7,266 research outputs found
Modes of wall induced granular crystallisation in vibrational packing
Granular crystallisation is an important phenomenon whereby ordered packing
structures form in granular matter under vibration. However, compared with the
well-developed principles of crystallisation at the atomic scale,
crystallisation in granular matter remains relatively poorly understood. To
investigate this behaviour further and bridge the fields of granular matter and
materials science, we simulated mono-disperse spheres confined in cylindrical
containers to study their structural dynamics during vibration. By applying
adequate vibration, disorder-to-order transitions were induced. Such
transitions were characterised at the particle scale through bond orientation
order parameters. As a result, emergent crystallisation was indicated by the
enhancement of the local order of individual particles and the number of
ordered particles. The observed heterogeneous crystallisation was characterised
by the evolution of the spatial distributions via coarse-graining the order
index. Crystalline regimes epitaxially grew from templates formed near the
container walls during vibration, here termed the wall effect. By varying the
geometrical dimensions of cylindrical containers, the obtained crystallised
structures were found to differ at the cylindrical wall zone and the planar
bottom wall zone. The formed packing structures were quantitatively compared to
X-ray tomography results using again these order parameters. The findings here
provide a microscopic perspective for developing laws governing structural
dynamics in granular matter
Dynamic Modeling and Simulation of a Real World Billiard
Gravitational billiards provide an experimentally accessible arena for
testing formulations of nonlinear dynamics. We present a mathematical model
that captures the essential dynamics required for describing the motion of a
realistic billiard for arbitrary boundaries. Simulations of the model are
applied to parabolic, wedge and hyperbolic billiards that are driven
sinusoidally. Direct comparisons are made between the model's predictions and
previously published experimental data. It is shown that the data can be
successfully modeled with a simple set of parameters without an assumption of
exotic energy dependence.Comment: 10 pages, 3 figure
Directly depicting granular ontologies
Published in extended form as "Endurants and Perdurants in Directly Depicting Ontologies",
We propose an ontological theory that is powerful enough to describe both complex spatio-temporal processes and the enduring entities that participate in such processes. For this purpose we distinguish between ontologies and metaontology. Ontologies are based on very simple directly depicting languages and fall into two major categories: ontologies of type SPAN and ontologies of type SNAP. These represent two complementary perspectives on reality and result in distinct though compatible systems of categories. In a SNAP (snapshot) ontology we have the enduring entities in a given domain as they exist to be inventoried at some given moment of time. In a SPAN ontology we have perduring entities such as processes and their parts and aggregates. We argue that both kinds of ontology are required, together with the meta-ontology which joins them together. On the level of meta-ontology we are able to impose constraints on ontologies of a sort which can support efficient processing of large amounts of data
Analysis of equivalence mapping for terminology services
This paper assesses the range of equivalence or mapping types required to facilitate interoperability in the context of a distributed terminology server. A detailed set of mapping types were examined, with a view to determining their validity for characterizing relationships between mappings from selected terminologies (AAT, LCSH, MeSH, and UNESCO) to the Dewey Decimal Classification (DDC) scheme. It was hypothesized that the detailed set of 19 match types proposed by Chaplan in 1995 is unnecessary in this context and that they could be reduced to a less detailed conceptually-based set. Results from an extensive mapping exercise support the main hypothesis and a generic suite of match types are proposed, although doubt remains over the current adequacy of the developing Simple Knowledge Organization System (SKOS) Core Mapping Vocabulary Specification (MVS) for inter-terminology mapping
Data granulation by the principles of uncertainty
Researches in granular modeling produced a variety of mathematical models,
such as intervals, (higher-order) fuzzy sets, rough sets, and shadowed sets,
which are all suitable to characterize the so-called information granules.
Modeling of the input data uncertainty is recognized as a crucial aspect in
information granulation. Moreover, the uncertainty is a well-studied concept in
many mathematical settings, such as those of probability theory, fuzzy set
theory, and possibility theory. This fact suggests that an appropriate
quantification of the uncertainty expressed by the information granule model
could be used to define an invariant property, to be exploited in practical
situations of information granulation. In this perspective, a procedure of
information granulation is effective if the uncertainty conveyed by the
synthesized information granule is in a monotonically increasing relation with
the uncertainty of the input data. In this paper, we present a data granulation
framework that elaborates over the principles of uncertainty introduced by
Klir. Being the uncertainty a mesoscopic descriptor of systems and data, it is
possible to apply such principles regardless of the input data type and the
specific mathematical setting adopted for the information granules. The
proposed framework is conceived (i) to offer a guideline for the synthesis of
information granules and (ii) to build a groundwork to compare and
quantitatively judge over different data granulation procedures. To provide a
suitable case study, we introduce a new data granulation technique based on the
minimum sum of distances, which is designed to generate type-2 fuzzy sets. We
analyze the procedure by performing different experiments on two distinct data
types: feature vectors and labeled graphs. Results show that the uncertainty of
the input data is suitably conveyed by the generated type-2 fuzzy set models.Comment: 16 pages, 9 figures, 52 reference
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