http://nopr.niscpr.res.in/handle/123456789/66081 2026-10-09T21:49:06Z http://nopr.niscpr.res.in/handle/123456789/67524 Title: Metamaterial absorbers: Comparative analysis of fabrication techniques and emerging trends Authors: Thakur, Sahil; Choudhury, Balamati; Tyagi, Sachin Abstract: The metamaterial absorbers have been artificially designed structures that have controlled and have manipulated electromagnetic waves across different frequency regimes, which have been important in stealth technology, EMI shielding, sensing, and energy harvesting. In particular, the efficiency and reliability of such absorbers have had a close dependence on fabrication methods used to fabricate these absorbers. This review has given an orderly exploration of some recent developments in the fabrication techniques of metamaterial absorbers, grouped into four major classes: Top Down, printingbased, mold-assisted, and laser-based approaches. Each technique has been qualitatively compared based on resolution, manufacturing cost, scalability, substrate compatibility, structural complexity, duration of fabrication, frequency suitability, and absorption efficiency. A general comparison has summarized the advantages and limitations of each technique. The review also has outlined emerging trends that could shape the next generation of high-performance metamaterial absorbers. Page(s): 669-683 2025-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67523 Title: Design, simulation, and experimental validation of a corrugated morphing airfoil actuated by SMA-Spring mechanism Authors: Parmar, Kartikeya; Anand Iyamperumal, Palani; Ranganathan, Santhanam Abstract: This research paper has presented the design, numerical analysis, and experimental validation of a bio-inspired morphing airfoil actuated through shape memory alloy (SMA) wire and spring elements. To facilitate controlled deflection, a corrugated morphing section has been embedded within an eppler airfoil, which has been selected through comparative aerodynamic analysis against a standard NACA 0012 profile. Finite element simulations have been conducted using ANSYS software to investigate tip deflection performance across varying morphing region lengths and actuator placements. A lightweight, three-dimensionally printed prototype incorporating shape memory alloy components has been developed and has been thoroughly evaluated using direct electrical heating methods. Experimental findings have shown a 4 mm downward deflection for a 1 mm actuator wire contraction, which has closely matched the numerical simulation predictions. To demonstrate scalability, a full-span wing prototype has been assembled utilizing three independent, actuated airfoil segments. The successful actuation of this system has validated the feasibility of shape memory alloy-driven morphing as a viable, lightweight alternative to traditional servo-based mechanisms in micro air vehicles and low-speed unmanned aerial vehicles. Furthermore, this research has established a practical foundation for future work aimed at enabling bi-directional actuation for enhanced aerodynamic control and maneuverability. Page(s): 684-693 2025-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67522 Title: Experimental study for performance evaluation of in-filled materials in trench wave barriers for vibration screening Authors: Shashi Bhushan, Kumar; Kumar Sahu, Anil; Goel, Rajeev Abstract: Vibrations which have been caused by non-seismic factors as high-speed rails, highway traffic, construction activities, machine foundations, blasting, underground explosions, etc. have not been considered safe for human life and structures around. Vibrations which have been generated by these sources have caused of occupant discomfort, settlement and shaking of building foundations, structural and non-structural damages to adjacent buildings, malfunctioning of ultra-sensitive medical equipment, etc. Vibration screeners in form of open or in-filled trench wave barriers have been used to reduce the effects of vibrations. This paper has described an experimental study for evaluating the performance of in-filled materials in trench wave barriers in an elastic, homogeneous and isotropic half space. The in-filled materials used are as rice husk, crumbed tyre rubber and sawdust. Key properties of the in-filled materials are have also been determined by geo-technical characterization to ascertain its suitability in terms of properties of in-filled materials. The important factors such as material damping and boundary conditions of soil have also been included. The effectiveness of geometric dimensions of the trench wave barrier, shear wave velocity and location of source from the barrier have also been investigated. In this study, a dimensionless approach have been used, where the geometrical parameters have been normalized by one of the characteristics i.e. wavelength of Rayleigh oscillatory wave in elastic half-space. The influence of parameters related to vibration isolation has been discussed in detail. Recommendations have been provided for the optimal selection of the geometry of trench wave barriers. Page(s): 694-711 2025-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67521 Title: Design and analysis of PV fed single-stage AC-DC bi-fold converter for onboard charging applications Authors: Bansal, Bhavya; Joshi, Dheeraj; Verma, Vishal Abstract: Traditional electric vehicle (EV) chargers typically employ a dual-stage configuration to achieve a significant step-down in voltage, which results in discontinuous input current and compromised efficiency. This paper has proposed a single-stage, single-phase high step-down bifold converter featuring synchronous rectification and ripple mitigation to address these challenges. By regulating the intermediate bus voltage (IBV) to provide only half of the output voltage, the converter ensures continuous input current with a near-unity power factor. A highly efficient 1.55KW prototype, converting from 230V AC and PV panel to 48V DC, has been developed, simulated and analyzed using MATLAB. The charger’s performance has been rigorously analyzed and harmonic compensator has been introduced to eliminate ripple components causing improvements in efficiency and reduction in THD along with operational stability. Page(s): 712-726 2025-12-01T00:00:00Z