1,949 research outputs found
Enhancing the Guidance of the Intentional Model "MAP": Graph Theory Application
The MAP model was introduced in information system engineering in order to
model processes on a flexible way. The intentional level of this model helps an
engineer to execute a process with a strong relationship to the situation of
the project at hand. In the literature, attempts for having a practical use of
maps are not numerous. Our aim is to enhance the guidance mechanisms of the
process execution by reusing graph algorithms. After clarifying the existing
relationship between graphs and maps, we improve the MAP model by adding
qualitative criteria. We then offer a way to express maps with graphs and
propose to use Graph theory algorithms to offer an automatic guidance of the
map. We illustrate our proposal by an example and discuss its limitations.Comment: 9 page
A Complete Grammar for Decomposing a Family of Graphs into 3-connected Components
Tutte has described in the book "Connectivity in graphs" a canonical
decomposition of any graph into 3-connected components. In this article we
translate (using the language of symbolic combinatorics)
Tutte's decomposition into a general grammar expressing any family of graphs
(with some stability conditions) in terms of the 3-connected subfamily. A key
ingredient we use is an extension of the so-called dissymmetry theorem, which
yields negative signs in the grammar.
As a main application we recover in a purely combinatorial way the analytic
expression found by Gim\'enez and Noy for the series counting labelled planar
graphs (such an expression is crucial to do asymptotic enumeration and to
obtain limit laws of various parameters on random planar graphs). Besides the
grammar, an important ingredient of our method is a recent bijective
construction of planar maps by Bouttier, Di Francesco and Guitter.Comment: 39 page
Stokes posets and serpent nests
We study two different objects attached to an arbitrary quadrangulation of a
regular polygon. The first one is a poset, closely related to the Stokes
polytopes introduced by Baryshnikov. The second one is a set of some paths
configurations inside the quadrangulation, satisfying some specific
constraints. These objects provide a generalisation of the existing
combinatorics of cluster algebras and nonnesting partitions of type A.Comment: 24 pages, 12 figure
Constant scallop height tool path generation
Journal ArticleAn approach for the automatic generation of constant scallop height tool paths is presented. An example is shown generated from a B-spline model, although it can be used with many types of sculptured surfaces. The approach utilizes surface subdivision techniques and a new algorithm for tool path generation. The new algorithm is based on computer graphics shading algorithms and on methods from graph theory. A tool path with a constant scallop height renders minimum waste tool moves and hence results in much better machine time. Since neither numerical methods nor high order derivatives are required by the algorithm, it provides an efficient and robust method for tool path computation. Besides, the new algorithm is capable of producing tool paths whose milling directions are based on local surface geometry
Laminations and groups of homeomorphisms of the circle
If M is an atoroidal 3-manifold with a taut foliation, Thurston showed that
pi_1(M) acts on a circle. Here, we show that some other classes of essential
laminations also give rise to actions on circles. In particular, we show this
for tight essential laminations with solid torus guts. We also show that
pseudo-Anosov flows induce actions on circles. In all cases, these actions can
be made into faithful ones, so pi_1(M) is isomorphic to a subgroup of
Homeo(S^1). In addition, we show that the fundamental group of the Weeks
manifold has no faithful action on S^1. As a corollary, the Weeks manifold does
not admit a tight essential lamination, a pseudo-Anosov flow, or a taut
foliation. Finally, we give a proof of Thurston's universal circle theorem for
taut foliations based on a new, purely topological, proof of the Leaf Pocket
Theorem.Comment: 50 pages, 12 figures. Ver 2: minor improvement
Declarative operations on nets
To increase the expressiveness of knowledge representations, the graph-theoretical basis of semantic networks is reconsidered. Directed labeled graphs are generalized to directed recursive labelnode hypergraphs, which permit a most natural representation of multi-level structures and n-ary relationships. This net formalism is embedded into the relational/functional programming language RELFUN. Operations on (generalized) graphs are specified in a declarative fashion to enhance readability and maintainability. For this, nets are represented as nested RELFUN terms kept in a normal form by rules associated directly with their constructors. These rules rely on equational axioms postulated in the formal definition of the generalized graphs as a constructor algebra. Certain kinds of sharing in net diagrams are mirrored by binding common subterms to logical variables. A package of declarative transformations on net terms is developed. It includes generalized set operations, structure-reducing operations, and extended path searching. The generation of parts lists is given as an application in mechanical engineering. Finally, imperative net storage and retrieval operations are discussed
Trajectory planning for industrial robot using genetic algorithms
En las últimas décadas, debido la importancia de sus aplicaciones, se han propuesto muchas investigaciones sobre la planificación de caminos y trayectorias para los manipuladores, algunos de los ámbitos en los que pueden encontrarse ejemplos de aplicación son; la robótica industrial, sistemas autónomos, creación de prototipos virtuales y diseño de fármacos asistido por ordenador. Por otro lado, los algoritmos evolutivos se han aplicado en muchos campos, lo que motiva el interés del autor por investigar sobre su aplicación a la planificación de caminos y trayectorias en robots industriales.
En este trabajo se ha llevado a cabo una búsqueda exhaustiva de la literatura existente relacionada con la tesis, que ha servido para crear una completa base de datos utilizada para realizar un examen detallado de la evolución histórica desde sus orÃgenes al estado actual de la técnica y las últimas tendencias.
Esta tesis presenta una nueva metodologÃa que utiliza algoritmos genéticos para desarrollar y evaluar técnicas para la planificación de caminos y trayectorias. El conocimiento de problemas especÃficos y el conocimiento heurÃstico se incorporan a la codificación, la evaluación y los operadores genéticos del algoritmo.
Esta metodologÃa introduce nuevos enfoques con el objetivo de resolver el problema de la planificación de caminos y la planificación de trayectorias para sistemas robóticos industriales que operan en entornos 3D con obstáculos estáticos, y que ha llevado a la creación de dos algoritmos (de alguna manera similares, con algunas variaciones), que son capaces de resolver los problemas de planificación mencionados.
El modelado de los obstáculos se ha realizado mediante el uso de combinaciones de objetos geométricos simples (esferas, cilindros, y los planos), de modo que se obtiene un algoritmo eficiente para la prevención de colisiones.
El algoritmo de planificación de caminos se basa en técnicas de
optimización globales, usando algoritmos genéticos para minimizar una función
objetivo considerando restricciones para evitar las colisiones con los obstáculos. El
camino está compuesto de configuraciones adyacentes obtenidas mediante una
técnica de optimización construida con algoritmos genéticos, buscando minimizar
una función multiobjetivo donde intervienen la distancia entre los puntos
significativos de las dos configuraciones adyacentes, asà como la distancia desde
los puntos de la configuración actual a la final. El planteamiento del problema
mediante algoritmos genéticos requiere de una modelización acorde al
procedimiento, definiendo los individuos y operadores capaces de proporcionar
soluciones eficientes para el problema.Abu-Dakka, FJM. (2011). Trajectory planning for industrial robot using genetic algorithms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/10294Palanci
Quadrotor control for persistent surveillance of dynamic environments
Thesis (M.S.)--Boston UniversityThe last decade has witnessed many advances in the field of small scale unmanned aerial vehicles (UAVs). In particular, the quadrotor has attracted significant attention. Due to its ability to perform vertical takeoff and landing, and to operate in cluttered spaces, the quadrotor is utilized in numerous practical applications, such as reconnaissance and information gathering in unsafe or otherwise unreachable environments.
This work considers the application of aerial surveillance over a city-like environment. The thesis presents a framework for automatic deployment of quadrotors to monitor and react to dynamically changing events. The framework has a hierarchical structure. At the top level, the UAVs perform complex behaviors that satisfy high- level mission specifications. At the bottom level, low-level controllers drive actuators on vehicles to perform the desired maneuvers.
In parallel with the development of controllers, this work covers the implementation of the system into an experimental testbed. The testbed emulates a city using physical objects to represent static features and projectors to display dynamic events occurring on the ground as seen by an aerial vehicle. The experimental platform features a motion capture system that provides position data for UAVs and physical features of the environment, allowing for precise, closed-loop control of the vehicles. Experimental runs in the testbed are used to validate the effectiveness of the developed control strategies
Transfer and architecture : views from chart parsing
The objective of this report is to describe the embedding of a transfer module within an alternative architectural approach for machine translation of spontaneous spoken language. The approach is cognitively oriented, i.e. it adapts some of the assumed properties of human language comprehension and production. The aspects to be modeled will include incrementality and robustness with respect to disturbances caused by the environment and performance phenomena of speech. Interaction between software modules is used to reduce ambiguity. The transfer stage of a translation system clearly has to obey these requirements to be an integral part of such a system. This paper outlines the kind of demands to be placed on the transfer module. Relations between the basic formalisms representing linguistic knowledge on the one hand and transfer on the other hand are demonstrated as well as the consequences for algorithms and data structures
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