724 research outputs found
On a property of random-oriented percolation in a quadrant
Grimmett's random-orientation percolation is formulated as follows. The
square lattice is used to generate an oriented graph such that each edge is
oriented rightwards (resp. upwards) with probability and leftwards (resp.
downwards) otherwise. We consider a variation of Grimmett's model proposed by
Hegarty, in which edges are oriented away from the origin with probability ,
and towards it with probability , which implies rotational instead of
translational symmetry. We show that both models could be considered as special
cases of random-oriented percolation in the NE-quadrant, provided that the
critical value for the latter is 1/2. As a corollary, we unconditionally obtain
a non-trivial lower bound for the critical value of Hegarty's
random-orientation model. The second part of the paper is devoted to higher
dimensions and we show that the Grimmett model percolates in any slab of height
at least 3 in .Comment: The abstract has been updated, discussion has been added to the end
of the articl
Neoliberalism as a Prevailing Force on the Conditions of Teacher Education in Canada
This paper examines the impact of neoliberalist macro-policy and culture on the conditions and practice of teacher education in Canada. The origins and central features of neoliberalism are unpacked to show how the centrality of the nation state of liberalism has been replaced under neoliberalism by the distorted myth of a minimalist state that in reality reshapes social institutions along market lines and uses state regulation machinery to ensure that the market model is dominant to the point of diminishing the idea of the âpublic good.â This has made the world very unstable, leading to civil strife, political violence and an ongoing diasporization associated with trans-national migration. Within this unstable world, higher education and teacher education in Canada take place. I then turn to examining the impact of neoliberalist policy on higher education as a foreground to examining the impact of neoliberalist policy conditions on Canadian teacher education. Three themes are extrapolated to demonstrate this impactâthe conflicted challenge between institutional legitimacy and professional identity that working in a higher education context presents to Canadian teacher educators; some unresolved issues of accessibility and accountability in Canadian teacher education programs; and the ways in which a commitment to social justice with its emphasis on inclusion, diversity, and multiculturalism that Canadian teacher educators name as important are frustrated and sometimes impeded. My thesis is that neoliberalism is using audit conditions of accountability to re-frame teachersâ work as an occupational relationship. My claim is that if economic rationalist accountability ends up trumping professional judgment, then teaching will potentially lose its professional status. And, if that happens, there will likely be no place for university teacher education.Cet article porte sur lâimpact de la macro-politique et la culture nĂ©olibĂ©rales sur les conditions et la pratique de la formation des enseignants au Canada. Les origines et les caractĂ©ristiques essentielles du nĂ©olibĂ©ralisme sont exposĂ©es afin de dĂ©montrer dans quelle mesure la centralitĂ© de lâĂ©tat nation du libĂ©ralisme a Ă©tĂ© remplacĂ©e sous le nĂ©olibĂ©ralisme par le mythe dĂ©formĂ© dâun Ă©tat minimaliste qui, en rĂ©alitĂ©, remanie les institutions sociales selon les principes de la libertĂ© du marchĂ© et utilise lâappareil de la rĂ©glementation Ă©tatique pour assurer que le modĂšle du marchĂ© domine jusquâau point de diminuer lâidĂ©e du « bien public ». Le rĂ©sultat en est un monde trĂšs instable caractĂ©risĂ© par des troubles civils, de la violence politique et des dĂ©placements constants liĂ©s Ă la migration transnationale. Câest dans ce contexte instable que se dĂ©roulent les Ă©tudes supĂ©rieures et la formation des enseignants au Canada. Lâexamen de lâimpact de la politique nĂ©olibĂ©rale sur les Ă©tudes supĂ©rieures sert de toile de fond pour lâĂ©tude de lâimpact des politiques nĂ©olibĂ©rales sur la formation des enseignants au Canada. Trois thĂšmes dĂ©montrent bien cet impact : le dĂ©fi que pose, pour les formateurs dâenseignants au Canada Ćuvrant dans les milieux des Ă©tudes supĂ©rieures, le conflit entre la lĂ©gitimitĂ© institutionnelle et lâidentitĂ© professionnelle; des problĂšmes non rĂ©solus dans les programmes de formation des enseignants et portant sur lâaccessibilitĂ© et la responsabilitĂ©; et les entraves qui se dressent parfois devant un engagement envers la justice sociale visant lâinclusion, la diversitĂ© et le multiculturalisme, Ă©lĂ©ments que les formateurs dâenseignants indiquent comme Ă©tant importants. Ma thĂšse propose que le nĂ©olibĂ©ralisme emploie des conditions de vĂ©rification pour reformuler le travail des enseignants comme une relation professionnelle. Jâaffirme que si les notions Ă©conomiques et rationalistes de la responsabilitĂ© finissent par lâemporter sur le jugement professionnel, lâenseignement pourrait perdre son statut professionnel. Si cela devait se produire, il est probable que la formation universitaire des enseignants nâaurait plus sa place au Canada.Mots clĂ©s : nĂ©olibĂ©ralisme, travail des enseignants, formation des enseignants, intellectuel publi
Dynamical Exchanges in Facilitated Models of Supercooled liquids
We investigate statistics of dynamical exchange events in coarse--grained
models of supercooled liquids in spatial dimensions , 2, and 3. The
models, based upon the concept of dynamical facilitation, capture generic
features of statistics of exchange times and persistence times. Here,
distributions for both times are related, and calculated for cases of strong
and fragile glass formers over a range of temperatures. Exchange time
distributions are shown to be particularly sensitive to the model parameters
and dimensions, and exhibit more structured and richer behavior than
persistence time distributions. Mean exchange times are shown to be Arrhenius,
regardless of models and spatial dimensions. Specifically, , with being the excitation concentration. Different dynamical
exchange processes are identified and characterized from the underlying
trajectories. We discuss experimental possibilities to test some of our
theoretical findings.Comment: 11 pages, 14 figures, minor corrections made, paper published in
Journal of Chemical Physic
Directed percolation effects emerging from superadditivity of quantum networks
Entanglement indcued non--additivity of classical communication capacity in
networks consisting of quantum channels is considered. Communication lattices
consisiting of butterfly-type entanglement breaking channels augmented, with
some probability, by identity channels are analyzed. The capacity
superadditivity in the network is manifested in directed correlated bond
percolation which we consider in two flavours: simply directed and randomly
oriented. The obtained percolation properties show that high capacity
information transfer sets in much faster in the regime of superadditive
communication capacity than otherwise possible. As a byproduct, this sheds
light on a new type of entanglement based quantum capacity percolation
phenomenon.Comment: 6 pages, 4 figure
Entanglement in the quantum Ising model
We study the asymptotic scaling of the entanglement of a block of spins for
the ground state of the one-dimensional quantum Ising model with transverse
field. When the field is sufficiently strong, the entanglement grows at most
logarithmically in the number of spins. The proof utilises a transformation to
a model of classical probability called the continuum random-cluster model, and
is based on a property of the latter model termed ratio weak-mixing. Our proof
applies equally to a large class of disordered interactions
Self-avoiding walks and connective constants
The connective constant of a quasi-transitive graph is the
asymptotic growth rate of the number of self-avoiding walks (SAWs) on from
a given starting vertex. We survey several aspects of the relationship between
the connective constant and the underlying graph .
We present upper and lower bounds for in terms of the
vertex-degree and girth of a transitive graph.
We discuss the question of whether for transitive
cubic graphs (where denotes the golden mean), and we introduce the
Fisher transformation for SAWs (that is, the replacement of vertices by
triangles).
We present strict inequalities for the connective constants
of transitive graphs , as varies.
As a consequence of the last, the connective constant of a Cayley
graph of a finitely generated group decreases strictly when a new relator is
added, and increases strictly when a non-trivial group element is declared to
be a further generator.
We describe so-called graph height functions within an account of
"bridges" for quasi-transitive graphs, and indicate that the bridge constant
equals the connective constant when the graph has a unimodular graph height
function.
A partial answer is given to the question of the locality of
connective constants, based around the existence of unimodular graph height
functions.
Examples are presented of Cayley graphs of finitely presented
groups that possess graph height functions (that are, in addition, harmonic and
unimodular), and that do not.
The review closes with a brief account of the "speed" of SAW.Comment: Accepted version. arXiv admin note: substantial text overlap with
arXiv:1304.721
Risk-bounded formation of fuzzy coalitions among service agents.
Cooperative autonomous agents form coalitions in order ro share and combine resources and services to efficiently respond to market demands. With the variety of resources and services provided online today, there is a need for stable and flexible techniques to support the automation of agent coalition formation in this context. This paper describes an approach to the problem based on fuzzy coalitions. Compared with a classic cooperative game with crisp coalitions (where each agent is a full member of exactly one coalition), an agent can participate in multiple coalitions with varying degrees of involvement. This gives the agent more freedom and flexibility, allowing them to make full use of their resources, thus maximising utility, even if only comparatively small coalitions are formed. An important aspect of our approach is that the agents can control and bound the risk caused by the possible failure or default of some partner agents by spreading their involvement in diverse coalitions
FSA field test report, 1980 - 1982
Photovoltaic modules made of new and developing materials were tested in a continuing study of weatherability, compatibility, and corrosion protection. Over a two-year period, 365 two-cell submodules have been exposed for various intervals at three outdoor sites in Southern California or subjected to laboratory acceptance tests. Results to date show little loss of maximum power output, except in two types of modules. In the first of these, failure is due to cell fracture from the stresses that arise as water is regained from the surrounding air by a hardboard substrate, which shrank as it dried during its encapsulation in plastic film at 150 C in vacuo. In the second, the glass superstrate is sensitive to cracking, which also damages the cells electrostatically bonded to it; inadequate bonding of interconnects to the cells is also a problem in these modules. In a third type of module, a polyurethane pottant has begun to yellow, though as yet without significant effect on maximum power output
Density classification on infinite lattices and trees
Consider an infinite graph with nodes initially labeled by independent
Bernoulli random variables of parameter p. We address the density
classification problem, that is, we want to design a (probabilistic or
deterministic) cellular automaton or a finite-range interacting particle system
that evolves on this graph and decides whether p is smaller or larger than 1/2.
Precisely, the trajectories should converge to the uniform configuration with
only 0's if p1/2. We present solutions to that problem
on the d-dimensional lattice, for any d>1, and on the regular infinite trees.
For Z, we propose some candidates that we back up with numerical simulations
Predicting Failure using Conditioning on Damage History: Demonstration on Percolation and Hierarchical Fiber Bundles
We formulate the problem of probabilistic predictions of global failure in
the simplest possible model based on site percolation and on one of the
simplest model of time-dependent rupture, a hierarchical fiber bundle model. We
show that conditioning the predictions on the knowledge of the current degree
of damage (occupancy density or number and size of cracks) and on some
information on the largest cluster improves significantly the prediction
accuracy, in particular by allowing to identify those realizations which have
anomalously low or large clusters (cracks). We quantify the prediction gains
using two measures, the relative specific information gain (which is the
variation of entropy obtained by adding new information) and the
root-mean-square of the prediction errors over a large ensemble of
realizations. The bulk of our simulations have been obtained with the
two-dimensional site percolation model on a lattice of size and hold true for other lattice sizes. For the hierarchical fiber
bundle model, conditioning the measures of damage on the information of the
location and size of the largest crack extends significantly the critical
region and the prediction skills. These examples illustrate how on-going damage
can be used as a revelation of both the realization-dependent pre-existing
heterogeneity and the damage scenario undertaken by each specific sample.Comment: 7 pages + 11 figure
- âŠ