In dynamic multi-objective optimization, environmental changes can rapidly invalidate converged solution sets. Therefore, achieving fast convergence recovery while maintaining solution-set distribution stability remains a key challenge. Existing methods often lack effective coordination between change response and subsequent optimization, which limits their recovery speed and long-term tracking stability. To address this issue, this paper proposes a dynamic multi-objective evolutionary algorithm with direction-guided hybrid response and sensitive-dimension-based two-stage evolution. First, a direction-guided hybrid response strategy is developed to improve post-change recovery. It estimates the population migration direction from the elite centroid and the population centroid, and then generates a response population through directional translation, change-intensity-related perturbation, and small-scale random reinitialization. The response population then provides the decision-space basis for sensitive-dimension identification. The identified dimensions further provide search guidance for the subsequent two-stage evolution. Second, a sensitive-dimension identification mechanism is constructed to locate decision variables that are more sensitive to environmental changes. Based on the dispersion characteristics of elite solutions in the decision space, the identified sensitive dimensions are used to guide a two-stage evolutionary process. Predictive search is performed on sensitive dimensions to accelerate Pareto-front tracking, while local refinement is conducted on relatively stable dimensions to improve solution-set distribution. Finally, a multi-source fusion elite recombination strategy is introduced to enhance the robustness of population updating. It removes duplicates and performs controlled replacement among the original population, two-stage candidate solutions, and elite information. Experimental results on FDA, DF, and JY benchmark problems under different change-frequency settings show that the proposed algorithm outperforms the competing algorithms on most test problems and remains competitive on the others. Further studies on aluminum electrolysis operating-parameter optimization and the dynamic multi-objective knapsack problem demonstrate its practical applicability in both continuous- and discrete-variable decision scenarios.
This study examined the effects of flexible structures with different blockage rates on pressure oscillations in hydrogen-methane explosions through semi-open pipeline experiments. Flame development and overpressure histories were recorded to analyze flame dynamics, overpressure evolution, and transient pressure-response characteristics. The results show that a low-blockage flexible facility placed in front of a rigid facility can reduce flame velocity and overpressure, with maximum attenuation rates of 2.47% and 30.89%, respectively. In contrast, excessive blockage rates or higher hydrogen fractions can intensify explosions, increasing flame velocity and overpressure by up to 9.03% and 41.67%, respectively. More importantly, the rigid-flexible facility arrangement changes the dynamic evolution of overpressure, including the periodic oscillations of pressure-rise rate and the variation in oscillation intensity. Increasing hydrogen content strengthens these oscillations and may aggravate structural damage. Overall, the overpressure response is closely related to the blockage rate of the flexible facility, indicating that the explosion hazard should be evaluated not only by peak parameters, but also by pressure oscillation and transient pressure-rise behavior.
Sandstone serves as a vital medium for CO2 geological storage. Wettability is a key parameter in assessing the CO2 storage capacity and the safety of sequestration within sandstone reservoirs. This article offers a comprehensive review of the mechanism underlying the wettability alteration (WA) in sandstone reservoirs subsequent to CO2 injection. It commences by reviewing the classification of wettability in sandstone reservoirs, elucidating the pros and cons of diverse methods and techniques used to measure sandstone wettability. Special attention is then given to the analysis of crucial parameters, including the phase state of CO2, storage conditions, initial wetting state, and chemical reactions. Their impacts on the WA of the CO2/brine/sandstone system are thoroughly evaluated. The paper also presents an overview of the latest research advancements in contact angle characterization through different methods over the years. It identifies the knowledge gaps existing in the inconsistent results of various characterization methods and in understanding the WA mechanism. Consequently, it proposes the imperative need for multi-scale quantitative wettability characterization and enhanced research on the wettability alteration mechanism. Finally, it underscores the significant influence of WA on the CO2 residual storage capacity. This review provides a valuable reference for the selection of optimal formations for future CO2 sequestration, as well as for the further assessment and implementation of CO2 geological storage projects.
Time-dependent heave deformation in red-bed soft rock (RBSR) subgrades poses a critical threat to high-speed railway safety. However, its creep mechanism remains unclear because of limited understanding of the creep properties of red-bed silty mudstone (RBSM) and the lack of suitable constitutive models. In this study, multistage loading creep tests with acoustic emission (AE) monitoring are conducted on RBSM under different water contents and low confining pressures. A unified nonlinear creep damage-coupled model is developed by combining statistical damage theory with fractional calculus. Experimental results show that RBSM exhibits stress-dependent nonlinear creep behavior, including viscoelastic deformation at low-stress levels, viscoelastic-viscoplastic deformation at intermediate stress levels, and trimodal deformation at high stress levels. The long-term strength remains within 64-75
Bi1−xCaxFeO3 (BCFO) single-layer and multilayer thin films were fabricated to investigate the effects of Ca doping and stacking architecture on photovoltaic (PV) performance. The optimal BCFO-20 (x = 0.2) single-layer film exhibits an open-circuit voltage (Voc) of 0.768 V and a short-circuit current density (Jsc) of 192.943 μA cm−2, compared with 0.647 V and 40.862 μA cm−2 for undoped bismuth ferrite (BiFeO3, BFO), corresponding to an increase of 0.121 V in Voc and an approximately 4.7-fold enhancement in Jsc. Further enhancement is achieved in compositional-gradient multilayer structures, where the BCFO-T4 stack delivers a Jsc of 278.002 Μa cm−2, nearly 6.8 times that of the BFO film, together with the highest power conversion efficiency (PCE) among all devices investigated in this work. The enhanced PV performance is likely related to the compositional-gradient multilayer design, which may improve the internal electrical environment and facilitate photogenerated carrier separation and transport. These results suggest that compositional-gradient multilayer design is a promising strategy for enhancing the photovoltaic response of oxide-based thin films.
