2,165 research outputs found
Modeling Network Populations via Graph Distances
This article introduces a new class of models for multiple networks. The core
idea is to parametrize a distribution on labelled graphs in terms of a
Fr\'{e}chet mean graph (which depends on a user-specified choice of metric or
graph distance) and a parameter that controls the concentration of this
distribution about its mean. Entropy is the natural parameter for such control,
varying from a point mass concentrated on the Fr\'{e}chet mean itself to a
uniform distribution over all graphs on a given vertex set. We provide a
hierarchical Bayesian approach for exploiting this construction, along with
straightforward strategies for sampling from the resultant posterior
distribution. We conclude by demonstrating the efficacy of our approach via
simulation studies and two multiple-network data analysis examples: one drawn
from systems biology and the other from neuroscience.Comment: 33 pages, 8 figure
IMPLEMENTATION AND UNIFORM MANAGEMENT OF MODELLING ENTITIES IN A MASSIVELY FEATURE-OBJECT ORIENTED ADVANCED CAD ENVIRONMENT
Today we are spectators of the transition process in computer aided design from traditional geometry based on design systems to advanced computer-based engineering systems. The key is the feature technology that allows both integrating and managing modelling entities in a coherent way. Feature technology is developing rapidly. New research topics and contexts are emerging from time to time. This paper introduces concept, design and technological feature-objects to support operational, structural and morphological modelling of mechanical products. First, the feature-centred approaches to conceptual design are summarized and evaluated. Then an implementation of concept feature-objects and the methodology for using them is presented. The strength of concept feature-objects is in their morphology inclusive nature. They appear as parametrized three-dimensional
skeletons providing geometrical representations for the modelled engineering conceptions. A concept feature-object models the physical ports, contact surfaces related to ports, bones between ports, DOF of ports, relevant physical parameters, scientific and empirical descriptions of intentional transformations and environmental effects. Concept feature-objects are related to design feature-objects that, in turn, are constructed of a relevant
set of technological feature-entities. Concept feature-objects refer to the configurable and parametrized design feature-objects through an indexing mechanism. The conceptions have been tested during the programming and further development of the authors' PRODES system
Mott physics and spin fluctuations: a functional viewpoint
We present a formalism for strongly correlated systems with fermions coupled
to bosonic modes. We construct the three-particle irreducible functional
by successive Legendre transformations of the free energy of the
system. We derive a closed set of equations for the fermionic and bosonic
self-energies for a given . We then introduce a local
approximation for , which extends the idea of dynamical mean field
theory (DMFT) approaches from two- to three-particle irreducibility. This
approximation entails the locality of the three-leg electron-boson vertex
, which is self-consistently computed using a quantum
impurity model with dynamical charge and spin interactions. This local vertex
is used to construct frequency- and momentum-dependent electronic self-energies
and polarizations. By construction, the method interpolates between the
spin-fluctuation or GW approximations at weak coupling and the atomic limit at
strong coupling. We apply it to the Hubbard model on two-dimensional square and
triangular lattices. We complement the results of Phys.Rev. B 92, 115109 by (i)
showing that, at half-filling, as DMFT, the method describes the Fermi-liquid
metallic state and the Mott insulator, separated by a first-order
interacting-driven Mott transition at low temperatures, (ii) investigating the
influence of frustration and (iii) discussing the influence of the bosonic
decoupling channel.Comment: 29 pages, 14 figure
A Shortcut to General Tree-level Scattering Amplitudes in N=4 SYM via Integrability
© 2014 WILEYâVCH Verlag GmbH & Co. KGaA, WeinheimWe combine recent applications of the two-dimensional quantum inverse scattering method to the scattering amplitude problem in four-dimensional N=4 Super Yang-Mills theory. Integrability allows us to obtain a general, explicit method for the derivation of the Yangian invariants relevant for tree-level scattering amplitudes in the N=4 model.Peer reviewe
Languages and Tools for Optimization of Large-Scale Systems
Modeling and simulation are established techniques for solving design problems in a wide range of engineering disciplines today. Dedicated computer languages, such as Modelica, and efficient software tools are available. In this thesis, an extension of Modelica, Optimica, targeted at dynamic optimization of Modelica models is proposed. In order to demonstrate the Optimica extension, supporting software has been developed. This includes a modularly extensible Modelica compiler, the JModelica compiler, and an extension that supports also Optimica. A Modelica library for paper machine dryer section modeling, DryLib, has been developed. The classes in the library enable structured and hierarchical modeling of dryer sections at the application user level, while offering extensibility for the expert user. Based on DryLib, a parameter optimization problem, a model reduction problem, and an optimization-based control problem have been formulated and solved. A start-up optimization problem for a plate reactor has been formulated in Optimica, and solved by means of the Optimica compiler. In addition, the robustness properties of the start-up trajectories have been evaluated by means of Monte-Carlo simulation. In many control systems, it is necessary to consider interaction with a user. In this thesis, a manual control scheme for an unstable inverted pendulum system, where the inputs are bounded, is presented. The proposed controller is based on the notion of reachability sets and guarantees semi global stability for all references. An inverted pendulum on a two wheels robot has been developed. A distributed control system, including sensor processing algorithms and a stabilizing control scheme has been implemented on three on-board embedded processors
A framework for domain-specific modeling on graph databases
La complexité du logiciel augmente tout le temps: les systÚmes deviennent plus grands et plus complexes. La modélisation est un élément central de génie logicielle pour relever les défis de la complexité. Cependant, un défi majeur auquel est confronté le développement de logiciels axés sur les modÚles est l'évolutivité des outils de modélisation avec une taille croissante de modÚles. Certaines initiatives ont commencé à explorer la modélisation tout en stockant des modÚles dans une base de données de graphes. Dans cette thÚse, nous présentons NMF, un framework pour créer et éditer des modÚles dans une base de données Neo4j élevée à l'abstraction du langage de modélisation.Software complexity increases all the time: systems become larger and more complex. Modeling is a central part of software engineering to tackle challenges of complexity. However, a prominent challenge model-driven software development is facing is scalability of modeling tools with a growing size of models. Some initiatives started exploring modeling while storing models in a graph database. In this thesis, we present NMF, a framework to create and edit MDE models in a Neo4j database lifted to the abstraction of the modeling language
Web Data Extraction, Applications and Techniques: A Survey
Web Data Extraction is an important problem that has been studied by means of
different scientific tools and in a broad range of applications. Many
approaches to extracting data from the Web have been designed to solve specific
problems and operate in ad-hoc domains. Other approaches, instead, heavily
reuse techniques and algorithms developed in the field of Information
Extraction.
This survey aims at providing a structured and comprehensive overview of the
literature in the field of Web Data Extraction. We provided a simple
classification framework in which existing Web Data Extraction applications are
grouped into two main classes, namely applications at the Enterprise level and
at the Social Web level. At the Enterprise level, Web Data Extraction
techniques emerge as a key tool to perform data analysis in Business and
Competitive Intelligence systems as well as for business process
re-engineering. At the Social Web level, Web Data Extraction techniques allow
to gather a large amount of structured data continuously generated and
disseminated by Web 2.0, Social Media and Online Social Network users and this
offers unprecedented opportunities to analyze human behavior at a very large
scale. We discuss also the potential of cross-fertilization, i.e., on the
possibility of re-using Web Data Extraction techniques originally designed to
work in a given domain, in other domains.Comment: Knowledge-based System
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