Faculty Publications
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Item Numerical study of TiO2 nanofluid in multistage-bifurcated microchannel subjected to hotspots(Pleiades journals, 2019) Kumar, A.; Narendran, G.; Arumuga Perumal, D.A.The present study discusses implementation of multiple passive structures along the flow length using TiO2 nanofluid with 0.1% volume fraction to analyze a multistage-bifurcated microchannel. Fully developed laminar flow for different multistage plate configurations is used for the computational study, and additional investigations were done to evaluate pressure drop for Reynolds Number ranging from 250 to 500. Two different heat fluxes have been used: 4000 W/cm2 given for hotspot area and 1000 W/cm2 for the entire heat sink. Furthermore, the influence of flow rate on bifurcation stages combined with hotspot is highly investigated. Also, the pressure drop, temperature distribution, and flow streamlines are studied to evaluate cooling performance. © Springer Nature Singapore Pte Ltd. 2019.Item Receiver architectures for 5g: Current status and future prospects(Springer Science and Business Media Deutschland GmbH, 2021) Kumar, A.; Sengar, B.S.; Chaudhary, S.; Pandey, S.K.; Pandey, S.K.; Hasan Raza Ansari, M.; Aaryashree, A.In this chapter, the recent progress in receiver architecture and various aspects of the available receiver architectures have been discussed. Besides, an overview of the systematic classification of architecture has been analyzed. Documentation of new possibilities and system-level trade has been closely inspected. Certainly, there is a requirement of low-power, flexible, and high-performance receiver architecture for the successful implementation of the 5G network. Different works in this regard have been considered as examples for discussing the status and prospects of architectures with respect to 5G future. Various architectures considered in this chapter can be very valuable to design 5G network in future and will expose the research community with new possibilties to explore for further improvements. © Springer Nature Singapore Pte Ltd. 2021.Item Recent advancements in growth and stability of phosphorene: Prospects for high-performance devices(CRC Press, 2022) Pandey, S.K.; Garg, V.; Izquierdo, N.; Kumar, A.Atomically thin two-dimensional (2D) materials like graphene and the transition metal dichalcogenides have made a significant impact in the field of electronics and optoelectronics devices. Graphene, however, has no bandgap, which creates hurdles for many device applications. Similarly, the modest carrier mobility of transition metal dichalcogenides makes them less suitable for high-performance electronic and optoelectronic device applications. Phosphorene, a monolayer or few-layer form of black phosphorus (BP), has attracted considerable interest owing to its unique anisotropic manner, layer-dependent direct bandgaps, high carrier mobility, and quasi-one-dimensional excitonic nature, which are not present in other abovementioned 2D materials. Phosphorene has a bandgap of ˜0.3 eV in the bulk form and can be increased with reducing layer thicknesses, approaching ˜2 eV for the monolayer. As a result, there have been stimulating reports on field-effect transistors and inverters fabricated in the material system. Phosphorene is also becoming an interesting material for solar cells and photodetectors. Despite novel properties, the development of this material itself remains in an embryonic state. One of the reasons for the slow progress is that phosphorene-based devices use either mechanical or liquid exfoliation method to deposit phosphorene from crystalline black phosphorus (c-BP). In these processes, one peels a thin layer of material from a bulk BP crystal using adhesive tape or by liquid intercalation. The exfoliation process for this material is possible due to its intralayer strong covalent bonds and interlayer weak van der Waals forces. The exfoliation method does not have the thickness, uniformity, position, orientation, and surface control needed to get repeatable experimental results. In this chapter, detailed information will be provided about phosphorene deposition using the abovementioned and other methods. Phosphorene demonstrates instability under ambient conditions, which is the main obstacle for its practical applications. Various studies have been conducted in the past to investigate the mechanism of the degradation of phosphorene and passivation techniques to resolve its problem of instability under ambient conditions. To know the various fundamental properties correctly, the stability of this 2D material is very important, which can be achieved by novel passivation strategies. Detailed passivation strategies of phosphorene are elaborated in this chapter. The effects of the passivation layers composition on the thermal stability of phosphorene are also provided. Different growth techniques are described to deposit the passivation layers without altering the properties of phosphorene. To understand the different properties of passivated phosphorene, different measurement techniques such as X-ray diffraction (XRD), Raman spectroscopy, optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM) are discussed in this chapter. The effects of annealing temperatures on the properties of passivated phosphorene are discussed in detail. Finally, an overview on the utilization of phosphorene for a variety of applications is also given. A detailed study about 2D phosphorene/3D materials-based next-generation devices are presented in this chapter. The roadmaps to address present challenges for phosphorene are investigated as the properties of this material are very appropriate for next-generation devices. The information presented in this chapter will accelerate the further development of high-performance phosphorene-based electronics and optoelectronics devices. © 2022 selection and editorial matter, Ashish Raman, Deep Shekhar and Naveen Kumar; individual chapters, the contributors.Item Overview of high-entropy alloys(De Gruyter, 2023) Prakash, O.; Chandrakar, R.; Kumar, A.; Michalska-Domańska, M.New materials and alloys are being developed by using latest technology and manufacturing techniques. Significant progress in alloy system has led to development of special alloys, such as alloys of iron, copper, superalloys, and high-entropy alloys. High-entropy alloys with multiple constituent elements, higher mixing entropy, improved property, and structure make them different from other alloy systems. High-entropy alloy concepts have come into focus after successful development of these alloys, from 2004. Basic concepts, design strategy, phase formation rule, and basic core effects for enhancements of property and structural stability of highentropy alloys are discussed in this chapter. © 2023 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Item Emerging processing routes(De Gruyter, 2023) Prakash, O.; Kumar, R.; Tapas, V.; Kumar, A.; Naveen, B.High-entropy alloys (HEAs) are produced using a number of processing techniques. HEAs have been produced in a variety of materials, including films, dense solid castings, and powder metallurgy components. The three types of processing routes-melting and casting, powder metallurgy, and deposition techniques-can be broadly divided into three classes. In order to create HEAs in the form of rods, bars, and ribbons, melting and casting procedures have been used, along with equilibrium and nonequilibrium cooling rates. The vacuum arc melting, vacuum induction melting, and melt spinning processes are the most widely used melt processing methods. The primary solid-state processing method to create sintered goods has been mechanical alloying (MA), followed by sintering. The surface modification methods utilized to create both thin films and thick layers of HEAs on various substrates include plasma nitriding, cladding, and sputtering. This chapter provides a brief overview of the various synthesis and processing methods used to create HEAs. The processing pathways for equiatomic and nonequiatomic HEAs are comparable. © 2023 Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.Item Stability Analysis of Structural Systems with Epistemic Uncertainties(Springer, 2024) Kumar, A.; Balu, A.S.Safety of structures is ensured by considering the sufficient strength of the structural element and geometric stability of the structure. In structural engineering, the failure of a structural system is characterized by material failure and geometric instability. Material failure occurs when the stresses induced in the structural element reach its yield strength, whereas the instability of the structure is due to the structural geometry and size only, which is known as buckling. It is of utmost significance to perform the stability analysis for the safety of structure. In most of the stability analyses, the structural property and load parameters are considered as certain, which is not the case in practical situations as the load applied to structure is never certain. In the present study, the stability analysis of structure is performed considering the uncertainty in the input parameters. Universal grey number theory and interval analysis are used to perform the stability analysis of the structural system and the results are compared with the combinatorial method (which is estimated to predict the accurate ranges). Results obtained from interval analysis were found to be overestimated because of the violation of the physical law and dependency problem in its arithmetic process whereas the Universal grey number theory showed confirming results with the combinatorial method, as universal grey theory obeys the physical law and does not suffer the dependency problem. In the present study, it is found that the universal grey number theory is computationally efficient when compared with the interval and combinatorial methods. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Machine Learning Techniques Used for Diagnosing Cardiac Abnormalities using Electrocardiogram(Apple Academic Press, 2024) Mohan Rao, B.; Kumar, A.; Marwaha, P.; Bage, A.Atrial fibrillation (AF) damages around 1–2% of the human body and is the most serious heart arrhythmia in human healthcare. As per the guidelines of World Health Organization (WHO), coronary thrombosis (CT) is the main cause of mortality throughout world and in India. As a consequence of coronary artery disorder, high blood pressure, alcoholic abuse, and a life in emotional stress, heart arrhythmias, or irregular heartbeats, are among the most prevalent CTs. In addition to the CTs described, an irregularity in heart rhythm is produced by mental stress in long duration, which is a difficult problem for researchers to solve. One of the most important areas of study after the development of the electrocardiogram (ECG) and robust machine learning algorithms is the early detection of cardiac arrhythmia using automated electronic methods. As a gold standard for studying heart function, cardiologists and researchers rely on the ECG because it records changes in electrical activity connected to the cardiac cycles. The research was conducted on ECG analysis and categorization utilizing classic and novel artificial intelligence (AI) methods. As a result of the research, a detailed report is expected. Recent years have seen a rise in the use of AI methods to detect arrhythmia signs automatically and early. This chapter examines the literature of the past few years to assess the performance of artificial intelligence and other computer-based systems for processing ECG data for the detection of heart problems. Performance measurements such as specificity, sensitivity, accuracy, positive predictive value (PPV), etc. are used to evaluate machine learning (ML) and deep learning (DL) methods for detecting the AF from ECG signal analysis and categorization. These are crucial in the early detection of AF because accurate detection of heart problems can reduce mortality. © 2025 Apple Academic Press, Inc.Item Towards evaluating resilience of SIP server under low rate DoS attack(2011) Kumar, A.; Santhi Thilagam, P.S.; Pais, A.R.; Sharma, V.; Sadalkar, K.Low rate Denial-of Service, DoS, attack recently emerged as the greatest threat to enterprise VoIP systems. Such attacks are difficult to detect and capable of discovering vulnerabilities in protocols with low rate traffic and it noticeably affects the performance of Session Initiation Protocol, SIP, communication. In this paper, we deeply analysis the resilience of SIP server against certain low rate DoS attacks. For this purpose we define performance metrics of SIP server under attack and non-attack scenarios. The performance degradation under attacks gives a measure of resilience of the SIP server. In order to generate normal SIP traffic and the attacks, we defined our own XML scenarios and implemented them using a popular open source tool known as SIPp. The system under evaluation was an open source SIP server. © 2011 Springer-Verlag.Item 3D Estimation and visualization of motion in a multicamera network for sports(2011) Kumar, A.; Chavan, P.S.; Sharatchandra, V.K.; Sumam David, S.S.; Kelly, P.; O’Connor, N.E.In this work, we develop image processing and computer vision techniques for visually tracking a tennis ball, in 3D, on a court instrumented with multiple low-cost IP cameras. The technique first obtains 2D ball tracking data from each camera view using 2D object tracking methods. Next, an automatic feature-based video synchronization method is applied. This technique uses the extracted 2D ball information from two or more camera views, plus camera calibration information. In order to find 3D trajectory, the temporal 3D locations of the ball is estimated using triangulation of correspondent 2D locations obtained from automatically synchronized videos. Furthermore, in order to improve the continuity of the tracked 3D ball during times when no two cameras have overlapping views of the ball location, we incorporate a physics-based trajectory model into the system. The resultant 3D ball tracks are then visualized in a virtual 3D graphical environment. Finally, we quantify the accuracy of our system in terms of reprojection error. © 2011 IEEE.Item Optimized low power low cost pulse oximeter for remote patient monitoring(IEEE Computer Society, 2013) Agrawal, N.; Agrawal, S.; Kumar, A.; Ramesh Kini, R.M.Pulsoximeter is a medical instrument for monitoring the blood oxygenation of a patient. This type of monitoring is especially useful for new born infants, during surgery and in determining Hypoxia. Blood oxygen content is an important indicator of human patient health and during anaesthesia. This aspect can be monitored by measuring the oxygen percentage in the blood timely and accurately with the help of our device. As our device is non invasive it proves out to be comfortable for the new born. Our slight modification to the standard approach that utilises pulse oximeter or Photoplethysmograph for this purpose, assures considerable decrease in current consumption thereby reducing overall power consumption which makes our device a low power device that can be used with much ease at places where power consumption is an issue. Patient's health parameters can be continuously monitored over a low power wireless network which aids in mobile monitoring. © 2013 IEEE.