Faculty Publications
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Publications by NITK Faculty
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Item Comparative Study of Millimeter-Wave-Over-Fiber Transmission Link with Different Photodiodes(Institute of Electrical and Electronics Engineers Inc., 2024) Singh, A.; Mishra, S.K.; Dinesh Achalaram, C.; Singh, M.In optical fiber communication, there is an expo- nential growth in data traffic demand. Hence, there is a need for advanced and efficient signal generation methods that offer a wider frequency range, higher tunability, and lower distortion. These optical fiber networks have long-distance capabilities and high data rates essential for intercontinental connections. This paper investigates the performance comparison of PIN photodetector and avalanche photodetector (APD) in optical fiber communication in terms of quality (Q) factor and eye patterns. The simulation model, utilizing microwave photonics (MWP) technology, implemented in OptiSystem software incorporates a Mach-Zehnder modulator (MZM) for optical signal modulation and a Bessel filter for spectral shaping. Photodetectors are susceptible to noise, which may occur due to thermal noise, shot noise, or dark current, and generate signals with increased bit error rate (BER) and degraded signal quality. To overcome these problems, photodetectors with suitable materials and designs are utilized to improve responsivity and reduce noise levels. A maximum Q factor of 7.6019 and minimum bit error rate of 1.4075 × 10-14 at 10 Gbps over a 25 km single-mode optical fiber network is obtained in the mm-wave wavelength range. Theoretical analysis of the suggested system is also discussed. © 2024 IEEE.Item Use of antioxidants for enhancing oxidative stability of bulk edible oils: a review(Blackwell Publishing Ltd, 2021) Mishra, S.K.; Belur, P.D.; Iyyaswami, R.Edible oils industry is using synthetic and natural antioxidants to enhance the oxidative stability of bulk edible oils. Due to safety concerns of BHA, BHT and TBHQ, there is an ongoing effort to find an effective and safe replacement. Finding a safe antioxidant or its synergistic mixture, which delays, retard or prevent the oxidation of bulk oil without changing the colour or flavour upon addition is a challenge. In this review, a brief account of chemical basis of oxidative deterioration of the stored oil is given. The effectiveness of most widely experimented antioxidants such as tocopherols, carotenoids, ascorbic acid and its derivatives, lignan compounds, flavonoids, polyphenols and phenolic acids in various edible oils have been reviewed. Further, the synergistic and antagonistic combination of these antioxidants in controlling oxidative degradation of edible oils has been discussed. © 2020 Institute of Food, Science and Technology (IFSTTF)Item From printing to performance: a review on 3D concrete printing processes, materials, and life cycle assessment(Springer Nature, 2025) Mishra, S.K.; Snehal, K.; Das, B.B.; C, R.; Barbhuiya, S.A paradigm shift in the construction sector has been driven by 3D concrete printing (3DCP), offering automated alternatives to conventional building methods. 3DCP enhances precision, efficiency, and consistency through robotic control and advanced printhead systems while reducing material waste and enabling design flexibility. This review examines the working principles, printer classifications (gantry-based and robotic arm-based), and operational parameters, highlighting printing speed, interlayer gap time, and nozzle size and shape as critical parameters for buildability, interlayer bonding, and extrusion quality. Their influence is discussed in relation to fresh properties (flowability, pumpability, extrudability, shape retention, and buildability) and hardened properties (compressive, tensile, and flexural strength, interlayer bonding, and durability). Mix design strategies for optimizing rheology, printability, and sustainable material selection are critically reviewed. Key durability concerns such as shrinkage, cracking, and weather resistance are addressed. Reinforcement methods, including steel bars, fibers, and embedment techniques, are also discussed. A life cycle analysis reveals that 3DCP reduces carbon dioxide emissions by up to 89.2% and construction costs by 30–40% through formwork elimination. Environmental impacts (waste generation, carbon footprint, and energy use) are assessed using regional and global data, considering embodied energy, transportation, and maintenance costs. Challenges such as regulatory hurdles, high initial investment, and the absence of standardized guidelines are identified. This review covers developments from the past decade, offering valuable insights for researchers, industry professionals, and policymakers regarding the advancements, limitations, and future directions of 3DCP. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.Item Comparison of efficacy of various natural and synthetic antioxidants in stabilizing the fish oil(John Wiley and Sons Inc, 2022) Mishra, S.K.; Belur, P.D.; Iyyaswami, R.Use of antioxidants (natural and synthetic) can retard oxidative degradation of fish oil having n-3 PUFA. The performance of each antioxidant is found to be affected by the composition of the oil, presence of impurities and storage condition. Hence an attempt was made to find the efficacy of catechin, resveratrol, β-carotene, caffeic acid, sinapic acid, ellagic acid, ferulic acid, vanillic acid, quercetin, rutin, TBHQ, BHA, and BHT at a concentration of 0.9 mM in the bulk fish oil, stored for 50 days exposed to air at 25°C under darkness. The extent of primary and secondary oxidation of the stored oil was determined every 5 days and were compared. The efficacy of TBHQ followed by BHA and BHT was found to be highest among all the antioxidants studied. Among the natural antioxidants, resveratrol and catechin were found to exhibit superior efficacy, whereas β-carotene was found to exhibit proxidant behavior. Novelty impact statement: This is the first comprehensive study carried out to find the most effective antioxidant involving ten natural and three synthetic antioxidants in n-3 PUFA containing fish oil. TBHQ exhibited superior efficacy among all the antioxidants tested and at a concentration of 0.9 mM, the change in TOTOX value by the end of 40 days of storage was about 80%. None of the other antioxidants studied here, exhibited such superior stability. Among the natural antioxidants, resveratrol and catechin were found to be superior. © 2022 Wiley Periodicals LLC.Item Designing of A Synergistic Mixture of Natural Antioxidants Through Statistical Approaches for Enhancing the Oxidative Stability of Sardine Oil(Enviro Research Publishers, 2023) Mishra, S.K.; Belur, P.D.; Chandrasekar, V.; Iyyaswami, R.Given the diverse routes of oxidation and a variety of oxidation products, the right combination of antioxidants is expected to exhibit synergistic effects in retarding refined sardine oil oxidation. In this study, a full factorial design (24) was utilized to choose a combination of natural antioxidants which exhibit interactive effect and response surface modelling (RSM) was used to identify the optimal concentration of the selected antioxidant mixture which exhibit synergistic effect. Catechin and resveratrol showed a strong interactive effect among the four natural antioxidants (sinapic acid, vanillic acid, catechin, and resveratrol) studied in sardine oil stored for 50 days at 25ºC under darkness. Two optimal concentrations of interactive antioxidants were found through RSM. Catechin and resveratrol at 0.5 mM and 0.625 mM respectively, exhibited a strong synergistic effect whereas, at 0.5 mM and 3.7 mM respectively, showed prooxidant effect. This is the first of its kind report on the formulation of a synergistic antioxidant mixture for retarding oxidation using statistical approaches. © 2023 The Author(s).Item Exploring the role of metakaolin in binary and ternary blended 3D printable mortars: deep insights into printability(Taylor and Francis Ltd., 2025) Mishra, S.K.; Upadhyay, B.; Das, B.B.This study investigates the utilisation of metakaolin and GGBS as partial replacements for OPC, examining their impact on printability, mechanical properties, microstructure and hydration kinetics in binary and ternary mortars. The printability of the mixes was thoroughly assessed through measurements of flowability, extrudability, open time, yield stress, shape retention, and buildability. It is observed that shape retention improved by 46% in the OPC–GGBS–metakaolin mix and 56.25% in the OPC–metakaolin mix, while the OPC–GGBS mix showed minimal improvement. Mechanical properties were evaluated, including water absorption, porosity, compressive, and flexural strength. Printed specimens exhibited anisotropic strength, with the lowest on the ZX plane and highest on the YZ plane. The 70% OPC, 20% GGBS, and 10% metakaolin mix demonstrated superior printability and mechanical performance, supported by optimal particle packing via the modified Andreasen and Andersen model. Furthermore, the denser microstructure observed in SEM micrographs, the decrease in Ca/Si ratio from EDX measurements, the emergence of additional C–S–H and C–A–S–H peaks in X-ray diffraction, the pronounced Si–O–Si/Al stretching bands in FTIR and the increased WH% (with consumption of CH) in TGA collectively confirm that GGBS and metakaolin significantly contributed to the secondary hydration reactions. © 2025 Informa UK Limited, trading as Taylor & Francis Group.Item 3D printing aspects of fly ash and GGBS admixed binary and ternary blended cementitious mortar(Taylor and Francis Ltd., 2025) Mishra, S.K.; Upadhyay, B.; Das, B.B.This study investigates the integration of Ground Granulated Blast Furnace Slag (GGBS) and fly ash to sustainably reduce the usage of Ordinary Portland Cement (OPC) in 3D printable mortar to enhance printability and engineering performance. Four mortar mixes were developed, and their printability parameters, such as flowability, extrudability, open time, yield stress, shape retention, and buildability, were assessed. Among mixes, O70G30 (70% OPC, 30% GGBS) showed the best printability, with an 18.3% and 54.3% higher shape retention factor than the control and O70F30 mixes, respectively, which can be attributed to improved particle packing and 5.5% higher yield stress. However, its open time was 22.2% lower than the control. This reduction can be attributed to the finer particle size and higher specific surface area of GGBS, which increased water demand and accelerated the loss of workability. In the hardened state, O70G30 exhibited 24% lower water absorption and 18.5% reduced permeable porosity than the control, indicating a denser microstructure. Printed specimens exhibited anisotropic strength, with the highest values observed on the YZ plane and the lowest on the ZX plane. Depending on the loading direction and mix composition, their compressive strength was 9.4–35.6% lower than that of mould-cast samples, while the flexural strength improved by 16.19% to 40.18%. Microstructural analysis revealed a denser matrix with a lower Ca/Si ratio and enhanced secondary hydration, evidenced by stronger C–S–H peaks in XRD, pronounced Si–O–Si/Al bands in FTIR, and 41.22% higher bound water (WH) with reduced portlandite (CH) in TGA compared to O70F30. These promising results can be attributed to GGBS’s role in enhancing hydration, refining the microstructure, and improving the performance of 3D printable mortar, offering a sustainable and effective pathway for digital construction. Also, the Life Cycle Impact Analysis (LCIA) revealed that the incorporation of supplementary cementitious materials (SCMs) significantly reduces environmental impacts compared to the control mix. © 2025 Informa UK Limited, trading as Taylor & Francis Group.