Search results for "Graph theory"

Circular law for sparse random regular digraphs

2020

Fix a constant $C\geq 1$ and let $d=d(n)$ satisfy $d\leq \ln^{C} n$ for every large integer $n$. Denote by $A_n$ the adjacency matrix of a uniform random directed $d$-regular graph on $n$ vertices. We show that, as long as $d\to\infty$ with $n$, the empirical spectral distribution of appropriately rescaled matrix $A_n$ converges weakly in probability to the circular law. This result, together with an earlier work of Cook, completely settles the problem of weak convergence of the empirical distribution in directed $d$-regular setting with the degree tending to infinity. As a crucial element of our proof, we develop a technique of bounding intermediate singular values of $A_n$ based on studyi…

Irregular motion recovery in fluorescein angiograms

1997

Abstract Fluorescein angiography is a common procedure in ophthalmic practice, mainly to evaluate vascular retinopathies and choroidopathies from sequences of ocular fundus images. In order to compare the images, a reliable overlying is essential. This paper proposes some methods for the recovery of irregular motion in fluorescein angiograms (FA). The overlying is done by a three step procedure: detection of relevant points, matching points from different images and estimation of the assumed linear geometric transformation. A stochastic model (closely related to the general linear model) allows to fuse the second and third steps. Two different estimators of the geometric transformation are …

The Study of Dynamic Objects Identification Algorithms Based on Anisotropic Properties of Generalized Amplitude-Phase Images

2018

The article presents some results of dynamical objects identification technology based on coincidence matrixes of templates and tested objects’ amplitude-phase images (APIm) calculated with discrete Hilbert transforms (DHT). DHT algorithms are modeled on basis of isotropic (HTI), anisotropic (HTA), generalized transforms – AP-analysis (APA) and the difference (residual) relative shifted phase (DRSP-) images to calculate the APIm. The identified objects are recognized as members of classes modeled with 3D templates – images of different types airplanes rotated in space. The dynamic anisotropic properties of APIm causes the increasing of sensitivity to circular angle rotation and make possibl…

Partial Melting and Counterclockwise P T Path of Subducted Oceanic Crust (Sierra del Convento Melange, Cuba)

2007

Between Strategic Cooperation and Distrustful Neighbourhood. Polish-German relations in the agendas of Polish governments, 1990–2019

2019

Since 1989 the building of new Polish-German relations has been carried out in the dimensions of both time (historical reconciliation) and space (reintegration eastern and western parts of Europe). This determines their fundamental importance for contemporary Europe. This article presents an analysis of Polish-German relations from the perspective of issue salience. The source base of this paper comprises Addresses by the Ministers of Foreign Affairs (AMFAs), i.e. annual speeches given by foreign ministers presenting the major goals of Poland’s foreign policy. It makes it possible to adopt a long-term perspective (1990-2018). The quantitative analysis was based on the rules of the Comparati…

Conodont association of the Bashkirian-Moscovian boundary interval of the Donets Basin, Ukraine

2018

Ten sections spanning the Bashkirian-Moscovian boundary interval were studied in the Donets Basin. Six of them contain most representative conodont and foraminifer associations. In this paper we focused on three the most complete sections that include stratigraphically important conodont species, which belong to the Declinognathodus, Idiognathoides, Idiognathodus, Neognathodus, “Streptognathodus”, Mesogondolella and Diplognathodus genera. The majority of those species are widely distributed, which makes the correlation to other areas reliable. Two biotic events in conodont evolution were discovered in these sections. Two conodont lineages established here are considered as potential markers…

Robust Graph Topology Learning and Application in Stock Market Inference

2019

In many applications, there are multiple interacting entities, generating time series of data over the space. To describe the relation within the set of data, the underlying topology may be used. In many real applications, not only the signal/data of interest is measured in noise, but it is also contaminated with outliers. The proposed method, called RGTL, infers the graph topology from noisy measurements and removes these outliers simultaneously. Here, it is assumed that we have no information about the space graph topology, while we know that graph signal are sampled consecutively in time and thus the graph in time domain is given. The simulation results show that the proposed algorithm h…

Bridging landscape graphs and genetic graphs for analysing habitat ecological connectivity

2021

Several key ecological processes for maintaining biodiversity rely upon the ecological connectivity of habitat. Accordingly, connectivity modelling methods have been developed for understanding precisely the influence of connectivity and deriving sound biodiversity conservation measures. Among them, landscape graphs represent habitat networks as sets of habitat patches (nodes) connected by potential dispersal paths (links). Yet, the ecological relevance of these tools required validation from biological data reflecting closely the influence of habitat connectivity. Genetic data allow for such validation as population genetic structure partly depends on dispersal-driven gene flow between hab…

A Multi-Scale Analysis to Measure Ecological Impact of LUCC in a Built Environment

2015

International audience; In human-dominated environments, efforts to preserve ecological connectivity between animal species habitats is an important issue. These areas are indeed concern by anthropogenic pressures leading to rapid land use and land cover changes (LUCC). This is particularly the case of urban fringes, affected by many changes (e.g. urban sprawl) specifically for several decades.Of all the methods to model the ecological networks connectivity, landscape graphs provide a relevant approach, which interest for decision support in land-use planning has already been highlighted (Foltête et al., 2014). This approach allows to represent ecological networks in a simplified way as gra…

Two Reflected Gray Code-Based Orders on Some Restricted Growth Sequences

2014

We consider two order relations: that induced by the m-ary reflected Gray code and a suffix partitioned variation of it. We show that both of them when applied to some sets of restricted growth sequences still yield Gray codes. These sets of sequences are: subexcedant and ascent sequences, restricted growth functions and staircase words. In particular, we give the first suffix partitioned Gray codes for restricted growth f unctions and ascent sequences; these latter sequences code various combinatorial classes as interval orders, upper triangular matrices without zero rows and zero columns whose non-negative integer entries sum up to n, and certain pattern-avoiding permutations. For each Gr…