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Volume 1, Issue 4, 2026

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Engineering systems based on integrated circuits (IC) and microsystem technologies (MST) increasingly rely on materials whose behaviour is governed by coupled thermal, mechanical, and transport processes. Among these materials, borophosphosilicate glass (BPSG) thin films deposited by chemical vapor deposition (CVD) exhibit distinctive low-temperature flow characteristics that critically influence device-level performance. This study aims to provide a physically grounded synthesis of the mechanisms governing the flow behaviour of low-temperature BPSG thin films and to examine their functional roles across IC, MST, and optical device technologies. The analysis integrates reported experimental observations and process data to interpret BPSG behaviour in terms of thermo-viscous flow, compositional dependence, and surface evolution under thermal treatment. The results show that the reduced glass transition temperature induced by boron and phosphorus incorporation enables controlled viscous flow at temperatures as low as approximately 700–800 ℃, leading to effective surface planarization, void elimination, and geometry reconfiguration in complex device reliefs. The interaction between thermal activation, film composition, and structural constraints governs key performance outcomes, including planarization efficiency, gap-filling capability, and stress evolution. In MST and optical applications, the same flow mechanisms enable the formation of sealed cavities, microfluidic channels, and optically functional structures such as microlenses and waveguide cladding layers. It is concluded that the engineering functionality of BPSG films arises from the coupled interaction between thermal processes, material composition, and geometrical confinement. This work provides a unified interpretation of these mechanisms and highlights their implications for process optimisation and device design in integrated and multiphysics engineering systems.

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The dynamic behavior of nanoscale beam structures is strongly influenced by material gradation, geometric discontinuities, foundation characteristics, and small-scale effects, all of which play critical roles in the performance of advanced multiphysics nano-engineering systems. In the present study, the free vibration characteristics of a perforated non-homogeneous nanobeam resting on a variable elastic foundation were investigated under sliding-end boundary conditions. Particular attention was devoted to applications involving resonators of microelectromechanical and nanoelectromechanical systems, nano-sensors, smart structural components, and coupled electromechanical nano-devices, where precise control of dynamic response is essential. Spatial variations in Young’s modulus and material density were incorporated to represent non-homogeneous material properties, while perforation effects were introduced through modified geometric and mechanical characteristics. Size-dependent nanoscale behavior was captured using Eringen’s nonlocal elasticity theory. Based on Euler-Bernoulli beam theory, the governing differential equation of motion was derived. The resulting eigenvalue problem was solved using the Galerkin method in conjunction with shifted Legendre polynomial admissible functions, enabling high numerical stability, rapid convergence, and computational efficiency. Validation of the proposed formulation was performed through comparisons with available benchmark results reported in the literature, and additional convergence studies were conducted. Investigations were carried out to evaluate the effects of perforation characteristics, non-homogeneity parameters, and spatially varying foundation stiffness on the natural frequencies and mode shapes of the nanobeam. It was demonstrated that significant alterations in dynamic response may be induced by the combined interaction of material gradation, perforation geometry, and foundation variability. The developed model provides an efficient and reliable computational framework for the dynamic characterization of perforated nanoscale structures and offers valuable insights for the design, optimization, and vibration control of next-generation multifunctional nano-engineering systems operating under coupled multiphysics environments.

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This paper presents a unique Modified Differential Evolution Optimization Algorithm (MDEOA) for the intelligent modification of proportional–integral–derivative (PID) controller settings. The proposed MDEOA is developed with particular emphasis on future PID controller tuning applications. Benchmark evaluations demonstrate significant improvements in convergence speed and optimization quality compared with Classical Differential Evolution (CDE), indicating its potential suitability for intelligent control parameter optimization. The study tackles the enduring drawbacks of CDE in control parameter optimization, including its inadequate exploration-exploitation balance and sluggish convergence when adjusting dynamic or nonlinear systems. The suggested MDEOA addresses these issues by introducing improved crossover, mutation, and adaptive control techniques that increase population diversity and hasten convergence toward ideal PID gains. To give a methodical comparison analysis, the PID tuning problem is subjected to both the traditional CDE and the suggested MDEOA. The MDEOA-based PID controller offers noticeably better dynamic performance, as shown by analytical simulations and experimental validation. In particular, it completely eliminates the maximum peak and steady-state error, corresponding to 100% reduction in both parameters. The MDEOA-based PID controller reduces the rise time by 10.18%, the peak time by 49.70%, and the settling time by 93.47% compared with the conventional PID controller. These enhancements are a direct result of the algorithm's modified operators' efficacy. Overall, the findings show that MDEOA is a strong and dependable substitute for conventional CDE in intelligent control system parameter optimization. MDEOA is a viable tool for future applications in sophisticated automation and real-time control contexts because of the large improvements in response characteristics, which demonstrate that the suggested alterations greatly increase the resilience, accuracy, and flexibility of PID tuning.

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Engineered cementitious composites (ECCs) are increasingly considered for protective structures because their fiber-bridging mechanism, tensile ductility, and energy absorption can restrict crack growth under severe loading. Their compressive response at high strain rates, however, remains difficult to represent using conventional concrete constitutive models, particularly when rate-dependent deformation and progressive damage occur concurrently. This study investigated the dynamic compressive behavior of ECC containing 2.0% polyvinyl alcohol fibers and developed a constitutive framework that couples nonlinear viscoelasticity with statistical damage evolution. Split Hopkinson pressure bar (SHPB) tests were conducted at four average strain-rate levels ranging from approximately 15 to 200 s$^{-1}$, with three specimens tested at each level. Relative to the lowest strain-rate level, the dynamic peak stress and peak strain increased by up to 41.0% and 98.6%, respectively, while their rates of increase gradually declined at the higher loading rates. A rate-dependent constitutive model was then formulated by combining the Zhu–Wang–Tang (ZWT) nonlinear viscoelastic model with a Weibull damage function. The model reproduced the ascending branch and peak region of the measured stress–strain curves, although larger discrepancies remained in the post-peak softening stage. After implementation in Livermore Software for DYnamic Analysis (LS-DYNA), the model reproduced the strain-rate-dependent stress–strain response and the transition from localized cracking to extensive fragmentation. The maximum deviations between the simulated and experimental increases in peak stress and peak strain were 8.2% and 6.5%, respectively. The proposed framework provides a physically interpretable representation of the coupled rate-dependent deformation and damage of ECC and supports numerical analysis of ECC components subjected to impact-type loading.

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The study of non-Newtonian nanofluid flow through magnetohydrodynamic (MHD) surfaces has attracted considerable research interest due to its relevance for polymer processing, heat treatment, metallurgical production and biomedical transport systems. Despite extensive literature on MHD Casson nanofluids, the concurrent effects of two-way stretching, porous media, thermal radiation, viscous dissipation, Brownian motion, thermophoresis, double diffusion and non-Fourier heat conduction have received relatively little attention in the same analytical framework. To bridge this gap, this study develops an analytical model for the unsteady flow of MHD Casson nanofluids across a two-way stretch surface by incorporating the Cattaneo-Christov formulation of the heat flux. This model accounts for finite-speed thermal propagation and thermal relaxation effects that are not considered in the conventional Fourier heat conduction model. The resulting non-linear partial differential equations are reduced to a system of coupled similarity equations and analysed by means of the homotopy analysis method (HAM). The velocity, temperature, and nanoparticle concentration profiles are analyzed in relation to the effects of the respective control parameters. We see that stronger magnetic forces and greater permeability of the porous medium reduce the speed of the liquid, while thermal radiation and viscous dissipation increase the temperature. The nanoparticle concentration and the thermal boundary layer properties are affected by Brownian motion and thermal phenomena, and the increase in the thermal diffusion parameter in the Cattaneo-Christov model decreases the temperature profile compared to the classical Fourier formulation, indicating the influence of finite-speed heat propagation and thermal relaxation effects. The analytical results presented here provide a comprehensive view of the combined momentum, thermal and mass transfer phenomena in cryogenic nanofluids and may be useful in designing and improving useful for improving thermal management systems and polymer-processing applications.
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