dielectric Constant and Percolation Threshold in Conductive Poly(styrene-Type Polymer and Carbon Black Composites

    Directory of Open Access Journals (Sweden)

    Mariana Castro Martínez

    2015-01-01

    Full Text Available We study the effect of dielectric constant of some poly(styrene-type polymer matrix on the percolation threshold in conductive polymer composites with carbon black (CB. We demonstrate that percolation threshold diminishes with an increment of the dielectric constant of polymer matrix. We chose polystyrene and other three polymers similar in structure and molecular weight but with different chemical nature. The corresponding dielectric constant and critical concentration, Xc, in volume fraction of carbon black, v/v CB, were the following: 4MePS (ε=2.43; Xc=0.058, PS (ε=2.60; Xc=0.054, 4BrPS (ε=2.82; Xc=0.051, and 4ClPS (ε=2.77; Xc=0.047. The correlation between both parameters confirms that the percolation threshold decreases while the dielectric constant increases. At microscopic level, this effect is attributed to an enhanced physical interaction of the CB particles with the asymmetric electric density produced by electronegative or inductive atoms/groups. Therefore, by controlling the chemical structure of the polymer matrix, the attraction forces between the polar groups on the carbon black surface particles with those of the polymer matrix can be improved, which in turn induces a better disaggregation and dispersion of those particles into the polymer matrix, allowing the percolation threshold reached at a lower filling fraction.

  1. Clustering and information in correlation based financial networks

    Science.gov (United States)

    Onnela, J.-P.; Kaski, K.; Kertész, J.

    2004-03-01

    Networks of companies can be constructed by using return correlations. A crucial issue in this approach is to select the relevant correlations from the correlation matrix. In order to study this problem, we start from an empty graph with no edges where the vertices correspond to stocks. Then, one by one, we insert edges between the vertices according to the rank of their correlation strength, resulting in a network called asset graph. We study its properties, such as topologically different growth types, number and size of clusters and clustering coefficient. These properties, calculated from empirical data, are compared against those of a random graph. The growth of the graph can be classified according to the topological role of the newly inserted edge. We find that the type of growth which is responsible for creating cycles in the graph sets in much earlier for the empirical asset graph than for the random graph, and thus reflects the high degree of networking present in the market. We also find the number of clusters in the random graph to be one order of magnitude higher than for the asset graph. At a critical threshold, the random graph undergoes a radical change in topology related to percolation transition and forms a single giant cluster, a phenomenon which is not observed for the asset graph. Differences in mean clustering coefficient lead us to conclude that most information is contained roughly within 10% of the edges.

  2. Critical Role of Energy Transfer Between Terbium Ions for Suppression of Back Energy Transfer in Nonanuclear Terbium Clusters.

    Science.gov (United States)

    Omagari, Shun; Nakanishi, Takayuki; Kitagawa, Yuichi; Seki, Tomohiro; Fushimi, Koji; Ito, Hajime; Meijerink, Andries; Hasegawa, Yasuchika

    2016-11-15

    Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy to reduce back energy transfer losses. Nonanuclear lanthanide clusters containing terbium and gadolinium ions, Tb n Gd 9-n clusters ([Tb n Gd 9-n (μ-OH) 10 (butylsalicylate) 16 ] + NO 3 - , n = 0, 1, 2, 5, 8, 9), were synthesized to investigate the effect of energy transfer between Tb(III) ions on back energy transfer. The photophysical properties of Tb n Gd 9-n clusters were studied by steady-state and time-resolved spectroscopic techniques and revealed a longer emission lifetime with increasing number of Tb(III) ions in Tb n Gd 9-n clusters. A kinetic analysis of temperature dependence of the emission lifetime show that the energy transfer between Tb(III) ions competes with back energy transfer. The experimental results are in agreement with a theoretical rate equation model that confirms the role of energy transfer between Tb(III) ions in reducing back energy transfer losses. The results provide a new strategy in molecular design for improving the luminescence efficiency in lanthanide complexes which is important for potential applications as luminescent materials.

  3. Percolation dans des reseaux realistes de nanostructures de carbone

    Science.gov (United States)

    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

  4. Bounds for percolation thresholds on directed and undirected graphs

    Science.gov (United States)

    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.

  5. Controlling electrical percolation in multicomponent carbon nanotube dispersions.

    Science.gov (United States)

    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.

  6. Mutational destabilization of the critical interface water cluster in Scapharca dimeric hemoglobin: structural basis for altered allosteric activity.

    Science.gov (United States)

    Pardanani, A; Gambacurta, A; Ascoli, F; Royer, W E

    1998-12-04

    A cluster of interface ordered water molecules has been proposed to act as a key mediator of intersubunit communication in the homodimeric hemoglobin of Scapharca inaequivalvis. Mutations of Thr72 to Val and Ile, which lack the hydroxyl group to hydrogen bond the deoxy interface water molecules, result in sharply altered functional properties. We have determined the high resolution (1.6-1. 8 A) crystal structures of these two mutants in both the deoxygenated and CO-liganded states. These structures show minimal protein structural changes relative to the same native derivatives, despite greater than 40-fold increases in oxygen affinity. In the deoxy state of both mutants two water molecules at the periphery of the water cluster are lost, and the remaining cluster water molecules are destabilized. The CO-liganded structures show key differences between the two mutants including a more optimal interface packing involving Ile72 that acts to stabilize its high affinity (R) state. This additional stabilization allows rationalization of its lowered cooperativity within the context of a two-state model. These studies support a key role of ordered water in cooperative functioning and illustrate how subtle structural alterations can result in significantly altered functional properties in an allosteric molecule. Copyright 1998 Academic Press

  7. Electrical Percolation Effect on Electromechanical Behavior of CNT Nanocomposites

    Directory of Open Access Journals (Sweden)

    Yves Ngabonziza

    2011-12-01

    Full Text Available Electrical resistance responses of multi-walled carbon nanotubes (MWCNT reinforced polypropylene (PP nanocomposites under mechanical tensile loading are studied in this paper. A standard tensile test was conducted while the electrical resistance was measured using 2-probe method. From our previous works on the CNT/PP nanocomposites, the percolation threshold of electrical conductivity is around 3.8 wt% of CNT. The influence of this percolation threshold on the electrical resistance upon mechanical loading was investigated. The results will be discussed and compared.

  8. Interdependent networks - Topological percolation research and application in finance

    Science.gov (United States)

    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 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 dynamic network model to simulate and analyze the initializing and spreading of financial crisis. Using different computational approaches and econometric tests, we find atypical behavior of the cross correlations and community formations in the financial networks that we study during the financial crisis of 2008. For example, the overall correlation of stock market increases during crisis while the correlation between

  9. Effects of varying mechanical deformations on the relationship between mesotexture and current percolation in (Bi, Pb)2Sr2Ca2Cu3O10/Ag superconductor tapes

    International Nuclear Information System (INIS)

    Tan, T T; Li, S; Lau, S P; Tay, Y Y; Sun, C Q; Zhou, S H; Dou, S X

    2003-01-01

    In this work, effects of varying mechanical deformations on the relationship between mesotexture and current percolation in (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10+x (Bi2223) tapes are investigated. Electron backscattered diffraction analysis demonstrates that the mesotexture distribution characteristics influence critical current density (J c ) as results of the processing variations. The disorientation angle distribution dependence of J c is also discussed using current percolation theory. The results show that improving the mesotexture distribution in central region of Bi2223 tapes through optimization of the mechanical deformation processing can significantly increase J c

  10. Finite element/percolation theory modelling of the micromechanical behavior of clayey soils.

    Science.gov (United States)

    Pérez-Rea, M Luz; Horta-Rangel, Jaime; López-Lara, Teresa; Hernández-Zaragoza, Juan B; Alcocer, Sergio M; Castaño, Victor M

    2015-01-01

    A hybrid model for soils, which combines percolation theory and finite element method is presented. The internal soil structure is modelled via the finite element method, and percolation networks are used for analyzing its mechanical behaviour. Through a microscopic characterization of elastic properties of soil grains, the model is generated. The effective percolation threshold obtained is lower than that of the network geometric percolation. The effective mechanical properties predicted are successfully compared to published experimental results.

  11. Finite element/percolation theory modelling of the micromechanical behavior of clayey soils

    OpenAIRE

    P?rez-Rea, M Luz; Horta-Rangel, Jaime; L?pez-Lara, Teresa; Hern?ndez-Zaragoza, Juan B; Alcocer, Sergio M; Casta?o, Victor M

    2015-01-01

    A hybrid model for soils, which combines percolation theory and finite element method is presented. The internal soil structure is modelled via the finite element method, and percolation networks are used for analyzing its mechanical behaviour. Through a microscopic characterization of elastic properties of soil grains, the model is generated. The effective percolation threshold obtained is lower than that of the network geometric percolation. The effective mechanical properties predicted are...

  12. A Simple Soil Percolation Test Device for Field Environmentalists

    Science.gov (United States)

    Smith, William H.; Stark, Phillip E.

    1977-01-01

    A primary responsibility of field environmental health workers is evaluation of individual sewage disposal system sites. The authors of this article developed a practical, accurate, and inexpensive measurement device for obtaining reliable percolation test results. Directions for the construction and use of the device are detailed. Drawings…

  13. Metastability thresholds for anisotropic bootstrap percolation in three dimensions

    NARCIS (Netherlands)

    Van Enter, A.C.D.; Fey, A.

    2012-01-01

    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

  14. Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions

    NARCIS (Netherlands)

    Van Enter, A.C.D.; Fey, A.

    2012-01-01

    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

  15. Finite-size effects for anisotropic bootstrap percolation : Logarithmic corrections

    NARCIS (Netherlands)

    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.

  16. Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions

    NARCIS (Netherlands)

    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

  17. Study of electrical percolation phenomenon from the dielectric and ...

    Indian Academy of Sciences (India)

    Abstract. Chitosan : AgI solid polymer composite films have been prepared by the well-known solution cast tech- nique. Electrical impedance spectroscopy was used to investigate the electrical percolation threshold phenomenon in this work. A wide dispersion can be seen in dielectric constant spectra at low frequencies.

  18. Reduction of self-perceived discomforts in critically ill patients in French intensive care units: study protocol for a cluster-randomized controlled trial.

    Science.gov (United States)

    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.

  19. THE TOPOLOGICAL AND DYNAMIC CHARACTERISTICS OF NEURONIC ENSEMBLES IN THE BRAIN AS PERCOLATING FRACTAL SETS

    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.

  20. Conductive paint-filled cement paste sensor for accelerated percolation

    Science.gov (United States)

    Laflamme, Simon; Pinto, Irvin; Saleem, Hussam S.; Elkashef, Mohamed; Wang, Kejin; Cochran, Eric

    2015-04-01

    Cementitious-based strain sensors can be used as robust monitoring systems for civil engineering applications, such as road pavements and historic structures. To enable large-scale deployments, the fillers used in creating a conductive material must be inexpensive and easy to mix homogeneously. Carbon black (CB) particles constitute a promising filler due to their low cost and ease of dispersion. However, a relatively high quantity of these particles needs to be mixed with cement in order to reach the percolation threshold. Such level may influence the physical properties of the cementitious material itself, such as compressive and tensile strengths. In this paper, we investigate the possibility of utilizing a polymer to create conductive chains of CB more quickly than in a cementitious-only medium. This way, while the resulting material would have a higher conductivity, the percolation threshold would be reached with fewer CB particles. Building on the principle that the percolation threshold provides great sensing sensitivity, it would be possible to fabricate sensors using less conducting particles. We present results from a preliminary investigation comparing the utilization of a conductive paint fabricated from a poly-Styrene-co-Ethylene-co-Butylene-co-Styrene (SEBS) polymer matrix and CB, and CB-only as fillers to create cementitious sensors. Preliminary results show that the percolation threshold can be attained with significantly less CB using the SEBS+CB mix. Also, the study of the strain sensing properties indicates that the SEBS+CB sensor has a strain sensitivity comparable to the one of a CB-only cementitious sensor when comparing specimens fabricated at their respective percolation thresholds.

  1. Charge transport in conjugated polymer-semiconductor nanoparticle composite near the percolation threshold

    Science.gov (United States)

    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.

  2. Flexibility of thought in high creative individuals represented by percolation analysis.

    Science.gov (United States)

    Kenett, Yoed N; Levy, Orr; Kenett, Dror Y; Stanley, H Eugene; Faust, Miriam; Havlin, Shlomo

    2018-01-30

    Flexibility of thought is theorized to play a critical role in the ability of high creative individuals to generate novel and innovative ideas. However, this has been examined only through indirect behavioral measures. Here we use network percolation analysis (removal of links in a network whose strength is below an increasing threshold) to computationally examine the robustness of the semantic memory networks of low and high creative individuals. Robustness of a network indicates its flexibility and thus can be used to quantify flexibility of thought as related to creativity. This is based on the assumption that the higher the robustness of the semantic network, the higher its flexibility. Our analysis reveals that the semantic network of high creative individuals is more robust to network percolation compared with the network of low creative individuals and that this higher robustness is related to differences in the structure of the networks. Specifically, we find that this higher robustness is related to stronger links connecting between different components of similar semantic words in the network, which may also help to facilitate spread of activation over their network. Thus, we directly and quantitatively examine the relation between flexibility of thought and creative ability. Our findings support the associative theory of creativity, which posits that high creative ability is related to a flexible structure of semantic memory. Finally, this approach may have further implications, by enabling a quantitative examination of flexibility of thought, in both healthy and clinical populations.

  3. 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

  4. Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition

    Science.gov (United States)

    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.

  5. 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.

  6. Conductivity switching of labyrinth metal films at the percolation threshold

    Science.gov (United States)

    Gushchin, M. G.; Gladskikh, I. A.; Vartanyan, T. A.

    2018-01-01

    Electrical properties of silver, gold and copper films at the percolation threshold were investigated experimentally. A convenient method to obtain films at the percolation threshold that consists of two phases: deposition of metal in vacuum on a dielectric substrate and subsequent thermal annealing has been developed. The metallic films produced in this way exist in two different states: a low-conductivity state and a high-conductivity state. The films can be switched between these states by the applied voltage with hysteresis of current-voltage characteristic curves. The conductivity difference between the states reaches seven orders of magnitude. The switching threshold voltage depends on the annealing time. The switching times differ considerably for different metals. They were 200 ns for silver, 2 µs for gold, and 60 µs for copper. A plausible explanation of the switching mechanism based on the voltage induced fine mechanical deformations is suggested and discussed.

  7. Deep Percolation in Arid Piedmont Slopes: Multiple Lines of Evidence Show How Land Use Change and Ecohydrological Properties Affect Groundwater Recharge

    Science.gov (United States)

    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.

  8. 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 ...

  9. Cell Invasion in Collagen Scaffold Architectures Characterized by Percolation Theory.

    Science.gov (United States)

    Ashworth, Jennifer C; Mehr, Marco; Buxton, Paul G; Best, Serena M; Cameron, Ruth E

    2015-06-24

    The relationship between biological scaffold interconnectivity and cell migration is an important but poorly understood factor in tissue regeneration. Here a scale-independent technique for characterization of collagen scaffold interconnectivity is presented, using a combination of X-ray microcomputed tomography and percolation theory. Confocal microscopy of connective tissue cells reveals this technique as highly relevant for determining the extent of cell invasion. © 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. 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...... method to sanitize VHSV infected water. Changes in temperature, pH, earth types in the area used for percolation etc. may change the virus reduction, though. As some of the fish cutting plants are also smoking rainbow trout fillets, the question arose whether a brine solution will inactivate VHSV....... In order to answer this question a small trial was set up. VHSV and NaCl was added to cell culture medium with 10% foetal bovine serum, in order to mimic a “dirty” environment, to obtain from 1.9% to 20.9% NaCl and kept in the dark at 4°C. Samples were titrated after 5 min, 1 h and 20 h. No reduction...

  11. Asymmetric percolation drives a double transition in sexual contact networks.

    Science.gov (United States)

    Allard, Antoine; Althouse, Benjamin M; Scarpino, Samuel V; Hébert-Dufresne, Laurent

    2017-08-22

    Zika virus (ZIKV) exhibits unique transmission dynamics in that it is concurrently spread by a mosquito vector and through sexual contact. Due to the highly asymmetric durations of infectiousness between males and females-it is estimated that males are infectious for periods up to 10 times longer than females-we show that this sexual component of ZIKV transmission behaves akin to an asymmetric percolation process on the network of sexual contacts. We exactly solve the properties of this asymmetric percolation on random sexual contact networks and show that this process exhibits two epidemic transitions corresponding to a core-periphery structure. This structure is not present in the underlying contact networks, which are not distinguishable from random networks, and emerges because of the asymmetric percolation. We provide an exact analytical description of this double transition and discuss the implications of our results in the context of ZIKV epidemics. Most importantly, our study suggests a bias in our current ZIKV surveillance, because the community most at risk is also one of the least likely to get tested.

  12. Effect of particle size and diluent type on critical parameters for ...

    African Journals Online (AJOL)

    dissolution and absorption [6,8]. The percolation theory scrutinizes the critical points or percolation thresholds of the system, which one ingredient of the system emerges a geometrical phase transition, creating the connection with the entire system. The formulation features such as the percentage of drug released, release ...

  13. Percolation Model of Sensory Transmission and Loss of Consciousness Under General Anesthesia

    Science.gov (United States)

    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.

  14. Memory effects, two color percolation, and the temperature dependence of Mott variable-range hopping

    Science.gov (United States)

    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.

  15. Percolation through voids around overlapping spheres: A dynamically based finite-size scaling analysis

    Science.gov (United States)

    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.

  16. 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.

  17. Application of groundwater thresholds for trace elements on percolation water: a case study on percolation water from Northern German lowlands.

    Science.gov (United States)

    Godbersen, L; Duijnisveld, W H M; Utermann, J; Gäbler, H-E; Kuhnt, G; Böttcher, J

    2012-01-01

    The German insignificance thresholds (GFS) for groundwater, derived with an added risk approach, will soon be adopted as trigger values for percolation water entering groundwater. The physicochemical properties of the vadose zone differ considerably from those of groundwater, which may lead to difficulties in the applicability of groundwater-derived GFS to percolation water. To test the applicability of the GFS to percolation water regarding the concentration level and the field-scale variability, 46 sites in Northern Germany were sampled, including arable land, grassland, and forest, situated on three spatially dominant parent materials: sand, glacial loam, and loess. Concentrations of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sn, V, Zn, and F were analyzed in percolation water from the transition between the unsaturated to the saturated zone. We compared median and 90th percentile values of the background concentrations with the GFS. In more than 10% of all samples, background concentrations of Cd, Co, Ni, V, or Zn exceeded the GFS. We evaluated the applicability of the GFS on field-scale medians of background concentrations taking field-scale interquartile distance and the bootstrap percentile confidence interval of the field scale median of trace element background concentrations into consideration. Statements about exceedance or nonexceedance of GFS values could only be made with acceptable statistical uncertainty (α ≤ 0.1) when operational median concentrations were about one third higher or lower than the corresponding GFS. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  18. Percolation properties of 3-D multiscale pore networks: how connectivity controls soil filtration processes

    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.

  19. CRITICAL CONFIGURATION FOR BERYLLIUM REFLECTED ASSEMBLIES OF U(93.15)O2 FUEL RODS (1.506-CM PITCH AND 7-TUBE CLUSTERS)

    Energy Technology Data Exchange (ETDEWEB)

    Margaret A. Marshall

    2012-05-01

    A series of critical experiments were completed in 1962-1965 at Oak Ridge National Laboratory’s Critical Experiments Facility in support of the Medium-Power Reactor Experiments (MPRE) program. In the late 1950’s efforts were made to study “power plants for the production of electrical power in space vehicles”. The MPRE program was a part of those efforts and studied the feasibility of a stainless steel system, boiling potassium 1 MW(t), or about 140 kW(e), reactor. The program was carried out in [fiscal years] 1964, 1965, and 1966. A summary of the program’s effort was compiled in 1967. The delayed critical experiments were a mockup of a small, potassium-cooled space power reactor for validation of reactor calculations and reactor physics methods. Initial experiments, performed in November and December of 1962, consisted of a core of 253 unmoderated stainless steel tubes, each containing 26 UO2 fuel pellets, surrounded by a graphite reflector. Measurements were made to determine critical reflector arrangements, fission-rate distributions, and cadmium ratio distributions. “The [assemblies were built] on [a] vertical assembly machine so that the movable part was the core and bottom reflector.” The first two experiments in the series were evaluated in HEU-COMP-FAST-001 (SCCA-FUND-EXP-001) and HEU-COMP-FAST-002 (SCCA-FUND-EXP-002). The first experiment had the 253 fuel tubes packed tightly into a 22.87 cm outside diameter (OD) core tank (References 1 and 2). The second experiment in the series, performed in early 1963, had the 253 fuel tubes at a 1.506-cm triangular lattice in a 25.96 cm OD core tank and graphite reflectors on all sides. The third set of experiments in the series, performed in mid-1963, which is studied in this evaluation, used beryllium reflectors. The beryllium reflected system was the preferred reactor configuration for this application because of the small thickness of the reflector. The two core configurations had the 253 fuel tubes

  20. Psychological Outcomes following a nurse-led Preventative Psychological Intervention for critically ill patients (POPPI): protocol for a cluster-randomised clinical trial of a complex intervention.

    Science.gov (United States)

    Richards-Belle, Alvin; Mouncey, Paul R; Wade, Dorothy; Brewin, Chris R; Emerson, Lydia M; Grieve, Richard; Harrison, David A; Harvey, Sheila; Howell, David; Mythen, Monty; Sadique, Zia; Smyth, Deborah; Weinman, John; Welch, John; Rowan, Kathryn M

    2018-02-08

    Acute psychological stress, as well as unusual experiences including hallucinations and delusions, are common in critical care unit patients and have been linked to post-critical care psychological morbidity such as post-traumatic stress disorder (PTSD), depression and anxiety. Little high-quality research has been conducted to evaluate psychological interventions that could alleviate longer-term psychological morbidity in the critical care unit setting. Our research team developed and piloted a nurse-led psychological intervention, aimed at reducing patient-reported PTSD symptom severity and other adverse psychological outcomes at 6 months, for evaluation in the POPPI trial. This is a multicentre, parallel group, cluster-randomised clinical trial with a staggered roll-out of the intervention. The trial is being carried out at 24 (12 intervention, 12 control) NHS adult, general, critical care units in the UK and is evaluating the clinical effectiveness and cost-effectiveness of a nurse-led preventative psychological intervention in reducing patient-reported PTSD symptom severity and other psychological morbidity at 6 months. All sites deliver usual care for 5 months (baseline period). Intervention group sites are then trained to carry out the POPPI intervention, and transition to delivering the intervention for the rest of the recruitment period. Control group sites deliver usual care for the duration of the recruitment period. The trial also includes a process evaluation conducted independently of the trial team. This protocol was reviewed and approved by the National Research Ethics Service South Central - Oxford B Research Ethics Committee (reference: 15/SC/0287). The first patient was recruited in September 2015 and results will be disseminated in 2018. The results will be presented at national and international conferences and published in peer reviewed medical journals. ISRCTN53448131; Pre-results. © Article author(s) (or their employer(s) unless

  1. 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.

  2. Predicting deep percolation with eddy covariance under mulch drip irrigation

    Science.gov (United States)

    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.

  3. Percolative Theory of Organic Magnetoresistance and Fringe-Field Magnetoresistance

    Science.gov (United States)

    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.

  4. Pathogen Mutation Modeled by Competition Between Site and Bond Percolation

    Science.gov (United States)

    Hébert-Dufresne, Laurent; Patterson-Lomba, Oscar; Goerg, Georg M.; Althouse, Benjamin M.

    2013-03-01

    While disease propagation is a main focus of network science, its coevolution with treatment has yet to be studied in this framework. We present a mean-field and stochastic analysis of an epidemic model with antiviral administration and resistance development. We show how this model maps to a coevolutive competition between site and bond percolation featuring hysteresis and both second- and first-order phase transitions. The latter, whose existence on networks is a long-standing question, imply that a microscopic change in infection rate can lead to macroscopic jumps in expected epidemic size.

  5. On the genre-fication of music: a percolation approach

    Science.gov (United States)

    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.

  6. Rapid self-organised initiation of ad hoc sensor networks close above the percolation threshold

    Science.gov (United States)

    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.

  7. Column percolation test for contaminated soils: Key factors for standardization.

    Science.gov (United States)

    Naka, Angelica; Yasutaka, Tetsuo; Sakanakura, Hirofumi; Kalbe, Ute; Watanabe, Yasutaka; Inoba, Seiji; Takeo, Miyuki; Inui, Toru; Katsumi, Takeshi; Fujikawa, Takuro; Sato, Kenichi; Higashino, Kazuo; Someya, Masayuki

    2016-12-15

    Column percolation tests may be suitable for prediction of chemical leaching from soil and soil materials. However, compared with batch leaching tests, they are time-consuming. It is therefore important to investigate ways to shorten the tests without affecting the quality of results. In this study, we evaluate the feasibility of decreasing testing time by increasing flow rate and decreasing equilibration time compared to the conditions specified in ISO/TS 21268-3, with equilibration periods of 48h and flow rate of 12mL/h. We tested three equilibration periods (0, 12-16, and 48h) and two flow rates (12 and 36mL/h) on four different soils and compared the inorganic constituent releases. For soils A and D, we observed similar values for all conditions except for the 0h-36mL/h case. For soil B, we observed no appreciable differences between the tested conditions, while for soil C there were no consistent trends probably due to the difference in ongoing oxidation reactions between soil samples. These results suggest that column percolation tests can be shortened from 20 to 30days to 7-9days by decreasing the equilibration time to 12-16h and increasing the flow rate to 36mL/h for inorganic substances. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

  8. Electron percolation in realistic models of carbon nanotube networks

    Science.gov (United States)

    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.

  9. Epoxy resin/carbon black composites below the percolation threshold.

    Science.gov (United States)

    Macutkevic, J; Kuzhir, P; Paddubskaya, A; Maksimenko, S; Banys, J; Celzard, A; Fierro, V; Stefanutti, E; Cataldo, A; Micciulla, F; Bellucci, S

    2013-08-01

    A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At room temperature, the dielectric permittivity is higher for epoxy loaded with CBH additives. In contrast, at high temperature, the electrical conductivity was found to be higher for composites with CBL embedded. The established influence of the CB surface area on the broadband dielectric characteristics can be exploited for the production of effective low-cost antistatic paints and coatings working at different temperatures.

  10. 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.

  11. 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.

  12. Pseudo-random-number generators and the square site percolation threshold.

    Science.gov (United States)

    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.

  13. Flame Spread and Group-Combustion Excitation in Randomly Distributed Droplet Clouds with Low-Volatility Fuel near the Excitation Limit: a Percolation Approach Based on Flame-Spread Characteristics in Microgravity

    Science.gov (United States)

    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.

  14. Percolation and permeability of fracture networks in Excavated Damaged Zones

    Science.gov (United States)

    Mourzenko, V.; Thovert, J.; Adler, P. M.

    2012-12-01

    Generally, the excavation process of a gallery generates fractures in its immediate vicinity. The corresponding zone which is called the Excavated Damaged Zone (EDZ), has a larger permeability than the intact surrounding medium. The properties of the EDZ are attracting more and more attention because of their potential importance in repositories of nuclear wastes. The EDZ which is induced by the excavation process may create along the galleries of the repositories a high permeability zone which could directly connect the storage area with the ground surface. Therefore, the studies of its properties are of crucial importance for applications such as the storage of nuclear wastes. Field observations (such as the ones which have been systematically performed at Mont Terri by [1, 2]) suggest that the fracture density is an exponentially decreasing function of the distance to the wall with a characteristic length of about 0.5 m and that the fracture orientation is anisotropic (most fractures are subparallel to the tunnel walls) and well approximated by a Fisher law whose pole is orthogonal to the wall. Numerical samples are generated according to these prescriptions. Their percolation status and hydraulic transmissivity can be calculated by the numerical codes which are detailed in [3]. Percolation is determined by a pseudo diffusion algorithm. Flow determination necessitates the meshing of the fracture networks and the discretisation of the Darcy equation by a finite volume technique; the resulting linear system is solved by a conjugate gradient algorithm. Only the flow properties of the EDZ along the directions which are parallel to the wall are of interest when a pressure gradient parallel to the wall is applied. The transmissivity T which relates the total flow rate per unit width Q along the wall through the whole EDZ to the pressure gradient grad p, is defined by Q = - T grad p/mu where mu is the fluid viscosity. The percolation status and hydraulic transmissivity

  15. Price of anarchy is maximized at the percolation threshold

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Brian

    2015-05-01

    When many independent users try to route traffic through a network, the flow can easily become suboptimal as a consequence of congestion of the most efficient paths. The degree of this suboptimality is quantified by the so-called \\price of anarchy" (POA), but so far there are no general rules for when to expect a large POA in a random network. Here I address this question by introducing a simple model of flow through a network with randomly-placed "congestible" and "incongestible" links. I show that the POA is maximized precisely when the fraction of congestible links matches the percolation threshold of the lattice. Further, for large networks the value of the POA appears to saturate at its theoretical maximum value.

  16. Active Percolation Analysis of Pyramidal Neurons of Somatosensory Cortex:

    Science.gov (United States)

    Costa, Luciano Da Fontoura; Barbosa, Marconi Soares; Schierwagen, Andreas; Alpár, Alán; Gärtner, Ulrich; Arendt, Thomas

    This article describes the investigation of morphological variations among two sets of neuronal cells, namely a control group of wild type mouse cells and a group of cells of a transgenic line. Special attention is given to singular points in the neuronal structure, namely the branching points and extremities of the dendritic processes. The characterization of the spatial distribution of such points is obtained by using a recently reported morphological technique based on forced percolation and window-size compensation, which is particularly suited to the analysis of scattered points, presenting several coexisting densities. Different dispersions were identified in our statistical analysis, suggesting that the transgenic line of neurons is characterized by a more pronounced morphological variation. A classification scheme based on a canonical discriminant function was also considered in order to identify the morphological differences.

  17. Mesoscopic Percolating Resistance Network in a Strained Manganite Thin Film

    KAUST Repository

    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.

  18. Band and percolation approaches to low temperature properties of manganites

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, L.P. (Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. L.D. Landau Inst. for Theoretical Physics (Russian Federation)); Kresin, V.Z. (Lawrence Berkeley Lab., CA (United States))

    1998-12-20

    Properties of the parent compound, LaMnO[sub 3] are greatly affected by strong Hund's coupling. Assuming the antiferromagnetic ordering (with a low Neel temperature) along one of the cubic axes, this coupling would result in formation of disconnected ferromagnetic layers. Furthermore, in the presence of the cooperative Jahn-Teller effect the compound becomes a band insulator. At small doping (La[sub 1[minus]x]Ca[sub x]MnO[sub 3], x [much lt] 1) the band insulator phase coexists with the presence of localized holes. An insulator-ferromagnetic metal transition occurs at the percolation point x[sub c] = 0.16.

  19. Large Dielectric Constant Enhancement in MXene Percolative Polymer Composites

    KAUST Repository

    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.

  20. Pretreatment Characteristics of Waste Oak Wood by Ammonia Percolation

    Science.gov (United States)

    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.

  1. Mesoscopic percolating resistance network in a strained manganite thin film.

    Science.gov (United States)

    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.

  2. Carbon composite microelectrodes: charge percolation and electroanalytical performance.

    Science.gov (United States)

    Ramírez-García, Sonia; Alegret, Salvador; Céspedes, Francisco; Forster, Robert J

    2004-02-01

    Microelectrodes based on two different epoxy-graphite composites (Araldite-M/HY5162 and Araldite-PY302-2/HY943) that are compatible with organic solvents have been developed and characterized. The variation in the bulk conductivity with graphite particle loading is described by percolation theory and indicates that the particles interact strongly with one another. The percolation threshold is 52% v/v loading of graphite, and this composite exhibits a bulk conductivity of 15 S m(-1). Microdisk electrodes of 25-microm diameter were produced by first etching a microcavity at the tip of a platinum microelectrode, which was then packed with a composite containing 60% v/v graphite so as to optimize both electrical conductivity and the electrode stability in acetonitrile and methanol solutions. Solution phase voltammetry of ferrocene is nearly ideal, and the responses are dominated by radial diffusion (slow scan rates) and semi-infinite linear diffusion (fast scan rates). The microelectrodes display high signal-to-noise ratios, good sensitivity, and low detection limits. The response times given by the product of the resistance, R, and capacitance, C, are 7.5 x 10(-4) and 1.4 x 10(-1) s for the Araldite M and PY302-2 composites, respectively. Although these response times are significantly slower than those associated with microelectrodes based on carbon fibers or metal wires, they are sufficient for time-resolved electroanalytical applications. The long response times arise from the large composite resistances, 3.1 x 10(11) and 8.3 x 10(11) Omega cm(-2) for Araldite M and PY302-2, respectively. Voltammetry of ferrocene in the absence of deliberately added supporting electrolyte is also reported. Significantly, indistinguishable slopes and intercepts for a calibration curve of peak current vs ferrocene concentration where 2 < [ferrocene] < 50 microM are obtained in the presence and absence of supporting electrolyte.

  3. Percolation effects in the capacitive properties of metal-oxide varistors in the range of high voltage

    Directory of Open Access Journals (Sweden)

    A. S. Tonkoshkur

    2014-04-01

    Full Text Available C–V characteristics of ZnO-based ceramic structures used in manufacturing high-voltage and low-voltage varistors of different chemical compositions and manufacturing techniques have been investigated. A correlation between the intensity of electric field corresponding to transition of the C–V characteristics to the negative capacitances and average sizes of grains of a varistor structure has been established. Obtained data have been interpreted with the use of notions of the percolation theory of electric conductivity. The Shklovskii–De Gennes model has been used. It has been shown that on the highly nonlinear segment of C–V characteristics of a varistor structure, the size of an infinite cluster are limited to several intercrystallite potential barriers. This result is observed in all kinds of investigated varistor ceramics.

  4. Percolation modeling investigation of TPB formation in a solid oxide fuel cell electrode-electrolyte interface

    International Nuclear Information System (INIS)

    Martinez, Andrew S.; Brouwer, Jacob

    2008-01-01

    A Monte Carlo percolation model has been developed and utilized to characterize the factors controlling triple phase boundary (TPB) formation in an SOFC electrode. The model accounts for (1) electronic conductor, ionic conductor, and gas phase percolation, (2) competition between percolation of gas and electronically conducting phases, and (3) determination of continuous, though not necessarily fully percolating, paths from TPBs to the bulk phases. The model results show that physical processes near the TPB, such as sorbate transport, significantly affect TPB formation in a composite electrode. Active TPB formation is found to be most significantly dependent upon continuous and competing percolation of multiple phases. Simultaneously requiring continuous paths and accounting for non-continuous boundary conditions results in lower active TPB formation levels (up to 8% of possible sites) than presented in the literature (75% of possible sites). In addition, the varying ratio of active to potential TPB sites predicted by the current model (up to 80%) differs significantly from the constant reported in the literature (80%), which lacks analyses of three-phase percolation, gas phase paths, and gas/current collector boundary conditions. This dependence of active TPB formation on percolation of all three phases is important to understand as a basis for determining SOFC performance and optimization

  5. Percolative core formation in planetesimals enabled by hysteresis in metal connectivity

    Science.gov (United States)

    Ghanbarzadeh, Soheil; Hesse, Marc A.; Prodanović, Maša

    2017-12-01

    The segregation of dense core-forming melts by porous flow is a natural mechanism for core formation in early planetesimals. However, experimental observations show that texturally equilibrated metallic melt does not wet the silicate grain boundaries and tends to reside in isolated pockets that prevent percolation. Here we use pore-scale simulations to determine the minimum melt fraction required to induce porous flow, the percolation threshold. The composition of terrestrial planets suggests that typical planetesimals contain enough metal to overcome this threshold. Nevertheless, it is currently thought that melt segregation is prevented by a pinch-off at melt fractions slightly below the percolation threshold. In contrast to previous work, our simulations on irregular grain geometries reveal that a texturally equilibrated melt network remains connected down to melt fractions of only 1 to 2%. This hysteresis in melt connectivity allows percolative core formation in planetesimals that contain enough metal to exceed the percolation threshold. Evidence for the percolation of metallic melt is provided by X-ray microtomography of primitive achondrite Northwest Africa (NWA) 2993. Microstructural analysis shows that the metal–silicate interface has characteristics expected for a texturally equilibrated pore network with a dihedral angle of ˜85°. The melt network therefore remained close to textural equilibrium despite a complex history. This suggests that the hysteresis in melt connectivity is a viable process for percolative core formation in the parent bodies of primitive achondrites.

  6. A precise determination of the void percolation threshold for two distributions of overlapping spheres

    Energy Technology Data Exchange (ETDEWEB)

    RINTOUL,MARK DANIEL

    2000-01-25

    The void percolation threshold is calculated for a distribution of overlapping spheres with equal radii, and for a binary sized distribution of overlapping spheres, where half of the spheres have radii twice as large as the other half. Using systems much larger than previous work, the authors determine a much more precise value for the percolation thresholds and correlation length exponent. The values for the percolation thresholds are shown to be significantly different, in contrast with previous, less precise works that speculated that the threshold might be universal with respect to sphere size distribution.

  7. Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites

    Science.gov (United States)

    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.

  8. Surfactant Incorporated Co Nanoparticles Polymer Composites with Uniform Dispersion and Double Percolation

    Directory of Open Access Journals (Sweden)

    Tajamal Hussain

    2017-01-01

    Full Text Available Series of Cobalt nanoparticles incorporated polymethylmethacrylate composites in the presence and absence of dodecyl-benzene-sulphonic acid (DBSA-CoNPs/PMMA and CoNPs/PMMA, resp. were synthesized by solution mixing methodology. UV-visible and FTIR techniques were used to confirm the formation of nanocomposite. UV-visible spectra of the composites showed the incorporation of filler particles in the polymer matrix. On the other hand, FTIR spectra indicated the physical interaction between the two phases of the composite. Moreover, the electrical nature of the composites was studied by plotting graphs between electrical conductivity (measured using LCR meter at 100 kHz and contents of the filler particles as introduced in the polymer matrix. An increase in electrical conductivity was first observed with increasing filler concentration up to the critical percolation threshold value (0.5% for DBSA-CoNPs/PMMA and 1% for CoNPs/PMMA, which then dropped upon further increments in the filler content. However, at higher concentrations, a second jump in the conductivity was observed in case of DBSA-CoNPs/PMMA composites.

  9. Percolation model for growth rates of aggregates and its application for business firm growth.

    Science.gov (United States)

    Fu, Dongfeng; Buldyrev, Sergey V; Salinger, Michael A; Stanley, H Eugene

    2006-09-01

    Motivated by recent empirical studies of business firm growth, we develop a dynamic percolation model which captures some of the features of the economical system--i.e., merging and splitting of business firms--represented as aggregates on a d-dimensional lattice. We find the steady-state distribution of the aggregate size and explore how this distribution depends on the model parameters. We find that at the critical threshold, the standard deviation of the aggregate growth rates, sigma, increases with aggregate size S as sigma approximately S(beta), where beta can be explained in terms of the connectedness length exponent nu and the fractal dimension d(f), with beta=1(2nud(f)) approximately 0.20 for d=2 and 0.125 for d-->infinity. The distributions of aggregate growth rates have a sharp peak at the center and pronounced wings extending over many standard deviations, giving the distribution a tent-shape form--the Laplace distribution. The distributions for different aggregate sizes scaled by their standard deviations collapse onto the same curve.

  10. Intersection statistics and percolation criteria for fractures of mixed shapes and sizes

    Science.gov (United States)

    Barker, John A.

    2018-03-01

    A model that has been widely applied to fractured rock comprises randomly distributed and oriented plates. Formulae are given for the intersection statistics of infinite systems of such plates of mixed shapes and sizes with lines, planes and each other; the results are expressed in terms of the number density, n, and of the average area 〈 A 〉 and perimeter 〈 P 〉 of the plates. From Monte-Carlo studies it has been found that a mixture of elliptical plates, each of area A and perimeter P, at the dimensionless density ρ = n with k = 0.774 is approximately invariant at the percolation threshold with a critical value of about ρc = 8.2 ± 0.2 for aspect ratios up to 16. The same result is found to apply to any mixture of convex plate shapes and sizes provided that for each plate A and P are replaced by the area and perimeter of an ellipse with the same aspect ratio and product AP . The results should be of particular value in the interpretation of observed fracture statistics and in the construction of discrete fracture network models.

  11. The influence of water percolation on flow of light non aqueous phase liquids in soil

    NARCIS (Netherlands)

    Marsman, A.

    2002-01-01

    Keywords ,: multi-phase flow, entrapment, numerical modeling, similarity solution, horizontal migration, percolation theory, relative permeability.

    In this thesis the physical behavior of Light Non-Aqueous Phase Liquids (LNAPL) at the capillary

  12. Novel scaling of the multiplicity distributions in the sequential fragmentation process and in the percolation

    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)

  13. PRETREATMENT AND FRACTIONATION OF CORN STOVER BY AMMONIA RECYCLE PERCOLATION PROCESS. (R831645)

    Science.gov (United States)

    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...

  14. Influence maximization in complex networks through optimal percolation

    Science.gov (United States)

    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)

  15. Influence maximization in complex networks through optimal percolation

    Science.gov (United States)

    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.

  16. Application of leaching tests on phosphogypsum by infiltration-percolation.

    Science.gov (United States)

    Hassoune, H; Lahhit, M; Khalid, A; Lachehab, A

    2017-10-01

    The phosphoric acid production obtained by attacking phosphate rock by sulphuric acid cogenerates considerable quantities of phosphogypsum. The world cogeneration is estimated about 100-280 Mt per year. In another context of sustainable development, the phosphate chemical industry develops different ways of phosphogypsum valorization, which makes its storage stack in a suitable way for its potential use as an industrial by-product. Although, this storage can cause an environmental impact largely due to the transfer of trace elements (TEs) to groundwater by leaching. It is therefore important to evaluate the impact linked to the storage in order to limit this transfer. The evaluation is usually performed through leaching tests in columns or reactor. In this work, leaching tests were performed in columns by infiltration-percolation on two filter mediums: phosphogypsum and synthetic sandy soils. The results showed that the phosphogypsum is acting as a filter, which retains and releases the TEs. Most of these TEs (Pb, Se, Ag, Zn and Cu) were highly retained in the synthetic soils surfaces and their contents in waters were considerably lower than the maximum contaminant levels (MCLs). Although As, Cd, Cr and Ni were strongly transferred to groundwater, their respective contents were higher than the MCLs.

  17. Water percolation estimated with time domain reflectometry (TDR) in drainage lysimeters

    OpenAIRE

    Alisson Jadavi Pereira da Silva; Eugênio Ferreira Coelho

    2013-01-01

    Due to the difficulty of estimating water percolation in unsaturated soils, the purpose of this study was to estimate water percolation based on time-domain reflectometry (TDR). In two drainage lysimeters with different soil textures TDR probes were installed, forming a water monitoring system consisting of different numbers of probes. The soils were saturated and covered with plastic to prevent evaporation. Tests of internal drainage were carried out using a TDR 100 unit with constant dielec...

  18. Percolating macropore networks in tilled topsoil: effects of sample size, minimum pore thickness and soil type

    Science.gov (United States)

    Jarvis, Nicholas; Larsbo, Mats; Koestel, John; Keck, Hannes

    2017-04-01

    The long-range connectivity of macropore networks may exert a strong control on near-saturated and saturated hydraulic conductivity and the occurrence of preferential flow through soil. It has been suggested that percolation concepts may provide a suitable theoretical framework to characterize and quantify macropore connectivity, although this idea has not yet been thoroughly investigated. We tested the applicability of percolation concepts to describe macropore networks quantified by X-ray scanning at a resolution of 0.24 mm in eighteen cylinders (20 cm diameter and height) sampled from the ploughed layer of four soils of contrasting texture in east-central Sweden. The analyses were performed for sample sizes ("regions of interest", ROI) varying between 3 and 12 cm in cube side-length and for minimum pore thicknesses ranging between image resolution and 1 mm. Finite sample size effects were clearly found for ROI's of cube side-length smaller than ca. 6 cm. For larger sample sizes, the results showed the relevance of percolation concepts to soil macropore networks, with a close relationship found between imaged porosity and the fraction of the pore space which percolated (i.e. was connected from top to bottom of the ROI). The percolating fraction increased rapidly as a function of porosity above a small percolation threshold (1-4%). This reflects the ordered nature of the pore networks. The percolation relationships were similar for all four soils. Although pores larger than 1 mm appeared to be somewhat better connected, only small effects of minimum pore thickness were noted across the range of tested pore sizes. The utility of percolation concepts to describe the connectivity of more anisotropic macropore networks (e.g. in subsoil horizons) should also be tested, although with current X-ray scanning equipment it may prove difficult in many cases to analyze sufficiently large samples that would avoid finite size effects.

  19. Effective modelling of percolation at the landscape scale using data-based approaches

    Science.gov (United States)

    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.

  20. Note: Optimization of the numerical data analysis for conductivity percolation studies of drying moist porous systems

    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.

  1. Effects of centrifugation through three different discontinuous Percoll gradients on boar sperm function.

    Science.gov (United States)

    Matás, C; Vieira, L; García-Vázquez, F A; Avilés-López, K; López-Úbeda, R; Carvajal, J A; Gadea, J

    2011-08-01

    In this study, different combinations of 2-step, discontinuous gradient centrifugation were used, consisting of three different combinations of isotonic Percoll (45/60, 60/75 and 45/90%) that allowed us to select different sperm subpopulations from fertile and normozoospermic boars. Our objective in this study is to evaluate the effects of centrifugation through three different discontinuous Percoll gradients on sperm function parameters (motility, viability, morphology, acrosome status, chromatin condensation, DNA fragmentation, ROS generation, tyrosine phosphorylation and intracellular calcium concentration) and the sperm penetrating capacity in an IVF system. All the Percoll treatments evaluated increased the percentage of spermatozoa with normal morphology, the proportion of un-damaged DNA, normal chromatin condensation, motion parameters measured by CASA and the percentage of capacitated spermatozoa with tyrosine phosphorylated proteins compared to control group. Finally, the in vitro oocyte penetrating capacity of boar spermatozoa was significantly affected by Percoll centrifugation. All the Percoll treatments increased the penetration rates and mean number of sperm per penetrated oocyte. Despite the efficiency of all three of the sperm treatments tested in selecting spermatozoa with improved sperm parameters and capacity to penetrate oocytes in vitro, the optimum performance of this system was demonstrated after preselecting spermatozoa by centrifugation on a discontinuous 45/90 Percoll gradient. The P45/90 treatment leads to obtain a higher percentage of spermatozoa which develop properly the capacitation process as it was shown measuring tyrosine phosphorylation and intracellular calcium concentration. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Deep percolation in greenhouse-cultivated celery using the technique of subsurface film strips placement

    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.

  3. Monte Carlo simulations of electrical percolation in multicomponent thin films with nanofillers

    Science.gov (United States)

    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.

  4. Fibrillar organization in tendons: A pattern revealed by percolation characteristics of the respective geometric network

    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.

  5. Perturbation waves in proteins and protein networks: applications of percolation and game theories in signaling and drug design.

    Science.gov (United States)

    Antal, Miklós A; Böde, Csaba; Csermely, Peter

    2009-04-01

    The network paradigm is increasingly used to describe the dynamics of complex systems. Here we review the current results and propose future development areas in the assessment of perturbation waves, i.e. propagating structural changes in amino acid networks building individual protein molecules and in protein-protein interaction networks (interactomes). We assess the possibilities and critically review the initial attempts for the application of game theory to the often rather complicated process, when two protein molecules approach each other, mutually adjust their conformations via multiple communication steps and finally, bind to each other. We also summarize available data on the application of percolation theory for the prediction of amino acid network- and interactome-dynamics. Furthermore, we give an overview of the dissection of signals and noise in the cellular context of various perturbations. Finally, we propose possible applications of the reviewed methodologies in drug design.

  6. AC and DC electrical behavior of MWCNT/epoxy nanocomposite near percolation threshold: Equivalent circuits and percolation limits

    Science.gov (United States)

    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.

  7. TreeCluster: Massively scalable transmission clustering using phylogenetic trees

    OpenAIRE

    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...

  8. Cluster headache

    Science.gov (United States)

    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 ...

  9. Cluster assembly in nitrogenase.

    Science.gov (United States)

    Sickerman, Nathaniel S; Rettberg, Lee A; Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W

    2017-05-09

    The versatile enzyme system nitrogenase accomplishes the challenging reduction of N 2 and other substrates through the use of two main metalloclusters. For molybdenum nitrogenase, the catalytic component NifDK contains the [Fe 8 S 7 ]-core P-cluster and a [MoFe 7 S 9 C-homocitrate] cofactor called the M-cluster. These chemically unprecedented metalloclusters play a critical role in the reduction of N 2 , and both originate from [Fe 4 S 4 ] clusters produced by the actions of NifS and NifU. Maturation of P-cluster begins with a pair of these [Fe 4 S 4 ] clusters on NifDK called the P*-cluster. An accessory protein NifZ aids in P-cluster fusion, and reductive coupling is facilitated by NifH in a stepwise manner to form P-cluster on each half of NifDK. For M-cluster biosynthesis, two [Fe 4 S 4 ] clusters on NifB are coupled with a carbon atom in a radical-SAM dependent process, and concomitant addition of a 'ninth' sulfur atom generates the [Fe 8 S 9 C]-core L-cluster. On the scaffold protein NifEN, L-cluster is matured to M-cluster by the addition of Mo and homocitrate provided by NifH. Finally, matured M-cluster in NifEN is directly transferred to NifDK, where a conformational change locks the cofactor in place. Mechanistic insights into these fascinating biosynthetic processes are detailed in this chapter. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  10. 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.

  11. Water percolation estimated with time domain reflectometry (TDR in drainage lysimeters

    Directory of Open Access Journals (Sweden)

    Alisson Jadavi Pereira da Silva

    2013-08-01

    Full Text Available Due to the difficulty of estimating water percolation in unsaturated soils, the purpose of this study was to estimate water percolation based on time-domain reflectometry (TDR. In two drainage lysimeters with different soil textures TDR probes were installed, forming a water monitoring system consisting of different numbers of probes. The soils were saturated and covered with plastic to prevent evaporation. Tests of internal drainage were carried out using a TDR 100 unit with constant dielectric readings (every 15 min. To test the consistency of TDR-estimated percolation levels in comparison with the observed leachate levels in the drainage lysimeters, the combined null hypothesis was tested at 5 % probability. A higher number of probes in the water monitoring system resulted in an approximation of the percolation levels estimated from TDR - based moisture data to the levels measured by lysimeters. The definition of the number of probes required for water monitoring to estimate water percolation by TDR depends on the soil physical properties. For sandy clay soils, three batteries with four probes installed at depths of 0.20, 0.40, 0.60, and 0.80 m, at a distance of 0.20, 0.40 and 0.6 m from the center of lysimeters were sufficient to estimate percolation levels equivalent to the observed. In the sandy loam soils, the observed and predicted percolation levels were not equivalent even when using four batteries with four probes each, at depths of 0.20, 0.40, 0.60, and 0.80 m.

  12. 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

  13. Electrical percolation threshold of magnetostrictive inclusions in a piezoelectric matrix composite as a function of relative particle size

    Science.gov (United States)

    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.

  14. A critical assessment of geographic clusters of breast and lung cancer incidences among residents living near the Tittabawassee and Saginaw Rivers, Michigan, USA.

    Science.gov (United States)

    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.

  15. A Critical Assessment of Geographic Clusters of Breast and Lung Cancer Incidences among Residents Living near the Tittabawassee and Saginaw Rivers, Michigan, USA

    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.

  16. A Critical Assessment of Geographic Clusters of Breast and Lung Cancer Incidences among Residents Living near the Tittabawassee and Saginaw Rivers, Michigan, USA

    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.

  17. Selective Laser Direct Patterning of Silver Nanowire Percolation Network Transparent Conductor for Capacitive Touch Panel.

    Science.gov (United States)

    Hong, Sukjoon; Yeo, Junyeob; Lee, Jinhwan; Lee, Habeom; Lee, Phillip; Lee, Seung S; Ko, Seung Hwan

    2015-03-01

    We introduce a facile method to enhance the functionality of a patterned metallic transparent conductor through selective laser ablation of metal nanowire percolation network. By scanning focused nanosecond pulsed laser on silver nanowire percolation network, silver nanowires are selectively ablated and patterned without using any conventional chemical etching or photolithography steps. Various arbitrary patterns of silver nanowire transparent conductors are readily created on the percolation network by changing various laser parameters such as repetition rate and power. The macroscopic optical and electrical properties of the percolation network transparent conductor can be easily tuned by changing the conductor pattern design via digital selective laser ablation. Further investigation on the silver nanowire based electrode line prepared by the ablation process substantiates that the general relation for a conducting thin film fails at a narrow width, which should be considered for the applications that requires a high resolution patterns. Finally, as a proof of concept, a capacitive touch sensor with diamond patterns has been demonstrated by selective laser ablation of metal nanowire percolation network.

  18. Dynamical arrest, percolation, gelation, and glass formation in model nanoparticle dispersions with thermoreversible adhesive interactions.

    Science.gov (United States)

    Eberle, Aaron P R; Castañeda-Priego, Ramón; Kim, Jung M; Wagner, Norman J

    2012-01-24

    We report an experimental study of the dynamical arrest transition for a model system consisting of octadecyl coated silica suspended in n-tetradecane from dilute to concentrated conditions spanning the state diagram. The dispersion's interparticle potential is tuned by temperature affecting the brush conformation leading to a thermoreversible model system. The critical temperature for dynamical arrest, T*, is determined as a function of dispersion volume fraction by small-amplitude dynamic oscillatory shear rheology. We corroborate this transition temperature by measuring a power-law decay of the autocorrelation function and a loss of ergodicity via fiber-optic quasi-elastic light scattering. The structure at T* is measured using small-angle neutron scattering. The scattering intensity is fit to extract the interparticle pair-potential using the Ornstein-Zernike equation with the Percus-Yevick closure approximation, assuming a square-well interaction potential with a short-range interaction (1% of particle diameter). (1) The strength of attraction is characterized using the Baxter temperature (2) and mapped onto the adhesive hard sphere state diagram. The experiments show a continuous dynamical arrest transition line that follows the predicted dynamical percolation line until ϕ ≈ 0.41 where it subtends the predictions toward the mode coupling theory attractive-driven glass line. An alternative analysis of the phase transition through the reduced second virial coefficient B(2)* shows a change in the functional dependence of B(2)* on particle concentration around ϕ ≈ 0.36. We propose this signifies the location of a gel-to-glass transition. The results presented herein differ from those observed for depletion flocculated dispersion of micrometer-sized particles in polymer solutions, where dynamical arrest is a consequence of multicomponent phase separation, suggesting dynamical arrest is sensitive to the physical mechanism of attraction.

  19. Percolation in finite space. A picture of nuclear fragmentation

    International Nuclear Information System (INIS)

    Biro, T.S.; Knoll, J.; Richert, J.

    1985-12-01

    The statistical aspects of cluster distributions as a decisive factor in high energy nuclear fragmentation are studied on a finite lattice model. The qualitative behaviour of the mass spectra is understood in terms of a simple model in which finite space constraints play the main role. Both, the light and the heavy mass sector of the spectrum are derived analytically. In the low density regime the model includes those results of Fisher's condensation theory which are frequently applied to nuclear fragmentation. (orig.)

  20. Dependence of mechanical performances of polymer/carbon nanotubes nanocomposites on percolation threshold

    Science.gov (United States)

    Nikfar, Nafiseh; Zare, Yasser; Rhee, Kyong Yop

    2018-03-01

    In this study, several models for the tensile modulus and strength of polymer/carbon nanotubes (CNT) nanocomposites (PCNT) are expressed as a function of percolation threshold. The roles of the CNT aspect ratio α and percolation threshold φp in the mechanical properties of PCNT are plotted according to the original and developed models. Furthermore, the effects of φp and various interfacial/interphase parameters on the PCNT tensile strength are presented through contour plots. The tensile modulus and strength of PCNT show a threshold at low φp values, indicating the important effect of the percolation behavior on the mechanical properties. Poor mechanical performances are seen at high φp values and different ranges of interfacial/interphase parameters. However, the lowest φp values and the highest ranges of interfacial/interphase parameters result in the most desirable PCNT strength.

  1. 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

    damage with TPL images being sensitive to both wavelength and polarization of illuminating light. We relate these effects to thermally induced morphological changes observed with scanning electron microscopy images. Exciting physics involved in light interaction with near-percolation metal films along...... 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...

  2. Continuum percolation of polydisperse rods in quadrupole fields: Theory and simulations

    Science.gov (United States)

    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.

  3. 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

  4. Percolation model of excess electrical noise in transition-edge sensors

    Energy Technology Data Exchange (ETDEWEB)

    Lindeman, M.A. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)]. E-mail: lindeman@wisp.physics.wisc.edu; Anderson, M.B. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Bandler, S.R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bilgri, N. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Chervenak, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gwynne Crowder, S. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Fallows, S. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Figueroa-Feliciano, E. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Finkbeiner, F. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Iyomoto, N. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Kelley, R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Kilbourne, C.A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Lai, T. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Man, J. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); McCammon, D. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Nelms, K.L. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Porter, F.S. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Rocks, L.E. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Saab, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Sadleir, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Vidugiris, G. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

    2006-04-15

    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{sub N}) and that perpendicular zebra stripes reduce noise and alpha of the TES by reducing percolation.

  5. Cluster Headache

    Science.gov (United States)

    ... re at risk of cluster headache. A family history. Having a parent or sibling who has had cluster headache might ... of Nondiscrimination Advertising Mayo Clinic is a not-for-profit organization ...

  6. The influence of percolation rate on the weathering rates of silicates in an E horizon of an Umbric Albaqualf

    NARCIS (Netherlands)

    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

  7. Meaningful Clusters

    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.

  8. Cluster formation of network-modifier cations in cesium silicate glasses

    Science.gov (United States)

    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.

  9. The effect of counterion and percolation on the toxicity of lead for the springtail Folsomia candida in soil.

    Science.gov (United States)

    Bongers, Marina; Rusch, Ben; Van Gestel, Cornelis A M

    2004-01-01

    In standard soil toxicity tests, heavy metals are amended as water-soluble salts. The role of the counterion in metal salt toxicity is scarcely looked into. In this study, we assessed the contribution of nitrate and chloride to the toxicity of lead to Folsomia candida in a natural standard soil. Both lead salts were tested according the standard test protocol as well as after percolation of the soil with deionized water. Lead nitrate was more toxic than lead chloride for survival as well as reproduction. Percolation proved to be an effective method to remove counterions from the soil. Survival of F. candida increased for both metal salts when percolation was included. Percolation reduced the reproduction toxicity of lead, the effect of which was largest for the nitrate salt. In percolated treatments, the nitrate and chloride lead salts did not differ in toxicity. It is concluded that counterions contribute to metal toxicity and that nitrate is more toxic to F. candida than chloride.

  10. Spatial Variability of accumulation across the Western Greenland Ice Sheet Percolation Zone from ground-penetrating-radar and shallow firn cores

    Science.gov (United States)

    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.

  11. [Experiment and numerical simulation of percolation control using evapotranspirative landfill cover system].

    Science.gov (United States)

    Liu, Chuan-shun; Zhao, Hui; Luo, Ji-wu

    2009-01-01

    An Evapotranspirative Landfill Cover (ET Landfill Cover) is a simple and economical percolation control system that involves a monolithic soil layer with a vegetative cover.Percolation control in an ET cover system relies on the storage of moisture within the cover soils during precipitation events and subsequently returns it to the atmosphere by evapotranspiration. Percolation control experiments of a bare soil cover and 5 different ET covers were implemented in comprehensive experimental station of water environment of Wuhan University and the water balance calculation of each cover system was conducted, the results shown that the ET cover of 60 cm loamy soil layer with shrub was the most effective among the 6 experimental disposals. However, the experiments demonstrated 60 cm thick of soil layer was not enough to prevent percolation during rainy season and keep the shrub alive during drought season without irrigation. So the Hydrus 2D was selected to simulate the soil water movement in ET covers with different cover thicknesses, the simulations shown that the optimal ET cover in Wuhan area should be 120-140 cm loamy soil layer with shrub.

  12. 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

  13. Extreme value theory, Poisson-Dirichlet distributions, and first passage percolation on random networks

    NARCIS (Netherlands)

    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

  14. The "weak" interdependence of infrastructure systems produces mixed percolation transitions in multilayer networks.

    Science.gov (United States)

    Liu, Run-Ran; Eisenberg, Daniel A; Seager, Thomas P; Lai, Ying-Cheng

    2018-02-01

    Previous studies of multilayer network robustness model cascading failures via a node-to-node percolation process that assumes "strong" interdependence across layers-once a node in any layer fails, its neighbors in other layers fail immediately and completely with all links removed. This assumption is not true of real interdependent infrastructures that have emergency procedures to buffer against cascades. In this work, we consider a node-to-link failure propagation mechanism and establish "weak" interdependence across layers via a tolerance parameter α which quantifies the likelihood that a node survives when one of its interdependent neighbors fails. Analytical and numerical results show that weak interdependence produces a striking phenomenon: layers at different positions within the multilayer system experience distinct percolation transitions. Especially, layers with high super degree values percolate in an abrupt manner, while those with low super degree values exhibit both continuous and discontinuous transitions. This novel phenomenon we call mixed percolation transitions has significant implications for network robustness. Previous results that do not consider cascade tolerance and layer super degree may be under- or over-estimating the vulnerability of real systems. Moreover, our model reveals how nodal protection activities influence failure dynamics in interdependent, multilayer systems.

  15. Global physics: from percolation to terrorism, guerilla warfare and clandestine activities

    Science.gov (United States)

    Galam, Serge

    2003-12-01

    The September 11 attack on the US has revealed an unprecedented terrorism with worldwide range of destruction. It is argued to result from the first worldwide percolation of passive supporters. They are people sympathetic to the terrorism cause but without being involved with it. They just do not oppose it in case they could. This scheme puts suppression of the percolation as the major strategic issue in the fight against terrorism. Acting on the population is shown to be useless. Instead a new strategic scheme is suggested to increase the terrorism percolation threshold and in turn suppress the percolation. The relevant associated space is identified as a multi-dimensional social space including both the ground earth surface and all various independent flags displayed by the terrorist group. Some hints are given on how to shrink the geographical spreading of terrorism threat. The model apply to a large spectrum of clandestine activities including guerilla warfare as well as tax evasion, corruption, illegal gambling, illegal prostitution and black markets.

  16. Lateral Percolation and Its Effect on Shale Gas Accumulation on the Basis of Complex Tectonic Background

    Directory of Open Access Journals (Sweden)

    Kun Zhang

    2018-01-01

    Full Text Available As a result of complex tectonic background, shale gas in China exhibits differential enrichment. Choosing a favorable exploration target accurately is a crucial problem to be solved. In this study, the tests show that there is a superior transportation pathway within shale layer. Gas in the shale layer percolates much more in the direction parallel to the plane. Therefore, the accumulation pattern of shale gas indicates a complex tectonic background. Gas in the lower part of the structure diffuses and percolates in the vertical direction into the surrounding rock. Most gas percolates towards the high part of the structure in the direction parallel to the plane. When the shale was exposed, gas percolated along the parallel direction into the air. In the case of fracture development, if there is a reverse fault, gas would be enriched in the footwall. However, if there is an unsealed fault, it would become a pathway for gas migration. The above accumulation pattern was proved in several Areas. Also, this research presented a basis of evaluation units division. According to the buried depth, fractures, and structural position, Xiuwu Basin was divided into five evaluation units and Unit A3 is the most favorable exploration target.

  17. Percolation blockage: A process that enables melt pond formation on first year Arctic sea ice

    Science.gov (United States)

    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.

  18. 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

  19. Electronic properties of GaV4S8: A percolation approach

    Indian Academy of Sciences (India)

    Electronic properties of GaV4S8: A percolation approach. I NAIK1,∗, S HANSDA1 and A K RASTOGI2. 1Department of Physics, North Orissa University, Baripada 757 003, India. 2School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 067, India. ∗. Corresponding author. E-mail: indrajit_naik@yahoo.co.

  20. Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, S.; Ambus, Per

    2014-01-01

    unplanted soil. Carbon dioxide partial pressure (pCO(2)), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO(2) varied between 0...

  1. 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

  2. Dispersion in porous media, continuous-time random walks, and percolation.

    Science.gov (United States)

    Sahimi, Muhammad

    2012-01-01

    A promising approach to the modeling of anomalous (non-Gaussian) dispersion in flow through heterogeneous porous media is the continuous-time random walk (CTRW) method. In such a formula on the waiting time distribution ψ(t) is usually assumed to be given by ψ(t)∼t-1-α, with α fitted to the experimental data. The exponent α is also related to the power-law growth of the mean-square displacement of the solute with the time t ∼ tζ. Invoking percolation and using a scaling analysis, we relate α to the geometrical exponents of percolation (ν, β, and βB) as well as the exponents μ and e that characterize the power-law behavior of the effective conductivity and permeability of porous media near the percolation threshold. We then explain the cause of the nonuniversality of α in terms of the nonuniversality of μ and e in continuum systems, and in percolation models with long-range correlations, and propose bounds for it. The results are consistent with the experimental data, both at the laboratory and field scales.

  3. 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

  4. Transmission electron microscopy for characterization of acrosomal damage after Percoll gradient centrifugation of cryopreserved bovine spermatozoa

    Science.gov (United States)

    Hossepian de Lima, Vera F. M.; Levenhagen, Marcelo A.; dos Santos, Ricarda M.; Assumpção, Terezinha I.; Jacomini, José O.; de Andrade, André F. C.; de Arruda, Rubens P.; Beletti, Marcelo E.

    2011-01-01

    The objective of this study was to characterize acrosomal ultrastructure following discontinuous Percoll gradient centrifugation of cryopreserved bovine sperm. Semen was collected from six bulls of different breeds and three ejaculates per bull were evaluated. Frozen semen samples were thawed and the acrosomal region of sperm cells was evaluated by transmission electron microscopy (TEM) before (n = 18) and after (n = 18) Percoll centrifugation. The evaluation of 20 sperm heads from each of the 36 samples analyzed ensured that a large number of cells were investigated. The data were subjected to analysis of variance at a level of significance of 5%. Percoll centrifugation reduced the percentage of sperm exhibiting normal acrosomes (from 61.77 to 30.24%), reduced the percentage of sperm presenting atypical acrosome reactions (from 28.38 to 4.84%) and increased the percentage of sperm exhibiting damage in the acrosome (from 6.14 to 64.26%). The percentage of sperm with typical acrosome reactions was not significantly different before (3.70%) and after (0.67%) centrifugation. TEM distinguished four different types of acrosomal status and enabled ultrastructural characterization of acrosomal injuries. The percentage of sperm exhibiting normal acrosomes decreased and damage in the acrosome was the most frequent acrosomal injury with the Percoll gradient centrifugation protocol utilized. PMID:21897100

  5. Explosive percolation on directed networks due to monotonic flow of activity

    Science.gov (United States)

    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.

  6. 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

  7. Rethinking Rice Preparation for Highly Efficient Removal of Inorganic Arsenic Using Percolating Cooking Water

    Science.gov (United States)

    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. PMID:26200355

  8. Data Clustering

    Science.gov (United States)

    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

  9. Influence of Rolling Friction Coefficient on Inter-Particle Percolation in a Packed Bed by Discrete Element Method

    Directory of Open Access Journals (Sweden)

    Zhou Heng

    2016-12-01

    Full Text Available Rolling friction representing the energy dissipation mechanism with the elastic deformation at the contact point could act directly on particle percolation. The present investigation intends to elucidate the influence of rolling friction coefficient on inter-particle percolation in a packed bed by discrete element method (DEM. The results show that the vertical velocity of percolating particles decreases with increasing the rolling friction coefficient. With the increase of rolling friction coefficient, the transverse dispersion coefficient decreases, but the longitudinal dispersion coefficient increases. Packing height has a limited effect on the transverse and longitudinal dispersion coefficient. In addition, with the increase of size ratio of bed particles to percolation ones, the percolation velocity increases. The transverse dispersion coefficient increases with the size ratio before D/d<14. And it would keep constant when the size ratio is greater than 14. The longitudinal dispersion coefficient decreases when the size ratio increases up to D/d=14, then increases with the increase of the size ratio. External forces affect the percolation behaviours. Increasing the magnitude of the upward force (e.g. from a gas stream reduces the percolation velocity, and decreases the dispersion coefficient.

  10. A New Insight in Determining the Percolation Threshold of Electrical Conductivity for Extrinsically Conducting Polymer Composites through Different Sigmoidal Models

    Directory of Open Access Journals (Sweden)

    Mostafizur Rahaman

    2017-10-01

    Full Text Available The electrical conductivity of extrinsically conducting polymer composite systems passes through a transition state known as percolation threshold. A discussion has been made on how different Sigmoidal models (S-models, such as Sigmoidal–Boltzmann (SB, Sigmoidal–Dose Response (SD, Sigmoidal–Hill (SH, Sigmoidal–Logistic (SL, and Sigmoidal–Logistic-1 (SL-1, can be applied to predict the percolation threshold of electrical conductivity for ethylene vinyl acetate copolymer (EVA and acrylonitrile butadiene copolymer (NBR conducting composite systems filled with different carbon fillers. An interesting finding that comes from these observations is that the percolation threshold for electrical conductivity determined by SB and SD models are similar, whereas, the other models give different result when estimated for a particular composite system. This similarity and discrepancy in the results of percolation threshold have been discussed by considering the strength, weakness, and limitation of the models. The percolation threshold value for the composites has also been determined using the classical percolation theory and compared with the sigmoidal models. Moreover, to check the universal applicability, these Sigmoidal models have also been tested on results from some published literature. Finally, it is revealed that, except SL-1 model, the remaining models can successfully be used to determine the percolation threshold of electrical conductivity for extrinsically conductive polymer composites.

  11. Weak-lensing calibration of a stellar mass-based mass proxy for redMaPPer and Voronoi Tessellation clusters in SDSS Stripe 82

    Science.gov (United States)

    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.

  12. Detecting Critical Scales in Fragmented Landscapes

    Directory of Open Access Journals (Sweden)

    Timothy Keitt

    1997-06-01

    Full Text Available We develop methods for quantifying habitat connectivity at multiple scales and assigning conservation priority to habitat patches based on their contribution to connectivity. By representing the habitat mosaic as a mathematical "graph," we show that percolation theory can be used to quantify connectivity at multiple scales from empirical landscape data. Our results indicate that connectivity of landscapes is highly scale dependent, exhibiting a marked transition at a characteristic distance and varying significantly for organisms with different dispersal behavior. More importantly, we show that the sensitivity and importance of landscape pattern is also scale dependent, peaking at scales associated with the percolation transition. In addition, the sensitivity analysis allows us to identify critical "stepping stone" patches that, when removed from the landscape, cause large changes in connectivity.

  13. A strategy for achieving low percolation and high electrical conductivity in melt-blended polycarbonate (PC/multiwall carbon nanotube (MWCNT nanocomposites: Electrical and thermo-mechanical properties

    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.

  14. CRITICAL CONFIGURATION AND PHYSICS MEASUREMENTS FOR BERYLLIUM REFLECTED ASSEMBLIES OF U(93.15)O2 FUEL RODS (1.506-CM PITCH AND 7-TUBE CLUSTERS)

    Energy Technology Data Exchange (ETDEWEB)

    Margaret A. Marshall

    2014-03-01

    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

  15. Critical Configuration and Physics Measurements for Beryllium Reflected Assemblies of U(93.15)O₂ Fuel Rods (1.506-cm Pitch and 7-Tube Clusters)

    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

  16. Detection of Percolating Paths in PMMA/CB Segregated Network Composites Using Electrostatic Force Microscopy and Conductive Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Waddell, J. [Georgia Institute of Technology; Ou, R. [Georgia Institute of Technology; Gupta, S. [Georgia Institute of Technology; Parker, A. [Georgia Institute of Technology; Gerhardt, Dr. Rosario [Georgia Institute of Technology; Seal, Katyayani [ORNL; Kalinin, Sergei V [ORNL; Baddorf, Arthur P [ORNL

    2009-01-01

    Composite specimens possessing polyhedral segregated network microstructures require a very small amount of nanosize filler, <1 vol %, to reach percolation because percolation occurs by accumulation of the fillers along the edges of the deformed polymer matrix particles. In this paper, electrostatic force microscopy (EFM) and conductive atomic force microscopy (C-AFM) were used to confirm the location of the nanosize fillers and the corresponding percolating paths in polymethyl methacrylate/carbon black composites. The EFM and C-AFM images revealed that the polyhedral polymer particles were coated with filler, primarily on the edges as predicted by the geometric models provided.

  17. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina

    2012-01-01

    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...

  18. Cluster editing

    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...

  19. Predicting saturated hydraulic conductivity from percolation test results in layered silt loam soils.

    Science.gov (United States)

    Jabro, Jay D

    2009-12-01

    The objectives of the study discussed in this article were to develop an empirical relationship between the saturated hydraulic conductivity (Ks) of layered soils and their percolation times (PT) in order to understand the influence of individual layers and compare this with the equations developed by Winneberger (1974) and Fritton, Ratvasky, and Petersen (1986). Field research was conducted on three silt loam soils. Six holes were spaced evenly in two parallel rows of three holes. The Ks was measured at three different layers for each soil using a constant head well permeameter. After completion of the second Ks measurement, the percolation test was conducted. Three linear equations for the upper, middle, and lower layers were developed between the Ks values of each individual layer in all three sites and the corresponding PT. Significant differences were found between the author's results and those predicted by Winneberger (1974) and Fritton and co-authors (1986).

  20. Transport processes in macroscopically disordered media from mean field theory to percolation

    CERN Document Server

    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...

  1. Charge percolation pathways in polymer blend photovoltaic diodes with sub-mesoscopic two-phase microstructures

    Science.gov (United States)

    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.

  2. 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...... occur even in periods of constant surface climate, and consequently unchanged mass balance, as a delayed response to previous changes of the local surface climate. Forcing the model with cyclic temperature variations mimicking fluctuations of West Greenland instrumental temperature records during...

  3. Interstellar Travel and Galactic Colonization: Insights from Percolation Theory and the Yule Process.

    Science.gov (United States)

    Lingam, Manasvi

    2016-06-01

    In this paper, percolation theory is employed to place tentative bounds on the probability p of interstellar travel and the emergence of a civilization (or panspermia) that colonizes the entire Galaxy. The ensuing ramifications with regard to the Fermi paradox are also explored. In particular, it is suggested that the correlation function of inhabited exoplanets can be used to observationally constrain p in the near future. It is shown, by using a mathematical evolution model known as the Yule process, that the probability distribution for civilizations with a given number of colonized worlds is likely to exhibit a power-law tail. Some of the dynamical aspects of this issue, including the question of timescales and generalizing percolation theory, were also studied. The limitations of these models, and other avenues for future inquiry, are also outlined. Complex life-Extraterrestrial life-Panspermia-Life detection-SETI. Astrobiology 16, 418-426.

  4. Evaluation of Mechanical Properties in Nanocomposites Containing Carbon Nanotubes Below and Above Percolation Threshold

    Science.gov (United States)

    Zare, Yasser; Rhee, Kyong Yop

    2017-12-01

    In this paper, several models are introduced for tensile modulus and strength of polymer nanocomposites containing dispersed and networked carbon nanotubes (CNT) below and above percolation threshold. The model predictions are compared in similar conditions to determine the role of nanoparticle structure in the mechanical properties of polymer/CNT nanocomposites (PCNT). The predictions are also compared with the experimental data of several samples to offer the suitable models for the mechanical properties of PCNT. Lastly, the influences of the main parameters on the tensile modulus and strength of PCNT are studied. The networked nanoparticles cause higher levels of modulus and strength compared to the dispersed nanoparticles. The high level of the CNT aspect ratio causes a small percolation threshold in PCNT, but the Ouali model shows the ineffective role of this parameter in their predictions.

  5. Measurement of cation exchange capacity (CEC) on natural zeolite by percolation method

    Science.gov (United States)

    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.

  6. A new percolation model for composite solid electrolytes and dispersed ionic conductors

    Science.gov (United States)

    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.

  7. Criticality in the slowed-down boiling crisis at zero gravity.

    Science.gov (United States)

    Charignon, T; Lloveras, P; Chatain, D; Truskinovsky, L; Vives, E; Beysens, D; Nikolayev, V S

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.

  8. Percolation network in resistive switching devices with the structure of silver/amorphous silicon/p-type silicon

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yanhong; Gao, Ping; Bi, Kaifeng; Peng, Wei [School of Physics and Optoelectronic Engineering, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi District, Dalian 116024 (China); Jiang, Xuening; Xu, Hongxia [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi District, Dalian116024 (China)

    2014-01-27

    Conducting pathway of percolation network was identified in resistive switching devices (RSDs) with the structure of silver/amorphous silicon/p-type silicon (Ag/a-Si/p-Si) based on its gradual RESET-process and the stochastic complex impedance spectroscopy characteristics (CIS). The formation of the percolation network is attributed to amounts of nanocrystalline Si particles as well as defect sites embedded in a-Si layer, in which the defect sites supply positions for Ag ions to nucleate and grow. The similar percolation network has been only observed in Ag-Ge-Se based RSD before. This report provides a better understanding for electric properties of RSD based on the percolation network.

  9. Microscale electrostatic fractional capacitors using reduced graphene oxide percolated polymer composites

    KAUST Repository

    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.

  10. Seasonal variation in bioaerosol exposure during biowaste collection and measurements of leaked percolate

    DEFF Research Database (Denmark)

    Nielsen, Birgitte Herbert; Nielsen, Eva Møller; Breum, Niels O.

    2000-01-01

    The seasonal variation in waste collectors' exposure to microorganisms, endotoxin and dust was measured with personal sampling equipment. The measurement was carried out in three different combinations of storage and collection system for biowaste: container/compactor truck (CIC), paper sack/comp...... of percolate generated in biowaste may constitute a potential health hazard to waste collectors on account of the high concentrations of microorganisms and the risk of splashing during collection....

  11. Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics

    OpenAIRE

    Park, Jae Sung; Kim, Taeil; Kim, Woo Soo

    2017-01-01

    We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 102 S/cm has been achieved from the demonstrated 3D...

  12. Parameterizing deep water percolation improves subsurface temperature simulations by a multilayer firn model

    Science.gov (United States)

    Marchenko, Sergey; van Pelt, Ward J. J.; Claremar, Björn; Pohjola, Veijo; Pettersson, Rickard; Machguth, Horst; Reijmer, Carleen

    2017-03-01

    Deep preferential percolation of melt water in snow and firn brings water lower along the vertical profile than a laterally homogeneous wetting front. This widely recognized process is an important source of uncertainty in simulations of subsurface temperature, density and water content in seasonal snow and in firn packs on glaciers and ice sheets. However, observation and quantification of preferential flow is challenging and therefore it is not accounted for by most of the contemporary snow/firn models. Here we use temperature measurements in the accumulation zone of Lomonosovfonna, Svalbard, done in April 2012 - 2015 using multiple thermistor strings to describe the process of water percolation in snow and firn. Effects of water flow through the snow and firn profile are further explored using a coupled surface energy balance - firn model forced by the output of the regional climate model WRF. In situ air temperature, radiation and surface height change measurements are used to constrain the surface energy and mass fluxes. To account for the effects of preferential water flow in snow and firn we test a set of depth-dependent functions allocating a certain fraction of the melt water available at the surface to each snow/firn layer. Experiments are performed for a range of characteristic percolation depths and results indicate a reduction in root mean square difference between the modeled and measured temperature by up to a factor of two compared to the results from the default water infiltration scheme. This illustrates the significance of accounting for preferential water percolation to simulate subsurface conditions. The suggested approach to parameterization of the preferential water flow requires low additional computational cost and can be implemented in layered snow/firn models applied both at local and regional scales, for distributed domains with multiple mesh points.

  13. Clustering Dycom

    KAUST Repository

    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.

  14. Quantitative characterization of the formation of an interpenetrating phase composite in polystyrene from the percolation of multiwalled carbon nanotubes

    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

  15. 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.

  16. 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)

  17. Gradient sperm selection for reproductive techniques in cattle: Is Isolate a suitable replacement for Percoll?

    Science.gov (United States)

    Sepúlveda, B; Arias, M E; Aguila, L; Zambrano, F; Sánchez, R; Felmer, R

    2018-04-01

    In assisted reproductive techniques, it is essential to perform a sperm selection to obtain spermatozoa with high motility and membrane integrity for in vitro fertilisation (IVF) and high-DNA integrity for intracytoplasmic sperm injection (ICSI). In this study, we evaluated whether Isolate ® was a suitable substitute for Percoll ® for assisted reproductive techniques. Commercial cryopreserved bovine semen was used after selection in both gradients, and plasma and acrosome membrane integrity, reactive oxygen species (ROS) levels, DNA integrity and mitochondrial membrane potential (ΔΨm) were assessed by flow cytometry. Motility parameters were also evaluated by CASA system. A similar percentage of spermatozoa with intact plasma membrane, acrosome integrity and high ΔΨm was observed in both sperm selection methods, but only Percoll ® showed higher percentage of spermatozoa with intact plasma and acrosome membrane compared to the post-thawing group. No differences were observed in the motility, ROS, DNA fragmentation and on the in vitro embryo production in all experimental groups. In conclusion, the selection of bovine spermatozoa with Isolate ® generates spermatozoa with similar quality parameters and embryonic development compared to Percoll ® providing a suitable alternative sperm selection method for assisted reproductive techniques in this species. © 2017 Blackwell Verlag GmbH.

  18. 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)

  19. Lightweight polypropylene/stainless-steel fiber composite foams with low percolation for efficient electromagnetic interference shielding.

    Science.gov (United States)

    Ameli, Aboutaleb; Nofar, Mohammadreza; Wang, Sai; Park, Chul B

    2014-07-23

    Lightweight polypropylene/stainless-steel fiber (PP-SSF) composites with 15-35% density reduction were fabricated using foam injection molding. The electrical percolation threshold, through-plane electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of the PP-SSF composite foams were characterized and compared against the solid counterparts. With 3 wt % CO2 dissolved in PP as a temporary plasticizer and lubricant, the fiber breakage was significantly decreased during injection molding, and well-dispersed fibers with unprecedentedly large aspect ratios of over 100 were achieved. The percolation threshold was dramatically decreased from 0.85 to 0.21 vol %, accounting for 75% reduction, which is highly superior, compared to 28% reduction of the previous PP-carbon fiber composite foam.1 Unlike the case of carbon fiber,1 SSFs were much longer than the cell size, and the percolation threshold reduction of PP-SSF composite foams was thus primarily governed by the decreased fiber breakage instead of fiber orientation. The specific EMI SE was also significantly enhanced. A maximum specific EMI SE of 75 dB·g(-1)·cm(3) was achieved in PP-1.1 vol % SSF composite foams, which was much higher than that of the solid counterpart. Also, the relationships between the microstructure and properties were discussed. The mechanism of EMI shielding enhancement was also studied.

  20. When the collective acts on its components: economic crisis autocatalytic percolation

    Science.gov (United States)

    Cantono, S.; Solomon, S.

    2010-07-01

    Agent-based models have improved the standards for empirical support and validation criteria in social, biological, cognitive and human sciences. Yet, the inclusion, in these models, of vertical interactions between various aggregation levels remains a challenge. We study analytically, numerically and by simulation the generic consequences of interactions between the collective and its individual components: the appearance of an autocatalytic loop between the dynamics of the collective and its components; the system, which is dominated by a limited number of factors amplified by this collectiveindividuals autocatalytic loop; the microscopic features, which are not involved in the autocatalytic loop and are irrelevant at the systemic level; and how the above clarify the interplay between macroscopic predictable features and the ones dependent on random unpredictable individual events. Using the social and market percolation framework, we study the dramatic effects of the collectiveindividuals autocatalytic loop on economic crisis propagation: the percolation transition becomes discontinuous; there are a few relevant regions and regimes corresponding to a quite diverse range of response policy options; there are stability ranges where appropriate policies can help to avoid macroscopic crisis percolation; and beyond those regions the systemic crisis might become unstoppable.

  1. Searching for low percolation thresholds within amphiphilic polymer membranes: The effect of side chain branching

    Science.gov (United States)

    Dorenbos, G.

    2015-06-01

    Percolation thresholds for solvent diffusion within hydrated model polymeric membranes are derived from dissipative particle dynamics in combination with Monte Carlo (MC) tracer diffusion calculations. The polymer backbones are composed of hydrophobic A beads to which at regular intervals Y-shaped side chains are attached. Each side chain is composed of eight A beads and contains two identical branches that are each terminated with a pendant hydrophilic C bead. Four types of side chains are considered for which the two branches (each represented as [C], [AC], [AAC], or [AAAC]) are splitting off from the 8th, 6th, 4th, or 2nd A bead, respectively. Water diffusion through the phase separated water containing pore networks is deduced from MC tracer diffusion calculations. The percolation threshold for the architectures containing the [C] and [AC] branches is at a water volume fraction of ˜0.07 and 0.08, respectively. These are much lower than those derived earlier for linear architectures of various side chain length and side chain distributions. Control of side chain architecture is thus a very interesting design parameter to decrease the percolation threshold for solvent and proton transports within flexible amphiphilic polymer membranes.

  2. Clustering analysis

    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

  3. Cluster analysis

    CERN Document Server

    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

  4. Occupational Clusters.

    Science.gov (United States)

    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…

  5. Cancer Clusters

    Science.gov (United States)

    ... Peer Review and Funding Outcomes Step 4: Award Negotiation & Issuance Manage Your Award Grants Management Contacts Monitoring ... potentially hazardous working conditions, including suspected cancer clusters. Employees, authorized employee representatives, and employers can request these ...

  6. Cluster generator

    Science.gov (United States)

    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.

  7. Reproducibility of up-flow column percolation tests for contaminated soils.

    Science.gov (United States)

    Yasutaka, Tetsuo; Naka, Angelica; Sakanakura, Hirofumi; Kurosawa, Akihiko; Inui, Toru; Takeo, Miyuki; Inoba, Seiji; Watanabe, Yasutaka; Fujikawa, Takuro; Miura, Toshihiko; Miyaguchi, Shinji; Nakajou, Kunihide; Sumikura, Mitsuhiro; Ito, Kenichi; Tamoto, Shuichi; Tatsuhara, Takeshi; Chida, Tomoyuki; Hirata, Kei; Ohori, Ken; Someya, Masayuki; Katoh, Masahiko; Umino, Madoka; Negishi, Masanori; Ito, Keijiro; Kojima, Junichi; Ogawa, Shohei

    2017-01-01

    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% in more than

  8. 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

  9. Cosmology and cluster formation

    International Nuclear Information System (INIS)

    Peebles, P.J.E.

    1990-01-01

    I discuss some issues that arise in the attempt to understand what rich clusters of galaxies might teach us about cosmology. First, the mean mass per galaxy in a cluster, if applied to all bright galaxies, yields a mean mass density ∼ 30 percent of the critical Einstein-de Sitter value. Is this because the mass per galaxy is biased low in clusters, or is there in a low density universe? Second, what is the sequence of creation? There are theories in which protoclusters form before galaxies, or after, or the two are more or less coeval. Third, can clusters have formed by gravitational instability out of Gaussian primeval density fluctuations? Or do the observations point to the non-Gaussian perturbations to be expected from cosmic strings, or explosions, or even some variants of inflation? These issues depend on a fourth: do we know the gross physical properties of clusters well enough to use them as constraints on cosmology? I argue that some are too well established to ignore. Their implications for the other issues are not so clear, but progress can be seen. (author)

  10. Bussines Clusters

    Directory of Open Access Journals (Sweden)

    Sarmiza Pencea

    2010-10-01

    Full Text Available Clusters are complex economic structures in which similar companies, their up-stream and down-stream business partners, universities, research institutes, educational units, various service providers, diverse private and public institutions concentrate geografically, striving to get economies of agglomeration and scale, to capitalize on the resulting spill over effects, to cut costs, to better harness resources, to exchange information and experience, to improve quality, innovation, skills and productivity. By somehow unexpectedly combining competition and cooperation, they form a new, sophisticated stage in the evolution of production structures in quest of higher efficiency. This paper forays into the world of clusters and clusterization, which seem to increasingly capture the interest of businesses, scholars and policy makers. It looks at what clusters are, how they arise, what are their specific features, what benefits and challenges they can generate for companies and for the regions in which they locate and if and how they should be fostered by industrial policy interventions. The conclusion is that clusters can be very important development triggers and therefore they should be encouraged and nurtured by adequate policy measures. They should not only be used as a regular policy tool, but be placed at the very center of the development strategies of emerging economies.

  11. CriticalEd

    DEFF Research Database (Denmark)

    Kjellberg, Caspar Mølholt; Meredith, David

    2014-01-01

    such as Sibelius or Finale. It was hypothesized that it would be possible to develop a Sibelius plug-in, written in Manuscript 6, that would improve the critical editing work flow, but it was found that the capabilities of this scripting language were insufficient. Instead, a 3-part system was designed and built......, 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......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...

  12. Statistical Significance for Hierarchical Clustering

    Science.gov (United States)

    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

  13. Synthesis and Properties of Metal Clusters in Polymeric Matrices

    Science.gov (United States)

    Kay, E.

    1986-06-01

    A one-step plasma deposition process is described which allows the uniform dispersion of small metal clusters throughout a thin film polymer matrix. Plasma parameters and plasma gas phase diagnostics relevant to the control of film composition and structure are discussed. Chemical and structural analytical techniques such as I.R. absorption spectroscopy, E.S.C.A., Auger electron spectroscopy, X-ray fluorescence, X-ray and electron diffraction and microscopy are used to characterize the cluster containing films. Changes in cluster size and shape as a function of volume fraction and as a result of post deposition annealing are described. Optical and electrical properties are presented below and above the onset of percolation and are evaluated in terms of contemporary effective medium theories.

  14. Cluster Correlation in Mixed Models

    Science.gov (United States)

    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.

  15. Percolation and particle transport in the unsaturated zone of a karst aquifer.

    Science.gov (United States)

    Pronk, Michiel; Goldscheider, Nico; Zopfi, Jakob; Zwahlen, Francxois

    2009-01-01

    Recharge and contamination of karst aquifers often occur via the unsaturated zone, but the functioning of this zone has not yet been fully understood. Therefore, irrigation and tracer experiments, along with monitoring of rainfall events, were used to examine water percolation and the transport of solutes, particles, and fecal bacteria between the land surface and a water outlet into a shallow cave. Monitored parameters included discharge, electrical conductivity, temperature, organic carbon, turbidity, particle-size distribution (PSD), fecal indicator bacteria, chloride, bromide, and uranine. Percolation following rainfall or irrigation can be subdivided into a lag phase (no response at the outlet), a piston-flow phase (release of epikarst storage water by pressure transfer), and a mixed-flow phase (increasing contribution of freshly infiltrated water), starting between 20 min and a few hours after the start of recharge event. Concerning particle and bacteria transport, results demonstrate that (1) a first turbidity signal occurs during increasing discharge due to remobilization of particles from fractures (pulse-through turbidity); (2) a second turbidity signal is caused by direct particle transfer from the soil (flow-through turbidity), often accompanied by high levels of fecal indicator bacteria, up to 17,000 Escherichia coli/100 mL; and (3) PSD allows differentiation between the two types of turbidity. A relative increase of fine particles (0.9 to 1.5 microm) coincides with microbial contamination. These findings help quantify water storage and percolation in the epikarst and better understand contaminant transport and attenuation. The use of PSD as "early-warning parameter" for microbial contamination in karst water is confirmed.

  16. FORMATION OF CALCITE AND SILICA FROM PERCOLATION IN A HYDROLOGICALLY UNSATURATED SETTING, YUCCA MOUNTAIN, NEVADA

    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

  17. Influence of percolation patterns on growth and yield of rice plants and uptake of cadmium from polluted paddy fields using soil dressing models

    OpenAIRE

    パウル, シャマル クマル; PAUL, Shyamal Kumar

    2011-01-01

    We investigated that influence of percolation patterns on growth and yield of rice plants and uptake of cadmium from polluted paddy flelds using soil dressing models. The experiment was conducted in the green house with open and closed system percolation models (M-1,M-2,M-3,M-4,MI5,M-6,MI7,M-8,M-9andM-10). Those models were consisted of stratified soil layers and two different percolation systems (open and closed system percolation) and operated by 12.5cm (M-1 to M-6),15cm (M-7 to M-8) and 20...

  18. Effects of plasticizer and strain on the percolation threshold in polyisoprene-carbon nanocomposites: Positron annihilation lifetime spectroscopy and electrical resistance measurements

    International Nuclear Information System (INIS)

    Knite, M.; Hill, A.J.; Pas, S.J.; Teteris, V.; Zavickis, J.

    2006-01-01

    A study of the effects of plasticizer and stretching strain on the percolation transition in polyisoprene-carbon nanocomposites (PCNC) is reported. The ortho-positronium (oPs) accessible free volume sites are measured by positron annihilation lifetime spectroscopy (PALS) in relaxed and stretched PCNC samples containing different amounts of plasticizer. The lifetime of oPs, τ 3 , is related to the size of the free volume, and the intensity, I 3 , to the concentration of free volume sites. The number of free volume cavities is found to decrease during stretching regardless of the content of either carbon nanoparticles (CNP) or plasticizer. The free volume cavity size reaches its maximum value in the region of percolation transition. The percolation threshold is determined by measurements of electrical resistance (ERM). Both PALS and ERM show that the percolation threshold shifts to higher concentration of CNP under stretching strain. A shift of the percolation threshold to lower concentration of CNP was observed for addition of plasticizer. It is interesting that addition of CNP increases the mean size of free volume cavities below the percolation threshold and decreases it at CNP concentrations exceeding the percolation threshold. The relative number of free volume cavities represented by I 3 also decreases at CNP concentrations exceeding the percolation threshold. The results are interpreted as filling of cavities above the percolation threshold. ERM during application of cyclic tensile stress revealed fatigue of the tensoresistance effect in samples containing 10 m.p. of CNP with and without added plasticizer

  19. Corrections to scaling in random resistor networks and diluted continuous spin models near the percolation threshold.

    Science.gov (United States)

    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).

  20. Two rigidity-percolation transitions on binary Bethe networks and the intermediate phase in glass.

    Science.gov (United States)

    Moukarzel, Cristian F

    2013-12-01

    Rigidity percolation is studied analytically on randomly bonded networks with two types of nodes, respectively, with coordination numbers z(1) and z(2), and with g(1) and g(2) degrees of freedom each. For certain cases that model chalcogenide glass networks, two transitions, both of first order, are found, with the first transition usually rather weak. The ensuing intermediate pase, although not isostatic in its entirety, has very low self-stress. Our results suggest a possible mechanism for the appearance of intermediate phases in glass that does not depend on a self-organization principle.

  1. Application of percolation theory in pathophoresis during multiple stages of the infected period

    Directory of Open Access Journals (Sweden)

    Yaxian HUO

    2016-04-01

    Full Text Available Network study combined with the generating function and percolation theory is used to study the outbreak of infectious disease with multiple infected stages among people, so the network topology is made more clear and convenient. The infected period is divided into n stages: I1, I2,…,In. The calculation of the disease outbreak threshold, the scale of outbreaks,the mean degree of infected nodes, and the mean degree of uninfected nodes in the spreading epidemic caused by one infected individual are obtained.

  2. 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...

  3. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan

    2000-01-01

    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...

  4. Cluster Matters

    DEFF Research Database (Denmark)

    Gulati, Mukesh; Lund-Thomsen, Peter; Suresh, Sangeetha

    2018-01-01

    In this chapter, we investigate corporate social responsibility (CSR) in industrial clusters in the Indian context. We use the definition of CSR as given in the Indian Ministry of Corporate Affairs’ National Voluntary Guidelines (NVGs) for Business Responsibility: ‘the commitment of an enterprise...

  5. A Numerical Study on Electrical Percolation of Polymer-Matrix Composites with Hybrid Fillers of Carbon Nanotubes and Carbon Black

    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.

  6. Ultralow percolation threshold of single walled carbon nanotube-epoxy composites synthesized via an ionic liquid dispersant/initiator

    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)

  7. Estimates of deep percolation beneath native vegetation, irrigated fields, and the Amargosa-River Channel, Amargosa Desert, Nye County, Nevada

    Science.gov (United States)

    Stonestrom, David A.; Prudic, David E.; Laczniak, Randell J.; Akstin, Katherine C.; Boyd, Robert A.; Henkelman, Katherine K.

    2003-01-01

    The presence and approximate rates of deep percolation beneath areas of native vegetation, irrigated fields, and the Amargosa-River channel in the Amargosa Desert of southern Nevada were evaluated using the chloride mass-balance method and inferred downward velocities of chloride and nitrate peaks. Estimates of deep-percolation rates in the Amargosa Desert are needed for the analysis of regional ground-water flow and transport. An understanding of regional flow patterns is important because ground water originating on the Nevada Test Site may pass through the area before discharging from springs at lower elevations in the Amargosa Desert and in Death Valley. Nine boreholes 10 to 16 meters deep were cored nearly continuously using a hollow-stem auger designed for gravelly sediments. Two boreholes were drilled in each of three irrigated fields in the Amargosa-Farms area, two in the Amargosa-River channel, and one in an undisturbed area of native vegetation. Data from previously cored boreholes beneath undisturbed, native vegetation were compared with the new data to further assess deep percolation under current climatic conditions and provide information on spatial variability.The profiles beneath native vegetation were characterized by large amounts of accumulated chloride just below the root zone with almost no further accumulation at greater depths. This pattern is typical of profiles beneath interfluvial areas in arid alluvial basins of the southwestern United States, where salts have been accumulating since the end of the Pleistocene. The profiles beneath irrigated fields and the Amargosa-River channel contained more than twice the volume of water compared to profiles beneath native vegetation, consistent with active deep percolation beneath these sites. Chloride profiles beneath two older fields (cultivated since the 1960’s) as well as the upstream Amargosa-River site were indicative of long-term, quasi-steady deep percolation. Chloride profiles beneath the

  8. Percolation-based risk index for pathogen invasion: application to soilborne disease in propagation systems.

    Science.gov (United States)

    Poggi, S; Neri, F M; Deytieux, V; Bates, A; Otten, W; Gilligan, C A; Bailey, D J

    2013-10-01

    Propagation systems for seedling growth play a major role in agriculture, and in notable cases (such as organic systems), are under constant threat from soil and seedborne fungal plant pathogens such as Rhizoctonia solani or Pythium spp. Yet, to date little is known that links the risk of disease invasion to the host density, which is an agronomic characteristic that can be readily controlled. We introduce here, for the first time in an agronomic system, a percolation framework to analyze the link. We set up an experiment to study the spread of the ubiquitous fungus R. solani in replicated propagation systems with different planting densities, and fit a percolation-based epidemiological model to the data using Bayesian inference methods. The estimated probability of pathogen transmission between infected and susceptible plants is used to calculate the risk of invasion. By comparing the transmission probability and the risk values obtained for different planting densities, we are able to give evidence of a nonlinear relationship between disease invasion and the inter-plant spacing, hence to demonstrate the existence of a spatial threshold for epidemic invasion. The implications and potential use of our methods for the evaluation of disease control strategies are discussed.

  9. [Treatment of tannery wastewater by infiltration percolation: chromium removal and speciation in soil].

    Science.gov (United States)

    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%.

  10. 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

  11. Regulation mechanism of negative permittivity in percolating composites via building blocks

    Science.gov (United States)

    Xie, Peitao; Wang, Zhongyang; Sun, Kai; Cheng, Chuanbing; Liu, Yao; Fan, Runhua

    2017-09-01

    Percolating composites with negative permittivity can be promising candidates for metamaterials; however, building blocks of negative permittivity have not yet been put forward in percolating composites. Here, the dielectric properties of a ternary composite with Fe and SiO2-coated Fe particles dispersed in a polymer matrix were investigated in the range of 10 MHz-1 GHz. By gradually controlling the Fe/coated-Fe ratio (x), a three-dimensional conductive network could be constructed when x exceeds 0.75. The Drude-type negative permittivity was achieved by the conductive network, and its Lorentz-type dispersion was mainly attributed to dielectric resonance of coated-Fe particles. Equivalent circuit analysis demonstrated that the inductive conductive network was the decisive building block to achieve negative permittivity. Moreover, the dielectric resonance caused by coated-Fe particles was LC resonance, and this indicated that the capacitive isolated metallic particles acted as another building block to control the dispersion of negative permittivity by LC resonance. Our reported work provides a highly efficient strategy to adjust negative permittivity and will facilitate applications of negative permittivity materials.

  12. 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.

  13. Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.

    Science.gov (United States)

    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.

  14. Studies on percolating characteristics of heavy oil and its application in Shengli petroliferous province

    Energy Technology Data Exchange (ETDEWEB)

    Min, L.Y.; Sun, J.F.; Wu, G.G. [SINOPEC, Shengli (China). Shengli Oil Field Co. Ltd.

    2006-07-01

    This paper provided details of a study that evaluated the percolating characteristics of heavy oil under various conditions. Oil samples with different viscosity and permeability levels were taken from 10 heavy oil blocks in an oilfield in China. The aim of the study was to develop an exploitation pattern and confirm the drainage radius. A laboratory experiment measured the flow rates and pressure differences of the samples at the inlets and outlets of porous media. Percolation characteristics of the heavy oil in the porous media were then transformed from pseudo-plastic to dilatant. The maximum drainage radius for the conventional production of the heavy oil was confirmed by examining starting pressure gradients and mobility. Results of the experiment demonstrated that conventional heavy oil flow is pseudoplastic, while extra-viscous oil flow is dilatant in porous media. Heavy oil flow was found to be non-Darcy Law within specified pressure gradients in porous media. Results also demonstrated that the starting pressure gradient of heavy oil was influenced by oil viscosity, permeability, and temperature. It was concluded that an improved understanding of the starting pressure gradient can help to confirm the maximum drainage radius of heavy oil wells and guide in the selection of development schemes. 9 refs., 1 tab., 9 figs.

  15. Normalized fluctuations, H2O vs n-hexane: Site-correlated percolation

    Science.gov (United States)

    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.

  16. Gibbs Measures Over Locally Tree-Like Graphs and Percolative Entropy Over Infinite Regular Trees

    Science.gov (United States)

    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.

  17. Electrical Transport and Network Percolation in Graphene and Boron Nitride Mixed-Platelet Structures.

    Science.gov (United States)

    Debbarma, Rousan; Behura, Sanjay; Nguyen, Phong; Sreeprasad, T S; Berry, Vikas

    2016-04-06

    Percolating network of mixed 2D nanomaterials (2DNs) can leverage the unique electronic structures of different 2DNs, their interfacial doping, manipulable conduction pathways, and local traps. Here, we report on the percolation mechanism and electro-capacitive transport pathways of mixed-platelet network of hexagonal boron nitride (hBN) and reduced graphene oxide (rGO), two isostructural and isoelectronic 2DNs. The transport mechanism is explained in terms of electron hopping through isolated hBN defect traps between rGO (possibly via electron tunneling/hopping through "funneling" points). With optical bandgaps of 4.57 and 4.08 eV for the hBN-domains and 2.18 eV for the rGO domains, the network of hBN with rGO exhibits Poole-Frenkel emission-based transport with mean hopping gap of 1.12 nm (∼hBN trilayer) and an activation barrier of ∼15 ± 0.7 meV. Further, hBN (1.7 pF) has a 6-fold lower capacitance than 1:1 hBN:rGO, which has a resistance 2 orders of magnitude higher than that of rGO (1.46 MΩ). These carrier transport results can be applied to other multi-2DN networks for development of next-generation functional 2D-devices.

  18. Collective Influence Algorithm to find influencers via optimal percolation in massively large social media

    Science.gov (United States)

    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.

  19. Microbially mediated alteration of crystalline basalts as identified from analogical reactive percolation experiments

    Science.gov (United States)

    Moore, Rachael; Ménez, Bénédicte; Stéphant, Sylvian; Dupraz, Sébastien; Ranchou-Peyruse, Magali; Ranchou-Peyruse, Anthony; Gérard, Emmanuelle

    2017-04-01

    Alteration in the ocean crust through fluid circulation is an ongoing process affecting the first kilometers and at low temperatures some alteration may be microbially mediated. Hydrothermal activity through the hard rock basement supports diverse microbial communities within the rock by providing nutrient and energy sources. Currently, the impact of basement hosted microbial communities on alteration is poorly understood. In order to identify and quantify the nature of microbially mediated alteration two reactive percolation experiments mimicking circulation of CO2 enriched ground water were performed at 35 °C and 30 bar for 21 days each. The experiments were performed using a crystalline basalt substrate from an earlier drilled deep Icelandic aquifer. One experiment was conducted on sterile rock while the other was conducted with the addition of a microbial inoculate derived from groundwater enrichment cultures obtained from the same aquifer. µCT on the experimental basaltic substrate before and after the reactive percolation experiment along with synchrotron radiation x-ray tomographic microscopy and the mineralogical characterization of resulting material allows for the comparative volumetric quantification of dissolution and precipitation. The unique design of this experiment allows for the identification of alteration which occurs solely abiotically and of microbially mediated alteration. Experimental results are compared to natural basaltic cores from Iceland retrieved following a large field CO2 injection experiment that stimulated microbial activity at depth.

  20. Cluster forcing

    DEFF Research Database (Denmark)

    Christensen, Thomas Budde

    , Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e.......g. sustainability or quality of life. The purpose of this paper is to explore how and to what extent public sector interventions that aim at forcing cluster development in industries can support sustainable development as defined in the Brundtland tradition and more recently elaborated in such concepts as eco...... in 2000 by the Welsh Automotive Task Force under the Welsh Assembly Government. The Accelerate programme takes basically different two directions: The first one, which was the first to be launched, is concerned with the upgrading of existing supply chains in the automotive industry in Wales. The programme...

  1. Regional Innovation Clusters

    Data.gov (United States)

    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,...

  2. Estimation of percolating water dynamics through the vadose zone of the Postojna cave on the basis of isotope composition

    Directory of Open Access Journals (Sweden)

    Janja Kogovšek

    2007-12-01

    Full Text Available Within the scope of monitoring water percolation through the 100-m thick vadose zone in the area of Postojnska jama continuous measurements of precipitation were carried out on the surface, and continuous measurements of water flowandphysicalandchemicalparametersof selected water trickles were performed under the surface. Occasional samples of percolating waters were taken for the analysis of water oxygen isotope composition. An exponential model of groundwater flowwaselaborated,bymeansofwhichtheretentiontime of water in individual trickles was estimated. Modelled retention times of groundwater range from 2.5 months to over one year.

  3. Critical properties of unlimited gliding: Unexpected flocking behavior driven by the exchange of information

    Science.gov (United States)

    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).

  4. 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

  5. Self-organized criticality: Does it have anything to do with criticality and is it useful?

    Directory of Open Access Journals (Sweden)

    D. L. Turcotte

    2001-01-01

    Full Text Available Three aspects of complexity are fractals, chaos, and self-organized criticality. There are many examples of the applicability of fractals in solid-earth geophysics, such as earthquakes and landforms. Chaos is widely accepted as being applicable to a variety of geophysical phenomena, for instance, tectonics and mantle convection. Several simple cellular-automata models have been said to exhibit self-organized criticality. Examples include the sandpile, forest fire and slider-blocks models. It is believed that these are directly applicable to landslides, actual forest fires, and earthquakes, respectively. The slider-block model has been shown to clearly exhibit deterministic chaos and fractal behaviour. The concept of self-similar cascades can explain self-organized critical behaviour. This approach also illustrates the similarities and differences with critical phenomena through association with the site-percolation and diffusion-limited aggregation models.

  6. Petrophysical and transport parameters evolution during acid percolation through structurally different limestones

    Science.gov (United States)

    Martinez Perez, Laura; Luquot, Linda

    2017-04-01

    Processes affecting geological media often show complex and unpredictable behavior due to the presence of heterogeneities. This remains problematic when facing contaminant transport problems, in the CO2 storage industry or dealing with the mechanisms underneath natural processes where chemical reactions can be observed during the percolation of rock non-equilibrated fluid (e.g. karst formation, seawater intrusion). To understand the mechanisms taking place in a porous medium as a result of this water-rock interaction, we need to know the flow parameters that control them, and how they evolve with time as a result of that concurrence. This is fundamental to ensure realistic predictions of the behavior of natural systems in response of reactive transport processes. We investigate the coupled influence of structural and hydrodynamic heterogeneities in limestone rock samples tracking its variations during chemical reactions. To do so we use laboratory petrophysical techniques such as helium porosimetry, gas permeability, centrifugue, electrical resistivity and sonic waves measurements to obtain the parameters that characterize flow within rock matrix (porosity, permeability, retention curve and pore size distribution, electrical conductivity, formation factor, cementation index and tortuosity) before and after percolation experiments. We built an experimental setup that allows injection of acid brine into core samples under well controlled conditions, monitor changes in hydrodynamic properties and obtain the chemical composition of the injected solution at different stages. 3D rock images were also acquired before and after the experiments using a micro-CT to locate the alteration processes and perform an acurate analysis of the structural changes. Two limestones with distinct textural classification and thus contrasting transport properties have been used in the laboratory experiments: a crinoid limestone and an oolithic limestone. Core samples dimensions were 1 inch

  7. Improved estimates of percolation and anisotropic permeability from 3-D X-ray microtomography using stochastic analyses and visualization

    Science.gov (United States)

    Liu, Jie; Regenauer-Lieb, Klaus; Hines, Chris; Liu, Keyu; Gaede, Oliver; Squelch, Andrew

    2009-05-01

    X-ray microtomography (micro-CT) with micron resolution enables new ways of characterizing microstructures and opens pathways for forward calculations of multiscale rock properties. A quantitative characterization of the microstructure is the first step in this challenge. We developed a new approach to extract scale-dependent characteristics of porosity, percolation, and anisotropic permeability from 3-D microstructural models of rocks. The Hoshen-Kopelman algorithm of percolation theory is employed for a standard percolation analysis. The anisotropy of permeability is calculated by means of the star volume distribution approach. The local porosity distribution and local percolation probability are obtained by using the local porosity theory. Additionally, the local anisotropy distribution is defined and analyzed through two empirical probability density functions, the isotropy index and the elongation index. For such a high-resolution data set, the typical data sizes of the CT images are on the order of gigabytes to tens of gigabytes; thus an extremely large number of calculations are required. To resolve this large memory problem parallelization in OpenMP was used to optimally harness the shared memory infrastructure on cache coherent Non-Uniform Memory Access architecture machines such as the iVEC SGI Altix 3700Bx2 Supercomputer. We see adequate visualization of the results as an important element in this first pioneering study.

  8. Evaluation of the effect of percolation and NaCl solutions on viral haemorrhagic septicaemia virus (VHSV) under experimental conditions

    DEFF Research Database (Denmark)

    Skall, Helle Frank; Jørgensen, Claus; Olesen, Niels Jørgen

    2015-01-01

    from any of the outlet samples. As the sensitivity of the virological examination was 13.9 TCID50/ml a reduction of >4 log was shown at the outlet. Percolation thus seems to be a usable method for sanitation of water contaminated with VHSV. Changes in temperature, pH, earth types etc. may potentially...

  9. PREDICTING ATTENUATION OF VIRUSES DURING PERCOLATION IN SOILS: 2. USER'S GUIDE TO THE VIRULO 1.0 COMPUTER MODEL

    Science.gov (United States)

    In the EPA document Predicting Attenuation of Viruses During Percolation in Soils 1. Probabilistic Model the conceptual, theoretical, and mathematical foundations for a predictive screening model were presented. In this current volume we present a User's Guide for the computer mo...

  10. Protonic conductivity of polycrystalline materials evaluated with effective medium percolation approach: A case study on lithium-carboxylate based MOF

    Czech Academy of Sciences Publication Activity Database

    Zima, Vítězslav; Shimakawa, K.; Lin, C. H.

    2016-01-01

    Roč. 292, 1 September (2016), s. 98-102 ISSN 0167-2738 R&D Projects: GA ČR(CZ) GA14-13368S Institutional support: RVO:61389013 Keywords : proton conductivity * impedance spectroscopy * percolation path approximation Subject RIV: CA - Inorganic Chemistry Impact factor: 2.354, year: 2016

  11. Renormalization group treatment of bond percolation in anisotropic and 'inhomogeneous' planar lattices

    International Nuclear Information System (INIS)

    Magalhaes, A.C.N. de; Tsallis, C.; Schwaccheim, G.

    1980-04-01

    The uncorrelated bond percolation problem is studied in three planar systems where there are two distinct occupancy probabilities. Two different real space renormalization group approaches (referred as the 'canonical' (CRG) and the 'parametric' (PRG) ones) are applied to the anisotropic first-neighbour square lattice, and both of them exhibit the expected tendency towards the exactly known phase boundary (p+q=1). Then, within the context of PRG calculations for increasingly large cells, an extrapolation method is introduced, which leads to analytic proposals for the other two lattices, namely p+q = 1/2 for the first-and second-neighbour square lattice (p and q are, respectively, the first and second neighbour occupancy probabilities), and 3 (p-1/2) = 4 [(1-q) 2 + (1-q) 3 ] (p and q are, respectively, the occupancy probabilities of the topologically different bonds which are in a 1:2 ratio) for the 4- 8 lattice. (Author) [pt

  12. Percolation transition in Yang-Mills matter at a finite number of colors.

    Science.gov (United States)

    Lottini, Stefano; Torrieri, Giorgio

    2011-10-07

    We examine baryonic matter at a quark chemical potential of the order of the confinement scale μ(q)∼Λ(QCD). In this regime, quarks are supposed to be confined but baryons are close to the "tightly packed limit" where they nearly overlap in configuration space. We show that this system will exhibit a percolation phase transition when varied in the number of colors N(c): at high N(c), large distance correlations at the quark level are possible even if the quarks are essentially confined. At low N(c), this does not happen. We discuss the relevance of this for dense nuclear matter, and argue that our results suggest a new "phase transition," varying N(c) at constant μ(q).

  13. Ag nanowire percolating network embedded in indium tin oxide nanoparticles for printable transparent conducting electrodes

    Science.gov (United States)

    Jeong, Jin-A.; Kim, Han-Ki

    2014-02-01

    Solution-based printable transparent conducting electrodes consisting of Ag nanowire (NW) and indium tin oxide (ITO) nanoparticles (NPs) were fabricated by simple brush painting at room temperature under atmospheric ambient conditions. Effectively embedding the Ag NW percolating network into the ITO NPs provided a conduction path, led to a metallic conduction behavior of the ITO NPs/Ag NW/ITO NPs multilayer and supplied electrons into the ITO NPs. The optimized ITO NPs/Ag NW/ITO NPs multilayer showed a sheet resistance of 16.57 Ω/sq and an optical transparency of 79.50% without post annealing. Based on high resolution transmission electron microscope analysis, we investigated the microstructure and interface structure of the ITO NPs/Ag NW/ITO NPs multilayer electrodes and suggested a possible mechanism to explain the low resistivity of the multilayers.

  14. Percolation of Carbon Nanoparticles in Poly(3-Hexylthiophene Enhancing Carrier Mobility in Organic Thin Film Transistors

    Directory of Open Access Journals (Sweden)

    Chang-Hung Lee

    2014-01-01

    Full Text Available To improve the field-effect mobility of all-inkjet-printed organic thin film transistors (OTFTs, a composite material consisted of carbon nanoparticles (CNPs and poly(3-hexylthiophene (P3HT was reported by using homemade inkjet-printing system. These all-inkjet-printed composite OTFTs represented superior characteristics compared to the all-inkjet-printed pristine P3HT OTFTs. To investigate the enhancement mechanism of the blended materials, the percolation model was established and experimentally verified to illustrate the enhancement of the electrical properties with different blending concentrations. In addition, experimental results of OTFT contact resistances showed that both contact resistance and channel resistance were halved. At the same time, X-ray diffraction measurements, Fourier transform infrared spectra, ultraviolet-visible light, and photoluminescence spectra were also accomplished to clarify the material blending effects. Therefore, this study demonstrates the potential and guideline of carbon-based nanocomposite materials in all-inkjet-printed organic electronics.

  15. A Percolation Perspective for Gutenburg-Richter Scaling and b-values for Fracking Assocated Seismicity

    Science.gov (United States)

    Norris, J. Q.

    2016-12-01

    Published 60 years ago, the Gutenburg-Richter law provides a universal frequency-magnitude distribution for natural and induced seismicity. The GR law is a two parameter power-law with the b-value specifying the relative frequency of small and large events. For large catalogs of natural seismicity, the observed b-values are near one, while fracking associated seismicity has observed b-values near two, indicating relatively fewer large events. We have developed a computationally inexpensive percolation model for fracking that allows us to generate large catalogs of fracking associated seismicity. Using these catalogs, we show that different power-law fitting procedures produce different b-values for the same data set. This shows that care must be taken when determining and comparing b-values for fracking associated seismicity.

  16. Universality of the emergent scaling in finite random binary percolation networks.

    Science.gov (United States)

    Zhai, Chongpu; Hanaor, Dorian; Gan, Yixiang

    2017-01-01

    In this paper we apply lattice models of finite binary percolation networks to examine the effects of network configuration on macroscopic network responses. We consider both square and rectangular lattice structures in which bonds between nodes are randomly assigned to be either resistors or capacitors. Results show that for given network geometries, the overall normalised frequency-dependent electrical conductivities for different capacitor proportions are found to converge at a characteristic frequency. Networks with sufficiently large size tend to share the same convergence point uninfluenced by the boundary and electrode conditions, can be then regarded as homogeneous media. For these networks, the span of the emergent scaling region is found to be primarily determined by the smaller network dimension (width or length). This study identifies the applicability of power-law scaling in random two phase systems of different topological configurations. This understanding has implications in the design and testing of disordered systems in diverse applications.

  17. A Route for Polymer Nanocomposites with Engineered Electrical Conductivity and Percolation Threshold

    Directory of Open Access Journals (Sweden)

    Lawrence T. Drzal

    2010-02-01

    Full Text Available Polymer nanocomposites with engineered electrical properties can be made by tuning the fabrication method, processing conditions and filler’s geometric and physical properties. This work focuses on investigating the effect of filler’s geometry (aspect ratio and shape, intrinsic electrical conductivity, alignment and dispersion within the polymer, and polymer crystallinity, on the percolation threshold and electrical conductivity of polypropylene based nanocomposites. The conductive reinforcements used are exfoliated graphite nanoplatelets, carbon black, vapor grown carbon fibers and polyacrylonitrile carbon fibers. The composites are made using melt mixing followed by injection molding. A coating method is also employed to improve the nanofiller’s dispersion within the polymer and compression molding is used to alter the nanofiller’s alignment.

  18. Percolation model for electron conduction in films of metal nanoparticles linked by organic molecules

    International Nuclear Information System (INIS)

    Muller, K.H.; Herrmann, J.; Raguse, B.; Baxter, G.; Reda, T.

    2002-01-01

    Full text: We have investigated theoretically and experimentally the temperature dependence of the conductance of films of Au nanoparticles linked by alkane dithiol molecules in the temperature range between 5 K and 300 K. Conduction in these films is due to tunneling of single electrons between neighbouring metal nanoparticles. During tunnelling an electron has to overcome the Coulomb charging energy. We find that the observed temperature dependence of the conductance is non-Arrhenius like and can be described in terms of a percolation theory which takes account of disorder in the system. Disorder in our nanoparticle films is caused by variations in the nanoparticle size, fluctuations in the separation gaps between adjacent nanoparticles and by offset charges. To explain in detail our experimental data, a wide distribution of separation gaps and charging energies is needed. We find that a wide Coulomb charging energy distribution can arise from random offset charges even if the nanoparticle size distribution is narrow

  19. Directed percolation process in the presence of velocity fluctuations: Effect of compressibility and finite correlation time

    Science.gov (United States)

    Antonov, N. V.; Hnatič, M.; Kapustin, A. S.; Lučivjanský, T.; Mižišin, L.

    2016-01-01

    The direct bond percolation process (Gribov process) is studied in the presence of random velocity fluctuations generated by the Gaussian self-similar ensemble with finite correlation time. We employ the renormalization group in order to analyze a combined effect of the compressibility and finite correlation time on the long-time behavior of the phase transition between an active and an absorbing state. The renormalization procedure is performed to the one-loop order. Stable fixed points of the renormalization group and their regions of stability are calculated in the one-loop approximation within the three-parameter (ɛ ,y ,η ) expansion. Different regimes corresponding to the rapid-change limit and frozen velocity field are discussed, and their fixed points' structure is determined in numerical fashion.

  20. Anisotropy and structural-defect contributions to percolative conduction in granular copper oxide superconductors

    International Nuclear Information System (INIS)

    Diaz, A.; Maza, J.; Vidal, F.

    1997-01-01

    A well-defined temperature-independent slope of the current-voltage characteristics (CVC) is a common feature of granular high-temperature superconductors in the paracoherent state (grains superconducting; intergranular regions normal). By analyzing the contributions of anisotropy and structural defects to percolative conduction processes both in the normal state and in the paracoherent state, we quantitatively account for the observed CVC slopes using only the normal-state resistivity values. In particular, from effective-medium theory it is found that the CVC slope of nontextured granular YBa 2 Cu 3 O 7-δ (YBCO) should be equal to approximately one-third of the normal-state resistivity extrapolated to zero temperature. Simultaneous measurements of the CVC and normal-state resistivity on a batch of granular YBCO samples are also presented that verify our predictions with no free parameters. copyright 1997 The American Physical Society

  1. Efficient Steplike Carrier Multiplication in Percolative Networks of Epitaxially Connected PbSe Nanocrystals.

    Science.gov (United States)

    Kulkarni, Aditya; Evers, Wiel H; Tomić, Stanko; Beard, Matthew C; Vanmaekelbergh, Daniel; Siebbeles, Laurens D A

    2018-01-23

    Carrier multiplication (CM) is a process in which a single photon excites two or more electrons. CM is of interest to enhance the efficiency of a solar cell. Until now, CM in thin films and solar cells of semiconductor nanocrystals (NCs) has been found at photon energies well above the minimum required energy of twice the band gap. The high threshold of CM strongly limits the benefits for solar cell applications. We show that CM is more efficient in a percolative network of directly connected PbSe NCs. The CM threshold is at twice the band gap and increases in a steplike fashion with photon energy. A lower CM efficiency is found for a solid of weaker coupled NCs. This demonstrates that the coupling between NCs strongly affects the CM efficiency. According to device simulations, the measured CM efficiency would significantly enhance the power conversion efficiency of a solar cell.

  2. Simulation of particle diffusion in a spectrum of electrostatic turbulence. Low frequency Bohm or percolation scaling

    International Nuclear Information System (INIS)

    Reuss, J.D.; Misguich, J.H.

    1996-02-01

    An important point for turbulent transport consists in determining the scaling law for the diffusion coefficient D due to electrostatic turbulence. It is well-known that for weak amplitudes or large frequencies, the reduced diffusion coefficient has a quasi-linear like (or gyro-Bohm like) scaling, while for large amplitudes or small frequencies it has been traditionally believed that the scaling is Bohm-like. The aim of this work consists to test this prediction for a given realistic model. This problem is studied by direct simulation of particle trajectories. Guiding centre diffusion in a spectrum of electrostatic turbulence is computed for test particles in a model spectrum, by means of a new parallelized code RADIGUET 2. The results indicate a continuous transition for large amplitudes toward a value which is compatible with the Isichenko percolation prediction. (author)

  3. 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...... behavior of reservoir resistivities of different wettabilities. It demonstrates that the resistivity index depends on saturation history and wettability. For strongly oil-wet systems, significant hysteresis is expected, while there is little hysteresis for strongly water-wet systems, and some hysteresis...

  4. Do satellite galaxies trace matter in galaxy clusters?

    Science.gov (United States)

    Wang, Chunxiang; Li, Ran; Gao, Liang; Shan, Huanyuan; Kneib, Jean-Paul; Wang, Wenting; Chen, Gang; Makler, Martin; Pereira, Maria E. S.; Wang, Lin; Maia, Marcio A. G.; Erben, Thomas

    2018-04-01

    The spatial distribution of satellite galaxies encodes rich information of the structure and assembly history of galaxy clusters. In this paper, we select a red-sequence Matched-filter Probabilistic Percolation cluster sample in SDSS Stripe 82 region with 0.1 ≤ z ≤ 0.33, 20 0.7. Using the high-quality weak lensing data from CS82 Survey, we constrain the mass profile of this sample. Then we compare directly the mass density profile with the satellite number density profile. We find that the total mass and number density profiles have the same shape, both well fitted by an NFW profile. The scale radii agree with each other within a 1σ error (r_s,gal=0.34_{-0.03}^{+0.04} Mpc versus r_s=0.37_{-0.10}^{+0.15} Mpc).

  5. Analysis of water/gas flows in argillites from Callovo-Oxfordian using gradient percolation

    International Nuclear Information System (INIS)

    Lefort, Philippe

    2014-01-01

    The work presented in this manuscript is motivated by the study of nuclear waste underground repository. In this context, we study the hyper slow drainage problem, which is related to the gas production, mainly hydrogen, taking place within the repository. Although the gas production rate is quite small, and thus the drainage hyper slow, the amount of produced gas is quite significant because the production takes place over thousands years. The study is performed within the framework of the theory of invasion percolation in a gradient. We first show that the hyper slow drainage process can be modelled using the traditional two-phase flow model based on the generalized Darcy's law. A crucial step is then to specify properly the parameters of the model. We show how they must be specified from the asymptotic behaviours of the parameters for an infinite medium as predicted by percolation theory. The obtained solution indicates that the hyper slow drainage operates in the vicinity of breakthrough pressure, which is the subject of a specific study. Furthermore, the hyper slow drainage is characterized by a weak desaturation of the medium and a great sensitivity to the model parameters in the range of high wetting fluid saturation. We also study the impact of coupling between the flow and the local deformation of porous matrix at the pore network scale from numerical simulations using a model coupling a pore network model and a deformation model based on a system of interconnected springs. The simulations indicate a major change of the invasion pattern compared to the rigid matrix with the self-generation of invasion preferential paths when the coupling is sufficiently strong. (author)

  6. Heavy hitters via cluster-preserving clustering

    DEFF Research Database (Denmark)

    Larsen, Kasper Green; Nelson, Jelani; Nguyen, Huy L.

    2016-01-01

    , providing correctness whp. In fact, a simpler version of our algorithm for p = 1 in the strict turnstile model answers queries even faster than the "dyadic trick" by roughly a log n factor, dominating it in all regards. Our main innovation is an efficient reduction from the heavy hitters to a clustering...... problem in which each heavy hitter is encoded as some form of noisy spectral cluster in a much bigger graph, and the goal is to identify every cluster. Since every heavy hitter must be found, correctness requires that every cluster be found. We thus need a "cluster-preserving clustering" algorithm......, that partitions the graph into clusters with the promise of not destroying any original cluster. To do this we first apply standard spectral graph partitioning, and then we use some novel combinatorial techniques to modify the cuts obtained so as to make sure that the original clusters are sufficiently preserved...

  7. Thinking Critically about Critical Thinking

    Science.gov (United States)

    Mulnix, Jennifer Wilson

    2012-01-01

    As a philosophy professor, one of my central goals is to teach students to think critically. However, one difficulty with determining whether critical thinking can be taught, or even measured, is that there is widespread disagreement over what critical thinking actually is. Here, I reflect on several conceptions of critical thinking, subjecting…

  8. Brightest Cluster Galaxies in REXCESS Clusters

    Science.gov (United States)

    Haarsma, Deborah B.; Leisman, L.; Bruch, S.; Donahue, M.

    2009-01-01

    Most galaxy clusters contain a Brightest Cluster Galaxy (BCG) which is larger than the other cluster ellipticals and has a more extended profile. In the hierarchical model, the BCG forms through many galaxy mergers in the crowded center of the cluster, and thus its properties give insight into the assembly of the cluster as a whole. In this project, we are working with the Representative XMM-Newton Cluster Structure Survey (REXCESS) team (Boehringer et al 2007) to study BCGs in 33 X-ray luminous galaxy clusters, 0.055 < z < 0.183. We are imaging the BCGs in R band at the Southern Observatory for Astrophysical Research (SOAR) in Chile. In this poster, we discuss our methods and give preliminary measurements of the BCG magnitudes, morphology, and stellar mass. We compare these BCG properties with the properties of their host clusters, particularly of the X-ray emitting gas.

  9. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  10. Response of deep percolation in the vadose zone to climate variability

    Science.gov (United States)

    Bruce, B. W.; Gurdak, J. J.; McMahon, P. B.; Hanson, R. T.

    2005-12-01

    A vadose zone monitoring network was instrumented in 2000-2002 beneath rangeland and agricultural settings across the High Plains regional aquifer with the objectives of measuring water and chemical fluxes, chemical storage and transit times through the thick (15 to 50 m) vadose zone. Generally, observations from individual monitoring stations reveal large nitrate reservoirs from natural and anthropogenic sources and long chemical transit times, suggesting the vadose zone will be a spatially extensive and long-term source of contaminants to the groundwater. During the past year, the total annual precipitation in the southern High Plains subregion was approximately twice the 20-year average and was partially coincident with natural climate variability, particularly the North American Monsoon System (NAMS), as identified from spectral analysis of hydrologic time-series data. This monsoon-driven precipitation increase resulted in a previously unobserved infiltration and deep (>7m) percolation event in the southern High Plains subregion, recorded using real-time monitoring of matric potential measured from a series of heat dissipation sensors installed vertically within the vadose zone. Adjacent subsurface moisture profiles obtained using a neutron moisture meter indicated a substantial increase in volumetric water content and further evidence of the deep percolation. The significance of the event is further illustrated using "before and after" chemical profiles from continuous core that reveal a downward mobilization of chloride and nitrate reservoirs beneath the rangeland setting. Water and chemical profiles and corresponding hydrologic time series are presented as evidence that episodic, deep-wetting events in semiarid and arid ecosystems results in nitrate leaching from the soil pool to the subsoil reservoir, producing characteristic conservative solute-accumulation profiles. Our findings show the importance of long-term monitoring of the vadose zone to

  11. Critical Care

    Science.gov (United States)

    Critical care helps people with life-threatening injuries and illnesses. It might treat problems such as complications from surgery, ... attention by a team of specially-trained health care providers. Critical care usually takes place in an ...

  12. High dielectric constant, low loss, and low percolation threshold dielectric composites based on polyvinylidene fluoride and ferroferric oxide nanorods

    Science.gov (United States)

    Li, Lili; Fu, Qiong; Li, Ya; Li, Weiping

    2016-08-01

    Dielectric super-capacitors call the excellent dielectric materials with high dielectric constant and low dielectric loss, both of which are not easy to obtain at the same time. The work synthesized the high aspect ratio and good crystalline ferroferric oxide (Fe3O4) nanorods by the hydrothermal process and used them as the filler to effectively reduce the percolation threshold value. It was found that the composites here based on the polyvinylidene fluoride (PVDF) polymer and these Fe3O4 nanorods exhibited ultra-high dielectric constant (>3000) and very low loss (<0.04) at very low filler fraction (0.35%). It was also proved that the high aspect ratio filler could help to improve the dielectric constant and suppress the dielectric loss in the percolative composites.

  13. Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

    Science.gov (United States)

    Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-05-01

    Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

  14. Percolation cooling of the Three Mile Island Unit 2 lower head by way of thermal cracking and gap formation

    DEFF Research Database (Denmark)

    Thomsen, K.L.

    2002-01-01

    Two partial models have been developed to elucidate the Three Mile Island Unit 2 lower head coolability by water percolation from above into the thermally cracking debris bed and into a gap between the debris and the wall The bulk permeability of the cracked top crust is estimated based on simple....... It is concluded that a three-dimensional model with an additional mechanism to explain the sudden water ingress to the hot spot center would be more appropriate....

  15. Atomic Fermi-Bose mixtures in inhomogeneous and random lattices: From Fermi glass to quantum spin glass and quantum percolation

    International Nuclear Information System (INIS)

    Sanpera, A.; Lewenstein, M.; Kantian, A.; Sanchez-Palencia, L.; Zakrzewski, J.

    2004-01-01

    We investigate strongly interacting atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. We derive an effective Hamiltonian for the system and discuss its low temperature physics. We demonstrate the possibility of controlling the interactions at local level in inhomogeneous but regular lattices. Such a control leads to the achievement of Fermi glass, quantum Fermi spin-glass, and quantum percolation regimes involving bare and/or composite fermions in random lattices

  16. Evaluation of interactions between soil and coal fly ash leachates using column percolation tests.

    Science.gov (United States)

    Tsiridis, V; Petala, M; Samaras, P; Sakellaropoulos, G P

    2015-09-01

    The aim of this work was the assessment of the environmental impact of different origin fly ashes with regard to their final disposal. The experimental procedure included the performance of single column tests and column tests of fly ash and soil in series. The appraisal of the potential environmental hazards was implemented using physicochemical analyses and bioassays. Two different fly ash samples were examined, one fly ash produced from the combustion of sub-bituminous coal (CFA) and one fly ash produced from the combustion of lignite (LFA). Single column percolation tests were performed according to NEN 7343 protocol, while fly ash/soil experiments were conducted incorporating slight modifications to this protocol. The study focused on the release of metals Ba, Cr, Cu, Mo, Se and Zn and the ecotoxic behavior of leachates on crustacean Daphnia magna and bacteria Vibrio fischeri. The infiltration of the leachates of both fly ashes through soil affected considerably their leaching profile. The transport of Cu and Zn was facilitated by the dynamic leaching conditions and influenced by the pH of the leachates. Moreover, the release and bioavailability of Cr, Cu and Zn was probably altered during the infiltration experiments and organisms' response was not always correlated with the concentration of metals. Nevertheless, the results are signalling that possible manipulations and final disposal of fly ash should be considered when environmental threats are investigated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Comparison of gastric ulcerogenicity of percolated extract of Anacardium occidentale (cashew nut) with indomethacin in rats.

    Science.gov (United States)

    Behravan, Effat; Heidari, Mahmoud Reza; Heidari, Mohammad; Fatemi, Ghasem; Etemad, Leila; Taghipour, Gholamhossein; Abbasifard, Mitra

    2012-01-01

    In traditional Iranian medicine, the core of the fruit of Anacardium occidentale (cashew nut) has been used in the management of the pain. In this study gastric ulcerogenicity effect of the percolated extract of A. occidentale was investigated in rats. The extract or indomethacin (200, 300, 400 and 800 mg/kg) was administrated orally. In the control group normal saline (5 ml/kg) was used. After getting extract, indomethacin or normal saline, animals were slaughtered. The stomachs were detached and 10ml of 2% formalin injected in to the stomach for fixing the internal coat of the gastric wall. The stomachs were then slitted open near the bigger curvature and lacerations in the glandular part were evaluated. The ulcer index was determined using j-score. Data demonstrated that the oral dose of 200mg/kg of the extract did not provoke any ulcerogenic consequence in the rat's stomach. Gastric ulcerginicity of the extract at the doses of 300, 400 and 800 mg/kg was less than the similar doses of indomethacin (poccidentale is an appropriate plant for ongoing search for establishing an analgesic agent with low gastro-intestinal side effects for clinical use.

  18. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    Science.gov (United States)

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-03-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10-2 s-1 the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10-2 s-1.

  19. Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics.

    Science.gov (United States)

    Park, Jae Sung; Kim, Taeil; Kim, Woo Soo

    2017-06-12

    We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 10 2  S/cm has been achieved from the demonstrated 3D printable composite with 1.9 vol. % loading of silver nanowires. Utilizing the high conductivity of the printable composites, 3D printing of designed battery electrode pastes is demonstrated. Rheology study shows superior printability of the electrode pastes aided by the cellulose's strong thixotropic rheology. The designed anode, electrolyte, and cathode pastes are sequentially printed to form a three-layered lithium battery for the demonstration of a charging profile. This study opens opportunities of 3D printable conductive materials to create printed electronics with the next generation additive manufacturing process.

  20. Mechanical reinforcement of gelatin hydrogel with nanofiber cellulose as a function of percolation concentration.

    Science.gov (United States)

    Wang, Wenhang; Zhang, Xiaowei; Teng, Anguo; Liu, Anjun

    2017-10-01

    Given a variety of distinguished aspect ratio-related characteristics of nanofiber cellulose (NFC), the impact of NFC on gelatin hydrogel performance involving strength, rheology, microstructure was investigated, focusing on concentration percolation mechanism for it. The inner topography displayed a compact three-dimensional network structure in the NFC-added gelatin gel, however, an NFC amount of 7.5gkg -1 caused more inhomogeneous aggregation. Texture profile analysis showed that the addition of NFC increased the hardness but reduced the elasticity of gelatin gel at 10°C, depending on NFC concentration. For static rheology, adding NFC transformed gelatin solution from the Newtonian action into pseudoplastic behavior at 60°C, with a marked increase of viscosity. Furthermore, NFC improved the temperature of sol-gel transition of gelatin, even no obvious transformation as ≥5gkg -1 NFC used. NFC reinforcement provides the potential to use as texture modifier along with gelatin in food field. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. A numerical study of water percolation through an unsaturated variable aperture fracture under coupled thermomechanical effects

    International Nuclear Information System (INIS)

    Tsang, C.F.; Noorishad, J.; Hale, F.V.

    1991-12-01

    In calculation of ground water travel times associated with performance assessment of a nuclear waste repository, the role of fractures may turn out to be very important. There are two aspects related to fracture flow that have not been fully resolved. The first is the effect of coupled thermomechanical impact on fracture apertures due to the thermal output of the nuclear waste repository. The second is the effect of the variable aperture nature of the fractures. The present paper is an exploratory study of the impact of these two effects on water percolation through unsaturated fractures. The paper is divided into two main sections. the first section describes a calculation of the thermomechanical behavior of the geologic formation around a waste repository. In this exploratory study we assume two major fractures, one vertical and one horizontal through the repository center. Temperatures and thermally induced stress fields are calculated. The second part of the paper considers the unsaturated case and describes a study of water infiltration from the land surface through the vertical fracture to the repository

  2. Water percolation conditions in Ilha Solteira dam (Parana River), using tracer techniques

    International Nuclear Information System (INIS)

    Sanchez, W.; Guidicini, G.; Silva, R.F. da.

    1975-01-01

    Radioisotopic techniques used in the study of water perconlation at the exact place of the construction of the canal lock of Ilha Solteira Dam, in its left side is presented. At the time of the drilling operations, it was discovered, by water leakage tests, total lost at 275,00 level. This water lost occurred at the vicinities of basalt lava-flows. The water leakage tests showed that the total absorption of pumping flow was about 80 liters per minute. To determine the velocity of water percolation in the probable cracks or fractures of the basalt a test of radioactive tracer 131 I was used. For the study of the radioactive tracer behaviour two techniques were tried: measurement of its dilution in the original of the well and the measurement of residence time. Results from the tests showed the existence of a crack or a set of cracks oriented from the radcoisotopic injection well to the artesian wells located at the left shore of Parana river, below Ilha Solteira Dam. The mentioned cracks are localized at the 272,00 level, close tr the contact between the basalt lava-flows

  3. Thermal transport in binary colloidal glasses: Composition dependence and percolation assessment

    Science.gov (United States)

    Ruckdeschel, Pia; Philipp, Alexandra; Kopera, Bernd A. F.; Bitterlich, Flora; Dulle, Martin; Pech-May, Nelson W.; Retsch, Markus

    2018-02-01

    The combination of various types of materials is often used to create superior composites that outperform the pure phase components. For any rational design, the thermal conductivity of the composite as a function of the volume fraction of the filler component needs to be known. When approaching the nanoscale, the homogeneous mixture of various components poses an additional challenge. Here, we investigate binary nanocomposite materials based on polymer latex beads and hollow silica nanoparticles. These form randomly mixed colloidal glasses on a sub-μ m scale. We focus on the heat transport properties through such binary assembly structures. The thermal conductivity can be well described by the effective medium theory. However, film formation of the soft polymer component leads to phase segregation and a mismatch between existing mixing models. We confirm our experimental data by finite element modeling. This additionally allowed us to assess the onset of thermal transport percolation in such random particulate structures. Our study contributes to a better understanding of thermal transport through heterostructured particulate assemblies.

  4. Comparison of percolation to batch and sequential leaching tests: theory and data.

    Science.gov (United States)

    Grathwohl, Peter; Susset, Bernd

    2009-10-01

    Leaching tests are becoming more relevant in assessing solid waste material, particularly with respect to groundwater risks. In the field, water infiltration is the dominant leaching mechanism, which is simulated in the lab with batch and column tests. In this study, we compared percolation, through analytical solutions of the advection-dispersion equation, to laboratory batch and sequential leaching tests. The analytical solutions are supported with comprehensive data from various field and laboratory leaching of different solutes from waste materials and soils collected in long-term joint research projects funded by the German Federal Ministry for Education and Research and the Federal Environment Agency. The comparison of theory and data is facilitated if concentrations and cumulative release are plotted versus the liquid-solid ratios (LS). Both theory and data indicate that leaching behaviour is independent of duration and physical dimensions of the leaching tests. This holds even if field lysimeters are compared to laboratory columns of different size, different flow velocities as well as different contact times. In general, laboratory batch tests over predict effluent concentrations (for LStests compares very well and agrees with the analytical solutions. Overall, reproducibility and agreement with theory of column tests are better than batch tests, presumably because the latter are prone to artefacts (e.g. in liquid-solid separation steps). Theory and data fit surprisingly well, despite the fact that the theory is based on the local equilibrium assumption; non-linear sorption and chemical reactions in the solid waste materials are not considered.

  5. Influence of a protein on percolation phenomena in water-in-oil micro-emulsions

    International Nuclear Information System (INIS)

    Huruguen, Jean-Pierre

    1991-01-01

    This research thesis addresses the study of a small protein named cytochrome c which has a peculiar affinity with the inner wall of droplets. This affinity is such that it increases the available interface in the system. The author first presents the properties and the solubilizing power of the ternary system made of AOT (sodium diethyl-hexyl sulfosuccinate, a surfactant), water and iso-octane. Then, he reports the study of the influence and behaviour of the protein in a dense micellar AOT/water/isooctane system: study of percolation phenomena and of light diffusion. The next part reports the structural study of the AOT/water/isooctane system in presence of the protein: models of polymer solutions, methods of exploitation of the diffused intensity, experimental conditions, study by X ray diffusion. The study of the reaction behaviour of the protein in dense medium is then reported: presentation of pulsed radiolysis, experimental results in presence or absence of cytochrome c. In the last part, the author reports the structural study of de-mixed phases: structural models, phase diagram, X and neutron diffusion of de-mixed phases, result interpretation [fr

  6. Aggregation, percolation and phase transitions in nematic liquid crystal EBBA doped with carbon nanotubes

    Science.gov (United States)

    Goncharuk, A. I.; Lebovka, N. I.; Lisetski, L. N.; Minenko, S. S.

    2009-08-01

    Electrical conductivity, optical transmittance and microstructure of multiwalled carbon nanotubes (MWCNTs) dispersed in nematic liquid crystal 4-ethoxybenzylidene-4'-n-butylaniline (EBBA) were studied in the temperature range between 287 and 363 K. The concentration C of MWCNTs was varied within 0.01-1% wt. The percolation threshold with a noticeable increase in electrical conductivity (by many orders of magnitude) was observed in the vicinity of C ≈ 0.1% wt. The heating-cooling hysteretic behaviour of electrical conductivity and optical transmittance thermal pre-history effects were studied. These effects reflected strong agglomeration and rearrangement of nanotubes during the thermal incubation. The estimates show that transient behaviour during the thermal incubation can be caused by Brownian motion of MWCNTs. The solidification of MWCNT + EBBA composite in the nematic range extended by conditions of supercooling was also studied as a function of temperature using electrical conductivity measurements. The solidification lag-time dependence on supercooling temperature followed the classical heterogeneous nucleation law, with MWCNTs serving as centres of EBBA solidification.

  7. Aggregation, percolation and phase transitions in nematic liquid crystal EBBA doped with carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Goncharuk, A I; Lebovka, N I [F Ovcharenko Institute of Biocolloidal Chemistry, NAS of Ukraine, 42 Vernadskii Prosp., Kyiv 03142 (Ukraine); Lisetski, L N; Minenko, S S, E-mail: lebovka@gmail.co [Institute for Scintillation Materials of STC ' Institute for Single Crystals' , NAS of Ukraine, 60 Lenin Ave., Kharkov 61001 (Ukraine)

    2009-08-21

    Electrical conductivity, optical transmittance and microstructure of multiwalled carbon nanotubes (MWCNTs) dispersed in nematic liquid crystal 4-ethoxybenzylidene-4'-n-butylaniline (EBBA) were studied in the temperature range between 287 and 363 K. The concentration C of MWCNTs was varied within 0.01-1% wt. The percolation threshold with a noticeable increase in electrical conductivity (by many orders of magnitude) was observed in the vicinity of C {approx} 0.1% wt. The heating-cooling hysteretic behaviour of electrical conductivity and optical transmittance thermal pre-history effects were studied. These effects reflected strong agglomeration and rearrangement of nanotubes during the thermal incubation. The estimates show that transient behaviour during the thermal incubation can be caused by Brownian motion of MWCNTs. The solidification of MWCNT + EBBA composite in the nematic range extended by conditions of supercooling was also studied as a function of temperature using electrical conductivity measurements. The solidification lag-time dependence on supercooling temperature followed the classical heterogeneous nucleation law, with MWCNTs serving as centres of EBBA solidification.

  8. Diversity among galaxy clusters

    International Nuclear Information System (INIS)

    Struble, M.F.; Rood, H.J.

    1988-01-01

    The classification of galaxy clusters is discussed. Consideration is given to the classification scheme of Abell (1950's), Zwicky (1950's), Morgan, Matthews, and Schmidt (1964), and Morgan-Bautz (1970). Galaxies can be classified based on morphology, chemical composition, spatial distribution, and motion. The correlation between a galaxy's environment and morphology is examined. The classification scheme of Rood-Sastry (1971), which is based on clusters's morphology and galaxy population, is described. The six types of clusters they define include: (1) a cD-cluster dominated by a single large galaxy, (2) a cluster dominated by a binary, (3) a core-halo cluster, (4) a cluster dominated by several bright galaxies, (5) a cluster appearing flattened, and (6) an irregularly shaped cluster. Attention is also given to the evolution of cluster structures, which is related to initial density and cluster motion

  9. Conduction in rectangular quasi-one-dimensional and two-dimensional random resistor networks away from the percolation threshold.

    Science.gov (United States)

    Kiefer, Thomas; Villanueva, Guillermo; Brugger, Jürgen

    2009-08-01

    In this study we investigate electrical conduction in finite rectangular random resistor networks in quasione and two dimensions far away from the percolation threshold p(c) by the use of a bond percolation model. Various topologies such as parallel linear chains in one dimension, as well as square and triangular lattices in two dimensions, are compared as a function of the geometrical aspect ratio. In particular we propose a linear approximation for conduction in two-dimensional systems far from p(c), which is useful for engineering purposes. We find that the same scaling function, which can be used for finite-size scaling of percolation thresholds, also applies to describe conduction away from p(c). This is in contrast to the quasi-one-dimensional case, which is highly nonlinear. The qualitative analysis of the range within which the linear approximation is legitimate is given. A brief link to real applications is made by taking into account a statistical distribution of the resistors in the network. Our results are of potential interest in fields such as nanostructured or composite materials and sensing applications.

  10. Tailoring percolating conductive networks of natural rubber composites for flexible strain sensors via a cellulose nanocrystal templated assembly.

    Science.gov (United States)

    Wang, Shuman; Zhang, Xinxing; Wu, Xiaodong; Lu, Canhui

    2016-01-21

    Conductive polymer composites (CPCs) just above the percolation threshold exhibit a unique strain-reversible electric response upon application of tensile strain, which can be used to prepare strain sensors. However, it is difficult to balance the electric conductivity which is fundamental to a stable output signal and the strain sensing sensitivity due to the relatively dense conductive pathways of the traditional CPCs. Constructing a "brittle" but effective conductive network structure in CPCs is the essential foundation of a desirable sensing material. Here, we demonstrate for the first time that highly flexible, stretchable, sensitive, and reversible strain sensors can be fabricated by a facile latex assembly approach, in which nontoxic, sustainable and biodegradable cellulose nanocrystals played a key role in tailoring the percolating network of conductive natural rubber (NR)/carbon nanotube (CNT) composites. The resulting nanocomposites with a continuous 3D conductive structure exhibited a very low electrical conductivity percolation threshold (4-fold lower than that of the conventional NR/CNT composites), high resistivity and sensitivity (gauge factor ≈ 43.5) and meanwhile good reproducibility of up to 100% strain. The proposed materials and principles in this study open up a novel practical approach to design high performance flexible sensors for a broad range of multifunctional applications.

  11. An Untrodden Path: Versatile Fabrication of Self-Supporting Polymer-Stabilized Percolation Membranes (PSPMs) for Gas Separation.

    Science.gov (United States)

    Friebe, Sebastian; Mundstock, Alexander; Schneider, Daniel; Caro, Jürgen

    2017-05-11

    The preparation and scalability of zeolite or metal organic framework (MOF) membranes remains a major challenge, and thus prevents the application of these materials in large-scale gas separation. Additionally, several zeolite or MOF materials are quite difficult or nearly impossible to grow as defect-free layers, and require expensive macroporous ceramic or polymer supports. Here, we present new self-supporting zeolite and MOF composite membranes, called Polymer-Stabilized Percolation Membranes (PSPMs), consisting of a pressed gas selective percolation network (in our case ZIF-8, NaX and MIL-140) and a gas-impermeable infiltrated epoxy resin for cohesion. We demonstrate the performance of these PSPMs by separating binary mixtures of H 2 /CO 2 and H 2 /CH 4 . We report the brickwork-like architecture featuring selective percolation pathways and the polymer as a stabilizer, compare the mechanical stability of said membranes with competing materials, and give an outlook on how economic these membranes may become. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Anisotropic percolation conduction in elastomer-carbon black composites investigated by polarization-sensitive terahertz time-domain spectroscopy

    Science.gov (United States)

    Okano, Makoto; Fujii, Misako; Watanabe, Shinichi

    2017-11-01

    We investigated the draw ratio (DR) dependence of the anisotropic dielectric function and conductivity of styrene butadiene rubbers (SBRs) with different carbon black (CB) concentrations by polarization-sensitive terahertz time-domain spectroscopy. From the frequency dependence of the conductivity in the unstretched SBRs ranging from direct current to terahertz frequencies, it is found that the SBR with a CB concentration above 30 wt. % exhibits percolation conductivity. We investigated the spectral shape of the dielectric function and conductivity of the SBR samples below and above the percolation threshold for two representative DRs in the terahertz frequency region. We found that the DR dependence of the spectral shape is well explained by the effective medium approximation, except for the sample with the CB concentration above 30 wt. % under the unstretched condition. The conductivity in that sample remarkably changes in the low terahertz frequency region, which suggests a change in the CB network by deformation. The investigation of the dielectric anisotropy and percolation conductivity using our polarization technique can be applied to a wide range of elastomer composites.

  13. Assessing clogging development in infiltration-percolation systems for wastewater treatment by electrical resistivity and induced polarisation methods

    Science.gov (United States)

    Tapias, Josefina C.; Himi, Mahjoub; Lovera, Raúl; de la Rocha, Angelica; Foch, Montserrat; Salvadó, Humbert; Casas, Albert

    2013-04-01

    Infiltration-percolation is a low technology process used to treat primary and secondary effluents. It consists in the intermittent application of sewage on buried sand filters where the infiltrated water percolates through unsaturated porous medium. The advantages over conventional mechanical sanitation systems are: low energy requirements, operation and maintenance that may be conducted by unskilled staff, and low sludge production because their simplicity and low operation costs. Nevertheless, clogging is a major operational and maintenance issue associated with the use of infiltration-percolation systems for wastewater treatment, and can ultimately limit the lifetime of the system. The clogging development causes decrease of hydraulic conductivity, reduced oxygen supply and further leads to a rapid decrease of the treatment performance. For this reason it is essential to assess in advance the evolution of clogging process and detect potential failures in the system. The preliminary results of this research conducted at the Hostalets de Pierola wastewater treatment plant (near Barcelona, Spain) show that electrical resistivity and induced polarisation geophysical methods can be very useful for delineating the clogging expansion. Then, this non-destructive metodology can help take the preventive measures for enlarge the lifetime of the treatment system.

  14. How Critical Is Critical Thinking?

    Science.gov (United States)

    Shaw, Ryan D.

    2014-01-01

    Recent educational discourse is full of references to the value of critical thinking as a 21st-century skill. In music education, critical thinking has been discussed in relation to problem solving and music listening, and some researchers suggest that training in critical thinking can improve students' responses to music. But what exactly is…

  15. Prediction of the percolation threshold and electrical conductivity of self-assembled antimony-doped tin oxide nanoparticles into ordered structures in PMMA/ATO nanocomposites.

    Science.gov (United States)

    Jin, Youngho; Gerhardt, Rosario A

    2014-12-24

    Electrical percolation in nanocomposites consisting of poly(methyl methacrylate) (PMMA) and antimony tin oxide (ATO) nanoparticles was investigated experimentally using monosize and polydisperse polymer particles. The nanocomposites were fabricated by compression molding at 170 °C. The matrix PMMA was transformed into space filling polyhedra while the ATO nanoparticles distributed along the sharp edges of the matrix, forming a 3D interconnected network. The measured electrical resistivity showed that percolation was achieved in these materials at a very low ATO content of 0.99 wt % ATO when monosize PMMA was used, whereas 1.48 wt % ATO was needed to achieve percolation when the PMMA was polydispersed. A parametric finite element approach was chosen to model this unique microstructure-driven self-assembling percolation behavior. COMSOL Multiphysics was used to solve the effects of phase segregation between the matrix and the filler using a 2D simplified model in the frequency domain of the AC/DC module. It was found that the percolation threshold (pc) is affected by the size ratio between the matrix and the filler in a systematic way. Furthermore, simulations indicate that small deviations from perfect interconnection result mostly in changes in the electrical resistivity while the minimum DC resistivity achievable in any given composite is governed by the electrical conductivity of the filler, which must be accurately known in order to obtain an accurate prediction. The model is quite general and is able to predict percolation behavior in a number of other similarly processed segregated network nanocomposites.

  16. A rule-of-thumb approach to estimate annual deep percolation and runoff in irrigated landscapes at field to farm scales

    Science.gov (United States)

    Selle, B.; Githui, F.; Thayalakumaran, T.

    2009-04-01

    The rootzone of a field or farm in irrigated landscapes is the logical unit that can be managed or influenced by farmers, catchment managers and water authorities. Increasing scarcity, variability and expensive nature of water supplies necessitates better understanding of the rootzone water balance in irrigated landscapes. The major terms of the annual water balance in the rootzone include rainfall, irrigation, evapotranspiration, deep percolation below the rootzone and runoff. While information on annual rainfall, irrigation and evapotranspiration can often be readily obtained at field to farm scales, deep percolation and runoff are typically unavailable as their continuous measurement is difficult and/or uneconomical. Consequently, these terms are often calculated using models that are able to simulate the rootzone water balance. In this case study, we developed a rule-of-thumb approach to estimate annual deep percolation and runoff for the Barr Creek catchment in northern Victoria, Australia. Firstly, annual deep percolation and runoff were calculated at field to farm scales using an integrated SWAT-MODFLOW model calibrated against a comprehensive data set including drain flows and salinity, remotely sensed evapotranspiration and watertable levels. Secondly, a rule-of-thumb approach was developed to approximate annual deep percolation and runoff from readily available information on annual irrigation, rainfall, evapotranspiration, soils, watertable levels and landuse. This rule-of-thumb approach can be applied to continuously estimate deep percolation and runoff.

  17. Competition of percolation and phase separation in a fluid of adhesive hard spheres

    NARCIS (Netherlands)

    Miller, M.A.; Frenkel, D.

    2003-01-01

    Using a combination of Monte Carlo techniques, we locate the liquid-vapor critical point of adhesive hard spheres. We find that the critical point lies deep inside the gel region of the phase diagram. The (reduced) critical temperature and density are τc = 0.1133±0.0005 and ρc = 0.508±0.01. We

  18. Clustering of correlated networks

    OpenAIRE

    Dorogovtsev, S. N.

    2003-01-01

    We obtain the clustering coefficient, the degree-dependent local clustering, and the mean clustering of networks with arbitrary correlations between the degrees of the nearest-neighbor vertices. The resulting formulas allow one to determine the nature of the clustering of a network.

  19. Cluster knockout reactions

    Indian Academy of Sciences (India)

    2014-04-07

    Apr 7, 2014 ... Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it ...

  20. What Makes Clusters Decline?

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark. The longit...

  1. Critical Jostling

    Directory of Open Access Journals (Sweden)

    Pippin Barr

    2016-11-01

    Full Text Available Games can serve a critical function in many different ways, from serious games about real world subjects to self-reflexive commentaries on the nature of games themselves. In this essay we discuss critical possibilities stemming from the area of critical design, and more specifically Carl DiSalvo’s adversarial design and its concept of reconfiguring the remainder. To illustrate such an approach, we present the design and outcomes of two games, Jostle Bastard and Jostle Parent. We show how the games specifically engage with two previous games, Hotline Miami and Octodad: Dadliest Catch, reconfiguring elements of those games to create interactive critical experiences and extensions of the source material. Through the presentation of specific design concerns and decisions, we provide a grounded illustration of a particular critical function of videogames and hope to highlight this form as another valuable approach in the larger area of videogame criticism.

  2. Analysis of Heat Flow to Estimate Percolation Flux in the Unsaturated Zone Beneath an Ephemeral Stream at Yucca Mountain, Nevada

    Science.gov (United States)

    Rousseau, J. P.; Kwicklis, E. M.

    2001-05-01

    Temperature data from a well-documented site in Pagany Wash at Yucca Mountain, Nevada indicate the presence of a significant heat-flow deficit between the Paintbrush nonwelded and underlying Topopah Spring welded hydrogeologic units that most likely is due to nonconductive heat-flow processes with substantial capacity to extract heat. Percolation fluxes on the order of 10 to 20 millimeters per year beneath Pagany Wash and on the order of 5 millimeters per year beneath the hillslopes bordering the channel can account for this apparent heat-flow deficit. Total heat flow within the unsaturated zone is the sum of its convective and conductive components. The conductive component can be calculated from the temperature gradient and thermal conductivity of the rocks comprising the section of interest. The convective component can be inferred from any observed decrease in the conductive component with increasing elevation in a borehole. Because the enthalpy and specific heat of water are well known, identification of the convectively transported heat component is equivalent to determining the percolation flux. Temperature data from two 120-meter deep boreholes, UZ#4 and UZ#5, in Pagany Wash were examined to determine the vertical distribution of upward, conductive heat flow in the unsaturated zone. The temperature data, in combination with estimates of thermal conductivity, adjusted for ambient saturation and porosity, indicated that upward conductive heat flow was approximately 15.5 mJ/s/m2 within the Pah Canyon Tuff. This heat flow estimate represents a substantial reduction in heat flow from the deeper unsaturated-zone(32 to 40 mJ/s/m2), as indicated on a map of regional heat-flow across the water table beneath Pagany Wash. Percolation fluxes of between 12.4 and 18.4 mm/yr for the depth interval between the Pah Canyon Tuff and the water table at UZ#4 and UZ#5 can account for the apparent heat-flow deficit in the deeper unsaturated zone. Two-dimensional numerical

  3. Clustering in analytical chemistry.

    Science.gov (United States)

    Drab, Klaudia; Daszykowski, Michal

    2014-01-01

    Data clustering plays an important role in the exploratory analysis of analytical data, and the use of clustering methods has been acknowledged in different fields of science. In this paper, principles of data clustering are presented with a direct focus on clustering of analytical data. The role of the clustering process in the analytical workflow is underlined, and its potential impact on the analytical workflow is emphasized.

  4. Mimicking pestcide percolation dynamics in ditches bed by successive column infltration experiment

    Science.gov (United States)

    Dages, Cecile; Samouelian, Anatja; Storck, Veronika; Negro, Sandrine; Huttel, Olivier; Voltz, Marc

    2014-05-01

    Soil layers underlying ditch beds acquire specific characteristics due to ii) hydrological and erosion/deposition processes occurring within the ditch and ii) management practices (burning, dredging, mowing, …). For example, organic matter contents of the ditch beds can be larger than those in neighboring fields, since ditches act as buffer zones. Besides, in Mediterranean catchments, farmed ditches are known to be zones of groundwater recharge and thereby may contribute to groundwater pollution. The role of farmed ditches in groundwater contamination needs therefore to be clarified. The purpose of this study was to determine the dynamic of pesticide percolation in infiltrating farmed ditches bed during a sequence of flood events. A complementary aim was to determine to which extent pesticide percolation from the ditches is correlated to surface flow water contamination. A succession of 9 flood simulations were performed on an undisturbed soil column sampled in the a ditch of the Roujan catchment (Hérault, France), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). The soil column was 15 cm long with a 15 cm inner-diameter. For the first 5 flood simulations, injected water was doped with 14C-diuron, an herbicide used in vineyards; uncontaminated water was injected for the last 4 simulations. Free drainage was imposed at the bottom of the column. Diuron concentration was kept constant during a simulated infiltration experiment, but it was progressively decreased from 1000 to 0 µg/L along the succession of the 9 events to mimic the observed seasonal variation of mean diuron concentration in surface flow at the study site (Louchart et al., 2001). Additionally, the first flood simulation was performed with tritium water to assess references on conservative transport within the soil column. For each simulation, the inflow and outflow hydrogram and chemogram were monitored. Extractable (water and solvent) and non

  5. Percolation transport theory and relevance to soil formation, vegetation growth, and productivity

    Science.gov (United States)

    Hunt, A. G.; Ghanbarian, B.

    2016-12-01

    Scaling laws of percolation theory have been applied to generate the time dependence of vegetation growth rates (both intensively managed and natural) and soil formation rates. The soil depth is thus equal to the solute vertical transport distance, the soil production function, chemical weathering rates, and C and N storage rates are all given by the time derivative of the soil depth. Approximate numerical coefficients based on the maximum flow rates in soils have been proposed, leading to a broad understanding of such processes. What is now required is an accurate understanding of the variability of the coefficients in the scaling relationships. The present abstract focuses on the scaling relationship for solute transport and soil formation. A soil formation rate relates length, x, and time, t, scales, meaning that the missing coefficient must include information about fundamental space and time scales, x0 and t0. x0 is proposed to be a fundamental mineral heterogeneity scale, i.e. a median particle diameter. to is then found from the ratio of x0 and a fundamental flow rate, v0, which is identified with the net infiltration rate. The net infiltration rate is equal to precipitation P less evapotranspiration, ET, plus run-on less run-off. Using this hypothesis, it is possible to predict soil depths and formation rates as functions of time and P - ET, and the formation rate as a function of depth, soil calcic and gypsic horizon depths as functions of P-ET. It is also possible to determine when soils are in equilibrium, and predict relationships of erosion rates and soil formation rates.

  6. Percolation theory and its application for interpretation of soil water retention curves

    International Nuclear Information System (INIS)

    Kodesova, R.

    2004-01-01

    The soil porous system has traditionally been deduced from the soil-water retention curve with the assumption of homogeneity and free accessibility of pores, defined as capillary tubes, from the sink/source of water. But real soil fabric is mostly characterized by aggregates. In this case, the soil porous system cannot be modeled as a homogeneous one. To examine the differences between homogeneous and heterogeneous soil porous systems, we studied two types of soils: sandy soil and coarse sandy soil. We applied image processing filters and the ARC/INFO Grid module to analyze pore sizes in both soils from their electron microscope images taken at two different magnifications. We used the resulting pore-size distribution data to generate 3-D porous media consisting of pores and throats. The homogeneous pore structure was created as a mono-modal pore-throat network with one pore-size distribution. The heterogeneous pore structure was designed as a bi-modal pore-throat network with two pore-size distributions, where the pore sizes were hierarchically arranged in the nodes of the network. We applied the percolation model to simulate water and air displacement in these networks. The distribution of water in the nodes of the networks was studied increasing/decreasing steps of pressure head and the drainage and wetting branches of the retention curves were evaluated. The soil-water retention curves modeled for the mono-modal and bi-modal porous systems had different characters. The simulated shape of the retention curve in the mono-modal case was close to the step-like form of a retention curve characteristic of unstructured soil. The shape of the simulated retention curve in the bi-modal case was smoother, more gradual, and closer to the shape of the retention curve of a real, structured soil. (author)

  7. Glass Transition Temperature of Saccharide Aqueous Solutions Estimated with the Free Volume/Percolation Model.

    Science.gov (United States)

    Constantin, Julian Gelman; Schneider, Matthias; Corti, Horacio R

    2016-06-09

    The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.

  8. Chemical alterations in three clayey soils from percolation and interaction with acid mine drainage (AMD

    Directory of Open Access Journals (Sweden)

    Emem-Obong Emmanuel Agbenyeku

    2016-07-01

    Full Text Available The issues of acid mine drainage (AMD from mining activities is not a new phenomenon to the present day developing South Africa as well as in most developed countries around the globe. However, the persistent rise in environmental contamination in South Africa is drastically attracting massive concerns. Vital concerns of AMD in South Africa still remain the threat to soil, surface, subsurface and ground water reserves among others, which consequentially impact human and environmental health. This insistent challenge has given rise to the need for investigating the buffering efficacy of clayey mineral soils for use as natural contaminant barriers to contaminant species from AMD. Therefore, the study presented herein, was channelled towards assessing the chemical alterations in three clayey soils from permeation and interaction with AMD via successive protracted percolation up to 18–25 pore volume passage of AMD through the respective soil medium. The final hydraulic conductivity measured, ranged between 1.3 × 10−11 m/s and 1.5 × 10−11 m/s. The obtained pH, electrical conductivity and solute breakthrough curves indicated the soils had low acid-buffering efficacies. Chemical species such as Na, Co and SO42− were highly dissolved due to attack on the soil grains by AMD. Chemical species were also released from the soils including the dissolution of metals and desorption of chemical species from AMD attack. As such, the study revealed that the buffering efficacies of the respective tested clayey soils to AMD chemical contaminants were generally ineffective.

  9. Critical Review

    DEFF Research Database (Denmark)

    Rosenbaum, Ralph K.; Olsen, Stig Irving

    2017-01-01

    Manipulation and mistakes in LCA studies are as old as the tool itself, and so is its critical review. Besides preventing misuse and unsupported claims, critical review may also help identifying mistakes and more justifiable assumptions as well as generally improve the quality of a study. It thus...

  10. Critical Muralism

    Science.gov (United States)

    Rosette, Arturo

    2009-01-01

    This study focuses on the development and practices of Critical Muralists--community-educator-artist-leader-activists--and situates these specifically in relation to the Mexican mural tradition of los Tres Grandes and in relation to the history of public art more generally. The study examines how Critical Muralists address artistic and…

  11. Critical exponents for diluted resistor networks.

    Science.gov (United States)

    Stenull, O; Janssen, H K; Oerding, K

    1999-05-01

    An approach by Stephen [Phys. Rev. B 17, 4444 (1978)] is used to investigate the critical properties of randomly diluted resistor networks near the percolation threshold by means of renormalized field theory. We reformulate an existing field theory by Harris and Lubensky [Phys. Rev. B 35, 6964 (1987)]. By a decomposition of the principal Feynman diagrams, we obtain diagrams which again can be interpreted as resistor networks. This interpretation provides for an alternative way of evaluating the Feynman diagrams for random resistor networks. We calculate the resistance crossover exponent phi up to second order in epsilon=6-d, where d is the spatial dimension. Our result phi=1+epsilon/42+4epsilon(2)/3087 verifies a previous calculation by Lubensky and Wang, which itself was based on the Potts-model formulation of the random resistor network.

  12. Management of cluster headache

    DEFF Research Database (Denmark)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    The prevalence of cluster headache is 0.1% and cluster headache is often not diagnosed or misdiagnosed as migraine or sinusitis. In cluster headache there is often a considerable diagnostic delay - an average of 7 years in a population-based survey. Cluster headache is characterized by very severe...... or severe orbital or periorbital pain with a duration of 15-180 minutes. The cluster headache attacks are accompanied by characteristic associated unilateral symptoms such as tearing, nasal congestion and/or rhinorrhoea, eyelid oedema, miosis and/or ptosis. In addition, there is a sense of restlessness...... and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment...

  13. Sexagem de espermatozoides bovinos por centrifugação em gradiente descontínuo de densidade de Percoll Sex selection in bovine spermatozoa by using Percoll discontinuos density gradient centrifugation

    Directory of Open Access Journals (Sweden)

    Vera Fernanda Martins Hossepian de Lima

    2011-08-01

    Full Text Available O objetivo neste trabalho foi desenvolver um método de seleção do sexo de espermatozoides bovinos por centrifugação em gradiente de densidade de Percoll. Utilizou-se sêmen congelado de touros mantidos em regime de colheita de sêmen. A fração de espermatozoides X ou Y foi separada por centrifugação em treze diferentes gradientes de densidade de Percoll formados por 1 a 12 camadas com densidades que variaram de 1,004 g/mL a 1,123 g/mL. As soluções com diferentes densidades foram preparadas misturando-se, em proporções diferentes, meio de cultura Hank's e uma solução estoque composta de NaCl 1,5 M e Percoll (1:9, v/v. Sobre cada gradiente foi colocado um total de 50 × 10(6 espermatozoides descongelados em 0,7 mL de meio Hank's e centrifugados a 250 X g por 30 minutos, em rotor horizontal, a 25°C. Os espermatozoides das frações superior e inferior foram tratados com Quinacrina Mustarda e analisados (200 deles quanto à presença do corpúsculo-F. Dos espermatozoides encontrados no sedimento de dois gradientes, compostos de 8 e 12 frações com densidades variando entre 1,050 a 1,120 g/mL e 1,044 a 1,123 g/mL, respectivamente, visualizaram-se 25% com corpúsculo-F e os 75% restantes prováveis portadores do cromossomo X. O aumento na porcentagem de espermatozoides X após a centrifugação em gradiente de densidade permitirá que esse método de sexagem seja usado em larga escala na produção comercial de carne e leite bem como no teste de progênie.The objective of this work was to develop a bovine spermatozoid sex selection method by using Percoll density gradient centrifugation. It was used frozen semen of bulls kept in semen collection regime. Fraction X or Y was separated by centrifugation in three different Percoll density gradient formed by 1 to 12 layers with densities varying from 1.004 g/mL to 1.123 g/mL. Solutions with different densities were prepared by mixing, at different proportions, Hank's culture medium and a

  14. Seleção em gradiente de Percoll® sobre os parâmetros espermáticos do sêmen bovino congelado Selection bovine frozen semen in Percoll® gradient on spermatic parameters

    Directory of Open Access Journals (Sweden)

    Charles Kiefer

    2008-06-01

    Full Text Available Na produção in vitro de embriões, técnicas de seleção espermática são usadas, dentre elas, o gradiente descontínuo de Percoll®. O objetivo foi avaliar a integridade da membrana plasmática (eosina-nigrosina, do acrossomo (trypan blue- Giemsa – TBG, lecitina do amendoim conjugada ao isotiocianato de fluoresceína associado ao iodeto de propídeo - Fitc-PNA/PI e da cromatina (azul de toluidina, em espermatozóide bovino congelado. Vinte e nove amostras foram analisadas nos momentos pós-descongelação (PD e pós-Percoll® (PP. As variáveis expressas em porcentagem foram submetidas à análise de variância e foi empregado o teste de Tuckey para a comparação entre médias. O estudo da associação entre variáveis foi feito pelo teste de correlação de Pearson. Constataram-se, entre os momentos PD e PP, diferenças significativas (p<0,05 para a motilidade, integridade de membrana plasmática e número de espermatozóides vivos com acrossomo íntegro (TBG e Fitc-PNA/PI, com maiores valores obtidos PP. O percentual de células com alteração na condensação da cromatina não diferiu entre os momentos estudados. Conclui-se que o gradiente descontínuo de Percoll® foi eficaz na seleção de uma maior população de células móveis, com membranas plasmática e acrossomal íntegras, sem haver alteração na condensação da cromatina nuclear.At in vitro embryo production sperm selection techniques are used, one of them is Percoll® density-gradient. The aim with this study was to evaluate the plasmatic membrane (eosin-nigrosin, acrosomal (trypan blue-Giemsa; fluorescein isothiocyanate conjugated peanut agglutinin lecitin/propidium iodide (FITC-PNA/PI and chromatin (toluidine blue integrity, in frozen bovine spermatozoa. Twenty nine samples were analysed at post-thaw (PD and post-Percoll® moments. Variable expressed in percentage were submitted to ANOVA and used Tuckey’s test for mean comparison. The association between variables

  15. Comprehensive cluster analysis with Transitivity Clustering.

    Science.gov (United States)

    Wittkop, Tobias; Emig, Dorothea; Truss, Anke; Albrecht, Mario; Böcker, Sebastian; Baumbach, Jan

    2011-03-01

    Transitivity Clustering is a method for the partitioning of biological data into groups of similar objects, such as genes, for instance. It provides integrated access to various functions addressing each step of a typical cluster analysis. To facilitate this, Transitivity Clustering is accessible online and offers three user-friendly interfaces: a powerful stand-alone version, a web interface, and a collection of Cytoscape plug-ins. In this paper, we describe three major workflows: (i) protein (super)family detection with Cytoscape, (ii) protein homology detection with incomplete gold standards and (iii) clustering of gene expression data. This protocol guides the user through the most important features of Transitivity Clustering and takes ∼1 h to complete.

  16. Critical-Thinking Types among Nursing and Management Undergraduates.

    Science.gov (United States)

    Thorpe, Karran; Loo, Robert

    2003-01-01

    The short form of the Watson-Glaser Critical Thinking Appraisal was completed by 233 nursing and 131 management students, yielding four clusters of critical thinking types. Discriminant analysis using cluster membership and subtest scores showed 96% were correctly classified. (Contains 40 references) (SK)

  17. Critical Arts

    African Journals Online (AJOL)

    both formal and informal) in culture and social theory. CRITICAL ARTS aims to challenge and ... Book Review: Brian McNair, An Introduction to Political Communication (3rd edition), London: Routledge, 2003, ISBN 0415307082, 272pp. Phil Joffe ...

  18. Critical proximity

    Directory of Open Access Journals (Sweden)

    Simon, Jane

    2010-01-01

    Full Text Available This essay considers how written language frames visual objects. Drawing on Michel Foucault’s response to Raymond Roussel’s obsessive description, the essay proposes a model of criticism where description might press up against its objects. This critical closeness is then mapped across the conceptual art practice and art criticism of Ian Burn. Burn attends to the differences between seeing and reading, and considers the conditions which frame how we look at images, including how we look at, and through words. The essay goes on to consider Meaghan Morris’s writing on Lynn Silverman’s photographs. Both Morris and Burn offer an alternative to a parasitic model of criticism and enact a patient way of looking across and through visual landscapes.

  19. Electronic properties of GaV4S8: A percolation approach

    Indian Academy of Sciences (India)

    This statement is strongly supported by the calculated band- width per cluster in GaV4S8 .... site in GaV4S8 are the same because of the identical chemical composition. 3.2 Resistivity. The resistivity of .... One of the authors (S Hansda) acknowledges UGC, New Delhi, India for the financial support through Rajiv Gandhi ...

  20. Manipulation of Microbubble Clusters Using Focused Ultrasound

    Science.gov (United States)

    Matsuzaki, Hironobu; Osaki, Taichi; Kawaguchi, Kei; Unga, Johan; Ichiyanagi, Mitsuhisa; Azuma, Takashi; Suzuki, Ryo; Maruyama, Kazuo; Takagi, Shu

    2017-11-01

    In recent years, microbubbles (MBs) are expected to be utilized for the ultrasound drug delivery system (DDS). For the MB-DDS, it is important to establish a method of controlling bubbles and bubble clusters using ultrasound field. The objective of this study is to clarify behaviors of bubble clusters with various physical conditions. MBs in the ultrasound field are subjected to the primary Bjerknes force. The force traps MBs at the focal region of the focused ultrasound field. The trapped MBs form a bubble cluster at the region. A bubble cluster continues growing with absorbing surrounding bubbles until it reaches a maximum size beyond which it disappears from the focal region. In the present study, two kinds of MBs are used for the experiment. One is Sonazoid with average diameter of 2.6 um and resonant frequency of 5 MHz. The other is developed by Teikyo Univ., with average diameter of 1.5 um and presumed resonant frequency of 4 MHz. The bubble cluster's behaviors are analyzed using the high-speed camera. Sonazoid clusters have larger critical size than the other in every frequency, and its cluster size is inversely proportional to the ultrasound frequency, while Teikyo-bubble clusters have different tendency. These results are discussed in the presentation.