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Sanjay Kumar

Publications and source records attributed to Sanjay Kumar.

At least 55 records · Page 3Linked to original sources
arXiv2021

Identifying Influential Nodes in Weighted Networks using k-shell based HookeRank Algorithm

Finding influential spreaders is a crucial task in the field of network analysis because of numerous theoretical and practical importance. These nodes play vital roles in the information diffusion process, like viral marketing. Many real-life networks are weighted networks, but relatively less work has been done for finding influential nodes in the case of weighted networks as compared to unweighted networks. In this paper, we propose a k-shell-based HookeRank (KSHR) algorithm to identify spreaders in weighted networks. First, we propose weighted k-shell centrality of the node u by using the k-shell value of $u$, the k-shell value of its neighbors ($v$), and edge weight ($w_{uv}$) between them. We model edges present in the network as springs and edge weights as spring constants. Based on the notion of Hooke's law of elasticity, we assume a force equal to the weighted k-shell value acts on each node. In this arrangement, we formulate the KSHR centrality of each node using associated weighted k-shell value and the equivalent edge weight by taking care of series and parallel combination of edges up to 3-hop neighbors from the source node. The proposed algorithm finds influential nodes that can spread the information to the maximum number of nodes in the network. We compare our proposed algorithm with popular existing algorithms and observe that it outperforms them on many real-life and synthetic networks suing Susceptible-Infected-Recovered (SIR) information diffusion model.

cs.SI↗
arXiv2020

Magnetic reconnections in the presence of three-dimensional magnetic nulls and quasi-separatrix layers

Three-dimensional (3D) magnetohydrodynamic simulations are carried out to explore magnetic reconnections in the presence of 3D magnetic nulls and quasi-separatrix layers (QSLs). The initial magnetic fields are created by superposing uniform vertical magnetic fields of two different magnitudes on a linear force-free field. The interior of the numerical box contains two 3D nulls with separatrix domes separated by a quasi-separator (or hyperbolic flux tube) with QSLs. In the first simulation, the uniform vertical field is so large that the nulls are located at low heights and the domes are separate. Initially unbalanced Lorentz forces drive rotational flows that form strong electric currents and strong torsional fan reconnection at the 3D nulls and weak QSL reconnection at the hyperbolic flux tube. Flipping or slipping of field lines is observed in both cases. In the second simulation, with a weaker vertical field and larger domes, the separatrix surfaces meet at the central quasi-separator and their rotation drives stronger QSL reconnection than before.

astro-ph.SR↗
arXiv2020

Fundamental shadow links realized as links in $S^3$

We use purely topological tools to construct several infinite families of hyperbolic links in the 3-sphere that satisfy the Turaev-Viro invariant volume conjecture posed by Chen and Yang. To show that our links satisfy the volume conjecture, we prove that each has complement homeomorphic to the complement of a fundamental shadow link. These are links in connected sums of copies of $S^2 \times S^1$ for which the conjecture is known due to Belletti, Detcherry, Kalfagianni, and Yang. Our methods also verify the conjecture for several hyperbolic links with crossing number less than twelve. In addition, we show that every link in the $3$-sphere is a sublink of a link that satisfies the conjecture. As an application of our results, we extend the class of known examples that satisfy the AMU conjecture on quantum representations of surface mapping class groups. For example, we give explicit elements in the mapping class group of a genus $g$ surface with four boundary components for any $g$. For this, we use techniques developed by Detcherry and Kalfagianni which relate the Turaev-Viro invariant volume conjecture to the AMU conjecture.

math.GT↗
arXiv2020

The perspective of fluid flow behavior of respiratory droplets and aerosols through the facemasks in context of SARS-CoV-2

In the unfortunate event of current ongoing pandemic COVID-19, where vaccination development is still at the initial stage, several preventive control measures such as social distancing, hand-hygiene, and personal protective equipment have been recommended by health professionals and organizations. Among them, the safe wearing of facemasks has played a vital role in reducing the likelihood and severity of infectious respiratory disease transmission. The reported research in facemasks has covered many of their material types, fabrication techniques, mechanism characterization, and application aspects. However, in more recent times, the focus has shifted towards the theoretical investigations of fluid flow mechanisms involved in the virus-laden particles prevention by facemasks. This exciting research domain aims to address the complex fluid transport that led to designing a facemask with a better performance. This review paper discusses the recent updates on fluid flow dynamics through the facemasks. Key design aspects such as thermal comfort and flow resistance are discussed. Furthermore, the recent progress in the investigations on the efficacy of facemasks for prevention of COVID 19 spread and the impact of wearing facemasks are presented. Finally, the potential research directions for analyzing the fluid flow behavior are highlighted.

physics.med-ph↗
arXiv2020

Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections and Coronal dimmings during the X2.1 flare in NOAA AR 11283

The magnetohydrodynamics of active region NOAA 11283 is simulated using an initial non-force-free magnetic field extrapolated from its photospheric vector magnetogram. We focus on the magnetic reconnections at a magnetic null point that participated in the X2.1 flare on 2011 September 6 around 22:21 UT (SOL2011-09-06T22:21X2.1) followed by the appearance of circular flare ribbons and coronal dimmings. The initial magnetic field from extrapolation displays a three-dimensional (3D) null topology overlying a sheared arcade. Prior to the flare, magnetic loops rise due to the initial Lorentz force, and reconnect at the 3D null, leading to expansion and loss of confined plasma that produce the observed pre-flare coronal dimmings. Further, the simulated dynamics documents the transfer of twist from the arcade to the overlying loops through reconnections, developing a flux rope. The non-parallel field lines comprising the rope and lower-lying arcades form an X-type geometry. Importantly, the simultaneous reconnections at the 3D null and the X-type geometry can explain the observed circular and parallel flare ribbons. Reconnections at the 3D null transform closed inner spine field lines into open field lines of the outer spine. The footpoints of these open field lines correspond to a ring-shaped coronal dimming region, tracing the dome. Further, the flux rope bifurcates because of these reconnections which also results in the generation of open magnetic field lines. The plasma loss along the open field lines can potentially explain the observed coronal dimming.

astro-ph.SR↗
arXiv2020

Experimental investigations of acoustic curtains for hospital environment noise mitigations

The continuous increase of hospital noise levels has become a vital challenge for society. The complex soundscapes in the hospital produce unpleasant noise, which may exceed the prescribed noise level for the patients and healthcare professionals. Previous studies have reported that extended exposure to loud noise may cause auditory and nonauditory disorders in healthcare professionals, medical staff, and patients. Therefore, there is an increased interest for the design and fabrication of effective noise barriers for the hospital premises. Herein, we have performed the thorough experimental investigations on the acoustical performances for PVC coated polyester fabrics and 100 % pure PVC sheets. The performances of these potential acoustic curtains have found to be superior to that of existing acoustic curtains for hospitals. Also, the results showed that the sound transmission class rating of PVC curtains are much higher than the existing commercial acoustic curtains.

physics.app-ph↗
arXiv2020

Experimental investigations of psychoacoustic characteristics of household vacuum cleaners

Vacuum cleaners are one of the most widely used household appliances associated with unpleasant noises. Previous studies have indicated the severity of vacuum cleaner noise and its impact on the users nearby. The quantified measurements of the generated noise standalone are not sufficient for the selection or designing of vacuum cleaners. The human perception must also be included for a better assessment of the quality of sound. A hybrid approach known as psychoacoustics, which comprises subjective and objective evaluations of sounds, is widely used in recent times. This paper focuses on the experimental assessment of psychoacoustical matrices for household vacuum cleaners. Three vacuum cleaners with different specifications have been selected as test candidates, and their sound qualities have been analyzed. Besides, the annoyance index has been assessed for these vacuum cleaners.

eess.AS↗
arXiv2020

Transport and tumbling of polymers in viscoelastic shear flow

Polymers in shear flow are ubiquitous and we study their motion in a viscoelastic fluid under shear. Employing dumbbells as representative, we find that the center of mass motion follows: $\langle x^2_c(t) \rangle \sim \dotγ^2 t^{α+2}, ~0< α<1$, generalizing the earlier result: $\langle x^2_c(t) \rangle \sim \dotγ^2t^3 ~(α= 1)$. Motion of the relative coordinate, on the other hand, is quite intriguing in that $\langle x^2_r(t) \rangle \sim t^β$ with $β= 2(1-α)$ for small $α$. This implies nonexistence of the steady state. We remedy this pathology by introducing a nonlinear spring with FENE-LJ interaction and study tumbling dynamics of the dumbbell. The overall effect of viscoelasticity is to slow down the dynamics in the experimentally observed ranges of the Weissenberg number. We numerically obtain the characteristic time of tumbling and show that small changes in $α$ result in large changes in tumbling times.

cond-mat.stat-mech↗
arXiv2019

Normality and Montel's Theorem

In this article, we prove a normality criterion for a family of meromorphic functions having zeros with some multiplicity which involves sharing of a holomorphic function by the members of the family. Our result generalizes Montel's normality test in a certain sense.

math.CV↗
arXiv2019

A normality Criterion for a Family of Meromorphic Functions

Schwick, in [6], states that let $\mathcal{F}$ be a family of meromorphic functions on a domain $D$ and if for each $f\in\mathcal{F}$, $(f^n)^{(k)}\neq 1$, for $z\in D$, where $n, k$ are positive integers such that $n\geq k+3$, then $\mathcal{F}$ is a normal family in $D$. In this paper, we investigate the opposite view that if for each $f\in\mathcal{F}$, $(f^n)^{(k)}(z)-ψ(z)$ has zeros in $D$, where $ψ(z)$ is a holomorphic function in $D$, then what can be said about the normality of the family $\mathcal{F}$?

math.CV↗
arXiv2019

Transformed Naive Ratio and Product Based Estimators for Estimating Population Mode in Simple Random Sampling

In this paper, we propose a transformed naïve ratio and product based estimators using the characterizing scalar in presence of auxiliary information of the study variable for estimating the population mode following simple random sampling without replacement. The bias, mean square errors, relative efficiency, ratios of the exact values of mean square errors to the simulated mean square errors and confidence interval are studied for the performance of the proposed transformed naïve ratio type estimator with the certain natural population as well as artificially generated data sets. We have shown that proposed transformed naïve ratio based estimator is more efficient than the naïve estimator and naïve ratio estimator of the population mode.

stat.ME↗
arXiv2019

Determination of Power of Groove fields under Dirichlet conditions associated with axisymmetric Electromagnetic fields

The present paper gives an interaction of electromagnetic waves with a smooth convex tri-angular obstacle and its adjacent wedge regions. We attempt to find the power of groove fields under Dirichlet conditions associated with axisymmetric electromagnetic field. A field intensity may be expressed in terms of a damped wave with a space attenuation depending on the physical parameters like conductivity, permittivity and permeability associated with an obstacle placed across the lines of force due to a given EM field. Groove field and their associated powers based on Dirichlet conditions on the groove surfaces have been determined. Knowledge of groove field is essential for precise designing of triangular corrugated structures for studying the blazing effect of propagating EM wave. We find that an echellete model or an antenna may act as a Sensor for receiving wide range of frequencies subject to the restriction lambda>2pi/xi_i whereas the said antenna would act as a Transmitter for radiating wide range of frequencies subject to the restriction lambda<2pi/xi_i. The governing Maxwell's equation is solved subject to the Dirichlet condition of the field intensity on the boundaries of the said groove regions. Theory of Fourier-Bessel series has been applied for the present purpose.

physics.class-ph↗
arXiv2019

Determination of Power of Groove fields belonging to the wedge regions adjacent to a convex triangular obstacle associated with Dirichlet conditions subject to axially independent EM fields

A convex triangular obstacle forms a vital part of a periodic echellete grating. A triangular grating is characterized by three parameters like period, depth and flare angle. Knowledge of groove field is essential for precise designing of triangular corrugated structures for studying the blazing effect of propagating EM wave. In the present paper, an attempt has been made to determine the power of Groove fields belonging to a pair of groove regions adjacent to a convex triangular prism. Groove fields and their associated powers based on Dirichlet conditions on the groove surfaces have been determined. The governing Helmholtz wave equation has been solved for determining the free surface field and the groove field. Fourier-Bessel series, oblique coordinate transformations and Lommel's integral are used as tools.

physics.class-ph↗
arXiv2018

On Solution of Second Order Complex Differential Equation

In this paper, we establish transcendental entire function $A(z)$ and polynomial $B(z)$ such that the differential equation $f''+A(z)f'+B(z)f=0$, has all non-trivial solution of infinite order. We use the notion of \emph{critical rays} of the function $e^{P(z)}$, where $A(z)=d(z)e^{P(z)}$ with some restrictions.

math.CV↗
arXiv2018

On Zeros and Growth of Solutions of Second Order Linear Differential Equations

For a second order linear differential equation $f''+A(z)f'+B(z)f=0$, with $ A(z)$ and $B(z)$ being transcendental entire functions under some restriction, we have established that all non-trivial solutions are of infinite order. In addition, we have proved that these solutions have infinite number of zeros. Also, we have extended these results to higher order linear differential equations.

math.CV↗