Journal Articles
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Item Influence of Refractory Elements on Mechanical Properties of High Entropy Alloys(Springer, 2021) Kumar Sinha, A.K.; Soni, V.K.; Chandrakar, R.; Kumar, A.High entropy alloys (HEAs) have become the most popular among the materials scientists and researchers due to their attributes like high strength, hardness and corrosion resistance when compared to conventional alloys. For sprawling use of HEAs in various domains such as aerospace, structural and automobile, it is necessary for researchers to explore more number of HEAs. In this endless endeavour of exploration, researchers have also developed refractory HEAs which possess better mechanical properties when compared to conventional HEAs. But, HEAs (without refractory elements) are more economical than refractory HEAs. This is due to the fact that most of the refractory elements are expensive. The present work focuses on the effect of refractory elements, namely, Mo, W, Ta, Nb, Ti and V on mechanical properties of HEAs. This review also provides an insight into the phase evolution in HEAs due to addition of refractory elements. Moreover, it also unfolds research gaps from past literature, which shows that there is scarcity of literature on dynamic characteristics, fatigue and creep analysis of Hf, Zr, Si and Cr based HEAs. © 2021, The Indian Institute of Metals - IIM.Item A review of various materials for additive manufacturing: Recent trends and processing issues(Elsevier Editora Ltda, 2022) Srivastava, M.; Rathee, S.; Patel, V.; Kumar, A.; Koppad, P.G.Tremendous growth has been witnessed in the field of additive manufacturing (AM) technology over the last few decades. It offers a plethora of applications and is already being utilized in almost every sphere of life. Owing to inherent differences between each AM technique, newer fields of research consistently emerge and demand attention. Also, the innovative applications of AM open up newer challenges and thus avenues for focused attention. One such avenue is AM materials. Raw material plays an important role in determining the properties of fabricated part. The type and form of raw material largely depend on the type of AM fabricators. There is a restriction on material compatibility with most of the established AM techniques. This review aims to provide an overview of various aspects of AM materials highlighting the progress made especially over the past two decades. © 2022 The Author(s).Item A Review on Mechanical Properties of Natural Fibre Reinforced PLA Composites(Bentham Science Publishers, 2023) Kumar Sinha, A.K.; Rao, K.R.; Soni, V.K.; Chandrakar, R.; Sharma, H.K.; Kumar, A.Presently, scientists and researchers are in an endless quest to develop green, recyclable, and eco-friendly materials. Natural fibre reinforced polymer composites became popular among materialists due to their lightweight, high strength-to-weight ratio, and biodegradability. However, all-natural fibre reinforced polymer composites are not biodegradable. Polymer matrices like poly-lactic acid (PLA) and poly-butylene succinate (PBS) are biodegradable, whereas epoxy, polypropylene, and polystyrene are non-biodegradable polymer matrices. Besides biodeg-radability, PLA has been known for its excellent physical and mechanical properties. This review emphasises the mechanical properties (tensile, flexural, and impact strengths) of natural fibre-reinforced PLA composites. Factors affecting the mechanical properties of PLA composites are also discussed. It also unveils research gaps from the previous literature, which shows that limited studies are reported based on modeling and prediction of mechanical properties of hybrid PLA composites reinforcing natural fibres like abaca, aloe vera, and bamboo fibres. © 2023 Bentham Science Publishers.Item The heart rate is a non-stationary signal, and its variation can contain indicators of current disease or warnings about impending cardiac diseases. The indicators can be present at all times or can occur at random, during certain intervals of the day. However, to study and pinpoint abnormalities in large quantities of data collected over several hours is strenuous and time consuming. Hence, heart rate variation measurement (instantaneous heart rate against time) has become a popular, non-invasive tool for assessing the autonomic nervous system. Computer-based analytical tools for the in-depth study and classification of data over day-long intervals can be very useful in diagnostics. The paper deals with the classification of cardiac rhythms using an artificial neural network and fuzzy relationships. The results indicate a high level of efficacy of the tools used, with an accuracy level of 80-85%. © IFMBE: 2004.(Classification of cardiac abnormalities using heart rate signals) Acharya, A.U.; Kumar, A.; Subbanna Bhat, P.; Lim, C.M.; Iyengar, S.S.; Kannathal, N.; Krishnan, S.M.2004Item Utilization of renewable agricultural residues for the production of extracellular halostable cellulase from newly isolated halomonas sp. strain PS47(2013) Shivanand, P.; Mugeraya, G.; Kumar, A.A newly isolated biopolymer-degrading halophilic bacterium, Halomonas sp. strain PS47, yielded higher cellulase activity (0.0076 U/ml) in mineral salt medium (MM63). Activity increased to 0.029 U/ml when carboxymethyl cellulose (0.5 % w/v) was used as carbon source and further to 0.138 U/ml when a combination of yeast extract and peptone was used as nitrogen source. Enzyme secretion was maximal during late exponential and stationary phases (0.15 U/ml, 48 h). Among different agro-residues (1 % w/v), wheat bran gave the highest activity (0.12 U/ml) at pH 7.5, 30 °C and 6 % (w/v) NaCl. The cellulase exhibited higher activity at pH 7.1 and 50 °C. The enzyme exhibited activity over a wide range of NaCl concentrations (0-4 M). Optimum activity was at 0-1 M NaCl. At 4 M NaCl, activity was reduced to 65 % of the initial value. The present investigation thus contributes to the limited information available on halostable cellulases. © Springer-Verlag Berlin Heidelberg and the University of Milan 2012.Item Establishing relationships for strength characteristics of lateritic soils with varying silt fractions(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Kumar, A.; George, V.; Marathe, S.Design and construction of highway embankments constitute a major component of highway engineering science. Poor sub-grade strength, overloading due to traffic loads, and seismic vibrations can cause distress to pavement sub-grades and embankments. Inadequate compaction and poor sub soil drainage, in addition to low bearing strength of soils cause failure of embankments especially in submersible regions. The present study is focused on performing investigations on the engineering properties of lateritic and lithomargic soils and the effect of fines on soil strength. Tests such as California Bearing Ratio (CBR), tests for unconfined compressive strength (UCS), and tri-axial tests are carried to study the strength behavior of soil on addition of lithomargic soils. Additionally, the development of regressions will help field engineers in estimating the value of the CBR based on simple laboratory experiments such as Unconfined Compression strength test, and the Triaxial test. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Design and development of ITO/Ag/ITO spectral beam splitter coating for photovoltaic-thermoelectric hybrid systems(Elsevier Ltd, 2017) Sibin, K.P.; Selvakumar, N.; Kumar, A.; Dey, A.; Sridhara, N.; Shashikala, H.D.; Sharma, A.K.; Barshilia, H.C.ITO/Ag/ITO (IAI) multilayer coatings were designed for spectral beam splitter applications and these coatings were deposited on glass substrates by magnetron sputtering method. The thicknesses of the component layers, namely, Ag and ITO were varied to achieve high visible transmittance, high NIR-IR reflectance and optimum cut-off wavelength. The optimized ITO/Ag/ITO exhibits high visible transmittance (?88%) and high NIR-IR reflectance (>90%) with an optimum cut-off wavelength (?900 nm). A novel chemical etching method was used to improve the transmittance of the plain glass substrate. The optimized IAI multilayer coating deposited on single side etched glass substrate resulted in increase in transmittance (?91%), which is due to the nano-porous morphology of the etched glass substrate. The angular and polarization dependence studies of IAI multilayer coatings were also studied in detail. © 2016 Elsevier LtdItem En-Route Filtering Techniques in Wireless Sensor Networks: A Survey(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Kumar, A.; Pais, A.R.Majority of wireless sensor networks (WSNs) are deployed in unattended environments and thus sensor nodes can be compromised easily. A compromised sensor node can be used to send fake sensing reports to the sink. If undetected these reports can raise false alarms. To deal with the problem of fake report generation, a number of en-route filtering schemes have been proposed. Each of these schemes uses different cryptographic methods to check the authenticity of reports while they are being forwarded hop by hop toward base station. However, majority of these techniques can handle only limited compromised nodes or they either need node localization or statically configured routes for sending reports. Furthermore, majority of en-route filtering techniques are vulnerable to various denial of service attacks. Our main aims in this survey are: (a) to describe the major en-route filtering techniques, (b) to analyze these techniques on various parameters including security and (c) to outline main unresolved research challenges in en-route filtering in WSNs. © 2017, Springer Science+Business Media New York.Item Deterministic En-Route Filtering of False Reports: A Combinatorial Design Based Approach(Institute of Electrical and Electronics Engineers Inc., 2018) Kumar, A.; Pais, A.R.Wireless sensor networks are an easy target for report fabrication attack, where compromised sensor nodes can be used by an adversary to flood the network with bogus/false reports. En-route filtering is a mechanism where intermediate forwarding nodes identify and drop false reports while they are being forwarded toward the sink. Most of the existing en-route filtering schemes are probabilistic, where sensor nodes in each cell share secret keys with a fixed probability with intermediate nodes. Thus, forwarded reports are verified probabilistically by intermediate nodes, because of which false reports can travel several hops before being dropped. Few deterministic en-route filtering schemes have also been proposed in the literature, but all such schemes require a source to send the reports through a fixed path to reach the sink. In this paper, we propose a novel deterministic en-route filtering scheme based on a combinatorial design to overcome the above-mentioned limitations of the existing schemes. The use of combinatorial design-based keys ensures direct communication between all the sensor nodes while maintaining low key storage overhead in the network. We provide a comprehensive analysis of the proposed scheme. The proposed scheme notably performs better than the existing schemes in terms of the expected filtering position of false reports. Furthermore, the proposed scheme improves data authenticity in the network and is more buoyant to selective forwarding and report disruption attacks. © 2013 IEEE.