arXiv subjects

Fawad Ali

Publications and source records attributed to Fawad Ali.

9 recordsLinked to original sources

arXiv2026

HPC Modeling of Coupled Elastic-Acoustic Wave Propagation in Biological Media: Numerical Validation

Accurate numerical models of sound propagation through biological media are an important tool for many applications, from medical physics to studying the auditory system of humans or other animals. We model high-frequency elastic and acoustic wave propagation through the head anatomy of a common bottlenose dolphin (Tursiops truncatus), by means of the open-source software packages \textsc{specfem3d}, based on the spectral-element method, and \textsc{{\it k}-wave}, based on the pseudospectral method. To achieve sufficiently high performance, we ported the latter solver to C++, for Multi-GPU CUDA support via the slab-decomposition of three-dimensional Fast Fourier Transform approach. Because the two schemes differ fundamentally in how the propagation medium is discretized and internal (in particular fluid-solid) interfaces are treated, similarity between modeled signals across methods is a legitimate measure of model accuracy. Plane waves, depending on time like four-cycle sinusoidal bursts of varying central frequency (20--100 kHz), are numerically propagated through a computed-tomography-based anatomy model using both solvers. The sound is ``recorded'' in front of the rostrum and at the right inner-ear locations for comparison. We successfully cross-validate both solvers on high-fidelity High-Performance Computing (HPC) clusters. We find that the stability of results from both solvers grows as the corresponding spatial resolution is refined. At their highest resolutions, the two methods show excellent agreement, with normalized correlation exceeding 0.99 across the entire 20--100 kHz frequency range. Together, our results provide a validated HPC-simulation framework for wave propagation in biological media, with broader implications, e.g., for biosonar research, auditory biomechanics, and medical ultrasound.

physics.med-ph↗

arXiv2025

Pseudo-spectral model of elastic-wave propagation through toothed-whale head anatomy, and implications for biosonar

The sound-localization and, in particular, biosonar system of toothed whales is exceptionally performant. How this is achieved is not clear, given that: (i) toothed whales have no pinnae; (ii) while their auditory pathways have been studied in detail, no specific feature apparently replacing the pinna has been identified. In this study, we employ a pseudo-spectral time domain (PSTD) numerical scheme to model three-dimensional elastic wave propagation through a toothed-whale head including soft tissues. Computed tomography (CT) scans were utilized to build a three-dimensional velocity-density model of the specimen's head, parametrized on a high-resolution $1.11$ mm voxel grid. We first validate our wave propagation solver, identifying a range of frequencies and spatial scale lengths where the PSTD scheme captures the complexities of elastic wave propagation through toothed-whale anatomy. We next focus on the toothed whale's ability to locate sources on the median plane, where the role of anatomy is crucial. A 45 kHz central frequency burst (dolphin-like click) was modeled and directed at elevation angles from $-90^\circ$ to $+90^\circ$ in $5^\circ$ steps along the midsagittal plane. We find that the incoming sound can be localized, via correlation, from the reverberated portion of the time-domain waveforms recorded at the tympano-periotic complex locations.

physics.comp-ph↗

arXiv2025

Optimization and Performance Evaluation of Cs$_2$CuBiCl$_6$ Double Perovskite Solar Cell for Lead-Free Photovoltaic Applications

In the previous decade, there has been a significant advancement in the performance of perovskite solar cells (PSCs), characterized by a notable increase in efficiency from 3.8% to 25%. Nonetheless, PSCs face many problems when we commercialize them because of their toxicity and stability. Consequently, lead-PSCs need an alternative solar cell with high performance and low processing cost; lead-free inorganic perovskites have been explored. Recent research showcased Cs$_2$CuBiCl$_6$, a lead-free inorganic double perovskite material with remarkable photoelectric characteristics and exceptional environmental robustness. To investigate the potential of Cs$_2$CuBiCl$_6$ material, the solar cell structure FTO/ETL/Cs$_2$CuBiCl$_6$/HTL/Au was used and analyzed through a solar cell capacitance simulator (SCAPS-1D). CeO$_2$ is used as the Electron transport layer (ETL), and CuI is the Hole transport layer (HTL). Furthermore, the research examined the optimization of different parameters of the absorber layer (AL), such as thickness, defect density, electron affinity, band gap, and operational temperature. In the end, it has been noticed that by setting the temperature at 300 K and an electron affinity of 4.3 eV of the absorber layer, the PSCs achieve the highest efficiency of 24.51 %, FF of 43.01 %, Voc of 1.73V, and Jsc of 32.82mA/cm$^2$. This is the highest Cs$_2$CuBiCl$_6$ double PSCs efficiency we've reached yet. In theoretical studies, 17.03% of PCE was achieved using Cs$_2$CuBiCl$_6$ as an active layer. The analysis underscores the significant potential of Cs$_2$CuBiCl$_6$ as an absorbing layer in developing highly efficient lead-free all-inorganic PSCs.

cond-mat.mtrl-sci↗

arXiv2025

Impact of Annealing Temperature on the Energy Storage Performance of CoO2 Nanoparticles Synthesized via Solid State Reaction

The solid-state reaction was used to synthesize CoO2 nanostructured material. Cobalt nitrate tetrahydrate and sodium oxide (NaOH) were combined to produce CoO2 nanostructured material. The three synthesized working electrodes were each tested individually, using 3 M KOH as the electrolyte. The CV analysis of a three-electrode system revealed redox peaks, indicating Faradaic processes. The estimated specific capacitances of CoO2, CoO2 (250oC), CoO2 (300oC) nanostructured material at scan rates of (10) mVs-1 is (223, 348, and 473) Fg-1. The diffraction peaks at 2{\theta} = 26.264o, 33.527o, 37.579, 51.264 and 54.367o correspond respectively to the diffraction planes of 111, 112, 200, 211, and 311 of CoO2 nanostructured material. The annealing temperature, which affects the bandgap, can influence the size, shape, and crystallinity of nanostructures. For the unannealed material, the energy bandgap of CoO2 is 2.00 eV, whereas for the annealed material it ranges from 1.77 to 1.86 eV.

cond-mat.mtrl-sci↗

arXiv2022

Hosoya properties of power graphs over certain groups

The power graph denoted by $\mathcal{P}(\mathcal{G})$ of a finite group $\mathcal{G}$ is a graph with vertex set $\mathcal{G}$ and there is an edge between two distinct elements $u, v \in \mathcal{G}$ if and only if $u^m = v$ or $v^m = u$ for some $m \in \mathbb{N}$. Depending on the distance, the Hosoya polynomial contains a lot of knowledge about graph invariants which can be used to determine well-known chemical descriptors. The Hosoya index of a graph $Γ$ is the total number of matchings in $Γ$. In this article, the Hosoya properties of the power graphs associated with a finite group, including the Hosoya index, Hosoya polynomial, and its reciprocal are calculated.

math.CO↗

arXiv2022

On the $A_α$ and $RD_α$ matrices over certain groups

The power graph $G = P(Ω)$ of a finite group $Ω$ is a graph with the vertex set $Ω$ and two vertices $u, v \in Ω$ form an edge if and only if one is an integral power of the other. Let $D(G)$, $A(G)$, $RT(G)$, and $RD(G)$ denote the degree diagonal matrix, adjacency matrix, the diagonal matrix of the vertex reciprocal transmission, and Harary matrix of the power graph $G$ respectively. Then the $A_α$ and $RD_α$ matrices of $G$ are defined as $A_α(G) = αD(G) + (1-α)A(G)$ and $RD_α(G) = αRT(G) + (1-α)RD(G)$. In this article, we determine the eigenvalues of $A_α$ and $RD_α$ matrices of the power graph of group $ \mathcal{G} = \langle s,r \, : r^{2^kp} = s^2 = e,~ srs^{-1} = r^{2^{k-1}p-1}\rangle$. In addition, we calculate its distant and detotar distance degree sequences, metric dimension, and strong metric dimension.

math.CO↗

arXiv2022

On the Spectral properties of power graphs over certain groups

The power graph $P(Ω)$ of a group $Ω$ is a graph with the vertex set $Ω$ such that two distinct vertices form an edge if and only if one of them is an integral power of the other. In this article, we determine the power graph of the group $\mathcal{G} = \langle s,r \, : r^{2^kp} = s^2 = e,~ srs^{-1} = r^{2^{k-1}p-1}\rangle$. Further, we compute its characteristic polynomial for the adjacency, Laplacian, and signless Laplacian matrices associated with this power graph. In addition, we determine its spectrum, Laplacian spectrum, and Laplacian energy.

math.CO↗

arXiv2022

On the power graph of a certain gyrogroup

The power graph $P(G)$ of a group $G$ is a simple graph with the vertex set $G$ such that two distinct vertices $u,v \in G$ are adjacent in $P(G)$ if and only if $u^m = v$ or $v^m = u$, for some $m \in \mathbb{N}$. The purpose of this paper is to introduce the notion of a power graph for gyrogroups. Using this, we investigate the combinatorial properties of a certain gyrogroup, say $G(n)$, of order $2^n$ for $n \geq 3$. In particular, we determine the Hamiltonicity and planarity of the power graph of $G(n)$. Consequently, we calculate distant properties, resolving polynomial, Hosoya and reciprocal Hosoya polynomials, characteristic polynomials, and the spectral radius of the power graph of $G(n)$.

math.CO↗

arXiv2017

Commuting graphs on Coxeter groups, Dynkin diagrams and finite subgroups of $SL(2,\mathbb{C})$

For a group $H$ and a non empty subset $Γ\subseteq H$, the commuting graph $G=\mathcal{C}(H,Γ)$ is the graph with $Γ$ as the node set and where any $x,y \in Γ$ are joined by an edge if $x$ and $y$ commute in $H$. We prove that any simple graph can be obtained as a commuting graph of a Coxeter group, solving the realizability problem in this setup. In particular we can recover every Dynkin diagram of ADE type as a commuting graph. Thanks to the relation between the ADE classification and finite subgroups of $\SL(2,\C)$, we are able to rephrase results from the {\em McKay correspondence} in terms of generators of the corresponding Coxeter groups. We finish the paper studying commuting graphs $\mathcal{C}(H,Γ)$ for every finite subgroup $H\subset\SL(2,\C)$ for different subsets $Γ\subseteq H$, and investigating metric properties of them when $Γ=H$.

math.GR↗