13,387 research outputs found
Non-regular graphs with minimal total irregularity
The {\it total irregularity} of a simple undirected graph is defined as
, where denotes the degree of a vertex .
Obviously, if and only if is regular. Here, we
characterize the non-regular graphs with minimal total irregularity and thereby
resolve the recent conjecture by Zhu, You and Yang~\cite{zyy-mtig-2014} about
the lower bound on the minimal total irregularity of non-regular connected
graphs. We show that the conjectured lower bound of is attained only if
non-regular connected graphs of even order are considered, while the sharp
lower bound of is attained by graphs of odd order. We also characterize
the non-regular graphs with the second and the third smallest total
irregularity
The Minimal Total Irregularity of Graphs
In \cite{2012a}, Abdo and Dimitov defined the total irregularity of a graph
as
\hskip3.3cm
\noindent where denotes the vertex degree of a vertex . In
this paper, we investigate the minimal total irregularity of the connected
graphs, determine the minimal, the second minimal, the third minimal total
irregularity of trees, unicyclic graphs, bicyclic graphs on vertices, and
propose an open problem for further research.Comment: 13 pages, 4 figure
The total irregularity of a graph
In this note a new measure of irregularity of a graph G is introduced. It is
named the total irregularity of a graph and is defined as irrt(G) = 1 / 2∑u,v
∈V(G) |dG(u)-dG(v)|, where dG(u) denotes the degree of a vertex u ∈V(G). All
graphs with maximal total irregularity are determined. It is also shown that
among all trees of the same order the star has the maximal total irregularity
Analysis of the contour structural irregularity of skin lesions using wavelet decomposition
The boundary irregularity of skin lesions is of clinical significance for the early detection of
malignant melanomas and to distinguish them from other lesions such as benign moles. The
structural components of the contour are of particular importance. To extract the structure from
the contour, wavelet decomposition was used as these components tend to locate in the lower
frequency sub-bands. Lesion contours were modeled as signatures with scale normalization to
give position and frequency resolution invariance. Energy distributions among different wavelet
sub-bands were then analyzed to extract those with significant levels and differences to enable
maximum discrimination.
Based on the coefficients in the significant sub-bands, structural components from the original
contours were modeled, and a set of statistical and geometric irregularity descriptors researched
that were applied at each of the significant sub-bands. The effectiveness of the descriptors was
measured using the Hausdorff distance between sets of data from melanoma and mole contours.
The best descriptor outputs were input to a back projection neural network to construct a
combined classifier system. Experimental results showed that thirteen features from four
sub-bands produced the best discrimination between sets of melanomas and moles, and that a
small training set of nine melanomas and nine moles was optimum
- …