Faculty Publications
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Item Introduction tо Microwave Photonics(SPIE, 2025) Raghuwanshi, S.K.; Singh, M.; Kumar, R.; Kumar, S.Microwave photonics is a rapidly growing field that lies at the intersection of microwave engineering and optics. The integration of photonics and microwave engineering has opened up new possibilities for high-speed communication, radar and sensing systems, and signal processing applications. This book contains both the basic theory and the experimental techniques to demonstrate the interdisciplinary applications of microwave photonic systems. It discusses the underlying concepts, techniques, and devices used in microwave photonics, as well as the latest advances in the photonic generation, processing, and distribution of arbitrary microwave waveforms. The role of fiber Bragg grating in microwave photonic systems is described from a dispersion compensation point of view. The book also provides a deeper understanding of microwave photonic sensor systems, highly steerable beamforming systems, and photonic excitation of antenna—the process of exciting the antenna using light or photons instead of electrical signals—with applications in aerospace, defense, telecommunication, and biomedical sensing. Overall, microwave photonics is an interdisciplinary field that deals with the interaction between light and microwaves. Its unique features, including high-speed, low-power consumption and large bandwidth, make it an attractive technology for future applications. This book is intended for researchers, engineers, and students who are interested in this exciting and rapidly evolving field. © 2025 Society of Photo-Optical Instrumentation Engineers (SPIE). All rights reserved.Item Chitosan and its derivatives as potential materials for membrane technology(CRC Press, 2015) Kumar, R.; Isloor, A.M.Chitosan (CS), a biomaterial obtained via alkaline N-deacetylation of chitin, has recently attracted much attention from scientists across the globe. After cellulose, it is the second highest naturally occurring polymer on earth. It shows many excellent biological properties such as nontoxicity, biodegradability, antimicrobial activity, and immunological activity. As a membrane material, it has got excellent film-forming nature and hydrophilic in nature. Although the polymer backbone consists of hydrophilic functional groups, CS is normally insoluble in water and most of the common organic solvents. Chemical modification of CS is the best method to enhance its solubility at neutral pH or in organic solvents. So the obtained derivatives have got vast applications in the biomedical field as well as membrane technology. © 2015 by Taylor & Francis Group, LLC.Item Mm-wave cmos power amplifiers for 5g(Springer Science and Business Media Deutschland GmbH, 2021) Gorre, P.; Kumar, R.; Song, H.; Kumar, S.The chapter discusses the basic elements in the design of mm-wave CMOS Power Amplifier (PA) for phased arrays integration, focusing the next-generation 5G mobile communication. Power Amplifier design metrics, along with implementation of beam-forming phased arrays to merge power over-the-air are discussed in brief. The explanation begins with CMOS unique advantages, real-time handset challenges, system-level constraints, and design challenges are conceptually demonstrated with the help of a basic single-stage transistor Power Amplifier. © Springer Nature Singapore Pte Ltd. 2021.Item Techniques to improve gain-bandwidth 5g ics(Springer Science and Business Media Deutschland GmbH, 2021) Vignesh, R.; Kumar, R.; Song, H.; Kumar, S.This chapter introduces a basics of designs and techniques to improve gain-bandwidth for 5G ICs. The major focus would be on the various network topologies that yield to provide easy implementation of on-chip components for 5G-ICs. Section 1 discusses the basics of RLC tank networks, which includes RC parallel network, RLC network and series to parallel resonant network. The parameters such as quality factor, noise of filter networks are shortly refresh while foundation of resonant circuits would set-up for 5G transceiver ICs. Section 2 introduces coupled resonator networks can be used as microwave components to achieve a better gain-bandwidth trade-off. Finally, Sect. 3 will provide transformer resonators and circuit to reduce bulky components and enhance gain-bandwidth of ICs. © Springer Nature Singapore Pte Ltd. 2021.Item Melting and casting route(De Gruyter, 2023) Chandrakar, R.; Prakash, O.; Kumar, R.; Tiyyagura, H.R.; Chandraker, S.The melting and casting route is the most common and relatively cheap route of production of high-entropy alloys. In this route, the constituent elements are mixed in liquid state. Multicomponent alloys in the shape of buttons, rods, ribbons, and bars have been created using the melting and casting route, with various cooling rates. Vacuum arc melting is the most common melting and processing process. This chapter reviews melting and casting routes and related synthesis techniques in manufacturing of high-entropy alloys. © 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 GAN-Based Encoder-Decoder Model for Multi-Label Diagnostic Scan Classification and Automated Radiology Report Generation(CRC Press, 2024) Kumar, R.; Karthik, K.; Kamath S․, S.S.X-ray imaging is one of the most popular diagnostic imaging techniques and plays a critical role in the diagnosis and treatment process. Given the huge volume of patients and scans performed in most hospitals each day, the current practice of manual analysis of such scan images by experienced radiologists is a time-consuming and often error-prone process, worsened by the cognitive burden experienced by the radiologists. Conventional diagnostic reports written by radiologists after radiological image capture contain radiography-specific keywords (tags), observations of different body parts in the image (findings), and the actual diagnosis (impression). Automated multi-label classification of X-ray scans for disease prediction, and generation of an associated textual diagnostic scan report can ease the burden for radiologists, while also enabling fast, localized, and explanatory analysis. In this work, GAN-MLC, a CNN-LSTM description generator model trained in the adversarial setup, is proposed for the multi-label classification of X-ray images and improved feature learning for capturing disease-specific findings. Experiments performed on the NIH Chest X-ray Dataset revealed that the proposed GAN-MLC outperformed CNN-based models by a significant margin of more than seven percent. For the text diagnostic report generation task, the GAN-MLC achieved promising BLEU scores and was more robust against overfitting issues. © 2024 selection and editorial matter, Bhanu Chander, Koppala Guravaiah, B. Anoop, and G. Kumaravelan; individual chapters, the contributors.Item Comparative study of ocean wave spectrum using ENVISAT SAR data and wave rider buoy data(2006) Pai, J.; Kumar, R.; Sarkar, A.; Hegde, A.V.; Dwarakish, G.S.A comparative study of ENVISAT ASAR data and corresponding wave rider buoy data has been attempted. An algorithm has been developed to retrieve Ocean Wave Spectrum from SAR data. The resulting spectrum is compared with the wave rider buoy measured wave spectrum. To compute the 2-D image spectrum from multi-look SAR data, various corrections to the original SAR data has been applied. Thereafter, Modulation Transfer Function has been computed and utilized to convert image spectrum to the Ocean Wave Spectrum. This final ocean wave height spectrum is used to estimate the ocean wave spectral parameters and has been compared with the in-situ measurements and model derived wave spectrum. An attempt has also been made to process the Single Look Complex (SLC) data to reduce the speckle noise in the SAR data using Fast Fourier Transform (FFT).Item Lossless compression of digital mammography using fixed block segmentation and pixel grouping(2008) Kumar, R.; Koliwad, S.; Dwarakish, G.S.A mammography is a specific type of imaging that uses low-dose x-ray system to examine breasts. This is an efficient means of early detection of breast cancer. High resolution is a common characteristic of such images. Archiving and retaining these data for at least three years is expensive, difficult and requires sophisticated data compression techniques. In this paper an efficient method is proposed for lossless compression of mammography images. After performing de-correlation of the image using two efficient predictors, the residue image is divided into 4x4 blocks. The blocks with all-zero pixels are identified using one bit code. Later, Second order of pixel grouping is employed to the remaining blocks to increase the coding efficiency. Such blocks are coded using Base offset method. Special techniques are used to save the header information. The method is tested using 25 mammograms from the MIAS database, each having a resolution of 1024x1024 pixels with 8 bits/pixel. Experimental results indicate better compression ratio when compared to JPEG 2000, JPEG-LS, PNG and JBIG. © 2008 IEEE.Item Exploring the effectiveness of social capabilities and goal alignment in computer supported collaborative learning(2010) Ai, H.; Kumar, R.; Nguyen, D.; Nagasunder, A.; Rosé, C.P.In this study, we describe a conversational agent designed to support collaborative learning interactions between pairs of students. We describe a study in which we independently manipulate the social capability and goal alignment of the agent in order to investigate the impact on student learning outcomes and student perceptions. Our results show a significant interaction effect between the two independent variables on student learning outcomes. While there are only a few perceived differences related to student satisfaction and tutor performance as evidenced in the questionnaire data, we observe significant differences in student conversational behavior, which offer tentative explanations for the learning outcomes we will investigate in subsequent work. © 2010 Springer-Verlag.