Browsing by Author "Kumar, D.S."

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    Antenna gain determination using a microwave CAD tool-HFSS
    (2008) Satheesh, B.V.; Srivatsan, R.; Raghavan, S.; Kumar, D.S.
    Antennas have been increasingly studied in recent years. Different antennas have been designed for different applications based on the characteristics of the receiving side. Antennas cannot be fabricated as such and then be studied on. This leads to waste of material and requires a lot of iterations until we get the final design. In order to study the characteristics of an antenna without fabricating it, we need a special tool called a "SIMULATOR TOOL". It can determine all possible characteristics of an antenna under test. In this paper we'll be simulate few of the antennas using HFSS simulator tool. � 2008 IEEE.
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    CAD tools for antennas
    (2008) Bhavatharini, S.; Raghavan, S.; Kumar, D.S.
    There are a number of CAD tools available in the market today for microwave designs. They enable the designer to try his hand at even very complex design very easily and quickly. They optimize MEMS designs prior to fabrication, which reduces prototype development cycle time and cuts manufacturing costs. This paper attempts to list a few of the popular CAD tools that are available in the market today and highlights on their special features that makes each tool unique. � 2008 IEEE.
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    Development of an industrial ferritic rolling process for IF grade steel
    (Taylor and Francis Ltd., 2020) Kumar, D.S.; Sambandam, M.; Bhat K, U.K.
    Interstitial free (IF) grade steels have high transformation temperatures and often results in non-uniform rolling and lower yields. In the present work, industrial ferritic rolling process is developed, where finish rolling is carried out below the Ar1 temperature for the IF grade steel. Offline simulation was carried out using a hot strip mill model (HSMM) software and full-scale ferritic rolling was carried out in a seven-stand hot strip mill under two different finishing and coiling temperatures and compared with austenitic rolling. Furnace drop-out temperature, mill speed and inter-stand cooling were controlled to achieve the desired low rolling temperatures. Both ferritic rolled coils had strained elongated grains and well-developed alpha (<110>//RD) and gamma (<111>//ND) textures. The lower finishing and coiling temperature processed coil shows higher microstructural and textural variation along with the thickness. This work established the optimum parameters for the industrial ferritic rolling process for IF grade steel. © 2020, © 2020 Institute of Materials, Minerals and Mining.
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    Fading mitigation technique for MIMO in free space optical system
    (2016) Jeyarani, J.; Kumar, D.S.; Ramya, S.
    Free space optical (FSO) communications is the line of sight technology and its cost-effective and wide-bandwidth access technique for high data rates applications. In FSO system, the performance analysis over turbulence channels is limited, when using multiple apertures at both transmitter and receiver sides. Fading mitigation technique conditions is generalized to explore the ergodic capacity of multiple-input multiple-output (MIMO) system. The gamma-gamma distribution is used to analyze the fluctuations of the irradiance of optical channels distorted by atmospheric conditions. To evaluate the receiver performance analytically, we use an ?-? distribution to efficiently approximate probability density function (PDF) of the sum of independent and identical distributed ET RVs through moment-based estimators. The sum of independent and but not necessarily identically distributed RVs is used to efficiently approximate PDF of Distribution. High signal to noise ratio is achieved for fading scheme to get insights into impact of system and channel parameter on ergodic capacity. Monte-carlo simulations is validated in our proposed results. � 2015 IEEE.
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    Optimization of Annealing Parameters for Ferritic Hot-Rolled IF Grade Steel
    (Springer, 2022) Kumar, D.S.; Sambandam, S.; Bhat, K.U.
    Ferritic hot rolling of low carbon steel is now widely adopted by steelmakers for reducing energy costs and increasing the yield. These ferritic hot-rolled coils carry forward different grain morphology and texture which result in variation in properties after cold rolling and annealing compared to austenitic hot-rolled coils. These ferritic hot-rolled coils require different annealing treatments based on the hot rolling temperature for better results. In the present work, a Nb–Ti stabilized interstitial free (IF) grade steel was hot rolled at two different temperatures in the ferritic regime in an industrial hot strip mill and was subsequently cold rolled. These cold-rolled sheets were subjected to different continuous annealing cycles with soaking temperatures varying from 740 to 820 °C on a thermo-mechanical simulator for optimization of temperatures and study its effect on microstructure and properties. These coils were compared with simulated conventional austenitic hot-rolled coils. Ferritic rolled coils show better elongation and a higher percentage of equiaxed grains indicating better formability. The optimum continuous annealing temperature was found to be a function of hot rolling temperature in the ferritic regime. Elongation and grain size increased with an increase in temperature in all the samples, but the ferritic rolled coils show faster change due to higher stored energy. Comparison of elongation and microstructure indicates that temperatures above 780 °C should be sufficient for achieving complete recrystallization in ferritic rolled samples, compared to 810 °C required in the conventional austenitic rolled sheets which is an industrial advantage. Based on simulation studies, full-scale plant continuous annealing was carried out under the optimized temperature conditions where microstructure and properties matched closely with the simulation results and electron backscatter diffraction (EBSD) analysis confirmed improved texture. © 2022, ASM International.
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    Optimization of Annealing Parameters for Ferritic Hot-Rolled IF Grade Steel
    (Springer, 2022) Kumar, D.S.; Sambandam, S.; Bhat, K.U.
    Ferritic hot rolling of low carbon steel is now widely adopted by steelmakers for reducing energy costs and increasing the yield. These ferritic hot-rolled coils carry forward different grain morphology and texture which result in variation in properties after cold rolling and annealing compared to austenitic hot-rolled coils. These ferritic hot-rolled coils require different annealing treatments based on the hot rolling temperature for better results. In the present work, a Nb–Ti stabilized interstitial free (IF) grade steel was hot rolled at two different temperatures in the ferritic regime in an industrial hot strip mill and was subsequently cold rolled. These cold-rolled sheets were subjected to different continuous annealing cycles with soaking temperatures varying from 740 to 820 °C on a thermo-mechanical simulator for optimization of temperatures and study its effect on microstructure and properties. These coils were compared with simulated conventional austenitic hot-rolled coils. Ferritic rolled coils show better elongation and a higher percentage of equiaxed grains indicating better formability. The optimum continuous annealing temperature was found to be a function of hot rolling temperature in the ferritic regime. Elongation and grain size increased with an increase in temperature in all the samples, but the ferritic rolled coils show faster change due to higher stored energy. Comparison of elongation and microstructure indicates that temperatures above 780 °C should be sufficient for achieving complete recrystallization in ferritic rolled samples, compared to 810 °C required in the conventional austenitic rolled sheets which is an industrial advantage. Based on simulation studies, full-scale plant continuous annealing was carried out under the optimized temperature conditions where microstructure and properties matched closely with the simulation results and electron backscatter diffraction (EBSD) analysis confirmed improved texture. © 2022, ASM International.
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    Solid-State Fermentation vs Submerged Fermentation for the Production of L-Asparaginase
    (Academic Press Inc. apjcs@harcourt.com, 2016) Doriya, K.; Jose, N.; Gowda, M.; Kumar, D.S.
    L-Asparaginase, an enzyme that catalyzes L-asparagine into aspartic acid and ammonia, has relevant applications in the pharmaceutical and food industry. So, this enzyme is used in the treatment of acute lymphoblastic leukemia, a malignant disorder in children. This enzyme is also able to reduce the amount of acrylamide found in carbohydrate-rich fried and baked foods which is carcinogenic to humans. The concentration of acrylamide in food can be reduced by deamination of asparagine using L-Asparaginase. L-Asparaginase is present in plants, animals, and microbes. Various microorganisms such as bacteria, yeast, and fungi are generally used for the production of L-Asparaginase as it is difficult to obtain the same from plants and animals. L-Asparaginase from bacteria causes anaphylaxis and other abnormal sensitive reactions. To overcome this, eukaryotic organisms such as fungi can be used for the production of L-Asparaginase. L-Asparaginase can be produced either by solid-state fermentation (SSF) or by submerged fermentation (SmF). SSF is preferred over SmF as it is cost effective, eco-friendly and it delivers high yield of enzyme. SSF process utilizes agricultural and industrial wastes as solid substrate. The contamination level is substantially reduced in SSF through low moisture content. Current chapter will discuss in detail the chemistry and applications of L-Asparaginase enzyme and various methods available for the production of the enzyme, especially focusing on the advantages and limitations of SSF and SmF processes. © 2016 Elsevier Inc.
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    Tailoring the surface characteristics and mechanical behavior of Ti-Nb stabilized IF steel through controlled shot peening coverage
    (Elsevier Ltd, 2025) Sahoo, B.; Udaya Bhat, K.; Kumar, D.S.
    The rising demand for a qualitative surface opens a new window of research in the domain of mechanical surface treatment, known as severe shot peening, especially in the automotive industry. The effectiveness of this method is usually affiliated with various process parameters, of which peening coverage is the most sought-after. It is anticipated to elevate the surface characteristics by proficiently optimizing the peening coverage. On this ground, the current investigation tries to gather the beneficial effect of peening coverage on the surface properties of Ti-Nb stabilized interstitial-free steel subjected to severe shot peening by considering four different coverages (100 %, 500 %, 1000 %, and 2000 %). The work attempts to interpret the impact of peening coverage on grain refinement and dislocation-induced microstructures at different depths of the as-treated sample. The crossectional microscopy unveiled a prominent grain refinement hardening and dislocation hardening in 2000 % peening coverage up to a depth of 90–120 µm, firmly agreeing with the microhardness depth profile. The optical microscopy identified four zones of deformation (severe deformation, deformation, transition, and undeformed zone) in the sample treated with the highest coverage. The transmission electron microscopy demonstrated the dominance of certain dislocation-derived features like dislocation forest, dislocation cells, tangled dislocations, dislocation bands, nanocrystalline region, stress concentration region, etc., at the deformed zone of the treated samples. Interestingly, the trace of these features was detected at a greater depth for the highest-peened sample than the lowest-peened sample, affirming the beneficial aspect of higher peening coverage. The stored energy and thermal stability assessment in the as-received and as-treated sample was done in the differential scanning calorimeter, revealing the favorable impact of severe peening on the substrate. The surface topographical study in a 3D profilometer also unveils the variation in the surface roughness and functional volume parameters. The present investigation also analyzed the maximum depth and mean density of furrows to verify the severe plastic deformation in the as-treated sample. © 2024