arXiv subjects

M. Ghanbari

Publications and source records attributed to M. Ghanbari.

3 recordsLinked to original sources

arXiv2023

Frequency-domain Blind Quality Assessment of Blurred and Blocking-artefact Images using Gaussian Process Regression model

Most of the standard image and video codecs are block-based and depending upon the compression ratio the compressed images/videos suffer from different distortions. At low ratios, blurriness is observed and as compression increases blocking artifacts occur. Generally, in order to reduce blockiness, images are low-pass filtered which leads to more blurriness. Also, in bokeh mode images they are commonly seen: blurriness as a result of intentional blurred background while blocking artifact and global blurriness arising due to compression. Therefore, such visual media suffer from both blockiness and blurriness distortions. Along with this, noise is also commonly encountered distortion. Most of the existing works on quality assessment quantify these distortions individually. This paper proposes a methodology to blindly measure overall quality of an image suffering from these distortions, individually as well as jointly. This is achieved by considering the sum of absolute values of low and high-frequency Discrete Frequency Transform (DFT) coefficients defined as sum magnitudes. The number of blocks lying in specific ranges of sum magnitudes including zero-valued AC coefficients and mean of 100 maximum and 100 minimum values of these sum magnitudes are used as feature vectors. These features are then fed to the Machine Learning (ML) based Gaussian Process Regression (GPR) model, which quantifies the image quality. The simulation results show that the proposed method can estimate the quality of images distorted with the blockiness, blurriness, noise and their combinations. It is relatively fast compared to many state-of-art methods, and therefore is suitable for real-time quality monitoring applications.

cs.CV↗

arXiv2021

Altered connectedness of the brain chronnectome during the progression of Alzheimer's disease

Graph theory has been extensively used to investigate brain network topology and its changes in disease cohorts. However, many graph theoretic analysis-based brain network studies focused on the shortest paths or, more generally, cost-efficiency. In this work, we use two new concepts, connectedness and 2-connectedness, to measure different global properties compared to the previously widely adopted ones.

q-bio.NC↗

arXiv2015

The f-Chromatic Index of Claw-free Graphs Whose f-Core is 2-regular

Let $G$ be a graph and $f:V(G)\rightarrow \mathbb{N}$ be a function. An $f$-coloring of a graph $G$ is an edge coloring such that each color appears at each vertex $v\in V(G)$ at most $f (v)$ times. The minimum number of colors needed to $f$-color $G$ is called the $f$-chromatic index of $G$ and is denoted by $χ'_{f}(G)$. It was shown that for every graph $G$, $Δ_{f}(G)\le χ'_{f}(G)\le Δ_{f}(G)+1$, where $Δ_{f}(G)=\max_{v\in V(G)} \lceil \frac{d_G(v)}{f(v)} \rceil$. A graph $G$ is said to be $f$-Class $1$ if $χ'_{f}(G)=Δ_{f}(G)$, and $f$-Class $2$, otherwise. Also, $G_{Δ_f}$ is the induced subgraph of $G$ on $\{v\in V(G):\,\frac{d_G(v)}{f(v)}=Δ_{f}(G)\}$. In this paper, we show that if $G$ is a connected graph with $Δ(G_{Δ_f})\leq 2$ and $G$ has an edge cut of size at most $Δ_f(G) -2$ which is a matching or a star, then $G$ is $f$-Class $1$. Also, we prove that if $G$ is a connected graph and every connected component of $G_{Δ_f}$ is a unicyclic graph or a tree and $G_{Δ_f}$ is not $2$-regular, then $G$ is $f$-Class $1$. Moreover, we show that except one graph, every connected claw-free graph $G$ whose $f$-core is $2$-regular with a vertex $v$ such that $f(v)\neq 1$ is $f$-Class $1$.

math.CO↗