Sukumar Kalpana

Pulse width modulation (PWM) is essential for voltage source inverters (VSI) to generate high-quality voltage outputs. Conventional deterministic PWM generates predictable harmonics, causing clusters that increase acoustic noise. Random PWM (RPWM) disperses harmonic power over a wider frequency range, reducing noise and electromagnetic interference. Many RPWM techniques improve inverter quality, but only partially suppress dominant harmonics and lack effective harmonic spreading. Most studies focus on simulations with limited FPGA implementation or hardware validation. The use of digital tools like VHDL, ModelSim, and MATLAB co-simulation remains underutilized. This paper proposes two-triangle RPWM strategies to enhance harmonic dispersion and reduce total harmonic distortion (THD). Co-simulation results are shown for both SPWM and RPWM, along with comparisons of fundamental voltages, THD, and HSF across different modulation indexes. Additionally, synthesis data for the Xilinx XC3S500E FPGA processor is supplied. The last section offers a comparative analysis and experimental validation of SPWM and RPWM. These techniques enable enhanced inverter performance, lower acoustic noise, and process innovations in power electronic systems.

Emphasizing the protection and reliability of hydrogen storage systems used in fuel cells, energy storage and manufacturing operations requires acoustic analysis of hydrogen cylinders. Which entails studying the interaction between sound waves and hydrogen gas at various filling pressures. Variations in pressure affect the acoustic characteristics of hydrogen, including its speed and impedance. To identify structural abnormalities or changes in gas properties, resonance frequency analysis measures variations in resonance frequencies. Frequent oscillations and regressive acoustic effects at large amplitudes cause acoustic fatigue, leading to complicated stress patterns and eventual material deterioration. When acoustic waves associate with type III hydrogen cylinder materials, a phenomenon known as acoustic coupling can occur. Due to acoustic coupling, the vibration is transferred to adjacent structures, leading to more noise and structural deformation. Uneven filling and pressure distribution generate structural stresses on the cylinder from acoustic pressure variation. Noise production is another issue since the enormous speed of gas flow produces remarkable amounts of noise, possibly degrading the cylinder material and the environment. The novelty of this work lies in hydrogen cylinder multi-material approach, analysing acoustic pressure variations and stress distribution at the PTFE-aluminium and aluminium-carbon fiber interfaces and compared detailed numerical validation against experimental data. This work also addresses research gaps in cavitation resistance and resonance frequency mitigation for aluminium liner hydrogen storage cylinder. The PTFE coating possesses a low-friction surface, reducing cavitation damage. Carbon fiber wrapping gives structural stability and damping capacity. Their combination enhances structural integrity and reduces noise generation for process innovation.

This study investigates the influence of calcium doping on the structural, optical, and photocatalytic properties of bismuth ferrite nanoparticles. Pure and calcium-doped BiFeO₃ nanoparticles (Ca@BFO) with doping concentrations of 0.05, 0.075, and 0.1 M were synthesized via a sol–gel method. X-ray diffraction analysis confirmed structural modifications and crystallite size reduction upon doping. Raman spectroscopy indicated enhanced peak intensities for Ca@BFO samples, suggesting improved structural ordering. UV–vis spectroscopy demonstrated a reduction in the wide bandgap to 2.24 eV for the 0.1 M Ca-doped BFO, leading to enhanced visible-light absorption. Photocatalytic activity was assessed by the degradation of methylene blue under different pH conditions, with the best performance observed at pH 8 for the 0.1 M Ca-doped BFO sample. Stability and reusability studies showed minimal activity loss over multiple cycles. These findings highlight the potential of Ca@BFO nanoparticles for efficient photocatalysis and environmental remediation applications.

In the present paper, an innovative approach to enhance the photocatalytic efficiency and energy of photovoltaics by modifying the surface morphology of TiO2 is demonstrated. The photovoltaic device provides sustainable power efficiency in TiO2 (TO) and Cd-TiO2 (CTO) thin films grown through spray pyrolysis. The structural and optical properties of the prepared undoped and Cd doped TiO2 thin films were studied. The morphology and content of the pro­duced samples were studied using scanning electron microscopy (SEM with EDAX). A UV-Vis spectrophotometer was used to record the optical absorption spectra of TiO2 nanoparticles. XRD analysis showed that TO and CTO had anatase structures, and the average crystalline size was calculated as 132.0 nm. The photocatalytic efficiency of TO and CTO for degradation of Rodhamine B (RhB) dye was examined. Also, power-voltage (P-V) and photocurrent-voltage (I-V) output current intensity relations were discussed.

Methylene blue (MB) dye is the most common harmful, toxic, and non-biodegradable effluent produced by the textile industries. The present study investigates the effect of zinc oxide (ZnO) nanoparticles (NPs) and Ag–Ni doped ZnO NPs on the performance of photocatalytic degradation of MB dye. Pure ZnO and Ag–Ni doped ZnO NPs are synthesized using the co-precipitation method. The crystalline nature and surface morphology of the synthesized pure ZnO and Ag–Ni doped ZnO NPs was characterized by powder X-ray diffraction, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) analysis. The presence of spherical-like morphologies was confirmed from SEM and HRTEM analysis. The presence of Ni–O and Zn–O bands in the synthesized materials was found by Fourier transform infrared (FTIR) spectroscopy analysis. The MB dye was degraded under UV-light exposure in various pH conditions. The Ag (0.02%)–Ni doped ZnO NPs exhibits highest photocatalytic activity of 77% under pH 4.