320 research outputs found
The extremal spectral radii of -uniform supertrees
In this paper, we study some extremal problems of three kinds of spectral
radii of -uniform hypergraphs (the adjacency spectral radius, the signless
Laplacian spectral radius and the incidence -spectral radius).
We call a connected and acyclic -uniform hypergraph a supertree. We
introduce the operation of "moving edges" for hypergraphs, together with the
two special cases of this operation: the edge-releasing operation and the total
grafting operation. By studying the perturbation of these kinds of spectral
radii of hypergraphs under these operations, we prove that for all these three
kinds of spectral radii, the hyperstar attains uniquely the
maximum spectral radius among all -uniform supertrees on vertices. We
also determine the unique -uniform supertree on vertices with the second
largest spectral radius (for these three kinds of spectral radii). We also
prove that for all these three kinds of spectral radii, the loose path
attains uniquely the minimum spectral radius among all
-th power hypertrees of vertices. Some bounds on the incidence
-spectral radius are given. The relation between the incidence -spectral
radius and the spectral radius of the matrix product of the incidence matrix
and its transpose is discussed
On a relationship between the characteristic and matching polynomials of a uniform hypertree
A hypertree is a connected hypergraph without cycles. Further a hypertree is
called an -tree if, additionally, it is -uniform. Note that 2-trees are
just ordinary trees. A classical result states that for any 2-tree with
characteristic polynomial and matching polynomial
, then More
generally, suppose is an -tree of size with . In
this paper, we extend the above classical relationship to -trees and
establish that where the product is over all
connected subgraphs of , and the exponent of the
factor can be written as where is the size of , is the boundary of , and
. In particular, for , the above correspondence
reduces to the classical result for ordinary trees. In addition, we resolve a
conjecture by Clark-Cooper [{\em Electron. J. Combin.}, 2018] and show that for
any subgraph of an -tree with ,
divides , and additionally
divides , if either or
is connected when . Moreover, a counterexample is given for the case
when is a disconnected subgraph of a 3-tree.Comment: 36 pages, 4 figure
Coastal Inundation from Sea Level Rise and Typhoon Maemi
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive
Efficient vanishing point detection method in unstructured road environments based on dark channel prior
Vanishing point detection is a key technique in the fields such as road detection, camera calibration and visual navigation. This study presents a new vanishing point detection method, which delivers efficiency by using a dark channel prior‐based segmentation method and an adaptive straight lines search mechanism in the road region. First, the dark channel prior information is used to segment the image into a series of regions. Then the straight lines are extracted from the region contours, and the straight lines in the road region are estimated by a vertical envelope and a perspective quadrilateral constraint. The vertical envelope roughly divides the whole image into sky region, vertical region and road region. The perspective quadrilateral constraint, as the authors defined herein, eliminates the vertical lines interference inside the road region to extract the approximate straight lines in the road region. Finally, the vanishing point is estimated by the meanshift clustering method, which are computed based on the proposed grouping strategies and the intersection principles. Experiments have been conducted with a large number of road images under different environmental conditions, and the results demonstrate that the authors’ proposed algorithm can estimate vanishing point accurately and efficiently in unstructured road scenes
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