arXiv subjects

Manish Agarwal

Publications and source records attributed to Manish Agarwal.

9 recordsLinked to original sources

arXiv2026

Suppression of Active Super-Diffusion: Impact of String Defects and Canted Multi-Domains

We investigate the transport dynamics of an active Brownian particle (ABP) traversing a complex, non-Newtonian liquid crystal (LC) matrix. Employing the Generalized Lebwohl-Lasher (GLL) model, we systematically vary higher-order orientational interactions to stabilize three distinct host environments: isotropic, uniform nematic, and structurally frustrated canted phases. Modeling the coupled system via off-lattice over-damped Langevin dynamics, the resulting trajectories are characterized by evaluating their step-size distributions (SSDs), mean-square displacements (MSDs), and Hurst exponents. In the uniform nematic phase, the anisotropic matrix elastically channels the ABP, producing a left-skewed exponential SSD and persistent ballistic motion parallel to the director $\hat{\mathbf{n}}$. Similarly, transverse transport obeys a Rayleigh distribution and acquires a prominent $t \ln t$ super-diffusive correction-an explicit signature of the particle coupling to the host's gapless transverse Goldstone modes, as predicted by Toner et al. [Phys. Rev. E {\bf 93}, 062610 (2016)]. Crucially, we reveal that this active super-diffusion is systematically suppressed when the long-range Goldstone fluctuations are disrupted by topological defects. This breakdown manifests both macroscopically within the fractured, multi-domain canted phase due to a structural mass gap, and locally in the unfrustrated nematic phase through scattering by vortex disclination lines. Consequently, while the local SSDs qualitatively mirror the ideal nematic state, the transverse $t \ln t$ scaling vanishes in the presence of these structural constraints. Our findings demonstrate that tuning the background defect architecture of a complex fluid can fundamentally alter the transport universality class of active matter, offering a novel paradigm for controlling microscopic mobility.

cond-mat.soft↗

arXiv2023

Controlled coalescence-induced droplet jumping on flexible superhydrophobic substrates

Sessile droplets coalescing on superhydrophobic substrates spontaneously jump from the surface. In this process, the excess surface energy available at the initiation of coalescence overcomes the minimal surface adhesion and manifests as sufficient kinetic energy to propel the droplets away from the substrate. Here, we show that the coalescence induced droplet jumping velocity is significantly curtailed if the superhydrophobic substrate is flexible in nature. Through detailed experimental measurements and numerical simulations, we demonstrate that the droplet jumping velocity and jumping height can be reduced by as much as 40 % and 64%, respectively, by synergistically tuning the substrate stiffness and substrate frequency. We show that this hitherto unexplored aspect of droplet coalescence jumping can be gainfully exploited in water harvesting from dew and fog harvesting. Additionally, through an exemplar butterfly wing substrate, we demonstrate that this effect is likely to manifest on many natural superhydrophobic substrates due to their inherent flexibility.

physics.flu-dyn↗

arXiv2022

Diffusion mechanism and electrochemical investigation of 1T phase Al-MoS$_{2}$@rGO nano-composite as a high-performance anode for sodium-ion batteries

We report the electrochemical investigation of 5% Al doped MoS$_2$@rGO composite as a high-performance anode for sodium (Na)-ion batteries. The x-ray diffraction (XRD), Raman spectroscopy and high-resolution transmission electron microscopy characterizations reveal that the Al doping increase the interlayer spacing of (002) plane of MoS$_2$ nanosheets and form a stable 1T phase. The galvanostatic charge-discharge measurements show the specific capacity stable around 450, 400, 350, 300 and 200 mAhg$^{-1}$ at current densities of 0.05, 0.1, 0.3, 0.5 and 1~Ag$^{-1}$, respectively. Also, we observe the capacity retentions of 86% and 66% at 0.1 and 0.3 Ag$^{-1}$, respectively, over 200 cycles with a consistent Coulombic efficiency of nearly 100%. The cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy are used to find the kinetic behavior and the obtained value of diffusion coefficient falls in the range of 10$^{-10}$ to 10$^{-12}$ cm$^2$s$^{-1}$. Intriguingly, the in-situ EIS also explains the electrochemical kinetics of the electrode at different charge-discharge states with the variation of charge transfer resistance. Moreover, the post cycling investigation using ex-situ XRD and photoemission spectroscopy indicate the coexistence of 1T/2H phase and field-emission scanning electron microscopy confirm the stable morphology after 500 cycles. Also, the Na-ion transport properties are calculated for 1T Al--MoS$_2$@rGO interface and Al--MoS$_2$--MoS$_2$ interlayer host structure by theoretical calculations using density functional theory.

cond-mat.mtrl-sci↗

arXiv2021

Looking Through Glass: Knowledge Discovery from Materials Science Literature using Natural Language Processing

Most of the knowledge in materials science literature is in the form of unstructured data such as text and images. Here, we present a framework employing natural language processing, which automates text and image comprehension and precision knowledge extraction from inorganic glasses' literature. The abstracts are automatically categorized using latent Dirichlet allocation (LDA), providing a way to classify and search semantically linked publications. Similarly, a comprehensive summary of images and plots are presented using the 'Caption Cluster Plot' (CCP), which provides direct access to the images buried in the papers. Finally, we combine the LDA and CCP with the chemical elements occurring in the manuscript to present an 'Elemental map', a topical and image-wise distribution of chemical elements in the literature. Overall, the framework presented here can be a generic and powerful tool to extract and disseminate material-specific information on composition-structure-processing-property dataspaces, allowing insights into fundamental problems relevant to the materials science community and accelerated materials discovery.

cs.DL↗

arXiv2018

Analyzing Molecular Simulations Trajectories by Utilizing CUDA on GPU Architecture

With the advent of high-performance computing techniques, the data for analysis has grown significantly. Here, graphic processing unit (GPU) based program kernels are discussed to exploit parallelism in the analysis codes specific to molecular simulations trajectories and data, hence reducing the time consumption. Commonly computed properties of systems which utilize static and dynamic correlations are considered. In static properties, order metrics based on two-particle correlations are shown to exhibit 10-50x speedups relative to conventional serial CPU codes. Efficiency in finding three-particle correlations, which are relatively more time consuming calculations, are also shown to be 10-45x faster depending on system size. In the case of dynamic properties, the viscosity is computed using Green-Kubo formalism at a 10-25x faster rate depending on the correlation time and total trajectory length. Similarly, for mean square displacement calculations, the speedup of approximately 40-80x is achieved for all system sizes and simulation times. Particularly for these embarrassingly parallel computationally intensive problems, the compute unified device architecture application programming interface affords maximum scale up with minimum implementation time. It is shown that all the GPU codes render 1-2 order of magnitude reduction in the analyses times. Hence these codes, in conjunction with GPU accelerated molecular simulations, can lead to an overall improved and efficient performance.

physics.comp-ph↗

arXiv2010

Relationship between Structure, Entropy and Diffusivity in Water and Water-like Liquids

Anomalous behaviour of the excess entropy ($S_e$) and the associated scaling relationship with diffusivity are compared in liquids with very different underlying interactions but similar water-like anomalies: water (SPC/E and TIP3P models), tetrahedral ionic melts (SiO$_2$ and BeF$_2$) and a fluid with core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence of an excess entropy anomaly in the two water models. Using length and energy scales appropriate for onset of anomalous behaviour, the density range of the excess entropy anomaly is shown to be much narrower in water than in ionic melts or the 2SRP fluid. While the reduced diffusivities ($D^*$) conform to the excess entropy scaling relation, $D^* =A\exp (αS_e)$ for all the systems (Y. Rosenfeld, Phys. Rev. A {\bf 1977}, {\it 15}, 2545), the exponential scaling parameter, $α$, shows a small isochore-dependence in the case of water. Replacing $S_e$ by pair correlation-based approximants accentuates the isochore-dependence of the diffusivity scaling. Isochores with similar diffusivity scaling parameters are shown to have the temperature dependence of the corresponding entropic contribution. The relationship between diffusivity, excess entropy and pair correlation approximants to the excess entropy are very similar in all the tetrahedral liquids.

cond-mat.soft↗

arXiv2009

Adaptive Training for Correlated Fading Channels with Feedback

We consider data transmission through a time-selective, correlated (first-order Markov) Rayleigh fading channel subject to an average power constraint. The channel is estimated at the receiver with a pilot signal, and the estimate is fed back to the transmitter. The estimate is used for coherent demodulation, and to adapt the data and pilot powers. We explicitly determine the optimal pilot and data power control policies in a continuous-time limit where the channel state evolves as an Ornstein-Uhlenbeck diffusion process, and is estimated by a Kalman filter at the receiver. The optimal pilot policy switches between zero and the maximum (peak-constrained) value (``bang-bang'' control), and approximates the optimal discrete-time policy at low Signal-to-Noise Ratios (equivalently, large bandwidths). The switching boundary is defined in terms of the system state (estimated channel mean and associated error variance), and can be explicitly computed. Under the optimal policy, the transmitter conserves power by decreasing the training power when the channel is faded, thereby increasing the data rate. Numerical results show a significant increase in achievable rate due to the adaptive training scheme with feedback, relative to constant (non-adaptive) training, which does not require feedback. The gain is more pronounced at relatively low SNRs and with fast fading. Results are further verified through Monte Carlo simulations.

cs.IT↗

arXiv2009

Limited-Rate Channel State Feedback for Multicarrier Block Fading Channels

The capacity of a fading channel can be substantially increased by feeding back channel state information from the receiver to the transmitter. With limited-rate feedback what state information to feed back and how to encode it are important open questions. This paper studies power loading in a multicarrier system using no more than one bit of feedback per sub-channel. The sub-channels can be correlated and full channel state information is assumed at the receiver.

cs.IT↗

arXiv2008

Estimating Entropy of Liquids from Atom-Atom Radial Distribution Functions: Silica, Beryllium Fluoride and Water

Molecular dynamics simulations of water, liquid beryllium fluoride and silica melt are used to study the accuracy with which the entropy of ionic and molecular liquids can be estimated from atom-atom radial distribution function data. All three systems are known to display similar liquid-state thermodynamic and kinetic anomalies due to a region of anomalous excess entropy behaviour where entropy rises on isothermal compression. The pair correlation entropy is demonstrated to be sufficiently accurate that the density-temperature regime of anomalous behaviour as well as the strength of the entropy anomaly can be predicted reliably for both ionic melts as well as different rigid-body pair potentials for water. Errors in the total thermodynamic entropy for ionic melts due to the pair correlation approximation are of the order of 10% or less for most state points but can be significantly larger in the anomalous regime at very low temperatures. In the case of water, as expected given the rigid-body constraints for a molecular liquids, the pair correlation approximation causes significantly larger errors, between 20 and 30%, for most state points. Comparison of the excess entropy, Se, of ionic melts with the pair correlation entropy, S2, shows that the temperature dependence of Se is well described by T ??2=5 scaling across both the normal and anomalous regimes, unlike in the case of S2. As a function of density, the Se(rho) curves shows only a single maximum while the S2(rho) curves show both a maximum and a minimum. These differences in the behaviour of S2 and Se are due to the fact that the residual multiparticle entropy, delta(S) = Se - S2, shows a strong negative correlation with tetrahedral order in the anomalous regime.

cond-mat.soft↗