M. Kumarasamy College of Engineering

Rare large-amplitude excursions, conventionally termed extreme events, can disproportionately influence the long-term collective dynamics of coupled excitable networks despite their low frequency of occurrence. Higher-order interactions, which couple three or more units simultaneously, are known to reshape collective dynamics in complex networks, but their influence on extreme-event activity has received little systematic attention. We address this question in a heterogeneous, globally coupled FitzHugh–Nagumo network by comparing two structurally distinct higher-order coupling schemes: a linear additive correction to the standard pairwise diffusive coupling, and an explicit nonlinear three-body interaction. The underlying pairwise network already produces rare large mean-field excursions, so the central question is how each higher-order scheme modifies this existing behaviour. Under a common numerical and extreme-value analysis framework, we find that the linear scheme preserves a broader region of extreme-event activity in parameter space, while the nonlinear three-body scheme contracts it considerably. An analytical mean-field reduction explains the mechanism: the linear coupling is algebraically equivalent to a rescaled pairwise diffusion and introduces no new mean-field dynamics, whereas the nonlinear coupling generates a negative feedback proportional to the spatial spread of node voltages, suppressing large collective excursions precisely when the network is most predisposed to produce them. These findings demonstrate that the algebraic form of higher-order interactions, not their amplitude, determines whether such couplings broaden or suppress extreme-event activity in excitable networks.

This work aimed optimize friction stir welding (FSW) to improve mechanical characteristics of AZ91/ZrC weldments. Metal matrix composites were fabricated utilizing magnesium alloy AZ91 and zirconium carbide of 10 μm size using stir casting procedure. Central composite design (CCD) method were utilized to structure FSW methods. The studies was conducted at a butt joint configuration by altering the tool rotational speed, plunge depth, axial load, and welding transverse speed. The optimal parameters were determined by evaluating microhardness and ultimate tensile strength. The influence of factors at output responses were examined graphically. Two optimization methods, specifically the desirability function and the genetic algorithm approach, were employed to determine ideal values of parameters. The outcomes produced using optimization methods were in strong concordance. The optimal values were corroborated by experimental data.

Conventional pregnancy testing methods face significant limitations including low sensitivity, cross-reactivity issues, and requirement for sophisticated laboratory equipment, particularly in resource-limited settings. This research introduces an innovative terahertz (THz) biosensor using a graphene-metallic hybrid metasurface architecture to improve pregnancy detection by optical sensing of human chorionic gonadotropin (hCG) indicators. The sensor demonstrates remarkable performance with a maximum sensitivity of 1000 GHz/RIU achieved at the optimal resonant frequency of 0.309 THz within the 0.1–0.55 THz frequency band, corresponding to a refractive index of 1.343 RIU. The frequency-dependent sensitivity analysis reveals that the maximum sensitivity of 1000 GHz/RIU is achieved at 0.309 THz, where the electromagnetic field enhancement reaches its peak value. This optimal operating point corresponds to the fundamental resonance mode of the hybrid metasurface structure, where the coupling between the central graphene resonator and the surrounding metallic rings creates the strongest field localization. The sensitivity decreases progressively at frequencies away from this resonant peak, with values of 500 GHz/RIU at 0.310 THz and 200 GHz/RIU at 0.311 THz, demonstrating the critical importance of precise frequency tuning for optimal sensor performance. Comparative analysis shows competitive or superior performance against existing biosensor designs, offering significant potential for point-of-care pregnancy testing applications with enhanced sensitivity, real-time detection capability, and reduced sample preparation requirements.

Early identification of brain tumors requires sensors capable of detecting subtle refractive index variations associated with pathological tissue changes in a label-free and non-invasive manner. Surface Plasmon Resonance (SPR) sensors utilize the surface plasmons excited by incident light to measure changes in the dielectric properties of thin layers placed adjacent to metal surfaces thus they are highly sensitive to dielectric property changes which makes them excellent platforms for biomedical diagnostics. In this work, a THz metasurface SPR sensor is designed and validated that incorporates a graphene base with gold (Au) and MoS₂ coated resonators arranged in a compact A-shaped metasurface configuration. The hybrid material used for the resonators, along with the resonator’s geometry, were both optimized to provide enhanced confinement and tunability of the electromagnetic fields within the terahertz frequency range. Simulation results indicate that the proposed sensor provides a maximum sensitivity of 2308 GHz/RIU with a stable FWHM of 0.111 THz and a peak FOM of 20.79 RIU− 1 across the refractive index range. A machine learning algorithm was applied as a data-driven analytical tool for modeling the relationships between sensor operating parameters and sensor responses, indicating correlation coefficients (R2) of unity for the simulated data sets. These results demonstrate that the proposed metasurface sensor offers a robust and high-performance design for RI based sensing. The findings presented are based on numerical validation and the demonstrated sensing parameters indicate that the design has a strong potential for future experimental prototype and early-stage brain tumor biomarker sensing contributing to SDG 3 (Good Health and Well-Being) through improved early diagnostic capability.

In this work, we prepared interfacial solar evaporators using bentonite clay with two different sintering temperatures such as 1000 degrees C and 800 degrees C, which are named as C-S1 and C-S2 evaporators. The as-prepared evaporators are investigated experimentally under indoor solar steam generation under 1000 W/m2 for 60 min. It results in an evaporation rate (EV) of 0.57 and 0.75 kg/m2h with C-S1 and C-S2 respectively. Further, cobalt oxide (Co3O4) nanomaterial is coated over the top evaporative surface of C-S1 and C-S2 evaporators, called C-S3 and C-S4 evaporators. It shows an EV of 0.78 and 1.01 kg/m2h, respectively. Among all the evaporators, C-S4 evaporator exhibits higher evaporation rate due to the following reasons: (i) Mercury intrusion porosimeter (MIP) analysis reveals that C-S2 (800 degrees C) exhibits a 12.5% higher total porosity and a 7.5% smaller median pore diameter compared to C-S1 (1000 degrees C), directly facilitating enhanced capillary-driven water supply as evidenced by the higher evaporation rate (ii) the Co3O4 coating over the top evaporative surface effectively uses the light energy usage for steam generation (iii) low thermal conductivity of the bentonite clay reducing the bulk water heating by hindering the heat flow (iv) increasing the surface roughness of the evaporator reducing the heat losses occurring via radiation (scattering and reflection). Additionally, C-S4 evaporator demonstrates an improved separation of dye molecules from dye water.