Nonlinear plasma evolution in microgravity cannot be reliably characterized under terrestrial gravity because buoyancy-driven convection modifies or suppresses the intrinsic instability mechanisms. Consequently, the predictive design and safe operation of electromagnetically actuated plasma engineering systems require a unified theoretical framework capable of distinguishing gravity-independent behavior from phenomena that emerge only under microgravity conditions. A microgravity nonlinear plasma platform was therefore established as a multi-physics governance framework that defines the physical and mathematical conditions under which nonlinear plasma evolution becomes microgravity-dependent while providing quantitative criteria for operational stability. A dimensionless governance ratio was introduced as the principal classification metric, coupling the electromagnetic control bandwidth with the nonlinear instability growth rate. The framework was further integrated with a three-tier distributed intelligent governance of stabilized plasmas supervisory architecture, through which electromagnetic actuation, thermal-ionization energy balance, and structural boundary response are coordinated across multiple interacting physical domains. Three operating regimes were thereby defined: admissible (R > 10), marginal (1 < R ≤ 10), and runaway (R ≤ 1), each associated with prescribed electromagnetic control actions, a diagnostic latency constraint, and mandatory termination logic. An analytical microgravity threshold was derived. Recent observations from the Plasma Kristall-4 (PK-4) complex plasma facility aboard the International Space Station (ISS) were shown to be consistent with the predicted emergence of field-aligned filamentary structures and anisotropic nonlinear transport under reduced-gravity conditions. Finally, five quantitative and experimentally falsifiable predictions were formulated to establish a systematic validation pathway for future microgravity plasma experiments. Collectively, the proposed framework provides a rigorous theoretical foundation for the analysis, governance, and engineering design of high-energy-density plasma systems operating in microgravity and establishes a general methodology for the development of next-generation plasma propulsion technologies, advanced confinement architectures, and reaction-boundary control systems in coupled multi-physics environments.

Flexible inflatable structures play an important role in emergency sealing and protection systems where rapid deployment and adaptive contact with complex boundaries are required. However, the operational performance of inflatable sealing systems is strongly influenced by the coupled interaction among internal pressure evolution, nonlinear membrane deformation, and interface contact behaviour under confined conditions. This study investigates the pressure-deformation-contact coupling behaviour of a Z-fold inflatable barrier during the sealing process of an underground tunnel. A nonlinear finite element model was developed using ABAQUS, in which the Yeoh hyperelastic constitutive model was adopted to describe the large deformation behaviour of the membrane material. The inflation process was simulated using the fluid cavity method, and the interaction between the inflatable membrane and tunnel boundary was defined through contact analysis. The evolution of structural morphology, stress distribution, volume variation, and contact development was systematically analysed to reveal the coupled mechanical response of the sealing system. The results showed that the deployment process consisted of three successive stages, including gravitational descent, inflation-driven expansion, and stable sealing. The complete deployment process was achieved within approximately 30 s. The maximum von Mises stress during inflation was 12.15 MPa, while the stabilized stress decreased to approximately 10.13 MPa, remaining considerably below the material tensile strength of 200 MPa. The airbag volume increased from 0.16 m³ to 5.79 m³, and the final contact area with the tunnel wall reached 4.55 m², corresponding to a sealing coverage rate of 81.3%. The results indicate that the sealing performance of inflatable tunnel barriers is governed by the coupled evolution of pressure loading, nonlinear structural deformation, and boundary contact interaction. This study provides new insights into the multiphysics response mechanism of flexible inflatable systems and offers a numerical basis for the design and optimization of rapid-response sealing devices in underground engineering applications.

Small-scale wind energy systems continue to attract attention as distributed renewable energy solutions; however, improving electrical output under varying operating conditions remains a challenge due to nonlinear interactions between environmental and operational parameters. This study investigates the optimization and predictive modelling of the current output of a tubular wind energy conversion system (WECS) through a statistically guided experimental framework. A response surface methodology based on central composite design (RSM–CCD) was employed to evaluate the combined influence of operating time and wind speed on system performance. Experimental observations were analysed using a quadratic polynomial model and analysis of variance (ANOVA) to establish the response relationship and identify operating conditions associated with improved electrical output. The results showed that the developed model achieved strong agreement between predicted and experimental responses with a coefficient of determination ($R^2$) of 0.962. Wind speed was identified as the dominant factor affecting current generation. The optimization analysis showed that the highest current output of 491.897 A was obtained at an operating time of 30 min and a wind speed of 6.88 m/s, corresponding to a desirability value of 0.998. The results indicate that the proposed modelling framework provides an effective approach for describing system response and identifying favourable operating conditions for compact wind energy systems. This study offers a practical methodology for experimental optimization and supports further development of data-driven performance enhancement strategies in renewable energy applications.

Complex engineering systems, including multi-degree-of-freedom structural assemblies, microelectromechanical systems resonators, electromechanical transducers, and fluid–structure interaction systems, are frequently represented by reduced-order nonlinear models in which a limited number of interacting modes govern the dominant dynamic response. The validity of such reductions depends fundamentally on whether the underlying Hamiltonian admits a second independent first integral that enables exact modal decoupling or whether the modal interaction remains intrinsically non-integrable. This question was investigated for a symmetric two-mode quartic Hamiltonian whose mathematical structure, although originally derived from the Friedmann–Robertson–Walker (FRW) cosmological model, is shared by a broad class of coupled nonlinear oscillators encountered in engineering applications and therefore provides a representative analytical surrogate for their dynamical behavior. The Kovalevskaya exponent method was applied to the similarity-invariant system, and the complete spectrum of exponents associated with each family of particular solutions was derived analytically. It was demonstrated that the Kovalevskaya exponents were generically irrational, indicating the absence of an additional analytic first integral and thereby establishing the generic non-integrability of the Hamiltonian in the Liouville sense. Three exceptional parameter regimes, within which all Kovalevskaya exponents remained rational, were identified explicitly and characterized analytically. Furthermore, Lyapunov’s theorem on holomorphic first integrals was employed to construct families of periodic solutions in the vicinity of every equilibrium configuration. The local dynamics were consequently classified into stable operating regimes and buckling-type unstable regimes, and the number of periodic vibration families was shown to be governed systematically by the model parameters $k, m^2, \Lambda$, and $\lambda$. This reveals the parameter regimes in which modal interactions remain unavoidable and reduced-order decoupling becomes mathematically inadmissible. These results provide a rigorous analytical criterion for assessing the applicability of reduced-order models and identifying parameter regions in which full nonlinear multi-physics simulations may be advisable to accurately predict stability, nonlinear energy transfer, and global system dynamics.