(SoE) School of Engineering

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

The development of low molecular weight molecule-mediated biocompatible soft supramolecular hydrogels, considered to be next-generation materials for biomedical applications, is a challenging task. In this context, the present work reports the synthesis of the hybrid hydrogel (CISZ2H) comprising ternary nanohybrids (Zn2+-Ag NPs@β-FeOOH@5′-CMP), consisting of greener components as a building block with hydrophobic tail (containing Zn2+ ions, Ag NPs, and β-FeOOH) and hydrophilic head (5′-cytidine monophosphate (5′-CMP)). The presence of Zn2+ ions and Ag NPs in the nanohybrids introduces new coordination sites and induces the puckering of the ribose sugar in 5′-CMP to generate the solid-like network in the self-assembly via micellar formation involving building blocks. Extensive cross-linking among organic and inorganic moieties provide these hydrogels with unique physicochemical features of improved mechanical strength (∼71 000 Pa), large water retention capability (600%), self-healing, and injectability as arrived at by thixotropic measurements, low toxicity, and enhanced drug/dye loading capabilities. Thus, the co-doped Zn2+ ions and Ag NPs in CISZ2H impart it with enhanced mechanical stability, shear thinning, external stimuli-responsiveness (pH and temperature), sustained slow drug release, surface enhanced Raman scattering (SERS) activity, and antibacterial features, thereby making this hydrogel safer for drug delivery, wound healing, sensing, and tissue engineering. The excellent features of the as-synthesized hydrogels make it a smart soft material for advanced applications with enormous future potential. © The Royal Society of Chemistry.

Chemical Engineering

World University root node

Dalton Transactions

Smart soft supramolecular hybrid hydrogels modulated by Zn2+/Ag NPs with unique multifunctional properties and applications

The numerical investigation of free radical polymerization (FRP) of methyl methacrylate under mixed feed condition at inlet is made for three microtubular reactor geometries, namely, straight tube, coiled tube, and coil flow inverter reactor. The effect of variation of fluid thermophysical properties (FTPP) (density, viscosity, and thermal conductivity) with reaction along with discrete variation of chemical species diffusion coefficient is studied. Predicted values of monomer conversion, number-average chain length (DPn), and polydispersity index (PDI) are found to be systematically lower for variable FTPP case compared to constant FTPP case. But contrary to expectations, results are found to be independent of reactor geometry for either case. Results clearly show the importance of modeling the variation of FTPP especially with respect to conversion. One case of varying diffusion coefficient of each chemical species based on free volume theory with constant FTPP is also simulated. Here again, the results are found to be independent of reactor geometry. Constant thermal conductivity and isothermal reactor condition are found to be good assumptions. This study clearly establishes the need not only for variable FTPP, thus coupling transport processes, but also for incorporating varying diffusion coefficient along with conversion in modeling of FRP in microreactors for better predictions. © 2020 Wiley-VCH GmbH

Fulltext

Macromolecular Theory and Simulations

Numerical Investigations of Perfectly Mixed Condition at the Inlet of Free Radical Polymerization Tubular Microreactors of Different Geometries

In the present article, the vibrational behaviour of a functionally graded plate (FGP) resting on elastic foundations under a thermal environment with geometric discontinuities and microstructural defects (porosity) has been investigated. The structural kinematics is based on the trigonometric shear-strain function with only four unknowns. The transverse shear stress varies nonlinearly along the thickness. The FGP has geometric discontinuities in the form of a circular cut-out of different dimensions at the centre. The various geometric imperfections are modelled using a generic function, whereas the microstructural defects (porosity) have been included using modified power law. The temperature variation between the surfaces is nonlinear along the thickness direction. The FEM-based solutions are presented using C0 continuous iso-parametric element. Convergence and validation study have been carried out to demonstrate the efficacy and reliability of the presented results. The effect of porosity inclusion, circular cut-out, elastic foundation, thermal environment, geometric imperfection modes and the volume fraction index have been analysed under conventional and unconventional boundary constraints. It is observed that after a specific dimension of circular cut-out, vibrational behaviour of FGPs exhibits nonlinearity in nature. © 2020, The Brazilian Society of Mechanical Sciences and Engineering.

Mechanical Engineering

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Influence of geometric discontinuities and geometric/microstructural defects on the temperature-dependent vibration response of functionally graded plates on elastic foundation

Owing to its good biocompatibility and low cost, stainless steel is one of the most widely utilized biomaterial. However, longtime assessment of stainless steel has shown problems related to material degradation, especially localized corrosion and bio-film formation. In addition, the leaching of toxic nickel and chromium ions from stainless steel leads to additional health complications. Here, we utilized submerged friction stir processing, a severe surface deformation technique for significantly enhancing its durability, bio-activity as well as antibacterial resistance. The processing was done with a wide variation in strain rates to produce tunable surface microstructure. High strain-rate processing resulted in nearly single-phase fine-grained microstructure, while slow strain-rate processing developed a dual-phase fine-grained microstructure. The bio-corrosion rate of processed steel was reduced by more than 60 \% along with significant enhancement in the pitting resistance. The processed steel showed nearly no bacterial adhesion/biofilm formation, evaluated using S. aureus and E. coli bacterial strains. Further, the processed stainless steel surface demonstrated minimum leaching of the toxic elements, significantly enhancing its appeal for bio-implant applications. The observed behavior was explained based on the formation of a stable passive layer, rich in Cr2O3, as determined using x-ray photoelectron microscopy (XPS) and increased hydrophilicity. © 2020 Elsevier B.V.

Colloids and Surfaces B: Biointerfaces

Enhanced durability, bio-activity and corrosion resistance of stainless steel through severe surface deformation

Here, an excellent cavitation erosion-corrosion resistance of stainless steel using a novel severe surface deformation technique, reciprocating friction processing (RFP) was demonstrated. The RFP treated stainless steel showed nano-grained, nano-twinned microstructure along with high dislocation density. The RFP treated steel significantly surpassed the performance of advanced structural materials including high entropy alloy (Al0.1CoCrFeNi) and complex concentrated alloy (SiC reinforced Al0.1CoCrFeNi), demonstrating the lowest cavitation erosion and cavitation erosion-corrosion rates for this class of materials. The RFP treated steel demonstrated outstanding corrosion behavior in 3.5\% NaCl solution as well. The unusual performance of RFP treated steel is attributed to its excellent mechanical strength and strong passivating behavior. © 2020 Elsevier B.V.

Mathematics

(SoNS) School of Natural Sciences

Wear

Cavitation erosion-corrosion resilient surfaces through reciprocating friction processing

An objective distortion measure is very crucial to accurately quantify the distortion introduced in the electroencephalogram (EEG) signal during the denoising process. Most of the existing algorithms report their denoising performance by comparing the original EEG signal and the reconstructed EEG signal using root mean square error (RMSE) and other similar measures. However, it is very important to quantify the distortion in each band of EEG signal since each band provides distinct information about the specific brain activity. Furthermore, quantification of band-wise distortion enables the selection of particular denoising algorithm for the application-specific EEG signal analysis. Therefore, in this paper, we propose two robust distortion measures such as weighted signal to noise ratio (WSNR) and weighted correlation coefficient (WCC) for accurately representing the objective reconstruction loss in each band. These performance measures are computed between the wavelet subbands of the original and the denoised/reconstructed signal with weights equal to the relative wavelet energy and wavelet entropy of the corresponding subband wavelet coefficients. To demonstrate the effectiveness of the proposed performance measures, we evaluate the performance of six existing denoising methods using these measures. Results depict that these measures can adequately provide high mutual agreement between objective scores and subjective analysis. © 1994-2012 IEEE.

Electrical Engineering

IEEE Signal Processing Letters

Wavelet Based Waveform Distortion Measures for Assessment of Denoised EEG Quality with Reference to Noise-Free EEG Signal

Superhydrophobic surfaces with high adhesion have attracted huge attention in recent research works due to their versatile applications including transportation of microdroplet without any loss. Modification of metallic surfaces to achieve such properties is important to extend their applications. Especially, the superhydrophobic surfaces with very low bacterial adhesion have attracted intense attention in medical, food, and pharmaceutical industries. Here, we have fabricated different micropatterns on aluminium surfaces using a simple and cost-effective micro-imprinting technique. The surface chemistry was modified through a coating of low surface energy material 1H, 1H, 2H, 2H-perfluorooctyl-trichlorosilane (FOTS) using vapor deposition technique. Surface morphology of the samples was investigated using scanning electron microscopy (SEM) and contact profilometer. Results show a significant influence of the surface morphology on the wetting, adhesion and anti-bacterial properties. Surfaces composed of discrete micropillars showed higher de-wetting compared to surface containing continuous zig-zag micro lines even despite lower roughness factor. However, the opposite trend was observed in case of adhesion. These results are explained based on wetting state and difference in liquid-air interface pinning. Further, the developed samples showed higher water-retaining ability compared to rose-petal along with superhydrophobicity. The surface with micropillar structures with higher roughness factor exhibited improved non-fouling behavior which has been quantified by spot assay and atomic force microscopy (AFM). This study opens up the possibility of fabricating multifunctional metal surfaces on a large scale by a cost-effective, environment friendly and easily scalable processing route. © 2020 IOP Publishing Ltd.

Physics

Surface Topography: Metrology and Properties

Effect of topography and chemical treatment on the hydrophobicity and antibacterial activities of micropatterned aluminium surfaces

Present work shows the flow effect of water mass per unit time (MFR) on the life cycle conversion efficiency (LCCE) of a single slope solar desalination unit (SSSDU) coupled with N identical evacuated tubular collectors (N-ETC). The analysis is observed for a typical days of May and December for the atmospheric situation of New Delhi with the help of analytical program fed in MATLAB. The input data required for the numerical computations have been taken from IMD, Pune, India. The average value of annual energy output has been computed based on the enegy outputs of summer and winter seasons followed by the evaluation of LCCE for the system. It has been concluded that the value of LCCE diminishes with the raise in the value of fluid flow mass/ unit time and values of LCCE becomes almost constant beyond 0.044 kg/s at given values of water depth and number of collectors. It has also been observed that the value of LCCE has similar trends at other number of collectors. © 2019 Elsevier Ltd.

Materials Today: Proceedings

Effect of flow of fluid mass per unit time on life cycle conversion efficiency of single slope solar desalination unit coupled with N identical evacuated tubular collectors

Utilization of solar photovoltaic (PV) as a power source in water pumping applications has emerged as one of the valuable solar applications. Solar PV water pumping system is used to fulfill the demand of water in the field of irrigation, livestock watering, and village water supply. Understanding of system design and selection of appropriate design parameters are essential to attain consistent and economical performance of any system. To design a solar water pumping system collection of the information regarding the system components and local climate data of the location are required. This information helps to obtain preferred design and results. In the present paper design optimization of PV system is done by simulation software tool PVsyst 5.52. This simulation software helps to design the system and shows how the different parameters affect the system performance results. Selection of PV array, controller, pumping unit, water supply network is needful to fulfill design requirements. The performance evaluation of a system located at Karansar, Jaipur (Rajasthan) is done with help of simulation software by using existing local data. The theoretical and simulation results are used to understand the system design and its performance by taking different parameters into consideration. © 2019 Elsevier Ltd. All rights resrved.

Design optimization of solar PV water pumping system

The present study examines the stability of a thinning straight jet in electrospinning process. The linear stability analysis is carried out to obtain the growth/decay rate of axisymmetric disturbance imposed on the thinning jet. The analysis captures the role of solvent evaporation in the stability behavior of the linear path of the electrospinning jet. In contrast to many prior stability analyses which consider the jet as a cylindrical filament with uniform radius, the present study analyzes the stability of a jet which exhibits thinning under realistic electrospinning conditions. Two different polymeric solutions are considered: the poly-isobutene (PIB) Boger fluid with low electrical conductivity and the highly conductive poly-ethylene oxide (PEO) solution in ethanol/water. At low extensional deformation, the rheology of the unentangled PIB-based Boger fluid is described by the Oldroyd-B model. The PEO solution, on the other hand, experiences a very high elongation rate due to the development of strong axial electric stress. The nonlinear rheology of the entangled PEO solution is appropriately described by the eXtended Pom–Pom (XPP) model, a variant of the classical tube model. The analysis reveals that the instability in low conductivity fluid is driven by the capillary forces, whereas the high conductivity fluid exhibits oscillatory conducting mode of instability driven by the coupled effect of axial electric field and surface charges. For both the reference fluids, the increase in solvent evaporation tends to decrease the disturbance growth rate to the extent that the axisymmetric instability is completely suppressed for a strong enough evaporation. The stabilizing role of solvent evaporation is attributed to the enhancement in fluid viscosity and elasticity due to increased polymer concentration upon evaporation. Thus, by suppressing the onset of axisymmetric instability during the straight jet path, solvent evaporation potentially helps produce smooth fibers without bead formation. © 2020 Elsevier Ltd