Search Results (1,332)

Cell therapies for gastric disorders lack minimally invasive delivery platforms that preserve cell viability during storage and enable effective tissue penetration, owing to the high toughness and harsh environment of the gastric wall. Herein, we developed a mechanically reinforced, porous silk-based cryogenic microneedle (silk-cryoMN) platform for in situ cell delivery to the gastric wall. The optimized 1.5% (w/v) silk scaffolds exhibited interconnected pores (24.4 ± 7.9 μm, ~81% porosity), a compressive strength (422.8 ± 73.4 MPa), and a 3.4-fold increase in β-sheet content. The silk-cryoMNs showed greater thermal stability than H₂O-cryoMNs, maintaining structural integrity for over 60 s at room temperature. With a cryopreservation medium containing 100 mM sucrose and 2% DMSO, post-thaw cell viability exceeded 80% after 11 days of freezing, and most cells were released within 1 h. Furthermore, ex vivo studies confirmed penetration of porcine gastric tissue to depths of 422–448 μm within 30 s. These results suggest that the platform may address several translational barriers, including tissue penetration, handling stability, and cell viability preservation. Further in vivo studies and long-term safety evaluations are needed before clinical translation can be considered. Full article

This study investigates the low-Reynolds-number rotation of two eccentric spheres within an incompressible fluid that accounts for both micro-rotational effects and the presence of a porous medium. The region between the spheres contains a rigid, stationary skeleton, and we model the resulting flow using the Brinkman-extended Darcy approach. We derive the governing field equations, which account for the resistance to rotation through specific fluid viscosity parameters, while also incorporating surface slip effects on the interior sphere. The system of equations is solved using a semi-analytical boundary collocation method, where the fluid motion is expressed through a series of mathematical expansions satisfied at discrete points along the spherical boundaries. Our numerical results demonstrate that the hydrodynamic torque exerted on the spheres is highly sensitive to the porous environment. Specifically, increasing the permeability of the medium from $0.001$ to $0.5$ results in a substantial torque increase of approximately $210\%$. Additionally, the fluid’s resistance to micro-rotation acts as a torque-enhancing factor, with a variation in viscosity parameters from $0.02$ to $0.45$ inducing a $5.25\%$ increase in torque under conditions of high eccentricity. These findings were validated against established benchmarks for standard fluids in non-porous media, showing excellent agreement. Full article

Polymer flooding is an important enhanced oil recovery technology for high-water-cut heterogeneous reservoirs, where long-term waterflooding commonly leads to preferential flow channels and insufficient mobilization of remaining oil in less-swept intervals. In this study, a hydrophobically modified partially hydrolyzed polyacrylamide-type polymer containing hydrophobic associative groups was evaluated for mobility control and enhanced oil recovery in heterogeneous porous media with the assistance of well-log-interpreted reservoir parameters. Reservoir heterogeneity was first characterized using interpreted effective thickness, porosity, permeability, oil saturation, and water saturation, and the polymer performance was then examined through rheological measurements, core-flooding experiments, and field production response analysis. The results show that the representative reservoir layers exhibit a wide permeability range of 7.9–186.5 mD, with higher water saturation in high-permeability layers and higher oil saturation in medium- and low-permeability layers. The polymer solution shows concentration-dependent thickening, shear-thinning behavior, salinity tolerance, and thermal-aging stability, retaining a viscosity of 139.5 mPa·s at 180,000 mg/L salinity and 74.9% viscosity retention after aging for 504 h. Core-flooding results indicate that the medium-permeability core achieves the highest polymer incremental recovery of 14.5 ± 0.8%, reflecting a favorable balance between injectivity and residual flow resistance. Field production data further show that daily oil production increases from 11.6 to 20.4 t/d, water cut decreases from 93.1% to 81.6%, and cumulative oil increment reaches 2055 t after polymer injection. The proposed mechanism involves associative thickening, pore-throat-adaptive transport, residual flow resistance, flow-path redistribution, and remaining-oil mobilization. This study establishes a heterogeneity-constrained mobility-control framework linking well-log-interpreted reservoir parameters, permeability-dependent polymer transport, residual flow resistance, and field production response, showing that effective polymer flooding depends on balancing injectivity, flow resistance, and remaining-oil availability rather than maximizing bulk viscosity alone. Full article

Rock-bed thermal energy storage (RTES) systems are attracting growing interest as low-cost, robust, and scalable sensible heat storage solutions for applications ranging from low-temperature building and greenhouse heating to medium- and high-temperature solar or waste-heat recovery systems. However, their thermo-hydraulic performance is strongly influenced by the complex interactions among heat-transfer-fluid flow, irregular rock morphology, porosity, pressure drop, interphase heat transfer, and transient thermal-front development. This review provides a focused evaluation of computational fluid dynamics (CFD) modelling strategies for packed beds of rocks, with particular attention to continuum porous-medium approaches and the closure correlations required for reliable simulation. First, the distinction between pore-scale and volume-averaged continuum modelling is discussed in terms of the trade-off between physical resolution and computational feasibility. The main pressure-drop and friction-factor correlations are then reviewed and compared, including classical packed-bed models and rock-bed-specific formulations. It is shown that hydraulic-resistance predictions are highly sensitive to particle shape, surface roughness, porosity, the bed-to-particle diameter ratio, and packing arrangement. Particle-fluid heat-transfer correlations are also examined and, when possible, converted into a consistent particle Nusselt-number form to enable direct comparison. Particular attention is given to generalized correlations, dispersion-corrected models, and air–rock-bed correlations applicable to thermal storage systems. Finally, a methodological framework for modelling RTES systems using local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) formulations is proposed. Dimensionless criteria, including the interphase thermal coupling number and particle Biot number, are introduced to support the selection between LTE and LTNE formulations. The selection of pressure-drop/friction-factor and solid–fluid heat-transfer/particle Nusselt-number correlations should be based on the similarity between the original experimental conditions and the target RTES system, and system-specific validation is recommended whenever possible. Full article

The utilisation potential of Brachypterum microphyllum, a fast-growing species introduced into plantation trials in Malaysia, remains relatively underexplored. Samples in this study were obtained from a Forest Research Institute Malaysia (FRIM) plantation trial in Selandar, Melaka, established using wild seedlings collected from Kampung Ulu Groh, Perak, where the species has been traditionally used by the Semai Orang Asli community. The plantation trial was initiated to assess its cultivation potential and to support sustainable raw material supply, thereby reducing reliance on natural forest resources. To date, research has mainly focused on the medicinal properties of the bark, while the wood characteristics and utilisation potential remain less studied. This study investigated the anatomical, chemical, physical, and mechanical properties of seven-year-old plantation-grown B. microphyllum. Microscopic analysis revealed diffuse-porous wood with very large solitary vessels, aliform to confluent parenchyma, medium-sized rays, and non-septate fibres. The absence of tyloses and silica may indicate favourable treatability and machinability, although this requires further confirmation through processing studies. Chemical analysis showed high holocellulose content (79.5%–81.9%), α-cellulose (~44%), moderate lignin content (22.6%–23.9%), and low extractives (0.9%–2.1%), indicating a high carbohydrate composition. Preliminary phytochemical screening identified flavonoids, tannins/polyphenols, and triterpenes/steroids, which may be relevant to further investigation of its reported traditional uses. The wood density ranged from 441.4 to 606.8 kg/m³ (mean: 524.1 kg/m³), classifying it as light to moderately heavy timber. Shrinkage values at 15% moisture content were 2.2% (tangential), 1.3% (radial), and 0.6% (longitudinal), with a T/R ratio of 1.6, indicating moderate dimensional stability. Mechanical properties were comparable to or higher than values reported for several plantation-grown species in the literature. Overall, the findings indicate that seven-year-old B. microphyllum has potential as a fast-growing plantation timber species with favourable physical and mechanical properties. Full article

Flexible piezoresistive sensors often face a trade-off between sensitivity and working range. In this work, a gradient porous poly(vinyl alcohol)/carbon black (PVA/CB) composite was fabricated via a simple sugar-templating method. The bilayer structure consists of a small-pore layer and a large-pore layer, enabling sequential deformation under external pressure. As a result, the sensor exhibits a sensitivity of −3.05 kPa⁻¹ in the low-pressure range (0–20 kPa) and maintains a stable response up to 120 kPa. Compared with uniform porous structures, the gradient design shows improved performance in the medium- and high-pressure ranges. The sensor also demonstrates good repeatability, fast response, and stability over 1000 cycles. Practical applications including respiration monitoring, vocal vibration detection, and motion sensing are demonstrated. This work provides a simple and scalable approach for developing flexible pressure sensors. Full article

In this paper, we consider a mathematical model for the flow of a dilute aqueous polymer solution through a heterogeneous porous medium. On the boundary of the flow region, the impermeability condition and a nonlinear Navier-type slip condition are prescribed. Our goal is to investigate the existence of weak solutions to the governing equations of this model, which is a challenging problem for both steady and unsteady flows. To prove the weak solvability, we use a modified Galerkin scheme with special basis elements in appropriate Sobolev spaces. We obtain the existence results without assuming smallness of the model data for the boundary value problem related to steady flows and prove the global-in-time solvability of the initial-boundary value problem describing unsteady flows. Moreover, energy equalities are established for weak solutions possessing additional regularity. Our results can serve as a starting point for further research on the problems under consideration, including numerical analysis and optimal control of polymer fluid flows. Full article

Metal-free polymeric semiconductor graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polycondensation using cyanamide with PVP as a medium, using SiO₂ nanospheres as sacrificial templates to suppress bulk agglomeration. Structural analysis using X-ray diffraction (XRD) confirmed the conservation of the g-C₃N₄ structure, while diffuse reflectance UV-Vis spectroscopy (DRS) showed that there is a slight change in optical absorption, modifying the band gap energy of g-C₃N₄ with the addition of SiO₂. Transmission electron microscopy (TEM) evidenced the formation of interconnected porous architectures, facilitating charge migration. Photocatalytic activity was evaluated under simulated solar irradiation using acetaminophen (ATP) as a model pharmaceutical pollutant. Kinetics experiments demonstrated that the sample containing 7% SiO₂ nanospheres achieved 65% degradation for 180 min. The best photocatalytic performance is attributed to the pore volume, which favors better adsorption, facilitating the degradation of acetaminophen. The participation of different reactive species during the photocatalytic degradation of ATP was determined. Experiments with scavenger agents indicate that the photogenerated holes are the predominant oxidizing reactive species. These results highlight the potential of g-C₃N₄ modified with SiO₂ nanospheres as an efficient photocatalyst for the degradation of emerging contaminants, thus advancing sustainable water treatment technologies. Full article

Clay, as a sediment material, is an attractive option for the production of porous ceramics due to its low price and high abundance. Porous ceramics possess a combination of essential properties of clay-based materials, including high porosity and thermal and chemical stability, making them suitable for various industrial applications, such as filters, heat insulators, and absorbents. In this study, thermally and chemically purified clay was mixed with boric acid as a pore-forming agent. Obtained results reveal that different contents of boric acid (2 wt.% and 0.5 wt.%) and variations in synthesis conditions, including low pressing pressures up to 60 MPa and low sintering temperatures of 1150 °C and 1300 °C, optimize the production of a filter medium with good separation and mechanical properties. Further, these findings indicate that an adequate combination of boric acid content and synthesis conditions positively affects mechanical properties, including values of hardness, Young’s modulus, compressive and tensile strength of clay-based filters. The clay-based filter with 2 wt.% boric acid exhibited a larger maximum pore diameter of nearly 0.2 mm, compared to the one with 0.5 wt.% boric acid. The filtering efficiencies of both filters were tested on pharmaceutical-grade ciprofloxacin with removal efficiency above 80% for two tested concentrations (6 μM and 9 μM). Full article

The present study investigates heat transfer characteristics in the thermally developing region of a porous tube under the local thermal nonequilibrium (LTNE) model. The influence of magnetohydrodynamic (MHD) flow on an electrically conducting fluid flowing through a porous medium under a transverse magnetic field is examined. Under the LTNE framework, two separate energy equations are employed to describe the temperature fields of the fluid and solid phases. The coupled governing equations are solved numerically using the Keller-box method. The results indicate that increasing the interphase heat transfer parameter strengthens thermal coupling between the fluid and solid phases, thereby reducing temperature differences and promoting local thermal equilibrium. In contrast, an increase in the Prandtl number reduces thermal diffusion, leading to larger temperature gradients and greater disparity between the two phases. Furthermore, the magnetic field suppresses both the velocity and temperature distributions through the Lorentz force. An increase in permeability reduces the velocity profiles due to the combined effects of the MHD and Prandtl numbers while increasing the temperature profiles. Increasing the interphase heat transfer rate drives the system from the LTNE to the LTE phase. The study confirms that LTNE effects play a significant role in thermal transfer processes in porous media and are relevant for various industrial heat transfer applications. Full article

Heat transport in heterogeneous materials can deviate markedly from classical Fourier behavior when microstructural disorder, trapping effects, nonlinear mobility, and long-range temporal correlations interact across multiple spatial and temporal scales. These mechanisms may produce delayed relaxation, persistent thermal footprints, front deformation, and non-classical spreading patterns that are not adequately represented by conventional integer-order diffusion models. In this study, a modeling and simulation framework is developed for anomalous heat transport in heterogeneous media using a two-dimensional time-fractional porous medium equation. The model combines a Caputo fractional time derivative, which represents thermal memory, with nonlinear degenerate porous-medium diffusion, spatially heterogeneous conductivity, localized volumetric heating, and Robin-type convective boundary exchange. A conservative fully discrete numerical scheme is constructed using flux-based finite differences for the heterogeneous nonlinear diffusion operator and an $L1$ approximation for the Caputo derivative. The nonlinear algebraic system at each time level is solved using an under-relaxed Picard frozen-coefficient iteration with non-negativity enforcement and sparse direct solution of the resulting linear systems. The numerical implementation is verified through a manufactured-solution convergence study, and additional analyses are performed to examine computational cost, Picard iteration behavior, coefficient-regularization sensitivity, strong-source effects, heterogeneous conductivity structures, and long-time thermal-footprint persistence. The results show that heterogeneous conductivity mainly redirects heat through preferential pathways and enlarges the spatial footprint while producing negligible changes in global heat content. Stronger fractional memory, represented by smaller fractional order, increases the persistence and spatial reach of moderate heating, whereas larger porous-medium exponents confine heat near the source and preserve higher local peaks. Source amplitude increases the thermal burden and footprint monotonically over the tested range, including strong forcing, without producing an abrupt localization-spreading transition. Boundary exchange remains secondary in the short-time interior-heating regime considered. These findings demonstrate that the proposed two-dimensional time-fractional porous medium framework provides a verified and physically interpretable model for non-Fourier heat transport in heterogeneous materials, where local intensity, global heat retention, and spatial thermal exposure must be assessed jointly. Full article

The blast furnace–basic oxygen furnace long process is the dominant steel production route in China. Increasing the scrap ratio is an effective way to reduce cost and carbon emissions, and scrap preheating is a key technology to achieve a high scrap ratio. To improve the low thermal efficiency and poor deep-bed melting performance of converter gas-based scrap preheating, an innovative process using oxygen-enriched combustion in a hot metal ladle is proposed. Numerical simulation is essential for capturing the complex multiphysics phenomena, as real-time monitoring of melting inside the packed scrap bed is extremely difficult. In this study, a novel multiphysics approach based on a User-Defined Function (UDF) is developed to dynamically track the progressive melting of the scrap skeleton, overcoming the key limitation of conventional enthalpy–porosity models that cannot capture the feedback between phase change and porous medium property evolution. A three-dimensional transient model was established, integrating turbulent combustion, gas–solid convective heat transfer in porous media, and solid–liquid phase change. The effects of impact pit depth, scrap porosity, and converter gas flow rate on temperature distribution, melting behavior, and thermal efficiency were systematically investigated. Results showed that porosity had the strongest influence; thermal efficiency increased from 33.92% to 65.59% as porosity rose from 0.6 to 0.8, due to a transition from conduction-dominated to coupled convection–conduction heat transfer. Converter gas flow rate exhibited a non-monotonic effect, peaking at 3688.14 m³·h⁻¹, highlighting a trade-off between energy input and gas residence time, while impact pit depth showed a limited effect with diminishing returns. A 600 s full-process simulation revealed stage-dependent melting, and the initial phase was crucial for process optimization. The optimal condition, with a pit depth of 64 cm, porosity of 0.8, and converter gas flow rate of 3688.14 m³·h⁻¹, achieved a 1.23% melting fraction and 65.59% thermal efficiency within 120 s. These findings clarify the combined roles of geometric confinement, permeability, and energy-residence time interactions, providing guidance for industrial scrap preheating design. Full article

Predicting thermal breakthrough and optimizing injection-production parameters are essential for sustainable geothermal development. Traditional hydrothermal coupled simulations in porous media entail substantial computational costs, which limits their use in dense multi-parameter screening. This study develops a physics-constrained surrogate workflow for the Qihe geothermal doublet system by using COMSOL to generate hydrothermal simulation data and a deep neural network (DNN) to emulate the simulator response within a predefined operating domain. The DNN was trained on physics-driven synthetic outputs rather than independent field observations, and a 2.0 °C decrease in production temperature was used as the thermal breakthrough criterion. Under scenario-wise validation, the surrogate model achieved a test-set R² of 0.9995 and an RMSE of 0.0351 °C, indicating accurate approximation of the deterministic simulator response within the bounded parameter space. The surrogate-based global scan identified a favorable operating region near a well spacing of 462 m, a reinjection temperature of 20 °C, and a reinjection rate of 150 m³/h. To evaluate whether this result was affected by sparse well-spacing sampling, additional COMSOL simulations were performed at 430, 440, 450, 460, 462, 470, 480, 490, and 500 m under the same reinjection temperature and rate. These simulator-based validation cases showed a continuous thermal response with increasing well spacing. The 2.0 °C thermal breakthrough time increased from 46 yr at 430 m to 61 yr at 500 m, while the 50-year cumulative heat extraction increased from 6594.2 to 6722.9 TJ. The 430 and 440 m cases experienced thermal breakthrough before the 50-year design life, whereas the 450 m case was close to the design boundary. The 460 and 462 m cases did not reach the 2.0 °C decline threshold within the 50-year design life and retained relatively high heat-extraction efficiency per unit well spacing. Therefore, the engineering recommendation is revised from a single precise optimum to a locally validated spacing interval of approximately 460–462 m under the present equivalent-porous-medium assumption. The proposed workflow does not replace hydrothermal simulation; instead, it provides a rapid screening tool that narrows the design space before targeted simulator verification and field calibration. Full article

The Porous Line is a drawing inquiry that uses materials and processes to engage in a dialogue with a suburban ecosystem. I follow the physicist David Bohm’s proposal to use dialogue as a mode of engagement where habitual modes of thought are suspended, a form of non-judgmental curiosity. I reflect on how immersing a large roll of French imported paper in my everyday environs reveals the porousness between nature and culture. The binary separation of nature and culture has undergone significant criticism as we deal with the climate crisis. As a foundational medium within western art and thought, how can drawing communicate this growing ontological shift? The essay engages in dialogue with Yolngu art from Yirrkala as a guide on what an ecological art practice entails. Their commitment to work with what ‘country’ provides has resulted in innovative and thoughtful new works. In response to propositions seen in Yolngu artworks, this essay engages with place, materiality, and relationality through the process of merging line and ground, the fundamentals of drawing, physically and conceptually. I reflect on the challenges that need to be addressed within western ontologies to develop an ecological approach in drawing. Full article

The transition toward circular economy practices and CO₂ reduction goals is driving the development of new sound absorption technologies. Traditional absorbers made from mineral wool or foams provide broadband absorption; however, their production is associated with intensive energy consumption and non-renewable resources. This is why the focus has been shifting from the mere substitution of materials to integrated solutions that combine sustainability with structure. This paper reviews recent innovations in sustainable absorbers based on bio-based and recycled materials. The acoustic performance of porous materials depends on such factors such as pore structure, airflow resistivity and geometric parameters such as thickness, multi-layer structure and resonances. At the same time, additive manufacturing (AM) allows creating geometry-controlled absorbers providing advanced acoustic properties. Despite many sustainable absorbers demonstrating sufficient sound absorption properties at medium and high frequencies, their use at low frequencies remains challenging. Additionally, concerns regarding durability, flame retardance, and environmental consistency continue to limit their broader application. Yet, hybrid, multi-material strategies, particularly those combining geopolymer matrices with bio-based or recycled fillers, are identified as a promising route to address these limitations. This review outlines current trends and highlights key challenges and future directions in the design of sustainable sound-absorbing systems. Full article