Symmetry

This study investigates the mechanical behavior and fatigue performance of orthotropic steel bridge decks, with a focus on rib-to-deck welded connections and the impact of geometric symmetry on stress distribution. Two full-scale models with full-penetration butt welds were tested under static compression loads, yielding failure forces of 27 kN (experimental) and 26 kN (analytical), with only a 3% difference. Finite element simulations using ANSYS 16.1 validated these results and enabled parametric studies. Rib plate thicknesses ranging from 5 mm to 9 mm were analyzed to assess their influence on stress distribution and deformation. The geometric ratio h′/tr, which reflects the symmetry of the trapezoidal rib web, was found to be a critical factor in stress behavior. At h′/tr = 38 (tr = 7 mm), compressive and tensile stresses are balanced, demonstrating a symmetric stress field; at h′/tr = 33 (tr = 8 mm), and fatigue performance at the RDW root drops by 47%. Increasing h′/tr improves fatigue life by increasing the number of load cycles to failure. Stress contours revealed that compressive stress concentrates in the rib plate above the weld toes, while tensile stress localizes at the RDW root. The study highlights how symmetric geometric configurations contribute to balanced stress fields and improved fatigue resistance. Multiple linear regression analysis (SPSS-25) produced predictive equations linking stress values to applied load and geometry, offering a reliable tool for estimating stress without full-scale simulations. These findings underscore the importance of optimizing h′/tr and leveraging structural symmetry to enhance resilience and fatigue resistance in welded joints. This research provides practical guidance for improving the design of orthotropic steel bridge decks and contributes to safer, longer-lasting infrastructure.

The biological accumulation of microcontaminants and associated antibiotic resistance in food poses significant threats to both human and environmental health. Therefore, it is particularly crucial to design and develop methods of efficient identification and detection. Recently, molecularly imprinted polymers (MIPs) and aptamers (Apts), as novel hybrid recognition elements, have received widespread attention from researchers. Because the dual recognition-based sensors have demonstrated enhanced performance and desirable characteristics, including high sensitivity, strong binding affinity, a low detection limit, and excellent stability under harsh environmental conditions, which are expected to be applied in food safety fields. This paper compares the characteristics of MIP and Apt, highlighting the significant advantages of molecularly imprinted polymer–aptamer (MIP-Apt) dual recognition in selectivity, sensitivity, and stability, which stems from their symmetric integration, akin to an extension of the ‘lock-and-key’ model. It then systematically discusses three synthetic strategies for MIP-Apt hybrid recognition systems and their applications for food safety detection, focusing on analyzing their detection strategies, sensing mechanisms, construction methodologies, performance evaluations, and potential application value. It also offers substantive perspectives on both the prevailing limitations and promising developmental pathways for MIP-Apt hybrid recognition-based sensing platforms.

The synthesis of high-performance adhesives imposes stringent requirements on the design of stirred reactors: simultaneous achievement of efficient mixing and minimal energy dissipation in highly viscous media remains the principal challenge. In this study, computational fluid dynamics (CFD) was employed to solve the Navier–Stokes equations for the high-viscosity epoxy system and numerically simulating the flow fields of four representative reactor configurations across a prescribed range of rotational speeds. Specifically, the four representative reactor configurations were (i) single-serrated shaft, (ii) eccentric single-serrated shaft, (iii) uniaxial single-blade paddle combined with a single-serrated dual-axis assembly, and (iv) biaxial single-blade paddle coupled with a single-serrated triaxial assembly. The mixing performance was quantitatively assessed by systematically comparing the evolution of mixing speed, vorticity fields, restricted power consumption, and mixing time across a range of rotational speeds. The results demonstrated that the synergistic deployment of an eccentric impeller and a differential-speed single-propeller shaft effectively disrupted the axisymmetric flow pattern, compressed the chaotic isolation zones, and intensified both axial exchange and global chaotic mixing. Among the configurations examined, the uniaxial single-propeller–single-serrated biaxial arrangement reduced the mixing time by 13.43% and cut the specific energy consumption by approximately 58.32%, thereby attaining markedly higher energy efficiency. This research will provide guidance for the study of efficient mixing of adhesives.