Physics and Astronomy, Multidisciplinary, Renewable Energy, Sustainability and the Environment, Materials Science
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Scopus Publications
Scopus Publications
Technical Analysis and Overview of Recent Advances in Materials Science of Polymers, Polymer Composites and Polymer Nanocomposites Kamal Nain Chopra, Ritu Walia Materials Science Forum, 2022 This paper discusses in detail Recent Trends in Tribology of Polymers, Polymer Composites and Polymer Nanocomposites, since they have certain properties unachievable with traditional materials. Important commercial materials used have been given. Some unique properties and applications of PPCs have been outlined. Carbon Nanotubes have been discussed in detail. Some explanation of the synthesis and experimental results of Cellulose-based hydrogels as reported in the literature , have been discussed in detail.
An exhaustive analysis of the characterization of photopolymer material (SZ2080) by two-photon polymerization, waves moving in a periodic potential, and two-photon absorption Ritu Walia, Kamal Nain Chopra Materials Science Forum, 2020 This paper presents an Exhaustive Analysis of the Characterization of Photopolymer Material (SZ2080) by Two-Photon Polymerization, and some of the modern concepts like Characterization of Photonic Crystals in Photopolymer SZ2080 by Two-Photon Polymerization, Waves Moving in a Periodic Potential, and Optical Quantum metamaterials. Two-photon polymerization for fabricating three-dimensional subdiffraction-limited structures has been discussed. Experimental and Computed Curves of line thickness (nm) vs feed rate (μm/s) have been technically analyzed. Waves moving in a Periodic Potential and Photonic Crystals have been technically discussed. In addition, Optical Quantum metamaterials have been discussed in terms of quantum coherence, and quantum dots with emphasis on cavity array metamaterial.
Technical analysis and overview of the application of artificial dielectric materials in the form of photonic crystal cavity with resonance in dirac leaky-wave antennas Ritu Walia, Kamal Nain Chopra Materials Science Forum, 2019 Application of Artificial Dielectric Materials in the form of Photonic crystal cavity with resonance in Dirac leaky-wave Antennas. The system investigated is a Photonic crystal cavity for the radiation properties of an antenna formed by a combination of a monopole radiation source and a cavity by a dielectric layer-by-layer 3D photonic crystal. The Photonic crystal cavity under study is working at resonance, since a high directivity, and a high power enhancement are obtainable at the resonant frequency of the cavity.In addition, an approach based on (i) Hughen's wavelets and (ii) the components of the incident Intensity after transmission through the system, is suggested for optimizing the performance of the optical antennas. Also, it has been discussed that the Optical antenna fabricated by Dielectric material - Photonic crystal is a better alternative to a conventional focusing lens, in Nanoscopy, in order to concentrate the laser radiation to dimensions smaller than the diffraction limit.
Decay instability of an upper hybrid wave in a magnetized dusty plasmas Ajay Gahlot, Ritu Walia, Jyotsna Sharma, Suresh C. Sharma, Rinku Sharma Physics of Plasmas, 2013 The decay instability of an upper hybrid wave into an upper hybrid sideband wave and low frequency ion-cyclotron wave are studied in a magnetized dusty plasma cylinder. The growth rate and ion-cyclotron mode frequencies were evaluated based on existing dusty plasma parameters. It is found that the unstable mode frequency increases linearly with δ (ion-to-electron density ratio). In addition, the growth rate of the unstable ion-cyclotron mode decreases sharply for lower values of δ in the presence of dust charge fluctuations, i.e., the dust grains increases the damping effect in three wave interaction process.
Effect of beam pre-bunching on gain and efficiency in a surface wave-pumped free electron laser SURESH C. SHARMA, JYOTSNA SHARMA, ANURADHA BHASIN, RITU WALIA Journal of Plasma Physics, 2012 A pre-bunched relativistic electron beam (REB) counter-propagating to the surface wave in the vacuum region Compton backscatters the surface wave into a high-frequency coherent radiation. Plasma supports the surface wave that acquires a large wave number k0z around pump wave frequency $\\omega _0 = {{\\omega _p } {/ {\\vphantom {{\\omega _p } {\\sqrt 2 }}} \\kern-\\nulldelimiterspace} {\\sqrt 2 }}$, where ωp is the plasma frequency. The surface wave extends into the vacuum region and can be employed as a wiggler for the generation of sub-millimeter waves. The growth rate, efficiency, and gain were evaluated based on experimentally known parameters relevant to free electron laser (FEL). It was found that the growth rate, efficiency, and gain of the surface wave-pumped FEL increase with the modulation index Δ, which has the maximum value when approaching unity in addition to when the frequency and wave number of the pre-bunched beam are comparable to that of the radiation wave, i.e., ω01 ~ ω1 and k01 ~ k1. The growth rate of FEL instability scales as one-third power of beam density in the Compton regime.
Ion beam driven ion-acoustic waves in a plasma cylinder with negatively charged dust grains Suresh C. Sharma, Kavita Sharma, Ritu Walia Physics of Plasmas, 2012 An ion beam propagating through a magnetized potassium plasma cylinder having negatively charged dust grains drives electrostatic ion-acoustic waves to instability via Cerenkov interaction. The phase velocity of sound wave increases with the relative density of negatively charged dust grains. The unstable wave frequencies and the growth rate increase, with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales as one-third power of the beam density. The real part of frequency of the unstable mode increases with the beam energy and scales as almost the one-half power of the beam energy.
Distortion of an amplitude modulated electromagnetic signal with time-dependent dust charging AJAY GAHLOT, RITU WALIA, SURESH C. SHARMA, R. P. SHARMA Journal of Plasma Physics, 2012 A large amplitude modulated Gaussian electromagnetic beam propagating in a dusty plasma with dust charge fluctuations has been studied. The electrons are heated non-uniformly by the electromagnetic beam. For non-steady state, we obtain nonlinear current density in the presence of dust grains. This expression has been used to study the non-stationary self-focusing and resulting self-distortion of the amplitude modulated electromagnetic beam. It has been observed that the dust charge fluctuation increases the self-focusing of electromagnetic beam. It is also found that the effect of dust charge fluctuations is significant on the modulation index.
Role of negatively charged ions in plasma on the growth and field emission properties of spherical carbon nanotube tip Aarti Tewari, Ritu Walia, Suresh C. Sharma Physics of Plasmas, 2012 The role of negatively charged ions in plasma on growth (without catalyst) and field emission properties of spherical carbon nanotube (CNT) tip has been theoretically investigated. A theoretical model of charge neutrality, including the kinetics of electrons, negatively and positively charged ions, neutral atoms, and the energy balance of various species has been developed. Numerical calculations of the spherical CNT tip radius for different relative density of negatively charged ions ɛr(=nSF6-/nC+, where nSF6- and nC+ are the equilibrium densities of sulphur hexafluoride and carbon ions, respectively) have been carried out for the typical glow discharge plasma parameters. It is found that the spherical CNT tip radius decreases with ɛr and hence the field emission of electrons from the spherical CNT tip increases. Some of our theoretical results are in accordance with the existing experimental observations.
Excitation of lower hybrid waves by a spiraling ion beam in a magnetized dusty plasma cylinder Suresh C. Sharma, Ritu Walia Physics of Plasmas, 2008 A spiraling ion beam propagating through a magnetized dusty plasma cylinder drives electrostatic lower hybrid waves to instability via cyclotron interaction. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the Princeton Q-1 device using the experimental dusty plasma parameters [e.g., Barkan et al., Planet. Space Sci. 43, 905 (1995)]. It is found that as the density ratio δ(=nio∕neo, where ni0 is the ion plasma density and ne0 is the electron density) of negatively charged dust grains to electrons increases, the unstable mode frequency of the lower hybrid waves increases. In addition, the growth rate of the instability also increases with the density ratio δ. In other words, the presence of negatively charged dust grains can further destabilize the lower hybrid wave instability. The growth rate has the largest value for the modes where Jl(pnro) is maximum [here pn=xn∕r0, where pn is the perpendicular wave number in cm−1, r0 is the plasma radius, and xn are the zeros of the Bessel function J1(x)] i.e., whose eigenfunctions peak at the location of the beam. The growth rate scales as one third power of the beam current.
