Journal Articles
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Item Critical review of ribbed solar air heater and performance evaluation of various V-rib configuration(Elsevier Ltd, 2021) Nidhul, K.; Yadav, A.K.; Anish, S.; Kumar, S.The low heat transfer rate in a flat plate solar air heater (SAH) is due to the development of a laminar sub-layer near the heated absorber plate. Owing to this, the plate temperature rises substantially, instigating losses and thus reducing the efficiency. Extensive research has been carried out to mitigate this problem, of which passive technique emerged to be a promising solution. The passive method involves the application of fins/turbulators/ribs on the surface where the boundary layer develops so that it breaks the same. Various profiles and configurations of the ribs ranging from transverse to inclined and continuous to discrete have been presented concisely. Correlations on Nusselt number (Nu) and friction factor (f) for different rib configurations have been summarized in order so that it can be accessed for future research. 3-D CFD analysis is carried out to gain insight into the flow pattern of various V-ribbed SAH, and with the help of streamlines and contours, the findings are established. Furthermore, various exergy destruction has been studied in detail for different V-rib configurations, namely– V-rib, multiple V-rib, and multiple V-rib with the gap, and analyzed in detail for prospective studies. Exergetic performance study of these rib configurations indicates that the multiple ribs and the multiple rib-gap combinations enhance exergetic efficiency (ηex) by 12% and 31.6%, respectively, in comparison to V-rib SAH. © 2021 Elsevier LtdItem Directional synthesis of aviation-, diesel-, and gasoline range hydrocarbon fuels by catalytic transformations of biomass components: An overview(Elsevier Ltd, 2023) Dutta, S.; Madav, V.; Joshi, G.; Naik, N.; Kumar, S.Selective conversion of heavily oxygenated biomolecules into hydrocarbon-based liquid transportation fuels with stipulated structural traits is of academic and industrial significance. This work provides an overview of producing fuel precursors from biomass components and their catalytic transformation into aviation-, diesel-, and gasoline-range hydrocarbon fuels (HCFs). Strategic applications of various organic transformations for the molecular design of targeted products have been rationalized. Construction and alteration of the carbon skeletal system in the fuel candidates via chemical-catalytic transformations have been highlighted. Emphasis has also been given to the process conditions and details of the catalysts employed in these processes. Critical analysis of the literature data presented in this review will assist the researchers in developing more proficient processes for the biorenewable production of drop-in HCFs. © 2023 Elsevier LtdItem A novel characterization and performance measurement of memristor devices for synaptic emulators in advanced neuro-computing(MDPI AG indexing@mdpi.com Postfach Basel CH-4005, 2020) Al-Shidaifat, A.; Chakrabartty, S.; Kumar, S.; Acharjee, S.; Song, H.The advanced neuro-computing field requires new memristor devices with great potential as synaptic emulators between pre-and postsynaptic neurons. This paper presents memristor devices with TiO2 Nanoparticles (NPs)/Ag(Silver) and Titanium Dioxide (TiO2) Nanoparticles (NPs)/Au(Gold) electrodes for synaptic emulators in an advanced neurocomputing application. A comparative study between Ag(Silver)-and Au(Gold)-based memristor devices is presented where the Ag electrode provides the improved performance, as compared to the Au electrode. Device characterization is observed by the Scanning Electron Microscope (SEM) image, which displays the grown electrode, while the morphology of nanoparticles (NPs) is verified by Atomic Force Microscopy (AFM). The resistive switching (RS) phenomena observed in Ag/TiO2 and Au/TiO2 shows the sweeping mechanism for low resistance and high resistance states. The resistive switching time of Au/TiO2 NPs and Ag/TiO2 NPs is calculated, while the theoretical validation of the memory window demonstrates memristor behavior as a synaptic emulator. Measurement of the capacitor-voltage curve shows that the memristor with Ag contact is a good candidate for charge storage as compared to Au. The classification of 3 x 3 pixel black/white image is demonstrated by the 3 x 3 cross bar memristor with pre-and post-neuron system. The proposed memristor devices with the Ag electrode demonstrate the adequate performance compared to the Au electrode, and may present noteworthy advantages in the field of neuromorphic computing. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Item Workplace spirituality as an antecedent of university teachers’ subjective well-being: Mediating role of job satisfaction and job performance(Rajarambapu Institute Of Technology, 2020) Kumar, S.There is a need to measure how university teachers' think and feel about their lives, especially when the work environment is dynamic and ever-changing. In this study, the scholar explores workplace spirituality's association with the teachers' subjective well-being directly and also indirectly through teachers’ job satisfaction and job performance. Data were collected through survey instrument from 395 teachers' working for various private engineering institutions located in the states of Telangana and Andhra Pradesh. Results showed a relationship between workplace spirituality and subjective well-being directly, although the path coefficient was weak. Interestingly, the results discovered the positive and significant indirect relationship between workplace spirituality and subjective well-being through teachers’ job satisfaction and job performance. The papers aim was to explore conceptually the role of spirituality contributing to University teachers’ satisfaction with life as a whole, which is essentially the teachers’ subjective well-being. The present study is probably one of its kind to explore the relationship between workplace spirituality and subjective well-being not only directly but also indirectly through job satisfaction and job performance. The outcomes of the study offer valuable insights and inputs for future research in the niche area of workplace spirituality. The implications of the study have been discussed in greater detail in the appropriate section. © 2020, Rajarambapu Institute Of Technology. All Rights Reserved.Item A novel chaotic modulation approach of packaged antenna for secured wireless medical sensor network in E-healthcare applications(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Jayawickrama, C.; Kumar, S.; Chakrabartty, S.; Song, H.This article first time reports the chaotic modulation approach toward RF signal processing for secured wireless medical sensor network (WMSN) in E-healthcare applications. A Lorenz based chaotic modulation approach is implemented which provides lowest bit error rate (BER). The definite analytical expressions for BER in a differential chaos-shift keying (DCSK) modulation scheme is derived and it predicted good correlation between simulated and theoretical. It is observed that proposed Lorenz chaos-based DCSK modulation scheme is a potential candidate to provide high security in the patient data for WMSN. An off-body UWB slotted antenna is designed which could avoid limitation of short-range distance like implanted ones. The entire work includes numerical, simulated and experimental data in three phases. In first phase, Lorenz chaotic oscillator with electronics compatibility is executed which acts as data acquisition unit and demonstrates two-dimensional and three-dimensional chaos attractors. While in the second phase, analysis of BER achieves value of less than 10?4 by providing pseudorandom bit sequence at 5 Gb/s. A chaos modulated envelope using Lorenz based DCSK modulation is obtained by delay element ?. Finally, the third phase is designed on-wafer off-body antenna and demonstrates 3.1 to 10.6 GHz UWB toward RF signal processing in E-healthcare applications. © 2019 Wiley Periodicals, Inc.Item A compact and efficient graphene FET based RF energy harvester for green communication(Elsevier GmbH, 2020) Singh, N.; Kumar, S.; Kumar Kanaujia, B.K.; Beg, M.T.; Mainuddin, M.; Kumar, S.This paper presents a graphene field effect transistor (FET) based rectenna with substrate-integrated waveguide (SIW) broadband approach for RF energy harvesting application. The proposed structure of integrated rectenna consists of a graphene FET rectifier and an SIW antenna operating in the (S11 < ?10 dB) range of 29–46 GHz. The peak gain of the SIW antenna observed is 8.12 dBi. In addition, a new matched circuit consisting of microstrip line and butterfly stub (without using any lumped elements) is designed. The matched circuit provides a miniaturized block by reducing the size and eliminating parasitic reactance in the integrated rectenna. The proposed rectenna is implemented and fabricated using two superimposed layers: RT/duroid 5880 and graphene substrate with a compatible approach. A measured conversion efficiency of 80.32% is obtained. The dimensions of the proposed antenna and rectifier are 3.2 × 3.2 × 0.4 mm3 and 3.2 × 10 × 0.4 mm3, respectively. The proposed rectenna covers Ka- and Q-band applications and could be a potential candidate for contemporary energy harvesting systems. © 2019 Elsevier GmbHItem Performance of cascode Class-EF?1 PA with built-in techniques for UWB radar toward monitoring of patient actions(Institution of Engineering and Technology kvukmirovic@theiet.org, 2020) Kumar, R.; Dwari, S.; Kumar Kanaujia, B.K.; Kumar, S.; Song, H.This work proposes a performance of the cascode Class-EF?1 power amplifier (PA) for UWB radar transmitter. The cascode Class-E PA with built-in techniques overcomes the traditional mismatch and provides good performance of PA. Incurs the resonance and switching effect is observed in cascode Class-E PA that compensates for the parasitic effects and provides a wide-impedance range. While design-II includes negative capacitance and inverse Class-F, which achieves a redundant performance of wide bandwidth and power-added efficiency (PAE). Design-II achieves the redundant performance compared with design-I. Both design-I and design-II are implemented and analysed through simulation and experimental results using RF 65 nm Samsung Magnachip Hynix CMOS process. Design-I achieves a wide-impedance bandwidth ranging from 3 to 11.7 GHz with drain efficiency (DE) and maximum PAE of 80 and 73% at the output power of 26.4 dBm. The global efficiency (GE) and error vector magnitude (EVM) of 70 and 5.2% are also achieving for design-I. The redundant performance in design-II achieves wide bandwidth with operating frequency range of 2-13 GHz with maximum DE and PAE of 85 and 76%. For design-II, GE and EVM are investigated as 68 and 4.9% that could validate the accuracy and robustness of the UWB radar. © The Institution of Engineering and Technology 2019Item A compact broadband GFET based rectenna for RF energy harvesting applications(Springer, 2020) Singh, N.; Kumar, S.; Kumar Kanaujia, B.K.; Beg, M.T.; Mainuddin, M.; Kumar, S.In this paper, a compact GFET-based rectifier integrated with a monopole antenna is proposed for wireless energy harvesting applications. The GFET increases impedance bandwidth of the rectifying circuit, thus covering a range of 22.5–27.5 GHz. The sensing antenna is a triangular monopole with truncated corners for realizing circular polarization at the frequencies 24.25 GHz and 27 GHz. By the help of ?/4 transformer, the sensing antenna is matched with the proposed GFET rectifier. The RF-DC conversion efficiency realized is 80% at 5 dBm for the load of 5 K?, and the output DC voltage observed is 6.8 V. The modified ground plane triangular monopole antenna shows a peak gain of 7.8 dBi. The designed rectenna prototype is fabricated and found simulated and measured results are in good agreement. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Influence of Integration of Phase Change Materials on Hydration and Microstructure Properties of Nanosilica Admixed Cementitious Mortar(American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2020) Snehal, K.; Das, B.B.; Kumar, S.The present study demonstrates the influence of integrating phase change materials (PCMs) on hydration and microstructure properties of nanosilica admixed cementitious mortar. First, the optimized dosage of nanosilica in correspondence to compressive strength was determined. Subsequently, the desired proportion of PCMs was identified pertaining to a designated compressive strength of 35 MPa at the curing age of 28 days. The hydration and microstructure studies were carried out through thermo gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Further, thermal properties were determined by means of differential scanning calorimetry (DSC). Incorporation of nanosilica into the cementitious mortar was found to have a positive influence on early strength development and durability, however, there was found to be an increase in chemical shrinkage as compared to the control mixture. PCMs integrated cementitious mortar improved the thermal efficiency as well as reduced the chemical shrinkage, but adversely affected the mechanical, hydration, and durability properties. With respect to development of compressive strength of the cementitious mortar, it is found that n-octadecane PCMs performed better amidst other PCMs, such as paraffin and sodium carbonate hydrates. Further, studies were carried out on cementitious mortar having both nanosilica (optimized proportion) and PCMs (the best performing). From the results, it is found that cementitious mortar comprising of both nanosilica and PCMs have compensated the drawbacks of one another. Blended mortar (having both nanosilica and PCMs) showed superior strength gain at early age, better durability resistance, low chemical shrinkage, and superior thermal performance. © 2020 American Society of Civil Engineers.Item Enhanced thermo-hydraulic performance in a V-ribbed triangular duct solar air heater: CFD and exergy analysis(Elsevier Ltd, 2020) Nidhul, K.; Kumar, S.; Yadav, A.; Anish, S.Computational fluid dynamics (CFD) and exergy analysis are conducted to investigate the impact of secondary flow produced by V-ribs on the overall performance of a triangular solar air heater (SAH) duct. For a fixed relative rib pitch (Rp = 10) and relative rib height (Rh = 0.05), the effect of rib inclination (?) is studied using CFD technique for varying Reynolds number (5000 ? Re ? 20000). Based on the CFD simulation results, empirical correlations capable of predicting Nu and f with an absolute variance of 8.7%, and 4.7%, respectively, are developed. Employing these correlations, exergetic performance analysis is carried out. Maximum effectiveness parameter (?) of 2.01 is obtained for ? = 45° at Re = 7500. The exergy analysis reveals that the entropy generated is lower for the ribbed triangular duct compared to the smooth duct with maximum enhancement in exergetic efficiency (?ex) as 23% for ? = 45°. The study is extended for the rectangular duct to compare the performance with the ribbed triangular duct SAH (? = 45°). Results show that ribbed triangular duct SAH (? = 45°) is superior over various configurations of the ribbed rectangular duct SAH at higher mass flow rates. © 2020 Elsevier Ltd