Search Results (3,045)

Differential enrichment of shale oil hydrocarbon fractions exerts a fundamental control on the spatial distribution of “sweet spots” and the efficiency of unconventional resource recovery. This study investigates the continental shales of the Upper Es4 Member in the Dongying Sag, Bohai Bay Basin, through an integrated analytical framework combining Laser Scanning Confocal Microscopy (LSCM), Scanning Electron Microscopy (SEM), and high-pressure mercury intrusion. By moving beyond qualitative observations, we characterize the micro-scale partitioning of light and heavy fractions and establish a deterministic hierarchy of controlling factors. Our results indicate the following. (1) Mineral composition functions as a “primary geochemical filter,” where carbonate minerals exhibit a preferential adsorption affinity for light fractions (≤ C₁₈), while clay minerals facilitate the selective retention of heavy components (> C₁₈). (2) Pore–throat architecture acts as a “secondary mobility modulator.” A statistically significant linear correlation (R² = 0.72, p < 0.05) was identified between mean pore diameter and the light-to-heavy fluorescence ratio, suggesting that interconnected macropores in carbonate laminae provide low-resistance conduits for light oil accumulation, whereas isolated mesopores in argillaceous matrices promote heavy-component sequestration. (3) Thermal maturity (Ro) drives a progressive shift in the light-to-heavy ratio, enhancing oil fluidity and regulating the transition from adsorption-dominated to migration-dominated enrichment. This study clarifies the lithofacies-dependent coupling mechanisms between mineral diagenesis and pore-scale fractionation, providing a semi-quantitative conceptual model for shale oil sweet-spot prediction in complex lacustrine basins. Full article

In this study, an eco-friendly geopolymer concrete (GPC) was synthesized using fly ash, slag, and rice husk ash as precursors, and glass fibers were incorporated to enhance its mechanical properties. And then this study investigates the residual mechanical properties and microstructure evolution of glass fiber-reinforced geopolymer concrete (GFGPC) following elevated temperature exposure and subsequent cooling. Specimens incorporating varying glass fiber volume fractions (0–2.5%) were subjected to temperatures ranging from 25 °C to 800 °C, followed by either natural cooling or water-spraying cooling. The uniaxial compressive strength, Brazilian splitting tensile strength, and three-point flexural strength of the glass fiber-reinforced GPC were experimentally determined. Furthermore, fracture performance indicators—including the energy absorption capacity at failure, characteristic length, and double-K fracture parameters—were systematically analyzed. Results indicate that a glass fiber content of 1.5% optimally enhances the composite’s mechanical performance. Under natural cooling, splitting tensile and flexural strengths exhibit a non-monotonic trend, peaking at 200 °C. Conversely, water-spraying cooling induced thermal shock generally degrades tensile and flexural properties. However, at extreme temperatures (600 °C and 800 °C), water-spray cooling facilitates matrix densification and secondary geopolymerization, resulting in a residual compressive strength increase of 12.16% and 20.77% compared to natural cooling. Furthermore, based on composite damage theory, a binary nonlinear prediction model was developed to accurately capture the coupled effects of temperature and fiber characteristics on the residual compressive strength (R² > 0.90). Coupled with scanning electron microscopy (SEM) observations, the profound effects of elevated temperatures and thermal shock on the GPC gel matrix were elucidated, and the microscopic mechanisms underlying the failure of the fiber-bridging effect at high temperatures were thoroughly investigated. The findings of this study provide a solid theoretical foundation and scientific reference for the performance assessment and repair decision-making of GPC structures post-fire exposure. Full article

This study examines the impact of alkaline treatment on hydrogels composed of acrylic acid (AAc), sodium alginate (SA), and poly(ethylene oxide) (PEO), produced via 5.5 MeV electron beam irradiation, emphasizing swelling behavior and functional performance. Hydrogels were treated with NaOH (0.25 M and 0.50 M) to modulate biodegradability, water retention capacity, and water retention ratio. The materials were characterized in terms of structural, morphological, thermal, and physicochemical properties using FTIR, SEM, and TGA/DSC, along with evaluations of gel fraction, cross-linking density, mesh size, porosity, swelling kinetics, and water retention. FTIR confirmed carboxyl group ionization and polymer chain reorganization, while SEM revealed structural changes, rougher surfaces, and larger pores that facilitate water uptake. Thermal stability of the hydrogels increased, with the T-onset rising from 236 °C in the untreated samples to 451 °C after alkaline treatment. Treatment with 0.25 M NaOH enhanced mesh size (127.97 ± 4.05 nm), porosity (99.74 ± 0.05%), and swelling capacity (428 ± 14 g/g), whereas 0.50 M induced partial degradation and reduced swelling. Despite a significant increase in degradability (>39.49 ± 1.94% after 28 days), treated hydrogels maintained functional performance, showing accelerated water uptake and improved rainwater retention. Overall, alkaline treatment enables tunable structural and functional modifications, optimizing hydrogel performance for agricultural water management. Full article

Plastic waste is estimated to represent 40–80% of the total amount of marine litter, with polyethylene (PE) and polypropylene (PP) being the most abundant polymeric components. The recovery and recycling of marine plastic debris are therefore essential to mitigate environmental pollution and limit the generation of secondary microplastics. In this work, a mechanical recycling strategy was investigated for the valorization of a polyethylene-rich plastic fraction (PE-rf) recovered from the marine environment, characterized by high heterogeneity and persistent inorganic contamination. Different pre-treatment routes, including cryogenic grinding and planetary ball milling, as well as blending approaches with recycled polyethylene and compatibilizing additives, were explored. The effects of composition and processing on the thermal, mechanical, and morphological properties of the resulting materials were systematically analyzed. The results show that intense mechanical homogenization and chemical compatibilization are not sufficient to overcome the intrinsic limitations imposed by contamination and compositional variability. As a proof of concept, selected formulations were processed into filaments and tested in fused filament fabrication, demonstrating basic 3D printability. Full article

Paraffins are attractive as phase-change materials (PCMs) due to their high latent heat capacity and adjustable phase transition temperatures. However, the individual high-purity paraffins, especially the long-chain ones, are labor-intensive and costly to produce and capable of storing and releasing latent heat only within a limited temperature range. Herein, we demonstrate the feasibility of a high-purity paraffin wax fraction (C13–C49) obtained via the Fischer–Tropsch (FT) process as a versatile latent heat storage additive within a wide range of phase transition temperatures (8.1–98.2 °C). To avoid the leakage, the FT wax was encapsulated via nanoemulsion interfacial polymerization of melamine formaldehyde (MF) shells with various core-to-monomer and melamine/formaldehyde ratios. Differential scanning calorimetry revealed that the latent heat storage capacity of the FT/MF capsules was 104.5–163.4 J/g depending on the FT loading efficiency, with the heat storage and release range of −0.7–100.2 °C and −9.8–85.8 °C, respectively. The capsules were tested as a thermoregulating additive to commercially available gypsum plaster. Unlike employment of the additives based on individual paraffins, the addition of FT/MF capsules led to a smooth reduction in heating/cooling rates of plaster layers in an extended temperature range. This makes FT/MF capsules a promising and versatile additive for a diversity of thermal energy storage applications. Full article

This paper presents a novel proportional–integral–derivative (PID) control framework for first $\alpha$-order systems evolving in fractal time. The main contribution is the extension of classical control theory to systems exhibiting anomalous temporal scaling by employing local fractal derivatives. In contrast to fractional-order PID (FOPID) approaches, which primarily model memory effects, the proposed fractal PID framework captures time-scaling behavior arising in non-smooth environments, such as viscoelastic friction and irregular contact surfaces. The closed-loop dynamics are formulated as a second $\alpha$-order fractal differential equation, from which a characteristic equation is derived to establish conditions for asymptotic stability. It is shown that, for a constant reference input and positive controller gains, the tracking error converges to zero as $t\to \infty$. In addition, a quantitative performance analysis demonstrates that the fractal-order $\alpha$ governs temporal stretching: smaller values of $\alpha$ lead to increased rise and settling times and reduced oscillation frequency. The effectiveness of the proposed approach is illustrated through applications to a thermal system with fractal heat input and robotic actuators operating in irregular environments. These results highlight the potential of fractal-time control as a systematic framework for modeling and controlling dynamical systems with non-integer temporal structure. Full article

Non-insulated heat exchangers in gas-to-gas service lose substantial energy to the surroundings. This study evaluates Al₂O₃ and ZnO ceramic coatings (200 $\mathsf{\mu }$m) as passive thermal retention layers on the inner surface of the outer tube in a copper double-pipe heat exchanger, using 3D CFD simulations verified for internal consistency against Log Mean Heat Transfer Rate analytical solutions. Six cases were modelled: three coating conditions across parallel-flow and counter-flow configurations under laminar conditions ($R{e}_i\approx 525$, $R{e}_o\approx 192$) with air as the working fluid. The coating elevates the outer tube inner wall temperature $T_3$, increasing the convective driving force to the cold fluid while suppressing ambient dissipation. In parallel flow, Al₂O₃ increases the net inter-fluid heat transfer rate by 35.7% and reduces ambient losses by 81.4%; ZnO achieves 30.9% and 70.4%, respectively. In counter-flow, Al₂O₃ yields a 26.6% enhancement and 73.2% loss reduction. The coated parallel-flow configuration outperforms the uncoated counter-flow baseline. Thermal circuit analysis shows that Al₂O₃ superiority arises from its higher conductivity (40 vs. 19 W m⁻¹ K⁻¹), which sustains a higher equilibrium $T_3$ and a heat partition ratio of 11.84 versus 7.17 for ZnO. These results show that a single ceramic coating layer can recover a large fraction of the thermal energy lost through non-insulated walls, offering a low-cost, retrofit-compatible pathway to improve the energy efficiency of gas-to-gas heat exchangers in HVAC, building energy recovery, and industrial process heat applications. Full article

Urban–climate interactions in a warming climate remain largely uncertain; therefore, it is crucial to realistically evaluate and project these feedbacks to establish effective adaptation strategies. This study investigates projected shifts in summertime urban–climate interactions over eastern North America by employing the GEM regional climate model coupled with the Town Energy Balance (TEB) scheme, driven by RCP4.5 and RCP8.5 scenarios for the 1981–2100 period. Evaluations for the current climate (1981–2010) demonstrate that the model simulates an urban-induced warming of 0.5–0.7 °C and a precipitation reduction of 0.2–0.4 mm/day with high fidelity. By the late 21st century (2071–2100), projections under the RCP8.5 scenario indicate a steady weakening of the summer mean Urban Heat Island (UHI) intensity by approximately 0.10 °C, with a more pronounced nighttime attenuation of 0.15 °C. Physically, this weakening is attributed to an enhanced urban-induced evaporative fraction, which limits solar radiation storage within the urban fabric during the day, thereby reducing the thermal energy available for post-sunset release. This UHI attenuation correlates strongly with localized increases in precipitation, particularly in coastal regions where urban-induced effects contribute 20–40% to the total precipitation rise. While this study intentionally utilizes static urban boundaries to isolate the specific sensitivities of current urban morphologies to global warming, these results emphasize that diverse climatological regions will undergo distinct urban–climate feedback changes, providing essential baseline data for resilient urban planning. Full article

In deep geothermal engineering, concrete slabs are prone to thermal cracking. The aggregates and pores are the core influencing factors for this failure behavior. However, existing research methods are unable to accurately capture the microscopic evolution process of thermal cracking and cannot clarify the intrinsic mechanism of how the characteristics of aggregates and pores affect the initiation and propagation of cracks. This limitation restricts the in-depth understanding of the laws of concrete thermal cracking. To address this deficiency, this study employs the discrete element method (DEM) and combines the particle flow program PFC2D to construct a microscopic model of concrete disks. By setting reasonable temperature parameters and thermal load boundaries, a numerical simulation system matching the actual deep geothermal high-temperature environment is established. Three sets of quantitative variables were designed: aggregate particle size (0.003, 0.004, 0.005, 0.006), aggregate volume fraction (0.35, 0.40, 0.45, 0.50), and porosity (0.11, 0.12, 0.13, 0.14). Through controlled variable simulations, the influence laws of each variable on the formation, propagation path, and time evolution of concrete thermal cracks were explored. The quantitative research results show that an increase in aggregate particle size significantly accelerates the generation and propagation of cracks. When the particle size is 0.006, the number of cracks is the highest and the propagation rate is the fastest. The aggregate volume fraction is negatively correlated with the final number of cracks, and 0.50 is the optimal fraction, at which the number of cracks is the smallest. A decrease in the fraction will lead to intensified stress concentration in the cement paste and a sudden increase in the number of cracks. An increase in porosity significantly disrupts the material continuity. When the porosity is 0.14, the bifurcation and connection of cracks are the most significant, while a low porosity of 0.11 can effectively inhibit the overall development process of thermal cracks. In addition, compared with traditional experimental methods and continuous medium numerical simulation techniques, the discrete element method has unique advantages in revealing the internal mechanism of concrete thermal cracking at the microscopic level. It can achieve real-time tracking of the evolution of discrete micro-cracks and the internal stress distribution characteristics. This study enriches the microscopic theoretical system of concrete thermal cracking and provides reliable quantitative references and technical support for the design of thermal crack resistance of concrete in deep geothermal engineering and the optimization of material composition. Full article

Hafnium oxide thin films have been extensively investigated for high-speed and low-power memory applications. Herein, we investigated the influence of oxygen vacancies and external stress on the ferroelectric characteristics of Al-doped HfO₂ (HfAlO). Compared with HfAlO with 14% oxygen vacancies, films with 21% oxygen vacancies could lower the polarization switching barrier and increase the fraction of the ferroelectric phase. Furthermore, significant external stress promotes ferroelectric phase formation, thereby enhancing ferroelectric characteristics. The remanent polarization achieved with W electrodes (2Pr = 38 µC/cm²) is about 18 times that of Au electrodes, owing to the lower thermal expansion coefficient of W electrodes. Density functional theory calculations and finite element analysis provide theoretical insights corroborating the experimental results, helping to pave the way for developing hafnium-based materials for next-generation in-memory computing applications. Full article

Mechanically activated pyrite plays an important role in gold extraction and coal utilization, but its reactivity may change markedly during storage. This study investigates how air deactivation during storage affects the crystal structure and subsequent thermal decomposition behavior of mechanically activated pyrite. Pyrite was mechanically activated and then stored in air for 0, 7 and 180 days. X-ray diffraction (XRD) combined with Rietveld refinement was used to characterize variations in lattice parameters and unit-cell-related structural features, while non-isothermal thermogravimetric–differential scanning calorimetry (TG-DSC) under an argon atmosphere, together with the Flynn–Wall–Ozawa (FWO) method, was applied to evaluate the decomposition kinetics. Air deactivation induced a non-monotonic evolution of lattice parameters and unit-cell volume, which is attributed to combined effects of residual stress relaxation and air-induced surface-related modification during storage. All samples exhibited two mass-loss stages during heating, reflecting stepwise thermal decomposition, and their decomposition behavior varied systematically with deactivation time. The apparent activation energy depended on both conversion fraction and deactivation degree, and nucleation-and-growth-type mechanisms were found to dominate the decomposition process, with their relative contributions evolving with storage time. These results clarify how prior air-deactivation history influences the structural evolution and subsequent thermal decomposition behavior of mechanically activated pyrite and provide useful insight for its storage and utilization in related processes. Full article

The sustainable renovation of ageing industrial buildings presents both a challenge and an opportunity to enhance energy efficiency while preserving architectural and structural integrity. This study develops an integrated methodological framework for assessing and optimising multilayer wall systems in such conversions, combining thermal, environmental, and durability analyses. Six composite wall configurations were designed and numerically evaluated using steady-state 2D heat conduction and vapour-diffusion models. The results reveal substantial thermal improvement compared to the reference uninsulated brick wall (U = 1.41 W/m²·K). The proposed systems achieved U-values between 0.351 and 0.172 W/m²·K, meeting or surpassing European energy standards. The BP–EPS wall exhibited the lowest U-value (0.172 W/m²·K), while the FC–EPSR configuration achieved superior corner performance with a 2D surface temperature (Tsi) of 17.99 °C and the highest surface temperature factor (fRsi = 0.943), along with a reduced condensation risk, indicating more balanced overall performance. Weight and thickness reductions of up to 80.5% and 52%, respectively, were observed, enhancing retrofit feasibility and space efficiency. Life Cycle Assessment results indicated that optimised wall configurations reduced embodied carbon (A1–A3) by up to 78% and total life cycle emissions (A1–A3 + B6) by over 86% relative to the reference case. Vapour-diffusion analysis confirmed the FC–EPSR wall’s lowest condensation fraction, indicating excellent hygrothermal durability. Multi-criteria evaluation using the simple additive weighting method and Monte Carlo robustness analysis verified FC–EPSR as the most balanced and reliable system. Overall, the findings present a validated and replicable pathway for the sustainable renovation of industrial buildings, supporting the goals of European carbon neutrality and the circular economy. Full article

The high mortality rate from microbial infections underscores the need to discover new antimicrobials. This work produced antibacterial Chitosan biofilms with and without the incorporation of the ethanolic extract of Libidibia ferrea stem bark and its ethyl acetate and aqueous fractions. The extract and fractions were subjected to FTIR and ¹H NMR analysis. The biofilms were characterized by FTIR, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry analysis. The ¹H NMR and FTIR data, as well as the colorimetric quantification of total phenolics, demonstrated the presence of phenolic compounds. Staphylococcus aureus and Bacillus cereus were the most susceptible bacteria for Chitosan/L. ferrea biofilms and fractions (growth inhibition zones values in the range of 10.8 ± 0.1 to 14.0 ± 0.1 mm, and minimum inhibitory or bactericidal concentration, MIC or MBC values of the fractions were in the range of 125 to 250 µg mL⁻¹. Only the fractions inhibited Pseudomonas aeruginosa (MIC = 250 µg mL⁻¹). Chitosan/L. ferrea biofilms exhibited efficient interactions between chitosan functional groups and secondary metabolites, good thermal stability, and increased rigidity in mechanical tests. This study reinforces the pharmacological potential of biodegradable Chitosan/L. ferrea biofilms as antibacterial agents biofilms. Full article

Ti-6Al-4V parts fabricated via selective laser melting (SLM) often exhibit severe surface irregularities that limit their direct engineering application. This study proposes a top-hat beam laser polishing method to improve surface quality. The results show that surface roughness (Sa) is reduced to 0.48 μm, a 95.3% decrease from the as-built condition. The uniform energy distribution of the top-hat beam stabilizes melt pool behavior, enabling effective surface leveling through valley filling and lateral melt flow. In contrast, Gaussian beam polishing induces strong Marangoni convection and wake effects, resulting in higher residual roughness. Microstructural analysis indicates an increased fraction of equiaxed α grains and a β-phase content of ~6% after top-hat polishing. The heat-affected zone likely exhibits a subcritical heat-treatment-like effect, promoting fine secondary α precipitation. Additionally, localized stresses induced by steep thermal gradients during SLM are effectively relieved. Overall, top-hat laser polishing is a promising post-processing technique for enhancing the surface quality of Ti-6Al-4V components. Full article

Light hydrocarbons in shale oil readily volatilize during conventional coring, surface handling, storage, and laboratory preparation. The resulting evaporative loss causes systematic underestimation of Rock-Eval S₁ peak (free hydrocarbons measured by programmed pyrolysis), which can bias oil-bearing evaluation, sweet-spot delineation, and resource assessment. Here we investigate Chang 7₃ lacustrine shale oil in the Ordos Basin (China) using frozen cores recovered by pressure-retained coring from four wells. Time-series Rock-Eval pyrolysis and thermal desorption–gas chromatography (TD–GC) were used to quantify the magnitude, temporal evolution, and practical equilibrium time of light-hydrocarbon loss and to establish a practical restoration model. S₁ decreases with storage time and exhibits a clear two-stage behavior. Shale shows a rapid-loss stage during 0–90 days, followed by a practical equilibrium stage after 90 days (S₁ change less than 5%). Sandstone interbeds lose light hydrocarbons faster and more completely, reaching practical equilibrium after 60 days. TD–GC indicates that the lost fraction is dominated by n-alkane components lighter than C₁₃, with gaseous hydrocarbons showing the greatest depletion; medium and heavy fractions decrease modestly. Loss is coupled with progressive desorption from kerogen and clays, leading to enrichment of heavier components in the residual free hydrocarbons and a shift of the modal carbon number toward higher values. At the shale equilibrium time, total organic carbon (TOC) and vitrinite reflectance (R_o) jointly control the restoration factor K. We propose a two-parameter restoration model: K = (0.4024·ln (TOC) + 0.821)·(0.652·R_o + 0.4292). Applying the model to more than 50 conventionally cored wells reveals that the Qingyang–Zhengning area in the southwestern basin is the principal enrichment zone of original free hydrocarbons, followed by the Jiyuan area in the north and the Huachi area in the central basin, whereas the eastern basin is relatively depleted. The workflow provides a robust and transferable approach for correcting S₁ and improving shale-oil evaluation in lacustrine systems. Full article