Browsing by Author "Kumar, Chandan"

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    Experimental investigation and numerical simulation of fiber laser welding of Ti-6Al-4V alloy and SS-316L
    (2018) Kumar, Chandan
    The full form of Laser is ‘Light Amplification by Stimulated Emission of Radiation’. The most attractive and important properties of laser beam which are significant in material processing are high power, low divergence, directional, coherent and monochromatic beam. One of the most important characteristics of laser beam is its high energy density due to which it is widely used in welding of materials having high melting point. Titanium and its alloys serve as a bridge between the ideal properties of aluminum and steel. It is recognized as a workhorse for aerospace and automotive industries and is widely used in many areas such as aerospace, medicinal, chemical and aviation industries etc. due to its excellent combination of both high strength and ductility, low density, better corrosion resistance and excellent biocompatibility. The main goal of ongoing research work is to investigate the weldability of similar materials of Ti-6Al-4V alloy having thicknesses of 5, 2 and 1.5 mm and austenitic stainless steel of grade 316L (SS-316L) having thickness of 3 mm using fiber laser autogenously.
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    Modeling, Optimization and Analysis of Wireless Information and Energy Transfer in Beyond 5g Iot Networks
    (2023) Kumar, Chandan
    This thesis focuses on system modeling, optimization and comprehensive performance analysis of wireless information and energy transfer to the Internet-of-Things (IoT) devices. These devices are likely to form a core component of beyond fifth generation (5G) wireless systems in order to support numerous applications foreseen in such systems. We first investigate whether a base station (BS) with massive number of antennas can support joint machine-centric communication among the IoT devices and human-centric communication among the mobile terminals. To this end, we derive downlink spectral efficiency (SE) of the IoT devices with maximum ratio precoding when channel estimates are acquired via the proposed distance-dependent grouping based hybrid pilot assignment strategy. As benchmarks, we also evaluate SE under non-orthogonal pilot assignment and distance-independent grouping. We show that under channel inversion based power control at the BS, the proposed pilot assignment and channel estimation strategy yields the highest sum SE and can serve the largest number of IoT devices when compared to the benchmarks. The corresponding performance under max-min power allocation is also presented