3,324 research outputs found
Precise toppling balance, quenched disorder, and universality for sandpiles
A single sandpile model with quenched random toppling matrices captures the
crucial features of different models of self-organized criticality. With
symmetric matrices avalanche statistics falls in the multiscaling BTW
universality class. In the asymmetric case the simple scaling of the Manna
model is observed. The presence or absence of a precise toppling balance
between the amount of sand released by a toppling site and the total quantity
the same site receives when all its neighbors topple once determines the
appropriate universality class.Comment: 5 Revtex pages, 4 figure
Confined optical phonon modes in polar tetrapod nanocrystals detected by resonant inelastic light scattering
We investigated CdTe nanocrystal tetrapods of different sizes by resonant
inelastic light scattering at room temperature and under cryogenic conditions.
We observe a strongly resonant behavior of the phonon scattering with the
excitonic structure of the tetrapods. Under resonant conditions we detect a set
of phonon modes that can be understood as confined longitudinal-optical
phonons, surface-optical phonons, and transverse-optical phonons in a nanowire
picture.Comment: 12 pages, 4 figure
Sandpile model on an optimized scale-free network on Euclidean space
Deterministic sandpile models are studied on a cost optimized
Barab\'asi-Albert (BA) scale-free network whose nodes are the sites of a square
lattice. For the optimized BA network, the sandpile model has the same critical
behaviour as the BTW sandpile, whereas for the un-optimized BA network the
critical behaviour is mean-field like.Comment: Five pages, four figure
Clustering properties of a generalised critical Euclidean network
Many real-world networks exhibit scale-free feature, have a small diameter
and a high clustering tendency. We have studied the properties of a growing
network, which has all these features, in which an incoming node is connected
to its th predecessor of degree with a link of length using a
probability proportional to . For , the
network is scale free at with the degree distribution and as in the Barab\'asi-Albert model (). We find a phase boundary in the plane along which
the network is scale-free. Interestingly, we find scale-free behaviour even for
for where the existence of a new universality class
is indicated from the behaviour of the degree distribution and the clustering
coefficients. The network has a small diameter in the entire scale-free region.
The clustering coefficients emulate the behaviour of most real networks for
increasing negative values of on the phase boundary.Comment: 4 pages REVTEX, 4 figure
Critical States in a Dissipative Sandpile Model
A directed dissipative sandpile model is studied in the two-dimension.
Numerical results indicate that the long time steady states of this model are
critical when grains are dropped only at the top or, everywhere. The critical
behaviour is mean-field like. We discuss the role of infinite avalanches of
dissipative models in periodic systems in determining the critical behaviour of
same models in open systems.Comment: 4 pages (Revtex), 5 ps figures (included
Path-integral representation for a stochastic sandpile
We introduce an operator description for a stochastic sandpile model with a
conserved particle density, and develop a path-integral representation for its
evolution. The resulting (exact) expression for the effective action highlights
certain interesting features of the model, for example, that it is nominally
massless, and that the dynamics is via cooperative diffusion. Using the
path-integral formalism, we construct a diagrammatic perturbation theory,
yielding a series expansion for the activity density in powers of the time.Comment: 22 pages, 6 figure
Self-Structuring of Granular Media under Internal Avalanches
We study the phenomenon of internal avalanching within the context of
recently proposed ``Tetris'' lattice models for granular media. We define a
recycling dynamics under which the system reaches a steady state which is
self-structured, i.e. it shows a complex interplay between textured internal
structures and critical avalanche behavior. Furthermore we develop a general
mean-field theory for this class of systems and discuss possible scenarios for
the breakdown of universality.Comment: 4 pages RevTex, 3 eps figures, revised version to appear in Phys.
Rev. Let
Exploring Employer Perspectives on Their Supportive Role in Accommodating Workers with Disabilities to Promote Sustainable RTW: A Qualitative Study
Purpose: Employers play an important role in facilitating sustainable return to work (RTW) by workers with disabilities. The aim of this qualitative study was to explore how employers who were successful in retaining workers with disabilities at work fulfilled their supportive role, and which facilitators were essential to support these workers throughout the RTW process. Methods: We conducted a semi-structured interview study among 27 employers who had experience in retaining workers with disabilities within their organization. We explored the different phases of RTW, from the onset of sick leave until the period, after 2-years of sick-leave, and when they can apply for disability benefit. We analyzed data by means of thematic analysis. Results: We identified three types of employer support: (1) instrumental (offering work accommodations), (2) emotional (encouragement, empathy, understanding) and (3) informational (providing information, setting boundaries). We identified three facilitators of employer support (at organizational and supervisor levels): (1) good collaboration, including (in)formal contact and (in)formal networks; (2) employer characteristics, including supportive organizational culture and leadership skills; and (3) worker characteristics, including flexibility and self-control. Conclusions: Employers described three different possible types of support for the worker with disabilities: instrumental, emotional, and informational. The type and intensity of employer support varies during the different phases, which is a finding that should be further investigated. Good collaboration and flexibility of both employer and worker were reported as facilitators of optimal supervisor/worker interaction during the RTW process, which may show that sick-listed workers and their supervisors have a joint responsibility for the RTW process. More insight is needed on how this supervisor/worker interaction develops during the RTW process
Scale-free network on a vertical plane
A scale-free network is grown in the Euclidean space with a global
directional bias. On a vertical plane, nodes are introduced at unit rate at
randomly selected points and a node is allowed to be connected only to the
subset of nodes which are below it using the attachment probability: . Our numerical results indicate that the directed
scale-free network for belongs to a different universality class
compared to the isotropic scale-free network. For the
degree distribution is stretched exponential in general which takes a pure
exponential form in the limit of . The link length
distribution is calculated analytically for all values of .Comment: 4 pages, 4 figure
Order Parameter and Scaling Fields in Self-Organized Criticality
We present a unified dynamical mean-field theory for stochastic
self-organized critical models. We use a single site approximation and we
include the details of different models by using effective parameters and
constraints. We identify the order parameter and the relevant scaling fields in
order to describe the critical behavior in terms of usual concepts of non
equilibrium lattice models with steady-states. We point out the inconsistencies
of previous mean-field approaches, which lead to different predictions.
Numerical simulations confirm the validity of our results beyond mean-field
theory.Comment: 4 RevTex pages and 2 postscript figure
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