Journal Articles
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Item Run-up, run-down and reflection characteristics of semicircular breakwater for varying seaside perforations(2012) Hegde, A.V.; Rao, S.; Kumar, K.Breakwaters are mainly used for the purpose of withstanding and dissipating the dynamic energy of ocean waves and thereby provide tranquillity conditions on the lee side. Semicircular breakwaters are being used increasingly around the globe because of their great advantages. The paper explains physical studies conducted on seaside-perforated semicircular breakwater models to evaluate the wave run-up, wave run-down, and reflection coefficient for various wave heights (H), wave periods (T), water depths (d), incident wave steepness (H i/gT 2), depth parameter (d/gT 2), and relative spacing S/D (S = c/c spacing of perforations, D = diameter of perforations) on the seaside. It is observed that as the incident wave steepness increases, there is a decrease in the reflection coefficient (K r), and relative run-down (R d/H i) but increase in relative run-up (R u/H i). As the S/D ratio decreased (percentage of perforations increased), there was drop in the reflection coefficient, relative run-up, and relative run-down. As the depth parameter increased, there was a decrease in the relative run-up and reflection coefficient, but increase in relative run-down. © 2012 Taylor & Francis Group, LLC.Item New extracellular thermostable oxalate oxidase produced from endophytic Ochrobactrum intermedium CL6: Purification and biochemical characterization(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2016) Kumar, K.; Belur, P.D.Oxalate oxidase (EC 1.2.3.4) catalyzes the oxidative cleavage of oxalate to carbon dioxide with the reduction of molecular oxygen to hydrogen peroxide. Oxalate oxidase found its application in clinical assay for oxalate in blood and urine. This study describes the purification and biochemical characterization of an oxalate oxidase produced from an endophytic bacterium, Ochrobactrum intermedium CL6. The cell-free fermentation broth was subjected to two-step enzyme purification, which resulted in a 58.74-fold purification with 83% recovery. Specific activity of the final purified enzyme was 26.78 U mg?1 protein. The enzyme displayed an optimum pH and temperature of 3.8 and 80°C, respectively, and high stability at 4–80°C for 6 h. The enzymatic activity was not influenced by metal ions and chemical agents (K+, Na+, Zn2+, Fe3+, Mn2+, Mg2+, glucose, urea, lactate) commonly found in serum and urine, with Cu2+ being the exception. The enzyme appears to be a metalloprotein stimulated by Ca2+ and Fe2+. Its Km and Kcat for oxalate were found to be 0.45 mM and 85 s?1, respectively. This enzyme is the only known oxalate oxidase which did not show substrate inhibition up to a substrate concentration of 50 mM. Thermostability, kinetic properties, and the absence of substrate inhibition make this enzyme an ideal candidate for clinical applications. © 2016, Copyright © Taylor & Francis Group, LLC.Item A Novel Enzymatic Process to Produce Oxalate Depleted Starch From Taro(Wiley-VCH Verlag info@wiley-vch.de, 2018) Kumar, K.; Belur, P.D.A novel process comprising treatment of Taro (Colocasia esculenta (L.) Schott) tuber flour with oxalate oxidase enzyme is developed to deplete the oxalate content. Oxalate oxidase enzyme produced by an endophyte, Ochrobactrum intermedium CL6 is employed to treat taro tuber flour. The treatment followed by extraction of starch results in a 97% reduction in total oxalate content. Further, several physicochemical properties such as paste clarity, swelling power, solubility, amylose content, granule size of starch produced out of enzyme treatment are studied and compared with properties of taro starch produced without enzyme treatment. The study reveals that enzyme treatment does not bring appreciable changes in the studied parameters. The taro starch produced by enzyme treatment shows very low paste clarity (9.38%), high swelling power (15.32 g/g), very low solubility (21.66%), and low amylose content (7.52%) at 100 °C compared to potato and sweet-potato starches. X-ray diffraction data reveal that taro starch possesses an A-crystalline form, unlike the B-crystalline form found in potato and sweet potato starch. To the best of the authors knowledge, for the first time, the use of oxalate oxidase to produce oxalate depleted taro starch is reported. One of the interesting food industry applications of oxalate-depleted taro starch, among many other uses could be for baby food formulation because of its small granule size. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem Production of oxalate oxidase from endophytic Ochrobactrum intermedium CL6(Journal of Pure and Applied Microbiology micro_drkhan@yahoo.com 54, Near Post Office, Thana Street, Shahjahanabad Bhopal 462 001, 2018) Kumar, K.; Belur, P.D.Four oxalate degrading endophytic bacteria were isolated from oxalate rich Colocasia esculenta tubers. Based upon the oxalate oxidase (EC 1.2.3.4) activity produced in nutrient medium, one bacterium was selected and identified as Ochrobactrum intermedium by 16S rDNA sequencing. Studies on effect of nutritional and non-nutritional parameters showed that oxalate oxidase production is inducible, requires Manganese ions in the medium, and very low fill-up volume is beneficial. Shake flask fermentation carried out with medium comprising Sucrose, Ammonium chloride, Sodium oxalate along with basal salts gave 0.5 UmL-1 oxalate oxidase activity and 0.454 Umg-1specific activity after 65h of fermentation. © 2018 The Author(s).Item Enhanced Power Density of Graphene Oxide–Phosphotetradecavanadate Nanohybrid for Supercapacitor Electrode(Springer, 2021) Maity, S.; Anandan Vannathan, A.A.; Kumar, K.; Das, P.P.; Mal, S.S.Successful exploration of supercapacitor (SC) material to integrate with high energy and high power density storage device still remains a daunting challenge. Conducting carbon nanostructures have been primarily used for this purpose; however, most of their surface area remains unutilized throughout the storage process. Herein, a new type of hybrid material has been reported by effectively using active sides of carbon nanostructures. Insertion of faradaic-type polyoxometalates (POMs), namely phosphotetradecavanadate (Na7[H2PV14O42], hereafter described as PV14), into the graphene oxide (GO) matrix creates a novel hybrid material for SC applications. Owing to the formation of nanohybrid, it can store charges both electrostatically and electrochemically. PV14/GO composite’s electrochemical behavior in different electrolyte (acidic/neutral) solutions shows different types of characteristics. The PV14/GO composite as a working electrode exhibits a high galvanostatic capacitance of 139 F/g while maintaining at a power density of 97.94 W/kg in 0.25 M H2SO4 electrolyte. The specific energy density was also found out to be around 56.58 Wh/kg at a 5 mV/s scan rate for the same electrolyte. Furthermore, in 1 M Na2SO4 solution, PV14/GO composite demonstrates a specific capacitance of 85.4 F/g at a scan rate of 5 mV/s. The equivalent series resistance for the device was found to be approximately 0.51 ? with a circuit resistance of 3.881 ?, using electrochemical impedance spectroscopy. The cell capacitance, employing the Nyquist plot, was calculated to be around 2.78 mF. © 2021, ASM International.Item A highly robust RF 65 nm CMOS power amplifier design using Quasi-Newton control algorithm for wireless system(Elsevier B.V., 2023) Kumar, K.; Kumar, S.; Kumar Kanaujia, B.K.This article reports a novel robust approach towards CMOS power amplifier (PA) using Quasi-newton (QN) control algorithm in 65 nm CMOS process which provides best performance parameters over redundant wide bandwidth ranging from 2.4 to 16.4 GHz frequency band. Each stage are designed and optimized using QN algorithm to get desired goals such as high linearity, small group delay variations and high PAE across the entire frequency band of interest. Moreover, pole-zeros compensation technique is adopted and derived to get better stability of the proposed PA. The simulation and measurement results of PA achieved a small signal power gain of 10.5–16.8 dB with input return loss of better than 10 dB over the frequency band of 2.4 GHz to 16.4 GHz. A small group delay variation of ±58 ps over full frequency band of operation is achieved by optimizing the design parametric analysis. It is also observed that within the frequency of 6.5 to 14.6 GHz, an excellent small group delay variation of only ±11 ps is achieved and this is due to stage-2 tuning compensation technique. It also demonstrates the achieved input power in 1 dB compression points are −3.1 to 4.3 dBm, leading to maximum power added efficiency of 36.3%, respectively. The proposed PA consumes a lower DC power of 20.5 mW under supply voltage of 1.5. In addition, Process, voltage and temperature (PVT) analysis is executed at different conditions in order to achieve a robustness of the proposed PA over the entire band of operation. © 2023 Elsevier B.V.Item Influence of water-methanol injection and turbocharging on the performance of a hydrogen-fueled spark ignition engine(John Wiley and Sons Inc, 2024) Chitragar, P.R.; Shivaprasad, K.V.; Ichchangi, M.; Ravi, R.; Yadav, M.S.; Kumar, K.This article presents a study that compares the performance and emission characteristics of a four-stroke, four-cylinder spark ignition (SI) engine fueled by gasoline and neat hydrogen. The engine was equipped with turbocharging to optimize ignition timing for power boosting and vaporized water–methanol injection to reduce emissions. Engine tests were conducted at speeds ranging from 2000 to 6000 rpm, with a fixed intake pressure and varying quantities of hydrogen and spark advance timings. The study compared the results of non-turbocharged and turbocharged engines with water–methanol injection in terms of combustion, performance, and emissions. The findings showed that the turbocharged water–methanol hydrogen operation had a higher brake thermal efficiency (BTE) than its counterpart, while the brake power of the hydrogen engine operation increased with turbocharging but slightly decreased with water–methanol injection. Additionally, volumetric efficiency improved by 7% for turbocharged and 4% for water-injected hydrogen engine operation compared to the counterpart. The cylinder pressure for turbocharging with water–methanol operation yielded 16.32% higher compared with counterpart gasoline engine operation. Finally, nitrogen oxides (NOx) emissions were reduced with turbocharging and water–methanol injection compared to the counterpart non-turbocharged hydrogen engine operation. © 2023 Wiley Periodicals LLC.Item Analytical modelling of ultra-small group delay variation of ultra-broadband RF power amplifier using NSGA-II algorithm(John Wiley and Sons Ltd, 2024) Kumar, K.; Kumar, S.; Kumar Kanaujia, B.K.This paper proposes a ± 9.4 ps ultra-small group delay (GD) variation of fully integrated 65 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) over 6.5–17 GHz broadband for wireless application. The proposed CMOS PA is realised by using broadband stage, RLC inter-stage and power stage topologies. The non-dominated sorting genetic algorithm (NSGA-II) is employed for PA parameter optimisation to ensure a small GD variation of ±9.4 ps over broadband with an excellent small signal gain flatness of 23.65 ± 1.85 for 6.5–17 GHz. The small GD variation of ±9.4 ps and ± 11.05 ps are attained under two cases of DC supply voltages of 2.4/1.2 V and 1.2/1.2 V, respectively. To the best of author's knowledge, the achieved GD variations are lowest among all CMOS PAs as reported so far. In addition, an analytical modelling of GD is derived to validating the minimum GD variation using zero-pole compensation. With supply voltages of 2.4/1.2 V at 6.5 GHz, the large signal power gain, Psat and OP1dB are 26 dB, 19.3 dBm and 17.94 dBm, respectively, while peak power added efficiency (PAE) is 38.196%. At reduced supply voltages of 1.2/1.2 V, the PA achieves maximum power gain of 17.7 dB and peak PAE of 35% at 6.5 GHz. The CMOS PA occupies an area of 0.206 mm2. © 2023 John Wiley & Sons Ltd.Item A novel approach to enhance the combustion quality of C5 alcohol with 2-Ethylhexyl nitrate as a cetane enhancer in common rail direct ignition diesel engine(Elsevier Ltd, 2024) Santhosh, S.; Kumar, K.; Bedar, P.The purpose of this investigation is to explore the effect of 1-Pentanol and 2-Ethylhexyl nitrate (2-EHN), on the characteristics of a common rail direct injection (CRDI) diesel engine. The major feedstock for the production of 1-pentanol (bio-alcohol) is non food biomass waste. The conversion of waste biomass into useful energy contributes to the cleaner production of fuel and its utilization. The trial was conducted in a 2-cylinder CRDI test rig. The engine was fuelled with diesel, 40P60D (40% 1-Pentanol & 60% diesel v/v) and then 500, 1000 and 2000 ppm of 2-EHN was doped to 40P60D. The addition of 1-Pentnaol showed a slight negative effect on combustion at low and medium loads. Furthermore, an extension in the delay period (DP) and combustion duration (CD) was seen for 1-Pentanol blend. The doping of 2-EHN, enhances the cetane count and leads to improvement in the combustion parameters and a reduction in DP and CD was noted. The 1000 ppm of 2-EHN doped blend showed 8.7% of higher BTE and 8.61% lower BSEC compared to 40P60D, also 1.89% and 50% lower HC and CO at 80% load and 36.9% lower NO at 60% load in contrast to diesel. Among all the concentrations 1000 ppm of 2-EHN showed satisfactory results. It is concluded that 40% of 1-Pentanol with 1000 ppm of 2-EHN can be used as an alternative fuel to pure diesel without compromising in performance of the engine. © 2024 Elsevier LtdItem Molecular surface-dependent light harvesting and photo charge separation in plant-derived carbon quantum dots for visible-light-driven OH radical generation for remediation of aromatic hydrocarbon pollutants and real wastewater(Academic Press Inc., 2024) Meena, S.; Sethi, M.; Saini, S.; Kumar, K.; Saini, P.; Meena, S.; Kashyap, S.; Yadav, M.; Meena, M.L.; Dandia, A.; Nirmal, N.K.; Parewa, V.Despite the growing emphasis on eco-friendly nanomaterials as energy harvesters, scientists are actively searching for metal-free photocatalysts to be used in environmental remediation strategies. Developing renewable resource-based carbon quantum dots (CQDs) as the sole photocatalyst to harvest visible light for efficient pollutant degradation is crucial yet challenging, particularly for addressing the escalating issue of water deterioration. Moreover, the photocatalytic decomposition of H2O2 under visible light irradiation remains an arduous task. Based on this, we designed two types of CQDs, C-CQDs (carboxylic-rich) and A-CQDs (amine-rich) with distinct molecular surfaces. Owing to the higher amount of upward band bending induced by amine-rich molecular surface, A-CQDs efficiently harvest the visible light and prevent recombination kinetics resulting in prolonged lifetimes (25 ps), and augmented charge carrier density (35.7 × 1018) of photoexcited charge carriers. A-CQDs enabled rapid visible-light-driven photolysis of H2O2 (k = 0.058 min−1) and produced higher quantity of •OH radicals (0.158 μmol/sec) for the mineralization of petroleum waste, BETX (i.e. Benzene, Ethylbenzene, Toluene and Xylene) (k = 0.017–0.026 min−1) and real textile wastewater (k = 0.026 min−1). To assess comparative toxicities of both remediated and non-remediated real wastewater samples in a time and dose depended manner, Drosophila melanogaster was used as a model organism. The findings unequivocally demonstrate the potential of remediated wastewater for watering urban forestry. © 2024 Elsevier Inc.