Search Results (661)

In high geothermal tunnels (>28 °C), curing temperature critically affects early-age concrete mechanics and durability. Uniaxial compression tests under six curing conditions, combined with CT scanning and machine learning-based crack analysis, were used to evaluate the impacts of curing age, temperature, and fiber content. The test results indicate that concrete exhibits optimal development of mechanical properties under ambient temperature conditions. Specifically, the elastic modulus increased by 33.85% with age in the room-temperature group (RT), by 23.35% in the fiber group (F), and decreased by 26.75% in the varying-temperature group (VT). A Weibull statistical damage-based constitutive model aligned strongly with the experimental data (R² > 0.99). Fractal analysis of CT-derived cracks revealed clear fractal characteristics in the log(Nr)–log(r) curves, demonstrating internal damage mechanisms under different thermal histories. Full article

The incorporation of phase change material (PCM) can enhance wall thermal performance and indoor thermal comfort, but practical applications still face challenges related to high costs and potential leakage issues. In this study, a novel dual-biomass-based shape-stabilized PCM (Bio-SSPCM) was proposed, wherein waste cooking fat and waste reed straw were, respectively, incorporated as the PCM substance and supporting material. The waste fat (lard) consisted of both saturated and unsaturated fatty acid glycerides, exhibiting a melting point about 21.2–41.1 °C and a melting enthalpy value of 40 J/g. Reed straw was carbonized to form a sustainable porous biochar supporting matrix, which was used for the vacuum adsorption of waste fat. The results demonstrate that the as-prepared dual-Bio-SSPCM exhibited excellent thermal performance, characterized by a latent heat capacity of 25.4 J/g. With the addition of 4 wt% of expanded graphite (EG), the thermal conductivity of the composite PCM reached 1.132 W/(m·K), which was 5.4 times higher than that of the primary lard. The thermal properties of the Bio-SSPCM were characterized using an analog T-history method. The results demonstrated that the dual-Bio-SSPCM exhibited exceptional and rapid heat storage and exothermic capabilities. The dual-Bio-SSPCM, prepared from waste cooking fat and reed straw, can be considered as environmentally friendly construction material for energy storage in line with the principles of the circular economy. Full article

The Varnous Mt. area in the northern Pelagonian Nappe is characterized by the intrusion of an Early Permian pluton, with its tectonic setting and igneous petrology well constrained in earlier studies. The metamorphic basement rocks warrant further detailed investigation due to their complex history. These rocks are polymetamorphosed, preserving a sequence of overprinting metamorphic and deformational events. The metapelitic rocks have undergone an initial, pre-Carboniferous regional metamorphism of unknown grade before or during Hercynian Orogeny, followed by a thermal metamorphic event associated with the intrusion of the Varnous pluton at 297 Ma. The assemblage attributed to this event is And + Crd + Bt + Ms (west), while the first assemblage identified at the eastern part is Sil + Bt + Gt. Additionally, three regional tectonometamorphic events occurred during the Alpine Orogeny. For the Alpine events, the assemblages are as follows: first, the development of St + Gt + Chl + Kfs + Pl + Qtz at 150–130 Ma; second, retrograde metamorphism of these assemblages with Cld + Gt + Ser + Mrg + Chl ± Sil (Fi) at 110–90 Ma; and finally, mylonitization of all previous assemblages at 90–70 Ma with simultaneous annealing and formation of Cld + Chl + Ms. Full article

The deformation behavior of polymers is influenced not only by service conditions such as temperature and the strain rate but also significantly by the formation process. However, existing simulation frameworks typically treat injection molding and the in-service mechanical response separately, making it difficult to capture the impact of the thermal history on large deformation behavior. In this study, the deformation behavior of injection-molded polycarbonate (PC) was investigated by accounting for its thermal history during formation, achieved through combined experimental characterization and constitutive modeling. PC specimens were prepared via injection molding followed by annealing at different molding/annealing temperatures and durations. Uniaxial tensile tests were conducted using a Zwick universal testing machine at strain rates of 10⁻³–10⁻¹ s⁻¹ and temperatures ranging from 293 K to 353 K to obtain stress–strain curves. The effects of the strain rate, testing temperature, and annealing conditions were thoroughly examined. Building upon a previously proposed phenomenological model, a new constitutive framework incorporating thermal history effects during formation was developed to characterize the large deformation behavior of PC. This model was implemented in ABAQUS/Explicit using a user-defined material subroutine. Predicted stress–strain curves exhibit excellent agreement with the experimental data, accurately reproducing elastic behavior, yield phenomena, and strain-softening and strain-hardening stages. Full article

Modern aircraft increasingly utilizes highly integrated electronic equipment, driving continuously increasing heat dissipation demands. Vapor compression refrigeration systems demonstrate stronger alignment with future aircraft thermal management trends, leveraging their superior volumetric cooling capacity, high energy efficiency, and independence from engine bleed air. This paper reviews global research progress on aircraft vapor compression refrigeration systems, covering performance optimization, dynamic characteristics, control strategies, fault detection, and international development histories and typical applications. Analysis identifies emerging challenges under large-temperature-range cooling requirements, with comparative assessment establishing zeotropic mixture auto-cascade vapor compression refrigeration systems as the optimal forward-looking solution. Finally, recognizing current research gaps, we propose future research directions for onboard auto-cascade vapor compression refrigeration systems: optimizing refrigerant mixtures for flight conditions, achieving efficient gas-liquid separation during variable overloads and attitude conditions, and developing model predictive control with intelligent optimization to ensure reliability. Full article

AISI 347H stainless steel is widely used in high-temperature environments due to its excellent creep strength and oxidation resistance; however, its corrosion performance remains highly sensitive to thermal oxidation, and the effects of thermal history on its passive film stability are not yet fully understood. This study addresses this knowledge gap by systematically investigating the influence of solution treatment on the corrosion and oxidation resistance of AISI 347H stainless steel. The specimens were subjected to solution heat treatment at 1050 °C, followed by air cooling, and then evaluated through electrochemical testing, high-temperature oxidation experiments at 550 °C, and multiscale surface characterization techniques. The solution treatment refined the austenitic microstructure by dissolving coarse Nb-rich precipitates, as confirmed by SEM and EBSD, and improved passive film integrity. The stabilizing effect of Nb also played a critical role in suppressing sensitization, thereby enhancing resistance to intergranular attack. Electrochemical measurements and EIS analysis revealed a lower corrosion current density and higher charge transfer resistance in the treated samples, indicating enhanced passivation behavior. ToF-SIMS depth profiling and oxide thickness analysis confirmed a slower parabolic oxide growth rate and reduced oxidation rate constant in the solution-treated condition. At 550 °C, oxidation was suppressed by the formation of compact, Cr-rich scales with dual-distributed Nb oxides, effectively limiting diffusion pathways and stabilizing the protective layer. These findings demonstrate that solution treatment is an effective strategy to improve the long-term corrosion and oxidation performance of AISI 347H stainless steel in harsh service environments. Full article

Ensuring the structural integrity of reinforced concrete (RC) components in nuclear facilities exposed to extreme conditions is essential for safe decommissioning. This study investigates the impact of high-temperature exposure on RC pedestal structures supported by steel ring-shaped shear connectors—critical elements for maintaining vertical and lateral load paths in containment systems. Scaled-down cyclic loading tests were performed on pedestal specimens with and without prior thermal exposure, simulating post-accident conditions observed at a damaged nuclear power plant. Experimental results show that thermal degradation significantly reduces lateral stiffness, with failure mechanisms concentrating at the interface between the concrete and the embedded steel skirt. Complementary finite element analyses, incorporating temperature-dependent material degradation, highlight the crucial role of load redistribution to steel components when concrete strength is compromised. Parametric studies reveal that while geometric variations in the inner skirt have limited influence, thermal history is the dominant factor affecting vertical capacity. Notably, even with substantial section loss in the concrete, the steel inner skirt maintained considerable load-bearing capacity. This study establishes a validated analytical framework for assessing structural performance under extreme conditions, offering critical insights for risk evaluation and retrofit strategies in the context of nuclear facility decommissioning. Full article

Additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), provides unmatched design flexibility for creating intricate steel structures with minimal post-processing. However, adopting L-PBF for high-performance applications is difficult due to the challenge of predicting microstructure evolution. This is because the process is sensitive to many parameters and has a complex thermal history. Thin-walled geometries present an added challenge because their dimensions often approach the scale of individual grains. Thus, microstructure becomes a critical factor in the overall integrity of the component. This study focuses on applying cellular automata (CA) modeling to establish robust and efficient process–structure relationships in L-PBF of 316L stainless steel. The CA framework simulates solidification-driven grain evolution and texture development across various processing conditions. Model predictions are evaluated against experimental electron backscatter diffraction (EBSD) data, with additional quantitative comparisons based on texture and morphology metrics. The results demonstrate that CA simulations calibrated with relevant process parameters can effectively reproduce key microstructural features, including grain size distributions, aspect ratios, and texture components, observed in thin-walled L-PBF structures. This work highlights the strengths and limitations of CA-based modeling and supports its role in reliably designing and optimizing complex L-PBF components. Full article

Asphalt–rubber binders (A-RBs) have a long and deep history of use; however, little is known regarding the interrelated chemical behaviors and miscibility of rubber with the asphalt fractions [saturates, aromatics, resins, and asphaltenes (SARA)]. This study comprehensively attempted to address this knowledge deficiency by employing Fourier transform infrared spectroscopy (FTIR) to investigate the chemical evolution of A-RBs. A-RB interacted at 190 °C and 3000 min⁻¹ for 8 h was deemed to have the optimal rheological performance. FTIR of the liquid fractions of A-RB 190–3000 showed a prominent chemical shift in the SARA fractions, with new peaks that showed rubber polybutadiene (PB) and polystyrene migration into asphaltenes. Meanwhile, decreases in peaks with C–H aromatic bending and S=O stretching for the A-RB 190–3000 saturates showed that the rubber absorbed low-molecular-weight maltenes during swelling. Peaks associated with C=C aromatic appeared in saturates and aromatics, respectively, emphasizing that unsaturated components migrated from the rubber into the asphalt. Thermal analysis showed that rubber dissolution for this sample reached 82%. While a PB peak existed in asphaltenes of A-RB 220–3000, its intensity was diminished by depolymerization, thus compromising the integrity of the migrated rubber structure and generating less rheological enhancement. This study concludes that FTIR characterization of SARA fractions offers valuable insights into the interactions between asphalt and rubber, and that regulated processing conditions are essential for enhancing binder performance. Full article

The ongoing exploration of planets such as Mars is producing a wealth of data to define habitable environments beyond the Earth. The inferred presence of neutral to alkaline aqueous fluids on Mars in its early history suggests that many potentially habitable environments existed on the planet. Terrestrial analogues with similar chemical and physical properties are being explored and characterized in order to assess their suitability for triggering the Origin of Life on Mars. Recently, a novel Mars analogue site has been identified in the Bagno dell’Acqua Lake, which is located in the island of Pantelleria in Sicily (Italy). We report here that microbialite from the Bagno dell’Acqua Lake acts as an efficient catalyst for prebiotic processes, starting from a ternary mixture of well-recognized chemical precursors, including ammonium formate, diaminomalonitrile, and alpha-amino acids. Under thermal conditions, significant amounts of building blocks of both RNA and PNA were obtained. Furthermore, samples of the water from the Bagno dell’Acqua Lake have been found to promote the polymerization of the H-form of 3′,5′-cyclic GMP, resulting in the generation of RNA oligomers of up to 15 units in length. Full article

The Jurassic Tamulangou Formation in the Hongqi Depression has favorable hydrocarbon generation conditions and great resource potential. This study systematically analyzes the geochemical characteristics and thermal evolution history of the source rocks using data from multiple key wells. The dark mudstone of the Tamulangou Formation has a thickness ranging from 50 to 200 m, with an average total organic carbon (TOC) content of 0.14–2.91%, an average chloroform bitumen “A” content of 0.168%, and an average hydrocarbon generation potential of 0.13–3.71 mg/g. The organic matter is primarily Type II and Type III kerogen, with an average vitrinite reflectance of 0.71–1.36%, indicating that the source rocks have generally reached the mature hydrocarbon generation stage and are classified as medium-quality source rocks. Thermal history simulation results show that the source rocks have undergone two major thermal evolution stages: a rapid heating phase from the Late Jurassic to Early Cretaceous and a slow cooling phase from the Late Cretaceous to the present. There are differences in the thermal evolution history of different parts of the Hongqi Depression. In the southern part, the Tamulangou Formation entered the hydrocarbon generation threshold at 138 Ma, reached the hydrocarbon generation peak at approximately 119 Ma, and is currently in a highly mature hydrocarbon generation stage. In contrast, the central part entered the hydrocarbon generation threshold at 128 Ma, reached a moderately mature stage around 74 Ma, and has remained at this stage to the present. Thermal history simulations indicate that the Hongqi Depression reached its maximum paleotemperature at 100 Ma in the Late Early Cretaceous. The temperature evolution pattern is characterized by an initial increase followed by a gradual decrease. During the Late Jurassic to Early Cretaceous, the Hongqi Depression experienced significant fault-controlled subsidence and sedimentation, with a maximum sedimentation rate of 340 m/Ma, accompanied by intense volcanic activity that created a high-temperature geothermal gradient of 40–65 °C/km, with paleotemperatures exceeding 140 °C and a heating rate of 1.38–2.02 °C/Ma. This thermal background is consistent with the relatively high thermal regime observed in northern Chinese basins during the Late Early Cretaceous. Subsequently, the basin underwent uplift and cooling, reducing subsidence and gradually lowering formation temperatures. Full article

This study joins a 20 mm thick 5000-series aluminum alloy using hot-wire insertion combined with narrow-gap laser welding to evaluate the feasibility and welding characteristics of this technique. The findings indicate that weld formation is primarily influenced by the laser energy density and material deposition rate. A strategy for improving weld beads is introduced incorporating a reoriented laser spot during the final pass on narrow-gap joints. This approach improves penetration and produces defect-free joints. The optimal processing conditions result in complete joint formation with four welding passes. Microstructural analysis reveals that the aluminum matrix morphology evolves according to the local thermal history during welding. Measurements show that the weld region is slightly harder than the base metal, whereas slightly lower hardness is observed at the fusion line and inter-pass boundaries, which correlates with the microstructure result. Full article

Emerging infectious diseases such as chytridiomycosis and ranavirosis, caused by Batrachochytrium dendrobatidis (Bd) and ranavirus (RV), respectively, are major contributors to global amphibian declines. Despite their significance, comprehensive data on the spatial epidemiology of these pathogens in South Korea remain limited. This study aimed to assess the nationwide co-occurrence and prevalence of Bd and RV across four anuran species in five administrative regions. Infection rates were analyzed in relation to host species, sex, and life history stage. Results indicated distinct prevalence patterns driven by ecological traits. Bd was predominantly detected in mountainous and coastal habitats, whereas RV was more common in flat inland areas. Both pathogens exhibited peak occurrence in central regions, likely reflecting seasonal transmission dynamics rather than stable endemic hotspots. The observed spatial heterogeneity appears to be influenced by pathogen-specific thermal tolerance and host ecology. These findings underscore the importance of understanding host–pathogen–environment interactions for effective disease surveillance and management. Continuous monitoring and integrative ecological approaches are essential to mitigate pathogen-induced biodiversity loss and to inform amphibian conservation strategies in East Asia. Full article

The prediction of microstructure evolution during thermal processing plays a crucial role in tailoring the mechanical properties of metallic components. Therefore, this work presents a comprehensive, multiscale modelling approach to simulating phase transformations in large-diameter steel rings during cooling. A finite-element-based thermal model was first used to simulate transient temperature distributions in a large-diameter ring under different cooling conditions, including air and water quenching. These thermal histories were subsequently employed in two complementary phase transformation models of different levels of complexity. The Avrami model provides a first-order approximation of the evolution of phase volume fractions, while a complex full-field cellular automata approach explicitly simulates the nucleation and growth of ferrite grains at the microstructural level, incorporating local kinetics and microstructural heterogeneities. The results highlight the sensitivity of final grain morphology to local cooling rates within the ring and initial austenite grain sizes. Simulations demonstrated the formation of heterogeneous microstructures, particularly pronounced in the ring’s surface region, due to sharp thermal gradients. This approach offers valuable insights for optimising heat treatment conditions to obtain high-quality large-diameter ring products. Full article

Aiming at the heat generation behavior of rubber products such as tires under complex loads, the thermal behavior of tread rubber materials under tensile and compressive loads is investigated by using a torsional fatigue testing machine to comparatively analyze the temperature difference between the inside and outside of the rubber cylinders and the heating history under different torsion angles and rotational speeds. Results demonstrate that during the initial rotation phase under cyclic loading, the external surface temperature of the rubber material exceeds internal measurements. However, with the continuation of cyclic loading, the internal temperature progressively escalates beyond surface temperatures. Furthermore, the temperature rise exhibited significant correlations with both imposed torsional angles and operational rotational speeds. This study provides valuable insights into heat generation patterns of rubber materials under complex working conditions. Full article