Search Results (11,695)

In this study, the seismic vulnerability of the Ferdowsi School building in Tabriz is investigated. The research began with comprehensive fieldwork, during which exploratory surveys and in-depth technical inspections of all structural components were performed. Experimental testing of prismatic masonry specimens was carried out to evaluate their mechanical characteristics, and the resulting properties were then incorporated as input parameters into the numerical model. The seismic vulnerability assessment was then carried out using nonlinear static (pushover) analysis, applying a lateral load pattern proportional to the first vibration mode of the structure. For numerical simulation, the building was modeled in the ABAQUS finite element software using the macro-modeling technique. The results of the nonlinear static analysis indicated that the building does not possess sufficient load-bearing capacity at the target displacement. Damage was primarily concentrated in the form of cracking in the masonry walls as well as in the dome-shaped sections of the roof, requiring the implementation of a seismic retrofitting scheme to enhance the structure’s seismic performance. To rehabilitate the structure, horizontal and vertical reinforced concrete beams were introduced as confining elements for the masonry walls and subsequently applied in the strengthening project. Furthermore, due to the presence of a domed roof at the first-floor level, it was strengthened using FRP composite materials to enhance tensile capacity and ductility. At the second-floor level, where the roof structure is made of timber elements, a steel cable system was employed to improve its strength and diaphragm action. As for the third-floor timber truss roof, the connections were upgraded and reinforced to provide reliable force transmission and to maintain the overall integrity of the structural system. Following the implementation of the retrofitting measures, the structural model was re-analyzed using nonlinear static analysis. The results demonstrated that the proposed strengthening scheme successfully increased the structural capacity up to the target displacement level and satisfied the intended performance requirements. In the final section of the paper, the implementation details of the retrofitting interventions, as well as the practical experiences gained during the implementation process, are presented and discussed. Full article

Unidirectional glass fiber reinforced polymer (GFRP) composite insulators are widely used in extra-high voltage (EHV) and ultra-high voltage (UHV) transmission lines due to their outstanding electrical and mechanical performance. However, the accurate prediction of the critical buckling load is crucial to satisfy the high reliability requirement under complex operations. In this paper, an improved Perry–Robertson theory to predict the critical buckling loads of GFRP composite insulators with different slenderness is proposed. Firstly, initial imperfection is expressed as a function of the insulator strut length, which enables the critical load to be formulated as a function of slenderness explicitly. It also allows for convenient comparisons with other theories, such as Euler and Johnson’s, and easy calibration with the magnitude of initial imperfections. Secondly, the nonlinear material behavior of the GFRP composite insulator strut, resulting from changes in glass fiber orientation in relation to the loading direction during buckling, is considered to further enhance the prediction accuracy. The predicted results with current theory were validated through compression tests of GFRP composite insulators with solid and hollow struts and different slenderness and boundary conditions, which shows an accuracy of over 85%. Thus, the proposed improved Perry–Robertson theory can be also applied in other fiber-reinforced composite buckling analyses. Full article

Powder Bed Fusion-Laser Beam/Polymer (PBF-LB/P) is a key additive manufacturing technology widely used in aerospace, but its process parameters are difficult to optimize for thermoplastic composites due to poor powder flowability and unstable melting regions. To address this challenge, this paper develops discrete element and finite element models to systematically determine the PBF process window for both powder spreading and sintering stages, with verified reliability. In the spreading stage, the powder layer performance is evaluated through surface profile, density, and uniformity. The effects of reinforcement phase, spreading speed, and layer thickness are analyzed, establishing reasonable spreading parameter windows. It is found that the optimal layer thickness for PEEK powder is determined to be 0.13 mm, while that for PEEK/CF composite powder is 0.12 mm. At the optimal layer thickness, the powder bed exhibits desirable properties, which minimize its adverse influence on the sintering process and serve as a prerequisite for subsequently establishing the sintering process window. For the sintering stage, sufficient sintering constraint criteria are established, and a systematic determination method is proposed. By analyzing microscopic sintering mechanisms and characterizing the effects of laser power, scanning speed, and hatching space on melt pool dimensions and temperature, a reasonable sintering process window can be efficiently determined. It is found that within the process window, the PEEK specimens achieved a maximum relative density of 99.31% and exhibited a tensile strength 13.1% higher than that of specimens processed outside the window, demonstrating a clear superiority. Full article

CoCrFeNi/WC-Nb high-entropy alloy (HEA) composite coating was prepared on the surface of Q235 steel by LC (laser cladding) technology, and the effects of WC and in situ NbC reinforcement on the coating were studied. The phase composition, phase characteristics, microhardness, and wear resistance of the cladding coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), friction and wear tester, and X-ray photoelectron spectroscopy (XPS), and the corrosion resistance was tested by a three-electrode electrochemical workstation. The results show that the CoCrFeNi/WC-Nb HEA coating consists of FCC, WC, NbC, and Laves phases, and the reinforcing phase causes grain refinement and lattice distortion. The microhardness reached (418.29 ± 16.72) HV, which was about 2.64-times higher than that of the CoCrFeNi HEA coating. The wear rate decreased to (1.150 ± 0.11) × 10⁻⁴ mm³N⁻¹m⁻¹, which was about 0.25 times that of the CoCrFeNi HEA coating, and the wear of the coating changed from abrasive wear to adhesive wear. The corrosion current density and corrosion voltage of the CoCrFeNi/WC-Nb HEA coating are (3.3820 ± 0.2103) × 10⁻⁶ A/cm² and −(0.7650 ± 0.0850) V, respectively. Full article

Corrosion of reinforcing steel and degradation of concrete caused by chloride penetration are the most critical forms of durability failure in marine environments. This requires that repair materials possess both high impermeability and stable chemical binding capacity. In this study, the impact patterns of sulfoaluminate cement (SAC) dosage on the chloride erosion durability of an OPC-GGBS-SAC ternary repair system were systematically evaluated. Through chloride ion binding capacity tests, electrical flux experiments, and microscopic analytical techniques including XRD, DTG and SEM-EDS, the synergistic regulation mechanisms of the dual functions of ‘physical barrier’ and ‘chemical binding’ in the composite material were elucidated. The findings show that the performance of the composite material was optimal at an SAC content of 10%. The electrical flux of composite materials at 28 d was 28.9% lower than that of the OPC system, whilst the chloride ion binding rate increased by 3.92%. Microstructural analysis indicates that an appropriate amount of SAC promoted the generation of ettringite (AFt) to optimize the early-age pore structure and stimulated the production of more C-S-H gel and AFm phases, thus synergistically enhancing impermeability and chemical binding capacity. When the SAC content exceeded 10%, excess gypsum inhibited the formation of AFm. Moreover, the concentration of early-stage hydration led to microdefects, resulting in a decline in durability. This study identifies the optimal dosage of SAC in the ternary system and clarifies the underlying mechanism, thereby providing a scientific basis for designing high-durability repair materials suitable for harsh ocean conditions. Full article

Ensuring the long-term serviceability of nearshore breakwaters constructed on weak seabeds is important for sustainable port infrastructure. This study investigates the wave-induced dynamic response of a vibro-compaction sand-pile composite foundation used in the Jinpai Port breakwater project in Lingao, Hainan, China. A coupled wave–structure–seabed numerical model was established using FssiCAS. Four representative monitoring points were selected inside and outside the structural influence zone and at different burial depths. The displacement, effective stress, shear stress, and pore water pressure responses were analyzed by combining full-field contour distributions with local time-history results. The results show that the foundation response is strongly location-dependent. The maximum horizontal displacement follows the order D > C > A > B, with values of approximately 10.8, 7.6, 0.5, and 0.3 mm, respectively. The final settlement follows the order A > B > C > D, with values of approximately 84, 43, 31, and 19 mm, respectively. Residual pore pressure is more significant beneath the breakwater, especially at Point B. The breakwater toes, structural boundaries, shallow seabed, and improved–natural foundation transition zones are identified as stability-sensitive zones, providing guidance for targeted monitoring, local reinforcement, drainage improvement, and maintenance planning. Full article

Limited data exists on the combined nutritional and phytochemical profiles of UK commercially available plant-based foods, limiting comprehensive compositional data available for dietary assessment and food formulation. This study addresses this gap by providing thorough compositional analysis of quinoa (red, black, organic), chia seeds (organic, white), pumpkin seeds (conventional, organic), flaxseeds (brown, golden, organic), and triticale grain (organic, cereal meal, rolled), profiling macronutrients, dietary fiber, amino acids, fatty acids, essential minerals, and bioactive phytochemicals. Pumpkin seeds exhibited the highest protein (29–36%) and fat (42–46%) contents, markedly exceeding quinoa and triticale, highlighting their role as a plant-based protein and energy source. Flaxseeds and chia seeds provided the greatest dietary fiber (15 g/100 g), while mineral analysis identified pumpkin seeds as particularly rich in phosphorus and magnesium, and white chia seeds as a rich source of calcium and iron. Targeted LC-MS/MS and HPLC screening (171 molecules) revealed substantial variation in phytochemical composition among products with red quinoa, golden flaxseed, and white chia seed containing the highest concentrations of quantified phytochemicals (up to 97.2 mg/100 g). These findings provide integrated data on the nutrient and phytochemical composition of selected commercially available products, reinforcing the practical importance of crop diversity for enhancing dietary nutrient and phytochemical diversity and informing future research, food innovation, and dietary assessment initiatives involving plant-based foods. Full article

The effects of practical parameters on the flexural behavior of reinforced concrete (RC) beams strengthened with steel strand mesh-reinforced engineered cementitious composite (ECC) were investigated, based on the finite element (FE) simulation. First, an FE model for strengthened RC beams was developed. The model was validated by comparing it with existing experimental data. Subsequently, the model was employed for parametric analysis on the flexural performance of the strengthened beams. The results showed that steel strand mesh-reinforced ECC significantly enhanced the flexural capacity, stiffness, and ductility of the RC beams, with improvements ranging from 7.81% to 61.84%, 6.35% to 40.90%, and 5.92% to 50.16%, respectively. As the reinforcement ratio of longitudinal steel strand, ECC thickness, and cracking strength increased, the flexural capacity increased. However, an increase in the reinforcement ratio of the longitudinal steel bars and the section height of the RC beam reduced the improvement in flexural capacity. The increase in the thickness of the strengthening layer and reinforcement ratio of the longitudinal steel strand enhanced the improvement of stiffness. Differently, an increase in the reinforcement ratio of longitudinal steel strand, concrete strength, and height of the RC beam diminished the improvement of stiffness. The enhancement of ductility increased with the concrete strength. Finally, formulas for calculating the bearing capacity and stiffness of RC beams strengthened with steel strand mesh-reinforced ECC and the limit of steel strand quantity were proposed. These formulas agreed well with experimental and numerical simulation FE results. Full article

This study presents an experimental investigation of reinforced concrete T-beams strengthened using ultra-high-performance concrete (UHPC) with steel plates, and in some cases, UHPC with a geotextile layer. Ten reinforced concrete specimens with the same internal reinforcement but different strengthening methods were tested. These included a control specimen and nine strengthened specimens. Four of the strengthened specimens had grooves in the wooden formwork before pouring to secure the strengthening composite plates inside it, four had it directly attached to the RC beam surface, and the last had vertical lines 10 mm deep to enhance bonding. The external composite plate consisted of four types: the first type included a composite of UHPC and steel plates as strips with 220 × 150 mm at 105 mm, while the remaining types consisted of a plate along the shear zones made of UHPC with steel, geotextiles, or steel and geotextiles. This study also included increasing the number of steel plate layers and the direction of strengthening placement. The results showed that all the strengthened beams failed in flexure, unlike the control specimen, which failed in shear. The strengthening systems improved the load-bearing capacity and overall structural behavior of the tested beams. Among the investigated specimens, beam IR-2S90SS, strengthened with two layers of steel plates, showed the highest improvement, achieving a 39.2% increase in ultimate load compared to the control beam. Debonding was observed in some specimens and was identified as one of the governing failure mechanisms. Overall, the investigated strengthening techniques demonstrated their effectiveness in improving the structural performance of reinforced T-beams. Full article

Additively manufactured composite architected discs offer a potential route for producing lightweight semi-finished blanks that can subsequently be shaped by conventional forming processes. However, the relationship between infill architecture, feature size, and deep-drawing formability remains poorly understood. This study investigates the deep-drawing response of material-extruded short-fibre-reinforced polymer composite discs by combining experimental tests and finite element simulations. Four infill strategies, namely perforated body, re-entrant, square and triangular, were first compared at drawing depths of 10 and 20 mm. The perforated body and re-entrant geometries were successfully formed at 10 mm, whereas only the perforated body withstood 20 mm without macroscopic failure. A second campaign focused on perforated discs with hole diameters of 2.5, 5, 7.5 and 10 mm. All configurations were drawable at 10 mm, while the 2.5 mm case failed at 20 mm. Statistical analysis confirmed that hole diameter significantly affected both retained cup height and side-hole aspect ratio. At 20 mm, larger holes reduced local ovalization but increased elastic recovery, leading to lower retained cup height. FEM simulations were used as an interpretative first-order model. They supported the experimental trends by comparing deformation modes, tensile/compressive stress redistribution, forming energy and strain localization. The results show that the formability of architected composite blanks is governed not only by material volume or porosity but by the ability of the internal architecture to accommodate deformation through a suitable balance between local stiffness and geometric compliance. These findings provide design-oriented guidelines for the development of additively manufactured architected blanks intended for hybrid additive–forming manufacturing routes. Full article

The Protected Denomination of Origin (PDO) and Protected Geographic Indication (PGI) labels were established to legally protect traditional cheeses, particularly those derived from small ruminants’ milk, through the definition of strict production standards. Nevertheless, the impact of certification has often fallen short of initial expectations in terms of sector valorisation and rural development. Increasing the economic sustainability of traditional small ruminants’ raw milk cheeses requires scaling without compromising their distinctive identity. In this context, increasingly stringent regulations on the hygiene and disinfection practices associated with milk refrigeration have significantly affected the characteristic properties of these cheeses, which are largely shaped by traditional manufacturing practices and the indigenous milk microbiota. This review synthesises distinctive attributes of Spanish and Portuguese PDO/PGI cheeses and emphasises the roles of cardoon (Cynara spp.) extracts and small ruminants’ raw milk microbiota in influencing the proteolysis, lipolysis, texture and flavour of such cheeses. Variability in cardoon ecotypes, enzyme activity, and microbial composition strongly affects cheese texture, aroma, and safety. Key challenges include inconsistent coagulant quality, the hygienic constraints associated with raw milk, regulatory limitations, and restricted market access. This review outlines strategies to address these challenges, including the standardisation and selection of elite cardoon ecotypes, improved milk hygiene practices, the development of tailored starter and non-starter cultures, and risk-based regulatory approaches. These measures are crucial to preserve authenticity while ensuring safety and economic resilience, thereby reinforcing the role of Iberian PDO/PGI cheeses in sustaining small ruminant dairy systems and rural economies. Full article

The Horned Lizard Optimization Algorithm (HLOA) is a newly proposed swarm intelligence optimizer mimicking the defensive and survival behaviors of horned lizards. The original HLOA suffers evident drawbacks when tackling high-dimensional, multimodal and heavily constrained complicated optimization problems. Rapid decline in population diversity in late iterations and insufficient local optimum escape strategies further trigger premature convergence and unsatisfactory optimization precision. To systematically address the above deficiencies and boost the global optimization and engineering applicability of HLOA, this paper proposes a hybrid-strategy improved Horned Lizard Optimization Algorithm (HSHLOA). First, an improved uniform Logistic chaotic mapping replaces conventional random initialization. It enhances the ergodicity and uniformity of initial populations across search spaces and upgrades the quality of initial solutions and population diversity. Second, an adaptive optimal guidance strategy is constructed via nonlinear dynamic adjustment factors. It prioritizes global exploration in early iterations and strengthens local exploitation in later iterations to accelerate convergence and raise optimization accuracy. Third, a lens imaging learning strategy is embedded. It generates adaptive opposite solutions following dynamic convex lens optical imaging rules, strengthens the capability to escape local optima and mitigates premature convergence. To verify the optimization performance of the proposed algorithm, comparative experiments are conducted on the CEC 2017 benchmark test suite under 30-dimensional and 100-dimensional high-dimensional settings. Seven mainstream swarm intelligence algorithms are selected for benchmark comparison. Quantitative analyses cover convergence rate, optimization precision, numerical stability and local optimum escaping ability. Experimental results reveal that HSHLOA outperforms all peer competitors on unimodal, multimodal, hybrid and composite functions with remarkable superiority. The proposed HSHLOA is further applied to three typical constrained engineering optimization cases, including reinforced concrete beam design, three-bar truss design and pressure vessel design. Application results prove that HSHLOA satisfies all engineering constraints steadily and obtains superior structural schemes with higher efficiency. The reliability and superiority of HSHLOA for practical engineering problems are therefore verified. Full article

Cryogenic environments impose severe thermal and mechanical stresses on polymer components, yet the effects of long-term cryogenic cycling on their subsequent room-temperature performance remain insufficiently understood. This study investigated the influence of cryogenic cyclic aging on the mechanical and tribological behaviour of polyimide (PI)-based materials, including neat PI and composites reinforced with MoS₂, graphite, and/or PTFE. Repeated cryogenic cycling was followed by mechanical characterisation and tribological testing at 25 °C in air and vacuum. This work systematically compares neat and filled PI materials after cryogenic cyclic aging and correlates mechanical changes with transfer-film formation and wear behaviour. Cryogenic cyclic aging had only minor effects on weight and thermal stability but significantly altered the viscoelastic behaviour, increasing creep and residual strain, with variations depending on the polymer structure and filler content. Fracture toughness showed a statistically significant improvement only for PI2 (up to 93%). Changes in PI1, PI3, PI4, and PI5 fell within the experimental scatter and were interpreted as non-significant trends. In air, abrasive wear dominated in unreinforced PI, while graphite/PI composites exhibited adhesive wear and improved transfer film formation, reducing wear rates by up to 26%. In vacuum, the wear rate of aged graphite/PI increased by up to two orders of magnitude. Full article

In response to the increasing needs for environmentally friendly products, lignocellulosic natural fibers have been of interest as potential replacements for synthetic reinforcement materials in textiles, composites, and related applications. Among these resources, bast fibers derived from plant stems (flax, hemp, nettle, jute, hop), which contain a high cellulose content, have good mechanical properties, low density, and are renewable, are highly promising. Steam explosion has emerged as a green fiber extraction, defibrillation, and surface modification pretreatment technology. Despite the growing number of studies on steam-exploded natural fibers, a comprehensive understanding of the relationships between processing conditions, fiber modifications, mechanisms, and end-use performance remains limited. This review investigates the structural, chemical, and morphological influences of steam explosion on bast fibers. Specifically, it focuses on the mechanism of steam explosion including the solubilization of hemicellulose, partial lignin redistribution or removal, fiber individualization, and cellulose enrichment. The literature indicates that steam explosion can improve fiber separation, fineness, surface morphology, and interfacial adhesion of the composite materials and reduce the use of hazardous chemicals compared with conventional extraction methods. Nonetheless, conflicting results have also been documented, where the same steam explosion conditions can yield distinct fiber characteristics according to biomass type, composition of biomass, moisture concentration, and the amount of processing involved. Excessive treatment severity may lead to fiber shortening, cellulose degradation, and deterioration of fiber quality, particularly for textile applications requiring long fibers. This review highlights current knowledge gaps regarding the optimization of processing conditions, the understanding of steam explosion mechanisms, and the scale-up of the technology for industrial applications. Full article

This paper introduces the Improved Runge–Kutta algorithm (IRUN), an enhanced optimization framework that addresses the limitations of the standard RUN method. By integrating success-history adaptation, an external archive, and linear population reduction, IRUN achieves a more effective exploration–exploitation balance, leading to faster and more stable convergence. Evaluations on twenty-three unimodal, multimodal, and composite benchmark functions confirm that IRUN consistently outperforms RUN, achieving markedly lower median errors, narrower interquartile ranges, and more reliable convergence trajectories. In a real-world 136-bus distribution system, IRUN reduces active and reactive power losses by 1.6%, lowers maximum and daily utility energy consumption by 5.9% and 2.5%, and produces smoother, more coordinated charging behavior for distributed BESS units. Voltage-quality indicators—including minimum/maximum voltages and total voltage deviation—demonstrate improved regulation and enhanced system stability, while convergence time is reduced by 16.3%, reinforcing IRUN’s suitability for real-time operational environments. Overall, the combined benchmark and distribution-system results establish IRUN as a robust, accurate, and computationally efficient optimization strategy for next-generation smart distribution networks. Full article