Search results for "Graph theory"

Boundary behavior of quasi-regular maps and the isodiametric profile

2001

We study obstructions for a quasi-regular mapping f : M → N f:M\rightarrow N of finite degree between Riemannian manifolds to blow up on or collapse on a non-trivial part of the boundary of M M .

Evaluating the structure and use of hiking trails in recreational areas using a mixed GPS tracking and graph theory approach

2014

Abstract Recreational trails encourage numerous outdoor leisure activities in a variety of urban, rural, and natural environments. Understanding the way trails function is crucial for the designers and managers of recreational sites to balance the needs of visitors and site capacities. This paper presents a new approach to evaluate the structure and use of hiking trails by combining GPS tracking and analytical methods based on graph theory. The study is based upon empirical data (N = 482 GPS tracks) collected in the Lobau, which is part of the Danube Floodplains National Park in Austria. The physical structure of trails (structural network; undirected graph) and their usage (functional netw…

Nonlinear rotation-invariant pattern recognition by use of the optical morphological correlation.

2000

We introduce a modification of the nonlinear morphological correlation for optical rotation-invariant pattern recognition. The high selectivity of the morphological correlation is conserved compared with standard linear correlation. The operation performs the common morphological correlation by extraction of the information by means of a circular-harmonic component of a reference. In spite of some loss of information good discrimination is obtained, especially for detecting images with a high degree of resemblance. Computer simulations are presented, as well as optical experiments implemented with a joint transform correlator.

Geographical Routing for Delay Tolerant Encounter Networks

2007

Delay Tolerant Networks (DTNs) are intermittently connected networks, where direct end--to--end path between communicating nodes may never exist. To achieve eventual delivery some nodes must store messages and wait opportunity to forward them. In mobile environment, one of the most challenging problems for routing protocols is to decide, which nodes should store the message to achieve eventual delivery as quick as possible. Common approach is to propagate message into large group of nodes, hoping one of them will reach the destination. These solutions, however, are not very scalable as they generate plenty of extra load and traffic to network. Further more, message carriers have no means to…

New path development between innovation systems and individual actors

2016

This special issue is devoted to studying mechanisms that may stimulate or hamper the renewal of existing industry paths and the growth of new paths. In this guest editorial, we look closely at the...

A note on rank 2 diagonals

2020

<p>We solve two questions regarding spaces with a (G<sub>δ</sub>)-diagonal of rank 2. One is a question of Basile, Bella and Ridderbos about weakly Lindelöf spaces with a G<sub>δ</sub>-diagonal of rank 2 and the other is a question of Arhangel’skii and Bella asking whether every space with a diagonal of rank 2 and cellularity continuum has cardinality at most continuum.</p>

A topological obstruction to the geodesibility of a foliation of odd dimension

1981

Let M be a compact Riemannian manifold of dimension n, and let ℱ be a smooth foliation on M. A topological obstruction is obtained, similar to results of R. Bott and J. Pasternack, to the existence of a metric on M for which ℱ is totally geodesic. In this case, necessarily that portion of the Pontryagin algebra of the subbundle ℱ must vanish in degree n if ℱ is odd-dimensional. Using the same methods simple proofs of the theorems of Bott and Pasternack are given.

MODELLING AND ANALYSING STUDENT DROPOUT IN COLOMBIAN HIGHER EDUCATION THROUGH POLICY AND PUBLIC MANAGEMENT

The complexity of the phenomenon of student dropout in higher education requires several modeling techniques. In this doctoral dissertation, findings of blending mathematical, statistical and Dynamic Performance Management as modelling techniques are presented to allow a deeper comprehension of Colombian student dropout in higher education.

Anti-concentration property for random digraphs and invertibility of their adjacency matrices

2016

Let Dn,dDn,d be the set of all directed d-regular graphs on n vertices. Let G be a graph chosen uniformly at random from Dn,dDn,d and M be its adjacency matrix. We show that M is invertible with probability at least View the MathML source1−Cln3⁡d/d for C≤d≤cn/ln2⁡nC≤d≤cn/ln2⁡n, where c,Cc,C are positive absolute constants. To this end, we establish a few properties of directed d-regular graphs. One of them, a Littlewood–Offord-type anti-concentration property, is of independent interest: let J be a subset of vertices of G with |J|≤cn/d|J|≤cn/d. Let δiδi be the indicator of the event that the vertex i is connected to J and δ=(δ1,δ2,…,δn)∈{0,1}nδ=(δ1,δ2,…,δn)∈{0,1}n. Then δ is not concentrate…

Epichristoffel Words and Minimization of Moore Automata

2014

This paper is focused on the connection between the combinatorics of words and minimization of automata. The three main ingredients are the epichristoffel words, Moore automata and a variant of Hopcroft's algorithm for their minimization. Epichristoffel words defined in [14] generalize some properties of circular sturmian words. Here we prove a factorization property and the existence of the reduction tree, that uniquely identifies the structure of the word. Furthermore, in the paper we investigate the problem of the minimization of Moore automata by defining a variant of Hopcroft's minimization algorithm. The use of this variant makes simpler the computation of the running time and consequ…