Saveetha Engineering College

In recent days, a substantial amount of research work has focused on speech improvement. A speech enhancement system is used in numerous applications like voice activity detection, human-machine interaction systems and acoustic emotion identification. Estimating noise statistics is a challenging task in the speech enhancement process while using non-stationary real-time models. Hence, a novel filtering-based speech enhancement framework is introduced in this work. The speech enhancement process is initiated by collecting the speech signal from standard resources. Further, the gathered signal is then processed for enhancement. Here, the new technique named Hybrid Filtering is introduced with the combination of Non-Local Means (NLM) and Kalman Filtering (KF), and this NLM approach performs the denoising operation on the collected speech signal. The KF effectively estimates the noise from the speech signal. Further, the speech enhancement performance of the Adaptive NLM with Kalman Filtering (ANLM-KF) is enhanced by optimizing the parameters with Innovated Clouded Leopard Optimization (ICLO). The proposed model efficiently enhances the speech signal by performing a Multi-scale denoising operation. Finally, the experimentation is conducted on the developed model over traditional methodologies to prove its effectiveness in the speech enhancement process. The proposed ICLO-ANLM-KF algorithm significantly outperforms all baseline optimization models across every quality metric. It achieves the lowest error rates, with a Mean Absolute Error (MAE) of 0.047 dB and a Root Mean Square Error (RMSE) of 0.216 dB. Moreover, the developed method yields the highest signal reconstruction quality, with a Peak Signal-to-Noise Ratio (PSNR) of 61.441 dB, which is a substantial improvement over models like DE-MCD, STC-STWF, SS-DWT, and TCN-MHA-Bi-GRU. These quantitative results confirm that the proposed ICLO-ANLM-KF is the most effective approach for enhancing speech signals while minimizing distortion.

Covellite (CuS) nanostructures were synthesized via a chelation-assisted hydrothermal route using EDTA and PEG, followed by annealing at 100 and 200 °C, to regulate their structural, optical, and electrochemical properties for organic pollutant degradation and energy storage applications. X-ray diffraction confirms a hexagonal covellite phase for all samples, with chelating agents promoting preferential (110) growth. PEG-assisted annealing induces a morphological transition from irregular aggregates to uniform nanoflower architectures, most pronounced for PEG–CuS annealed at 200 °C. BET analysis shows that CuS–PEG has a higher surface area (28.70 m2 g−1, 15.7 nm pores) than CuS–EDTA (27.58 m2 g−1, 23.30 nm), with uniform mesopores that enhance active sites and ion diffusion. XPS verifies availability of Cu and S. The bandgap is tunable from 1.1 to 1.4 eV and correlates with crystallite size, enabling strong visible-light absorption, while suppressed electron–hole recombination enhances charge separation. Under natural sunlight, methyl orange acts as a photosensitizer, injecting excited electrons into the CuS conduction band and significantly improving photocatalytic activity. Scavenger studies and DFT-based Fukui function analysis confirm a dominant photo-sensitized charge-transfer pathway, with hydroxyl radicals as secondary reactive species. Beyond photocatalysis, PEG-derived CuS nanoflowers demonstrate excellent electrochemical performance as the positive electrode in an asymmetric supercapacitor, delivering 415 F g−1 at 1 A g−1, an energy density of 147 Wh kg−1 at 856 W kg−1, and 98

Dye-sensitized solar cells (DSSCs) are promising low-cost photovoltaics, but their dependence on expensive platinum counter electrodes limits practical application. In this regard, we fabricated the CeO2/Co3O4@BC composite counter electrode via a straightforward hydrothermal technique, incorporating CeO2 and Co3O4 nanoparticles onto a biocarbon. The physicochemical characteristics of the prepared samples were systematically examined using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results demonstrated the coexistence of cubic CeO2 and spinel Co3O4 phases uniformly anchored on the porous BC surface without structural distortion. XPS analysis confirmed the existence of mixed oxidation states of Ce3⁺/Ce4⁺ and Co2⁺/Co3⁺, facilitating rapid redox conversion at the electrode–electrolyte interface. The CeO2/Co3O4@BC composite demonstrated a substantial surface area with pronounced mesoporosity, promoting improved electrolyte infiltration and ion transport. The pristine biocarbon electrode demonstrated moderate electrocatalytic activity attributed to its conductive and porous characteristics, however the CeO2/Co3O4@BC composite exhibited markedly improved performance due to synergistic interactions between the metal oxides and the carbon matrix. Electrochemical characterization by cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS) demonstrated superior catalytic activity and reduced charge-transfer resistance (Rct ≈ 7.5 Ω cm2) toward the I₃⁻/I⁻ redox couple. The fabricated DSSC incorporating CeO2/Co3O4@BC as a counter electrode achieved a promising power conversion efficiency (PCE) of 7.5

Li7La3Zr2O12 (LLZO) garnet ceramics co-doped with Ta5+ and Bi3+ were synthesized via a conventional solid-state reaction method and systematically investigated for their structural, photoluminescence, and dielectric properties. X-ray diffraction analysis revealed that the synthesized samples predominantly exhibit the tetragonal garnet-type LLZO phase, accompanied by minor secondary phases. Microstructural analysis using transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed well-defined crystalline domains, while x-ray photoelectron spectroscopy (XPS) confirmed the presence of Li, La, Zr, Ta, O, and Bi within the host lattice. Photoluminescence measurements under 236 nm excitation exhibited a prominent yellow emission centered at 558 nm attributed to the Bi3+ (3P1 → 1S0) transition. In contrast, weak blue emission from the host lattice is associated with oxygen-vacancy-related defect states. The emission characteristics were found to depend on Bi3+ concentration due to concentration quenching. Dielectric measurements demonstrated frequency-dependent polarization behavior with relatively low dielectric loss at higher frequencies. The results indicate that Bi3+-activated Ta-stabilized LLZO ceramics exhibit tunable optical emission and stable dielectric response, highlighting their potential as multifunctional materials for electronic and optoelectronic applications.

Calcium molybdate (CaMoO4) green-emitting phosphors were synthesized via the co-precipitation method, subsequently sintered at different temperatures (100–900 °C) in order to study the influence of sintering conditions on their structural, morphological, and luminescent properties. The phase-pure tetragonal scheelite-type structure is identified and confirmed using Powder X-ray diffraction (PXRD) analysis. Green emission at 500 nm is observed, which can be related to charge transfer transitions of the MoO_4^2- tetrahedral groups. The highest intensity of the emission peak is observed for the phosphor prepared by sintering at 800 °C for 2 h. The morphological and XPS analyses confirm the uniform growth of the phosphors and the elemental composition. Thus, it is elucidated that CaMoO4 phosphors prepared and sintered at 800 °C for 2 h have good luminescent properties, which can be used for optoelectronic device applications.